Marcelo Arenas, Juan L. Reutter, Etienne Toussaint, Martín Ugarte · 6 authors
In the consensus protocols used in most cryptocurrencies, participants called miners must find valid blocks of transactions and append them to a shared tree-like data structure. Ideally, the rules of the protocol should ensure that miners maximize their gains if they follow a default strategy, which consists on appending blocks only to the longest branch of the tree, called the blockchain. Our goal is to understand under which circumstances are miners encouraged to follow the default strategy. Unfortunately, most of the existing models work with simplified payoff functions, without considering the possibility that rewards decrease over time because of the game rules (like in Bitcoin), nor integrating the fact that a miner naturally prefers to be paid earlier than later (the economic concept of discount). In order to integrate these factors, we consider a more general model where issues such as economic discount and decreasing rewards can be set as parameters of an infinite stochastic game. In this model, we study the limit situation in which a miner does not receive a full reward for a block if it stops being in the blockchain. We show that if rewards are not decreasing, then miners do not have incentives to create new branches, no matter how high their computational power is. On the other hand, when working with decreasing rewards similar to those in Bitcoin, we show that miners have an incentive to create such branches. Nevertheless, this incentive only occurs when a miner controls a proportion of the computational power which is close to half of the computational power of the entire network.
One of important issues of information security in the interaction of users is the use of methods and tools, allowing one party to make sure of the authenticity of another party. The proof of knowledge protocols which have the additional property of zero-knowledge are applied to solve this problem. The protocols based on asymmetric encryption have received wide acceptance, such as the Fiat-Shamir, Schnorr, Okamoto, Guillou-Quisquater, Brickell-McCurley, Feige-Fiat-Shamir protocols. Cryptographic strength of these protocols is defined by discrete logarithms in a finite prime field, as well as an increase in the number of accreditation cycles. As a result of the development of methods and tools of cryptanalysis and rapid development of technologies and power of computing systems, there is a need to increase the sizes of system-wide parameters of the protocol, leading to increased resource intensity and performance complexity of basic operations in the fields.Cryptographic zero-knowledge protocols on elliptic curves are proposed in the paper. The strength of cryptosystems on elliptic curves is based on the difficulty of solving the discrete logarithm problem in the group of elliptic curve points, and is more difficult than the discrete logarithm problem in the finite field. The completeness and soundness of protocols were determined, computation examples were given. The tools of the Strength Protocol Animator package were applied to verify the protocols for resistance to enemy attacks. Consequently, the use of cryptographic protocols on elliptic curves will significantly reduce the sizes of protocol parameters and increase the cryptographic strength
Background: Accessibility to essential drugs is a public right, therefore it's the government responsibility to make them available.Previously before the era of regional autonomy, public drug management in all districts/cities was performed by the so-called District Pharmaceutical Warehouses (GFK).However, nowadays the situation has changed because of the difference in vision and perception of each regional government on the former warehouses.Some public drug management units in certain districts/cities are not functioning optimally.Inefficient drug procurement regarding the number and kind of drugs as well as timeliness results in gap between drug need and procurement.Furthermore, loosening in drug supply procedure makes essential drugs more unavailable to public.On the other hand, decentralization policy in drug management also undeniably brings advantages to the districts, for example capacity building in drug procurement, increasing capability in budget management and negotiation with district decision makers as well as enhancing regional economic activity.In revitalizing district pharmaceutical warehouses so as to attain minimal health care standards in districts/cities, baseline data in drug management and financing in several districts/cities should make a valuable contribution.Methods: A cross sectional descriptive study had been carried out during July-December 2006 in 26 districts/cities out of 11 provinces.Samples were 26 district health offices (Dinas Kesehatan Kabupaten/Kota) and 26 District Pharmaceutical Warehouses (GFK) where as respondents were head of drug section and head of warehousing respectively.Data were collected by means of structured questionnaires and in-depth interviews as well as the collection of secondary data of drug logistics.Qualitative and quantitative analysis was performed. Results:The study shows that: 1) although health budget in general had risen, the average percentage of drug budget allocation from 21 district health authorities was only 12.06%, reflecting the low drug priority in district health policy because drug expenditures may amount up to 40% of the total health budget.2) Public drug management was mostly performed by the so-called regional technical provider unit (UPTD) with some limitations concerning human resources and material in achieving an effective and efficient drug management, and 3) there was still lack of pharmacist assistants to manage drugs in primary health care (Puskesmas) up to 20% and even more piteously the lack of pharmacist in district drug management unit (GF/UPOP Kabupaten/Kota, 12,5%).Conclusions: Apart from the achievement of predetermined indicators stated in minimal health care standards in districts/ cities, especially regarding essential and generic drugs, drug management in general has been well performed concerning planning and drug availability.More support and commitment from the district government is a must considering that regional development can not be separated from the health development of the subject themselves.
Marcin Andrychowicz, Stefan Dziembowski, Daniel Malinowski, Łukasz Mazurek
BitCoin transactions are malleable in a sense that given a transaction an adversary can easily construct an equivalent transaction which has a different hash. This can pose a serious problem in some BitCoin distributed contracts in which changing a transaction's hash may result in the protocol disruption and a financial loss. The problem mostly concerns protocols, which use a "refund" transaction to withdraw a deposit in a case of the protocol interruption. In this short note, we show a general technique for creating malleability-resilient "refund" transactions, which does not require any modification of the BitCoin protocol. Applying our technique to our previous paper "Fair Two-Party Computations via the BitCoin Deposits" (Cryptology ePrint Archive, 2013) allows to achieve fairness in any Two-Party Computation using the BitCoin protocol in its current version.
Designed to compete with fiat currencies, bitcoin proposes it is a crypto-currency alternative. Bitcoin makes a number of false claims, including: solving the double-spending problem is a good thing; bitcoin can be a reserve currency for banking; hoarding equals saving, and that we should believe bitcoin can expand by deflation to become a global transactional currency supply. Bitcoin's developers combine technical implementation proficiency with ignorance of currency and banking fundamentals. This has resulted in a failed attempt to change finance. A set of recommendations to change finance are provided in the Afterword: Investment/venture banking for the masses; Venture banking to bring back what investment banks once were; Open-outcry exchange for all CDS contracts; Attempting to develop CDS type contracts on investments in startup and existing enterprises; and Improving the connection between startup tech/ideas, business organization and investment.
Bitcoin is the latest fantasy object of utopian thinkers far and wide. Angry with the banks? It sidesteps them. Fed up with governments? They can’t regulate it. Annoyed by corporations? Bitcoin transcends them. Worried about fraud? Bitcoin uses the latest cryptography. Keen to make a buck (so to speak) by participating in a boom? Come on down and plug in.
Digital currencies have emerged as a new fascinating phenomenon in the financial markets. Recent events on the most popular of the digital currencies--BitCoin--have risen crucial questions about behavior of its exchange rates and they offer a field to study dynamics of the market which consists practically only of speculative traders with no fundamentalists as there is no fundamental value to the currency. In the paper, we connect two phenomena of the latest years--digital currencies, namely BitCoin, and search queries on Google Trends and Wikipedia--and study their relationship. We show that not only are the search queries and the prices connected but there also exists a pronounced asymmetry between the effect of an increased interest in the currency while being above or below its trend value.
Nearly every aspect of a hacked computer and a users online life can be and has been commoditized. Recent trends into crypto currencies have made the former even more true as cyber criminals are now committing crime for monetary benefit and not just to out smart each other. In this study, I look more closely at Bitcoin, a de-centralized crypto currency which has become increasingly popular in the last six months. This study focuses on the analysis of the bitcoin economy, the involvement of malware and botnets and its effect to the currency.
Abstract The process of decentralisation of public administration was based on the transfer of competences from state administration to municipalities and on the setting of new conditions for financing of municipalities. In the process of decentralization of public administration and fiscal decentralization, the range of original and transferred competences, as well as the tasks of municipalities and the corresponding instruments of financing, were set there by mutual agreement between the state bodies and the local self-government. The transfer of competences on municipalities in the field of education was not a simple process. The first steps in the management of schools and educational facilities did not entail without problems. Many of the misunderstandings grew up mainly from a lack of knowledge of the relevant laws governing the specific educational and training activities, operation, financing, personnel and material-technical provision of schools and educational facilities. The aim of the contribution is legislative and financial definition of current system of provision of services by municipalities in the Slovak Republic in the field of regional education, because this area is complicated and disorganized the laws dealing with education and its financing have undergone many amendments. The following compact and comprehensive issues can serve as a framework for further research.
Describing, understanding, and modeling the emergent behavior of self-organizing software systems remains an open challenge. Such systems can solve problems in computing domains where traditional, centralized models are impractical or problematic, including ubiquitous and pervasive computing, peer-to-peer networks, large-scale grids, and Ultra-Large-Scale Systems. Self-organizing approaches have demonstrated great promise in building adaptive behavior into decentralized systems, enabling cooperative, autonomous self-management and the exploitation of the heterogeneity of system components. My investigation of self-organizing software systems has revolved around Myconet, an unstructured overlay protocol for peer-to-peer networks. Myconet takes inspiration from fungal growth patterns in order to build an efficient self-optimizing superpeer topology that can also rapidly self-heal in response to damage orattacks. Myconet has proven to be flexible, and has been used as a platform for the development of other self-organizing applications in large-scale distributed systems, including load-balancing in distributed service networks (Mycoload), and detection and mitigation of attacks against the overlay (Hormone-Inspired Topology Adaptation Protection [HITAP] and Self-Organized Degree Adaptation Protection [SODAP]). Each extension has given additional insights into the self-organizing dynamics of such systems, but has also shown the limitations of ad hoc approaches to the design and analysis of new applications. These experiences have led me to investigate formal tools and models that may provide the designer of a self-organizing system with early and accurate insight through augmented analytical power. This research selects a small set of synergistic modeling techniques, and builds an integrated approach to modeling for the design and validation of self-organizing software systems. These tools are used to model the core Myconet platform and its currently developed extensions, particularly focusing on the SODAP layer which provides self-protection features to a superpeer-based P2P overlay network. Once established, this modeling approach can be applied to the principled design of further Myconet extensions, as well as other self-organizing systems, thus advancing the understanding of how to model and engineer self-organization in software systems.
The general purpose of this study is to thoroughly examine decentralization in education according to the literature and previous research, and to discuss the applicability of educational decentralization practices in Turkey. The literature was reviewed for the study and findings reported. It has been observed that decentralization in education practices were realized in many countries after the 1980’s. It is obvious that the educational system in Turkey has difficulty in meeting the needs, and encounters many problems due to its present centralist state. Educational decentralization can provide effective solutions for stakeholder engagement, educational financing and for problems in decision making and operation within the education system. However, the present state of local governments, the legal framework, geographical, cultural and social features indicate that Turkey’s conditions are not ready for decentralization in education. A decentralization model realized in the long run according to Turkey’s conditions, and as a result of a social consensus, can help resolve the problems of the Turkish education system.
Simone Fatichi, Sebastian Leuzinger, Christian Körner
Knowledge of future terrestrial carbon (C) pools and fluxes is based on simulations by Dynamic Global Vegetation Models (DGVMs; Cox et al., 2000; Sitch et al., 2008). For simplicity we used the DGVMs acronym to include all of the models able to simulate C and vegetation dynamics at large spatial scales, which are sometimes referred to as Terrestrial Biosphere Models, Terrestrial Ecosystem Models, vegetation components of Earth System Models, and Land Ecosystem Models. DGVMs are now typically coupled to climate models to account for biophysical and biogeochemical feedback caused by vegetation (Bonan, 2008; Chapin et al., 2008; Anderson et al., 2011). The ultimate aim is to simulate climate–vegetation dynamics that explicitly account for mutual interactions and thus provide us with a better spatiotemporal description of water fluxes together with the most realistic scenarios for the future climate and C cycle (Friedlingstein et al., 2006; Thornton et al., 2007; Bonan et al., 2011). Current DGVMs are simulating long-term tree and forest stand growth as a consequence of the amount of assimilated C, triggering an inevitable positive feedback between C assimilation and growth. The key factors affecting stomatal aperture and C assimilation are atmospheric CO2 concentration, water availability, light, vapor pressure deficit and temperature (Sellers et al., 1997; Lawson et al., 2011). However, direct control of C sinks (defined as growth in the sense of C investment on plant tissue expansion) via environmental factors has been shown to be more important than indirect control via photosynthesis (the C source, see Fig. 1). For example, water- or temperature-limited plants tend to reduce growth but increase C storage (Körner, 2003; Sala & Hoch, 2009; Woodruff & Meinzer, 2011; Sala et al., 2012), which suggests that environmental controls act first on sink activity rather than source activity (Körner, 2013). Nevertheless, in all existing DGVMs, plant growth is driven by photosynthesis directly without considering water and thermal limitations via metabolic, cambial and meristematic activity (blue arrows in Fig. 1; Bonan et al., 2003; Sitch et al., 2003; Krinner et al., 2005). The entire photosynthesized net C (the source) is then partitioned among different C pools, mostly based on allometric rules derived from observations (Poorter et al., 2012) or using simplified functional allocation schemes (Friedlingstein et al., 1998; Franklin et al., 2012). Allocation to carbohydrate reserves, root exudates and export to symbionts are mostly missing. This opens up a huge discrepancy between the way plant growth is modeled today (blue arrows in Fig. 1) and the way it is understood based on experimental evidence (red arrows in Fig. 1). In this article, we suggest a revised hierarchy of plant growth control by removing the causal link from C assimilation to plant growth and by providing a description of the mechanistic connections among processes. Available soil water, temperature, nutrients, light, and CO2 are indisputably the key drivers of plant growth (Boisvenue & Running, 2006; McMurtrie et al., 2008; Ågren et al., 2012; Fig. 1). The former three (water, temperature, and nutrients) are fundamentally different from the latter two (light and CO2) because they can affect both sink and source activities, while light and CO2 only affect the source activity (C assimilation, Fig. 1). In this section, we compare the hierarchy of such limitations based on experimental evidence, which will lead into the discussion of strategies for modeling plant growth. When water limitations occur, there is evidence that cambial and leaf growth are inhibited at much lower levels of water stress (higher water potentials) than photosynthesis (Fig. 2; Boyer, 1970; Hsiao, 1973; Hsiao et al., 1976; Muller et al., 2011; Tardieu et al., 2011). Because organ expansion is affected earlier and more intensively than photosynthesis, plants experiencing soil water deficit often accumulate nonstructural carbohydrates (NSC) and reduce growth (Würth et al., 2005; Woodruff & Meinzer, 2011). Drought stressed or more apical parts of trees show lower xylem- or leaf-water potential than well-watered or more basal parts. This decrease in xylem- or leaf-water potential implies a reduction in cell turgor and in the capacity to transport sugars (Woodruff et al., 2004; Sala et al., 2011; Woodruff & Meinzer, 2011). Specifically, lower cell turgor has the potential to limit cell wall expansion, cell wall synthesis and protein synthesis (Lockhart, 1965; Hsiao, 1973; Sala et al., 2011). This means that C assimilation continues while sink activity (tissue growth) is inhibited, which most likely explains the accumulation of NSC in stressed plants (Körner, 2003). For example, Sala & Hoch (2009) showed that in Pinus ponderosa, mobile C compounds increase with increasing tree height. The possibility of plants actively prioritizing storage over growth allows additional interpretations of the role of accumulating NSC, for example, to maintain the integrity of the hydraulic system (Sala et al., 2012) or for signaling purposes (Rolland et al., 2006). However, recent evidence seems to support that when hydraulic transport is not affected, NSC is significantly depleted as a consequence of C demand (Hartmann et al., 2013; Sevanto et al., 2013). Exacerbation of these mechanisms (low turgor and incapability to transport sugars) also seems to play an important role in tree mortality and therefore long-term forest dynamics (McDowell, 2011; McDowell et al., 2011). Inhibition of sink activity via low water potentials and the resulting accumulation of photo-assimilates in leaves can also lead to direct feedback, that is downregulating photosynthesis (Paul & Foyer, 2001; Nikinmaa et al., 2013), which demonstrates a direct control of photosynthesis via growth (red horizontal arrow in Fig. 1). Similarly to water stressed plants, temperature-limited plants such as trees at the treeline and winter crops are typically limited by sink activity (tissue expansion) earlier than by source activity (C assimilation; Fig. 1; Körner, 2012). Consequently, cold-limited plants show an increase rather than a decrease in NSC with colder temperatures (Körner, 2008; Fajardo et al., 2012; Hoch & Körner, 2012). Temperature influences several metabolic processes (e.g. cell doubling time), determining the potential growth rate of organs in the absence of other growth limiting factors (Pantin et al., 2012). Most temperature-controlled processes of plant growth have been summarized by Boltzmann–Arrhenius type equations, which describe a decrease in growth rates at sub-optimal and supra-optimal temperatures (Parent et al., 2010). Furthermore, a 5–6°C threshold has often been identified to limit growth in cold adapted species, irrespective of photosynthetic activity which typically ceases only at freezing point (Körner, 2008). Nutrient limitation is well known to exert a negative feedback on photosynthesis via the amount of fundamental enzymes needed for C assimilation that can be produced. The amount of synthesized Rubisco, for example, is strongly controlled by nitrogen availability (Kattge et al., 2009). However, nutrients also act as direct plant growth control due to the relatively constant stoichiometry of plant tissue composition (Sterner et al., 2002; Leuzinger & Hättenschwiler, 2013). This has emerged clearly from FACE experiments where progressive nitrogen limitation (Luo et al., 2004) has been demonstrated to limit plant growth (Norby et al., 2010). While plants have the capacity to recruit additional nutrients by expanding their root system and via mycorrhizal symbioses, nutrient limitations are likely to progressively emerge at the landscape scale. Importantly, no study has been able to clearly quantify nutrient limitation acting on sink (tissue growth) vs source activity (C assimilation). Light as well as atmospheric CO2 clearly limit photosynthesis (the source), and unlike the previous factors discussed, they do not affect the C sinks directly. Therefore, the question here is whether (and if yes, when) the effect of CO2 and light is limiting sink activity (growth) via source activity (blue arrows from source to sink activity via the tree in Fig. 1). In other words, is plant growth C limited and under what conditions? Arguments in favor of C limitation of plant growth are either based on young seedlings and saplings in the forest understory or on individual leaves in dense canopies that are almost always operating below light saturation (Turner, 2001; Lloyd & Farquhar, 2008). Accordingly, CO2 was found to have a stimulatory effect on growth of plants in the understory (Würth et al., 1998; Hättenschwiler & Körner, 2000). Lloyd & Farquhar (2008) inferred that growth of tropical forests is C limited using the relationship between growth and photosynthesis: Np = Gp[1 − φ] where Np is net primary production (new growth), Gp is the average rate of photosynthesis, and φ is the proportion of assimilated C lost via total respiration plus volatile organic C emissions and root C exudation. They argue that higher Gp as a consequence of increasing CO2 concentration or incoming light necessarily leads to enhanced growth. However, we propose that this equation should generally read Np = Gp(Np)[1 − φ(Gp(Np))], thus not be interpreted as a direct causal link between photosynthesis and growth, because φ is a function of Gp, and Np can feedback on photosynthesis, that is, Gp = f(Np). Rewritten in these terms the equation is highly nonlinear and an increase in Gp does not imply a proportional increase in growth. Leaf level light responses of seedling and single leaves are difficult to extrapolate to the forest level, because this would imply that a forest stand behaves like a single leaf or shadowed tree. Light and consequently CO2 limitations of individual leaves, saplings or trees are not a demonstration that the entire forest community operates below its CO2 uptake capacity and even less that C acquisition is limiting forest growth (Körner, 2009; Clark et al., 2013). The Leaf Area Index (LAI) in several ecosystems (e.g. tropical forest, alpine grassland) may be higher than needed to sustain maximal productivity (Amiro et al., 2010; Gough et al., 2013; S. Fatichi, M. J. Zeeman, J. Fuhrer & P. Burlando, unpublished). Many studies suggest that partial (moderate) defoliation hardly affects tree growth or forest productivity (Ericsson et al., 1985; Hoogesteger & Karlsson, 1992; Reich et al., 1993; Kaitaniemi et al., 1999; Volin et al., 2002). A larger than necessary LAI typically has evolutionary rather than physiological reasons: to shade competing neighbors and thus limit their performance; as insurance against herbivory and storm damage; and as an additional option to store nutrients (especially in evergreen trees). Therefore, while light and CO2 may limit growth at the leaf or plant level, they unlikely do so at the landscape (whole forest) level and in the longer term (Leuzinger & Hättenschwiler, 2013). Short-term benefits of extra light (Graham et al., 2003) or elevated CO2 (Norby & Zak, 2011) can only be sustained to the extent a higher growth rate is supported by higher nutrient availability. Current atmospheric CO2 concentration (close to 400 ppm) additionally represents a rather exceptional forcing in the evolutionary context, with the current species having evolved in CO2 concentrations between 180 and 290 ppm (Siegenthaler et al., 2005; Lüthi et al., 2008). This suggests that C availability is at least less limiting nowadays (Körner, 2006). Accordingly, CO2 enrichment experiments with closed forest canopies did not show a sustained stimulation of growth by elevated CO2, except under high nutrient availability (Finzi et al., 2007; Norby et al., 2010; Bader et al., 2013; Sigurdsson et al., 2013). The differential sensitivity of C source and sink activities to water, temperature, and nutrient controls could lead to an imbalance between C supplied by photosynthesis and C used for tissue growth and respiratory costs. A mismatch between these two quantities would be sub-optimal and create a long-term surplus of assimilated C. In normal conditions, this situation is avoided through at least three mechanisms. First, in the short term, acclimation of photosynthesis occurs through negative feedback given by accumulation of starch or higher concentration of sucrose at the leaf level (Paul & Foyer, 2001). However, such a strategy would not be very effective to counteract mid/long-term source–sink imbalance. Second, therefore, in the mid-term, plants use sophisticated mechanisms of C storage at the leaf and whole plant level through accumulation and depletion of NSC (Kozlowski, 1992; Hoch et al., 2003; Gough et al., 2009; Richardson et al., 2013). Fluctuations of NSC are expected to buffer the difference between C supply and demand for timescales from hours to a few years. NSC dynamics are likely to be actively controlled by plants rather than a pure passive deposit of C (Sala et al., 2012). Third, in the long-term, evolutionary processes likely fine-tuned the photosynthesis apparatus (C source) to match long-term investment capacity (C sinks), which is the first to be controlled by environmental limitations. This of source–sink can be summarized as controls (Körner, and the between sinks and which is likely for the hierarchy of controls in the enrichment experiments as well as of water or temperature limitations have the possibility to the between C and For an increase of NSC is typically found in CO2 enrichment Furthermore, atmospheric CO2 almost always enhanced photosynthesis with or no et al., 2005; Bader et al., 2010). However, this typically does not into enhanced growth, in the term and for forests (Leuzinger et al., 2011; Norby & Zak, 2011; Bader et al., 2013). Because the C has to be this imbalance has several the of the & 2013). the extra C is and et al., 2006). Therefore, the of the extra C in CO2 experiments is to root exudates and export to et al., 2012). C assimilation respiration because of the larger and and thus transport respiration & 2000). if root is as a et al., a larger concentration in would more exudates due to the concentration the nutrient limitation through under elevated CO2 et al., 1993; Hättenschwiler & Körner, The use of experiments (e.g. with elevated CO2) is to the C source–sink and therefore the drivers of plant growth, under different environmental there is evidence that tissue growth is mostly under direct control of environmental rather than via the of assimilated C (Fig. and arrows in Fig. which for a of the hierarchy of plant growth control in This implies a from the current C source driven to where C sinks are the Because processes shown in Fig. are strongly and by it is to with either in the short For example, production will decrease with whether the is on growth or whether temperature assimilation and thus growth. However, the processes are fundamentally argue that if these processes and the are not it is unlikely DGVMs will simulate future C storage except under when photosynthesis may as shown in a in Fig. Furthermore, forest and composition are likely to feedback on C assimilation, they will also in long-term C the role of temperature and plant water in growth, of the existing DGVMs we are of include such a even in a simplified or et al., et al., 1997; et al., 2001; Bonan et al., 2003; Sitch et al., 2003; Krinner et al., 2005; et al., 2007; et al., 2009; Clark et al., 2011; et al., 2013; et al., 2013). the of the potential role of nutrients in limiting C from ecosystems et al., nitrogen and more have been in DGVMs et al., 2006; & 2008; & 2010; et al., 2012). However, all these models thermal and water limitations only in to C assimilation but not in to cambial or meristematic The of DGVMs also the that C processes such as photosynthesis (e.g. leaf are while processes of plant growth such as the rate of cell cell expansion, transport or cambial growth (C sink are much to quantify at high (Körner, 2013), even and to a source of et al., 2006; et al., 2013; & 2013). The of C fluxes and the between C and water through stomatal mostly to the of models and of and photosynthesis fluxes (Sellers et al., rather than plant growth. models that et al., to up the of DGVMs, and while they C assimilation, they in plant growth control that is based on observations in controlled but supported by observations in a the key of DGVMs and are almost to of the photosynthesis as for by et Fig. see also Bonan et al., 2012). short few from such DGVMs are typically by C fluxes derived from et al., 2006; et al., However, such only C and not plant growth that is they at show a over a given DGVMs are used to future from C pools and in models may lead us to a because of the Fig. that in models allocation can be controlled to extent by nutrients and environmental For water and light availability can control the differential C allocation to and (Friedlingstein et al., 1998; Krinner et al., 2005). However, this is rather different from having environmental directly control growth because the assimilated C is necessarily to C export to symbionts are mostly and mobile C are only in a of models in a simplified et al., 2005; et al., 2008; & 2010; et al., 2012; et al., 2012; et al., 2013). Therefore, C assimilation is typically to growth, which evidence that between assimilation and growth et al., 2006; Gough et al., 2009; Richardson et al., 2013). This also implies that if more C is assimilated in a under of elevated atmospheric CO2) the vegetation will more with positive feedback to C assimilation through which us with the for the way is to to the existing of DGVMs by direct growth control based on environmental drivers (Leuzinger et al., 2013; see also Fig. we tissue is controlled by environmental the amount of C to be to growth at a given should be of the amount of assimilated C. growth is by the limiting the of all other factors water, and nutrient are this with the that is the C source However, we argue that this is and only under such as in a a modeling the of or of species or plant functional type growth responses to environmental controls (water, temperature, This does not to the current of the could be but no longer the amount of C used for growth. The needed for such will a large of experimental A more to DGVMs on a more realistic of C models that simulate C and water fluxes the nutrient allocation to and from nonstructural C storage and to and root (Fig. This in its was in studies and more have been in models that et al., 2005; et al., 2010; et al., 2012) simulate transport et al., 2002; et al., as well as fluxes and cell growth activities & 2010; et al., 2010). This in the most components where C and water fluxes and are the plant between and in the (Fig. modeling of C assimilation and 1) is in most DGVMs et al., 2011). However, in the water and assimilated C are by leaf water and C and are to buffer the of C assimilation, an almost constant of sucrose to the at the & growth and can be explicitly modeled as a function of cell wall and protein and cell the that nutrients and C are is driven by cell turgor a threshold (Lockhart, which for water limitation to growth. cell typically a Boltzmann–Arrhenius function of temperature (Parent et al., with a temperature most for growth, which represents the thermal limitation to growth. When these two controls are plant growth can be A given by the of water potential and pressure that in also on sucrose concentration, is turgor In to for and et al., can be used for and transport and This will create a coupled system where and in and in and tissue (e.g. are The C is modeled as the of carbohydrates in the and by the of storage This C is then for growth, and for root and export to growth control by nutrients can also be in such a because nutrient through root uptake or can be explicitly and are up both via and actively through the of concentration et al., 2003; & 2012). C can be modeled as a et al., while modeling with is more and from understood which a in providing see While the mechanistic of for example, the leaf water and C or transport is relatively and can be into a of for the of C storage and sink as well as with to storage is a function of plant environmental and For at and C is from storage at the of the to support cambial activity and growth. also C their for example, leaves storage the is not and likely to with plant and plant stress (e.g. such of C allocation are not understood and the of Fig. will a spatial of C allocation with the more parts less C. a of the C sink is and the key for such a that a of the in Fig. is not given the limited we argue that current is for modeling most of the also that such components may to be in DGVMs and would a large of However, its can the for of environmental control of growth and of mechanistic C allocation schemes that could be into A where plant transport and tissue expansion are using well and among as was for photosynthesis is likely to way of modeling plant growth. a can also the of on plant C storage and sink which is fundamental for increasing and long-term scenarios for the C The of photosynthetic and the of mechanistic models of C assimilation that simulate observations have the of DGVMs, which have few over the identified 2006; et al., the of models mostly However, current physiological of tissue growth and expansion is in to it is in Current scenarios the between climate and vegetation are likely affected by a of plant growth and are therefore argue that direct environmental controls water and nutrient on tissue expansion and meristematic activity are fundamental than on the of C because they mostly limiting to plant growth photosynthesis Because C can only be to the extent other nutrients as well as water availability and temperature these drivers of growth will be over C assimilation This in of plant growth drivers has for the of terrestrial C fluxes and storage in the The of the in DGVMs will be but fundamental for future of the C In to this we two of different to growth in current DGVMs to growth limiting to mechanistic of plant transport and tissue expansion as was for photosynthesis While additional may be to of the we argue that there is evidence to the of the of current DGVMs, from to a plant growth. The three and the for on an earlier of this with are also
The purpose of this article is to compare systems of fiscal decentralization in EU member states according to selected quantitative criteria. The results indicate that a higher number of lower levels of government usually indicate a greater share of local finance; however, this finding does not confirm the inverse link. Although the structure of expenditures is similar, the shares of funds for the implementation of individual tasks differ significantly. On average, the countries allocate most funds to education, social security, healthcare, and administration, with only a quarter of the countries recording the same or higher amounts of revenues than expenditures. Most countries still cover the existing deficit through transfers from the central government, equalization schemes, or borrowed funds.
Since action for itself requires a particular content and a determinate end, whereas duty in the abstract contains nothing of the kind, the question arises: what is duty? For this definition [Bestimmung], all that is available so far is this: to do right, and to promote welfare, one’s own welfare and welfare in its universal determination, the welfare of others. (Hegel, 1991 [1821], 161, §134) Nothing in particular follows from general concepts of the right, the good, the just, or the virtuous; not even in bioethics. Even to sort useful information from noise, one must first specify a moral context within which to make decisions. Without particular content, morality cannot provide definitive guidance for choosing among different accounts of human flourishing or the proper ranking of virtues, much less how to proceed when the right and the good conflict.1 If morality is to be more than a mere formalism—for example, the empty repetition of rhetorical phrases, such as “respect patient autonomy” or “preserve human dignity”—then particular content must be specified to orient proper decision making.2 Among the challenges is that medicine is an applied science as well as a social endeavor. Medical science and the treatment of patients are always set within particular cultures and human interests. Consequently, the actual practice of health care involves an overlapping set of communities (scientific, moral, religious, and political) striving to understand and to manipulate the world in ways that humans find socially useful, morally appropriate, aesthetically pleasing, or otherwise fitting. As a result, medical reality and the expectations of clinical judgment are inevitably historically and culturally conditioned. In turn, such taken for granted background conditions impact our appreciation of moral obligations. This issue of The Journal of Medicine and Philosophy brings together three clusters of essays, focused in turn on research ethics, clinical ethics, and moral theory. Despite the array of topics, each author carefully explores core questions of bioethics: Which moral standard? Whose account of moral obligations ought to guide health care as both a theoretical and a practical endeavor? The first cluster of articles explores moral standards for guiding medical research. In medicine, one must abandon the assumption that accepted treatments are good simply because they are accepted. Instead, one must critically examine the standard of care together with new and innovative alternatives. Thorough scientific research together with robust scholarly debate is integral to reigning in the untutored human desire to ameliorate pain and suffering so that treatments do more benefit than harm. Moreover, it is difficult to know truly in medicine. Problems such as spontaneous remission and natural cures, physician remembrance of therapeutic triumphs more clearly than failures, the psychology of discovery, and the placebo effect distort judgments of a treatment’s effectiveness. At times and in various ways, patients, physicians, and scientists see what they anticipate. Medicine adds to these challenges the all too human urge to help those in need. Yet, as the history of medicine pays witness, many interventions do more harm than benefit. Human suffering caused by ill-founded but well meaning treatments has been significant. As Gelfand (2013), Meyerson (2013), and Potts et al. (2013) each make clear, rigorous scientific research and open scholarly debate are central to the advancement of medical practice and the protection of patients. Gelfand and Meyerson document, for example, the way in which clinical research with human subjects often involves a conflict between judgments regarding the proper treatment of patients and appropriate methods for obtaining good scientific data. Physicians who are both researchers and clinicians have competing professional interests, for example. The primary goal of clinicians is generally doing what is best for one’s patients within certain constraints, such as informed consent, the standard of care, and resource availability. Clinicians recommend treatments and interventions based on what they believe is in the best interests of particular patients. The primary goal of researchers, however, is the discovery of data to address research questions. The objective in a scientific inquiry is to follow an approved protocol to obtain data, to test research hypotheses or theoretical constructions, and to contribute to the base of scientific knowledge. Researchers are, however, constrained in how they may use subjects who may or may not benefit from the study design. Particular moral standards, such as “clinical equipoise,” the “precautionary principle,” and prohibitions against lying, are routinely identified as essential for fulfilling our duties to protect patients from unethical researcher conduct. Consider, for example, “clinical equipoise” which requires that clinician-researchers terminate a study when accumulated evidence so thoroughly supports one treatment arm that “the committee of investigators believe no open-minded clinician informed of the results would still favor” the other treatments being tested (Freedman, 1987, 145; cited in Gelfand, 2013, 593). Is clinical equipoise an adequate guide to appropriate ethical research on human subjects? Gelfand concludes that clinical equipoise is both morally and conceptually problematic. Morally, the difficulty is that clinical equipoise, if taken seriously, requires shutting down too many well-structured randomized clinical trials as unethical. Conceptually, the challenge lies in attempting to flesh out the ambiguous “open-minded clinician” standard. Although there is some disagreement concerning who should determine whether clinical equipoise exists, I will assume, as do most others, that this determination should be made by the physician-researcher conducting the randomized clinical trial. Presumably, the physician-researcher should begin this process by attributing knowledge of preliminary studies to these clinicians. In addition, she would have to assume that clinicians in her clinical community were aware of the general facts/theories/beliefs relevant to the clinical trial. Put differently, whether one will conclude that clinical equipoise exists depends, among other things, on what beliefs one attributes to members of the clinical community. (Gelfand, 2013, 594–95) Gelfand rightly notes that it is a very common psychological phenomenon to conclude that those who disagree with you “. . . are wrong or unaware of all the relevant facts or for some reason misunderstand the issue. Many of us often assume that if others truly understood the issues, they would agree with us” (2013, 595). Clinical equipoise, he argues, assumes that all “properly open-minded” clinicians who are informed regarding the research data would share the same background information, beliefs, standards for evaluation, and interpretation of results, as well as clinical or research goals. Having reasoned in such a fashion, however, once the physician-researcher conducting the trial concludes that clinical equipoise does not exist, he may terminate important clinical trials before adequate data can be collected. Researchers who disagree with such a conclusion may be easily ruled out as failing to be properly “open minded.” The “precautionary principle” raises related challenges. As with other human endeavors, medicine can become infatuated with the seemingly original and progressive. That technological or surgical innovations are new, however, guarantees neither superiority nor safety. The underlying rationale of the precautionary principle is to treat unproven scientific innovation with appropriate regulatory caution. When there is good reason to conclude that an innovation may cause serious harm, even though uncertainty exists regarding the probability or level of risk, the precautionary principle holds that regulatory action should proceed as if such innovation is in fact dangerous. Meyerson argues that the core difficulty with the precautionary principle is that it is unduly vague. Again, there is a need for the specification of a particular standard. All choices involve risk. How much risk and of what sort is morally acceptable? Taken too weakly, the precautionary principle offers almost no guidance: “. . . if all that is meant by the precautionary principle is that the absence of scientific certainty does not necessarily justify the refusal to regulate risky new technologies, then it is hard to see what is supposed to be distinctive about the guidance it offers” (Meyerson, 2013, 610). On the other hand, understood in a very strong manner, the principle rules out beneficial innovation: “At its strongest, the precautionary principle insists that potential benefits should be foregone unless it can be shown that they pose no risk at all. This is obviously an unacceptable position” (Sunstein, 2005; Meyerson, 2013, 610). Seeking to clarify a more moderate approach, Meyerson argues that there should be a general presumption in favor of restricting innovative technologies when they appear to pose a serious risk of harm. Proponents of the new technology, she concludes, bear the burden of proof to demonstrate the utility and relative safety of the innovation. Applied to the example of innovative surgical techniques, Meyerson argues that such a moderate approach helps to avoid the dangers that occur when surgeons are prone to bias in favor of new innovations, especially when they have a financial stake in the use of the invention, while also permitting advocates to demonstrate the safety and effectiveness of new technology. Discerning readers might at this point wish to raise the following questions: What are the risks of a bias in favor of the status quo? How should we assess the dangers of delaying innovation?3 What if, for example, scientific debate is stifled so as to preserve the status quo? In this issue, Potts et al. (2013) explore just such key concerns. For example, should researchers self censure scientific results that might undermine public confidence in medical judgment, such as the diagnosis of brain death? And, should professional journals refuse to publish articles that call into question current medical orthodoxy on such matters? Recent debate has brought brain-oriented criteria for determining death and donation after cardiac death policies into public scrutiny (see, e.g., Bernat, 2010; Iltis and Cherry, 2010; Khushf, 2010; Miller, Truog, and Brock, 2010; Shewmon, 2010; and Veatch, 2010). Some proponents of organ transplantation have argued that responsible scholarship requires refusing to publish any such results. As Potts et al. summarize: Some articles call for a closing of the debate over the criteria for death since such criteria are related to organ donation, and an ongoing debate about death criteria may negatively affect the public’s willingness to donate. They suggest allowing only ‘responsible scholarship’ in the area (according to which ‘irresponsible scholarship’ is considered to be critiquing brain-based criteria for death. . . . (2013, 626) Such debate, critics argue, creates unnecessary doubt among members of the public regarding the certainty of brain-oriented determinations of death and, consequently, for the appropriateness of procuring organs from donors who have been declared dead based on such criteria. To further complicate matters, institutional policy for determining that brain-based criteria for death has been satisfied may vary among institutions. Potts and his colleagues argue that without sustained and open debate, the harms caused by adherence to the status quo may never be adequately exposed. Is it morally appropriate to stifle or otherwise censor open-minded and scientific debate so as to further one’s preferred social goal, such as greater access to organ transplantation (or, perhaps, ever more government action on so-called human-caused global warming)? The next brace of essays turn the discussion to moral duties in clinical ethics. Mills (2013) and Reed (2013) focus on elements of procreative liberty, Stoyles and Costreie (2013) rethink voluntary euthanasia, whereas Cohen and Shapiro explore whether placebo treatment violates moral prohibitions against lying. To begin, Mills argues that reproductive liberty ought to be appreciated as a positive entitlement: “that is, a freedom to make oneself according to various ethical and aesthetic principles or values” (2013, 639). Mills contends that Michel Faucult’s analysis of the “practice of liberty” together with a naturalistic approach to rights entails at least limited positive claim rights in support of reproductive autonomy, “. . . one that requires that reproductive projects are promoted rather than simply honored, for example” (2013, 655). Reed in turn shifts our attention to an exploration of Plan B “emergency” contraception. Reed’s conceptual geography maps the moral location of emergency contraceptive pills relative to the ongoing abortion debates. He argues, for example, that “If we know that there are no postfertilization effects, then emergency contraception becomes morally similar to barrier methods: it prevents pregnancy without interfering with a fertilized egg” (2013, 670). However, insofar as Plan B contraception has a postimplantation effect, resulting in the abortion of a fetus, then abortion is an intended consequence of emergency contraception. As a result, abortion would not rightly be described as an unintended side effect of taking Plan B contraception; utilizing emergency contraception would be morally similar to other forms of early abortion. How should we appreciate reproductive liberty? And, which moral context applies to such choices? Sometimes to gain insight into the proper standards for clinical ethics, we must learn to see moral debates from new perspectives. The next two essays seek to reframe the bioethical debates regarding euthanasia and patient deception in terms of the “patient’s interests.” Stoyles and Costreie (2013) hold that the euthanasia debate has gone astray by emphasizing the importance of such distinctions as voluntary, involuntary, and nonvoluntary euthanasia. The question, they believe, is whether the practice of euthanasia accords with the “patient’s interests.” Insofar as euthanasia advances a patient’s interests, it ought to be appreciated as morally permissible. Similarly, Cohen and Shapiro conclude that while lying to patients is, all things considered, morally wrong, placebos are permissible precisely when they advance the patient’s interests in ways comparable to other forms of therapy. For example: Placebo analgesia refers to the reduction in pain following the administration of an otherwise inert substance, e.g., administering a starch pill (that does not directly alter pain physiology), which is believed by the subject to be an analgesic drug. The administration of a placebo is not inert, however, and its effects far from imaginary. Most strikingly, various findings show that placebo analgesia can under certain conditions mimic the actions of opiates on the opioidergic system, the most potent pain reducing system of the body. (2013, 699) An undue focus on deception, they argue, inappropriately skews the moral analysis. Insofar, as placebo treatment has an appropriate therapeutic effect comparable to other forms of therapy, it should not be morally ruled out. In each case, the authors challenge the reader’s perspective on such bioethical questions so as to assist us to see our moral duties anew. The final two essays take a conceptual step back from applied ethics, actively to engage moral theory. Sjöstrand et al. (2013) argue that preserving the value of patient autonomy may require medical paternalism, whereas Pamental (2013) explores the utility of pragmatism as a moral theory to guide bioethical decision making. On the one hand, Sjöstrand et al. (2013) hold that there are good reasons to support patient autonomy and to promote autonomy as a value in healthcare decision making. As a practical matter, however, sometimes weak forms of paternalism ought to be accepted to promote patient autonomy over the long term. Theoretical clarity regarding autonomy as a value is necessary, they argue, if we are to determine how best to respond to patient choices that appear to limit autonomy. If only capacity is valuable, paternalism is easily justified as soon as a patient acts or decides in a way that threatens her future autonomy. It seems strange to claim that autonomy is valuable, but that there is no value in actually having one’s autonomous decisions regarding important things in life respected. If exercise of autonomy is also valuable, paternalism for the sake of autonomy is less easily justified, since any infringement of a person’s exercise of her autonomy would be of direct negative value. (2013, 719–20) Pragmatism, on the other hand, Pamental argues, embraces the view that the role of philosophy is to change the world. Pragmatism is a form of what he terms “radical empiricism”: “At its heart, radical empiricism presupposes two things: first, that experience is more than simply phenomenological . . . [and second] experience can provide us with both the tools for making things better and the criteria for evaluating what better means” (2013, 728). Moreover, pragmatism is a form of moral contextualism: “. . . any feature of a situation is potentially morally significant, but that even generally accepted moral features are not always so” (2013, 737). As a result, moral principles are not absolutes; they are contingent and relative to the subjective interests of particular individuals, who themselves are situated within particular cultural and social backgrounds. It is this practical starting point, he argues, that both sets the moral context and directs moral inquiry in the clinical setting. What are our moral duties? In terms of which ranking of cardinal human goods and right-making conditions ought we to evaluate the moral significance of medical research on human subjects, reproductive liberty and abortion, organ transplantation, medical deception and euthanasia? As this issue of The Journal of Medicine and Philosophy makes clear, the field of bioethics faces a plurality of moral rationalities that are grounded in various rankings of cardinal values and right-making conditions, calculations of harms and benefits, claims to virtue or vice, as well as competing understandings of human flourishing. Different rankings and accounts of right-making conditions also presume divergent rules of moral evidence and valid moral inference. All such standards also appear to be deeply embedded within and conditioned by particular cultural and social circumstances (see, e.g., Cherry, 2012; Delkeskamp-Hayes, 2012; Engelhardt, 2012). Insofar, as all we have to work with are our and contingent subjective of itself to be once precisely on is the of all
Claudio Ronco, G. Mason, A. Nayak Karopadi, Ashlea Bennett Milburn · 5 authors
Today, health policy seems to be on the top of governments' agendas around the world. Healthcare systems are challenged by a number of phenomena happening on a global scale; these trends include demographic change in terms of an ageing population, an increase in chronic disease, patients having higher expectations on healthcare delivery and above all a major pressure on public finances to slow increasing healthcare expenditures. Such developments are forcing policy-makers to reform healthcare systems. First, there is a tendency towards decentralization of responsibilities. Second, governments are moving towards reimbursement schemes rewarding good outcomes and performance. Third, great importance is being attributed to transparency and accountability, and to introduce competition in healthcare. Fourth, attention is being shifted from simple treatment of a disease towards preventive initiatives, in a more holistic approach to health. Finally, healthcare policy-makers are recognizing the importance of empowering patients to give them control over decisions regarding their own health. These dynamics can be observed in chronic kidney disease, the management of which is a huge economic burden to healthcare systems globally, and which represents a good example of a field where important changes can be witnessed in therapy, technology, delivery and financing.
Open access
Chronic Disease Management Strategies
Health Systems, Economic Evaluations, Quality of Life
This Note discusses the relationship of Bitcoins, a cyber-currency, to the Bank Secrecy Act and discusses money laundering and tax evasion. This Note highlights the use and potentially problematic implications of Bitcoins in commerce and discusses their current regulation by the government, both within the United States and internationally, to guard against these threats. This Note addresses the regulation of Bitcoin exchanges, the exchanges' vulnerability to cyber-attacks, and the value of trust to the users of Bitcoin exchanges. This Note concludes that well known exchanges that operate both within and outside the United States generally self-regulate in order to gain the trust of their users despite the cyber-attacks on exchanges in the past. This Note also addresses the tax-reporting implications of foreign Bitcoin exchanges, looking by analogy at attempts to gain information from known tax havens.This Note argues that, given the applicability of the BSA to Bitcoin exchanges, the Bitcoin system poses serious questions relating to money laundering and tax reporting, mostly with regard to the less trustworthy exchanges known for their illegal activity. Some Bitcoin exchanges and e-wallets may also have the potential to become the next tax havens. Many exchanges voluntarily implement measures amounting to self-regulation in attempts to appear more trustworthy to wary consumers or in attempts to avoid criminal or civil sanctions. Whether this self-regulation is sufficient to achieve the goals of preventing money laundering and other criminal activity is debatable. Exchanges that have no need to appear trustworthy, however, still pose the same risks of money laundering and other illegal activity contemplated by the FBI. Moreover, ways exist in which criminals can work around the current regulatory scheme to achieve criminal goals; in that respect, the current regulatory scheme is ineffective to prevent the targeted criminal activity. This Note recommends a supplemental regulatory scheme that would target the areas that current regulation fails to address in combating money laundering, tax evasion, and other criminal activity.
Liu and Carless (2006) propose that peer assessment through peer feedback giving has its potential for enhanced student learning. Introducing formative assessment, using valid and reliable rubrics, can be beneficial to both teachers and learners in the process of learner improvement. However, Carless’s experiences in Hong Kong, a Confucius-based society where high-stake summative examinations are heavily prioritised, are solid proofs of how culture can interfere with education. In Asian societies, including Thailand, teachers having superior and absolute power in assessment are respected by students and hence, teacher voices take precedence over those of their peers. Implementing peer assessment in Asian classrooms, therefore, is problematic and to a certain extent, impossible. In this research, in order to expand our students’ learning boundaries beyond familiar, traditional ways of teacher assessment of which an end result is a grade, we introduced peer assessment rubrics to our reading classroom to allow them to monitor their friends’ reading progress. The peer evaluation results and comments were analyzed and compared with that of the teacher. An in-depth interview was also conducted with six subjects after the assessment process. The findings showed that as most of our students were engineering students and the texts they were reading were literary excerpts, employing rubrics was very helpful in the learning process. Nevertheless, as a result of long standing culture, final grades were still their priority. Our conclusive suggestions were that structural changes in assessment would be needed and they would certainly take time amidst the assessment culture in Thailand. DOI: 10.5901/mjss.2013.v4n14p279
Dubravka Jurlina Alibegović, Sunčana Slijepčević, Željka Kordej-De Villa
Decentralization can be generally described as a process in which selected functions are assigned to sub-national units. The literature identifies number of positive consequences of decentralization which all lead to better satisfaction of citizens? needs for public services. Although decentralization process in Croatia started more than 10 years ago, it still has not been finished. It led to new division of authorities and responsibilities to the local government units, but the level of fiscal decentralization remained lower than in the EU countries. The efficient decentralization should incorporate delegation of authorities, responsibilities and resources to local government units based on the clear criteria, but also should ensure better coordination and cooperation of all entities in providing public functions. In the paper we analyze fiscal capacity of local government units to provide an insight into the main problems of decentralization in Croatia. We show that the most of local government units have very low fiscal capacity and cannot finance basic public functions from their own resources. The paper also presents result of the performed survey about decentralization process among local councilors at the regional level in Croatia. We explore how local councilors at regional level in Croatia evaluate different goals of decentralization. Having in mind the lack of fiscal capacity, we identify two possible solutions for an optimal provision of public functions. The first one is level of political will for the joint provision of public functions between different local units, and the second one is change in territorial division of the country. We measure the difference in the attitudes toward these questions across counties.
The Bitcoin cryptocurrency records its transactions in a public log called the blockchain. Its security rests critically on the distributed protocol that maintains the blockchain, run by participants called miners. Conventional wisdom asserts that the protocol is incentive-compatible and secure against colluding minority groups, i.e., it incentivizes miners to follow the protocol as prescribed. We show that the Bitcoin protocol is not incentive-compatible. We present an attack with which colluding miners obtain a revenue larger than their fair share. This attack can have significant consequences for Bitcoin: Rational miners will prefer to join the selfish miners, and the colluding group will increase in size until it becomes a majority. At this point, the Bitcoin system ceases to be a decentralized currency. Selfish mining is feasible for any group size of colluding miners. We propose a practical modification to the Bitcoin protocol that protects against selfish mining pools that command less than 1/4 of the resources. This threshold is lower than the wrongly assumed 1/2 bound, but better than the current reality where a group of any size can compromise the system.
Bitcoin is a "crypto currency", a decentralized electronic payment scheme based on cryptography which has recently gained excessive popularity. Scientific research on bitcoin is less abundant. A paper at Financial Cryptography 2012 conference explains that it is a system which "uses no fancy cryptography", and is "by no means perfect". It depends on a well-known cryptographic standard SHA-256. In this paper we revisit the cryptographic process which allows one to make money by producing bitcoins. We reformulate this problem as a Constrained Input Small Output (CISO) hashing problem and reduce the problem to a pure block cipher problem. We estimate the speed of this process and we show that the cost of this process is less than it seems and it depends on a certain cryptographic constant which we estimated to be at most 1.86. These optimizations enable bitcoin miners to save tens of millions of dollars per year in electricity bills. Miners who set up mining operations face many economic incertitudes such as high volatility. In this paper we point out that there are fundamental incertitudes which depend very strongly on the bitcoin specification. The energy efficiency of bitcoin miners have already been improved by a factor of about 10,000, and we claim that further improvements are inevitable. Better technology is bound to be invented, would it be quantum miners. More importantly, the specification is likely to change. A major change have been proposed in May 2013 at Bitcoin conference in San Diego by Dan Kaminsky. However, any sort of change could be flatly rejected by the community which have heavily invested in mining with the current technology. Another question is the reward halving scheme in bitcoin. The current bitcoin specification mandates a strong 4-year cyclic property. We find this property totally unreasonable and harmful and explain why and how it needs to be changed.
Sarah Meiklejohn, Marjori Pomarole, Grant Jordan, Kirill Levchenko · 7 authors
Bitcoin is a purely online virtual currency, unbacked by either physical commodities or sovereign obligation; instead, it relies on a combination of cryptographic protection and a peer-to-peer protocol for witnessing settlements. Consequently, Bitcoin has the unintuitive property that while the ownership of money is implicitly anonymous, its flow is globally visible. In this paper we explore this unique characteristic further, using heuristic clustering to group Bitcoin wallets based on evidence of shared authority, and then using re-identification attacks (i.e., empirical purchasing of goods and services) to classify the operators of those clusters. From this analysis, we characterize longitudinal changes in the Bitcoin market, the stresses these changes are placing on the system, and the challenges for those seeking to use Bitcoin for criminal or fraudulent purposes at scale.
Hormones, growth factors, and cytokines coordinate metabolism between tissues and within tissues. The transforming growth factor superfamily signaling pathway encompasses members of the TGFβ, activin, bone morphogenetic protein, Nodal, and growth and differentiation factor subfamilies, in addition to numerous other ligands, receptors, coreceptors, downstream signaling effectors, and regulating molecules. The elaborate multifunctional effects of this superfamily are highly cell-type and context-dependent (1, 2). Many of these ligands are involved in organ specification, patterning, proliferation, and differentiation, including important roles in the pancreas (3, 4). Studies of transgenic and knockout mice highlight the importance of this signaling pathway in islet development (5), and more recent work has also implicated the TGFβ superfamily in adult β-cell function and maturity (6, 7). In this issue of Endocrinology, Boerner and colleagues (8) report a novel role for Nodal, a secreted TGFβ superfamily member known for its roles in early embryogenesis and its mitogenic signaling through Smad2/3 and Smad4. Detailed studies on the role of Nodal in adult β-cells had not been reported. Boerner et al (8) identified Nodel in adult islets and used complementary techniques, including flow cytometry, to demonstrate that Nodal stimulates human pancreatic β-cell proliferation. This contrasts with studies employing pancreatic cell lines wherein Nodal was reported to induce apoptosis and inhibit proliferation (9, 10) and highlights the need to perform proliferation studies in nontransformed cells. This novel role of Nodal adds to the numerous roles that this family appears to have on adult pancreatic cells. Here, we will review developments in the field of TGFβ signaling in islets and emphasize that delineating clear roles of this signaling pathway has been quite challenging. Genetically engineered mouse models have provided insight, as well as confusion, on the roles of TGFβ family members (Table 1). Life-long global knockouts can provide information on gene function in the whole organism over its entire lifetime. Distinguishing effects of TGFβ family members on adult β-cell physiology from effects on development is not possible without conditional loss-of-function or gain-of-function models, but these are relatively few in number (11–13). Despite these caveats, a picture of multiple effects of TGFβ signaling on adult β-cell homeostasis has begun to emerge. A recurring phenotype manifested in adult mice carrying mutations in various TGFβ superfamily genes includes decreased β-cell mass, impaired glucose tolerance, and in some cases diabetes. Table 1 provides a glimpse of the plethora of effects of this superfamily, and its downstream signaling molecules, on pancreatic islets. Deletion of the negative downstream effector of TGFβ signaling Smad7 (14) in Pdx1-expressing cells decreased hormone-positive cells in late development (5). On the other hand, conditional overexpression of Smad7 in adult Pdx1-expressing cells altered the β-cell gene signature and reduced pancreatic insulin production and release, leading to diabetes (11). Furthermore, Smad7 appears to be crucial for beta-cell proliferation after partial pancreatectomy (50). Thus, the same TGFβ effector can have opposing roles depending on the temporal context. Moreover, the TGFβ signaling effectors can have opposing roles, given that Smad3 appears to be a negative regulator of insulin secretion and glucose tolerance (13). Taken together, many lines of evidence clearly suggest a role of this signaling pathway in regulating β-cell mass and function. More inducible knockout mouse studies are needed to clarify the specific cell targets and mechanisms of actions of this family on pancreatic cells. Pancreatic Actions of the TGFβ Superfamily Abbreviations: ALK, activin receptor-like kinase, ActR, activin receptor; BMP, bone morphogenetic protein; GDF, growth and differentiation factor. Pancreatic Actions of the TGFβ Superfamily Abbreviations: ALK, activin receptor-like kinase, ActR, activin receptor; BMP, bone morphogenetic protein; GDF, growth and differentiation factor. The effects of the TGFβ superfamily ligands on adult pancreatic β-cells can be directly tested in vitro, bypassing the complexities of the in vivo environment. For example, acute activin A treatment increased glucose-stimulated insulin secretion from human (15) and rat (16) islets, whereas prolonged treatment decreased glucose-stimulated insulin secretion from mouse islets, an effect reversed by the endogenous antagonist follistatin (17). β-Cell proliferation was increased by activin A treatment in adult rat islets (18) and a mouse β-cell line (17). Interestingly, there appears to be a species difference in the islet expression and action of activin A, follistatin, and TGFβ1 (19). Although TGFβ1 acutely stimulates glucose-stimulated insulin release from rat islets (19), prolonged treatment of human islet cells with TGFβ1 had a negative impact on the expression of genes important for β-cell function, likely via the Smad3 pathway (13). Interestingly, Boerner et al (8) did not report evidence of β-cell dedifferentiation, although β-cell function remains to be rigorously investigated in this model. The range of (and sometimes opposing) effects of the same factors observed on pancreatic cells illustrates the complexity and context-dependence of this signaling pathway. Although studies using animals with genetic manipulations are crucial, results from human islets are vital to uncover any species differences and for future clinical translation. One of the most important contributions of the Boerner study was the use of islets from human donors (8). Studies with human islets, or at least >1-year-old mice (which are equally refractory to β-cell proliferation), are crucial for clinical translation of the limited basic knowledge around primary β-cell proliferation mechanisms (20). The ultimate goal of this research is to provide the basis for a diabetes cure. Diabetes results from the immune-mediated destruction (type 1 diabetes) or functional failure (type 2 diabetes) of pancreatic insulin-producing β-cells (21). There are theoretically numerous approaches to treating or reversing diabetes using cell-based therapy, including in vivo regeneration via induction of replication of remaining β-cells, transdifferentiation of other adult cell types (in vivo and in vitro) and differentiation of embryonic (or induced) pluripotent stem cells into functional β-cells (22). Significant preclinical obstacles remain for each of these approaches. At this point, islet transplantation from cadaveric donors remains the only viable alternative to insulin therapy for treating type 1 diabetes (23). Nevertheless, the lack of islet donor tissue prevents widespread patient access to this therapy. Hence, the expansion of primary human islets is of great interest to the diabetes research community. Various studies have shown efficient induction of young rodent β-cell proliferation, yet the same approaches have either not been tested or failed to produce significant results on adult human β-cells (20, 24). Failure to induce proliferation in human islets could be in part a species difference and the fact that the human islet donor age is generally much higher in relative comparison with the young adolescent mice being used for studies (25). As has been elegantly shown, β-cell proliferation in mice and humans ceases to nearly zero after 1 and 30 years of age, respectively (26, 27). Hence, any study showing that a ligand can overcome this resistance of adult human β-cells to reenter the cell cycle, and stimulate proliferation even modestly, is an important contribution to the field. Boerner et al (8) found an ∼1.5-fold increase in human β-cell proliferation with Nodal treatment without affecting viability. Because it is estimated that only 1% of type 1 diabetes patients can be treated with the current scarce availability of donor islets (28) and the fact that a single patient requires at least 103 islet equivalents (from ∼2 pancreas donors) per kilogram of body weight (29), the expansion of islets from a single human donor pancreas would require at least an ∼200-fold increase for a widespread application of human islet transplantation. Therefore, more extensive research in human β-cell expansion is needed. Boerner et al (8) echoed statements by many in the field when they proposed in their paper that the ultimate therapeutic approach may require simultaneously harnessing multiple local signaling pathways. Indeed, genomic advances have revealed that islets produce hundreds of soluble ligands and express hundreds of receptors for ligands produced locally and in other tissues (30). It is clear that using high-throughput approaches will be required to make breakthroughs in this area. Pancreatic β-cell proliferation is exceedingly hard to measure in samples from humans and older adult rodents, given the rarity of events and the potential for false-positives with semiautomated counting. This means that there must be exceptional rigor. Bulk measurements of DNA synthesis are clearly unacceptable in heterogeneous human islet cell cultures where β-cells usually make up a minority of endocrine cells, to mention nothing of the fibroblast-like cells that dominate these cultures after a few days. Imaging must be of sufficient X, Y, and Z resolution such that highly proliferative fibroblasts, which overlay virtually all human islet cultures, are not mistaken for proliferating β-cells. In this regard, the use of flow cytometry by Boerner et al (8) to detect human β-cell proliferation is an important technical proof-of-concept. Clearly, the bar for measuring β-cell proliferation needs to continue to get higher to prevent costly false-positives in the field. Even considering the technical limitations, only a handful of studies have shown significant in vitro stimulation of human β-cell proliferation. These include cocktails of 1) hepatocyte growth factor, fibroblast growth factor 4, nicotinamide and fibrin gel (∼2-fold) (31), the L-type calcium channel agonist Bay K8644 (∼1.5-fold) (32), a diarylamide compound WS6 (∼5-fold) (33), and glycogen synthase kinase-3 inhibitors (∼2-fold) (34). It remains unclear whether any ligand alone will be able to safely increase human β-cell proliferation to therapeutic levels in vivo. It is not clear at this point whether TGFβ superfamily ligands are useful therapeutic targets for manipulating β-cell mass or function in vivo, because they may have off-target systemic effects. Most of the TGFβ family ligands share the same receptors, downstream effectors and antagonists (1) and are expressed ubiquitously in various tissues, including pancreatic islets (8, 12, 17, 19, 30, 35). Thus, the local concentration and length of exposure of the ligands as well as the combination of receptors, effectors and antagonists locally expressed will ultimately provide the final concerted effect on the β-cell, both in vivo and in vitro. Nodal and other TGFβ family members may be more promising factors for in vitro differentiation, expansion, and maturation of pancreatic β-cells. However, for human in vitro β-cell expansion to become clinically relevant, much more potent mitogens and/or combinations of factors working synergistically to retain β-cell maturity, viability, and function need to be evaluated. It will take the collaborative efforts between disciplines from basic β-cell biologists to physicians and engineers (36) to accomplish such an endeavor. Disclosure Summary: The authors have nothing to disclose.
Issue Serbia started the process of decentralization soon after the first phases of reforms were completed, as the integral part of the European integration process. The Law on Health Care has enabled decentralization in the primary health care sector, in order to strength the democratic governance and to improve administrative and service delivery effectiveness. Through the project with the Norwegian Association of Local and Regional Authorities (KS), the Serbian Standing Conference of Towns and Municipalities in cooperation with public health experts, assisted capacity building of local authorities. The aim of establishing Decentralized Service Improvement Networks is to advance the role of local authorities in public health and primary health care institutions, and to foster horizontal coordination between other social policy areas. Description of the problem Local governments were not aware of opportunities they have as founders of primary health care institutions- to monitor the effects of the undertaken measures in the field of financing, preventive actions and public health protection. Results DSIN for primary health care was established for the six chosen municipalities, comprising of at least 3 representatives of each local government. The cycle of 6 meetings started with a managerial meeting (mayor, heads of the services) in order to agree on a coordinated approach in the municipality and pointing out the challenges for such approach, applying SWOT analysis. DSIN have improved access to relevant statistical and administrative data, set the list of indicators to be monitored at the local level, developed and piloted the methodology for periodical survey of users satisfaction with primary health care and actively analysed and shared experiences (local and international). Furthermore, this network sucessfuly cooperated with the relevant institutions from education, social protection, NGOs, and users of services. Based on the review of all collected relevant data, every municipality have chosen to improve one priority public health service. Lesson The practice of DSIN is based on critical analysis of own performance in the context of performance of other similar institutions, on the basis of opinions of clients of the service and with wide utilization of best practices tested already in other local governments. Key messages Professional network at the local level motivates municipal authorities to perform better, to adopt innovative approaches and to learn from other experiences and good practices. The network enables local governments to learn from each other and to discuss and agree how to best use emerging good and European practice to improve the target services in their municipalities.