192 research outputs found
Elastic effects on relaxation volume tensor calculations
Relaxation volume tensors quantify the effect of stress on diffusion of
crystal defects. Continuum linear elasticity predicts that calculations of
these parameters using periodic boundary conditions do not suffer from
systematic deviations due to elastic image effects and should be independent of
supercell size or symmetry. In practice, however, calculations of formation
volume tensors of the interstitial in Stillinger-Weber silicon
demonstrate that changes in bonding at the defect affect the elastic moduli and
result in system-size dependent relaxation volumes. These vary with the inverse
of the system size. Knowing the rate of convergence permits accurate estimates
of these quantities from modestly sized calculations. Furthermore, within the
continuum linear elasticity assumptions the average stress can be used to
estimate the relaxation volume tensor from constant volume calculations.Comment: 31 pages, 6 figures, submitted to Phys. Rev.
Non-equilibrium emission of complex fragments from p+Au collisions at 2.5 GeV proton beam energy
Energy and angular dependence of double differential cross sections
d/ddE was measured for reactions induced by 2.5 GeV protons
on Au target with isotopic identification of light products (H, He, Li, Be, and
B) and with elemental identification of heavier intermediate mass fragments (C,
N, O, F, Ne, Na, Mg, and Al). It was found that two different reaction
mechanisms give comparable contributions to the cross sections. The
intranuclear cascade of nucleon-nucleon collisions followed by evaporation from
an equilibrated residuum describes low energy part of the energy distributions
whereas another reaction mechanism is responsible for high energy part of the
spectra of composite particles. Phenomenological model description of the
differential cross sections by isotropic emission from two moving sources led
to a very good description of all measured data. Values of the extracted
parameters of the emitting sources are compatible with the hypothesis claiming
that the high energy particles emerge from pre-equilibrium processes consisting
in a breakup of the target into three groups of nucleons; small, fast and hot
fireball of 8 nucleons, and two larger, excited prefragments, which
emits the light charged particles and intermediate mass fragments. The smaller
of them contains 20 nucleons and moves with velocity larger than the CM
velocity of the proton projectile and the target. The heavier prefragment
behaves similarly as the heavy residuum of the intranuclear cascade of
nucleon-nucleon collisions. %The mass and charge dependence of the total
production cross %sections was extracted from the above analysis for all
observed %reaction products. This dependence follows the power low behavior
%(A or Z)
The future of sovereignty in multilevel governance Europe: a constructivist reading
Multilevel governance presents a depiction of contemporary structures in EU Europe as consisting of overlapping authorities and competing competencies. By focusing on emerging non-anarchical structures in the international system, hence moving beyond the conventional hierarchy/anarchy dichotomy to distinguish domestic and international arenas, this seems a radical transformation of the familiar Westphalian system and to undermine state sovereignty. Paradoxically, however, the principle of sovereignty proves to be resilient despite its alleged empirical decline. This article argues that social constructivism can explain the paradox, by considering sovereign statehood as a process-dependent institutional fact, and by showing that multilevel governance can feed into this process
Species and abundance of ectoparasitic flies (Diptera) in pied flycatcher nests in Fennoscandia
Peer reviewe
Federated Benchmarking of Medical Artificial Intelligence With MedPerf
Medical artificial intelligence (AI) has tremendous potential to advance healthcare by supporting and contributing to the evidence-based practice of medicine, personalizing patient treatment, reducing costs, and improving both healthcare provider and patient experience. Unlocking this potential requires systematic, quantitative evaluation of the performance of medical AI models on large-scale, heterogeneous data capturing diverse patient populations. Here, to meet this need, we introduce MedPerf, an open platform for benchmarking AI models in the medical domain. MedPerf focuses on enabling federated evaluation of AI models, by securely distributing them to different facilities, such as healthcare organizations. This process of bringing the model to the data empowers each facility to assess and verify the performance of AI models in an efficient and human-supervised process, while prioritizing privacy. We describe the current challenges healthcare and AI communities face, the need for an open platform, the design philosophy of MedPerf, its current implementation status and real-world deployment, our roadmap and, importantly, the use of MedPerf with multiple international institutions within cloud-based technology and on-premises scenarios. Finally, we welcome new contributions by researchers and organizations to further strengthen MedPerf as an open benchmarking platform
Institutions for Asian Integration: Innovation and Reform
The formation of regional production networks in East Asia has occurred mainly through market forces, without much help from regional institutions in promoting the creation of a single Asian market. While this approach has served the region well in the past, the drastic changes experienced since the 2008 - 2009 financial crisis and the challenges Asian countries are facing - rowing inequalities and competition, on the one hand, and enhanced threats to the environment and people's health on the other - have rendered more urgent the need for intergovernmental cooperation at global and regional levels. Asia's institutions for regionalism need strengthening through reform and innovation such as better governance and resourcing, greater and more effective participation and delegation of powers, overall streamlining of regional architecture, including the phasing out of outdated or irrelevant institutions and, where needed, the creation of new ones. Ultimately, given its rootedness in regional order, institutional efficacy is a function of the ability and willingness of its members, especially influential stakeholders, to collaborate
The choice for EU theorists: Establishing a common framework for analysis
European Union (EU) studies have entered a highly contentious and, arguably, creative phase. A range of theoretical perspectives, seemingly quite highly differentiated from one another, now compete for influence and lsquospacersquo. However, the questions remain: is EU studies developing theories which are truly competing theories? Or is it developing theories that do not compete so much as they aim to explain distinctly different pieces of the EU puzzle? This paper responds directly to these two questions, while reviewing recent literature on EU governance. It argues, first, that we lack theories of EU governance that are true rivals; and, second, that leading models explain different outcomes at different levels in a multi-level system of governance. The result is somewhat phoney debates between compatible theories masquerading as rivals, and between lsquocomparative politicsrsquo and lsquointernational relationsrsquo approaches. Above all, perhaps, we find middle range theories posing as general or lsquometa-theoriesrsquo. In the absence of a plausible general theory of EU governance, theorists must choose precisely which type of outcome theywish to explain
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