Zero-temperature criticality in the two-dimensional gauge glass model

The zero-temperature critical state of the two-dimensional gauge glass model is investigated. It is found that low-energy vortex configurations afford a simple description in terms of gapless, weakly interacting vortex-antivortex pair excitations. A linear dielectric screening calculation is presented in a renormalization group setting that yields a power-law decay of spin-wave stiffness with distance. These properties are in agreement with low-temperature specific heat and spin-glass susceptibility data obtained in large-scale multi-canonical Monte Carlo simulations.Comment: 4 pages, 4 figure

SGXIO: Generic Trusted I/O Path for Intel SGX

Application security traditionally strongly relies upon security of the underlying operating system. However, operating systems often fall victim to software attacks, compromising security of applications as well. To overcome this dependency, Intel introduced SGX, which allows to protect application code against a subverted or malicious OS by running it in a hardware-protected enclave. However, SGX lacks support for generic trusted I/O paths to protect user input and output between enclaves and I/O devices. This work presents SGXIO, a generic trusted path architecture for SGX, allowing user applications to run securely on top of an untrusted OS, while at the same time supporting trusted paths to generic I/O devices. To achieve this, SGXIO combines the benefits of SGX's easy programming model with traditional hypervisor-based trusted path architectures. Moreover, SGXIO can tweak insecure debug enclaves to behave like secure production enclaves. SGXIO surpasses traditional use cases in cloud computing and makes SGX technology usable for protecting user-centric, local applications against kernel-level keyloggers and likewise. It is compatible to unmodified operating systems and works on a modern commodity notebook out of the box. Hence, SGXIO is particularly promising for the broad x86 community to which SGX is readily available.Comment: To appear in CODASPY'1

The observation of a positive magnetoresistance and close correlation among lattice, spin and charge around TC in antipervoskite SnCMn3

The temperature dependences of magnetization, electrical transport, and thermal transport properties of antiperovskite compound SnCMn3 have been investigated systematically. A positive magnetoresistance (~11%) is observed around the ferrimagnetic-paramagnetic transition (TC ~ 280 K) in the field of 50 kOe, which can be attributed to the field-induced magnetic phase transition. The abnormalities of resistivity, Seebeck coefficient, normal Hall effect and thermal conductivity near TC are suggested to be associated with an abrupt reconstruction of electronic structure. Further, our results indicate an essential interaction among lattice, spin and charge degrees of freedom around TC. Such an interaction among various degrees of freedom associated with sudden phase transition is suggested to be characteristic of Mn-based antiperovskite compounds.Comment: 13 pages, 5 figure

Validating soil denitrification models based on laboratory N2 and N2O fluxes and underlying processes derived by stable isotope approaches: concept, methods and regulation of measured fluxes

Robust denitrification data suitable to validate soil N2 fluxes in denitrification models are scarce due to methodical limitations and the extreme spatio-temporal heterogeneity of denitrification in soils. Numerical models have become essential tools to predict denitrification at different scales. Model performance could either be tested for total gaseous flux (NO + N2O + N2), individual denitrification products (e.g. N2O and/or NO) or for the effect of denitrification factors (e.g. C-availability, respiration, diffusivity, anaerobic volume, etc.). While there are numerous examples for validating N2O fluxes, there are neither robust field data of N2 fluxes nor sufficiently resolved measurements of control factors used as state variables in the models. Here we present the concept, methods and first results of collecting model validation data. This is part of the coordinated research unit “Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales” (DASIM). Novel approaches are used including analysis of stable isotopes, microbial communities, pore structure and organic matter fractions to provide denitrification data sets comprising as much detail on activity and regulation as possible. This will be the basis to validate existing and calibrate new denitrification models that are applied and/or developed by DASIM subprojects. To allow model testing in a wide range of conditions, denitrification control factors are varied in the initial settings (pore volume, plant residues, mineral N, pH) but also over time, where moisture, temperature, and mineral N are manipulated according to typical time patterns in the field. This is realized by including precipitation events, fertilization (via irrigation), drainage (via water potential) and temperature in the course of incubations. Moreover, oxygen concentration is varied to simulate anaerobic events. The 15N gas flux method is employed to quantify N2 and N2O emissions from various pools and processes

Simple de Sitter Solutions

We present a framework for de Sitter model building in type IIA string theory, illustrated with specific examples. We find metastable dS minima of the potential for moduli obtained from a compactification on a product of two Nil three-manifolds (which have negative scalar curvature) combined with orientifolds, branes, fractional Chern-Simons forms, and fluxes. As a discrete quantum number is taken large, the curvature, field strengths, inverse volume, and four dimensional string coupling become parametrically small, and the de Sitter Hubble scale can be tuned parametrically smaller than the scales of the moduli, KK, and winding mode masses. A subtle point in the construction is that although the curvature remains consistently weak, the circle fibers of the nilmanifolds become very small in this limit (though this is avoided in illustrative solutions at modest values of the parameters). In the simplest version of the construction, the heaviest moduli masses are parametrically of the same order as the lightest KK and winding masses. However, we provide a method for separating these marginally overlapping scales, and more generally the underlying supersymmetry of the model protects against large corrections to the low-energy moduli potential.Comment: 37 pages, harvmac big, 4 figures. v3: small correction

Portfolio configuration and foreign entry decisions: A juxtaposition of real options and risk diversification theories

Research Summary Research on foreign market entry has rarely considered that multinational firms' new entries may be affected by the configuration of their existing affiliates. We argue that in making entry decisions, firms take into account how an entry into a new location helps increase the operational flexibility of their affiliate portfolios due to options to switch operations across affiliates in case of diverging labor cost developments across host countries. We juxtapose this real options‐based explanation with a risk diversification explanation. Analysis of Japanese multinational firms' foreign entry decisions suggests that the two explanations are complementary. We also establish portfolio‐level boundary conditions to the influence of operational flexibility considerations on entry, in the form of product diversification and the nature of dispersion of labor cost levels. Managerial Summary When deciding on whether to enter a foreign market, managers of a multinational firm are intuitively aware that they need to consider how the economic environment of the target host country is related to the environments of the existing countries in which the firm operates. The less the environments are correlated with each other, whether in terms of input cost or market demand conditions, the greater the chance that the firm may capture cost savings and reduce sales volatility globally. These benefits arise from a switching option to shift operations flexibly across countries and from an ability to reduce risk by holding a portfolio of diversified global investments. Our findings support both sets of considerations, suggesting that companies do give due attention to correlations in labor cost and market demand between the target host country to enter and the existing host countries

Magnetic Catalysis in AdS4

We study the formation of fermion condensates in Anti de Sitter space. In particular, we describe a novel version of magnetic catalysis that arises for fermions in asymptotically AdS4 geometries which cap off in the infra-red with a hard wall. We show that the presence of a magnetic field induces a fermion condensate in the bulk that spontaneously breaks CP symmetry. From the perspective of the dual boundary theory, this corresponds to a strongly coupled version of magnetic catalysis in d=2+1.Comment: 22 pages, 4 figures. v2: References added, factors of 2 corrected, extra comments added in appendix. v3: extra comments about fermion modes in a hard wall background. v4: A final factor of

Cost effectiveness of using cognitive screening tests for detecting dementia and mild cognitive impairment in primary care.

INTRODUCTION: We estimated the cost effectiveness of different cognitive screening tests for use by General Practitioners (GPs) to detect cognitive impairment in England. METHODS: A patient-level cost-effectiveness model was developed using a simulated cohort that represents the elderly population in England (65 years and older). Each patient was followed over a lifetime period. Data from published sources were used to populate the model. The costs include government funded health and social care, private social care and informal care. Patient health benefit was measured and valued in Quality Adjusted Life Years (QALYs). RESULTS: Base-case analyses found that adopting any of the three cognitive tests (Mini-Mental State Examination, 6-Item Cognitive Impairment Test or GPCOG (General Practitioner Assessment of Cognition)) delivered more QALYs for patients over their lifetime and made savings across sectors including healthcare, social care and informal care compared with GP unassisted judgement. The benefits were due to early access to medications. Among the three cognitive tests, adopting the GPCOG was considered the most cost-effective option with the highest Incremental Net Benefit (INB) at the threshold of £30 000 per QALY from both the National Health Service and Personal Social Service (NHS PSS) perspective (£195 034 per 1000 patients) and the broader perspective that includes private social care and informal care (£196 251 per 1000 patients). Uncertainty was assessed in both deterministic and probabilistic sensitivity analyses. CONCLUSIONS: Our analyses indicate that the use of any of the three cognitive tests could be considered a cost-effective strategy compared with GP unassisted judgement. The most cost-effective option in the base-case was the GPCOG. Copyright © 2016 John Wiley & Sons, Ltd