Study of one-dimensional nature of (Sr,Ba)_2Cu(PO_4)_2 and BaCuP_2O_7 via 31P NMR

The magnetic behavior of the low-dimensional phosphates (Sr,Ba)_2 Cu(PO_4)_2 and BaCuP_2O_7 was investigated by means of magnetic susceptibility and ^{31}P nuclear magnetic resonance (NMR) measurements. We present here the NMR shift K(T), the spin-lattice 1/T_1 and spin-spin 1/T_2 relaxation-rate data over a wide temperature range 0.02 K < T < 300 K. The T-dependence of the NMR K(T) is well described by the S=1/2 Heisenberg antiferromagnetic chain model with an intrachain exchange of J/k_B = 165 K, 151 K, and 108 K in Sr_2Cu(PO_4)_2, Ba_2Cu(PO_4)_2, and BaCuP_2O_7, respectively. Our measurements suggest the presence of magnetic ordering at 0.8 K in BaCuP_2O_7 (J/k_B = 108 K). For all the samples, we find that 1/T_1 is nearly T-independent at low-temperatures (1 K < T < 10 K), which is theoretically expected for 1D chains when relaxation is dominated by fluctuations of the staggered susceptibility. At high temperatures, 1/T_1 varies nearly linearly with temperature

Evaluation of Directive-Based GPU Programming Models on a Block Eigensolver with Consideration of Large Sparse Matrices

Achieving high performance and performance portability for large-scale scientific applications is a major challenge on heterogeneous computing systems such as many-core CPUs and accelerators like GPUs. In this work, we implement a widely used block eigensolver, Locally Optimal Block Preconditioned Conjugate Gradient (LOBPCG), using two popular directive based programming models (OpenMP and OpenACC) for GPU-accelerated systems. Our work differs from existing work in that it adopts a holistic approach that optimizes the full solver performance rather than narrowing the problem into small kernels (e.g., SpMM, SpMV). Our LOPBCG GPU implementation achieves a 2.8$${\times }$$–4.3$${\times }$$ speedup over an optimized CPU implementation when tested with four different input matrices. The evaluated configuration compared one Skylake CPU to one Skylake CPU and one NVIDIA V100 GPU. Our OpenMP and OpenACC LOBPCG GPU implementations gave nearly identical performance. We also consider how to create an efficient LOBPCG solver that can solve problems larger than GPU memory capacity. To this end, we create microbenchmarks representing the two dominant kernels (inner product and SpMM kernel) in LOBPCG and then evaluate performance when using two different programming approaches: tiling the kernels, and using Unified Memory with the original kernels. Our tiled SpMM implementation achieves a 2.9$${\times }$$ and 48.2$${\times }$$ speedup over the Unified Memory implementation on supercomputers with PCIe Gen3 and NVLink 2.0 CPU to GPU interconnects, respectively

Once more on the Witten index of 3d supersymmetric YM-CS theory

The problem of counting the vacuum states in the supersymmetric 3d Yang-Mills-Chern-Simons theory is reconsidered. We resolve the controversy between its original calculation by Witten at large volumes and the calculation based on the evaluation of the effective Lagrangian in the small volume limit. We show that the latter calculation suffers from uncertainties associated with the singularities in the moduli space of classical vacua where the Born-Oppenheimer approximation breaks down. We also show that these singularities can be accurately treated in the Hamiltonian Born-Oppenheimer method, where one has to match carefully the effective wave functions on the Abelian valley and the wave functions of reduced non-Abelian QM theory near the singularities. This gives the same result as original Witten's calculation.Comment: 27 page

The relation between hemispheric lateralisation and measures of immune competence and adherence in Human Immunodeficiency Virus Type 1 (HIV-1)

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited - Copyright © 2012 Sumner et al

Off-plane motion of an oblate capsule in a simple shear flow

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.We investigate the mechanical equilibrium state of an oblate capsule when its revolution axis is initially off the shear plane. We consider an oblate capsule with an aspect ratio of 0.5 and a strain-hardening membrane. The three-dimensional fluid-structure interaction problem is solved numerically by coupling a finite element method with a boundary integral method. The capsule converges towards the same mechanical equilibrium state whatever the initial orientation. This equilibrium depends on the capillary number Ca, which compares the viscous to the elastic forces and on the viscosity ratio between the internal and external fluids. For = 1, the tumbling and swinging motions, observed when the revolution axis is initially in the shear plane, are mechanically stable until Ca 1; when Ca is further increased, the capsule assumes the rolling motion that is observed when its revolution axis is initially aligned with the vorticity axis. When is increased, the tumbling-to-swinging transition appears for higher Ca and the swinging-to-rolling transition for lower Ca. For 5, the swinging regime completely disappears: depending on Ca, it is then either the tumbling or the rolling motion that is the mechanical equilibrium state

The importance of thinking styles in predicting binge eating

Impulsivity, Body Mass Index, negative emotions and irrational food beliefs are often reported as predictors of binge eating. In the current study we explored the role played by two thinking styles, namely food thought suppression and desire thinking, in predicting binge eating among young adults controlling for established predictors of this condition. A total of 338 university students (268 females) participated in this study by completing a battery of questionnaires measuring the study variables. Path analysis revealed that impulsivity was not associated with binge eating, that Body Mass Index and negative emotions predicted binge eating, and that irrational food beliefs only influenced binge eating via food thought suppression and desire thinking. In conclusion, thinking styles appear an important predictor of binge eating and they should be taken into consideration when developing clinical interventions for binge eating

Extending the depth of field with chromatic aberration for dual-wavelength iris imaging

We propose a method of extending the depth of field to twice that achievable by conventional lenses for the purpose of a low cost iris recognition front-facing camera in mobile phones. By introducing intrinsic primary chromatic aberration in the lens, the depth of field is doubled by means of dual wavelength illumination. The lens parameters (radius of curvature, optical power) can be found analytically by using paraxial raytracing. The effective range of distances covered increases with dispersion of the glass chosen and with larger distance for the near object point

Ultrasoft NLL Running of the Nonrelativistic O(v) QCD Quark Potential

Using the nonrelativistic effective field theory vNRQCD, we determine the contribution to the next-to-leading logarithmic (NLL) running of the effective quark-antiquark potential at order v (1/mk) from diagrams with one potential and two ultrasoft loops, v being the velocity of the quarks in the c.m. frame. The results are numerically important and complete the description of ultrasoft next-to-next-to-leading logarithmic (NNLL) order effects in heavy quark pair production and annihilation close to threshold.Comment: 25 pages, 7 figures, 3 tables; minor modifications, typos corrected, references added, footnote adde

Analytic Results for Massless Three-Loop Form Factors

We evaluate, exactly in d, the master integrals contributing to massless three-loop QCD form factors. The calculation is based on a combination of a method recently suggested by one of the authors (R.L.) with other techniques: sector decomposition implemented in FIESTA, the method of Mellin--Barnes representation, and the PSLQ algorithm. Using our results for the master integrals we obtain analytical expressions for two missing constants in the ep-expansion of the two most complicated master integrals and present the form factors in a completely analytic form.Comment: minor revisions, to appear in JHE