Efficiency and accuracy of GPU-parallelized Fourier spectral methods for solving phase-field models

Phase-field models are widely employed to simulate microstructure evolution during processes such as solidification or heat treatment. The resulting partial differential equations, often strongly coupled together, may be solved by a broad range of numerical methods, but this often results in a high computational cost, which calls for advanced numerical methods to accelerate their resolution. Here, we quantitatively test the efficiency and accuracy of semi-implicit Fourier spectral-based methods, implemented in Python programming language and parallelized on a graphics processing unit (GPU), for solving a phase-field model coupling Cahn-Hilliard and Allen-Cahn equations. We compare computational performance and accuracy with a standard explicit finite difference (FD) implementation with similar GPU parallelization on the same hardware. For a similar spatial discretization, the semi-implicit Fourier spectral (FS) solvers outperform the FD resolution as soon as the time step can be taken 5 to 6 times higher than afforded for the stability of the FD scheme. The accuracy of the FS methods also remains excellent even for coarse grids, while that of FD deteriorates significantly. Therefore, for an equivalent level of accuracy, semi-implicit FS methods severely outperform explicit FD, by up to 4 orders of magnitude, as they allow much coarser spatial and temporal discretization

Approximation algorithms and hardness of approximation for knapsack problems

We show various hardness of approximation algorithms for knapsack and related problems; in particular we will show that unless the Exponential-Time Hypothesis is false, then subset-sum cannot be approximated any better than with an FPTAS. We also give a simple new algorithm for approximating knapsack and subset-sum, that can be adapted to work for small space, or in small parallel time. Finally, we prove that knapsack can not be solved in Mulmuley's parallel PRAM model, even when the input is restricted to small bit-length

CD4+ T-cell responses to Epstein-Barr virus (EBV) latent-cycle antigens and the recognition of EBV-transformed lymphoblastoid cell lines

There is considerable interest in the potential of Epstein-Barr virus (EBV) latent antigen-specific CD4$^+$ T cells to act as direct effectors controlling EBV-induced B lymphoproliferations. Such activity would require direct CD4$^+$ T-cell recognition of latently infected cells through epitopes derived from endogenously expressed viral proteins and presented on the target cell surface in association with HLA class II molecules. It is therefore important to know how often these conditions are met. Here we provide CD4$^+$ epitope maps for four EBV nuclear antigens, EBNA1, -2, -3A, and -3C, and establish CD4$^+$ T-cell clones against 12 representative epitopes. For each epitope we identify the relevant HLA class II restricting allele and determine the efficiency with which epitope-specific effectors recognize the autologous EBV-transformed B-lymphoblastoid cell line (LCL). The level of recognition measured by gamma interferon release was consistent among clones to the same epitope but varied between epitopes, with values ranging from 0 to 35% of the maximum seen against the epitope peptide-loaded LCL. These epitope-specific differences, also apparent in short-term cytotoxicity and longer-term outgrowth assays on LCL targets, did not relate to the identity of the source antigen and could not be explained by the different functional avidities of the CD4$^+$ clones; rather, they appeared to reflect different levels of epitope display at the LCL surface. Thus, while CD4$^+$ T-cell responses are detectable against many epitopes in EBV latent proteins, only a minority of these responses are likely to have therapeutic potential as effectors directly recognizing latently infected target cells

Conception and preliminary evaluation of an optical fibre sensor for simultaneous measurement of pressure and temperature

peer-reviewedThis paper presents a novel concept of simultaneously measuring pressure and temperature using a silica optical fibre extrinsic Fabry-Perot interferometric (EFPI) pressure sensor incorporating a fibre Bragg grating (FBG), which is constructed entirely from fusedsilica. The novel device is used to simultaneously provide accurate pressure and temperature readings at the point of measurement. Furthermore, the FBG temperature measurement is used to eliminate the temperature cross-sensitivity of the EFPI pressure sensorPUBLISHEDpeer reviewe

“It's like you’re actually playing as yourself”: Development and preliminary evaluation of ‘Green Acres High’, a serious game-based primary intervention to combat adolescent dating violence

AbstractThis paper provides an overview of the development of ‘Green Acres High’, a serious game-based primary intervention to raise awareness of and change attitudes towards dating violence in adolescents, and an analysis of how adolescents described their experience of playing this game. Transcripts from focus group data were analysed using thematic analysis. The global theme that was developed, Assessment of the game, was represented by two organising themes, Positive assessment: Pedagogical Underpinnings and Negative Assessment: Functionality Limitations and Frustrations. These represented the fact that overall the learning experience was positive based on the pedagogical principles and content that could be embedded in this digital game but that technical issues with the game needed to be addressed as these could impinge on the learning experience of the adolescents. It was seen that using a serious game was a valid and meaningful way for adolescents to learn about dating violence and that this is a viable alternative or adjunct to traditional teaching methods

Study on Relationship Between Individual Work Value and Work Performance of Civil Servants-Based on the Research in China

Civil servants are the key power to government’s development and social demands. However, present large amount of researches on public HR management mainly study from macro fields such as policy, education and team setup, the study of civil servants’ inner factors and outer work performance is comparatively much less, while the demonstrative study is the least. This paper proposes research hypothesis of civil servants’ work value and work performance on the basis of literature review; with the design of questionnaire, statistics analysis and research, finds the influencing factors and reasons why individual work value affects work performance; gets the specific influencing degree the parameters affect work performance. On the basis of demonstrative study, this paper proposes applicable methods and suggestions for civil servants’ work value on individual work performance management in administration departments, suggestions especially for HR management, screening and selection, stimulating, training and development.Key words: Civil servant; Work value; Work performanc

Comparison of Human Memory CD8 T Cell Responses to Adenoviral Early and Late Proteins in Peripheral Blood and Lymphoid Tissue

Treatment of invasive adenovirus (Ad) disease in hematopoietic stem cell transplant (SCT) recipients with capsid protein hexon-specific donor T cells is under investigation. We propose that cytotoxic T cells (CTLs) targeted to the late protein hexon may be inefficient in vivo because the early Ad protein E3-19K downregulates HLA class I antigens in infected cells. In this study, CD8+ T cells targeted to highly conserved HLA A2-restricted epitopes from the early regulatory protein DNA polymerase (P-977) and late protein hexon (H-892) were compared in peripheral blood (PB) and tonsils of naturally infected adults. In tonsils, epitope-specific pentamers detected a significantly higher frequency of P-977+CD8+ T cells compared to H-892+CD8+ T cells; this trend was reversed in PB. Tonsil epitope-specific CD8+ T cells expressed IFN-γ and IL-2 but not perforin or TNF-α, whereas PB T cells were positive for IFN-γ, TNF-α, and perforin. Tonsil epitope-specific T cells expressed lymphoid homing marker CCR7 and exhibited lower levels of the activation marker CD25 but higher proliferative potential than PB T cells. Finally, in parallel with the kinetics of mRNA expression, P-977-specific CTLs lysed targets as early as 8 hrs post infection. In contrast, H-892-specific CTLs did not kill unless infected fibroblasts were pretreated with IFN-γ to up regulate HLA class I antigens, and cytotoxicity was delayed until 16–24 hours. These data show that, in contrast to hexon CTLs, central memory type DNA polymerase CTLs dominate the lymphoid compartment and kill fibroblasts earlier after infection without requiring exogenous IFN-γ. Thus, use of CTLs targeted to both early and late Ad proteins may improve the efficacy of immunotherapy for life-threatening Ad disease in SCT recipients