AutoGraph: Imperative-style Coding with Graph-based Performance

There is a perceived trade-off between machine learning code that is easy to write, and machine learning code that is scalable or fast to execute. In machine learning, imperative style libraries like Autograd and PyTorch are easy to write, but suffer from high interpretive overhead and are not easily deployable in production or mobile settings. Graph-based libraries like TensorFlow and Theano benefit from whole-program optimization and can be deployed broadly, but make expressing complex models more cumbersome. We describe how the use of staged programming in Python, via source code transformation, offers a midpoint between these two library design patterns, capturing the benefits of both. A key insight is to delay all type-dependent decisions until runtime, via dynamic dispatch. We instantiate these principles in AutoGraph, a software system that improves the programming experience of the TensorFlow library, and demonstrate usability improvements with no loss in performance compared to native TensorFlow graphs. We also show that our system is backend agnostic, and demonstrate targeting an alternate IR with characteristics not found in TensorFlow graphs

International Migration of Doctors, and Its Impact on Availability of Psychiatrists in Low and Middle Income Countries

Background:Migration of health professionals from low and middle income countries to rich countries is a large scale and long-standing phenomenon, which is detrimental to the health systems in the donor countries. We sought to explore the extent of psychiatric migration. Methods: In our study, we use the respective professional databases in each country to establish the numbers of psychiatrists currently registered in the UK, US, New Zealand, and Australia who originate from other countries. We also estimate the impact of this migration on the psychiatrist population ratios in the donor countries. Findings: We document large numbers of psychiatrists currently registered in the UK, US, New Zealand and Australia originating from India (4687 psychiatrists), Pakistan (1158), Bangladesh (149) , Nigeria (384) , Egypt (484), Sri Lanka (142), Philippines (1593). For some countries of origin, the numbers of psychiatrists currently registered within high-income countries' professional databases are very small (e.g., 5 psychiatrists of Tanzanian origin registered in the 4 high-income countries we studied), but this number is very significant compared to the 15 psychiatrists currently registered in Tanzania). Without such emigration, many countries would have more than double the number of psychiatrists per 100, 000 population (e.g. Bangladesh, Myanmar, Afghanistan, Egypt, Syria, Lebanon); and some countries would have had five to eight times more psychiatrists per 100,000 (e.g. Philippines, Pakistan, Sri Lanka, Liberia, Nigeria and Zambia). Conclusions: Large numbers of psychiatrists originating from key low and middle income countries are currently registered in the UK, US, New Zealand and Australia, with concomitant impact on the psychiatrist/ population ratio n the originating countries. We suggest that creative international policy approaches are needed to ensure the individual migration rights of health professionals do not compromise societal population rights to health, and that there are public and fair agreements between countries within an internationally agreed framework. © 2010 Jenkins et al

Mapping an epitope in EBNA-1 that is recognized by monoclonal antibodies to EBNA-1 that cross-react with dsDNA

Introduction: The Epstein Barr Virus (EBV) has been associated with the autoimmune disease, Systemic Lupus Erythematosus (SLE). EBV nuclear antigen-I (EBNA-1) is the major nuclear protein of EBV. We previously generated an IgG monoclonal antibody (MAb) to EBNA-1, 3D4, and demonstrated that it crossreacts with double stranded DNA (dsDNA) and binds the 148 amino acid viral binding site (VBS) in the carboxyl region of EBNA-1. The aim of the present study was to characterize another antibody to EBNA-1 that cross-reacts with dsDNA, compare its immunoglobulin genes to 3D4, and finely map the epitope in EBNA-1 that is recognized by these cross-reactive antibodies. Methods: We generated an IgM MAb to EBNA-1, 16D2, from EBNA-1 injected mice and demonstrated by ELISA that it cross-reacts with dsDNA and binds the 148 amino acid VBS. We sequenced the variable heavy and light chain genes of 3D4 and 16D2 and compared V gene usage. To more finely map the epitope in EBNA-1 recognized by these MAbs, we examined their binding by ELISA to 15 overlapping peptides spanning the 148 amino acid domain. Results: Sequence analysis revealed that 3D4 and 16D2 utilize different VH and VL genes but identical JH and Jk regions with minimal junctional diversity. This accounts for similarities in their CDR3 regions and may explain their similar dual binding specificity. Epitope mapping revealed 3D4 and 16D2 bind the same peptide in the VBS. Based on the crystal structure of EBNA-1, we observed that this peptide resides at the base of an exposed proline rich loop in EBNA-1. Conclusion: We have demonstrated that two MAbs that bind EBNA-1 and crossreact with dsDNA, recognize the same peptide in the VBS. This peptide may serve as a mimetope for dsDNA and may be of diagnostic and therapeutic value in SLE

Localization of the Epstein-Barr virus protein LMP 1 to exosomes

The Epstein-Barr virus latent membrane protein (LMP 1) functions as a constitutively active signalling molecule and associates in lipid rafts clustered with other signalling molecules. Using immunofluorescent confocal microscopy, LMP 1 was shown to have an heterogeneous distribution among individual cells which was not related to the cell cycle stage. LMP 1 was shown to localize to intracellular compartments in cells other than the plasma membrane, Co-labelling of cells with both an LIMP 1 antibody and an antibody to the Golgi protein GS15 revealed that the intracellular LMP 1 partly co-localized with the Golgi apparatus. Further confirmation of intracellular LMP 1 localization was obtained by immunoelectron microscopy with rabbit polyclonal LIMP 1 antibodies and cryosectioning. As well as being present in intracellular foci, LMP 1 co-localized in part with MHC-II and was present on exosomes derived from a lymphoblastoid cell line. Preparations of LMP 1 containing exosomes were shown to inhibit the proliferation of peripheral blood mononuclear cells, suggesting that LIMP 1 could be involved in immune regulation. This may be of particular relevance in EBV-associated tumours such as nasopharyngeal carcinoma and Hodgkin's disease, as LMP 1-containing exosomes may be taken up by infiltrating T-lymphocytes, where LMP 1 could exert an anti-proliferative effect, allowing the tumour cells to evade the immune system

Physiological changes affecting performance in masters athletes

Reviews the research that has examined the effect of age on speed, endurance and strength performance in masters athletes