557 research outputs found
Conjectures about certain parabolic Kazhdan--Lusztig polynomials
Irreducibility results for parabolic induction of representations of the
general linear group over a local non-archimedean field can be formulated in
terms of Kazhdan--Lusztig polynomials of type . Spurred by these results and
some computer calculations, we conjecture that certain alternating sums of
Kazhdan--Lusztig polynomials known as parabolic Kazhdan--Lusztig polynomials
satisfy properties analogous to those of the ordinary ones.Comment: final versio
CD4 T cells remain the major source of HIV-1 during end stage disease.
OBJECTIVE: To assess the source of HIV-1 production in lymphoid tissue biopsies from HIV-infected patients, with no prior anti-retroviral protease inhibitor treatment, with a CD4 cell count > 150 x 10(6)/l (group I) or < 50 x 10(6)/l (group II), co-infected with Mycobacterium tuberculosis or Mycobacterium avium complex. DESIGN AND METHODS: Lymphoid tissue biopsies from 11 HIV-1-infected patients, taken for diagnostic purposes, were studied by HIV-1 RNA in situ hybridization and immunohistochemistry. RESULTS: Patients of group I showed well organized granulomas, in contrast with patients of group II, in which granuloma formation was absent. HIV-1 RNA-positive cells in group I patients were found mainly around the granulomas, whereas in group II HIV-1-producing cells were confined to areas with remaining intact lymphoid tissue. Despite the abundant presence of macrophages, the productively infected HIV-1-positive cells in both groups were almost exclusively CD4 T cells. CONCLUSION: In contrast with previously published data, CD4 T cells appear to remain the major source of HIV-1 production in end-stage disease
Sorting Permutations: Games, Genomes, and Cycles
Permutation sorting, one of the fundamental steps in pre-processing data for
the efficient application of other algorithms, has a long history in
mathematical research literature and has numerous applications. Two
special-purpose sorting operations are considered in this paper: context
directed swap, abbreviated cds, and context directed reversal, abbreviated cdr.
These are special cases of sorting operations that were studied in prior work
on permutation sorting. Moreover, cds and cdr have been postulated to model
molecular sorting events that occur in the genome maintenance program of
certain species of single-celled organisms called ciliates.
This paper investigates mathematical aspects of these two sorting operations.
The main result of this paper is a generalization of previously discovered
characterizations of cds-sortability of a permutation. The combinatorial
structure underlying this generalization suggests natural combinatorial
two-player games. These games are the main mathematical innovation of this
paper.Comment: to appear in Discrete Mathematics, Algorithms and Application
Broadening of coreceptor usage by human immunodeficiency virus type 2 does not correlate with increased pathogenicity in an in vivo model.
The pathogenic properties of four primary human immunodeficiency virus type 2 (HIV-2) isolates and two primary HIV-2 biological clones were studied in an in vivo human-to-mouse chimeric model. The cell-associated viral load and the ability to reduce the severity of the induced graft-versus-host disease symptoms, the CD4/CD8 ratio and the level of repopulation of the mouse tissues by the graft, were determined. All HIV-2 strains, irrespective of their in vitro biological phenotype, replicated to high titres and significantly reduced graft-versus-host disease symptoms as well as the CD4/CD8 ratios. Reduction of graft repopulation caused by infection with the respective HIV-2 strains showed that the in vitro replication rate, syncytium-inducing capacity and ability to infect human macrophages did influence the in vivo pathogenic potential whereas broadening of coreceptor usage did not
The vulnerability of public spaces: challenges for UK hospitals under the 'new' terrorist threat
This article considers the challenges for hospitals in the United Kingdom that arise from the threats of mass-casualty terrorism. Whilst much has been written about the role of health care as a rescuer in terrorist attacks and other mass-casualty crises, little has been written about health care as a victim within a mass-emergency setting. Yet, health care is a key component of any nation's contingency planning and an erosion of its capabilities would have a significant impact on the generation of a wider crisis following a mass-casualty event. This article seeks to highlight the nature of the challenges facing elements of UK health care, with a focus on hospitals both as essential contingency responders under the United Kingdom's civil contingencies legislation and as potential victims of terrorism. It seeks to explore the potential gaps that exist between the task demands facing hospitals and the vulnerabilities that exist within them
First Dark Matter Limits from a Large-Mass, Low-Background Superheated Droplet Detector
We report on the fabrication aspects and calibration of the first large
active mass ( g) modules of SIMPLE, a search for particle dark matter
using Superheated Droplet Detectors (SDDs). While still limited by the
statistical uncertainty of the small data sample on hand, the first weeks of
operation in the new underground laboratory of Rustrel-Pays d'Apt already
provide a sensitivity to axially-coupled Weakly Interacting Massive Particles
(WIMPs) competitive with leading experiments, confirming SDDs as a convenient,
low-cost alternative for WIMP detection.Comment: Final version, Phys. Rev. Lett. (in press
Towards developing a consensus assessment framework for global emergency medicine fellowships
Abstract
Background
The number of Global Emergency Medicine (GEM) Fellowship training programs are increasing worldwide. Despite the increasing number of GEM fellowships, there is not an agreed upon approach for assessment of GEM trainees.
Main body
In order to study the lack of standardized assessment in GEM fellowship training, a working group was established between the International EM Fellowship Consortium (IEMFC) and the International Federation for Emergency Medicine (IFEM). A needs assessment survey of IEMFC members and a review were undertaken to identify assessment tools currently in use by GEM fellowship programs; what relevant frameworks exist; and common elements used by programs with a wide diversity of emphases. A consensus framework was developed through iterative working group discussions. Thirty-two of 40 GEM fellowships responded (80% response). There is variability in the use and format of formal assessment between programs. Thirty programs reported training GEM fellows in the last 3 years (94%). Eighteen (56%) reported only informal assessments of trainees. Twenty-seven (84%) reported regular meetings for assessment of trainees. Eleven (34%) reported use of a structured assessment of any sort for GEM fellows and, of these, only 2 (18%) used validated instruments modified from general EM residency assessment tools. Only 3 (27%) programs reported incorporation of formal written feedback from partners in other countries. Using these results along with a review of the available assessment tools in GEM the working group developed a set of principles to guide GEM fellowship assessments along with a sample assessment for use by GEM fellowship programs seeking to create their own customized assessments.
Conclusion
There are currently no widely used assessment frameworks for GEM fellowship training. The working group made recommendations for developing standardized assessments aligned with competencies defined by the programs, that characterize goals and objectives of training, and document progress of trainees towards achieving those goals. Frameworks used should include perspectives of multiple stakeholders including partners in other countries where trainees conduct field work. Future work may evaluate the usability, validity and reliability of assessment frameworks in GEM fellowship training
Designing a Good Life: A Matrix for the Technological Mediation of Morality
Technologies fulfill a social role in the sense that they influence the moral actions of people, often in unintended and unforeseen ways. Scientists and engineers are already accepting much responsibility for the technological, economical and environmental aspects of their work. This article asks them to take an extra step, and now also consider the social role of their products. The aim is to enable engineers to take a prospective responsibility for the future social roles of their technologies by providing them with a matrix that helps to explore in advance how emerging technologies might plausibly affect the reasons behind people’s (moral) actions. On the horizontal axis of the matrix, we distinguished the three basic types of reasons that play a role in practical judgment: what is the case, what can be done and what should be done. On the vertical axis we distinguished the morally relevant classes of issues: stakeholders, consequences and the good life. To illustrate how this matrix may work in practice, the final section applies the matrix to the case of the Google PowerMeter
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