3,070 research outputs found
Holographic aspects of three dimensional QCD from string theory
We study two aspects of 3D QCD with massless fermions in a holographic set-up
from string theory, based on D3/D7 branes; parity anomaly and baryons as baby
Skyrmions. We first give a novel account of parity anomaly of 3D QCD with odd
number of flavors from the IR holographic viewpoint by observing a subtle point
in D7 brane embeddings with a given fixed UV theory. We also discuss its UV
origin in terms of weakly coupled D-brane pictures. We then focus on the
parity-symmetric case of even number of N_F flavors, and study baryons in the
holographic model. We identify the monopoles of U(N_F) gauge theory dynamically
broken down to U(N_F/2)x U(N_F/2) in the holographic 4 dimensional bulk as a
holographic counter-part of 3D baby-Skyrmions for baryons in large N limit, and
work out some details how the mapping goes. In particular, we show that the
correct baryon charges emerge from the Witten effect with a space-varying theta
angle.Comment: 33 pages, 10 figures; v2: references added with comments, typos
corrected; v3: more references added; v4: holographic baryon profile and the
analysis of its baryon charge is significantly revised, correcting errors in
the previous discussio
Quantum Hall Effect in a Holographic Model
We consider a holographic description of a system of strongly coupled
fermions in 2+1 dimensions based on a D7-brane probe in the background of
D3-branes, and construct stable embeddings by turning on worldvolume fluxes. We
study the system at finite temperature and charge density, and in the presence
of a background magnetic field. We show that Minkowski-like embeddings that
terminate above the horizon describe a family of quantum Hall states with
filling fractions that are parameterized by a single discrete parameter. The
quantization of the Hall conductivity is a direct consequence of the
topological quantization of the fluxes. When the magnetic field is varied
relative to the charge density away from these discrete filling fractions, the
embeddings deform continuously into black-hole-like embeddings that enter the
horizon and that describe metallic states. We also study the thermodynamics of
this system and show that there is a first order phase transition at a critical
temperature from the quantum Hall state to the metallic state.Comment: v2: 27 pages, 12 figures. There is a major revision in the
quantitative analysis. The qualitative results and conclusions are unchanged,
with one exception: we show that the quantum Hall state embeddings, which
exist for discrete values of the filling fraction, deform continuously into
metallic state embeddings away from these filling fraction
Holographic two dimensional QCD and Chern-Simons term
We present a holographic realization of large Nc massless QCD in two
dimensions using a D2/D8 brane construction. The flavor axial anomaly is dual
to a three dimensional Chern-Simons term which turns out to be of leading
order, and it affects the meson spectrum and holographic renormalization in
crucial ways. The massless flavor bosons that exist in the spectrum are found
to decouple from the heavier mesons, in agreement with the general lore of
non-Abelian bosonization. We also show that an external dynamical photon
acquires a mass through the three dimensional Chern-Simons term as expected
from the Schwinger mechanism. Massless two dimensional QCD at large Nc exhibits
anti-vector-meson dominance due to the axial anomaly.Comment: 22 page
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Sporormiella as a tool for detecting the presence of large herbivores in the Neotropics
The reliability of using the abundance of Sporormiella spores as a proxy for the presence and abundance of megaherbivores was tested in southern Brazil. Mud-water interface samples from nine lakes, in which cattle-use was categorized as high, medium, or low, were assayed for Sporormiella representation. The sampling design allowed an analysis of both the influence of the number of animals using the shoreline and the distance of the sampling site from the nearest shoreline. Sporormiella was found to be a reliable proxy for the presence of large livestock. The concentration and abundance of spores declined from the edge of the lake toward the center, with the strongest response being in sites with high livestock use. Consistent with prior studies in temperate regions, we find that Sporormiella spores are a useful proxy to study the extinction of Pleistocene megafauna or the arrival of European livestock in Neotropical landscapes
Study of Sexual Functioning Determinants in Breast Cancer Survivors
Our goal was to identify the treatment, personal, interpersonal, and hormonal (testosterone) factors in breast cancer survivors (BCSs) that determine sexual dysfunction. The treatment variables studied were type of surgery, chemotherapy, radiation, and tamoxifen. The personal, interpersonal, and physiologic factors were depression, body image, age, relationship distress, and testosterone levels. A sample of 55 female breast cancer survivors seen for routine follow-up appointments from July 2002 to September 2002 were recruited to complete the Female Sexual Functioning Index (FSFI), Hamilton Depression Inventory (HDI), Body Image Survey (BIS), Marital Satisfaction Inventory-Revised (MSI-R), a demographic questionnaire, and have a serum testosterone level drawn. The average time since diagnosis was 4.4 years (SD 3.4 years). No associations were found between the type of cancer treatment, hormonal levels, and sexual functioning. BCS sexual functioning was significantly poorer than published normal controls in all areas but desire. The BCSsâ level of relationship distress was the most significant variable affecting arousal, orgasm, lubrication, satisfaction, and sexual pain. Depression and having traditional role preferences were the most important determinants of lower sexual desire. BCSs on antidepressants had higher levels of arousal and orgasm dysfunction. Women who were older had significantly more concerns about vaginal lubrication and pain. Relationship concerns, depression, and age are important influences in the development of BCS sexual dysfunction. The relationship of testosterone and sexual dysfunction needs further study with larger samples and more accurate assay techniques.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72034/1/j.1075-122X.2005.00131.x.pd
Neurospora from natural populations: Population genomics insights into the Life history of a model microbial Eukaryote
The ascomycete filamentous fungus Neurospora crassa played a historic role in experimental biology and became a model system for genetic research. Stimulated by a systematic effort to collect wild strains initiated by Stanford geneticist David Perkins, the genus Neurospora has also become a basic model for the study of evolutionary processes, speciation, and population biology. In this chapter, we will first trace the history that brought Neurospora into the era of population genomics. We will then cover the major contributions of population genomic investigations using Neurospora to our understanding of microbial biogeography and speciation, and review recent work using population genomics and genome-wide association mapping that illustrates the unique potential of Neurospora as a model for identifying the genetic basis of (potentially adaptive) phenotypes in filamentous fungi. The advent of population genomics has contributed to firmly establish Neurospora as a complete model system and we hope our review will entice biologists to include Neurospora in their research
Neonatal umbilical cord blood transplantation halts skeletal disease progression in the murine model of MPS-I
Umbilical cord blood (UCB) is a promising source of stem cells to use in early haematopoietic stem
cell transplantation (HSCT) approaches for several genetic diseases that can be diagnosed at birth. Mucopolysaccharidosis type I (MPS-I) is a progressive multi-system disorder caused by deficiency
of lysosomal enzyme α-L-iduronidase, and patients treated with allogeneic HSCT at the onset
have improved outcome, suggesting to administer such therapy as early as possible. Given that
the best characterized MPS-I murine model is an immunocompetent mouse, we here developed a transplantation system based on murine UCB. With the final aim of testing the therapeutic efficacy of UCB in MPS-I mice transplanted at birth, we first defined the features of murine UCB cells and demonstrated that they are capable of multi-lineage haematopoietic repopulation of myeloablated adult mice similarly to bone marrow cells. We then assessed the effectiveness of murine UCB cells transplantation in busulfan-conditioned newborn MPS-I mice. Twenty weeks after treatment, iduronidase activity was increased in visceral organs of MPS-I animals, glycosaminoglycans storage was reduced, and skeletal phenotype was ameliorated. This study explores a potential therapy for MPS-I at a very early stage in life and represents a novel model to test UCB-based transplantation approaches for various diseases
Integrating a health-related-quality-of-life module within electronic health records: a comparative case study assessing value added
<p>Abstract</p> <p>Background</p> <p>Health information technology (HIT) applications that incorporate point-of-care use of health-related quality of life (HRQL) assessments are believed to promote patient-centered interactions between seriously ill patients and physicians. However, it is unclear how willing primary care providers are to use such HRQL HIT applications. The specific aim of this study was to explore factors that providers consider when assessing the value added of an HRQL application for their geriatric patients.</p> <p>Methods</p> <p>Three case studies were developed using the following data sources: baseline surveys with providers and staff, observations of staff and patients, audio recordings of patient-provider interactions, and semi-structured interviews with providers and staff.</p> <p>Results</p> <p>The primary factors providers considered when assessing value added were whether the HRQL information from the module was (1) duplicative of information gathered via other means during the encounter; (2) specific enough to be useful and/or acted upon, and; (3) useful for enough patients to warrant time spent reviewing it for all geriatric patients. Secondary considerations included level of integration of the HRQL and EHR, impact on nursing workflow, and patient reluctance to provide HRQL information.</p> <p>Conclusions</p> <p>Health-related quality of life modules within electronic health record systems offer the potential benefit of improving patient centeredness and quality of care. However, the modules must provide benefits that are substantial and prominent in order for physicians to decide that they are worthwhile and sustainable. Implications of this study for future research include the identification of perceived "costs" as well as a foundation for operationalizing the concept of "usefulness" in the context of such modules. Finally, developers of these modules may need to make their products customizable for practices to account for variation in EHR capabilities and practice workflows.</p
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