Conductivity and superlattice ordering in an icosahedral Al-Pd-Mn phase

9 págs.; 6 figs.; PACS number(s): 61.44.Br, 61.10.Nz, 71.30.1h>In situ> conductivity measurements on Al-Pd-Mn quasicrystals have been combined with synchrotron x-ray-diffraction experiments for studying its behavior during phase transformations. In order to confidently reduce the possible contribution to the conductivity of defects and grain boundaries, single-crystal samples have been annealed in situ under UHV conditions. This combined experiment allows us to affirm unambiguously that the structural state of the i-Al-Pd-Mn single crystal influences the electrical conductivity. ©2003 American Physical SocietyThe authors thank Y. Calvayrac and A. Kvick for providing the sample, the ESRF for the beamtime allocation, and J. J. de Miguel for careful reading.Peer Reviewe

Epidemiology of HIV among American Indians and Alaska Natives – United States, 2008-2011

American Indians/Alaska Natives (AI/AN) diagnosed with HIV infection have poorer survivorship and a higher percentage of Stage 3 (AIDS] diagnoses within one year of HIV diagnosis, compared to most race/ethnicity groups. National HIV surveillance data for 2008-2011 were used to determine diagnosis rates of HIV infection, persons living with HIV, and persons with a late diagnosis (Stage 3 within three months of HIV diagnosis) by selected characteristics for AI/AN and a combined other race/ethnicity group. The highest percentages of 862 AI/AN diagnosed with HIV infection were among males (75.7%), AI/AN aged 25-34 years (32.9%), persons living in large metropolitan areas (53.4%), and those diagnosed in outpatient facilities (39.4%). Among males, the majority of infections were attributed to male-to-male sexual contact (MSM) (71.8%). The percentage of infections attributed to injection drug use (IDU) for AI/AN females (28.5%) was greater than the other race/ethnicity group (15.2%). Probability of late diagnosis among AI/AN males was associated with: age \u3e35 years, and diagnosis in emergency room or hospital, or outpatient settings, and among AI/AN females, diagnosis in hospital or emergency room. Early detection of HIV infection along with linkage to and retention in care are important for all populations, including AI/AN. Routine HIV screening at a variety of public health and outpatient facilities, and linkage to care are important to decrease HIV transmission and improve survival

An Extended Scaling Scheme for Critically Divergent Quantities in Ferromagnets and Spin Glasses

From a consideration of high temperature series expansions in ferromagnets and in spin glasses, we propose an extended scaling scaling scheme involving a set of scaling formulae which express to leading order the temperature (T) and the system size (L) dependences of thermodynamic observables over a much wider range of T than the corresponding one in the conventional scaling scheme. The extended scaling, illustrated by data on the canonical 2d ferromagnet and on the 3d binomial Ising spin glass, leads to consistency for the estimates of critical parameters obtained from scaling analyses for different observables.Comment: 4+epsilon pages, 6 figures. Published versio

HIV Transmission Rates in the United States, 2006-2008

National HIV incidence for a given year x [I(x)] equals prevalence [P(x)] times the transmission rate [T(x)]. Or, simply rearranging the terms, T(x) = [I(x)/P(x)]*100 (where T(x) is the number of HIV transmissions per 100 persons living with HIV in a given year). The transmission rate is an underutilized measure of the speed at which the epidemic is spreading. Here, we utilize recently updated information about HIV incidence and prevalence in the U.S. to estimate the national HIV transmission rate for 2006 through 2008, and present a novel method to express the level of uncertainty in these estimates. Transmission rate estimates for 2006 through 2008 are as follows (respectively): 4.39 (4.01 to 4.73); 4.90 (4.49 to 5.28); and 4.06 (3.70 to 4.38). Although there are methodological challenges inherent in making these estimates, they do give some indications that the U.S. HIV transmission rate is at a historically low level

A Quantitative Content Analysis of Mercer University Theses

Quantitative content analysis of a body of research not only helps budding researchers understand the culture, language, and expectations of scholarship, it helps identify deficiencies and inform policy and practice. Because of these benefits, an analysis of a census of 980 Mercer University M.Ed., Ed.S., and doctoral theses was conducted. Each thesis was coded on 10 variables. The descriptive characteristics of the theses, the predictors of the length of the theses, and the predictors of the type of research method used were investigated. The main results were that: (a) the vast majority of thesis authors was female, (b) the number of qualitative theses was on the rise, (c) there were slight variations in research method and length based on location of publication, (d) the page length of M.Ed. theses had been slightly decreasing over time, (e) mathematics instruction was the most frequent subject descriptor of theses, and (f) the proportion of male authors increased over time

The drivers of tropical speciation

© 2014 Macmillan Publishers Limited. All rights reserved. Since the recognition that allopatric speciation can be induced by large-scale reconfigurations of the landscape that isolate formerly continuous populations, such as the separation of continents by plate tectonics, the uplift of mountains or the formation of large rivers, landscape change has been viewed as a primary driver of biological diversification. This process is referred to in biogeography as vicariance. In the most species-rich region of the world, the Neotropics, the sundering of populations associated with the Andean uplift is ascribed this principal role in speciation. An alternative model posits that rather than being directly linked to landscape change, allopatric speciation is initiated to a greater extent by dispersal events, with the principal drivers of speciation being organism-specific abilities to persist and disperse in the landscape. Landscape change is not a necessity for speciation in this model. Here we show that spatial and temporal patterns of genetic differentiation in Neotropical birds are highly discordant across lineages and are not reconcilable with a model linking speciation solely to landscape change. Instead, the strongest predictors of speciation are the amount of time a lineage has persisted in the landscape and the ability of birds to move through the landscape matrix. These results, augmented by the observation that most species-level diversity originated after episodes of major Andean uplift in the Neogene period, suggest that dispersal and differentiation on a matrix previously shaped by large-scale landscape events was a major driver of avian speciation in lowland Neotropical rainforests

Allocating HIV Prevention Funds in the United States: Recommendations from an Optimization Model

The Centers for Disease Control and Prevention (CDC) had an annual budget of approximately $327 million to fund health departments and community-based organizations for core HIV testing and prevention programs domestically between 2001 and 2006. Annual HIV incidence has been relatively stable since the year 2000 [1] and was estimated at 48,600 cases in 2006 and 48,100 in 2009 [2]. Using estimates on HIV incidence, prevalence, prevention program costs and benefits, and current spending, we created an HIV resource allocation model that can generate a mathematically optimal allocation of the Division of HIV/AIDS Prevention’s extramural budget for HIV testing, and counseling and education programs. The model’s data inputs and methods were reviewed by subject matter experts internal and external to the CDC via an extensive validation process. The model projects the HIV epidemic for the United States under different allocation strategies under a fixed budget. Our objective is to support national HIV prevention planning efforts and inform the decision-making process for HIV resource allocation. Model results can be summarized into three main recommendations. First, more funds should be allocated to testing and these should further target men who have sex with men and injecting drug users. Second, counseling and education interventions ought to provide a greater focus on HIV positive persons who are aware of their status. And lastly, interventions should target those at high risk for transmitting or acquiring HIV, rather than lower-risk members of the general population. The main conclusions of the HIV resource allocation model have played a role in the introduction of new programs and provide valuable guidance to target resources and improve the impact of HIV prevention efforts in the United States

Simple Epidemiological Dynamics Explain Phylogenetic Clustering of HIV from Patients with Recent Infection

Phylogenies of highly genetically variable viruses such as HIV-1 are potentially informative of epidemiological dynamics. Several studies have demonstrated the presence of clusters of highly related HIV-1 sequences, particularly among recently HIV-infected individuals, which have been used to argue for a high transmission rate during acute infection. Using a large set of HIV-1 subtype B pol sequences collected from men who have sex with men, we demonstrate that virus from recent infections tend to be phylogenetically clustered at a greater rate than virus from patients with chronic infection (‘excess clustering’) and also tend to cluster with other recent HIV infections rather than chronic, established infections (‘excess co-clustering’), consistent with previous reports. To determine the role that a higher infectivity during acute infection may play in excess clustering and co-clustering, we developed a simple model of HIV infection that incorporates an early period of intensified transmission, and explicitly considers the dynamics of phylogenetic clusters alongside the dynamics of acute and chronic infected cases. We explored the potential for clustering statistics to be used for inference of acute stage transmission rates and found that no single statistic explains very much variance in parameters controlling acute stage transmission rates. We demonstrate that high transmission rates during the acute stage is not the main cause of excess clustering of virus from patients with early/acute infection compared to chronic infection, which may simply reflect the shorter time since transmission in acute infection. Higher transmission during acute infection can result in excess co-clustering of sequences, while the extent of clustering observed is most sensitive to the fraction of infections sampled

Limited Awareness and Low Immediate Uptake of Pre-Exposure Prophylaxis among Men Who Have Sex with Men Using an Internet Social Networking Site

Background: In 2010, the iPrEx trial demonstrated that oral antiretroviral pre-exposure prophylaxis (PrEP) reduced the risk of HIV acquisition among high-risk men who have sex with men (MSM). The impact of iPrEx on PrEP knowledge and actual use among at-risk MSM is unknown. Online surveys were conducted to assess PrEP awareness, interest and experience among at-risk MSM before and after iPrEx, and to determine demographic and behavioral factors associated with these measures. Methods and Findings: Cross-sectional, national, internet-based surveys were administered to U.S. based members of the most popular American MSM social networking site 2 months before (n = 398) and 1 month after (n = 4 558) publication of iPrEx results. Comparisons were made between these samples with regards to PrEP knowledge, interest, and experience. Data were collected on demographics, sexual risk, and experience with post-exposure prophylaxis (PEP). Regression analyses were performed to identify factors associated with PrEP awareness, interest, and experience post-iPrEx. Most participants were white, educated, and indicated high-risk sexual behaviors. Awareness of PrEP was limited pre- and post-iPrEx (13% vs. 19%), whereas interest levels after being provided with a description of PrEP remained high (76% vs. 79%). PrEP use remained uncommon (0.7% vs. 0.9%). PrEP use was associated with PEP awareness (OR 7.46; CI 1.52–36.6) and PEP experience (OR 34.2; CI 13.3–88.4). PrEP interest was associated with older age (OR 1.01; CI 1.00–1.02), unprotected anal intercourse with ≥1 male partner in the prior 3 months (OR 1.40; CI 1.10–1.77), and perceiving oneself at increased risk for HIV acquisition (OR 1.20; CI 1.13–1.27). Conclusions: Among MSM engaged in online networking, awareness of PrEP was limited 1 month after the iPrEx data were released. Utilization was low, although some MSM who reported high-risk behaviors were interested in using PrEP. Studies are needed to understand barriers to PrEP utilization by at-risk MSM