Today, four of seven PLoS journals published new articles. I took a look and picked (under the fold) those I found interesting and/or 'bloggable'. As always, you should rate the articles, post notes and comments and send trackbacks when you blog about the papers. You can now also easily place articles on various social services (CiteULike, Mendeley, Connotea, Stumbleupon, Facebook and Digg) with just one click. Here are my own picks for the week - you go and look for your own favourites:
Mapping the Evolution of Scientific Fields:
Despite the apparent cross-disciplinary interactions among scientific fields, a formal description of their evolution is lacking. Here we describe a novel approach to study the dynamics and evolution of scientific fields using a network-based analysis. We build an idea network consisting of American Physical Society Physics and Astronomy Classification Scheme (PACS) numbers as nodes representing scientific concepts. Two PACS numbers are linked if there exist publications that reference them simultaneously. We locate scientific fields using a community finding algorithm, and describe the time evolution of these fields over the course of 1985-2006. The communities we identify map to known scientific fields, and their age depends on their size and activity. We expect our approach to quantifying the evolution of ideas to be relevant for making predictions about the future of science and thus help to guide its development.
Sex and the Single Cell. II. There Is a Time and Place for Sex:
Morphologically, fruit flies are either male or female. The specification of sex is a multi-step process that depends on whether the fertilized egg has only one X chromosome (will develop as male) or two X chromosomes (will develop as female). This initial assessment of sex activates a cascade of regulatory genes that ultimately results in expression of either the male or female version of the protein encoded by the doublesex gene (dsx). These sex-specific proteins from the dsx gene direct most aspects of somatic sexual development, including the development of all of the secondary sexual characteristics that visibly distinguish males and females. In flies, as in most animal species, only some tissues are obviously different between the two sexes, so we asked the question of whether all cells in the animal nevertheless know which sex they are. That is, do all cells express dsx? We have developed a genetic tool that lets us visualize the cells in which the dsx is expressed. Strikingly, dsx is only expressed in a subset of tissues. Thus, adult flies of both sexes appear to be mosaics of cells that do know their sex and cells that do not know their sex.
Every now and then, a new infectious disease appears in a human population or an old disease becomes much more common or more geographically widespread. Recently, several such "emerging infectious diseases" have become major public health problems. For example, HIV/AIDS, hepatitis C, and severe acute respiratory syndrome (SARS) have all emerged in the past three decades and spread rapidly round the world. When an outbreak (epidemic) of an emerging infectious disease occurs, epidemiologists (scientists who study the causes, distribution, and control of diseases in populations) swing into action, collecting and analyzing data on the new threat to human health. Epidemiological studies are rapidly launched to identify the causative agent of the new disease, to investigate how the disease spreads, to define diagnostic criteria for the disease, to evaluate potential treatments, and to devise ways to control the disease's spread. Public health officials then use the results of these studies to bring the epidemic under control.
A Glucose BioFuel Cell Implanted in Rats:
Powering future generations of implanted medical devices will require cumbersome transcutaneous energy transfer or harvesting energy from the human body. No functional solution that harvests power from the body is currently available, despite attempts to use the Seebeck thermoelectric effect, vibrations or body movements. Glucose fuel cells appear more promising, since they produce electrical energy from glucose and dioxygen, two substrates present in physiological fluids. The most powerful ones, Glucose BioFuel Cells (GBFCs), are based on enzymes electrically wired by redox mediators. However, GBFCs cannot be implanted in animals, mainly because the enzymes they rely on either require low pH or are inhibited by chloride or urate anions, present in the Extra Cellular Fluid (ECF). Here we present the first functional implantable GBFC, working in the retroperitoneal space of freely moving rats. The breakthrough relies on the design of a new family of GBFCs, characterized by an innovative and simple mechanical confinement of various enzymes and redox mediators: enzymes are no longer covalently bound to the surface of the electron collectors, which enables use of a wide variety of enzymes and redox mediators, augments the quantity of active enzymes, and simplifies GBFC construction. Our most efficient GBFC was based on composite graphite discs containing glucose oxidase and ubiquinone at the anode, polyphenol oxidase (PPO) and quinone at the cathode. PPO reduces dioxygen into water, at pH 7 and in the presence of chloride ions and urates at physiological concentrations. This GBFC, with electrodes of 0.133 mL, produced a peak specific power of 24.4 µW mLâ1, which is better than pacemakers' requirements and paves the way for the development of a new generation of implantable artificial organs, covering a wide range of medical applications.
Extreme Endurance Migration: What Is the Limit to Non-Stop Flight?:
Migratory birds have a history of challenging conventional wisdom about the limits of their endurance. More than half a century ago, many ornithologists doubted that a non-stop flight of 860 km across the Gulf of Mexico was possible for migratory (humming) birds [1]. But circumstantial and more direct evidence gathered in the following decade revealed that the Gulf of Mexico is a mere ditch to migratory birds [2],[3], and that some are capable of non-stop flights of up to 5,000 km [4],[5]. And now migratory birds have given their observers reason to pause yet again. In the past year, Gill et al. [6] have provided direct evidence that a shorebird, the Alaskan bar-tailed godwit (Limosa lapponica baueri) (Figure 1), makes its eight-day, 11,000-km autumn migration from Alaska to New Zealand in one step, with no stopovers to rest or refuel. This roughly doubles the previous maximum direct flight distance in birds, challenging experts to square this remarkable marathon migration with our understanding of aerodynamic theory and endurance physiology.
About 10% of cancers in women occur in the cervix, the structure that connects the womb to the vagina. Every year, globally, more than a quarter of a million women die because of cervical cancer, which only occurs after the cervix has been infected with a human papillomavirus (HPV) through sexual intercourse. There are many types of HPV, a virus that infects the skin and the mucosa (the moist membranes that line various parts of the body, including the cervix). Although most people become infected with HPV at some time in their life, most never know they are infected. However, some HPV types cause harmless warts on the skin or around the genital area and several--in particular, HPV 16 and HPV 18, so-called high-risk HPVs--can cause cervical cancer. HPV infections are usually cleared by the immune system, but about 10% of women infected with a high-risk HPV develop a long-term infection that puts them at risk of developing cervical cancer.
Trophic Structure in a Seabird Host-Parasite Food Web: Insights from Stable Isotope Analyses:
Ecological studies on food webs rarely include parasites, partly due to the complexity and dimensionality of host-parasite interaction networks. Multiple co-occurring parasites can show different feeding strategies and thus lead to complex and cryptic trophic relationships, which are often difficult to disentangle by traditional methods. We analyzed stable isotope ratios of C (13C/12C, δ13C) and N (15N/14N, δ15N) of host and ectoparasite tissues to investigate trophic structure in 4 co-occurring ectoparasites: three lice and one flea species, on two closely related and spatially segregated seabird hosts (Calonectris shearwaters). δ13C isotopic signatures confirmed feathers as the main food resource for the three lice species and blood for the flea species. All ectoparasite species showed a significant enrichment in δ15N relatively to the host tissue consumed (discrimination factors ranged from 2 to 5Ⱐdepending on the species). Isotopic differences were consistent across multiple host-ectoparasite locations, despite of some geographic variability in baseline isotopic levels. Our findings illustrate the influence of both ectoparasite and host trophic ecology in the isotopic structuring of the Calonectris ectoparasite community. This study highlights the potential of stable isotope analyses in disentangling the nature and complexity of trophic relationships in symbiotic systems.
An American was sitting in a Paris cafe eating soup when a fly dropped into her bowl. "There's un mouche in my soup!" she exclaimed. A nearby waiter corrected her. "Non, Madame. Une mouche." The American replied, "Wow, you French have good eyes!"
Although flies look pretty much alike to most people, to scientists working with Drosophila melanogaster fruit flies under a dissecting microscope, the differences between adult male flies and female flies are obvious. For starters, the abdomens of females are elongated and pointy, whereas those of males are more rounded and have a distinctive dark patch. In addition, males have sex combs--a fringe of blunt bristles on their first legs. However, in most tissues and organs, there are no discernable differences between the sexes. So does this sexually amorphic tissue actually "know" what sex it is? Carmen Robinett, Bruce Baker, and their colleagues address this question in their paper "Sex and the Single Cell. II. There Is a Time and Place for Sex" in this issue of PLoS Biology.
To report on the trend in all-cause mortality in a rural district of Malawi that has successfully scaled-up HIV/AIDS care including antiretroviral treatment (ART) to its population, through corroborative evidence from a) registered deaths at traditional authorities (TAs), b) coffin sales and c) church funerals. Retrospective study in 5 of 12 TAs (covering approximately 50% of the population) during the period 2000-2007. A total of 210 villages, 24 coffin workshops and 23 churches were included. There were a total of 18,473 registered deaths at TAs, 15781 coffins sold, and 2762 church funerals. Between 2000 and 2007, there was a highly significant linear downward trend in death rates, sale of coffins and church funerals (X2 for linear trend: 338.4 P<0.0001, 989 P<0.0001 and 197, P<0.0001 respectively). Using data from TAs as the most reliable source of data on deaths, overall death rate reduction was 37% (95% CI:33-40) for the period. The mean annual incremental death rate reduction was 0.52/1000/year. Death rates decreased over time as the percentage of people living with HIV/AIDS enrolled into care and ART increased. Extrapolating these data to the entire district population, an estimated 10,156 (95% CI: 9786-10259) deaths would have been averted during the 8-year period. Registered deaths at traditional authorities, the sale of coffins and church funerals showed a significant downward trend over a 8-year period which we believe was associated with the scaling up HIV/AIDS care and ART.
One of the most controversial areas of global health diplomacy over the past five years has involved negotiations to increase equitable access to vaccines for highly pathogenic avian influenza A (H5N1) (HPAI-H5N1) and pandemic 2009 influenza A (H1N1) (2009-H1N1). The limited results produced by these negotiations have stimulated calls for a new global framework to improve equitable access to influenza vaccines. The prospects for such a framework are not, however, promising, because the national interests of most developed states vis-Ã -vis dangerous influenza strains favor retaining the existing imbalanced, reactive, and ad hoc approach to vaccine access. This article examines why negotiating equitable access to influenza vaccines in the context of HPAI-H5N1 and 2009-H1N1 has been, and promises to continue to be, a difficult diplomatic endeavor.
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