The effect of potassium infusion on proximal sodium reabsorption and renin release in the dog

The effect of potassium infusion on proximal sodium reabsorption and renin release in the dog. The effect of infusions of potassium chloride (KC1) on sodium reabsorption by the proximal tubule and renal renin release was measured in 18 dogs. Following renal arterial infusions of 8 or 16 µEq/min/kg potassium chloride, fractional and absolute sodium reabsorption by the proximal tubule, measured by micropuncture techniques, was not significantly altered. As compared to five control dogs, urinary sodium excretion was significantly increased following both infusions of KC1. The release of renin was significantly decreased following both rates of potassium infusion. The inhibition of renin release was not associated with consistent changes in either glomerular filtration rate or renal plasma flow. The data indicate that the inhibition of renin release following the infusion of potassium is probably not the result of a marked increase in sodium delivery from the proximal tubule

Does the Red Queen reign in the kingdom of digital organisms?

In competition experiments between two RNA viruses of equal or almost equal fitness, often both strains gain in fitness before one eventually excludes the other. This observation has been linked to the Red Queen effect, which describes a situation in which organisms have to constantly adapt just to keep their status quo. I carried out experiments with digital organisms (self-replicating computer programs) in order to clarify how the competing strains' location in fitness space influences the Red-Queen effect. I found that gains in fitness during competition were prevalent for organisms that were taken from the base of a fitness peak, but absent or rare for organisms that were taken from the top of a peak or from a considerable distance away from the nearest peak. In the latter two cases, either neutral drift and loss of the fittest mutants or the waiting time to the first beneficial mutation were more important factors. Moreover, I found that the Red-Queen dynamic in general led to faster exclusion than the other two mechanisms.Comment: 10 pages, 5 eps figure

The Convergence of Digital-Libraries and the Peer-Review Process

Pre-print repositories have seen a significant increase in use over the past fifteen years across multiple research domains. Researchers are beginning to develop applications capable of using these repositories to assist the scientific community above and beyond the pure dissemination of information. The contribution set forth by this paper emphasizes a deconstructed publication model in which the peer-review process is mediated by an OAI-PMH peer-review service. This peer-review service uses a social-network algorithm to determine potential reviewers for a submitted manuscript and for weighting the relative influence of each participating reviewer's evaluations. This paper also suggests a set of peer-review specific metadata tags that can accompany a pre-print's existing metadata record. The combinations of these contributions provide a unique repository-centric peer-review model that fits within the widely deployed OAI-PMH framework.Comment: Journal of Information Science [in press

Inferring Deleterious-Mutation Parameters in Natural Daphnia Populations

Deng and Lynch (1, 2) proposed to characterize deleterious genomic mutations from changes in the mean and genetic variance of fitness traits upon selfing in outcrossing populations. Such observations can be readily acquired in cyclical parthenogens. Selfing and life-table experiments were performed for two such Daphnia populations. A significant inbreeding depression and an increase of genetic variance for all traits analyzed were observed. Deng and Lynch's (2) procedures were employed to estimate the genomic mutation rate (U), mean dominance coefficient ( [Image: see text] ), mean selection coefficient ( [Image: see text] ), and scaled genomic mutational variance ( [Image: see text] ). On average, [Image: see text] , [Image: see text] , [Image: see text] and [Image: see text] (^ indicates an estimate) are 0.84, 0.30, 0.14 and 4.6E-4 respectively. For the true values, the [Image: see text] and [Image: see text] are lower bounds, and [Image: see text] and [Image: see text] upper bounds

Fate and effect of antibiotics in beef and dairy manure during static and turned composting

Manure composting has general benefits for production of soil amendment, but the effects of composting on antibiotic persistence and effects of antibiotics on the composting process are not well-characterized, especially for antibiotics commonly used in dairy cattle. This study provides a comprehensive, head-to-head, replicated comparison of the effect of static and turned composting on typical antibiotics used in beef and dairy cattle in their actual excreted form and corresponding influence on composting efficacy. Manure from steers (with or without chlortetracycline, sulfamethazine, and tylosin feeding) and dairy cows (with or without pirlimycin and cephapirin administration) were composted at small scale (wet mass: 20-22 kg) in triplicate under static and turned conditions adapted to represent US Food and Drug Administration guidelines. Thermophilic temperature (>55°C) was attained and maintained for 3 d in all composts, with no measureable effect of compost method on the pattern, rate, or extent of disappearance of the antibiotics examined, except tylosin. Disappearance of all antibiotics, except pirlimycin, followed bi-phasic first-order kinetics. However, individual antibiotics displayed different fate patterns in response to the treatments. Reduction in concentration of chlortetracycline (71-84%) and tetracycline (66-72%) was substantial, while near-complete removal of sulfamethazine (97-98%) and pirlimycin (100%) was achieved. Tylosin removal during composting was relatively poor. Both static and turned composting were generally effective for reducing most beef and dairy antibiotic residuals excreted in manure, with no apparent negative impact of antibiotics on the composting process, but with some antibiotics apparently more recalcitrant than others

The Digital Life of Walkable Streets

Walkability has many health, environmental, and economic benefits. That is why web and mobile services have been offering ways of computing walkability scores of individual street segments. Those scores are generally computed from survey data and manual counting (of even trees). However, that is costly, owing to the high time, effort, and financial costs. To partly automate the computation of those scores, we explore the possibility of using the social media data of Flickr and Foursquare to automatically identify safe and walkable streets. We find that unsafe streets tend to be photographed during the day, while walkable streets are tagged with walkability-related keywords. These results open up practical opportunities (for, e.g., room booking services, urban route recommenders, and real-estate sites) and have theoretical implications for researchers who might resort to the use social media data to tackle previously unanswered questions in the area of walkability.Comment: 10 pages, 7 figures, Proceedings of International World Wide Web Conference (WWW 2015

Local influence of boundary conditions on a confined supercooled colloidal liquid

We study confined colloidal suspensions as a model system which approximates the behavior of confined small molecule glass-formers. Dense colloidal suspensions become glassier when confined between parallel glass plates. We use confocal microscopy to study the motion of confined colloidal particles. In particular, we examine the influence particles stuck to the glass plates have on nearby free particles. Confinement appears to be the primary influence slowing free particle motion, and proximity to stuck particles causes a secondary reduction in the mobility of free particles. Overall, particle mobility is fairly constant across the width of the sample chamber, but a strong asymmetry in boundary conditions results in a slight gradient of particle mobility.Comment: For conference proceedings, "Dynamics in Confinement", Grenoble, March 201

Absence of lattice strain anomalies at the electronic topological transition in zinc at high pressure

High pressure structural distortions of the hexagonal close packed (hcp) element zinc have been a subject of controversy. Earlier experimental results and theory showed a large anomaly in lattice strain with compression in zinc at about 10 GPa which was explained theoretically by a change in Fermi surface topology. Later hydrostatic experiments showed no such anomaly, resulting in a discrepancy between theory and experiment. We have computed the compression and lattice strain of hcp zinc over a wide range of compressions using the linearized augmented plane wave (LAPW) method paying special attention to k-point convergence. We find that the behavior of the lattice strain is strongly dependent on k-point sampling, and with large k-point sets the previously computed anomaly in lattice parameters under compression disappears, in agreement with recent experiments.Comment: 9 pages, 6 figures, Phys. Rev. B (in press

Framework for evaluating the health impact of the scale-up of malaria control interventions on all-cause child mortality in Sub-Saharan Africa

Concerted efforts from national and international partners have scaled up malaria control interventions, including insecticide-treated nets, indoor residual spraying, diagnostics, prompt and effective treatment of malaria cases, and intermittent preventive treatment during pregnancy in sub-Saharan Africa (SSA). This scale-up warrants an assessment of its health impact to guide future efforts and investments; however, measuring malaria-specific mortality and the overall impact of malaria control interventions remains challenging. In 2007, Roll Back Malaria's Monitoring and Evaluation Reference Group proposed a theoretical framework for evaluating the impact of full-coverage malaria control interventions on morbidity and mortality in high-burden SSA countries. Recently, several evaluations have contributed new ideas and lessons to strengthen this plausibility design. This paper harnesses that new evaluation experience to expand the framework, with additional features, such as stratification, to examine subgroups most likely to experience improvement if control programs are working; the use of a national platform framework; and analysis of complete birth histories from national household surveys. The refined framework has shown that, despite persisting data challenges, combining multiple sources of data, considering potential contributions from both fundamental and proximate contextual factors, and conducting subnational analyses allows identification of the plausible contributions of malaria control interventions on malaria morbidity and mortality

Triggering an eruptive flare by emerging flux in a solar active-region complex

A flare and fast coronal mass ejection originated between solar active regions NOAA 11514 and 11515 on July 1, 2012 in response to flux emergence in front of the leading sunspot of the trailing region 11515. Analyzing the evolution of the photospheric magnetic flux and the coronal structure, we find that the flux emergence triggered the eruption by interaction with overlying flux in a non-standard way. The new flux neither had the opposite orientation nor a location near the polarity inversion line, which are favorable for strong reconnection with the arcade flux under which it emerged. Moreover, its flux content remained significantly smaller than that of the arcade (approximately 40 %). However, a loop system rooted in the trailing active region ran in part under the arcade between the active regions, passing over the site of flux emergence. The reconnection with the emerging flux, leading to a series of jet emissions into the loop system, caused a strong but confined rise of the loop system. This lifted the arcade between the two active regions, weakening its downward tension force and thus destabilizing the considerably sheared flux under the arcade. The complex event was also associated with supporting precursor activity in an enhanced network near the active regions, acting on the large-scale overlying flux, and with two simultaneous confined flares within the active regions.Comment: Accepted for publication in Topical Issue of Solar Physics: Solar and Stellar Flares. 25 pages, 12 figure