Light attenuation characteristics of glacially-fed lakes

Transparency is a fundamental characteristic of aquatic ecosystems and is highly responsive to changes in climate and land use. The transparency of glacially-fed lakes may be a particularly sensitive sentinel characteristic of these changes. However, little is known about the relative contributions of glacial flour versus other factors affecting light attenuation in these lakes. We sampled 18 glacially-fed lakes in Chile, New Zealand, and the U.S. and Canadian Rocky Mountains to characterize how dissolved absorption, algal biomass (approximated by chlorophyll a), water, and glacial flour contributed to attenuation of ultraviolet radiation (UVR) and photosynthetically active radiation (PAR, 400–700 nm). Variation in attenuation across lakes was related to turbidity, which we used as a proxy for the concentration of glacial flour. Turbidity-specific diffuse attenuation coefficients increased with decreasing wavelength and distance from glaciers. Regional differences in turbidity-specific diffuse attenuation coefficients were observed in short UVR wavelengths (305 and 320 nm) but not at longer UVR wavelengths (380 nm) or PAR. Dissolved absorption coefficients, which are closely correlated with diffuse attenuation coefficients in most non-glacially-fed lakes, represented only about one quarter of diffuse attenuation coefficients in study lakes here, whereas glacial flour contributed about two thirds across UVR and PAR. Understanding the optical characteristics of substances that regulate light attenuation in glacially-fed lakes will help elucidate the signals that these systems provide of broader environmental changes and forecast the effects of climate change on these aquatic ecosystems

The effect of food type on the portion size effect in children aged 2-12 years: A systematic review and meta-analysis.

Visual cues such as plate size, amount of food served and packaging are known to influence the effects of portion size on food intake. Unit bias is a well characterised heuristic and helps to determine consumption norms. In an obesogenic environment where large portions are common place, the unit or segmentation bias may be overridden promoting overconsumption of both amorphous or unit foods. The aim of this review was to investigate the impact of offering unit or amorphous food on the portion size effect (PSE) in children aged 2–12 years. A systematic search for literature was conducted in Medline, PsycInfo and Web of Science in February 2018. A total of 1197 papers were retrieved following the searches. Twenty-one papers were included in the systematic review, of which 15 provided requisite statistical information for inclusion in a random effects meta-analysis. Increasing children's food portion size by 51–100% led to a significant increase in intake (SMD = 0.47, 95% CI: 0.39–0.55). There was no evidence to suggest that increases in consumption were related to food type (p = 0.33), child age (p = 0.47) or initial portion size served (p=0.14). Residual heterogeneity was not significant (p=0.24). The PSE was demonstrated in children aged 2–12 years when offered both unit and amorphous food items. The effect was not restricted by food type, child age or influenced by initial portion size served. Of the studies included in the meta-analysis between study heterogeneity was low suggesting minimal variation in treatment effects between studies, however, more research is required to understand the mechanisms of the PSE in preschool children. Future research should determine feasible methods to downsize portion sizes served to children

Calmodulin Binds a Highly Extended HIV-1 MA Protein That Refolds Upon Its Release

Calmodulin (CaM) expression is upregulated upon HIV-1 infection and interacts with proteins involved in viral processing, including the multifunctional HIV-1 MA protein. We present here the results of studies utilizing small-angle neutron scattering with contrast variation that, when considered in the light of earlier fluorescence and NMR data, show CaM binds MA in an extended open-clamp conformation via interactions with two tryptophans that are widely spaced in sequence and space. The interaction requires a disruption of the MA tertiary fold such that MA becomes highly extended in a long snakelike conformation. The CaM-MA interface is extensive, covering ∼70% of the length of the MA such that regions known to be important in MA interactions with critical binding partners would be impacted. The CaM conformation is semiextended and as such is distinct from the classical CaM-collapse about short α-helical targets. NMR data show that upon dissociation of the CaM-MA complex, either by the removal of Ca2+ or increasing ionic strength, MA reforms its native tertiary contacts. Thus, we observe a high level of structural plasticity in MA that may facilitate regulation of its activities via intracellular Ca2+-signaling during viral processing. © 2012 Biophysical Society

Prevalence and risk factors for chronic kidney disease of unknown cause in Malawi: a cross-sectional analysis in a rural and urban population

Background: An epidemic of chronic kidney disease of unknown cause (CKDu) is occurring in rural communities in tropical regions of low-and middle-income countries in South America and India. Little information is available from Southern African countries which have similar climatic and occupational characteristics to CKDu-endemic countries. We investigated whether CKDu is prevalent in Malawi and identified its potential risk factors in this setting. / Methods: We conducted a cross-sectional study from January–August 2018 collecting bio samples and anthropometric data in two Malawian populations. The sample comprised adults > 18 years (n = 821) without diabetes, hypertension, and proteinuria. Estimates of glomerular filtration rate (eGFR) were calculated using the CKD-EPI equation. Linear and logistic regression models were applied with potential risk factors, to estimate risk of reduced eGFR. / Results: The mean eGFR was 117.1 ± 16.0 ml/min per 1.73m2 and the mean participant age was 33.5 ± 12.7 years. The prevalence of eGFR< 60 was 0.2% (95% confidence interval (95% CI) 0.1, 0.9); the prevalence of eGFR< 90 was 5% (95% CI =3.2, 6.3). We observed a higher prevalence in the rural population (5% (3.6, 7.8)), versus urban (3% (1.4, 6.7)). Age and BMI were associated with reduced eGFR< 90 [Odds ratio (OR) (95%CI) =3.59 (2.58, 5.21) per ten-year increment]; [OR (95%CI) =2.01 (1.27, 3.43) per 5 kg/m2 increment] respectively. No increased risk of eGFR < 90 was observed for rural participants [OR (95%CI) =1.75 (0.50, 6.30)]. / Conclusions: Reduced kidney function consistent with the definition of CKDu is not common in the areas of Malawi sampled, compared to that observed in other tropical or sub-tropical countries in Central America and South Asia. Reduced eGFR< 90 was related to age, BMI, and was more common in rural areas. These findings are important as they contradict some current hypothesis that CKDu is endemic across tropical and sub-tropical countries. This study has enabled standardized comparisons of impaired kidney function between and within tropical/subtropical regions of the world and will help form the basis for further etiological research, surveillance strategies, and the implementation and evaluation of interventions

Socio-Economic Instability and the Scaling of Energy Use with Population Size

The size of the human population is relevant to the development of a sustainable world, yet the forces setting growth or declines in the human population are poorly understood. Generally, population growth rates depend on whether new individuals compete for the same energy (leading to Malthusian or density-dependent growth) or help to generate new energy (leading to exponential and super-exponential growth). It has been hypothesized that exponential and super-exponential growth in humans has resulted from carrying capacity, which is in part determined by energy availability, keeping pace with or exceeding the rate of population growth. We evaluated the relationship between energy use and population size for countries with long records of both and the world as a whole to assess whether energy yields are consistent with the idea of an increasing carrying capacity. We find that on average energy use has indeed kept pace with population size over long time periods. We also show, however, that the energy-population scaling exponent plummets during, and its temporal variability increases preceding, periods of social, political, technological, and environmental change. We suggest that efforts to increase the reliability of future energy yields may be essential for stabilizing both population growth and the global socio-economic system

Toward High-Precision Measures of Large-Scale Structure

I review some results of estimation of the power spectrum of density fluctuations from galaxy redshift surveys and discuss advances that may be possible with the Sloan Digital Sky Survey. I then examine the realities of power spectrum estimation in the presence of Galactic extinction, photometric errors, galaxy evolution, clustering evolution, and uncertainty about the background cosmology.Comment: 24 pages, including 11 postscript figures. Uses crckapb.sty (included in submission). To appear in ``Ringberg Workshop on Large-Scale Structure,'' ed D. Hamilton (Kluwer, Amsterdam), p. 39

Careers of an elite cohort of U.S. basic life science postdoctoral fellows and the influence of their mentor's citation record

<p>Abstract</p> <p>Background</p> <p>There is general agreement that the number of U.S. science PhDs being trained far exceeds the number of future academic positions. One suggested approach to this problem is to significantly reduce the number of PhD positions. A counter argument is that students are aware of the limited academic positions but have chosen a PhD track because it opens other, non-academic, opportunities. The latter view requires that students have objective information about what careers options will be available for them.</p> <p>Methods</p> <p>The scientific careers of the 1992-94 cohort of NIH National Institute of General Medical Sciences (NIGMS) Kirchstein-NRSA F32 postdoctoral fellows (PD) was determined by following their publications (PubMed), grants (NIH and NSF), and faculty and industry positions through 2009. These basic life science PDs receive support through individual grant applications and represent the most successful class of NIH PDs as judged by academic careers and grants. The sex dependence of the career and grant success and the influence of the PD mentor's citation record were also determined</p> <p>Results</p> <p>Of the 439 1992-94 NIGMS F32 fellows, the careers of 417 could be determined. Although females had significantly higher rates of dropping out of science (22% females, 9% males) there was no significant difference in the fraction of females that ended up as associate or full professors at research universities (22.8% females, 29.1% for males). More males then females ended up in industry (34% males, 22% females). Although there was no significant correlation between male grant success and their mentor's publication record (h index, citations, publications), there was a significant correlation for females. Females whose mentor's h index was in the top quartile were nearly 3 times as likely to receive a major grant as those whose mentors were in the bottom quartile (38.7% versus 13.3%).</p> <p>Conclusions</p> <p>Sixteen years after starting their PD, only 9% of males had dropped out of science. More females (28%) have dropped out of science, primarily because fewer went into industry positions. The mentor's publication record does not affect the future grant success of males but it has a dramatic effect on female grant success.</p

Detection of weak gravitational lensing distortions of distant galaxies by cosmic dark matter at large scales

Most of the matter in the universe is not luminous and can be observed directly only through its gravitational effect. An emerging technique called weak gravitational lensing uses background galaxies to reveal the foreground dark matter distribution on large scales. Light from very distant galaxies travels to us through many intervening overdensities which gravitationally distort their apparent shapes. The observed ellipticity pattern of these distant galaxies thus encodes information about the large-scale structure of the universe, but attempts to measure this effect have been inconclusive due to systematic errors. We report the first detection of this ``cosmic shear'' using 145,000 background galaxies to reveal the dark matter distribution on angular scales up to half a degree in three separate lines of sight. The observed angular dependence of this effect is consistent with that predicted by two leading cosmological models, providing new and independent support for these models.Comment: 18 pages, 5 figures: To appear in Nature. (This replacement fixes tex errors and typos.

A reverse engineering approach to the suppression of citation biases reveals universal properties of citation distributions

The large amount of information contained in bibliographic databases has recently boosted the use of citations, and other indicators based on citation numbers, as tools for the quantitative assessment of scientific research. Citations counts are often interpreted as proxies for the scientific influence of papers, journals, scholars, and institutions. However, a rigorous and scientifically grounded methodology for a correct use of citation counts is still missing. In particular, cross-disciplinary comparisons in terms of raw citation counts systematically favors scientific disciplines with higher citation and publication rates. Here we perform an exhaustive study of the citation patterns of millions of papers, and derive a simple transformation of citation counts able to suppress the disproportionate citation counts among scientific domains. We find that the transformation is well described by a power-law function, and that the parameter values of the transformation are typical features of each scientific discipline. Universal properties of citation patterns descend therefore from the fact that citation distributions for papers in a specific field are all part of the same family of univariate distributions.Comment: 9 pages, 6 figures. Supporting information files available at http://filrad.homelinux.or

Rings in the Solar System: a short review

Rings are ubiquitous around giant planets in our Solar System. They evolve jointly with the nearby satellite system. They could form either during the giant planet formation process or much later, as a result of large scale dynamical instabilities either in the local satellite system, or at the planetary scale. We review here the main characteristics of rings in our solar system, and discuss their main evolution processes and possible origin. We also discuss the recent discovery of rings around small bodies.Comment: Accepted for the Handbook of Exoplanet