Seething Horizontal Magnetic Fields in the Quiet Solar Photosphere

The photospheric magnetic field outside of active regions and the network has a ubiquitous and dynamic line-of-sight component that strengthens from disk center to limb as expected for a nearly horizontal orientation. This component shows a striking time variation with an average temporal rms near the limb of 1.7 G at ~3" resolution. In our moderate resolution observations the nearly horizontal component has a frequency variation power law exponent of -1.4 below 1.5 mHz and is spatially patchy on scales up to ~15 arcsec. The field may be a manifestation of changing magnetic connections between eruptions and evolution of small magnetic flux elements in response to convective motions. It shows no detectable latitude or longitude variations.Comment: 7 pages, 6 figures, submitted to ApJ letters, quality of figures significantly degraded here by compression requirement

Spontaneous mutation accumulation in multiple strains of the green alga, Chlamydomonas reinhardtii

Estimates of mutational parameters, such as the average fitness effect of a new mutation and the rate at which new genetic variation for fitness is created by mutation, are important for the understanding of many biological processes. However, the causes of interspecific variation in mutational parameters and the extent to which they vary within species remain largely unknown. We maintained multiple strains of the unicellular eukaryote Chlamydomonas reinhardtii, for approximately 1000 generations under relaxed selection by transferring a single cell every ∼10 generations. Mean fitness of the lines tended to decline with generations of mutation accumulation whereas mutational variance increased. We did not find any evidence for differences among strains in any of the mutational parameters estimated. The overall change in mean fitness per cell division and rate of input of mutational variance per cell division were more similar to values observed in multicellular organisms than to those in other single-celled microbes. However, after taking into account differences in genome size among species, estimates from multicellular organisms and microbes, including our new estimates from C. reinhardtii, become substantially more similar. Thus, we suggest that variation in genome size is an important determinant of interspecific variation in mutational parameters

A comparison of probe-level and probeset models for small-sample gene expression data

<p>Abstract</p> <p>Background</p> <p>Statistical methods to tentatively identify differentially expressed genes in microarray studies typically assume larger sample sizes than are practical or even possible in some settings.</p> <p>Results</p> <p>The performance of several probe-level and probeset models was assessed graphically and numerically using three spike-in datasets. Based on the Affymetrix GeneChip, a novel nested factorial model was developed and found to perform competitively on small-sample spike-in experiments.</p> <p>Conclusions</p> <p>Statistical methods with test statistics related to the estimated log fold change tend to be more consistent in their performance on small-sample gene expression data. For such small-sample experiments, the nested factorial model can be a useful statistical tool. This method is implemented in freely-available R code (affyNFM), available with a tutorial document at <url>http://www.stat.usu.edu/~jrstevens</url>.</p

Outbreak of an acute aflatoxicosis in Tanzania during 2016

In June 2016, an outbreak of an unknown disease was reported to affect clusters of families in two regions of the central part of Tanzania. A rapid epidemiological survey was conducted in the affected villages, with a detailed house-to-house survey in selected households. A total of 68 cases occurred between 14 May and 14 November 2016, of which 20 died, making a case fatality rate of 30%. Over 50% of the cases were below the age of 15 years. The cases presented with jaundice (n=60), abdominal pain (n=59), vomiting (n=56), diarrhoea (n=34) and ascites (n=32). The responsible food item appeared to be home grown maize. The rate ratio indicated that the occurrence of illnesses was associated with ingestion of food contaminated with high levels of aflatoxins (contamination range: 10-51,100 μg/kg and 2.4-285 μg/kg for case and control households, respectively). Serum aflatoxin biomarker indicated that cases were more likely to have higher than 1000 pg/mg aflatoxin-albumin adduct level in their sera compared to controls (Odds Ratio = 13.5; 95% confidence intervals = 1.5-165.3; range of aflatoxin-albumin adduct level = 36- 32,800 pg/mg for cases and 10-4020 pg/mg for controls). Beside aflatoxins, maize samples were also contaminated with high levels of fumonisins (range of contamination; 945-12,630 μg/kg) with 8 of 10 samples analysed from case households co-contaminated with both toxins at levels above the maximum limit of 5 or 10 μg/kg set for AFB1 or total aflatoxins and 2,000 μg/kg for fumonisins. Clinical presentation and high levels of aflatoxin in food samples coupled with high levels of serum aflatoxin-albumin adducts among the cases support the causal role of aflatoxins