Characterization of site-specific GPS errors using a short-baseline network of braced monuments at Yucca Mountain, southern Nevada

We use a short-baseline network of braced monuments to investigate site-specific GPS effects. The network has baseline lengths of ∼10, 100, and 1000 m. Baseline time series have root mean square (RMS) residuals, about a model for the seasonal cycle, of 0.05–0.24 mm for the horizontal components and 0.20–0.72 mm for the radial. Seasonal cycles occur, with amplitudes of 0.04–0.60 mm, even for the horizontal components and even for the shortest baselines. For many time series these lag seasonal cycles in local temperature measurements by 23–43 days. This could suggest that they are related to bedrock thermal expansion. Both shorter-period signals and seasonal cycles for shorter baselines to REP2, the one short-braced monument in our network, are correlated with temperature, with no lag time. Differences between REP2 and the other stations, which are deep-braced, should reflect processes occurring in the upper few meters of the ground. These correlations may be related to thermal expansion of these upper ground layers, and/or thermal expansion of the monuments themselves. Even over these short distances we see a systematic increase in RMS values with increasing baseline length. This, and the low RMS levels, suggests that site-specific effects are unlikely to be the limiting factor in the use of similar GPS sites for geophysical investigations

Microbial Nanowires: Is the Subsurface Hardwired ?

The Earth\u27s shallow subsurface results from integrated biological, geochemical, and physical processes. Methods are sought to remotely assess these interactive processes, especially those catalysed by micro-organisms. Using saturated sand columns and the metal reducing bacterium Shewanella oneidensis MR-1, we show that electrically conductive appendages called bacterial nanowires are directly associated with electrical potentials. No significant electrical potentials were detectable in columns inoculated with mutant strains that produced non-conductive appendages. Scanning electron microscopy imaging revealed a network of nanowires linking cells-cells and cells to mineral surfaces, hardwiring the entire length of the column. We hypothesize that the nanowires serve as conduits for transfer of electrons from bacteria in the anaerobic part of the column to bacteria at the surface that have access to oxygen, akin to a biogeobattery. These results advance understanding of the mechanisms of electron transport in subsurface environments and of how microorganisms cycle geologic material and share energy

Phosphofructokinase 1 Glycosylation Regulates Cell Growth and Metabolism

Cancer cells must satisfy the metabolic demands of rapid cell growth within a continually changing microenvironment. We demonstrated that the dynamic posttranslational modification of proteins by O-linked β-N-acetylglucosamine (O-GlcNAcylation) is a key metabolic regulator of glucose metabolism. O-GlcNAcylation was induced at serine 529 of phosphofructokinase 1 (PFK1) in response to hypoxia. Glycosylation inhibited PFK1 activity and redirected glucose flux through the pentose phosphate pathway, thereby conferring a selective growth advantage on cancer cells. Blocking glycosylation of PFK1 at serine 529 reduced cancer cell proliferation in vitro and impaired tumor formation in vivo. These studies reveal a previously uncharacterized mechanism for the regulation of metabolic pathways in cancer and a possible target for therapeutic intervention

Methods to Minimize Confounding Effects of Hematocrit and Hemoglobin when using Dried Blood Spots

Dried blood spots (DBS) are an alternative method of collecting venous blood samples that can be used to measure blood biomarkers. Two confounding factors, hemoglobin and hematocrit, limit the validity of DBS in comparison to the gold standard serum sample. The saturation of biomarkers on DBS filter paper is affected by the sample’s hematocrit and hemoglobin. Also hemoglobin contamination is known to confounder for antibody binding in assay systems. The purpose of this study was two-fold: 1) to evaluate a DBS punching technique designed to limit the effects of hematocrit whilst minimizing sample volume and 2) to evaluate a novel device designed to remove hemoglobin from plasma during DBS collection (Seraform™). A bead-based multiplex assay of nine cardiovascular disease risk (CVD) biomarkers (C-reactive protein, fibrinogen, L-selectin, Haptoglobin, serum amyloid protein, von Willebrand factor, adipsin, α2-macroglobulin, and α1-acid glycoprotein) was measured and compared using the various DBS treatments. Outcomes were compared using linear regression analysis examining the R2 change with hematocrit and hemoglobin as covariates. Significance was set at

Are megaquakes clustered?

We study statistical properties of the number of large earthquakes over the past century. We analyze the cumulative distribution of the number of earthquakes with magnitude larger than threshold M in time interval T, and quantify the statistical significance of these results by simulating a large number of synthetic random catalogs. We find that in general, the earthquake record cannot be distinguished from a process that is random in time. This conclusion holds whether aftershocks are removed or not, except at magnitudes below M = 7.3. At long time intervals (T = 2-5 years), we find that statistically significant clustering is present in the catalog for lower magnitude thresholds (M = 7-7.2). However, this clustering is due to a large number of earthquakes on record in the early part of the 20th century, when magnitudes are less certain.Comment: 5 pages, 5 figure

Vol. 2 Ch. 5 Scale and Community in Hopewell Networks (SCHoN): Summary of Preliminary Results

https://ideaexchange.uakron.edu/encountering_hopewell/1015/thumbnail.jp

Sex Differences in Change in Skin Temperature When Exercising in a Hot, Humid Environment

The risk for heat-related illness is increased when exercising in a hot, humid environment. In an effort to protect the athlete, body temperature is measured continuously while exercising in extreme environments. Currently, researchers and laboratory personnel employ the use of mean skin temperature to monitor athlete safety; however, this measurement fails to consider localized changes in temperature that may arise as a function of sex and exercise time. Therefore, the purpose of this study was to examine potential sex differences in the change in skin temperature at 17 different upper body locations while exercising in a hot, humid environment. Young men and women were recruited and completed a 60-min walk/jog interval protocol in a hot (34.1 ± 1 °C), humid (64 ± 8%) environment while skin temperature was continuously measured. To account for differences that may have arisen due to differing workloads between men and women, energy expenditure and metabolic heat production were calculated after the completion of exercise. Data was analyzed either a repeated-measures ANOVA (change in skin temperature) or t-test­ (energy expenditure and metabolic heat production). Location of interaction effects was determined using a Fisher’s Least Significant Difference test. Significance was set a p\u3c0.05 for all statistical testing. There was no difference between men and women in total energy expenditure; however, men were found to have a higher metabolic heat production. Women had a higher change in skin temperature at three locations on the back (left upper, right upper, and right mid-back). Conversely, there were no differences at any time point between men and women in the change in core temperature from baseline measurements. This study highlights the need to further investigate sex differences in cooling mechanisms while exercising in a hot, humid environment