Annular Gas Seals And Rotordynamics Of Compressors And Turbines.

Tutorialpg. 201-220The possible negative or positive impact of annular seal on rotordynamics of compressors and steam turbines is discussed. The nature of destabilizing forces that can be developed by "seethrough" and interlocking labyrinths is discussed. Improving the rotordynamic behavior of labyrinths via swirl brakes and shunt injection is explained using measured test results. Improving rotordynamics through replacement of labyrinths with either smooth-rotor/honeycomb-stator seals (honeycomb seals) or pocket damper seals is also discussed. For long seals (L > 2 in or 50 mm) honeycomb seals leak about a third less than a standard labyrinth, have much higher values of effective damping, and potentially high stiffness values for high-pressure compressors. The pocket damper seal is a patented device with damping values that can be a hundred times higher than a standard labyrinth seal. Recent test results are presented for both seal types, and case studies are cited and reviewed where unstable compressors have been "cured" through application of these seals

Developmental Defects Mediated by the P1/HC-Pro Potyviral Silencing Suppressor Are Not Due to Misregulation of AUXIN RESPONSE FACTOR 8

Plant viral suppressors of RNA silencing induce developmental defects similar to those caused by mutations in genes involved in the microRNA pathway. A recent report has attributed viral suppressor-mediated developmental defects to up-regulation of AUXIN RESPONSE FACTOR 8 (ARF8), a target of miR167. The key piece of evidence was that the developmental defects in transgenic Arabidopsis (Arabidopsis thaliana) expressing viral suppressors were greatly alleviated in the F1 progeny of a cross with plants carrying the arf8-6 mutation. Arf8-6 is a SALK line T-DNA insertion mutant, a class of mutations prone to inducing transcriptional silencing of transgenes expressed from the 35S promoter. We have reinvestigated the role of ARF8 in viral suppressor-mediated developmental defects, using two independent arf8 mutations and the P1/HC-Pro potyviral suppressor of silencing. Progeny of a cross between P1/HC-Pro transgenic Arabidopsis and the arf8-6 T-DNA insertion mutant showed little effect on the P1/HC-Pro phenotype in the F1 generation, but almost all arf8-6/P1/HC-Pro progeny had lost the phenotype in the F2 generation. However, the loss of phenotype in the F2 generation was not correlated with the number of functional copies of the ARF8 gene. Instead, it reflected transcriptional silencing of the P1/HC-Pro transgene, as evidenced by a pronounced decrease in P1/HC-Pro mRNA and the appearance of 35S promoter small interfering RNAs. Furthermore, an independent loss-of-function point mutation, Arf8-8, had no detectable effects on P1/HC-Pro phenotype in either the F1 or F2 generations. Together, these data argue against the previously reported role of increased ARF8 expression in developmental defects caused by P1/HC-Pro

RegenBase: a knowledge base of spinal cord injury biology for translational research.

Spinal cord injury (SCI) research is a data-rich field that aims to identify the biological mechanisms resulting in loss of function and mobility after SCI, as well as develop therapies that promote recovery after injury. SCI experimental methods, data and domain knowledge are locked in the largely unstructured text of scientific publications, making large scale integration with existing bioinformatics resources and subsequent analysis infeasible. The lack of standard reporting for experiment variables and results also makes experiment replicability a significant challenge. To address these challenges, we have developed RegenBase, a knowledge base of SCI biology. RegenBase integrates curated literature-sourced facts and experimental details, raw assay data profiling the effect of compounds on enzyme activity and cell growth, and structured SCI domain knowledge in the form of the first ontology for SCI, using Semantic Web representation languages and frameworks. RegenBase uses consistent identifier schemes and data representations that enable automated linking among RegenBase statements and also to other biological databases and electronic resources. By querying RegenBase, we have identified novel biological hypotheses linking the effects of perturbagens to observed behavioral outcomes after SCI. RegenBase is publicly available for browsing, querying and download.Database URL:http://regenbase.org

Ultrasound-Assisted Peripheral Venous Access in Young Children: A Randomized Controlled Trial and Pilot Feasibility Study

OBJECTIVES: Intravenous (IV) access in children treated in the emergency department (ED) is frequently required and often difficult to obtain. While it has been shown that ultrasound can be useful in adults for both central and peripheral venous access, research regarding children has been limited. We sought to determine if the use of a static ultrasound technique could, a) allow clinicians to visualize peripheral veins and b) improve success rates of peripheral venous cannulation in young children in the ED.METHODS: We performed a randomized clinical trial of children < 7 years in an academic pediatric ED who required IV access and who had failed the first IV attempt. We randomized patients to either continued standard IV attempts or ultrasound-assisted attempts. Clinicians involved in the study received one hour of training in ultrasound localization of peripheral veins. In the ultrasound group, vein localization was performed by an ED physician who marked the skin overlying the target vessel. Intravenous cannulation attempts were then immediately performed by a pediatric ED nurse who relied on the skin mark for vessel location. We allowed for technique cross-over after two failed IV attempts. We recorded success rate and location of access attempts. We compared group success rates using differences in 95% confidence intervals (CI).RESULTS: We enrolled 44 children over a one-year period. The median age of enrollees was 9.5 months. We visualized peripheral veins in all patients in the ultrasound group (n=23) and in those who crossed over to ultrasound after failed standard technique attempts (n= 8). Venipuncture was successful on the first attempt in the ultrasound group in 13/23 (57%, CI, 35% to 77%), versus 12/21 (57%, CI, 34% to 78%) in the standard group, difference between groups 0.6% (95% CI -30% to 29%). First attempt cannulation success in the ultrasound group was 8/23 (35%, CI, 16% to 57%), versus 6/21 (29%, CI, 11% to 52%) in the standard group, difference between groups 6% (95% CI -21% to 34%).CONCLUSION: Ultrasound allows physicians to visualize peripheral veins of young children in the ED. We were unable to demonstrate, however, a clinically important benefit to a static ultrasound aided vein cannulation technique performed by clinicians with limited ultrasound training over standard technique after one failed IV attempt in an academic pediatric ED

Future thermal regimes for epaulette sharks (Hemiscyllium ocellatum): growth and metabolic performance cease to be optimal

Climate change is affecting thermal regimes globally, and organisms relying on their environment to regulate biological processes face unknown consequences. In ectotherms, temperature affects development rates, body condition, and performance. Embryonic stages may be the most vulnerable life history stages, especially for oviparous species already living at the warm edge of their distribution, as embryos cannot relocate during this developmental window. We reared 27 epaulette shark (Hemiscyllium ocellatum) embryos under average summer conditions (27 °C) or temperatures predicted for the middle and end of the twenty-first century with climate change (i.e., 29 and 31 °C) and tracked growth, development, and metabolic costs both in ovo and upon hatch. Rearing sharks at 31 °C impacted embryonic growth, yolk consumption, and metabolic rates. Upon hatch, 31 °C-reared sharks weighed significantly less than their 27 °C-reared counterparts and exhibited reduced metabolic performance. Many important growth and development traits in this species may peak after 27 °C and start to become negatively impacted nearing 31 °C. We hypothesize that 31 °C approximates the pejus temperature (i.e., temperatures at which performance of a trait begin to decline) for this species, which is alarming, given that this temperature range is well within ocean warming scenarios predicted for this species’ distribution over the next century

The Maine Annex, vol. 2, no. 14

The Maine Annex introduces a new \u27man on the street\u27 feature and covers the release of Prologue, Maine\u27s first inter-collegiate magazine

Transcript profiling of two alfalfa genotypes with contrasting cell wall composition in stems using a cross-species platform: optimizing analysis by masking biased probes

<p>Abstract</p> <p>Background</p> <p>The GeneChip^®<it>Medicago </it>Genome Array, developed for <it>Medicago truncatula</it>, is a suitable platform for transcript profiling in tetraploid alfalfa [<it>Medicago sativa </it>(L.) subsp. <it>sativa</it>]. However, previous research involving cross-species hybridization (CSH) has shown that sequence variation between two species can bias transcript profiling by decreasing sensitivity (number of expressed genes detected) and the accuracy of measuring fold-differences in gene expression.</p> <p>Results</p> <p>Transcript profiling using the <it>Medicago </it>GeneChip^®was conducted with elongating stem (ES) and post-elongation stem (PES) internodes from alfalfa genotypes 252 and 1283 that differ in stem cell wall concentrations of cellulose and lignin. A protocol was developed that masked probes targeting inter-species variable (ISV) regions of alfalfa transcripts. A probe signal intensity threshold was selected that optimized both sensitivity and accuracy. After masking for both ISV regions and previously identified single-feature polymorphisms (SFPs), the number of differentially expressed genes between the two genotypes in both ES and PES internodes was approximately 2-fold greater than the number detected prior to masking. Regulatory genes, including transcription factor and receptor kinase genes that may play a role in development of secondary xylem, were significantly over-represented among genes up-regulated in 252 PES internodes compared to 1283 PES internodes. Several cell wall-related genes were also up-regulated in genotype 252 PES internodes. Real-time quantitative RT-PCR of differentially expressed regulatory and cell wall-related genes demonstrated increased sensitivity and accuracy after masking for both ISV regions and SFPs. Over 1,000 genes that were differentially expressed in ES and PES internodes of genotypes 252 and 1283 were mapped onto putative orthologous loci on <it>M. truncatula </it>chromosomes. Clustering simulation analysis of the differentially expressed genes suggested co-expression of some neighbouring genes on <it>Medicago </it>chromosomes.</p> <p>Conclusions</p> <p>The problems associated with transcript profiling in alfalfa stems using the <it>Medicago </it>GeneChip as a CSH platform were mitigated by masking probes targeting ISV regions and SFPs. Using this masking protocol resulted in the identification of numerous candidate genes that may contribute to differences in cell wall concentration and composition of stems of two alfalfa genotypes.</p

The Otterbein Miscellany - May 1967

https://digitalcommons.otterbein.edu/miscellany/1008/thumbnail.jp

Conserved cis-regulatory modules control robustness in Msx1 expression at single cell resolution

The process of transcription is highly stochastic leading to cell-to-cell variations and noise in gene expression levels. However, key essential genes have to be precisely expressed at the correct amount and time to ensure proper cellular development and function. Studies in yeast and bacterial systems have shown that gene expression noise decreases as mean expression levels increase, a relationship that is controlled by promoter DNA sequence. However, the function of distal cis-regulatory modules (CRMs), an evolutionary novelty of metazoans, in controlling transcriptional robustness and variability is poorly understood. In this study, we used live cell imaging of transfected reporters combined with a mathematical modelling and statistical inference scheme to quantify the function of conserved Msx1 CRMs and promoters in modulating single-cell real-time transcription rates in C2C12 mouse myoblasts. The results show that the mean expression–noise relationship is solely promoter controlled for this key pluripotency regulator. In addition, we demonstrate that CRMs modulate single-cell basal promoter rate distributions in a graded manner across a population of cells. This extends the rheostatic model of CRM action to provide a more detailed understanding of CRM function at single-cell resolution. We also identify a novel CRM transcriptional filter function that acts to reduce intracellular variability in transcription rates and show that this can be phylogenetically separable from rate modulating CRM activities. These results are important for understanding how the expression of key vertebrate developmental transcription factors is precisely controlled both within and between individual cells