8,222 research outputs found
Lean - Mean: Tree climbing machine!
Staying fit and healthy is essential if you are planning a long and productive climbing career. Keys to maintaining good fitness and health, along with treating injuries carefully will be discussed in this interactive session. Some simple safety tips will also be up for debate.
Knowing how to integrate healthy choices into your lifestyle and work could save your career and possibly more. Want to be a Lean - Mean - Tree Climbing Machine? Come along and be a part of the discussion.
This session will be formed with the collaboration between health professionals and sports coache
The Role of Microenvironment Reagent Solubility on Reaction Kinetics of 4-Nitrophenol Reduction
The Role of Microenvironment Reagent Solubility on Reaction Kinetics of 4-Nitrophenol Reduction
Michael Zeevi1 with Andrew Harrison1 and Christina Tang, PhD1
1Department of Chemical and Life Science Engineering, VCU School of Engineering
Introduction: Nanoparticles are of increasing interest due to their high surface area to volume ratio, as well as that they enable fine-tuning of the reaction microenvironment. Through flash nanoprecipitation, core-shell polymer nanoreactors were formed by directed self-assembly. Using the reduction of 4-nitrophenol as a model reduction reaction, we investigated the effect of reagent solubility in the nanoreactor microenvironment’s on nanoreactor kinetics.
Methods: The standard reaction was conducted at room temperature, with a 1000-fold excess of sodium borohydride in a quartz cuvette for real-time in situ UV-Vis analysis. Reagent concentrations were varied to examine the resulting effect on the calculated reaction rate constant. Reagent solubility limits in the nanoreactor microenvironment were estimated from solubility measurements in solvents with similar Hansen solubility parameters. Ethanol was chosen to represent the hydrophilic poly(ethylene) glycol phase and chloroform was chosen to represent the hydrophobic polystyrene phase. The hydrophilic phase had a visual absorbance at nm, and thus UV-Vis spectrometry was used to determine the saturation concentration. 1H NMR analysis with chloroform-D containing an internal standard (v/v TMS 0.03%) was used to measure the reagent solubility in the hydrophobic phase.
Results: 4-nitrophenol solubility in ethanol was determined by UV-Vis spectrometry to be . The solubility in chloroform-D was determined by 1H NMR to be . When 4-nitrophenol concentration is varied independently of sodium borohydride, an inverse relationship is observed with respect to the rate constant. However, when 4-nitrophenol and sodium borohydride concentrations are varied concurrently, no change is witnessed in the rate constant above the standard reaction concentration.
Conclusions: This experiment demonstrated that the rate of reaction in polystyrene core nanoreactors is not dependent on the reagent concentrations above the standard concentration. Solubility in each phase was measured in an effort to explain this behavior. The differences in solubility observed between the hydrophobic and hydrophilic phases may serve to explain this behavior if the interior, hydrophobic phase is saturated by 4-nitrophenol at the standard concentration. Future work should include study of concentrations at lower values than the standard concentration to determine when a change in the observed rate constant occurs.https://scholarscompass.vcu.edu/uresposters/1287/thumbnail.jp
Scott Ranks of Classifications of the Admissibility Equivalence Relation
Let be a recursive language. Let be the set of
-structures with domain . Let be a function with the property that
for all , if and only if
. Then there is some
so that
Investigation of feeding devices and development of design considerations for a new feeder for micro-sheet forming
Recent review in micro-forming research and technological development suggested that the trend of the development is more focused on the manufacturing processes, machines and tooling, and efforts on the methods and systems for integrated precision material handling are insufficient. Most of the developed micro-forming machines were based on standalone concepts which do not support efficient integration to make them fully automated and integrated. At present, material feeding in micro-forming is not of sufficient precision and reliability for high throughput manufacturing applications. Precise feeding is necessary to ensure that micro-parts can be produced with sufficient accuracy, especially in multi-stage forming, while high-speed feeding is a must to meet the production-rate requirements. Therefore, design of a new high-precision and high-speed feeder for micro-forming is proposed. Several possible approaches are examined with a view to establishing feasible concepts. Based on the investigation, several concepts for thin sheet-metal feeding for micro-forming are generated, they being argued and assessed with applicable loads and forces analysis. These form a basis of designing a new feeder
The interaction of social and perceivable causal factors in shaping ‘over-imitation’
Over-imitation has become a well-documented phenomenon. However there is evidence that both social and visible, physically causal factors can influence the occurrence of over-imitation in children. Here we explore the interplay between these two factors, manipulating both task opacity and social information. Four- to 7-year-old children were given either a causally opaque or transparent box, before which they experienced either (1) a condition where they witnessed a taught, knowledgeable person demonstrate an inefficient method and an untaught model demonstrate a more efficient method; or (2) a baseline condition where they witnessed efficient and inefficient methods performed by two untaught models. Results showed that the level of imitation increased with greater task opacity and when children received social information about knowledgeability consequent on teaching, but only for 6- to 7-year-olds. The findings show that children are selectively attuned to both causal and social factors when learning new cultural knowledge
The date of composition of D.H. Lawrence's 'Laura Philippine'
This note draws on new archival evidence to correctly date the composition of D. H. Lawrence's article 'Laura Philippine'
G-spots cause incorrect expression measurement in Affymetrix microarrays
Abstract
Background
High Density Oligonucleotide arrays (HDONAs), such as the Affymetrix HG-U133A GeneChip, use sets of probes chosen to match specified genes, with the expectation that if a particular gene is highly expressed then all the probes in that gene's probe set will provide a consistent message signifying the gene's presence. However, probes that contain a G-spot (a sequence of four or more guanines) behave abnormally and it has been suggested that these probes are responding to some biochemical effect such as the formation of G-quadruplexes.
Results
We have tested this expectation by examining the correlation coefficients between pairs of probes using the data on thousands of arrays that are available in the NCBI Gene Expression Omnibus (GEO) repository. We confirm the finding that G-spot probes are poorly correlated with others in their probesets and reveal that, by contrast, they are highly correlated with one another. We demonstrate that the correlation is most marked when the G-spot is at the 5' end of the probe.
Conclusion
Since these G-spot probes generally show little correlation with the other members of their probesets they are not fit for purpose and their values should be excluded when calculating gene expression values. This has serious implications, since more than 40% of the probesets in the HG-U133A GeneChip contain at least one such probe. Future array designs should avoid these untrustworthy probes.
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Affymetrix probes containing runs of contiguous guanines are not gene-specific
High Density Oligonucleotide arrays (HDONAs), such as the Affymetrix HG-U133A GeneChip, use sets of probes chosen to match specified genes, with the expectation that if a particular gene is highly expressed then all the probes in the designated probe set will provide a consistent message signifying the gene's presence. However, we demonstrate by data mining thousands of CEL files from NCBI's GEO database that 4G-probes (defined as probes containing sequences of four or more consecutive guanine (G) bases) do not react in the intended way. Rather, possibly due to the formation of G-quadruplexes, most 4G-probes are correlated, irrespective of the expression of the thousands of genes for which they were separately intended. It follows that 4G-probes should be ignored when calculating gene expression levels. Furthermore, future microarray designs should make no use of 4G-probes
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