3,707 research outputs found
Root Cause Analysis and Method Development of Calorimetry Experiments
First year chemistry students learn a broad range of concepts that are also proven out in the lab environment. These concepts are a basis for a solid foundation for future chemistry learning. When the lab experiments don’t produce the expected results, students understanding in these concepts diminish and overall confidence and grades suffer. Our project details the root cause analysis and subsequent method development work for two experiments related to calorimetry; heat of solution and freezing point depression. The team sought to refine these experiments after finding that many of the students were unable to generate the expected results for the experiment. The focus of the work was twofold; 1) determine the cause of the failures and 2) recommend and validate changes to the current experiments. Isolating and mitigating the issues impacting these experiments should provide future students with a deeper understanding of chemistry and how it is applied to various situations
The Determinants of Mortality
Mortality rates have fallen dramatically over time, starting in a few countries in the 18th century, and continuing to fall today. In just the past century, life expectancy has increased by over 30 years. At the same time, mortality rates remain much higher in poor countries, with a difference in life expectancy between rich and poor countries of also about 30 years. This difference persists despite the remarkable progress in health improvement in the last half century, at least until the HIV/AIDS pandemic. In both the time-series and the cross-section data, there is a strong correlation between income per capita and mortality rates, a correlation that also exists within countries, where richer, better-educated people live longer. We review the determinants of these patterns: over history, over countries, and across groups within countries. While there is no consensus about the causal mechanisms, we tentatively identify the application of scientific advance and technical progress (some of which is induced by income and facilitated by education) as the ultimate determinant of health. Such an explanation allows a consistent interpretation of the historical, cross-country, and within-country evidence. We downplay direct causal mechanisms running from income to health.
Physics-Based Swarm Intelligence for Disaster Relief Communications
This study explores how a swarm of aerial mobile vehicles can provide network
connectivity and meet the stringent requirements of public protection and
disaster relief operations. In this context, we design a physics-based
controlled mobility strategy, which we name the extended Virtual Force Protocol
(VFPe), allowing self-propelled nodes, and in particular here unmanned aerial
vehicles, to fly autonomously and cooperatively. In this way, ground devices
scattered on the operation site may establish communications through the
wireless multi-hop communication routes formed by the network of aerial nodes.
We further investigate through simulations the behavior of the VFPe protocol,
notably focusing on the way node location information is disseminated into the
network as well as on the impact of the number of exploration nodes on the
overall network performance.Comment: in International Conference on Ad Hoc Networks and Wireless, Jul
2016, Lille, Franc
Dental Pulp-derived Stem Cells (DPSC) Differentiation In Vitro into Odontoblast and Neuronal Progenitors during Cell Passaging is Associated with Alterations in Cell Survival and Viability
Early onset airway obstruction in response to organic dust in the horse
Equine recurrent airway obstruction (RAO) has been used as a naturally occurring model of human asthma. However, it is unknown whether there is an early-phase response in RAO. The aim of this study was to determine whether exposure to organic dust induces immediate changes in lung function in RAO-affected horses, which could be mediated by airway mast cells. Six RAO-affected horses in remission and six control horses were challenged with hay-straw dust suspension by nebulization. Total respiratory resistance at 1 Hz, measured by forced oscillation, was increased from 0.62 +/- 0.09 cmH(2)O.l(-1).s (mean +/- SE) to 1.23 +/- 0.20 cmH(2)O.l(-1).s 15 min after nebulization in control horses (P = 0.023) but did not change significantly in the RAO group. Total respiratory reactance at 1 Hz (P = 0.005) was significantly lower in the control horses (-0.77 +/- 0.07 cmH(2)O.l(-1).s) than in the RAO group (-0.49 +/- 0.04 cmH(2)O.l(-1).s) 15 min after nebulization. Bronchoalveolar lavage fluid (BALF) histamine concentration was significantly elevated 10 and 20 min postnebulization in control horses but not in RAO horses. Minimum reactance at 1 Hz in the early postnebulization period significantly correlated with both prechallenge BALF mast cell numbers (r = -0.65, P = 0.02) and peak BALF histamine concentration postnebulization (r = -0.61, P = 0.04). In conclusion, RAO horses, unlike human asthmatic patients, do not exhibit an early-phase response. However, healthy control horses do demonstrate a mild but significant early (<20 min) phase response to inhaled organic dust. This response may serve to decrease the subsequent dose of dust inhaled and as such provide a protective mechanism, which may be compromised in RAO horses
Role of CpG island methylation and MBD2 in immune cell gene regulation
The phenomenon of cell type-specific DNA methylation has received much attention
in recent years and a number of DNA methylation differences have been described
between cells of the immune system. Of particular interest when studying DNA
methylation are CpG islands (CGIs) which are distinct from the rest of the genome
due to their elevated CpG content, generally unmethylated state and promoter
association. In the instances when they become methylated this is associated with
gene repression although it is unclear the extent to which differential methylation
corresponds to differential gene expression. I have used an immune system model to
assess the role of CGI methylation and the role of the methylation reader MBD2 in
regulation of gene expression.
A relatively small number of DNA methylation differences were seen between
immune cell types with the most developmentally related cells showing the fewest
methylation differences. Interestingly, the vast majority of CGI-associated cellspecific
methylation occurred at intragenic CGIs located, not at transcription start
sites, but in the gene body. Increased intragenic CGI methylation tended to associate
with gene repression, although the precise reason for this remains unclear. Most
differentially methylated CGIs were depleted for the active chromatin mark
H3K4me3 regardless of their methylation state but some of these were associated
with the silencing mark H3K27me3 when unmethylated. These findings suggest that
intragenic CGIs are a distinct class of genomic element particularly susceptible to
cell type-specific methylation. I also looked at the effect of removing the methyl-
CpG binding domain protein MBD2 from immune system cells. Immune cells from
Mbd2-/- mice showed a number of previously uncharacterised phenotypes as well as
a number of differences in gene expression compared to wild-type animals. Most of
these genes increased their expression in the absence of MBD2 consistent with
MBD2’s role as a transcriptional repressor and Mbd2-/- Th1 cells showed increases
in histone H3 acetylation compared to wild-type Th1 cells. This work provides an
insight into the role played by cell-specific CGI methylation and MBD2 in regulating
gene expression
Neutron star-black hole mergers with a nuclear equation of state and neutrino cooling: Dependence in the binary parameters
We present a first exploration of the results of neutron star-black hole
mergers using black hole masses in the most likely range of
, a neutrino leakage scheme, and a modeling of the neutron
star material through a finite-temperature nuclear-theory based equation of
state. In the range of black hole spins in which the neutron star is tidally
disrupted (), we show that the merger consistently
produces large amounts of cool (), unbound,
neutron-rich material (). A comparable
amount of bound matter is initially divided between a hot disk () with typical neutrino luminosity , and a cooler tidal tail. After a short period of rapid
protonization of the disk lasting , the accretion disk cools
down under the combined effects of the fall-back of cool material from the
tail, continued accretion of the hottest material onto the black hole, and
neutrino emission. As the temperature decreases, the disk progressively becomes
more neutron-rich, with dimmer neutrino emission. This cooling process should
stop once the viscous heating in the disk (not included in our simulations)
balances the cooling. These mergers of neutron star-black hole binaries with
black hole masses and black hole spins high
enough for the neutron star to disrupt provide promising candidates for the
production of short gamma-ray bursts, of bright infrared post-merger signals
due to the radioactive decay of unbound material, and of large amounts of
r-process nuclei.Comment: 20 pages, 19 figure
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