11,002 research outputs found
Quasi-Chemical and Structural Analysis of Polarizable Anion Hydration
Quasi-chemical theory is utilized to analyze the roles of solute polarization
and size in determining the structure and thermodynamics of bulk anion
hydration for the Hofmeister series Cl, Br, and I. Excellent
agreement with experiment is obtained for whole salt hydration free energies
using the polarizable AMOEBA force field. The quasi-chemical approach exactly
partitions the solvation free energy into inner-shell, outer-shell packing, and
outer-shell long-ranged contributions by means of a hard-sphere condition.
Small conditioning radii, even well inside the first maximum of the
ion-water(oxygen) radial distribution function, result in Gaussian behavior for
the long-ranged contribution that dominates the ion hydration free energy. The
spatial partitioning allows for a mean-field treatment of the long-ranged
contribution, leading to a natural division into first-order electrostatic,
induction, and van der Waals terms. The induction piece exhibits the strongest
ion polarizability dependence, while the larger-magnitude first-order
electrostatic piece yields an opposing but weaker polarizability dependence. In
addition, a structural analysis is performed to examine the solvation
anisotropy around the anions. As opposed to the hydration free energies, the
solvation anisotropy depends more on ion polarizability than on ion size:
increased polarizability leads to increased anisotropy. The water dipole
moments near the ion are similar in magnitude to bulk water, while the ion
dipole moments are found to be significantly larger than those observed in
quantum mechanical studies. Possible impacts of the observed over-polarization
of the ions on simulated anion surface segregation are discussed.Comment: slight revision, in press at J. Chem. Phy
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Nox2 redox signaling maintains essential cell populations in the brain.
Reactive oxygen species (ROS) are conventionally classified as toxic consequences of aerobic life, and the brain is particularly susceptible to ROS-induced oxidative stress and damage owing to its high energy and oxygen demands. NADPH oxidases (Nox) are a widespread source of brain ROS implicated in seizures, stroke and neurodegeneration. A physiological role for ROS generation in normal brain function has not been established, despite the fact that mice and humans lacking functional Nox proteins have cognitive deficits. Using molecular imaging with Peroxyfluor-6 (PF6), a new selective fluorescent indicator for hydrogen peroxide (H(2)O(2)), we show that adult hippocampal stem/progenitor cells (AHPs) generate H(2)O(2) through Nox2 to regulate intracellular growth signaling pathways, which in turn maintains their normal proliferation in vitro and in vivo. Our results challenge the traditional view that brain ROS are solely deleterious by demonstrating that controlled ROS chemistry is needed for maintaining specific cell populations
A Model Of Information Technology Impacts: An Invariance Analysis By Executive Position
The invariance, by executive position in the organization, of an information technology impacts model is examined. The theoretical model links computer training, end-user previous computer experience, information (provided by the system) quality, ease of system use, customer knowledge in the firm’s industry, and the tasks performed using the system to individual and firm performance impacts through system use and satisfaction. The empirical examination uses data from a national mail survey. The respondents are business executives at four different organizational levels (i.e., owners, senior executives, marketing executives, and middle/operational executives). The quantitative technique used is invariance analysis based on structural equation modeling. The results indicate that the interrelationships among the theoretical constructs in the model are generally invariant across these different organizational positions. The one difference identified is the path from information quality to system use. Examining each executive group individually shows that this path is significant for marketing executives, but no other executive group. Thus, the identified difference appears to be produced by the importance of information quality on marketing executives’ use of computer systems. Managerial implications, conclusions, and suggestions for future research are discussed based upon these results
Ab initio investigation of intermolecular interactions in solid benzene
A computational strategy for the evaluation of the crystal lattice constants
and cohesive energy of the weakly bound molecular solids is proposed. The
strategy is based on the high level ab initio coupled-cluster determination of
the pairwise additive contribution to the interaction energy. The
zero-point-energy correction and non-additive contributions to the interaction
energy are treated using density functional methods. The experimental crystal
lattice constants of the solid benzene are reproduced, and the value of 480
meV/molecule is calculated for its cohesive energy
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Dynamic Clinical Data Mining: Search Engine-Based Decision Support
The research world is undergoing a transformation into one in which data, on massive levels, is freely shared. In the clinical world, the capture of data on a consistent basis has only recently begun. We propose an operational vision for a digitally based care system that incorporates data-based clinical decision making. The system would aggregate individual patient electronic medical data in the course of care; query a universal, de-identified clinical database using modified search engine technology in real time; identify prior cases of sufficient similarity as to be instructive to the case at hand; and populate the individual patient's electronic medical record with pertinent decision support material such as suggested interventions and prognosis, based on prior outcomes. Every individual's course, including subsequent outcomes, would then further populate the population database to create a feedback loop to benefit the care of future patients
Electrical Modification of Combustion and the Affect of Electrode Geometry on the Field Produced
There has been extensive work to show how electric fields can influence combustion. However, many different set ups are used. This work shows how different set ups produce different field strengths and that the field is not always uniformly distributed. The field strength is modelled using Ansys Maxwell. The type of material used is discussed and the set up of apparatus. It is recommended to use parallel plates for experimentation. Parallel plates produce the most uniform field this allow's it's influence to be directly investigated and related to the field strength
Reducing dietary wild derived fishmeal inclusion levels in production diets for large yellowtail kingfish (Seriola lalandi)
Further research to understand the effect of dietary wild derived fishmeal (WD-FM) substitution with commercially relevant alternative ingredients for large yellowtail kingfish (Seriola lalandi; YTK) was investigated. This 36-week study was designed to replace dietary inclusions of WD-FM with alternative protein ingredients including poultry meal, soy protein concentrate and by-product fishmeal (PM, SPC and BP-FM) and measure the effect on the growth performance, feed utilisation, and health of large YTK (2.5 kg initial weight) at ambient water temperatures (average 16.6 °C). Six diets were formulated on a digestible basis to contain 39% digestible protein (∼45–46% crude protein), 23% digestible lipid (∼24–25% crude lipid), and a digestible energy level of 17 MJ kg−1 (∼19 MJ kg−1 gross energy level). Fish were fed to apparent satiation once daily at 10:00 h. Substitution of fish meal with alternative ingredients did not significantly impact fish growth, feed utilisation, gastrointestinal health, blood haematology or measured biochemistry indices. Results from the current study will allow reductions to the dietary WD-FM inclusion levels, with tangible sustainability benefits. The inclusion of the alternative protein sources resulted in improvements in the fish in-fish out ratios of up to 35.1%. This study suggests formulation criteria for large YTK should include a minimum of 10% WD-FM. Further to this, at least 30% of the diet should consist of a combination of poultry meal, soy protein concentrate and fishmeal (both wild and by-product). Our data further support the use of BP-FM up to ∼20% inclusion, while PM and SPC should be limited to ∼10% inclusion until further data is available on these raw materials in YTK feeds. These recommendations will facilitate formulation flexibility for large YTK feeds, enabling formulators to adapt to changes to extrinsic factors such as raw material availability, and sustainability while minimising cost and performance impacts
Using 3D gastrointestinal tract in vitro models with microfold cells and mucus secreting ability to assess the hazard of copper oxide nanomaterials
Abstract:
Background: Copper oxide nanomaterials (CuO NMs) are exploited in many products including inks, cosmetics,
textiles, wood preservatives and food contact materials. Their incorporation into these products may enhance oral
exposure in consumer, environmental and occupational settings. Undifferentiated and differentiated monocultures of
Caco-2 cells are commonly used to assess NM toxicity to the intestine in vitro. However, the integration of other cell
types into Caco-2 in vitro models increases their physiological relevance. Therefore, the aim of this study is to evaluate
the toxicity of CuO NMs and copper sulphate (
CuSO4) to intestinal microfold (M) cell (Caco-2/Raji B) and mucus secreting
(Caco-2/HT29-MTX) co-culture in vitro models via assessment of their impact on barrier integrity, viability and
interleukin (IL)-8 secretion. The translocation of CuO NMs and CuSO4
across the intestinal barrier was also investigated
in vitro.
Results: CuO NMs and CuSO4
impaired the function of the intestinal barrier in the co-culture models [as indicated by
a reduction in transepithelial electrical resistance (TEER) and Zonular occludens (ZO-1) staining intensity]. Cu translocation
was observed in both models but was greatest in the Caco-2/Raji B co-culture. CuO NMs and CuSO4
stimulated
an increase in IL-8 secretion, which was greatest in the Caco-2/HT29-MTX co-culture model. CuO NMs and CuSO4
did not stimulate a loss of cell viability, when assessed using light microscopy, nuclei counts and scanning electron
microscopy. CuO NMs demonstrated a relatively similar level of toxicity to CuO4
in both Caco-2/Raji B and Caco-2/
HT29-MTX co- culture models.
Conclusions: The Caco-2/Raji B co-culture model was more sensitive to CuO NM and CuSO4
toxicity than the
Caco-2/HT29-MTX co-culture model. However, both co-culture models were less sensitive to CuO NM and CuSO4
toxicity than simple monocultures of undifferentiated and differentiated Caco-2 cells, which are more routinely used
to investigate NM toxicity to the intestine. Obtained data can therefore feed into the design of future studies which
assess the toxicity of substances (e.g. NMs) and pathogens to the intestine (e.g. by informing model and endpoint
selection). However, more testing with a wider panel of NMs would be beneficial in order to help select which in vitro
models and endpoints to prioritise when screening the safety of ingested NMs. Comparisons with in vivo findings will
also be essential to identify the most suitable in vitro model to screen the safety of ingested NMs
Epistemic Uncertainty-Weighted Loss for Visual Bias Mitigation
Deep neural networks are highly susceptible to learning biases in visual
data. While various methods have been proposed to mitigate such bias, the
majority require explicit knowledge of the biases present in the training data
in order to mitigate. We argue the relevance of exploring methods which are
completely ignorant of the presence of any bias, but are capable of identifying
and mitigating them. Furthermore, we propose using Bayesian neural networks
with an epistemic uncertainty-weighted loss function to dynamically identify
potential bias in individual training samples and to weight them during
training. We find a positive correlation between samples subject to bias and
higher epistemic uncertainties. Finally, we show the method has potential to
mitigate visual bias on a bias benchmark dataset and on a real-world face
detection problem, and we consider the merits and weaknesses of our approach.Comment: To be published in 2022 IEEE CVPR Workshop on Fair, Data Efficient
and Trusted Computer Visio
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