746 research outputs found
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Fluorescent and colorimetric molecular recognition probe for hydrogen bond acceptors
YesThe association constants for formation of 1 : 1 complexes between a H-bond donor, 1-naphthol, and a diverse range of charged and neutral H-bond acceptors have been measured using UV/vis absorption and fluorescence emission titrations. The performance of 1-naphthol as a dual colorimetric and fluorescent molecular recognition probe for determining the H-bond acceptor (HBA) parameters of charged and neutral solutes has been investigated in three solvents. The data were employed to establish self-consistent H-bond acceptor parameters (β) for benzoate, azide, chloride, thiocyanate anions, a series of phosphine oxides, phosphate ester, sulfoxide and a tertiary amide. The results demonstrate both the transferability of H-bond parameters between different solvents and the utility of the naphthol-based dual molecular recognition probe to exploit orthogonal spectroscopic techniques to determine the HBA properties of neutral and charged solutes. The benzoate anion is the strongest HBA studied with a β parameter of 15.4, and the neutral tertiary amide is the weakest H-bond acceptor investigated with a β parameter of 8.5. The H-bond acceptor strength of the azide anion is higher than that of chloride (12.8 and 12.2 respectively), and the thiocyanate anion has a β value of 10.8 and thus is a significantly weaker H-bond acceptor than both the azide and chloride anions.Supported by the ESPRC
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Solvatomorphism of Reichardt's dye
YesA systematic study of the influence of solvent on the crystal packing behaviour of Reichardt's dye demonstrates that the structure of the assembly formed in the solid state depends on the nature of the solvent–solute interactions present in the solution phase. Apolar aprotic solvents lead to solvates with a hexagonal channel topology, but this supramolecular assembly is perturbed by the presence of aromatic or polar protic solvents
A solvent-resistant halogen bond
The effect of solvent on the stabilities of complexes involving a single H-bond or halogen-bond (X-bond) has been quantified. Association constants for binary complexes of 4-(phenylazo)phenol, molecular iodine, tetramethylurea and tetramethylthiourea have been measured in fifteen different solvents by UV/vis absorption and 1H NMR titration experiments. The stabilities of the H-bonded complexes decrease by more than three orders of magnitude with increasing solvent polarity. In contrast, the X-bonded complex of molecular iodine with tetramethylthiourea is remarkably insensitive to the nature of the solvent (association constants measured in alkanes and alcohols are similar). The results suggest that, in contrast to H-bonds, where electrostatics determine thermodynamic stability, charge-transfer interactions make a major contribution to the stability of these X-bonded complexes rendering them resistant to increases in solvent polarity
Decision Problems for Nash Equilibria in Stochastic Games
We analyse the computational complexity of finding Nash equilibria in
stochastic multiplayer games with -regular objectives. While the
existence of an equilibrium whose payoff falls into a certain interval may be
undecidable, we single out several decidable restrictions of the problem.
First, restricting the search space to stationary, or pure stationary,
equilibria results in problems that are typically contained in PSPACE and NP,
respectively. Second, we show that the existence of an equilibrium with a
binary payoff (i.e. an equilibrium where each player either wins or loses with
probability 1) is decidable. We also establish that the existence of a Nash
equilibrium with a certain binary payoff entails the existence of an
equilibrium with the same payoff in pure, finite-state strategies.Comment: 22 pages, revised versio
Transcending Lifshitz theory: reliable prediction of adhesion forces between hydrocarbon surfaces in condensed phases using molecular contact thermodynamics
Lifshitz theory is widely used to calculate interfacial interaction energies and underpins established approaches to the interpretation of measurement data from experimental methods including the surface forces apparatus and the atomic force microscope. However, a significant limitation of Lifshitz theory is that it uses the bulk dielectric properties of the medium to predict the work of adhesion. Here, we demonstrate that a different approach, in which the interactions between molecules at surfaces and in the medium are described by a set of surface site interaction points (SSIPs), yields interaction free energies that are correlated better with experimentally determined values. The work of adhesion W(Lifshitz) between hydrocarbon surfaces was calculated in 260 liquids using Lifshitz theory and compared with interaction free energies ΔΔG calculated using the SSIP model. The predictions of these models diverge in significant ways. In particular, ΔΔG values for hydrocarbon surfaces are typically small and vary little, but in contrast, W(Lifshitz) values span 4 orders of magnitude. Moreover, the SSIP model yields significantly different ΔΔG values in some liquids for which Lifshitz theory predicts similar values of W(Lifshitz). These divergent predictions were tested using atomic force microscopy. Experimentally determined works of adhesion were closer to the values predicted using the SSIP model than Lifshitz theory. In mixtures of methanol and benzyl alcohol, even greater differences were found in the interaction energies calculated using the two models: the value of ΔΔG calculated using the SSIP model declines smoothly as the benzyl alcohol concentration increases, and values are well correlated with experimental data; however, W(Lifshitz) decreases to a minimum and then increases, reaching a larger value for benzyl alcohol than for methanol. We conclude that the SSIP model provides more reliable estimates of the work of adhesion than Lifshitz theory
Simvastatin Prevents and Reverses Depigmentation in a Mouse Model of Vitiligo
Vitiligo is a common autoimmune disease of the skin that results in disfiguring white spots. There are no Food and Drug Administration (FDA)-approved treatments, and current treatments are time-consuming, expensive, and of low efficacy. We sought to identify new treatments for vitiligo, and first considered repurposed medications because of the availability of safety data and expedited regulatory approval. We previously reported that the IFN-γ-induced chemokine CXCL10 is expressed in lesional skin from vitiligo patients, and that it is critical for the progression and maintenance of depigmentation in our mouse model of vitiligo. We hypothesized that targeting IFN-γ signaling might be an effective new treatment strategy. Activation of signal transducer and activator of transcription 1 (STAT1) is required for IFN-γ signaling and recent studies revealed that simvastatin, an FDA-approved cholesterol-lowering medication, inhibited STAT1 activation in vitro. Therefore, we hypothesized that simvastatin may be an effective treatment for vitiligo. We found that simvastatin both prevented and reversed depigmentation in our mouse model of vitiligo, and reduced the number of infiltrating autoreactive CD8+ T cells in the skin. Treatment of melanocyte-specific, CD8+ T cells in vitro decreased proliferation and IFN-γ production, suggesting additional effects of simvastatin directly on T cells. Based on these data, simvastatin may be a safe, targeted treatment option for patients with vitiligo. © 2015 The Society for Investigative Dermatology
Effects of supplementation of limit-fed growing diets with either soybean meal or nonenzymatically browned soybean meal on steer performance
Seventy two individually fed Angus × Hereford
steers (642 lb) were used to evaluate the
effects of supplementing limit-fed, growing diets
with either soybean meal (SBM) or nonenzymatically
browned soybean meal (NSBM).
Eight steers were allotted to a control diet
composed of 39.1% high-moisture corn, 42%
cottonseed hulls, 10.4% ground corn, 5% cane
molasses 2.25% urea, and 1.5% vitamins and
minerals (dry basis). The remaining steers were
allotted to diets that derived 100, 80, 60, or
40% of their supplemental protein from SBM or
60, 45, 30, or 15% of their supplemental protein
from NSBN. The balance of supplemental
protein came from urea. All diets were formulated
to contain 13.0% crude protein (dry
basis). Steers were fed once daily for 80 days
at 2.25% of BW. Average daily gain and
efficiency did not differ (P>.05) between
sources (ADG=1.932 + .103 × (% CP from
SBM) + .097 × (% CP from NSBM);
gain:feed=.140 + .0058 × (% CP from SBM) +
.0051 × (% CP from NSBM)). The lack of
response to NBSBM supplementation above
that for SBM suggests that either degradable
intake protein was limiting in the basal diet or a
large proportion of the amino acids in the
NSBM were unavailable due to overprocessing
Assessment of Current Jet Noise Prediction Capabilities
An assessment was made of the capability of jet noise prediction codes over a broad range of jet flows, with the objective of quantifying current capabilities and identifying areas requiring future research investment. Three separate codes in NASA s possession, representative of two classes of jet noise prediction codes, were evaluated, one empirical and two statistical. The empirical code is the Stone Jet Noise Module (ST2JET) contained within the ANOPP aircraft noise prediction code. It is well documented, and represents the state of the art in semi-empirical acoustic prediction codes where virtual sources are attributed to various aspects of noise generation in each jet. These sources, in combination, predict the spectral directivity of a jet plume. A total of 258 jet noise cases were examined on the ST2JET code, each run requiring only fractions of a second to complete. Two statistical jet noise prediction codes were also evaluated, JeNo v1, and Jet3D. Fewer cases were run for the statistical prediction methods because they require substantially more resources, typically a Reynolds-Averaged Navier-Stokes solution of the jet, volume integration of the source statistical models over the entire plume, and a numerical solution of the governing propagation equation within the jet. In the evaluation process, substantial justification of experimental datasets used in the evaluations was made. In the end, none of the current codes can predict jet noise within experimental uncertainty. The empirical code came within 2dB on a 1/3 octave spectral basis for a wide range of flows. The statistical code Jet3D was within experimental uncertainty at broadside angles for hot supersonic jets, but errors in peak frequency and amplitude put it out of experimental uncertainty at cooler, lower speed conditions. Jet3D did not predict changes in directivity in the downstream angles. The statistical code JeNo,v1 was within experimental uncertainty predicting noise from cold subsonic jets at all angles, but did not predict changes with heating of the jet and did not account for directivity changes at supersonic conditions. Shortcomings addressed here give direction for future work relevant to the statistical-based prediction methods. A full report will be released as a chapter in a NASA publication assessing the state of the art in aircraft noise prediction
Betaine as a dietary supplement for finishing cattle
One hundred seventy five steers (902 lb
initial body weight) were used in a finishing
study to determine the effect of betaine,
provided either as feed-grade betaine
(Betafin-S6, Finnsugar Bioproducts) or as
concentrated separator by-product (CSB; desugared
beet molasses), on animal performance and carcass characteristics. Steers were fed a finishing diet based on steam-flaked and dry-rolled corn. Treatments included 10.5 or 21 g/steer daily supplemental feed-grade betaine or 250 g (15.5 betaine) or 500 g (31 g betaine) of CSB per steer
daily. Dry matter intakes increased (linear,
P<0.1) for steers supplemented with feed-
grade betaine. Average daily gains and feed
efficiencies were not affected by treatments.
Dressing percent and twelfth rib back fat
increased (P<0.1) for steers that received
feed-grade betaine. Rib-eye area decreased
(P<0.1) when steers were supplemented with
either feed-grade betaine or CSB. Yield
grades were significantly higher (linear,
P<0.1) for cattle receiving supplemental CSB
or feed-grade betaine (quadratic, P<.05). Hot carcass weights, KPH, marbling scores, and percentage of carcasses grading USDA
Choice were not affected by supplemental
betaine. In this study, betaine supplementation did not markedly alter growth performance, but carcass fatness tended to increase
for both supplements
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Combined virtual/experimental multicomponent solid forms screening of sildenafil: new salts, cocrystals, and hybrid salt-cocrystals
YesNew multicomponent solid forms of sildenafil have been discovered
by means of a combined virtual/experimental cocrystal screening. Coformer
selection of candidates was conducted based on an in silico screening method from
a database of more than 2000 organic compounds, and the intensive experimental
screen produced 23 new solid forms. Since the 12 coformers chosen have a
combination of phenol and carboxylic acid groups, a variety of cocrystals, salts, and
hybrid salt-cocrystals were discovered and characterized
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