8,024 research outputs found
Vlasov Description Of Dense Quark Matter
We discuss properties of quark matter at finite baryon densities and zero
temperature in a Vlasov approach. We use a screened interquark Richardson's
potential consistent with the indications of Lattice QCD calculations.
We analyze the choices of the quark masses and the parameters entering the
potential which reproduce the binding energy (B.E.) of infinite nuclear matter.
There is a transition from nuclear to quark matter at densities 5 times above
normal nuclear matter density. The transition could be revealed from the
determination of the position of the shifted meson masses in dense baryonic
matter. A scaling form of the meson masses in dense matter is given.Comment: 15 pages 4 figure
In vitro antioxidant capacities and antidiabetic properties of phenolic extracts from selected citrus peels
This study aims to determine the antioxidant capacities (AC) and antidiabetic properties of phenolic extracts (free and bound) from white Tambun pomelo peels, kaffir lime peels, lime peels and calamansi peels. AC, total phenolic content (TPC) and antidiabetic properties of selected citrus peels extracts were determined pectrophotometrically using 2,2-Diphenyl-1-picrylhydrazyl free radical (DPPH) scavenging, ferric-reducing antioxidant power (FRAP), Folin-Ciocalteu (FC) and α-amylase and α-glucosidase inhibition assay, respectively. This study found that the methanolic extract of kaffir lime showed the best AC with the lowest IC50 value of DPPH radical (7.51 ± 0.50 mg/ml) and highest FRAP value [369.48 ± 20.15 mM Fe (II) E/g DW]. TPC of free phenolic extracts of all citrus peels were significantly (p< 0.05) higher compared to the bound phenolic extracts with extract of calamansi showed the highest TPC. Free- and bound phenolic extract of calamansi also had the highest α-amylase inhibition activity (61.79 ± 4.13%; 45.30 ± 5.35%) respectively. The highest inhibitory effect in α-glucosidase inhibition assay of free- and bound phenolic extracts were white Tambun pomelo (41.06 ± 10.94%) and calamansi (43.99 ± 22.03%) respectively. Hence, the citrus peels could be furthered study for their potential in management and/or prevention of diabetes
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On the mechanism of protein fold-switching by a molecular sensor
Alternate frame folding (AFF) is a mechanism by which conformational change can be engineered into a protein. The protein structure switches from the wild-type fold (N) to a circularly-permuted fold (N\u27), or vice versa, in response to a signaling event such as ligand binding. Despite the fact that the two native states have similar structures, their interconversion involves folding and unfolding of large parts of the molecule. This rearrangement is reported by fluorescent groups whose relative proximities change as a result of the order-disorder transition. The nature of the conformational change is expected to be similar from protein to protein; thus, it may be possible to employ AFF as a general method to create optical biosensors. Toward that goal, we test basic aspects of the AFF mechanism using the AFF variant of calbindin D(9k). A simple three-state model for fold switching holds that N and N\u27 interconvert through the unfolded state. This model predicts that the fundamental properties of the switch--calcium binding affinity, signal response (i.e., fluorescence change upon binding), and switching rate--can be controlled by altering the relative stabilities of N and N\u27. We find that selectively destabilizing N or N\u27 changes the equilibrium properties of the switch (binding affinity and signal response) in accordance with the model. However, kinetic data indicate that the switching pathway does not require whole-molecule unfolding. The rate is instead limited by unfolding of a portion of the protein, possibly in concert with folding of a corresponding region
The Dynamical Distinction between Elliptical and Lenticular Galaxies in Distant Clusters: Further Evidence for the Recent Origin of S0 Galaxies
We examine resolved spectroscopic data obtained with the Keck II telescope
for 44 spheroidal galaxies in the fields of two rich clusters, Cl0024+16
(z=0.40) and MS0451-03 (z=0.54), and contrast this with similar data for 23
galaxies within the redshift interval 0.3<z<0.65 in the GOODS northern field.
For each galaxy we examine the case for systemic rotation, derive central
stellar velocity dispersions sigma and photometric ellipticities, epsilon.
Using morphological classifications obtained via Hubble Space Telescope imaging
as the basis, we explore the utility of our kinematic quantities in
distinguishing between pressure-supported ellipticals and
rotationally-supported lenticulars (S0s). We demonstrate the reliability of
using the v/(1-epsilon) vs sigma and v/sigma vs epsilon distributions as
discriminators, finding that the two criteria correctly identify 63%+-3% and
80%+-2% of S0s at z~0.5, respectively, along with 76%+8-3% and 79%+-2% of
ellipticals. We test these diagnostics using equivalent local data in the Coma
cluster, and find that the diagnostics are similarly accurate at z=0. Our
measured accuracies are comparable to the accuracy of visual classification of
morphologies, but avoid the band-shifting and surface brightness effects that
hinder visual classification at high redshifts. As an example application of
our kinematic discriminators, we then examine the morphology-density relation
for elliptical and S0 galaxies separately at z~0.5. We confirm, from kinematic
data alone, the recent growth of rotationally-supported spheroidals. We discuss
the feasibility of extending the method to a more comprehensive study of
cluster and field galaxies to z~1, in order to verify in detail the recent
density-dependent growth of S0 galaxies.Comment: 7 pages, 4 figures, updated with version accepted to Ap
Microminiaturized, biopotential conditioning system (MBCS)
Multichannel, medical monitoring system allows almost complete freedom of movement for subject during monitoring periods. System comprises monitoring unit (biobelt), transmission line, and data acquisition unit. Belt, made of polybenzimidizole fabric, is wrapped around individual's waist and held in place by overlapping sections of Velcro closure material
Evaluation of three accelerometer devices for physical activity measurement amongst south Asians and Europeans
We recruited 62 South Asians and 40 Europeans aged 25 to 75 years, to assess the potential validity of three physical activity accelerometers for use amongst South Asians. Participants completed an exercise treadmill test (following Bruce protocol) while wearing the 3 accelerometers: Actigraph GT3X+ [GT3X+] and Geneactiv [GA] on ankle, waist and wrist; and Actiheart [AH] on chest. We compared relationships between energy expenditure (EE) measured by accelerometers (Measured) and actual EE on the treadmill (Actual) in the two ethnicities and tested for potential confounding effects. All accelerometers under-reported EE. Difference between Measured and Actual EE was smallest for GT3X+ankle (Measured – Actual at peak exercise [Mets]: GT3X+ankle –6.52 (1.77); GT3X+waist –8.46 (1.29); GT3X+wrist –11.17 (1.03); GAankle –8.17 (1.19); GAwaist –10.24 (0.64); GAwrist –11.21 (1.10); AHchest –9.09 (1.43), P 0.05). Relationship between Measured and Actual EE was not influenced by age, gender, height, waist, weight or waist-hip ratio (all P > 0.05). Amongst the devices and positions tested, GT3X+ankle is the most accurate device for measuring EE during an exercise treadmill test. Accelerometer performance is similar in South Asians and Europeans and is not influenced by anthropometric differences between the two populations
Toward Interpretable Deep Reinforcement Learning with Linear Model U-Trees
Deep Reinforcement Learning (DRL) has achieved impressive success in many
applications. A key component of many DRL models is a neural network
representing a Q function, to estimate the expected cumulative reward following
a state-action pair. The Q function neural network contains a lot of implicit
knowledge about the RL problems, but often remains unexamined and
uninterpreted. To our knowledge, this work develops the first mimic learning
framework for Q functions in DRL. We introduce Linear Model U-trees (LMUTs) to
approximate neural network predictions. An LMUT is learned using a novel
on-line algorithm that is well-suited for an active play setting, where the
mimic learner observes an ongoing interaction between the neural net and the
environment. Empirical evaluation shows that an LMUT mimics a Q function
substantially better than five baseline methods. The transparent tree structure
of an LMUT facilitates understanding the network's learned knowledge by
analyzing feature influence, extracting rules, and highlighting the
super-pixels in image inputs.Comment: This paper is accepted by ECML-PKDD 201
Theory of monolayers with boundaries: Exact results and Perturbative analysis
Domains and bubbles in tilted phases of Langmuir monolayers contain a class
of textures knows as boojums. The boundaries of such domains and bubbles may
display either cusp-like features or indentations. We derive analytic
expressions for the textures within domains and surrounding bubbles, and for
the shapes of the boundaries of these regions. The derivation is perturbative
in the deviation of the bounding curve from a circle. This method is not
expected to be accurate when the boundary suffers large distortions, but it
does provide important clues with regard to the influence of various energetic
terms on the order-parameter texture and the shape of the domain or bubble
bounding curve. We also look into the effects of thermal fluctuations, which
include a sample-size-dependent effective line tension.Comment: replaced with published version, 21 pages, 16 figures include
Efficient calculation of imaginary time displaced correlation functions in the projector auxiliary field quantum Monte-Carlo algorithm
The calculation of imaginary time displaced correlation functions with the
auxiliary field projector quantum Monte-Carlo algorithm provides valuable
insight (such as spin and charge gaps) in the model under consideration. One of
the authors and M. Imada [F.F. Assaad and M. Imada, J. Phys. Soc. Jpn. 65 189
(1996).] have proposed a numerically stable method to compute those quantities.
Although precise this method is expensive in CPU time. Here, we present an
alternative approach which is an order of magnitude quicker, just as precise,
and very simple to implement. The method is based on the observation that for a
given auxiliary field the equal time Green function matrix, , is a
projector: .Comment: 4 papes, 1 figure in eps forma
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