1,040 research outputs found
Mathematical models of magnetospheric convection and its coupling to the ionosphere
Mathematical models of magnetospheric convection and its coupling to ionospher
Recognition and Accommodation at the Androgen Receptor Coactivator Binding Interface
Prostate cancer is a leading killer of men in the industrialized world. Underlying this disease is the aberrant action of the androgen receptor (AR). AR is distinguished from other nuclear receptors in that after hormone binding, it preferentially responds to a specialized set of coactivators bearing aromatic-rich motifs, while responding poorly to coactivators bearing the leucine-rich “NR box” motifs favored by other nuclear receptors. Under normal conditions, interactions with these AR-specific coactivators through aromatic-rich motifs underlie targeted gene transcription. However, during prostate cancer, abnormal association with such coactivators, as well as with coactivators containing canonical leucine-rich motifs, promotes disease progression. To understand the paradox of this unusual selectivity, we have derived a complete set of peptide motifs that interact with AR using phage display. Binding affinities were measured for a selected set of these peptides and their interactions with AR determined by X-ray crystallography. Structures of AR in complex with FxxLF, LxxLL, FxxLW, WxxLF, WxxVW, FxxFF, and FxxYF motifs reveal a changing surface of the AR coactivator binding interface that permits accommodation of both AR-specific aromatic-rich motifs and canonical leucine-rich motifs. Induced fit provides perfect mating of the motifs representing the known family of AR coactivators and suggests a framework for the design of AR coactivator antagonists
Spectroscopic parameters for silacyclopropynylidene, SiC, from extensive astronomical observations toward CW Leo (IRC +10216) with the Herschel satellite
A molecular line survey has been carried out toward the carbon-rich
asymptotic giant branch star CW Leo employing the HIFI instrument on board of
the Herschel satellite. Numerous features from 480 GHz to beyond 1100 GHz could
be assigned unambiguously to the fairly floppy SiC molecule. However,
predictions from laboratory data exhibited large deviations from the observed
frequencies even after some lower frequency data from this survey were
incorporated into a fit. Therefore, we present a combined fit of all available
laboratory data together with data from radio-astronomical observations.Comment: 7 pages, 1 figure, J. Mol. Spectrosc., appeared; CDMS links corrected
(version 2; current version: 3; may be updated later this year
Crystal growth of copper-rich ytterbium compounds: The predicted giant unit cell structures YbCu4.4 and YbCu4.25
Two new phases YbCu4.4 and YbCu4.25 are found as a result of careful phase
diagram investigations. Between the congruent and peritectic formation of
YbCu4.5 and YbCu3.5, respectively, the phases YbCu4.4 and YbCu4.25 are formed
peritectically at 934(2)degC and 931(3)degC. Crystal growth was realised using
a Bridgman technique and single crystalline grains of about 50-100 10^{-6}m
were analyzed by electron diffraction and single crystal X-ray diffraction. Due
to the only slight differences in both compositions and formation temperatures
the growth of larger single crystals of a defined superstructure is
challenging. The compounds YbCu4.4 and YbCu4.25 fit in Cerny`s (J. Solid State
Chem. 174 (2003) 125) building principle {(RECu5)n(RECu2)} where RE = Yb with n
= 4 and 3. YbCu4.4 and YbCu4.25 base on AuBe5/MgCu2-type substructures and
contain approximately 4570 and 2780 atoms per unit cell. The new phases close
the gap in the series of known copper-rich rare earth compounds for n = 1, 2
(DyCu3.5, DyCu4.0) and n = 5 (YbCu4.5, DyCu4.5)
Quark Number Susceptibility with Finite Chemical Potential in Holographic QCD
We study the quark number susceptibility in holographic QCD with a finite
chemical potential or under an external magnetic field at finite temperature.
We first consider the quark number susceptibility with the chemical potential.
We observe that approaching the critical temperature from high temperature
regime, the quark number susceptibility divided by temperature square develops
a peak as we increase the chemical potential, which confirms recent lattice QCD
results. We discuss this behavior in connection with the existence of the
critical end point in the QCD phase diagram. We also consider the quark number
susceptibility under the external magnetic field. We predict that the quark
number susceptibility exhibits a blow-up behavior at low temperature as we
raise the value of the magnetic field. We finally spell out some limitations of
our study.Comment: 25 pages, 3 figures, published versio
Evaluating Retinal Function in Age-Related Maculopathy with the ERG Photostress Test
PURPOSE. To evaluate the diagnostic potential of the electroretinogram (ERG) photostress test and the focal cone ERG in age-related maculopathy (ARM).
METHODS. The cohort comprised 31 patients with ARM and 27 age-matched control subjects. The ERG photostress test was used to monitor cone adaptation after intense light adaptation. Focal 41- and 5-Hz cone ERGs were recorded monocularly (central 20°) to assess steady state retinal function. Univariate analysis identified electrophysiological parameters that differed between groups, and receiver operating characteristic (ROC) curves were constructed to assess their diagnostic potential. Logistic regression analysis determined the diagnostic potential of a model incorporating several independent predictors of ARM.
RESULTS. The rate of recovery of the ERG photostress test was reduced (recovery was slower) in subjects with ARM. The parameter exhibited good diagnostic potential (P = 0.002, area under ROC curve = 0.74). The implicit times of the 5-Hz (a-wave, P = 0.002; b-wave, P < 0.001) and the 41-Hz (P < 0.001) focal cone ERGs were increased, and the 41-Hz focal cone ERG amplitude (P = 0.003) and focal to full-field amplitude ratio (P = 0.001) were reduced in the ARM group. Logistic regression analysis identified three independent predictors of ARM, including the rate of recovery of the ERG photostress test.
CONCLUSIONS. Early ARM has a marked effect on the kinetics of cone adaptation. The clinical application of the ERG photostress test increases the sensitivity and specificity of a model for the diagnosis of ARM. Improved assessment of the functional integrity of the central retina will facilitate early diagnosis and evaluation of therapeutic interventions
A model study of quark number susceptibility at finite temperature beyond rainbow-ladder approximation
In this paper we calculate the quark number susceptibility (QNS) of QCD at
finite temperature under the rainbow-ladder and Ball-Chiu type truncation
schemes of the Dyson-Schwinger approach. It is found that the difference
between the result of the rainbow-ladder truncation and that of Ball-Chiu type
truncation is small, which shows that the dressing effect of the quark-gluon
vertex on the QNS at finite temperature is small. It is also found that at low
temperature the quark number susceptibility is nearly zero and it increases
sharply when the temperature approaches the chiral phase transition point. A
comparison between the result in the present paper with those in the literature
is made.Comment: 17 pages, 6 figure
The U(1) Gross-Neveu Model at Non-Zero Chemical Potential
The four-fermi model with continuous chiral symmetry is studied in three
dimensions at non-zero chemical potential using both the
expansion and computer simulations. For strong coupling this model
spontaneously breaks its U(1) chiral symmetry at zero chemical potential and
the Goldstone mechanism is realized through massless pions. The computer
simulation predicts a critical chemical potential close to the lightest
fermion mass in the model. As is increased beyond , the pion
screening mass increases rapidly from zero to a nonvanishing value indicating
symmetry restoration. Some lessons are drawn relevant to lattice QCD
simulations at non-zero .Comment: 26 pages of RevTeX, + 24 figure
Salience-based selection: attentional capture by distractors less salient than the target
Current accounts of attentional capture predict the most salient stimulus to be invariably selected first. However, existing salience and visual search models assume noise in the map computation or selection process. Consequently, they predict the first selection to be stochastically dependent on salience, implying that attention could even be captured first by the second most salient (instead of the most salient) stimulus in the field. Yet, capture by less salient distractors has not been reported and salience-based selection accounts claim that the distractor has to be more salient in order to capture attention. We tested this prediction using an empirical and modeling approach of the visual search distractor paradigm. For the empirical part, we manipulated salience of target and distractor parametrically and measured reaction time interference when a distractor was present compared to absent. Reaction time interference was strongly correlated with distractor salience relative to the target. Moreover, even distractors less salient than the target captured attention, as measured by reaction time interference and oculomotor capture. In the modeling part, we simulated first selection in the distractor paradigm using behavioral measures of salience and considering the time course of selection including noise. We were able to replicate the result pattern we obtained in the empirical part. We conclude that each salience value follows a specific selection time distribution and attentional capture occurs when the selection time distributions of target and distractor overlap. Hence, selection is stochastic in nature and attentional capture occurs with a certain probability depending on relative salience
Quantum mechanical calculation of the effects of stiff and rigid constraints in the conformational equilibrium of the Alanine dipeptide
If constraints are imposed on a macromolecule, two inequivalent classical
models may be used: the stiff and the rigid one. This work studies the effects
of such constraints on the Conformational Equilibrium Distribution (CED) of the
model dipeptide HCO-L-Ala-NH2 without any simplifying assumption. We use ab
initio Quantum Mechanics calculations including electron correlation at the MP2
level to describe the system, and we measure the conformational dependence of
all the correcting terms to the naive CED based in the Potential Energy Surface
(PES) that appear when the constraints are considered. These terms are related
to mass-metric tensors determinants and also occur in the Fixman's compensating
potential. We show that some of the corrections are non-negligible if one is
interested in the whole Ramachandran space. On the other hand, if only the
energetically lower region, containing the principal secondary structure
elements, is assumed to be relevant, then, all correcting terms may be
neglected up to peptides of considerable length. This is the first time, as far
as we know, that the analysis of the conformational dependence of these
correcting terms is performed in a relevant biomolecule with a realistic
potential energy function.Comment: 37 pages, 4 figures, LaTeX, BibTeX, AMSTe
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