775 research outputs found
Helix vs. Sheet Formation in a Small Peptide
Segments with the amino acid sequence EKAYLRT appear in natural occurring
proteins both in -helices and -sheets. For this reason, we have
use this peptide to study how secondary structure formation in proteins depends
on the local environment. Our data rely on multicanonical Monte Carlo
simulations where the interactions among all atoms are taken into account.
Results in gas phase are compared with that in an implicit solvent. We find
that both in gas phase and solvated EKAYLRT forms an -helix when not
interacting with other molecules. However, in the vicinity of a -strand,
the peptide forms a -strand. Because of this change in secondary
structure our peptide may provide a simple model for the
transition that is supposedly related to the outbreak of Prion diseases and
similar illnesses.Comment: to appear in Physical Review
Numerical comparison of two approaches for the study of phase transitions in small systems
We compare two recently proposed methods for the characterization of phase
transitions in small systems. The validity and usefulness of these approaches
are studied for the case of the q=4 and q=5 Potts model, i.e. systems where a
thermodynamic limit and exact results exist. Guided by this analysis we discuss
then the helix-coil transition in polyalanine, an example of structural
transitions in biological molecules.Comment: 16 pages and 7 figure
A transparent dialogue between iconography and chemical characterisation: a set of foreign stained glasses in Portugal
This work presents the first results of the iconographic study and analytical characterisation of a set of four stained-glass panels that are part of the collection of National Palace of Pena (Sintra, Portugal). These panels were collected by the King Ferdinand II in the mid-nineteenth century, for his main residence the Palace of Necessidades (Lisbon, Portugal), and only first presented to the general public in 2011. This study contributes with the knowledge of Technical Art History and Heritage Science to a better and deeper understanding of their history, materials and techniques used in the production, where an art-historical and a scientific approach are applied to attribute their origins. Based on the analysis of the formal and stylistic characteristic of the panels, it is proposed that the drawings used for the production of three of these panels may be based on the design and painting being carried out in the same workshop, and that the four panels have the same provenance (Germany). The composition of the glass and grisaille was determined and colourising elements were identified. Through this approach, conclusive correlation between the analysed glasses was possible: all are calcium rich or calciumâpotassium rich types, and the results also suggest that the same source of silica was used for their production. A typical mixture of glass and lead oxide was found in the grisaille applied on the painted panels. However, less usual was the use of a copper oxide pigment for the black grisaille. All these findings support the proposals made regarding provenance and production period (fifteenth century)
Effective treatment of a case of pregnancy toxemia in sheep - case report
ABSTRACT Pregnancy toxemia has a high mortality rate and few cases with effective treatment are reported, especially when associated with secondary diseases. Therefore, the present work reports the case of a sheep, which was referred to the veterinary hospital of UFMG, in the last month of pregnancy, presenting apathy, hyporexia and sternal recumbency. After the diagnosis of pregnancy toxemia, the fetuses were removed while still alive, but did not survive. Monitoring was started with blood gas analysis, blood glucose assessments and laboratory tests. The results were consistent with liver damage, which was justified by the condition of lipolysis. Treatment consisted of electrolyte replacement plus 50% glucose and potassium chloride, along with administration of antibiotics (ceftiofur, 5mg/kg/SID/IM/7 days), flunixim meglumine (2.2mg/kg/SID/IM first day and 1.1mg/kg/SID/IM on the second and third days) and omeprazole (4mg/kg/SID/oral). The patient had secondarily clinical laminitis, which was treated with cryotherapy and anti-inflammatory drugs, in addition to mastitis, using a single dose of intramammary antibiotics. The work demonstrated the effectiveness of the treatment of pregnancy toxemia, when performed early and intensively, associated with daily clinical and laboratory monitoring of the animal
A Binary Lensing Event Toward the LMC: Observations and Dark Matter Implications
The MACHO collaboration has recently analyzed 2.1 years of photometric data
for about 8.5 million stars in the Large Magellanic Cloud (LMC). This analysis
has revealed 8 candidate microlensing events and a total microlensing optical
depth of . This significantly
exceeds the number of events (1.1) and the microlensing optical depth predicted
from known stellar populations: , but it is
consistent with models in which about half of the standard dark halo mass is
composed of Machos of mass \sim 0.5 \msun. One of these 8 events appears to
be a binary lensing event with a caustic crossing that is partially resolved
which allows us to estimate the distance to the lenses. If the source star is
not a short period binary star, then we show that the lens system is very
likely to reside in the LMC. However, if we assume that the optical depth for
LMC-LMC lensing is large enough to account for our entire lensing signal, then
the binary event does not appear to be consistent with lensing of a single LMC
source star by a binary residing in the LMC. Thus, while the binary lens may
indeed reside in the LMC, there is no indication that most of the lenses reside
in the LMC.Comment: 5 pages, 3 postscript figures included; To appear in the Proceedings
of the Dark Matter '96 Conference held in Santa Monica, CA, Feb., 199
Design-controlled synthesis of IrO2 sub-monolayers on Au nanoflowers: Marrying plasmonic and electrocatalytic properties
We develop herein plasmonicâcatalytic AuâIrO2 nanostructures with a morphology optimized for efficient light harvesting and catalytic surface area; the nanoparticles have a nanoflower morphology, with closely spaced Au branches all partially covered by an ultrathin (1 nm) IrO2 shell. This nanoparticle architecture optimizes optical features due to the interactions of closely spaced plasmonic branches forming electromagnetic hot spots, and the ultra-thin IrO2 layer maximizes efficient use of this expensive catalyst. This concept was evaluated towards the enhancement of the electrocatalytic performances towards the oxygen evolution reaction (OER) as a model transformation. The OER can play a central role in meeting future energy demands but the performance of conventional electrocatalysts in this reaction is limited by the sluggish OER kinetics. We demonstrate an improvement of the OER performance for one of the most active OER catalysts, IrO2, by harvesting plasmonic effects from visible light illumination in multimetallic nanoparticles. We find that the OER activity for the AuâIrO2 nanoflowers can be improved under LSPR excitation, matching best properties reported in the literature. Our simulations and electrocatalytic data demonstrate that the enhancement in OER activities can be attributed to an electronic interaction between Au and IrO2 and to the activation of IrâO bonds by LSPR excited hot holes, leading to a change in the reaction mechanism (rate-determinant step) under visible light illumination
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Comparação de diferentes doses de colagenase em modelo de indução de tendinite para eqĂŒinos: estudo clĂnico e ultra-sonogrĂĄfico
The MACHO Project 2nd Year LMC Microlensing Results and Dark Matter Implications
The MACHO Project is searching for galactic dark matter in the form of
massive compact halo objects (Machos). Millions of stars in the Large
Magellanic Cloud (LMC), Small Magellanic Cloud (SMC), and Galactic bulge are
photometrically monitored in an attempt to detect rare gravitational
microlensing events caused by otherwise invisible Machos. Analysis of two years
of photometry on 8.5 million stars in the LMC reveals 8 candidate microlensing
events, far more than the event expected from lensing by low-mass stars
in known galactic populations. From these eight events we estimate the optical
depth towards the LMC from events with 2 < \that < 200 days to be
\tau_2^{200} \approx 2.9 ^{+1.4}_{-0.9} \ten{-7}. This exceeds the optical
depth of 0.5\ten{-7} expected from known stars and is to be compared with an
optical depth of 4.7\ten{-7} predicted for a ``standard'' halo composed
entirely of Machos. The total mass in this lensing population is \approx
2^{+1.2}_{-0.7} \ten{11} \msun (within 50 kpc from the Galactic center). Event
timescales yield a most probable Macho mass of 0.5^{+0.3}_{-0.2}\msun,
although this value is quite model dependent.Comment: 10 pages, 6 epsf figures and style file included, 451k, also at
http://wwwmacho.mcmaster.ca/Pubs/Pubs.html; To appear in the Proceedings of
"Sources and Detection of Dark Matter in the Universe", Santa Monica, CA,
Feb., 199
Molecular Mechanism of the Constitutive Activation of the L250Q Human Melanocortin-4 Receptor Polymorphism â
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65471/1/j.1747-0285.2006.00362.x.pd
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