541 research outputs found
First-principles Calculation of the Formation Energy in MgO-CaO Solid Solutions
The electronic structure and total energy were calculated for ordered and
disordered MgO-CaO solid solutions within the multiple scattering theory in
real space and the local density approximation. Based on the dependence of the
total energy on the unit cell volume the equilibrium lattice parameter and
formation energy were determined for different solution compositions. The
formation energy of the solid solutions is found to be positive that is in
agreement with the experimental phase diagram, which shows a miscibility gap.Comment: 11 pages, 3 figure
The Uncertainty in Newton's Constant and Precision Predictions of the Primordial Helium Abundance
The current uncertainty in Newton's constant, G_N, is of the order of 0.15%.
For values of the baryon to photon ratio consistent with both cosmic microwave
background observations and the primordial deuterium abundance, this
uncertainty in G_N corresponds to an uncertainty in the primordial 4He mass
fraction, Y_P, of +-1.3 x 10^{-4}. This uncertainty in Y_P is comparable to the
effect from the current uncertainty in the neutron lifetime, which is often
treated as the dominant uncertainty in calculations of Y_P. Recent measurements
of G_N seem to be converging within a smaller range; a reduction in the
estimated error on G_N by a factor of 10 would essentially eliminate it as a
source of uncertainty in the calculation of the primordial 4He abundance.Comment: 3 pages, no figures, fixed typos, to appear in Phys. Rev.
Magnetic relaxation phenomena and cluster glass properties of La{0.7-x}Y{x}Ca{0.3}MnO{3} manganites
The dynamic magnetic properties of the distorted perovskite system
La{0.7-x}Y{x}Ca{0.3}MnO{3} (0 <= x <= 0.15) have been investigated by
ac-susceptibility and dc magnetization measurements, with emphasis on
relaxation and aging studies. They evidence for x >= 0.10 the appearance of a
metallic cluster glass phase, that develops just below the ferromagnetic
transition temperature. The clusters grow with decreasing temperature down to a
temperature T(f0) at which they freeze due to severe intercluster frustration.
The formation of these clusters is explained by the presence of yttrium induced
local structural distortions that create localized spin disorder in a magnetic
lattice where double-exchange ferromagnetism is dominant.Comment: Accepted for publication in Phys. Rev.
Electronic structure of nuclear-spin-polarization-induced quantum dots
We study a system in which electrons in a two-dimensional electron gas are
confined by a nonhomogeneous nuclear spin polarization. The system consists of
a heterostructure that has non-zero nuclei spins. We show that in this system
electrons can be confined into a dot region through a local nuclear spin
polarization. The nuclear-spin-polarization-induced quantum dot has interesting
properties indicating that electron energy levels are time-dependent because of
the nuclear spin relaxation and diffusion processes. Electron confining
potential is a solution of diffusion equation with relaxation. Experimental
investigations of the time-dependence of electron energy levels will result in
more information about nuclear spin interactions in solids
Quantum and classical localisation, the spin quantum Hall effect and generalisations
We consider network models for localisation problems belonging to symmetry
class C. This symmetry class arises in a description of the dynamics of
quasiparticles for disordered spin-singlet superconductors which have a
Bogoliubov - de Gennes Hamiltonian that is invariant under spin rotations but
not under time-reversal. Our models include but also generalise the one studied
previously in the context of the spin quantum Hall effect. For these systems we
express the disorder-averaged conductance and density of states in terms of
sums over certain classical random walks, which are self-avoiding and have
attractive interactions. A transition between localised and extended phases of
the quantum system maps in this way to a similar transition for the classical
walks. In the case of the spin quantum Hall effect, the classical walks are the
hulls of percolation clusters, and our approach provides an alternative
derivation of a mapping first established by Gruzberg, Read and Ludwig, Phys.
Rev. Lett. 82, 4254 (1999).Comment: 11 pages, 5 figure
Isolated right ventricular failure in hyperthyroidism: a clinical dilemma
We present a unique case of a 42-year-old gentleman with newly diagnosed Graves’ disease and isolated right ventricular failure. Extensive evaluation to include echocardiogram and cardiac catheterization were negative for significant pulmonary hypertension or coronary artery disease as potential etiologies. Hyperthyroid induced vasospasm is a rare but reported clinical entity that serves to be a clinical and diagnostic dilemma
A novel 96-microwell-based high-throughput spectrophotometric assay for pharmaceutical quality control of crizotinib, a novel potent drug for the treatment of non-small cell lung cancer
This study describes the development and validation of a novel 96-microwell-based high throughput spectrophotometric assay for pharmaceutical quality control of crizotinib (CZT), a novel drug for the treatment of non-small cell lung cancer. We examined the reaction between CZT and 1,2-naphthoquinone-4-sulphonate, a chromogenic reagent. A red-colored product showing a maximum absorption peak (λmax) at 490 nm was produced in an alkaline medium (pH 9). We examined stoichiometry of the reaction and postulated the reaction mechanism. To our knowledge, this is the first study to describe a color-developing reaction for the proposed assay. The reaction was performed in a 96-microwell plate, and the absorbance of the colored product was measured using an absorbance reader at 490 nm. Under optimized reaction conditions, Beer's law, which shows a correlation between absorbance and CZT concentration, was obeyed in the range of 4-50 µg/well with an appropriate correlation coefficient (0.999). The limits of detection and quantification were 1.73 and 5.23 µg/well, respectively. The assay showed high precision and accuracy. The proposed assay was applied successfully for the determination of CZT in capsules. Thus, the assay proposed in this study is practical and valuable for routine application in pharmaceutical quality control laboratories.</p
Erasmus Language students in a British University – a case study
Students’ assessment of their academic experience is actively sought by Higher Education institutions, as evidenced in the National Student Survey introduced in 2005. Erasmus students, despite their growing numbers, tend to be excluded from these satisfaction surveys, even though they, too, are primary customers of a University. This study aims to present results from bespoke questionnaires and semi-structured interviews with a sample of Erasmus students studying languages in a British University. These methods allow us insight into the experience of these students and their assessment as a primary customer, with a focus on language learning and teaching, university facilities and student support. It investigates to what extent these factors influence their levels of satisfaction and what costs of adaptation if any, they encounter. Although excellent levels of satisfaction were found, some costs affect their experience. They relate to difficulties in adapting to a learning methodology based on a low number of hours and independent learning and to a guidance and support system seen as too stifling. The results portray this cohort’s British University as a well-equipped and well-meaning but ultimately overbearing institution, which may indicate that minimising costs can eliminate some sources of dissatisfaction
Lattice QCD Simulations in External Background Fields
We discuss recent results and future prospects regarding the investigation,
by lattice simulations, of the non-perturbative properties of QCD and of its
phase diagram in presence of magnetic or chromomagnetic background fields.
After a brief introduction to the formulation of lattice QCD in presence of
external fields, we focus on studies regarding the effects of external fields
on chiral symmetry breaking, on its restoration at finite temperature and on
deconfinement. We conclude with a few comments regarding the effects of
electromagnetic background fields on gluodynamics.Comment: 31 pages, 10 figures, minor changes and references added. To appear
in Lect. Notes Phys. "Strongly interacting matter in magnetic fields"
(Springer), edited by D. Kharzeev, K. Landsteiner, A. Schmitt, H.-U. Ye
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