648 research outputs found
ZnSe/GaAs(001) heterostructures with defected interfaces: structural, thermodynamic and electronic properties
We have performed accurate \emph{ab--initio} pseudopotential calculations for
the structural and electronic properties of ZnSe/GaAs(001) heterostructures
with interface configurations accounting for charge neutrality prescriptions.
Beside the simplest configurations with atomic interdiffusion we consider also
some configurations characterized by As depletion and cation vacancies,
motivated by the recent successfull growth of ZnSe/GaAs pseudomorphic
structures with minimum stacking fault density characterized by the presence of
a defected (Zn,Ga)Se alloy in the interface region. We find that--under
particular thermodynamic conditions--some defected configurations are favoured
with respect to undefected ones with simple anion or cation mixing, and that
the calculated band offsets for some defected structures are compatible with
those measured. Although it is not possible to extract indications about the
precise interface composition and vacancy concentration, our results support
the experimental indication of (Zn,Ga)Se defected compounds in high-quality
ZnSe/GaAs(001) heterojunctions with low native stacking fault density. The
range of measured band offset suggests that different atoms at interfaces
rearrange, with possible presence of vacancies, in such a way that not only
local charges but also ionic dipoles are vanishing.Comment: 26 pages. 5 figures, revised version, in press (Physical Review B
Million-atom molecular dynamics simulation by order-N electronic structure theory and parallel computation
Parallelism of tight-binding molecular dynamics simulations is presented by
means of the order-N electronic structure theory with the Wannier states,
recently developed (J. Phys. Soc. Jpn. 69,3773 (2000)). An application is
tested for silicon nanocrystals of more than millions atoms with the
transferable tight-binding Hamiltonian. The efficiency of parallelism is
perfect, 98.8 %, and the method is the most suitable to parallel computation.
The elapse time for a system of atoms is 3.0 minutes by a
computer system of 64 processors of SGI Origin 3800. The calculated results are
in good agreement with the results of the exact diagonalization, with an error
of 2 % for the lattice constant and errors less than 10 % for elastic
constants.Comment: 5 pages, 3 figure
Effect of pressure on the Raman modes of antimony
The effect of pressure on the zone-center optical phonon modes of antimony in
the A7 structure has been investigated by Raman spectroscopy. The A_g and E_g
frequencies exhibit a pronounced softening with increasing pressure, the effect
being related to a gradual suppression of the Peierls-like distortion of the A7
phase relative to a cubic primitive lattice. Also, both Raman modes broaden
significantly under pressure. Spectra taken at low temperature indicate that
the broadening is at least partly caused by phonon-phonon interactions. We also
report results of ab initio frozen-phonon calculations of the A_g and E_g mode
frequencies. Presence of strong anharmonicity is clearly apparent in calculated
total energy versus atom displacement relations. Pronounced nonlinearities in
the force versus displacement relations are observed. Structural instabilities
of the Sb-A7 phase are briefly addressed in the Appendix.Comment: 10 pages, 8 figure
Indacaterol provides 24-hour bronchodilation in COPD: a placebo-controlled blinded comparison with tiotropium
1022-103 Does Primary Angioplasty Improve the Prognosis of Patients with Diabetes and Acute Myocardial Infarction?
To examine the effect of different reperfusion modalities in pts with DM, the multicenter PAMI database was analyzed, in which 395 pts within 12 hours onset of acute MI were prospectively randomized to treatment with t-PA (n=200) vs. primary PTCA (n=195). DM was present in 50 (13%) pts. Compared to pts without DM, pts with DM were older (65 vs. 59 yrs, p=0.002), more often female (40% vs. 25%, p=0.03), more frequently had HTN (68% vs. 39%, P=0.0001), prior CHF (8% vs. 1%, P=0.0001). multivessel disease (76% vs. 51%, P=0.01) and presented later (3.8 vs. 3.0hours, p=0.03).In-hospital mortality was 10.0% in pts with DM vs. 3.8% in pts without DM (p<0.05). By multivariate analysis of 16 variables, however, advanced age and treatment by PTCA rather than t-PA, but not DM correlated with in-hospital mortality.Mortality stratified by treatment appears in the graph. Despite the apparently improved prognosis of pts with DM treated with PTCA vs. t-PA, the p value forthe x2 test for interaction effect between DM and treatment modality was 0.86; most of the benefit of PTCA was present in the elderly population.In conclusionPts with DM and acute MI have increased mortality, primarily because of advanced age. The outcome after PTCA compared to t-PA is improved in DM largely because of PTCA's beneficial effect in the elderly
Brewing of filter coffee
We report progress on mathematical modelling of coffee grounds in a drip filter coffee machine. The report focuses on the evolution of the shape of the bed of coffee grounds during extraction with some work also carried out on the chemistry of extraction. This work was sponsored by Philips who are interested in understanding an observed correlation between the final shape of the coffee grounds and the quality of the coffee. We used experimental data gathered by Philips and ourselves to identify regimes in the coffee brewing process and relevant regions of parameter space. Our work makes it clear that a number of separate processes define the shape of the coffee bed depending on the values of the parameters involved e.g. the size of the grains and the speed of fluid flow during extraction. We began work on constructing mathematical models of the redistribution of the coffee grounds specialised to each region and on a model of extraction. A variety of analytic and numerical tools were used. Furthermore our research has progressed far enough to allow us to begin to exploit connections between this problem and other areas of science, in particular the areas of sedimentology and geomorphology, where the processes we have observed in coffee brewing have been studied
Pressure Dependence of the Elastic Moduli in Aluminum Rich Al-Li Compounds
I have carried out numerical first principles calculations of the pressure
dependence of the elastic moduli for several ordered structures in the
Aluminum-Lithium system, specifically FCC Al, FCC and BCC Li, L1_2 Al_3Li, and
an ordered FCC Al_7Li supercell. The calculations were performed using the full
potential linear augmented plane wave method (LAPW) to calculate the total
energy as a function of strain, after which the data was fit to a polynomial
function of the strain to determine the modulus. A procedure for estimating the
errors in this process is also given. The predicted equilibrium lattice
parameters are slightly smaller than found experimentally, consistent with
other LDA calculations. The computed elastic moduli are within approximately
10% of the experimentally measured moduli, provided the calculations are
carried out at the experimental lattice constant. The LDA equilibrium shear
modulus C11-C12 increases from 59.3 GPa in Al, to 76.0 GPa in Al_7Li, to 106.2
GPa in Al_3Li. The modulus C_44 increases from 38.4 GPa in Al to 46.1 GPa in
Al_7Li, then falls to 40.7 GPa in Al_3Li. All of the calculated elastic moduli
increase with pressure with the exception of BCC Li, which becomes elastically
unstable at about 2 GPa, where C_11-C_12 vanishes.Comment: 17 pages (REVTEX) + 7 postscript figure
Efficacy and safety of indacaterol 150 ÎĽg once-daily in COPD: a double-blind, randomised, 12-week study
<p>Abstract</p> <p>Background</p> <p>Indacaterol is a novel, once-daily (o.d.) inhaled, long-acting <it>β</it><sub>2</sub>-agonist in development for chronic obstructive pulmonary disease (COPD). This 12-week, double-blind study compared the efficacy, safety, and tolerability of indacaterol to that of placebo in patients with moderate-to-severe COPD.</p> <p>Methods</p> <p>Efficacy variables included 24-h trough FEV<sub>1 </sub>(mean of 23 h 10 min and 23 h 45 min post-dose) at Week 12 (primary endpoint) and after Day 1, and the percentage of COPD days with poor control (i.e., worsening symptoms). Safety was assessed by adverse events (AEs), mean serum potassium and blood glucose, QTc (Fridericia), and vital signs.</p> <p>Results</p> <p>Patients were randomised (n = 416, mean age 63 years) to receive either indacaterol 150 <it>μ</it>g o.d. (n = 211) or placebo (n = 205) via a single-dose dry-powder inhaler; 87.5% completed the study. Trough FEV<sub>1 </sub>(LSM ± SEM) at Week 12 was 1.48 ± 0.018 L for indacaterol and 1.35 ± 0.019 L for placebo, a clinically relevant difference of 130 ± 24 mL (p < 0.001). Trough FEV<sub>1 </sub>after one dose was significantly higher with indacaterol than placebo (p < 0.001). Indacaterol demonstrated significantly higher peak FEV<sub>1 </sub>than placebo, both on Day 1 and at Week 12, with indacaterol-placebo differences (LSM ± SEM) of 190 ± 28 (p < 0.001) and 160 ± 28 mL (p < 0.001), respectively. Standardised AUC measurements for FEV<sub>1 </sub>(between 5 min and 4 h, 5 min and 1 h, and 1 and 4 h post-dose) at Week 12 were all significantly greater with indacaterol than placebo (p < 0.001), with LSM (± SEM) differences of 170 ± 24, 180 ± 24, and 170 ± 24 mL, respectively. Indacaterol significantly reduced the percentage of days of poor control versus placebo by 22.5% (p < 0.001) and was also associated with significantly reduced use of rescue medication (p < 0.001). The overall rates of AEs were comparable between the groups (indacaterol 49.3%, placebo 46.8%), with the most common AEs being COPD worsening (indacaterol 8.5%, placebo 12.2%) and cough (indacaterol 6.2%, placebo 7.3%). One patient died in the placebo group. Serum potassium and blood glucose levels did not differ significantly between the two groups, and no patient had QTc >500 ms.</p> <p>Conclusions</p> <p>Indacaterol 150 <it>μ</it>g o.d. provided clinically significant and sustained bronchodilation, reduced rescue medication use, and had a safety and tolerability profile similar to placebo.</p> <p>Trial registration</p> <p>NCT00624286</p
Spinless fermions ladders at half filling
We study a half filled ladder of spinless fermions. We show that contrarily
to a single chain, the ladder becomes a Mott insulator for arbitrarily small
repulsive interactions. We obtain the full phase diagram and physical
quantities such as the charge gap. We show that there is only a single
insulating phase for repulsive interactions, regardless of the stength of the
interchain hopping and single chain Mott gap. There is thus no
confinement-deconfinement transition in this system but a simple crossover. We
show that upon doping the system becomes a Luttinger liquid with a universal
parameter different from the one of the single chain ().Comment: 9 pages, 6 figures, uses revtex4 beta4 and natbib(included);
submitted to PR
The US Legal System on Data Protection in the Field of Law Enforcement. Safeguards, Rights and Remedies for EU Citizens
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