216 research outputs found
Chiral and herringbone symmetry breaking in water-surface monolayers
We report the observation from monolayers of eicosanoic acid in the L′2 phase of three distinct out-of-plane first-order diffraction peaks, indicating molecular tilt in a nonsymmetry direction and hence the absence of mirror symmetry. At lower pressures the molecules tilt in the direction of their nearest neighbors. In this region we find a structural transition, which we tentatively identify as the rotator-herringbone transition L2d−L2h
Pulmonary rehabilitation in patients with mustard gas lung disease: a study protocol for a randomized controlled trial
Background More than 60,000 people have health problems due to chemical weapons exposure during the Iran–Iraq war. Respiratory consequences of mustard gas exposure are common and disabling; medical interventions have limited effect. Patients complain of cough, sputum, breathlessness and exercise limitation. We hypothesized that patients with this condition would benefit from pulmonary rehabilitation. Methods We outline the protocol for an assessor-blind, two-armed, parallel-design randomized controlled clinical trial (IRCT2016051127848N1). Sixty patients with respiratory disease due to documented sulfur mustard gas exposure will be randomized to either take part in a 6-week pulmonary rehabilitation programme or receive usual care. Inclusion criteria include forced expiratory volume in 1 second < 80% predicted and Medical Research Council dyspnoea score ≥ 3. The primary endpoint will be the change in cycle endurance time at 70% baseline exercise capacity at 6 weeks. Lung function, physical activity, the strength and endurance of the quadriceps muscle, and quality of life will also be compared. Outcomes will be assessed at 6 weeks and 12 months. Health care utilization will also be assessed. Discussion If the study confirms that rehabilitation is effective for patients with mustard gas lung disease this should prompt provision of the intervention to this patient group
Mechanism of carrier-induced ferromagnetism in magnetic semiconductors
Taking into account both random impurity distribution and thermal
fluctuations of localized spins, we have performed a model calculation for the
carrier (hole) state in GaMnAs by using the coherent potential
approximation (CPA). The result reveals that a {\it p}-hole in the band tail of
GaMnAs is not like a free carrier but is rather virtually bounded
to impurity sites. The carrier spin strongly couples to the localized {\it d}
spins on Mn ions. The hopping of the carrier among Mn sites causes the
ferromagnetic ordering of the localized spins through the double-exchange
mechanism. The Curie temperature obtained by using conventional parameters
agrees well with the experimental result.Comment: 7 pages, 4 figure
First measurement and shell model interpretation of the g factor of the 21+ state in self-conjugate radioactive 44Ti
AbstractThe g factor of the 21+ state in radioactive 44Ti has been measured for the first time with the technique of α transfer to 40Ca beams in inverse kinematics in combination with transient magnetic fields, yielding the value, g(21+)=+0.52(15). In addition, the lifetimes of the 21+, τ=3.97(28) ps, and the 41+ states, τ=0.65(6) ps, were redetermined with higher precision using the Doppler shift attenuation method. The deduced B(E2)'s and the g factor were well explained by a full fp shell model calculation using the FPD6 effective NN interaction. The g factor can also be accounted for by a simple rotational model (g=Z/A). However, if one also considers the B(E2)'s and the E(41+)/E(21+) ratios, then an imperfect vibrator picture gives better agreement with the data
Magnetization plateau in a two-dimensional multiple-spin exchange model
We study a multiple-spin exchange model on a triangular lattice, which is a
possible model for low-density solid 3He films. Due to strong competitions
between ferromagnetic three-spin exchange and antiferromagnetic four-spin one,
the ground states are highly degenerate in the classical limit. At least
2^{L/2}-fold degeneracy exists on the L*L triangular lattice except for the
SO(3) symmetry. In the magnetization process, we found a plateau at
m/m_{sat}=1/2, in which the ground state is "uuud state" (a collinear state
with four sublattices). The 1/2-plateau appears due to the strong four-spin
exchange interaction. This plateau survives against both quantum and thermal
fluctuations. Under a magnetic field which realizes the "uuud" ordered state, a
phase transition occurs at a finite temperature. We predict that low-density
solid 3He thin films may show the 1/2-plateau in the magnetization process.
Experimental observation of the plateau will verify strength of the four-spin
exchange. It is also discussed that this magnetization plateau can be
understood as an insulating-conducting transition in a particle picture.Comment: 10 pages, RevTeX, 12 figures, added a reference and corrected typos,
to be published in Phys.Rev.B (01 APR 99
Possible chiral phase transition in two-dimensional solid He
We study a spin system with two- and four-spin exchange interactions on the
triangular lattice, which is a possible model for the nuclear magnetism of
solid He layers. It is found that a novel spin structure with scalar chiral
order appears if the four-spin interaction is dominant. Ground-state properties
are studied using the spin-wave approximation. A phase transition concerning
the scalar chirality occurs at a finite temperature, even though the
dimensionality of the system is two and the interaction has isotropic spin
symmetry. Critical properties of this transition are studied with Monte Carlo
simulations in the classical limit.Comment: 4 pages, Revtex, 4 figures, to appear in Phys.Rev.Let
Randomised controlled trial of adjunctive inspiratory muscle training for patients with COPD.
BACKGROUND: This study aimed to investigate whether adjunctive inspiratory muscle training (IMT) can enhance the well-established benefits of pulmonary rehabilitation (PR) in patients with COPD. METHODS: 219 patients with COPD (FEV1: 42%±16% predicted) with inspiratory muscle weakness (PImax: 51±15 cm H2O) were randomised into an intervention group (IMT+PR; n=110) or a control group (Sham-IMT+PR; n=109) in this double-blind, multicentre randomised controlled trial between February 2012 and October 2016 (ClinicalTrials.gov NCT01397396). Improvement in 6 min walking distance (6MWD) was a priori defined as the primary outcome. Prespecified secondary outcomes included respiratory muscle function and endurance cycling time. FINDINGS: No significant differences between the intervention group (n=89) and the control group (n=85) in improvements in 6MWD were observed (0.3 m, 95% CI -13 to 14, p=0.967). Patients who completed assessments in the intervention group achieved larger gains in inspiratory muscle strength (effect size: 1.07, p<0.001) and endurance (effect size: 0.79, p<0.001) than patients in the control group. 75 s additional improvement in endurance cycling time (95% CI 1 to 149, p=0.048) and significant reductions in Borg dyspnoea score at isotime during the cycling test (95% CI -1.5 to -0.01, p=0.049) were observed in the intervention group. INTERPRETATION: Improvements in respiratory muscle function after adjunctive IMT did not translate into additional improvements in 6MWD (primary outcome). Additional gains in endurance time and reductions in symptoms of dyspnoea were observed during an endurance cycling test (secondary outcome) TRIAL REGISTRATION NUMBER: NCT01397396; Results
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