92 research outputs found
Effect of annealing on the depth profile of hole concentration in (Ga,Mn)As
The effect of annealing at 250 C on the carrier depth profile, Mn
distribution, electrical conductivity, and Curie temperature of (Ga,Mn)As
layers with thicknesses > 200 nm, grown by molecular-beam epitaxy at low
temperatures, is studied by a variety of analytical methods. The vertical
gradient in hole concentration, revealed by electrochemical capacitance-voltage
profiling, is shown to play a key role in the understanding of conductivity and
magnetization data. The gradient, basically already present in as-grown
samples, is strongly influenced by post-growth annealing. From secondary ion
mass spectroscopy it can be concluded that, at least in thick layers, the
change in carrier depth profile and thus in conductivity is not primarily due
to out-diffusion of Mn interstitials during annealing. Two alternative possible
models are discussed.Comment: 8 pages, 8 figures, to appear in Phys. Rev.
Curie temperature and carrier concentration gradients in MBE grown GaMnAs layers
We report on detailed investigations of the electronic and magnetic
properties of ferromagnetic GaMnAs layers, which have been fabricated by
low-temperature molecular-beam epitaxy. Superconducting quantum interference
device measurements reveal a decrease of the Curie temperature from the surface
to the GaMnAs/GaAs interface. While high resolution x-ray diffraction clearly
shows a homogeneous Mn distribution, a pronounced decrease of the carrier
concentration from the surface towards the GaMnAs/GaAs interface has been found
by Raman spectroscopy as well as electrochemical capacitance-voltage profiling.
The gradient in Curie temperature seems to be a general feature of GaMnAs
layers grown at low-temperature. Possible explanations are discussed.Comment: 3 pages, 4 figures, submitted to AP
Subclinical thyroid function and cardiovascular events in patients with atrial fibrillation
Objective: To evaluate if subclinical thyroid dysfunction is associated with cardiovascular (CV) risk in patients with atrial fibrillation (AF). Methods: Swiss-AF is a prospective cohort of community-dwelling participants aged â„ 65 years with AF. Primary outcome was a composite endpoint of CV events (myocardial infarctions, stroke/transitory ischemic events, systemic embolism, heart failure (HF) hospitalizations, CV deaths). Secondary outcomes were component endpoints, total mortality, and AF-progression. Exposures were thyroid dysfunction categories, TSH and fT4. Sensitivity analyses were performed for amiodarone use, thyroid hormones use, and competing events. Results: 2415 patients were included (mean age: 73.2 years; 27% women). 196 (8.4%) had subclinical hypothyroidism and 53 (2.3%) subclinical hyperthyroidism. Subclinical thyroid dysfunction was not associated with CV events, during a median follow-up of 2.1 years (max 5 years): age- and sex-adjusted hazard ratio (adjHR) of 0.99 (95% CI: 0.69-1.41) for subclinical hypothyroidism and 0.55 (95% CI: 0.23-1.32) for subclinical hyperthyroidism. Results remained robust following multivariable adjustment and sensitivity analyses. In euthyroid patients, fT4 levels were associated with an increased risk for the composite endpoint and HF (adjHR: 1.46, 95% CI: 1.04-2.05; adjHR: 1.70, 95% CI: 1.08-2.66, respectively, for the highest quintile vs the middle quintile). Results remained similar following multivariable adjustment and remained significant for HF in sensitivity analyses. No association between subclinical thyroid dysfunction and total mortality or AF-progression was found. Conclusions: Subclinical hypothyroidism was not associated with increased CV risk in AF patients. Higher levels of fT4 with normal TSH were associated with a higher risk for HF
Clientelism as civil society? Unpacking the relationship between clientelism and democracy at the local level in South Africa
This article, building on analyses from the global south, attempts to reframe democratic expectations by considering where previously maligned practices such as clientelism may hold moments of democracy. It does so by comparing the theory of civil society with that of clientelism, and its African counterpart neo-patrimonialism. It argues that clientelism as civil society may fulfil democratic tasks such as holding the (local) state accountable, strengthening civil and political liberties and providing channels of access for previously marginalised groups. Clientelism is not necessarily a reflection of imposed power relations but, at times, can demonstrate a conscious political strategy, to generate development, on the part of its protagonists.IS
Effect of gender difference on platelet reactivity
Background Previous studies have suggested that women do not accrue equal therapeutic benefit from antiplatelet medication as compared with men. The physiological mechanism and clinical implications behind this gender disparity have yet to be established. Methods On-treatment platelet reactivity was determined in 717 men and 234 women on dual antiplatelet therapy, undergoing elective coronary stent implantation. Platelet function testing was performed using arachidonic acid and adenosine diphosphate-induced light transmittance aggregometry (LTA) and the VerifyNow P2Y12 and Aspirin assays. Also the incidence of all-cause death, non-fatal acute myocardial infarction, stent thrombosis and ischaemic stroke was evaluated. Results Women had higher baseline platelet counts than men. Women exhibited a higher magnitude of on-aspirin platelet reactivity using LTA, but not using the VerifyNow Aspirin assay. The magnitude of on-clopidogrel platelet reactivity was significantly higher in women as compared with men with both tests used. The cut-off value to identify patients at risk as well as the incidence of clinical endpoints was similar between women and men (16/234[6.8%] vs. 62/717[8.6%], p=0.38). Conclusion Although the magnitude of platelet reactivity was higher in women, the absolute difference between genders was small and both the cut-off value to identify patients at risk and the incidence of the composite endpoint were similar between genders. Thus, it is unlikely that the difference in platelet reactivity accounts for a worse prognosis in women
Can postoperative mean transprosthetic pressure gradient predict survival after aortic valve replacement?
Penumbral Rescue by normobaric O = O administration in patients with ischemic stroke and target mismatch proFile (PROOF): Study protocol of a phase IIb trial.
Oxygen is essential for cellular energy metabolism. Neurons are particularly vulnerable to hypoxia. Increasing oxygen supply shortly after stroke onset could preserve the ischemic penumbra until revascularization occurs.
PROOF investigates the use of normobaric oxygen (NBO) therapy within 6 h of symptom onset/notice for brain-protective bridging until endovascular revascularization of acute intracranial anterior-circulation occlusion.
Randomized (1:1), standard treatment-controlled, open-label, blinded endpoint, multicenter adaptive phase IIb trial.
Primary outcome is ischemic core growth (mL) from baseline to 24 h (intention-to-treat analysis). Secondary efficacy outcomes include change in NIHSS from baseline to 24 h, mRS at 90 days, cognitive and emotional function, and quality of life. Safety outcomes include mortality, intracranial hemorrhage, and respiratory failure. Exploratory analyses of imaging and blood biomarkers will be conducted.
Using an adaptive design with interim analysis at 80 patients per arm, up to 456 participants (228 per arm) would be needed for 80% power (one-sided alpha 0.05) to detect a mean reduction of ischemic core growth by 6.68 mL, assuming 21.4 mL standard deviation.
By enrolling endovascular thrombectomy candidates in an early time window, the trial replicates insights from preclinical studies in which NBO showed beneficial effects, namely early initiation of near 100% inspired oxygen during short temporary ischemia. Primary outcome assessment at 24 h on follow-up imaging reduces variability due to withdrawal of care and early clinical confounders such as delayed extubation and aspiration pneumonia.
ClinicalTrials.gov: NCT03500939; EudraCT: 2017-001355-31
Cardiac autonomic function in patients with acute exacerbation of chronic obstructive pulmonary disease with and without ventricular tachycardia
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