403 research outputs found
Distribution of magnetic domain pinning fields in GaMnAs ferromagnetic films
Using the angular dependence of the planar Hall effect in GaMnAs
ferromagnetic films, we were able to determine the distribution of magnetic
domain pinning fields in this material. Interestingly, there is a major
difference between the pinning field distribution in as-grown and in annealed
films, the former showing a strikingly narrower distribution than the latter.
This conspicuous difference can be attributed to the degree of non-uniformity
of magnetic anisotropy in both types of films. This finding provides a better
understanding of the magnetic domain landscape in GaMnAs that has been the
subject of intense debate
Carrier-mediated antiferromagnetic interlayer exchange coupling in diluted magnetic semiconductor multilayers GaMnAs/GaAs:Be
We use neutron reflectometry to investigate the interlayer exchange coupling
between GaMnAs ferromagnetic semiconductor layers separated
by non-magnetic Be-doped GaAs spacers. Polarized neutron reflectivity measured
below the Curie temperature of GaMnAs reveals a
characteristic splitting at the wave vector corresponding to twice the
multilayer period, indicating that the coupling between the ferromagnetic
layers are antiferromagnetic (AFM). When the applied field is increased to
above the saturation field, this AFM coupling is suppressed. This behavior is
not observed when the spacers are undoped, suggesting that the observed AFM
coupling is mediated by charge carriers introduced via Be doping. The behavior
of magnetization of the multilayers measured by DC magnetometry is consistent
with the neutron reflectometry results.Comment: 4 pages, 4 figure
Repurposing metformin for cancer treatment: current clinical studies.
In recent years, several studies have presented evidence suggesting a potential role for metformin in anti-cancer therapy. Preclinical studies have demonstrated several anticancer molecular mechanisms of metformin including mTOR inhibition, cytotoxic effects, and immunomodulation. Epidemiologic data have demonstrated decreased cancer incidence and mortality in patients taking metformin. Several clinical trials, focused on evaluation of metformin as an anti-cancer agent are presently underway. Data published from a small number of completed trials has put forth intriguing results. Clinical trials in pre-surgical endometrial cancer patients exhibited a significant decrease in Ki67 with metformin monotherapy. Another interesting observation was made in patients with breast cancer, wherein a trend towards improvement in cancer proliferation markers was noted in patients without insulin resistance. Data on survival outcomes with the use of metformin as an anti-cancer agent is awaited. This manuscript will critically review the role of metformin as a potential cancer treatment
Crossover critical behavior of Ga1-xMnxAs
The critical behavior of Ga1-xMnxAs in a close vicinity of the Curie
temperature was experimentally studied by using the thermal diffusivity
measurements. Taking into account that the inverse of the thermal diffusivity
has the same critical behavior as the specific heat, the critical exponent
{\alpha} for the samples investigated has been determined. With approaching
close to the critical temperature, the crossover from the mean-field-like to
the Ising-like critical behavior has been observed. From the crossover behavior
the values of the Ginzburg number and the exchange interaction length in
Ga1-xMnxAs with different concentrations of Mn were determined.Comment: 17 pages, 5 figure
Unveiling the carrier transport mechanism in epitaxial graphene for forming wafer-scale, single-domain graphene
Graphene epitaxy on the Si face of a SiC wafer offers monolayer graphene with unique crystal orientation at the wafer-scale. However, due to carrier scattering near vicinal steps and excess bilayer stripes, the size of electrically uniform domains is limited to the width of the terraces extending up to a few microns. Nevertheless, the origin of carrier scattering at the SiC vicinal steps has not been clarified so far. A layer-resolved graphene transfer (LRGT) technique enables exfoliation of the epitaxial graphene formed on SiC wafers and transfer to flat Si wafers, which prepares crystallographically single-crystalline monolayer graphene. Because the LRGT flattens the deformed graphene at the terrace edges and permits an access to the graphene formed at the side wall of vicinal steps, components that affect the mobility of graphene formed near the vicinal steps of SiC could be individually investigated. Here, we reveal that the graphene formed at the side walls of step edges is pristine, and scattering near the steps is mainly attributed by the deformation of graphene at step edges of vicinalized SiC while partially from stripes of bilayer graphene. This study suggests that the two-step LRGT can prepare electrically single-domain graphene at the wafer-scale by removing the major possible sources of electrical degradation
Automatic segmentation of multiple cardiovascular structures from cardiac computed tomography angiography images using deep learning.
OBJECTIVES:To develop, demonstrate and evaluate an automated deep learning method for multiple cardiovascular structure segmentation. BACKGROUND:Segmentation of cardiovascular images is resource-intensive. We design an automated deep learning method for the segmentation of multiple structures from Coronary Computed Tomography Angiography (CCTA) images. METHODS:Images from a multicenter registry of patients that underwent clinically-indicated CCTA were used. The proximal ascending and descending aorta (PAA, DA), superior and inferior vena cavae (SVC, IVC), pulmonary artery (PA), coronary sinus (CS), right ventricular wall (RVW) and left atrial wall (LAW) were annotated as ground truth. The U-net-derived deep learning model was trained, validated and tested in a 70:20:10 split. RESULTS:The dataset comprised 206 patients, with 5.130 billion pixels. Mean age was 59.9 ± 9.4 yrs., and was 42.7% female. An overall median Dice score of 0.820 (0.782, 0.843) was achieved. Median Dice scores for PAA, DA, SVC, IVC, PA, CS, RVW and LAW were 0.969 (0.979, 0.988), 0.953 (0.955, 0.983), 0.937 (0.934, 0.965), 0.903 (0.897, 0.948), 0.775 (0.724, 0.925), 0.720 (0.642, 0.809), 0.685 (0.631, 0.761) and 0.625 (0.596, 0.749) respectively. Apart from the CS, there were no significant differences in performance between sexes or age groups. CONCLUSIONS:An automated deep learning model demonstrated segmentation of multiple cardiovascular structures from CCTA images with reasonable overall accuracy when evaluated on a pixel level
Critical role of next-nearest-neighbor interlayer interaction in magnetic behavior of magnetic/nonmagnetic multilayers
We report magnetoresistance data in magnetic semiconductor multilayers, which
exhibit a clear step-wise behavior as a function of external field. We
attribute this highly non-trivial step-wise behavior to next-nearest-neighbor
interlayer exchange coupling. Our microscopic calculation suggests that this
next-nearest-neighbor coupling can be as large as 24% of the nearest-neighbor
coupling. It is argued that such unusually long-range interaction is made
possible by the quasi-one-dimensional nature of the system and by the long
Fermi wavelength characteristic of magnetic semiconductors
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Percent atheroma volume: Optimal variable to report whole-heart atherosclerotic plaque burden with coronary CTA, the PARADIGM study.
BACKGROUND AND AIMS:Different methodologies to report whole-heart atherosclerotic plaque on coronary computed tomography angiography (CCTA) have been utilized. We examined which of the three commonly used plaque burden definitions was least affected by differences in body surface area (BSA) and sex. METHODS:The PARADIGM study includes symptomatic patients with suspected coronary atherosclerosis who underwent serial CCTA >2 years apart. Coronary lumen, vessel, and plaque were quantified from the coronary tree on a 0.5 mm cross-sectional basis by a core-lab, and summed to per-patient. Three quantitative methods of plaque burden were employed: (1) total plaque volume (PV) in mm3, (2) percent atheroma volume (PAV) in % [which equaled: PV/vessel volume * 100%], and (3) normalized total atheroma volume (TAVnorm) in mm3 [which equaled: PV/vessel length * mean population vessel length]. Only data from the baseline CCTA were used. PV, PAV, and TAVnorm were compared between patients in the top quartile of BSA vs the remaining, and between sexes. Associations between vessel volume, BSA, and the three plaque burden methodologies were assessed. RESULTS:The study population comprised 1479 patients (age 60.7 ± 9.3 years, 58.4% male) who underwent CCTA. A total of 17,649 coronary artery segments were evaluated with a median of 12 (IQR 11-13) segments per-patient (from a 16-segment coronary tree). Patients with a large BSA (top quartile), compared with the remaining patients, had a larger PV and TAVnorm, but similar PAV. The relation between larger BSA and larger absolute plaque volume (PV and TAVnorm) was mediated by the coronary vessel volume. Independent from the atherosclerotic cardiovascular disease risk (ASCVD) score, vessel volume correlated with PV (P < 0.001), and TAVnorm (P = 0.003), but not with PAV (P = 0.201). The three plaque burden methods were equally affected by sex. CONCLUSIONS:PAV was less affected by patient's body surface area then PV and TAVnorm and may be the preferred method to report coronary atherosclerotic burden
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