351 research outputs found
Low-energy electronic interactions in ferrimagnetic Sr2CrReO6 thin films
We reveal in this study the fundamental low-energy landscape in the
ferrimagnetic Sr2CrReO6 double perovskite and describe the underlying
mechanisms responsible for the three low-energy excitations below 1.4 eV. Based
on resonant inelastic x-ray scattering and magnetic dynamics calculations, and
experiments collected from both Sr2CrReO6 powders and epitaxially strained thin
films, we reveal a strong competition between spin-orbit coupling, Hund's
coupling, and the strain-induced tetragonal crystal field. We also demonstrate
that a spin-flip process is at the origin of the lowest excitation at 200 meV,
and we bring insights into the predicted presence of orbital ordering in this
material. We study the nature of the magnons through a combination of ab initio
and spin-wave theory calculations, and show that two nondegenerate magnon bands
exist and are dominated either by rhenium or chromium spins. The rhenium band
is found to be flat at about 200 meV (25 meV) through X-L-W-U
high-symmetry points and is dispersive toward Comment: 6 figure
Interface structures of i n c l i n e d ZnO thin film on ( 011 ) -MgO substrate with bulk-like optical properties
Abstract(#br)Combining different phase structure materials with unique properties to design novel devices plays a significant role in the development of modern electronics. Here, we explore the characteristics of this type of complex interface and epitaxy structures based on the coupling between hexagonal ZnO film and cubic MgO substrate. The ZnO film was prepared by the molecular beam epitaxy technique on the MgO ( 011 ) substrate. The analysis results from the in situ reflection high energy electron diffraction patterns, X-ray diffraction (XRD)-pole figures and high resolution transmission electron microscopy images demonstrate that the film exhibits two-fold symmetry domains with a growth direction deviated from c-axis at about 31 ° along the [ 010 ] MgO or [ 0 1 ¯ 0 ] MgO azimuth. Despite the intertwined diffusion from Zn and Mg atoms in the interface, which is the possible origin of a blue shift of about 0.083 eV in the Photoluminescence (PL) spectrum, the inclined film shows a full width at half maximum value that is close to the reported value from the high quality film. This work hopefully provides useful insights to the design and exploration of the novel optoelectronic devices that involve the integration of materials with different structure and different properties
Quantitative analysis and comparison of 3D morphology between viable and apoptotic MCF-7 breast cancer cells and characterization of nuclear fragmentation
Morphological changes in apoptotic cells provide essential markers for defining and detection
of apoptosis as a fundamental mechanism of cell death. Among these changes, the
nuclear fragmentation and condensation have been regarded as the important markers but
quantitative characterization of these changes is yet to be achieved. We have acquired confocal
image stacks of 206 viable and apoptotic MCF-7 cells stained by three fluorescent
dyes. Three-dimensional (3D) parameters were extracted to quantify and compare their differences
in morphology. To analyze nuclear fragmentation, a new method has been developed
to determine clustering of nuclear voxels in the reconstructed cells due to fluorescence
intensity changes in nuclei of apoptotic cells. The results of these studies reveal that the 3D
morphological changes in cytoplasm and nuclear membranes in apoptotic cells provide sensitive
targets for label-free detection and staging of apoptosis. Furthermore, the clustering
analysis and morphological data on nuclear fragmentation are highly useful for derivation of
optical cell models and simulation of diffraction images to investigate light scattering by
early apoptotic cells, which can lead to future development of label-free and rapid methods
of apoptosis assay based on cell morphology.Open Access Fundin
Platelet factor-4 and its p17-70 peptide inhibit myeloma proliferation and angiogenesis in vivo
<p>Abstract</p> <p>Background</p> <p>Angiogenesis plays an important role in the development of multiple myeloma (MM). The interaction between MM cells and the bone marrow microenvironment stimulates the proliferation and migration of endothelial progenitor cells (EPCs). Vascular endothelial growth factor (VEGF) contributes to the formation of new blood vessels by actively recruiting circulating EPCs. The production of proangiogenic and antiangiogenic factors is also dysregulated in MM. Platelet factor 4 (PF4) is a potent angiostatic cytokine that inhibits angiogenesis and tumor growth in several animal models.</p> <p>Methods</p> <p>In this study, we stably transfected human myeloma cell lines with the PF4 gene or the sequence encoding its more potent p17-70 peptide and investigated the effects of PF4 and p17-70 on angiogenesis and tumor growth <it>in vitro </it>and in a SCID-rab myeloma model.</p> <p>Results</p> <p>PF4 and p17-70 significantly attenuated VEGF production, both <it>in vitro </it>and <it>in vivo</it>. In a migration study using a Transwell system, PF4 or p17-70 markedly suppressed the migration of co-cultured human endothelial progenitor cells. PF4 or p17-70 also caused a significant reduction in microvessel densities in myeloma xenografts and markedly reduced the tumor volume in the SCID mice. Kaplan-Meier analysis demonstrated that PF4 and p17-70 significantly extended the overall survival of SCID mice bearing human myeloma xenografts.</p> <p>Conclusions</p> <p>Our findings indicate that PF4 or p17-70 could be valuable in combating multiple myeloma by disrupting tumor angiogenesis.</p
Measurement report: The 4-year variability and influence of the Winter Olympics and other special events on air quality in urban Beijing during wintertime
Comprehensive measurements are vital to obtain big enough
datasets for better understanding the complex atmosphere and further
improving the air quality. To investigate the 4-year variation of air
quality and the influences of special events (Beijing Winter Olympics, COVID
lockdown and Chinese New Year) on it during the wintertime in polluted urban
air, we conducted comprehensive observations in Beijing, China, during
1 January–20 February, in the years from 2019 to 2022. The
mass concentration of PM2.5 and its composition (organics, nitrate,
sulfate, ammonium, chloride and black carbon) and the number size distributions of
particles (down to ∼1 nm) and ions, gaseous pollutants (CO,
NOx, SO2, O3) and condensable vapors (sulfuric acid and
oxygenated organic molecules), as well as meteorological parameters, were
simultaneously measured. The days before 22 January without any
special events in each year were selected to investigate the 4-year
variability of air quality. We found that the concentrations of CO,
NOx, total oxygenated organic molecules (OOMs), total PM2.5,
organics, chloride and black carbon and the number concentration of sub-3 nm
particles (N1.3−3) showed similar variations, decreasing from 2019 to
2021 and then increasing in 2022. For SO2, however, its concentration
decreased year by year due to the significant emission reduction, further
leading to the decrease of gaseous sulfuric acid and particulate sulfate
from 2019 to 2022. O3 concentration showed an opposite 4-year
variation compared with NOx. Meanwhile, both the oxygen and nitrogen
contents of oxygenated organic molecules increased year by year, implying
that not only the oxidation state of those compounds increased, but also
NOx was involved more efficiently in their formation processes. With
higher sulfuric acid concentrations and new particle formation (NPF) frequencies in 2021 than in
2022, and with the lowest concentrations of background aerosols and the
lowest ambient temperatures in 2021, N1.3−3 was still the lowest in
2021. Unlike N1.3−3, the ion concentrations in both 0.8–2 and
2–4 nm size ranges were higher in 2021 than in the other years. Then, the
days after 4 February were chosen to explore the influence of special
events. The non-event days within this date range in 2019 and 2021 were
chosen as the reference period. Due to the favorable meteorological
conditions together with reductions in anthropogenic emissions, there were
basically no haze events during the Olympics. Therefore, CO, NOx,
SO2, total OOMs, accumulation-mode particles (N100−1000), and total
PM2.5 and its composition were much lower, while ion concentrations
were much higher compared with the reference period. Although there was also
emission reduction during COVID, especially for NOx, the
enhancement of secondary inorganic aerosol formation, together with
unfavorable meteorological conditions, caused severe haze events during this
period. Hence, CO, total OOMs and all PM2.5 compositions during
COVID increased dramatically compared with the reference period. Influenced
by SO2, condensation sink and sunlight, sulfuric acid concentration was
found to be comparable between the Olympics and the reference period but was
lower during COVID and Chinese New Year. Additionally, N1.3−3 was
almost at the same level during different periods, indicating that the
special events only had little impact on the NPF
processes. These results provide useful information to the development of
more targeted pollution control plans.</p
Sequences of B-Chain/Domain 1−10/1−9 of Insulin and Insulin-like Growth Factor 1 Determine Their Different Folding Behavior †
Discovery of Pod Shatter-Resistant Associated SNPs by Deep Sequencing of a Representative Library Followed by Bulk Segregant Analysis in Rapeseed
Background: Single nucleotide polymorphisms (SNPs) are an important class of genetic marker for target gene mapping. As of yet, there is no rapid and effective method to identify SNPs linked with agronomic traits in rapeseed and other crop species. Methodology/Principal Findings: We demonstrate a novel method for identifying SNP markers in rapeseed by deep sequencing a representative library and performing bulk segregant analysis. With this method, SNPs associated with rapeseed pod shatter-resistance were discovered. Firstly, a reduced representation of the rapeseed genome was used. Genomic fragments ranging from 450–550 bp were prepared from the susceptible bulk (ten F2 plants with the silique shattering resistance index, SSRI,0.10) and the resistance bulk (ten F2 plants with SSRI.0.90), and also Solexa sequencingproduced 90 bp reads. Approximately 50 million of these sequence reads were assembled into contigs to a depth of 20-fold coverage. Secondly, 60,396 ‘simple SNPs ’ were identified, and the statistical significance was evaluated using Fisher’s exact test. There were 70 associated SNPs whose –log10p value over 16 were selected to be further analyzed. The distribution of these SNPs appeared a tight cluster, which consisted of 14 associated SNPs within a 396 kb region on chromosome A09. Our evidence indicates that this region contains a major quantitative trait locus (QTL). Finally, two associated SNPs from this region were mapped on a major QTL region
Zinc Overload Enhances APP Cleavage and Aβ Deposition in the Alzheimer Mouse Brain
BACKGROUND: Abnormal zinc homeostasis is involved in β-amyloid (Aβ) plaque formation and, therefore, the zinc load is a contributing factor in Alzheimer's disease (AD). However, the involvement of zinc in amyloid precursor protein (APP) processing and Aβ deposition has not been well established in AD animal models in vivo. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, APP and presenilin 1 (PS1) double transgenic mice were treated with a high dose of zinc (20 mg/ml ZnSO4 in drinking water). This zinc treatment increased APP expression, enhanced amyloidogenic APP cleavage and Aβ deposition, and impaired spatial learning and memory in the transgenic mice. We further examined the effects of zinc overload on APP processing in SHSY-5Y cells overexpressing human APPsw. The zinc enhancement of APP expression and cleavage was further confirmed in vitro. CONCLUSIONS/SIGNIFICANCE: The present data indicate that excess zinc exposure could be a risk factor for AD pathological processes, and alteration of zinc homeostasis is a potential strategy for the prevention and treatment of AD
Diagnostic value of fine-needle aspiration biopsy for breast mass: a systematic review and meta-analysis
<p>Abstract</p> <p>Background</p> <p>Fine-needle aspiration biopsy (FNAB) of the breast is a minimally invasive yet maximally diagnostic method. However, the clinical use of FNAB has been questioned. The purpose of our study was to establish the overall value of FNAC in the diagnosis of breast lesions.</p> <p>Methods</p> <p>After a review and quality assessment of 46 studies, sensitivity, specificity and other measures of accuracy of FNAB for evaluating breast lesions were pooled using random-effects models. Summary receiver operating characteristic curves were used to summarize overall accuracy. The sensitivity and specificity for the studies data (included unsatisfactory samples) and underestimation rate of unsatisfactory samples were also calculated.</p> <p>Results</p> <p>The summary estimates for FNAB in diagnosis of breast carcinoma were as follows (unsatisfactory samples was temporarily exluded): sensitivity, 0.927 (95% confidence interval [CI], 0.921 to 0.933); specificity, 0.948 (95% CI, 0.943 to 0.952); positive likelihood ratio, 25.72 (95% CI, 17.35 to 28.13); negative likelihood ratio, 0.08 (95% CI, 0.06 to 0.11); diagnostic odds ratio, 429.73 (95% CI, 241.75 to 763.87); The pooled sensitivity and specificity for 11 studies, which reported unsatisfactory samples (unsatisfactory samples was considered to be positive in this classification) were 0.920 (95% CI, 0.906 to 0.933) and 0.768 (95% CI, 0.751 to 0.784) respectively. The pooled proportion of unsatisfactory samples that were subsequently upgraded to various grade cancers was 27.5% (95% CI, 0.221 to 0.296).</p> <p>Conclusions</p> <p>FNAB is an accurate biopsy for evaluating breast malignancy if rigorous criteria are used. With regard to unsatisfactory samples, futher invasive procedures are required in order to minimize the chance of a missed diagnosis of breast cancer.</p
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