2,753 research outputs found
Tailoring excitonic states of van der Waals bilayers through stacking configuration, band alignment and valley-spin
Excitons in monolayer semiconductors have large optical transition dipole for
strong coupling with light field. Interlayer excitons in heterobilayers, with
layer separation of electron and hole components, feature large electric dipole
that enables strong coupling with electric field and exciton-exciton
interaction, at the cost that the optical dipole is substantially quenched (by
several orders of magnitude). In this letter, we demonstrate the ability to
create a new class of excitons in transition metal dichalcogenide (TMD) hetero-
and homo-bilayers that combines the advantages of monolayer- and
interlayer-excitons, i.e. featuring both large optical dipole and large
electric dipole. These excitons consist of an electron that is well confined in
an individual layer, and a hole that is well extended in both layers, realized
here through the carrier-species specific layer-hybridization controlled
through the interplay of rotational, translational, band offset, and
valley-spin degrees of freedom. We observe different species of such
layer-hybridized valley excitons in different heterobilayer and homobilayer
systems, which can be utilized for realizing strongly interacting
excitonic/polaritonic gases, as well as optical quantum coherent controls of
bidirectional interlayer carrier transfer either with upper conversion or down
conversion in energy
Portal Vein Gas in a Diabetic Patient with Gas-forming Pararenal Abscess
The incidence of portal vein gas (PVG), which used to be an ominous sign of intestinal sepsis, has increased with progressive improvements in imaging modalities. Therefore, the clinical significance of PVG has changed. Emphysematous pyelonephritis (EPN) is a rare, potentially life-threatening and gas-forming infection of the renal parenchyma and/or its surroundings. Gas-forming pararenal abscess presenting with PVG is even rarer. We hereby present the case of a diabetic female with poor glycemic control, who was diagnosed to have EPN and PVG concurrently by computed tomography. She underwent percutaneous catheter drainage (PCD) of the pyelonephritis. Both cultures of blood and pus grew Klebsiella pneumoniae. Her subsequent clinical course was uneventful. In summary, EPN is a rare but potentially fatal urinary tract infection in diabetic patients, and finding PVG on computed tomography can aid in diagnosis. Conservative treatment with intravenous antibiotics and PCD of pus may be adequate for the patient with EPN. However, nephrectomy may be necessary if the patient deteriorates and PCD fails to contain the infection
Implementation and Evaluation of Scalable Approaches for Automatic Chinese Text Categorization
Interleukin 10 promoter haplotype is associated with alcoholic liver cirrhosis in Taiwanese patients
AbstractAlcoholic liver cirrhosis is a severe form of alcohol-related liver damage. More than 95% of heavy drinkers develop a fatty liver, but only 35% of them develop cirrhosis. We postulate that genetic factors may play a role in this difference. Genetic polymorphisms of the cytokine genes may influence Kupffer cells cytokine genes expression. In this study, we evaluated the promoter polymorphisms of interleukin (IL) 1β, IL 6, IL 10, and tumor necrosis factor alpha (TNFα) and aimed to clarify the association between the polymorphisms and the disease. Forty alcoholic patients with liver cirrhosis and 64 healthy volunteers were included in our investigation. Genotyping on IL 1β –511 T>C, IL 6 –572 G>C, IL 10 –819 C>T, IL 10 –1082 G>A, and TNFα –308 G>A was done. Another 36 patients with recurrent alcoholic pancreatitis were included as an additional control group. Genotyping on IL 10 –819 C>T and IL 10 –1082 G>A was done. The polymorphisms on IL 1 and IL 6 showed no significant association. The p value for TNFα –308 G>A was 0.028 in comparison with healthy volunteers. Although the p value was less than 0.05, it did not reach significance after Bonferroni correction. The p values for IL 10 –819 C>T and IL 10 –1082 G>A were respectively 0.031 and 0.026 in healthy volunteers and 0.028 and 0.023 in the alcoholic pancreatitis group. The results also did not reach significance after Bonferroni correction. Among the participants with the GCC haplotype, healthy volunteers had p = 0.027 (p < 0.05) and an odds ratio (OR) of 0.124 [confidence interval (95%) CI, 0.015–0.997], whereas the alcoholic pancreatitis group had p = 0.023 (p < 0.05) and an OR of 0.106 (95% CI, 0.012–0.912). The odds ratio of people having one ATA haplotype was 6.233 (95% CI, 0.739–52.547) in healthy volunteers and 6.588 (95% CI, 0.727–59.679) in the alcoholic pancreatitis group; the corresponding rate was 10.521 (95% CI, 1.252–88.440) and 12.833 (95% CI 1.408–117.008) for people with two ATA haplotypes. The p values in these groups were 0.031 (p < 0.05) and 0.028 (p < 0.05), respectively. The presence of a GCC haplotype could have protective effect against alcoholic liver disease, whereas the presence of an ATA haplotype could predispose carriers to the disease. The IL 10 promoter haplotype is associated with alcoholic liver cirrhosis in Taiwanese patients
Point Defects and Localized Excitons in 2D WSe2
Identifying the point defects in 2D materials is important for many
applications. Recent studies have proposed that W vacancies are the predominant
point defect in 2D WSe2, in contrast to theoretical studies, which predict that
chalcogen vacancies are the most likely intrinsic point defects in transition
metal dichalcogenide semiconductors. We show using first principles
calculations, scanning tunneling microscopy (STM) and scanning transmission
electron microscopy experiments, that W vacancies are not present in our
CVD-grown 2D WSe2. We predict that O-passivated Se vacancies (O_Se) and O
interstitials (Oins) are present in 2D WSe2, because of facile O2 dissociation
at Se vacancies, or due to the presence of WO3 precursors in CVD growth. These
defects give STM images in good agreement with experiment. The optical
properties of point defects in 2D WSe2 are important because single photon
emission (SPE) from 2D WSe2 has been observed experimentally. While strain
gradients funnel the exciton in real space, point defects are necessary for the
localization of the exciton at length scales that enable photons to be emitted
one at a time. Using state-of-the-art GW-Bethe-Salpeter-equation calculations,
we predict that only Oins defects give localized excitons within the energy
range of SPE in previous experiments, making them a likely source of previously
observed SPE. No other point defects (O_Se, Se vacancies, W vacancies and Se_W
antisites) give localized excitons in the same energy range. Our predictions
suggest ways to realize SPE in related 2D materials and point experimentalists
toward other energy ranges for SPE in 2D WSe2
Construction of Papaya Male and Female BAC Libraries and Application in Physical Mapping of the Sex Chromosomes
Papaya is a major fruit crop in the tropics and has recently evolved sex chromosomes. Towards sequencing the papaya sex chromosomes, two bacterial artificial chromosome (BAC) libraries were constructed from papaya male and female genomic DNA. The female BAC library was constructed using restriction enzyme BstY I and consists of 36,864 clones with an average insert size of 104 kb, providing 10.3x genome equivalents. The male BAC library was constructed using restriction enzyme EcoR I and consists of 55,296 clones with an average insert size of 101 kb, providing 15.0x genome equivalents. The male BAC library was used in constructing the physical map of the male-specific region of the male Y chromosome (MSY) and in filling gaps and extending the physical map of the hermaphrodite-specific region of the Yh chromosome (HSY) and the X chromosome physical map. The female BAC library was used to extend the X physical map gap. The MSY, HSY, and X physical maps offer a unique opportunity to study chromosomal rearrangements, Y chromosome degeneration, and dosage compensation of the papaya nascent sex chromosomes
Toona Sinensis Extracts Induced Cell Cycle Arrest and Apoptosis in the Human Lung Large Cell Carcinoma
Toona sinensis extracts have been shown to exhibit anti-cancer effects in human ovarian cancer cell lines, human promyelocytic leukemia cells and human lung adenocarcinoma. Its safety has also been confirmed in animal studies. However, its anti-cancer properties in human lung large cell carcinoma have not been studied. Here, we used a powder obtained by freeze-drying the super-natant of centrifuged crude extract from Toona sinensis leaves (TSL-1) to treat the human lung carcinoma cell line H661. Cell viability was evaluated by the 3-(4-,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Flow cytometry analysis revealed that TSL-1 blocked H661 cell cycle progression. Western blot analysis showed decreased expression of cell cycle proteins that promote cell cycle progression, including cyclin-dependent kinase 4 and cyclin D1, and increased the expression of proteins that inhibit cell cycle progression, including p27. Furthermore, flow cytometry analysis showed that TSL-1 induced H661 cell apoptosis. Western blot analysis showed that TSL-1 reduced the expression of the anti-apoptotic protein B-cell lymphoma 2, and degraded the DNA repair protein, poly(ADP-ribose) polymerase. TSL-1 shows potential as a novel therapeutic agent or for use as an adjuvant for treating human lung large cell carcinoma
Universal geometrical factor of protein conformations as a consequence of energy minimization
The biological activity and functional specificity of proteins depend on
their native three-dimensional structures determined by inter- and
intra-molecular interactions. In this paper, we investigate the geometrical
factor of protein conformation as a consequence of energy minimization in
protein folding. Folding simulations of 10 polypeptides with chain length
ranging from 183 to 548 residues manifest that the dimensionless ratio
(V/(A)) of the van der Waals volume V to the surface area A and average
atomic radius of the folded structures, calculated with atomic radii
setting used in SMMP [Eisenmenger F., et. al., Comput. Phys. Commun., 138
(2001) 192], approach 0.49 quickly during the course of energy minimization. A
large scale analysis of protein structures show that the ratio for real and
well-designed proteins is universal and equal to 0.491\pm0.005. The fractional
composition of hydrophobic and hydrophilic residues does not affect the ratio
substantially. The ratio also holds for intrinsically disordered proteins,
while it ceases to be universal for polypeptides with bad folding properties.Comment: 6 pages, 1 table, 4 figure
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