Controlling spin-orbit coupling to tailor type-II Dirac bands

NiTe2, a type-II Dirac semimetal with strongly tilted Dirac band, has been explored extensively to understand its intriguing topological properties. Here, using density-functional theory (DFT) calculations, we report that the strength of spin-orbit coupling (SOC) in NiTe2 can be tuned by Se substitution. This results in negative shifts of the bulk Dirac point (BDP) while preserving the type-II Dirac band. Indeed, combined studies using scanning tunneling spectroscopy (STS) and angle-resolved photoemission spectroscopy (ARPES) confirm that the BDP in the NiTe2-xSex alloy moves from +0.1 eV (NiTe2) to -0.3 eV (NiTeSe) depending on the Se concentrations, indicating the effective tunability of type-II Dirac fermions. Our results demonstrate an approach to tailor the type-II Dirac band in NiTe2 by controlling the SOC strength via chalcogen substitution. This approach can be applicable to different types of topological materials.Comment: 25 pages, 4 figure

Identification of the Hard X-Ray Source Dominating the E > 25 keV Emission of the Nearby Galaxy M31

We report the identification of a bright hard X-ray source dominating the M31 bulge above 25 keV from a simultaneous NuSTAR–Swift observation. We find that this source is the counterpart to Swift J0042.6+4112, which was previously detected in the Swift BAT All-sky Hard X-ray Survey. This Swift BAT source had been suggested to be the combined emission from a number of point sources; our new observations have identified a single X-ray source from 0.5 to 50 keV as the counterpart for the first time. In the 0.5–10 keV band, the source had been classified as an X-ray Binary candidate in various Chandra and XMM-Newton studies; however, since it was not clearly associated with Swift J0042.6+4112, the previous E 3M⊙ donors at the location of this source. The best interpretation for the nature of this source is an X-ray pulsar with an intermediate-mass <3M⊙ companion or a symbiotic X-ray binary. We discuss other possibilities in more detail

Effects of sn-2 palmitic acid-fortified vegetable oil and fructooligosaccharide on calcium metabolism in growing rats fed casein based diet

This study was carried out to investigate the efficacy of sn-2 palmitic acid-fortified vegetable oil (Sn2PA) on calcium absorption and to confirm the synergistic effects of fructooligosaccharide on calcium absorption. Male SD rats were fed 6 kinds of casein based diets containing vegetable oil (control), sn-2 palmitic acid-fortified vegetable oil (Sn2PA) and Sn2PA with fructooligosaccharide(Sn2PAFO) in two levels of calcium (normal 0.5% and high 1.0%) for 3 weeks. Total lipids, cholesterol, triglyceride and calcium in blood were measured. Feces were collected using cages for 4 days. Serum concentrations of total lipids and calcium were not significantly different among groups. However, serum triglyceride was significantly decreased by fructooligosaccharide supplementation regardless of dietary calcium level. The lipid absorption was not significantly different among experimental groups. Calcium absorption was significantly higher in Sn2PAFO group than other groups. Calcium solubility of intestine was increased by sn-2 palmitic acid supplementation. These results suggest that sn-2 palmitic acid and fructooligosaccharide supplementation could be beneficial for baby foods including infant formula, with regard to increasing absorption of calcium by more soluble calcium in the small intestinal content

Nonlinear disintegration of the internal tide

Author Posting. © American Meteorological Society, 2008. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 38 (2008): 686-701, doi:10.1175/2007JPO3826.1.The disintegration of a first-mode internal tide into shorter solitary-like waves is considered. Since observations frequently show both tides and waves with amplitudes beyond the restrictions of weakly nonlinear theory, the evolution is studied using a fully nonlinear, weakly nonhydrostatic two-layer theory that includes rotation. In the hydrostatic limit, the governing equations have periodic, nonlinear inertia–gravity solutions that are explored as models of the nonlinear internal tide. These long waves are shown to be robust to weak nonhydrostatic effects. Numerical solutions show that the disintegration of an initial sinusoidal linear internal tide is closely linked to the presence of these nonlinear waves. The initial tide steepens due to nonlinearity and sheds energy into short solitary waves. The disintegration is halted as the longwave part of the solution settles onto a state close to one of the nonlinear hydrostatic solutions, with the short solitary waves superimposed. The degree of disintegration is a function of initial amplitude of the tide and the properties of the underlying nonlinear hydrostatic solutions, which, depending on stratification and tidal frequency, exist only for a finite range of amplitudes (or energies). There is a lower threshold below which no short solitary waves are produced. However, for initial amplitudes above another threshold, given approximately by the energy of the limiting nonlinear hydrostatic inertia–gravity wave, most of the initial tidal energy goes into solitary waves. Recent observations in the South China Sea are briefly discussed.KRH was supported by a Woods Hole Oceanographic Institution Mellon Independent Study Award and ONR Grant N000140610798

Outcomes of respiratory viral-bacterial co-infection in adult hospitalized patients

Background: Viral infections of the respiratory tract represent a major global health concern. Co-infection with bacteria may contribute to severe disease and increased mortality in patients. Nevertheless, viral-bacterial co-infection patterns and their clinical outcomes have not been well characterized to date. This study aimed to evaluate the clinical features and outcomes of patients with viral-bacterial respiratory tract co-infections. Methods: We included 19,361 patients with respiratory infection due to respiratory viruses [influenza A and B, respiratory syncytial virus (RSV), parainfluenza] and/or bacteria in four tertiary hospitals in Hong Kong from 2013 to 2017 using a large territory-wide healthcare database. All microbiological tests were conducted within 48 h of hospital admission. Four etiological groups were included: (1) viral infection alone; (2) bacterial infection alone; (3) laboratory-confirmed viral-bacterial co-infection and (4) clinically suspected viral-bacterial co-infection who were tested positive for respiratory virus and negative for bacteria but had received at least four days of antibiotics. Clinical features and outcomes were recorded for laboratory-confirmed viral-bacterial co-infection patients compared to other three groups as control. The primary outcome was 30-day mortality. Secondary outcomes were intensive care unit (ICU) admission and length of hospital stay. Propensity score matching estimated by binary logistic regression was used to adjust for the potential bias that may affect the association between outcomes and covariates. Findings: Among 15,906 patients with respiratory viral infection, there were 8451 (53.1%) clinically suspected and 1,087 (6.8%) laboratory-confirmed viral-bacterial co-infection. Among all the bacterial species, Haemophilus influenzae (226/1,087, 20.8%), Pseudomonas aeruginosa (180/1087, 16.6%) and Streptococcus pneumoniae (123/1087, 11.3%) were the three most common bacterial pathogens in the laboratory-confirmed co-infection group. Respiratory viruses co-infected with non-pneumococcal streptococci or methicillin-resistant Staphylococcus aureus was associated with the highest death rate [9/30 (30%) and 13/48 (27.1%), respectively] in this cohort. Compared with other infection groups, patients with laboratory-confirmed co-infection had higher ICU admission rate (p < 0.001) and mortality rate at 30 days (p = 0.028), and these results persisted after adjustment for potential confounders using propensity score matching. Furthermore, patients with laboratory-confirmed co-infection had significantly higher mortality compared to patients with bacterial infection alone. Interpretation: In our cohort, bacterial co-infection is common in hospitalized patients with viral respiratory tract infection and is associated with higher ICU admission rate and mortality. Therefore, active surveillance for bacterial co-infection and early antibiotic treatment may be required to improve outcomes in patients with respiratory viral infection