Developing large-eddy simulation (LES) wall models for separated flows is challenging. We propose to leverage the significance of separated flow data, for which existing theories are not applicable, and the existing knowledge of wall-bounded flows (such as the law of the wall) along with embedded learning to address this issue. The proposed so-called features-embedded-learning (FEL) wall model comprises two submodels: one for predicting the wall shear stress and another for calculating the eddy viscosity at the first off-wall grid nodes. We train the former using the wall-resolved LES (WRLES) data of the periodic hill flow and the law of the wall. For the latter, we propose a modified mixing length model, with the model coefficient trained using the ensemble Kalman method. The proposed FEL model is assessed using the separated flows with different flow configurations, grid resolutions and Reynolds numbers. Overall good a posteriori performance is observed for predicting the statistics of the recirculation bubble, wall stresses and turbulence characteristics. The statistics of the modelled subgrid-scale (SGS) stresses at the first off-wall grids are compared with those calculated using the WRLES data. The comparison shows that the amplitude and distribution of the SGS stresses and energy transfer obtained using the proposed model agree better with the reference data when compared with the conventional SGS model.

In this work, the shape of a bluff body is optimized to mitigate velocity fluctuations of turbulent wake flows based on large-eddy simulations (LES). The Reynolds-averaged Navier–Stokes method fails to capture velocity fluctuations, while direct numerical simulations are computationally prohibitive. This necessitates using the LES method for shape optimization given its scale-resolving capability and relatively affordable computational cost. However, using LES for optimization faces challenges in sensitivity estimation as the chaotic nature of turbulent flows can lead to the blowup of the conventional adjoint-based gradient. Here, we propose using the regularized ensemble Kalman method for the LES-based optimization. The method is a statistical optimization approach that uses the sample covariance between geometric parameters and LES predictions to estimate the model gradient, circumventing the blowup issue of the adjoint method for chaotic systems. Moreover, the method allows for the imposition of smoothness constraints with one additional regularization step. The ensemble-based gradient is first evaluated for the Lorenz system, demonstrating its accuracy in the gradient calculation of the chaotic problem. Further, with the proposed method, the cylinder is optimized to be an asymmetric oval, which significantly reduces turbulent kinetic energy and meander amplitudes in the wake flows. The spectral analysis methods are used to characterize the flow field around the optimized shape, identifying large-scale flow structures responsible for the reduction in velocity fluctuations. Furthermore, it is found that the velocity difference in the shear layer is decreased with the shape change, which alleviates the Kelvin–Helmholtz instability and the wake meandering.

A permeable disk serves as a simplified model for the conversion of wind energy by a horizontal axis wind turbine. In this study, we investigate how inflow turbulence intensity (TI), $I_\infty$, and inflow turbulence integral length scale, $L_\infty$, influence the flow recovery in the wake, the capability of a permeable disk in extracting turbulence kinetic energy (TKE) of the incoming flow, and the statistics of wake-added turbulence using large-eddy simulation. The simulated inflows include various TIs (i.e. $I_\infty =2.5\,\%$–$25\,\%$) and integral length scales (i.e. $L_\infty / D =0.5$–$2.0$) for two thrust coefficients. Simulation results show that both inflow TI and integral length scale influence flow recovery via enhanced ejections and sweeps across the wake boundary, with the former strongly affecting the position where the wake starts to recover and the latter mainly on the recovery rate. Moreover, it is shown that increasing $I_\infty$ and $L_\infty$ increases the TKE extraction by the disk, occurring mainly at scales ($s$) greater than $0.5D$ and frequencies depending on the inflow integral length scale. As for the wake-added TKE, the inflow TI mainly affects its intensity, while the inflow integral length scale affects both its intensity and the sensitive frequencies, with the spectral distributions in scale space ($s$) being similar and the peak located around $s/D=1.0$ for the considered inflows.

Gestational diabetes mellitus (GDM) is a frequent complication of pregnancy. The specific mechanisms underlying GDM have not yet been fully elucidated. Contemporary research indicates a potential association between liver enzyme irregularities and an increased risk of metabolic disorders, including diabetes. The alanine aminotransferase (ALT) level is recognized as a sensitive marker of liver injury. An increase in ALT levels is hypothesized to be linked to the pathogenesis of insulin resistance and diabetes. Nonetheless, the definitive causal link between ALT levels and GDM still needs to be determined. This investigation utilized two-sample Mendelian randomization (MR) to examine the genetic causation between alanine aminotransferase (ALT) and GDM. We acquired alanine aminotransferase (ALT)-related GWAS summary data from the UK Biobank, Million Veteran Program, Rotterdam Study, and Lifeline Study. Gestational diabetes data were obtained from the FinnGen Consortium. We employed various MR analysis techniques, including inverse-variance weighted (IVW), MR Egger, weighted median, simple, and weighted weighting. In addition to MR-Egger intercepts, Cochrane’s Q test was also used to assess heterogeneity in the MR data, and the MR-PRESSO test was used to assess horizontal pleiotropy. To assess the association’s sensitivity, a leave-one-out approach was employed. The IVW results confirmed the independent risk factor for GDM development, as indicated by the ALT level (p = .011). As shown by leave-one-out analysis, horizontal pleiotrophy did not significantly skew the causative link (p > .05). Our dual-sample MR analysis provides substantiated evidence of a genetic causal relationship between alanine aminotransferase (ALT) levels and gestational diabetes.

Mineral-microbe interactions are widespread in a number of environmental processes such as mineral weathering, decomposition, and transformation. Both clay minerals and silicate-weathering bacteria are widely distributed in nature, and the latter contribute to weathering, diagenesis, and mineralization of major rock-forming minerals. The purpose of this study was to observe changes in the chemical composition and structure, especially the phase transformation, of smectite after processing by a silicate-weathering bacterium. The interaction between Bacillus mucilaginosus and bentonite was studied using custom culture media. Results from Inductively Coupled Plasma-Atomic Emission Spectrometry revealed that the bacterium promoted release of Si and Al from solid bentonite to solution. Concomitantly, the Ka nd Fe contents of the mineral increased as shown by X-ray photoelectron spectroscopy results. After interaction with the bacterium, the montmorillonite underwent a possible structure transformation to smectite, as indicated by the emergence of a new weak peak (d = 9.08 Å) shown by X-ray diffraction patterns. The mineralogical changes were also demonstrated by the decrease in the specific surface area of the mineral from 33.0 to 24.0 m2/g (these lower values for SSA of bentonite are related to the particle size of the smectite examined (120-160 mesh) and the weakened absorption bands in Al-O-H and Si-O-Si vibrations by Micro Fourier-transform infrared spectroscopy. The morphology changes in the bacteria observed by environmental scanning electron microscopy and atomic force microscopy revealed an obvious growth of the flagella in the presence of bentonite.

This study is performed to figure out how the presence of diabetes affects the infection, progression and prognosis of 2019 novel coronavirus disease (COVID-19), and the effective therapy that can treat the diabetes-complicated patients with COVID-19. A multicentre study was performed in four hospitals. COVID-19 patients with diabetes mellitus (DM) or hyperglycaemia were compared with those without these conditions and matched by propensity score matching for their clinical progress and outcome. Totally, 2444 confirmed COVID-19 patients were recruited, from whom 336 had DM. Compared to 1344 non-DM patients with age and sex matched, DM-COVID-19 patients had significantly higher rates of intensive care unit entrance (12.43% vs. 6.58%, P = 0.014), kidney failure (9.20% vs. 4.05%, P = 0.027) and mortality (25.00% vs. 18.15%, P < 0.001). Age and sex-stratified comparison revealed increased susceptibility to COVID-19 only from females with DM. For either non-DM or DM group, hyperglycaemia was associated with adverse outcomes, featured by higher rates of severe pneumonia and mortality, in comparison with non-hyperglycaemia. This was accompanied by significantly altered laboratory indicators including lymphocyte and neutrophil percentage, C-reactive protein and urea nitrogen level, all with correlation coefficients >0.35. Both diabetes and hyperglycaemia were independently associated with adverse prognosis of COVID-19, with hazard ratios of 10.41 and 3.58, respectively.

Yaks (Bos grunniens) live primarily in the Qinghai-Tibetan plateau (altitude: 2000–5000 m). Their milk presents unusual characteristics, containing large amounts of solids including fat and protein, and it is, therefore, important to understand the genetic makeup of the yak. To identify potentially critical genes playing a role in yak mammary tissue from colostrum to mature milk phase of lactogenesis, the early lactation (colostrum) stage (ELS; day 1 after parturition) and mature lactation (milk) stage (MLS; day 15) were chosen for comparison. An ELS-specific cDNA library was established by suppression subtractive hybridization and 25 expressed sequence tags at ELS were identified by sequencing and alignment. To further confirm our results the expression levels of 21 genes during the lactation cycle were measured using quantitative real-time RT-PCR (qRT-PCR). The qRT-PCR results confirmed 9 significantly up-regulated genes at ELS vs. MLS in yak mammary tissue, in which the l-amino acid oxidase 1 (LAO1) and collagen, type I, alpha I (COL1A1) were the most significantly up-regulated. During the lactation cycle, the highest expression of some milk fat genes (i.e., XDH and FABP3) in yak mammary tissue appears earlier than that in dairy cow. Our data also indicate MYC potentially playing a central role through putative regulation of COL1A1, CD44, SPARC, FASN and GPAM.

Accelerator mass spectrometry (AMS) is the most sensitive method for measuring 129I in environmental samples available today, with a detection limit of about 10–15 for 129I/127I. A drawback of the technique is the time-consuming chemical separation required to prepare AMS targets from raw samples. This step significantly limits applications requiring rapid analyses and large numbers of samples, for example, in monitoring studies associated with nuclear accidents. This work introduces a direct method for 129I measurements by AMS that does not require chemical separation. In this approach, stable iodine (127I) is added to a matrix of niobium (Nb) powder and mixed with dried raw sample. This mixture is pressed directly into a sputter target for AMS analysis. Two types of environmental samples have been tested in this work, seaweed and sediment. No anomalous behavior was noted in the Cs+ sputtering behavior of the targets prepared from these materials. The 129I/127I ratios and 129I concentrations measured by this rapid method were found to be in agreement with reported values that used a conventional AMS method for the same material. Based on our findings, we expect that such rapid measurements can be applied to a wide variety of materials, in addition to seaweed and sediment, as long as the sputtering-induced adverse effects do not prevent the stable operation of the ion source. The method is especially useful for screening large numbers of samples before more precise analyses are made.

The association of 24 h urinary Na and potassium excretion with the risk of the metabolic syndrome (MetS) has not been studied in China. The aim of the present study was to examine this association by analysing the data from 1906 study participants living in north China. To this end, 24 h urine samples were collected. Of the 1906 participants, 471 (24·7 %) had the MetS. The mean urinary Na and K excretion was 228·7 and 40·8 mmol/d, respectively. After multivariate adjustment, the odds of the MetS significantly increased across the increasing tertiles of urinary Na excretion (1·00, 1·40 and 1·54, respectively). For the components of the MetS, the odds of central obesity, elevated blood pressure and elevated TAG, but not the odds of low HDL-cholesterol and elevated fasting glucose, significantly increased with the successive tertiles of urinary Na excretion. Furthermore, for every 100 mmol/d increase in urinary Na excretion, the odds of the MetS, central obesity, elevated blood pressure and elevated TAG was significantly increased by 29, 63, 22 and 21 %, respectively. However, urinary K excretion was not significantly associated with the risk of the MetS. These findings suggest that high Na intake might be an important risk factor for the MetS in Chinese adults.

In the present work, ZnO and ZnO:Cu thin films with c-axis preferred orientation were prepared on porous silicon, silicon and glass substrates by radio frequency magnetron sputtering technique. X-ray diffraction measurements revealed that the particle size of all samples was in the range of 11.41 ~ 17.67 nm. All the samples exhibited a compressive stress. Fourier transform infrared spectroscopy showed the presence of Si-O-Si stretching appeared at 1067 cm–1, which was assigned to the transverse optical mode of the asymmetric vibration. The E2 (high) mode indicated that the residual stress was observed in the Raman spectra. The optical transmission and absorption spectra were studied, indicating that the optical band gap value shifted to a longer wavelength after Cu doping. Effect of substrate material and Cu doping on the photoluminescence properties of ZnO thin films, along with the origin of some emission peaks, was discussed in detail. The experiment results indicate that the ZnO and ZnO:Cu thin films grown directly on the Si substrates have a high quality of crystallization and intense blue luminescent properties.

Fast linear transformer driver (FLTD) has some advantages in repetitive operation compared with traditional pulsed power generators. However, different types of gas switches applied in the field of pulsed power technology in recent years cannot reach the requirements of repetitive operation of FLTD. Therefore, the capability of repetitive operation of a multigap gas switch has been investigated in a circuit similar to the basic discharge loop named as brick in this paper. The switch has been triggered more than 2000 times and the distribution of delay time and switch jitter are analyzed and reported. Also, the self-breakdown voltages of the switch during different segments of the triggered breakdown experiment have been tested. The experimental results indicate that the delay time obeys the Gauss distribution and the jitter of 2000 times of discharge is about 2.3 ns.

During the lifetime of a galaxy, secular radial mass redistribution is expected to gradually build up a bulge and transform the Hubble type from late to early. The dominant dynamical process responsible for this transformation is a collective instability mediated by density-wave collisionless shocks (Zhang 1996, 1998, 1999). The ability of this new mechanism to secularly redistribute the STELLAR mass provides a general pathway for the formation and evolution of the majority of Hubble types, ranging from late type disk galaxiess to disky ellipticals. ATLAS3D results (Cappellari et al. 2013) showed that spirals and S0s and disky ellipticals form a continuous trend of evolution which also coincides with the aging of the stellar population of galactic disks. The importance of stellar accretion is also revealed in the results of the COSMOS team which showed that the evolution of the black-hole-mass/bulge-mass correlation since z = 1 was mainly due to the mass redistribution on pre-existing STELLAR disks which were already in place by z = 1 (Cisternas et al. 2011). The weaker correlation between the masses of late-type bulges and AGNs observed at any given epoch in our view is a result of the quicker initial onset of accretion events in AGN disks compared to that in galactic disks, since the dynamical timescale is shorter for smaller AGN accretion disks.

The same secular dynamical process can produce and maintain the well-known scaling relations and universal rotation curves of observed galaxies during their Hubble-type transformation (Zhang 2008), as well as reproduce many other observed structural and kinematic properties of galaxies such as the size-line-width relation of the interstellar medium and the age-velocity dispersion relation of solar neighborhood stars in our own Galaxy. A by-product of this analysis is a powerful new method for locating the multiple corotation resonances in galaxies (Zhang & Buta 2007; Buta & Zhang 2009).

The current work also highlights the connection between collective effects in galactic dynamics and nonequilibrium phase transition processes in other branches of physics such as fluid turbulence and spontaneous breaking of gauge symmetry in high-energy physics. The continuous build-up of the Hubble sequence of galaxies through secular mass accretion also hints at the baryonic nature of galactic dark matter and poses challenges to the existing LCDM paradigm, since the well-known adiabatic compression process during baryonic mass inflow produced by secular evolution would lead to a concentration of the cold dark matter to the central region of early-type galaxies, which is not observed.

Deep surveys conducted during the past decades have shown that galaxies in the distant universe are generally of more irregular shapes, and are disky in appearance and in their star formation rate, compared to galaxies in similar environments in the nearby universe. Given that the merger rate between z= 2 and the local universe is far from adequate to account for this observed morphological transformation rate, an internal mechanism for the morphological transformation of galaxies is to be sought, whose operation can be further aided by environmental factors. The secular evolution mechanism, especially with the discovery of a collisionless dissipation mechanism for stars within the secular evolution paradigm, has provided just such a framework for understanding the morphological evolution of galaxies across the Hubble time. In this paper we will summarize the past theoretical results on the dynamical mechanisms for secular evolution, and highlight new results in the analysis of the observational data, which confirmed that density waves in physical galaxies possess the kind of characteristics which could produce theáobserved rates of morphological transformation for both cluster and field galaxies.

The approaches proposed in the past for determining the pattern speeds and corotation radii of the density waves in spiral and barred galaxies are mostly limited in their scope and accuracy. In this work, we have developed a general approach for the determination of corotation radii, which is applicable to any galaxy whose density wave modes have reached quasi-steady state – a condition empirically found to be the case for most nearby disk galaxies. The method utilizes an azimuthal phase shift between the potential and the density distributions for the density wave modes, the existence and the radial variations of which are closely related to the dynamical mechanism leading to the secular evolution of the basic state of the same disk galaxies (Zhang 1996, ApJ, 457, 125). We have used this method to derive corotation radii of over 100 galaxies using the near-infrared images of the Ohio State University Bright Galaxy Survey (OSUBGS, Eskridge et al. 2002, ApJS, 143, 73).

We present a novel nanotube-on-insulator (NOI) approach to produce high-yield nanotube devices based on aligned single-walled carbon nanotubes. First, we managed to grow aligned nanotube arrays with controlled density on crystalline, insulating sapphire substrates, which bear analogy to industry-adopted silicon-on-insulator substrates. Based on the nanotube arrays, we demonstrated registration-free fabrication of both top-gated and polymer-electrolyte-gated field-effect transistors with minimized parasitic capacitance. In addition, we have successfully developed a way to transfer these aligned nanotube arrays to flexible substrates. Our approach has great potential for high-density, large-scale integrated systems based on carbon nanotubes for both micro- and flexible electronics.

We have successfully used a transfer printing technique to directly transfer vacuum-filtered nanotube film to glass and plastic substrates. Our typical SWNT-film has a transparency of ∼80% and a sheet resistance around 400 Ohm/square. Further improvement to the nanotube film includes SOCl2 doping and PEDOT passivation, which significantly improve the sheet conductance and surface quality of the nanotube films. We have applied the optimized SWNT films as hole injection electrodes to demonstrate OLEDs on both rigid glass and flexible substrates.

InN nanowires were synthesized and characterized using a variety of techniques. A two-zone chemical vapor deposition technique was used to operate the vapor generation and the nanowire growth at differential temperatures, leading to high-quality single-crystalline nanowires and growth rates as high as 4–10 μm/h. Precise diameter control was achieved by using monodispersed gold clusters as the catalyst. Photoluminescence and Raman studies have been carried out for the InN nanowires at room temperature. Devices consisting of single nanowires have been fabricated to explore their electronic transport properties. The temperature dependence of the conductance revealed thermal emission as the dominating transport mechanism.

In2O3 nanowire and carbon nanotube transistors were used to study the chemical gating effects in response to LDL particles. Low density lipoprotein (LDL) cholesterol in blood constitutes a risk factor for coronary artery disease (heart attack). The interactions of LDL particles with these two different surfaces were investigated. The degree of LDL particles binding to carbon nanotubes was ten-fold higher than to In2O3 nanowires possibly owing to the hydrophobic/hydrophilic interactions. The conductance of field effect transistors (FET) based on nanowires and nanotubes showed complementary responses after exposure to LDL particles. While In2O3 nanowire transistors exhibited higher conductance accompanied by a negative shift of the threshold voltage, nanotube transistors displayed a lower conductance. This phenomenon was attributed to the complementary doping between the n-type In2O3 nanowires and p-type carbon nanotubes.