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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.
To examine the association of 24 h urinary Na excretion and Na:K with obesity in Chinese adults.
Population-based cross-sectional study using a four-stage stratified sampling strategy.
Shandong Province, China.
Chinese adults (n 1906) aged 18–69 years who provided complete 24 h urine samples.
Odds of obesity increased significantly across increasing quartiles of urinary Na excretion (1·00, 1·54, 1·69 and 2·52, respectively, for overweight; 1·00, 1·20, 1·50, and 2·03, respectively, for obesity; 1·00, 1·44, 1·85 and 2·53, respectively, for abdominal obesity (assessed by waist circumference); and 1·00, 1·28, 1·44 and 1·75, respectively, for abdominal obesity (assessed by waist-to-height ratio); P for linear trend <0·001 for all). In addition, odds of abdominal obesity, but not odds of overweight and obesity, increased significantly with successive Na:K quartiles. Additionally, for each increment in urinary Na excretion of 100 mmol, odds of overweight, obesity, abdominal obesity (by waist circumference) and abdominal obesity (by waist-to-height ratio) increased significantly by 46 %, 39 %, 55 % and 33 %, respectively. Similarly, with a 1 sd increase in Na:K, odds of abdominal obesity (by waist circumference) and abdominal obesity (by waist-to-height ratio) increased significantly by 12 % and 15 %, respectively.
These findings suggest that 24 h urinary Na excretion and Na:K might be important risk factors for obesity in Chinese adults.
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.
The secular evolution process which slowly transforms the morphology of a given galaxy over its lifetime through mostly internal dynamical mechanisms could naturally account for most of the observed properties of physical galaxies (Zhang 2003a). As an emerging paradigm for galaxy evolution, its dynamical foundations had been established in the past few years (Zhang 1996, 1998, 1999). in this paper, we explore further implications of the secular morphological evolution process in reproducing the well-known scaling relations of galaxies.
We present a new approach to engineer the band structure of carbon nanotube field-effect transistors via selected area chemical gating. By exposing the center part or the contacts of the nanotube devices to oxidizing or reducing gases, a good control over the threshold voltage and subthreshold swing has been achieved. Our experiments reveal that NO2 shifts the threshold voltage higher while NH3 shifts it lower for both center-exposed and contact-exposed devices. However, modulations to the subthreshold swing are in opposite directions for center-exposed and contact-exposed devices: NO2 lowers the subthreshold swing of the contact-exposed devices, but increases that of the center-exposed devices; In contrast, NH3 reduces the subthreshold swing of the center-exposed devices, but increases that of the contact-exposed devices. A model has been developed based on Langmuir isotherm, and the experimental results can be well explained.
Chemical vapor deposition (CVD) using gold nanoparticles as the catalyst to grow high-quality single-crystal gallium nitride nanowires was developed. This method enables control over several important aspects of the growth, including control of the nanowire diameter by using monodispersed gold clusters, control of the nanowire location via e-beam patterning of the catalyst sites, and control of the nanowire orientation via epitaxial growth ona-plane sapphire substrates. Our work opens up new ways to use GaN nanowires as nanobuilding blocks.
Single crystalline In203 nanowires were successful synthesized using a laser ablation method. Extensive material characterization such as X-ray diffraction (XRD) and selected area electron diffraction (SAED) revealed a cubic crystal structure for these nanowires with  as the growth direction. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) are used to determine the diameter and length of our nanowires. By using monodispersed gold clusters as the catalyst, these nanowires can be grown with well-defined diameters around 10 nm. Individual In2O3 nanowires have been utilized to construct field effect transistors, which confirmed In2O3 nanowires as n-type semiconductors and exhibited on / off ratios as high as 104 at room temperature. The temperature-dependence of the conductance revealed thermal emission as the dominating transport mechanism. Our work can lead to important applications such as chemical sensing for In2O3 nanowires.
InN nanowires were synthesized and characterized using a variety of techniques. A two-zone chemical vapor deposition technique was employed to operate the vapor generation and the nanowire growth at differential temperatures, leading to high-quality products and growth rates as high as 4–10 μm/hour. The as-grown nanowires showed highly single-crystalline structures and precisely controlled diameters by using monodispersed gold clusters as the catalyst. 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.
Single crystalline In2O3 nanowires were synthesized and then utilized to construct field effect transistors (FETs) consisting of individual nanowires. Chemical sensors based on these In2O3 nanowire FETs have been demonstrated. Upon exposure to gaseous molecules such as NO2 and NH3, the electrical conductance of the In2O3 nanowire FETs are found to dramatically decrease rapidly, accompanied by substantial shifts in threshold gate voltage. Our In2O3 nanowire sensors exhibit significantly improved sensitivity, as well as shortened response times compared to most existing solid-state gas sensors. In addition, ultraviolet (UV) light is found to be able to greatly enhance the surface molecular desorption kinetics and serve as a “gas cleanser” for the In2O3 nanowire chemical sensors. It has been demonstrated that the recovery time of our devices can be shortened to ∼30 s by illuminating the devices with UV light in vacuum.