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A multichannel calorimeter system is designed and constructed which is capable of delivering single-shot and broad-band spectral measurement of terahertz (THz) radiation generated in intense laser–plasma interactions. The generation mechanism of backward THz radiation (BTR) is studied by using the multichannel calorimeter system in an intense picosecond laser–solid interaction experiment. The dependence of the BTR energy and spectrum on laser energy, target thickness and pre-plasma scale length is obtained. These results indicate that coherent transition radiation is responsible for the low-frequency component (
1 THz) of BTR. It is also observed that a large-scale pre-plasma primarily enhances the high-frequency component (
3 THz) of BTR.
Hand, foot, and mouth disease (HFMD), usually a self-limiting illness for young children, could cause a significant burden for parents because it can take up to 1–2 weeks for a sick child to recover. We conducted a two-wave longitudinal study over one summer peak season (May–July 2014) of HFMD to examine parents’ HFMD-related risk perceptions and protective responses. In total, 618 parents with at least one child aged ⩽12 years, recruited using randomly-dialled household telephone calls completed the baseline survey interview, 452 of whom subsequently completed the follow-up survey. Around two-thirds of participants perceived the chance of their child being infected by HFMD was ‘zero/very small/small’ but the likelihood of being hospitalized once infected was ‘somewhat likely/likely/very likely’. At follow-up, 82% reported washing child's hands frequently (Hygiene), 16% would keep their child away from school if HFMD cases were identified in school (Distancing) and 23% were ‘very likely/certainly’ to take the child for HFMD vaccination if available (Vaccination). Anticipated regret was consistently the strongest predictor for Hygiene (OR 3.34), and intention of Distancing (OR 2.58) and Vaccination (OR 3.16). Interventions focusing on anticipated regret may be effective to promote protective behaviour against HFMD among parents for their children.
Both growth and immune capacity are important traits in animal breeding. The animal quantitative trait loci (QTL) database is a valuable resource and can be used for interpreting the genetic mechanisms that underlie growth and immune traits. However, QTL intervals often involve too many candidate genes to find the true causal genes. Therefore, the aim of this study was to provide an effective annotation pipeline that can make full use of the information of Gene Ontology terms annotation, linkage gene blocks and pathways to further identify pleiotropic genes and gene sets in the overlapping intervals of growth-related and immunity-related QTLs. In total, 55 non-redundant QTL overlapping intervals were identified, 1893 growth-related genes and 713 immunity-related genes were further classified into overlapping intervals and 405 pleiotropic genes shared by the two gene sets were determined. In addition, 19 pleiotropic gene linkage blocks and 67 pathways related to immunity and growth traits were discovered. A total of 343 growth-related genes and 144 immunity-related genes involved in pleiotropic pathways were also identified, respectively. We also sequenced and genotyped 284 individuals from Chinese Meishan pigs and European pigs and mapped the single nucleotide polymorphisms (SNPs) to the pleiotropic genes and gene sets that we identified. A total of 971 high-confidence SNPs were mapped to the pleiotropic genes and gene sets that we identified, and among them 743 SNPs were statistically significant in allele frequency between Meishan and European pigs. This study explores the relationship between growth and immunity traits from the view of QTL overlapping intervals and can be generalized to explore the relationships between other traits.
Hepatitis C virus (HCV) has become a global public health problem. Many studies have been conducted to identify risk factors for HCV infection. However, some of these studies reported inconsistent results. Using data collected from 11 methadone clinics, we fit both a non-spatial logistical regression and a geographically weighted logistic regression to analyse the association between HCV infection and some factors at the individual level. This study enrolled 5401 patients with 30·0% HCV infection prevalence. The non-spatial logistical regression found that injection history, drug rehabilitation history and senior high-school education or above were related to HCV infection; and being married was negatively associated with HCV infection. Using the spatial model, we found that Yi ethnicity was negatively related to HCV infection in 62·0% of townships, and being married was negatively associated with HCV infection in 81·0% of townships. Senior high-school education or above was positively associated with HCV infection in 55·2% of townships of the Yi Autonomous Prefecture. The spatial model offers better understanding of the geographical variations of the risk factors associated with HCV infection. The geographical variations may be useful for customizing intervention strategies for local regions for more efficient allocation of limited resources to control transmission of HCV.
Temperature is a key environmental factor in determining the population size of Cnaphalocrocis medinalis in summer. High temperatures inhibit survival, development and fecundity of this insect. However, biological responses of female and male adults to heat shock, and physiological mechanism of high temperature suppressing population development are still ambiguous. We experimentally tested the impact of heat shock (5 h day−1) on biological traits, spermatogenesis and sperm transfer of adults of C. medinalis. The result showed that heat exposure to 39 and 40 °C for 5 h reduced longevity and copulation frequency of adults, and hatchability of eggs. Immediate survival rate of males was lower than that of females after 3 days of exposure to 41 °C. The oviposition period, copulation frequency, fecundity of adults and hatchability of eggs were significantly lower when male adults were exposed to 40 or 41 °C for 3 days. Heat shock decreased frequency and success rate of mating when males were exposed, and it also resulted in postponement of mating behaviour and prolongation of mating duration as both the female and male adults were exposed. Heat shock did not affect spermatogenesis, but significantly inhibited sperms maturation. Moreover, males could not ejaculate sperm into females during copulation when these male moths received heat shock. Heat shock remarkably suppressed mating behaviour and sperm transfer, which led to a dramatic decline of rice leaf folder populations.
To study the activation of caspase-9 and its potential influence in conditioning, longissimus thoracis (LT), semitendinosus (STN) and psoas minor (PMi) muscles were used to analyze the ratio of pro-apoptotic bax to anti-apoptotic bcl-2 in fresh tissues and observe the changes in ATP, cytosolic cytochrome c and caspase-9 activity levels during storage at 4°C. Caspase-9 activity at 5 h is higher than the activity at 0 and 24 h in the muscles (P<0.001). The ATP content decreased between 0 and 3 h, between 8 and 14 h in the PMi and LT muscles (P<0.0001), whereas between 0 and 5 h, between 8 and 14 h in the STN muscle (P<0.0001). There is 60.2%, 55.3% and 43.1% available ATP in the STN, LT and PMi muscles at 5 h, respectively. The cytosolic cytochrome c level increased during 5 and 24 h storage in the LT and PMi muscles (P<0.0001), during 5 and 96 h in the STN muscle (P<0.0001). The cytosolic cytochrome c at 24 h (P<0.001) and ratio of bax to bcl-2 (P<0.05) was higher in the PMi than in other muscles. We concluded that the increase in cytosolic cytochrome c and available intracellular ATP should be responsible for the increase in caspase-9 activity; the activation of caspase-9 could be limited by the subsequent depletion of ATP; the postmortem release level of cytochrome c could be determined by the ratio of bax to bcl-2 in fresh tissues.
Fatty acid translocase (FAT/CD36) is a membrane receptor that facilitates long-chain fatty acid uptake. To investigate its role in the regulation of long-chain fatty acid composition in muscle tissue, we studied and compared FAT/CD36 gene expression in muscle tissues of commercial broiler chickens and Chinese local Silky fowls. The results from gas chromatography–mass spectrometry analysis of muscle samples demonstrated that Chinese local Silky fowls had significantly higher (P < 0.05) proportions of linoleic acid (LA) and palmitic acid, lower proportions (P < 0.05) of arachidonic acid (AA) and oleic acid than the commercial broiler chickens. The mRNA expression levels of fatty acid (FA) transporters (FA transport protein-1, membrane FA-binding protein, FAT/CD36 and caveolin-1) in the m. ipsilateral pectoralis and biceps femoris were analyzed by Q-PCR, and FAT/CD36 expression levels showed significant differences between these types of chickens (P < 0.01). Interestingly, the levels of FAT/CD36 expression are positively correlated with LA content (r = 0.567, P < 0.01) but negatively correlated with palmitic acid content (r = −0.568, P < 0.01). Further experiments in the stably transfected Chinese hamster oocytes cells with chicken FAT/CD36 cDNA demonstrated that overexpression of FAT/CD36 improves total FA uptake with a significant increase in the proportion of LA and AA, and a decreased proportion of palmitic acid. These results suggest that chicken FAT/CD36 may selectively transport LA and AA, which may lead to the higher LA deposition in muscle tissue.
74Ge nanocrystals were formed by ion beam synthesis in SiO2. Transmission Electron Microscopy was used to characterize the structure and properties of these Ge nanocrystals before and after liberation from the matrix. The liberation from the SiO2 matrix was achieved through selective etching in a HF bath. High-resolution micrographs and selective area diffraction confirm that the crystallinity is retained in this process. Transfer of released nanocrystals is achieved through ultrasonic dispersion in methanol and deposition onto lacey carbon films via evaporation of methanol. In an effort to determine the melting point of Ge nanocrystals and observe the growth and evolution of nanocrystals embedded in the amorphous SiO2 during heat treatment, as-grown nanocrystals were heated in-situ up to 1192°C±60°C in a JEOL 200CX analytical electron microscope. Electron diffraction patterns are recorded using a Charge-Coupled Device. A large melting hysteresis was observed around the melting temperature of bulk Ge.
Isotopically pure 70Ge and 74Ge nanocrystals embedded in SiO2 thin films on Si substrates have been fabricated through ion implantation and thermal annealing. Nanocrystals were subsequently exposed using a hydrofluoric acid etching procedure to selectively remove the oxide matrix while retaining up to 69% of the implanted Ge. Comparison of transmission electron micrographs (TEM) of as-grown crystals to atomic force microscope (AFM) data of exposed crystals reveals that the nanocrystal size distribution is very nearly preserved during etching. Therefore, this process provides a new means to use AFM for rapid and straightforward determination of size distributions of nanocrystals formed in a silica matrix. Once exposed, nanocrystals may be transferred to a variety of substrates, such as conducting metal films and optically transparent insulators for further characterization.
Under certain conditions, nucleation and growth can lead to substantial stresses in nanocrystals embedded in a host matrix. These stresses may be relaxed through subsequent annealing treatments. A model is presented for the relaxation of these stresses via diffusive processes within the matrix. The model reflects the effects of surface tension, potential phase transformations at or near the processing temperature, and differential thermal expansion. It is demonstrated that the model describes well the stress relaxation of ion beam synthesized Ge nanocrystals embedded in a silica matrix.
Hydrogenated nanocrystalline silicon (nc-Si:H) films with room temperature luminescence have been prepared in a PECVD system. Heavily H2 diluted silane and large negative bias accompanying low deposition temperature are used to decrease the crystalline size. The films comprise nanocrystallites surrounded by an interfacial phase with wurtzite structure characterized by 495cm−1 feature in the Raman spectrum. The X-ray diffraction spectrum shows the average grain size is about 4-5nm. The room temperature photoluminescence (PL) spectrum consists of two peaks, one at 2.21eV which may be induced by the transitions of the quantum subbands in the nanocrystalline phase, the other at 2.84eV which may be attributed to some kinds of localized centers in the interfacial phase. The photoluminescence excitation (PLE) spectrum also shows two peaks, a low one at 3.4eV approaching the bulk like transitions between Г25'V-Г15c while the high energy envelope around 5.0eV has a complicated configuration, and might be related to both the bulk like transition between Λ3v-Λ3cand band transitions of (Si-H2)n chains.
Ion implantation into silica followed by thermal annealing is an established growth method for Si and Ge nanocrystals. We demonstrate that growth of Group IV semiconductor nanocrystals can be suppressed by co-implantation of oxygen prior to annealing. For Si nanocrystals, at low Si/O dose ratios, oxygen co-implantation leads to a reduction of the average nanocrystal size and a blue-shift of the photoluminescence emission energy. For both Si and Ge nanocrystals, at larger Si/O or Ge/O dose ratios, the implanted specie is oxidized and nanocrystals do not form. This chemical deactivation was utilized to achieve patterned growth of Si and Ge nanocrystals. Si was implanted into a thin SiO2 film on a Si substrate followed by oxygen implantation through an electron beam lithographically defined stencil mask. Thermal annealing of the co-implanted structure yields two-dimensionally patterned growth of Si nanocrystals under the masked regions. We applied a previously developed process to obtain exposed nanocrystals by selective HF etching of the silica matrix to these patterned structures. Atomic force microscopy (AFM) of etched structures revealed that exposed nanocrystals are not laterally displaced from their original positions during the etching process. Therefore, this process provides a means of achieving patterned structures of exposed nanocrystals. The possibilities for scaling this chemical-based lithography process to smaller features and for extending it to 3-D patterning is discussed.
A method to liberate germanium (Ge) nanocrystals from silicon dioxide (SiO2) thin films by hydrofluoric acid (HF) vapor etching is presented. Multi-energy implantation of mass separated Ge ions into 500-nm-thick wet oxide layers on silicon (Si) substrates followed by thermal annealing produces nanocrystals that are 2 to 8 nm in diameter. Raman spectra exhibit the expected asymmetric line shapes due to the phonon confinement effect, but with a higher peak frequency than predicted. To free the nanocrystals, samples are etched in HF vapor to selectively remove the SiO2 matrix and expose the nanocrystal surfaces. Raman spectra of etched samples display peak frequencies consistent with relief of compressive stress. The liberated nanocrystals show long-term stability under ambient atmospheric conditions. Ge nanocrystals can be removed from etched surfaces using an ultrasonic methanol cleaning procedure. The nanocrystal-containing solution is applied to a TEM grid and the solvent is evaporated. Subsequently obtained electron diffraction patterns confirm that the nanocrystals survive this transfer step. Thus, liberated Ge nanocrystals are expected to be accessible for a wide range of manipulation processes and direct characterization techniques.
A porous polymer material, which is made of a two-phase composite and contains 35% porosity with a pore size less than 50Å, is found to have a dielectric constant of 1.8. It absorbs almost no water. The electrical properties, such as capacitance and leakage current, do not change with time and temperature.
74Ge nanocrystals are formed in a sapphire matrix by ion implantation followed by thermal annealing. Transmission electron microscopy (TEM) of as-grown samples reveals that the nanocrystals are faceted and have a bi-modal size distribution. Notably, the matrix remains crystalline despite the large implantation dose and corresponding damage. Embedded nanocrystals experience large compressive stress relative to bulk, as measured by Raman spectroscopy of the zone center optical phonon. In contrast, ion-beam-synthesized nanocrystals embedded in silica are observed to be spherical and experience considerably lower stresses. Also, in situ TEM reveals that nanocrystals embedded in sapphire melt very close to the bulk melting point (Tm= 936 °C) whereas those embedded in silica exhibit a significant melting point hysteresis around Tm.
The relative dispersion of a scalar plume is examined experimentally. A passive fluorescent tracer is continuously released from a flush-bed mounted source into the turbulent boundary layer of a laboratory-generated open channel flow. A two-dimensional particle image velocimetry–laser-induced florescence (PIV–LIF) technique is applied to measure the instantaneous horizontal velocity and concentration fields. Measured results are used to investigate the relationship between the boundary-layer turbulence and the evolution of the distance-neighbour function, namely the probability density distribution of the separation distance between two marked fluid particles within a cloud of particles. Special attention is paid to the hypothesis that a diffusion equation can describe the evolution of the distance-neighbour function. The diffusion coefficient in such an equation, termed the ‘relative diffusivity’, is directly calculated based on the concentration distribution. The results indicate that the relative diffusivity statistically depends on particle separation lengths instead of the overall size of the plume. Measurements at all stages of the dispersing plume collapse onto a single curve and follow a 4/3 power law in the inertial subrange. The Richardson–Obukhov constant is estimated from the presented dataset. The relationship between the one-dimensional (1D) representation of the distance-neighbour function and its three-dimensional (3D) representation is discussed. An extended model for relative diffusivity beyond the inertial subrange is proposed based on the structure of the turbulent velocity field, and it agrees well with measurements. The experimental evidence implies that, while the diffusion of the distance-neighbour function is completely determined by the underlying turbulence, the overall growth rate of the plume is affected by both the turbulent flow and its actual concentration distribution.
The dispersion relation for superluminal waves in degenerated and isotropic electron–positron plasmas is investigated. The dispersion equation of linear waves is derived from the relativistically correct form of the dielectric function and the Fermi distribution function. Analytical dispersion laws for the real part of the wave frequency are derived by applying the long-wavelength approximation and the short-wavelength approximation. Using the numerical simulation method, we obtain the full dispersion curve which cannot be given by an analytic method.
The available data provide inconsistent results on the efficacy of small-dose remifentanil attenuating the cardiovascular response to intubation in children. Therefore, this randomized double-blind study was designed to assess the ability of different small doses of remifentanil on the cardiovascular intubation response in children, with the aim of determining the optimal dose of remifentanil for this purpose.
One hundred and twenty-four children aged 3–9 yr were randomized to one of four groups to receive the following in a double-blind manner: normal saline (Group 1), remifentanil 0.75 μg kg−1 (Group 2), remifentanil 1 μg kg−1 (Group 3) and remifentanil 1.25 μg kg−1 (Group 4). Non-invasive blood pressure and heart rate were recorded before anaesthesia induction (baseline value), immediately before intubation (postinduction values), at intubation and at 1 min intervals for 5 min after intubation.
Tracheal intubation caused significant increases in systolic blood pressure and heart rate in Groups 1–3 compared with the baseline values. The maximum percent increases of systolic blood pressure and heart rate were 10% and 26% of the baseline values, respectively, in Group 2; 5% and 14% in Group 3; and 1% and 8% in Group 4 compared with 27% and 37% in Group 1. Except for the Group 3 vs. Group 4 comparison, there were significant differences among the four groups in the maximum percent increases of systolic blood pressure and heart rate.
When used as part of anaesthesia induction with propofol and vecuronium in children, bolus administration of remifentanil resulted in a dose-related attenuation of the cardiovascular intubation response.
This paper describes nine brachiopod species (including two uncertain species) in eight genera of the Orthotetidina from the uppermost Changhsingian (latest Permian) of South China. They are the youngest silicified Permian brachiopods known in the world and the last representatives of the Orthotetida, a major brachiopod group that disappeared during the end-Permian mass extinction. Other than two uncertain species, all taxa are new, including Meekella dongluoensis, Perigeyerella guangxiensis, Ombonia capilla, Derbyia nigpi, Schuchertella fushuiensis, Streptorhynchus ovata, and Tropidelasma elongata.