[The potential effect mechanism and research progress of extreme temperature exposure on asthma attacks]

Asthma is one of the common chronic respiratory diseases, and its incidence has been increasing worldwide in recent years. In the context of climate change, the frequency and intensity of extreme weather events are increasing. A large body of evidence suggests that exposure to extreme temperatures can increase the risk of asthma attacks, but the underlying mechanisms that trigger asthma attacks are still unclear. This study aims to systematically review the research progress on the association between extreme temperature and asthma attacks, and to elucidate the synergistic effects of extreme temperatures, indoor/outdoor environments, and individual vulnerabilities on asthma attacks. Additionally, this review discusses the potential mechanisms of asthma attacks triggered by extreme temperature, and highlights the important role of immune regulation and neuroregulation in the inflammatory response of asthma induced by extreme temperature. Moreover, we propose a potential mechanism framework to explain the disease pathogenesis of asthma which is induced by the interactions between extreme temperature and environmental factors, in order to provide a scientific basis for addressing the adverse impacts of extreme weather events and climate change.

Perfluorooctane sulfonate affects mouse oocyte maturation in vitro by promoting oxidative stress and apoptosis induced bymitochondrial dysfunction

Perfluorooctane sulphonate (PFOS), as a surfactant, is widely applied in the agricultural production activities and has become a potential menace to human health. The mechanism of its effect on the maturation of mammalian oocytes is unclear. This study explored the toxic effect of PFOS on mouse oocyte maturation in vitro. The results revealed that PFOS under a concentration of 600 μM could significantly reduce the polar body extrusion rate (PBE) of mouse oocytes and cause symmetrical cell division. Further experiments showed that PFOS resulted in the abnormal cytoskeleton of the oocytes, causing the abnormal spindles and misplaced chromosomes, as well as the impaired dynamics of actin. Moreover, PFOS exposure inhibited the process of oocyte meiosis, which reflected in the slower spindle migration and continuous activation of spindle assembly checkpoint (SAC), then ultimately increased the probability of aneuploidy. Most importantly, PFOS exposure reduced the quality of oocytes, specifically by disrupting the function of mitochondria, inducing cell oxidative stress, and triggering early apoptosis. Furthermore, the level of methylation of histones is additionally influenced. In summary, our findings showed that PFOS exposure interfered with the maturation of mouse oocytes through affecting cytoskeletal dynamics, meiotic progression, oocyte quality, and histone modifications.

Perfluorodecanoic acid induces meiotic defects and deterioration of mice oocytes in vitro

Perfluorodecanoic acid (PFDA) is a member of the perfluoroalkyl substances, which are toxic to organic functions. Recently, it has been found in follicular fluid, seriously interfering with reproduction. Follicular fluid provides the oocyte with necessary resources during the process of oocytes maturation. However, the effects of PFDA on the oocyte need investigation. Our study evaluated the impacts of PFDA on the meiosis and development potential of mouse oocytes by exposing oocytes to PFDA in vitro at 350, 400, and 450 μM concentrations. The results showed that exposure to PFDA resulted in the first meiotic prophase arrest by obstructing the function of the maturation-promoting factor. It also induced the dysfunction of the spindle assembly checkpoint, expedited the progression of the first meiotic process, and increased the risk of aneuploidy. The oocytes treated with PFDA had a broken cytoskeleton which also contributed to meiotic maturation failure. Besides, PFDA exposure caused mitochondria defections, increased the reactive oxygen species level in oocytes, and consequently induced oocyte apoptosis. Moreover, PFDA produced epigenetic modifications in oocytes and increased the frequency of mature oocytes with declined development potential. In summary, our data indicated that PFDA disturbs the meiotic process and induces oocyte quality deterioration.

Fbf1 regulates mouse oocyte meiosis by influencing Plk1

Fas binding factor 1 (Fbf1) is one of the distal appendage proteins in the centriole, located at its distal and proximal ends. It influences the duplication and separation of centrosomes, thereby affecting the progression of the cell cycle during mitosis. However, the function of Fbf1 in meiosis has remained unclear. To explore the role of Fbf1 in the in vitro maturation of mouse oocyte, immunofluorescence staining was used to examine the Fbf1 location in the oocyte and their phenotype after protein deletion. Western blot was used to examine the protein abundance. This study showed that mouse oocytes express Fbf1 which locates at the spindle poles and around the microtubules. Through taxol and nocodazole treatment, and microinjection of siRNA, it was demonstrated that Fbf1 had an important role in the spindle assembly and chromosome separation during mouse oocyte meiosis In particular, microinjection of Fbf1-siRNA resulted in severe abnormalities in the spindle and chromosome arrangement, decreased aggregation of microtubules, disrupted the first oocyte meiosis, and the extrusion of the first polar body. Furthermore, in the Fbf1-siRNA group, there was reduced expression of Plk1 and its agglutination at the spindle poles, along with retarded chromosome segregation due to the activation of the spindle assembly checkpoint (SAC) component BubR1. These results indicate that Fbf1 may function in microtubule depolymerization and agglutination, control the microtubule dynamics, spindle assembly and chromosome arrangement and, thus, influence the mouse oocyte meiotic maturation.

[Molecular epidemiology of Japanese encephalitis viruses isolated in Yunnan province, 1977-2010]

Objective: To understand the genetic and molecular epidemiologic characteristics of 63 strains of Japanese encephalitis virus (JEV) isolated in Yunnan province, China during 1977-2010. Methods: Suckling mice were inoculated with viruses continuously and the viral nucleic acid were extracted from the brain-grinding supernatants of the infected and moribund mice, then the gene fragments of E region were amplified by RT-PCR. Bioinformatics (Clustal X, DNAstar, Mega 5.0 and other software) was used to analyze the nucleotide and deduced amino acid sequences and phylogenetic trees. Results: Yunnan strains of JEV could cause illness and deaths in suckling mice. The results of virus nucleic acid detection and sequencing indicated that nucleotide sequences of E gene of the 63 virus strains were obtained. Phylogenetic tree and homology analyses based on E genomes showed that 47 strains of the experimental virus belonged to genotype 1 (G-1) and 16 strains belonged to genotype 3 (G-3). The 47 isolates of G-1 were divided into 2 clades, of them, the earliest isolates of G-1 (M28, 1977 and BN82215, 1982) in Yunnan of China and the early isolates of G-1 (U70416, 1982; DQ084229, the year is unknown) in Thailand were in one clade, and the isolates of G-1 from 2007-2010 in Yunnan could be divided into 2 subgroups. The 16 isolates of G-3 from Yunnan were divided into 3 clades, among them, the isolates from 1970-1990s in Yunnan were in two clades, and the isolates from 2004 in Yunnan were in one clade. In addition, their main amino acid sites of antigenicity, pathogenic, virulence of both G-1 and G-3 had no significant change. Conclusion: JEV G-1 and G-3 co-circulated in Yunnan, and G-1 was predominant. The JEV strains isolated in different years and areas in Yunnan had different molecular epidemiologic characteristics and genetic diversity. The results of this study suggested that JEV G-1 might originate from Yunnan of China and adjacent Southeast Asia region.

Microstructure change of ZnO nanowire induced by energetic x-ray radiation and its effect on the field emission properties

The changes in the microstructure of ZnO nanowire were studied after exposure to different radiation doses of energetic x-rays. Detailed structural, composition and optical analyses were carried out. It was found that the surface composition changed and defects were formed in the irradiated ZnO nanowires. The structural change of ZnO nanowires after thermal treatment was also studied and similar defects were observed. It is proposed that phonon-induced localized heating is the main reason for the observed changes in microstructure. Finally, the field emission properties of ZnO nanowires before and after x-ray radiation were studied. It was found that the increase of work function and change in morphology induced by the irradiation were the reasons for the observed change in field emission properties.

Precisely-controlled fabrication of single ZnO nanoemitter arrays and their possible application in low energy parallel electron beam exposure

Precisely-controlled fabrication of single ZnO nanoemitter arrays and their possible application in low energy parallel electron beam exposure are reported. A well defined polymethyl methacrylate (PMMA) nanohole template was employed for local solution-phase growth of single ZnO nanoemitter arrays. Chlorine plasma etching for surface smoothing and pulsed-laser illumination in nitrogen for nitrogen doping were performed, which can significantly enhance the electron emission and improve the emitter-to-emitter uniformity in performance. Mechanisms responsible for the field emission enhancing effect are proposed. Low voltage (368 V) e-beam exposure was performed by using a ZnO nanoemitter array and a periodical hole pattern (0.72-1.26 μm in diameter) was produced on a thin (25 nm) PMMA. The work demonstrates the feasibility of utilizing single ZnO nano-field emitter arrays for low voltage parallel electron beam lithography.

A novel lift-off method for fabricating patterned and vertically-aligned W18O49 nanowire arrays with good field emission performance

A novel lift-off method has been developed for fabricating patterned W(18)O(49) nanowires in vertical arrays and on a large scale. These W(18)O(49) nanowire arrays have an average diameter of about 30 nm, and their lengths range from 2-3 μm. In every pattern of a 2 inch sample, the nanowires exhibit the same morphology and growth density. They are single crystals with monoclinic structure and grow along the [010] direction. Field emission (FE) measurements show that they have a turn-on field of 6.2 V μm(-1) and their emission current density can reach 500 μA cm(-2) at an electric field of 10.9 V μm(-1). Because the W(18)O(49) nanowire patterns synthesized by this simple method still have good FE performance, comparable to many cathode nanostructures with excellent FE properties, it suggests that it may provide an effective and simple preparation technique for patterned growth of nanowire arrays in future FE applications.

Controlled synthesis of ultra-long AlN nanowires in different densities and in situ investigation of the physical properties of an individual AlN nanowire

The controlled synthesis of different growth densities of ultra-long AlN nanowires has been successfully realized by nitridation of Al powders for the first time. These AlN nanowires have an average diameter of about 100 nm and their mean length is over 50 μm. All the synthesized ultra-long nanowires are pure single crystalline h-AlN structures with a growth orientation of [0001]. We preferred the self-catalyzing vapor-liquid-solid (VLS) mechanism to illustrate their growth process. Although the sample with the middle growth density (3.2×10(7) per cm2) of AlN nanowire performs the best field emission (FE) properties, the emission uniformity is not good enough for field emission display applications, which may be attributed to their low intrinsic conductivity. Moreover, the electrical transport and FE properties of an individual ultra-long AlN nanowire are further investigated in situ to find the decisive factor responsible for their FE behaviors. An individual AlN nanowire is observed to have a mean 1 nA field of 440 V μm(-1) and 1 μA field of 480 V μm(-1) as well as an average electrical conductivity of about 2.7×10(-4)Ω(-1) cm(-1), which is lower than that of some cathode materials with excellent FE properties. Therefore we come to the conclusion that the electrical conductivity of the AlN nanowire must be improved to a higher level by some effective ways in order to realize their practical FE device applications.

Tip-morphology-dependent field emission from ZnO nanorod arrays

Vertically well-aligned ZnO nanorod arrays with three kinds of tip morphology-abruptly sharpened, tapered and plane-have been controllably fabricated with wafer size uniformity by vapor phase transport and condensation. Except that the tip morphology is distinctly different, all of these nanorods are single crystalline, growing along their wurtzite 0001 axis, with similar diameters, lengths and densities. The field emission properties of these nanorod arrays are comparatively investigated and are found to be strongly affected by the tip morphology. A nanorod with the abruptly sharpened tip possesses the lowest turn-on and threshold electric fields as well as the highest field enhancement factor. Further analysis reveals that the abruptly sharpened tip morphology can reduce the screening effect more efficiently than the others. These results are very helpful for the design, fabrication and optimization of integrated field emitters using 1D nanostructures as the cathode material.

Damages of screen-printed carbon nanotube cold cathode during the field emission process

The field emission properties of the screen-printed carbon nanotube (CNT) composite cathode have close relationship with its microstructure. In this study, carbon nanotube composite cold cathode with ZnO nano-particles as binding material was prepared using screen-printing method. Electric field cycles were used to post-treat the carbon nanotube composite cold cathode. During the process of electric field cycle treatment, obvious heat-induced damages were observed from the cathode. Scanning electron microscope and transmission electron microscope were employed to analyze the morphology and microstructure of the cathode. The possible mechanisms responsible for damages were discussed.

Study on effect of hydrogen treatment on amorphous carbon film using scanning probe microscopy

Amorphous carbon film was treated by hydrogen plasma. The change of surface structure, conductivity, and work function distribution is characterized by scanning probe microscope technique and local electron emission is also analyzed. We find that chemical effect of hydrogen plasma on the a-C film is small, but the etching effect is strong and the surface morphology and conductance are obviously changed after hydrogen treatment. Electron emission enhancement is not due to the decrease of work function or existence of sp(2) conductive channels, but from the mutual effect between sp(2) and sp(3) phase. We suggest that the enhancement is due to the internal electron injection from the sp(2)-rich interface layer into the surface sp(3)-rich grains.

Self-assembly of Au-Ag alloy nanoparticles by thermal annealing

Hemispherical Au-Ag alloy nanoparticles were prepared on 2-inch Si wafer by thermal annealing Au-Ag alloy thin film in protective ambient. The nanoparticles were evenly distributed on the substrate surface. The diameter of the nanoparticles is dependent of the deposition duration of the Au-Ag alloy thin film, and also the separation between the nanoparticles. The minimum and maximum diameters of the nanoparticles obtained so far are about 5 nm and 160 nm, respectively. Experimental evidences indicated that the formation of the hemispherical nanoparticles is due to the surface tensile stressing induced by the lattice expansion.

Preparation of Cu2S dendritic, double-comb-like nanostructures by gas-solid reaction method

Synthesis of Cu2S dendritic nanostructures by a gas-solid reaction method has been achieved. The Cu2S dendritic nanostructure consists of a backbone and small branches aligning symmetrically and densely on the backbone like a double comb. Transmission electron microscopy has revealed that the backbone is along the c axis of monoclinic Cu2S and branches are along the b axis. Preoxidation of copper substrate is found to be important for high yield synthesis of the dendritic nanostructures. An oxide-assisted growth model is proposed to explain the formation of the dendritic nanostructures. Good field emission characteristics are also obtained from films of the dendritic Cu2S nanostructures.

Mechanism responsible for initiating carbon nanotube vacuum breakdown

We report a physical mechanism responsible for initiating a vacuum breakdown process of a single carbon nanotube (CNT) during field emission. A quasidynamic method has been developed to simulate the breakdown process and calculate the critical field, critical emission current density and critical temperature beyond which thermal runaway occurs before the CNT temperature reaches its melting point. This model is in good agreement with experiments carried out with a single CNT on a silicon microtip.

Effect of carbon nanotube structural parameters on field emission properties

Experimental studies were devoted to the effect of structural parameters, i.e., tube diameter and density, on the field electron emission characteristics of carbon nanotubes. Thermal chemical vapor deposition system was employed to synthesize carbon nanotubes. Nanotubes with different diameters and densities were obtained by adjusting the thickness of the iron (Fe) catalyst film. The morphologies of the Fe and carbon nanotube film were characterized by scanning electron microscopy respectively. Further field emission measurement confirmed that the tube diameter and density could significantly affect the electron emission properties of the carbon nanotube. Possible physical reasons for the effect are discussed.

The application of carbon nanotubes in high-efficiency low power consumption field-emission luminescent tube

In this report, details are given of our recent experimental study of using carbon nanotubes (CNTs) as cathode of the luminescent tubes. The CNT film is synthesized by thermal chemical vapor deposition. Two kinds of luminescent tubes that have different gaps have been fabricated. The luminescent tube with 0.1mm gap has a low threshold voltage of about 780V and high emission current of 300 microA when the gate voltage is 970V. The DC power consumption of the luminescent tube with a 0.1mm gap is approximately 1.12W. The results show that the CNTs are very good emission sources and suitable for application in the luminescent tube.

A cold cathode lighting element prototype

In this study, we present a prototype of lighting element in which a carbon-containing field emission material is used as the cathode. The operating characteristics, i.e. current-voltage characteristics, current stability, luminance and lifetime of the lighting element are tested. By applying high-voltage phosphor, a maximum brightness of 10000cd/m(2) has been recorded and a lighting element under lifetime test has been operating in DC driving mode for over 2500h without decay in emission current and brightness. These results imply that the prototype lighting element is suitable for commercial application.

Resonant field emission through amorphous diamond thin films (a model study)

A model for field emission through an amorphous diamond thin film with defects is constructed. Theoretical study shows that the emission is enhanced by attractive defects which would make the resonant emission observable for films with thickness of about 10nm. The emitted current density in typical parameters is calculated as functions of thickness, field strength and defect density. The energy distribution of emitted electrons is attained.

Study of field electron emission spectral characteristics of amorphous carbon-nitride film

The study of field electron energy spectra from amorphous carbon-nitride (a-CN) films is essential to understand the mechanism of field emission from this promising material. In this work, the electron energy spectrum is studied by measuring the distribution of electron field emitted from individual emitting sites. The spectra are recorded at different electrical fields. It is found that the peak shift as well as the half-width increase with increasing applied fields. Furthermore, multi-peak features are observed at the low-energy side of the spectra. It is assumed that these peaks might originate from the interband states of a-CN film. We propose that although the emission mainly originates from current injection into conduction band of a-CN film, the electrons may also be emitted from interband states.

Characterization of a high voltage flat panel display unit using nanotube-based emitters

Details are given of an experimental investigation carried out to study the field electron emission characteristics of a field emission flat panel display unit using a carbon nanotube-epoxy composite as electron emission material. These include: (i) dependence of direct emission current-voltage characteristic on vacuum gap spacing, (ii) the variation of the proportion of emission current passing through an aperture hole of a gate electrode with changing structural parameters of the device, and (iii) the uniformity and display characteristics of a typical display unit. Our findings indicate that it is very likely for one to produce a near-market prototype high voltage field emission flat panel display, if more sophisticated fabrication and assembly technique is adapted.

Microfabrication and characterization of gated amorphous diamond-based field emission electron sources

Gated field emission electron sources of amorphous diamond (a-D) coated Si tips and a-D diodes on a rough Si substrate were studied, detailing the deposition and characterization of the thin film, the fabrication processes and the emission behavior of the electron sources. Mechanisms responsible for the emission process of the a-D coated devices are proposed. A comparison of the field emission performance of the two types of devices is presented. In addition, future improvements of the a-D diode on a rough Si cathode are discussed.

Study of the frequency response of the thin film cold cathode electron source of a lighting element

Details of the recent experimental and theoretical studies of the frequency characteristic of the field emission electron source of a lighting element are given. The response times at different frequencies (0.02-200 kHz) and applied gap fields, acting on cathode surface, have been studied. A correlation has been found to exist between the response time and the frequency of applied voltage pulse. The response time remains almost constant within a range of frequencies between 1 and 30 kHz, and it remains nearly constant with increasing applied gap field higher than the threshold field. Finally, the cutoff frequency of the electron source is found, and with the current design of the electron source, it can be as high as 40 kHz. An equivalent circuit model is proposed, and theoretical results based on this model agree well with experimental findings.