Patterns of salt transport and factors affecting typical shrub in desert-oases transition areas.

Soil salinization and water deficits are considered the primary factors limiting economic development and environmental improvement in arid areas. However, there remains limited knowledge of the adaptability of typical shrubs to salinization of desert areas in arid zones. This study was conducted in a desert oasis transition zone (Tarim River, China), aiming to investigate: i) the spatial-temporal changes in soil salinity; ii) the interactions between the pedoenvironment vs typical shrub (Calligonum mongolicum). The van Genuchten soil salinity retention ensemble model (TVGSSREM-3D) was developed to simulate variations in soil water-salt transport in the desert-oasis zone and to accurately explain the main factors influencing Calligonum mongolicum desert-oases transition areas. The results showed that monthly average salinity ranged from 2.0 to 8.0 g kg-1, with a peak in August (9.17 g kg-1). The presence of human activities (Salt Drainage Canal) and the distribution of Calligonum mongolicum resulted in a clear spatial salinity zonation. Moreover, analysis of environmental indicators using the TVGSSREM-3D model revealed strong correlations between the distribution of salinity in Calligonum mongolicum desert-oases transition areas and groundwater depth (GD), minimum relative humidity (MRH), and water vapor pressure (WVP). These findings provide a scientific basis for stabilizing, restoring, and reconstructing the ecosystem of the oasis-desert transition zone.

Reconfigurable microwave photonic mixer for hybrid macro-micro cellular systems.

Microwave photonic mixing can realize the frequency conversion of microwave signals in the optical domain, breaking through the bandwidth bottleneck and electromagnetic interference problems of traditional microwave mixing methods. In the background of the hybrid macro-micro cellular system, a wideband, large dynamic range and reconfigurable microwave photonic mixer is proposed, theoretically analyzed and experimentally demonstrated in this paper. By adjusting the modulator bias voltages and matching the proper digital domain operations, a microwave photonic mixer with reconfigurable functions including single-ended dispersion immune mixing, I/Q frequency down-conversion, image rejection mixing, and double-balanced mixing are realized, respectively. Meanwhile, optimizing the electrical attenuator using convex optimization can suppress the third-order intermodulation distortion (IMD3), maximize the conversion gain, and finally improve the spur-free dynamic range (SFDR). Experimental results show that the proposed scheme can be operated with a frequency from 5 to 20 GHz, and the SFDR can achieve 118.3 dB·Hz4/5. Over the whole frequency range, I/Q frequency down-conversion can be well conducted with an amplitude imbalance below 0.7 dB and a phase imbalance below ±0.7°. After an I/Q imbalance compensation algorithm, the image rejection ratio of over 60 dB is produced. The power fading caused by fiber dispersion is also compensated successfully. For a vector signal with 16 quadrature amplitude modulation, the best error vector magnitude (EVM) reaches 3.4%.

Cassegrain antenna for a laser diode source using an E-A system to improve the transmission efficiency.

To solve the serious loss problem for central energy of the Cassegrain antenna, this paper designs a beam-shaping system, named E-A system, to convert the elliptical divergent beam with astigmatism from a laser diode into an annular collimation beam. This E-A system, comprised only of lenses with quadratic surfaces, can simultaneously realize four functions, i.e., aberration correction, beam circularization, beam collimation, and dark hollow beam generation. By adjusting the parameters, the E-A system can be used to shape elliptical astigmatic beams with different parameters. Further, the E-A system can maintain good performance at wavelengths from 500 to 1647 nm. After considering various practical factors, the transmission efficiency of the entire transmitting system can be increased to 93.91% at a wavelength of 1550 nm.

Loss ratio parameter γ to analyze transmission characteristics for optical antenna systems.

Analyzing optical antenna systems through geometrical optics is quite popular for its convenience, which, however, may cause remarkable errors. This paper uses both geometrical optics and diffraction theory to analyze the performance of a traditional optical antenna system, and the results calculated through the two methods are carefully compared. Based on the comparison, it shows the situations in which geometric optics will cause significant errors. In addition, a parameter γ is defined to quickly determine whether geometrical optics is suitable for analyzing optical antenna systems under some situations. This paper can help engineers quickly choose the proper method for designing and analyzing optical antenna systems.

Freeform reflector antenna design method to improve transmission efficiency and control output intensity distribution.

In this paper, a reflector antenna design method is proposed to improve transmission efficiency and control output intensity distribution. Primary and secondary mirrors are constructed segment by segment using a numerical method according to the law of energy conservation, the vector theory of reflection, and Fermat's principle that the optical path length of each ray must be equal. To verify the effectiveness and practicability of this method, an example of an antenna with the prescribed intensity distribution of the output beam is given. The transmission efficiency of the antenna system designed by this method reaches 100% in theory. The effects of output intensity distribution and deviation on transmission efficiency were also analyzed. We believe that the results show that the proposed method is a highly efficient approach to the design of a freeform reflector antenna to improve transmission efficiency and control the output intensity distribution.

Modified ray transfer matrix method for accurate non-sequential ray tracing between arbitrary reflective mirrors.

The ray transfer matrix method is widely used for analyzing beam-transmission properties and designing multi-pass systems. In this paper, a modified ray transfer matrix method is proposed for tracing an accurate non-sequential ray in three-dimensional space based on a vector reflection theory. The modified ray transfer matrix method can be utilized to analyze a ray transmitting between arbitrary surfaces, which is not confined to rotational symmetrical structures. There is no need to project rays onto two perpendicular planes, nor to introduce a paraxial approximation in our calculation. Since the length and angle of every ray can be calculated accurately, almost no deviation is accumulated in multi-pass system. The modified ray transfer matrix method can be applied in optical design, especially in the design of multi-pass cavities and multi-pass cells.

Research for propagation properties of LG beam through Cassegrain antenna system in a turbulent atmosphere.

In this paper, the propagation properties of the Laguerre-Gaussian (LG) beam passing through Cassegrain antenna system in a turbulent atmosphere have been researched. The accurate analytical function for the diffraction field of LG beam passing through Cassegrain antenna, the average intensity, and the cross-talk among different orbital angular momentum (OAM) modes of LG beam passing through Cassegrain antenna in Kolmogorov turbulent have been derived. The simulation results show that LG beam with ring-like distribution is selected to enhance the emission efficiency of Cassegrain antenna. The cross-talk among different OAM modes can remarkably reduce through using Cassegrain antenna. The analysis process can also apply to accurately analyzing the propagation properties of other kinds of beams through different optical systems in turbulent atmosphere.

Improving the transmission efficiency of the Cassegrain optical system for Bessel-Gaussian beams.

With the improvement of the transmission efficiency, the Cassegrain antenna can be widely used in space optical communication. In this paper, the Bessel-Gaussian (BG) beam is used to avoid the central energy loss of a Cassegrain antenna system. The intensity distribution and the phase distribution of the BG beam passing through a Cassegrain antenna are theoretically derived and simulated. At a wavelength of 1550 nm, this method can theoretically improve the transmission efficiency to approach 100% under the situation in which the obscuration ratio is nonzero, and the transmission efficiency can reach more than 80% when obscuration ratio is in the range of from 0 to 0.1252 with $l=4$l=4. The effects of on-axial defocusing on the light field and the transmission efficiency are studied. The method proposed in this paper can remarkably improve the transmission efficiency of a Cassegrain antenna in a practical and uncomplicated approach.

A Novel Self-Adaptive Control Method for Plasma Electrolytic Oxidation Processing of Aluminum Alloys.

Plasma electrolytic oxidation processing is a novel promising surface modification approach for various materials. However, its large-scale application is still restricted, mainly due to the problem of high energy consumption of the plasma electrolytic oxidation processing. In order to solve this problem, a novel intelligent self-adaptive control technology based on real-time active diagnostics and on the precision adjustment of the process parameters was developed. Both the electrical characteristics of the plasma electrolytic oxidation process and the microstructure of the coating were investigated. During the plasma electrolytic oxidation process, the discharges are maintained in the soft-sparking regime and the coating exhibits a good uniformity and compactness. A total specific energy consumption of 1.8 kW h m-2 µm-1 was achieved by using such self-adaptive plasma electrolytic oxidation processing on pre-anodized 6061 aluminum alloy samples.

Discharge Behavior and Dielectric Breakdown of Oxide Films during Single Pulse Anodizing of Aluminum Micro-Electrodes.

Micro-arc discharge events and dielectric breakdown of oxide films play an important role in the formation process of plasma electrolytic oxidation coating. Single pulse anodization of micro-electrodes was employed to study the discharge behavior and dielectric breakdown of oxide films deposited on aluminum in an alkaline silicate electrolyte. Voltage and current waveforms of applied pulses were measured and surface morphology of micro-electrodes was characterized from images obtained using scanning electron microscope (SEM). A feasible identification method for the critical breakdown voltage of oxide film was introduced. Different current transients of voltage pulses were obtained, depending on applied pulse voltage and duration. In addition, the active capacitive effect and complex non-linear nature of plasma electrolytic oxidation process is confirmed using dynamic electrical characteristic curves. A good correlation between the pulse parameters and shape of discharge channels was observed. Circular opened pores were found to close with increasing potential and pulse width. Finally, the characteristic parameters of a single discharge event were estimated.

Structure design of a conic lens pair for improving the transmission efficiency of a Cassegrain antenna.

Central energy loss is a critical factor decreasing the transmission efficiency of a Cassegrain antenna. In this paper, a pair of conic lenses are designed and set in front of a Cassegrain antenna to improve the transmission efficiency of the antenna instead of designing a complicated antenna structure. On the basis of the analysis, the optimized conic lens pair can theoretically improve the transmission efficiency up to 100% at a wavelength of 1550 nm under ideal conditions. After several practical factors are considered, such as the dispersion of the material, the transmissivity and chamfering of the conic lens, and the reflectivity of the mirrors composing the Cassegrain antenna, the conic lens pair can still increase the transmission efficiency of the Cassegrain antenna up to 92.37% at a wavelength of 1550 nm. Compared with designing a complicated antenna, the method proposed here provides a more practical approach to improve the transmission efficiency of a Cassegrain antenna.

Design and analysis for annular focus antenna with off-axial parabolic and slanting hyperbolic rotating surfaces configuration.

We propose a novel annular focus antenna with an off-axial parabolic primary mirror and slanting hyperbolic secondary mirror. Ray tracing based on three-dimensional vector reflection theory is utilized to design and analyze the structural parameters of the antenna. In ideal conditions, there is no geometric loss in theory and the transmitting efficiency increases by 24.54% compared with the conventional Cassegrain optical antenna. The transmitting efficiency is also calculated in the conditions of off-axial and on-axial defocus. The simulated results demonstrate that this design can increase transmission efficiency of the optical antenna effectively.

Design and analysis for a bend-resistant and large-mode-area photonic crystal fiber with hybrid cladding.

In this paper, an asymmetric large-mode-area photonic crystal fiber (LMA-PCF) with low bending loss at a smaller bending radius is designed. The finite-element method with a perfectly matched layer boundary is used to analyze the performance of the PCF. To achieve LMA-PCF with low bending loss, the air holes with double lattice constants and different sizes at the core are designed. Numerical results show that this structure can achieve low bending loss and LMA with a smaller bending radius at the wavelength of 1.55 µm. The effective mode area of the fundamental mode is larger than 1000 µm2 when the bending radius is ≥10 cm. The bending loss of the fundamental mode is just 0.0113 dB/m, and the difference between the fundamental and high-order modes of the bending loss is larger than 103 when the bending radius is 10 cm. Simulation results show this novel PCF can achieve LMA and have effective single-mode operation when the bending orientation angle ranges in ±110°. This novel photonic crystal has potential application in high-power fiber lasers.

Effects of Texture and Grain Size on the Yield Strength of ZK61 Alloy Rods Processed by Cyclic Extrusion and Compression.

The ZK61 alloy rods with different grain sizes and crystallographic texture were successfully fabricated by cyclic extrusion and compression (CEC). Their room-temperature tension & compression yield strength displayed a significant dependence on grain size and texture, essentially attributed to {10-12} twinning. The texture variations were characterized by the angle θ between the c-axis of the grain and the extrusion direction (ED) during the process. The contour map of room-temperature yield strength as a function of grain size and the angle θ was obtained. It showed that both the tension yield strength and the compression yield strength of ZK61 alloy were fully consistent with the Hall-Patch relationship at a certain texture, but the change trends of the tension yield strength and the compression yield strength were completely opposite at the same grain size while texture altered. The friction stresses of different deformation modes calculated based on the texture confirmed the tension yield strength of the CECed ZK61 alloy rods, which was determined by both the basal slip and the tension twinning slip during the tension deformation at room temperature, while the compression yield strength was mainly determined by the basal slip during the compression deformation.

The Effect of Welding Energy on the Microstructural and Mechanical Properties of Ultrasonic-Welded Copper Joints.

The effects of welding energy on the mechanical and microstructural characteristics of ultrasonic-welded pure copper plates were investigated. Complex dynamic recrystallization and grain growth occurred inside the weld zone during ultrasonic welding. At a low welding energy, a thin band of straight weld interfaces was observed and had an ultra-fine grain structure. With an increase in welding energy, the weld interface progressively changed from flat to sinusoidal, and eventually turned into a convoluted wavy pattern, bearing similarities to shear instabilities, as observed in fluid dynamics. The lap shear load of the joints initially increased and then remained stable as the welding energy increased. The tensile characteristics of the joints significantly depended on the development of plastic deformation at the interface. The influence of the microstructure on the hardness was also discussed.

Sevoflurane prevents lipopolysaccharide-induced barrier dysfunction in human lung microvascular endothelial cells: Rho-mediated alterations of VE-cadherin.

Acute lung injury (ALI) mainly occurs as increased permeability of lung tissue and pleural effusion. Inhaled anesthetic sevoflurane has been demonstrated to alleviate lung permeability by upregulating junction proteins after ischemia-reperfusion. However, the exact mechanisms of its protective effect on reperfusion injury remain elusive. The aim of this study was to assess possible preconditioning with sevoflurane in an in vitro model of lipopolysaccharide (LPS)-induced barrier dysfunction in human lung microvascular endothelial cells (HMVEC-Ls). In this study, HMVEC-Ls were exposed to minimum alveolar concentration of sevoflurane for 2 h. LPS significantly increased the permeability of HMVEC-L. Moreover, the distribution of junction protein, vascular endothelial (VE)-cadherin, in cell-cell junction area and the total expression in HMVEC-Ls were significantly decreased by LPS treatment. However, the abnormal distribution and decreased expression of VE-cadherin and hyperpermeability of HMVEC-Ls were significantly reversed by pretreatment with sevoflurane. Furthermore, LPS-induced activation of the RhoA/ROCK signaling pathway was significantly inhibited with sevoflurane. Such activation, abnormal distribution and decreased expression of VE-cadherin and hyperpermeability of HMVEC-Ls were significantly inhibited with sevoflurane pretreatment or knockdown of RhoA or ROCK-2. In conclusion, sevoflurane prevented LPS-induced rupture of HMVEC-L monolayers by suppressing the RhoA/ROCK-mediated VE-cadherin signaling pathway. Our results may explain, at least in part, some beneficial effects of sevoflurane on pulmonary dysfunction such as ischemia-reperfusion injury.

Effects of nitric oxide on notexin-induced muscle inflammatory responses.

Excessive inflammatory response may delay the regeneration and damage the normal muscle fibers upon myoinjury. It would be important to be able to attenuate the inflammatory response and decrease inflammatory cells infiltration in order to improve muscle regeneration formation, resulting in better muscle functional recovery after myoinjury. This study was undertaken to explore the role of Nitric oxide (NO) during skeletal muscle inflammatory process, using a mouse model of Notexin induced myoinjury. Intramuscular injection (tibialis anterior, TA) of Notexin was performed for preparing mice myoinjury. NO synthase inhibitor (L-NAME) or NO donor (SNP) was intraperitoneally injected into model mice. On day 4 and 7 post-injury, expression of muscle-autoantigens and toll-like receptors (TLRs) was evaluated from muscle tissue by qRT-PCR and Western Blot; the intramuscular infiltration of monocytes/macrophage (CD11b(+) or F4/80(+) cells), CD8(+) T cell (CD3ε(+)CD8α(+)), apoptotic cell (CD11b(+)caspase3(+)), and MHC-I molecule H-2K(b)-expressing myofibers in damaged muscle were assessed by imunoflourecence analysis; the mRNAs expression of cytokines and chemokines associated with the preferential biological role during the muscle damage-induced inflammation response, were assessed by qRT-PCR. We detected the reduced monocytes/macrophages infiltration, and increased apoptotic cells in the damaged muscle treated with SNP comparing to untreatment. As well, SNP treatment down-regulated mRNA and protein levels of muscle autoantigens, TLR3, and mRNA levels of TNF-α, IL-6, MCP-1, MCP-3, and MIP-1α in damaged muscle. On the contrary, L-NAME induced more severe intramuscular infiltration of inflammatory cells, and mRNA level elevation of the above inflammatory mediators. Notably, we observed an increased number of MHC-I (H2-K(b)) positive new myofibers, and of the infiltrated CD8(+) T cells in damaged muscle at the day 7 after L-NAME treatment. The result herein shows that, NO can act as an endogenous anti-inflammatory molecule during the ongoing muscle inflammation. Our finding may provide new insight to optimize NO-based therapies for improving muscle regeneration after myoinjury.

[Effects of mechanical stimulation on expression of autoantigens in myoblasts].

OBJECTIVE: To explore the effects of mechanical stimulation on the expression of autoantigens in myoblasts. METHODS: According to different processing methods, C2C12 cells were divided into the experimental group and control group; the experimental group was divided into 4 subgroups: 2-, 4-, and 6-day and 1-day stretch groups. In 2-, 4-, and 6-day stretch groups, mechanical loading was added on the C2C12 cells at a stretching frequency of 0.25 Hz and cellular deformation amplitude of 10%, 2 hours a day for 2, 4, and 6 days respectively by Flexercell 5000 strain unit, and at a stretching frequency of 1 Hz and cellular deformation amplitude of 15% for 1 hour in 1-day stretch group. In the control group, the cells were routinely cultured for 1, 2, 4, and 6 days (1-, 2-, 4-, and 6-day control). The cells were observed by inverted phase contrast microscope. The cell proliferation was detected by flow cytometry; the expressions of autoantigens were detected by Western blot method, including the Ku/the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), U1-70 (A part of ATP-dependent DNA helicase II), histidyl tRNA synthetase (HRS), and Mi-2 (reconfigurable components deacetylase complexes of NuRD). RESULTS: The exfoliated cells were found in 1-day stretch group, but no exfoliated cell was seen in the control group for 1-day culture. The cells proliferated more obviously in 2-day stretch group than in the control group for 2-day culture; cell differentiation was found in 4-day stretch group, and cell fusion in 6-day stretch group, which were similar to those in the control group for 4- and 6-day culture. After single stretching, cell apoptosis was found in 1-day stretch group, showing no significant difference in the relative DNA proliferation index (DPI) when compared with DPI of control group for 1-day culture (t = 0.346, P = 0.747). After cyclic stretching, DPIs of 2- and 4- day stretch groups were significantly increased when compared with those of the control group for 2- and 4-day culture (P < 0.05), but no significant difference was found between control group for 6-day culture and 6-day stretch group (t = 1.191, P = 0.303). Compared with the control group for 2-day culture, the relative protein expression of autoantigens (DNA-Pkcs, Mi-2, HRS, and U1-70) in 2-day stretch group decreased significantly (P < 0.05), but no significant difference was found between control group for 4-day culture and 4-day stretch group (P > 0.05). The relative protein expressions of autoantigens in 4-day stretch group significantly increased when compared with those of 2-day stretch group (P < 0.05), but the relative protein expressions of autoantigens in the control group for 4-day culture significantly decreased when compared with those of the control group for 2-day culture (P < 0.05). CONCLUSION: Short-term mechanical stimulation can inhibit the expressions of autoantigens in myoblasts, but with the time prolonging, cell differentiation and fusion and adaptation to mechanical stimulation would result in diminished inhibitory effect.

[Changes in serum electrolyte levels after seawater immersion of open abdominal wound and drowning in dogs].

OBJECTIVE: To assess the effects of seawater immersion of open abdominal wound and drowning on plasma electrolyte levels in dogs. METHODS: Twenty-one dogs with open abdominal wounds were randomly divided into 3 groups, namely the control group (n=7), seawater immersion group (n=7) and seawater immersion and drowning group (n=7). The dogs in the control group were subjected to simple open abdominal wound, and those in the latter two groups were immersed into seawater after the abdominal injury. The changes in the plasma electrolytes and osmotic pressure were observed after the treatments. RESULTS AMD CONCLUSION: Seawater immersion of the open abdominal wound results in hypematremia, hyperkalemia and hypertonic dehydration, and the effect is proportional to the length of immersion time, but seawater airway perfusion does not cause obvious changes of the plasma electrolytes and osmotic pressure in dogs.

[Analysis of spectral intensity of fermi resonance of molecules].

Raman spectra of liquid carbon disulfide (CS) and carbon tetrachloride (CCl4) were measured. And the spectral intensity was analyzed using the J. F. Bertran theory and the group theory. The rule about Fermi resonance was obtained from the Raman spectra of carbon disulfide (CS) and carbon tetrachloride (CCL4): (1) The energy can transfer between a fundamental and an overtone frequency about Fermi resonance; the two spectra have the same intensity. The spectral intensity of the two spectra was equal (R=1) about Fermi resonance, when the difference between fundamental of Fermi resonance and overtone of Fermi resonance was very small. (2) The intensity of overtone is stronger than that of fundamental's. (3) The spectrum of Fermi resonance was observed, but the fundamental frequency was not. This article has very good reference value for the assignments in the molecular structure and the research of contents.