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A grid of equidistant electron stripes is generated during the collision of two laser pulses under a small angle in underdense plasma. Due to the oblique incidence, transverse standing wave in plasma is observed, in addition to the longitudinal traveling wave of the compound laser field. This standing wave results in the generation of plasma density grating. The ratio of the peak stripe density to background density can reach the value of 20:1. The grating period is determined by the interaction angle. Analytical theory of the compound electric fields is provided for plane waves. The grating formation is then verified via particle-in-cell simulations for short Gaussian laser pulses with typical experimental parameters. In addition, the interference pattern was also observed during experiments with Diocles laser. The results presented here are relevant for many laser-plasma applications, such as Raman scattering, inertial confinement fusion, plasma photonic crystals and laser wakefield acceleration.

Flame retardant-modified sepiolite nanofiber (PSPHD-SEP) was fabricated through chemical grafting by introducing intumescent flame retardant oligomer (PSPHD) onto the surface of sepiolite fiber. Various sepiolite/low-density polyethylene (SEP/LDPE) composites have been prepared successfully via melt blending. The dispersion of various SEPs in LDPE matrix was observed by scanning electron microscope and transmission electron microscope. The thermal degradation behaviors of various SEP/LDPE composites with 3 mass% acid-modified sepiolite fiber (a-SEP) or PSPHD-SEP have been investigated employing thermogravimetric analysis/derivative thermogravimetry. The thermal degradation kinetics of neat LDPE, a-SEP/LDPE and PSPHD-SEP/LDPE systems was comparatively analyzed by means of Friedman and Flynn–Wall–Ozawa methods to further comprehend the effect of a-SEP and PSPHD-SEP on the thermal stability of LDPE. Due to the addition of PSPHD-SEP, the limiting oxygen index value of PSPHD-SEP/LDPE composite can reach 21.3%, and the UL-94V-2 rating is obtained. The cone calorimetry (CONE) tests showed that a reduced peak heat release rate can be achieved for PSPHD-SEP/LDPE composite accompanying with gas-phase fire retardant action.

Plasma electrolytic oxidation of a cast A356 aluminum alloy was carried out in aluminate electrolytes to develop wear and corrosion resistant coatings. Different concentrations of 2, 16 and 24 g/L NaAlO 2 solutions and a silicate electrolyte (for comparison) were employed for the investigation. Wear performance and corrosion resistance of the coatings were evaluated by WC (tungsten carbide) ball-on-flat dry sliding tests and electrochemical methods, respectively. The results show that the coating formed for a short duration of 480 s in 24 g/L NaAlO 2 solution generated the best protection. The coating sustained 30 N load for sliding time of 1800 s, showing very low wear rate of ∼4.5×10 −7 mm 3 /(N·m). A low corrosion current density of ∼8.81×10 −9 A/cm 2 was also recorded. Despite low α -Al 2 O 3 content of the coating, the compact and nearly single layer nature of the coating guaranteed the excellent performances.

Birefringence and extinction coefficients of positive nematic liquid crystal (NLC) MLC-2142 and negative NLC BHR28000-400 are measured by terahertz time-domain spectroscopy system (THz-TDS). Frequency ranging from 0.1 to 0.6 THz, the birefringence of positive NLC MLC-2142 increases with the increase of frequency, and keeps larger than 0.23, which exhibits application potential in tunable broadband LC THz device where a large birefringence is required. In contrast, the birefringence of BHR28000-400 decreases with the increased frequency, which shows a completely different optical property from the positive NLC. The extinction coefficient of the above two kinds of liquid crystals are also investigated.

Sepiolite (SEP) nanofibers have been modified by grafting with poly(pentaerythritol diphosphonate dichloride-hexamethylendiamine) (PSPHD) and compounded with low density polyethylene (LDPE) to form a nanocomposite. The various modified SEPs were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared, transmission electron microscopy (TEM), and thermogravimetric analysis. The Fourier transform infrared and X-ray photoelectron spectroscopy tests show that covalent bonding exists between SEP fiber and modifiers. The nanoscale size and morphologies of SEP fiber and modified SEP nanofibers can be observed clearly by TEM. The thermogravimetric analysis results reveal that the multi-step thermal degradation process of SEP fiber is changed by grafting modification. The various LDPE/SEP nanocomposites were characterized by scanning electron micrograph, TEM, dynamic mechanical analysis, and tensile test. The results suggest that a good interfacial modification effect has been obtained between PSPHD-SEP and LDPE matrix. A particular improvement in tensile strength is reflected in tensile tests. Dynamic mechanical analysis shows that the storage moduli (E') of PSPHD-SEP/LDPE nanocomposites are much higher than that of neat LDPE and a-SEP/LDPE systems. Copyright © 2015 John Wiley & Sons, Ltd.

The intumescent flame retardant poly-pentaerythritol diphosphonate dichloride- hexamethylendiamine (PSPHD) grafting sepiolite (PSPHD-SEP) and LDPE/PSPHD-SEP/IFR composites have been prepared. Cone calorimeter technique was employed to characterize the combustion behavior of LDPE/PSPHD-SEP/IFR composites. The results show that the peak and average heat release rates decreased significantly when 5% PSPHD-SEP was added in LDPE. The PSPHD-SEP can promote the char layer to form earlier and be more compact and increase the char residue yield. The compact char residue layer can prohibit the transfer of gas and heat during the burning, showing the improvement of flame retardance.

The blasting vibration in Qingdao Cross-harbor Tunnel Guide Line Project is monitored and analyzed. We discover that the surface particle vibration velocity in the range of 5metres around the working face reduces fast, and that does not conform to Sadaovsk formula. This inquiry adopts the hypothesis-fitting-testing method to modify Sadaovsk formula. The empirical formula of the ground vibration velocity caused by blasting in tunnel is obtained.

This paper measures moisture porosity of explosive lining test pieces after long-term water immersion, so are the test pieces in standard curing condition and in equal curing condition. We have analyzed the measured moisture porosity data of three kinds of test pieces after long-term water immersion. The results indicate that the moisture porosity of explosive lining test pieces is higher than that in standard curing condition and in equal curing condition.

The article was based upon analysis of the front-and-back surface vibration velocity of the working surface by monitoring the blasting operation at hidden digging section of Jiaozhou Bay cross-harbour tunnel in Tuandao road exit ramp. Research shows that the maxim-um value of the surface blasting vibration velocity appears on the front and back of the ground ,raging from 2 m to 7 m ,just above the working surface instead of the ground just above of the working surface. However, the surface vibration velocity generates behind the working surface was 1.2 to 1.4 times greater than the one generates at the front of the working surface. The front-and-back surface vibration velocity tends to be flattening on the ground which was more than 20 m away from the working surface, just above it.

Genome plasticity resulting from frequent rearrangement of the bacterial genome is a fascinating but poorly understood phenomenon. First reported in Salmonella typhi, it has been observed only in a small number of Salmonella serovars, although the over 2,500 known Salmonella serovars are all very closely related. To gain insights into this phenomenon and elucidate its roles in bacterial evolution, especially those involved in the formation of particular pathogens, we systematically analyzed the genomes of 127 wild-type S. typhi strains isolated from many places of the world and compared them with the two sequenced strains, Ty2 and CT18, attempting to find possible associations between genome rearrangement and other significant genomic features. Like other host-adapted Salmonella serovars, S. typhi contained large genome insertions, including the 134 kb Salmonella pathogenicity island, SPI7. Our analyses showed that SPI7 disrupted the physical balance of the bacterial genome between the replication origin (ori) and terminus (ter) when this DNA segment was inserted into the genome, and rearrangement in individual strains further changed the genome balance status, with a general tendency toward a better balanced genome structure. In a given S. typhi strain, genome diversification occurred and resulted in different structures among cells in the culture. Under a stressed condition, bacterial cells with better balanced genome structures were selected to greatly increase in proportion; in such cases, bacteria with better balanced genomes formed larger colonies and grew with shorter generation times. Our results support the hypothesis that genome plasticity as a result of frequent rearrangement provides the opportunity for the bacterial genome to adopt a better balanced structure and thus eventually stabilizes the genome during evolution.