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Zinc bioavailability to aquatic organisms varies greatly under different pH values. In the present study, five native species in China and four common international test species were selected to investigate the influence of changing pH on acute zinc toxicity. The results showed that the higher trophic levels exhibited increasing sensitivity to zinc as pH decreased. However, when the pH value was between 8 and 11, the acute toxicity of zinc was relatively constant. In addition, by using a species-sensitivity distribution (SSD) method, the short-term hazardous concentrations of zinc at different pH values (based on the 5th percentiles of the pH-specific SSDs) were determined to be 17.26 µg/L (pH 4), 48.31 µg/L (pH 5), 80.34 µg/L (pH 6) and 230.6 µg/L (pH 7), respectively. The present study provides useful information for deriving water quality criteria and assessing the risks of metals in the near future.

Conventional longwall layout (CLL) for mining coal, trona, etc. is still fraught with problems including low resource recovery, wavy ground surface subsidence, bumps or rockbursts, gateroad support and maintenance, poisonous air hazard, spontaneous combustion in coal mines, instability of equipment at inclined, or steeply inclined working face, etc. In order to improve longwall mining, a novel alternate longwall panel layout that has been employed for over 20 years in China, Australia, and Russia, etc. is proposed termed “split-level longwall layout” (SLL). Gateroads on either end of the same SLL panel are split level, i.e., placed in different levels. This paper provides a review of existing research literature and insights on the problems encountered in CLL and the improvement of the new approach. Theoretical, numerical analysis, and field observation results of the new strategy demonstrate that the problems mentioned above in CLL are mitigated, and the development entries using the improved longwall system have a better stress environment with associated reduction in large roadway convergence, coal bumps or outbursts, and many other issues on ground control. Based on the current development of SLL and the future requirement of mining industry, the prospects as well as its applications, limitations, and concerns for SLL are presented.

The optimum viscosity of heavy oil is the key index to maintain the normal production of gas wells. This paper designs a new detection and optimization method of visit oil visibility and visibility reducer in alx gas well. Firstly, through the flow pattern criterion and flow pattern distribution diagram of gas-liquid two-phase flow in horizontal pipe, the propagation velocity of wave in the downstream is determined by extreme value method, and the maximum viscosity equation of heavy oil carried by air in annular fog state is established. Then, according to the maximum viscosity equation, the maximum viscosity of the heavy oil carried by the gas flow is 513.7 MPa. Finally, taking alx gas well as an example, 11 kinds of viscosity reducer were selected from water-based viscosity reducer and oil-based viscosity reducer. Under the conditions of wellhead temperature of 9 ° C and bottom hole temperature of 34 ° C, five samples with different concentrations were mixed with heavy oil, the rheological properties of the sample set were tested, and the rheological parameters and apparent viscosity of heavy oil were calculated. The experimental results show that low dosage of oil-based tackifier can effectively reduce the viscosity of heavy oil, and the optimal dosage range is 22% to 25%.

Spider pulsars are neutron stars that have a companion star in a close orbit. The companion star sheds material to the neutron star, spinning it up to millisecond rotation periods, while the orbit shortens to hours. The companion is eventually ablated and destroyed by the pulsar wind and radiation 1 , 2 . Spider pulsars are key for studying the evolutionary link between accreting X-ray pulsars and isolated millisecond pulsars, pulsar irradiation effects and the birth of massive neutron stars 3 – 6 . Black widow pulsars in extremely compact orbits (as short as 62 minutes 7 ) have companions with masses much smaller than 0.1  M ⊙ . They may have evolved from redback pulsars with companion masses of about 0.1–0.4  M ⊙ and orbital periods of less than 1 day 8 . If this is true, then there should be a population of millisecond pulsars with moderate-mass companions and very short orbital periods 9 , but, hitherto, no such system was known. Here we report radio observations of the binary millisecond pulsar PSR J1953+1844 (M71E) that show it to have an orbital period of 53.3 minutes and a companion with a mass of around 0.07  M ⊙ . It is a faint X-ray source and located 2.5 arcminutes from the centre of the globular cluster M71. PSR J1953+1844 (M71E) has an orbital period of 53.3 minutes and a companion with a mass of 0.07  M ⊙ , making it a bridging object between redbacks and black widows in the evolutionary track.

In order to study the load-bearing performance of electrically conductive concrete lightning protection poles, a finite element model of electrically conductive concrete lightning protection poles was established and the deformation capacity and load-bearing performance of the poles were analyzed using ABAQUS software. The results show that the use of prestressed reinforcement can significantly improve the bending capacity and ultimate deformation of the pole. Increasing the reinforcement ratio and outer diameter of lightning protection poles can improve the bending load capacity, but increasing the wall thickness has limited effect on enhancing the bending load capacity of lightning protection poles. This study can provide a theoretical basis for the technical application of electrically conductive concrete lightning protection poles.

Purpose The purpose of this study was to evaluate the efficacy and safety of the anterior Kugel herniorrhaphy approach when the onlay patch is omitted. Methods The study population comprised patients who underwent anterior Kugel herniorrhaphy without the onlay patch from 1 May 2009, to 31 June 2012. The onlay patch was omitted if the posterior wall defect did not exceed the inner Posiflex ® ring diameter. After reviewing the clinical follow-up records and conducting telephone interviews, the postoperative results were recorded and analyzed. Results A total of 163 patients underwent 175 hernia repairs. One patient developed recurrence after undergoing our herniorrhaphy method. The most common postoperative complaints were mild soreness, indescribable discomfort, and foreign body sensations (11 patients). The mean operative time and hospital stay were 67 min and 2 days, respectively. More serious complications included one scrotal hematoma, one hydrocele, and one wound infection that resulted in epididymitis. Conclusions The onlay patch can be omitted with low recurrence and complication rates if the posterior wall defects do not exceed the inner Posiflex ® ring diameter.

Tissue engineering scaffolds with controlled long-term release of growth factors are constructed in an attempt to mimic the intelligent ability of the extracellular matrix (ECM) to release endogenous growth factors. In this study, collagen sponges (Collagen group) were modified by N -(3-dimethylaminopropyl)- N -ethylcarbodiimide hydrochloride (EDC) and N -hydroxysuccinimide (NHS) crosslinking (EDC/NHS group) and heparin immobilization (EDC/NHS-H group), and subsequently seeded with human umbilical vein endothelial cells (HUVECs). Native and modified sponges were pre-adsorbed with basic fibroblast growth factor (bFGF) to evaluate the sustained release and bioactive maintenance of bFGF from the sponges. We found that modified collagen matrices permitted HUVECs to proliferate and migrate well and to distribute uniformly. The EDC/NHS-H group exhibited an excellent sustained-release profile and bioactive maintenance of the pre-adsorbed bFGF as compared with the Collagen and EDC/NHS groups. These results suggest that heparin-functionalized collagen matrices can support a controlled release of bFGF and thus, have potential as a tissue engineering scaffold.

A series of Ca 3− x Gd x Co 4 O 9+δ precursor powders were synthesized by the polyacrylamide gel method, and their ceramics were obtained by the Spark Plasma Sintering (SPS). There were lots of defects in the sheet-like grains from SEM and TEM observations. The electrical and the thermal transport properties were obviously affected by the material microstructure. The small polaron hopping conduction mechanism was determined above 600 K, and the hopping activation energy increased with the increase of doping contents. It was found that the Seebeck coefficient and the resistivity of doped samples were markly enhanced due to the impurity compensation effect, and their thermal conductivities were decreased due to the defects scattering. The maximum figure of merit of ZT  = 0.24 at 973 K was obtained for Ca 2.7 Gd 0.3 Co 4 O 9+δ .

In the present study, multibiomarker effects of the river water of three representative sections in Nanjing section of the Yangtze River were investigated in goldfish (Carassius auratus). The organic toxicants were extracted from the water samples using solid phase extraction. Acetylcholinesterase (AChE), glutathione-S-transferase (GST), 7-ethoxyresorufin-O-deethylase (EROD), glutathione peroxidase (GPx) and Na⁺/K⁺-ATPase activities were determined after exposure of the extracted components. The fractions of water samples from three sections (Daqiao, Sanchahe and Jiangxinzhou) altered these enzymatic activities. With the change of the extracts polarity, the levels of AChE, GST, EROD, Na⁺/K⁺-ATPase activities were different. The responses of enzymatic activities were mostly significant for those exposures of intermediate polar components (50-80% methanol extracts) and weakly polar components (ether and ether/hexane extracts). It has been shown that toxicants were mainly concentrated in these fractions in the Yangtze River (Nanjing section). With regard to response for different sections, EROD and GST activities seem to be more sensitive biomarkers. Integrated biomarker response index (IBR) were calculated and used to evaluate an integrated impact of pollutants from different sampling sections. The order of negative biological effects of the three sections was Jiangxinzhou > Sanchahe > Daqiao. The wild fish living in Nanjing section of the Yangtze River were at potential ecological risk.

Pulsars radiate radio signals when they rotate. However, some old pulsars often stop radiating for some periods. The underlying mechanism remains unknown, as the magnetosphere during nulling phases is hard to probe due to the absence of emission measurements. Here we report the detection and accurate polarization measurements of sporadic, weak, narrow dwarf pulses detected in the ordinary nulling state of pulsar B2111+46 via the Five-Hundred-Meter Aperture Spherical radio Telescope. Further analysis shows that their polarization angles follow the average polarization angle curve of normal pulses, suggesting no change of the magnetic-field structure in the emission region in the two emission states. Whereas radio emission of normal individual pulses is radiated by a ‘thunderstorm’ of particles produced by copious discharges in regularly formed gaps, dwarf pulses are produced by one or a few ‘raindrops’ of particles generated by pair production in a fragile gap of this near-death pulsar.The intensity of radio emission from a pulsar is shown to relate to the quantity of particles discharging in the magnetosphere rather than to changes of the structure of the magnetic field in the magnetosphere itself.