Influence of different weather events on concentrations of particulate matter with different sizes in Lanzhou,China

The formation and development of weather events has a great impact on the diffusion, accumulation and transport of air pollutants, and causes great changes in the particulate pollution level. It is very important to study their influence on particulate pollution. Lanzhou is one of the most particulate-polluted cities in China and even in the world. Particulate matter （PM） including TSP, PM〉10, PMzs-10, PM2.5 and PM1.0 concentrations were simultaneously measured during 2005-2007 in Lanzhou to evaluate the influence of three kinds of weather events - dost, precipitation and cold front - on the concentrations of PM with different sizes and detect the temporal evolution. The main results are as follows： （1） the PM pollution in Lanzhou during dust events was very heavy and the rate of increase in the concentration of PM2.5-10 was the highest of the five kinds of particles. During dust-storm events, the highest peaks of the concentrations of fine particles （PM2.5 and PM1.0） occurred 3 hr later than those of coarse particles （PM〉10 and PM/.5-10）. （2） The major effect of precipitation events on PM is wet scavenging. The scavenging rates of particles were closely associated with the kinds of precipitation events. The scavenging rates of TSP, PM〉10 and PMa.5-10 by convective precipitation were several times as high as those caused by frontal precipitation for the same precipitation amount, the reason being the different formation mechanism and precipitation characteristics of the two kinds of precipitation. Moreover, there exists a limiting value for the scavenging rates of particles by precipitation. （3） The major effect of cold-front events on particles is clearance. However, during cold-front passages, the PM concentrations could sometimes rise first and decrease afterwards, which is the critical difference in the influence of cold fronts on the concentrations of particulate pollutants vs. gaseous pollutants.

Flotation kinetics performance of different coal size fractions with nanobubbles

The flotation kinetics of different size fractions of conventional and nanobubble(NB) flotation were compared to investigate the effect of NBs on the flotation performance of various coal particle sizes. Six flotation kinetics models were selected to fit the flotation data, and NBs were observed on a hydrophobic surface under hydrodynamic cavitation by atomic force microscope scanning. Flotation results indicated that the best flotation performance of size fraction at-0.125+0.074 mm can be obtained either in conventional or NB flotation. NBs increase the combustible recovery of almost all the size fractions, but they increase the product ash content of-0.25+0.074 mm and reduce the product ash content of-0.045 mm at the same time. The first-order models can be used to fit the flotation data in conventional and NB flotation, and the classical first-order model is the most suitable one. NBs considerably enhance flotation rate on coarse size fraction(-0.5+0.25 mm) but decrease the flotation rate of the medium size(-0.25+0.074 mm). The improvement of flotation speed on fine coal particles(-0.074 mm) is probably the reason for the improved performance of raw sample flotation.

Improved finite difference method for pressure distribution of aerostatic bearing

An improved finite difference method （FDM）is described to solve existing problems such as low efficiency and poor convergence performance in the traditional method adopted to derive the pressure distribution of aerostatic bearings. A detailed theoretical analysis of the pressure distribution of the orifice-compensated aerostatic journal bearing is presented. The nonlinear dimensionless Reynolds equation of the aerostatic journal bearing is solved by the finite difference method. Based on the principle of flow equilibrium, a new iterative algorithm named the variable step size successive approximation method is presented to adjust the pressure at the orifice in the iterative process and enhance the efficiency and convergence performance of the algorithm. A general program is developed to analyze the pressure distribution of the aerostatic journal bearing by Matlab tool. The results show that the improved finite difference method is highly effective, reliable, stable, and convergent. Even when very thin gas film thicknesses （less than 2 Win）are considered, the improved calculation method still yields a result and converges fast.

Environmental change inferred from Rb and Sr of lacustrine sediments in Huangqihai Lake,Inner Mongolia

Based on the geochemical elements Rb and Sr in sediments with three different grain size fractions from profile H3 on the northern lacustrine bottomland 13 m above the Huangqihai Lake surface in 1986,the paper investigates the record of palaeolake stand state, sedimentary environmental evolution,and winter monsoon change.First,these samples are separated into three different grain size fractions,i.e.,total sediments,77-20μm and〈20μm. Second,the chemical elements-Rb and Sr-of the grain size separation were tested and analyzed systematically in this paper.Then the elements compositions of these samples are measured using VP-320 mode fluorescence spectrum instrument,respectively.The magnetic susceptibility of these samples is measured using Kappabridge KLY-3 mode instrument made in Czech AGICO Company.The results showed the elements and the ratios varied regularly with the grain size.But the ratio of Rb/Sr in the sediments〈20μm correlates positively with the magnetic susceptibility of these samples.Therefore,the ratio of Rb/Sr in the fraction〈20 μm from the lake sediments reflected the strengthening of the weathering in the deposition sites.It is a good indicator of the summer monsoon-induced weathering and pedogenesis fluctuations and can be used to reconstruct the conditions of the paleoclimate and paleoenvironment.

Efficient visual learning by bumble bees in virtual-reality conditions:Size does not matter

Recent developments allowed establishing virtual-reality (VR) setups to study multiple aspects of visual learning in honey bees under controlled experimental conditions. Here, we adopted a VR environment to investigate the visual learning in the buff-tailed bumble bee Bombus terrestris. Based on responses to appetitive and aversive reinforcements used for conditioning, we show that bumble bees had the proper appetitive motivation to engage in the VR experiments and that they learned efficiently elemental color discriminations. In doing so, they reduced the latency to make a choice, increased the proportion of direct paths toward the virtual stimuli and walked faster toward them. Performance in a short-term retention test showed that bumble bees chose and fixated longer on the correct stimulus in the absence of reinforcement. Body size and weight, although variable across individuals, did not affect cognitive performances and had a mild impact on motor performances. Overall, we show that bumble bees are suitable experimental subjects for experiments on visual learning under VR conditions, which opens important perspectives for invasive studies on the neural and molecular bases of such learning given the robustness of these insects and the accessibility of their brain.

Ag2S nanoparticles as an emerging single-component theranostic agent

Last two decades,with the rapid changes and development of nanotechnology and biological materials,diverse multi-functional nanomaterials emerging,which offers a novel way to treat and diagnose diseases,and therefore spawned the new biomedical technology of theranostics,which integrates the treatment and diagnosis or monitoring of diseases into one.Ag2S as a bio-nanomaterial with low biotoxicity has attracted more and more attention due to its good photoluminescence properties and fluorescence imaging of small animals in the second near-infrared region(NIR-Ⅱ).Meanwhile,Ag2S has the ability to absorb near-infrared light strongly because of its local surface plasma resonance(LSPR)effect and had become a kind of photothermal conve rters with good photothermal conve rsion efficiency.More interestingly,both photothermal effect and fluorescence characteristics of Ag2S nanoparticles(NPs)are closely related to their particle sizes.However,the relationship between photothermal effect and fluorescence characteristics of Ag2S NPs and their sizes has not been reviewed so far.Herein,the synthesis methods and influencing factors of synthesize Ag2S NPs with different sizes were compared firstly,and then the photothermal effect and fluorescence characte ristics of Ag2S NPs with different sizes were summarized.Finally,the possibilities and challenges of using Ag2S NPs to construct theranostic agent were discussed in the end.

Development of a fast neutron spectrometer based on a plastic fiber array

Objective A three-dimensional position-sensitive fast neutron spectrometer is designed to measure fast neutron spectrum over 10 MeV.Methods The detector consists of a 16×16 mutually perpendicular plastic scintillation fiber array coupled to 2×2 Hamamatsu H8500C position-sensitive photomultiplier tubes by optical fibers.The fiber array is fabricated with 0.5 mm×3 mm fibers and 3-mm square fibers.Results Due to the combined application of different sizes of fibers,the detector can broaden energy dynamic range and meanwhile have good detection efficiency.The method of the combined application of different sizes of plastic fibers in the array may provide a solution to measure wider energy range of solar neutrons.Conclusion In this paper,we used FLUKA to simulate the performance of the detector model and report the results of experimental studies with neutrons from a pulsed D-T neutron.

Experimental and computational studies on flow behavior of gas-solid fluidized bed with disparately sized binary particles

This paper presents experimental and computational studies on the flow behavior of a gas-solid fluidized bed with disparately sized binary particle mixtures. The mixing/segregation behavior and segregation efficiency of the small and large particles are investigated experimentally. Particle composition and operating conditions that influence the fluidization behavior of mixing/segregation are examined. Based on the granular kinetics theory, a multi-fluid CFD model has been developed and verified against the experimental results. The simulation results are in reasonable agreement with experimental data. The results showed that the smaller particles are found near the bed surface while the larger particles tend to settle down to the bed bottom in turbulent fluidized bed. However, complete segregation of the binary particles does not occur in the gas velocity range of 0.695-0.904 m/s. Segregation efficiency increases with increasing gas velocity and mean residence time of the binary particles, but decreases with increasing the small particle concentration. The calculated results also show that the small particles move downward in the wall region and upward in the core. Due to the effect of large particles on the movement of small particles, the small particles present a more turbulent velocity profile in the dense phase than that in the dilute phase.

Extraction of fish body oil from Sardinella longiceps by employing direct steaming method and its quantitative and qualitative assessment

Objective:To analyze the quantitative and qualitative properties of the extracted fish oil from Sardinella longiceps(S.longiceps).Methods:Four size groups of S.longiceps were examined for the extraction of fish oil based on length.The size groups included Group I(size range of 7.1-10.0 cm),Group II(size range of 10.1-13.0 cm),Group III(size range of 13.1-16.0 cm)and Group IV(size range of 16.1-19.0 cm).Fish oil was extracted from the tissues of S.longiceps by direct steaming method.The oil was then subjected to the determination of specific gravity,refractive index,moisture content,free fatty acids,iodine value,peroxide value,saponification value and observation of colour.Results:The four groups showed different yield of fish oil that Group IV recorded the highest values of(165.00±1.00)mL/kg followed by Group III[(145.66±1.15)mL/kg]and Group II[(129.33±0.58)mL/kg],whereas Group I recorded the lowest values of(78.33±0.58)mL/kg in monsoon season,and the average yield was(180.0±4.9)mL/kg fish tissues.These analytical values of the crude oil were well within the acceptable standard values for both fresh and stocked samples.Conclusions:The information generated in the present study pertaining to the quantitative and qualitative analysis of fish oil will serve as a reference baseline for entrepreneurs and industrialists in future for the successful commercial production of fish oil by employing oil sardines.

Inner Ear Size May Account for Spatial Orientation Differences Between Sexes

男性的空间方位感总体上比女性的要好,这是为什么呢?最近多伦多大学的研究者发现造成这种差别的主要原因是由于二者内耳的长度不同。