Accumulation of heavy metals in two crop seeds due to soil contamination as determined by neutron activation analysis techniques

Samples of two crop seeds (corn and sesame) grown on different contaminated soil sources were collected and prepared for neutron activation analysis. Soil contamination sources were organic waste compost applied to soil amendments namely, sewage sludge(Bs) and municipal solid waste (MSW) at 4%, 6% and 8% respectively. The non destructive NAA technique was used to determine some trace elements accumulation in plant seeds. Results revealed that increasing rate of tested organic waste resulted in dramatic increase in tested heavy metals levels in seeds(i.e., Fe, Zn, Co, Cr, Sc and Hg). Sesame seeds showed higher affinity to accumulate trace elements than corn grains in most tested elements. Moreover, MSW addition enhanced the accumulation of tested metals in seeds more than Bs compost.

Activation Cross Section Measurement for the ^(165)Ho(n,γ)^(166)Ho^(m) Reaction

The cross sections for the 165Ho（n.γ）166Ho? reaction have been measured rel-ative to the 197Au（n.γ）198Au reaction at neutron energies of 203,676 and 974 keV usingthe activation technique in combination With high resolution HPGe detector gamma rayspectroscopy Experimental data were given for the first time.

An effective technique for isolating adult activated Schwann cells

BACKGROUND： Schwann cells （SCs） are neuroglial cells of peripheral nerve and play a key role in repairing peripheral nerve injury; therefore, it provides an important evidence for transplantation of SCs which are characterized by active proliferation and adult high-purity in vitro after nerve injury in clinic, and also develops a new therapeutic way for nerve injury.OBJECTEVE： To investigate an effective technique for isolating adult activated Schwann cells,DESIGN： Controlled observational study.SETTING： Mudanjiang Medical College.MATERIALS： The experiment was completed at the Department of Medical Genetics of Harbin Medical University from March 2003 to April 2005. Health female Wistar rats, aged 2 months, weighting 150-160 g, were randomly divided into 3 groups with 5 in each group.METHODS： The right sciatic nerves from 15 Wistar rats were exposed and transected at the mid thigh under pentobarbital anesthesia （4 mg/kg, Lp）. Seven days later, the distal segments of the predegenerated nerves were removed and used to produce adult Schwann cell cultures. The distal segment of the predegenerated nerve, 20 mm in length, was resected. The nerve was cut into pieces 1 mm in length and incubated for 3 hours under CO2 at 37 ℃ with an enzyme mixture of 0.05% collagenase/dispase. Rats were divided into 3 groups： ① Group 1： The nerve fragments were explanted in poly-L-lysine and laminin-coated dishes with BS medium from the 1st to the 6th day, On the 6^th day, the fragments were removed into a new poly-L-lysine-laminin-coated dish and the BS medium was changed to BS with 10% FBS, The nerve fragments were replaced repeatedly in the same way in new dishes on the 12^th and the 18th days. ② Group 2： For the first 3 days, the nerve fragments were fed with BS with 10% FBS. This medium was changed to BS medium on the third day. The nerve fragments were removed to another dish on day 6 and BS medium was changed to BS with 25 mI.JL FBS. Hereafter the culture method was the same as for group 1. ③ Group 3： For the first 6 days, nerve fragments were incubated in a dish not coated with poly-L-lysine and laminin, in BS medium supplemented with 8×10^7 U/L of penicillin-streptomycin. On the 6th day, the nerve fragments were removed to a poly-L-lysine-laminin-coated dish and cultured in BS with 25 mI.JL FBS, On the 12th day, the nerve fragments were explanted a second dish and fed with BS containing 100 mL/L FBS. On the 18^th day, they were explanted to a third poly-L-lysine-laminin-coated dish, SCs were obtained from all 3 dishes on the 21st day, Finally, purity and density of SCs were identified and proliferation index was calculated at the same time.MAIN OUTCOME MEASURES ： Purity and density of SCs cultured with various methods in the three groups for 21 days.RESULTS ： ① Isolation and proliferation of SCs： In the group 1, they increased in number after 4 days and both purity and density of cultured SCs were significantly higher than those from group 2. In the group 2, there were few fibroblasts. In the group 3, both purity and density of cultured SCs were remarkably higher than in those from groups 1 or 2. Then optimal proliferation was soon seen and the rapid expansion of SC populations suppressed the development of contaminating fibroblasts. On the 21st day, SCs proliferated to achieve maximal density and were too crowded to be counted. With Chi-square test, the data of the purity and the density were analyzed from groups 1 to 3, the result indicated X^2=430.47, P 〈 0.05. ② Characterization and proliferation rate of SCs： Immunostaining for S100 protein was evident in the cell soma and the processes of all three groups in cultures of SCs. SCs in vitro demonstrated typical bior tri-polar morphology, had oval nuclei, and stained brightly for $100. The proliferation rate of SCs was assessed with double fluorescence staining for BrdU and S100 on the 21^st day of all three groups in cultures. About 40%-50% of the total SCs in the each group showed BrdU incorporation.CONCLUSION： The method is to use predegeneration in vivo, differential speed culture supplemented with the penicillin-streptomycin in low concentration, and changing of the concentration of FBS in the BS medium from 0 to 100 mL/L. This method allows remarkable suppression of fibroblast growth and attainment of SC proliferation and purity, in a short time, from adult nerves.

Preliminary Research Results for the Generation and Diagnostics of High Power Ion Beams on FLASH II Accelerator

The preliminary experimental results of the generation and diagnostics of high power ion beams on FLASH II accelerator are reported. The high-power ion beams presently are being produced in a pinched diode. The method for enhancing the ratio of ion to electron current is to increase the electron residing time by pinching the electron flow. Furthermore, electron beam pinching can be combined with electron reflexing to achieve ion beams with even higher efficiency and intensity. The anode plasma is generated by anode foil bombarded with electron and anode foil surface flashover. In recent experiments on FLASH II accelerator, ion beams have been produced with a current of 160 kA and an.energy of 500 keV corresponding to an ion beam peak power of about 80 GW. The ion number and current of high power ion beams were determined by monitoring delayed radioactivity from nuclear reactions induced in a 12C target by the proton beams. The prompt 7-rays and diode bremsstrahlung X-rays were measured with a PIN semi-conductor detector and a plastic scintillator detector. The current density distribution of ion beam were measured with a biased ion collector array. The ion beams were also recorded with a CR-39 detector.

Microstructure and properties of the joints of ZrO2 ceramic/ stainless steel brazed in vacuum with AgCuTi active filler metal

The ZrO2 ceranfic was successfully jointed to stainless steel by vacuum brazing with active filler metal. The AgCuTi active filler metal was used and the joining was performed at a temperature of 850 ℃ for 10 rain. The microstructures of the joints were characterized by metallographic microscopy, scanning electron microscopy （SEM）, and energy dispersive spectroscopy （EDS）. Metallographic microscopy analysis shows that the morphology of the cross section was a sandwich structure and the TiO is observed in the surface of ZrO2/ stainless steel. The diffusion and enrichment of the elements are the key roles in the brazing of ZrO2 ceramic and stainless steel. The formation of TiCu compounds inhibited the further diffusion of titanium into stainless steel or the ZrO2 ceramic to form TiO compound. In the experimental conditions, the average tensile strength is 80MPa for the joint of ZrO2 ceramic / AgCuTi/ stainless steel systems. A complete joint is formed between the ZrO2 ceramic and stainless steel with the leakage rate at the degree of 10 ^-12 Pa · m^3/s.

Preliminary study of a dispersed fringe type sensing system

Telescopes with large aspherical primary mirrors collect more light and are therefore sought after by astronomers. Instead of using a single large one-piece mirror, smaller segments can be assembled into a useable telescopic primary. Because the segments must fit together to create the effect of a single mirror, segmented optics present unique challenges to the fabrication and testing that are absent in monolithic optics. A dispersed fringe sensor （DFS） using a broadband point source is an efficient method for cophasing and is also highly automated and robust. Unlike the widely adopted Shack- Hartmann Wavefront sensor and curvature wavefront sensor with edge sensors for calibration of relative pistons, DFS can estimate the piston between segments by only using the spectrum formed by the transmissive grating＇s dispersion, and therefore can replace the edge sensors, which are difficult to calibrate. We introduce the theory of the DFS and Dispersed Hartmann Sensor （DHS） for further utilization of the coarse phasing method of DFS. According to the theory, we bring out the preliminary system design of the cophasing experimental system based on DFS and DHS which is now established in our institute. Finally, a summary is reached.

Control of Vehicle Active Front Steering Based on Active Disturbance Rejection Feedback Controller

A control method of active front steering(AFS)based on active disturbance rejection technique was proposed for solving the model nonlinearity and parameter decoupling control in the traditional control methods.The AFS controller consists of the proportional and derivative(PD)feed-forward controller and the active disturbance rejection feedback controller.To improve the steering response characteristics of a vehicle,a PD controller is designed to realize variable steering gear ratio,and to enhance the safety of vehicle when steering.An active disturbance rejection controller(ADRC)is designed to follow the expected yaw rate of the vehicle.According to the input and output of system,extended state observer(ESO)of ADRC can dynamically estimate internal and external disturbance of the system,thus easily realizing the model nonlinear and parameter decoupling control.The AFS controller is simulated and validated in Matlab and CarSim.The simulating results of double lane change(DLC)test and pylon course slalom(PCS)test show that the ADRC can well control the vehicle model to complete the road simulation test of DLC and PCS with small path tracking error.The simulating results of angle step test of steering wheel show that the vehicle under the control of ADRC demonstrates good lateral response characteristic.The controller regulates a wide range of parameters.The model has less precision requirements with good robustness.

Active Optics in LAMOST

Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) is one of the major national projects under construction in China. Active optics is one of the most important technologies for new large telescopes. It is used for correcting telescope errors generated by gravitational and thermal changes. Here, however, we use this technology to realize the configuration of LAMOST,—a task that cannot be done in the traditional way. A comprehensive and intensive research on the active optics used in LAMOST is also reported, including an open-loop control method and an auxiliary closed-loop control method. Another important development is in our pre-calibration method of open-loop control, which is with some new features: simultaneous calculation of the forces and displacements of force actuators and displacement actuators; the profile of mirror can be arbitrary; the mirror surface shape is not expressed by a fitting polynomial, but is derived from the mirror surface shape formula which is highly accurate; a proof is given that the solution of the pre-calibration method is the same as the least squares solution.

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST)

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, also called the Guo Shou Jing Telescope) is a special reflecting Schmidt telescope. LAMOST’s special design allows both a large aperture (effective aperture of 3.6 m–4.9 m) and a wide field of view (FOV) (5°). It has an innovative active reflecting Schmidt configuration which continuously changes the mirror’s surface that adjusts during the observation process and combines thin deformable mirror active optics with segmented active optics. Its primary mirror (6.67m×6.05 m) and active Schmidt mirror (5.74m×4.40 m) are both segmented, and composed of 37 and 24 hexagonal sub-mirrors respectively. By using a parallel controllable fiber positioning technique, the focal surface of 1.75 m in diameter can accommodate 4000 optical fibers. Also, LAMOST has 16 spectrographs with 32 CCD cameras. LAMOST will be the telescope with the highest rate of spectral acquisition. As a national large scientific project, the LAMOST project was formally proposed in 1996, and approved by the Chinese government in 1997. The construction started in 2001, was completed in 2008 and passed the official acceptance in June 2009. The LAMOST pilot survey was started in October 2011 and the spectroscopic survey will launch in September 2012. Up to now, LAMOST has released more than 480 000 spectra of objects. LAMOST will make an important contribution to the study of the large-scale structure of the Universe, structure and evolution of the Galaxy, and cross-identification of multiwaveband properties in celestial objects.

Simulation of oxygen transfer in liquid lead under influence of nanoparticles by using lattice Boltzmann method

Oxygen transfer presents a serious challenge in the application of liquid lead as a nuclear coolant in advanced reactors. To mitigate corrosion by liquid lead in contact with steel, carefully controlling the oxygen concentration has been used as an effective way. Oxygen needs to mix in liquid lead uniformly and quickly. To enhance oxygen transport in liquid lead, nanoparticles are added to the liquid metal. In the current study, a lattice Boltzmann method is applied to investigate natural convection of copper/lead and aluminum oxide/lead in two-dimensional simplified container. Two thermal boundary cases are evaluated in order to check the effect of different natural convection flow patterns on oxygen transport. Some useful information are obtained such as improvement in natural convection and reduction in oxygen equilibrium time.

Cobalt in alluvial Egyptian soils as affected by industrial activities

Twenty five surface (0—20 cm) soil samples were collected from different locations in Egypt representing non polluted, moderately and highly polluted soils. The aim of this study was to evaluate total Co content in alluvial soils of Delta in Egypt using the delayed neturen activation analysis technique (DNAA). The two prominent gamma ray lines at 1173 2 and 1332 5 keV was efficiently used for 60 Co determination. Co content in non polluted soil samples ranged between 13 12 to 23 20 ppm Co with an average of 18 16±4.38 ppm. Cobalt content in moderately polluted soils ranged between 26 5 to 30 00 ppm with an average of 28 3±1.3 ppm. The highest Co levels (ranged from 36 to 64 69 ppm with an average of 51 9±9.5); were observed in soil samples collected from, either highly polluted agricultural soils due to prolonged irrigation with industrial wastewater or surface soil samples from industrial sites.

High resolution spectroscopy of two young active late type stars within 20 parsecs of the Sun

We present high-resolution optical echell spectroscopy of HIP 544 and HIP 46843, two nearby solar like stars. The discovery of these young stars at such a close distance to the Sun is really a surprising phenomenon. It will help us to have a better understanding of the structure and evolutionary history of the Milky Way. The radial velocities （RV） of HIP 544 and HIP 46843 are measured to be -6.88±0.13km s^-1 and 8.30±0.16km s^-1, respectively, which are more accurate than before. The equivalent widths （EW） of the Li I 6707.8A absorption line of HIP 544 and HIP 46843 are measured to be 110±5 mA and 195±5 mA respectively. Based on these properties, HIP 544 is estimated to be 100-800Myr old and HIP 46843 30-100Myr old using three relatively creditable methods.

Teaching Large Classes： Problems and Prospects

There is no global definition of what constitutes a large class. The literature, for example, shows large classes as ranging between 25-30 learners in the United Kingdom, more than 35 learners in the US, and 60 or more learners in developing countries. The current study attempted to establish what instructional strategies could be introduced for improvement of teaching learning in the prevailing large classes. A review of research on teaching of large classes highlighted challenges that both teachers and students experience. Effective teaching and learning throughout the study was conceptualized as that situated within a social constructivist framework. This is a descriptive study in design. The literature component of the study utilized a content analysis methodology with a view to identifying strategies of practical application and potential to facilitate learning in large classes, such as Active Learning, Collaborativb Learning, Cooperative Learning, Inductive Teaching Methods, and novel practices including issues on environment for change are suggested. The empirical data indicated that teachers had devised strategies to cope with the large classes, but these needed further development. The implication for these findings is the need for teacher professional development through reflective practice.

e-VLBI observations of GRB 080409 afterglow with an Australasian radio telescope network

Transcontinental e-VLBI observations were conducted in June 2008 with telescopes in Australia, China and Japan. Detections were made of the radio-loud quasar PKS B0727-115, which shows superlu- minal motion, and the intra-day variable quasar PKS B0524＋034. The latter source was used as a phase reference calibrator for observations at the position of the gamma-ray burst GRB 080409, for which an upper limit to the radio emission is set. Australia Telescope Compact Array data were also used to derive a limit on the radio flux density of the GRB afterglow. These observations demonstrate the capability to form a large Australasian radio telescope network for e-VLBI, with data transported and processed in realtime over high capacity networks. This campaign represents the first step towards more regular e-VLBI observations in this region.

An experimental indoor phasing system based on active optics using dispersed Hartmann sensing technology in the visible waveband

A telescope with a larger primary mirror can collect much more light and resolve objects much better than one with a smaller mirror, and so the larger version is always pursued by astronomers and astronomical technicians. Instead of using a monolithic primary mirror, more and more large telescopes, which are currently being planned or in construction, have adopted a segmented primary mirror design. Therefore, how to sense and phase such a primary mirror is a key issue for the future of extremely large optical/infrared telescopes. The Dispersed Fringe Sensor （DFS）, or Dispersed Hartmann Sensor （DHS）, is a non-contact method using broadband point light sources and it can estimate the piston by the two-directional spectrum formed by the transmissive grating＇s dispersion and lenslet array. Thus it can implement the combination of co-focusing by Shack-Hartmann technology and phasing by dispersed fringe sensing technologies such as the template-mapping method and the Hartmann method. We introduce the successful design, construction and alignment of our dis- persed Hartmann sensor together with its design principles and simulations. We also conduct many successful real phasing tests and phasing corrections in the visible waveband using our existing indoor segmented mirror optics platform. Finally, some conclusions are reached based on the test and correction of experimental results.

Cross sections for 14 MeV neutron interaction with lutetium isotopes and their theoretical excitation functions

The cross-sections for the 175Lu(n,p)175Yb,175Lu(n,α)172Tm,176Lu(n,α)173Tm,175Lu(n,2n)174mLu,and 175Lu(n,2n)174gLu reactions at 13.57,14.0314.62,and 14.86 MeV neutron energies were measured using an activation technique.The theoretical excitation functions of these reactions were calculated using the Talys-1.95 code.The reaction cross-section data experimentally obtained were analyzed and compared with experimental data reported in the literature,data from five major evaluated nuclear data libraries of IAEA,and theoretical values based on Talys-1.95.The data obtained at some neutron energies agree with some of the data reported in the literature and theoretical values based on Talys-1.95.The consistency of the theoretical curves of excitation functions based on Talys-1.95 with the data obtained in this study and those reported in the literature is higher than that of the evaluation curves of excitation functions for the 175Lu(n,p)175Yb,175Lu(n,α)172 Tm,and 176Lu(n,α)173Tm reactions.This study is helpful because it provides new evaluated reaction cross-section data on lutetium(which is a fusion reactor material),improves the quality of neutron-induced reaction cross section data libraries,and advances the research on related applications.

Cross-section measurements for(n,2n)reactions on stannum isotopes in the neutron energy range of 13.5 to 14.6 MeV

Cross-sections for （n, 2n） reactions have been measured on stannum isotopes at the neutron energies of 13.5 to 14.6 MeV using the activation technique. Data are reported for the following reactions： ^112Sn（n, 2n）^111Sn, ^118Sn（n, 2n）^117Sn and ^124Sn（n, 2n）^123mSn. The neutron fluences were determined using the monitor reaction ^93Nb（n, 2n）^92mNb or ^27Al（n, α）^24Na. The results of present work were compared with data published previously.

Cross-section measurement for Ni(n,x)^(58)(m+g)Co,Ni(n,x)^(60m)Co,Ni(n,x)^(61)Co and Ni(n,x)^(62m)Co reactions induced by neutrons around 14 MeV

The cross sections of Ni（n, x）^58（m＋g）CO, Ni（n, x）^60mCO, Ni（n, x）^61Co and Ni（n, x）^62mCO reactions induced by neutrons around 14 MeV were measured in this work and calculated by a previously developed formula in this work. The neutron flux was determined using the monitor reaction 27Al（n, α）24Na and the neutron energies were measured with the method of cross-section ratios for ^90Zr（n, 2n）^89Zr to ^93Nb（n, 2n）^92mNb reactions.