全球招聘新闻

博士后[美国]Arizona State UniversityArizona State University Graduate College is now acceptingPostdoctoral Applications for the Bisgrove Postdoctoral ScholarsProgram.The Award(sponsored by the Science Foundation Arizona)is designed to attract the nation's best early     

Kinetics of blue-green light-induced state transition and fluorescence quenching in the wild-type cyanobacterium Synechocystis PCC 6803 and apcD − and apcF − mutants

State transition and blue-green light-induced fluorescence quenching are two short-term processes in cyanobacteria. The details of their kinetics and the relationship between these processes have not been elucidated. In this work, these two processes were studied in the wildtype cyanobacterium Synechocystis PCC 6803 cells as well as in apcD^- and apcF^- mutants by monitoring their time- dependent 77 K fluorescence responses to blue-green light （430-540 nm） at a series of intensities ranging from 20-800 μE m^-2 s^-1. The lowest light intensity to induce fluorescence quenching in wild-type cells was 160 μE m^-2 s^-1 under the selected experimental conditions, while state transition took place at the intensities lower than 160 μE m^-2 s^-1 at a conservative level, but at variable rates. The quenching level increased at intensities higher than 160 μE m^-2 s^-1, reaching the maximum level at intensities equal to or higher than 200 μEm^-2 s^-1. Fluorescence kinetics indicated that both the length of the induction period and time required to reach the maximum level were functions of light intensity. State transitions as well as fluorescence quenching took place in both wildtype and mutant cells, but might involve different mechanisms.     

Kinetics of blue-green light-induced state transition and fluorescence quenching in the wild-type cyanobacterium Synechocystis PCC 6803 and apc D2 and apc F2 mutants

State transition and blue-green light-induced fluorescence quenching are two short-term processes in cyanobacteria. The details of their kinetics and the relationship between these processes have not been elucidated.In this work, these two processes were studied in the wildtype cyanobacterium Synechocystis PCC 6803 cells as well as in apc D-and apc F-mutants by monitoring their timedependent 77 K fluorescence responses to blue-green light(430–540 nm) at a series of intensities ranging from20–800 l E m-2s-1. The lowest light intensity to induce fluorescence quenching in wild-type cells was160 l E m-2s-1under the selected experimental conditions, while state transition took place at the intensities lower than 160 l E m-2s-1at a conservative level, but at variable rates. The quenching level increased at intensities higher than 160 l E m-2s-1, reaching the maximum level at intensities equal to or higher than 200 l E m-2s-1.Fluorescence kinetics indicated that both the length of the induction period and time required to reach the maximum level were functions of light intensity. State transitions as well as fluorescence quenching took place in both wildtype and mutant cells, but might involve different mechanisms.     

Coastal seafloor observatory at Xiaoqushan in the East China Sea

The seafloor observation system is becoming an important infrastructure for marine research because it is transforming oceanic research from temporal investigation to long term observation.The East China Sea coastal seafloor observatory,located between 30°31′44″N,122°15′12″E and 30°31′34″N,122°14′40″E,is constructed near the Xiaoqushan Island outside the Hangzhou Bay on the inner continental shelf of the East China Sea.The observatory is connected by a submarine optical fiber composite power cable that is more than one kilometer long and consists of a special junction box that transmits power and communication signals to different instruments.The special junction box has a variety of waterproof plugs and connects to three different instruments installed in a trawl preventer.The submarine optical fiber composite power cable is landed on the platform by The East China Sea Branch,State Oceanic Administration and the power is continuously supplied by the solar panels and solar battery on the top of the platform.The real time data are directly sent through the cable to the platform and are transmitted by CDMA wireless to the receiver at the State Key Laboratory of Marine Geology of Tongji University.Measurements at the observatory have been taken since April 20,2009 after installation and the results have been interpreted.The characteristics of the near bottom boundary are constrained by a sediment suspension model using portion of the observed data.In particular,discussion is provided on the sea surface height anomaly at Xiaoqushan Island influenced by the tsunami driven by the 2010 Earthquake in Chile.The successful establishment of the coastal seafloor observatory is the first step toward future development of seafloor observation systems in China.It not only accumulates experiences in technology and engineering,but also paves the way for performing important oceanic research using the long term continuous observation platform.     

一个面向服务的教学计划框架体系

The science of services constitutes a breakthrough in the traditional way of thinking of the place of informatics in the economic development of a State,a Region,an enterprise and consequently in the teaching programs.The question is no more only a question of computer science.We are in front of a more complex situation,which requires not only a multidisciplinary approach,but an interoperable approach at the intellectual level.This paper is an introduction to this complexity and it is also an attempt to propose crucial questions about the new bachelor programs and master programs.     

Tsinghua Research Achievements Win 2007 State Science and Technology Awards

Seventeen Tsinghua research achievements recently won 2007 State Science and Technology Awards. Tsinghua professors accepted the awards on January 8, 2008, in Beijing at the annual National Science-Technology Award Ceremony in the Great Hall of the People. Tsinghua＇s research achievements ranked first among Chinese universities. Of Tsinghua＇s seventeen awards, one was a State Natural Science Award second prize; eight were State Technological Invention Award second prizes; and eight were State Scientific and Technological Progress Award second prizes. Altogether nine research achievements were completed by Tsinghua as the lead research institution in collaboration with others.     

全球招聘新闻

正博士后[美国]Pennsylvania State University Pennsylvania State University opens a postdoctoral fellowshipposition.The focus of the research will be the study of geneticvariants for the involvement in cancer risk in human populations.Large case-control populations will be screened in geneticassociation studies,in vivo measurements of metabolite levels inhuman samples will be compared to genotype,and in vitro activityassays and expression studies will be performed to assessfunction of genetic variants.See the following link for     

2013-01 全球招聘新闻

博士后 [美国] Kent State UniversityThe Kent State University (ReMedIKS) is seeking to recruit two postdoctoral research associates that will work closely with one another and with the core members of the Initiative.     

Effect of temper rolling on the bake-hardening behavior of low carbon steel

In a typical process, low carbon steel was annealed at two different temperatures (660℃ and 750℃), and then was temper rolled to improve the mechanical properties. Pre-straining and baking treatments were subsequently carried out to measure the bake-hardening (BH) values. The influences of annealing temperature and temper rolling on the BH behavior of the steel were investigated. The results indicated that the microstructure evolution during temper rolling was related to carbon atoms and dislocations. After an apparent increase, the BH value of the steel significantly decreased when the temper rolling reduction was increased from 0% to 5%. This was attributed to the increase in solute carbon concentration and dislocation density. The maximum BH values of the steel annealed at 660℃ and 750℃ were 80 MPa and 89 MPa at the reductions of 3% and 4%, respectively. Moreover, increasing the annealing temperature from 660 to 750℃ resulted in an obvious increase in the BH value due to carbide dissolution.     

Effect of controlled rolling on the martensitic hardenability of dual phase steel

The C-Mn and C-Mn-Nb steels were thermo-mechanically processed to develop dual phase steel and to study the effect of controlled rolling on the martensitic hardenability of austenite. The steel specimens were intercritically annealed at 790℃, rolled at that temperature to the reductions of 10%, 23%, and 47% and immediately cooled at different rates. Quantitative metallography was used to construct the microstructure map, which illustrated that increasing deformation progressively reduced the proportion of new ferrite formed at all cooling rates and increased the amount of martensite at fast and intermediate rates. The martensitic hardenability of austenite remaining after all the rolling reductions was plotted as a function of cooling rates. It was observed that for the austenite-martensite conversion efficiencies greater than about 25%, controlled rolling increased the martensitic hardenability of austenite.     

Effects of heat treatment on the intermetallic compounds and mechanical properties of the stainless steel 321-aluminum 1230 explosive-welding interface

The effects of heat treatment on the microstructure and mechanical properties of intermetallic compounds in the interface of stainless steel 321 explosively bonded to aluminum 1230 were investigated in this study. Experimental investigations were performed by optical microscopy, scanning electron microscopy, and microhardness and shear tensile strength testing. Prior to heat treatment, increasing the stand-off distance between samples from 1 to 2.5 mm caused their interface to become wavy and the thickness of intermetallic layers to increase from 3.5 to 102.3 μm. The microhardness increased from HV 766 in the sample prepared at a stand-off distance of 1 mm to HV 927 in the sample prepared at a stand-off distance of 2.5 mm; in addition, the sample strength increased from 103.2 to 214.5 MPa. Heat treatment at 450℃ for 6 h increased the thickness of intermetallic compound layers to 4.4 and 118.5 μm in the samples prepared at stand-off distances of 1 and 2.5 mm, respectively. These results indicated that increasing the duration and temperature of heat treatment decreased the microhardness and strength of the interface of explosively welded stainless steel 321-Al 1230 and increased the thickness of the intermetallic region.     

Ecological and environmental explanation of microbiotic crusts on sand dune scales in the Gurbantonggut Desert, Xinjiang

Results obtained from the field investigation and the analysis in laboratory show that many species of microbiotic crusts of lichens, mosses and algae develop extensively in the Gurbantonggut Desert, Xinjiang. The formation, species and distribution are closely related to the environmental conditions at the different positions of sand dunes. The animalcule crusts develop mainly on the mobile or semi-mobile sand surface of dune tops, the alga crusts develop mainly at the upper to middle parts of dune slopes, the lichen crusts develop at middle and lower parts of dune slopes, and the moss crusts are mainly distributed at the lower part of dune slopes and the interdune lowlands. The species, thickness and developing degree of microbiotic crusts increase from the upper part to the middle and lower parts of dune slopes and the interdune lowlands, and an obvious contrast between the microbiotic crusts and the different species of plant communities forms. The development and differentiation of microbiotic crusts at the different positions of dunes are the ecological appearance and the natural selection of synthetic adaptability of the different microbiotic crust species to the local environmental conditions, and are closely related to the ecological conditions, such as the physiochemical properties of soils and stability of topsoil texture.     

Microstructural evolution of a superaustenitic stainless steel during a two-step deformation process

Single- and two-step hot compression experiments were carried out on 16Cr25Ni6Mo superaustenitic stainless steel in the temperature range from 950 to 1150℃ and at a strain rate of 0.1 s-1. In the two-step tests, the first pass was interrupted at a strain of 0.2; after an interpass time of 5, 20, 40, 60, or 80 s, the test was resumed. The progress of dynamic recrystallization at the interruption strain was less than 10%. The static softening in the interpass period increased with increasing deformation temperature and increasing interpass time. The static recrystallization was found to be responsible for fast static softening in the temperature range from 950 to 1050℃. However, the gentle static softening at 1100 and 1150℃ was attributed to the combination of static and metadynamic recrystallizations. The correlation between calculated fractional softening and microstructural observations showed that approximately 30% of interpass softening could be attributed to the static recovery. The microstructural observations illustrated the formation of fine recrystallized grains at the grain boundaries at longer interpass time. The Avrami kinetics equation was used to establish a relationship between the fractional softening and the interpass period. The activation energy for static softening was determined as 276 kJ/mol.     

Multiuser MIMO Downlink Transmission Schemes over Time-Varying Channels

The performance of multiuser multiple-input-multiple-output （MIMO） downlink systems with block diagonalization （BD） depends on the accuracy of the channel state information （CSI） available at the trans- mitter and the receiver. In time-varying channels, the CSI available at the transmitter （CSIT） is always out-dated due to an inherent time delay between the uplink channel estimation and the downlink data transmission in time division duplexing （TDD） systems. This leads to a drastic degradation of system capacity. This paper first analyzes the effect of the outdated CSIT on multiuser MIMO downlink systems using the BD method and then proposes two linear processing methods, BD precoding with user selection and scheduling at the transmitter and total minimum mean squared error （MMSE） decoding at the receiver （TBDUSS-RTMMSE） and BD preceding at the transmitter with partial MMSE decoding at the receiver （TBD-RPMMSE）, to mitigate the interference among data streams and users. Analysis and simulation results show that these methods can effectively reduce the impairment of the outdated CSIT to increase the system sum capacity in a suitable time delay region of the CSIT.     

Key technology for construction of connection between steel pylon and concrete pile cap of middle pylon of Taizhou Bridge

Taizhou Yangtze River Bridge is a suspension bridge with three pylons and two 1080m main spans. The middle pylon is a steel frame with longitudinal herringbone shape and lateral gate shape. The connection between steel pylon and concrete pile cap is a key part to transfer the huge inner force from the pylon to the foundation. Its construction quality is a critical factor to the overall structural loading of the whole bridge, therefore the contact ratio between the bearing steel plate of pylon and concrete pile cap is required to be over 75%. The inclined joint surface in two directions, longitudinally at 39/1920 and laterally at 1/4, posted a challenge to the construction works. Technological tests were carried out to find an optimal construction method by comparison, and finally the Post-Injection method was selected as it can meet the requirement of concrete strength and contact ratio at the connection. The successfully application of the Post-Injection method at Taizhou Yangtze River Bridge has provided an example and reference for similar projects in the future.     

Tsinghua Research Achievements Win 23 State Science and Technology Awards

Twenty-three Tsinghua research achievements recently were recognized at the 2008 State Science and Technology Awards.Tsinghua professors accepted the awards on January 9,2009 at the annual National Science-Technology Award Ceremony in the Great Hall of the People in Beijing. Chinese President Hu Jintao,Premier Wen Jiabao,Standing Committee of the Political Bureau of the CPC Central Committee Member Li Changchun,Chinese Vice President Xi Jinping,and Vice Premier Li Keqiang attended     

RECONSTRUCTION OF AXLE-TREADLE LOOM IN HAN DYNASTY

The axle-treadle mechanism of Han loom consists of a set of components, including two pedals controlling one shaft via a central axle. Based on the new archaeological finds, especially the pottery loom model, the collection of Krishna Riboud, and the historical document, a kind of axle treadle loom with oblique warp frame was reconstructed by author. It might be applied in the central China at that time, especially in Shandong and Jiangsu areas, and it was not later than the Warring State period for the oblique axle treadle loom to come into being and reach a peak in the Han Dynasty. After that time, it was used with the vertical frame but lost the importance gradually.     

Induction of phenylalanine ammonia-lyase and lipoxygenase in cotton seedlings by mechanical wounding and aphid infestation

It has been suggested that infestation of plants causes increases in the activities of phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX), key enzymes in the phenolic compounds synthesis pathway and the octadecanoid pathway, respectively. The purpose of this work is to investigate whether the infestation of cotton aphid （Aphis gossypii） and mechanical wound can cause the induction of PAL and LOX activities in cotton seedlings, and whether the induction occurs in healthy seedlings growing nearby the attacked ones. The specific activities of PAL and LOX were measured using spectrophotometric method after aphid infestation and mechanical wounding. Result indicated that PAL activity and LOX activity were greatly induced by mechanical wounding and aphid infestation in cotton seedlings. The induction of PAL and LOX occurred not only in wounded and infested seedlings but also in intact healthy seedlings growing nearby. After exposed to the aphid infestation-induced volatiles, the specific activity of PAL in cotton seedlings increased by 6% at 24 h, 80% at 48 h, 235% at 72 h compared to the control, and the specific activity of LOX increased by 18% at 24 h, 34% at 48 h, 24% at 72 h, respectively. In comparison, the specific activity of PAL in unwounded seedlings exposed to wound-induced volatiles increased by 0.0 at 24 h, 200% at 48 h, 164% at 72 h, respectively and the specific activity of LOX increased by 28% at 24 h, 37% at 48 h, 8% at 72 h, respectively. It suggests that the induced volatiles are involved in plant-plant communication as airborne transferred signals.     

热轧和退火温度对SP-700合金组织和力学性能的影响

The effect of rolling temperature on both two- and single-phase regions and annealing in a temperature range of 700–950°C on the microstructure and mechanical properties of Ti?5Al?4V?2Fe?1Mo alloy was investigated. The results indicated that the best balance of strength and ductility is obtained by rolling in the two-phase region due to the globularization of the alpha phase and increase in its volume fraction. After rolling in the two-phase region, the ductility of the specimens annealed at 700 to 800°C increased because of the finer size and globularized alpha phase, while the reduction in strength was attributed to a decrease in the alpha phase volume fraction. However, at 950°C, the strength increased and ductility dropped by the formation of acicular alpha phase due to an increase in the phase boundary area. Annealing and aging after rolling in the beta-phase region increased the strength and decreased the ductility, which is attributed to the formation of a secondary alpha phase. A combination of favorable yield strength (1113 MPa) and elongation (13.3%) was obtained through rolling at 850°C followed by annealing at 750°C and aging at 570°C.     

Tsinghua Alumnus Academician Wu Zhengyi Won 2007 National S＆T Top Award

The annual national science-technology award ceremony was held at the Great Hall of the People in Beijing on January 8, 2008. Renowned botanist Wu Zhengyi, a Tsinghua alumnus, and petrochemical scientist Min Enze won the 2007 State S＆T top awards for their outstanding achievements. Chinese President Hu Jintao and other senior leaders including Wen Jiabao, Li Changchun, Xi Jinping, and Li Keqiang, attended the ceremony. Chinese Presi- dent Hu presented the award to two scientists. Botanist Wu, 91, has been engaged in botanical research and education for 70 years. The botany professor, also a CAS senior academician, graduated from the biology department of Tsinghua University in 1937 and later became director of the botany institute of CAS.