Selective excitation of vibrational states by shaping of light-induced potentials

In this Letter we describe a method for population transfer using intense, ultrafast laser pulses. The selectivity is accomplished by careful shaping of light-induced potentials (LIPs). Creation and control of the LIPs is accomplished by choosing pairs of pulses with proper frequency detunings and time delays. As an example, selective population transfer is demonstrated for a three-state model of the sodium dimer.     

Universal torsion-induced interaction from large extra dimensions

We consider the Kaluza-Klein (KK) scenario in which only gravity exists in the bulk. Without the assumption of symmetric connection, the presence of brane fermions induces torsion. The result is a universal axial contact interaction that dominates those induced by KK gravitons. This enhancement arises from a large spin density on the brane. Using a global fit to Z-pole observables, we find the 3sigma bound on the scale of quantum gravity to be 28 TeV for n = 2. If Dirac or light sterile neutrinos are present, the data from SN1987A increase the bound to sqrt[n] M(S)>/=210 TeV.     

电功率20 GW重复频率强流电子束二极管研究

采用静电场模拟对二极管结构及导引磁场位形分布进行了优化设计，并在20GW脉冲功率源上进行了重复频率运行实验研究，二极管输出电子束电压超过1MV，电流达20kA，脉冲宽度45ns，重复频率100Hz，达到了设计指标.     

利用量子对应态原理预测氦-3 p-v-T性质

利用量子对应态原理与Ne,4He的实验数据预测了3He的p-v-T性质。结果表明,在12-20K温区内,压力的计算值与Gibbons实验数据的平均相对误差是2.008%,最大误差是9.131%;在20-60K温区内,压力的计算值与Gibbons实验数据的平均相对误差是1.692%,最大误差是2.276%。获得了比较满意的预测结果。     

利用TEM对Si基片与MgO基片上生长的薄膜特性的研究

对生长在Si和MgO单晶基片上的不同厚度的单层NbN薄膜、双层薄膜AlN/NbN以及三层薄膜NbN/AlN/NbN应用透射电子显微镜(Transmission Electron Microscope,TEM)技术进行了分析研究,对这几种薄膜样品的微观结构、薄膜厚度以及各个边界的一些直观细节给出了较为清晰的图像。由透射电子显微镜的电子衍射图案计算了薄膜和单晶衬底的晶格常数,并与我们以前采用X射线衍射技术分析的结果进行了比较,结果有很好的吻合。     

蒸镀法制备全有机并五苯薄膜场效应晶体管

以全蒸镀方法在真空室内一次性制备了正装结构的全有机并五苯薄膜场效应晶体管。正装结构全蒸镀法有利于简化工艺制备程序,缩小器件尺寸,提高集成度。制备的绝缘层厚度仅为50nm的全有机薄膜场效应晶体管,器件的工作电压降至10V,相同电压下饱和输出电流有了明显提高。筛选适当的有机绝缘材料,改善全有机薄膜场效应晶体管有源层/绝缘层的界面性能,使阈值电压几乎降至0V,场效应迁移率提高了3倍多,输出饱和电流也有了明显的提高。     

MgO和Si上NbN超薄薄膜的生长研究

我们在单晶MgO(100)、Si(100)和SiOx/Si基片上成功生长了纳米厚度的超薄NbN薄膜,利用现代分析手段:X射线衍射(XRD)、透射电子显微镜(TEM)、原子力显微镜(AFM)等技术分析研究了所制备的超薄NbN薄膜的微观结构、厚度、表面界面情况等物理特性。研究表明,在MgO(100)基片上获得了外延生长的单晶NbN超薄薄膜,在Si(100)和SiOx/Si基片上获得的是多晶NbN超薄薄膜。厚度均约6nm左右。这些超薄薄膜的超导转变温度分别为:MgO上薄膜是14.46K,Si和SiOx上薄膜分别是8.74K和9.01K.     

A Comparative ESR Study on Blood and Tissue Nitric Oxide Concentration during Renal Ischemia-Reperfusion Injury

Electron paramagnetic resonance (EPR) spin trapping technology is a sensitive and unambiguous method for detection of nitric oxide (NO). Due to the short lifetime, NO must be trapped before EPR measurement. There are two EPR spin trapping techniques used currently, including the detections of EPR signals of diethyldithiocarbamate-iron-nitric oxide (DETC₂-Fe²⁺-NO) and nitrosyl hemoglobin (HbNO). In this study, we firstly investigated the kinetics of the EPR signal of DETC₂-Fe²⁺-NO in normal and ischemia-reperfused kidneys. In normal rat kidneys, the signal of DETC₂-Fe²⁺-NO was found at 5 min after the spin trappers Fe²⁺/DETC were administrated, the peak concentration was at 15 min and the period with relatively stable signal intensity was at the time range from 15 to 70 min. In the ischemia-reperfused rat kidneys, the signal of DETC₂-Fe²⁺-NO was increased at 30 min of ischemia and decreased at 60 min of ischemia after the occlusion of renal artery (corresponding to the time course of 60 and 90 min after Fe²⁺/DETC injection respectively). We then investigated the EPR signal of HbNO in blood. No characteristic HbNO signal was found in the rats of the sham control and 30 min of ischemia. An HbNO signal occurred in the rats exposed to 60 min of ischemia and it became pronounced with increased duration of reperfusion. The signal intensity reached a plateau at 150 min of reperfusion. The results suggest that the DETC₂-Fe²⁺-NO signal can be only suitable for the NO measurement in the short-term ischemia-reperfusion model, whereas the HbNO signal can be applied to represent NO in the relatively long-term ischemia-reperfusion model. In addition, N^G-nitro-L-arginine (L-NAME) and allopurinol were used to identify the source of NO. By detecting the HbNO signal, we demonstrated that the activation of xanthine oxidase is an important source of NO formation at the long-term period of ischemia and reperfusion. Authors' address: Jiangang Shen, School of Chinese Medicine, University of Hong Kong, 10 Sassoon Road, Hong Kong SAR, China     

Semiconductor quantum dots in high magnetic fields

We review and extend the composite fermion theory for semiconductor quantum dots in high magnetic fields. The mean-field model of composite fermions is unsatisfactory for the qualitative physics at high angular momenta. Extensive numerical calculations demonstrate that the microscopic CF theory, which incorporates interactions between composite fermions, provides an excellent qualitative and quantitative account of the quantum dot ground state down to the largest angular momenta studied, and allows systematic improvements by inclusion of mixing between composite fermion Landau levels (called Λ levels).