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To observe the effect of modafinil on the visual function of 16-h flight. Methods 5 male healthy subjects were double-blind: placebo group (n = 5) and modafinil group (n = 5), Autologous control. Carry out 16 h (h) continuous simulated long flight test across day and night. First, the visual function is detected before flight, In pairs, at the same time, First phase 8 h at 15:30, After 200 mg, of modafenib or placebo 00:00 Completion of phase 2 h 8 flights, After the flight, the visual function was detected again and the state changes of far and near vision were compared before and after the flight. Results Compared with placebo, the use of modafinil had no significant effect on far and near vision, but increased the long vision of both eyes during flight. Conclusion Routine single dose of modafinil has no significant adverse effect on visual function and can reduce human fatigue perception.

Outward Foreign Direct Investment (OFDI) is influenced by many factors. In these factors, the impact of the financial development of the investing country is very important and obvious. An important support for an enterprise to make OFDI is to get a sufficient source of funding, and the source of funding depends on the degree of development of domestic financial market. From the early research, we can find that OFDI in developing countries, at least to some extent, is the result of economic structural improvements and financial innovations. Taking China as an example, this paper studies the role of developing countries in the level of financial development in OFDI. By using the panel data of 30 provinces and autonomous regions in China during the five-year period from 2010 to 2014, we want to examine the development of financial markets in various regions impact on China’s outward foreign direct investment.

Peer relationship plays an important role in non-suicidal self-injury (NSSI). However, little is known about how and in what conditions peer relationship may influence NSSI. By integrating multiple theories (i.e., attachment theory, the emotional regulation model of self-compassion and NSSI, and the differential-susceptibility theory), the current study investigated two potential mediators (i.e., self-compassion and depressive symptoms) and one potential moderator (i.e., behavioral impulsivity) of the relation between peer acceptance and NSSI. Participants were 813 Chinese adolescents (43% female; Mage at Wave 1 = 13.15 years) from a two-wave longitudinal study with data spanning one year. The results revealed that the indirect pathways linking peer acceptance and NSSI were conditioned on the level of behavioral impulsivity. Specifically, for adolescents with lower levels of impulsivity, a higher level of peer acceptance was related to fewer depressive symptoms directly or indirectly through self-compassion; fewer depressive symptoms, in turn, were linked to fewer NSSI behaviors longitudinally. For adolescents with higher levels of behavioral impulsivity, peer acceptance was related to fewer NSSI behaviors only through self-compassion. Results indicate that increasing peer acceptance is important in reducing adolescent NSSI. Interventions designed to reduce adolescent NSSI may also be effective if they focus on promoting adolescent self-compassion, particularly for adolescents with higher levels of behavioral impulsivity.

Summary Background Over the last decade, complementary and alternative medicine (CAM) has been widely used in maternity practice all over the world. Women from different cultural backgrounds prefer the use of specific CAM modalities. Objective The objectives of this study were to explore the use of CAM, the types of CAM practitioners consulted, and perceptions of the efficacy of CAM among a sample of Chinese postpartum women. The study's second objective was to investigate common patterns of CAM provided and the reasons for a CAM recommendation to childbearing women, from the perspective of obstetric staff. Methods This cross-sectional survey was undertaken at a university-affiliated general hospital and a maternity and child health hospital in Guangzhou, China. Patients were approached from both the postnatal wards and the postnatal outpatient departments, and healthcare professionals were obstetric staff, including doctors, midwives and nurses who work in the department of obstetrics. Results A total of 306 patients and 225 obstetric staff completed the questionnaire. The mean age of these patients and obstetric staff was 29.28 (SD 4.31), and 31.01 (SD 6.97) years old, respectively. Questionnaire data revealed the prevalence of CAM use among patients was 42.8%. Common types of CAM used and provided by the studied hospitals include acupressure (43.5%), massage therapy (32.0%), reflexology (30.2%), acupuncture (23.5%), and herbal medicine (20.0%). Most Chinese women used CAM therapies during the postnatal period (30.9%). These women mainly used CAM for pain relief (22.2%) and relaxation (18.3%). The most common reasons for health professionals to recommend CAM to patients, were patient demand (81.3%) and CAM's proven efficacy (81.3%). Conclusions In order to communicate effectively about CAM, health professionals should undertake continuing professional development on updated perspectives of CAM use in obstetrics, and equip themselves with updated knowledge about the evidence-base for CAM, in order to provide efficient and qualified care to potential CAM users.

Objective: Explore the effect of TCM external treatment of glutinous rice roots decoction sponge bath method treatment to the children with sweating. Methods: To collect 70 sweating syndrome of children in the pediatric clinic of Guangdong Provincial Hospital of Traditional Chinese Medicine and the First Affiliated Hospital of Guangzhou University of Traditional Chinese Medicine, were randomly divided into 2 groups, the control group and the experimental group. Each group has 35 children. The control group is using traditional Chinese medicine Oral treatment, the experimental group is using traditional Chinese Herbs and sponging bath with the decoction of glutinous rice root. Results: In this study, we had collected 70 cases of children suffering from sweating. Ultimately the effective number of cases: 29 cases in the control group and 31 cases in the experimental group. 7 days after the intervention, the related indicators of the experimental group of lung health is not solid and other evidence were improved. Sweating symptoms were improved, and have statistically significant in the efficacy difference compared with the control group (lung health is not solid of the two groups p=0.017, other syndromes of the two groups p=0.006). The effect was significantly of lung health is not solid of the two groups after the intervention in sodium food, urine, tongue (P

Introduction Monolayers of Caco-2 cells have been widely accepted as one of the well-established in vitro models to predict intestinal drug permeability and absorption in humans. However, the procedure for culturing the traditional 21-day Caco-2 model is labor intensive and time consuming, which limits its wide application in drug development. The objective of the present study was to develop a rapid Caco-2 model with a 7-day cell culture process. Methods A few modifications of the BIOCOAT® HTS Caco-2 Assay System were introduced including changing the cell seeding density, the composition of cell culture media, and the interval to change media. The monolayer structure was visualized through confocal microscopy. The transepithelial electrical resistance (TEER), apparent permeability coefficients (P app ), and functional activity of P-glycoprotein (P-gp) were determined and compared with the 21-day model. Moreover, pharmacokinetic studies were performed in animal models to evaluate the absolute bioavailability of oral doses (F oral ) of different compounds. Results Our newly developed 7-day Caco-2 model displayed comparable cellular morphology and integrity with the traditional 21-day model. No significant difference in paracellular and transcellular permeability was observed between the two systems. The efflux ratios of transporting digoxin, the prototypical substrate of P-gp in 21- and 7-day systems were 16.04 and 24.92, respectively. When the P-gp inhibitor verapamil was present, the efflux ratios of 21- and 7-day systems were 1.37 and 0.86, respectively, suggesting the comparability of the P-gp functional activity in both systems. Furthermore, pharmacokinetic studies of several compounds performed in animal models revealed that the absolute bioavailability of oral doses in vivo was well correlated with the Caco-2 permeability in vitro . Discussion The novel system provides a rapid and economical option for assessing the drug permeability, and is applicable to the studies of intestinal drug absorption.

Using a simple sol–gel/spin-coating method, mesoporous SiO 2 thin films were prepared on glass slides. All of the prepared thin films were colorless and transparent as original glass substrates. XRD and TEM measurements revealed that the prepared SiO 2 thin films coated 3–12 times possess hexagonal mesoporous structure. The mesoporous SiO 2 thin films performed the superhydrophilicity and antifogging property in the absence of UV light irradiation. The results suggested that the appropriate film thickness and mesoporous structures can improve the surface superhydrophilic behavior of SiO 2 thin films.

A theoretical study is presented for the magnetic behaviors of a nanostructure consisting of two ferromagnetic (FM) layers separated by a nonmagnetic (NM) layer under the influence of a spin-polarized current. A modified magnetic dynamic equation was developed. The spin accumulation in the FM layer was investigated and the spin polarization factors at the interfaces were obtained by calculating the spin-polarized current of each layer. The injected current not only produces a spin transfer torque, but also alters the effective magnetic field, and thus affects the magnetic damping. The competition between damping and spin accumulation determines the dynamic behaviors of magnetization switching and oscillation. We discussed the conditions and characteristics of irreversible magnetic switching and stable spin precession.

A Si/SiGe HBT-type phototransistor with 10 Ge-dot layers (8ML in each layer, separated by 30 nm Si spacer) incorporated in the base-collector junction was grown by UHV-CVD. To achieve low dark current density and high photo-responsivity, a high-low emitter profile consisting of a heavily doped polysilicon contact on top of a thin epitaxial emitter cap has been fabricated. At room temperature, I–V measurement showed a low dark current density of 3 × 10−5 A/cm2 at 3 V. The measured breakdown voltage BVceo was about 12 V. A photo-responsivity of 1.94 and 0.028 mA/W was achieved at 1.31 and 1.55 μm for normal incidence, respectively. Compared to a p–i–n reference detector with the same quantum-dot layer, the responsivity is improved by a factor of 45 and 20 at 1.31 and 1.55 μm, respectively.

ZnO based magnetic semiconductors (MSs) are prominent candidates for the spintronic devices because of their high Curie temperatures and low conductance mismatches. In this paper the spin-polarized transport in MS/nonmagnetic semiconductor (NMS) p–n junction is investigated. A model is established based on semiconductor drift–diffusion theory and continuity equation. Boundary conditions are obtained from the quasi-chemical potential (QCP) relations at the junction interface. For a ZnO based magnetic p–n junction, we calculate the distributions of carrier/spin density and spin polarization at room temperature. It is demonstrated that by choosing proper parameters, effective spin-polarized injection from ZnO based MS into ZnO can be achieved at room temperature without external spin-polarized injection (ESPI) or large bias.

Shape evolution of SiGe islands fabricated by ultra-high vacuum chemical vapor deposition (UHV/CVD) using different SiH 4 flow was investigated by atomic force microscopy. It is found that the threshold size at which SiGe islands change from pyramids to domes (44, 50 and 65 nm) increases with Si content in islands (0.032, 0.09 and 0.20). With Si content being considered, an improved model was established to explain the dependence of threshold size on Si content. According to the model, the threshold size as well as the shape and size distribution of self-assembled SiGe islands could be effectively controlled by adjusting Si content in islands (here using different SiH 4 flow during growth). Based on our model, threshold size of self-assembled SiGe islands can be calculated from Raman scattering spectra.

Atomic force microscopy was used to study the shape transition of SiGe islands on Si (1 0 0) by ultra-high vacuum chemical vapor deposition. The influence of Si concentration on shape transition of SiGe islands was investigated. The results show that the critical volume increases with Si concentration, at which the islands change from pyramids to domes. A modified model was developed to explain the influence of Si concentration on the shape transition. Unimodal dome-shaped and pyramid-shaped SiGe islands were grown under proper conditions, respectively. This work demonstrates that the shape and size of SiGe islands can be controlled accurately through adjusting Si concentration in islands.

Resonant tunneling diodes (RTD) are considered as one of the most promising band-gap engineering heterostructure devices for negative differential resistance (NDR) feature in the current–voltage trace. In this letter, a p-well SiGe/Si RTD is proposed and demonstrated. Its I–V relationship is obtained by Keithley 4200 semiconductor parameter analyzer, and NDR feature can be observed obviously at room temperature. The obtained peak current density is 45.92 kA/cm 2 , and peak to valley current ratio (PVCR) is 2.21. Considering the influence of series resistance on the I–V relationship, the DC-parameter of RTD was extracted from the experimental data. This work is helpful to improve the performance of RTD and design of RTD-based circuits.

The change of electrical performance of SiGc HBT and Si BJT is studied after irradiation with 1.3×1013 and 1.0×1014 reactor fast neutrons cm−2. Ic and β decrease, while Ib increases generally with an increasing neutron irradiation fluence for SiGe HBT. For Si BJT, Ic increases at low Vbe bias, decreases at high Vbe bias; Ib increases; and β decreases much more than a SiGe HBT at the same fluence. It is shown that a SiGe HBT has much better anti-radiation performance than a Si BJT. The mechanism of performance changes induced by irradiation is discussed.

Due to the high hole mobility both in the surface strained Si and buried relaxed SiGe channels, we successfully fabricated a novel strained Si/relaxed SiGe channel PMOSFET on the heterostructure strained Si/relaxed SiGe/strained Si/relaxed SiGe buffer layer/grading Si1−xGex layer, grown by home-made UHV/CVD system, which is commonly used in the ‘buried’ SiGe NMOSFET. This device is easier to integrate with SiGe NMOSFET to form SiGe CMOS, than strained SiGe channel PMOSFET. Then the process is presented. With Vgs=3.5 V, the maximum saturated transconductance is found to be twice as large as that of the control Si PMOS, and approximates to that of a traditional strained SiGe channel PMOS.

An ultrahigh vacuum chemical vapor deposition system suitable for deposition of epitaxial GeSi layers has been constructed. Its reaction chamber is a rectangular quartz tube that is heated by a graphite heater. Using this system, two high-quality structures of Si/Ge 0.18 Si 0.82 /Ge x Si 1 −x /Si nMOSFET and n-Si/p + -Ge 0.2 Si 0.8 /n-Si HBT with controllable doping were successfully grown at 600 and 550°C.

The n-Si/i-p-i SiGe/n-Si structure, grown by ultra-high-vacuum chemical molecular epitaxy, was analyzed by cross-sectional transmission electron microscopy and secondary ion mass spectroscopy. It is shown that no defects are observed in the n-Si/i-p-i SiGe/n-Si structure, the interfaces between the SiGe layer and the n-Si layers are clear and planar, both the Ge and boron atoms are uniformly distributed in the p-SiGe, and the profiles of boron and Ge are abrupt from the n-Si to the SiGe layer. A high-performance microwave power SiGe heterojunction bipolar transistor was fabricated using the n-Si/i-p-i SiGe/n-Si structure. Therefore, ultra-high-vacuum chemical molecular epitaxy is one of the most promising methods for the growth of the Si/SiGe strained epilayers.

The n-Si/i-p+-i SiGe/n-Si structure was grown by ultra high vacuum chemical molecular epitaxy, and analysed by high resolution X-ray diffraction, cross-sectional transmission electron microscopy, and secondary ion mass spectroscopy. A high-quality SiGe base layer with an abrupt interface to the Si was obtained. No defects were observed in the n-Si/i-p+-i SiGe/n-Si structure. Both the Ge and boron atoms are uniformly distributed in the p+-SiGe layer, and the changes of profile of both boron and Ge atoms are abrupt from the n-Si to the SiGe layer. A high-performance microwave power SiGe heterojunction bipolar transistor (HBT) was made from the n-Si/i-p+-i SiGe/n-Si structure. Therefore, device-quality n-Si/i-p+-i SiGe/n-Si structures can be grown by ultra high vacuum chemical molecular epitaxy.

By using a stacked structure, adding an SiO2 dielectric cavity and an Al mirror, and evaporating a SiO anti-reflecting layer on the back of the substrate, the peak detectivity D-(5.5,D-1000,D-1)* of an unbiased P+-GexSi1-x/p-Si heterojunction internal photoemission (HIP) infrared detector at 77 K has been improved to 1.1 X 10(10) cm Hz(1/2)/W, with a peak quantum efficiency of similar to 2.8% and a photoresponse range of 2-8 mu m. Its D-p* is of the same order of magnitude as that of the PtSi infrared detectors being used in practice. In addition, an improved electrode structure is used in order to improve the performance and reliability of the device. (C) 1998 Elsevier Science B.V. All rights reserved.

An improved nonuniformity correction algorithm is presented which is suitable for infrared focal plane arrays with a nonlinearity of the photoresponse characteristic. Compared to older algorithms, it is simpler, faster and easier to implement by software or hardware. At the same time, it is shown that the correction precision and the correction effect of the new algorithm are substantially the same as that of the old one through theoretical analysis and comparisons of simulation results.

Empirical research in embedded systems is lagging behind the accomplishments in theory and methodology. One reason for this is that it is difficult to create a convincing case study with the diverse expertise required, the tools needed, and the time demanded. The other reason is the difficulty to maintain such a case study across the ever changing environment of students graduating and new students arriving.

In this paper, bi-layered structural ferroelectric materials Sr1−xBaxBi4Ti4O15(SBBT) (x=0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) were prepared using sol–gel method. The stable precursors were fabricated by mixing the salts of strontium (Sr), barium (Ba), bismuth (Bi) and titanium butoxide in acetic acid together with ethanolamine as a catalyzer and acetylacetone as a stable agent. The structural evolution of SBBT after Ba2+ doping was studied. The experimental results confirm that complete solid solutions of SrBi4Ti4O15 and BaBi4Ti4O15 are formed. The perovskite lattice will expand after the doping of Ba2+ because of the difference of ionic radii of strontium and barium cations, which will lead to increasing of the lattice spacing. With the increase of the content of Ba cations the grain size of SBBT powder increases, the granularity distribution widens and average particle size of SBBT powder also increases. The average particle size of SrBi4Ti4O15 and BaBi4Ti4O15 is 82.5 and 165.2 nm, respectively.

Introduction: The extent of lymph nodes (LNs) metastasis is a major determinant for the staging and the most reliable adverse prognostic factor. Primary tumours can induce lymphatics and vasculature reorganisations within sentinel LN before the arrival of cancer cells and these key blood vessels are identified as high endothelial venules (HEV). The alterations of HEV in the presence of cancer, coupled with the increased proliferation rate of the endothelial cells, results in a functional shift of HEV from immune response mediator to blood flow carrier. We aim to evaluate tumour-induced vascularisation in regional LN of cancer patients by studying the morphological and functional alterations of HEV and its correlation to clinico-pathological features. Materials and Methods: This multi-centre study with a prospective database identified 65 consecutive patients with tongue squamous cell carcinoma (SCC) who underwent primary surgical treatment from 2001 to 2005. Immunohistochemical staining for HEV and image analysis were performed and analysed with correlation to the patients’ clinico-pathological features. Results: The total number of HEV is significantly associated to disease-free interval when controlling for the group (P = 0.022) as well as combining both groups as one cohort (P = 0.023). There is also a similar association comparing the HEV parameters to overall survival. Conclusion: Our results suggest that HEV possibly plays a key role in the pathogenesis of lymphatic and subsequent distant metastases and may provide the missing link in cancer metastasis. Confirmation of this hypothesis would offer a novel therapeutic approach to preventing metastasis by blocking the remodeling processes of HEV in LN. Key words: High endothelial venules, Cancer metastasis, Angioegenesis

Unmanned ground vehicles (UGVs) allow people to remotely access and perform tasks in dangerous or inconvenient locations more effectively. They have been successfully used for practical applications such as mine detection, sample retrieval, and exploration and mapping. One of the fundamental requirements for the autonomous operation of any vehicle is the capability to traverse its environment safely. To accomplish this, UGVs rely on the data from their on-board sensors to solve the problems of localization, mapping, path planning, and controls. This paper proposes a combined mapping, path planning, and controls solution that will allow a skidsteer UGV to navigate safely through unknown environments and reach a goal location. The mapping algorithm generates 2D maps of the traversable environment, the path planner uses these maps to find kinodynamically feasible paths to the goal, and the tracking controller ensures that the vehicle stays on the generated path during traversal. All of the algorithms are computationally efficient enough to run onboard the robot in real-time, and the proposed solution has been experimentally verified on a custom built skid-steer vehicle allowing it to navigate to desired GPS waypoints through a variety of unknown environments.

Due to their ability to hover, rotorcraft can be used in many cluttered and narrow environments that are unsuitable for other unmanned aerial vehicles (UAVs). However in such environments, it is usually dicult to nd paths that are both collision-free and dynamically feasible. This paper introduces a computationally ecient algorithm for nding safe paths, through known static three dimensional environments, that satisfy the kinodynamic constraints of a quadrotor. First, a collision-free path that ignores kinodynamic constraints is found using probabilistic roadmaps (PRM). Next, a heuristic re-sampling algorithm is used to make improvements to this path. Finally, the path is separated into a series of motion primitives that satisfy kinodynamic constraints. To ensure corner path segments remain collision-free, a method of bounding the vehicle deviation from the piece-wise linear path at each corner is introduced. Finally, the control inputs required to traverse the transformed path are calculated using kinematics and become the feed-forward inputs for a position controller. In simulation, the algorithm is able to successfully compute safe kinodynamic paths through cluttered and narrow environments, while using limited computational resources.

We present a model to explain the spin-polarized injection from ferromagnetic metal into organic semiconductor. Thermionic emission mechanism is considered as the dominant transport mechanism at the interface at low bias. Boundary condition is determined from the relationship of the spin-dependent quasi-electrochemical potentials across the interface. The dependences of the current spin polarization on the control parameters, which include the Schottky barrier height at the interface, the spontaneous spin polarization in ferromagnetic metal, and the bias, are demonstrated.

The interfacial effect on spin polarization is studied in a pseudo-spin-valve structure (PSVs) consisting of two ferromagnetic layers (FM) separated by a nonmagnetic metallic layer (NM). We adopt the macroscopic two-current drift-diffusion model and boundary conditions taking spin flip at FM/NM interfaces into account. The two FM/NM interfaces with respect to the spacer NM layer are combined into a single interface under some appropriate assumptions and new formulae for spin transport boundary conditions are derived. The analytical solutions of spin polarization for both side interfaces of the free layer are calculated from those boundary conditions.

The current induced magnetic dynamics of a nano-scale pseudo-spin-valve (PSV) structure was theoretically studied. The spin relaxation mechanisms and the influence of ferromagnetic/nonmagnetic (FM/NM) interfaces on the current polarization were investigated, and a modified magnetic dynamic equation was developed. Both the free layer's local magnetic moments and itinerant electrons' spins were regarded as a macro-spin, whose movement was resulted from two items: spin relaxation due to the magnetic damping and spin accumulation due to the polarized current. The injected current not only produces a spin transfer torque, but also alters the effective magnetic field, and thus affects the damping. Therefore, the damping is nonlinear and correlated to the current. Based on the analysis of the competition between magnetic damping and spin accumulation, the dynamic behaviors of magnetization switching and oscillation can be explained.

The ferromagnetic/nonmagnetic (FM/NM) interfacial effects on the spin accumulation in the free layer were studied in a pseudo-spin-valve structure (PSVs) consisting of two FM layers separated by a NM spacer layer. We developed a spin current model for the current-induced magnetic switching (CIMS) effect based on the spin diffusion equations and appropriate boundary conditions, and derived a new formula for the spin-dependent electrochemical potentials that are related to the spin-dependent density of states. The results indicate that the spin accumulation in the free layer mainly depends on the interfacial spin asymmetry coefficient Ξ?which originates from the spin-dependent interfacial conductance. In the parallel (anti-parallel) configuration of the magnetization direction for the free and fixed layer, the positive (negative) electron current (electrons from the free layer to the fixed layer and vice versa) drives the spin current polarization factor at the interface between the top electrode and the free layer to vary from Ξ? (-Ξ?) to 0, while at the interface between the free layer and the spacer layer the spin current polarization factor vary from Ξ? (0) to Ξ?/2, which means the total spin current polarization factor in the free layer varies from 0 (Ξ?) to Ξ?/2. These results show that the anti-parallel configuration has a less critical switching current than that of the parallel configuration. Thus, we can design PSVs with symmetrical critical current based on the model.

In this paper, the spin-polarized injection through n-magnetic/p-nonmagnetic semiconductor heterojunction was investigated theoretically. Based on the drift-diffusion theory and continuity equation, a model was established to explain the spin-polarized injection through the magnetic heterojunction. Boundary conditions were determined by analyzing the relations of the quasi-chemical potentials in n and p regions. The distributions of the charge density, spin density and spin-polarization were calculated using this model. The results demonstrate that an effective spin-polarized electric injection through the heterojunction may be achieved without external spin injection or the application of a large bias. The factors affecting the nonequilibrium spin-polarization (NESP) in the nonmagnetic region were also given based on the simulation results.

As the basis of molecular electronic devices, more attentions have been concentrated on the electron transfer in single-molecule junctions. In present paper, molecular junctions were constructed by using a sandwich structure that consists of metal film/self-assembled monolayers (SAM)/Au coated conducting-probe atomic force microscopy (CP-AFM) tip. The dependence of I-V characteristics on the length of molecules was investigated to explain electron transfer process in saturated molecules such as alkanethiol monolayer. The experiment results show that the molecular conductance decreases with increasing of molecule chain length. Rectification effect was found in the sandwich structure.

Si based Ge quantum dot infrared photodetector (QDIP) has the potential of being a serious candidate for applications in optical fiber communications. In this paper, 20 periods of stacked Ge quantum dots were grown on Si(100) by gas source molecular beam epitaxy (GSMBE). Using the stacked quantum dots as active region, a P-I-N structure quantum dot infrared photodetector was fabricated. To improve absorptivity, then responsivity of QDIP, transfer matrix method was used to calculate the absorptivity (at 1.31 mum) for different thickness of Si spacer layers and different periods of Ge/Si bilayers. The simulation results showed that 20 periods of Ge/Si bilayers and 25 nm of Si spacer layers provided higher absorptivity. At room temperature, I-V measurement showed a low dark current density of 1.1 times 10-5 A/cm2 with applied voltage of -1V. A photocurrent responsivity of 0.158 mA/W was achieved at 1.31 mum. Compared with results we fabricated before [Wei et al., 2005], the responsivity was improved. The experimental results agree well with the simulation results

One of the molecular systems that has been studied extensively is saturated molecules, such as alkanethiol CH3(CH2) n-1-SH. In present paper, molecular junctions were constructed by using a sandwich structure that consists of metal electrode/self-assembled monolayers (SAM)/Au coated conducting-probe atomic force microscopy (CP-AFM) tip. The dependence of I-V characteristics on the length of molecules was investigated to explain electron transfer process in saturated molecules. Tunneling was confirmed as the dominant mechanism. Rectification effect was demonstrated in the sandwich structure, and possible explanation based on the tunneling model was proposed