Controllable modification of transport properties of single-walled carbon nanotube field effect transistors with in situ Al decoration

We use an in situ Al decoration technique to control the transport characteristics of single-walled carbon nanotube field effect transistors (SWNT-FETs). Al nanoparticle decoration in a high vacuum caused the devices to change from p -type to n -type FETs, and subsequent exposure to the ambient atmosphere induced a gradual recovery of p -type character. In comparison with the bare SWNT-FETs under high vacuum, the channel-open devices with decorated Al particles exhibited reduced current under ambient conditions. However, selective Al decoration only at the contact resulted in an improved p -type current in ambient air.open182

Simulation for generation of 15 fs laser pulses by Raman backscatter in plasmas

Pulse compression using the Raman backscatter (RBS) in plasmas was numerically investigated for the strong kinetic regime. It was found that shortening of a seed pulse is more effective when the interaction length is smaller, which is contradictory to the general expectation. In a representative case, compression of up to 14 fs could be obtained from the RBS interaction length less than 0.1 mm. Behavior of the Raman amplification system for such a short interaction distance was not addressed before. Estimation with realistic parameters indicates that the output power can reach tens of terawatts.open3

An integrated decision-making framework of a heterogeneous aerial robotic swarm for cooperative tasks with minimum requirements

Given a cooperative mission consisting of multiple tasks spatially distributed, an aerial robotic swarm’s decision-making issues include team formation, team-to-task assignment, agent-to-work-position assignment and trajectory optimisation with collision avoidance. The problem becomes even more complicated when involving heterogeneous agents, tasks’ minimum requirements and fair allocation. This paper formulates all the combined issues as an optimisation problem and then proposes an integrated framework that addresses the problem in a decentralised fashion. We approximate and decouple the complex original problem into three subproblems (i.e. coalition formation, position allocation and path planning), which are sequentially addressed by three different proposed modules. The coalition formation module based on game theories deals with a max-min problem, the objective of which is to partition the agents into disjoint task-specific teams in a way that balances the agents’ work resources in proportion to the task’s minimum workload requirements. For agents assigned to the same task, given reasonable assumptions, the position allocation subproblem can be efficiently addressed in terms of computational complexity. For the trajectory optimisation, we utilise a Model Predictive Control and Sequential Convex Programming algorithm, which reduces the size of the problem so that the agents can generate collision-free trajectories on a real-time basis. As a proof of concept, we implement the framework into an unmanned aerial vehicle swarm’s cooperative stand-in jamming mission scenario and show its feasibility, fault tolerance and near-optimality based on numerical experiment

Cooperative control for a flight array of UAVs and an application in radar jamming

This paper proposes a flight array system and an integrated approach to cope with its operational issues raised in mission-planning level (i.e., task allocation) and control level (i.e., control allocation). The proposed flight array system consists of multiple ducted-fan UAVs that can assemble with each other to fly together, as well as dissemble themselves to fly individually for accomplishing a given mission. To address the task allocation problem, a game-theoretical framework is developed. This framework enables agents to converge into an agreed task allocation in a decentralised and scalable manner, while guaranteeing a certain level of global optimality. In addition, this paper suggests a cooperative control scheme based on sliding mode control and weighted pseudo-inverse techniques so that the system’s non-linearity and control allocation issue are effectively handled. As a proof-of-concept, a prototype simulation program is developed and validated in a cooperative jamming mission. The numerical simulations manifest the feasibility of effectiveness of the proposed approach

Real-Time Monitoring of Neural Differentiation of Human Mesenchymal Stem Cells by Electric Cell-Substrate Impedance Sensing

Stem cells are useful for cell replacement therapy. Stem cell differentiation must be monitored thoroughly and precisely prior to transplantation. In this study we evaluated the usefulness of electric cell-substrate impedance sensing (ECIS) for in vitro real-time monitoring of neural differentiation of human mesenchymal stem cells (hMSCs). We cultured hMSCs in neural differentiation media (NDM) for 6 days and examined the time-course of impedance changes with an ECIS array. We also monitored the expression of markers for neural differentiation, total cell count, and cell cycle profiles. Cellular expression of neuron and oligodendrocyte markers increased. The resistance value of cells cultured in NDM was automatically measured in real-time and found to increase much more slowly over time compared to cells cultured in non-differentiation media. The relatively slow resistance changes observed in differentiating MSCs were determined to be due to their lower growth capacity achieved by induction of cell cycle arrest in G0/G1. Overall results suggest that the relatively slow change in resistance values measured by ECIS method can be used as a parameter for slowly growing neural-differentiating cells. However, to enhance the competence of ECIS for in vitro real-time monitoring of neural differentiation of MSCs, more elaborate studies are needed

Transcatheter Arterial Chemoembolization of Hepatocellular Carcinoma: Prevalence and Causative Factors of Extrahepatic Collateral Arteries in 479 Patients

OBJECTIVE: We wanted to investigate the prevalence and causative factors of extrahepatic arterial blood supply to hepatocellular carcinoma (HCC) at its initial presentation and during chemoembolization. MATERIALS AND METHODS: Between February 1998 and April 2000, consecutive 479 patients with newly diagnosed HCC were prospectively enrolled into this study. A total of 1629 sessions of transcatheter arterial chemoembolization (TACE) were performed in these patients (range: 1-15 sessions; mean: 3.4 sessions) until April 2004. For each TACE procedure, we determined the potential extrahepatic collateral arteries (ExCAs) depending on the location of the tumor, and we performed selective angiography of all suspected collaterals that could supply the tumor. The prevalence of ExCAs and the causative factors were analyzed. RESULTS: At initial presentation, 82 (17%) of these 479 patients showed 108 ExCAs supplying tumors. Univariate analysis showed that tumor size (p or =5 cm) was significantly higher than that for those patients with a small tumor (< 5 cm) (p < 0.01). CONCLUSION: The presence of ExCAs supplying HCC is rather common, and the tumor size is a significant causative factor for the development of these collateral arteries.This study was supported by a grant (0620220-1) from the National R & D Program for Cancer Control, Ministry of Health & Welfare, Republic of Korea

Relative Etiologic Role of Hepatitis B Virus and Hepatitis C Virus in Chronic Liver Diseases and Hepatocellular Carc inoma among Age-Spec i f ic Groups in Ko rea: the Poss ib Ie Presence of Non-B, Non-C Agents

Korea is one of the endemic areas of chronic hepatitis B virus (HBV) infection. To investigate the relative etiologic role of HBV and hepatitis C virus (HCV) in chronic liver diseases (CLD) including hepatocellular carcinoma (HCC) among age-specific groups in Korea, we enrolled consecutively 673 patients with chronic active hepatitis (CAH), 677 patients with liver cirrhosis (LC) and patients with HCC who had been diagnosed in the liver unit at Seoul National University Hospital. HBsAg and anti-HCV were tested using commercially available radioimmunoassay and enzyme immunoassay kits, respectively. From this study, we were reached at suggestion for the possible presence of non-B, non-C type CLD agent(s) by exclusion method. The prevalence rates of HBsAg were 45.3%, 62.5% and 69.3% in patients with CAH, LC and HCC, respectively. The general prevalence rates of anti-HCV in patients with CAH, LC and HCC were 27.3%, 19. 6% and 17%, respectively, and, however, in HBsAg-negative patients with CAH, LC and HCC those were 48.1%, 46.1% and 42.7%, respectively. The coinfection rates of HBV and HCV in patients with CAH, LC and Hec were 1%, 2.4% and 3. 9%, respectively. The rates of CAH, LC and HCC patients who were negative for both HBsAg and anti-HCV and therefore, serologically classified as non-B, non-C type were 28.4%, 20.2% and 17.6%, respectively. There was a significant differeence in mean age between B- and C-type, and Band non-B, non-C type patients with CAH (41.7 vs 54.5 and 50.4 years), LC (48.5 vs 60.1 and 54.9 years) and HCC (51.6 vs 60.4 and 56.1 years) (p < 0.001, respectively). Before the age of 50, the etiology of CAH and LC was almost exclusively HBV, while over the age of 50, the etiologic role of HCV and non-B, non-C was more predominant than that of HBV. In elderly (older than 60 years of age) patients even with HCC, HCV played an etiologic role as important as HBV. In conclusion, H8V is the most common etiologic agent of CLD in Korea. However, HCV and non-B, non-C infection is a more important etiology in elderly patients with CLD older than 50 years of age

Cytomegalovirus-associated esophageal ulcer in an immunocompetent infant: When should ganciclovir be administered?

Cytomegalovirus (CMV)-associated esophageal ulcer is rare in immunocompetent infants. The presence of inclusion bodies and immunohistochemical staining for CMV in biopsy specimens obtained during esophagogastroduodenoscopy (EGD) indicate that such ulcers occur because of CMV infection. A 7-week-old female infant who experienced frequent vomiting and feeding intolerance was diagnosed with a massive CMV-associated ulcer in the distal esophagus. The ulcer improved after conservative treatment using proton-pump inhibitors; however, ganciclovir was not administered. In a follow-up EGD biopsy specimen, no CMV inclusion bodies were present, and immunohistochemical staining results for this virus were negative. The presence of CMV inclusion bodies indicates active viral replication. If persistent inclusion bodies or positive immunohistochemical staining for CMV is observed in follow-up biopsy specimens, ganciclovir may be used to treat CMV-associated esophageal ulcers

Catalytic Performance for Hydrocarbon Production from Syngas on the Promoted Co-Based Hybrid Catalysts; Influence of Pt Contents

Fischer-Tropsch synthesis (FTS) reaction from syngas was investigated on the Pt-promoted cobalt-based hybrid catalysts prepared by co-precipitation method in a slurry of ZSM-5 (Si/Al=25). The hybrid catalysts were compared with each other for the different content of Pt as a promoter and are characterized using BET, XRD, H2-TPR and NH3-TPD. Their physicochemical properties were correlated with the activity and selectivity of the catalysts. As results, all hybrid catalysts show the C5-C9 yield (%) higher than that of Co-Al2O3/ZSM-5 catalyst. The Pt-promoted hybrid catalysts were found to be more promising towards production of the hydrocarbons of gasoline range and over C10.