PROBING QUANTUM TRANSPORT IN THREE-TERMINAL NANOJUNCTIONS

One-dimensional (1D) nanoscale systems—structures with the lateral dimensions ranging from 1 nm to 100 nm — have received significant research interest due to their unique structure-guided properties that promise functionalities far more superior than their bulk counterparts. The quantum confinement effect in 1D nanostructures provides us with a very powerful tool to tune their electrical, magnetic, optical and thermal properties and opens the gateway for their multifunctional usages in next-generation electronics. In particular, carbon nanotubes and semiconductor nanowires are found to offer tremendous opportunities to form the junction devices with controlled electronic and optoelectronic properties crucial to predictable device functions. Along with the experimental progress in synthesis and fabrication techniques leading to nano-dimensional devices with diverse applications, theoretical insights at the level of electronic structure is equally important to tune various material properties for achieving greater device performance coupled with a wider range of functionalities. This thesis provides a theoretical description of the quantum transport properties in semiconductor core-shell nanowire field effect transistors (FETs) and (8,0) single-wall carbon nanotube contacted to ferromagnetic electrodes using the first principles density functional theory (DFT) in conjunction with the coherent single-particle many-body Green’s functions approach. The first project of the thesis outlines the superior performance of a semiconductor Si-Ge core-shell nanowire quantum dot FET over its pristine Si nanowire counterpart. In this work, we have unlocked the switching mechanism responsible for the superior performance of the Si-Ge nanowire FET with the pz-orbitals in the (outer)shell-layer providing the carrier pathway in both nanowire FETs. This is followed by a work on charge transport in semiconductor Ge-Si core-shell nanowire quantum dot FETs of two different Ge-core diameters. Here, we have identified the most probable tunneling pathway of electrons in Ge-Si FETs with an orbital spatial level resolution which demonstrates the gate-bias-driven decoupling of carrier transport between the core and shell-region. Our calculations hold a qualitative agreement with the experimentally reported results. Irrespective of the Ge core diameter, we observed excellent FET characteristics within a certain threshold gate bias after which the drain current is found to drop rapidly leading to the negative differential resistance (NDR). An orbital level analysis reveals a strong coupling between the pz-orbitals of the core-Ge and the s-orbitals of the gold electrode giving rise to the peak state of NDR; no such coupling is found at the valley NDR state for which the contribution comes solely from the pz-orbitals of the shell-Si. The final project of this thesis comprises the result of our work on spin transport in an (8,0) singlewall carbon nanotube - nickel magnetic tunnel junction. We found an oscillatory tunnel magnetoresistance showing a wide variation in its amplitude and width with the gate bias coupled with TMR sign reversals as observed in the experiment. Analysis of our calculation revealed a nonlinear coupling at the interface with s- and d-orbitals of different Ni atoms hybridized with pz orbitals of different interfacial carbon atoms at each gate bias points. Inserting an oxide layer at the interface is found to tune the oscillation in TMR in a predictable manner resulting in a much smoother oscillation critical to its application

Strengthening Research-Education-Extension (R-E-E) Linkage in New Context of Federal Structured Nepal

Objective: The objective of this paper to examine the major limitations of past efforts in Nepal regarding the link between agriculture research, education, and extension and to highlight the government’s strategy and policy measures to overcome these limitations in the new federal structure in Nepal.   Methodology: The paper is based on the government policy paper, articles, books, reports, and website. Policymakers, faculties, and researchers from three major stakeholders of REE blended through key informant interviews.  Result:  Paper concluded that linkages between the research, education, and service delivery are the weakest. Lack of extension policy, lack of joint ventures or common programs, no functional link between universities, agricultural ministry, research institute, and private sector in policy forums are weakening REE linkages. Rural extension and community development can be developed as a three-way partnership. i) land-grant university/college in each state including municipalities, ii) state government through ministry and department iii) local government through municipalities, and Community Agriculture Extension Service Centers (CAESC).   Implication: A typological model is suggested to explain organizational and operational linkage strategies. Taking these together, the scattered efforts and services being provided by the existing structure, Agriculture Academic Institution (AAI) should able to fulfill these gaps with the close collaboration of community initiative as suggested by Agriculture Development Strategy (ADS). While doing so, the existing institutional structure can also be restructured and revitalized.&nbsp

Patency and Complication Rates of the Arteriovenous Fistula: A Systematic Review

Advantages of fistulas, which include long patency and low complication rates, were ascertained over two decades ago and may not apply to the contemporary dialysis population. We conducted a systematic review to summarize the patency and complication rates of fistulas from literature published after 1999. We screened 7,008 citations and 62 articles met our criteria. The risk of primary failure was 27% (95% confidence interval (CI): 23–32%). When primary failures were included, the primary and secondary patency rates were 59% (CI 53–64%) and 66% (CI 58–74%) at one year, respectively. The median rates of infection, ischemic steal syndrome, and thrombosis were 0.11 (range 0.01–1.0), 0.05 (range 0.0–0.1), and 0.27 (range 0.04–0.68) events per 1000 patient-days. When considering the fistula as the preferred option, the initial high risk of primary failure and complication rates should be considered alongside the long-term benefits of using this access

Single door approach for planning, implementation and operation of rural WATSAN projects in Nepal

Too many stakeholders (e.g. Governmental and Non-Governmental Organisations, Donor Agencies, and Private Sectors) are involved in rural Water Supply and Sanitation (WATSAN) sector, and are currently executing projects in their own approach and modality which is easier and comfortable to them. The lack of single approach has not only brought confusion among recipient communities but also created managerial dilemma among various stakeholders. Therefore, in order to make a well established single approach in rural WATSAN sector, Department of Local Infrastructure Development and Agricultural Roads (DoLIDAR) has taken initiative. Thereto, DoLIDAR prepared an outline of the approach which was then revised by the centre level consultative meeting of major rural WATSAN stakeholders. Regional level workshops were also organized to collects comments/suggestion/aspirations from different stakeholders. The single approach thus prepared and endorsed by all stakeholders will be a milestone towards moving to Sector Wide Approach (SWAp) in rural WATSAN sector in Nepal

Testing of bio-rational and synthetic pesticides to manage cabbage aphid (Brevicoryne brassicae L.) in cabbage field at Rampur, Chitwan, Nepal

Cabbage aphid (Brevicoryne brassicae L.) is an important pest of cabbage which reduces the yield and quality of the cabbage head. Farmers haven been using chemical pesticides to manage them but unfortunately these practices are toxic for human health, biodiversity and the environment. The study was conducted to test the efficacy of different bio-rational insecticides along with the chemical insecticide. ‘Green Coronet’ cabbage variety was used and the field experiment was laid out in the experimental farm of Agriculture and Forestry University (AFU), Rampur, Chitwan during the winter season of 2014.  The Experiment was designed in randomized complete block design with having 7 treatments (bio-rational insecticides with chemical and control)  and 3 replications. Plot size was 5.76 m2 (2.4m×2.4m) and spacing of 1 m was maintained between each blocks and plots. Field experiment showed that the highest reduction of cabbage aphid was obtained in Dimethoate (30 EC) treated plot followed by Derisom treated plot. The highest yield of cabbage head was obtained in Dimethoate treated plots (66.47 mt/ha) which was significantly at par with the Derisom (58.79 mt/ ha) treated plots. The yield for other treated plots were 47.60 mt/ha for Margosom, 43.77 mt/ha for Verticillium, 41.63 mt/ ha for Cow urine, 36.77 mt/ ha for Spinosad and control (33.45 mt/ ha) in terms of cabbage head yield. And, at the same time, natural enemies’ population was significantly lower to Dimethoate treated plots compared to bio-rational insecticides. Thus, Derisom (Derris based botanical) might be the best viable alternative in eco-friendly management of cabbage aphid considering cabbage head yield and protection of natural enemies. It was also evident from the research that Margosom (Neem based botanical) was found beneficial not only to conserve natural enemies in the cabbage field but also to minimize cabbage aphid population

A multistage FE updating procedure for damage identification in large-scale structures based on multiobjective evolutionary optimization

This study aims to develop a multistage scheme for damage detection for large structures based on experimental modal data and on finite element (FE) model updating methods applied on simple FE models. In the first stage, occurrence and approximate location of damage is performed by using damage functions in order to decrease the number of parameters to be updated. The goal in the second stage is to identify the specific damaged members and damage extent by considering only the members belonging to the regions detected as damage in the first stage. To improve identification, the optimization procedure is formulated in a multiobjective context solved by using evolutionary algorithms. Modal flexibilities and a damage location criterion dependent on frequencies and mode shapes are used as two objective functions of the multiobjective problem. The proposal is implemented in simulated case studies and in a case study of a real bridge experimentally tested with successful results

Particle swarm optimization with sequential niche technique for dynamic finite element model updating

Peer reviewedPostprin

Perception and clinical practice regarding mucus clearance devices with chronic obstructive pulmonary disease: a cross-sectional study of healthcare providers in Saudi Arabia

OBJECTIVES: Clearing secretions from the airway can be difficult for people with chronic obstructive pulmonary disease (COPD). Mucus clearance devices (MCDs) are an option in disease management to help with this, but healthcare provider awareness and knowledge about them as well as current clinical practice in Saudi Arabia are not known. DESIGN: A cross-sectional online survey consisting of four themes; demographics, awareness, recommendations and clinical practice, for MCDs with COPD patients. SETTING: Saudi Arabia. PARTICIPANTS: 1188 healthcare providers including general practitioners, family physicians, pulmonologists, nursing staff, respiratory therapists and physiotherapists. PRIMARY OUTCOME MEASURES: Healthcare providers' level of awareness about MCDs, and the identification of current clinical practices of COPD care in Saudi Arabia. RESULTS: 1188 healthcare providers (44.4% female) completed the survey. Regarding devices, 54.2% were aware of the Flutter, 23.8% the Acapella and 5.4% the positive expiratory pressure mask. 40.7% of the respondents identified the Acapella, and 22.3% the Flutter as first choice for COPD management. 75% would usually or always consider their use in COPD patients reporting daily difficulty clearing mucus, whereas 55.9% would sometimes or usually consider the use of MCDs with COPD patients who produced and were able to clear mucus with cough. In clinical practice, 380 (32%) of the respondents would prescribe MCDs, 378 (31.8%) would give MCDs without prescriptions, 314 (26.4%) would not provide them at all and 116 (9.8%) would only advise patients about them. CONCLUSION: Healthcare providers are aware of the existence of MCDs and their benefits for sputum clearance and believe that MCDs are beneficial for sputum clearance in some COPD patients. TRIAL REGISTRATION NUMBER: ISRCTN44651852