First principles design of divacancy defected graphene nanoribbon based rectifying and negative differential resistance device

We have elaborately studied the electronic structure of 555-777 divacancy (DV) defected armchair edged graphene nanoribbon (AGNR) and transport properties of AGNR based two-terminal device constructed with one defected electrode and one N doped electrode, by using density functional theory and non-equilibrium Green's function based approach. The introduction of 555-777 DV defect into AGNRs, results in a shifting of the {\pi} and {\pi}* bands towards the higher energy value which indicates a shifting of the Fermi level towards the lower energy. Formation of a potential barrier, very similar to that of conventional p-n junction, has been observed across the junction of defected and N doped AGNR. The prominent asymmetric feature of the current in the positive and negative bias indicates the diode like property of the device with high rectifying efficiency within wide range of bias voltages. The device also shows robust negative differential resistance (NDR) with very high peak-to-valley ratio. The analysis of the shifting of the energy states of the electrodes and the modification of the transmission function with applied bias provides an insight into the nonlinearity and asymmetry observed in the I-V characteristics. Variation of the transport properties on the width of the ribbon has also been discussed.Comment: 28 Pages, 12 Figures and 1 tabl

The outcome of cannulated cancellous screw fixation for treatment of base of fifth metatarsal fractures

Background: The fracture of the base of the fifth metatarsal is one of the common fractures that occur in 5th decade of life in the foot. Stable fixation with the cannulated cancellous screw provided early healing and patients can return to their work early. Aims and Objectives: The aim of the study is to find the functional outcome of closed reduction and internal fixation with cannulated cancellous screw fixation for the displaced base of fifth metatarsal fractures, to evaluate the clinical and radiological union of fifth metatarsal fractures, and to study the complications of treatment of fifth metatarsal fractures. Materials and Methods: This prospective study was conducted in the Department of Orthopaedics Manipal teaching hospital Pokhara, Nepal, from February 2022 to January 2023. A total of 35 patients with the fractured fifth metatarsal base were included in the study. The patient was kept in a supine position with a pillow under the knee so that the knee was flexed to 90° and the foot was plantigrade. A cannulated cancellous screw of the appropriate size was inserted along with a washer to fix the fracture. Results: There were a total of 35 patients with the base of 5th metatarsal fractures. The mean age of the patient was 36.94±8.04 years, with males 22 (62.9%) and females 13 (37.1%). The left side commonly involves 22 (62.9%). The history twisting injury is the most common mode of injury. All patients had a union of fracture by 7.09±1.07 weeks ranging from 6 to 9 weeks. There were no cases of sural nerve injuries in our study. Conclusion: The base of fifth metatarsal fractures is commonly seen in athletes and patients around 40 years of age. Closed reduction under image guidance and stable fixation with cannulated cancellous screw fixation provides early healing of fractures. Patients can return to work early

Evaluation of host-specificity of Zygogramma bicolorata Pallister (Coleoptra: Chrysomelidae) for the biological control of Parthenium hysterophorus L. (Asteraceae: Heliantheae) in Nepal

Host-specificity test of Zygogramma bicolorata Pallister (Coleoptra: Chrysomelidae) was conducted in the field and laboratory of National Entomology Research Center, Khumaltar, Lalitpur, Nepal during April to September, 2017. Multiple-choice and no-choice tests were conducted on Agerataum houstoniamum Mill., Bidens pilosa L., Chrysanthemum indicum L., Dahlia pinnata Cav, Guizotia abyssinica L., Helianthus annuus L., Lactuca sativa L., Parthenium hysterophorus L., Perilla frutescence L., Xanthium strumarium L., Zinnia elegans Jacq. and Jasminum officinale L. Among tested plant species, P. hysterophorus was only a preferred host of Z. bicolorata on which both larvae and adults fed. Ovipostion, larval development, pupation and adult emergence of Z. bicolorata occurred successfully on P. hysterophorus completing its life cycle. Larvae consumed H. anuus but could not pupate, and adults fed on it when starved for 5 days in no-choice test.   Both adults and larvae of Z. bicolorata consumed X. strumarium and completed larval and pupal developments, but adults did not oviposit. Adult longevity was significantly reduced after feeding on H. annus (19.00 days) and X. strumarium (29.33 days) compared to P. hysterophorus (83.33 days)

Mobile drawing methods in landscape research: collaborative drawing in Kathmandu Valley, Nepal

In this paper, we show how mobile drawing methodologies can bring the dynamic, relational and non-representational qualities of landscape encounters to the foreground. The research paper discusses a mobile drawing project that took place in the Kathmandu Valley, Nepal. The project entitled ‘Taxi Guff-Gaff’ invited participants to undertake a collaborative drawing and conversational journey. Mobile drawing together on a bumpy taxi journey required artist participants to move together and literally ‘pay attention to the moment at hand’. In so doing it produced imagery that foregrounds the inherent dynamic quality of all our landscape encounters. We propose that mobile drawing offers an immersive way to relate to the urban landscape and each other and can open up spaces of landscape research that centre on speculative forms of thinking, being, drawing and conversation

Association of Preoperative mid-stream urine culture, Renal pelvic urine culture and Renal stone culture in the detection of Systemic inflammatory response syndrome/urosepsis post Percutaneous Nephrolithotomy

Introduction: Urosepsis post Percutaneous Nephrolithotomy (PCNL) is a dreaded complication with high mortality rate. Objective: To find the association of preoperative midstream urine culture (PMUC), renal pelvic urine culture (RPUC) and renal stone culture (RSC) in the post-operative development of Systemic Inflammatory Response Syndrome (SIRS) and urosepsis. Methods: It was a prospective cross-sectional observational study. The study included all symptomatic patients meeting the inclusion criteria who underwent Percutaneous Nephrolithotomy from 18th August, 2019 to 28th March, 2020. PMUC, RPUC and RSC were done and analyzed accordingly. Results: A total of 140 (73 males, 67 females) patients underwent PCNL. PMUC was positive in 15% (21/140) as compared to RPUC and RSC which were 7.9 % (11/140) and 4.3% (6/140) of total cases. None of the patients had simultaneous culture positivity in all the three types of specimens. Only two (1.42%) patients had simultaneous positivity in pelvic urine culture and stone culture. The organisms obtained in pelvic urine culture and stone culture were same i.e. Klebsiella and Escherichia coli respectively. Only two (1.42%) patients developed SIRS post PCNL, where in both the cases stone culture were positive but PMUC and RPUC were negative. Urosepsis was found in none of the patients. In the Fischer Exact test PMUC and RPUC were not statistically significant in the detection of SIRS post PCNL. Whereas only RSC showed statistical significance in the detection of SIRS. Conclusion: Stone culture has high prediction for SIRS and it might be considered for patients undergoing PCNL in order to prevent stone related infective complications

An oxygen reduction catalytic process through superoxo adsorption states on n-type doped h-BN: A first-principles study

Dioxygen adsorption and activation on metal-ligand systems are the key elements for biological oxidative metabolisms and also catalyst design for the oxygen reduction reaction (ORR). We show, through first-principles calculations, that similar dioxygen adducts can form on metal-free n-type doped hexagonal boron nitride (h-BN) nanostructures. The density of electron donors determines the charge state of dioxygen, either in superoxo and peroxo, which exactly correlates with the 'end-on' and 'side-on' configurations, respectively. Activated O-2 in the superoxo state shows a better catalytic performance possibly mediating the direct four-electron reduction. The formation of hydrogen peroxide (H2O2) is practically eliminated, and thus we suggest that a surface coated with the n-type doped h-BN can be the basis for an ORR catalyst with increased stability. (C) 2015 Elsevier B.V. All rights reserved.close

Ab Initio Study of Thin Oxide-Metal Over layers as an Inverse Catalytic System for Dioxygen Reduction and Enhanced CO Tolerance

Using first-principles density functional theory calculations, we used a thin oxide overlayer, such as MgO, on a metal surface as an inverse catalyst for dioxygen reduction. Surface distortions in the oxide layer, combined with the tunneling of electron from the underneath metal, activated the adsorbed O2 in the form of a superoxo or peroxo. On the other hand, the thin MgO overlayer readily prevents the ??-back-bonding between CO and the metal surface, thereby efficiently mitigating the affinity of the metal surface for CO. The operating potential and overpotential for the oxygen reduction reaction (ORR) process have been estimated for various combinations of thin insulators and metals. The strongest binding intermediate in the overall reaction pathway influenced the overpotential. We show that for a Ag(100)-supported MgO surface, the ORR commences with a low overpotential, which is comparable to that of the Pt(111) surface. This suggests that an optimally chosen insulator-metal overlayer structure can yield a sharply tuned free energy profile for ORR.close

Magnetic, elastic and optical properties of zinc peroxide (ZnO2): First principles study

Using first principles method we elaborately discuss the magnetic, elastic and optical properties of pure, Zn and O vacant ZnO2. It is found that the electronic structure and band gap of ZnO2 is not sensitive to the active on-site Coulomb interaction term U-d, but found to be depending on the term U-p. The role of orbitals subject to the correlation is thus completely opposite for the case of ZnO2 in respect of ZnO. Interestingly, the Zn vacancy converts ZnO2 as "d(0) magnet''. Indeed, our analysis show that, Zn vacancy transmuted O-2(2) state into O-2(delta+2) state, indicating the partially filled pi* states are the governing reason for the d(0) magnetism. Both HSE06 and PBE0 functional confirm the same. The similar phenomena has been observed for other peroxide materials XO2 (X = Mg, Ca, Sr, Ba) studied here. Our results suggest that this class of materials can be studied further to exploit its potential in spintronic devices. Further the elastic properties have been estimated for pure ZnO2 at different pressures and for Zn and O vacant ZnO2 to know the stability of the system. Zn vacancy in ZnO2 also tunes optical properties, indicating its potential application in other areas.close