Tunneling Experiments with Dirac Electrons in Graphene Heterojunctions

This dissertation presents results of scanning tunneling microscopy/spectroscopy experiments performed on graphene, a two-dimensional membrane of carbon atoms arranged in a honeycomb lattice, where charge carriers behave like massless fermions described by the Dirac equation. Our findings demonstrate that interface engineering is a viable route to control and further enhance the electronic properties of graphene. In the first experiment, by transferring chemical vapor deposited (CVD) graphene onto substrates of opposite polarization - H-terminated Si-face and C-faces of hexagonal silicon carbide (SiC), we show that the type of charge carrier in graphene can be controlled by substrate polarization. Furthermore, we find that the charge carrier in epitaxial graphene/Si-face SiC(0001) convert from n- to p-type upon H-intercalation at the interface. Finally, we observe the formation of ripples in the graphene H-terminated SiC heterojunctions, which causes atomic scale fluctuations in the Dirac point. Density functional theory calculations suggest the formation of a Schottky dipole just ~ 1 nm at the graphene/SiC interface, thus the Dirac point depends strongly on the spacing between graphene and SiC. As a result, ripples, i.e., atomic scale topographic fluctuations of graphene with respect to the substrate, lead to the variations in the Dirac point. In the second experiment, we discover two types of intrinsic atomic-scale inhomogeneities that can cause fluctuations in the Schottky barrier height at graphene/semiconductor junctions: graphene ripples and/or trapped charge impurities and surface states of the semiconductor. These findings provide insight into the fundamental physics of nanoscale devices based on graphene - semiconductor junctions. In the third experiment, we experimentally demonstrate proximity-induced spin-orbit coupling in graphene-topological insulator van der Waals (vdW) heterostructures fabricated by transferring CVD graphene onto Bi2Se3 grown by molecular beam epitaxy. We observe a spin-orbit splitting of up to 80 meV in the graphene Dirac states, an enhancement of several orders of magnitude compared to the intrinsic value. Moreover, the spin-orbit splitting exhibits spatial variations of ±20 meV, as a result of the lack of epitaxial relation between the graphene and Bi2Se3 layers. Density functional theory calculations further reveal that this giant spin-orbit splitting of the graphene bands is a consequence of the orthogonalization requirement on the overlapping wave functions, rather than arising from simple direct bonding at the interface. This revelation of the indirect bonding mechanism of the proximity effect is an enabling step towards more effective engineering of desired properties in vdW heterostructures

Direct comparison of current-induced spin polarization in topological insulator Bi2Se3 and InAs Rashba states

Three-dimensional topological insulators (TIs) exhibit time-reversal symmetry protected, linearly dispersing Dirac surface states. Band bending at the TI surface may also lead to coexisting trivial two-dimensional electron gas (2DEG) states with parabolic energy dispersion that exist as spin-split pairs due to Rashba spin-orbit coupling (SOC). A bias current is expected to generate spin polarization in both systems arising from their helical spin-momentum locking. However, their induced spin polarization is expected to be different in both magnitude and sign. Here, we compare spin potentiometric measurements of bias current-generated spin polarization in Bi2Se3(111) films where Dirac surface states coexist with trivial 2DEG states, with identical measurements on InAs(001) samples where only trivial 2DEG states are present. We observe spin polarization arising from spin-momentum locking in both cases, with opposite signs of the spin voltage. We present a model based on spin dependent electrochemical potentials to directly derive the signs expected for the TI surface states, and unambiguously show that the dominant contribution to the current-generated spin polarization measured in the TI is from the Dirac surface states. This direct electrical access of the helical spin texture of Dirac and Rashba 2DEG states is an enabling step towards the electrical manipulation of spins in next generation TI and SOC based quantum devices

Hormonal and non-hormonal oral contraceptives given long-term to pubertal rats differently affect bone mass, quality and metabolism

IntroductionWe investigated the effects of hormonal and non-hormonal oral contraceptives (OCs) on bone mass, mineralization, composition, mechanical properties, and metabolites in pubertal female SD rats.MethodsOCs were given for 3-, and 7 months at human equivalent doses. The combined hormonal contraceptive (CHC) was ethinyl estradiol and progestin, whereas the non-hormonal contraceptive (NHC) was ormeloxifene. MicroCT was used to assess bone microarchitecture and BMD. Bone formation and mineralization were assessed by static and dynamic histomorphometry. The 3-point bending test, nanoindentation, FTIR, and cyclic reference point indentation (cRPI) measured the changes in bone strength and material composition. Bone and serum metabolomes were studied to identify potential biomarkers of drug efficacy and safety and gain insight into the underlying mechanisms of action of the OCs.ResultsNHC increased bone mass in the femur metaphysis after 3 months, but the gain was lost after 7 months. After 7 months, both OCs decreased bone mass and deteriorated trabecular microarchitecture in the femur metaphysis and lumbar spine. Also, both OCs decreased the mineral: matrix ratio and increased the unmineralized matrix after 7 months. After 3 months, the OCs increased carbonate: phosphate and carbonate: amide I ratios, indicating a disordered hydroxyapatite crystal structure susceptible to resorption, but these changes mostly reversed after 7 months, indicating that the early changes contributed to demineralization at the later time. In the femur 3-point bending test, CHC reduced energy storage, resilience, and ultimate stress, indicating increased susceptibility to micro-damage and fracture, while NHC only decreased energy storage. In the cyclic loading test, both OCs decreased creep indentation distance, but CHC increased the average unloading slope, implying decreased microdamage risk and improved deformation resistance by the OCs. Thus, reduced bone mineralization by the OCs appears to affect bone mechanical properties under static loading, but not its cyclic loading ability. When compared to an age-matched control, after 7 months, CHC affected 24 metabolic pathways in bone and 9 in serum, whereas NHC altered 17 in bone and none in serum. 6 metabolites were common between the serum and bone of CHC rats, suggesting their potential as biomarkers of bone health in women taking CHC.ConclusionBoth OCs have adverse effects on various skeletal parameters, with CHC having a greater negative impact on bone strength

Upsurge in biomedical waste due to COVID-19 in India: A statistical correlation, challenges and recommendations

Proper management of Biomedical Waste (BMW) is an essential component of any sustainable healthcare sector. With the burst of COVID-19 pandemic when every hospital and treatment facility was overburdened patients, efficient handling of the huge amount of generated BMW became a task for the entire world. This review compares the BMW generated before and during the second wave of COVID-19, highlights the challenges in managing the exuberated amount of COVID-19 waste and sites recommendations to promote sustainable design thinking, in order to address this grave concern in the current setting of the Indian system. The study indicated that inappropriate management of waste and the lacunae in the entire chain from segregation to collection until its disposal has posed a serious threat to the wellbeing of healthcare workers, sanitation staff as well as the operators and housekeeping staff at the hospitals, isolation centers and Municipal Corporation. Many states had inadequate number of common BMW treatment facilities (CBMWTFs) leading to inefficient treatment of the excess waste. The behavioural and attitudinal barriers of neglect and ignorance of different stakeholders further aggravated the problem of BMW management to manifolds. To achieve better management we recommend spreading awareness regarding the kind and infectious nature of waste generated by COVID-19 patients and their caregivers, segregation and decontamination of such waste at source and increasing the capacity as well as number of CBMWTFs. Creative ways to recycle the waste must be devised so as to reduce the burden on disposal sites

'Bhavishya Shakti: Empowering the Future': establishing and evaluating a pilot community mobile teaching kitchen as an innovative model, training marginalised women to become nutrition champions and culinary health educators in Kolkata, India.

BACKGROUND: Malnutrition is a global emergency, creating an overlapping burden on individual, public and economic health. The double burden of malnutrition affects approximately 2.3 billion adults worldwide. Following 3 years of capacity building work in Kolkata, with assistance of local volunteers and organisations, we established an empowering nutrition education model in the form of a 'mobile teaching kitchen (MTK)' with the aim of creating culinary health educators from lay slum-dwelling women. AIMS: To evaluate the piloting of a novel MTK nutrition education platform and its effects on the participants, alongside data collection feasibility. METHODS: Over 6 months, marginalised (RG Kar and Chetla slums) women underwent nutrition training using the MTK supported by dietitians, doctors and volunteers. Preintervention and postintervention assessments of knowledge, attitudes and practices (KAP), as well as anthropometric and clinical nutritional status of both the women and their children were recorded. The education was delivered by a 'See One, Do One, Teach One' approach with a final assessment of teaching delivery performed in the final session. RESULTS: Twelve women were trained in total, six from each slum. Statistically significant improvements were noted in sections of KAP, with improvements in nutrition knowledge (+4.8) and practices (+0.8). In addition, statistically significant positive changes were seen in 'understanding of healthy nutrition for their children' (p=0.02), 'sources of protein rich food' (p=0.02) and 'not skipping meals if a child is ill' (p≤0.001). CONCLUSION: The MTK as a public health intervention managed to educate, empower and upskill two groups of lay marginalised women into MTK Champions from the urban slums of Kolkata, India. Improvements in their nutrition KAP demonstrate just some of the effects of this programme. By the provision of healthy meals and nutritional messages, the MTK Champions are key drivers nudging improvements in nutrition and health related awareness with a ripple effect across the communities that they serve. There is potential to upscale and adapt this programme to other settings, or developing into a microenterprise model, that can help future MTK Champions earn a stable income

Three-year review of a capacity building pilot for a sustainable regional network on food, nutrition and health systems education in India.

BACKGROUND: In Kolkata (India), there are high rates of malnourished children (45.9%) under the age of three, impacting growth, organ development, function, and cognition. Mothers have a major role to play during this crucial development stage, with research showing nutrition knowledge, attitudes and practices (KAP) of mothers are important determinants of childhood malnutrition. AIMS: To document 3 years of capacity building towards a sustainable nutrition education network in Kolkata, India, while assessing the ability to perform data collection in the form of needs assessments, impact assessments and capacity reviews. METHODS: Descriptive review and analysis of engagement and impact from 3 years of work by the NNEdPro Global Centre for Nutrition and Health, initiating locally led nutrition education interventions. Mapping to the Indian National Nutrition Strategy was also performed to review adherence to nationwide priorities surrounding nutrition and determine the wider application potential of the network. RESULTS: Two simultaneous projects were taken forward by a team of local healthcare professionals and student champions. Project 1-medical college workshops for medical student nutrition education with added focus on underserved populations, Project 2-preparation for a 'Mobile Teaching Kitchen' (MTK) in marginalised communities to empower local women as nutrition educators.Data collection methods used for analysing markers of impact and sustainability were semi-structured interviews of the community members, and KAP questionnaires to assess response to educational sessions. CONCLUSION: With local support it is possible to create and sustain fieldwork for an extended period with meaningful outputs and impact. This initiative demonstrates that it is possible to use healthcare professionals, students and volunteers with low-intensity training and a low-cost approach to produce action research with considerable impact and results in rapid, reliable and robust manner

Effect of Link location, support and joint with Graphene base dampers for Seismic Stability on Metallic Structure

Hence, it is required to construct such structures which can resist earthquake. The construction of earthquake resistant structures and its effective design is much more required all over the world, particularly, the places where earthquake vulnerability is maximum. This paper is reviewed and tested experimentally for the innovative design of earthquake resistant building which is proposed by engineers and scientists all over the world.in this paper we create multiplex with different link arrangements to minimize the seismic effect and make structure dynamically stable. Other part of the paper concentrates on bolting and busing system with graphene multilayer coting as a vibration isolation and damper

An exploratory study on use of tobacco among adolescent students in selected schools of Moradabad (up) India

Statement: An Exploratory Study on Use of Tobacco Among Adolescent Students in Selected Schools of Moradabad (Up). Objectives: Main Objective- To explore the use of tobacco among adolescent students using semi structured questionnaire. Assumptions: 1) Use of tobacco is more common in adolescents; 2) A high-risk group for tobacco consumption is adolescents; 3) Tobacco consumption in any form has its impact on the general health status of the individuals; 4) Practice of using tobacco and its products is more common in the general population. Methodology:  Qualitative Research approach was used for this current study. Research design used was exploratory research design. The study setting was Alam Inter College, Mehlakpur Road, Pakwara, a senior secondary school of Moradabad (UP). The study population for this study was 11th and 12th class school students at Moradabad (UP. Snowball sampling technique (non-probability sampling) was used to obtain the sample. Total 12 students were interviewed using semi structured questionnaires. Result: Exploring adolescent’s awareness of substances and associated harm to health from their uses of tobacco

A quasi-experimental study on effect of ‘clutch hold’ method of breast feeding on comfort level of post cesarean mothers admitted in obstetrics units of Nehru Hospital, Pgimer, Chandigarh

Statement: A Quasi-Experimental Study on Effect of ‘Clutch Hold’ Method of Breast Feeding on ‘Comfort Level’ of Post Cesarean Mothers Admitted in Obstetrics Units of Nehru Hospital, PGIMER, Chandigarh. Objectives: Main Objective- To study the effect of ‘clutch hold’ method of breast feeding on comfort level of post caesarean mothers. Sub-objectives- 1) To select tool and use it to measure comfort level in caesarean mothers while breast feeding. 2) To develop protocol of clutch-hold method for breast feeding and use it among experimental study subjects. 3) To assess and compare the findings. Methodology: A quasi- experimental research approach was used with cross-over study design. Population was 76 cesarean mothers who met the inclusion criteria and were admitted in obstetrics unit of Nehru Hospital, PGIMER, UT, Chandigarh (India). Result: The present study revealed that that comfort level in post caesarean mothers while breast feeding is independent of methods of breast feeding as it is evident by ‘p’ value 0.122, i.e., ‘p’ value is not significant. Mothers who were exposed to ‘clutch-hold’ & ‘cradle-hold’ methods of breast feeding after caesarean section, experienced no significant difference on comfort level while breast feeding.&nbsp