Theoretical study of pressure dependence of superconducting state parameters of some metals using pseudopotential approach

In the present theoretical study, we have calculated superconducting state parameters (SSPs) viz; electron-phonon coupling strength (λ), Coulomb pseudopotential (µ*), critical temperature (Tc), effective interaction strength (N0V) and isotopic effect parameter ( α) of some polyvalent metals (Pb, Ga, In, Sn and Tl) using well-established structured local pseudopotential due to Fiolhais et al. (1995). The pseudopotential with its individual set of parameters has been found to be good in predicting transition temperature Tc for all the metals. Looking to such success, we have extended the present model for the theoretical study of pressure dependence of transition temperature Tc using Debye- Gruneisen model. Our predicted critical volumes using different approaches are well agreed with each other and also with other reported findings. Thus, the present model is consistent and better than nonlocal norm conserving pseudopotentials because it is found to be transferable without any kind of adjustment of its parameters along with its simplicity and predictivity

LIFESTYLE FACTORS: AN ALARM TOWARDS HYPERTENSION

Cardiovascular disease is the number one cause of death worldwide in which hypertension is responsible for an annual death of 7.1 million. There exist a causal relationship between low levels of occupational and/or leisure-time Physical Activity and an increased risk of cardiovascular disease. An additional possible reasons may be reduced sleep duration/quality and individuals knowledge of their disease and its treatment. Objective: This study was conducted to assess the prevalence of hypertension and risk factors associated, concentrating on literacy status, physical exercise, occupation and sleep pattern in rural population. Method: It was a questionnaire based study carried out in two phases with Blood Pressure measurement. Result: The study results showed low literacy rate and maximum prevalence of hypertension in farmers and house wives, with a lifestyle devoid of routine physical exercises and with advancing age. Conclusion: The study concluded with the positive relationship between risk factors. Keywords: Hypertension, Physical Exercise, Literacy, Occupation, Risk Factors

Angstrom‐confined Electrochemical Synthesis of Sub‐unit Cell non van der Waals 2D Metal Oxides

Bottom-up electrochemical synthesis of atomically thin materials is desirable yet challenging, especially for non-van der Waals (vdW) materials. Thicknesses below few nm have not been reported yet, posing the question how thin can non-vdW materials be electrochemically synthesized? This is important as materials with (sub-) unit cell thickness often show remarkably different properties compared to their bulk form or thin films of several nm thickness. Here, we introduce a straightforward electrochemical method utilizing the angstrom-confinement of laminar reduced graphene oxide (rGO) nanochannels to obtain a centimeter-scale network of atomically thin (< 4.3 Å) 2D-transition metal oxides (2D-TMO). The angstrom-confinement provides a thickness limitation, forcing sub-unit cell growth of 2D-TMO with oxygen and metal vacancies. We showcase that Cr2O3, a material without significant catalytic activity for OER in bulk form, can be activated as a high-performing catalyst if synthesized in the 2D sub-unit cell form. Our method displays the high activity of sub-unit cell form while retaining the stability of bulk form, promising to yield unexplored fundamental science and applications. We show that while retaining the advantages of bottom-up electrochemical synthesis like simplicity, high yield, and mild conditions, the thickness of TMO can be limited to sub-unit cell dimensions

Nanocarbon-Based photovoltaics

Carbon materials are excellent candidates for photovoltaic solar cells: they are Earth-abundant, possess high optical absorption, and superior thermal and photostability. Here we report on solar cells with active layers made solely of carbon nanomaterials that present the same advantages of conjugated polymer-based solar cells - namely solution processable, potentially flexible, and chemically tunable - but with significantly increased photostability and the possibility to revert photodegradation. The device active layer composition is optimized using ab-initio density functional theory calculations to predict type-II band alignment and Schottky barrier formation. The best device fabricated is composed of PC70BM fullerene, semiconducting single-walled carbon nanotubes and reduced graphene oxide. It achieves a power conversion efficiency of 1.3% - a record for solar cells based on carbon as the active material - and shows significantly improved lifetime than a polymer-based device. We calculate efficiency limits of up to 13% for the devices fabricated in this work, comparable to those predicted for polymer solar cells. There is great promise for improving carbon-based solar cells considering the novelty of this type of device, the superior photostability, and the availability of a large number of carbon materials with yet untapped potential for photovoltaics. Our results indicate a new strategy for efficient carbon-based, solution-processable, thin film, photostable solar cells

Controversy and consensus on the management of elevated sperm DNA fragmentation in male infertility: A global survey, current guidelines, and expert recommendations

Purpose Sperm DNA fragmentation (SDF) has been associated with male infertility and poor outcomes of assisted reproductive technology (ART). The purpose of this study was to investigate global practices related to the management of elevated SDF in infertile men, summarize the relevant professional society recommendations, and provide expert recommendations for managing this condition. Materials and Methods An online global survey on clinical practices related to SDF was disseminated to reproductive clinicians, according to the CHERRIES checklist criteria. Management protocols for various conditions associated with SDF were captured and compared to the relevant recommendations in professional society guidelines and the appropriate available evidence. Expert recommendations and consensus on the management of infertile men with elevated SDF were then formulated and adapted using the Delphi method. Results A total of 436 experts from 55 different countries submitted responses. As an initial approach, 79.1% of reproductive experts recommend lifestyle modifications for infertile men with elevated SDF, and 76.9% prescribe empiric antioxidants. Regarding antioxidant duration, 39.3% recommend 4–6 months and 38.1% recommend 3 months. For men with unexplained or idiopathic infertility, and couples experiencing recurrent miscarriages associated with elevated SDF, most respondents refer to ART 6 months after failure of conservative and empiric medical management. Infertile men with clinical varicocele, normal conventional semen parameters, and elevated SDF are offered varicocele repair immediately after diagnosis by 31.4%, and after failure of antioxidants and conservative measures by 40.9%. Sperm selection techniques and testicular sperm extraction are also management options for couples undergoing ART. For most questions, heterogenous practices were demonstrated. Conclusions This paper presents the results of a large global survey on the management of infertile men with elevated SDF and reveals a lack of consensus among clinicians. Furthermore, it demonstrates the scarcity of professional society guidelines in this regard and attempts to highlight the relevant evidence. Expert recommendations are proposed to help guide clinicians

Tailoring Energy Transfer from Hot Electrons to Adsorbate Vibrations for Plasmon-Enhanced Catalysis

Chemical reactions can be enhanced on surfaces of bimetallic nanoparticles composed of a core plasmonic metal and a catalytically active shell when illuminated with light. However, the atomic-level details of the steps that govern such photochemical reactions are not yet understood. One critical process is the non-adiabatic energy transfer from hot electrons that transiently populate the unoccupied electronic orbitals of the adsorbate to the vibrational modes of the adsorbed reactants. This occurs via electron–vibration coupling and could potentially be tailored by changing the composition of the shell. Here, we apply an ab initio method based on density functional theory to investigate this coupling at various sp- and d-band metal–adsorbate interfaces. Our calculations demonstrate the importance of d-bands in enhancing and tuning this energy transfer at the interface. Further, they highlight specific choices of metals that could be utilized as shells for efficient photochemical reactions. From these calculations, we extract a simple descriptor (dependent on the coupling matrix element and equilibrium bond length) that can account for the coupling strength at a metal–adsorbate interface, thus representing a valuable tool for rational shell design for different reactions. We show the utility of this descriptor for photocatalysis with calculations for a specific photochemical reaction. The introduction of this descriptor should also impact other processes such as light-triggered drug release that exploit hot electrons, and surface-enhanced Raman spectroscopy, where electron–vibration coupling plays a key role.ISSN:2155-543

Tailoring Energy Transfer from Hot Electrons to Adsorbate Vibrations for Plasmon-Enhanced Catalysis

Chemical reactions can be enhanced on surfaces of bimetallic nanoparticles composed of a core plasmonic metal and a catalytically active shell when illuminated with light. However, the atomic-level details of the steps that govern such photochemical reactions are not yet understood. One critical process is the non-adiabatic energy transfer from hot electrons that transiently populate the unoccupied electronic orbitals of the adsorbate to the vibrational modes of the adsorbed reactants. This occurs via electron–vibration coupling and could potentially be tailored by changing the composition of the shell. Here, we apply an <i>ab initio</i> method based on density functional theory to investigate this coupling at various sp- and d-band metal–adsorbate interfaces. Our calculations demonstrate the importance of d-bands in enhancing and tuning this energy transfer at the interface. Further, they highlight specific choices of metals that could be utilized as shells for efficient photochemical reactions. From these calculations, we extract a simple descriptor (dependent on the coupling matrix element and equilibrium bond length) that can account for the coupling strength at a metal–adsorbate interface, thus representing a valuable tool for rational shell design for different reactions. We show the utility of this descriptor for photocatalysis with calculations for a specific photochemical reaction. The introduction of this descriptor should also impact other processes such as light-triggered drug release that exploit hot electrons, and surface-enhanced Raman spectroscopy, where electron–vibration coupling plays a key role

Graphene Oxide as a Promising Hole Injection Layer for MoS[subscript 2]-based Electronic Devices

The excellent physical and semiconducting properties of transition metal dichalcogenide (TMDC) monolayers make them promising materials for many applications. The TMDC monolayer MoS[subscript 2] has gained significant attention as a channel material for next-generation transistors. However, while n-type single-layer MoS2 devices can be made with relative ease, fabrication of p-type transistors remains a challenge as the Fermi-level of elemental metals used as contacts are pinned close to the conduction band leading to large p-type Schottky barrier heights (SBH). Here, we propose the utilization of graphene oxide (GO) as an efficient hole injection layer for single-layer MoS[subscript 2]-based electronic and optoelectronic devices. Using first-principles computations, we demonstrate that GO forms a p-type contact with monolayer MoS[subscript 2], and that the p-type SBH can be made smaller by increasing the oxygen concentration and the fraction of epoxy functional groups in GO. Our analysis shows that this is possible due to the high work function of GO and the relatively weak Fermi-level pinning at the MoS[subscript 2]/GO interfaces compared to traditional MoS[subscript 2]/metal systems (common metals are Ag, Al, Au, Ir, Pd, Pt). The combination of easy-to-fabricate and inexpensive GO with MoS[subscript 2] could be promising for the development of hybrid all-2D p-type electronic and optoelectronic devices on flexible substrates.Eni S.p.A. (Firm) (Eni-MIT Alliance Solar Frontiers Program

The Impact of Functionalization on the Stability, Work Function, and Photoluminescence of Reduced Graphene Oxide

Reduced graphene oxide (rGO) is a promising material for a variety of thin-film optoelectronic applications. Two main barriers to its widespread use are the lack of (1) fabrication protocols leading to tailored functionalization of the graphene sheet with oxygen-containing chemical groups, and (2) understanding of the impact of such functional groups on the stability and on the optical and electronic properties of rGO. We carry out classical molecular dynamics and density functional theory calculations on a large set of realistic rGO structures to decompose the effects of different functional groups on the stability, work function, and photoluminescence. Our calculations indicate the metastable nature of carbonyl-rich rGO and its favorable transformation to hydroxyl-rich rGO at room temperature <i>via</i> carbonyl-to-hydroxyl conversion reactions near carbon vacancies and holes. We demonstrate a significant tunability in the work function of rGO up to 2.5 eV by altering the composition of oxygen-containing functional groups for a fixed oxygen concentration, and of the photoluminescence emission by modulating the fraction of epoxy and carbonyl groups. Taken together, our results guide the application of tailored rGO structures in devices for optoelectronics and renewable energy

Graphene- and Graphene Oxide-Based Nanocomposite Platforms for Electrochemical Biosensing Applications

Graphene and its derivatives such as graphene oxide (GO) and reduced GO (rGO) offer excellent electrical, mechanical and electrochemical properties. Further, due to the presence of high surface area, and a rich oxygen and defect framework, they are able to form nanocomposites with metal/semiconductor nanoparticles, metal oxides, quantum dots and polymers. Such nanocomposites are becoming increasingly useful as electrochemical biosensing platforms. In this review, we present a brief introduction on the aforementioned graphene derivatives, and discuss their synthetic strategies and structure-property relationships important for biosensing. We then highlight different nanocomposite platforms that have been developed for electrochemical biosensing, introducing enzymatic biosensors, followed by non-enzymatic biosensors and immunosensors. Additionally, we briefly discuss their role in the emerging field of biomedical cell capture. Finally, a brief outlook on these topics is presented