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Träfflista för sökning "WFRF:(Ahuja N) "

Sökning: WFRF:(Ahuja N)

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1.
  • Aad, G, et al. (författare)
  • 2015
  • swepub:Mat__t
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4.
  • Dubrovinsky, L. S., et al. (författare)
  • Materials science - The hardest known oxide
  • 2001
  • Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 410:6829, s. 653-654
  • Tidskriftsartikel (refereegranskat)
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5.
  • Gerkin, RC, et al. (författare)
  • The best COVID-19 predictor is recent smell loss: a cross-sectional study
  • 2020
  • Ingår i: medRxiv : the preprint server for health sciences. - : Cold Spring Harbor Laboratory.
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • BackgroundCOVID-19 has heterogeneous manifestations, though one of the most common symptoms is a sudden loss of smell (anosmia or hyposmia). We investigated whether olfactory loss is a reliable predictor of COVID-19.MethodsThis preregistered, cross-sectional study used a crowdsourced questionnaire in 23 languages to assess symptoms in individuals self-reporting recent respiratory illness. We quantified changes in chemosensory abilities during the course of the respiratory illness using 0-100 visual analog scales (VAS) for participants reporting a positive (C19+; n=4148) or negative (C19-; n=546) COVID-19 laboratory test outcome. Logistic regression models identified singular and cumulative predictors of COVID-19 status and post-COVID-19 olfactory recovery.ResultsBoth C19+ and C19-groups exhibited smell loss, but it was significantly larger in C19+ participants (mean±SD, C19+: -82.5±27.2 points; C19-: -59.8±37.7). Smell loss during illness was the best predictor of COVID-19 in both single and cumulative feature models (ROC AUC=0.72), with additional features providing negligible model improvement. VAS ratings of smell loss were more predictive than binary chemosensory yes/no-questions or other cardinal symptoms, such as fever or cough. Olfactory recovery within 40 days was reported for ∼50% of participants and was best predicted by time since illness onset.ConclusionsAs smell loss is the best predictor of COVID-19, we developed the ODoR-19 tool, a 0-10 scale to screen for recent olfactory loss. Numeric ratings ≤2 indicate high odds of symptomatic COVID-19 (4<OR<10), which can be deployed when viral lab tests are impractical or unavailable.
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7.
  • Williamson, Alice, et al. (författare)
  • Genome-wide association study and functional characterization identifies candidate genes for insulin-stimulated glucose uptake
  • 2023
  • Ingår i: Nature Genetics. - : Springer Nature. - 1061-4036 .- 1546-1718. ; 55:6, s. 973-983
  • Tidskriftsartikel (refereegranskat)abstract
    • Distinct tissue-specific mechanisms mediate insulin action in fasting and postprandial states. Previous genetic studies have largely focused on insulin resistance in the fasting state, where hepatic insulin action dominates. Here we studied genetic variants influencing insulin levels measured 2 h after a glucose challenge in >55,000 participants from three ancestry groups. We identified ten new loci (P < 5 × 10-8) not previously associated with postchallenge insulin resistance, eight of which were shown to share their genetic architecture with type 2 diabetes in colocalization analyses. We investigated candidate genes at a subset of associated loci in cultured cells and identified nine candidate genes newly implicated in the expression or trafficking of GLUT4, the key glucose transporter in postprandial glucose uptake in muscle and fat. By focusing on postprandial insulin resistance, we highlighted the mechanisms of action at type 2 diabetes loci that are not adequately captured by studies of fasting glycemic traits.
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8.
  • Abdel-Hafiez, Mahmoud, et al. (författare)
  • Pressure-induced reentrant transition in NbS3 phases : Combined Raman scattering and x-ray diffraction study
  • 2019
  • Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 99:23
  • Tidskriftsartikel (refereegranskat)abstract
    • We report the evolution of charge density wave states under pressure for two NbS3 phases: triclinic (phase I) and monoclinic (phase II) at room temperature. Raman and x-ray diffraction (XRD) techniques are applied. The x-ray studies on the monoclinic phase under pressure show a compression of the lattice at different rates below and above similar to 7 GPa but without a change in space group symmetry. The Raman spectra of the two phases evolve similarly with pressure; all peaks almost disappear in the similar to 6-8 GPa range, indicating a transition from an insulating to a metallic state, and peaks at new positions appear above 8 GPa. The results suggest suppression of the ambient charge-density waves and their subsequent recovery with new orderings above 8 GPa.
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11.
  • Ahuja, Rajeev, et al. (författare)
  • Electronic and optical properties of lead iodide
  • 2002
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:12, s. 7219-7224
  • Tidskriftsartikel (refereegranskat)abstract
    • The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising detector material with a large technological applicability. Its band-gap energy as a function of temperature has also been measured by optical absorption. The temperature dependence has been fitted by two different relations, and a discussion of these fittings is given.
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12.
  • Ahuja, Rajeev, et al. (författare)
  • Optical properties of 4H-SiC
  • 2002
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 91:4, s. 2099-2103
  • Tidskriftsartikel (refereegranskat)abstract
    • The optical band gap energy and the dielectric functions of n-type 4H-SiC have been investigated experimentally by transmission spectroscopy and spectroscopic ellipsometry and theoretically by an ab initio full-potential linear muffin-tin-orbital method. We present the real and imaginary parts of the dielectric functions, resolved into the transverse and longitudinal photon moment a, and we show that the anisotropy is small in 4H-SiC. The measurements and the calculations fall closely together in a wide range of energies.
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13.
  • Ahuja, R., et al. (författare)
  • Optical properties of 4H-SiC
  • 2002
  • Ingår i: J. Appl. Phys.. ; 91:4, s. 2099-2103
  • Tidskriftsartikel (refereegranskat)
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14.
  • Ahuja, R, et al. (författare)
  • Theoretical and experimental study of the graphite 1s x-ray absorption edges
  • 1996
  • Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMER INST PHYSICS. - 0163-1829. ; 54:20, s. 14396-14404
  • Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
    • Theoretical calculations in combination with experiments for the pi* and sigma* x-ray absorption edges are reported for graphite. Theory and experiment agree well for the leading pi* and sigma* resonances. By comparing theoretical calculations for a singl
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16.
  • Astrath, N. G. C., et al. (författare)
  • Thermal lens and photoacoustic spectroscopy to determine the thermo-optical properties of semiconductors
  • 2005
  • Ingår i: Journal de Physique IV. - : EDP Sciences. - 1155-4339 .- 1764-7177. ; 125, s. 181-183
  • Tidskriftsartikel (refereegranskat)abstract
    • In this work we used photoacoustic and thermal lens spectroscopy to study four different semiconductor samples: PbI2, 4HSiC, NiCrO and NiO. The results showed that the combination of these two techniques provided the values of the band gap energies and the thermal diffusivities.
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19.
  • Belonoshko, Anatoly B., et al. (författare)
  • High-pressure melting of MgSiO3
  • 2005
  • Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 94:19
  • Tidskriftsartikel (refereegranskat)abstract
    • The melting curve of MgSiO3 perovskite has been determined by means of ab initio molecular dynamics complemented by effective pair potentials, and a new phenomenological model of melting. Using first principles ground state calculations, we find that the MgSiO3 perovskite phase transforms into post perovskite at pressures above 100 GPa, in agreement with recent theoretical and experimental studies. We find that the melting curve of MgSiO3, being very steep at pressures below 60 GPa, rapidly flattens on increasing pressure. The experimental controversy on the melting of the MgSiO3 perovskite at high pressures is resolved, confirming the data by Zerr and Boehler.
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20.
  • Benhouria, Y., et al. (författare)
  • Dynamic magneto-caloric effect of a multilayer nanographene : Dynamic quantum Monte Carlo
  • 2019
  • Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier BV. - 1386-9477 .- 1873-1759. ; 105, s. 139-145
  • Tidskriftsartikel (refereegranskat)abstract
    • Using the dynamic quantum Monte Carlo simulation, the dynamic magnetocaloric effect of a ferromagnetic multilayer nanographene (MNG) is studied within the dynamic Ising model under the applied of a time-dependent oscillating (h(t)) magnetic field. The influence of the amplitude h(0) and the period tau of the h(t) and the transverse field Omega on the thermal behavior of the dynamic order parameter and the dynamic magnetocaloric properties (the dynamic isothermal Delta S-T (T, h(t)) entropy change and the dynamic Delta T-ad (T, h(t)) adiabatic change of temperature), the dynamic specific heat, the dynamic entropy and as well as the dynamic relative cooling power (RCP(t)) ferrimagnetic MNG are studied. Our predicted results may be a reference for future experiment and theoretical studies of the nanostructures.
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21.
  • Bhuyan, Prabal Dev, et al. (författare)
  • Metallic one-dimensional heterostructure for gas molecule sensing
  • 2021
  • Ingår i: Scientific Reports. - : Springer Nature. - 2045-2322. ; 11:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We have investigated a new metallic core-shell nanowire (NW) geometry of that could be obtained experimentally, that is silicon (Si) and germanium (Ge) NWs with cores constituted by group-10 elements palladium (Pd) and platinum (Pt). These NWs are optimized with two different diameters of 1.5 angstrom and 2.5 angstrom. The nanowires having diameter of 1.5 angstrom show semi-metallic nature with GGA-PBE calculation and metallic nature while spin orbit interaction (SOC) is included. The quantum conductance of the NWs increases with the diameter of the nanowire. We have investigated current-voltage (IV) characteristics for the considered NWs. It has been found that current values in accordance with applied voltage show strong dependence on the diameter of the NWs. The optical study of the NWs shows that absorption co-efficient peak moves to lower energies; due to quantum confinement effect. Furthermore, we have extensively studied optical response of Pd and Pt based core-shell NWs in O-2 and CO2 environment. Our study on Si and Ge based metallic core/shell NW show a comprehensive picture as possible electron connector in future nano-electronic devices as well as nano gas detector for detecting O-2 gas.
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22.
  • Bhuyan, Prabal Dev, et al. (författare)
  • Ultrathin nanowire PdX2 (X = P, As) : stability, electronic transport and thermoelectric properties
  • 2020
  • Ingår i: New Journal of Chemistry. - : Royal Society of Chemistry (RSC). - 1144-0546 .- 1369-9261. ; 44:36, s. 15617-15624
  • Tidskriftsartikel (refereegranskat)abstract
    • In the last few decades, the miniaturization of devices has been taking place and therefore the quest for new nanowires has become more significant. In the present study, we have investigated the geometry of new ultrathin nanowires (NWs) of PdP2 and PdAs2 that could be obtained experimentally. We have optimized the pentagonal structures of both the NWs and studied their dynamical stability using the phonon dispersion curve. The electronic band structure shows semiconducting behaviour of PdP2 NWs with a band gap of 380 meV and PdAs2 NWs with a band gap of 294 meV, with higher charge carrier mobility than that of their 2D counterparts. The NWs show a band gap of 840 meV and 740 meV for PdP2 and PdAs2, respectively, through hybrid potential calculations. The PdX2 structure shows a transition from semiconducting to semi-metallic behaviour at a compressive strain of 8% within a sustainable pressure of 0.2–0.3 GPa. A negative differential conductance (NDC) effect is observed in the current–voltage graph for both the NWs. The semi-metallic behaviour with an asymmetric density of states near the Fermi energy boosts the Seebeck co-efficient value and therefore the ZTe value is enhanced for both the nanowires. The strained PdP2 and PdAs2 NWs show ZTe values of 4.75 and 5.49, respectively. Our study stimulates the feasibility of both nanowires and thermoelectric applications for the conversion of waste heat into electricity.
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23.
  • Bouziani, I., et al. (författare)
  • Two-dimensional Janus Sn2SSe and SnGeS2 semiconductors as strong absorber candidates for photovoltaic solar cells : First principles computations
  • 2021
  • Ingår i: Physica. E, Low-Dimensional systems and nanostructures. - : Elsevier. - 1386-9477 .- 1873-1759. ; 134
  • Tidskriftsartikel (refereegranskat)abstract
    • Two-dimensional materials provide new opportunities for the next generation of effective and ultrathin photovoltaic solar cells. Herein, we propose Janus monolayers of Tin monochalcogenides, especially Janus Sn2SSe (type TA) and SnGeS2 (type TB) nanosheets, as strong absorber candidates for solar energy conversion, referring to their excellent electronic and optical properties. Interestingly, based on the first-principles computations, both Janus Sn2SSe and SnGeS2 monolayers possess semiconductor character with indirect and moderate band gaps of 1.60 and 1.61 eV, respectively. Accordingly, the considered systems, Sn2SSe and SnGeS2 single-layers, have high absorption coefficient, reaching up to 49.7 and 62.5 mu m(-1), high optical conductivity of about 4513 and 3559 Omega(-1)cm(-1), as well as low reflectivity never exceed 34.6 and 38.5 % in visible region, respectively. Additionally, the maximum photovoltaic efficiency of single-junction solar cells based on SnGeS2 and Sn2SSe nanosheets can reach as high as 27.47 % and 28.12 %, respectively. The present outstanding results would motivate both theoretical and experimental researchers to deepen the study of the potential applications of twodimensional Janus materials based on Tin monochalcogenides in solar cell technology.
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24.
  • Caron, Bénédicte, et al. (författare)
  • IOIBD Recommendations for Clinical Trials in Ulcerative Proctitis : the PROCTRIAL Consensus
  • 2022
  • Ingår i: Clinical Gastroenterology and Hepatology. - : Elsevier. - 1542-3565 .- 1542-7714. ; 20:11, s. 2169-2627.e1
  • Tidskriftsartikel (refereegranskat)abstract
    • BACKGROUND AND AIMS: Clinical trials evaluating biologics and small molecules in patients with ulcerative colitis are predominantly excluding ulcerative proctitis. The objective of the PROCTRIAL (Definition and endpoints for ulcerative PROCtitis in clinical TRIALs) initiative was to develop consensus statements for definitions, inclusion criteria, and endpoints for the evaluation of ulcerative proctitis in adults.METHODS: Thirty-five international experts held a consensus meeting to define ulcerative proctitis, and the endpoints to use in clinical trials. Based on a systematic review of the literature, statements were generated, discussed, and approved by the working group participants using a modified Delphi method. Consensus was defined as at least 75% agreement among voters.RESULTS: The group agreed that the diagnosis of ulcerative proctitis should be made by ileocolonoscopy and confirmed by histopathology, with the exclusion of infections, drug-induced causes, radiation, trauma, and Crohn's disease. Ulcerative proctitis was defined as macroscopic extent of lesions limited to 15 cm distance from the anal verge in adults. Primary and secondary endpoints were identified to capture response of ulcerative proctitis to therapy. A combined clinical and endoscopic primary endpoint for the evaluation of ulcerative proctitis disease activity is proposed. Secondary endpoints which should be evaluated include endoscopic remission, histological remission, mucosal healing, histologic endoscopic mucosal improvement, disability, fecal incontinence, urgency, constipation, and health-related quality of life.CONCLUSION: In response to the need for guidance on the design of clinical trials in patients with ulcerative proctitis, the PROCTRIAL consensus provides recommendations on the definition and endpoints for ulcerative proctitis clinical trials.
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25.
  • da Rocha, V. N., et al. (författare)
  • Electronic, mechanical, and optical properties of BP nanotubes : A first-principles study
  • 2023
  • Ingår i: COMPUTATIONAL CONDENSED MATTER. - : Elsevier. - 2352-2143. ; 34
  • Tidskriftsartikel (refereegranskat)abstract
    • The electronic, mechanical, and optical properties of (3,3), (5,5), (7,7) and (9,9) armchair and (4,0), (6,0), (8,0), (10,0) and (12,0) zigzag boron phosphide nanotubes (BPNT's) have been investigated using density functional theory calculations. We find that, with the exception of the (5,5) nanotube, they are direct band gap semiconductors, as the BP monolayer. The (3,3) and (4,0) nanotubes are verified to be unstable through phonon band structure calculations. The 1D stretching moduli and elastic moduli show that the BP NT's are as stiff as carbon nanotubes of comparable diameters. The absorption spectra of the BP nanotubes have thresholds in the visible region, differently from carbon and boron nitride nanotubes of comparable dimensions.
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26.
  • Da Silva, A. F., et al. (författare)
  • Electronic and optical properties of TiO2
  • 2005
  • Konferensbidrag (refereegranskat)abstract
    • The electronic and optical properties of the rutile titanium dioxide compound have been investigated experimentally by absorption measurements and theoretically by a full-potential linearized augmented plane wave (FPLAPW) method within the local density approximation (LDA). The thin films for the absorption measurements were prepared by DC magnetron sputtering. The theoretical results for the absorption compared qualitatively well with the experimental findings. The dielectric functions and band-structure have also been calculated, and the LDA band-gap energy is corrected by an on-site Coulomb potential.
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27.
  • da Silva, A. F., et al. (författare)
  • Electronic and optical properties of wurztzie and zinc-blende TlN and AlN
  • 2005
  • Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 281:1, s. 151-160
  • Tidskriftsartikel (refereegranskat)abstract
    • We present calculations of the band structure, density of states and the real and imaginary parts of the dielectric functions in intrinsic TIN and AlN, both for wurtzite and the zinc-blende polytypes. They are based on the local density approximation (LDA) within the density functional theory (DFT), employing the first-principles, full-potential linearized augmented plane wave (FPLAPW) method. We correct the band gap of the AlN by using a quasi-particle method proposed by Bechstedt and Del Sole. The calculated energy gaps, lattice constants and dielectric constants for AlN are in good agreement with available experimental values while for TIN there is no experimental investigation.
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28.
  • Da Silva, A. F., et al. (författare)
  • Linear optical response of Si1-xGex compounds
  • 2005
  • Ingår i: Quantum Sensing and Nanophotonic Devices II. - : SPIE - International Society for Optical Engineering. - 081945706X ; 5732:1, s. 556-564
  • Konferensbidrag (refereegranskat)abstract
    • Si1-xGex is a good candidate as a substitute material for Si in a low-power and high-speed semiconductor device technologies. Optical devices, such as heterojunction bipolar transistors, are already in industrial production. The samples are grown on Si(001) with both n-and p-type impurities and with different Ge concentrations. The linear optical response of Si 1-x Gex is investigated theoretically using a full-potential linearized augmented plane wave method with respect to composition x. The calculated real and imaginary parts of the dielectric function ε e(ω) = ε1(ω) + iε 2(ω) were found to be in good agreement with recent spectroscopic ellipsometry measurements performed by Bahng et al., J. Phys.: Condens. Matter 13, 777 (2001). We also perform absorption measurements for different type of samples showing the variation of energy gaps as a function of Ge concentrations.
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29.
  • Dantas, N. S., et al. (författare)
  • Novel semiconducting materials for optoelectronic applications : Al1-xTlxN alloys
  • 2008
  • Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 92:12
  • Tidskriftsartikel (refereegranskat)abstract
    • We proprose the ternary semiconducting Al1-xTlxN alloys as new material for optoelectronic applications. Ab initio calculations have been performed to study structural, electronic, and optical properties of the theoretically designed thallium-aluminum based nitride alloys. We found that the lattice constants vary linearly with thallium composition whereas the band gap and absorption edge span from ultraviolet to infrared energy region by increasing thallium content which make the predicted material interesting for infrared optical devices among other technological applications.
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30.
  • Das, Suman, et al. (författare)
  • Alloying in an Intercalation Host : Metal Titanium Niobates as Anodes for Rechargeable Alkali-Ion Batteries
  • 2018
  • Ingår i: Chemistry - An Asian Journal. - : Wiley-VCH Verlagsgesellschaft. - 1861-4728 .- 1861-471X. ; 13:3, s. 299-310
  • Tidskriftsartikel (refereegranskat)abstract
    • We discuss here a unique flexible non-carbonaceous layered host, namely, metal titanium niobates (M-Ti-niobate, M: Al3+, Pb2+, Sb3+, Ba2+, Mg2+), which can synergistically store both lithium ions and sodium ions via a simultaneous intercalation and alloying mechanisms. M-Ti-niobate is formed by ion exchange of the K+ ions, which are specifically located inside galleries between the layers formed by edge and corner sharing TiO6 and NbO6 octahedral units in the sol-gel synthesized potassium titanium niobate (KTiNbO5). Drastic volume changes (approximately 300-400%) typically associated with an alloying mechanism of storage are completely tackled chemically by the unique chemical composition and structure of the M-Ti-niobates. The free space between the adjustable Ti/Nb octahedral layers easily accommodates the volume changes. Due to the presence of an optimum amount of multivalent alloying metal ions (50-75% of total K+) in the M-Ti-niobate, an efficient alloying reaction takes place directly with ions and completely eliminates any form of mechanical degradation of the electroactive particles. The M-Ti-niobate can be cycled over a wide voltage range (as low as 0.01V) and displays remarkably stable Li+ and Na+ ion cyclability (>2 Li+/Na+ per formula unit) for widely varying current densities over few hundreds to thousands of successive cycles. The simultaneous intercalation and alloying storage mechanisms is also studied within the density functional theory (DFT) framework. DFT expectedly shows a very small variation in the volume of Al-titanium niobate following lithium alloying. Moreover, the theoretical investigations also conclusively support the occurrence of the alloying process of Li ions with the Al ions along with the intercalation process during discharge. The M-Ti-niobates studied here demonstrate a paradigm shift in chemical design of electrodes and will pave the way for the development of a multitude of improved electrodes for different battery chemistries.
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34.
  • Dubrovinskaia, N., et al. (författare)
  • Beating the miscibility barrier between iron group elements and magnesium by high-pressure alloying
  • 2005
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 95:24
  • Tidskriftsartikel (refereegranskat)abstract
    • Iron and magnesium are almost immiscible at ambient pressure. The low solubility of Mg in Fe is due to a very large size mismatch between the alloy components. However, the compressibility of Mg is much higher than that of Fe, and therefore the difference in atomic sizes between elements decreases dramatically with pressure. Based on the predictions of ab initio calculations, we demonstrate in a series of experiments in a multianvil apparatus and in electrically and laser-heated diamond anvil cells that high pressure promotes solubility of magnesium in iron. At the megabar pressure range, more than 10 at. % of Mg can dissolve in Fe and then the alloy can be quenched to ambient conditions. A generality of the concept of high-pressure alloying between immiscible elements is demonstrated by its application to two other Fe group elements, Co and Ni.
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35.
  • Dubrovinsky, L., et al. (författare)
  • Noblest of all metals is structurally unstable at high pressure
  • 2007
  • Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 98:4
  • Tidskriftsartikel (refereegranskat)abstract
    • In a series of experiments in externally electrically heated diamond anvil cells we demonstrate that at pressures above similar to 240 GPa gold adopts a hexagonal-close-packed structure. Ab initio calculations predict that at pressures about 250 GPa different stacking sequences of close-packed atomic layers in gold become virtually degenerate in energy, strongly supporting the experimental observations.
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40.
  • Gerkin, Richard C., et al. (författare)
  • Recent Smell Loss Is the Best Predictor of COVID-19 Among Individuals With Recent Respiratory Symptoms
  • 2021
  • Ingår i: Chemical Senses. - : Oxford University Press (OUP). - 0379-864X .- 1464-3553. ; 46
  • Tidskriftsartikel (refereegranskat)abstract
    • In a preregistered, cross-sectional study, we investigated whether olfactory loss is a reliable predictor of COVID-19 using a crowdsourced questionnaire in 23 languages to assess symptoms in individuals self-reporting recent respiratory illness. We quantified changes in chemosensory abilities during the course of the respiratory illness using 0–100 visual analog scales (VAS) for participants reporting a positive (C19+; n = 4148) or negative (C19−; n = 546) COVID-19 laboratory test outcome. Logistic regression models identified univariate and multivariate predictors of COVID-19 status and post-COVID-19 olfactory recovery. Both C19+ and C19− groups exhibited smell loss, but it was significantly larger in C19+ participants (mean ± SD, C19+: −82.5 ± 27.2 points; C19−: −59.8 ± 37.7). Smell loss during illness was the best predictor of COVID-19 in both univariate and multivariate models (ROC AUC = 0.72). Additional variables provide negligible model improvement. VAS ratings of smell loss were more predictive than binary chemosensory yes/no-questions or other cardinal symptoms (e.g., fever). Olfactory recovery within 40 days of respiratory symptom onset was reported for ~50% of participants and was best predicted by time since respiratory symptom onset. We find that quantified smell loss is the best predictor of COVID-19 amongst those with symptoms of respiratory illness. To aid clinicians and contact tracers in identifying individuals with a high likelihood of having COVID-19, we propose a novel 0–10 scale to screen for recent olfactory loss, the ODoR-19. We find that numeric ratings ≤2 indicate high odds of symptomatic COVID-19 (4 < OR < 10). Once independently validated, this tool could be deployed when viral lab tests are impractical or unavailable.
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42.
  • Jayakumar, O. D., et al. (författare)
  • Experimental and theoretical investigations on magnetic behavior of (Al,Co) co-doped ZnO nanoparticles
  • 2010
  • Ingår i: Nanoscale. - : Royal Society of Chemistry (RSC). - 2040-3364 .- 2040-3372. ; 2:8, s. 1505-1511
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the structural and magnetic properties of Zn0.95-xCo0.05AlxO (x = 0.0 to 0.1) nanoparticles, synthesized by a novel sol-gel route followed by pyrolysis. Powder X-ray diffraction data confirms the formation of a single phase wurtzite type ZnO structure for all the compositions. The Zn0.95Co0.05O nanoparticles show diamagnetic behavior at room temperature. However, when Al is co-doped with Co with x = 0.0 to 0.10 in Zn0.95-xCo0.05AlxO, a systematic increase in ferromagnetic moment is observed up to x = 0.07 at 300 K. Above x = 0.07 (e.g. for x = 0.10) a drastic decrease in ferromagnetic nature is observed which is concomitant with the segregation of poorly crystalline Al rich ZnO phase as evidenced from TEM studies. Theoretical studies using density functional calculations on Zn0.95-xCo0.05AlxO suggest that the partial occupancy of S2 states leads to an increased double exchange interaction favoring the ferromagnetic ground states. Such ferromagnetic interactions are favorable beyond a threshold limit. At a high level doping of Al, the exchange splitting is reduced, which suppresses the ferromagnetic ordering.
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44.
  • Lakhani, Krupa, et al. (författare)
  • Dissociation of air pollutants on the uniform surface of pentagonal BeP2
  • 2021
  • Ingår i: Applied Surface Science. - : Elsevier. - 0169-4332 .- 1873-5584. ; 570
  • Tidskriftsartikel (refereegranskat)abstract
    • In this present work, the investigation was carried out using density functional theory (DFT) for the dissociation of noxious gas molecules such as carbon and nitrogen-based molecules (CO, CO2, N-2, NH3, NO, and NO2) on a pentagonal two-dimensional beryllium diphosphide (BeP2). The pentagonal BeP2 monolayer has a similar band structure as graphene. Here, some carbon and nitrogen-based noxious gases such as CO, CO2, N-2, NH3, NO, and NO2 with Van der Waals (vdW) interaction behave like physisorbed, while strong covalent (Be-O) interactions of O-2 on BeP2 formed chemisorption. Due to the chemisorption of O-2 gas molecules, the bandgap at Dirac point at P-site on BeP2 opens. While CO, CO2, N-2, NO, and NO2 are dissociated at the C-site, only CO, N-2, and NO are dissociated at the P-site. Beryllium diphosphide's band-gap shifts resulting from interactions with CO, N-2, and O-2 molecules are just 6%, 12.1%, and 22.2%, respectively, meaning that the BeP2 material has a moderate and high sensitivity towards CO, N-2, and O-2 molecules. BeP2 appears to be a potential catalyst for the dissociation of CO, CO2, N-2, NO, NO2, and O-2 gas molecules, which is even more interesting.
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45.
  • Lee, Jae-chul, et al. (författare)
  • Se concentration dependent band gap engineering in ZnO1-xSex thin film for optoelectronic applications
  • 2014
  • Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 585, s. 94-97
  • Tidskriftsartikel (refereegranskat)abstract
    • ZnO1-xSex films with various selenium concentrations are deposited on the sapphire substrate (0001) by pulsed laser deposition technique. Structural properties of the thin films studied by X-ray diffraction (XRD) and chemical bonding studied by X-ray photoelectron spectroscopy (XPS) reveals that Se is substituted in O site during the growth of ZnO1-xSex films. Optical properties are analyzed by UV-Visible spectrometer. From the plot for (alpha h upsilon)(2) vs photon energy, it is inferred that the band gap energy of ZnO1-xSex gradually reduces to 2.85 eV with increasing Se concentration.
  •  
46.
  • Mattesini, M., et al. (författare)
  • Cubic TiO2 as a potential light absorber in solar-energy conversion
  • 2004
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 70:11
  • Tidskriftsartikel (refereegranskat)abstract
    • Materials are currently sought for use in the photo-induced decomposition of water on crystalline electrodes. Titanium dioxide is valuable in this respect. The electronic structural properties of cubic TiO2 polymorphs were investigated by means of first-principles methods. We demonstrate that both fluorite- and pyrite-type TiO2 have important optical absorptive transitions in the region of the visible light. A cubic TiO2 phase that can efficiently absorb the sunlight would be an important candidate material for the development of the solar cells. Also, we present results on the Ti L edges for the two different titania forms. We predict that a qualitative spectroscopic discrimination of the cubic polymorphs can be achieved by following the Ti 2p → 3d x-ray transitions.
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47.
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48.
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49.
  • Mikhaylushkin, A. S., et al. (författare)
  • Structural and magnetic properties of FeHx (x=0.25; 0.50; 0.75)
  • 2006
  • Ingår i: AIP Conf. Proc.. - : AIP. - 0735403295 - 9780735403291 ; , s. 161-167
  • Konferensbidrag (refereegranskat)abstract
    • The structural and magnetic properties of the FeHx (x=0.25; 0.50; 0.75) compounds have been studied using the projector augmented wave (PAW) method within the generalized gradient approximation (GGA). We compare the hcp, dhcp and fcc structures and find that for the considered concentrations of hydrogen the hcp structure is most stable in a wide pressure range. The magnetic behavior of iron is crucially influenced by hydrogen. In particular, the local moment on a Fe atom depends on the number of hydrogen atoms in the atom surroundings. Iron atoms, which are crystallographically equivalent in their original structures (hcp, fcc) but have different number of hydrogen neighbors, are shown to have different local magnetic moments. This finding suggests that the experimental observations of two magnetic moments in iron hydride can be explained by nonstoichiometry of the hydride and might not be a direct evidence for the presence of the dhcp phase.
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50.
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