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1.
Phys Rev Lett ; 132(17): 171001, 2024 Apr 26.
Artigo em Inglês | MEDLINE | ID: mdl-38728703

RESUMO

Recently a dark matter-electron (DM-electron) paradigm has drawn much attention. Models beyond the standard halo model describing DM accelerated by high energy celestial bodies are under intense examination as well. In this Letter, a velocity components analysis (VCA) method dedicated to swift analysis of accelerated DM-electron interactions via semiconductor detectors is proposed and the first HPGe detector-based accelerated DM-electron analysis is realized. Utilizing the method, the first germanium based constraint on sub-GeV solar reflected DM-electron interaction is presented with the 205.4 kg·day dataset from the CDEX-10 experiment. In the heavy mediator scenario, our result excels in the mass range of 5-15 keV/c^{2}, achieving a 3 orders of magnitude improvement comparing with previous semiconductor experiments. In the light mediator scenario, the strongest laboratory constraint for DM lighter than 0.1 MeV/c^{2} is presented. The result proves the feasibility and demonstrates the vast potential of the VCA technique in future accelerated DM-electron analyses with semiconductor detectors.

2.
Niger J Clin Pract ; 27(4): 448-454, 2024 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-38679766

RESUMO

BACKGROUND: Root coverage procedures are very technique sensitive and require patients' compliance for successful treatment outcomes. Post operative complications can influence patients' acceptance of treatment and compromise further periodontal maintenance. AIM: The aim of this study was to evaluate the frequency and severity of complications after a modified coronally advanced flap procedure. METHODS AND MATERIALS: A total of 78 modified coronally advanced flap procedures were performed in 42 patients for root coverage. Duration of surgical procedure, history of smoking, gender, and age were recorded for each patient. A questionnaire was given to every patient to fill in at first post operative week regarding their experience of postoperative pain, swelling, and bleeding. RESULTS: Pain and duration of surgery had a correlation (OR: 1.05, P < 0.05). Post operative bleeding was significantly correlated with duration of surgery (OR: 1.03, P < 0.05). Current smokers experienced post operative swelling (P < 0.05). However, post operative pain in current smokers was not significantly different (P > 0.05) as compared to nonsmokers. Descriptive statistics were expressed as mean and standard deviations. Odd's ratio was obtained to evaluate risk indicators for moderate to severe types of complications. P < 0.05 was considered as significant. CONCLUSIONS: The duration of the surgery, long duration, and the presence of smoking can increase the frequency and severity of post operative complications.


Assuntos
Complicações Pós-Operatórias , Retalhos Cirúrgicos , Humanos , Masculino , Feminino , Estudos Prospectivos , Adulto , Complicações Pós-Operatórias/epidemiologia , Pessoa de Meia-Idade , Dor Pós-Operatória/epidemiologia , Adulto Jovem , Raiz Dentária/cirurgia , Inquéritos e Questionários , Retração Gengival/cirurgia , Fumar/efeitos adversos , Fumar/epidemiologia , Resultado do Tratamento
3.
Sci Rep ; 14(1): 4828, 2024 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-38413650

RESUMO

The agroforestry system is the best option to achieve the net zero carbon emissions target for India. Keeping this view, carbon sequestration and credit potential of gamhar based agroforestry system has been assessed. The experiment was carried out in randomized block design in seven different treatments with five replications. Gamhar tree biomass accumulation was higher in gamhar based agroforestry system compared to sole gamhar. Among different tree components, stem contributed a maximum to total gamhar tree biomass followed by roots, leaves and branches. The average contributions of stems, roots, leaves and branches in total tree biomass in two annual cycles (2016-17 and 2017-18) varied between 50 and 60, 19.8 and 20, 19.2 and 20, and 10.7 and 12.7 percent, respectively. In case of crops, above ground, below ground and total biomass was significantly higher in sole intercrops than gamhar based agroforestry system. Total (Tree + interrops + Soil) carbon stock, carbon sequestration, carbon credit and carbon price were significantly affected by treatments, and was maximum in Sole Greengram-Mustard. Net carbon emission was also recorded lowest in Sole Greengram-Mustard for which the values were 811.55% and 725.24% and 760.69% lower than Sole Gamhar in 2016-17, 2017-18 and in pooled data, respectively.


Assuntos
Sequestro de Carbono , Carbono , Árvores , Solo , Biomassa
4.
J Postgrad Med ; 70(1): 53-55, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38197335

RESUMO

Raw area on the breast, especially when it is lactating, can lead to complications, including hyperprolactinemia and development of milk fistulae. A 25-year-old female presented with raw area over the left breast after 2 months of childbirth. She had history suggestive of necrotizing disease, which had primarily been managed elsewhere with debridement and dressings. We excised the raw area and applied split thickness skin grafts with minimal meshing. Bulky dressing prevented breastfeeding. On postoperative day 3, there were blebs containing milk underneath the graft. The blebs were drained and oral cabergoline was administered for 3 months. The skin graft healed well. If expression of breast milk is not possible then suppression of lactation should be considered before definitive cover of the raw area of breast.


Assuntos
Lactação , Transplante de Pele , Feminino , Humanos , Adulto , Leite Humano , Aleitamento Materno , Bandagens
5.
Phys Rev Lett ; 129(22): 221802, 2022 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-36493447

RESUMO

A search for exotic dark matter (DM) in the sub-GeV mass range has been conducted using 205 kg day data taken from a p-type point contact germanium detector of the CDEX-10 experiment at China's Jinping underground laboratory. New low-mass dark matter searching channels, neutral current fermionic DM absorption (χ+A→ν+A) and DM-nucleus 3→2 scattering (χ+χ+A→ϕ+A), have been analyzed with an energy threshold of 160 eVee. No significant signal was found; thus new limits on the DM-nucleon interaction cross section are set for both models at the sub-GeV DM mass region. A cross section limit for the fermionic DM absorption is set to be 2.5×10^{-46} cm^{2} (90% C.L.) at DM mass of 10 MeV/c^{2}. For the DM-nucleus 3→2 scattering scenario, limits are extended to DM mass of 5 and 14 MeV/c^{2} for the massless dark photon and bound DM final state, respectively.


Assuntos
Núcleo Celular , Fótons
6.
Clin Oncol (R Coll Radiol) ; 33(7): e315-e321, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33608206

RESUMO

AIMS: There is a lack of consensus regarding the management of post-chemotherapy residual mass in classical seminoma. The use of fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) may aid the detection of residual masses harbouring viable disease and help to tailor therapy. The aim of this study was to evaluate if PET-CT could identify patients who will benefit from locoregional radiotherapy. MATERIALS AND METHODS: This ethics-approved study included patients with advanced classical seminoma primarily treated with standard platinum-based first-line chemotherapy. Patients were either observed or given adjuvant radiotherapy based on the clinician's preference and followed up. For this study, patients were stratified into two groups based on FDG PET-CT residual nodal maximum standardised uptake value (SUVmax): low risk (SUVmax <3) and high risk (SUVmax ≥3). Further subgroup analysis was carried out for patients with residual nodal size ≥3 cm and SUVmax ≥3, and this was considered as the very high risk group. The diagnostic accuracy of FDG PET-CT was assessed and survival was compared between the different groups. RESULTS: Sixty-nine patients were included in the study: 48 patients were observed and 21 received radiotherapy. The low and high risk groups contained 50.7% and 49.3% of the patients, respectively. The very high risk subgroup had 24 patients. At a median follow-up of 44 months, locoregional failures in the radiotherapy and observation cohorts were 0% and 30% (P = 0.059) in the very high risk subgroup and 5.8% and 29.4% (P = 0.078) in the high risk group. The positive predictive value for the very high risk and high risk groups was 30% and 17.1%, respectively. The benefit of locoregional control failed to translate into overall survival benefit. CONCLUSION: A tailored, FDG PET-based risk-adapted treatment approach can refine the management of post-chemotherapy residual masses in seminoma. In this study, with the largest cohort of advanced seminoma patients treated with radiotherapy reported to date, radiotherapy seems to benefit patients with post-chemotherapy residual mass SUVmax ≥3.


Assuntos
Seminoma , Neoplasias Testiculares , Fluordesoxiglucose F18 , Humanos , Masculino , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Compostos Radiofarmacêuticos , Seminoma/diagnóstico por imagem , Seminoma/tratamento farmacológico , Seminoma/radioterapia , Neoplasias Testiculares/diagnóstico por imagem , Neoplasias Testiculares/tratamento farmacológico , Neoplasias Testiculares/radioterapia
7.
Chemistry ; 26(43): 9475-9480, 2020 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-32428256

RESUMO

The oxidation of cis-[Pt(NH3 )2 (OAc)2 ] with H2 O2 yields a mixture of two isomers: ctc-[Pt(NH3 )2 (OH)2 (OAc)2 ] and ctc-[Pt(NH3 )2 (OH)(OAc)(OH)(OAc)]. Following modification with 4-phenylbutyric (PhB) anhydride, two isomers were separated and characterized; the symmetric ctc-[Pt(NH3 )2 (PhB)2 (OAc)2 ] (1) and the nonsymmetric ctc-[Pt(NH3 )2 (PhB)(OAc)(PhB)(OAc)] (2). They differ in their log P values and despite having similar cellular uptake and similar DNA platination levels, the symmetric ctc-[Pt(NH3 )2 (OH)2 (OAc)2 ] is more than 4-fold more potent than the nonsymmetric isomer in a panel of 4 cancer cell lines.

8.
Sci Total Environ ; 726: 138600, 2020 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-32305771

RESUMO

Existing flood modeling studies over coastal catchments involving different combinations of model chain setup imparting complex information fails to entail the needs of policy or decision-makers. Thus, a comprehensive framework that pertains to the requirements of practitioners and provides more perspicuous flood hazard information is required. In this paper, a novel approach translating complex flood hazard information in the form of decision priority maps derived using a rational combination of models (physical and statistical) is elucidated at the finest administrative scale. The proposed methodology is illustrated over a highly flood-prone deltaic region in Mahanadi River Basin, India, to characterize impacts of climate change for a 1:100 years return period flood event under future conditions (2026-2055). The modeled flood events are further analyzed to capture the transformation dynamics of flood hazard classes (FHCs) in near-future, for prioritizing areas with greater hazard potential. Interestingly, the results capture a high transformation characteristic from low to high FHCs in agriculture-dominated areas, which are significantly greater than the areas experiencing flood hazard reduction. The results show a significant increase of 12.5% and 27.35% in areas with high FHCs under RCP4.5 and RCP8.5 scenarios, respectively. Moreover, a notable climate change response is indicated under both climate change scenarios, with approximately 22% (RCP4.5) and 25% (RCP8.5) in villages showing a drastic increment in flood hazard magnitude. The results thus highlight the importance of identifying and prioritizing the areas for flood adaptation where a relative change in flood hazard potential is higher due to climate change. Therefore, we conclude that this study can provide an insight into the implication of new approaches for effective communication of flood information by bridging the gaps between scientific communities and decision-makers in appraisal for better flood adaptation measures.

9.
J Phys Condens Matter ; 31(24): 245701, 2019 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-30708359

RESUMO

The inverse spinel nickel aluminate micro-particles was successfully synthesized via solid-state synthesis techniques. The single phase cubic structure with space group Fd3m of the as-prepared sample was entrenched from Rietveld refinement of x-ray diffraction pattern. In addition, the photoluminescence (PL) and FTIR spectra were also performed to give strong evidence of its pure phase formation. The narrow hysteresis m-h loop and UV-DRS spectra at room temperature demonstrate its weak ferromagnetic and semiconducting nature with saturation magnetization 64.96 × 10-3 emu gm-1 and direct optical band gap 2.03 eV respectively. The high-resolution FESEM micrographs and EDS elemental analysis exhibit its grain growth in µm range (217 µm) and presence of elemental compound Ni, Al and O respectively. The electrical transport properties were accomplished by complex impedance spectroscopy as a function of frequency (100 Hz-1 MHz) with the evolution of high temperature (300 °C-500 °C). The Nyquist plots (Z″ versus Z') were well fitted with an equivalent circuit model (QR) (QR) consisting of a series combination of intra and inter-granular contribution. Furthermore, the imaginary modulus spectra were also fitted with Kohlrausch-Williams-Watts (KWW) function, which represents two thermally activated peaks of grain and grain boundary effects. The low-frequency dispersive ac conductivity was elucidated using the following equation: [Formula: see text]. The increasing nature of temperature dependent frequency exponent (n) suggests the quantum mechanical tunneling: non-overlapping small polaron tunneling (NSPT) concept for conduction mechanism. In low-frequency region, the lattice and charge carrier polarization simultaneously contribute in dielectric permittivity.

10.
Eur Arch Paediatr Dent ; 20(4): 377-381, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30536193

RESUMO

AIM: To analyse the effect of colours on children's emotions and variations in anxiety levels using six different coloured attires, white, pink, yellow, green, purple and black. METHODS: Seventy-two children aged between 5-9 years old who had come for restorative treatment in the Department of Paediatric and Preventive Dentistry, I.T.S. Dental College, Muradnagar, Ghaziabad, India were chosen and divided according to Corah's dental anxiety scale into 4 levels of anxiety. Eighteen children from each level were then assigned six different colours (3 children for each colour). A two factor study was conducted to determine the influence of colours, anxiety levels or facial expressions on oxygen saturation levels and pulse rate of the children. Data was analysed using SPSS 16.0 for ANOVA. RESULTS: There was significant difference between colours influencing oxygen saturation levels (p = 0.001) and pulse rate (p = 0.038). A post-hoc test indicated that black colour was significantly different from most of the other colours. No interaction effect was found to exist between colours and facial expression. CONCLUSIONS: Data suggested that yellow, pink and purple colours may have reduced anxiety among children whereas black colour could have enhanced it.


Assuntos
Ansiedade ao Tratamento Odontológico , Emoções , Criança , Pré-Escolar , Cor , Humanos , Índia , Projetos Piloto
11.
J Appl Microbiol ; 125(1): 190-202, 2018 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-29573511

RESUMO

AIMS: A novel approach was employed to study the growth of three cyanobacterial strains namely Oscillatoria sp. (AP17), Leptolyngbya sp. (AP3b) and Chroococcus sp. (AP3U). Furthermore, their broad metabolite profile, production of pigments, exopolysaccharide (EPS) and antimicrobial activity were evaluated in response to contrasting cultivation modes: biofilm or planktonic. METHODS AND RESULTS: The biofilm culture mode was carried out in the patented conico-cylindrical flask (CCF) and the planktonic culture mode was carried out in an Erlenmeyer flask (EF). The amount of polysaccharide that was released and that remained capsular/bound was higher in CCF compared to EF cultivation. Amount of chlorophyll a produced by Oscillatoria (AP17) was higher in the CCF compared to the EF cultivation. Highest antimicrobial activities were exhibited by Leptolyngbya (AP3b) biofilm than other biofilms as well as planktonic biomass. Metabolite profiles of Cyanobacteria were revealed by various chromatographic techniques and showed clear differences among the two contrasting modes of cultivation. CONCLUSIONS: The results showed clear differences in the mode of growth for achieving maximum chlorophyll a, EPS and bioactive metabolite production of the Cyanobacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study augmented the information which can enhance wider exploration of the biofilm mode of cultivation of Cyanobacteria.


Assuntos
Biofilmes/crescimento & desenvolvimento , Reatores Biológicos/microbiologia , Cianobactérias , Plâncton , Técnicas de Cultura de Células/instrumentação , Cianobactérias/crescimento & desenvolvimento , Cianobactérias/metabolismo , Plâncton/crescimento & desenvolvimento , Plâncton/metabolismo , Áreas Alagadas
12.
New Microbes New Infect ; 21: 72-74, 2018 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-29234496

RESUMO

Cholera toxin (CT) is the principal virulence factor of Vibrio cholerae for fatal cholera diarrhoea. Serogroups O1 and O139 harbour CT and are known to be epidemic strains. The remaining serogroups (nonO1/nonO139) are non-toxigenic and may be associated with mild disease. O1 serogroup emerged with a variant of CT known as Haitian cholera toxin (HCT). The HCT strains are hypervirulent and have been associated with severe cholera outbreaks in India, Western Africa and Haiti. Here, we report the presence of HCT (ctxB7) in a nonO1/nonO139 isolate causing persistent diarrhoea.

14.
Scand J Rheumatol ; 45(5): 379-83, 2016 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26982203

RESUMO

OBJECTIVES: Inflammation in diseases such as rheumatoid arthritis (RA) stimulates osteoclast-mediated articular bone erosion and inhibits osteoblast-mediated bone formation, leading to a net loss of bone. Pro-inflammatory cytokines and antagonists of the Wnt signalling pathway have been implicated in the inhibition of osteoblast differentiation and activity in RA, contributing to the erosive process and impairing erosion healing. Importantly, osteoblast differentiation and function are also regulated by the osteogenic bone morphogenetic protein (BMP) signalling pathway, which is antagonized by BMP3. We therefore examined the potential role of BMP3 in inflammatory arthritis. METHOD: Two murine models of RA, K/BxN serum transfer arthritis (STA) and antigen-induced arthritis (AIA), were used to establish the temporal expression of BMP3 and the cellular sources of BMP3 mRNA and protein in inflammatory arthritis. To determine the effects of inflammation on the expression of BMP3 in osteoblasts, murine calvarial osteoblasts were treated with pro-inflammatory cytokines and BMP3 expression was assessed. RESULTS: In both murine models of RA, BMP3 mRNA and protein are highly expressed by osteoblasts lining inflammation-bone interfaces late in the course of arthritis. Synovial tissues are not a significant source of BMP3. BMP3 expression is induced in osteocalcin-expressing osteoblasts in vitro following stimulation by tumour necrosis factor (TNF). CONCLUSIONS: These data implicate BMP3 as a novel factor that may act locally to contribute to the erosive process and inhibit the repair of articular bone in RA through inhibition of osteoblast differentiation and function.


Assuntos
Artrite Experimental/genética , Proteína Morfogenética Óssea 3/genética , Osteoblastos/metabolismo , RNA Mensageiro/metabolismo , Animais , Artrite Experimental/metabolismo , Western Blotting , Proteína Morfogenética Óssea 3/metabolismo , Técnicas In Vitro , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Osteoblastos/efeitos dos fármacos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Crânio/citologia , Fator de Necrose Tumoral alfa/farmacologia
15.
Nanotechnology ; 27(13): 135101, 2016 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-26894508

RESUMO

We present a unique way to detect base-pair mismatches in DNA, leading to a different epigenetic disorder by the method of nanopore sequencing. Based on a tight-binding formulation of a graphene-based nanopore device, using the Green's function approach we study the changes in the electronic transport properties of the device as we translocate a double-stranded DNA through the nanopore embedded in a zigzag graphene nanoribbon. In the present work we are not only successful in detecting the usual AT and GC pairs but also a set of possible mismatches in the complementary base pairing.


Assuntos
Pareamento Incorreto de Bases , Grafite/química , Análise de Sequência de DNA/instrumentação , Algoritmos , Pareamento de Bases , DNA/análise , Epigênese Genética , Nanoporos
16.
Oncogene ; 35(31): 4112-21, 2016 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-26751774

RESUMO

MUC5AC is a secretory mucin aberrantly expressed in various cancers. In lung cancer, MUC5AC is overexpressed in both primary and metastatic lesions; however, its functional role is not well understood. The present study was aimed at evaluating mechanistic role of MUC5AC on metastasis of lung cancer cells. Clinically, the overexpression of MUC5AC was observed in lung cancer patient tissues and was associated with poor survival. In addition, the overexpression of Muc5ac was also observed in genetically engineered mouse lung adenocarcinoma tissues (Kras(G12D); Trp53(R172H/+); AdCre) in comparison with normal lung tissues. Our functional studies showed that MUC5AC knockdown resulted in significantly decreased migration in two lung cancer cell lines (A549 and H1437) as compared with scramble cells. Expression of integrins (α5, ß1, ß3, ß4 and ß5) was decreased in MUC5AC knockdown cells. As both integrins and MUC5AC have a von Willebrand factor domain, we assessed for possible interaction of MUC5AC and integrins in lung cancer cells. MUC5AC strongly interacted only with integrin ß4. The co-localization of MUC5AC and integrin ß4 was observed both in A549 lung cancer cells as well as genetically engineered mouse adenocarcinoma tissues. Activated integrins recruit focal adhesion kinase (FAK) that mediates metastatic downstream signaling pathways. Phosphorylation of FAK (Y397) was decreased in MUC5AC knockdown cells. MUC5AC/integrin ß4/FAK-mediated lung cancer cell migration was confirmed through experiments utilizing a phosphorylation (Y397)-specific FAK inhibitor. In conclusion, overexpression of MUC5AC is a poor prognostic marker in lung cancer. MUC5AC interacts with integrin ß4 that mediates phosphorylation of FAK at Y397 leading to lung cancer cell migration.


Assuntos
Proteína-Tirosina Quinases de Adesão Focal/fisiologia , Integrina beta4/fisiologia , Neoplasias Pulmonares/patologia , Mucina-5AC/fisiologia , Transdução de Sinais/fisiologia , Animais , Linhagem Celular Tumoral , Movimento Celular , Proliferação de Células , Cisplatino/uso terapêutico , Resistencia a Medicamentos Antineoplásicos , Humanos , Integrina beta4/análise , Masculino , Camundongos , Mucina-5AC/análise , Fosforilação
17.
Biochim Biophys Acta ; 1860(1 Pt B): 211-21, 2016 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-26073614

RESUMO

BACKGROUND: α-Crystallin acts like a molecular chaperone by interacting with its substrate proteins and thus prevents their aggregation. It also interacts with various kinds of small molecules that affect its structure and function. SCOPE OF REVIEW: In this article we will present a review of work done with respect to the interaction of ATP, peptide generated from lens crystallin and other proteins and some bivalent metal ions with α-crystallin and discuss the role of these interactions on its structure and function and cataract formation. We will also discuss the interaction of some hydrophobic fluorescence probes and surface active agents with α-crystallin. MAJOR CONCLUSIONS: Small molecule interaction controls the structure and function of α-crystallin. ATP and Zn+2 stabilize its structure and enhance chaperone function. Therefore the depletion of these small molecules can be detrimental to maintenance of lens transparency. However, the accumulation of small peptides due to protease activity in the lens can also be harmful as the interaction of these peptides with α-crystallin and other crystallin proteins in the lens promotes aggregation and loss of lens transparency. The use of hydrophobic probe has led to a wealth of information regarding the location of substrate binding site and nature of chaperone-substrate interaction. Interaction of surface active agents with α-crystallin has helped us to understand the structural stability and oligomeric dissociation in α-crystallin. GENERAL SIGNIFICANCE: These interactions are very helpful in understanding the mechanistic details of the structural changes and chaperone function of α-crystallin. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.


Assuntos
Trifosfato de Adenosina/química , Metais/química , Peptídeos/química , Tensoativos/química , alfa-Cristalinas/química , alfa-Cristalinas/ultraestrutura , Sítios de Ligação , Interações Hidrofóbicas e Hidrofílicas , Modelos Químicos , Ligação Proteica , Conformação Proteica , Relação Estrutura-Atividade
18.
J Phys Condens Matter ; 28(1): 015602, 2016 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-26656791

RESUMO

We report the high-pressure vibrational properties and a pressure-induced electronic topological transition in the wide bandgap semiconductor Sb2S3 (E g = 1.7-1.8 eV) using Raman spectroscopy, resistivity and x-ray diffraction (XRD) studies. In this report, high-pressure Raman spectroscopy and resistivity studies of Sb2S3 have been carried out to 22 GPa and 11 GPa, respectively. We observed the softening of phonon modes [Formula: see text], [Formula: see text] and B 2g and a sharp anomaly in their line widths at 4 GPa. The resistivity studies corroborate this anomaly around similar pressures. The changes in resistivity as well as Raman line widths can be ascribed to the strong phonon-phonon coupling, indicating clear evidence of isostructural electronic topological transition in Sb2S3. The previously reported pressure dependence of a/c ratio plot obtained also showed a minimum at ~5 GPa consistent with our high-pressure Raman and resistivity results.

19.
Phys Rev Lett ; 114(16): 166402, 2015 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-25955060

RESUMO

The electrical and optical properties of the Mott insulator Sr2VO4 are investigated under high pressure on a phase pure polycrystalline sample. The system undergoes a pressure-driven insulator to metal transition (IMT) with a crossover between 20 and 24 GPa. The effect of pressure on the thermally driven electronic changes resulting from spin-orbital ordering transitions is studied. A multiorbital analysis of the low frequency optical conductivity spectra suggests a bandwidth-controlled and orbital selective nature of the Mott IMT transition. Dramatic enhancement of the low energy spectral weight in the high pressure correlated metallic phase is explained in terms of the formation of a quasiparticle peak in the spectral function of the narrow and degenerate d(yz,zx) orbitals. Our results overall establish a novel electronic phase diagram of tetragonal Sr2VO4.

20.
Artigo em Inglês | MEDLINE | ID: mdl-24730886

RESUMO

In this work we propose a model for the DNA double helix within the tight-binding framework that incorporates the helicity of the molecules. We have studied the localization properties of three DNA sequences, the periodic poly(dG)-poly(dC) and poly(dA)-poly(dT) sequences and the random ATGC sequence (where A is adenine, T is thymine, G is guanine, and C is cytosine), all of which are coupled to the backbone with random site energies representing the environmental fluctuations. We observe that due to the helicity of DNA, electron transport is greatly enhanced and there exists an almost disorder-strength-independent critical value of the hopping integral, which accounts for the helicity of DNA, for which the electronic states become maximally extended. We have also investigated the effect of backbone energetics on the transmission and I-V characteristics of DNA.


Assuntos
DNA/química , DNA/ultraestrutura , Modelos Químicos , Modelos Moleculares , Simulação por Computador , Impedância Elétrica , Transporte de Elétrons , Conformação de Ácido Nucleico , Eletricidade Estática
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