Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 531
Filtrar
2.
Nanoscale Adv ; 5(24): 6944-6957, 2023 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-38059027

RESUMO

The current article presents a huge enhancement in the field emission characteristics of zinc oxide (ZnO) micro/nanorods by nickel doping. The synthesis of pure and nickel-doped zinc oxide (ZnO) micro/nanorods was done by a simple low-temperature chemical method. Both the as-prepared pure and doped samples were analyzed by X-ray diffraction and electron microscopy to confirm the proper phase formation and the developed microstructure. UV-vis transmittance spectra helped in determining the band gap of the samples. Fourier-Transform Infrared Spectroscopy (FTIR) spectra showed the different bonds present in the sample, whereas X-ray Photoelectron Spectroscopy (XPS) confirmed the presence of nickel in the doped sample. Photoluminescence (PL) spectra showed that after doping, the band-to-band transition was affected, whereas defect-induced transition had increased significantly. After the nickel doping, contact angle measurement revealed a significant decrease in the sample's surface energy, leading to a remarkably high water contact angle (within the superhydrophobic region). Simulation through ANSYS suggested that the doped sample has the potential to function as an efficient cold emitter, which was also verified experimentally. The cold emission characteristics of the doped sample showed a significant improvement, with the turn-on field (corresponding to J = 1 µA cm-2) reduced from 5.34 to 2.84 V µm-1. The enhancement factor for the doped sample reached 3426, approximately 1.5 times higher compared to pure ZnO. Efforts have been made to explain the results, given the favorable band bending as well as the increased number of effective emission sites.

3.
Phys Rev Lett ; 131(16): 161801, 2023 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-37925688

RESUMO

Thermal dark matter models with particle χ masses below the electroweak scale can provide an explanation for the observed relic dark matter density. This would imply the existence of a new feeble interaction between the dark and ordinary matter. We report on a new search for the sub-GeV χ production through the interaction mediated by a new vector boson, called the dark photon A^{'}, in collisions of 100 GeV electrons with the active target of the NA64 experiment at the CERN SPS. With 9.37×10^{11} electrons on target collected during 2016-2022 runs NA64 probes for the first time the well-motivated region of parameter space of benchmark thermal scalar and fermionic dark matter models. No evidence for dark matter production has been found. This allows us to set the most sensitive limits on the A^{'} couplings to photons for masses m_{A^{'}}≲0.35 GeV, and to exclude scalar and Majorana dark matter with the χ-A^{'} coupling α_{D}≤0.1 for masses 0.001≲m_{χ}≲0.1 GeV and 3m_{χ}≤m_{A^{'}}.

4.
Phys Chem Chem Phys ; 25(32): 21479-21491, 2023 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-37539659

RESUMO

In recent times, ultra-thin films of hafnium oxide (HfO2) have shown ferroelectricity (FE) attributed to the orthorhombic (o) phase of HfO2 with space group Pca21. This polar o-phase could be stabilized in the doped thin film of the oxide. In the present work, both polar and non-polar o-phases of HfO2 could be stabilized in Gd-doped bulk polycrystalline HfO2. Rietveld analysis of XRD data shows that the relative population of o-phases in the presence of the monoclinic (m) phase of HfO2 increases with increasing Gd-content. The local environment around the host atom has been investigated by time differential perturbed angular correlation (TDPAC) spectroscopy, synchrotron based X-ray near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) measurements showed a reduction in grain size with increasing Gd-dopant indicating a solute drag effect. It could be established that the segregation of the Gd-dopant in the grain boundary is a thermodynamically favorable process and the solute drag effect plays an important role in nucleation of the o-phase in bulk HfO2. Stabilization of Gd in both Pbca and Pca21 phases of HfO2 was supported by defect formation energy calculations using density functional theory (DFT). The present study has important implications in future applications of HfO2 in ferroelectric devices and in understanding the role of dopants in stabilizing the o-phase of HfO2 in the bulk.

5.
Eur J Surg Oncol ; 49(10): 107004, 2023 10.
Artigo em Inglês | MEDLINE | ID: mdl-37573665

RESUMO

Disorders or differences of sexual development encompasses an important group of conditions that affects up to 1 in 5,000 live births. Many individuals living in the female gender includes Turner syndrome, congenital adrenal hyperplasia and conditions with 46XY karyotype such as gonadal dysgenesis (Swyer syndrome). Individuals are commenced on high dose oestrogen to initiate and maintain development of secondary sexual characteristics such as breasts which is paramount in them identifying in the female gender. We highlight the first case of a patient with Swyer syndrome who was treated with long term oestrogen therapy and later developed breast cancer. In individuals with gonadal dysgenesis, testicular malignancy is a recognised risk and is screened for. Prolonged exposure to exogenous and endogenous hormones can increase the risk of breast cancer however how much this risk increases in those taking high dose hormones is not documented in the literature. We aim to highlight the importance of breast cancer treatment and surgical reconstruction in this group and whether they should be considered for early breast cancer screening. CONCLUSION: It is imperative that triple assessment is undertaken in every patient with a breast lump, regardless of gender identification. Clinicians must not delay investigations in this patient group due to a misunderstanding of their condition. Those on long term hormone supplementation should be entered into the breast screening program at an earlier age with Magnetic Resonance Imaging surveillance. Careful consideration of post treatment endocrine therapy is required and under the care of the multi-disciplinary team.


Assuntos
Neoplasias da Mama , Disgenesia Gonadal 46 XY , Disgenesia Gonadal , Feminino , Humanos , Neoplasias da Mama/terapia , Estrogênios , Disgenesia Gonadal 46 XY/diagnóstico , Disgenesia Gonadal 46 XY/cirurgia , Desenvolvimento Sexual
6.
Phys Chem Chem Phys ; 24(46): 28271-28282, 2022 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-36382658

RESUMO

Manganese tungstate (MnWO4) has been widely studied over the past few years due to its outstanding magnetic, catalytic, and sensing features. However, the electrochemical properties of the morphology tuned MnWO4 nanoform is less explored in the literature. Herein, we report the synthesis of MnWO4 nanostructures of different aspect ratios by subtle tuning of the reaction temperature and reaction time. An immediate utility of the size-controlled nanostructures is their use as the electrode material for supercapacitors. The impact of various reaction parameters, namely the growth time and processing temperature, over the MnWO4 nanorods size was studied by different characterization techniques, such as X-ray diffraction, field emission scanning electron microscopy, and Raman spectroscopy. It was shown that all the samples showed considerably good charge-storage properties with the highest values of specific capacitance being 455.07 and 239.07 F g-1 at 2 mV s-1 and 1 A g-1, respectively. The corresponding sample further showed an appreciable capacitance retention of ∼94% even after 10 000 long charge-discharge cycles, indicating a high electrochemical stability of the electrode. Theoretical analysis using density functional theory predicted that the presence of electronic states near Fermi level and the enhanced quantum capacitance were the prime reasons behind the excellent charge-storage performance of the as-synthesized MnWO4.

7.
Phys Rev Lett ; 129(16): 161801, 2022 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-36306760

RESUMO

A search for a new Z^{'} gauge boson associated with (un)broken B-L symmetry in the keV-GeV mass range is carried out for the first time using the missing-energy technique in the NA64 experiment at the CERN SPS. From the analysis of the data with 3.22×10^{11} electrons on target collected during 2016-2021 runs, no signal events were found. This allows us to derive new constraints on the Z^{'}-e coupling strength, which, for the mass range 0.3≲m_{Z^{'}}≲100 MeV, are more stringent compared to those obtained from the neutrino-electron scattering data.

8.
BMC Nephrol ; 23(1): 9, 2022 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-34979961

RESUMO

People with type 1 and type 2 diabetes are at risk of developing progressive chronic kidney disease (CKD) and end-stage kidney failure. Hypertension is a major, reversible risk factor in people with diabetes for development of albuminuria, impaired kidney function, end-stage kidney disease and cardiovascular disease. Blood pressure control has been shown to be beneficial in people with diabetes in slowing progression of kidney disease and reducing cardiovascular events. However, randomised controlled trial evidence differs in type 1 and type 2 diabetes and different stages of CKD in terms of target blood pressure. Activation of the renin-angiotensin-aldosterone system (RAAS) is an important mechanism for the development and progression of CKD and cardiovascular disease. Randomised trials demonstrate that RAAS blockade is effective in preventing/ slowing progression of CKD and reducing cardiovascular events in people with type 1 and type 2 diabetes, albeit differently according to the stage of CKD. Emerging therapy with sodium glucose cotransporter-2 (SGLT-2) inhibitors, non-steroidal selective mineralocorticoid antagonists and endothelin-A receptor antagonists have been shown in randomised trials to lower blood pressure and further reduce the risk of progression of CKD and cardiovascular disease in people with type 2 diabetes. This guideline reviews the current evidence and makes recommendations about blood pressure control and the use of RAAS-blocking agents in different stages of CKD in people with both type 1 and type 2 diabetes.


Assuntos
Anti-Hipertensivos/uso terapêutico , Angiopatias Diabéticas/tratamento farmacológico , Nefropatias Diabéticas/tratamento farmacológico , Hipertensão/tratamento farmacológico , Sistema Renina-Angiotensina/efeitos dos fármacos , Adulto , Albuminúria , Monitorização Ambulatorial da Pressão Arterial , Diabetes Mellitus Tipo 1/complicações , Diabetes Mellitus Tipo 2/complicações , Angiopatias Diabéticas/fisiopatologia , Angiopatias Diabéticas/urina , Nefropatias Diabéticas/fisiopatologia , Nefropatias Diabéticas/urina , Humanos , Hipertensão/fisiopatologia , Hipertensão/urina , Cooperação do Paciente , Comportamento de Redução do Risco , Reino Unido
9.
Eur Phys J C Part Fields ; 81(10): 959, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34790033

RESUMO

We report the results of a search for a new vector boson ( A ' ) decaying into two dark matter particles χ 1 χ 2 of different mass. The heavier χ 2 particle subsequently decays to χ 1 and an off-shell Dark Photon A ' ∗ → e + e - . For a sufficiently large mass splitting, this model can explain in terms of new physics the recently confirmed discrepancy observed in the muon anomalous magnetic moment at Fermilab. Remarkably, it also predicts the observed yield of thermal dark matter relic abundance. A detailed Monte-Carlo simulation was used to determine the signal yield and detection efficiency for this channel in the NA64 setup. The results were obtained re-analyzing the previous NA64 searches for an invisible decay A ' → χ χ ¯ and axion-like or pseudo-scalar particles a → γ γ . With this method, we exclude a significant portion of the parameter space justifying the muon g-2 anomaly and being compatible with the observed dark matter relic density for A ' masses from 2 m e up to 390 MeV and mixing parameter ε between 3 × 10 - 5 and 2 × 10 - 2 .

10.
Phys Chem Chem Phys ; 23(30): 16258-16267, 2021 Aug 04.
Artigo em Inglês | MEDLINE | ID: mdl-34309608

RESUMO

The recent observation of ferroelectricity in ultra thin films of hafnium oxide (HfO2) has been attributed to the orthorhombic (o) phase of HfO2 with space group Pca21. Although this oxide is polymorphic in nature, this polar o-phase is known to be stabilized in the doped thin film oxide. The objective of the present experiment is to stabilize the o-phases in La doped bulk polycrystalline HfO2 and investigate their evolution with the doping concentration through Time Differential Perturbed Angular Correlation (TDPAC), X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) measurements. The present work reports the presence of both the polar Pca21 phase and the antipolar Pbca phase at different La-concentrations. Two o-phases of HfO2 with space groups Pca21 and Pbca, difficult to distinguish by other complimentary methods, could be unambiguously identified by utilizing the atomic scale sensitivity of the electric field gradient (EFG) embedded in TDPAC spectroscopy. The determination of the oxidation state and the local environment of La-atoms by XANES and EXAFS measurements illuminates the microscopic role of the dopant in stabilizing the o-phase. The "solute drag model" proposes a critical crystallite size for the nucleation of the o-phase in bulk HfO2 and explains the role of the La-dopant in stabilizing the o-phase. Thus the present study shows the possibility of stabilizing the polar o-phase and hence attaining ferroelectricity in bulk HfO2 to augment the scope of future application for this ferroelectric device.

11.
Phys Rev Lett ; 126(21): 211802, 2021 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-34114842

RESUMO

We performed a search for a new generic X boson, which could be a scalar (S), pseudoscalar (P), vector (V), or an axial vector (A) particle produced in the 100 GeV electron scattering off nuclei, e^{-}Z→e^{-}ZX, followed by its invisible decay in the NA64 experiment at CERN. No evidence for such a process was found in the full NA64 dataset of 2.84×10^{11} electrons on target. We place new bounds on the S, P, V, A coupling strengths to electrons, and set constraints on their contributions to the electron anomalous magnetic moment a_{e}, |Δa_{X}|≲10^{-15}-10^{-13} for the X mass region 1 MeV≲m_{X}≲1 GeV. These results are an order of magnitude more sensitive compared to the current accuracy on a_{e} from the electron g-2 experiments and recent high-precision determination of the fine structure constant.

12.
Eur Phys J C Part Fields ; 80(12): 1159, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33343226

RESUMO

Recently, the ATOMKI experiment has reported new evidence for the excess of e + e - events with a mass ∼ 17 MeV in the nuclear transitions of 4 He, that they previously observed in measurements with 8 Be. These observations could be explained by the existence of a new vector X 17 boson. So far, the search for the decay X 17 → e + e - with the NA64 experiment at the CERN SPS gave negative results. Here, we present a new technique that could be implemented in NA64 aiming to improve the sensitivity and to cover the remaining X 17 parameter space. If a signal-like event is detected, an unambiguous observation is achieved by reconstructing the invariant mass of the X 17 decay with the proposed method. To reach this goal an optimization of the X 17 production target, as well as an efficient and accurate reconstruction of two close decay tracks, is required. A dedicated analysis of the available experimental data making use of the trackers information is presented. This method provides independent confirmation of the NA64 published results [1], validating the tracking procedure. The detailed Monte Carlo study of the proposed setup and the background estimate show that the goal of the proposed search is feasible.

13.
Pain Res Manag ; 2020: 3284623, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33014213

RESUMO

Introduction: Pain is a universal human experience tied to an individual's health but difficult to understand. It is especially important in health emergencies. We performed a two-step quality improvement project to assess pain management by the SAMU ambulance service in Kigali, Rwanda, examining how pain is assessed and treated by ambulance staff to facilitate development of standardized guidelines of pain management in the prehospital setting, which did not exist at the time of the study. Materials and Methods: Deidentified ambulance service records from December 2012 to May 2016 were analyzed descriptively for patient demographics, emergency conditions, pain assessment, and medications given. Then, anonymized, semistructured interviews of ambulance staff were conducted until thematic saturation was achieved. Data were analyzed using a grounded theory approach. Results: SAMU managed 11,161 patients over the study period, of which 6,168 (55%) were documented as reporting pain and 5,010 (45%) received pain medications. Men had greater odds of receiving pain medications compared to women (OR = 3.8, 95% CI (3.5, 4.1), p < 0.01). Twenty interviews were conducted with SAMU staff. They indicated that patients communicate pain in different ways. They reported using informal ways to measure pain or a standardized granular numeric scale. The SAMU team reviewed these results and developed plans to modify practices. Conclusions: We reviewed the existing quality of pain management in the prehospital setting in Kigali, Rwanda, assessed the SAMU staff's perceptions of pain, and facilitated standardization of prehospital pain management through context-specific guidelines.


Assuntos
Serviços Médicos de Emergência/normas , Manejo da Dor/normas , Medição da Dor/normas , Dor/epidemiologia , Melhoria de Qualidade/normas , Adulto , Ambulâncias/normas , Estudos Transversais , Serviços Médicos de Emergência/métodos , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Dor/diagnóstico , Manejo da Dor/métodos , Medição da Dor/métodos , Ruanda/epidemiologia
14.
Phys Rev Lett ; 125(8): 081801, 2020 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-32909809

RESUMO

We carried out a model-independent search for light scalar (s) and pseudoscalar axionlike (a) particles that couple to two photons by using the high-energy CERN SPS H4 electron beam. The new particles, if they exist, could be produced through the Primakoff effect in interactions of hard bremsstrahlung photons generated by 100 GeV electrons in the NA64 active dump with virtual photons provided by the nuclei of the dump. The a(s) would penetrate the downstream HCAL module, serving as a shield, and would be observed either through their a(s)→γγ decay in the rest of the HCAL detector, or as events with a large missing energy if the a(s) decays downstream of the HCAL. This method allows for the probing of the a(s) parameter space, including those from generic axion models, inaccessible to previous experiments. No evidence of such processes has been found from the analysis of the data corresponding to 2.84×10^{11} electrons on target, allowing us to set new limits on the a(s)γγ-coupling strength for a(s) masses below 55 MeV.

15.
Indian Dermatol Online J ; 11(3): 387-390, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32695699

RESUMO

BACKGROUND AND AIMS: The risk of liver damage in psoriasis increases with increase in cumulative dose of methotrexate and guidelines suggest use of liver biopsy for risk mitigation. Recently, transient elastography (TE) has been used for detection of liver fibrosis. Most studies for TE are in hepatitis B and C patients. However, psoriasis patients have risk factors like metabolic syndrome which predisposes them to increased risk of liver damage due to methotrexate. This underlying liver disease may change the TE values in patients with psoriasis. The aim of this study is to determine utility of transient elastography in detection of liver fibrosis in patients with psoriasis. METHODS: 82 patients with chronic plaque psoriasis requiring systemic therapy or already on methotrexate were included in the study. Clinical examinationand biochemical investigations were conducted. Data were analysed using STATA 12.1 (Texas, USA). Univariate analysis using Chi-square and independent't-test' was carried out to evaluate the association between categorical variables and outcomes. RESULTS: Patients consists of 62 males and 20 females. TE value >7 kPa (kilopascal) were seen in 23 patients and <7 kPa were seen in 59 patients. Value of >7 kPa was significantly associated with age, waist circumference, diastolic blood pressure, fasting and post prandial blood sugar, AST, PASI and presence of metabolic syndrome. Cumulative methotrexate dose was not significantly associated with high TE value. Mean TE value in patients with metabolic syndrome was significantly higher. LIMITATIONS: Small sample size and inability to confirm TE findings on liver biopsy. CONCLUSION: TE is a non-invasive tool for detection of liver fibrosis. Value of >7 kPa correlates with liver fibrosis in most chronic liver diseases. However, high prevalence of metabolic syndrome in psoriasis patientsmayconfound utility of TE for monitoring of methotrexate toxicity.

16.
J Clin Microbiol ; 58(7)2020 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-32321780

RESUMO

Group A streptococcus (GAS) species cause bacterial pharyngitis in both adults and children. Early and accurate diagnosis of GAS is important for appropriate antibiotic therapy to prevent GAS sequalae. The Revogene Strep A molecular assay (Meridian Bioscience Canada Inc, Quebec City, QC, Canada) is an automated real-time PCR assay for GAS detection from throat swab specimens within approximately 70 min. This multicenter prospective study evaluated the performance of the Revogene Strep A molecular assay compared to that of bacterial culture. Dual throat swab specimens in either liquid Amies or Stuart medium were collected from eligible subjects (pediatric population and adults) enrolled across 7 sites (USA and Canada). Revogene Strep A and reference testing was performed within 7 days and 48 h of sample collection, respectively. Of the 604 evaluable specimens, GAS was detected in 154 (25.5%) samples by the reference method and in 175 (29%) samples by the Revogene Strep A assay. Revogene Strep A assay sensitivity and specificity were reported to be 98.1% (95% confidence interval [CI], 94.4 to 99.3) and 94.7% (95% CI, 92.2 to 96.4), respectively. The positive predictive value was 86.3% (95% CI, 80.4 to 90.6), negative predictive value was 99.3% (95% CI, 98.0 to 99.8) with a 1.0% invalid rate. Discrepant analysis with alternative PCR/bidirectional sequencing was performed for 24 false-positive (FP) and 3 false-negative (FN) specimens. Concordant results were reported for 17 (FP only) of 27 discordant specimens. The Revogene Strep A assay had high sensitivity and specificity for GAS detection and provides a faster alternative for GAS diagnosis.


Assuntos
Faringite , Infecções Estreptocócicas , Adulto , Canadá , Criança , Humanos , Faringite/diagnóstico , Faringe , Estudos Prospectivos , Quebeque , Sensibilidade e Especificidade , Infecções Estreptocócicas/diagnóstico , Streptococcus pyogenes/genética
18.
Phys Rev Lett ; 123(12): 121801, 2019 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-31633975

RESUMO

A search for sub-GeV dark matter production mediated by a new vector boson A^{'}, called a dark photon, is performed by the NA64 experiment in missing energy events from 100 GeV electron interactions in an active beam dump at the CERN SPS. From the analysis of the data collected in the years 2016, 2017, and 2018 with 2.84×10^{11} electrons on target no evidence of such a process has been found. The most stringent constraints on the A^{'} mixing strength with photons and the parameter space for the scalar and fermionic dark matter in the mass range ≲0.2 GeV are derived, thus demonstrating the power of the active beam dump approach for the dark matter search.

19.
Acute Med ; 18(2): 96-104, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31127798

RESUMO

Acute heart failure (HF) admissions are common. They are often associated with prolonged hospitalisations and poor outcomes. One-third of chronic HF patients also suffer from chronic kidney disease (CKD). Hence, acute admissions of HF with CKD are common and are associated with longer length of stay and increased mortality. Hyperkalaemia and acute on chronic renal impairment are important challenges in the management of these cases. Cautious introduction of high-dose diuretic therapy, followed by the re-commencement of renin-angiotensin-aldosterone (RAAS) inhibitors, improves length of stay, quality of life, and prognosis. During an admission on to the medical assessment unit careful monitoring and management of the patient's clinical condition and biochemistry is essential.


Assuntos
Insuficiência Cardíaca , Qualidade de Vida , Insuficiência Renal Crônica , Insuficiência Cardíaca/complicações , Insuficiência Cardíaca/terapia , Hospitalização , Humanos , Prognóstico , Insuficiência Renal Crônica/complicações , Insuficiência Renal Crônica/terapia
20.
J Chem Phys ; 150(12): 124903, 2019 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-30927892

RESUMO

Assembly of spherical colloidal particles into extended structures, including linear strings, in the absence of directional interparticle bonding interactions or external perturbation could facilitate the design of new functional materials. Here, we use methods of inverse design to discover isotropic pair potentials that promote the formation of single-stranded, polydisperse strings of colloids "colloidomers" as well as size-specific, compact colloidal clusters. Based on the designed potentials, a simple model pair interaction with a short-range attraction and a longer-range repulsion is proposed which stabilizes a variety of different particle morphologies including (i) dispersed fluid of monomers, (ii) ergodic short particle chains as well as porous networks of percolated strings, (iii) compact clusters, and (iv) thick cylindrical structures including trihelical Bernal spirals.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA