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1.
Sci Rep ; 11(1): 17037, 2021 Aug 23.
Artículo en Inglés | MEDLINE | ID: mdl-34426607

RESUMEN

Two-dimensional layered materials offer the possibility to create artificial vertically stacked structures possessing an additional degree of freedom-the interlayer twist. We present a comprehensive optical study of artificially stacked bilayers (BLs) MoS[Formula: see text] encapsulated in hexagonal BN with interlayer twist angle ranging from 0[Formula: see text] to 60[Formula: see text] using Raman scattering and photoluminescence spectroscopies. It is found that the strength of the interlayer coupling in the studied BLs can be estimated using the energy dependence of indirect emission versus the A[Formula: see text]-E[Formula: see text] energy separation. Due to the hybridization of electronic states in the valence band, the emission line related to the interlayer exciton is apparent in both the natural (2H) and artificial (62[Formula: see text]) MoS[Formula: see text] BLs, while it is absent in the structures with other twist angles. The interlayer coupling energy is estimated to be of about 50 meV. The effect of temperature on energies and intensities of the direct and indirect emission lines in MoS[Formula: see text] BLs is also quantified.

2.
Sci Rep ; 11(1): 924, 2021 Jan 13.
Artículo en Inglés | MEDLINE | ID: mdl-33441595

RESUMEN

The temperature effect on the Raman scattering efficiency is investigated in [Formula: see text]-GaSe and [Formula: see text]-InSe crystals. We found that varying the temperature over a broad range from 5 to 350 K permits to achieve both the resonant conditions and the antiresonance behaviour in Raman scattering of the studied materials. The resonant conditions of Raman scattering are observed at about 270 K under the 1.96 eV excitation for GaSe due to the energy proximity of the optical band gap. In the case of InSe, the resonant Raman spectra are apparent at about 50 and 270 K under correspondingly the 2.41 eV and 2.54 eV excitations as a result of the energy proximity of the so-called B transition. Interestingly, the observed resonances for both materials are followed by an antiresonance behaviour noticeable at higher temperatures than the detected resonances. The significant variations of phonon-modes intensities can be explained in terms of electron-phonon coupling and quantum interference of contributions from different points of the Brillouin zone.

3.
Nanoscale ; 12(35): 18153-18159, 2020 Sep 17.
Artículo en Inglés | MEDLINE | ID: mdl-32853305

RESUMEN

Low temperature and polarization resolved magneto-photoluminescence experiments are used to investigate the properties of dark excitons and dark trions in a monolayer of WS2 encapsulated in hexagonal BN (hBN). We find that this system is an n-type doped semiconductor and that dark trions dominate the emission spectrum. In line with previous studies on WSe2, we identify the Coulomb exchange interaction coupled neutral dark and grey excitons through their polarization properties, while an analogous effect is not observed for dark trions. Applying the magnetic field in both perpendicular and parallel configurations with respect to the monolayer plane, we determine the g-factor of dark trions to be g ∼ -8.6. Their decay rate is close to 0.5 ns, more than 2 orders of magnitude longer than that of bright excitons.

4.
Sci Rep ; 10(1): 4981, 2020 Mar 18.
Artículo en Inglés | MEDLINE | ID: mdl-32188877

RESUMEN

Atomically thin materials, like semiconducting transition metal dichalcogenides (S-TMDs), are highly sensitive to the environment. This opens up an opportunity to externally control their properties by changing their surroundings. Photoluminescence and reflectance contrast techniques are employed to investigate the effect of metallic substrates on optical properties of MoSe2 monolayer (ML). The optical spectra of MoSe2 MLs deposited on Pt, Au, Mo and Zr have distinctive metal-related lineshapes. In particular, a substantial variation in the intensity ratio and the energy separation between a negative trion and a neutral exciton is observed. It is shown that using metals as substrates affects the doping of S-TMD MLs. The explanation of the effect involves the Schottky barrier formation at the interface between the MoSe2 ML and the metallic substrates. The alignment of energy levels at the metal/semiconductor junction allows for the transfer of charge carriers between them. We argue that a proper selection of metallic substrates can be a way to inject appropriate types of carriers into the respective bands of S-TMDs.

5.
Sci Rep ; 8(1): 17745, 2018 Dec 10.
Artículo en Inglés | MEDLINE | ID: mdl-30531971

RESUMEN

We report a study of Raman scattering in few-layer MoTe2 focused on high-frequency out-of-plane vibrational modes near 291 cm-1 which are associated with the bulk-inactive [Formula: see text] mode. Our temperature-dependent measurements reveal a double peak structure of the feature related to these modes in the Raman scattering spectra of 4- and 5-layer MoTe2. In accordance with literature data, the doublet's lower- and higher-energy components are ascribed to the Raman-active A1g/[Formula: see text] vibrations involving, respectively, only the inner and surface layers. We demonstrate a strong enhancement of the inner mode's intensity at low temperature for 1.91 eV and 1.96 eV laser light excitation which suggests a resonant character of the Raman scattering processes probed under such conditions. A resonance of the laser light with a singularity of the electronic density of states at the M point of the MoTe2 Brillouin zone is proposed to be responsible for the observed effects.

6.
Transplant Proc ; 48(5): 1431-4, 2016 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-27496422

RESUMEN

BACKGROUND: Chronic kidney disease is one of the medical conditions that affect hemostasis. Patients undergoing hemodialysis present both hemorrhagic and prothrombotic tendencies. Platelet adhesion to the artificial surface of the dialyzer's membrane, blood vessel endothelial wall disruption, and quantitative and qualitative changes in clothing factors are thought to be causative agents of the above-mentioned conditions. Thromboelastometry and impedance aggregometry enable precise assessment of clot formation and platelet function abnormalities, including changes related to chronic renal failure in patients undergoing renal replacement therapy. METHODS: A prospective study with control group was designed. The study group consisted of 17 adults with diagnosed chronic renal failure undergoing hemodialysis. The control group consisted of 13 healthy volunteers. EXTEM and FIBTEM tests in rotational thromboelastometry and TRAPtest in impedance aggregometry analyzer were performed. RESULTS: EXTEM parameter test results were comparable between analyzed groups, whereas FIBTEM test results were significantly increased in the study group. Platelet aggregation as measured by the TRAPtests was significantly decreased in patients undergoing hemodialysis. CONCLUSIONS: In end-stage renal disease patients undergoing hemodialysis, whole-blood clot formation is not disturbed, even though platelet dysfunction occurs. Increased fibrin clot formation reflected by FIBTEM results may compensate the observed platelet disorders. The compilation of ROTEM and Multiplate may support appropriate hemostatic control and decision-making during kidney transplantation.


Asunto(s)
Hemostasis , Fallo Renal Crónico/sangre , Trasplante de Riñón , Diálisis Renal , Tromboelastografía/métodos , Adulto , Anciano , Coagulación Sanguínea , Pruebas de Coagulación Sanguínea , Plaquetas , Estudios de Casos y Controles , Impedancia Eléctrica , Femenino , Humanos , Fallo Renal Crónico/terapia , Masculino , Persona de Mediana Edad , Agregación Plaquetaria , Recuento de Plaquetas , Pruebas de Función Plaquetaria , Periodo Preoperatorio , Estudios Prospectivos
7.
Transplant Proc ; 46(8): 2598-601, 2014 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-25380875

RESUMEN

INTRODUCTION: Although renal replacement therapy can lead to improved health, it also can cause emotional disturbances in patients. It is believed that the success of renal replacement therapy hinges not only on medical parameters, but also on psychosocial factors, which is why modern medicine provides an ever-increasing role in the improvement of patients' quality of life. PURPOSE: The purpose of this study was to compare the level of life satisfaction, purpose in life, and basic hope in patients who had received renal replacement due to chronic kidney disease. We also tested whether the specific type of renal replacement therapy and kidney function parameters were influential factors on the above variables. PATIENTS AND METHODS: Sixty-one adult patients treated via renal replacement for chronic kidney disease took part in the study. Patients were divided into two groups: 31 hemodialysis patients (15 women and 16 men, ages 23-77 years, mean 51.19 years, SD 14.53 years) and 30 patients who had undergone kidney transplantation (14 women and 16 men, ages 22-69 years, mean 48.40 years, SD 12.64 years). The following research tools were used for analysis: Satisfaction With Life Scale (SWLS), Purpose in Life Test (PIL), and Basic Hope Inventory (BHI-12). RESULTS: There were no statistical differences in the level of satisfaction with life between hemodialysis patients and postkidney transplant patients. The results for the SWLS obtained from both groups fell within the normal range. The average SWLS for hemodialysis patients remained 20.61, SD = 5.79; for postkidney transplant patients, it was 22.57, SD = 5.16. The PIL level in the group of hemodialysis patients (101.5, SD = 15.64) was significantly lower than in the group of postkidney transplant patients (109.7, SD = 15.54). The average BHI-12 level was similar in both groups. The average BHI-12 result for hemodialysis patients was 29.00 (SD = 5.06), and for postkidney transplant patients 29.93 (SD = 3.55). The correlations between the psychological variables and selected biochemical parameters are worthy of particular attention. Among hemodialysis patients, there was an additional correlation between SWLS and hematocrit; whereas for postkidney transplant patients, there was an additional correlation of PIL and eGFR. CONCLUSIONS: Our data show that satisfaction with life and basic hope do not increase in patients after renal replacement therapy. The form of renal replacement therapy (hemodialysis or kidney transplantation) does not change the above variables. Patients treated via renal replacement require specialized psychological support to improve the efficacy of renal replacement therapy.


Asunto(s)
Esperanza , Fallo Renal Crónico/psicología , Fallo Renal Crónico/terapia , Trasplante de Riñón/psicología , Satisfacción Personal , Diálisis Renal , Adulto , Anciano , Femenino , Humanos , Riñón/fisiopatología , Fallo Renal Crónico/cirugía , Masculino , Persona de Mediana Edad , Calidad de Vida , Adulto Joven
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