Frequency dependent electrical characteristics of (Ni/Au)/AlGaN/AlN/GaN heterostructures

The main electrical parameters such as ideality factor (n), zero bias barrier height (Bo), series resistances (R s), depletion layer width (W D) and interface state densities (N SS) of (Ni/Au)/AlGaN/AlN/GaN heterostructures have been extracted from the current-voltage (I-V) at room temperature, and frequency dependent capacitance voltage (C-V) and conductance-voltage (G/w-V) measurements. The high value of n and R s were attributed to the existence of an interfacial layer (IL) and particular distribution of N ss. The density distrubition profile of N ss was obtained from both forward bias I-V data and low-high frequency (C LF-C HF) measurement methods. In addition, the voltage dependent R s profile obtained both I-V and admittance measurements are in good agreement. As a result, the existence of an IL, R s and N ss lead to deviation from the ideal case of these heterostructures

Frequency and temperature dependence of the dielectric and AC electrical conductivity in (Ni/Au)/AlGaN/AlN/GaN heterostructures

The dielectric properties and AC electrical conductivity (σ ac)of the (Ni/Au)/Al 0.22Ga 0.78N/AlN/GaN heterostructures, with and without the SiNx passivation, have been investigated by capacitance-voltage and conductance-voltage measurements in the wide frequency (5kHz-5 MHz) and temperature (80-400 K) range. The experimental values of the dielectric constant (ε'), dielectric loss (ε' '), loss tangent (tand), σ ac and the real and imaginary part of the electric modulus (M' and M' ') were found to be a strong function of frequency and temperature. A decrease in the values of ε' and ε' ' was observed, in which they both showed an increase in frequency and temperature. The values of M' and M' ' increase with increasing frequency and temperature. The σ ac increases with increasing frequency, while it decreases with increasing temperature. It can be concluded, therefore, that the interfacial polarization can occur more easily at low frequencies and temperatures with the number of interface states density located at the metal/semiconductor interface. It contributes to the e' and σ ac. © 2009 Elsevier B.V. All rights reserved

Current transport mechanisms and trap state investigations in (Ni/Au)-AlN/GaN Schottky barrier diodes

The current transport mechanisms in (Ni/Au)-AlN/GaN Schottky barrier diodes (SBDs) were investigated by the use of current-voltage characteristics in the temperature range of 80-380 K. In order to determine the true current transport mechanisms for (Ni/Au)-AlN/GaN SBDs, by taking the Js(tunnel), E 0, and Rs as adjustable fit parameters, the experimental J-V data were fitted to the analytical expressions given for the current transport mechanisms in a wide range of applied biases and at different temperatures. Fitting results show the weak temperature dependent behavior in the saturation current and the temperature independent behavior of the tunneling parameters in this temperature range. Therefore, it has been concluded that the mechanism of charge transport in (Ni/Au)-AlN/GaN SBDs, along the dislocations intersecting the space charge region, is performed by tunneling. In addition, in order to analyze the trapping effects in (Ni/Au)-AlN/GaN SBDs, the capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics were measured in the frequency range 0.7-50 kHz. A detailed analysis of the frequency-dependent capacitance and conductance data was performed, assuming the models in which traps are located at the heterojunction interface. The density (Dt) and time constants (τt) of the trap states have been determined as a function of energy separation from the conduction-band edge (Ec - Et) as Dt≅ (5-8)×10 12eV-1 cm-2andτt≅(43-102) μs, respectively. © 2010 Elsevier Ltd. All rights reserved

Electrical characterization of MS and MIS structures on AlGaN/AlN/GaN heterostructures

The forward and reverse bias I-V, C-V, and G/ω-V characteristics of (Ni/Au) Schottky barrier diodes (SBDs) on the Al 0.22Ga 0.78N/AlN/GaN high-electron-mobility-transistor (HEMTs) without and with SiN x insulator layer were measured at room temperature in order to investigate the effects of the insulator layer (SiN x) on the main electrical parameters such as the ideality factor (n), zero-bias barrier height ( B0), series resistance (R s), interface-state density (N ss). The energy density distribution profiles of the N ss were obtained from the forward bias I-V characteristics by taking into account the voltage dependence of the effective barrier height ( e) and ideality factor (n V) of devices. In addition, the N ss as a function of E c-E ss was determined from the low-high frequency capacitance methods. It was found that the values of N ss and R s in SBD HEMTs decreases with increasing insulator layer thickness. © 2010 Elsevier Ltd. All rights reserved

Recovery of dialysis patients with COVID-19 : health outcomes 3 months after diagnosis in ERACODA

Background. Coronavirus disease 2019 (COVID-19)-related short-term mortality is high in dialysis patients, but longer-term outcomes are largely unknown. We therefore assessed patient recovery in a large cohort of dialysis patients 3 months after their COVID-19 diagnosis. Methods. We analyzed data on dialysis patients diagnosed with COVID-19 from 1 February 2020 to 31 March 2021 from the European Renal Association COVID-19 Database (ERACODA). The outcomes studied were patient survival, residence and functional and mental health status (estimated by their treating physician) 3 months after COVID-19 diagnosis. Complete follow-up data were available for 854 surviving patients. Patient characteristics associated with recovery were analyzed using logistic regression. Results. In 2449 hemodialysis patients (mean ± SD age 67.5 ± 14.4 years, 62% male), survival probabilities at 3 months after COVID-19 diagnosis were 90% for nonhospitalized patients (n = 1087), 73% for patients admitted to the hospital but not to an intensive care unit (ICU) (n = 1165) and 40% for those admitted to an ICU (n = 197). Patient survival hardly decreased between 28 days and 3 months after COVID-19 diagnosis. At 3 months, 87% functioned at their pre-existent functional and 94% at their pre-existent mental level. Only few of the surviving patients were still admitted to the hospital (0.8-6.3%) or a nursing home (∼5%). A higher age and frailty score at presentation and ICU admission were associated with worse functional outcome. Conclusions. Mortality between 28 days and 3 months after COVID-19 diagnosis was low and the majority of patients who survived COVID-19 recovered to their pre-existent functional and mental health level at 3 months after diagnosis

Dose related inhibitor effect of enrofloxacin on in vitro feline spontaneous myometrial contractility

Enrofloxacin is one of the most widely used antibacterial drugs in feline medicine. This study investigated the effects of enrofloxacin on in vitro feline spontaneous myometrial contractility at different sexual stages. Uterine samples of the 20 queen cats at different sexual periods were placed in a tissue bath, and in vitro spontaneous stretch-induced myometrial contractions were recorded for 10 min. The tissue bath was adjusted for cumulative enrofloxacin concentrations of 0.25 mM, 0.50 mM, 1.00 mM, and 2.00 mM, respectively. Myometrial contractions were recorded for 10 min after each dose was adjusted in the tissue bath. It was observed that enrofloxacin caused a significant decrease in the peak amplitude and area under curve, while causing an increase the frequency of stretch-induced myometrial contractions in a dose dependent manner in vitro at all sexual stages. The current preliminary study concluded that enrofloxacin has an inhibitory effect on in vitro feline uterine myometrial activity at all sexual stages. It is recommended to take this medical effect into consideration and apply enrofloxacin and uterotonics together in treatment of uterine infections in feline medicine. © 2022 Elsevier B.V.We would like to thank Cuneyt Disbudak for assistance of language revision. The authors declare that there is no conflict of interest

Quantitative Analysis of the Olfactory System in COVID-19: An MR Imaging Study

BACKGROUND AND PURPOSE: Anosmia or hyposmia, often accompanied by changes in taste, is recognized as a common symptom that can assist in the diagnosis of coronavirus disease 2019 (COVID-19). The pathogenesis of olfactory dysfunction in COVID-19 is not yet fully understood. MR imaging represents a useful anatomic imaging method for the evaluation of olfactory dysfunction associated with varying etiologies, including viral infection, trauma, and neurodegenerative processes. This case-control study was conducted to compare quantitative measurements of olfactory anatomic structures between patients diagnosed with COVID-19 associated with persistent olfactory dysfunction and healthy controls. MATERIALS AND METHODS: This study has a retrospective design. Cranial MR imaging was performed on all participants in both the patient and control groups. The bilateral olfactory bulb volume, olfactory tract length, and olfactory sulcus depth were measured in all patients. RESULTS: A total of 116 people aged 18?60?years, including 36 patients diagnosed with COVID-19 and 80 controls, were included in the study. All measured values were compared between the patient and control groups. The right, left, and total olfactory bulb volume values were significantly lower in the patient group than in the control group. The patient group also had significantly lower right and left olfactory sulcus depth and olfactory tract length values compared with those in the control group. CONCLUSIONS: MR imaging findings can be used to demonstrate olfactory injury in patients with COVID-19. The olfactory pathway may represent an alternative route for virus entry into the central nervous system