Determination of the carrier concentration in InGaAsN∕GaAs single quantum wells using Raman scattering

Raman scattering from longitudinal optical phonon-plasmon coupled mode was observed in a series of InGaAsN∕GaAs single quantum well samples grown by metalorganic vapor phase epitaxy. The phonon-plasmon mode spectra were fitted with the dielectric constant function based on Drude model that contains contributions from both lattice vibrations and conduction electrons. The carrier concentration is calculated directly from the plasmon frequency, which is obtained from the fitting procedure. An empirical expression for the electron concentration, [n], in InGaAsN∕GaAs samples is determined as [n]≈{2.35×1016(ωm−502)}cm−3, where ωm is the peak of the upper frequency branch, L+, of the phonon-plasmon mode measured in unit of cm−1. The phonon-plasmon coupled mode was also investigated in rapid thermally annealed samples

Improvement of n-GaN Schottky diode rectifying characteristics using KOH etching

KOH etch was investigated as a means to improve the I–Vcharacteristics of Schottky diodes onn-type GaNgrown by molecular-beam epitaxy on sapphire, or on hydride vapor phase epitaxy templates. Atomic force microscopy images and I–Vcharacteristics are presented. After etching as-grown films in molten KOH, Schottky diodes on c-plane GaN had orders of magnitude reduction in reverse leakage current. The best devices had leakage currents less than 10−12 A (10−8 A/cm2) at −5 V, and ideality factors of 1.04. Measurements on several different sample structures indicate a correlation between surface roughness and saturation current, and an improvement in ideality factor when etched in KOH. Phosphoric acid was also investigated, but did not result in significant improvements in I–Vcharacteristics

Surface band bending in as-grown and plasma-treated n-type GaN films using surface potential electric force microscopy

The surface band bending, as well as the effect of plasma-induced damage on band bending, on GaN surfaces, was investigated. The upward band bending, measured by surface potentialelectric force microscopy (a variant of atomic force microscopy), for the as-grown n -type GaNwas about 1.0 eV which increased to ∼1.4 eV after reactive ion etching (RIE). UV illuminationdecreased the band bending by 0.3 eV with time constants on the order of seconds and hundreds of seconds for the as-grown and RIE treated GaN, respectively. This implies that there is a higher density of the surface states in the samples subjected to the RIE process. After the RIE treatment, the shape of the photoluminescence spectrum remained unchanged, but the intensity dropped by a factor of 3. This effect can be attributed to nonradiative defects created near the surface by the RIE treatment

Liquid Metal Feeding Through Dendritic Region in Ni-Hard White Iron

ABSTRACT Liquid permeability in the dendritic regions is one of the factors that determine porosity formation and macro segregation in castings. Permeability in the dendritic structure of Ni-Hard white iron was measured as a function of temperature. Effect of microstructural coarsening on the permeability was also investigated. Permeability increased with coarsening dendritic structure in Ni-Hard white iron

Thermal stability of electron traps in GaN grown by metalorganic chemical vapor deposition

Deep level transient spectroscopy was used to investigate the thermal stability of electron traps in n-type GaN grown by metalorganic chemical vapor deposition. The concentration of traps at 160 and at 500K increased more than fivefold over the course of several 700Kanneal cycles, while a peak at 320K increased by a factor of only 1.19. The increase in the trap concentration with repeated annealing might be due to a mobile trap or loss of passivant. Hydrogen is very likely present in high concentration in the epilayer, and its passivating effects may be lost with annealing

Observation of Magnetic Moments in the Superconducting State of YBa2_2Cu3_3O6.6_{6.6}

Neutron Scattering measurements for YBa$_2$Cu$_3$O$_{6.6}$ have identified small magnetic moments that increase in strength as the temperature is reduced below $T^\ast$ and further increase below $T_c$. An analysis of the data shows the moments are antiferromagnetic between the Cu-O planes with a correlation length of longer than 195 \AA in the $a$-$b$ plane and about 35 \AA along the c-axis. The origin of the moments is unknown, and their properties are discusssed both in terms of Cu spin magnetism and orbital bond currents.Comment: 9 pages, and 4 figure

Prognostic factors of perioperative FLOT regimen in operable gastric and gastroesophageal junction tumors: real-life data (Turkish Oncology Group)

Background/aim: Perioperative FLOT regimen is a standard of care in locally advanced operable gastric and GEJ adenocarcinoma. We aimed to determine the efficacy, prognostic factors of perioperative FLOT chemotherapy in real-life gastric and GEJ tumors. Materials and methods: The data of patients who were treated with perioperative FLOT chemotherapy were retrospectively analyzed from 34 different oncology centers in Turkey. Baseline clinical and demographic characteristics, pretreatment laboratory values, histological and molecular characteristics were recorded. Results: A total of 441 patients were included in the study. The median of age our study population was 60 years. The majority of patients with radiological staging were cT3-4N(+) (89.9%, n = 338). After median 13.5 months (IQR: 8.5–20.5) follow-up, the median overall survival was NR (95% CI, NR to NR), and median disease free survival was 22.9 (95% CI, 18.6 to 27.3) months. The estimated overall survival at 24 months was 62%. Complete pathological response (pCR) and near pCR was achieved in 23.8% of all patients. Patients with lower NLR or PLR have significantly longer median OS (p = 0.007 and p = 0.033, respectively), and patients with lower NLR have significantly longer median DFS (p = 0.039), but PLR level did not affect DFS (p = 0.062). The OS and DFS of patients with better ECOG performance scores and those who could receive FLOT as adjuvant chemotherapy instead of other regimens were found to be better. NLR was found to be independent prognostic factor for OS in the multivariant analysis. At least one adverse event reported in 57.6% of the patients and grade 3–4 toxicity was seen in 23.6% patients. Conclusion: Real-life perioperative FLOT regimen in operable gastric and GEJ tumors showed similar oncologic outcomes compared to clinical trials. Better performance status, receiving adjuvant chemotherapy as same regimen, low grade and low NLR and PLR improved outcomes in real-life. However, in multivariate analysis, only NLR affected OS. © TÜBİTAK

The effect of hydrogen etching on 6H-SiC studied by temperature-dependent current-voltage and atomic force microscopy

6H–SiC was etched with hydrogen at temperatures between 1000 and 1450°C. The etchedSi-terminated face for the 6H‐SiC wafer was investigated by atomic force microscopy and temperature-dependent current–voltage (I–V–T)measurements. Mechanical polishing damage was effectively removed by hydrogen etching at temperatures above 1250°C. Atomic force microscopy images revealed that very good surface morphology, atomic layer flatness, and large and large step width were achieved. Schottky diode characteristics were investigated in detail by current–voltage and temperature-dependent current–voltage measurements, and the results showed a transition from defect assisted tunneling to thermionic emission as the annealingtemperature was increased from 1250 to 1450°C

Effect of n+-GaN subcontact layer on 4H–SiC high-power photoconductive switch

High-power photoconductive semiconductor switching devices were fabricated on 4H–SiC. In order to prevent current crowding, reduce the contact resistance, and avoid contact degradation, a highly n-doped GaN subcontact layer was inserted between the contact metal and the high resistivity SiC bulk. This method led to a two orders of magnitude reduction in the on-state resistance and, similarly, the photocurrent efficiency was increased by two orders of magnitude with the GaN subcontact layer following the initial high current operation. Both dry etching and wet etching were used to remove the GaN subcontact layer in the channel area. Wet etching was found to be more suitable than dry etching

Sedoanalgesia Administration with Propofol and Ketamine for Minor Urologic Interventions

Aim: In this study we aimed to administer sedoanalgesia with propofol and ketamine combination in patients undergoing planned minor urologic interventions with limited anesthesia. By combining these two medications, lower doses may be used, and we aimed to provide sufficient sedation, analgesia and amnesia without disrupting hemodynamic and respiratory stability and to increase patient and surgeon satisfaction. Material-Method: The study included 53 patients with planned minor urologic interventions aged from 19 to 85 years and physical situation ASA I-III. After six hours starvation, patients were taken to the surgery. Patients were monitored for electrocardiography (ECG), oxygen saturation (SPO2 ) and non-invasive blood pressure. For use if necessary a nasal O2 cannula was inserted. A vein in the back of the left hand was opened and 5 ml/min isotonic sodium chloride infusion was begun. Patient heart rate (HR), systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP) and oxygen saturation (SpO2 ) values were measured and a 5 point sedation scale (Table 1) was used to measure sedation scores. Basal values were recorded (0 min). Later patients were randomly divided into two groups with Group I administered intraurethral lidocaine gel for local anesthesia by the surgeon, while Group II were administered intravenous 0.015 mg/kg midazolam, 0.5 mg/kg 1% ketamine and 0.5 mg/kg 1% propofol by the authors for sedoanalgesia. At five minute intervals the HR, SAP, DAP, MAP, SpO2 values and sedation scores were measured and recorded. Results: Statistical evaluation found a statistically significant increase in SAP, DAP and MAP values measured at the 5th minute in Group I patients compared to preoperative values. In Group I patients, when the heart rate measured in the 1st and 5th minutes are compared with preoperative values there was a statistically significant increase identified. In Group II patients, there was a statistically significant fall in SpO2 values in the 1st and 5th minutes compared with preoperative values. When patient and surgeon satisfaction are compared with Group I, Group II was found to be statistically significantly higher. Though the blood pressure and heart rate increases in Group I patients were statistically significant, they were not at levels that required clinical intervention and/or treatment. Similarly the SpO2 decrease observed in Group II patients did not fall below 90% in any patient in spite of being statistically significant and rose again without clinical intervention and/or treatment. Conclusion: In this study we showed that sedoanalgesia administration with propofol and ketamine may be an alternative method for patients undergoing minor urology interventions that does not disrupt hemodynamic and respiratory stability, does not delay patient discharge, has low side effect incidence and has high patient and surgeon satisfaction