K. V. Reddy

Observation of domain wall pinning in Dy/sub 0.73/Tb/sub 0.27/Fe/sub 2-x/Ni/sub x/ and Ho/sub 0.85/Tb/sub 0.15/Fe/sub 2-y/Ni/sub y/ systems

Magnetization studies were carried out on the cubic Laves phase Dy/sub 0.73/Tb/sub 0.27/Fe/sub 2-x/Ni/sub x/ and Ho/sub 0.85/Tb/sub 0.15/Fe/sub 2-y/Ni/sub y/ [x=y=0, 0.5, 1.0, 1.5 and 2.0] systems at 4.2 K. These studies indicate that the magnetization process is influenced by the domain wall pinning. The value of the propagation field observed increases with Ni concentration in both the systems up to x=y=1.5 and falls to a small value for x=y=2.0. The pinning effect is more pronounced in the case of Dy/sub 0.73/Tb/sub 0.27/Fe/sub 2-x/Ni/sub x/ when compared with Ho/sub 0.85/Tb/sub 0.15/Fe/sub 2-y/Ni/sub y/ because of the larger K/sub 1/ value for Dy/sub 0.73/Tb/sub 0.27/Fe/sub 2/ compared to Ho/sub 0.85/Tb/sub 0.15/Fe/sub 2/.

A.c. magnetic susceptibility studies on the Dy0.73Tb0.27Fe2−xNix and Ho0.85Tb0.15Fe2−yNiy intermetallics

A.c. magnetic susceptibility measurements were carried out on the intermetallic compounds Dy0.73Tb0.27Fe2−xNix and Ho0.85Tb0.15Fe2−yNiy [x = y = 0–] in the temperature range 14–300 K. Several anomalies were observed in the temperature variation of the a.c. susceptibility for various samples. These are identified as the transitions due to spin reorientation and Curie temperature. In the case ofx = y = 1.5, the transition due to Curie temperature is observed in the form of a step, and in the case ofx = y = 2.0 this transition is observed as a sharp peak. This behaviour is attributed to the role played by the magnetic anisotropy below the Curie temperature.

Cadmium diffusion in thin films

Cadmium diffusion in thin films was studied in the temperature range 165 - . films were deposited by the flash evaporation technique. A thin film of cadmium was deposited and annealed at different temperatures. Cadmium depth profiles were determined by the Rutherford backscattering technique. These profiles were fitted to a complementary error function solution and the diffusion coefficients at four different temperatures were evaluated. The Arrhenius plot of the diffusion coefficients could be fitted to the equation . It is shown that the cadmium diffuses via copper vacancies.

Effect of Ni substitution on the magnetic and electrical properties of Dy0.73Tb0.27Fe2

Alloys of Dy0.73Tb0.27Fe2−xNix [0≤x≤2] were prepared and the lattice parameters obtained at room temperature showed a deviation from Vegard’s law owing to the presence of magnetovolume effect. Magnetization studies were carried out up to an applied field of 10 kOe in the temperature range 4.2–750 K. Magnetization data at 4.2 K indicate the effect of domain wall pinning. Temperature dependence of magnetization curves showed maxima at low temperatures as a consequence of this pinning effect. Electrical resistivity studies were carried out in the temperature range 16–750 K. A minimum observed for x=2 in the vicinity of its Curie temperature is attributed to the presence of critical fluctuations due to short‐range spin ordering of the rare earths. All the samples, except x=2, showed a T2 dependence at low temperatures and this has been attributed to electron‐spin wave scattering mechanism.

Lateral self-diffusion of selenium in CuInSe2 thin films

Abstract In this paper, we report the results of lateral self-diffusion studies of selenium in polycrystalline CuInSe2 thin films using a radioactive tracer scanning technique. The self-diffusion coefficients were determined in the temperature range 200–400°C; a pre-exponential factor of 5.53 × 10−4 cm2 s−1 and an activation energy of 0.26 ± 0.02 eV were evaluated. The activation energy is attributed to selenium diffusion via grain boundaries. The grain boundary energy was also estimated and was found to decrease with increase of temperature.

Magnetic and electrical studies on Ho0.85Tb0.15Fe2−xNix system

Cubic Laves phase alloys of Ho0.85Tb0.15Fe2−xNix (0≤x≤2) were prepared and the lattice parameters, evaluated as a function of x at room temperature, show deviation from Vegard’s law. This was attributed to the presence of a magnetovolume effect and charge transfer. Magnetization measurements were performed in the temperature range 77–700 K. The results suggest that the system undergoes a gradual transition from ferri‐ to ferromagnetic with increasing x. This has been explained based on the 3d band model. Furthermore, a monotonic decrease in Curie temperature with x was observed. Electrical resistivity studies were carried out in the temperature range 16–700 K. An anomaly was found in the vicinity of the Curie temperature for x=2 which has been attributed to the existence of the long‐range nature of the critical fluctuations due to short‐range spin ordering.

Growth of dielectric layers on the InSb surface

Abstract InSb is a compound semiconductor which is used in many device applications. The use of native oxides as a dielectric layer in semiconductor devices has the advantages of being relatively free from contamination and the ease of growth as compared to the deposition of dielectric layers by other methods. Two methods of oxidation of InSb surfaces were tried, thermal and anodic oxidation. It was found that the thermal oxides were conducting in nature and have low electrical resistivity. On the other hand, anodic oxides exhibited good dielectric properties with resistivity varying in the range 10 8 to 10 10 Ω cm. To explain this behaviour X-ray photoelectron spectroscopy studies were performed on the surface as well as in the bulk of the oxides. It was found that the thermal oxides contain free antimony which was absent in anodically grown oxides. The results were analysed and the kinetics of oxidation are discussed. The use of anodic oxidation for diffusion depth profiling is also illustrated.

Waiting-list prioritization in the National Health Service

The aim of this study was to find out whether there is a consensus of opinion among healthcare providers and different sections of the public on the relative prioritization of common otolaryngological conditions for outpatient consultations and inpatient treatment. ENT consultants, general practitioners, administrators, NHS employees, non-ENT patients and members of the general public were given common scenarios of otolaryngological conditions and asked to prioritize them in order of importance. All the groups gave top priority for patients with suspected cancer of the larynx (outpatients) and for surgical treatment of cancer. Children with hearing problems were more commonly ranked in the top three categories than children requiring treatment for sore throats. All groups assigned those requiring rhinoplasty, treatment for snoring or hearing aids to the last three ranks. This study shows that there is a remarkable uniformity of opinion in determining clinical priorities which is similar to the traditional policies practised by UK ENT consultants.

A low-temperature facility for Mössbauer and electrical resistivity studies using a closed-cycle helium refrigerator

A closed-cycle helium refrigerator is utilized for the development of a facility for performing Mossbauer and electrical resistivity studies at low temperatures down to 18 K. This facility includes a vibration isolation assembly in order to isolate the sample holder from the vibrations arising from the cold head of the closed-cycle refrigerator. A top-loading chamber and a set of bellows are used for this purpose. The performance of the system was tested by recording the spectra of natural iron foil at 300 K when the closed-cycle refrigerator was on and when it was off. The typical width of the outer lines of the Fe spectra obtained was , which indicates the effective isolation of vibration. A facility for electrical resistivity measurements by a four-probe method was also developed for use in the same facility for Mossbauer studies.

Metastatic Embryonal Cell Carcinoma with High Testosterone and Absence of Secondary Sexual Characteristics

ABSTRACT Objective: Embryonal cell carcinoma of the testicle with markedly elevated β-human chorionic gonadotropin (β-HCG) and testosterone concentrations with a paradoxical absence of secondary sexual characteristics has not been previously reported. Methods: A patient with a history of type 1 diabetes reported low libido and absent secondary sexual characteristics. A left testicular mass was discovered on examination. Further work up revealed high testosterone levels, suppressed luteinizing hormone and follicle-stimulating hormone levels, and erythrocytosis. Imaging studies revealed a 1-cm heavily calcified conglomerate mass in the left testicle and metastatic cancer involving axillary, supraclavicular, mediastinal, retroperitoneal, and pelvic lymph nodes. Results: Lymph node biopsy and surgical left orchiectomy specimens confirmed embryonal cell carcinoma with hyperplasia of Leydig cells. The patient was treated preoperatively with chemotherapy. Polycythemia and secondary sexual characteristics were re...