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Biomedical subjects

J Narayan

Publications and source records attributed to J Narayan.

13 recordsLinked to original sources
PubMed2006

Growth and observation of low-field giant magnetoresistance in La0.7Sr0.3MnO3/ZnO superlattice structures.

We report the growth of a new class of superlattice structure, consisting of alternate layers of La0.7Sr0.3MnO3 (LSMO) and ZnO, which exhibits giant magnetoresistance at low fields. These superlattices were fabricated using a novel pulsed-laser deposition technique with a specially designed target assembly. Giant magnetoresistance of > 250% has been observed in these structures in current-in-plane configuration on the application of just -400 Gauss of magnetic field over the broad temperature range 15-200 K. Observation of giant magnetoresistance at such low magnetic fields is a groundbreaking step in the field of novel magnetic materials and devices.

Crystallization↗
PubMed2004

Novel methods of forming self-assembled nanostructured materials: Ni nanodots in Al2O3 and TiN matrices.

We have developed two novel methods of growing self-assembled nanodot arrays of uniform size (diameter 2-50 nm) of a variety of materials in crystalline as well as amorphous matrices. These methods employ a pulsed laser deposition technique and are classified as: (a) sequential growth method; and (b) simultaneous growth method. In the first method, the nanodots and matrix material are formed sequentially, while in the second method, nanodots and matrix materials grow simultaneously. In the sequential growth, self-assembly of nanodots is controlled by the flux of materials, interfacial energy, intervening matrix layer, substrate and laser parameters. For the simultaneous growth method of self-assembly of nanodots, there is additional requirement that the material of the nanodot and the matrix should be such that the Gibb's free energy of oxidation of the constituent of matrix material is much lower than that of the nanodot material.

Aluminum Oxide↗
PubMed2003

Role of self-assembled gold nanodots in improving the electrical and optical characteristics of zinc oxide films.

We have studied the effect of embedding nanocrystalline Au particles on the electrical and optical characteristics of ZnO films. Au-embedded epitaxial ZnO films were deposited on (0001) sapphire substrates with a pulsed laser deposition technique. The crystalline quality of both the ZnO matrix and Au nanoparticles was investigated by X-ray diffraction and transmission electron microscopy. Composite films were characterized by photoluminescence, optical absorption, and low-temperature electrical resistivity measurements. Photoluminescence spectra of theses films showed a sharp excitonic peak at 3.22 +/- 0.05 eV without any signature of green band emission. Electrical resistivity measurements showed these films to be highly conducting, with a room-temperature resistivity of 3.4 +/- 0.2 m omega-cm.

Crystallization↗
PubMed1993

Factors influencing the expectations of parents for their mentally retarded children.

In terms of treatment for cure, education, training and general information, parental expectations for their mentally retarded children are influenced by various factors such as the age and sex of the retarded child, the level of mental retardation, the education and occupation of the parents, and the socio-economic status and area of living. In the present study, an attempt has been made to find out the correlation of six variables namely, age, sex, literacy, locality of living, level of retardation and duration of follow-up on the expectation of one hundred parents of mentally retarded children who attend the home-based services at the National Institute for the Mentally Handicapped, Secunderabad, India. The intercorrelation among the six independent variables and the dependent variable revealed that age of the child and duration of follow-up have a high correlation (P < 0.01), and literacy of the parents and duration of follow-up were positively correlated (P < 0.05 level). It was also found that age and duration of follow-up have a positive correlation. Further detailed multiple regression analysis was conducted and the results are discussed.

Adolescent↗
PubMed1991

Consanguinity and mental retardation.

Consanguinity among parents as a cause of mental retardation in their children is debatable. The present study was conducted to find out the effect of consanguinity on mental retardation where the causative factor is not established. A total of 517 mentally retarded persons and their families were studied out of which 160 were born of consanguineous marriage and 357 were of non-consanguineous marriage. The results indicated that, when there is a history of mental retardation in the family and if the parents are consanguineously married, the risk of mental retardation in the offspring is significantly high (chi 2 = 11.52; P less than 0.001). Among the consanguineously married families, the blood relationship of uncle-niece seems to have the highest risk of affecting the offsprings. The implications are discussed in detail.

Adolescent↗