Search Results - (Author, Cooperation:C. A. Ross)

2014-08-19

Nature Publishing Group (NPG)

0028-0836

1476-4687

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

Animals ; Cell Differentiation ; Fibroblasts ; Glutamine/metabolism ; Humans ; Induced Pluripotent Stem Cells/metabolism/*pathology ; Male ; Mental Disorders/genetics/metabolism/*pathology ; Mice ; Mutant Proteins/genetics/metabolism ; Mutation/genetics ; Nerve Tissue Proteins/genetics/metabolism ; Neurons/cytology/metabolism/pathology ; Pedigree ; Presynaptic Terminals/metabolism/pathology ; Prosencephalon/metabolism/pathology ; Protein Binding ; Synapses/metabolism/*pathology ; Transcriptome

2012-06-09

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

1089-7550

AIP Digital Archive

Physics

The interdiffusivity within multilayered electrodeposited thin films of NiPx/NiPy has been measured using an x-ray technique. The NiPx, which can be deposited in the range 0≤x≤25 at. %, is crystalline at low phosphorus content but amorphous at high phosphorus content, so that films with a range of crystalline and amorphous structures could be prepared. Measurements on fully amorphous multilayers, where x,y(approximately-greater-than)18 at. %, give an interdiffusivity of order 10−22 m2 s−1 at 120 °C, which decreases with time, probably due to structural relaxation. The diffusivity decreases with decreasing repeat length of the films, with a critical repeat length of 40 A(ring). Crystalline/amorphous films show qualitatively different behavior, with the low-phosphorus layer governing the extent of a more limited diffusion phenomenon. This has been interpreted as the diffusion of phosphorus into a limited number of sites within the grain boundaries of the crystalline layers.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Iron oxide films have been grown onto MgO and oxidized silicon substrates using pulsed laser deposition with a KrF laser. Films deposited in vacuum consisted of the stoichiometric ferrimagnetic γ-Fe2O3 phase, with a saturation magnetization of 371±27 kA/m. However, films deposited in an O2 atmosphere were iron deficient and consisted of the antiferromagnetic α-Fe2O3 phase, with a saturation magnetization of 40±10 kA/m. Films predominantly consisting of the metastable γ-Fe2O3 phase at least 680 nm in thickness could be grown on MgO (001) substrates, which is thicker than films reported elsewhere. The effects of stoichiometry, thickness, and annealing on the magnetic properties of the films are discussed. © 2002 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Large area arrays of cobalt and nickel particles with truncated conical shapes and diameters of 80–120 nm have been prepared using interference lithography combined with an evaporation and lift-off process. The magnetic hysteresis has been measured and the remanent states of the particles have been compared with a three-dimensional micromagnetic model. The model shows a transition from "flower" to "vortex" magnetization states as the particle size increases. The distribution of switching fields and the magnetostatic interactions between particles have been characterized. Both lead to a slow approach to saturation in the hysteresis loops. The suitability of such arrays for data storage is discussed. © 2001 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The switching fields of nickel cylinders with ∼100 nm dimensions have been compared to the predictions of a numerical micromagnetic model. The switching field decreases with increasing diameter and decreasing aspect ratio, and there is a good agreement between the measured and calculated values. The samples have a strong 〈111〉 preferred crystal orientation, and the large increase in switching field and switching field distribution with decreasing temperature can be explained by the large increase in magnetocrystalline anisotropy at low temperatures. © 2002 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Measurements of stress and magnetostriction have been made in longitudinal CoCrTa magnetic recording media. The stress in Cr and CoCrTa/Cr films deposited onto grooved substrates is higher parallel to the grooves compared to perpendicular to the grooves by up to a few hundred MPa. Combined with a magnetostriction coefficient of −3×10−5 in CoCr10Ta6/Cr, magnetostriction makes a contribution to the in-plane anisotropy observed in such media. © 1996 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

NiAl has been proposed as a replacement for the Cr underlayer in longitudinal recording media.1 NiAl has a B2 ordered structure with a lattice parameter close to that of Cr. Hence the same epitaxial relationships that exist in CoCrPt/Cr could also exist in CoCrPt/NiAl. Although high coercivity media have been made using a NiAl underlayer, a detailed microstructural study of the CoCrPt/NiAl is lacking. We have investigated the crystal orientation and epitaxial relationships in CoCrPt/NiAl bilayers deposited by DCM sputtering at a range of deposition temperatures up to 250 °C and sputter rates of 0.5–10 nm/s. Samples were examined by high resolution transmission electron microscopy in cross section and plan view. None of the samples showed the (002) NiAl/(11¨20)Co orientation that would be expected by analogy to CoCrPt/Cr films deposited at high temperatures. The CoCrPt crystals in the CoCrPt/NiAl are oriented with their c axes at a range of angles to the film plane, accounting for the lower squareness (Sq) of the magnetic hysteresis loop compared to samples on Cr underlayers. There is no evidence of the "bicrystal" structure in CoCrPt/NiAl as is seen on films grown on Cr.2 Grain size in NiAl is smaller than in Cr giving a smaller grain size in the CoCrPt overlayer and potentially lower medium noise. However, coercivity of CoCrPt/NiAl is lower than CoCrPt/Cr. The coercivity increases as the NiAl film thickness increases, and this is believed to be caused by topographic isolation of the magnetic grains.3 Recording measurements on CoCrPt/NiAl and CoCrPt/Cr media show that noise is lower in isotropic media made on the NiAl underlayer compared to oriented media made on the Cr underlayer. The microstructural results will be compared with previously published results on NiAl underlayers and the utility of NiAl as an underlayer in high density media will be assessed. © 1997 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

An electrodeposition technique for making multilayered thin films, based on controlled deposition from two different solutions, is described. Ni/NiPx and NiPx/NiPy multilayered thin films with repeat lengths as low as 20 A(ring) have been prepared. They show up to three low-angle x-ray peaks corresponding to the electron density modulation.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

The magnetization reversal exhibited by arrays of 70-nm-wide pseudo-spin-valve (PSV) elements has been investigated by measurements of minor hysteresis loops. Samples were patterned from sputtered NiFe (6 nm)/Cu (3 and 6 nm)/Co (4 nm)/Cu (4 nm) magnetic thin film stacks. The overall room temperature magnetic behavior of the arrays can be understood by considering a distribution of switching fields for both the hard (Co) and soft (NiFe) magnetic layers. Such layers interact through exchange and magnetostatic coupling. Increasing the lengths of the elements leads to narrower switching field distributions and higher mean switching fields (particularly for the hard layer). On the other hand, decreasing the thickness of the Cu spacer leads to an increase of the switching field of the hard layer. Results obtained are well described by a model that treats each PSV as a coupled pair of rectangular single-domain films and uses the values of the interaction field between layers deduced from experimental minor loops. © 2001 American Institute of Physics.

Electronic Resource

1077-3118

AIP Digital Archive

Physics

Directional solidification of cylinder forming block copolymer films confined between a directionally crystallizing solvent (benzoic acid) and a topographically patterned silicon substrate imparts a particular orientation to the block copolymer microdomains that is dependent of the solidification direction and the local film thickness. The substrate features (30 nm high, 2μm wide square mesas on a 4μm sq lattice) shape the film morphology by periodically modulating the local film thickness. Thicker regions between substrate features (plateaus) exhibit in-plane cylinders aligned in the crystallization direction and thinner regions over the substrate features (mesas) display vertically aligned cylindrical domains. This approach is a simple and general technique for engineering an intended domain orientation in specific areas of a block copolymer film. Development of this method for nanolithographic applications is demonstrated through oxygen plasma reactive ion etching of the patterned cylindrical domains. © 2001 American Institute of Physics.

Electronic Resource

1749-6632

Blackwell Publishing Journal Backfiles 1879-2005

Natural Sciences in General

Electronic Resource

1089-7550

AIP Digital Archive

Physics

Longitudinal recording media made with chromium and with nickel-aluminum underlayers are compared. NiAl films have smaller grains and random crystallographic orientation, while Cr films have larger grains and either a {110} or a {200} preferred orientation depending on the deposition conditions. Cobalt alloy films grown on NiAl have nearly random crystallographic orientation and significant c-axis out-of-plane component, and lower hysteresis loop squareness and coercivity than films made on a heated Cr underlayer. NiAl-underlayer media do not exhibit in-plane magnetic anisotropy induced by the substrate texture lines. CoCrTaPt/Cr/NiAl media had higher overwrite than CoCrTaPt/Cr media due to higher coercive squareness and a sharper hysteresis loop closure. © 1997 American Institute of Physics.

Electronic Resource

1089-7550

AIP Digital Archive

Physics

The electromigration drift velocity has been measured, using the Blech–Kinsbron [Thin Solid Films 25, 327 (1975)] edge displacement method, for aluminum thin films under different thicknesses of anodization. The drift velocity is found to decrease with increasing anodization thickness. The results are interpreted in terms of a change in the self-diffusivity of aluminum as a result of the compressive stresses imposed by the anodized layer. The effect of the variation of diffusivity with stress on the stress distribution within a drifting thin-film sample is discussed.

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] T. congolense infected tsetse flies produce very few metacyclic trypanosomes and this inhibits examination of metacyclic variable antigen type (M-VAT) heterogeneity using fly-derived metacyclics. Recently, however, a culture system for generating T. congolense metacyclics in vitro has been ...

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] BOVINE pancreatic ribonuclease (RNase) is the only enzyme the primary structure of which is known1. A great deal of work has been done on the secondary and tertiary structure of this protein, but it is not possible to make any definite formulation of the conformation in aqueous solution2. In fact, ...

Electronic Resource

1432-1203

Springer Online Journal Archives 1860-2000

Biology

Medicine

Abstract Dentatorubral pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder caused by expansion of an unstable, tandemly repeated trinucleotide sequence, (CAG)n, in a novel gene on human chromosome 12p12-pter. Molecular diagnosis of DRPLA uses the polymerase chain reaction (PCR) to amplify and characterize the number of CAG repeats carried by individuals. The PCR analysis is fairly straightforward when two alleles are identified. However, when only a single allele is observed, it is difficult to know whether the sample is homozygous or whether there was failure to amplify the second allele. We describe a Southern analysis for detection of the DRPLA CAG repeat, providing an independent method for the assessment of expanded alleles.

Electronic Resource

1432-2021

Springer Online Journal Archives 1860-2000

Chemistry and Pharmacology

Geosciences

Physics

Abstract Mössbauer spectra of glauconite and nontronite recorded at temperatures down to 1.3K and in applied fields up to 4.5 T show that Fe III spin configurations are respectively ferromagnetic and antiferromagnetic. It is shown that in a particular material depending on the distribution and concentration of Fe III in the silicate sheet either mode might occur. A new model of competing nearest-neighbour (J 1) and next-nearest-neighbour (J 2) magnetic exchange interactions in the triangular lattice is introduced to account for the results. From available magnetic susceptibilities we estimate ∣J 1∣∼6∣J 2∣. The results lead to the conclusion that the Fe III cations are highly ordered in glauconite and occupy cis sites so as to maximize their mutual separations.

Electronic Resource

1573-7438

Springer Online Journal Archives 1860-2000

Medicine

Résumé Cet article couvre les différents aspects de la recherche menée à CTVM pendant les 25 dernières années sur les trypanosomiases animales. Cet article présente le travail sur la variation antigénique, la culture de tissue, la résistance aux drogues, l'immunologie, la biochimie et la pathologie deTrypanosoma bruce, T. congolense, T. gambiense etT. evansi. Ceci n'est pas présenté comme une revue exhaustive du sujet mais porte sur certains aspects de ces différents domaines qui sont présentés en relation avec le travail mené dans la communauté scientifique au sens large.

Resumen Este artículo ofrece una revisión de los trabajos de investigación sobre tripanosomiasis illevados a cabo en el CTVM durante los últimos 25 años. Se incluyen trabajos sobre variabilidad antigénica, cultivo tisular, resistencia a fármacos, inmunologia, bioquímica y patología deTrypanosoma brucei, T. congolense, T. gambiense yT. evansi. El artículo no pretende ser una revisión exhaustiva del tema, sino que discute alguno de los trabajos presentados en relación a investigaciones illevadas a cabo en otros centros.

Summary This review covers aspects of research work carried out on animal trypanosomes at the Centre for Tropical Veterinary Medicine (CTVM) during the last 25 years. The review covers work on antigenic variation, tissue culture, drug resistance, immunology, biochemistry and pathology ofTrypanosoma brucei, T. congolense, T. gambiense andT. evansi. It is not intended as an exhaustive review of the subject but focuses on certain aspects of these areas which are presented in relation to work carried out within the broader scientific community.

Electronic Resource

1435-1463

Association study ; B37 CAG repeat locus ; chromosome 12 ; schizophrenia ; periodic catatonia

Springer Online Journal Archives 1860-2000

Medicine

Summary Clinical evidence for a dominant mode of inheritance and anticipation in periodic catatonia, a distinct subtype of schizophrenia, indicates that genes with triplet repeat expansions or other unstable repetitive elements affecting gene expression may be involved in the etiology of this disorder. Because patients affected with dentatorubral-pallidoluysian atrophy (DRPLA) may present with “schizophrenic” symptoms, we have investigated the DRPLA (B 37 CAG repeat) locus on chromosome 12 in 41 patients with periodic catatonia. The B 37 CAG repeat locus was highly polymorphic but all alleles in both the patient and control group had repeat sizes within the normal range. We conclude that variation at the DRPLA locus is unlikely to be associated with periodic catatonia. The evidence for dominant inheritance and anticipation as well as the high prevalence of human brain genes containing trinucleotide repeats justifies further screening for triplet repeat expansions in periodic catatonia.

Electronic Resource