1,345 research outputs found
Assignment of the Human and Mouse Prion Protein Genes to Homologous Chromosomes
Purified preparations of scrapie prions contain one major macromolecule, designated prion protein (PrP). Genes encoding PrP are found in normal animals and humans but not within the infectious particles. The PrP gene was assigned to human chromosome 20 and the corresponding mouse chromosome 2 using somatic cell hybrids. In situ hybridization studies mapped the human PrP gene to band 20p12→pter. Our results should lead to studies of genetic loci syntenic with the PrP gene, which may play a role in the pathogenesis of prion diseases or other degenerative neurologic disorders
The Red-Sequence Luminosity Function in Galaxy Clusters since z~1
We use a statistical sample of ~500 rich clusters taken from 72 square
degrees of the Red-Sequence Cluster Survey (RCS-1) to study the evolution of
~30,000 red-sequence galaxies in clusters over the redshift range 0.35<z<0.95.
We construct red-sequence luminosity functions (RSLFs) for a well-defined,
homogeneously selected, richness limited sample. The RSLF at higher redshifts
shows a deficit of faint red galaxies (to M_V=> -19.7) with their numbers
increasing towards the present epoch. This is consistent with the `down-sizing`
picture in which star-formation ended at earlier times for the most massive
(luminous) galaxies and more recently for less massive (fainter) galaxies. We
observe a richness dependence to the down-sizing effect in the sense that, at a
given redshift, the drop-off of faint red galaxies is greater for poorer (less
massive) clusters, suggesting that star-formation ended earlier for galaxies in
more massive clusters. The decrease in faint red-sequence galaxies is
accompanied by an increase in faint blue galaxies, implying that the process
responsible for this evolution of faint galaxies is the termination of
star-formation, possibly with little or no need for merging. At the bright end,
we also see an increase in the number of blue galaxies with increasing
redshift, suggesting that termination of star-formation in higher mass galaxies
may also be an important formation mechanism for higher mass ellipticals. By
comparing with a low-redshift Abell Cluster sample, we find that the
down-sizing trend seen within RCS-1 has continued to the local universe.Comment: ApJ accepted. 11 pages, 5 figure
Normal random matrix ensemble as a growth problem
In general or normal random matrix ensembles, the support of eigenvalues of
large size matrices is a planar domain (or several domains) with a sharp
boundary. This domain evolves under a change of parameters of the potential and
of the size of matrices. The boundary of the support of eigenvalues is a real
section of a complex curve. Algebro-geometrical properties of this curve encode
physical properties of random matrix ensembles. This curve can be treated as a
limit of a spectral curve which is canonically defined for models of finite
matrices. We interpret the evolution of the eigenvalue distribution as a growth
problem, and describe the growth in terms of evolution of the spectral curve.
We discuss algebro-geometrical properties of the spectral curve and describe
the wave functions (normalized characteristic polynomials) in terms of
differentials on the curve. General formulae and emergence of the spectral
curve are illustrated by three meaningful examples.Comment: 44 pages, 14 figures; contains the first part of the original file.
The second part will be submitted separatel
Ciliary Abnormalities Due to Defects in the Retrograde Transport Protein DYNC2H1 in Short-Rib Polydactyly Syndrome
The short-rib polydactyly (SRP) syndromes are a heterogenous group of perinatal lethal skeletal disorders with polydactyly and multisystem organ abnormalities. Homozygosity by descent mapping in a consanguineous SRP family identified a genomic region that contained DYNC2H1, a cytoplasmic dynein involved in retrograde transport in the cilium. Affected individuals in the family were homozygous for an exon 12 missense mutation that predicted the amino acid substitution R587C. Compound heterozygosity for one missense and one null mutation was identified in two additional nonconsanguineous SRP families. Cultured chondrocytes from affected individuals showed morphologically abnormal, shortened cilia. In addition, the chondrocytes showed abnormal cytoskeletal microtubule architecture, implicating an altered microtubule network as part of the disease process. These findings establish SRP as a cilia disorder and demonstrate that DYNC2H1 is essential for skeletogenesis and growth
The engine reformer: Syngas production in an engine for compact gas-to-liquids synthesis
Methane (CH[subscript 4]) reforming was carried out in an internal combustion engine (an “engine reformer”). We successfully produced syngas from the partial oxidation of natural gas in the cylinder of a diesel engine that was reconfigured to perform spark ignition. Performing the reaction in an engine cylinder allows some of the exothermicity to be captured as useful work. Intake conditions of 110 kPa and up to 480 °C allowed low cycle-to-cycle variability (COV[subscript nimep] 2.4, but < 1 mg/L below these equivalence ratios. These results demonstrate that the engine reformer could be a key component of a compact gas-to-liquids synthesis plant by highlighting the operating conditions under which high gas conversion, high H[subscript 2]-to-CO ratios close to 2.0, and low soot production are possible.United States. Advanced Research Projects Agency-Energy (Award DE-AR0000506)Research Triangle InitiativeMIT Energy InitiativeMassachusetts Institute of Technology. Tata Center for Technology and Desig
The telomere of human chromosome 1p contains at least two independent autosomal dominant congenital cataract genes.
AIMS: Multiple genetic causes of congenital cataract have been identified, both as a component of syndromes and in families that present with isolated congenital cataract. Linkage analysis was used to map the genetic locus in a six generation Australian family presenting with total congenital cataract. METHODS: Microsatellite markers located across all known autosomal dominant congenital cataract loci were genotyped in all recruited family members of the Tasmanian family. Both two point and multipoint linkage analysis were used to assess each locus under an autosomal dominant model. RESULTS: Significant linkage was detected at the telomere of the p arm of chromosome 1, with a maximum two point LOD of 4.21 at marker D1S507, a maximum multipoint exact LOD of 5.44, and an estimated location score of 5.61 at marker D1S507. Haplotype analysis places the gene inside a critical region between D1S228 and D1S199, a distance of approximately 6 megabases. The candidate gene PAX7 residing within the critical interval was excluded by direct sequencing in affected individuals. CONCLUSION: This is the third report of congenital cataract linkage to 1ptel. The critical region as defined by the shared haplotype in this family is clearly centromeric from the Volkmann cataract locus identified through study of a Danish family, indicating that two genes causing autosomal dominant congenital cataract map to the telomeric region of chromosome 1p
‘It Takes Two Hands to Clap’: How Gaddi Shepherds in the Indian Himalayas Negotiate Access to Grazing
This article examines the effects of state intervention on the workings of informal institutions that coordinate the communal use and management of natural resources. Specifically it focuses on the case of the nomadic Gaddi
shepherds and official attempts to regulate their access to grazing pastures in the Indian Himalayas. It is often predicted that the increased presence of the modern state critically undermines locally appropriate and community-based resource management arrangements. Drawing on the work of Pauline Peters and Francis Cleaver, I identify key instances of socially embedded ‘common’ management institutions and explain the evolution of these arrangements
through dynamic interactions between individuals, communities and the agents of the state. Through describing the ‘living space’ of Gaddi shepherds across the annual cycle of nomadic migration with their flocks I explore the
ways in which they have been able to creatively reinterpret external interventions, and suggest how contemporary arrangements for accessing pasture at different moments of the annual cycle involve complex combinations of the
formal and the informal, the ‘traditional’ and the ‘modern’
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