26,392 research outputs found
Energy and system size dependence of charged particle elliptic flow and v_2/\eps scaling
We report measurements of charged particle elliptic flow %() at
mid-rapidity in Au+Au and Cu+Cu collisions at and 200
GeV. Using correlations between main STAR TPC and Forward TPCs ensures minimal
bias due to non-flow effects. We further investigate the effect of flow
fluctuations on v_2/\eps scaling studying initial geometry eccentricity
fluctuations in Monte-Carlo Glauber model, consistent with STAR direct
measurements of elliptic flow fluctuations. It is found that accounting for the
effect of flow fluctuations improves v_2/\eps scaling.Comment: 4 pages, Quark Matter 2006 proceeding
Tirisporella gen. nov., an ascomycete from the mangrove palm Nypa fruticans
Tirisporella beccariana comb.nov. is redescribed from decomposing leaf petiole (or rachis) bases of Nypa fruticans recently collected in Malaysia and the Philippiines. The superficial ascomata bear bitunicate asci with (3-)5(-7)-septate ascospores that are brown and verrucose, except for the prominent hyaline basal cell, and furnished with a distinctive apical appendage that arises from the spore wall. Te ultrastructure of the fungus is contrasted with that of species of Corollospora and Corallicola, with particular reference to the mode of ascospore appendage formation. The species was originally described from a Sarawak collection as Sphaeria becariana and later transferred to Melanomma and given the new name Melanomma cesatianum. Gibberidea nipae is a synonym. The recent collections were compared with type specimens. The fungus is not properly placed in Melanomma or Gibberidea or other known genera and a new genus Tiriporella is described.published_or_final_versio
Dating the dead: New radiocarbon dates from the lower Ica Valley, south coast Peru
This article presents radiocarbon dates from human bone samples (n = 13) from seven pre-Columbian cemeteries in the Samaca and Ullujaya Basins of the lower Ica Valley, south coast of Peru, spanning from the end of the Early Horizon to the Inca Late Horizon. These contexts have been severely looted. Yet, in all cases, their putative dating by material culture remains is confirmed by these 14C dates. This shows that such disturbed contexts, sadly typical of the Peruvian coast, can nonetheless still yield valuable bioarchaeological and burial practice data. These dates elaborate upon an emerging picture of the absolute dating of the cultural phases of the wider south coast region, in particular casting new light on the poorly understood Middle Horizon to Late Intermediate period transition. A paucity of archaeological data for this 3-century period has been taken as evidence of some sort of environmentally or socially induced lacuna. Instead, the 14C dates presented here suggest that the basins of the lower Ica Valley were continuously occupied over this period.We thank the Ministerio de Cultural del Perú for granting permission for the fieldwork (No. 0028-2010-VMPCIC-MC) and analysis of samples for dating (No. 369-2011-VMPCIC-MC); Alberto Benavides Ganoza and the people of Samaca for facilitating fieldwork; the Arts and Humanities Research Council for LC's doctoral funding; the NERC Radiocarbon Facility for funding radiocarbon dating (grant number NF/2012/1/7 to TCO’C and LC); and Tom Higham, Diane Baker, Ingmar Unkel and Elmo Leon for their help and advice.This is the final version of the article. It first appeared from University of Arizona via http://dx.doi.org/10.2458/azu_rc.57.1834
Predicting the Remaining Lifespan and Cultivation-Related Loss of Osteogenic Capacity of Bone Marrow Multipotential Stromal Cells Applicable across a Broad Donor Age Range
Background and Objectives. Culture expanded multipotential stromal cells (MSCs) have considerable potential for bone regeneration therapy but their wider use is constrained by the lack of simple and predictive assays of functional potency. Extended passaging leads to loss of multipotency but speed of decline depends on MSC donor age. The aim of this study was to develop an assay predictive of MSC culture longevity applicable to a broad donor age range. Materials and Methods. Bone marrow (BM, =7) was obtained from a diverse range (2–72 years) of healthy donors. MSCs were culture expanded to senescence and their osteoprogenitor content, gene expression profiles, epigenetic signature, and telomere behaviour were measured throughout. Output data was combined for modelling purposes. Results. Regardless of donor age, cultures’ osteoprogenitor content correlated better with remaining lifespan (population doublings before senescence, PD-BS) than proliferative history (accrued PDs). Individual gene’s expression or telomere length did not predict PD-BS but methylation of individual CpG islands did, PRAMEF2 in particular ( = 0.775). Coupling the steep relationship of relative SPARC expression with PD-BS ( = −0.753) the formula SPARC × 1/PREMEF2 gave an improved correlation ( = −0.893).Conclusion. A formula based on SPARC mRNA and PRAMEF2 methylation may be used to predict remaining BM-MSC longevity and related loss of multipotentiality independent of donor age
Solid-state photoreactivity of 9-substituted acridizinium bromide salts
A series of substituted acridizinium bromides was studied to determine how substituents affect the regioselectivity of the solid-state [4 + 4] photodimerisation.This is the final version. It was first published by RSC at http://pubs.rsc.org/en/Content/ArticleLanding/2014/CE/C4CE01622J#!divAbstrac
The Power of Non-Determinism in Higher-Order Implicit Complexity
We investigate the power of non-determinism in purely functional programming
languages with higher-order types. Specifically, we consider cons-free programs
of varying data orders, equipped with explicit non-deterministic choice.
Cons-freeness roughly means that data constructors cannot occur in function
bodies and all manipulation of storage space thus has to happen indirectly
using the call stack.
While cons-free programs have previously been used by several authors to
characterise complexity classes, the work on non-deterministic programs has
almost exclusively considered programs of data order 0. Previous work has shown
that adding explicit non-determinism to cons-free programs taking data of order
0 does not increase expressivity; we prove that this - dramatically - is not
the case for higher data orders: adding non-determinism to programs with data
order at least 1 allows for a characterisation of the entire class of
elementary-time decidable sets.
Finally we show how, even with non-deterministic choice, the original
hierarchy of characterisations is restored by imposing different restrictions.Comment: pre-edition version of a paper accepted for publication at ESOP'1
Optical frequency comb generation from a monolithic microresonator
Optical frequency combs provide equidistant frequency markers in the
infrared, visible and ultra-violet and can link an unknown optical frequency to
a radio or microwave frequency reference. Since their inception frequency combs
have triggered major advances in optical frequency metrology and precision
measurements and in applications such as broadband laser-based gas sensing8 and
molecular fingerprinting. Early work generated frequency combs by intra-cavity
phase modulation while to date frequency combs are generated utilizing the
comb-like mode structure of mode-locked lasers, whose repetition rate and
carrier envelope phase can be stabilized. Here, we report an entirely novel
approach in which equally spaced frequency markers are generated from a
continuous wave (CW) pump laser of a known frequency interacting with the modes
of a monolithic high-Q microresonator13 via the Kerr nonlinearity. The
intrinsically broadband nature of parametric gain enables the generation of
discrete comb modes over a 500 nm wide span (ca. 70 THz) around 1550 nm without
relying on any external spectral broadening. Optical-heterodyne-based
measurements reveal that cascaded parametric interactions give rise to an
optical frequency comb, overcoming passive cavity dispersion. The uniformity of
the mode spacing has been verified to within a relative experimental precision
of 7.3*10(-18).Comment: Manuscript and Supplementary Informatio
Global transcript and phenotypic analysis of yeast cells expressing Ssa1, Ssa2, Ssa3 or Ssa4 as sole source of cytosolic Hsp70-Ssa chaperone activity.
BACKGROUND: Cytosolic Hsp70 is a ubiquitous molecular chaperone that is involved in responding to a variety of cellular stresses. A major function of Hsp70 is to prevent the aggregation of denatured proteins by binding to exposed hydrophobic regions and preventing the accumulation of amorphous aggregates. To gain further insight into the functional redundancy and specialisation of the highly homologous yeast Hsp70-Ssa family we expressed each of the individual Ssa proteins as the sole source of Hsp70 in the cell and assessed phenotypic differences in prion propagation and stress resistance. Additionally we also analysed the global gene expression patterns in yeast strains expressing individual Ssa proteins, using microarray and RT-qPCR analysis. RESULTS: We confirm and extend previous studies demonstrating that cells expressing different Hsp70-Ssa isoforms vary in their ability to propagate the yeast [PSI+] prion, with Ssa3 being the most proficient. Of the four Ssa family members the heat inducible isoforms are more proficient in acquiring thermotolerance and we show a greater requirement than was previously thought, for cellular processes in addition to the traditional Hsp104 protein disaggregase machinery, in acquiring such thermotolerance. Cells expressing different Hsp70-Ssa isoforms also display differences in phenotypic response to exposure to cell wall damaging and oxidative stress agents, again with the heat inducible isoforms providing better protection than constitutive isoforms. We assessed global transcriptome profiles for cells expressing individual Hsp70-Ssa isoforms as the sole source of cytosolic Hsp70, and identified a significant difference in cellular gene expression between these strains. Differences in gene expression profiles provide a rationale for some phenotypic differences we observed in this study. We also demonstrate a high degree of correlation between microarray data and RT-qPCR analysis for a selection of genes. CONCLUSIONS: The Hsp70-Ssa family provide both redundant and variant-specific functions within the yeast cell. Yeast cells expressing individual members of the Hsp70-Ssa family as the sole source of Ssa protein display differences in global gene expression profiles. These changes in global gene expression may contribute significantly to the phenotypic differences observed between the Hsp70-Ssa family members
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