4,738 research outputs found
Behaviour and process in the formation of the North European Acheulean record: Towards a Unified Palaeolithic Landscape Approach
The Acheulean record of northern France and southern Britain has long been acknowledged as internationally important, having played an important historical role in the development of the discipline. Abundant artefacts have been recovered, primarily from fluvial gravel archives, allowing the responses of Middle Pleistocene human populations on the edge of their geographical distribution to be interrogated. The richness of the record from such deposits can most simply be read as reflecting absolute population numbers – and changes in this over time. However, factors such as regional super-abundance of high quality flint (related to solid geology) and intensity of aggregate exploitation also played their part in generating the apparently regionally dense record of finds. This paper investigates the inter-related patterns of human behaviour, preservation, artefact release and research tradition which underpin these basic distribution maps. We here present a framework for understanding the processes which have created the current distribution map – in terms of where we find material, and which periods are best represented within it. We term this the Unified Palaeolithic Landscape Approach and outline ways in which the spatial and temporal range of the Acheulean record can be addressed through the archaeological record of its heartland
Coreless Terrestrial Exoplanets
Differentiation in terrestrial planets is expected to include the formation
of a metallic iron core. We predict the existence of terrestrial planets that
have differentiated but have no metallic core--planets that are effectively a
giant silicate mantle. We discuss two paths to forming a coreless terrestrial
planet, whereby the oxidation state during planetary accretion and
solidification will determine the size or existence of any metallic core. Under
this hypothesis, any metallic iron in the bulk accreting material is oxidized
by water, binding the iron in the form of iron oxide into the silicate minerals
of the planetary mantle. The existence of such silicate planets has
consequences for interpreting the compositions and interior density structures
of exoplanets based on their mass and radius measurements.Comment: ApJ, in press. 22 pages, 5 figure
pkCSM: Predicting Small-Molecule Pharmacokinetic and Toxicity Properties Using Graph-Based Signatures.
Drug development has a high attrition rate, with poor pharmacokinetic and safety properties a significant hurdle. Computational approaches may help minimize these risks. We have developed a novel approach (pkCSM) which uses graph-based signatures to develop predictive models of central ADMET properties for drug development. pkCSM performs as well or better than current methods. A freely accessible web server (http://structure.bioc.cam.ac.uk/pkcsm), which retains no information submitted to it, provides an integrated platform to rapidly evaluate pharmacokinetic and toxicity properties.Newton Fund RCUK-CONFAP grant awarded by The Medical
Research Council (MRC) and Fundac
a
o de Amparo a
Pesquisa
do Estado de Minas Gerais (FAPEMIG) [to D.E.V.P., T.L.B,.
and D.B.A.]; Conselho Nacional de Desenvolvimento
Cienti
fi
co e Tecnolo
gico (CNPq), and Centro de Pesquisas
Rene
Rachou (CPqRR/FIOCRUZ Minas), Brazil [to
D.E.V.P.]; NHMRC CJ Martin Fellowship [APP1072476 to
D.B.A.]; University of Cambridge and The Wellcome Trust for
facilities and support [to T.L.B.]. Funding for open access
charge: The Wellcome Trust.This is the final version. It was first published by ACS at http://pubs.acs.org/doi/abs/10.1021/acs.jmedchem.5b00104
Spatially resolved spectra of 3C galaxy nuclei
We present and discuss visible-wavelength long-slit spectra of four low
redshift 3C galaxies obtained with the STIS instrument on the Hubble Space
Telescope. The slit was aligned with near-nuclear jet-like structure seen in
HST images of the galaxies, to give unprecedented spatial resolution of the
galaxy inner regions. In 3C 135 and 3C 171, the spectra reveal clumpy emission
line structures that indicate outward motions of a few hundred km s
within a centrally illuminated and ionised biconical region. There may also be
some low-ionisation high-velocity material associated with 3C 135. In 3C 264
and 3C 78, the jets have blue featureless spectra consistent with their
proposed synchrotron origin. There is weak associated line emission in the
innermost part of the jets with mild outflow velocity. These jets are bright
and highly collimated only within a circumnuclear region of lower galaxy
luminosity, which is not dusty. We discuss the origins of these central regions
and their connection with relativistic jets.Comment: 15 pages incl Tables, 12 diagrams, To appear in A
Determination of the Critical Point and Exponents from short-time Dynamics
The dynamic process for the two dimensional three state Potts model in the
critical domain is simulated by the Monte Carlo method. It is shown that the
critical point can rigorously be located from the universal short-time
behaviour. This makes it possible to investigate critical dynamics
independently of the equilibrium state. From the power law behaviour of the
magnetization the exponents and are determined.Comment: 6 pages, 4 figure
On the sensitivity of condensed-matter P- and T-violation experiments
Experiments searching for parity- and time-reversal-invariance-violating
effects that rely on measuring magnetization of a condensed-matter sample
induced by application of an electric field are considered. A limit on
statistical sensitivity arises due to random fluctuations of the spins in the
sample. The scaling of this limit with the number of spins and their relaxation
time is derived. Application to an experiment searching for nuclear Schiff
moment in a ferroelectric is discussed.Comment: 6 pages, no figure
The transition from quasar radio-loud to radio-quiet state in the framework of the black hole scalability hypothesis
There are several lines of evidence that active galactic nuclei (AGN) can be
regarded as scaled-up X-ray binaries (XRB). The timescales of the evolutionary
phenomena in these two classes are proportional to the black hole (BH) masses.
Consequently, unlike in the case of XRBs, the evolution of AGNs is too slow to
be followed directly. What could be done, however, is to assign particular
types of active galaxies to different evolutionary stages observable in XRBs.
We studied such an assignment for three quasars with clear signatures of a
recent transition from the radio-loud to the radio-quiet state. The quasars we
investigated have large-scale radio lobes that are clearly asymmetric -- one
lobe is of Fanaroff-Riley II type, while the other one is a diffuse relic
devoid of a hotspot. We suggest that the prime cause of the asymmetry of these
radio sources is that the nuclei of their host galaxies currently produce no
jets. To prove that, we observed them with milliarcsecond resolution to check
if they are similar to those in radio-quiet quasars. The observations carried
out with the EVN revealed that the nuclei of the quasars under investigation
are not of a core-jet type that is characteristic for radio-loud,
lobe-dominated quasars. It follows that the lobes are no longer fuelled and
that the apparent asymmetry results from the orientation, which causes a time
lag of the order of 10^6 years between their images: the lobe perceived as a
relic is nearer than the lobe with a hotspot and so it is observed in a later
stage of the decay. The three AGNs under investigation were radio-loud earlier,
but now they have switched to the radio-quiet state. In the framework of the
XRB/AGN unification, the above means that they have left the very high state
and have moved now to the high/soft state. (abridged)Comment: 8 pages, 4 figures, A&A in pres
In silico functional dissection of saturation mutagenesis: Interpreting the relationship between phenotypes and changes in protein stability, interactions and activity.
Despite interest in associating polymorphisms with clinical or experimental phenotypes, functional interpretation of mutation data has lagged behind generation of data from modern high-throughput techniques and the accurate prediction of the molecular impact of a mutation remains a non-trivial task. We present here an integrated knowledge-driven computational workflow designed to evaluate the effects of experimental and disease missense mutations on protein structure and interactions. We exemplify its application with analyses of saturation mutagenesis of DBR1 and Gal4 and show that the experimental phenotypes for over 80% of the mutations correlate well with predicted effects of mutations on protein stability and RNA binding affinity. We also show that analysis of mutations in VHL using our workflow provides valuable insights into the effects of mutations, and their links to the risk of developing renal carcinoma. Taken together the analyses of the three examples demonstrate that structural bioinformatics tools, when applied in a systematic, integrated way, can rapidly analyse a given system to provide a powerful approach for predicting structural and functional effects of thousands of mutations in order to reveal molecular mechanisms leading to a phenotype. Missense or non-synonymous mutations are nucleotide substitutions that alter the amino acid sequence of a protein. Their effects can range from modifying transcription, translation, processing and splicing, localization, changing stability of the protein, altering its dynamics or interactions with other proteins, nucleic acids and ligands, including small molecules and metal ions. The advent of high-throughput techniques including sequencing and saturation mutagenesis has provided large amounts of phenotypic data linked to mutations. However, one of the hurdles has been understanding and quantifying the effects of a particular mutation, and how they translate into a given phenotype. One approach to overcome this is to use robust, accurate and scalable computational methods to understand and correlate structural effects of mutations with disease.Newton Fund RCUK-CONFAP Grant awarded by The Medical Research Council (MRC) and Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) [to D.E.V.P, T.L.B. and D.B.A.]. Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and René Rachou Research Center (CPqRR/FIOCRUZ Minas), Brazil [to D.E.V.P.]; NHMRC CJ Martin Fellowship [APP1072476 to D.B.A.]; University of Cambridge and The Wellcome Trust for facilities and support [to T.L.B.]. Funding for open access charge: The Wellcome Trust.This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/srep1984
Unconventional charge density wave in the organic conductor alpha-(BEDT-TTF)_2KHg(SCN)_4
The low temperature phase (LTP) of alpha-(BEDT-TTF)_2KHg(SCN)_4 salt is known
for its surprising angular dependent magnetoresistance (ADMR), which has been
studied intensively in the last decade. However, the nature of the LTP has not
been understood until now. Here we analyse theoretically ADMR in unconventional
(or nodal) charge density wave (UCDW). In magnetic field the quasiparticle
spectrum in UCDW is quantized, which gives rise to spectacular ADMR. The
present model accounts for many striking features of ADMR data in
alpha-(BEDT-TTF)_2KHg(SCN)_4.Comment: 5 pages, 6 figure
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