1,747 research outputs found
Combined analysis of KamLAND and Borexino neutrino signals from Th and U decays in the Earth's interior
The KamLAND and Borexino experiments have detected electron antineutrinos
produced in the decay chains of natural thorium and uranium (Th and U
geoneutrinos). We analyze the energy spectra of current geoneutrino data in
combination with solar and long-baseline reactor neutrino data, with
marginalized three-neutrino oscillation parameters. We consider the case with
unconstrained Th and U event rates in KamLAND and Borexino, as well as cases
with fewer degrees of freedom, as obtained by successively assuming for both
experiments a common Th/U ratio, a common scaling of Th+U event rates, and a
chondritic Th/U value. In combination, KamLAND and Borexino can reject the null
hypothesis (no geoneutrino signal) at 5 sigma. Interesting bounds or
indications emerge on the Th+U geoneutrino rates and on the Th/U ratio, in
broad agreement with typical Earth model expectations. Conversely, the results
disfavor the hypothesis of a georeactor in the Earth's core, if its power
exceeds a few TW. The interplay of KamLAND and Borexino geoneutrino data is
highlighted.Comment: 12 pages, including 6 figure
Neutrino Constraints on Inelastic Dark Matter after CDMS II
We discuss the neutrino constraints from solar and terrestrial dark matter
(DM) annihilations in the inelastic dark matter (iDM) scenario after the recent
CDMS II results. To reconcile the DAMA/LIBRA data with constraints from all
other direct experiments, the iDM needs to be light ( GeV) and
have a large DM-nucleon cross section ( 10 pb in the
spin-independent (SI) scattering and 10 pb in the
spin-dependent (SD) scattering). The dominant contribution to the iDM capture
in the Sun is from scattering off Fe/Al in the SI/SD case. Current bounds from
Super-Kamiokande exclude the hard DM annihilation channels, such as ,
, and . For soft channels such as and
, the limits are loose, but could be tested or further constrained
by future IceCube plus DeepCore. For neutrino constraints from the DM
annihilation in the Earth, due to the weaker gravitational effect of the Earth
and inelastic capture condition, the constraint exists only for small mass
splitting 40 keV and GeV even in the channel.Comment: 11 pages, 8 figure
Siderophile Element Profile Measurements in Iron Meteorites Using Laser Ablation ICP-MS
Understanding the behaviour of siderophile elements during cooling of iron meteorites can lead to insight into the general thermal histories of the meteorites as well as their respective parent bodies. Traditionally trace element analyses in meteorites have been done using techniques that only measure the average concentration in each phase. With these methods, all of the spatial information with respect to the distribution of an element within one phase is lost. Measuring concentration profiles of trace elements in meteorites is now possible, with the advent of high-resolution analytical techniques such as laser ablation, inductively coupled plasma mass spectrometry (LA-ICP-MS) with spatial resolution <20 microns. [e.g. 1,2] and secondary ion mass spectrometry [3]. These profiles can give more insight into both the partitioning and diffusive behavior of siderophile elements in metal systems relevant to iron meteorites, as well as parent body cooling rates
Poisson transition rates from time-domain measurements with finite bandwidth
In time-domain measurements of a Poisson two-level system, the observed
transition rates are always smaller than those of the actual system, a general
consequence of finite measurement bandwidth in an experiment. This
underestimation of the rates is significant even when the measurement and
detection apparatus is ten times faster than the process under study. We derive
here a quantitative form for this correction using a straightforward
state-transition model that includes the detection apparatus, and provide a
method for determining a system's actual transition rates from
bandwidth-limited measurements. We support our results with computer
simulations and experimental data from time-domain measurements of
quasiparticle tunneling in a single-Cooper-pair transistor.Comment: 4 pages, 5 figure
Teleology and Realism in Leibniz's Philosophy of Science
This paper argues for an interpretation of Leibniz’s claim that physics requires both mechanical and teleological principles as a view regarding the interpretation of physical theories. Granting that Leibniz’s fundamental ontology remains non-physical, or mentalistic, it argues that teleological principles nevertheless ground a realist commitment about mechanical descriptions of phenomena. The empirical results of the new sciences, according to Leibniz, have genuine truth conditions: there is a fact of the matter about the regularities observed in experience. Taking this stance, however, requires bringing non-empirical reasons to bear upon mechanical causal claims. This paper first evaluates extant interpretations of Leibniz’s thesis that there are two realms in physics as describing parallel, self-sufficient sets of laws. It then examines Leibniz’s use of teleological principles to interpret scientific results in the context of his interventions in debates in seventeenth-century kinematic theory, and in the teaching of Copernicanism. Leibniz’s use of the principle of continuity and the principle of simplicity, for instance, reveal an underlying commitment to the truth-aptness, or approximate truth-aptness, of the new natural sciences. The paper concludes with a brief remark on the relation between metaphysics, theology, and physics in Leibniz
A gene-tree test of the traditional taxonomy of American deer: the importance of voucher specimens, geographic data, and dense sampling
The taxonomy of American deer has been established almost entirely on the basis of morphological data and without the use of explicit phylogenetic methods; hence, phylogenetic analyses including data for all of the currently recognized species, even if based on a single gene, might improve current understanding of their taxonomy. We tested the monophyly of the morphology-defined genera and species of New World deer (Odocoileini) with phylogenetic analyses of mitochondrial DNA sequences. This is the first such test conducted using extensive geographic and taxonomic sampling. Our results do not support the monophyly of Mazama, Odocoileus, Pudu, M. americana, M. nemorivaga, Od. hemionus, and Od. virginianus. Mazama contains species that belong to other genera. We found a novel sister-taxon relationship between “Mazama” pandora and a clade formed by Od. hemionus columbianus and Od. h. sitkensis, and transfer pandora to Odocoileus. The clade formed by Od. h. columbianus and Od. h. sitkensis may represent a valid species, whereas the remaining subspecies of Od. hemionus appear closer to Od. virginianus. Pudu (Pudu) puda was not found sister to Pudu (Pudella) mephistophiles. If confirmed, this result will prompt the recognition of the monotypic Pudella as a distinct genus. We provide evidence for the existence of an undescribed species now confused with Mazama americana, and identify other instances of cryptic, taxonomically unrecognized species-level diversity among populations here regarded as Mazama temama, “Mazama” nemorivaga, and Hippocamelus antisensis. Noteworthy records that substantially extend the known distributions of M. temama and “M.” gouazoubira are provided, and we unveil a surprising ambiguity regarding the distribution of “M.” nemorivaga, as it is described in the literature. The study of deer of the tribe Odocoileini has been hampered by the paucity of information regarding voucher specimens and the provenance of sequences deposited in GenBank. We pinpoint priorities for future systematic research on the tribe Odocoileini.Eliécer E. Gutiérrez, Kristofer M. Helgen, Molly M. McDonough, Franziska Bauer, Melissa T.R. Hawkins, Luis A. Escobedo-Morales, Bruce D. Patterson, Jesus E. Maldonad
Multiscale, multimodal analysis of tumor heterogeneity in IDH1 mutant vs wild-type diffuse gliomas.
Glioma is recognized to be a highly heterogeneous CNS malignancy, whose diverse cellular composition and cellular interactions have not been well characterized. To gain new clinical- and biological-insights into the genetically-bifurcated IDH1 mutant (mt) vs wildtype (wt) forms of glioma, we integrated data from protein, genomic and MR imaging from 20 treatment-naïve glioma cases and 16 recurrent GBM cases. Multiplexed immunofluorescence (MxIF) was used to generate single cell data for 43 protein markers representing all cancer hallmarks, Genomic sequencing (exome and RNA (normal and tumor) and magnetic resonance imaging (MRI) quantitative features (protocols were T1-post, FLAIR and ADC) from whole tumor, peritumoral edema and enhancing core vs equivalent normal region were also collected from patients. Based on MxIF analysis, 85,767 cells (glioma cases) and 56,304 cells (GBM cases) were used to generate cell-level data for 24 biomarkers. K-means clustering was used to generate 7 distinct groups of cells with divergent biomarker profiles and deconvolution was used to assign RNA data into three classes. Spatial and molecular heterogeneity metrics were generated for the cell data. All features were compared between IDH mt and IDHwt patients and were finally combined to provide a holistic/integrated comparison. Protein expression by hallmark was generally lower in the IDHmt vs wt patients. Molecular and spatial heterogeneity scores for angiogenesis and cell invasion also differed between IDHmt and wt gliomas irrespective of prior treatment and tumor grade; these differences also persisted in the MR imaging features of peritumoral edema and contrast enhancement volumes. A coherent picture of enhanced angiogenesis in IDHwt tumors was derived from multiple platforms (genomic, proteomic and imaging) and scales from individual proteins to cell clusters and heterogeneity, as well as bulk tumor RNA and imaging features. Longer overall survival for IDH1mt glioma patients may reflect mutation-driven alterations in cellular, molecular, and spatial heterogeneity which manifest in discernable radiological manifestations
Geo-neutrinos: A systematic approach to uncertainties and correlations
Geo-neutrinos emitted by heat-producing elements (U, Th and K) represent a
unique probe of the Earth interior. The characterization of their fluxes is
subject, however, to rather large and highly correlated uncertainties. The
geochemical covariance of the U, Th and K abundances in various Earth
reservoirs induces positive correlations among the associated geo-neutrino
fluxes, and between these and the radiogenic heat. Mass-balance constraints in
the Bulk Silicate Earth (BSE) tend instead to anti-correlate the radiogenic
element abundances in complementary reservoirs. Experimental geo-neutrino
observables may be further (anti)correlated by instrumental effects. In this
context, we propose a systematic approach to covariance matrices, based on the
fact that all the relevant geo-neutrino observables and constraints can be
expressed as linear functions of the U, Th and K abundances in the Earth's
reservoirs (with relatively well-known coefficients). We briefly discuss here
the construction of a tentative "geo-neutrino source model" (GNSM) for the U,
Th, and K abundances in the main Earth reservoirs, based on selected
geophysical and geochemical data and models (when available), on plausible
hypotheses (when possible), and admittedly on arbitrary assumptions (when
unavoidable). We use then the GNSM to make predictions about several
experiments ("forward approach"), and to show how future data can constrain - a
posteriori - the error matrix of the model itself ("backward approach"). The
method may provide a useful statistical framework for evaluating the impact and
the global consistency of prospective geo-neutrino measurements and Earth
models.Comment: 17 pages, including 4 figures. To appear on "Earth, Moon, and
Planets," Special Issue on "Neutrino Geophysics," Proceedings of Neutrino
Science 2005 (Honolulu, Hawaii, Dec. 2005
The 21 cm Signature of Shock Heated and Diffuse Cosmic String Wakes
The analysis of the 21 cm signature of cosmic string wakes is extended in
several ways. First we consider the constraints on from the absorption
signal of shock heated wakes laid down much later than matter radiation
equality. Secondly we analyze the signal of diffuse wake, that is those wakes
in which there is a baryon overdensity but which have not shock heated. Finally
we compare the size of these signals compared to the expected thermal noise per
pixel which dominates over the background cosmic gas brightness temperature and
find that the cosmic string signal will exceed the thermal noise of an
individual pixel in the Square Kilometre Array for string tensions .Comment: 10 pages, 4 figures, Appendix added, version published in JCA
Organizational Agility through Project Portfolio Management
In dynamic environments, organizational agility is essential for survival; organizations must be able to adapt to change in order to succeed. In project-based organizations, a dynamic project portfolio management (PPM) capability can enhance organizational agility. PPM is an important organizational capability that enables organizations to manage and balance the portfolio holistically, to align projects with strategy, and to ensure adequate resourcing for projects in order to maximize the benefits from project investments. A dynamic PPM capability enables organizations to be agile and flexible by facilitating adjustments to the project portfolio and reallocating resources in response to the changes in the environment. In order for the PPM capability to remain relevant, it must evolve to reflect changes in the environment. Examples of aspects of PPM that enhance organizational agility are outlined in this paper to provide guidance for practitioners
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