852 research outputs found
Feynman graph polynomials
The integrand of any multi-loop integral is characterised after Feynman
parametrisation by two polynomials. In this review we summarise the properties
of these polynomials. Topics covered in this article include among others:
Spanning trees and spanning forests, the all-minors matrix-tree theorem,
recursion relations due to contraction and deletion of edges, Dodgson's
identity and matroids.Comment: 35 pages, references adde
Search for a bound di-neutron by comparing He(e,e'p)d and H(e,e'p)X measurements
We report on a search for a bound di-neutron by comparing electron-induced
proton-knockout measurements from Helium-3 (He) and Tritium
(H). The measurements were performed at Jefferson Lab Hall A with a 4.326
GeV electron beam, and kinematics of large momentum transfer
(GeV/) and , to minimize contributions from non quasi-elastic
(QE) reaction mechanisms. Analyzing the measured He missing mass
() and missing energy () distributions, we can distinguish
the two-body break-up reaction, in which the residual proton-neutron system
remains bound as a deuteron. In the H mirror case, under the exact same
kinematic conditions, we do not identify a signature for a bound di-neutron
with similar binding energy to that of the deuteron. We calculate exclusion
limits as a function of the di-neutron binding energy and find that, for
binding equivalent to the deuteron, the two-body break-up cross section on
H is less than 0.9% of that on He in the measured kinematics at the 95%
confidence level.Comment: 6 pages, 3 figure
Keratinocytes drive the epithelial hyperplasia key to sea lice resistance in coho salmon
Background Salmonid species have followed markedly divergent evolutionary trajectories in their interactions with sea lice. While sea lice parasitism poses significant economic, environmental, and animal welfare challenges for Atlantic salmon (Salmo salar) aquaculture, coho salmon (Oncorhynchus kisutch) exhibit near-complete resistance to sea lice, achieved through a potent epithelial hyperplasia response leading to rapid louse detachment. The molecular mechanisms underlying these divergent responses to sea lice are unknown. Results We characterized the cellular and molecular responses of Atlantic salmon and coho salmon to sea lice using single-nuclei RNA sequencing. Juvenile fish were exposed to copepodid sea lice (Lepeophtheirus salmonis), and lice attached pelvic fin and skin samples were collected 12 h, 24 h, 36 h, 48 h, and 60 h after exposure, along with control samples. Comparative analysis of control and treatment samples revealed an immune and wound-healing response that was common to both species, but attenuated in Atlantic salmon, potentially reflecting greater sea louse immunomodulation. Our results revealed unique but complementary roles of three layers of keratinocytes in the epithelial hyperplasia response leading to rapid sea lice rejection in coho salmon. Our results suggest that basal keratinocytes direct the expansion and mobility of intermediate and, especially, superficial keratinocytes, which eventually encapsulate the parasite. Conclusions Our results highlight the key role of keratinocytes in coho salmon’s sea lice resistance and the diverged biological response of the two salmonid host species when interacting with this parasite. This study has identified key pathways and candidate genes that could be manipulated using various biotechnological solutions to improve Atlantic salmon sea lice resistance.publishedVersio
UKGEOS: Glasgow Geothermal Energy Research Field Site (GGERFS): initial summary of the geological platform
The preferred second UKGEOS site is at Clyde Gateway, in the east end of Glasgow, Scotland. The focus of this, the Glasgow Geothermal Energy Research Field Site (GGERFS), is on characterising and monitoring the subsurface for minewater and hot sedimentary aquifer geothermal energy, and for cooling and heat storage.
This report details BGS data and knowledge at late 2016, to define initial characterisation of the ‘geological platform’ relevant for the planning of a geothermal research facility and associated environmental baseline monitoring. The report covers knowledge of the bedrock and superficial deposits geology, abandoned coal mines, hydrogeology, geothermal datasets, geochemistry, remote sensed data, seismicity, stress fields, engineering geology and rock property datasets.
BGS holds a great deal of legacy borehole, mining and geochemistry data and has updated existing bedrock and superficial deposits models of the area. However, deep borehole and seismic data are lacking to define the geology and structure of the area below a few hundred metres. Hydrogeological and temperature data are also lacking for the bedrock strata. Regional datasets and knowledge have (and can be further) used to reduce uncertainty and risk in these aspects of the geological characterisation
A Search for Sigma^0_5, N^0_5 and Theta^++ Pentaquark States
A high-resolution (sigma_instr. = 1.5 MeV) search for narrow states (Gamma <
10 MeV) with masses of M_x approx 1500-1850 MeV in ep -> e'K^+ X, e'K^- X and
e' pi^+ X electroproduction at small angles and low Q^2 was performed. These
states would be candidate partner states of the reported Theta^+(1540)
pentaquark. No statistically significant signal was observed in any of the
channels at 90% C.L. Upper limits on forward production were determined to be
between 0.7% and 4.2% of the Lambda(1520) production cross section, depending
on the channel and the assumed mass and width of the state.Comment: 5 pages, 5 figures, to appear in Phys. Rev. C, update with responses
to referee suggestion
Precision measurements of large scale structure with future type Ia supernova surveys
Type Ia supernovae are currently the best known standard candles at
cosmological distances. In addition to providing a powerful probe of dark
energy they are an ideal source of information about the peculiar velocity
field of the local universe. Even with the very small number of supernovae
presently available it has been possible to measure the dipole and quadrupole
of the local velocity field out to z~0.025. With future continuous all-sky
surveys like the LSST project the luminosity distances of tens of thousands of
nearby supernovae will be measured accurately. This will allow for a
determination of the local velocity structure of the universe as a function of
redshift with unprecedented accuracy, provided the redshifts of the host
galaxies are known. Using catalogues of mock surveys we estimate that future
low redshift supernova surveys will be able to probe sigma-8 to a precision of
roughly 5% at 95% C.L. This is comparable to the precision in future galaxy and
weak lensing surveys and with a relatively modest observational effort it will
provide a crucial cross-check on future measurements of the matter power
spectrum.Comment: 18 pages, 9 figures, submitted to JCA
Controlling the melting transition of semi-crystalline self-assembled block copolymer aggregates: controlling release rates of ibuprofen
Bicontinuous nanospheres and multi-lamellar micelles were self-assembled from poly[ethylene oxide]-block-(poly[octadecyl methacrylate]-random-poly[docosyl methacrylate]), (PEO-b-[PODMA-co-PDSMA]) where PEO is the hydrophilic block (25 wt%) and PODMA/PDSMA is the semi-crystalline hydrophobic block (75 wt%) that gives a thermoresponsive component to the self-assembled aggregates. By varying the relative molar proportion of DSMA to ODMA (from 0 : 1 to 1 : 0) in the synthesis of the copolymers by atom transfer radical polymerisation, the melting transition Tm of the hydrophobic block could be varied from 21.5 to 41.1 °C in the solid state. When self-assembled in aqueous dispersions the Tm range was 23.4 to 41.3 °C, closely matching that of the solid samples. Preliminary analysis of the rate of release of ibuprofen from three of the block copolymer aggregates demonstrated that the rate of release was correlated with the degree of crystallinity of the hydrophobic block and that increasing temperature causes melting and a significantly enhanced release rate
Approximate Quantum Cloning with Nuclear Magnetic Resonance
Here we describe a Nuclear Magnetic Resonance (NMR) experiment that uses a
three qubit NMR device to implement the one to two approximate quantum cloning
network of Buzek et al.Comment: 4 pages RevTeX4 including 5 postscript figures. Submitted to PR
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