3,988 research outputs found
The expression and potential function of bone morphogenetic proteins 2 and 4 in bovine trophectoderm
<p>Abstract</p> <p>Background</p> <p>Bone morphogenetic proteins (BMPs) were first described for their roles in bone formation, but they now also are known to possess additional activities, including those relating to embryogenesis. The objectives of this work were to 1) determine if peri-attachment bovine conceptuses and bovine trophoblast cells (CT1) contain transcripts for <it>BMP2 </it>and <it>4</it>, an innate inhibitor noggin (<it>NOG</it>), and BMP2/4 receptors (<it>BMPRII</it>, <it>ACVR1</it>, <it>BMPR1A</it>, <it>BMPR1B</it>), and 2) determine if BMP2 or 4 supplementation to CT1 cells affects cell proliferation, differentiation or trophoblast-specific gene expression.</p> <p>Methods</p> <p>RNA was isolated from day 17 bovine conceptuses and CT1 cells. After RT-PCR, amplified products were cloned and sequenced. In other studies CT1 cells were treated with BMP2 or 4 at various concentrations and effects on cell viability, cell differentiation and abundance of IFNT and CSH1 mRNA were evaluated.</p> <p>Results</p> <p>Transcripts for <it>BMP2 </it>and <it>4 </it>were detected in bovine conceptuses and CT1 cells. Also, transcripts for each BMP receptor were detected in conceptuses and CT1 cells. Transcripts for <it>NOG </it>were detected in conceptuses but not CT1 cells. Cell proliferation was reduced by BMP4 but not BMP2 supplementation. Both factors reduced <it>IFNT </it>mRNA abundance but had no effect on <it>CSH1 </it>mRNA abundance in CT1 cells.</p> <p>Conclusions</p> <p>The BMP2/4 ligand and receptor system presides within bovine trophectoderm prior to uterine attachment. BMP4 negatively impacts CT1 cell growth and both BMPs affect IFNT mRNA abundance.</p
Temperature Dependence of the Cu(2) NQR Line Width in YBaCuO
Systematic measurements of the Cu(2) NQR line width were performed in
underdoped YBaCuO samples over the temperature range 4.2 K
K. It was shown that the copper NQR line width monotonically increases
upon lowering temperature in the below-critical region, resembling temperature
behavior of the superconducting gap. The observed dependence is explained by
the fact that the energy of a condensate of sliding charge-current states of
the charge-density-wave type depends on the phase of order parameter.
Calculations show that this dependence appears only at . Quantitative
estimates of the line broadening at agree with the measurement results.Comment: 4 pages, 2 figure
Building the Full Fermion-Photon Vertex of QED by Imposing Multiplicative Renormalizability of the Schwinger-Dyson Equations for the Fermion and Photon Propagators
In principle, calculation of a full Green's function in any field theory
requires knowledge of the infinite set of multi-point Green's functions, unless
one can find some way of truncating the corresponding Schwinger-Dyson
equations. For the fermion and boson propagators in QED this requires an {\it
ansatz} for the full three point vertex. Here we illustrate how the properties
of gauge invariance, gauge covariance and multiplicative renormalizability
impose severe constraints on this fermion-boson interaction, allowing a
consistent truncation of the propagator equations. We demonstrate how these
conditions imply that the 3-point vertex {\bf in the propagator equations} is
largely determined by the behaviour of the fermion propagator itself and not by
knowledge of the many higher point functions. We give an explicit form for the
fermion-photon vertex, which in the fermion and photon propagator fulfills
these constraints to all orders in leading logarithms for massless QED, and
accords with the weak coupling limit in perturbation theory at . This provides the first attempt to deduce non-perturbative Feynman
rules for strong physics calculations of propagators in massless QED that
ensures a more consistent truncation of the 2-point Schwinger-Dyson equations.
The generalisation to next-to-leading order and masses will be described in a
longer publication.Comment: 57 pages, 3 figure
NMR relaxation rates for the spin-1/2 Heisenberg chain
The spin-lattice relaxation rate and the spin echo decay rate
for the spin- antiferromagnetic Heisenberg chain are
calculated using quantum Monte Carlo and maximum entropy analytic continuation.
The results are compared with recent analytical calculations by Sachdev. If the
nuclear hyperfine form factor is strongly peaked around the
predicted low-temperature behavior [, ] extends up to temperatures as high as . If has significant weight for there are large
contributions from diffusive long-wavelength processes not taken into account
in the theory, and very low temperatures are needed in order to observe the
asymptotic forms.Comment: 9 pages, Revtex 3.0, 5 uuencoded ps figures To appear in Phys. Rev.
B, Rapid Com
Can S-LCA methodology support responsible sourcing of raw materials in EU policy context?
Purpose: Access, affordability and sustainability of raw material supply chains are crucial to the sustainable development of the European Union (EU) for both society and economy. The study investigates whether and how the social life cycle assessment (S-LCA) methodology can support responsible sourcing of raw materials in Europe. The potential of social indicators already available in an S-LCA database is tested for the development of new metrics to monitor social risks in raw material industries at EU policy level. Methods: The Product Social Impact Life Cycle Assessment (PSILCA) database was identified as a data and indicators source to assess social risks in raw material industries in EU-28 and extra-EU countries. Six raw material country sectors in the scope of the European policy on raw materials were identified and aggregated among those available in PSILCA. The selection of indicators for the assessment was based on the RACER (Relevance, Acceptance, Credibility, Ease, Robustness) analysis, leading to the proposal of 9 social impact categories. An S-LCA of the selected raw material industries was, thus, performed for the EU-28 region, followed by a contribution analysis to detect direct and indirect impacts and investigate related supply chains. Finally, the social performance of raw material sectors in EU-28 was compared with that of six extra-EU countries. Results and discussion: Considering the overall social risks in raw material industries, “Corruption”, “Fair salary”, “Health and safety” and “Freedom of association and collective bargaining” emerged as the most significant categories both in EU and extra-EU. EU-28 shows an above-average performance where the only exception is represented by the mining and quarrying sector. An investigation of the most contributing processes to social impact categories for EU-28 led to the identification of important risks originating in the supply chain and in extra-EU areas. Therefore, the S-LCA methodology confirmed the potential of a life cycle perspective to detect burdens shifting and trade-offs. However, only a limited view on the sectoral social performance could be obtained from the research due to a lack of social data. Conclusions: The S-LCA methodology and indicators appear appropriate to perform an initial social sustainability screening, thus enabling the identification of hotspots in raw material supply chains and the prioritization of areas of action in EU policies. Further methodological developments in the S-LCA field are necessary to make the approach proposed in the paper fully adequate to support EU policies on raw materials
Constraint on the QED Vertex from the Mass Anomalous Dimension
We discuss the structure of the non-perturbative fermion-boson vertex in
quenched QED. We show that it is possible to construct a vertex which not only
ensures that the fermion propagator is multiplicatively renormalizable, obeys
the appropriate Ward-Takahashi identity, reproduces perturbation theory for
weak couplings and guarantees that the critical coupling at which the mass is
dynamically generated is gauge independent but also makes sure that the value
for the anomalous dimension for the mass function is strictly 1, as Holdom and
Mahanta have proposed.Comment: 8 pages, LaTeX, October 199
ONE LOOP QED VERTEX IN ANY COVARIANT GAUGE: ITS COMPLETE ANALYTIC FORM
The one loop vertex in QED is calculated in arbitrary covariant gauges as an
analytic function of its momenta. The vertex is decomposed into a longitudinal
part, that is fully responsible for ensuring the Ward and Ward-Takahashi
identities are satisfied, and a transverse part. The transverse part is
decomposed into 8 independent components each being separately free of
kinematic singularities in covariant gauge in a basis that modifies
that proposed by Ball and Chiu. Analytic expressions for all 11 components of
the vertex are given explicitly in terms of elementary functions
and one Spence function. These results greatly simplify in particular kinematic
regimes.Comment: 35 pages, latex, 2 figures, Complete postscript file available from:
ftp://cpt1.dur.ac.uk/pub/preprints/dtp95/dtp9506/dtp9406.p
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