1,990 research outputs found
An exploration of the relationship of chemical and physical parameters in the micromechanical characterisation of the apparent interfacial strength in glass fibre epoxy systems
This paper focuses on the cure shrinkage and the thermomechanical properties of an amine cured epoxy resin system and its adhesion to glass fibre. The fibre-matrix interfacial shear strength (IFSS) was characterized using the microbond test over a range of test temperatures and a range of amine:epoxy ratios. The apparent IFSS in this glass-epoxy system was shown to be strongly dependent on the testing temperature and the matrix stoichiometry. High levels of cure shrinkage were measured in the IFSS microdroplets which resulted in internal stresses causing significant levels of droplet deformation. The results presented here can be interpreted as providing further support for the hypothesis that a significant fraction of the interfacial stress transfer capability in epoxy composites can be attributed to a combination of residual radial compressive stress and static friction at the fibre-matrix interface
Ether-a-go-go related gene-1a potassium channel abundance varies within specific skeletal muscle fiber type
A Java Middleware for Guaranteeing Privacy of Distributed Tuple Spaces
The tuple space communication model, such as the one used in Linda, provides great flexibility for modeling concurrent, distributed and mobile processes. In a distributed setting with mobile agents, particular attention is needed for protecting sites and information. We have designed and developed a Java middleware, Klava, for implementing distributed tuple spaces and operations to support agent interaction and mobility. In this paper, we extend the Klava middleware with cryptographic primitives that enable encryption and decryption of tuple fields. We describe the actual implementation of the new primitives and provide a few examples. The proposed extension is general enough to be applied to similar Java frameworks using multiple distributed tuples spaces possibly dealing with mobility
Green's function for gravitational waves in FRW spacetimes
A method for calculating the retarded Green's function for the gravitational
wave equation in Friedmann-Roberson-Walker spacetimes, within the formalism of
linearized Einstein gravity is developed. Hadamard's general solution to
Cauchy's problem for second-order, linear partial differential equations is
applied to the FRW gravitational wave equation. The retarded Green's function
may be calculated for any FRW spacetime, with curved or flat spatial sections,
for which the functional form of the Ricci scalar curvature is known. The
retarded Green's function for gravitational waves propagating through a
cosmological fluid composed of both radiation and dust is calculated
analytically for the first time. It is also shown that for all FRW spacetimes
in which the Ricci scalar curvatures does not vanish, , the Green's
function violates Huygens' principle; the Green's function has support inside
the light-cone due to the scatter of gravitational waves off the background
curvature.Comment: 9 pages, FERMILAB-Pub-93/189-
The Quantized Sigma Model Has No Continuum Limit in Four Dimensions. I. Theoretical Framework
The nonlinear sigma model for which the field takes its values in the coset
space is similar to quantum gravity in being
perturbatively nonrenormalizable and having a noncompact curved configuration
space. It is therefore a good model for testing nonperturbative methods that
may be useful in quantum gravity, especially methods based on lattice field
theory. In this paper we develop the theoretical framework necessary for
recognizing and studying a consistent nonperturbative quantum field theory of
the model. We describe the action, the geometry of the
configuration space, the conserved Noether currents, and the current algebra,
and we construct a version of the Ward-Slavnov identity that makes it easy to
switch from a given field to a nonlinearly related one. Renormalization of the
model is defined via the effective action and via current algebra. The two
definitions are shown to be equivalent. In a companion paper we develop a
lattice formulation of the theory that is particularly well suited to the sigma
model, and we report the results of Monte Carlo simulations of this lattice
model. These simulations indicate that as the lattice cutoff is removed the
theory becomes that of a pair of massless free fields. Because the geometry and
symmetries of these fields differ from those of the original model we conclude
that a continuum limit of the model which preserves
these properties does not exist.Comment: 25 pages, no figure
The Maturation of Interference Suppression and Response Inhibition: ERP Analysis of a Cued Go/Nogo Task
Inhibitory control is a core function that allows us to resist interference from our surroundings and to stop an ongoing action. To date, it is not clear whether inhibitory control is a single process or whether it is composed of different processes. Further, whether these processes are separate or clustered in childhood is under debate. In this study, we investigated the existence and development of two hypothesized component processes of inhibitory control-interference suppression and response inhibition-using a single task and event related potential components. Twenty 8-year-old children and seventeen adults performed a spatially cued Go/Nogo task while their brain activity was recorded using electroencephalography. Mean N2 amplitudes confirmed the expected pattern for response inhibition with both the children and the adults showing more negative N2 for Nogo vs. Go trials. The interference suppression N2 effect was only present in adults and appeared as a more negative N2 in response to Go trials with a congruent cue than Go trials with an incongruent cue. Contrary to previous findings, there was no evidence that the interference suppression N2 effect was later occurring than the response inhibition N2 effect. Overall, response inhibition was present in both the children and the adults whereas interference suppression was only present in the adults. These results provide evidence of distinct maturational processes for both component processes of inhibitory control, with interference suppression probably continuing to develop into late childhood.This study was supported by a PhD scholarship received by LV from the Faculty of Education at the University of Cambridge, UK
Fertilization in C. elegans requires an intact C-terminal RING finger in sperm protein SPE-42
<p>Abstract</p> <p>Background</p> <p>The <it>C. elegans </it>sperm protein SPE-42, a membrane protein of unknown structure and molecular function, is required for fertilization. Sperm from worms with <it>spe-42 </it>mutations appear normal but are unable to fertilize eggs. Sequence analysis revealed the presence of 8 conserved cysteine residues in the C-terminal cytoplasmic domain of this protein suggesting these residues form a zinc-coordinating RING finger structure.</p> <p>Results</p> <p>We made an <it>in silico </it>structural model of the SPE-42 RING finger domain based on primary sequence analysis and previously reported RING structures. To test the model, we created <it>spe-42 </it>transgenes coding for mutations in each of the 8 cysteine residues predicted to coordinate Zn<sup>++ </sup>ions in the RING finger motif. Transgenes were crossed into a <it>spe-42 </it>null background and protein function was measured by counting progeny. We found that all 8 cysteines are required for protein function. We also showed that sequence differences between the C-terminal 29 and 30 amino acids in <it>C. elegans </it>and <it>C. briggsae </it>SPE-42 following the RING finger domain are not responsible for the failure of the <it>C. briggsae </it>SPE-42 homolog to rescue <it>C. elegans spe-42 </it>mutants.</p> <p>Conclusions</p> <p>The results suggest that a <it>bona fide </it>RING domain is present at the C-terminus of the SPE-42 protein and that this motif is required for sperm-egg interactions during <it>C. elegans </it>fertilization. Our structural model of the RING domain provides a starting point for further structure-function analysis of this critical region of the protein. The C-terminal domain swap experiment suggests that the incompatibility between the <it>C. elegans </it>and <it>C. briggsae </it>SPE-42 proteins is caused by small amino acid differences outside the C-terminal domain.</p
C/EBPβ-1 promotes transformation and chemoresistance in Ewing sarcoma cells.
CEBPB copy number gain in Ewing sarcoma was previously shown to be associated with worse clinical outcome compared to tumors with normal CEBPB copy number, although the mechanism was not characterized. We employed gene knockdown and rescue assays to explore the consequences of altered CEBPB gene expression in Ewing sarcoma cell lines. Knockdown of EWS-FLI1 expression led to a decrease in expression of all three C/EBPβ isoforms while re-expression of EWS-FLI1 rescued C/EBPβ expression. Overexpression of C/EBPβ-1, the largest of the three C/EBPβ isoforms, led to a significant increase in colony formation when cells were grown in soft agar compared to empty vector transduced cells. In addition, depletion of C/EBPβ decreased colony formation, and re-expression of either C/EBPβ-1 or C/EBPβ-2 rescued the phenotype. We identified the cancer stem cell marker ALDH1A1 as a target of C/EBPβ in Ewing sarcoma. Furthermore, increased expression of C/EBPβ led to resistance to chemotherapeutic agents. In summary, we have identified CEBPB as an oncogene in Ewing sarcoma. Overexpression of C/EBPβ-1 increases transformation, upregulates expression of the cancer stem cell marker ALDH1A1, and leads to chemoresistance
79/81Br nuclear quadrupole resonance spectroscopic characterization of halogen bonds in supramolecular assemblies
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