A survey of partial differential equations in geometric design

YesComputer aided geometric design is an area where the improvement of surface generation techniques is an everlasting demand since faster and more accurate geometric models are required. Traditional methods for generating surfaces were initially mainly based upon interpolation algorithms. Recently, partial differential equations (PDE) were introduced as a valuable tool for geometric modelling since they offer a number of features from which these areas can benefit. This work summarises the uses given to PDE surfaces as a surface generation technique togethe

Expression of connexins in human preimplantation embryos in vitro

Intercellular communication via gap junctions is required to coordinate developmental processes in the mammalian embryo. We have investigated if the connexin (Cx) isoforms known to form gap junctions in rodent preimplantation embryos are also expressed in human embryos, with the aim of identifying species differences in communication patterns in early development. Using a combination of polyA PCR and immunocytochemistry we have assessed the expression of Cx26, Cx31, Cx32, Cx40, Cx43 and Cx45 which are thought to be important in early rodent embryos. The results demonstrate that Cx31 and Cx43 are the main connexin isoforms expressed in human preimplantation embryos and that these isoforms are co-expressed in the blastocyst. Cx45 protein is expressed in the blastocyst but the protein may be translated from a generally low level of transcripts: which could only be detected in the PN to 4-cell embryos. Interestingly, Cx40, which is expressed by the extravillous trophoblast in the early human placenta, was not found to be expressed in the blastocyst trophectoderm from which this tissue develops. All of the connexin isoforms in human preimplantation embryos are also found in rodents pointing to a common regulation of these connexins in development of rodent and human early embryos and perhaps other species

Interactive design of complex mechanical parts using a parametric representation.

Ye

Temperature dependence of non-linear electrical conduction behavior in a screen-printed multi-component nanocomposite

Nanocomposite materials are of growing applications importance in many areas, particularly touch sensitive surfaces. Here, current-voltage measurements were performed over a range of temperatures and static compressive loadings on a new variant of a multi-component, screen-printed nanocomposite ink, in order to understand the physical nature of the electrical transport behavior. A physical model, combining a linear percolative electrical conductance and a highly non-linear conductance, that is ascribed to field assisted quantum tunneling, was successful in describing the temperature dependence of the I-V. This provides a theoretical underpinning for conduction in these functional nanocomposites

Strake/delta wing interactions at high angles of attack

The method of vortex discretization is used to analyze the interaction of the vorticity generated by a strake, with the flow over a delta wing. The validity of the approach is first established by making comparisons with established methods for dealing with delta wings, after which compound delta planforms are discussed. An understanding of the favorable interference effects normally associated with this type of configuration is obtained and results are presented to quantify the expected lift increments resulting from the strake interaction

Why do people opt-out or not opt-out of automatic enrolment? A focus group study of automatic enrolment into a workplace pension in the United Kingdom

Automatic enrolment (AE) into a workplace pension is an important recent development in pension policy. An important question for this policy is why do people opt-out or not opt-out of AE? This question is important for understanding the power of suggestion associated with AE as well as responding to concerns that women might face undue pressure to opt-out. This article addresses this question through a focus group study into the United Kingdom’s new AE policy. Women were more likely than men to cite lack of affordability as a reason for opting out. Lack of information also seemed important for the power of suggestion associated with AE. Further research should explore how to make AE less gender blind as well as the types of information or advice that should be provided alongside AE

A numerical study of a binary Yukawa model in regimes characteristic of globular proteins in solutions

The main goal of this paper is to assess the limits of validity, in the regime of low concentration and strong Coulomb coupling (high molecular charges), for a simple perturbative approximation to the radial distribution functions (RDF), based upon a low-density expansion of the potential of mean force and proposed to describe protein-protein interactions in a recent Small-Angle-Scattering (SAS) experimental study. A highly simplified Yukawa (screened Coulomb) model of monomers and dimers of a charged globular protein ($\beta$-lactoglobulin) in solution is considered. We test the accuracy of the RDF approximation, as a necessary complementary part of the previous experimental investigation, by comparison with the fluid structure predicted by approximate integral equations and exact Monte Carlo (MC) simulations. In the MC calculations, an Ewald construction for Yukawa potentials has been used to take into account the long-range part of the interactions in the weakly screened cases. Our results confirm that the perturbative first-order approximation is valid for this system even at strong Coulomb coupling, provided that the screening is not too weak (i.e., for Debye length smaller than monomer radius). A comparison of the MC results with integral equation calculations shows that both the hypernetted-chain (HNC) and the Percus-Yevick (PY) closures have a satisfactory behavior under these regimes, with the HNC being superior throughout. The relevance of our findings for interpreting SAS results is also discussed.Comment: Physical Review E, in press (2005

Vapor sensing properties of a conductive polymer composite containing Nickel particles with nano-scale surface features

This paper presents an unusual conductive polymer composite, produced by Peratech Ltd under the trademark QTC™, which has many vapor sensing applications. Nickel particles are intimately coated by an elastomeric binder such that no percolative conduction can occur. However, the nickel particles are shown to possess spiky nanoscale surface features, which promote conduction by a field-assisted quantum tunneling mechanism. Granular QTC™ can be dispersed into a polymer matrix to produce a vapor sensor. Under exposure to vapor, the polymer swells and the resistance of the composite increases. In this work, granular sensors are subjected to acetone and tetrahydrofuran (THF) vapors. The response for THF shows an increase in resistance of a factor of 108, over a time-scale of a few seconds. This response is larger and faster than many conventional vapor sensing composites. This is a significantly larger response than that obtained historically for the same sensor, suggesting that some degree of sensor aging is desirable. The response and subsequent recovery can be explained by a case II diffusion model, and linked to Hildebrand solubility parameters of the vapor and polymer components

Reduction of Experimental Myocardial Infarct Size by Corticosteroid Administration

The influence of the administration of pharmacologic doses of hydrocortisone on the extent and severity of acute myocardial ischemic injury and on subsequent necrosis after acute coronary occlusion was investigated in 28 dogs. In order to study acute myocardial injury, repeated epicardial electrocardiograms were recorded from 10 to 15 sites on the anterior surface of the left ventricle. Average ST segment elevation (ST) and the number of sites in which ST segment elevation exceeded 2 mV (NST), indices of the magnitude and extent of myocardial injury, respectively, were analyzed at 30 and 60 min after coronary occlusion. In the control group ST and NST did not change significantly in this time interval while in the treated group, which received 50 mg/kg hydrocortisone just after the 30 min recording, ST fell from 3.5+/-0.8 to 1.1+/-0.4 mV (P 2 mV) in the control group showed histologic changes compatible with early myocardial infarction in 96% of specimens, while this occurred only in 61% and 63% of specimens, respectively, in the treated groups, showing that over one third of the sites were protected from undergoing necrosis due to the intervening hydrocortisone treatment. Thus pharmacological doses of hydrocortisone prevent myocardial cells from progressing to ischemic necrosis even when administration is initiated 6 h after coronary occlusion