An improved perturbation approach to the 2D Edwards polymer -- corrections to scaling

We present the results of a new perturbation calculation in polymer statistics which starts from a ground state that already correctly predicts the long chain length behaviour of the mean square end--to--end distance $\langle R_N^2 \rangle\$, namely the solution to the 2~dimensional~(2D) Edwards model. The $\langle R_N^2 \rangle$ thus calculated is shown to be convergent in $N$, the number of steps in the chain, in contrast to previous methods which start from the free random walk solution. This allows us to calculate a new value for the leading correction--to--scaling exponent~$\Delta$. Writing $\langle R_N^2 \rangle = AN^{2\nu}(1+BN^{-\Delta} + CN^{-1}+...)$, where $\nu = 3/4$ in 2D, our result shows that $\Delta = 1/2$. This value is also supported by an analysis of 2D self--avoiding walks on the {\em continuum}.Comment: 17 Pages of Revtex. No figures. Submitted to J. Phys.

Capacitors can radiate - some consequences of the two-capacitor problem with radiation

We fill a gap in the arguments of Boykin et al [American Journal of Physics, Vol 70 No. 4, pp 415-420 (2002)] by not invoking an electric current loop (i.e. magnetic dipole model) to account for the radiation energy loss, since an obvious corollary of their results is that the capacitors should radiate directly even if the connecting wires are shrunk to zero length. That this is so is shown here by a direct derivation of capacitor radiation using an oscillating electric dipole radiator model for the capacitors as well as the alternative less widely known magnetic 'charge' current loop representation for an electric dipole [see for example "Electromagnetic Waves" by S.A.Schlekunoff, van Nostrand (1948)]. Implications for Electromagnetic Compliance (EMC) issues as well as novel antenna designs further motivate the purpose of this paper.Comment: 5 Pages with No figure

3D Depthwise Convolution: Reducing Model Parameters in 3D Vision Tasks

Standard 3D convolution operations require much larger amounts of memory and computation cost than 2D convolution operations. The fact has hindered the development of deep neural nets in many 3D vision tasks. In this paper, we investigate the possibility of applying depthwise separable convolutions in 3D scenario and introduce the use of 3D depthwise convolution. A 3D depthwise convolution splits a single standard 3D convolution into two separate steps, which would drastically reduce the number of parameters in 3D convolutions with more than one order of magnitude. We experiment with 3D depthwise convolution on popular CNN architectures and also compare it with a similar structure called pseudo-3D convolution. The results demonstrate that, with 3D depthwise convolutions, 3D vision tasks like classification and reconstruction can be carried out with more light-weighted neural networks while still delivering comparable performances.Comment: Work in progres

The Van der Waals interaction of the hydrogen molecule - an exact local energy density functional

We verify that the van der Waals interaction and hence all dispersion interactions for the hydrogen molecule given by: W"= -{A/R^6}-{B/R^8}-{C/R^10}- ..., in which R is the internuclear separation, are exactly soluble. The constants A=6.4990267..., B=124.3990835 ... and C=1135.2140398... (in Hartree units) first obtained approximately by Pauling and Beach (PB) [1] using a linear variational method, can be shown to be obtainable to any desired accuracy via our exact solution. In addition we shall show that a local energy density functional can be obtained, whose variational solution rederives the exact solution for this problem. This demonstrates explicitly that a static local density functional theory exists for this system. We conclude with remarks about generalising the method to other hydrogenic systems and also to helium.Comment: 11 pages, 13 figures and 28 reference

Glass particle contamination of parenteral preparations of intravenous drugs in anaesthetic practice

This was a prospective, randomised, single-blinded comparative study to assess the amount of glass particle contamination in single-use drug ampoules, and to compare the differences between the filter straw (B Braun Filter Straw® 5 micron), 23G hypodermic needles and 18G drawing-up needles in reducing contamination. A total of 360 ampoules of expired drugs was collected and randomised into three groups. The content of each ampoule was syringed out using either a 23G needle, an 18G needle or a B Braun 5 micron Filter Straw®. The content was then emptied onto white filter paper, which was examined under microscopy. Glass particle contaminations were seen in 15 of the 360 ampoules (4.2%). The Filter Straw® group yielded no contaminants when compared with the 18G needle group (p = 0.001). The difference was not significant between the Filter Straw® and the 23G needle group (p = 0.644). The use of smaller gauge (23G) needles prevented glass particle contamination significantly when compared to bigger (18G) needles (p = 0.021). It can be concluded that larger ampoules (10 ml) produce significantly (p = 0.01) higher percentages of contaminants, even when compared to the smaller three ampoule groups combined (1 ml, 2 ml and 5 ml)

Bioactive coatings

From traditional approaches of employing bulk materials to the new generation of bioactive coated implants, the design of such medical tools is being directed towards the implementation bioactive compounds to allow the direct bonding of living tissues and osteoconduction. However, the development of an optimal bioactive implant for tissue regeneration has not been achieved. The research for novel materials is hindered by the biocompatibility and bioactivity of the compound as well as their mechanical properties. To improve the bioactivity of the implants, the increase of surface area of the implant as well as the use of resorbable compounds is being studied with promising results. Among all different materials and composite employed, the common materials include calcium phosphates and resorbable bioglasses inspired in natural scaffold composition of bones and teeth. In some cases, this material is being used as a coating and combined with further treatments and functional coatings which may reinforce its bioresponsive properties, and in some cases, it can provide additional properties such as antimicrobial activity. In addition, a specific class of bioactive coatings based on biodegradable polymers has also been developed. These coatings temporally aim at accelerating wound healing and forming new tissue at the material-tissue interface around implanted devices or protecting those implants against biomaterial-associated infections. Bioactive, degradable coatings can be generated both from natural and synthetic polymers. Common strategies, reviewed here, are based on natural polymers like proteins, polysaccharides, or glycosaminoglycanes to improve their bioactivity either by chemical functionalization of the biopolymer itself (e.g. introduction of bioactive groups) or by immobilization of bioactive components (e.g. cell adhesion peptides). Degradable or at least water-soluble synthetic polymers as polylactones or polyethylene glycols have been used for long time to create carrier materials for bioactive agents. As exemplary illustrated, those polymers are also used creating either substrate-adhering nanofilms or hydrogel-based thick coatings with high bioactivity to stimulate cell adhesion or avoid microbial adhesion. This chapter aims to summarize all recent approaches in the development of various bioactive coating materials, as well as the coating techniques and further treatment, functionalization and surface modification

Theoretical and experimental studies of doping effects on thermodynamic properties of (Dy, Y)-ZrO2

Ionic oxide materials play a vital role in technical applications owing to their high-temperature capability and when used as thermal barrier coating (TBC) materials, for example, they have environmentally friendly effects such as improved fuel efficiency and reduced emissions. Doped ZrO2 based solid solution is attracting attention, whereas doping effects on thermodynamic properties are not well understood. This work reports the synthesis and characterization of doped ZrO2 with Dy3+ and Y3+ via a sol-gel route. The relationship between chemical composition and thermodynamic properties is investigated via experiment and molecular dynamics (MD) simulation. MD simulation has been employed to theoretically explore the crystal structure and to calculate the intrinsic thermal conductivity, which agrees well with the experiment measurement. The thermal conductivity of dense samples is lower than that of conventional 6–8 wt.% Y2O3 stabilized ZrO2 (equivalent to 4 mol% Y2O3 stabilized ZrO2, 4YSZ) at room temperature. The coefficient of thermal expansion is higher due to the doping Dy3+ ion compared with that of 4YSZ. The thermochemical compatibility of Dy0.06Y0.072Zr0.868O1.934 with Al2O3 which is critical for the durability of the TBC system has been studied and can be maintained up to 1500 °C