Adsorption of pathogenic prion protein to quartz sand

Management responses to prion diseases of cattle, deer, and elk create a significant need for safe and effective disposal of infected carcasses and other materials. Furthermore, soil may contribute to the horizontal transmission of sheep scrapie and cervid chronic wasting disease by serving as an environmental reservoirforthe infectious agent. As an initial step toward understanding prion mobility in porous materials such as soil and landfilled waste, the influence of pH and ionic strength (l) on pathogenic prion protein (PrPsc) properties (viz. aggregation state and zeta-potential) and adsorption to quartz sand was investigated. The apparent average isoelectric point of PrPsc aggregates was 4.6. PrPsc aggregate size was largest between pH 4 and 6, and increased with increasing l at pH 7. Adsorption to quartz sand was maximal near the apparent isoelectric point of PrPsc aggregates and decreased as pH either declined or increased. PrPsc adsorption increased as suspension l increased, and reached an apparent plateau at l approximately 0.1 M. While trends with pH and l in PrPsc attachment to quartz surfaces were consistent with predictions based on Born-DLVO theory, non-DLVO forces appeared to contribute to adsorption at pH 7 and 9 (l = 10 mM). Our findings suggest that disposal strategies that elevate pH (e.g., burial in lime or fly ash), may increase PrPsc mobility. Similarly, PrPsc mobility may increase as a landfill ages, due to increases in pH and decreases in l of the leachate.     

In vitro skin permeation and retention of parabens from cosmetic formulations

Parabens are antimicrobial agents widely used in foods, cosmetics and pharmaceutical products. Although non-mutagenic, non-teratogenic and non-carcinogenic, parabens can induce allergic contact dermatitis and posses estrogenic activity. The aim of this work was to assess the skin permeation and retention of methyl- (MP), ethyl- (EP) and propyl- (PP) paraben from three commercial cosmetic creams. The results obtained indicate that parabens are capable of permeating through and accumulating in the skin. The extent of penetration depends more on paraben characteristics (solubility, lipophilicity) than on the composition of the formulation. In particular, the percentage permeated across the skin was independent of the composition of the cream used and decreased in the order MP, EP and PP, in accordance with decreasing solubility. After 8 h of contact with the skin, 60% of MP, 40% of EP and 20% of PP were found across the skin. Concerning skin retention, the percentage remaining in the skin after 8 h depends on both paraben characteristics and on the composition of the formulation used. In conclusion, it appears that only the type of paraben, in particular its water solubility, affects skin penetration whereas the composition of the emulsion, which influences skin retention, plays a secondary role. Finally, excised rabbit ear skin can be considered as a good model for human skin for in vitro experiments.     

Few electron double quantum dots in InAs/InP nanowire heterostructures

We report on fabrication of double quantum dots in catalytically grown InAs/InP nanowire heterostructures. In the few-electron regime, starting with both dots empty, our low-temperature transport measurements reveal a clear shell structure for sequential charging of the larger of the two dots with up to 12 electrons. The resonant current through the double dot is found to depend on the orbital coupling between states of different radial symmetry. The charging energies are well described by a capacitance model if next-neighbor capacitances are taken into account.     

Color Image Modification with and without Hue Preservation

Color image modification is an essential component for several applications and the grayscale transformation is generally mapped to the color image indirectly. Although several techniques have been used for this transfer, they suffer from gamut mapping issue. In this paper, it is aimed to study the mapping of grayscale transformations to the color scale in different perspectives. Modifying the image in different color space than the original retains hue to a promising extent, but suffers from the gamut problem. A generic scheme to map grayscale changes to the color space for all kinds of spatial modification is proposed here. The hue preserving color image enhancement (HPCE) scheme discussed here is free of gamut-mapping issue and shows promising results in transferring the grayscale transformation to the color image in a simplistic manner. The proposed HPCE scheme is analysed qualitatively through visual appearance and quantitatively using color difference metrics SHAME and CID, gray image difference and EBCM measures. Different gray scale transformations such as S-type enhancement and different forms of histogram equalization techniques are applied on Berkeley dataset of 500 images to prove the efficacy of proposed algorithm.     

A direct derivation of the equations of motion for 3D-flexible mechanical systems

Equations of motion for rigid bodies with the body-fixed co-ordinate system placed at or away from the centre of mass are derived in a clear and direct way by making use of the two basic equations of mechanics (Newton's second law and the corresponding law of angular momentum). The dynamic equations for flexible mechanical systems are derived using the principle of virtual work, which introduces inertia in a straightforward manner, because this principle treats inertia as a force. The flexible formulation is exemplified by the use of circular beam elements and some basic matrices are derived in a direct way using skew-symmetric matrices. The capabilities of the formulation are demonstrated through examples. Results are compared with and verified by examples from the literature. Derivations throughout the paper are simplified by means of skew-symmetric matrices. © 1998 John Wiley & Sons, Ltd.     

Preparation of crosslinked and thermostable paste poly(vinyl chloride)

The grafting of a mercaptoalkyltrialkoxysilane onto an activated poly(vinyl chloride) (PVC) paste resin with subsequent hydrolytic crosslinking has been studied. The resins were prepared by copolymerization of vinyl chloride monomer and glycidylmethacrylate (GMA). The grafting of a mercaptosilane was carried out during gelation of the plastisol. In this step the formation of a chemical network was avoided. By steaming at 120°C for 30 min the grafted samples crosslinked. The gel yield increased with increasing fraction of GMA and up to a given level with the fraction of the mercaptosilane. When using a resin of PVC homopolymer no crosslinking occurred. The silane grafted and crosslinked samples were found to have satisfactory thermal stability. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:849–853, 1998     

Small-angle neutron scattering and differential scanning calorimetry studies on the copper clustering stage of Fe–Si–B–Nb–Cu nanocrystalline alloys

The kinetics of copper clustering and primary crystallization of FINEMET type alloys with the compositions Fe_74.5−xSi_13.5B₉Nb₃Cu_x and Fe₇₇Si₁₁B₉Nb_3−xCu_x have been studied by small-angle neutron scattering (SANS) and high-sensitivity differential scanning calorimetry (DSC) in order to explain the different optimized Cu contents, x, for obtaining the highest permeability in these two alloys. SANS results have shown that the alloys with the optimized Cu contents have the finest nanocrystalline microstructures. Kinetic analyses of Cu clustering prior to primary crystallization have shown that the number density of Cu clusters becomes highest at the crystallization stage of -Fe primary crystals in the alloy containing an optimized amount of Cu.     

Behavioural interactions between prey (trout smolts) and predators (pike and pikeperch) in an impounded river

Movements of radio‐tagged pike Esox lucius (L.), pikeperch Stizostedion lucioperca (L.) and outward migrating sea trout smolts Salmo trutta (L.) were studied in a shallow Danish reservoir to obtain information of predator–prey interactions between these species. Twenty pikeperch (55–74 cm) and 19 pike (52–72 cm) were tagged. Female pikeperch spent more time near the outlet sluice during the smolt run (May) than at other times of the year, apparently actively hunting the smolts delayed in this area. In contrast, male pikeperch did not seem to participate in the smolt predation but remained stationary during the smolt run, presumably guarding their nests. Most tagged pike were present at the spawning grounds during the peak of the smolt run, where they had little chance of smolt encounter. Twenty migrating trout smolts were radio‐tagged in the river upstream of the reservoir. Ten of these were located in the vicinity of the outlet sluice at least once, but were unwilling or unable to find and enter the sub‐surface outlet sluice. Only one tagged smolt left the reservoir. After 1–12 days in the reservoir, the remaining smolts were eaten by pikeperch or pike and the results indicate that female pikeperch and few female pike have adjusted their behaviour to predation on smolts during the smolt run. The smolt predation in this man‐made reservoir is higher than in natural lakes, probably due to the changed physical environment and introduced predators, such as pikeperch. The outlet sluice practice and the temporal overlap between smolt run and predator‐spawning may be key factors in smolt survival. Copyright © 2000 John Wiley & Sons, Ltd.