Green Documentary: Environmental Documentary in the 21st Century by Helen Hughes

David M. Lawrence reviews Green Documentary: Environmental Documentary in the 21st Century by Helen Hughes

Using UV laser surface treatment to modify the wettability characteristics of polyamide 6,6 and its effects on osteoblast cell activity

Lasers can be used to modify the surface characteristics of a number of different materials for many applications. This paper details the way in which a KrF 248 nm excimer laser can be utilized to surface pattern and whole area irradiate nylon 6,6. 50 and 100 µm dimensioned trench and hatch patterns were induced in addition to the whole area irradiative processing which covered an area of 3.75 cm2 with fluencies ranging from 26 to 70 mJcm-2. The surface topography and roughness were determined with the use of a white light interferometer. From this it was found that the largest roughness, Sa, was 1.53 µm which arose from the 100 µm hatch excimer patterned sample. Wettability characteristics were obtained for each sample using a sessile drop device in which it was observed that the contact angle increased by up to 25° for the patterned samples and decreased by up to 15° for the large area processed samples. It is believed that the observed increase in contact angle can be attributed to the likely existence of a mixed-state wetting regime in which both Wenzel and Cassie-Baxter regimes are present over the liquid-solid interface. As a result of the small variation in surface roughness for the large area processed samples the observed decrease in contact angle can be explained by a modification of the surface chemistry and an increase in polar component (γp) and total surface energy (γT). Osteoblast cell activity was analyzed by carrying out cytotoxicity and alkaline leukocyte phosphatase (ALP) activity experiments, two major factors which are linked to sufficient cell growth and proliferation

Modulation of osteoblast cell response through laser surface processing of nylon 6,6

With an ageing population demand on medical facilities is growing, especially for bio-implants. Therefore, there is a need for cheaper, more efficient implants. This paper details how CO2 and KrF excimer lasers can be employed to modulate osteoblast cell growth on nylon 6,6 in relation to laser-modified wettability characteristics. Through patterning the contact angle, θ, increased by up to 19°, indicating the presence of a mixed state wetting regime; whereas θ decreased by up to 20° for the whole area irradiative processed samples. After 24 hours and 4 days incubation the cell cover density and cell count was somewhat modulated over the laser-modified samples compared to the as-received sample. A likely increase in surface toxicity gave rise to a hindered cell response for those samples with high energy densities and high incident pulse numbers. No strong correlations were determined for the laser-induced patterned samples which can be attributed to the likely mixed-state wetting regime. Correlative trends were found between the cell response, θ, polar component and surface oxygen content for the whole area irradiative processed samples. Thus, allowing one to identify the potential for this technology in regenerative medicine

Li I enhancement during a long-duration stellar flare

We report the possible detection of a Li I 6708 AA line enhancement during an unusual long-duration optical flare in the recently discovered, X-ray/EUV selected, chromospherically active binary 2RE J0743+224. The Li I equivalent width (EW) variations follow the temporal evolution of the flare and large changes are observed in the intensity of the line. The maximum Li I enhancement occurs just after the maximum chromospheric emission observed in the flare. A significant increase of the 6Li/7Li isotopic ratio is also detected. No significant simultaneous variations are detected in other photospheric lines. Neither line blends nor starspots seem to be the primary cause of the observed Li I line variation. From all this we suggest that this Li I enhancement is produced by spallation reactions during the flare.Comment: Latex file with 5 pages, 2 figures tar'ed gzip'ed. Full postscript (text and figures) available at http://www.ucm.es/OTROS/Astrof/pub_dmg.html To be published in A&A, Lette

Health Care: Public Good or Private Enterprise? 7th Annual Herbert Lourie Memorial Lecture on Health Policy

I start with the premise that the success of our efforts in health care is best measured by our ability to impact the health status of our citizens in the most affordable way possible. This brief provides an overview of the history of organized health care systems, then discusses several of the conundrums that are posted by knowledge of that history.

Social Costs of Mass Privatization

According to leading economic theorists, creating capitalism out of communism requires rapid privatization. In this article we empirically test the welfare implications of privatization policies in Post-Soviet countries by using cross-national panel mortality data as an indicator of social costs. We find that rapid privatization ñ whether measured by a novel measure of mass privatization program implementation or Enterprise Bank for Reconstruction and Development privatization outcome scores ñ is a critical determinant of life expectancy losses, and that when privatization policies are reversed, life expectancy improves. Using selection models, we show that endogeneity understates the social costs of rapid privatization.http://deepblue.lib.umich.edu/bitstream/2027.42/64393/1/wp890.pd

Laser cleaning of the output window in a laser ignition system for gas turbines

Laser ignition (LI) of both liquid fuels and gaseous combustible mixtures in gas turbines offers the potential for reduced emissions and increased reliability. During the combustion process, carbon and other by-products accumulate on the walls of the combustion chamber. For laser based ignition systems, this could potentially reduce the transmissive properties of the output window required for transmission of the laser radiation into the combustion chamber. Presented in this paper is an empirical study into the laser cleaning of an output window for the removal of accumulated carbon prior to laser ignition, with the mechanism of removal discussed

A vanishing theorem for weight one syzygies

Inspired by the methods of Voisin, the first two authors recently proved that one could read off the gonality of a curve C from the syzygies of its ideal in any one embedding of sufficiently large degree. This was deduced from from a vanishing theorem for the asymptotic syzygies associated to an arbitrary line bundle B on C. The present paper extends this vanishing theorem to a smooth projective variety X of arbitrary dimension. Specifically, given a line bundle B on X, we prove that if B is p-jet very ample (i.e. the sections of B separate jets of total weight p+1) then the weight one Koszul cohomology group K_{p,1}(X, B; L) vanishes for all sufficiently positive L. In the other direction, we show that if there is a reduced cycle of length p+1 that fails to impose independent conditions on sections of B, then the Koszul group in question is non-zero for very positive L.Comment: Heuristic outline of argument added. Small errors corrected. To appear in Algebra and Number Theor