Near-term and late biological effects of acute and low-dose-rate continuous gamma-ray exposure in dogs and monkeys

Monkeys (Macaca mulatta) and dogs (beagle) were given thirteen 100-rad gamma-ray doses at 28-day intervals. The comparative response (inury and recovery) of the hematopoietic system of the two species was observed at 7-day intervals during the exposure regime. At 84 days after the thirteenth gamma-ray dose, the 1300-rad conditioned and control dogs and monkeys were challenged continuously with gamma rays at 35 r/day until death to determine the amount of radiation-induced injry remaining in conditioned animals as a reduction in mean survival time. Dogs (50%) and monkeys (8%) died from injury incurred during conditioning exposures. Thus, the comparative response (in terms of lethality) of dogs and monkeys to dose protraction by acute dose fractionation was similar to what we would expect from a single acute dose. The mean survival times for nonconditioned dogs and monkeys during continuous exposure at 35 R/day were the same (approx. 1400 h). Thus, the hematopoietic response of the two species by this method of dose protraction was not significantly different. Mean survival times of conditioned dogs and monkeys during the continuous 35-R/day gamma-ray challenge exposure were greater (significant in dogs but not in monkeys) than for their control counterparts. Thus, long-term radiation-induced injury was not measurable by this method. Conditioning doses of more than 4 times the acute LD/sub 50//sup 30/ in dogs and approximately 2 times that in monkeys served only to increase both mean survival time and variance in a gamma-ray stress environment with a dose rate of 35 Rat/day

Young women and limits to the normalisation of condom use: a qualitative study

Encouraging condom use among young women is a major focus of HIV/STI prevention efforts but the degree to which they see themselves as being at risk limits their use of the method. In this paper, we examine the extent to which condom use has become normalised among young women. In-depth interviews were conducted with 20 year old women from eastern Scotland (N = 20). Purposive sampling was used to select a heterogeneous group with different levels of sexual experience and from different social backgrounds. All of the interviewees had used (male) condoms but only three reported consistent use. The rest had changed to other methods, most often the pill, though they typically went back to using condoms occasionally. Condoms were talked about as the most readily available contraceptive method, and were most often the first contraceptive method used. The young women had ingrained expectations of use, but for most, these norms centred only on their new or casual partners, with whom not using condoms was thought to be irresponsible. Many reported negative experiences with condoms, and condom dislike and failure were common, lessening trust in the method. Although the sexually transmitted infection (STI) prevention provided by condoms was important, this was seen as additional, and secondary, to pregnancy prevention. As the perceived risks of STIs lessened in relationships with boyfriends, so did condom use. The promotion of condoms for STI prevention alone fails to consider the wider influences of partners and young women's negative experiences of the method. Focusing on the development of condom negotiation skills alone will not address these issues. Interventions to counter dislike, method failure, and the limits of the normalisation of condom use should be included in STI prevention efforts

Blooms of cyanobacteria in a temperate Australian lagoon system post and prior to European settlement

Blooms of noxious N2 fixing cyanobacteria such as Nodularia spumigena are a recurring problem in some estuaries; however, the historic occurrence of such blooms in unclear in many cases. Here we report the results of a palaeoecological study on a temperate Australian lagoon system (the Gippsland Lakes) where we used stable isotopes and pigment biomarkers in dated cores as proxies for eutrophication and blooms of cyanobacteria. Pigment proxies show a clear signal, with an increase in cyanobacterial pigments (echinenone, canthaxanthin and zeaxanthin) in the period coinciding with recent blooms. Another excursion in these proxies was observed prior to the opening of an artificial entrance to the lakes in 1889, which markedly increased the salinity of the Gippsland Lakes. A coincident increase in the sediment organic-carbon content in the period prior to the opening of the artificial entrance suggests that the bottom waters of the lakes were more stratified and hypoxic, which would have led to an increase in the recycling of phosphorus. After the opening of the artificial entrance, there was a  ∼  60-year period with low values for the cyanobacterial proxies as well as a low sediment organic-carbon content suggesting a period of low bloom activity associated with the increased salinity of the lakes. During the 1940s, the current period of re-eutrophication commenced, as indicated by a steadily increasing sediment organic-carbon content and cyanobacterial pigments. We suggest that increasing nitrogen inputs from the catchment led to the return of hypoxia and increased phosphorus release from the sediment, which drove the re-emergence of cyanobacterial blooms

Thermodynamic formalism for contracting Lorenz flows

We study the expansion properties of the contracting Lorenz flow introduced by Rovella via thermodynamic formalism. Specifically, we prove the existence of an equilibrium state for the natural potential $\hat\phi_t(x,y, z):=-t\log J_{(x, y, z)}^{cu}$ for the contracting Lorenz flow and for $t$ in an interval containing $[0,1]$. We also analyse the Lyapunov spectrum of the flow in terms of the pressure

Missing OH source in a suburban environment near Beijing: observed and modelled OH an HO2 concentrations in summer 2006

Measurements of ambient OH and HO₂ radicals were performed by laser induced fluorescence (LIF) during CAREBeijing2006 (Campaigns of Air Quality Research in Beijing and Surrounding Region 2006) at the suburban site Yufa in the south of Beijing in summer 2006. On most days, local air chemistry was influenced by aged air pollution that was advected by a slow, almost stagnant wind from southern regions. Observed daily maxima of OH and HO₂^* were in the range of (4–17) × 10⁶ cm^−3 and (2–24) × 10⁸ cm^−3, respectively. During daytime, OH reactivities were generally high (10–30 s^−1) and mainly contributed by VOCs and their oxidation products. The comparison of modelled and measured HO_x concentrations reveals a systematic underprediction of OH as a function of NO. A large discrepancy of a factor 2.6 is found at the lowest NO concentration encountered (0.1 ppb), whereas the discrepancy becomes insignificant above 1 ppb NO. This study extends similar observations from the Pearl-River Delta (PRD) in South China to a more urban environment. The OH discrepancy at Yufa can be resolved, if NO-independent additional OH recycling is assumed in the model. The postulated Leuven Isoprene Mechanism (LIM) has the potential to explain the gap between modelled and measured OH at Beijing taking into account conservative error estimates, but still lacks experimental confirmation. This and the hereby unresolved discrepancy at PRD suggest that other VOCs besides isoprene might be involved in the required, additional OH recycling. Fast primary production of RO_x radicals up to 7 ppb h^−1 was determined at Beijing which was dominated by the photolysis of O₃, HONO, HCHO, and dicarbonyls. For a special case, 20 August, when the plume of Beijing city was encountered, a missing primary HO_x source (≈ 3 ppb h^−1) was determined under high NO_x conditions similar to other urban areas like Mexico city. CAREBeijing2006 emphasizes the important role of OVOCs as a radical source and sink, and the need for further investigation of the chemical degradation of VOCs in order to better understand radical chemistry in VOC-rich air

Exploring the atmospheric chemistry of nitrous acid (HONO) at a rural site in Southern China

We performed measurements of nitrous acid (HONO) during the PRIDE-PRD2006 campaign in the Pearl River Delta region 60 km north of Guangzhou, China, for 4 weeks in June 2006. HONO was measured by a LOPAP in-situ instrument which was setup in one of the campaign supersites along with a variety of instruments measuring hydroxyl radicals, trace gases, aerosols, and meteorological parameters. Maximum diurnal HONO mixing ratios of 1–5 ppb were observed during the nights. We found that the nighttime build-up of HONO can be attributed to the heterogeneous NO2 to HONO conversion on ground surfaces and the OH + NO reaction. In addition to elevated nighttime mixing ratios, measured noontime values of ≈200 ppt indicate the existence of a daytime source higher than the OH + NO→HONO reaction. Using the simultaneously recorded OH, NO, and HONO photolysis frequency, a daytime additional source strength of HONO (PM) was calculated to be 0.77 ppb h−1 on average. This value compares well to previous measurements in other environments. Our analysis of PM provides evidence that the photolysis of HNO3 adsorbed on ground surfaces contributes to the HONO formation

Consumer mobility and well-being among changing places and shifting ethnicities

International audience(Market)places are spatial entities which individuals and groups might experience as meaningful. By highlighting the role of place in ethnic consumer research, this article argues that increased mobility and changing places render relatively stable notions of ethnicity outdated. We identify three main trajectories to revitalize future research on ethnicity. First, we demonstrate the need for research on ethnic identity to be underpinned by a better understanding of the role of place in identity processes. Second, we contend that the established migration/acculturation paradigm should be replaced by the mobility/adaptiveness paradigm. Third, we consider the profound effects of interethnic contact among mobile and immobile populations within shared places on individual and societal well-being

The Kuiper Belt and Other Debris Disks

We discuss the current knowledge of the Solar system, focusing on bodies in the outer regions, on the information they provide concerning Solar system formation, and on the possible relationships that may exist between our system and the debris disks of other stars. Beyond the domains of the Terrestrial and giant planets, the comets in the Kuiper belt and the Oort cloud preserve some of our most pristine materials. The Kuiper belt, in particular, is a collisional dust source and a scientific bridge to the dusty "debris disks" observed around many nearby main-sequence stars. Study of the Solar system provides a level of detail that we cannot discern in the distant disks while observations of the disks may help to set the Solar system in proper context.Comment: 50 pages, 25 Figures. To appear in conference proceedings book "Astrophysics in the Next Decade