Chernobyl: Living with Risk and Uncertainty

The nuclear accident in Chernobyl in 1986 is a dramatic example of the type of incidents that are characteristic of a risk society. The consequences of the incident are indeterminate, the causes complex and future developments unpredictable. Nothing can compensate for its effects and it affects a broad population indiscriminately. This paper examines the lived experience of those who experienced biographical disruption as residents of the region on the basis of qualitative case studies carried out in 2003 in the Chernobyl regions of Russia, Ukraine and Belarus. Our analysis indicates that informants tend to view their future as highly uncertain and unpredictable; they experience uncertainty about whether they are already contaminated, and they have to take hazardous decisions about where to go and what to eat. Fear, rumours and experts compete in supplying information to residents about the actual and potential consequences of the disaster, but there is little trust in, and only limited awareness of, the information that is provided. Most informants continue with their lives and do what they must or even what they like, even where the risks are known. They often describe their behaviour as being due to economic circumstances; where there is extreme poverty, even hazardous food sources are better than none. Unlike previous studies, we identify a pronounced tendency among informants not to separate the problems associated with the disaster from the hardships that have resulted from the break-up of the USSR, with both events creating a deep-seated sense of resignation and fatalism. Although most informants hold their governments to blame for lack of information, support and preventive measures, there is little or no collective action to have these put in place. This contrasts with previous research which has suggested that populations affected by disasters attribute crucial significance to that incident and, as a consequence, become increasingly politicized with regard to related policy agendas.

Artemisinins act through at least two targets in a yeast model

Artemisinin and related compounds are potent and widely used antimalarial drugs but their biochemical mode of action is not clear. There is strong evidence that ATP-dependent calcium transporters are a key target in the malarial parasite. However, work using Saccharomyces cerevisiae suggests that disruption of mitochondrial function is critical in the cell killing activity of these compounds. Here it is shown that, in the absence of reducing agents, artemisinin and artesunate targeted the S. cerevisiae calcium channels Pmr1p and Pmc1p. Both compounds affected the growth of yeast on fermentable and nonfermentable media. This growth inhibition was not seen in a yeast strain in which the genes encoding both calcium channels were deleted. In the presence of reducing agents, which break the endoperoxide bridge in the drugs, growth inhibition was only observed in nonfermentable media. This inhibition could be partially relieved by the addition of a free radical scavenger. These results suggest that the drugs have two biochemical modes of action - one acting by specific binding to calcium channels and one involving free radical production in the mitochondria.

Measurement of single mode imprint in laser ablative drive of a thin Al foil by extreme ultraviolet laser radiography

The temporal development of laser driven single mode perturbations in thin A1 foils has been measured using extreme ultraviolet (XUV) laser radiography. 15, 30, 70 and 90 mu m single modes were imprinted on 2 mu m thick A1 foils with an optical driver laser at 527 nm for intensities in the range 5 x 10(12) to 1.5 x 10(13) W cm(-2). The magnitude of the imprinted perturbation at the time of shock break out was determined by fitting to the data estimated curves of growth of the Rayleigh-Taylor instability after shock break out. The efficiency of imprinting is independent of perturbation wavelength in the parameter range of this experiment, suggesting little influence of thermal conduction smoothing. The results are of interest for directly driven inertially confined fusion. (C) 1998 American Institute of Physics.

Instituting order: the limitations of Nasser’s post-colonial planning visions for Cairo in the case of the indigenous quarter of Bulaq (1952–1970)

This paper investigates the limitations of postcolonial planning practices that aimed to modernise Cairo’s urban spaces during Gamal Abdel Nasser rule (1952–70). Following the Free Officers revolution of 1952, ambition to display urban order through forceful change in the city’s built environment was in action. Nasser’s visions of modernity were explicit in a series of attempts to reshape several prime locations in central Cairo, which included the old traditional waterfront quarter, in Bulaq Abul Ela. An analysis of the Bulaq planning scheme drafted in 1966 reveals insights into how notions of order were spatialised to integrate with Cairo’s complex urban fabric. The official plans to regularise Bulaq also strongly demonstrates how this was a top-down, centralised process in terms of governance, with full utilisation of state resources, namely the military and the media. From a wider perspective, planning practices under Nasser demonstrated an evident break with the past to eliminate memories of colonisation and disorder. Drawing on original resources, archival material, meeting minutes and maps of this historical but dilapidated quarter of Cairo, this paper gives an insight into how Nasser’s government attempted to convey a sense of order in a revolutionary country without, however, having an understanding of order as a coherent, multilayered and sequential process of change.

Physicochemical and drug diffusion analysis of rifampicin containing polyethylene glycol-poly(epsilon-caprolactone) networks designed for medical device applications

This study reports the physicochemical and drug diffusion properties of rifampicin containing poly(epsilon-caprolactone) (PCL)/polyethylene glycol (PEG) networks, designed as bioactive biomaterials. Uniquely, the effects of the states of both rifampicin and PEG and the interplay between these components on these properties are described. PCL matrices containing rifampicin (1-5%, w/w) and PEG 200 (0-15%, w/w) were prepared by casting from an organic solvent (dichloromethane). The films were subsequently characterized in terms of their thermal/thermorheological, surface and tensile properties, biodegradation and drug diffusion/release properties. Incorporation of PEG and/or rifampicin significantly affected the tensile and surface properties of PCL, lowering the ultimate tensile strength, % elongation at break, Young modulus and storage and loss moduli. Both in the absence and presence of PEG, solubilisation of rifampicin within the crystalline domains of PCL was observed. PEG was present as a dispersed liquid phase. The release of rifampicin (3% loading) was unaffected by the presence of PEG. Similarly the release of rifampicin (5%) was unaffected by low concentrations of PEG (5-10%) however, at higher loadings, the release rate of rifampicin was enhanced by the presence of PEG. Rifampicin release (10% loading) was enhanced by the presence of PEG in a concentration dependent fashion. These observations were accredited to enhanced porosity of the matrix. In all cases, diffusion-controlled release of rifampicin occurred which was unaffected by polymer degradation. This study has uniquely illustrated the effect of hydrophilic pore formers on the physicochemical properties of PCL. Interestingly, enhanced diffusion controlled release was only observed from biomaterials containing high loadings of PEG and rifampicin (5, 10%), concentrations that were shown to affect the mechanical properties of the biomaterials. Care should therefore be shown when adopting this strategy to enhance release of bioactive agents from biomaterials. (C) 2011 Elsevier B.V. All rights reserved.

Effects of storage on thermomechanical properties of poly(epsilon-caprolactone) blends containing poly(vinyl pyrrolidone/iodine)

This study reports the effects of: the molecular weight ratio of poly(epsilon -caprolactone) (PCL) in blends containing polymer of high (50 000 g mol(-1)) and low (4000 g mol(-1)) molecular weight; the concentration (0, 1, and 5 wt-%) of poly(vinyl pyrrolidone/iodine) (PVP/I); and storage at 30 degreesC and 75% relative humidity; on the thermomechanical properties of films prepared by solvent evaporation from solutions containing both PCL and PVP/I. The tensile properties were found to be statistically dependent on the molecular weight ratio of PCL but not on the concentration of PVP/I. The reductions in tensile strength and elongation at break associated with increasing amounts of low molecular weight PCL were attributed to a reduction in the concentration of chain entanglements. No changes were observed in viscoelastic properties or the glass transition temperature. Following storage there were no changes in the tensile strength, glass transition temperature, or viscoelastic properties of the films; however, significant reductions in elongation at break were observed. It is suggested that this is due to hydrolytic chain scission of amorphous PCL. Inclusion of 5 wt-% PVP/I increased this process in films containing 100:0 and 80:20 high/low molecular weight PCL (but not 60.40), but the extent of this was small. This study highlighted significant aging properties of PCL in a moist atmosphere. Consequently, it is recommended that suitable packaging materials should be employed to control the exposure of PCL films to water during storage.

FASCIOLA-HEPATICA - ULTRASTRUCTURAL-CHANGES TO THE TEGUMENT OF JUVENILE FLUKES FOLLOWING INCUBATION IN-VITRO WITH THE DEACETYLATED (AMINE) METABOLITE OF DIAMPHENETHIDE

Ultrastructural changes to the tegument of 5-week-old, 3-week-old and freshly-excysted Fasciola hepatica following in vitro incubation with the deacetylated (amine) metabolite of diamphenethide (DAMD, 10 mu gml(-1)) were examined by transmission electron microscopy, A similar sequence of tegumental changes occurred in all three age groups of fluke, although, with increasing fluke age, the time before onset increased and the damage became more extensive. The 5-week-old flukes showed an initial stress response after 3 h, typified by blebbing of the apical plasma membrane, formation of microvilli and an accumulation and accelerated release of secretory bodies at the tegumental apex, as well as swelling of the basal infolds, The swelling increased in extent with progressively longer periods of incubation in DAMD, leading to extreme edema and sloughing of the tegument after 9 h. The 3-week-old flukes showed a stress response and swelling of the basal infolds after only 1.5 h, although sloughing of the tegument did not occur until after 9 h. In the freshly-excysted metacercaria, a stress response and some sloughing of the tegument were evident after only 0.5 h. At all stages of development, the ventral tegument was more severely affected than the dorsal, Changes also occurred to the tegumental cells which were indicative of a disruption in the synthesis and release of tegumental secretory bodies: the amount of GER became reduced, the cisternae became swollen and their ribosomal covering decreased, the Golgi complexes disappeared from the cells and the numbers of secretory bodies in the cells also decreased, The heterochromatin content of the nuclei increased and eventually the tegumental cells began to break down, Again, the changes became apparent more rapidly at the earlier stages of development. The ultrastructural changes to the tegument are linked to a possible mode of action for diamphenethide as an inhibitor of protein synthesis. In turn, the results may help to explain the drug's high efficacy against juvenile stages of F. hepatica.

DNA damage induction in dry and hydrated DNA by synchrotron radiation

Radiation biophysics has sought to understand at a molecular level, the mechanisms through which ionizing radiations damage DNA, and other molecules within living cells. The complexity of lesions produced in the DNA by ionizing radiations is thought to depend on the amount of energy deposited at the site of each lesion. To study the relationship between the energy deposited and the damage produced, we have developed novel techniques for irradiating dry prasmid DNA, partially re-hydrated DNA and DNA in solution using monochromatic vacuum-UV synchrotron radiation. We have used photons in the energy range 7-150 eV, corresponding to the range of energies typically involved in the efficient production of DNA single-strand (SSB), and double-strand breaks (DSB) by ionizing radiation. The data show that both types of breaks are produced at all energies investigated (with, or without water present). Also, the energy dependence for DSB induction follows a similar trend to SSB induction but at a 20-30-fold reduced incidence, suggesting a common precursor for both types of damage. Preliminary studies where DNA has been irradiated in solution indicate a change in the shape of the dose-effect curve (from linear, to linear-quadratic for double-strand break induction) and a large increase in sensitivity due to the presence of water.

An investigation of clustered radiation-induced lesions in DNA

Recent track structure modelling studies indicate that radiation induced damage to DNA consists of a spectrum of different lesions of varying complexity. There is considerable evidence to suggest that, in repair-proficient systems, it is only the small proportion of more complex forms that is responsible for most of the biological effect. The complex lesions induced consist initially of clustered radical sites and a knowledge of their special chemistry is important in modelling how they react to form the more stable products that are processed by the repair systems. However, much of the current understanding of the chemical stage of radiation has developed from single-radical systems and there is a need to translate this to the more complex reactions that are likely to occur at the important multiple radical sites. With low LET radiation, DNA dsb may derive either from single-radical attack that damages both strands by a transfer mechanism, or from pairs of radical sites induced in close proximity, with one or more radical on each strand. With high LET radiation, modelling studies indicate that there is an increased probability of dsb arising from sites with more than two radical centres, leading to a greater frequency of more complex types of break. The spectrum of these lesions depends on the overall outcome of consecutive physical and chemical processes. The initial pattern of radical damage is determined by the energy depositions on and around the DNA, according to the type of radiation. This pattern is then modified by scavengers that inhibit the formation of radicals on the DNA, and by agents that either chemically repair (e.g. thiols) or fix (e.g. oxygen) a large fraction of these radicals. The reaction kinetics associated with clustered radical sites will differ from those of single sites: (1) because of the opportunities for interactions between the radicals themselves; and (2) because certain endpoints, e.g. a dsb, may require a combination of the products of two or more radicals. Fast response techniques using pulsed low and high LET irradiation have been established to measure the reactions of radical sites on pBR322 plasmid DNA with oxygen and thiols with a view to obtaining information about cluster size. This paper describes experimental approaches to explore the role of the chemical stage of the radiation effect in relation to lesion complexity.

Local DNA damage by proton microbeam irradiation induces poly(ADP-ribose) synthesis in mammalian cells

Cellular recovery from ionizing radiation (IR)-induced damage involves poly(ADP-ribose) polymerase (PARP-1 and PARP-2) activity, resulting in the induction of a signalling network responsible for the maintenance of genomic integrity. In the present work, a charged particle microbeam delivering 3.2 MeV protons from a Van de Graaff accelerator has been used to locally irradiate mammalian cells. We show the immediate response of PARPs to local irradiation, concomitant with the recruitment of ATM and Rad51 at sites of DNA damage, both proteins being involved in DNA strand break repair. We found a co-localization but no connection between two DNA damage-dependent post-translational modifications, namely poly(ADP-ribosyl)ation of nuclear proteins and phosphorylation of histone H2AX. Both of them, however, should be considered and used as bona fide immediate sensitive markers of IR damage in living cells. This technique thus provides a powerful approach aimed at understanding the interactions between the signals originating from sites of DNA damage and the subsequent activation of DNA strand break repair mechanisms.

Evidence for the direct binding of phosphorylated p53 to sites of DNA breaks in vivo

Despite a clear link between ataxia-telangiectasia mutated (ATM)-dependent phosphorylation of p53 and cell cycle checkpoint control, the intracellular biology and subcellular localization of p53 phosphoforms during the initial sensing of DNA damage is poorly understood. Using GO-G, confluent primary human diploid fibroblast cultures, we show that endogenous p53, phosphorylated at Ser(15) (p53(Ser15)), accumulates as discrete, dose-dependent and chromatin-bound foci within 30 minutes following induction of DNA breaks or DNA base damage. This biologicafly distinct subpool of p53(Ser15) is ATM dependent and resistant to 26S-proteasomal degradation. p53(Ser15) colocalizes and coimmunoprecipitates with gamma-H2AX with kinetics similar to that of biochemical DNA double-strand break (DNA-dsb) rejoining. Subnuclear micro-beam irradiation studies confirm p53 S,,15 is recruited to sites of DNA damage containing gamma-H2AX, ATM(Ser1981), and DNA-PKcs(Thr2609) in vivo. Furthermore, studies using isogenic human and murine cells, which express Ser(15) or Ser(18) phosphomutant proteins, respectively, show defective nuclear foci formation, decreased induction of p21(WAF) decreased gamma-H2AX association, and altered DNA-dsb kinetics following DNA damage. Our results suggest a unique biology for this p53 phosphoform in the initial steps of DNA damage signaling and implicates ATM-p53 chromatin-based interactions as mediators of cell cycle checkpoint control and DNA repair to prevent carcinogenesis. (Cancer Res 2005; 65(23): 10810-21).

2ND-HARMONIC LIGHT GENERATION IN THE INTERACTION OF LASER-BEAMS WITH UNDERCRITICAL PLASMAS

The process of second harmonic generation (SHG) in undercritical plasmas is studied. It is shown that filamentation and self-focusing of the laser beam in the plasma can break the plasma density symmetry and lead to SHG by free electrons. In turn, second harmonic emission may be used to investigate the plasma parameters and to diagnose the process of laser beam filamentation itself.

Electrical Breakdown in Water Vapor

In this paper investigations of the voltage required to break down water vapor are reported for the region around the Paschen minimum and to the left of it. In spite of numerous applications of discharges in biomedicine, and recent studies of discharges in water and vapor bubbles and discharges with liquid water electrodes, studies of the basic parameters of breakdown are lacking. Paschen curves have been measured by recording voltages and currents in the low-current Townsend regime and extrapolating them to zero current. The minimum electrical breakdown voltage for water vapor was found to be 480 V at a pressure times electrode distance (pd) value of around 0.6 Torr cm (similar to 0.8 Pa m). The present measurements are also interpreted using (and add additional insight into) the developing understanding of relevant atomic and particularly surface processes associated with electrical breakdown.

Recycled carbon fiber filled polyethylene composites

Composites of recycled carbon fiber (CF) with up to 30 wt % loading with polyethylene (PE) were prepared via melt compounding. The morphology of the composites and the degree of dispersion of the CF in the PE matrix was examined using scanning electron microscopy, and revealed the CF to be highly dispersed at all loadings and strong interfacial adhesion to exist between the CF and PE. Raman and FTIR spectroscopy were used to characterize the surface chemistry and potential bonding sites of recycled CF. Both the Young's modulus and ultimate tensile stress increased with increasing CF loading, but the percentage stress at break was unchanged up to 5 wt % loading, then decreased with further successive addition of CF. The effect of CF on the elastic modulus of PE was examined using the Halpin-Tsai and modified Cox models, the former giving a better fit with the values determined experimentally. The electrical conductivity of the PE matrix was enhanced by about 11 orders of magnitude on addition of recycled CF with a percolation threshold of 7 and 15 wt % for 500-mu m and 3-mm thick samples. (c) 2007 Wiley Periodicals, Inc.