Detailed analysis of the cell-inactivation mechanism by accelerated protons and light ions

Published survival data for V79 cells irradiated by monoenergetic protons, helium-3, carbon, and oxygen ions and for CHO cells irradiated by carbon ions have been analyzed using the probabilistic two-stage model of cell inactivation. Three different classes of DNA damages formed by traversing particles have been distinguished, namely severe single-track damages which might lead to cell inactivation directly, less severe damages where cell inactivation is caused by their combinations, and damages of negligible severity that can be repaired easily. Probabilities of single ions to form these damages have been assessed in dependence on their linear energy transfer (LET) values. Damage induction probabilities increase with atomic number and LET. While combined damages play crucial role at lower LET values, single-track damages dominate in high-LET regions. The yields of single-track lethal damages for protons have been compared with the Monte Carlo estimates of complex DNA lesions, indicating that lethal events correlate well with complex DNA double-strand breaks. The decrease in the single-track damage probability for protons of LET above approx. 30 keV/$\mu$m, suggested by limited experimental evidence, is discussed, together with the consequent differences in the mechanisms of biological effects between protons and heavier ions. Applications of the results in hadrontherapy treatment planning are outlined.Comment: submitted to Physics in Medicine and Biolog

Spallation reactions. A successful interplay between modeling and applications

The spallation reactions are a type of nuclear reaction which occur in space by interaction of the cosmic rays with interstellar bodies. The first spallation reactions induced with an accelerator took place in 1947 at the Berkeley cyclotron (University of California) with 200 MeV deuterons and 400 MeV alpha beams. They highlighted the multiple emission of neutrons and charged particles and the production of a large number of residual nuclei far different from the target nuclei. The same year R. Serber describes the reaction in two steps: a first and fast one with high-energy particle emission leading to an excited remnant nucleus, and a second one, much slower, the de-excitation of the remnant. In 2010 IAEA organized a worskhop to present the results of the most widely used spallation codes within a benchmark of spallation models. If one of the goals was to understand the deficiencies, if any, in each code, one remarkable outcome points out the overall high-quality level of some models and so the great improvements achieved since Serber. Particle transport codes can then rely on such spallation models to treat the reactions between a light particle and an atomic nucleus with energies spanning from few tens of MeV up to some GeV. An overview of the spallation reactions modeling is presented in order to point out the incomparable contribution of models based on basic physics to numerous applications where such reactions occur. Validations or benchmarks, which are necessary steps in the improvement process, are also addressed, as well as the potential future domains of development. Spallation reactions modeling is a representative case of continuous studies aiming at understanding a reaction mechanism and which end up in a powerful tool.Comment: 59 pages, 54 figures, Revie

Virus Infection Suppresses Nicotiana benthamiana Adaptive Phenotypic Plasticity

Competition and parasitism are two important selective forces that shape life-histories, migration rates and population dynamics. Recently, it has been shown in various pathosystems that parasites can modify intraspecific competition, thus generating an indirect cost of parasitism. Here, we investigated if this phenomenon was present in a plant-potyvirus system using two viruses of different virulence (Tobacco etch virus and Turnip mosaic virus). Moreover, we asked if parasitism interacted with the shade avoidance syndrome, the plant-specific phenotypic plasticity in response to intraspecific competition. Our results indicate that the modification of intraspecific competition by parasitism is not present in the Nicotiana benthamiana – potyvirus system and suggests that this phenomenon is not universal but depends on the peculiarities of each pathosystem. However, whereas the healthy N. benthamiana presented a clear shade avoidance syndrome, this phenotypic plasticity totally disappeared when the plants were infected with TEV and TuMV, very likely resulting in a fitness loss and being another form of indirect cost of parasitism. This result suggests that the suppression or the alteration of adaptive phenotypic plasticity might be a component of virulence that is often overlooked

Winter curing of Prunus dulcis cv ‘Butte,’ P. webbii and their interspecific hybrid in response to Xylella fastidiosa infections

Clonal replicates of Prunus dulcis cv ‘Butte,’ P. webbii and their interspecific hybrid P 63-61 were inoculated with Xylella fastidiosa strain M23 and evaluated for almond leaf scorch disease and subsequent winter curing of infections during three growing seasons. Initial inoculations established greater than 90% infection in each of the accessions, based on PCR diagnoses from petiole tissues sampled near the inoculation site. Classic leaf scorch symptoms were evident in each population during the first growing season in a controlled greenhouse environment. Trees were removed from the greenhouse during the winters to accumulate chill hours and to provide the possibility of winter curing X. fastidiosa infections. Both PCR diagnostics and in vitro cultivation were used during the second and third growing seasons to determine the persistence of X. fastidiosa in clones among the three populations. Tree survival and the degree of winter cured infections differed among the three populations, with P. webbii and P 63-61 demonstrating enhanced levels of survivorship over ‘Butte.’ After two cycles of ambient winter temperatures and subsequent growth, ‘Butte’ averaged 21.2% winter cured trees with 73.1% mean survival. Tree survival and winter cured infections were nearly 100% for both P. webbii and P 63-61, demonstrating the utility of P. webbii in almond breeding efforts aimed at reducing tree vulnerability to X. fastidiosa infections

Quality Assurance of ARM Program Climate Research Facility Data

This report documents key aspects of the Atmospheric Radiation Measurement (ARM) Climate Research Facility (ACRF) data quality assurance program as it existed in 2008. The performance of ACRF instruments, sites, and data systems is measured in terms of the availability, usability, and accessibility of the data to a user. First, the data must be available to users; that is, the data must be collected by instrument systems, processed, and delivered to a central repository in a timely manner. Second, the data must be usable; that is, the data must be inspected and deemed of sufficient quality for scientific research purposes, and data users must be able to readily tell where there are known problems in the data. Finally, the data must be accessible; that is, data users must be able to easily find, obtain, and work with the data from the central repository. The processes described in this report include instrument deployment and calibration; instrument and facility maintenance; data collection and processing infrastructure; data stream inspection and assessment; the roles of value-added data processing and field campaigns in specifying data quality and haracterizing the basic measurement; data archival, display, and distribution; data stream reprocessing; and engineering and operations management processes and procedures. Future directions in ACRF data quality assurance also are presented

Repressive coping style and positive self-presentation

Objective - This paper reviews 59 studies looking at cognitive, individual differences and physiological correlates of the repressive coping style, as defined by Weinberger,Schwartz, and Davidson (1979). A central aim is to evaluate the relative importance of the anxiety and social desirability components of repression. Thus, the empirical studyinvestigates the relationships between repression and a number of relevant, but hitherto unexamined, constructs, including trait emotional intelligence (trait EI), self-estimated intelligence, functional and dysfunctional impulsivity, and stoicism. It was hypothesized that repressors would score higher than the other three groups on trait EI, self-estimated IQ and functional impulsivity, but lower on dysfunctional impulsivity. Method - In total, 259 (174 females) participants from three British universities completed questionnaires measuring the dependent and independent variables. Participants were divided into four groups (truly low anxious, non-defensive/high anxious, defensive/high anxious and repressors) based on their scores on anxiety and social desirability. Analyses -moderated multiple regressions (and ANOVAs) were conducted both on the total sample as well as on ‘extreme-scoring’ individuals. Results - Where there were significant differences, the hypotheses were supported,particularly with respect to trait EI, self-estimated IQ and impulsivity. Using ‘extreme-scoring’ groups did not effectively change the results. The regressions revealed an absence of signicant interactions between anxiety and social desirability. Conclusion - Results are discussed in terms of the now replicated effect that repressors present a highly positive and optimistic self-image, despite cognitive and behavioural data suggesting that their coping style is psychologically unhealthy. In addition, it is argued that many findings in the repressive coping style literature can be parsimoniously explained through main effects of anxiety or social desirability alone (i.e., without invoking a construct that combines the two)

Measurement of proton production cross sections of {sup 10}Be and {sup 26}Al from elements found in lunar rocks

Cosmic rays penetrate the lunar surface and interact with the lunar rocks to produce both radionuclides and stable nuclides. Production depth profiles for long-lived radionuclides produce in lunar rocks are measured using Accelerator Mass Spectrometry (AMS). For a particular radionuclide these production depth profiles can be interpreted to give an estimate for the solar proton flux over a time period characterized by the half life of the radionuclide under study. This analysis is possible if and only if all the cross sections for the interactions of all cosmic ray particles with all elements found in lunar rocks are well known. In practice, the most important cross sections needed are the proton production cross sections, because 98% of solar cosmic rays and {similar_to}87% of galactic cosmic rays are protons. The cross sections for the production of long-lived radionuclides were very difficult to measure before the development of AMS and only in recent years has significant progress been made in determining these essential cross sections. Oxygen and silicon are major constituents of lunar rocks. We have reported already {sup 14}C production cross sections from O and Si for proton energies 25-500 MeV, and O(p,x){sup 10}Be from 58 160 MeV[6]. Here we present new measurements for the cross sections O(p,x){sup 10}Be,O(p,x){sup 7}Be, Si(p,x){sup 7}Be,Si(p,x){sup 26}Al, and Si(p,x){sup 22}Na from {approximately}30 - 500 MeV

Repressive coping style and positive self-presentation

Objective - This paper reviews 59 studies looking at cognitive, individual differences and physiological correlates of the repressive coping style, as defined by Weinberger,Schwartz, and Davidson (1979). A central aim is to evaluate the relative importance of the anxiety and social desirability components of repression. Thus, the empirical studyinvestigates the relationships between repression and a number of relevant, but hitherto unexamined, constructs, including trait emotional intelligence (trait EI), self-estimated intelligence, functional and dysfunctional impulsivity, and stoicism. It was hypothesized that repressors would score higher than the other three groups on trait EI, self-estimated IQ and functional impulsivity, but lower on dysfunctional impulsivity. Method - In total, 259 (174 females) participants from three British universities completed questionnaires measuring the dependent and independent variables. Participants were divided into four groups (truly low anxious, non-defensive/high anxious, defensive/high anxious and repressors) based on their scores on anxiety and social desirability. Analyses -moderated multiple regressions (and ANOVAs) were conducted both on the total sample as well as on ‘extreme-scoring’ individuals. Results - Where there were significant differences, the hypotheses were supported,particularly with respect to trait EI, self-estimated IQ and impulsivity. Using ‘extreme-scoring’ groups did not effectively change the results. The regressions revealed an absence of signicant interactions between anxiety and social desirability. Conclusion - Results are discussed in terms of the now replicated effect that repressors present a highly positive and optimistic self-image, despite cognitive and behavioural data suggesting that their coping style is psychologically unhealthy. In addition, it is argued that many findings in the repressive coping style literature can be parsimoniously explained through main effects of anxiety or social desirability alone (i.e., without invoking a construct that combines the two)

Hydrogen-isotope geochemistry of the CM chondrites

Hydration of initially anhydrous silicates and oxides is a common and significant early solar system processes recorded by the carbonaceous chondrites We present new data constraining the hydrogen isotope geochemistry of the CM chondrites, which are characterised by a wide range in degree of hydration. Our study makes use of a recently developed method for analysis of D/H ratios of 10^(-9) mol quantities of water released by heating small (10's of microgram) solid samples