Collisional and thermal ionization of sodium Rydberg atoms I. Experiment for nS and nD atoms with n=8-20

Collisional and thermal ionization of sodium nS and nD Rydberg atoms with n=8-20 has been studied. The experiments were performed using a two-step pulsed laser excitation in an effusive atomic beam at atom density of about 2 10^{10} cm^{-3}. Molecular and atomic ions from associative, Penning, and thermal ionization processes were detected. It has been found that the atomic ions were created mainly due to photoionization of Rydberg atoms by photons of blackbody radiation at the ambient temperature of 300K. Blackbody ionization rates and effective lifetimes of Rydberg states of interest were determined. The molecular ions were found to be from associative ionization in Na(nL)+Na(3S) collisions. Rate constants of associative ionization have been measured using an original method based on relative measurements of Na_{2}^{+} and Na^{+} ion signals.Comment: 23 pages, 10 figure

Managing hedgerows for nocturnal wildlife:Do bats and their insect prey benefit from targeted agri-environment schemes?

1. Mitigating the detrimental impacts of intensive farming on biodiversity requires the implementation of cost-effective conservation actions. Targeted agri-environment-schemes (AESs) to enhance populations of threatened species inhabiting farmland have been proposed for this purpose, yet their effectiveness for nocturnal wildlife remains unknown. 2. We assessed whether hedgerow management prescribed by targeted AESs to improve habitat conditions for the greater horseshoe bat (Rhinolophus ferrumequinum) in England may positively influence the species, the entire bat assemblage and the insect prey of bats. We specifically investigated the responses of bats (occurrence, activity, and species richness) and insects (biomass, abundance, and diversity) to time since last trimming (from 1 up to 10 years). We explored the mechanisms underlying the effects of AES via changes in trimming regime on bats. Moreover, we investigated the effects of landscape context on bats as we expected that highly mobile species would benefit further from landscape-scale management. 3. Bat species richness significantly increased with time since last trimming. Three bat taxa of major conservation concern in Western Europe substantially benefited from the targeted prescription, namely R. ferrumequinum, R. hipposideros and Plecotus spp. Insect-family richness and dipteran abundance were also significantly greater at hedgerows that were untrimmed for at least three years. The activity of more common bat species (i.e. pipistrelle bats) was not influenced by time since last trimming. 4. Changes in trimming regime strongly affected hedgerow height which directly and indirectly (by increasing prey abundance) influenced bat occurrence, activity and species richness along hedgerows. 5. The activity of highly mobile bat species was mainly associated with a range of landscape attributes. The amount of semi-natural grassland within 0.5 km of the sampling sites positively influenced R. ferrumequinum while the presence of urban areas negatively affected light-sensitive bat species. 6. Synthesis and applications. The implementation of targeted agri-environment-schemes can include effective measures to enhance bats and their insect prey in farmland. Although we highlight the success of current prescriptions on hedgerow management, we suggest that their effectiveness can easily be optimized by encouraging farmers to keep hedgerows untrimmed for longer periods (>3 up to 10 years). We also highlight that a multi-scale management approach is required to successfully promote bats in farmland

Atomic excitation during recollision-free ultrafast multi-electron tunnel ionization

Modern intense ultrafast pulsed lasers generate an electric field of sufficient strength to permit tunnel ionization of the valence electrons in atoms. This process is usually treated as a rapid succession of isolated events, in which the states of the remaining electrons are neglected. Such electronic interactions are predicted to be weak, the exception being recollision excitation and ionization caused by linearly-polarized radiation. In contrast, it has recently been suggested that intense field ionization may be accompanied by a two-stage `shake-up' reaction. Here we report a unique combination of experimental techniques that enables us to accurately measure the tunnel ionization probability for argon exposed to 50 femtosecond laser pulses. Most significantly for the current study, this measurement is independent of the optical focal geometry, equivalent to a homogenous electric field. Furthermore, circularly-polarized radiation negates recollision. The present measurements indicate that tunnel ionization results in simultaneous excitation of one or more remaining electrons through shake-up. From an atomic physics standpoint, it may be possible to induce ionization from specific states, and will influence the development of coherent attosecond XUV radiation sources. Such pulses have vital scientific and economic potential in areas such as high-resolution imaging of in-vivo cells and nanoscale XUV lithography.Comment: 17 pages, 4 figures, original format as accepted by Nature Physic

Evasion of cytotoxic T lymphocyte (CTL) responses by nef-dependent induction of Fas ligand (CD95L) expression on simian immunodeficiency virus-infected cells.

Published versio

Massively Parallel Sequencing Reveals the Complex Structure of an Irradiated Human Chromosome on a Mouse Background in the Tc1 Model of Down Syndrome

Down syndrome (DS) is caused by trisomy of chromosome 21 (Hsa21) and presents a complex phenotype that arises from abnormal dosage of genes on this chromosome. However, the individual dosage-sensitive genes underlying each phenotype remain largely unknown. To help dissect genotype – phenotype correlations in this complex syndrome, the first fully transchromosomic mouse model, the Tc1 mouse, which carries a copy of human chromosome 21 was produced in 2005. The Tc1 strain is trisomic for the majority of genes that cause phenotypes associated with DS, and this freely available mouse strain has become used widely to study DS, the effects of gene dosage abnormalities, and the effect on the basic biology of cells when a mouse carries a freely segregating human chromosome. Tc1 mice were created by a process that included irradiation microcell-mediated chromosome transfer of Hsa21 into recipient mouse embryonic stem cells. Here, the combination of next generation sequencing, array-CGH and fluorescence in situ hybridization technologies has enabled us to identify unsuspected rearrangements of Hsa21 in this mouse model; revealing one deletion, six duplications and more than 25 de novo structural rearrangements. Our study is not only essential for informing functional studies of the Tc1 mouse but also (1) presents for the first time a detailed sequence analysis of the effects of gamma radiation on an entire human chromosome, which gives some mechanistic insight into the effects of radiation damage on DNA, and (2) overcomes specific technical difficulties of assaying a human chromosome on a mouse background where highly conserved sequences may confound the analysis. Sequence data generated in this study is deposited in the ENA database, Study Accession number: ERP000439

The Global Garden project: Imagining plant science

Plants are rich sources of drugs and other high-value chemicals that are used by humans. Many of the plant species that produce important molecules grow in remote locations and have extensive histories of indigenous use. Global concerns about sustainable supply have in some cases led to the development of alternative methods for production using biotechnological approaches. Consideration of responsible stewardship and use of the world's plants and associated traditional knowledge for the greater human good are at the heart of the Convention on Biological Diversity and the recently implemented Nagoya Protocol. The development of fora that enable open discussion and exploration of issues relating to these aspects will be critical in endeavors to protect and preserve both the environment and present and future generations. Summary: Here, we investigate the application of cross-disciplinary approaches to explore societal perceptions of plants and their uses, focusing on high-value chemicals. The Global Garden project engages the public, researchers, and regulators in day-long workshops that combine science, poetry, and visual arts practice to foster participants’ skill in imagining and re-imagining relationships between high-value plant products, biotechnology, and social and ethical aspects of these. The project represents an intervention into discussions of science communications and public engagement, addressing the uses and benefits of arts-based approaches to foster imaginative engagement with plant science. The workshop reported here began with real plant case studies and a discussion of the aims of scientists using them. Participants were invited to respond to the issues of relationships among plants, chemicals, and people raised by the case studies through poetry and visual artwork. The poems and artwork that were produced show variation in the participants’ imaginings of plant science. They present distinctive visions of research and innovation and of the associated ethical and social implications. This type of forum, based on creative immersion, opens up opportunities for engaging with and exploring complex relations between plant biotechnology, society, and ethics. This article offers a reflection on the uses, challenges, and implications of arts-based approaches to research communications and public engagement that disrupts traditional knowledge transfer structures. In doing so, we frame the project within science communication pedagogies and consider public engagement a form of pedagogy

The role of parental achievement goals in predicting autonomy-supportive and controlling parenting

Although autonomy-supportive and controlling parenting are linked to numerous positive and negative child outcomes respectively, fewer studies have focused on their determinants. Drawing on achievement goal theory and self-determination theory, we propose that parental achievement goals (i.e., achievement goals that parents have for their children) can be mastery, performance-approach or performance-avoidance oriented and that types of goals predict mothers' tendency to adopt autonomy-supportive and controlling behaviors. A total of 67 mothers (aged 30-53 years) reported their goals for their adolescent (aged 13-16 years; 19.4 % girls), while their adolescent evaluated their mothers' behaviors. Hierarchical regression analyses showed that parental performance-approach goals predict more controlling parenting and prevent acknowledgement of feelings, one autonomy-supportive behavior. In addition, mothers who have mastery goals and who endorse performance-avoidance goals are less likely to use guilt-inducing criticisms. These findings were observed while controlling for the effect of maternal anxiety

Lead exposures and biological responses in military weapons systems: Aerosol characteristics and acute lead effects among US Army artillerymen: Final report

This study was to determine the concentration and chemical nature of lead (Pb) aerosols produced during the firing of artillery and to determine the exposures and biological responses of crew members exposed to lead aerosols during such firing. The concentrations of lead-containing aerosols at crew positions depended on wind conditions, with higher concentrations when firing into a head wind. Aerosol concentrations were highest in the muzzle blast zone. Concentrations of lead in the blood of crew members rose during the first 12 days of exposure to elevated airborne lead concentrations and then leveled off. There was no rapid decrease in blood lead concentrations after completion of firing. Small decreases in hematocrit and small increases in free erythrocyte porphyrin were correlated with increasing exposure to airborne lead. These changes were reversed by seven weeks after firing. Changes in nerve conduction velocity had borderline statistical significance to airborne lead exposure. In measuring nerve conduction velocity, differences in skin temperature must be taken into account

Method for evaluating the snagging propensity of roofing membranes in buildings by roosting bats

Many buildings suitable as bat roosts contain synthetic roofing materials, hereafter referred to as Non-Bitumen Coated Roofing Membranes (NBCRMs) - this includes Breathable Roofing Membranes (BRMs) and non-Permeable Roofing Membranes (nPRMs), rather than 1F felts. Building regulations require all construction materials to be fit for purpose, but some BRMs (although appropriate for their intended purpose) can potentially threaten the viability of existing, legally protected roosts because of the way bats physically interact with their surface. With the assistance of the Isle of Wight Bat Hospital and real-world observations of how bats physically interact with NBCRMs within a roof void, we present a new laboratory test method capable of reproducing the progressive disintegration of NBCRM surfaces due to the plucking effect of bat claws. The resistance to NBCRM disintegration was characterised using a modified laboratory fabric pilling box test method. The method reproduced the ‘fluffing’ effects and projections of loops of filaments on the surface of BRMs that have been observed within bat roosts. It was established that spunbond nonwoven BRMs, can be highly susceptible to surface disintegration. The newly developed method is intended to aid selection of NBCRMs that reduce the risk to bats in their roosts, promoting bat conservation

A robust model for read count data in exome sequencing experiments and implications for copy number variant calling

Exome sequencing has proven to be an effective tool to discover the genetic basis of Mendelian disorders. It is well established that copy number variants (CNVs) contribute to the etiology of these disorders. However, calling CNVs from exome sequence data is challenging. A typical read depth strategy consists of using another sample (or a combination of samples) as a reference to control for the variability at the capture and sequencing steps. However, technical variability between samples complicates the analysis and can create spurious CNV calls