Multiphoton ionization and stabilization of helium in superintense xuv fields

Multiphoton ionization of helium is investigated in the superintense field regime, with particular emphasis on the role of the electron-electron interaction in the ionization and stabilization dynamics. To accomplish this, we solve ab initio the time-dependent Schr\"odinger equation with the full electron-electron interaction included. By comparing the ionization yields obtained from the full calculations with corresponding results of an independent-electron model, we come to the somewhat counterintuitive conclusion that the single-particle picture breaks down at superstrong field strengths. We explain this finding from the perspective of the so-called Kramers-Henneberger frame, the reference frame of a free (classical) electron moving in the field. The breakdown is tied to the fact that shake-up and shake-off processes cannot be properly accounted for in commonly used independent-electron models. In addition, we see evidence of a change from the multiphoton to the shake-off ionization regime in the energy distributions of the electrons. From the angular distribution it is apparent that correlation is an important factor even in this regime

Investigating sorption behaviour of Perfluoroalkyl Substances to biochar

The toxicity, mobility and recalcitrant nature of the chemical class known as Perfluoroalkyl Substances (PFAS) is increasingly being demonstrated to pose a threat to human and environmental health globally. The identification of the risk posed by PFAS by numerous governments and scientific organisations has been a driver for further investigation into potential PFAS management options. Biochar has been considered as a possible sustainable approach to PFAS immobilisation due to being derived from waste biomass materials and having a demonstrated ability to sorb a variety of organic and inorganic contaminants. This study was undertaken to determine if manipulation of biochar characteristics by varying pyrolysis conditions, such as feedstock and pyrolysis temperature, significantly impacted upon biochar PFAS sorption capacity. In addition, the influence of soil matrix was studied, accumulatively demonstrating that with further research biochar could be reverse engineered as an effective and sustainable PFAS sorbent. It was found that by varying feedstock type, and pyrolysis temperature, a wide variety of physiochemical parameters could be manipulated. To better understand what type of physiochemical characteristic were more beneficial for PFAS sorption, a kinetic and sorption study was undertaken at environmentally relevant concentrations for a suite of biochars (pine and pea-straw feedstocks pyrolyzed at 300, 500 and 700°C). A specially developed direct aqueous injection liquid chromatography mass spectrometry method, associated sample preparation technique, and serial sorption method were developed to undertake appropriately sensitive, accurate and robust sample analysis for serial sorption biochar experiments. Through the study of kinetic and sorption behaviour it was found that all tested biochars did not adequately sorb short chain PFAS, PFBA and PFBS. Further, low temperature biochar (350°C) sorbed far less PFAS from solution (<50 %) than its higher temperature counterparts. Sorption equilibriums were found to be reached within 0 - 96 hours to for most PFAS, with the bulk of sorption occurring in the first hour. High temperature pine biochar was demonstrated to be the most effective sorbent for PFHxA, PFHxS, PFOA and PFOS. This suggests that key characteristics for the sorption of longer chain PFAS compounds are high surface area, high aromaticity and hydrophobicity. Isotherms demonstrated complex sorption behaviour, including the formation of monolayers and micelles for some PFAS compounds. This behaviour was greatly influenced by PFAS molecular structure, primarily functional group type, and subsequently chain length. Desorption was less reversible for higher temperature biochars, with all PFAS desorbing less than 20% of sorbed fraction. Sorption behaviour was demonstrated to be impacted by intra PFAS conger interaction, with positive or negative impacts on sorption and desorption dependant on the specific biochar - PFAS congener combination. Further investigation explored the efficacy of pine biochar produced at 750°C as a PFAS sorbent in soils. Soils used in experiments where characterised by their contrasting levels of organic matter and clay. It was found that soil type had a notable impact on biochar efficiency, with biochar being more efficient as a sorbent in soils characterised by higher clay, than in that with higher organic matter. This work strongly suggests biochar can be employed as sustainable sorbents for PFAS. To achieve this goal, further investigation surrounding reverse engineering of biochar over a greater range of temperatures, residence times and feedstocks is required. Additionally, biochar application should be tailored to matrix type, environment type and target PFAS, for optimum performance at environmentally relevant PFAS concentrations

Local structure change evidenced by temperature-dependent elastic measurements: Case study on Bi1/2Na1/2TiO3-based lead-free relaxor piezoceramics

The temperature-dependent Young's modulus Y(T) of the lead-free piezoceramics of 0.8Bi(1/2)Na(1/2)TiO(3)-0.2Bi(1/2)K(1/2)TiO(3) (20BKT) and 0.96(0.8Bi(1/2)Na(1/2)TiO(3)-0.2Bi(1/2)K(1/2)TiO(3))-0.04 BiZn1/2Ti1/2O3 (4BZT) is measured with the impulse excitation technique and contrasted with corresponding dielectric and structural data. While the dielectric properties suggest a phase transition, the high resolution XRD patterns remain virtually unchanged from room temperature up to high temperatures, confirming no change in their long-range order. In contrast, the elastic properties indicate a broad and diffuse ferroelastic transition denoted by a minimum in Y(T). By analogy to the elastic and dielectric data of PbZrxTi1-xO3 and PLZT, it is concluded that 20BKT and 4BZT are relaxors with polar nanoregions embedded in a metrically cubic matrix. Interestingly, no indication for the freezing temperature was reflected in any of the employed measurement techniques. From the saturation of Y(T), it is suggested that the Burns temperature may be approximated as 700 degrees C. Moreover, it is found that the modification with the ternary end-member BiZn1/2Ti1/2O3 results in an increase in Young's modulus. A comparison with the Bi1/2Na1/2TiO3-BaTiO3-K0.5Na0.5NbO3 yields the same results.open0

Technical assistance, neo-colonialism or mutual trade? The experience of an Anglo/Ukrainian/Russian social work practice learning project

Since the collapse of the Soviet Union there has been a steady stream of Western consultants ready to work in Eastern Europe and Russia and share professional and academic expertise and experience. Social work, unknown as a discrete discipline or profession in the Soviet Union, has been a growth area with funding from a variety of sources to help promote East-West partnerships.Social work theory and practice emphasises critical appraisal of policy and embraces issues of power, discrimination and oppression. Social work educators should therefore be especially alert to the complex ethical questions which these kinds of collaborations raise, and adept at finding practical solutions or workable compromises. This article explores these ethical and political issues with reference to a project to develop social work practice learning in a Russian oblast' (region). The project was an ambitious partnership of British, Ukrainian and Russian educators, involving numerous Russian social work and related agencies, and four Russian universities and colleges in one oblast'. The authors use a series of vignettes to help the reader achieve insights into these East-West transactions. The article concludes with a discussion of different interpretations of these dealings, using three prisms: technical assistance, neo-colonialism and mutual trade

Mass-Spectrometry Based Proteome Comparison of Extracellular Vesicle Isolation Methods:Comparison of ME-kit, Size-Exclusion Chromatography, and High-Speed Centrifugation

Extracellular vesicles (EVs) are small membrane-enclosed particles released by cells under various conditions specific to cells’ biological states. Hence, mass-spectrometry (MS) based proteome analysis of EVs in plasma has gained much attention as a method to discover novel protein biomarkers. MS analysis of EVs in plasma is challenging and EV isolation is usually necessary. Therefore, we compared differences in abundance, subtypes, and contamination for EVs isolated by high-speed centrifugation, size exclusion chromatography (SEC), and peptide-affinity precipitation (PAP/ME kit) for subsequent MS-based proteome analysis. Successful EV isolation was evaluated by nanoparticle-tracking analysis, immunoblotting, and transmission electron microscopy, while EV abundance, EV subtypes, and contamination was evaluated by label-free tandem MS. High-speed centrifugation and SEC isolates showed high EV abundance at the expense of contamination by non-EV proteins and lipoproteins, respectively. These two methods also resulted in EVs of a similar type, however, with smaller EVs in SEC isolates. PAP isolates had a relatively low EV abundance and high contamination. We consider high-speed centrifugation and SEC suitable as EV isolation for MS biomarker studies, where the choice between the two should depend on the scientific questions and whether the focus is on larger or smaller EVs or a combination of both

Values - reviewing the construct and drawing implications for values work in organisation and leadership. Kap. 2

I: H.Askeland, G. Espedal, B. Jelstad Løvaas & S. Sirris (Eds.), Understanding values work : Institutional perspectives in organizations and leadershipThis chapter outlines the trajectory of values, particularly within streams of organisational institutionalism, in order to analyse its application to values work in organisation and leadership. Conveying a frame for discussing values work, it aims at clarifying how to conceptualise the term values. Discussing classic and recent contributions, the chapter proposes seeing values as individual and collective conceptions of desirable trans-situational behaviours, objectives and ideals, serving to guide or valuate practice. Despite being an essential part of defining organisational institutionalism, and its sub-streams, values are seldom explicated. Utilising values in organisational and leadership research requires attention to their situatedness in contexts, and this chapter argues they are salient to organisations operating in pluralistic institutional environment. Studying values work, attention should be given to who and how such work is performed.publishedVersio

Acoustic Response of a Layer of Spherical Inclusions with a Random or Periodic Arrangement

Starting with the classic work of Ying and Truell [1], the scattering of a plane elastic wave by an isolated elastic sphere embedded in an unbounded medium has been studied in great detail. Similarly, the propagation of an effective elastic wave in an elastic matrix containing a random or periodic distribution of inclusions has received considerable attention. By comparison, an intermediate level of microstructure — a single layer of inclusions in an elastic matrix — has received very little attention. Apart from the fact that this problem is worth studying in its own right because of its inherent value as a canonical problem in elastodynamics of materials with a microstructure, it has applications in geophysics and quantitative nondestructive evaluation

School based screening for tuberculosis infection in Norway: comparison of positive tuberculin skin test with interferon-gamma release assay

<p>Abstract</p> <p>Background</p> <p>In Norway, screening for tuberculosis infection by tuberculin skin test (TST) has been offered for several decades to all children in 9th grade of school, prior to BCG-vaccination. The incidence of tuberculosis in Norway is low and infection with <it>M. tuberculosis </it>is considered rare. QuantiFERON^®TB Gold (QFT) is a new and specific blood test for tuberculosis infection. So far, there have been few reports of QFT used in screening of predominantly unexposed, healthy, TST-positive children, including first and second generation immigrants. In order to evaluate the current TST screening and BCG-vaccination programme we aimed to (1) measure the prevalence of QFT positivity among TST positive children identified in the school based screening, and (2) measure the association between demographic and clinical risk factors for tuberculosis infection and QFT positivity.</p> <p>Methods</p> <p>This cross-sectional multi-centre study was conducted during the school year 2005–6 and the TST positive children were recruited from seven public hospitals covering rural and urban areas in Norway. Participation included a QFT test and a questionnaire regarding demographic and clinical risk factors for latent infection. All positive QFT results were confirmed by re-analysis of the same plasma sample. If the confirmatory test was negative the result was reported as non-conclusive and the participant was offered a new test.</p> <p>Results</p> <p>Among 511 TST positive children only 9% (44) had a confirmed positive QFT result. QFT positivity was associated with larger TST induration, origin outside Western countries and known exposure to tuberculosis. Most children (79%) had TST reactions in the range of 6–14 mm; 5% of these were QFT positive. Discrepant results between the tests were common even for TST reactions above 15 mm, as only 22 % had a positive QFT.</p> <p>Conclusion</p> <p>The results support the assumption that factors other than tuberculosis infection are widely contributing to positive TST results in this group and indicate the improved specificity of QFT for latent tuberculosis. Our study suggests a very low prevalence of latent tuberculosis infection among 9th grade school children in Norway. The result will inform the discussion in Norway of the usefulness of the current TST screening and BCG-policy.</p