P-T-t path for the Archean Pikwitonei Granulite Domain and Cross Lake Subprovince, Manitoba, Canada

The rationale was outlined for constructing pressure-temperature-time (P-T-t) paths by using U-Pb dating of garnet produced in thermobarometrically sensitive reactions. In an example from the Pikwitonei granulites of the Northwestern Superior Province of the Canadian Shield, garnets were formed at 2744-2742 Ma, 2700-2689 Ma, and 2605-2590 Ma, the latter events coinciding with times recorded by U-Pb zircon systems. Garnet grew during metamorphism at 6.5 kbar, 630 to 750 C and later at 7.2 to 7.5 kbar, 800 C; the later metamorphism apparently did not exceed the U-Pb closure temperature. The resultant P-T-t path is counterclockwise, with late isobaric cooling, interpreted to result from magmatic heating at an Andean margin

Excitation dynamics in polyacene molecules on rare-gas clusters

Laser-induced fluorescence spectra and excitation lifetimes of anthracene, tetracene, and pentacene molecules attached to the surface of solid argon clusters have been measured with respect to cluster size, density of molecules, and excitation density. Results are compared to previous studies on the same sample molecules attached to neon clusters. A contrasting lifetime behavior of anthracene on neon and argon clusters is discussed, and mechanisms are suggested to interpret the results. Although both neon and argon clusters are considered to be weakly interacting environments, we find that the excitation decay dynamics of the studied acenes depends significantly on the cluster material. Moreover, we find even qualitative differences regarding the dependence on the dopant density. Based on these observations, previous assignments of collective radiative and non-radiative decay mechanisms are discussed in the context of the new experimental findings.& nbsp;(c) 2022 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/)

An ontology-based modelling system (OBMS) for representing behaviour change theories applied to 76 theories [version 1; peer review: awaiting peer review]

BACKGROUND: To efficiently search, compare, test and integrate behaviour change theories, they need to be specified in a way that is clear, consistent and computable. An ontology-based modelling system (OBMS) has previously been shown to be able to represent five commonly used theories in this way. We aimed to assess whether the OBMS could be applied more widely and to create a database of behaviour change theories, their constructs and propositions. METHODS: We labelled the constructs within 71 theories and used the OBMS to represent the relationships between the constructs. Diagrams of each theory were sent to authors or experts for feedback and amendment. The 71 finalised diagrams plus the five previously generated diagrams were used to create a searchable database of 76 theories in the form of construct-relationship-construct triples. We conducted a set of illustrative analyses to characterise theories in the database. RESULTS: All 71 theories could be satisfactorily represented using this system. In total, 35 (49%) were finalised with no or very minor amendment. The remaining 36 (51%) were finalised after changes to the constructs (seven theories), relationships between constructs (15 theories) or both (14 theories) following author/expert feedback. The mean number of constructs per theory was 20 (min. = 6, max. = 72), with the mean number of triples per theory 31 (min. = 7, max. = 89). Fourteen distinct relationship types were used, of which the most commonly used was ‘influences’, followed by ‘part of’. CONCLUSIONS: The OBMS can represent a wide array of behavioural theories in a precise, computable format. This system should provide a basis for better integration and synthesis of theories than has hitherto been possible

ОЦЕНКА АНАЛИТИЧЕСКИХ ВОЗМОЖНОСТЕЙ РЕНТГЕНОФЛУОРЕСЦЕНТНОЙ СПЕКТРОМЕТРИИ С ПОЛНЫМ ВНЕШНИМ ОТРАЖЕНИЕМ ПРИ АНАЛИЗЕ НАПИТКОВ С МАТРИЦЕЙ САХАРОЗЫ

Multielement analysis of food products, including drinks, is important for an assessment of the content of the useful and toxic elements for the human body. In this paper, the main problems and their solutions in the analysis of sugar-containing drinks by Total Reflection X-ray Fluorescence Spectrometry (TXRF) method have been considered. The organic sucrose matrix causes certain difficulties both in the preparation of the samples and in the processing of measurement data for TXRF. The following most common sample preparation procedures for TXRF were considered: direct, based on the analysis of initial sample, dilution with water and acid digestion. In order to assess the fulfillment of the thin layer criterion, the physical characteristics of dried samples on the carriers were determined after applying each of the above-mentioned preparation procedures, and the corresponding surface density values were established. The obtained values were compared with the theoretical ones. Based on the calculation of mass absorption coefficients for C12H22O11 matrix, it was found that the method of acid digestion was suitable for the quantitative determination of light (14 Z 20) elements. When analyzing the sample without the preliminary preparation or after diluting the sample with water, the influence of absorption effects was noted due to the mismatch of the surface density with the thin layer criterion. This mismatch of the samples in the direct analysis was confirmed by the measurements using a method based on an angle incidence scanning of the primary radiation on the sample, establishing a violation of the conditions for the effect of total external reflection. The detection limits were calculated for the considered sample preparation procedures, and it was concluded that the quantitative identification of Fe, Ni, Cu, Zn, Rb, Sr, and Pb trace elements at the level of tens of μg/l was possible by the acid digestion procedure. The application of the addition method to assess the trueness of elemental determination led to the conclusion that it was possible to use the direct analysis of sugar-containing drinks for the elements with Z ≥ 24 in the concentration ranges of 0.5–10 mg/l.Key words: X-ray fluorescence, TXRF, soft drinks, matrix effects, absorption effects, sucrose, multielement analysis, addition method(Russian)DOI: http://dx.doi.org/10.15826/analitika.2019.23.4.009A.S. Maltsev1, 2, A. von Bohlen3, R.A. Yusupov2, S.A. Bakhteev2 1 Institute of the Earth’s Crust, SB RAS, Lermontov st., 128, Irkutsk, 664033, Russian Federation2 Kazan National Research Technological University, Marksa st., 68, Kazan, 420012, Russian Federation3 Leibniz-Institut für Analytische Wissenschften ISAS, Bunsen-Kirchhoff-Str. 11, Dortmund, 44139, GermanyМногоэлементный анализ пищевой продукции, в т.ч. напитков, важен при оценке содержания полезных и токсичных для организма элементов. В данной работе рассмотрены основные проблемы и их решения при анализе сахаросодержащих напитков методом рентгенофлуоресцентной спектрометрии с полным внешним отражением (TXRF). Органическая матрица сахарозы вызывает определенные сложности как при подготовке проб, так и при обработке данных измерений для TXRF. Рассмотрены наиболее распространенные для TXRF способы подготовки проб: прямой, заключающийся в анализе исходного образца, разбавление водой и кислотное разложение. Для оценки выполнения критерия тонкого слоя определены физические характеристики высушенных проб на подложках после применения каждого из способов подготовки и установлены значения поверхностной плотности. Полученные значения сравнили с теоретическими, исходя из расчета массовых коэффициентов поглощениядля матрицы C12H22O11, и установили, что для количественного определения легких (14 Z 20) элементов подходит способ кислотного разложения. При анализе образца без предварительной подготовки или после разбавления образца водой отмечено влияние эффектов поглощения, обусловленные несоответствием поверхностной плотности критерию тонкого слоя. Это несоответствие проб при прямом анализе подтвердили с помощью измерений с использованием способа, основанного на сканировании угла падения первичного излучения на образец, установив нарушение условий эффекта полного внешнего отражения. Для рассмотренных вариантов пробоподготовки рассчитаны пределы обнаружения, и сделан вывод о том, что при кислотном разложении возможна количественная идентификация микроэлементов Fe, Ni, Cu, Zn, Rb, Sr, Pb на уровне десятков мкг/л. Применение способа добавок, используемого для контроля правильности определения элементов, позволило заключить о возможности использования прямого способа анализа сахаросодержащих напитков для элементов c Z ≥ 24 в диапазонах концентраций 0.5-10 мг/л.Ключевые слова: рентгенофлуоресцентный анализ, РФА ПВО, напитки, матричные эффекты, эффекты поглощения, сахароза, многоэлементный анализ, способ добавокDOI: http://dx.doi.org/10.15826/analitika.2019.23.4.00

Real-time dynamics of the formation of hydrated electrons upon irradiation of water clusters with extreme ultraviolet light

Free electrons in a polar liquid can form a bound state via interaction with the molecular environment. This so-called hydrated electron state in water is of fundamental importance e.g.~in cellular biology or radiation chemistry. Hydrated electrons are highly reactive radicals that can either directly interact with DNA or enzymes, or form highly excited hydrogen (H∗) after being captured by protons. Here, we investigate the formation of the hydrated electron in real-time employing XUV femtosecond pulses from a free electron laser, in this way observing the initial steps of the hydration process. Using time-resolved photoelectron spectroscopy we find formation timescales in the low picosecond range and resolve the prominent dynamics of forming excited hydrogen states

Clusters in Light Nuclei

A great deal of research work has been undertaken in the alpha-clustering study since the pioneering discovery, half a century ago, of 12C+12C molecular resonances. Our knowledge of the field of the physics of nuclear molecules has increased considerably and nuclear clustering remains one of the most fruitful domains of nuclear physics, facing some of the greatest challenges and opportunities in the years ahead. In this work, the occurence of "exotic" shapes in light N=Z alpha-like nuclei is investigated. Various approaches of superdeformed and hyperdeformed bands associated with quasimolecular resonant structures are presented. Results on clustering aspects are also discussed for light neutron-rich Oxygen isotopes.Comment: 12 pages, 5 figures. Invited Talk presented by C. Beck at the Zakopane Conference on Nuclear Physics "Extremes of the Nuclear Landscape" XLV in the series of Zakopane Schools of Physics - International Symposium - Zakopane, Poland, August 30 - September 5, 2010.To be publihed in Acta Physica Polonica B42 no 3, March 201

Hartree Fock Calculations in the Density Matrix Expansion Approach

The density matrix expansion is used to derive a local energy density functional for finite range interactions with a realistic meson exchange structure. Exchange contributions are treated in a local momentum approximation. A generalized Slater approximation is used for the density matrix where an effective local Fermi momentum is chosen such that the next to leading order off-diagonal term is canceled. Hartree-Fock equations are derived incorporating the momentum structure of the underlying finite range interaction. For applications a density dependent effective interaction is determined from a G-matrix which is renormalized such that the saturation properties of symmetric nuclear matter are reproduced. Intending applications to systems far off stability special attention is paid to the low density regime and asymmetric nuclear matter. Results are compared to predictions obtained from Skyrme interactions. The ground state properties of stable nuclei are well reproduced without further adjustments of parameters. The potential of the approach is further exemplified in calculations for A=100...140 tin isotopes. Rather extended neutron skins are found beyond 130Sn corresponding to solid layers of neutron matter surrounding a core of normal composition.Comment: Revtex, 29 pages including 14 eps figures, using epsfig.st

The FLASHForward Facility at DESY

The FLASHForward project at DESY is a pioneering plasma-wakefield acceleration experiment that aims to produce, in a few centimetres of ionised hydrogen, beams with energy of order GeV that are of quality sufficient to be used in a free-electron laser. The plasma wave will be driven by high-current density electron beams from the FLASH linear accelerator and will explore both external and internal witness-beam injection techniques. The plasma is created by ionising a gas in a gas cell with a multi-TW laser system, which can also be used to provide optical diagnostics of the plasma and electron beams due to the <30 fs synchronisation between the laser and the driving electron beam. The operation parameters of the experiment are discussed, as well as the scientific program.Comment: 19 pages, 9 figure

Large-basis shell-model calculations for p-shell nuclei

Results of large-basis shell-model calculations for nuclei with A=7-11 are presented. The effective interactions used in the study were derived microscopically from the Reid93 potential and take into account the Coulomb potential as well as the charge dependence of T=1 partial waves. For A=7, a $6\hbar\Omega$ model space was used, while for the rest of the studied nuclides, the calculations were performed in a $4\hbar\Omega$ model space. It is demonstrated that the shell model combined with microscopic effective interactions derived from modern nucleon-nucleon potentials is capable of providing good agreement with the experimental properties of the ground state as well as with those of the low-lying excited states.Comment: 17 pages. REVTEX. 16 PostScript figure

Density Dependent Hadron Field Theory

A fully covariant approach to a density dependent hadron field theory is presented. The relation between in--medium NN interactions and field--theoretical meson--nucleon vertices is discussed. The medium dependence of nuclear interactions is described by a functional dependence of the meson--nucleon vertices on the baryon field operators. As a consequence, the Euler--Lagrange equations lead to baryon rearrangement self--energies which are not obtained when only a parametric dependence of the vertices on the density is assumed. It is shown that the approach is energy--momentum conserving and thermodynamically consistent. Solutions of the field equations are studied in the mean--field approximation. Descriptions of the medium dependence in terms of the baryon scalar and vector density are investigated. Applications to infinite nuclear matter and finite nuclei are discussed. Density dependent coupling constants obtained from Dirac--Brueckner calculations with the Bonn NN-potentials are used. Results from Hartree calculations for energy spectra, binding energies and charge density distributions of $^{16}O$, $^{40,48}Ca$ and $^{208}Pb$ are presented. Comparisons to data strongly support the importance of rearrangement in a relativistic density dependent field theory. Most striking is the simultanuous improvement of charge radii, charge densities and binding energies. The results indicate the appearance of a new "Coester line" in the nuclear matter equation of state.Comment: 48 LateX pages, 12 Figures, figures and full paper are available as postscript files by anonymous ftp at ftp://theorie.physik.uni-giessen.de/dd