Nondispersive X-ray emission analysis for geochemical exploration

Nondispersive X-ray emission technique uses lightweight, and rugged X-ray fluorescence units. The X-ray pulse-height spectra is excited by radioactive isotope sources. The technique is applicable for quantitative and qualitative analyses on complex chemical systems, and satisfies the goals for a lunar geochemical exploration device

Thermoluminescence Dating of Late Pleistocene Sediments, St. Lawrence Lowland, Québec

This paper presents the results of a thermoluminescence (TL) dating program applied to waterlaid sediments of Late Pleistocene age, collected in the central St. Lawrence Lowland, in eastern Canada. The apparent TL ages were obtained using a partial bleach method (R-Gamma) in which the TL from light-sensitive traps is separated from the total TL. Fluvial (modern), marine (late-glacial) lacustrine (interstadial) and glacio-lacustrine (stadial) sediments yielded apparent ages ranging from 4 to 135 ka, and in general, these ages agreed with available stratigraphic evidence. Whilst testing the zeroing assumption, apparent TL ages obtained from modern fluvial and late glacial sediments suggest that laboratory overbleaching or insufficient natural bleaching may result in over-estimation of the apparent TL ages by 4-5 ka. All samples display anomalous fading, a problem that can be overcome by introducing a three month delay between artificial irradiation and glowing. Future research should focus on sediments for which the age as well as the sedimentology are well documented, such as the late glacial Champlain Sea sediments.Cet article présente les résultats d'un projet de datation par thermoluminescence (TL) de sédiments des basses terres du Saint-Laurent datant du Pléistocène supérieur. Les âges TL apparents ont été obtenus en utilisant une méthode de lessivage partiel (R-Gamma) par laquelle la TL émanant de pièges cristallins sensibles à la lumière a pu être séparée de la TL totale. Les sédiments, d'origines fluviatile (modernes), marine (tardiglaciaires), lacustre (interstadiaires) et glaciolacustre (stadiaires) ont livré des âges entre 4 et 135 ka et, erï général, les âges obtenus correspondent aux données stratigraphiques. Des expériences menées sur le phénomène de « remise à zéro » ont été menées sur des sédiments fluviatiles modernes et marins tardiglaciaires. Elles démontrent que, dans les cas où le lessivage solaire a pu être insuffisant ou le lessivage simulé en laboratoire trop intense, les âges TL apparents peuvent être surestimés de 4 à 5 ka. Tous les échantillons montrent un affaiblissement anormal du signal de thermoluminescence. Ce problème peut être résolu par l'introduction d'un délai de trois mois entre l'irradiation artificielle et la mesure de l'échantillon. À l'avenir la recherche devrait se faire sur des sédiments dont la chronologie et la sédimentologie sont bien connues, tels les sédiments tardiglaciaires champlainiens.Dieser Artikel stellt die Ergebnisse eines Datierungsprojekts mittles Thermoluminiszenz (TL) dar, angewandt auf angeschwemmte Sedimente aus dem spaten Pleistozàn, die in Ostkanada, in der zentralen Sankt-Lorenz Tiefebene gesammelt wurden. Die offensichtlichen TL-Alter wurden mittels einer partiellen Bleichmethode (R-Gamma) gewonnen, in welcher die TL der lichtempfindlichen Fallen von der totalen TL getrennt wurde. Die Sedimente von FIuB (modem), Meer (Spâtglazial), See (Interstadial) und Glazio-See (Stadial) lieferten offensichtliche Alter zwischen 4 bis 135 ka, und im allgemeinene stimmten dièse Alter mit den verfùgbaren stratigraphischen Zeugnissen ùberein. Wohingegen beim Testen mittels der 'NuII-Annahme' die offensichtlichen TL-Alter, die aus modernen FluBsedimenten und spaten glazialen Sedimenten gewonnen wurden, vermuten lassen, daB zu intensives Bleichen im Labor oder ungenùgendes Bleichen in der Natur zu einer Ùberschàtzung der offensichtlichen TL-Alter von 4 bis 5 ka fuhren. Allé Proben weisen eine anormale Abschwâchung des TL-Signals auf. Dies Problem kann durch die Einfùhrung eines Aufschubs von drei Monaten zwischen der kùnstlichen Bestrahlung und dem Messen der Probe gelôstwerden. Die kùnftige Forschung sollte sich auf Sedimente konzentrieren, deren Alter als auch Sédimentologie gut dokumentiert sind, wie z.B. die spàtglazialenChamplain-Meer-Sedimente

Symmetry group analysis of an ideal plastic flow

In this paper, we study the Lie point symmetry group of a system describing an ideal plastic plane flow in two dimensions in order to find analytical solutions. The infinitesimal generators that span the Lie algebra for this system are obtained. We completely classify the subalgebras of up to codimension two in conjugacy classes under the action of the symmetry group. Based on invariant forms, we use Ansatzes to compute symmetry reductions in such a way that the obtained solutions cover simultaneously many invariant and partially invariant solutions. We calculate solutions of the algebraic, trigonometric, inverse trigonometric and elliptic type. Some solutions depending on one or two arbitrary functions of one variable have also been found. In some cases, the shape of a potentially feasible extrusion die corresponding to the solution is deduced. These tools could be used to thin, curve, undulate or shape a ring in an ideal plastic material

Engineering, applications, and future perspectives of GPCR-based genetically encoded fluorescent indicators for neuromodulators

This review explores the evolving landscape of G-protein-coupled receptor (GPCR)-based genetically encoded fluorescent indicators (GEFIs), with a focus on their development, structural components, engineering strategies, and applications. We highlight the unique features of this indicator class, emphasizing the importance of both the sensing domain (GPCR structure and activation mechanism) and the reporting domain (circularly permuted fluorescent protein (cpFP) structure and fluorescence modulation). Further, we discuss indicator engineering approaches, including the selection of suitable cpFPs and expression systems. Additionally, we showcase the diversity and flexibility of their application by presenting a summary of studies where such indicators were used. Along with all the advantages, we also focus on the current limitations as well as common misconceptions that arise when using these indicators. Finally, we discuss future directions in indicator engineering, including strategies for screening with increased throughput, optimization of the ligand-binding properties, structural insights, and spectral diversity

Multimode solutions of first-order elliptic quasilinear systems obtained from Riemann invariants

Two new approaches to solving first-order quasilinear elliptic systems of PDEs in many dimensions are proposed. The first method is based on an analysis of multimode solutions expressible in terms of Riemann invariants, based on links between two techniques, that of the symmetry reduction method and of the generalized method of characteristics. A variant of the conditional symmetry method for constructing this type of solution is proposed. A specific feature of that approach is an algebraic-geometric point of view, which allows the introduction of specific first-order side conditions consistent with the original system of PDEs, leading to a generalization of the Riemann invariant method for solving elliptic homogeneous systems of PDEs. A further generalization of the Riemann invariants method to the case of inhomogeneous systems, based on the introduction of specific rotation matrices, enables us to weaken the integrability condition. It allows us to establish a connection between the structure of the set of integral elements and the possibility of constructing specific classes of simple mode solutions. These theoretical considerations are illustrated by the examples of an ideal plastic flow in its elliptic region and a system describing a nonlinear interaction of waves and particles. Several new classes of solutions are obtained in explicit form, including the general integral for the latter system of equations

Luminosity indicators in dusty photoionized environments

The luminosity of the central source in ionizing radiation is an essential parameter in a photoionized environment, and one of the most fundamental physical quantities one can measure. We outline a method of determining luminosity for any emission-line region using only infrared data. In dusty environments, grains compete with hydrogen in absorbing continuum radiation. Grains produce infrared emission, and hydrogen produces recombination lines. We have computed a very large variety of photoionization models, using ranges of abundances, grain mixtures, ionizing continua, densities, and ionization parameters. The conditions were appropriate for such diverse objects as H II regions, planetary nebulae, starburst galaxies, and the narrow and broad line regions of active nuclei. The ratio of the total thermal grain emission relative to H$\beta$ (IR/H$\beta$) is the primary indicator of whether the cloud behaves as a classical Str\"{o}mgren sphere (a hydrogen-bounded nebula) or whether grains absorb most of the incident continuum (a dust-bounded nebula). We find two global limits: when $IR/H\beta<100$ infrared recombination lines determine the source luminosity in ionizing photons; when $IR/H\beta\gg100$ the grains act as a bolometer to measure the luminosity.Comment: 12 pages 3 figures. Accepted ASP Sept.9

The distribution and movement patterns of four woodland caribou herds in Quebec and Labrador

Recent studies of woodland caribou (Rangifer tarandus caribou) in northern Quebec and central Labrador have demonstrated similar patterns of seasonal movements and distribution among four herds. Aerial surveys and radio-telemetry indicated that animals occupied forest-wetland habitat at densities of 0.03 caribou km2, or lower, for most of the year. Although females were widely dispersed at calving individuals demonstrated fidelity toward specific calving locations, in successive years. Caribou did not form large post-calving aggregations. Movement was greatest in the spring, prior to calving, and in the fall, during or immediately after rutting. Caribou were generally sedentary during summer and winter, although some moved relatively long distances to late-winter range. Although the herds occupy continuous range across Quebec and Labrador, our data indicate that the herds are largely discreete and should be managed individually

Urinary Allantoin as an Estimate of Microbial Protein Synthesis

Allantoin excretion in the urine was evaluated as a marker for bacterial protein production in lactating and dry cows grazing Sandhills range and meadows. Allantoin excretion declined with season as diet digestibility declined. Bacterial protein predicted from allantoin was significantly related (R2 = .62) to bacterial protein predicted by NRC. Urinary allantoin has potential as a tool to predict bacterial protein production in grazing cattle

Microbial Protein Synthesis and Efficiency in Nursing Calves

Microbial protein synthesis and efficiency were estimated in springborn nursing calves grazing native range and subirrigated meadow. Forage intake increased from 1.5 lb/ day (0.6% BW) in June to 5.9 lb/day (1.2% BW) in September while milk intake decreased over the same period. Microbial protein (MCP) synthesis increased from 67 g/day in May to 278 g/day right before weaning in September. Urinary allantoin was used as a marker. Efficiency of MCP synthesis was approximately 19% of forage digestible organic matter (OM) intake