A small angle neutron scattering and Mössbauer spectrometry study of magnetic structures in nanocrystalline Ni3Fe

Results are reported from small angle neutron scattering and Mössbauer spectrometry measurements on nanocrystalline Ni3Fe. The nanocrystalline materials were prepared by mechanical attrition and studied in the as-milled state, after annealing at 265 °C to relieve internal stress, and after annealing 600 °C to prepare a control sample comprising large crystals. The small angle neutron scattering (SANS) measurements were performed for a range of applied magnetic fields. Small differences were found in how the different samples reached magnetic saturation. From the SANS data obtained at magnetic saturation, we found little difference in the nuclear scattering of the as-milled material and the material annealed at 265 °C. Reductions in nuclear scattering and magnetic scattering were observed for the control sample, and this was interpreted as grain growth. The material annealed at 265 °C also showed a reduction in magnetic SANS compared to the as-milled material. This was interpreted as an increase in magnetic moments of atoms at the grain boundaries after a low temperature annealing. Both Mössbauer spectroscopy and small angle neutron scattering showed an increase in the grain boundary magnetic moments after the 265 °C annealing (0.2 and 0.4µB/atom, respectively), even though there was little change in the grain boundary atomic density

Vibrational entropy and microstructural effects on the thermodynamics of partially disordered and ordered Ni3V

Samples of Ni3V were prepared with two microstructures: (1) with equilibrium D022 order, and (2) with partial disorder (having a large D022 chemical order parameter, but without the tetragonality of the unit cell). For both materials, we measured the difference in their heat capacities from 60 to 325 K, inelastic neutron-scattering spectra at four values of Q at 11 and at 300 K, and Young's moduli and coefficients of thermal expansion. The difference in heat capacity at low temperatures was consistent with a harmonic model using the phonon density of states (DOS) curves determined from the inelastic neutron-scattering spectra. In contrast, at temperatures greater than 160 K the difference in heat capacity did not approach zero, as expected of harmonic behavior. The temperature dependence of the phonon DOS can be used to approximately account for the anharmonic contributions to the differential heat capacity. We also argue that some of the anharmonic behavior should originate with a microstructural contribution to the heat capacity involving anisotropic thermal contractions of the D022 structure. We estimate the difference in vibrational entropy between partially disordered and ordered Ni3V to be Spdis -Sord =(+0.038±0.015)kB /atom at 300 K

Influence of regional geology and hydrogeology on river habitat quality: examples from Mill Brook and Elderkin Brook, Kings County, Nova Scotia

Elderkin Brook and Mill Brook are tributaries of the Cornwallis River and were investigated with the intent of understanding the geological conditions that could influence both habitat quality and river restoration efforts. The Cornwallis River and its tributaries have been the focus of restoration efforts in an attempt to re-establish brook trout (Sahelinus fontinalis) and Atlantic salmon (Salmo salar) populations. Both tributaries are relatively short, high-gradient headwater streams that are ungraded along much of their length. Data from Elderkin Brook indicate that pyrite-rich slate of the Kentville and Halifax formations that dominate the watershed geology do not govern the pH of the river discharge. The carbonaceous New Canaan Formation buffers regional groundwater and has resulted in elevated pH levels (7.5-8.0). Springs in the ungraded portion of Elderkin Brook introduce slightly acidic iron-rich groundwater into the system and, upon contact with the alkaline discharge, have produced sporadic masses of flocculated ferric hydroxide (Fe(OH)5). Along the upper reaches of Mill Brook, iron-rich acidic groundwater (pH 5.O-5.5) originating from the Kentville Formation influences the chemistry of the river discharge during low-flow conditions. However, groundwater input from the porous, calcareous-cemented Wolfville Formation that underlies the lower portion of Mill Brook has resulted in locally elevated pH levels (6.0-6.5) and the precipitation of extensive Fe(OH)5 deposits. In both Elderkin Brook and Mill Brook, the precipitation, deposition and preservation of ferric hydroxide is controlled by regional and local, geological and hydrogeological conditions. During the winter and spring, increased discharge and dilution of the groundwater chemistry by precipitation keep iron in either solution or suspension. During low-flow periods (primarily in the fall) flocculated ferric hydroxide accumulations develop coincident with the spawning of both fish species. These conditions result in both temporally and spatially constrained habitat degradation that may be difficult to recognise using the habitat evaluation techniques that are presently being employed by river management groups. RÉSUMÉ Le ruisseau Elderkin et le ruisseau Mill sont des affluents de la rivière Cornwallis; on les étudies dans le but de comprendre les conditions géologiques qui pourraient influer tant sur la qualité de l'habitat que sur les efforts de remise en état de la rivière. La rivière Cornwallis et ses affluents ont fait l'objet de travaux de remise en état visant à rétablir les populations d'ombles de fontaine (Salvelinus fontinalis) et de saumons atlantiques (Salmo salar). Les deux affluents sont des cours d'eau d'amont relativement peu étendus a forte déclivité et au lit accidenté sur une bonne partie de leur longueur. Les données provenant du ruisseau Elderkin révèlent que l'ardoise riche en pyrite des formations de Kentville et d'Halifax qui prédomine dans la structure géologique du bassin versant ne regit pas le pH du débit fluviatile. La Formation carbonée de New Canaan tamponne l'eau souterraine de la région et elle a entrainé des pH eleves (7,5-8,0). Les sources qui coulent dans la partie accidentée du ruisseau Elderkin introduisent de l'eau souterraine riche en fer légèrement acide dans le réscau et elles ont, au contact avec l'écoulement alcalin, produit des masses sporadiques d'hydroxy de ferrique [Fe(OH)5] floculé. Le long des sections supérieures du ruisseau Mill, l'eau souterraine acide riche en fer (pH de 5,0-5,5) en provenance de la Formation de Kentville influence la composition chimique du débit fluviatile à l'étiage. L'apport d'eau souterraine de la Formation a ciment calcaire poreux de Wolfville sous-jacente à la partie inférieure du ruisseau Mill a entrainé des pH localement élevés (6,0-6,5) et la precipitation de vastes dépôts de Fe(OH)5 Dans les ruisseaux Elderkin et Mill, la precipitation, la sedimentation et la conservation de l'hydroxyde ferrique sont fonction des conditions géologiques et hydrogeologiques régionales et locales. En hiver et au printemps, l'écoulement accru d'eau souterraine et la dilution de sa composition chimique due à la précipitation maintient du fer en place en solution ou en suspension. Pendant les périodes d'étiage (surtout l'automne), l'hydroxyde ferrique floculé s'accumule au moment de la periode de frayage des deux especés de poissons. Ces conditions entrainent une degradation de l'habitat qui est soumis à des contraintes temporelles et spatiales qu'il pourrait etre difficile de caractériser au moyen des techniques devaluation de l'habitat présentement employées par les groupes de gestion des rivières. Traduit par la rédactio

Pulse-Shape Discrimination of CaF2(Eu)

We measured the decay time of the scintillation pulses produced by electron and nuclear recoils in CaF2(Eu) by a new fitting method. In the recoil energy region 5-30 keVee, we found differences of the decay time between electron and nuclear recoil events. In the recoil energy region above 20 keVee, we found that the decay time is independent of the recoil energy.Comment: 10 pages, 4 figure

A new genus of Rhinotragini for \u3ci\u3eMolorchus laticornis\u3c/i\u3e Klug, 1825 (Coleoptera, Cerambycidae)

Klugiatragus gen. nov. is described for Epimelitta laticornis (Klug, 1825) because this species has closed procoxal cavities, a crucial diagnostic incompatible with Epimelitta Bates, 1870, which has open procoxal cavities. Both sexes of this species are illustrated

A new genus of Rhinotragini for \u3ci\u3eMolorchus laticornis\u3c/i\u3e Klug, 1825 (Coleoptera, Cerambycidae)

Klugiatragus gen. nov. is described for Epimelitta laticornis (Klug, 1825) because this species has closed procoxal cavities, a crucial diagnostic incompatible with Epimelitta Bates, 1870, which has open procoxal cavities. Both sexes of this species are illustrated

Longitudinal patterns in an Arkansas River Valley stream: an Application of the River Continuum Concept

The River Continuum Concept (RCC) provides the framework for studying how lotic ecosystems vary from headwater streams to large rivers. The RCC was developed in streams in eastern deciduous forests of North America, but watershed characteristics and land uses differ across ecoregions, presenting unique opportunities to study how predictions of the RCC may differ across regions. Additionally, RCC predictions may vary due to the influence of fishes, but few studies have used fish taxa as a metric for evaluating predictions of the RCC. Our goal was to determine if RCC predictions for stream orders 1 through 5 were supported by primary producer, macroinvertebrate, and fish communities in Cadron Creek of the Arkansas River Valley. We sampled chlorophyll a, macroinvertebrates, and fishes at five stream reaches across a gradient of watershed size. Contrary to RCC predictions, chlorophyll a did not increase in concentration with catchment size. As the RCC predicts, fish and macroinvertebrate diversity increased with catchment size. Shredding and collecting macroinvertebrate taxa supported RCC predictions, respectively decreasing and increasing in composition as catchment area increased. Herbivorous and predaceous fish did not follow RCC predictions; however, surface-water column feeding fish were abundant at all sites as predicted. We hypothesize some predictions of the RCC were not supported in headwater reaches of this system due to regional differences in watershed characteristics and altered resource availability due to land use surrounding sampling sites

A model for uranium mobility in groundwater in the Grand Pré region, Nova Scotia, Canada

Elevated levels of uranium that surpass maximum allowable concentrations have been recognized in some well water samples throughout Nova Scotia. In this study we examine the influence of redox conditions and regional geology on the mobility of uranium in groundwater in the Grand Pré region, located in the eastern end of the Annapolis-Cornwallis Valley in southwestern Nova Scotia. The study site is underlain by carbon-rich shale and arkosic sandstone of the Late Mississippian Horton Bluff Formation and the arenaceous sandstone of the Triassic Wolfville Formation. Water samples from drilled wells were analyzed on site for various water quality parameters (pH, conductivity, temperature, dissolved oxygen) and in the laboratory to determine alkalinity and cation (72) and major anion (9) concentrations. Several samples exceeded Health Canada (2011) limits for uranium (20 μg/L) with values up to 50.8 μg/L and aesthetic objectives (AO) for iron (up to 605 μg/L), manganese (up to 2.28 mg/L) and other cations. Data show that different redox conditions occur in the study area. The geospatial arrangement of the chemical data suggests that the lithology of the underlying aquifer strongly influences the availability of uranium in groundwater. Reduced groundwater in Horton Bluff sandstone typically contains elevated concentrations of Fe 2+ and Mn 2+ , whereas groundwater containing high concentrations of U is found primary in oxidizing environments in quartz arenite sandstone units in the Wolfville Formation. Consumption of groundwater in the Grand Pré region may pose a health risk; however, the level of risk remains unknown. This study emphasizes that in the area of Grand Pré, water that is considered aesthetically undesirable (containing high Fe and Mn) may pose less of a health risk (low U) than waters that are aesthetically pleasing.Des niveaux élevés d’uranium qui dépassent les concentrations maximales admises ont été détectés dans certains échantillons d’eau de puits en Nouvelle Écosse. Dans cette étude, nous examinons les effets de la réduction-oxydation et de la géologie régionale sur la mobilité de l’uranium dans l’eau souterraine de la région de Grand Pré, dans l’extrémité est de la vallée d’Annapolis-Cornwallis, dans le sud ouest de la Nouvelle Écosse. Le site étudié repose sur du schiste charbonneux et du grès arkosique de la Formation de Horton Bluff, du Mississippien tardif, et sur du grès arénacé de la Formation de Wolfville, du Trias. Les échantillons d’eau de puits creusés ont été analysés sur place pour ce qui est de divers paramètres de qualité de l’eau (pH, conductivité, température, oxygène dissous) et des analyses ont eu lieu en laboratoire pour établir l’alcalinité et les concentrations de cations (72) et de principaux anions (9). Plusieurs échantillons dépassaient les limites permises par Santé Canada (2011), en ce qui concerne la teneur en uranium (20 μg/L), certaines teneurs ayant atteint 50,8 μg/L. Il en allait de même en ce qui concerne les critères esthétiques pour le fer (des teneurs ayant atteint 605 μg/L), le manganèse (des teneurs ayant atteint 2,28 mg/L) et d’autres cations. Les données indiquent que divers phénomènes de réduction-oxydation surviennent dans le secteur étudié. Le contexte géospatial des données chimiques porte à croire que la lithologie de la couche aquifère sous jacente exerce une forte influence sur la disponibilité de l’uranium dans l’eau souterraine. L’eau souterraine qui a subi une réduction dans le grès de Horton Bluff contient généralement des concentrations élevées de Fe 2+ et de Mn 2+ , tandis que l’eau souterraine à forte concentration d’uranium est surtout observée dans les milieux oxydants de grès de quartz-arénite de la Formation de Wolfville. La consommation de l’eau souterraine dans la région de Grand Pré peut poser un risque pour la santé, mais le degré de risque demeure inconnu. Cette étude met en lumière le risque moindre pour la santé (faible teneur en U) de l’eau dans la région de Grand Pré, qui a une apparence pouvant laisse à désirer (elle a une forte teneur en Fe et en Mn), comparativement à d’autres sources d’eau d’apparence plus agréable. [Traduit par la redaction