Observations géophysiques sur le pergélisol des environs du lac Minto, Nouveau-Québec

À l'aide de techniques géophysiques, on a étudié le pergélisol de la région du lac Minto, Nouveau-Québec. Le pergélisol a une distribution discontinue et son épaisseur varie selon les caractéristiques biophysiques des stations inventoriées. Le pergélisol est mince ou absent sur les terrasses lacustres boisées, ainsi que dans les fens et les sédiments grossiers d'origine fluvioglaciaire. Il est par contre présent dans les stations exposées aux vents et peu enneigées, autant dans les sédiments minéraux (terrasses de tills remaniés, buttes minérales cryogènes) qu'organiques (palses, plateaux palsiques dans les fens de la région). L'importance du mollisol et du pergélisol a fait l'objet d'une cartographie détaillée dans un secteur diversifié au point de vue écologique. La neige, le ruissellement et la capacité de rétention d'eau des sédiments semblent être les principaux facteurs déterminant la présence et l'importance du pergélisol.This paper is concerned with permafrost distribution in Lake Minto area, Nouveau-Québec, studied with the aid of geophysical techniques. Permafrost has a discontinuous distribution and its depth varies greatly with biophysical conditions of sampled sites. Permafrost is shallow or absent on wooded lacustrine terraces, fens and coarse fluvioglacial deposits, whereas it is well developped on windy and snow-free sites, either in mineral deposits (reworked till terraces, cryogenic mineral mounds) or organic ones (palsas and peat plateaus). In an ecologically well diversified area the active layer and permafrost were mapped in detail. Snow, run-off, and soil water capacity seem to be the main factor responsible for the presence and importance of permafrost

Conception et réalisation d'un appareil de désaimantation par champs alternatifs et son utilisation dans les études paleomagnétiques

Dieser Aufsatz behandelt Entwurf, Konstruktion, Kenndaten und Betrieb eines Apparates zur Entmagnetisierung mittels Wechselfeldern. Parameter von Solenoiden mit innerem Halbmesser von 12,0 bis 22,2 cm weisen darauf hin, daß Wechselfelder von einigen Tausend Orsted zu erreichen sind mit Benutzung von Leitern großen Querschnitts, weil für die Konstruktion solcher Solenoide der Ohmsche Widerstand maßgebend ist. Gleichförmigkeit des Feldes, Kerngröße, die entwickelte Hochspannung und Temperaturanstieg begrenzen die Möglichkeit der Parameterwahl und erschweren die technische Lösung. Ausführlich wird beschrieben ein Solenoid mit 12,0 cm Kern, das Wechselfelder mit Spitzenwerten von 2000 Orsted entwickeln kann. Dieses Solenoid ermöglicht die Untersuchung von bestimmter Fossilmagnetisierung in Gesteinen mittels zweier Autotransformatoren, die eine Abminderung des Wechselfeldes erlauben. Der Durchmesser des Solenoidkernes ist groß genug, um das Einsetzen einer Kippeinrichtung zu gestatten, die allgemein benutzt wird, um die Orientation der Gesteinsprobe zu ändern und dadurch die remanente anhysteretische Magnetisierung zu verhindern. Die Einzelteile des Entmagnetisierungsapparates werden der Reihe nach besprochen.This paper deals with the conception, construction, characteristics and operation of an alternating field demagnetizing unit. The parameters of solenoids having internal diameters ranging from 4.7 to 8.7 inches (12,0 to 22,2 cm) show that, in order to obtain alternating fields of some thousands of Orsted, it is necessary to use a conducting wire having a large section because the resistance is the main factor influencing the construction of such solenoids. The uniformity of the field, the size of the core, the high tension created and the increase in temperature narrow the range for the choice of these parameters and increase the technical difficulties in their construction. A solenoid (core = 12,0 cm) capable of creating altemating fields of 2000 Orsted (peak to peak) is described in detail. With the help of two autotransformers allowing a decrease of the alternating field, this solenoid is used to study paleomagnetic properties of rocks and the behaviour (experimental psychology) of small animals (Bartley white rats, baby rabbits and cats) in alternating fields of relatively high intensity. The diameter of the solenoid core is sufficiently large to allow the insertion of a tumbler used to change the orientation of the rock sample in order to minimize the acquisition of anhysteretic remanent magnetisation. The essential parts of the demagnetizing apparatus are investigated one after the other

An integrative SDT-based investigation of the relation between financial incentives, motivation, and performance

To this day, researchers are debating the adequacy of using financial incentives to bolster performance in work settings. Our goal was to contribute to current understanding by considering the moderating role of distributive justice in the relation between financial incentives, motivation, and performance. Based on self-determination theory, we hypothesized that when bonuses are fairly distributed, using financial incentives makes employees feel more competent and autonomous, which in turn fosters greater autonomous motivation and lower controlled motivation, and better work performance. Results from path analyses in three samples supported our hypotheses, suggesting that the effect of financial incentives is contextual, and that compensation plans using financial incentives and bonuses can be effective when properly managed

Vascularization of the human intervertebral disc: A scoping review

Intervertebral discs (IVDs) are often referred to as the largest avascular structures of the human body, yet a collective resource characterizing the vascularization of the IVD does not exist. To address this gap, the objective of this study was to conduct a comprehensive search of the literature to review and summarize current knowledge of the prevalence and localization of blood supply in human IVDs, with a scoping review. A comprehensive search of peer-reviewed publications on the topic of IVD vascularization in humans was conducted across six electronic databases: PubMed, EMBASE, MEDLINE, Scopus, Web of Science, and BIOSIS Previews. Studies of humans were included regardless of age, sex, ethnicity, and health status, with the exception of IVD herniation. Two independent reviewers screened titles and abstracts and full-texts according to eligibility criteria. The review was conducted and reported according to Preferred Reporting Items for Systematic Reviews Extension for Scoping Reviews guidelines. Our search yielded 3122 articles, with 22 articles meeting the inclusion criteria. The study samples ranged in age from fetal to \u3e90 years and included both sexes, various health statuses, and used different methodologies (eg, histology, medical imaging, and gross dissection) to assess vasculature. Overall, consistent observations were that (a) the nucleus pulposus of the IVD is avascular throughout life, (b) both the cartilage endplates and annulus fibrosus receive considerable blood supply early in life that diminishes over the lifespan, and (c) vascular ingrowth into the cartilage endplates and inner layers of the annulus fibrosus is commonly associated with damaged or disrupted tissue, irrespective of age. Histology and immunohistochemistry are often used to report vascularization of the IVD. The body of the current literature suggests that the IVD should not be generalized as an avascular tissue. Instead, vascularization of the IVD differs based on the constituent tissues, their age, and state of degeneration or damage

Dystrophic calcification and heterotopic ossification in fibrocartilaginous tissues of the spine in diffuse idiopathic skeletal hyperostosis (DISH)

© 2020, The Author(s). Diffuse idiopathic skeletal hyperostosis (DISH) is a prevalent noninflammatory spondyloarthropathy characterized by ectopic mineral formation along the anterolateral aspect of the vertebral column, yet little is known about its underlying pathogenesis. Our objective was to evaluate the histopathological features and composition of ectopic mineral within spinal tissues affected by DISH in humans. Thoracic spine segments from six embalmed cadaveric donors (one female and five males; median age 82 years) meeting the radiographic diagnostic criteria for DISH were evaluated using radiological, histological, and physical analyses. Overall, the histological features of ectopic mineralization at individual motion segments were heterogeneous, including regions of heterotopic ossification and dystrophic calcification. Heterotopic ossifications were characterized by woven and lamellar bone, multifocal areas of metaplastic cartilage, and bony bridges along the anterior aspect of the intervertebral disc space. Dystrophic calcifications were characterized by an amorphous appearance, a high content of calcium and phosphorus, an X-ray diffraction pattern matching that of hydroxyapatite, and radiodensities exceeding that of cortical bone. Dystrophic calcifications were found within the anterior longitudinal ligament and annulus fibrosus in motion segments both meeting and not meeting the radiographic criteria for DISH. In summary, our findings indicate that in DISH, ectopic mineral forms along the anterior aspect of the spine by both heterotopic ossification and dystrophic calcification of fibrocartilaginous tissues. Although both types of ectopic mineralization are captured by current radiographic criteria for DISH, dystrophic calcification may reflect a distinct disease process or an early stage in the pathogenesis of DISH

Assessment of ion kinetic effects in shock-driven inertial confinement fusion implosions using fusion burn imaging

The significance and nature of ion kinetic effects in D3He-filled, shock-driven inertial confinement fusion implosions are assessed through measurements of fusion burn profiles. Over this series of experiments, the ratio of ion-ion mean free path to minimum shell radius (the Knudsen number, NK) was varied from 0.3 to 9 in order to probe hydrodynamic-like to strongly kinetic plasma conditions; as the Knudsen number increased, hydrodynamic models increasingly failed to match measured yields, while an empirically-tuned, first-step model of ion kinetic effects better captured the observed yield trends [Rosenberg et al., Phys. Rev. Lett. 112, 185001 (2014)]. Here, spatially resolved measurements of the fusion burn are used to examine kinetic ion transport effects in greater detail, adding an additional dimension of understanding that goes beyond zero-dimensional integrated quantities to one-dimensional profiles. In agreement with the previous findings, a comparison of measured and simulated burn profiles shows that models including ion transport effects are able to better match the experimental results. In implosions characterized by large Knudsen numbers (NK3), the fusion burn profiles predicted by hydrodynamics simulations that exclude ion mean free path effects are peaked far from the origin, in stark disagreement with the experimentally observed profiles, which are centrally peaked. In contrast, a hydrodynamics simulation that includes a model of ion diffusion is able to qualitatively match the measured profile shapes. Therefore, ion diffusion or diffusion-like processes are identified as a plausible explanation of the observed trends, though further refinement of the models is needed for a more complete and quantitative understanding of ion kinetic effects

Characterizations of how species mediate ecosystem properties require more comprehensive functional effect descriptors

The importance of individual species in mediating ecosystem process and functioning is generally accepted, but categorical descriptors that summarize species-specific contributions to ecosystems tend to reference a limited number of biological traits and underestimate the importance of how organisms interact with their environment. Here, we show how three functionally contrasting sediment-dwelling marine invertebrates affect fluid and particle transport - important processes in mediating nutrient cycling - and use high-resolution reconstructions of burrow geometry to determine the extent and nature of biogenic modification. We find that individual functional effect descriptors fall short of being able to adequately characterize how species mediate the stocks and flows of important ecosystem properties and that, in contrary to common practice and understanding, they are not substitutable with one another because they emphasize different aspects of species activity and behavior. When information derived from these metrics is combined with knowledge of how species behave and modify their environment, however, detailed mechanistic information emerges that increases the likelihood that a species functional standing will be appropriately summarized. Our study provides evidence that more comprehensive functional effect descriptors are required if they are to be of value to those tasked with projecting how altered biodiversity will influence future ecosystems