Transfer-matrix theory of surface spin-echo experiments with molecules

${}^3$He beam spin-echo experiments have been used to study surface morphology, molecular and atomic surface diffusion, phonon dispersions, phason dispersions and phase transitions of ionic liquids. However, the interactions between ${}^3$He atoms and surfaces or their adsorbates are typically isotropic and weak. To overcome these limitations, one can use molecules instead of ${}^3$He in surface spin-echo experiments. The molecular degrees of freedom, such as rotation, may be exploited to provide additional insight into surfaces and the behaviour of their adsorbates. Indeed, a recent experiment has shown that $\textit{ortho}$-hydrogen can be used as a probe that is sensitive to the orientation of a Cu(115) surface [Godsi et al., Nat. Comm. $\textbf{8}$, 15357 (2017)]. However, the additional degrees of freedom offered by molecules also pose a theoretical challenge: a large manifold of molecular states and magnetic field-induced couplings between internal states. Here, we present a fully quantum mechanical approach to model molecular surface spin-echo experiments and connect the experimental signal to the elements of the time-independent molecule-surface scattering matrix. We present a one-dimensional transfer matrix method that includes the molecular hyperfine degrees of freedom and accounts for the spatial separation of the molecular wavepackets due to the magnetic control fields. We apply the method to the case of $\textit{ortho}$-hydrogen, show that the calculated experimental signal is sensitive to the scattering matrix elements, and perform a preliminary comparison to experiment. This work sets the stage for Bayesian optimization to determine the scattering matrix elements from experimental measurements and for a framework that describes molecular surface spin-echo experiments to study dynamic surfaces.Comment: 32 pages, 9 figures. Generalized discussion on rotation matrices and updated Figures 3-7. Accepted in Physical Review A (https://journals.aps.org/pra/

Aging yields a smaller number of fixations and a reduced gaze amplitude when driving in a simulator

With the increasing number of elderly drivers, it is important to better understand if strategies for capturing visual information are affected by age and by the complexity of the driving contexts. Ten young (aged 21-31 years) and older (aged 65-75 years) active drivers drove through a continuous simulated scenario (STISIM, v2.0). The scenario included drinving on open roads (less demanding), stopping at intersections and passing maneuvers (more demanding). Eye movements were recorded with an oculometer (ASL, model 510). Compared to younger drivers, older drivers showed a smaller horizontal amplitude between fixations and a smaller variance in the amplitude of the eye movements. They also showed a smaller number of fixations/sec for the more complex driving maneuvers that were analyzed (passing maneuvers). Overall, this may reveal a "tunnel effect" (or perceptual narrowing) phenomenon when the driving context increases in complexity

Morphometric and Histopathologic Changes in Skeletal Muscle Induced for Injectable PLGA Microparticles

Galdames, IS (Galdames, Ivan Suazo).Univ Talca, Talca, ChileThe administration of microencapsulated drug in a matrix acid poly(lactic-co-glycolic acid) (PLGA) by intramuscular (IM) in humans has been approved by the FDA for various applications though it is not clear what effect they have on the morphological parameters of muscle tissue. The aim of this study was to analyze the morphological changes in the skeletal muscle tissue with their use. We used 12 adult female Sprague Dawley rats (Rattus novergicus) that were injected into their right gastrocnemius muscle belly with: sterile vehicle solution (01, n = 4), 0.5 mg PLGA microparticle (02, n = 4) and 0.75 mg PLGA microparticle (03, n = 4), both dissolved in a sterile vehicle solution. At 14 days post injection the number and diameter of muscle fibers, the level of inflammation and histology appearance in terms of organization of muscle fibers, cellular distribution, tissue morphology and the presence of polymer waste were determined and the results between the groups compared. The administration of the compound in a single dose did not alter the morphometric parameters (number and diameter of muscle fibers) despite generating a mild inflammation in the tissue associated with the presence of polymeric residues, suggesting that the PLGA microparticles were well tolerated by the muscle tissue at concentrations tested (0.5 and 0.75 mg). n Number: WOS:00029366100001

Identification d'un réseau hydrométrique pour le suivi des modifications climatiques dans la province de Québec

Depuis une dizaine d'années, la communauté scientifique s'est beaucoup intéressée à l'hypothèse d'un réchauffement à l'échelle planétaire. De nombreuses études ont porté sur l'analyse de ces modifications climatiques éventuelles ainsi que sur la modélisation de leurs impacts sur les ressources en eau. Cependant, malgré l'attention croissante que reçoit le sujet des modifications climatiques, très peu de travail a été accompli pour mettre en place des réseaux de mesure spécialement conçus pour l'étude des modifications climatiques et leurs impacts sur les ressources en eau, et pour créer des bases de données adaptées à cet objectif. Cette tâche est encore plus nécessaire dans le cadre des réductions budgétaires auxquelles sont soumis les réseaux hydrométriques dans certains pays développés. Cet article présente les bases d'une étude dont l'objectif est la conception d'un réseau hydrométrique pour le suivi des modifications climatiques dans la province de Québec, Canada. Le but est d'identifier, afin de les conserver, les stations de jaugeage les plus adéquates pour accomplir cette tâche. L'article présente aussi une brève revue des types de modifications climatiques qui peuvent être observés et de certains tests qui existent pour leur détection et leur quantification. Une procédure bayésienne de détection des sauts de la moyenne a été sélectionnée sur la base de ses avantages théoriques, et appliquée aux séries de données des stations retenues au Québec.The 1980s and 1990s contained most of the warmest years since the beginning of worldwide temperature recording nearly 140 years ago. Widely accepted estimates project that the earth's average temperature might increase by about 2°C over the next 100 years. It is also expected that, as a result of global warming, the frequency and intensity of floods and droughts may change. However, despite the increasing attention that the issue of climate change receives, there has been little effort to develop a systematic approach for the collection of relevant data, and to establish observational networks specifically designed for the analysis of climate variability and change and their impact on hydrologic regimes and water resources in general. This task is particularly important given the major network reductions that result from recent cutbacks in the funding of monitoring programs in Canada and other countries. This paper presents the results of a rigorous study that was carried out recently, and aimed at establishing a hydrometric network for the study of the attributes of climate change and variability across the province of Quebec (Canada) and their impact on water resources. The approach is based on identifying and maintaining stations that can help provide an understanding of the physical processes within the hydrological cycle and account for climate variations across the province. This network will be of fundamental importance in establishing scientific evidence of the magnitude and direction of possible shifts in climate patterns across the province. These aspects are of global significance and must be considered during the rationalization of monitoring networks. The results of the application of this procedure to the hydrometric network of the province of Quebec are presented. The paper presents also a brief review of the various types of non-stationarities that can be observed in hydrologic data series, and some of the current approaches that can be used for the detection of these non-stationarities. Several statistical tests and procedures have been proposed in the literature for the analysis of the characteristics of data samples and for hypothesis testing, for various types of non-stationarity. A Bayesian procedure, proposed by Lee and Heghinian (1977) and generalized by Bernier (1994), for the detection of shifts in the mean of hydrological and meteorological time-series is selected based on its theoretical advantages (Faucher et al., 1997). The procedure is then applied for the analysis of all streamflow series of selected stations in the province of Quebec with the objective of extracting information on possible climatic changes. Results indicate the presence of significant non-stationarities for a number of the series analyzed. For five stations, the most probable date for the shift in the mean level falls in the period 1983-1985. Recommandations are made for future research activities

Effectiveness of saline water and lidocaine injection treatment of intractable plantar keratoma: a randomised feasibility study

Background: An intractable plantar keratoma (IPK) is a conical thickening of the epidermis' stratum corneum and a common cause of foot pain which can have a significant, detrimental impact on the mobility, quality of life and independence of individuals. Conservative treatments are currently offered to patients with IPK, but they are unsatisfactory since they do not offer a sufficient or permanent reduction of symptoms. The purpose of this study was the evaluation of the feasibility, safety and effectiveness of innovative treatments for intractable plantar keratoma (IPK). Methods: A randomized single blind trial with 40 patients divided with block randomization in four parallel groups was conducted to compare treatment combinations: conservative sharp debridement only or sharp debridement with needle insertion, physiological water injection or lidocaine injection. All patients obtained the same treatment four times at a four-week interval. At each visit, visual analog scale (VAS), Foot Function Index (FFI) and IPK size were evaluated. VAS and FFI were also completed at a six and twelve-month follow-up. Results: Our findings in regards to feasibility demonstrated recruitment challenges because of the anticipated pain that would be provoked by needle insertion may not be worth the potential pain relief compared to debridement alone from the patient's perspective. This was also the principal cause of drop out. Our preliminary results show no main effect of group for any of the clinical outcomes: pain felt on VAS, FFI score, IPK's size (p > 0.05). However, the analysis revealed a statistically significant effect of time on VAS (p 0.05). Conclusions: This study demonstrates that IPK treatment consisting of sharp debridement with needle insertion, physiological saline water injection or lidocaine injection is feasible and safe. There was a non-statistically significant trend toward diminishing pain intensity compared to scalpel debridement alone. The pain provoked by needle insertion and injection treatments must be addressed with a scientifically proven protocol to make it more comfortable for patients before these treatments could be considered in further studies. Trial registration: ClinicalTrials.gov, NCT04777227. 2 March, 2021 - Retrospectively registered (All participants were recruited prior to registration)

Lower limb biomechanics during drop jump landing in individuals with chronic ankle instability

ABSTRACT Context: Individuals with chronic ankle instability (CAI) exhibit impaired lower limb biomechanics during unilateral drop jump landing on a flat surface. However, lower limb biomechanical adaptations during unilateral drop jump landing on more challenging surfaces such as unstable or inclined are yet to be described. Objective: Determine how unilateral drop jump landing surfaces (flat, unstable and inclined) influence lower limb EMG, kinematics and kinetics in individuals with CAI. Design: Descriptive laboratory study. Setting: Biomechanics laboratory. Patients or Other Participants: Twenty-two young adults with CAI Interventions: Participants completed five trials of unilateral drop jump landing from a 46 cm height platform on flat (DROP), unstable (FOAM) and laterally inclined (WEDGE) surfaces. Main outcome measure(s): EMG of gluteus medius, vastus lateralis, gastrocnemius medialis, peroneus longus and tibialis anterior muscles were recorded. Knee and ankle angles and moments were calculated using a three-dimensional motion analysis system and a force plate. Biomechanical variables were compared between tasks using one-dimensional statistical nonparametric mapping. Results: During DROP, greater ankle dorsiflexion angles, knee extension moments and vastus lateralis muscle activity (FOAM only) were observed compared to FOAM and WEDGE. Greater ankle inversion angles were observed during FOAM and WEDGE compared to DROP. Peroneus longus muscle activity was greater during DROP compared to FOAM. During FOAM, greater ankle inversion and knee extension angles, ankle inversion and internal rotation moments as well as smaller peroneus longus muscle activity were observed compared to WEDGE. Conclusions: The greater ankle inversion and plantarflexion angles as well as the lack of increase in peroneus longus muscle activation during FOAM and WEDGE could increase the risk of recurrent LAS in individuals with CAI. The results of this study improve our understanding of lower limb biomechanics changes when landing on more challenging surfaces and will help clinicians better targeting deficits associated with CAI during rehabilitation

Lower limb biomechanics in individuals with chronic ankle instability during gait: a case-control study

Individuals with chronic ankle instability (CAI) exhibit many biomechanical changes to lower limbs during walking. However, only a few studies have investigated the differences in lower limb biomechanics of individuals with CAI compared to healthy controls using a comprehensive approach including kinematic, kinetic and electromyography (EMG) measures. Consequently, the theoretical framework explaining the biomechanical adaptations in individuals with CAI is mostly based on the results of studies including heterogenous methods and participants’ specificities (e.g., level of disability). More studies using a comprehensive approach are needed to better understand the biomechanical adaptations associated with CAI. The objective of this case-control study was to identify the kinematic, kinetic and EMG differences between individuals with CAI and healthy controls during walking

Marginal Reefs Under Stress: Physiological Limits Render Galápagos Corals Susceptible to Ocean Acidification and Thermal Stress

Ocean acidification (OA) and thermal stress may undermine corals' ability to calcify and support diverse reef communities, particularly in marginal environments. Coral calcification depends on aragonite supersaturation (Ω » 1) of the calcifying fluid (cf) from which the skeleton precipitates. Corals actively upregulate pHcf relative to seawater to buffer against changes in temperature and dissolved inorganic carbon, which together control Ωcf. Here we assess the buffering capacity of modern and fossil corals from the Galápagos Islands that have been exposed to sub-optimal conditions, extreme thermal stress, and OA. We demonstrate a significant decline in pHcf and Ωcf since the pre-industrial era, trends which are exacerbated during extreme warm years. These results suggest that there are likely physiological limits to corals' pH buffering capacity, and that these constraints render marginal reefs particularly susceptible to OA