Bulk meltwater flow and liquid water content of snowpacks mapped using the electrical self-potential (SP) method

Our ability to measure, quantify and assimilate hydrological properties and processes of snow in operational models is disproportionally poor compared to the significance of seasonal snowmelt as a global water resource and major risk factor in flood and avalanche forecasting. We show here that strong electrical self-potential fields are generated in melting in situ snowpacks at Rhone Glacier and Jungfraujoch Glacier, Switzerland. In agreement with theory, the diurnal evolution of self-potential magnitudes ( ∼ 60–250mV) relates to those of bulk meltwater fluxes (0–1.2 × 10−6m3s−1) principally through the permeability and the content, electrical conductivity and pH of liquid water. Previous work revealed that when fresh snow melts, ions are eluted in sequence and electrical conductivity, pH and self-potential data change diagnostically. Our snowpacks had experienced earlier stages of melt, and complementary snow pit measurements revealed that electrical conductivity ( ∼ 1–5 × 10−6Sm−1) and pH ( ∼ 6.5–6.7) as well as permeabilities (respectively  ∼ 9.7 × 10−5 and  ∼ 4.3 × 10−5m2 at Rhone Glacier and Jungfraujoch Glacier) were invariant. This implies, first, that preferential elution of ions was complete and, second, that our self-potential measurements reflect daily changes in liquid water contents. These were calculated to increase within the pendular regime from  ∼ 1 to 5 and  ∼ 3 to 5.5% respectively at Rhone Glacier and Jungfraujoch Glacier, as confirmed by ground truth measurements. We conclude that the electrical self-potential method is a promising snow and firn hydrology sensor owing to its suitability for (1) sensing lateral and vertical liquid water flows directly and minimally invasively, (2) complementing established observational programs through multidimensional spatial mapping of meltwater fluxes or liquid water content and (3) monitoring autonomously at a low cost. Future work should focus on the development of self-potential sensor arrays compatible with existing weather and snow monitoring technology and observational programs, and the integration of self-potential data into analytical frameworks.ISSN:1994-0416ISSN:1994-042

The effect of intermittent umbilical cord occlusion on elastin composition in the ovine fetus.

This study aimed to determine the effect of varying degrees of intermittent umbilical cord occlusion (UCO) on arterial elastin composition. Over 4 days, chronically catheterized late gestation fetal sheep received 5 total UCO per day lasting 1 min/h (mild group: n = 6), 2 min/h (moderate group: n = 4), 3 min/h (severe group; n = 6); or no occlusion (control group: n = 7). Each group was evaluated for elastin content of the carotid and superior mesenteric artery (SMA), the arterial pressure response to UCO, and plasma cortisol concentration. Elastin content of the carotid artery was significantly increased by severe UCO (9.5 µg/mg versus 6.4 µg/mg; P \u3c .05) and insignificantly increased in mild and moderate groups, whereas UCO had no effect on elastin content of the SMA. This dose- and site-dependent response of the vasculature appears attributable to the hemodynamic changes that accompany UCO

CCL2 nitration is a negative regulator of chemokine-mediated inflammation.

Chemokines promote leukocyte recruitment during inflammation. The oxidative burst is an important effector mechanism, this leads to the generation of reactive nitrogen species (RNS), including peroxynitrite (ONOO). The current study was performed to determine the potential for nitration to alter the chemical and biological properties of the prototypical CC chemokine, CCL2. Immunofluorescence was performed to assess the presence of RNS in kidney biopsies. Co-localisation was observed between RNS-modified tyrosine residues and the chemokine CCL2 in diseased kidneys. Nitration reduced the potential of CCL2 to stimulate monocyte migration in diffusion gradient chemotaxis assays (p < 0.05). This was consistent with a trend towards reduced affinity of the nitrated chemokine for its cognate receptor CCR2b. The nitrated chemokine was unable to induce transendothelial monocyte migration in vitro and failed to promote leukocyte recruitment when added to murine air pouches (p < 0.05). This could potentially be attributed to reduced glycosaminoglycan binding ability, as surface plasmon resonance spectroscopy showed that nitration reduced heparan sulphate binding by CCL2. Importantly, intravenous administration of nitrated CCL2 also inhibited the normal recruitment of leukocytes to murine air pouches filled with unmodified CCL2. Together these data suggest that nitration of CCL2 during inflammation provides a mechanism to limit and resolve acute inflammation

Directional Charge Separation in Isolated Organic Semiconductor Crystalline Nanowires

One of the fundamental design paradigms in organic photovoltaic device engineering is based on the idea that charge separation is an extrinsically driven process requiring an interface for exciton fission. This idea has driven an enormous materials science engineering effort focused on construction of domain sizes commensurate with a nominal exciton diffusion length of order 10 nm. Here, we show that polarized optical excitation of isolated pristine crystalline nanowires of a small molecule n-type organic semiconductor, 7,8,15,16-tetraazaterrylene, generates a significant population of charge-separated polaron pairs along the π-stacking direction. Charge separation was signalled by pronounced power-law photoluminescence decay polarized along the same axis. In the transverse direction, we observed exponential decay associated with excitons localized on individual monomers. We propose that this effect derives from an intrinsic directional charge-transfer interaction that can ultimately be programmed by molecular packing geometry

Validity of energy expenditure estimation methods during 10 days of military training

Wearable physical activity (PA) monitors have improved the ability to estimate free-living total energy expenditure (TEE) but their application during arduous military training alongside more well-established research methods has not been widely documented. This study aimed to assess the validity of two wrist-worn activity monitors and a PA log against doubly-labelled water (DLW) during British Army Officer Cadet (OC) training. For 10 days of training, twenty (10 male and 10 female) OCs (mean ± SD: age 23 ± 2 years, height 1.74 ± 0.09 m, body mass 77.0 ± 9.3 kg) wore one research-grade accelerometer (GENEActiv, Cambridge, UK) on the dominant wrist, wore one commercially-available monitor (Fitbit SURGE, USA) on the non-dominant wrist and completed a self-report PA log. Immediately prior to this 10-day period, participants consumed a bolus of DLW and provided daily urine samples, which were analysed by mass spectrometry to determine TEE. Bivariate correlations and limits of agreement (LoA) were employed to compare TEE from each estimation method to DLW. Average daily TEE from DLW was 4112 ± 652 kcal·day against which the GENEActiv showed near identical average TEE (mean bias ± LoA: -15 ± 851 kcal day ) while Fitbit tended to underestimate (-656 ± 683 kcal·day ) and the PA log substantially overestimate (+1946 ± 1637 kcal·day ). Wearable physical activity monitors provide a cheaper and more practical method for estimating free-living TEE than DLW in military settings. The GENEActiv accelerometer demonstrated good validity for assessing daily TEE and would appear suitable for use in large-scale, longitudinal military studies

A Hydrogen Bond in Loop A Is Critical for the Binding and Function of the 5-HT3 Receptor†

The binding sites of Cys-loop receptors are formed from at least six loops (A−F). Here we have used mutagenesis, radioligand binding, voltage clamp electrophysiology, and homology modeling to probe the role of two residues in loop A of the 5-HT_3 receptor: Asn128 and Glu129. The data show that substitution of Asn128, with a range of alternative natural and unnatural amino acids, changed the EC_(50) (from ∼10-fold more potent to ∼10-fold less potent than that of the wild type), increased the maximal peak current for mCPBG compared to 5-HT (R_(max)) 2−19-fold, and decreased n_H, indicating this residue is involved in receptor gating; we propose Asn128 faces away from the binding pocket and plays a role in facilitating transitions between conformational states. Substitutions of Glu129 resulted in functional receptors only when the residue could accept a hydrogen bond, but with both these and other substitutions, no [^3H]granisetron binding could be detected, indicating a role in ligand binding. We propose that Glu129 faces into the binding pocket, where, through its ability to hydrogen bond, it plays a critical role in ligand binding. Thus, the data support a modified model of the 5-HT_3 receptor binding site and show that loop A plays a critical role in both the ligand binding and function of this receptor

The Development and Validation of a Mental Toughness Scale for Adolescents

The present study examined the validity of a newly developed instrument, the Mental Toughness Scale for Adolescents (MTS-A), which examines the attributes of challenge, commitment, confidence (abilities and interpersonal) and control (life and emotion). The six factor model was supporting using Exploratory Factor Analysis (EFA, n = 373) and Confirmatory Factor Analysis (CFA, n = 372). In addition, the mental toughness attributes correlated with adolescents’ academic motivation and engagement (n = 439), well-being (depression and anxiety) (n = 279) and test anxiety (n = 279), indicating relations with a number of affective, cognitive and behavioural dispositions, and demonstrating relevance in education and potentially mental health contexts

Extracorporeal membrane oxygenation support after the Fontan operation

ObjectiveExtracorporeal membrane oxygenation has been used to support children with cardiac failure after the Fontan operation. Mortality is high, and causes of mortality remain unclear. We evaluated the in-hospital mortality and factors associated with mortality in these patients.MethodsExtracorporeal Life Support Organization registry data on patients requiring extracorporeal membrane oxygenation after the Fontan operation from 1987 to 2009 were retrospectively analyzed. Demographics and extracorporeal membrane oxygenation data were compared for survivors and nonsurvivors. A multivariable logistic regression model was used to identify factors associated with mortality.ResultsOf 230 patients, 81 (35%) survived to hospital discharge. Cardiopulmonary resuscitation was more frequent (34% vs 17%, P = .04), and median fraction of inspired oxygen concentration was higher (1 [confidence interval, 0.9–1.0] vs 0.9 [confidence interval, 0.8–1.0], P = .03) before extracorporeal membrane oxygenation in nonsurvivors compared with survivors. Extracorporeal membrane oxygenation duration and incidence of complications, including surgical bleeding, neurologic injury, renal failure, inotrope use on extracorporeal membrane oxygenation, and bloodstream infection, were higher in nonsurvivors compared with survivors (P < .05 for all). In a multivariable model, neurologic injury (odds ratio, 5.18; 95% confidence interval, 1.97–13.61), surgical bleeding (odds ratio, 2.36; 95% confidence interval, 1.22–4.56), and renal failure (odds ratio, 2.81; 95% confidence interval, 1.41–5.59) increased mortality. Extracorporeal membrane oxygenation duration of more than 65 hours to 119 hours (odds ratio, 0.33; 95% confidence interval, 0.14–0.76) was associated with decreased mortality.ConclusionsCardiac failure requiring extracorporeal membrane oxygenation after the Fontan operation is associated with high mortality. Complications during extracorporeal membrane oxygenation support increase mortality odds. Prompt correction of surgical bleeding when possible may improve survival