Contrasting Behavior Research Articles

Magmatic evolution and metal systematics of back-arc volcanic rocks of north–east Japan and implications for deposition of massive sulphide Kuroko ores

The Hokuroku region of north-eastern Japan is endowed with important volcanic-hosted massive sulphide Zn–Pb–Cu deposits, which are considered the archetype of Kuroko (black ore) deposits worldwide. The bimodal, felsic-dominated volcanic succession that hosts the ore was deposited in a continental rift formed during continental extension in the final stages of the Miocene back-arc opening that led to the formation of the Japan Sea. In this study, we define some of the fundamental intensive parameters of this volcanism (temperature, pressure of crystallisation, fluid saturation, fO2) based on rock textures, and analyses of whole-rock samples, minerals and melt inclusions. Based on the melt inclusion analyses, we assess the behaviour of metals during magma evolution and degassing, and evaluate the possible implications for ore deposition. Plagioclase-melt geothermometry in felsic tuff and lava samples collected from both the units underlying and overlying the Kuroko indicates temperatures of 880–940 °C, and Fe–Ti oxide equilibrium indicates oxygen fugacity of ca. FMQ + 1.5. Melt inclusions have high-SiO2 rhyolite compositions (> 75 wt%, on an anhydrous basis), and the plot of normative mineral compositions in the granitic triplot indicates low pressure of magma stalling and crystallisation (< 1 kbar) at cotectic compositions. Melt inclusion metal contents plotted vs incompatible element Y suggest contrasting behaviour of different metals during fractionation and degassing. Zinc was mostly retained in the melt during crystallisation, whereas other metals, such as Pb, Cu, Sn and Mo, were released to an exsolving fluid phase. The latter may have thus been transferred to the hydrothermal system from a degassing magma. Shallow storage of relatively hot magma would have induced vigorous hydrothermal circulation on the seafloor, a precondition for ore deposition.

The influence of exercise training versus intensive insulin therapy on insulin resistance development in type 1 diabetes

The etiology of insulin resistance (IR) in Type 1 Diabetes (T1D) is unclear; however, intramyocellular lipids (IMCL) are likely contributors. While exercise lessens IR and IMCL content; T1D patients elevate glycemia to offset exercise-induced hypoglycemic risk. The preferred treatment for T1D patients is tight glucose management through intensive insulin therapy (IIT); however, IIT is accompanied with a sedentary lifestyle. The purpose of this study was to examine IR development and IMCL in combined exercise (DARE; aerobic/resistance) and IIT-treated T1D animals. 76 rats were divided into control sedentary (C), diabetic sedentary (CD), diabetes sedentary intensive insulin therapy (DIT) and DARE groups. Following streptozotocin (STZ), glycemia was maintained at either 9-15 mM (CD, DARE) or 5-9 mM (DIT) using insulin. DARE alternated between running and weighted climbing for 12 weeks. Results demonstrate that DARE exhibited reduced onset of IR compared with C, DIT and CD, indicated by increased glucose infusion rate (hyperinsulinemic-euglycemic-clamp). A shift in lipid metabolism was evident whereby diacylglycerol was elevated in DIT compared to DARE, while triacylglycerol was elevated in DARE. These findings indicate enhanced IMCL metabolism and the sequestration of fat as neutral triacylglycerol leads to reduced IR in DARE. In contrast, IIT and sedentary behavior leads to diacylglycerol accumulation and IR.

On the altitude profile of lower ionospheric D-region response time delay during solar flares

The D-region ionosphere is sluggish in nature while responding to the incoming solar radiation. We study the altitude (h) profile of mid-latitude D-region response time delay (Δt) during three chosen solar flares, namely, C5.2, M5.2, and X2.2 classes. We solve “electron continuity equation” numerically at each and every h to obtain Δt-h profile. We investigate the 1) latitudinal variation (over both Northern and Southern hemispheres) and 2) seasonal variation (throughout the year) of Δt-h profiles of each of these solar flares separately. We go over noteworthy variations of Δt-h profile for both 1) and 2) with reasonably different results over different hemispheres. Also, we study some contrasting behaviours of Δt-h profile of X2.2 class for both 1) and 2) in comparison to C5.2 or M5.2 classes. We conclude the outcome with possible explanations.

STM/STS Study of the Density of States and Contrast Behavior at the Boundary between (7 × 7)N and (8 × 8) Structures in the SiN/Si(111) System

The origin of the contrast appearing in STM images at the boundary between diverse ordered structures is studied using the example of two structures, (7 × 7)N and (8 × 8), formed in the system of a two-dimensional silicon nitride layer on the Si(111) surface during ammonia nitridation. A significant dependence of the contrast between these structures on the voltage applied to the tunnel gap was found and studied both experimentally and theoretically. Variations in the contrast were quantitatively studied in the range from −3 V to +3 V, and they were studied in more detail for the positive biases on the sample from +1 V to +2.5 V, where the contrast was changed more than 2 times. Within the one-dimensional Wentzel–Kramers–Brillouin (WKB) model for the tunnel current, a comparatively simple procedure is proposed for the correction of the experimental STS-spectra of differential conductivity to identify the adequate (feasible) density of electron states (DOS). It is shown that the (8 × 8) structure DOS corresponds to a graphene-like layer of silicon nitride structure. The proposed correction procedure of the empirical differential conductivity spectra measured by STS will be useful for the quantitative determination of the DOS of new two-dimensional materials and surface structures.

Experimental Investigation on the Impacts of Fracture Roughness and Fluid Composition on the Formation of Bubble Bridges through the Microbubble Fluid Flow.

The colloidal gas Aphron (CGA) drilling fluids are an alternative to ordinary drilling mud to minimize formation damage by blocking rock pores with microbubbles in low-pressure or depleted reservoirs. Fractured formations usually have different characteristics and behavior in contrast to conventional ones and need to be investigated for Aphron applications. In this research, a series of core flood tests were conducted to understand the factors controlling the pore-blocking mechanisms of microbubbles in fractured formations. For the first time, a synthetic metal plug was used to simulate the fracture walls and eliminate the formation matrix effect. This study analyzed the effects of three fluid compositions, considering the polymer and surfactant concentrations at reservoir conditions, including temperature and overburden pressure. Additionally, fracture surface roughness as one of the parameters affecting the microbubble fluid penetration through the fracture path and bubble blockage were studied. The results indicated that microbubble fluid composition would not affect the bubble size or blockage probability. The different stable microbubble fluids resulted in the same pattern and conditions. Besides, fluid penetration would be more challenging if the fracture roughness decreased. Due to the accumulation of bubbles and the fact that some of them were trapped in the fracture's rough surface, the blockage possibility increased. According to the range of roughness for the steel core in previous studies and compared with the roughness of carbonate reservoir rocks, the roughness of fractured reservoir rocks is much higher than that of the steel surface. Accordingly, the observed trend in the experiments showed that when it is possible to form a bubble bridge in steel cores, then in carbonate rocks, we will definitely see blockage with any roughness, provided that other parameters are acceptable.

Is there still something to eat for trees in the soils of the Strengbach catchment?

The global demand for wood is growing and the sustainability of forests has become an increasingly important issue. The first metre of soil represents the reserve of nutrients cations (K, Ca, Mg) for trees. The depletion of these elements in the soil gradually leads to a decrease in soil fertility, which can have a strong impact on the development and health of forests.The aim of this study was to better understand the source and dynamics of nutrients in forested soils from a base poor environment by combining mineralogic, chemical, isotopic and numerical tools through an experimental approach. We designed batch experiments to follow the leaching of soils from two experimental plots (under spruce and under beech from the Strengbach catchment, Vosges Mountain, NE France). The studied elements show highly contrasting behaviours. Mg release results from a mixing between cationic exchange, mineral dissolution (mainly smectite) and organic matter mineralization. The dynamics of K are underestimated by modelling, which may be attributed either to an unknown source of K or to an overestimation of the secondary phase precipitation. The Sr isotopic approach, used as a proxy to identify the sources of Ca, shows that the exchangeable complex supplies nutrients first and rapidly to the solution, followed by the clay compartment and at the very end, the bulk soils. Na is mainly controlled by albite dissolution.The release of Ca is significantly lower than that of other cations as Mg or K. Our results suggest that the exchangeable Ca, estimated through classical extractions, is only partly available for plants, due to strong chemical binding with organic matter and/or the occurrence of Ca-chemical bridges between clay and organic matter. Sustainable management should thus consider that exchangeable Ca, conventionally determined, does not necessarily provide an accurate picture of the real availability of Ca and therefore of the fertility of soils, with a risk of overestimation of nutrient reservoir for trees. Calcium tree nutrition at these sites has to rely on the long term on atmospheric deposition and an efficient recycling through biological cycling. This is also true for the other nutrient cations, but to a lesser extent since soil intrinsic fluxes (i.e., weathering, mineralisation of OM…) are not null and may thus supply the exchangeable pools and participate substantially to tree nutrition. Harvesting and biomass exportation could rapidly impact the biological cycle and threaten the sustainability of these ecosystems, similar to changing tree species that may influence the nature of the litter, its turnover and the input of nutrients to the soil.

New insights into the decadal variability in glacier volume of a tropical ice cap, Antisana (0°29′ S, 78°09′ W), explained by the morpho-topographic and climatic context

Abstract. We present a comprehensive study of the evolution of the glaciers on the Antisana ice cap (tropical Andes) over the period 1956–2016. Based on geodetic observations of aerial photographs and high-resolution satellite images, we explore the effects of morpho-topographic and climate variables on glacier volumes. Contrasting behaviour was observed over the whole period, with two periods of strong mass loss, 1956–1964 (−0.72 m w.e. yr−1) and 1979–1997 (−0.82 m w.e. yr−1), and two periods with slight mass loss, 1965–1978 (0.10 m w.e. yr−1) and 1998–2016 (−0.26 m w.e. yr−1). There was a 42 % reduction in the total surface area of the ice cap. Individually, glacier responses were modulated by morpho-topographic variables (e.g. maximum and median altitude and surface area), particularly in the case of the small tongues located at low elevations (Glacier 1, 5 and 16) which have been undergoing accelerated disintegration since the 1990s and will likely disappear in the coming years. Moreover, thanks to the availability of aerial data, a surging event was detected on the Antisana Glacier 8 (G8) in the 2009–2011 period; such an event is extremely rare in this region and deserves a dedicated study. Despite the effect of the complex topography, glaciers have reacted in agreement with changes in climate forcing, with a stepwise transition towards warmer and alternating wet–dry conditions since the mid-1970s. Long-term decadal variability is consistent with the warm–cold conditions observed in the Pacific Ocean represented by the Southern Oscillation index.

Energy Harvesting for Robots with Adaptive Morphology.

Robots primarily made of soft and elastic materials have potential applications such as traveling in confined spaces due to their adaptive morphology. However, their energy efficiency is still subject to improvement. Although a possible approach to increase efficiency is by harvesting the energy used during their behavioral motion, it is not trivial to do so due to their complex dynamics. This work seeks to pioneer a study that exploits the tight coupling between a robot's adaptive morphology, control, and consequent behaviors to harvest energy and increase energy efficiency. It is hypothesized that since varying the robot's morphology may change the energy use that leads to contrasting behavior and efficiency, harvesting the robot's energy will need to be adapted to its morphology. To verify the hypothesis, we developed a shape-changing robot with an elastic structure that achieves locomotion via vibration controlled by a single motor, such that the complex dynamics of the robot can be characterized through its resonance frequencies. It will be shown that harvesting energy at opportune occasions is more important than maximizing the harvest capacity to increase energy efficiency. We will also show how the robot's shape affects energy use in locomotion and how energy harvesting will feedback additional energy that increases the magnitude and affects the robot's behavior. We conclude with an understanding of the role of the robot's morphology, that is, shape, in using the energy provided to the robot and how the understanding can be used to harvest the robot's energy to increase its efficiency.

Extreme methane clumped isotopologue bio-signatures of aerobic and anaerobic methanotrophy: Insights from the Lake Pavin and the Black Sea sediments

Microbial methane oxidation - or methanotrophy - is a key control of the global methane budget on Earth, and perhaps in other planetary systems. Here, we explore the potential role of mass-18 isotopologues of methane, expressed as Δ13CH3D and Δ12CH2D2 values, in tracking both aerobic and anaerobic methanotrophy in nature. We examine two well documented methanotrophic environments: the Lake Pavin (France) water column, where methane degradation is dominated by aerobic methanotrophy (AeOM), and the Black Sea sediments (offshore Romania), dominated by anaerobic methanotrophy (AOM) coupled to sulfate-reduction. In both settings, lighter isotopologues are preferentially consumed, generating elevated 13CH4/12CH4, 12CH3D/12CH4, 13CH3D/12CH4 and 12CH2D2/12CH4 ratios. This results in increasing of δ13C and δD values in the residual methane for both settings, as observed commonly in systems dominated by methanotrophy. As a result, AeOM and AOM cannot be easily distinguished by the development of δ13C and δD. In contrast, the Δ13CH3D and Δ12CH2D2 (departure from stochastic) values have opposite trajectories, with minimal decreases in the case of the AeOM-dominated system, but dramatic increases in the case of AOM, with Δ13CH3D and Δ12CH2D2 reaching values as high as 15.7 ‰ and 76.6 ‰, respectively. This contrasting behavior of clumped isotopologues signatures illustrates fundamental distinction between the two processes and the way they segregate methane isotopologues. These data demonstrate that both AeOM and AOM have distinctive kinetic isotope effects in natural settings, consistent with preliminary laboratory work. In particular, we find that γ-values (which measure the deviation to the product of ‘normal’ bulk isotope fractionation factors) are close to unity in the case of AeOM (i.e. a negligible clumped isotope effect), but significantly below unity in the case of AOM (i.e. strong clumped isotope effect). In addition, our data also illustrate how AOM under low-sulfate conditions may promote methane isotopologue equilibration. Taken together, we suggest these data and apparent isotopologue fractionation factors extrapolated from these two environments may help refine the potential bio-signatures of methane affected by methanotrophy.

Analysis of Electrode Degradation By High-Potential Environment-Using Electrochemical Impedance Spectroscopy in Polymer Electrolyte Membrane Fuel Cells

A Polymer electrolyte membrane fuel cell (PEMFC) is one of the most important applications for decarbonization of energy using hydrogen as an energy source and is considered a promising future power source due to its high efficiency, low operating temperature, fast startup, and low noxious emissions. In particular, improvement in durability of PEMFC is one of the major issues to spur the commercialization of the PEMFC system. Therefore, to improve the durability of PEMFC systems, diagnostic strategies are required to identify faulty conditions of PEMFC systems such as fuel starvation, dehydration, flooding, load cycling, and startup-shutdown (SU/SD). The problematic form of the membrane electrode assembly (MEA) that causes a decrease in the performance of PEMFCs in steady-state and dynamic operating conditions includes Pt dissolution, ionomer degradation, carbon corrosion [1] , and mechanical problems of the membrane in some circumstances. Among them, the undesired corrosion reaction, namely, the electrochemical carbon oxidation reaction, results in a drastic decrease in electrochemical double layer capacitance (EDLC), generation of oxygen functional groups in carbon supports, and severe electrochemical surface area (ECSA) fading [2, 3], followed by deteriorated PEMFC performance. Typically, the high potential inducing carbon corrosion reactions would occur during SU/SD and fuel starvation conditions. In detail, as for fuel starvation, a temporary shortage of H2 supply to one or several cells in a PEMFC stack causes the cell voltage reversal, accompanied by a potential strike over 1.0 V vs. RHE (Figure 1) with significant electrode degradation [4 , 5]. Also, the generation of hydrogen/air boundary at the anode due to the gas crossover through the membrane results in a high potential (~1.4 V vs. RHE), accelerating the decomposition of carbon support [6]. Therefore, in this work, to investigate the effects of high potential inducing electrode degradation on PEMFC performance, we conducted accelerated stress tests (AST), and in particular, we studied the correlation between electrode degradation behaviors as well as structural properties of porous carbon such as ionic resistance, EDLC with PEMFC performance in the systemic point of view. Specially, we could see the contrasting degradation behaviors and various performance decay rates using electrochemical impedance spectroscopy (EIS) analysis. EIS can be used to isolate the contribution of many processes to performance loss, allowing investigation of the effect of carbon corrosion-induced catalyst layer changes on fuel cell performance [ 7]. The measured EIS data is evaluated through the parametric fitting of the transmission line model (TLM) to the EIS spectrum. In addition, relaxation time distribution (DRT) analysis for direct analysis of internal resistance factors by reinforcing the TLM-based impedance analysis results was applied as a diagnostic method to evaluate electrode degradation. During the ASTs, electrochemical measurements (i-V, CV, LSV, and EIS) were performed to estimate the degree of PEMFC degradation, we also conducted ex-situ surface analysis of MEA using SEM, TEM, and XPS to elucidate the specific degradation components.

Impact and control of the COVID pandemic in an elite sports club: Real Madrid.

The incidence and risk factors for poor outcome in patients with COVID are well known, as are the protective measures in high-risk populations. In contrast, the epidemiological and clinical behavior of this disease in the population of elite athletes who are the paradigm of good health is poorly understood. Data on COVID in athletes are scarce and have focused preferentially on the consequences on sports performance of confinement measures and on the pathophysiological risks of infected athletes. Real Madrid is a large elite sports institution with facilities in the City of Madrid where 600 athletes train daily. The incidence of COVID during a study period of 671 days of observation in athletes, professional or amateur, working in the institution has been 0,74 per 1,000 days of exposure. The disease has been asymptomatic or oligosymptomatic in all athletes and did not require any hospital admissions. The different teams did not have to suspend any of its sportive commitments for COVID during the study period and there was no evidence of outbreaks of internal transmission between members of the different teams.

Sub-pixel energy-weighting techniques for metallic contaminant highlighting in a pharmaceutical hard capsule using a Timepix3 CdZnTe hybrid pixel detector

The presented work describes the capabilities of a state-of-the-art spectroscopic photon-counting hybrid pixel detector for use in non-destructive testing, as a contaminant detector with potential uses in the food and pharmaceutical industries. A pharmaceutical hard capsule containing vitamin powder, contaminated with Steel (ST) and Tungsten (W) was prepared under controlled conditions. Both contaminants are distinguished from the powder by combining sub-pixel imaging with spectroscopic imaging analysis, made possible by the use of a 2 mm CdZnTe sensor coupled to a Timepix3 ASIC, operated in Time-over-Threshold and Time-of-Arrival mode. The sub-pixelization technique achieves a spatial resolution of 18.3 μm, with a maximum photon flux of 2.5× 106 photons/s· cm2. For the spectral analysis technique implemented, each energy bin image is energy-weighted, with weights optimally defined by considering the bin contrast and noise behavior, and combined to form an integrated-spectrum enhanced image with increased contaminant visibility. Contrast-to-Noise Ratio (CNR) for each contaminant type was used for performance assessment of the approach. A CNR increase of 106% above the reference unweighted-spectrum image was achieved for the ST contaminant, while the denser W contaminant showed a CNR increase of 80%. This means that the presented spectroscopic imaging technique is feasible for implementation in material visibility enhancement.

Triazolyl- vs Pyridyl-Functionalized N-Heterocyclic Carbene Complexes: Impact of the Pendant N-Donor Ligand on Intramolecular C-C Bond Formation.

Organometallic Rh(Cp*) (Cp* = η5-pentamethylcyclopentadienyl) complexes with monodentate N-heterocyclic carbene (NHC) ligands bearing a pendant anthracenyl substituent have been shown to undergo intramolecular C-C coupling reactions. Herein, two bidentate NHC ligands substituted with pyridyl or triazolyl donor groups were prepared along with the corresponding MII/III (M = RuII, OsII, RhIII, IrIII) complexes. While the Rh(Cp*) complex featuring an NHC-triazole bidentate ligand underwent the equivalent reaction as the monodentate Rh(NHC) complex, i.e., it formed a polydentate ligand, the pyridyl-pendant derivative was unequivocally shown to be unreactive. This contrasting behavior was further investigated by density functional theory (DFT) calculations that highlighted significant differences between the two types of Rh(III) complexes with pendant pyridyl or triazolyl N-coordinating groups. Modeling of the reaction pathways suggests that the initial formation of a dicationic Rh(III) species is unfavorable and that the internal ligand transformation proceeds first by dissociation of the coordinated N atom of the pendant group from the Rh center. After the formation of a neutral η4-fulvene ligand via combined proton/single electron transfer, a cycloaddition occurs between the exo-ene bond of fulvene and the 9' and 10' positions on the pendant anthracenyl group. The resulting experimental UV-visible spectrum recorded in methanol of the polydentate triazolyl-based Rh species revealed the loss of the vibronic coupling typically associated with an anthracenyl functional group. Moreover, TD-DFT modeling indicates the presence of an equilibrium process whereby the N-coordination of the pendant triazolyl group to the RhIII center appears to be highly labile. Charge decomposition analysis (CDA) of the DFT-modeled species with the dissociated triazolyl group revealed a pseudo-η3-allylic interaction between the π-type MOs of the transformed anthracenyl group and the RhIII center; thus, the singly attached chelating ligand is classified as having rare nonadenticity.

Possible unconventional order parameter in single crystals of SrPt3P superconductor

Anisotropic properties of single crystals of SrPt3P were studied using London penetration depth and electrical resistivity measurements. The upper critical field, , was determined from four-probe electrical resistivity measurements for three orthogonal directions of a magnetic field with respect to the crystal. The London penetration depth, , was determined from the magnetic susceptibility of the Meissner–London state measured using a tunnel-diode resonator technique. Whereas and the normal-state are practically identical for all three magnetic field orientations, the London penetration depth shows significant unidirectional anisotropy. The low-temperature is exponentially attenuated when a small excitation radiofrequency magnetic field, H rf , is applied along the -direction, in which case screening currents flow in the -plane, while for the other two orientations, and , the London penetration depth shows a much stronger, , variation. Such unusual and contrasting behavior of the two anisotropies, and , imposes significant constraints on the possible order parameter. Although our measurements are insufficient to derive conclusively the superconducting gap anisotropy, the order parameter with two point nodes and a modulation in the perpendicular direction is qualitatively consistent with the experimental observations.

Specifics of slope movements on slopes with contrasting structural conditions: Evidence from tree-ring records

The geological structure of a slope is one of the key factors that drives the development of landslide types. Various landslide types, although occurring in the same locality, can result in different spatio-temporal dynamics of their movements. Moreover, the presence of shallow creep movements on such slopes can modify the effect of slide movements and possibly cause the false impression of landslide activity. The nonstandard combination of detailed tree-ring-based (dendrogeomorphic) approaches involving the careful assessment of growth disturbance properties (the duration, intensity, mutual ratio of different disturbances), the statistical testing of the spatial pattern of disturbed trees, the analysis of possible extreme precipitation triggers, and geophysical sounding was used in this study in an attempt to distinguish creep and slide movements and assess the general slope movement activity on slopes with contrasting geological structures. Data from 1032 tree-ring series of 516 disturbed individuals of common spruce (Picea abies (L.) Karst.) enabled the reconstruction of 13 slope movements on all three studied sites (3, 7, and 3) for the last approximately 70 years. Although some indices correspond with the general assumption of a specific landslide type to the structure of induced growth disturbances (e.g., an increased ratio of reaction wood on rotational landslides), the advanced dendrogeomorphic approach used suggests that not all dated events are of slide origin and that creep movements significantly modify the effect of original slide movement on tree growth. Some dated events are probably the result of only creep movements themselves. Thus, the present study critically assesses results of the dendrogeomorphic dating of various landslides, presents contrasting behavior of slope movements on slopes with contrasting geological structures, and recommends the use of more advanced tree-ring-based approaches for more effective dendrogeomorphic research of landslides.

Sensing lysozyme fibrils by salicylaldimine substituted BODIPY dyes - A correlation with molecular structure

Quick and efficient detection of protein fibrils has enormous impact on the diagnosis and treatment of amyloid related neurological diseases. Among several methods, fluorescence based techniques have garnered most importance in the detection of amyloid fibrils due to its high sensitivity and extreme simplicity. Among other classes of molecular probes, BODIPY derivatives have been employed extensively for the detection of amyloid fibrils. However, there are very few studies on the relationship between the molecular structure of BODIPY dyes and their amyloid sensing activity. Here in a BODIPY based salicylaldimine Schiff base and its corresponding boron complex have been evaluated for their ability to sense amyloid fibrils from hen-egg white lysozyme using steady state and time-resolved spectroscopic techniques. Both dyes show fluorescence enhancement as well as increase in their excited state lifetime upon their binding with lysozyme fibrils. However, the BODIPY derivative which shows more emission enhancement in fibrillar solution has much lower affinity towards amyloid fibrils as compared to other derivative. This contrasting behaviour in the emission enhancement and binding affinity has been explained on the basis of differences in their photophysical properties in water and amyloid fibril originating from the difference in their molecular structure. Such correlation between the amyloid sensitivity and the molecular structure of the probe can open up a new strategy for designing new efficient amyloid probes.

Contrasting behaviors of groundwater arsenic and fluoride in the lower reaches of the Yellow River basin, China: Geochemical and modeling evidences

Genesis of the contrasting distributions of high arsenic (>10 μg/L) and fluoride (>1 mg/L) groundwater and their negative correlations remain poorly understood. We investigated spatial distributions of groundwater arsenic and fluoride concentrations in the lower reaches of the Yellow River basin, Henan Province, China, using bivariate statistical analyses and geochemical simulations. Results suggest that high arsenic and fluoride groundwater showed contrasting distributions with few overlapped area. Groundwater arsenic concentrations were significantly negatively correlated with oxidation-reduction potential (ORP) values and positively with NH4+ and Fe(II) concentrations, while the opposites were true for groundwater fluoride concentrations. These may suggest that high arsenic groundwater is related to stronger organic matter degradation and Fe(III) oxide reduction, while groundwater fluoride enrichment occurs with less extent of organic matter degradation. Geochemical calculations supported that groundwater fluoride enrichment was governed by extent of fluorite dissolution, which was constrained by varied saturation indices of fluorite in groundwater. However, groundwater arsenic mobility may be explained by different solubility of Fe(III) oxides. Higher Fe(III) oxide solubility corresponding to goethite and lepidocrocite was related to higher arsenic concentrations, while hematite was too low in solubility to produce high arsenic groundwater. The study presented both geochemical and modeling evidences for the contrasting behaviors of groundwater arsenic and fluoride concentrations in anoxic aquifers.

Investigations of equatorial plasma bubbles as observed in the OI 630 nm nightglow emissions over off-equatorial and low-latitudinal locations over Indian longitudes

Equatorial plasma bubbles (EPBs), generated over the dip-equator during the sunset time, get mapped over to the low-latitudes through the geomagnetic field lines and contribute to structures of different scales in the nighttime thermosphere-ionosphere system. In the present study, the EPBs are observed in the OI 630 nm nightglow emissions over Mt. Abu and Kolhapur using a High Throughput Imaging Echelle spectrograph (HiTIES) and All-Sky Imager (ASI), respectively. Similar periodicities obtained in these measurements consistently corroborate the presence of the EPBs at both these locations. The strength of the Pre-Reversal Enhancement (PRE) in the zonal electric field has been investigated using the ionosonde data over Trivandrum, a dip-equatorial location. The strength of PRE decides the latitudinal extent of the EPBs. The eastward movement of the EPBs has been estimated to be in the range of 190–90 ms−1, decreasing in magnitude from post-sunset to midnight. The wave number analysis carried out using the observed OI 630 nm emissions in the zonal direction has resulted in a contrasting behaviour during the presence/absence of the EPBs. Based on the analysis of around 1300 images of data, it is revealed that the scale sizes in the range of 250–300 km are omnipresent, whereas, shorter scale sizes (50–250 km) are present only during the presence of EPBs. It is inferred that these shorter scale size gravity waves played a significant role in the seeding the perturbation of the EPBs.

Impact of autonomy, innovativeness, risk-taking, proactiveness, and competitive aggressiveness on students’ intention to start a new venture

This study examines the impact of entrepreneurial orientation dimensions on students’ intentions to start new businesses in Saudi universities. Using a 21-item questionnaire with a 5-point Likert scale, the authors collected data on students’ demographics, entrepreneurial orientation, and entrepreneurial behavioral intention. The sample consisted of 341 business students from two public universities in Saudi Arabia. Specifically, business students were chosen for this study because they were potential entrepreneurs. Through structural equation modeling, AMOS software was used to analyze the study model. Results showed a strong relationship between entrepreneurial intention and greater autonomy, innovativeness, risk-taking, and proactiveness. In contrast, competitive and aggressive behavior, is not strongly related to entrepreneurial intention. These findings are important because they shed new light on the factors that shape future entrepreneurs, thereby making a significant theoretical contribution to the literature on entrepreneurial orientation, particularly in the context of university business students. As countries embrace the importance of innovation and entrepreneurship in enhancing their global competitiveness, this study also makes a practical contribution to policymakers’ efforts to identify potential entrepreneurs and transform them into successful ones.

Contrasting behaviors of 210Po, 210Pb and 234Th in the East China Sea during a severe red tide: Enhanced scavenging and promoted fractionation

Contrasting behaviors of 210Po, 210Pb and 234Th in the East China Sea during a severe red tide: Enhanced scavenging and promoted fractionation