Low Transport Rates Research Articles

Investigation of sugar binding kinetics of the E. coli sugar/H+ symporter XylE using solid-supported membrane-based electrophysiology

Bacterial transporters are difficult to study using conventional electrophysiology because of their low transport rates and the small size of bacterial cells. Here, we applied solid-supported membrane–based electrophysiology to derive kinetic parameters of sugar translocation by the Escherichia coli xylose permease (XylE), including functionally relevant mutants. Many aspects of the fucose permease (FucP) and lactose permease (LacY) have also been investigated, which allow for more comprehensive conclusions regarding the mechanism of sugar translocation by transporters of the major facilitator superfamily. In all three of these symporters, we observed sugar binding and transport in real time to determine KM, Vmax, KD, and kobs values for different sugar substrates. KD and kobs values were attainable because of a conserved sugar-induced electrogenic conformational transition within these transporters. We also analyzed interactions between the residues in the available X-ray sugar/H+ symporter structures obtained with different bound sugars. We found that different sugars induce different conformational states, possibly correlating with different charge displacements in the electrophysiological assay upon sugar binding. Finally, we found that mutations in XylE altered the kinetics of glucose binding and transport, as Q175 and L297 are necessary for uncoupling H+ and d-glucose translocation. Based on the rates for the electrogenic conformational transition upon sugar binding (>300 s−1) and for sugar translocation (2 s−1 − 30 s−1 for different substrates), we propose a multiple-step mechanism and postulate an energy profile for sugar translocation. We also suggest a mechanism by which d-glucose can act as an inhibitor for XylE.

Fast and Selective Ionic Transport: From Ion-Conducting Channels to Ion Exchange Membranes for Flow Batteries

This review discusses selective and fast transport of ionic species (ions and their associates) through systems as diverse as ion-conducting transmembrane proteins and ion exchange membranes (IEMs) in aqueous environments, with special emphasis on the role of electrostatics, specific chemical interactions, and morphology (steric effects). Contrary to the current doctrine, we suggest that properly balanced ion-coordinating interactions are more important than steric effects for selective ion transport in biological systems. Steric effects are more relevant to the selectivity of ionic transport through IEMs. As a general rule, decreased hydration leads to higher selectivity but also to lower transport rate. Near-perfect selectivity is achieved by ion-conducting channels in which unhydrated ions transfer through extremely short hydrophobic passages separating aqueous environments. In IEMs, ionic species practically keep their hydration shell and their transport is sterically constrained by the width of aqueous pathways. We discuss the trade-off between selectivity and transport rates and make suggestions for choosing, optimizing, or developing membranes for technological applications such as vanadium-redox-flow batteries.

Declining Use of Pre-Hospital Emergency Medical Services During the COVID-19 Pandemic in 2020: Descriptive Study Based on Routinely Collected Dispatch Data in Bavaria, Germany

Background: The COVID-19 pandemic affects utilisation of health care services and posed organizational challenges. To determine the effect on utilisation of pre-hospital emergency medical care, we investigate utilisation throughout the year of 2020. Methods: This retrospective, descriptive analysis of routine data from 26 dispatch centres in Bavaria, Germany investigates the number of emergencies per 100,000 population as well as relative change in emergency rates and transport rates in 2020, compared to the two previous years. Boxplots show distributions across Bavarian districts per calendar week. Mean rates and standard deviations as well as relative changes are presented for specific periods and a paired samples t-test is used to compares rates. Findings: Compared to the average of the two previous years, emergency rates in 2020 were lower in 35 out of 52 calendar weeks. Strongest reductions were observed during the first wave, where the average emergency rate declined by 12∙9% (SD 6∙8, p Interpretation: Utilisation of pre-hospital emergency medical services decreased in 2020, especially during periods with strict measures. This could be due to lower morbidity from behavioural changes during the pandemic, but also to avoidance of medical services for probably both, less urgent and severe conditions. While a reduction in unnecessary care would be beneficial, patients must be encouraged to seek necessary urgent care, even during a pandemic. Funding: None to declare.Declaration of Interest: None to declare. Ethical Approval: The study was approved by the ethics committee of the medical faculty of the University of Munich (Project-No 21-0641 KB).

Towards upscaling microbial desalination cell technology: A comprehensive review on current challenges and future prospects

Abstract Shortage of potable water is the driving force behind desalination practices mainly performed by conventional thermal and membrane-based technologies. However, conventional desalination technologies are unsustainable due to their high energy requirements. This highlights the necessity of developing more sustainable and eco-friendly alternatives. As an emerging technology, microbial desalination cell (MDC) has attracted a great deal of attention due to its ability to desalinate seawater, treat wastewater, and recover electricity and value-added products in a single reactor. The technology produces electricity through the biodegradation of organics present in wastewater. The recovered electricity derives the migration of ions, and is subsequently collected as value-added product. The present review summarizes the prospects of MDC as (i) a sustainable green desalination technology, (ii) a cost-effective approach for simultaneous wastewater treatment and recovery of value-added products (i.e., HCl, NaOH, H2O2, H2, humic and fulvic acid), and (iii) an electrochemical process for + removal of targeted pollutants (i.e., NH4+-N, Cu, Cr, Pb, Ni, As). Despite the favorable environmental and economic attributes of MDCs, large-scale application of those technology is limited due to a number of engineering and operational challenges. Therefore, this review carefully summarizes all the challenges associated with engineering parameters (i.e., reactor design, internal resistance, cost-effectiveness of electrodes and membranes, membrane fouling), and operating factors (i.e., pH imbalance due to ion migration, low ion transport rate, growth and adhesion of electroactive biofilms, and biofilm inhibition). The interrelationships between the engineering/operational challenges and MDC performances are also concisely explained. Finally, research needs to scale up MDCs for simultaneous desalination, wastewater treatment, and energy-resource recovery are proposed.

Control of IgG glycosylation in CHO cell perfusion cultures by GReBA mathematical model supported by a novel targeted feed, TAFE

The N-linked glycosylation pattern is an important quality attribute of therapeutic glycoproteins. It has been reported by our group and by others that different carbon sources, such as glucose, mannose and galactose, can differently impact the glycosylation profile of glycoproteins in mammalian cell culture. Acting on the sugar feeding is thus an attractive strategy to tune the glycan pattern. However, in case of feeding of more than one carbon source simultaneously, the cells give priority to the one with the highest uptake rate, which limits the usage of this tuning, e.g. the cells favor consuming glucose in comparison to galactose.We present here a new feeding strategy (named ‘TAFE’ for targeted feeding) for perfusion culture to adjust the concentrations of fed sugars influencing the glycosylation. The strategy consists in setting the sugar feeding such that the cells are forced to consume these substrates at a target cell specific consumption rate decided by the operator and taking into account the cell specific perfusion rate (CSPR). This strategy is applied in perfusion cultures of Chinese hamster ovary (CHO) cells, illustrated by ten different regimes of sugar feeding, including glucose, galactose and mannose. Applying the TAFE strategy, different glycan profiles were obtained using the different feeding regimes. Furthermore, we successfully forced the cells to consume higher proportions of non-glucose sugars, which have lower transport rates than glucose in presence of this latter, in a controlled way.In previous work, a mathematical model named Glycan Residues Balance Analysis (GReBA) was developed to model the glycosylation profile based on the fed carbon sources. The present data were applied to the GReBA to design a feeding regime targeting a given glycosylation profile. The ability of the model to achieve this objective was confirmed by a multi-round of leave-one-out cross-validation (LOOCV), leading to the conclusion that the GReBA model can be used to design the feeding regime of a perfusion cell culture to obtain a desired glycosylation profile.

On capital utilization in the hydrogen economy: The quest to minimize idle capacity in renewables-rich energy systems

The hydrogen economy is currently experiencing a surge in attention, partly due to the possibility of absorbing variable renewable energy (VRE) production peaks through electrolysis. A fundamental challenge with this approach is low utilization rates of various parts of the integrated electricity-hydrogen system. To assess the importance of capacity utilization, this paper introduces a novel stylized numerical energy system model incorporating the major elements of electricity and hydrogen generation, transmission and storage, including both “green” hydrogen from electrolysis and “blue” hydrogen from natural gas reforming with CO2 capture and storage (CCS). Concurrent optimization of all major system elements revealed that balancing VRE with electrolysis involves substantial additional costs beyond reduced electrolyzer capacity factors. Depending on the location of electrolyzers, greater capital expenditures are also required for hydrogen pipelines and storage infrastructure (to handle intermittent hydrogen production) or electricity transmission networks (to transmit VRE peaks to electrolyzers). Blue hydrogen scenarios face similar constraints. High VRE shares impose low utilization rates of CO2 capture, transport and storage infrastructure for conventional CCS, and of hydrogen transmission and storage infrastructure for a novel process (gas switching reforming) that enables flexible power and hydrogen production. In conclusion, all major system elements must be considered to accurately reflect the costs of using hydrogen to integrate higher VRE shares.

Comparing Cournot and Bertrand Equilibria in the Presence of Spatial Barriers and R&D

We compare the equilibria under Bertrand and Cournot competition in the spatial barbell model where spatial barriers and process R&D are involved. We show that when the market becomes more competitive by switching from Cournot to Bertrand competition, R&D investment may increase (decrease) depending upon a low (high) transport rate. Next, we find that under Cournot competition total output, consumer surplus, and welfare are higher, but profit is lower than is true for Bertrand competition, when the transport rate is high, which overturns the traditional result.

How does the bed surface impact low‐magnitude bedload transport rates over gravel‐bed rivers?

AbstractBedload transport is a complex phenomenon that is not well understood, especially for poorly sorted sediment and low transport rates, which is what is typically found in alpine gravel‐bed rivers. In this paper, the interaction between bedload rate, bed stability and flow is investigated using flume experiments. Significant differences in bedload rates were observed for experiments conducted on beds formed with the same gravel material but presenting diverse arrangements and bedforms. Tests were performed under regimes of low transport rate, which are mainly controlled by gravel‐bed roughness. Different scales of roughness were identified using the statistical characteristics of detailed bed elevation measurements: grain, structure and large bedform scales. The role played by these different roughness scales in bedload dynamics was examined. For quasi‐flat beds, bed stability was quantified using a combination of bed surface criteria describing grain and structure scales. It was found that bed stability affects the bedload rate directly and not only through its influence on the flow or on the incipient motion. For beds with large bedforms, the analysis of bedload dynamics also showed the importance of accounting for effective bed shear stress distributions. An empirical bedload model for low transport regimes was suggested. Compared with previous formulae developed for alpine rivers, this model accounts for bed stability and distribution of effective bed shear stress. It significantly improves the understanding of gravel dynamics over complex beds such as arranged beds or those with large bedforms. However, further tests are needed to use the model outside the range of conditions of this study. © 2019 John Wiley & Sons, Ltd.

Medical Tent Utilization at 10-km Road Races: Injury, Illness, and Influencing Factors.

To increase awareness of the need for coordinated medical care at 10-km races and to help direct future medical planning for these events. We related medical encounter data from nineteen 10-km road races to runner, race, and environmental characteristics. We quantified the most commonly used resources and described the disposition of runners in these encounters. Across the 19 races and 90,265 finishers, there were 562 medical events for a cumulative incidence of 6.2 events per 1000 finishers (95% confidence interval, 5.7-6.8). Race size was associated with an increased incidence of medical events. Overall, the most common diagnosis was heat-related illness (1.6 per 1000 finishers), followed by musculoskeletal complaints (1.3 per 1000 finishers) and fluid-electrolyte imbalances (1.2 per 1000 finishers). For all diagnoses, runners with finishing times in the first performance quintile and in the fifth performance quintile had greater representation in the medical tent than mid-pack runners. Most runners were treated with supportive care, basic first aid, and oral rehydration. Ninety-four runners (1.0 per 1000 finishers) required ice water immersion for exertional heat stroke. There were low rates of hospital transport (0.2 per 1000 finishers), and no fatalities. In 10-km road races, injury rates are low compared with longer races in similar weather conditions. Common medical issues can be managed with basic resources in the on-site medical tent. Green flag start race conditions may not predict race safety with regard to exertional heat stroke risk. There were no deaths in nearly 100,000 finishers.

Efficient Water Transport and Solar Steam Generation via Radially, Hierarchically Structured Aerogels

A nature-inspired water-cycling system, akin to trees, to perform effective water and solar energy management for photosynthesis and transpiration is considered to be a promising strategy to solve water scarcity issues globally. However, challenges remain in terms of the relatively low transport rate, short transport distance, and unsatisfactory extraction efficiency. Herein, enlightened by conifer tracheid construction, an efficient water transport and evaporation system composed of a hierarchical structured aerogel is reported. This architecture with radially aligned channels, micron pores, and molecular meshes is realized by applying a radial ice-template method and in situ cryopolymerization technique. This nature-inspired design benefits the aerogel excellent capillary rise performance, realizing a long-distance (>28 cm at 190 min) and quick (>1 cm at 1 s, >9 cm at 300 s) antigravity water transport on a macroscopic scale, regardless of clean water, seawater, sandy groundwater, or dye-including effluent. Furthermore, an efficient water transpiration and collection is performed by the bilayer-structured aerogel with a carbon heat collector on an aerogel top, demonstrating a solar steam generation rate of 2.0 kg m-2 h-1 with the energy conversion efficiency up to 85.7% under one solar illumination. This biomimetic design with the advantage of water transport and evaporation provides a potential approach to realize water purification, regeneration, and desalination.

Effects of Al-Si coating and Zn coating on the hydrogen uptake and embrittlement of ultra-high strength press-hardened steel

Press-hardened steel (PHS), used for automotive safety-related structure parts, is sensitive to hydrogen embrittlement due to its martensitic microstructure. Hydrogen is introduced in PHS during the hot press forming (HPF) process, by an atmospheric corrosion process. In this study, the hydrogen embrittlement behavior of uncoated, aluminized, and galvanized PHSs was investigated. The Al-10%Si coating promoted the absorption of diffusible hydrogen at elevated temperature during the HPF while the reacted coating layer prevented the absorbed hydrogen from out-diffusing through the reacted coating surface layer at room temperature. Therefore, the aluminized PHS showed a greater sensitivity to both the hydrogen uptake and the resultant embrittlement, as compared to the uncoated and galvanized PHSs. Use of galvanized PHS for HPF application reduces the risk of hydrogen embrittlement, since the Zn coating effectively prevents the hydrogen uptake. The greater embrittlement resistance of the galvanized PHS is possibly due to the inhibition of the hydrogen generation reaction by the surface ZnO oxide layer and the low rate of hydrogen transport through the liquid Zn phase.

A model for predicting bubble velocity in yield stress fluid at low Reynolds number

Currently, studies on bubble velocity in yield stress fluids with low Reynolds numbers are lacking. In most engineering applications, such value is often calculated using predictive models developed for viscous fluids. However, these models are only applicable to yield stress fluids in limited conditions because the bubble rise velocity is affected by the yield stress in these fluids significantly. In this study, a velocity field model around a bubble is first developed by performing an infinitesimal analysis of the velocity field in the equatorial plane of the bubble and combining the continuity equation with the constitutive equation of yield stress fluids. Next, a new model is proposed for predicting bubble velocity in yield stress fluids at a low transport rate by integrating the model of velocity field around the bubble with energy conservation equations. Finally, experimental studies are performed to analyze the bubble transport behavior in yield stress fluids at low Reynolds numbers. The experimental results showed that under a low Reynolds number, the bubble rise velocity is dominated by the yield stress of the fluid. Hence, we further validated the proposed bubble velocity prediction model with experimental measurements, which match closely with each other. We conclude that for a Reynolds number less than 0.4, the model developed in this study can be used to predict the bubble velocity in yield stress fluids with high accuracy.

Peritoneal Protein Clearance Is a Function of Local Inflammation and Membrane Area Whereas Systemic Inflammation and Comorbidity Predict Survival of Incident Peritoneal Dialysis Patients.

It is not clear whether the association of increased peritoneal protein clearance (PPCl) with worse survival on peritoneal dialysis (PD) is a consequence of either local or systemic inflammation or indicative of generalized endothelial dysfunction associated with comorbidity. To investigate this we determined the relationship of PPCl to comorbidity, membrane area (equivalent to low molecular weight peritoneal solute transport rate), local and systemic inflammation and hypoalbuminaemia, and for each of these with patient survival. 257 incident patients from three GLOBAL Fluid Study centers were included in this analysis. Clinical profiles were collected at baseline along with a peritoneal equilibration test, 24-h dialysate protein and paired plasma and dialysate cytokine measurements. Although peritoneal protein clearance was associated with increased age and severe comorbidity on univariate analysis, only dialysate IL-6, peritoneal solute transport rate, plasma albumin and cardiac comorbidities (ischaemic heart disease and left ventricular dysfunction) were independent explanatory variables on multivariate analysis. While peritoneal protein clearance and daily peritoneal protein loss were associated with survival in univariate analysis, on multivariate analysis only plasma IL-6, age, residual kidney function, comorbidity, and plasma albumin were independent predictors. Peritoneal protein clearance is primarily a function of peritoneal membrane area and local membrane inflammation. The association with comorbidity and survival is predominantly explained by its inverse relationship to hypoalbuminaemia, especially in diabetics.

Mango leaf extract incorporated chitosan antioxidant film for active food packaging

Health hazards associated with usage of plastic films for food preservation demands for development of active films from non-toxic and antioxidant rich bio-sources. The reported work highlights the development, characterization and application studies of chitosan films enhanced for their antioxidant activity by mango leaf extract (MLE) incorporation. Effect of MLE variation (1–5%) on the morphology, optical nature, water exposure and mechanical characteristics of the chitosan-MLE composite films was studied. Increase in the MLE concentration resulted in films with increased thickness and decreased moisture content. Contact angle, water solubility and vapor permeability analysis demonstrated the reduced hydrophilicity and water vapor penetrability of the films due to MLE inclusion. MLE films possessed better tensile strength (maximum of 23.06 ± 0.19 MPa) with reduced elongation ratio than the pure chitosan film (18.14 ± 0.72 MPa). Antioxidants assessment in terms of total phenolic content, DPPH radical scavenging, ferric reducing power and ABTS radical scavenging showed improved antioxidant activity with the incremental amounts of MLE in the chitosan films. Microscopic studies revealed the smooth, compact and dense nature of the MLE-chitosan films favouring low oxygen transport rates. Application studies to cashew nuts preservation for 28 days storage indicated 56% higher oxidation resistance for the 5% MLE film than a commercial polyamide/polyethylene film. Results highlight the potential and promising nature of MLE impregnated chitosan films as suitable alternative for active packaging films for food preservation.

Development of a rapid functional assay that predicts GLUT1 disease severity.

ObjectiveTo examine the genotype to phenotype connection in glucose transporter type 1 (GLUT1) deficiency and whether a simple functional assay can predict disease outcome from genetic sequence alone.MethodsGLUT1 deficiency, due to mutations in SLC2A1, causes a wide range of epilepsies. One possible mechanism for this is variable impact of mutations on GLUT1 function. To test this, we measured glucose transport by GLUT1 variants identified in population controls and patients with mild to severe epilepsies. Controls were reference sequence from the NCBI and 4 population missense variants chosen from public reference control databases. Nine variants associated with epilepsies or movement disorders, with normal intellect in all individuals, formed the mild group. The severe group included 5 missense variants associated with classical GLUT1 encephalopathy. GLUT1 variants were expressed in Xenopus laevis oocytes, and glucose uptake was measured to determine kinetics (Vmax) and affinity (Km).ResultsDisease severity inversely correlated with rate of glucose transport between control (Vmax = 28 ± 5), mild (Vmax = 16 ± 3), and severe (Vmax = 3 ± 1) groups, respectively. Affinities of glucose binding in control (Km = 55 ± 18) and mild (Km = 43 ± 10) groups were not significantly different, whereas affinity was indeterminate in the severe group because of low transport rates. Simplified analysis of glucose transport at high concentration (100 mM) was equally effective at separating the groups.ConclusionsDisease severity can be partly explained by the extent of GLUT1 dysfunction. This simple Xenopus oocyte assay complements genetic and clinical assessments. In prenatal diagnosis, this simple oocyte glucose uptake assay could be useful because standard clinical assessments are not available.

Effect of surface profiling of a cation-exchange membrane on the phenylalanine and NaCl separation performances in diffusion dialysis

Abstract Diffusion dialysis (DD) is an environmentally appropriate method for separating components, which are unstable under the external influences (high temperature, high pressure, presence of electric field). The roadblock to the wider application of the DD method for separation and purification of amino acids is relatively low rate and selectivity of diffusion transport of these substances through ion-exchange membranes. In this paper, mechanisms of amino acid selective transport and possibilities to increase its flux across a cation-exchange membrane are considered. In particular, the effect of replacement of a flat membrane with a profiled one, prepared by the method of hot pressing, when using the same material is examined. Experimental and theoretical study is carried out using solutions of phenylalanine amino acid and NaCl when applying a commercial flat MK-40 cation-exchange membrane and its modification MK-40pr with profiled surface. It is found that the relatively high selective transport of phenylalanine is due to its facilitated diffusion, while the NaCl diffusion is reduced by the Donnan effect. The MK-40pr membrane allows a 8-fold increase in phenylalanine flux in comparison with the MK-40 membrane. This increase in partly due to the increased surface available for mass transfer (in 2.3 times), but also to better hydrodynamics reducing the diffusion layer thickness and to a higher fraction of conductive surface and higher pore radius. The latter is caused by water evaporation within the membrane pores in the course of its profiling.

Rodents, rabbits and pellets in a fluvial terrace (PRERESA site, Madrid, Spain)

The aim of this work is to study from a taphonomic view the small mammals assemblage located on the Pleistocene site known as PRERESA. The small mammal fossiliferous layer is a silt level located at a fluvial terrace. The samples studied included remains from rodents (Minimum Number of Elements: MNE = 373) and lagomorphs (MNE = 372). During the excavation seasons, a distinct high concentration of small mammals was recovered apart, named as fossil ‘pellet’. We consider this ‘fossil pellet’ to be an aggregation of several pellets and it has been taphonomically analyzed apart and included in this study. The presence of such concentrations/aggregations is uncommon in this type of open-air sites. This aggregation contains 253 MNE fossil bones. The taphonomic study has considered three main aspects: anatomical representation, fragmentation, and corrosion by digestion. Due to the location of the site on a fluvial system, transport effects and abrasion were analyzed as well. The results obtained show a high representation of cranial elements (especially lagomorphs) as well as a high fragmentation of both cranial and postcranial elements. Digestion observed in this assemblage affects dental remains below 30% in both rodents and lagomorphs, being light and moderate digestion the most frequent degrees, but all samples reach extreme grades of digestion (in molars < 3%). Transport was analyzed using Voorhies groups (1969). All groups were present, even the easiest to transport. Group III (cranial remains) was the best represented. The simultaneous presence of all Voorhies groups suggests a low or null rate of transport. Results could indicate that the small mammal assemblage of PRERESA were produced by a nocturnal raptor, most likely an Eagle owl (Bubo bubo), whose nest or roosting site was installed near the fluvial channel.

Methyl-β-cyclodextrin quaternary ammonium chitosan conjugate: nanoparticles vs macromolecular soluble complex.

PurposeThe present study aimed to compare a novel cyclodextrin–polymer–drug complex in solution with a dispersed supramolecular nanosize system, made of the same complex, for ability to carry dexamethasone (DEX) across excised rat intestine.ResultsMethyl-β-cyclodextrin-quaternary ammonium chitosan conjugate (QA-Ch-MCD) was obtained by covalent grafting through a 10-atom spacer. The conjugate was characterized by 1H-NMR, resulting in 24.4% w/w of MCD content. Phase solubility profile analysis of the QA-Ch-MCD/DEX complex yielded an association constant of 14037 M−1, vs 4428 M−1 for the plain MCD/DEX complex. Nanoparticle (NP) dispersions resulted from ionotropic gelation of the QA-Ch-MCD/DEX complex by sodium tripolyphosphate, leading to 9.9%±1.4% drug loading efficiency. The mean diameter and zeta potential for NP were 299±32 nm (polydispersity index [PI] 0.049) and 11.5±1.1 mV, respectively. Those for QA-Ch-MCD/DEX were 2.7±0.4 nm (PI 0.048) and 6.7±0.6 mV. QA-Ch-MCD/DEX solutions and corresponding NP dispersions were compared in vitro for water-assisted transport through mucus, DEX permeation through excised rat intestine, and ex vivo mucoadhesivity. The complex showed higher mucoadhesion and lower transport rate through mucus; also, it provided faster drug permeation across excised rat intestine.ConclusionCarrier adhesion to mucus surface has played a most important role in favoring transepithelial permeation. Then, within the concerns of the present study, the use of NP seems not to provide any determinant advantage over using the simpler macromolecular complex.

Structural Dynamics of Strongly Segregated Block Copolymer Electrolytes

Polymer electrolytes are promising materials for high energy density rechargeable batteries. However, they have low ion transport rates and gradually lose electrode adhesion during cycling. These effects are dependent on polymer structure and dynamics. This motivates an investigation of diblock copolymer electrolyte dynamics. Structural and stress relaxations have been measured with X-ray photon correlation spectroscopy (XPCS) and rheology, respectively, as a function of salt concentration and temperature. The polymer electrolyte studied in this work is a mixture of poly(styrene-b-ethylene oxide), SEO, and lithium bistrifluoromethanesulfonimide (LiTFSI). Results from XPCS experiments showed hyperdiffusive motion for various lithium salt concentrations and at varying temperatures, which is indicative of soft glassy materials. This behavior is attributed to cooperative dynamics. The decay time was a weak, nonmonotonic function of salt concentration and decreased with increasing temperature, in an Arrhenius fashion. In contrast, the shear modulus decreased with increasing salt concentration and increasing temperature. The entanglement relaxation from rheological measurements followed Vogel–Fulcher–Tammann behavior. The structural decay time was slower than the entanglement relaxation time at temperatures above the glass transition temperature, but they were approximately equal at Tg regardless of salt concentration. This may indicate a fundamental connection between cooperative structural motion and polymer chain motion in this material.

Effect of Meteorological Patterns on the Intensity of Streambank Erosion in a Proglacial Gravel-Bed River (Spitsbergen)

Lower parts of proglacial rivers are commonly assumed to be characterised by a multiannual aggradation trend, and streambank erosion is considered to occur rarely and locally. In the years 2009–2013, detailed measurements of channel processes were performed in the Scott River (SW Spitsbergen). More than 60% of its surface area (10 km2) occupies non-glaciated valleys. Since the end of the Little Ice Age, the Scott Glacier has been subject to intensive retreat, resulting in the expansion of the terminoglacial and paraglacial zones. In this area, the Scott River develops an alluvial valley with a proglacial river, which has led to a comparatively low rate of fluvial transport, dominance of suspension over bedload, and the occurrence of various channel patterns. Measurements, performed in the lower course of the valley in two fixed cross-sections of the Scott River channel, document variable annual tendencies with a prevalence of scour over deposition processes in the channel bottom. The balance of scour and fill also differs in particular measurement cross-sections and during the summer season. The maximum erosion indices (1.7 m2) were related to single periods of floods with snow-glacier melt and rainfall origin. The contribution of streambank erosion was usually lower than that of deep erosion both in the annual cycle and during extreme events. The channel-widening index also suggests variable annual (from −1 m to +1 m) and inter-annual tendencies. During a three-day flood from August 2013, in a measurement profile at the mouth of the river, the NNW bank was laterally shifted by as much as 3 m. Annual and inter-seasonal indices of total channel erosion, however, show that changes in the channel-bottom morphology are equalised relatively fast, and in terms of balance the changes usually do not exceed 0.5% of a cross section’s area.