Varying Ion Concentrations Research Articles

Sensitivity of the RNA Structure to Ion Conditions as Probed by Molecular Dynamics Simulations of Common Canonical RNA Duplexes.

RNA molecules play a key role in countless biochemical processes. RNA interactions, which are of highly diverse nature, are determined by the fact that RNA is a highly negatively charged polyelectrolyte, which leads to intimate interactions with an ion atmosphere. Although RNA molecules are formally single-stranded, canonical (Watson-Crick) duplexes are key components of folded RNAs. A double-stranded (ds) RNA is also important for the design of RNA-based nanostructures and assemblies. Despite the fact that the description of canonical dsRNA is considered the least problematic part of RNA modeling, the imperfect shape and flexibility of dsRNA can lead to imbalances in the simulations of larger RNAs and RNA-containing assemblies. We present a comprehensive set of molecular dynamics (MD) simulations of four canonical A-RNA duplexes. Our focus was directed toward the characterization of the influence of varying ion concentrations and of the size of the solvation box. We compared several water models and four RNA force fields. The simulations showed that the A-RNA shape was most sensitive to the RNA force field, with some force fields leading to a reduced inclination of the A-RNA duplexes. The ions and water models played a minor role. The effect of the box size was negligible, and even boxes with a small fraction of the bulk solvent outside the RNA hydration sphere were sufficient for the simulation of the dsRNA.

Towards the Use of Individual Fluorescent Nanoparticles as Ratiometric Sensors: Spectral Robustness of Ultrabright Nanoporous Silica Nanoparticles

Here we address an important roadblock that prevents the use of bright fluorescent nanoparticles as individual ratiometric sensors: the possible variation of fluorescence spectra between individual nanoparticles. Ratiometric measurements using florescent dyes have shown their utility in measuring the spatial distribution of temperature, acidity, and concentration of various ions. However, the dyes have a serious limitation in their use as sensors; namely, their fluorescent spectra can change due to interactions with the surrounding dye. Encapsulation of the d, e in a porous material can solve this issue. Recently, we demonstrated the use of ultrabright nanoporous silica nanoparticles (UNSNP) to measure temperature and acidity. The particles have at least two kinds of encapsulated dyes. Ultrahigh brightness of the particles allows measuring of the signal of interest at the single particle level. However, it raises the problem of spectral variation between particles, which is impossible to control at the nanoscale. Here, we study spectral variations between the UNSNP which have two different encapsulated dyes: rhodamine R6G and RB. The dyes can be used to measure temperature. We synthesized these particles using three different ratios of the dyes. We measured the spectra of individual nanoparticles and compared them with simulations. We observed a rather small variation of fluorescence spectra between individual UNSNP, and the spectra were in very good agreement with the results of our simulations. Thus, one can conclude that individual UNSNP can be used as effective ratiometric sensors.

Fertilizer-Holding Performance of Graphene on Soil Colloids Based on Double Electric Layer Theory

Soil nutrient loss, which leads to low plant utilization, has become an urgent issue. Graphene can improve soil fertilizer-holding properties given its small size effect, strong adsorption properties, and large specific surface area. Herein, different amounts of graphene were added to soil samples to study its effect on soil nutrient retention and growth of pepper seedlings. The colloidal double electric layer theory forms the basis for an analysis of variations in soil nutrient concentration through measurements of the zeta potential, which is affected by variations in ion concentrations in soil colloids. We measured the zeta potential of graphene and soil mixed colloids and found that graphene could increase the concentration of nutrient ions in soil colloids. In addition, graphene reduced the loss of nutrients; increased the contents of ammonium nitrogen, effective phosphorus, and fast-acting potassium in the soil after leaching; and enhanced the stability of soil aggregates after leaching. In addition, pepper seedlings grown under graphene treatment for 60 days outperformed seedlings grown without graphene treatment, in terms of plant height and nutrient content. This study demonstrates that the addition of graphene to soil can reduce nutrient loss and promote fertility and plant growth.

იონური არხები და მათზე მოქმედი სამკურნალო საშუალებები

Ion channels are parts of the nerve cell membrane that provide the selective permeability of ions, i.e. positively and negatively charged particles, and participate in the regulation of the body's vital processes. They are responsible for regulating the flow of ions in the plasma and membranes of all cells, controlling the intracellular concentrations of various ions. The alternating closing and opening of sodium, potassium and calcium ion channels ensures the spread of the nerve impulse. Blockage of ion channels causes serious changes in the body. In today's medicine, a number of diseases are explained precisely by the malfunction of ion channels. Widespread pathologies in the world population: angina pectoris, arterial hypertension, arrhythmia, epilepsy, diabetes, etc. This is a small list of diseases that are caused by malfunctioning of ion channels in the human body. Based on this, the diseases caused by ion channel malfunctions and the effective remedies for their treatment are an urgent issue for the world population.

Lipid exchange among electroneutral Sulfo-DIBMA nanodiscs is independent of ion concentration.

Polymer-encapsulated nanodiscs enable membrane proteins to be investigated within a native-like lipid-bilayer environment. Unlike other bilayer-based membrane mimetics, these nanodiscs are equilibrium structures that permit lipid exchange on experimentally relevant timescales. Therefore, examining the kinetics and mechanisms of lipid exchange is of great interest. Since the high charge densities of existing anionic polymers can interfere with protein-protein and protein-lipid interactions as well as charge-sensitive analysis techniques, electroneutral nanodisc-forming polymers have been recently introduced. However, it has remained unclear how the electroneutrality of these polymers affects the lipid-exchange behavior of the nanodiscs. Here, we use time-resolved Förster resonance energy transfer to study the kinetics and the mechanisms of lipid exchange among nanodiscs formed by the electroneutral polymer Sulfo-DIBMA. We also examine the role of coulombic repulsion and specific counterion association in lipid exchange. Our results show that Sulfo-DIBMA nanodiscs exchange lipids on a similar timescale as DIBMA nanodiscs. In contrast with nanodiscs made from polyanionic DIBMA, however, the presence of mono- and divalent cations does not influence lipid exchange among Sulfo-DIBMA nanodiscs, as expected from their electroneutrality. The robustness of Sulfo-DIBMA nanodiscs against varying ion concentrations opens new possibilities for investigating charge-sensitive processes involving membrane proteins.

Microneedle-Coupled Epidermal Sensors for In-Situ-Multiplexed Ion Detection in Interstitial Fluids.

Maintaining the concentrations of various ions in body fluids is critical to all living organisms. In this contribution, we designed a flexible microneedle patch coupled electrode array (MNP-EA) for the in situ multiplexed detection of ion species (Na+, K+, Ca2+, and H+) in tissue interstitial fluid (ISF). The microneedles (MNs) are mechanically robust for skin or cuticle penetration (0.21 N/needle) and highly swellable to quickly extract sufficient ISF onto the ion-selective electrochemical electrodes (∼6.87 μL/needle in 5 min). The potentiometric sensor can simultaneously detect these ion species with nearly Nernstian response in the ranges wider enough for diagnosis purposes (Na+: 0.75-200 mM, K+: 1-128 mM, Ca2+: 0.25-4.25 mM, pH: 5.5-8.5). The in vivo experiments on mice, humans, and plants demonstrate the feasibility of MNP-EA for timely and convenient diagnosis of ion imbalances with minimal invasiveness. This transdermal sensing platform shall be instrumental to home-based diagnosis and health monitoring of chronic diseases and is also promising for smart agriculture and the study of plant biology.

Assessment of Groundwater Quality for Pre- and Post-Monsoon Variations in Molakalmur Taluk, Chitradurga District, Karnataka, India

Objectives: To ascertain whether the groundwater in Molakalmur Taluk is suitable for human consumption and it is anticipated that the study will assist regulators and policymakers in taking the proper actions to provide the study area’s population with safe domestic water. The study’s overall goal is to examine the suitability of groundwater for domestic purposes in accordance to WHO and BIS standards. Methods: The current study was carried out to analyze the water quality and spatial distribution of physicochemical parameters of groundwater in study area. A total of 92 groundwater samples were collected in the study region for study during both pre- and post-monsoon monsoon period, ArcGIS 10.1 was used to create a spatial distribution map based on a geographic information system. The concentrations of various ions like Ca+2, K+1, Cl-1, Mg+2, HCO3 -1, Na+1, CO3 -2, and SO4 -2 were evaluated as per BIS 3025 (2014) and compared with BIS and WHO standards for drinking purpose. Findings: The Gibbs diagram shows that the two main elements that affect the chemical composition of groundwater are evaporation and rock-water interaction. Weathering of silicate minerals and carbonate minerals are the principal sources of carbonate and bicarbonates. Roughly 68% and 58% of the samples exceeded the permissible level of 500 mg/l for TDS. According to the interpretation of Piper’s trilinear diagram, the majority of the water samples fell into the categories of mixed CaMgHCO3, MgHCO3, and CaCl2 types, in that order of dominance. The plot shows that alkaline earths correspond to 75% of the samples. Novelty: The major ion chemistry of the groundwater in Molakalmur Taluk has never been studied, and there is no perennial river in the research area. The current investigation makes an effort to investigate if water is suitable for domestic purpose. The study’s conclusions will help with the gathering of vital information on the condition of the groundwater in Molakalmur Taluk. The study’s conclusions may also beuseful to groundwater managers and city planners in their efforts to restore and enhance groundwater quality. Keywords: Groundwater; Physicochemical Parameters; Gibbs Diagram; Pre-Monsoon; Post-Monsoon Water Quality; Geographic Information System; Pipers Chart

Bias history impacts the analog resistance change of HfOx-based neuromorphic synapses

Resistive random-access memory (RRAM) devices have been widely studied for neuromorphic, in-memory computing. One of the most studied RRAM structures consists of a titanium capping layer and a HfOx adaptive oxide. Although these devices show promise in improving neuromorphic circuits, high variability, non-linearity, and asymmetric resistance changes limit their usefulness. Many studies have improved linearity by changing materials in or around the device, the circuitry, or the analog bias conditions. However, the impact of prior biasing conditions on the observed analog resistance change is not well understood. Experimental results in this study demonstrate that prior higher reset voltages used after forming cause a greater resistance change during subsequent identical analog pulsing. A multiphysics finite element model suggests that this greater analog resistance change is due to a higher concentration of oxygen ions stored in the titanium capping layer with increasing magnitude of the reset voltage. This work suggests that local ion concentration variations in the titanium capping layer of just tens of atoms cause significant resistance variation during analog operation.

Osmotic pressure enables facile high yield assembly of cell-like giant unilamellar vesicles in solutions of physiological ionic strength.

Giant unilamellar vesicles (GUVs) are single-walled, closed phospholipid bilayers that are useful as cellular mimics for synthetic biology and drug delivery. The assembly of GUVs in solutions of ionic concentrations >150 mM Na/KCl (salty solutions) is challenging. Here, we investigate the effects of temperature, chemical identity of small molecule and macromolecular polymers on the molar yield of free-floating GUVs in salty solutions using high resolution confocal microscopy and large dataset image analysis. We find that low gelling temperature agarose is the singular compound that produces free-floating GUVs at molar yields >10 % in salty solutions. All other macromolecular polymers, such as polyvinyl alcohol (PVA), fructose, and ultralow gelling temperature agarose, produced yields of GUVs of <7 %. Surface images show that for these other compounds, the formation of large numbers of lipid-polymer pseudobuds due to polymer dewetting reduces yields of GUVs. We propose a free-energy model of GUV assembly to explain the effects of polymers on the assembly of GUVs. Modulating the adhesion potential by varying ion concentration and valency yielded experimental data that supports our model's prediction - the free-energy for bud formation can be reduced by a contribution to the osmotic pressure of dissolving polymers. These results provide a quantitative comparison between established and novel methodology, as well as experimental and theoretical framework to guide studies for obtaining GUVs in physiological salt solutions.

Glucose exchange parameters in a subset of physiological conditions.

The chemical exchange of labile protons of the hydroxyl groups can be exploited in a variety of magnetic resonance experiments to gain information about the groups and their physicochemical environment. The exchangeable -OH protons provide important contributions to the T2 of water signals thus contributing to the T2-weighted contrast of MRI images. This exchange can be exploited more specifically and sensitively in chemical exchange saturation transfer (CEST) or longitudinal rotating frame relaxation (T1,ρ) experiments. Since glucose is omnipresent in living organisms, it may be seen as a rather universal probe. Even though the potential was first recognized many years ago, practical use has remained scarce due to numerous challenges. The major limitation is the rather low glucose concentration in most tissues. The other obstacles are related to multiple dependencies of the exchange parameters, such as temperature, pH, and concentration of various ions that are not known in sufficient detail for glucose. Thus, we embarked on evaluating the exchange parameters of a model that included every relevant chemical site for all -OH protons in both dominant enantiomers of glucose. We have (1) obtained conventional one-dimensional proton NMR spectra of glucose solutions in suitable temperature ranges, (2) we have iterated through several exchange models with various degrees of freedom determined by the number of distinguishable -OH proton sites and compared their performance, (3) we extrapolated the parameters of the best model of physiological temperature and (4) we demonstrated the use of the parameters in virtual experiments. As the main results, (1) we have obtained the temperature dependence of exchange parameters with reliable confidence intervals in three different pH values, with two of them reaching physiological temperature, and (2) we show how the parameters can be used in virtual experiments, helping to develop new applications for glucose as an NMR/MRI probe.

Unsynchronized migrations of different salt ions and ice microstructure development during unidirectional freeze-thaw

Brackish water columns with three initial salinity gradients were frozen at −15 °C and then thawed at 20 °C. Vertical distributions of six ions (Na+, K+, Ca2+, Mg2+, Cl− and SO42−) among five ice layers were compared after unidirectional freezing, and the temporal variations of ion concentrations at five melting stages were recorded during unidirectional thawing. Meanwhile, the evolvement of ice microstructure was also observed. Our results show that: (1) Driven by the rejection of ice crystals and gravity during unidirectional freezing, the total dissolved salts (TDS) of the bottom ice layer were approximately three times that of the top layer. (2) Specifically, 45 % of the total amount of Na+ and Cl− was observed at the bottom layer after unidirectional freezing, and the 30 % of Ca2+ appeared to concentrate in the middle layer. (3) During unidirectional thawing, the desalination rates reached over 80 % after 14 h. With greater initial salinity, the brine channel connectivity was more distinguished. (4) The percent proportions of Na+, K+, Cl− and SO42− showed two peaks during unidirectional melting, where 30 % to 50 % of individual total amount was discharged. The percent proportion of Ca2+ merely peaked once, with 25 % being discharged.

Experimental 3D concentration profiles along an electrodialysis channel reveal a strong effect of natural convection

Electrodialysis and electrodeionization separate ionic components from processed water solutions by applying a DC electric field on a stack of ion-exchange membranes. The ion separation indicates ionic concentration changes along the channels in the membrane modules. Simultaneously, concentration polarization at the ion-exchange membranes causes ionic concentration variations across the channels. We constructed a milifluidic cell with a diluate channel to measure spatial concentration profiles under single-path electrodialysis conditions. Desalination of 0.1 M NaCl solution showed that the concentration decreases linearly along the channel when connecting relatively low average current densities (< 30 A/m2), yielding <70 % desalination. Higher average current densities causing desalination close to 100 % produced nonlinear concentration profiles characterized by a steep linear drop followed by an almost constant and small concentration region. We show that at a current density of 50 A/m2, only one-third of the diluate channel is employed for desalination. Interestingly, uniform concentration profiles developed across the channels even at high polarization current densities. Unlike constant concentrations across the channel, we found substantial concentration variation in the vertical direction of the channel, indicating the effect of density gradients and natural convection. This effect was confirmed by optical microscopy and particle image velocimetry of this convection in stagnant solution layers. Natural convection, thus, can represent a mechanism intensifying the mass transfer from the solution bulk to the membrane surfaces.

Self-healing of high-performance engineered cementitious materials with crystalline admixture in the seawater environment

The present paper studies the crack healing effect of high-performance cement-based materials mixed with crystalline admixture (CA) in seawater environments. Specifically, the healing effects of specimens with different initial crack widths in tap water and seawater environments were investigated through the seepage healing test (simulating a structure that a side contact with water and the other side contact with air). The variations of seepage velocity and water flow in the early 24 h of healing were mainly investigated. It was found that crystalline materials delay the healing of cracks in the initial stage of healing and this defect is more obvious under the seawater healing condition. Inductive Coupled Plasma (ICP) test was used to detect the variation of ion concentration in seawater; XRD, FTIR, and TG tests were carried out for characterizing the composition and relative content of healing products in the crack under the seawater and tap water healing conditions. Moreover, the effect of CA on the composition of healing products and the effect of crack width on healing products were quantified. The distribution characteristics of healing products along the crack depth under seawater seepage and seawater immersion healing conditions were then obtained.

Analysis of the Interaction between Lake and Groundwater Based on Water-Salt Balance Method and Stable Isotopic Characteristics.

To better protect lacustrine ecologies and understand the evolutionary process of lake environments, it is critical to study the interacting mechanisms between lakes and the surrounding groundwater. The Wuliangsu Lake watershed is the largest wetland in the Yellow River basin and is the discharge area of the Hetao Irrigation District (HID), which is one of the three largest agricultural production areas in China. Due to the influence of human activities, the discharge water from the HID has led to the deterioration of the Wuliangsu Lake ecology and the degradation of the lake environment. Based on long-term observation data and water sampling data collected in 2021, a water–salt equilibrium model was used to analyze the recharge rate of groundwater to the lake. The contribution rate of groundwater to lake recharge in the study area was calculated with a Bayesian mixing model by combining D and 18O stable isotope data. Furthermore, the environmental evolutionary process of the lake was also analyzed using the collected water quality data. The results show that channel drainage was the main source of recharge to Wuliangsu Lake, accounting for more than 75%, while groundwater contributed less than 5% of lake recharge. After implementing the ecological water supplement plan, the concentration of various ions in the lake decreased, the concentration of the total dissolved solids (TDS) in the lake decreased from 1.7 g/L in 2016 to 1.28 g/L in 2021, and the ecological environment was improved. The contribution of groundwater to lake recharge was quantitatively analyzed. The results of this study can facilitate the development of vital strategies for preventing the further deterioration of lake water quality and for protecting wetland ecologies.

Groundwater Quality Assessment Using GIS for Agricultural Propose in Molakalmur Taluk, Karnataka

Objectives: To assess the carbonate concentration in relation to calcium and magnesium concentrations and to determine TDS and sodium concentration in relation to other cations. The study’s overall goal is to examine the suitability of groundwater for irrigation/agricultural purposes in Molakalmur Taluk of Chitradurga District, Karnataka, India. Methods: The current study was carried out to analyze the water quality and spatial distribution of physicochemical parameters of groundwater in study area. A total of 92 groundwater samples were collected during the pre-monsoon period; ArcGIS 9.2 was used to create a spatial distribution map based on a geographic information system. The concentrations of various ions like Ca+2, K+1, Cl-1, Mg+2, HCO3 -1, Na+1, CO3 -2, and SO4 -2 were evaluated as per BIS 3025 (2014) and compared to various irrigation standards like Sodium Adsorption Ratio (SAR), Percentage of Sodium (%Na), Magnesium Adsorption Ratio (MAR), Kelley’s Ratio/Kelly’s Index (KI), Permeability Index (PI) Electrical Conductivity (EC), Total Hardness (TH), Total Salt Concentration, Chloride in irrigation water and integrated standards such as USSL and Wilcox diagram. Findings: During the pre-monsoon period, the majority of the samples in the study area fell into the hard to very hard water category. According to Evaluated water quality indices like SAR, MAR, PI, KI, SSP, Cl and total salt concentration around 5 to 15 percent water samples are not good for agricultural purpose and as per the integrated parameters like USSL and Wilcox the percentage samples that are unsuitable for irrigation is going up to 30 percentage due to presence of higher Electrical conductivity. Novelty: In the study region, there is no perennial river and the main ion chemistry of Molakalmur Taluk’s groundwater has never been investigated before. The present work attempts to study the suitability of water for agricultural purpose. The findings of the study will aid in the collecting of crucial data on groundwater quality in Molakalmur Taluk. The findings of the study could also help groundwater managers and urban planners to restore and improve groundwater quality. Keywords: Physicochemical parameters; Irrigational water quality; Salinity hazard; Alkalinity hazard; Geographic Information System

Investigation on overvoltage caused by vacuum circuit breaker switching off shunt reactor in offshore wind farms

The multiple reignitions of vacuum circuit braker (VCB) while switching off the shunt reactor in an offshore wind farm (OWF) would produce a high overvoltage. The post-arc process of ion movement in the vacuum interrupter is analysed. Considering the sheath growth and ion concentration variation, the expression for dielectric recovery strength inside the VCB interrupter is derived. A novel VCB model is implemented in the environment of electromagnetic transient programme based on the new reignition criterion. Then, the switching overvoltage is computed and analysed in detail. For the OWF with high rising rate of transient recovery voltage, the sheath growth must be considered in the VCB model; otherwise, the overvoltage may be underestimated. Using resistor–capacitor (RC) snubber, a new installation scheme is proposed to suppress the overvoltage in the OWF. The results indicate that the proposed scheme can not only reduce the peak and steepness of overvoltage but also damp the high-frequency oscillation. It would not affect the steady-state operation of OWF. Besides, the capacitor of RC snubber normally does not bear the electric stress, and its life expectancy would be greatly enhanced.

The Broad Institute Scores Another Victory in Its Battle with the University of California over the Patenting of CRIPSR

The Broad Institute Scores Another Victory in Its Battle with the University of California over the Patenting of CRIPSR

High-performance solid-state metal-air batteries with an innovative dual-gel electrolyte

An innovative dual-gel electrolyte design is proposed in this work for solid-state metal-air batteries, which utilizes the acid-alkaline dual-gel for the Al-air and Zn-air batteries, and the acid-salt dual-gel for the Mg-air battery. During battery storage, a plastic thin-film can be used for dual-gel separation, which can be removed before battery usage. And during battery working, benefited from the higher ionic diffusion resistance of gel electrolytes, the mixing of different electrolytes is significantly reduced without using complex flowing system or expensive bipolar membrane separator, ensuring a pseudo-stable battery system. The acid-alkaline dual-gel Al-air and Zn-air batteries can provide ∼0.5 V higher voltage output than the corresponding alkaline single-gel batteries, and the discharge lifetime is not compromised too much due to the effective suppression of acid-alkaline neutralization. As for the acid-salt dual-gel Mg-air battery, attributed to the Mg(OH)2 dissolution by crossovered acid, both a 0.65 V higher discharge voltage and a 5.5 times longer discharge lifetime are achieved compared with the salt single-gel battery. By simulating the variation of ion concentration inside gels during battery discharge, it is found that the effective ion diffusivity in gel plays a vital role in the battery stability. In general, a moderate value is favored to avoid both the ion shortage at the electrode-electrolyte interface and the vigorous neutralization at the gel-gel contact surface. Furthermore, a flexible version of the dual-gel metal-air battery is demonstrated by using paper-based gel electrolytes.

A unified physiological framework of transitions between seizures, sustained ictal activity and depolarization block at the single neuron level

The majority of seizures recorded in humans and experimental animal models can be described by a generic phenomenological mathematical model, the Epileptor. In this model, seizure-like events (SLEs) are driven by a slow variable and occur via saddle node (SN) and homoclinic bifurcations at seizure onset and offset, respectively. Here we investigated SLEs at the single cell level using a biophysically relevant neuron model including a slow/fast system of four equations. The two equations for the slow subsystem describe ion concentration variations and the two equations of the fast subsystem delineate the electrophysiological activities of the neuron. Using extracellular K+ as a slow variable, we report that SLEs with SN/homoclinic bifurcations can readily occur at the single cell level when extracellular K+ reaches a critical value. In patients and experimental models, seizures can also evolve into sustained ictal activity (SIA) and depolarization block (DB), activities which are also parts of the dynamic repertoire of the Epileptor. Increasing extracellular concentration of K+ in the model to values found during experimental status epilepticus and DB, we show that SIA and DB can also occur at the single cell level. Thus, seizures, SIA, and DB, which have been first identified as network events, can exist in a unified framework of a biophysical model at the single neuron level and exhibit similar dynamics as observed in the Epileptor.Author Summary: Epilepsy is a neurological disorder characterized by the occurrence of seizures. Seizures have been characterized in patients in experimental models at both macroscopic and microscopic scales using electrophysiological recordings. Experimental works allowed the establishment of a detailed taxonomy of seizures, which can be described by mathematical models. We can distinguish two main types of models. Phenomenological (generic) models have few parameters and variables and permit detailed dynamical studies often capturing a majority of activities observed in experimental conditions. But they also have abstract parameters, making biological interpretation difficult. Biophysical models, on the other hand, use a large number of variables and parameters due to the complexity of the biological systems they represent. Because of the multiplicity of solutions, it is difficult to extract general dynamical rules. In the present work, we integrate both approaches and reduce a detailed biophysical model to sufficiently low-dimensional equations, and thus maintaining the advantages of a generic model. We propose, at the single cell level, a unified framework of different pathological activities that are seizures, depolarization block, and sustained ictal activity.

Long-term elemental trends in drip waters from monitoring Bunker Cave: New insights for past precipitation variability

A seven-year (2006–2013) monitoring was conducted in Bunker Cave, northwest Germany. The monitoring programme incorporates cave air temperature, the amount of precipitation, drip rates at five drip sites (TS 1, 2, 3, 5, 8) in the cave, and the analyses of cation (Ca2+, Mg2+, Sr2+, Na+, K+) and anion (HCO3−, NO3−, SO42−, Cl−) concentrations of rain, soil, and drip waters with a monthly (2006–2011) and bimonthly (2012−2013) interval. Further, the Ca, Mg, and Sr concentrations of the two host rock components, limestone and dolomite, were analysed.The analysis of rain, soil, and drip waters allowed to distinguish between geogenic and anthropogenic influences on the hydrochemistry of the cave. The limestone is the source of Ca2+, Mg2+, Sr2+, and HCO3− in all drip waters, as well as SO42− from pyrite dissolution from the limestone. Chloride and NO3− were inserted by anthropogenic sources such as aerosols from road salt, fertilisers, and industry. Drip site TS 1 shows a strong seasonal drip rate, which is simultaneous with a seasonal variation in ion concentrations (Ca2+, Mg2+, Sr2+, HCO3−, SO42−), induced by younger water transported by fracture flow during episodes of fast drip rates. Drip water at drip site TS 5 is recharged by water which probably dissolves prior calcite precipitation (PCP), resulting in low and constant Mg2+ and Sr2+ concentrations. Drip water at drip sites TS 2, 3, and 8 are mainly influenced by PCP, whereas drip waters at TS 2 and 8 are additionally influenced by incongruent dolomite dissolution indicated by their increasing Mg2+ and stable Sr2+ concentrations. Furthermore, Cl− and SO42− concentrations show increasing and decreasing long-term trends for these three PCP-influenced drip waters at sites TS 2, 3, and 8, respectively.The decreasing pattern in infiltration/precipitation from 2000 to 2013 is not very pronounced; however, the continuous draining of the aquifer is visible in the decreasing drip rates over the seven-year monitoring period. This is reflected in the long-term increasing trends of Mg/Ca, Sr/Ca ratios induced by PCP, and Cl− concentrations, as well as in the decreasing long-term trend of the SO42− concentrations in drip waters of drip sites TS 2, 3, and 8.For a better understanding of the cave system with its complex processes, a multi-element-proxy long-term cave monitoring of rain, soil, and drip waters appears to be a reasonable step to be followed by the interpretation of the element proxies of speleothems. This monitoring emphasizes Mg/Ca and Sr/Ca ratios, as well as Cl− and in particular SO42− concentrations as potential past infiltration/precipitation proxies. Mg/Ca and Sr/Ca ratios are the strongest proxies to reconstruct infiltration/precipitation of measured elements in stalagmites, in cases Sr/Ca is not overprinted by growth rate influences. In addition, the sulphur concentration in speleothems may be an infiltration/precipitation proxy in the case of a geogenic source from the host rock.