Single Channel Type Research Articles

Niobate Anodes for High Rate Lithium-Ion Batteries

Fast charging is one of the key performance requirements for next generation lithium ion batteries, and is directly related to the ease of ionic and electronic transport. However, lithium ion diffusion rates of promising anode materials, such as Li4Ti5O12, anatase TiO2, T-Nb2O5 and Nb18W16O93, are still insufficient. Therefore, nanosizing of the active electrode material is a common strategy to increase the effective lithium ion diffusion transport rate, which unfortunately also decreases the volumetric energy/power density and stability of the battery.Recently, we demonstrated nickel niobate, NiNb2O6, for the first time as a new intrinsic high-rate electrode material,[1] which exhibits an intrinsic high rate performance enabled by its suitable host crystal structure without the requirement of realizing nano-architectures. The NiNb2O6 host crystal structure exhibits only a single type of channel for lithium ion intercalation and can be fully lithiated up to Li3NiNb2O6 with a capacity of about 244 mAh/g at low current densities. Interestingly, a high diffusion coefficient of 10-12 cm2/s at 300 K enables fast (dis)charging at high current densities resulting in high capacities of 140 and 50 mAh/g for respectively 10C and 100C. The minimal volume change during lithiation is the origin of the stable reversible lithiation process in NiNb2O6 and leads to a capacity retention of 81% after 20.000 cycles at 100C. The structural stability and electrochemical behaviour were investigated by various experimental techniques and confirmed by density functional theory (DFT) calculations. Finally, full cell systems against LiFePO4 and NCM811 cathodes demonstrate the promising energy storage performance of nickel niobate anodes in practical battery devices.Our results strongly suggest that niobate-based materials are intrinsic high-rate anode materials without the requirement of realizing nano-architectures as typical for numerous titanium- and niobium-based oxides through complex synthesis procedures to minimize the length scales for lithium diffusion. Recently, we have replaced nickel by other transition metal ions to widen the exploration of niobate compounds for fast lithium ion diffusion. Large variations in electrochemical performance are observed, and the latest results will be presented. This will provide a new perspective on the role of intrinsic high-rate electrode materials for realizing ultrafast anode materials for future energy storage devices.[1] R. Xia et al., Advanced Energy Materials 12 (2022) 2102972.

The Upper Triassic Braided River Thin-Bedded Tight Sandstone in the Yanchang Formation, Ordos Basin: Sedimentary Characteristics, Seismic Forecasting Method, and Implication

In the Ordos Basin, Chang 81, a Member of the Yanchang Formation, features the development of braided river thin-bedded tight sandstones. These sandstones constitute one of the main production layers of tight oil and gas in the Yanchang Formation within the basin. This study integrates data from core samples, drilling, and seismic information to identify braided river thin-bedded sandstones in the Chang 81 Member at Daijiaping, Ordos Basin, using a method of constrained correlation between seismic waveform and seismic facies. This approach aids in determining the sedimentary microfacies types and reservoir characteristics of thin-bedded tight sandstones. We establish a quantitative fitting formula for the width-to-thickness ratio of braided channel sand bodies to finely characterize sand body stacking patterns and spatial distribution of thin-bedded tight sandstones in braided channels. Braided delta plain deposits in the Chang 81 Member at Daijiaping mainly comprise four types of sedimentary microfacies: braided channels, crevasse channels, floodplains, and swamps. The thickness of the reservoir sand body of Chang 81 member is mainly concentrated between 5–25 m, with low porosity and permeability, making it a typical thin-bedded tight sandstone reservoir. A method of constrained correlation between seismic waveforms and seismic facies was employed to identify sand bodies of braided river thin-bedded sandstones in the Chang 81 Member, summarizing four sand body stacking patterns: longitudinal incision type, longitudinal separation type, lateral shifting type, and single channel type. Furthermore, a quantitative forecasting formula of width-to-thickness ratio was established for the river channel scale, providing accurate guidance for well deployment. Horizontal wells deployed from the sand body’s side towards its center in a river channel yield a production 1.8 times higher than that of horizontal wells deployed in the opposite direction. Thin-bedded tight sandstones in braided channels, characterized by flat-top and convex-bottom lenticular seismic facies, hold practical significance in guiding the deployment of horizontal well patterns for tight oil and enhancing oil and gas recovery.

Uncovering the Interplay of Competing Distortions in the Prussian Blue Analogue K2Cu[Fe(CN)6

We report the synthesis, crystal structure, thermal response, and electrochemical behavior of the Prussian blue analogue (PBA) K2Cu[Fe(CN)6]. From a structural perspective, this is the most complex PBA yet characterized: its triclinic crystal structure results from an interplay of cooperative Jahn–Teller order, octahedral tilts, and a collective “slide” distortion involving K-ion displacements. These different distortions give rise to two crystallographically distinct K-ion channels with different mobilities. Variable-temperature X-ray powder diffraction measurements show that K-ion slides are the lowest-energy distortion mechanism at play, as they are the only distortion to be switched off with increasing temperature. Electrochemically, the material operates as a K-ion cathode with a high operating voltage and an improved initial capacity relative to higher-vacancy PBA alternatives. On charging, K+ ions are selectively removed from a single K-ion channel type, and the slide distortions are again switched on and off accordingly. We discuss the functional importance of various aspects of structural complexity in this system, placing our discussion in the context of other related PBAs.

Nickel Niobate Anodes for High Rate Lithium‐Ion Batteries

AbstractFast charging is one of the key requirements for next‐generation lithium‐ion batteries, however, lithium‐ion diffusion rates of typical electrode materials are limited. Nanosizing of active electrode material is a common strategy to increase the effective lithium‐ion diffusion transport rate, but it also decreases the volumetric energy/power density and stability of the battery. In this work, nickel niobate NiNb2O6 is demonstrated for the first time as a new intrinsic high‐rate anode material for lithium‐ion batteries without the requirement of realizing nano‐architectures. The NiNb2O6 host crystal structure exhibits only a single type of channel for lithium‐ion intercalation and can be fully lithiated with a capacity of about 244 mAh g−1 at low current densities. Interestingly, a high diffusion coefficient of 10−12 cm2 s−1 at 300 K enables fast (dis)charging at high current densities resulting in high capacities of 140 and 50 mAh g−1 for 10 and 100C respectively. The minimal volume change during lithiation is the origin of the stable reversible lithiation process in NiNb2O6 and leads to 81% capacity retention after 20 000 cycles at 100C. Finally, full cell systems against LiFePO4 and Li[Ni0.8Co0.1Mn0.1]O2 (NCM811) cathodes demonstrate the promising energy storage performance of nickel niobate anodes in practical battery devices.

Detection and Identification of Sediment Layer to Discover the Marine Mineral Resources Potential in Aruah Islands

<p>Aruah Islands is located on an international shipping line adjacent to Malaysia. The important aspect in borderline management is the maritime resource potential, one of which is sea minerals. In order to dig the information about marine mineral resources in Aruah Islands, a high-resolution seismic reflection with low frequency was applied, which capable to detect the depth and identify the sedimentary layers clearly and accurately. The depth of water and sediment layers were detected using an echosounder, reason Navi sound type 210 with a tow fish 100 kHz and shallow seismic boomer with a single channel type and wave energy 200 Joules. Gravity core and grab sampler were used to collect the sediment sample. There were three stages on seismic interpretation: sequence analysis, facies analysis, and reflection character identification. Furthermore, sediments containing coarse sand-sized minerals were observed using a microscope. The measurement result of Aruah Islands water depth was ranging from 0-80 m, the deepest part is on the Northern of Batu Mandi island which was 80 m depth. Seismic profiles indicated that the upper layer of tertiary sedimentary as the youngest rocks. Based on sediment thickness, the thickest area was found on the Western (approx. 50 m) and the Northern (approx. 32 m). In line with the island’s Southern part condition, which was plain or shallow sea exposure, the Southeastern island sediment thickness ranged only about 10-18 m. Generally, based on the analyzed sediment sample, quartz was the main mineral found, which was 60-80% of the composition. Other minerals were zircon, tin, hematite, magnetite, limonite, biotite, and dolomite.</p>

Sarcoplasmic Reticulum Ca2+ Release Uses a Cascading Network of Intra-SR and Channel Countercurrents

In muscle, Ca2+ release from the sarcoplasmic reticulum (SR) into the cytosol is mediated through the ryanodine receptors (RyRs) and sustained by countercurrents that keep the SR membrane potential near 0 mV. Likewise, Ca2+ reuptake by the sarco/endoplasmic reticulum Ca2+ ATPase pump requires countercurrent. Although evidence has suggested that TRIC K+ channels and/or RyR K+ influx provide these countercurrents, the exact sources have not yet been determined. We used an equivalent circuit compartment model of a cardiac SR, the surrounding cytosol, and the dyadic cleft to probe the sources of countercurrent during a complete cardiac cycle. By removing and relocating TRIC K+ channels, as well as limiting when they are active, we explored the various possible sources of SR countercurrent under many conditions. Our simulations indicate that no single channel type is essential for countercurrent. Rather, a cascading network of countercurrents is present with anion fluxes within the SR redistributing charges throughout the full SR volume. This allows ion channels in the entire SR membrane, far from the Ca2+ fluxes through the RyRs in the junctional SR and sarco/endoplasmic reticulum Ca2+ ATPase pump in the nonjunctional SR, to mediate countercurrents that support Ca2+ release and reuptake. This multifactorial network of countercurrents allows Ca2+ release to be remarkably robust.

On the mobility, membrane location and functionality of mechanosensitive channels in Escherichia coli.

Bacterial mechanosensitive channels protect cells from structural damage during hypoosmotic shock. MscS, MscL and MscK are the most abundant channels in E. coli and arguably the most important ones in osmoprotection. By combining physiological assays with quantitative photo-activated localization microscopy (qPALM), we find an almost linear relationship between channel abundance and cell survival. A minimum of 100 MscL (or MscS) channels is needed for protection when a single type of channel is expressed. Under native-like conditions MscL, MscS as well as MscK distribute homogeneously over the cytoplasmic membrane and the lateral diffusion of the channels is in accordance with their relative protein mass. However, we observe cluster formation and a reduced mobility of MscL when the majority of the subunits of the pentameric channel contain the fluorescent mEos3.2 protein. These data provide new insights into the quantitative biology of mechanosensitive channels and emphasizes the need for care in analysing protein complexes even when the fluorescent tag has been optimized for monomeric behaviour.

Cell-Type Specific Channelopathies in the Prefrontal Cortex of the fmr1-/y Mouse Model of Fragile X Syndrome.

Fragile X syndrome (FXS) is caused by transcriptional silencing of the fmr1 gene resulting in the loss of fragile X mental retardation protein (FMRP) expression. FXS patients display several behavioral phenotypes associated with prefrontal cortex (PFC) dysfunction. Voltage-gated ion channels, some of which are regulated by FMRP, heavily influence PFC neuron function. Although there is evidence for brain region-specific alterations to the function a single type of ion channel in FXS, it is unclear whether subtypes of principal neurons within a brain region are affected uniformly. We tested for alterations to ion channels critical in regulating neural excitability in two subtypes of prefrontal L5 pyramidal neurons. Using somatic and dendritic patch-clamp recordings, we provide evidence that the functional expression of h-channels (Ih) is down-regulated, whereas A-type K+ channel function is up-regulated in pyramidal tract-projecting (PT) neurons in the fmr1-/y mouse PFC. This is the opposite pattern of results from published findings from hippocampus where Ih is up-regulated and A-type K+ channel function is down-regulated. Additionally, we find that somatic Kv1-mediated current is down-regulated, resulting in increased excitability of fmr1-/y PT neurons. Importantly, these h- and K+ channel differences do not extend to neighboring intratelencephalic-projecting neurons. Thus, the absence of FMRP has divergent effects on the function of individual types of ion channels not only between brain regions, but also variable effects across cell types within the same brain region. Given the importance of ion channels in regulating neural circuits, these results suggest cell-type-specific phenotypes for the disease.

Improved Transresistance Characteristics of Inductance-gate Type SFFT Using AFM Lithography

An atomic force microscope (AFM) was used to locally anodize the serial channels of an inductance-gate type superconducting ux ow transistor (SFFT) as narrow slits with a width of 50 μm, a space of 25 μm, and 12 turns, to improve the transresistance value. Among the serial channels that were anodized with the scanning tip of the AFM in the drain current line, channels 1 and 2 were 7.3 and 7.9 μm wide, and 531 and 461 nm high, respectively. The critical current density in the serial channel of the fabricated SFFT, which was determined using an AFM modi cation method, was decreased by increasing the gate current. The measured current-voltage curves were compared with the simulated ones. The maximum transresistance value was 0.56 Ω at the drain current of 20 mA when the gate current was 6 mA. The transresistance characteristics of the inductance-gate type SFFT could be more improved than that of the single-channel type SFFT using an inductively coupled plasma lithography method

Model Neural Membrane Droplet Interface Bilayers from Brain Total Lipid Extract for Studying Membrane-Peptide Interactions with Amyloid-β

ABSTRACTDroplet interface bilayers (DIBs) are formed using brain total lipid extract (BTLE) to create a synthetic bilayer whose lipid composition mimics that of neural cells. The electrical properties of BTLE DIBs, specifically membrane resistance, capacitance, and rupture potential, are determined and compared to the properties of bilayers formed using DPhPC, the most common lipid within the growing DIB field. There is no significant difference in the resistance or rupture potential of BTLE and DPhPC bilayers, for instance with average nominal resistance over 200 GΩ and rupture potential around 200 mV. In electrical measurements with either DPhPC or BTLE bilayers, applied voltages of up to ±150 mV yield low levels of leakage current. Upon interaction with the pore-forming amyloid-beta (Aβ) peptide, both bilayers display sudden significant voltage-dependent increases in conductance with characteristic threshold voltages well below 150 mV. Discrete single-channel type events are observed in the case of Aβ-BTLE whereas disordered fluctuating conductance is observed with Aβ-DPhPC. Circular dichroism is measured for Aβ incubated with BTLE and DPhPC liposomes, as well as pure Aβ, at a range of temperatures over a period of several weeks. Changes in secondary structure of liposome-bound and pure Aβ are significantly affected by both lipid type and temperature. A key finding includes the 100% conversion of Aβ to alpha-helical confirmation within 24 hours when incubated with liposomes (of either type) at physiologically relevant 37°C. The 100% alpha-helical Aβ is maintained for up to 2 weeks at 37°C when incubated with liposomes, although other structures begin to emerge after the 14 day mark. Between 14-31 days after reconstitution, Aβ incubated at 37C with BTLE bilayers displays longer lasting alpha-helical content than DPhPC. At the same temperature, pure Aβ is 100% alpha helical only at the 1 day mark with apparent restructuring from day 2 through day 31. Refrigerated Ab samples do not display 100% alpha-helical structure across the entire 31 day testing period. The differences observed between BTLE and DPhPC in both electrophysiological and spectroscopic experiments may be a result of phase separations or other variations in membrane fluidity that result from the use of a homogeneous total lipid extract. Time and temperature play essential roles in the aggregation and restructuring of potentially toxic Aβ oligomers, and there is motivation for further efforts to elicit the mechanistic differences in interactions of Ab with BTLE compared to DPhPC.

A geometric understanding of how fast activating potassium channels promote bursting in pituitary cells

The electrical activity of endocrine pituitary cells is mediated by a plethora of ionic currents and establishing the role of a single channel type is difficult. Experimental observations have shown however that fast-activating voltage- and calcium-dependent potassium (BK) current tends to promote bursting in pituitary cells. This burst promoting effect requires fast activation of the BK current, otherwise it is inhibitory to bursting. In this work, we analyze a pituitary cell model in order to answer the question of why the BK activation must be fast to promote bursting. We also examine how the interplay between the activation rate and conductance of the BK current shapes the bursting activity. We use the multiple timescale structure of the model to our advantage and employ geometric singular perturbation theory to demonstrate the origin of the bursting behaviour. In particular, we show that the bursting can arise from either canard dynamics or slow passage through a dynamic Hopf bifurcation. We then compare our theoretical predictions with experimental data using the dynamic clamp technique and find that the data is consistent with a burst mechanism due to a slow passage through a Hopf.

Application of queuing theory to patient satisfaction at a tertiary hospital in Nigeria

Background:Queuing theory is the mathematical approach to the analysis of waiting lines in any setting where arrival rate of subjects is faster than the system can handle. It is applicable to healthcare settings where the systems have excess capacity to accommodate random variations.Materials and Methods:A cross-sectional descriptive survey was done. Questionnaires were administered to patients who attended the general outpatient department. Observations were also made on the queuing model and the service discipline at the clinic. Questions were meant to obtain demographic characteristics and the time spent on the queue by patients before being seen by a doctor, time spent with the doctor, their views about the time spent on the queue and useful suggestions on how to reduce the time spent on the queue. A total of 210 patients were surveyed.Results:Majority of the patients (164, 78.1%) spent 2 h or less on the queue before being seen by a doctor and less than 1 h to see the doctor. Majority of the patients (144, 68.5%) were satisfied with the time they spent on the queue before being seen by a doctor. Useful suggestions proffered by the patients to decrease the time spent on the queue before seeing a doctor at the clinic included: that more doctors be employed (46, 21.9%), that doctors should come to work on time (25, 11.9%), that first-come-first served be observed strictly (32, 15.2%) and others suggested that the records staff should desist from collecting bribes from patients in order to place their cards before others. The queuing method employed at the clinic is the multiple single channel type and the service discipline is priority service. The patients who spent less time on the queue (<1 h) before seeing the doctor were more satisfied than those who spent more time (P < 0.05).Conclusion:The study has revealed that majority of the patients were satisfied with the practice at the general outpatient department. However, there is a need to employ measures to respond to the suggestions given by the patients who are the beneficiaries of the hospital services.

Silent mutation in long QT syndrome: Pathogenicity prediction by computer simulation

s Congenital long QT syndrome (LQTS) is an inherited cardiac disorder characterized by prolongation of the QT interval on the surface electrocardiogram. Patients with LQTS are predisposed to ventricular tachyarrhythmias, torsade de pointes, leading to recurrent syncope and sudden cardiac death. The estimated frequency of this disorder is 1 in 2000. Currently, hundreds of mutations in 13 different enes have been described as causal to LQTS pathology, but utations in KCNQ1, KCNH2, and SCN5A genes comprise 0% of all the mutations. Among all the LQTS causal genes, KCNQ1 is by far the predominant mutation-harboring gene. The KCNQ1 gene encodes for the potassium-channel protein Kv7.1, which is responsible for the slow component of the delayed rectifier repolarizing current (IKs). Mutations nvolving the KCNQ1 gene result in a reduction in the epolarizing IKs current and prolongation of the QT interval. This reduction in IKs current could be mediated by one of the two mechanisms: 1) trafficking defect of the mutant protein, which could not be transported properly to the cell membrane and lacks incorporation into the tetrameric channel, and 2) mutant KCNQ1 makes a protein that is defective in channel function and exerts a dominant negative effect on the channel. It may be mentioned here that normal repoarization is accomplished by multiple different potassium hannels, which is a potential safety reserve for normal epolarization. In physiological situations, the pharmacological block or impairment of one single type of potassium channel does not always lead to QT interval prolongation, which depends on the severity of the mutant. In the presence of a mild/subclinical impairment of the repolarization process, an otherwise mild potassium-channel block, and/or accelerated heart rate, sudden adrenergic accentuation is thought to precipitate QT prolongation, resulting in torsades de pointes arrhythmia. Mutations in the transmembrane, linker, or pore-forming regions of the KCNQ1 (also KCNH2) gene are frequently

Automated Patch Clamp on mESC-Derived Cardiomyocytes for Cardiotoxicity Prediction

Cardiovascular side effects are critical in drug development and have frequently led to late-stage project terminations or even drug withdrawal from the market. Physiologically relevant and predictive assays for cardiotoxicity are hence strongly demanded by the pharmaceutical industry. To identify a potential impact of test compounds on ventricular repolarization, typically a variety of ion channels in diverse heterologously expressing cells have to be investigated. Similar to primary cells, in vitro-generated stem cell-derived cardiomyocytes simultaneously express cardiac ion channels. Thus, they more accurately represent the native situation compared with cell lines overexpressing only a single type of ion channel. The aim of this study was to determine if stem cell-derived cardiomyocytes are suited for use in an automated patch clamp system. The authors show recordings of cardiac ion currents as well as action potential recordings in readily available stem cell-derived cardiomyocytes. Besides monitoring inhibitory effects of reference compounds on typical cardiac ion currents, the authors revealed for the first time drug-induced modulation of cardiac action potentials in an automated patch clamp system. The combination of an in vitro cardiac cell model with higher throughput patch clamp screening technology allows for a cost-effective cardiotoxicity prediction in a physiologically relevant cell system.

SCWR single channel stability analysis using a response matrix method

A system response matrix method, which directly solves the linearized differential equations in the matrix form without Laplace transformation, is introduced for the supercritical fluids flow instability analysis. The model is developed and applied to the single channel or parallel channel type instability analyses of a typical proposed Supercritical Water Reactor (SCWR) design. A uniform axial heat flux is assumed, and the dynamics of the fuel rods and water rods are not considered in this paper. The sensitivity of the decay ratio (DR) to the axial mesh size is analyzed and found that the DR is not sensitive to mesh size once sufficient number of axial nodes is applied. The sensitivity of the stability to inlet orifice coefficient is conducted for the hot channel and found that a higher inlet orifice coefficient will make the system more stable. The susceptibility of stability to operating parameters such as mass flow rate, power and system pressure is also performed. It is found that the SCWR stability sensitivity feature can be improved by carefully choosing the inlet orifice coefficients and operating parameters. The stability feature of the average channel is also analyzed with an equivalent inlet orifice coefficient. Finally, the manufacturing feasibility of the inlet orifices for both the hot channel and average channel is studied and found to be favorable.

Recapitulation of an Ion Channel IV Curve Using Frequency Components

INTRODUCTION: Presently, there are no established methods to measure multiple ion channel types simultaneously and decompose the measured current into portions attributable to each channel type. This study demonstrates how impedance spectroscopy may be used to identify specific frequencies that highly correlate with the steady state current amplitude measured during voltage clamp experiments. The method involves inserting a noise function containing specific frequencies into the voltage step protocol. In the work presented, a model cell is used to demonstrate that no high correlations are introduced by the voltage clamp circuitry, and also that the noise function itself does not introduce any high correlations when no ion channels are present. This validation is necessary before the technique can be applied to preparations containing ion channels. The purpose of the protocol presented is to demonstrate how to characterize the frequency response of a single ion channel type to a noise function. Once specific frequencies have been identified in an individual channel type, they can be used to reproduce the steady state current voltage (IV) curve. Frequencies that highly correlate with one channel type and minimally correlate with other channel types may then be used to estimate the current contribution of multiple channel types measured simultaneously.METHODS: Voltage clamp measurements were performed on a model cell using a standard voltage step protocol (-150 to +50 mV, 5mV steps). Noise functions containing equal magnitudes of 1-15 kHz frequencies (zero to peak amplitudes: 50 or 100mV) were inserted into each voltage step. The real component of the Fast Fourier transform (FFT) of the output signal was calculated with and without noise for each step potential. The magnitude of each frequency as a function of voltage step was correlated with the current amplitude at the corresponding voltages.RESULTS AND CONCLUSIONS: In the absence of noise (control), magnitudes of all frequencies except the DC component correlated poorly (|R|<0.5) with the IV curve, whereas the DC component had a correlation coefficient greater than 0.999 in all measurements. The quality of correlation between individual frequencies and the IV curve did not change when a noise function was added to the voltage step protocol. Likewise, increasing the amplitude of the noise function also did not increase the correlation. Control measurements demonstrate that the voltage clamp circuitry by itself does not cause any frequencies above 0 Hz to highly correlate with the steady-state IV curve. Likewise, measurements in the presence of the noise function demonstrate that the noise function does not cause any frequencies above 0 Hz to correlate with the steady-state IV curve when no ion channels are present. Based on this verification, the method can now be applied to preparations containing a single ion channel type with the intent of identifying frequencies whose amplitudes correlate specifically with that channel type.

Recapitulation of an Ion Channel IV Curve Using Frequency Components

INTRODUCTION: Presently, there are no established methods to measure multiple ion channel types simultaneously and decompose the measured current into portions attributable to each channel type. This study demonstrates how impedance spectroscopy may be used to identify specific frequencies that highly correlate with the steady state current amplitude measured during voltage clamp experiments. The method involves inserting a noise function containing specific frequencies into the voltage step protocol. In the work presented, a model cell is used to demonstrate that no high correlations are introduced by the voltage clamp circuitry, and also that the noise function itself does not introduce any high correlations when no ion channels are present. This validation is necessary before the technique can be applied to preparations containing ion channels. The purpose of the protocol presented is to demonstrate how to characterize the frequency response of a single ion channel type to a noise function. Once specific frequencies have been identified in an individual channel type, they can be used to reproduce the steady state current voltage (IV) curve. Frequencies that highly correlate with one channel type and minimally correlate with other channel types may then be used to estimate the current contribution of multiple channel types measured simultaneously. METHODS: Voltage clamp measurements were performed on a model cell using a standard voltage step protocol (-150 to +50 mV, 5mV steps). Noise functions containing equal magnitudes of 1-15 kHz frequencies (zero to peak amplitudes: 50 or 100mV) were inserted into each voltage step. The real component of the Fast Fourier transform (FFT) of the output signal was calculated with and without noise for each step potential. The magnitude of each frequency as a function of voltage step was correlated with the current amplitude at the corresponding voltages. RESULTS AND CONCLUSIONS: In the absence of noise (control), magnitudes of all frequencies except the DC component correlated poorly (|R|<0.5) with the IV curve, whereas the DC component had a correlation coefficient greater than 0.999 in all measurements. The quality of correlation between individual frequencies and the IV curve did not change when a noise function was added to the voltage step protocol. Likewise, increasing the amplitude of the noise function also did not increase the correlation. Control measurements demonstrate that the voltage clamp circuitry by itself does not cause any frequencies above 0 Hz to highly correlate with the steady-state IV curve. Likewise, measurements in the presence of the noise function demonstrate that the noise function does not cause any frequencies above 0 Hz to correlate with the steady-state IV curve when no ion channels are present. Based on this verification, the method can now be applied to preparations containing a single ion channel type with the intent of identifying frequencies whose amplitudes correlate specifically with that channel type.

A multi-channel wireless connection system for structural health monitoring applications

SUMMARY To overcome the drawbacks related to a wired solution for structural health monitoring applications, many kinds of wireless sensors have been proposed and prototyped. Most of these sensors are of the single channel type. Multi-channel solutions also exist and they are mainly based on time-division multiplexing (TDM). Both these types of wireless communication systems cause large time delays when a large number of sensors nodes are deployed. In this paper, a different multi-channel wireless sensor solution, based on a mixed approach that exploits both TDM and frequency-division multiplexing (FDM), is introduced. As a result, the time delay is independent of the number of sensor nodes. The real-time multi-channel feature represents a key aspect of the proposed wireless sensing network. The wireless scheme is initially intended a simple solution for analog cable replacement and it is preliminarily tested in a laboratory environment. The powerful and flexible system-on-chip single-chip wireless transceiver, which can operate in the Industrial, scientific and medical (ISM) license-free frequency bands, is employed to perform both the control function and the wireless communication. The goal is to reach a good balance among communication range, power consumption, data rate, and link quality. The overall design, the implementation, and an experimental validation of the proposed multi-channel wireless sensor solution are presented. Copyright r 2010 John Wiley & Sons, Ltd. Received 5 February 2010; Revised 9 May 2010; Accepted 14 May 2010

A tale from the Crypt: splice variants of BK channels in colonic potassium secretion

A tale from the Crypt: splice variants of BK channels in colonic potassium secretion

NMDAR-mediated EPSCs are maintained and accelerate in time course during maturation of mouse and rat auditory brainstemin vitro

NMDA receptors (NMDARs) mediate a slow EPSC at excitatory glutamatergic synapses throughout the brain. In many areas the magnitude of the NMDAR-mediated EPSC declines with development and is associated with changes in subunit composition, but the mature channel composition is often unknown. We have employed the calyx of Held terminal with its target, the principal neuron of the medial nucleus of the trapezoid body (MNTB), to examine the NMDAR-mediated EPSC during synapse maturation from P10 to P40. Our data show that the calyx has reached a mature state by around P18. The NMDAR-mediated EPSC amplitude (and dominant decay ) fell from around 5 nA (: 40-50 ms) at P10/11 to 0.3-0.5 nA (: 10-15 ms) by P18. The mature NMDAR-EPSC showed no sensitivity to ifenprodil, indicating lack of NR2B subunits, and no block by submicromolar concentrations of zinc, consistent with NR1-1b subunit expression. Additionally, from P11 to P18 there was a reduction in voltage-dependent block and the apparent dissociation constant for [Mg(2+)](o) (K(o)) changed from 7.5 to 14 mm. Quantitative PCR showed that the relative expression of NR2A and NR2C increased, while immunohistochemistry confirmed the presence of NR2A, NR2B and NR2C protein. Although the mature NMDAR-EPSC is small, it is well coupled to NO signalling, as indicated by DAR-4M imaging. We conclude that native mature NMDAR channels at the calyx of Held have a fast time course and reduced block by [Mg(2+)](o), consistent with dominance of NR2C subunits and functional exclusion of NR2B subunits. The pharmacology suggests a single channel type and we postulate that the mature NMDARs consist of heterotrimers of NR1-1b-NR2A-NR2C.