Higher Current Intensity Research Articles

Electroosmotic dewatering of cellulose nanocrystals

One of the main challenges for industrial production of cellulose nanocrystals is the high energy demand during the dewatering of dilute aqueous suspensions. It is addressed in this study by utilising electroosmotic dewatering to increase the solid content of suspensions of cellulose nanocrystals. The solid content was increased from 2.3 up to 15.3 wt%, i.e. removal of more than 85% of all the water present in the system, at a much lower energy demand than that of thermal drying. Increasing the strength of the electric field increased not only the dewatering rate but also the specific energy demand of the dewatering operation: the electric field strength used in potential industrial applications is thus a trade-off between the rate of dewatering and the energy demand. Additionally, it was found that high local current intensity had the potential of degrading cellulose nanocrystals in contact with the anode. The maximum strength of the electric field applied should therefore be limited depending on the equipment design and the suspension conditions.

Comparison of cortical responses to the activation of retina by visual stimulation and transcorneal electrical stimulation

BackgroundElectrical stimulation has been widely used in many ophthalmic diseases to modulate neuronal activities or restore partial visual function. Due to the different processing pathways and mechanisms, responses to visual and electrical stimulation in the primary visual cortex and higher visual areas might be different. This differences would shed some light on the properties of cortical responses evoked by electrical stimulation. ObjectiveThis study's goal was to directly compare the cortical responses evoked by visual and electrical stimulation and investigate the cortical processing of visual information and extrinsic electrical signal. MethodsOptical imaging of intrinsic signals (OIS) was used to probe the cortical hemodynamic responses in 11 cats. Transcorneal electrical stimulation (TES) through an ERG-jet contact lens electrode was used to activate visual cortices. Full-field and peripheral drifting gratings were used as the visual stimuli. ResultsThe response latency evoked by TES was shorter than that responding to visual stimulation (VS). Cortical responses evoked by VS were retinotopically organized, which was consistent with previous studies. On the other hand, the cortical region activated by TES was preferentially located in the secondary visual cortex (Area 18), while the primary visual cortex (Area 17) was activated by a higher current intensity. Compared with the full-field VS, the cortical response in Area 18 to TES with a current intensity above 1.2 mA was significantly stronger. ConclusionAccording to our results, we provided some evidence that the cortical processing of TES was influenced by the distribution of the electrical field in the retina and the activating threshold of different retinal ganglion cells.

Direct effects of transcranial electric stimulation on brain circuits in rats and humans

Transcranial electric stimulation is a non-invasive tool that can influence brain activity; however, the parameters necessary to affect local circuits in vivo remain to be explored. Here, we report that in rodents and human cadaver brains, ~75% of scalp-applied currents are attenuated by soft tissue and skull. Using intracellular and extracellular recordings in rats, we find that at least 1 mV/mm voltage gradient is necessary to affect neuronal spiking and subthreshold currents. We designed an ‘intersectional short pulse’ stimulation method to inject sufficiently high current intensities into the brain, while keeping the charge density and sensation on the scalp surface relatively low. We verify the regional specificity of this novel method in rodents; in humans, we demonstrate how it affects the amplitude of simultaneously recorded EEG alpha waves. Our combined results establish that neuronal circuits are instantaneously affected by intensity currents that are higher than those used in conventional protocols.

Disrupted Co-activation of Interneurons and Hippocampal Network after Focal Kainate Lesion.

GABAergic interneurons are known to control activity balance in physiological conditions and to coordinate hippocampal networks during cognitive tasks. In temporal lobe epilepsy interneuron loss and consecutive network imbalance could favor pathological hypersynchronous epileptic discharges. We tested this hypothesis in mice by in vivo unilateral epileptogenic hippocampal kainate lesion followed by in vitro recording of extracellular potentials and patch-clamp from GFP-expressing interneurons in CA3, in an optimized recording chamber. Slices from lesioned mice displayed, in addition to control synchronous events, larger epileptiform discharges. Despite some ipsi/contralateral and layer variation, interneuron density tended to decrease, average soma size to increase. Their membrane resistance decreased, capacitance increased and contralateral interneuron required higher current intensity to fire action potentials. Examination of synchronous discharges of control and larger amplitudes, revealed that interneurons were biased to fire predominantly with the largest population discharges. Altogether, these observations suggest that the overall effect of reactive cell loss, hypertrophy and reduced contralateral excitability corresponds to interneuron activity tuning to fire with larger population discharges. Such cellular and network mechanisms may contribute to a runaway path toward epilepsy.

Role of the negative motor area in general praxis: A high frequency electrical cortical stimulation study

Background: The negative motor area (NMA) is defined as a cortical area where 50 Hz electrical cortical stimulation produces inhibition of the voluntary movement such as finger tapping. The function of NMA has not been well investigated since previous studies mainly focused on the all or none response, namely, arrest of finger tapping at high current intensity.

Analytical solution to the transient beam loading effects of a superconducting cavity**Supported by National Natural Science Foundation of China (11525523, 91426303)

Transient beam loading is one of the key issues in any high beam current intensity superconducting accelerators, and needs to be carefully investigated. The core problem in the analysis is to obtain the time evolution of effective cavity voltage under transient beam loading. To simplify the problem, the second order ordinary differential equation describing the behavior of the effective cavity voltage is intuitively simplified to a first order one, with the aid of two critical approximations which lack proof of their validity. In this paper, the validity is examined mathematically in some specific cases, resulting in a criterion for the simplification. It is popular to solve the approximate equation for the effective cavity voltage numerically, while this paper shows that it can also be solved analytically under the step function approximation for the driven term. With the analytical solution to the effective cavity voltage, the transient reflected power from the cavity and the energy gain of the central particle in the bunch can also be calculated analytically. The validity of the step function approximation for the driven term is examined by direct evaluations. After that, the analytical results are compared with the numerical ones.

P 63 Investigating the effects of tRNS variants and task dependency on cortical excitability

Background Transcranial random noise stimulation (tRNS) has specific benefits and is fundamentally different as compared to more established methods such as transcranial direct current stimulation (tDCS) in modulating brain function (Terney et al., 2008; Ambrus et al., 2010). For example, previous research in the motor system has shown corticospinal excitability (CSE) to be task-dependent (Terney et al., 2008). It remains unresolved and largely unaddressed what the critical stimulation parameters of tRNS are, e.g. with regard to noise type (i.e. Gaussian, uniform) or current intensity (i.e. peak-to-peak amplitude, I max; effective current, I eff ). To study the effects of different tRNS parameters and task-dependency, Experiment 1 compared conventional, Gaussian tRNS (g-tRNS, 1 mA I max ) with uniform tRNS (u-tRNS, 1 mA I max ). Experiment 2 compared tRNS to anodal tDCS at higher, but equivalent effective current intensities (0.8 mA I eff ). The hypotheses were that (i) effects would be independent of noise distribution type and dependent on current intensity and (ii) that anodal tDCS and tRNS would induce similar effects if applied with comparable current intensities. The primary outcome measure was corticospinal excitability (CSE). Methods Twenty-nine healthy, right-handed individuals received stimulation over the left M1 in a double-blind, sham-controlled, within-subjects study design. Experiment 1 investigated g-tRNS (1 mA I max , 0.22 mA I eff ) and u-tRNS (1 mA I max ; 0.52 mA I eff ). Experiment 2 investigated tRNS (0.8 mA I eff ; 1.51 mA I max ) and anodal tDCS (0.8 mA I eff ; 0.8 mA I max ). Participants were randomly assigned one of two motor tasks to perform during tRNS/tDCS or sham stimulation. Half of the participants performed a simple motor task associated with cortical excitation (finger tapping-task, FT), the others performed a complex motor task associated with response inhibition (go/no-go-task, GNG). CSE was evaluated with 20 MEPs from the FDI prior to- and after 10 min of stimulation with task-execution. Results In Experiment 1, both g-tRNS and u-tRNS did not affect CSE. At higher current intensities, Experiment 2 found diverging task dependent effects comparing tRNS to anodal tDCS. TRNS facilitated CSE in the FT-group (331 μ V, +/−133 μ V) while inhibiting CSE in the GNG-group (−113 μ V, +/−59 μ V) with a significant difference between groups (pairwise comparisons, p = 0.004). TDCS in the FT group, significantly inhibited CSE (−80 μ V +/−106 μ V; pairwise comparisons, p = 0.044) and showed no effect in the GNG group. Conclusions Low tRNS current intensities do not influence CSE. Higher tRNS intensities (0.8 mA I eff ), but not anodal tDCS (0.8 mA), modulate CSE in a task-dependent manner. Future studies may benefit from the higher effective current intensities possible with uniform but not Gaussian noise and may take advantage of task dependency to potentiate the effect of tRNS.

Enhanced electrochemical removal of arsenic and heavy metals from mine tailings

Electrochemical remediation process can be used to separate arsenic and heavy metals from mine tailings and prevent them from leaching into the environment. Citric acid, EDTA, NaOH, HCl and H2O were used as chemical extractants in the electrokinetic process. The electrochemical extraction with citric acid as extractant was the most effective method to remove arsenic, iron and manganese from mine tailings highly contaminated. As, Fe and Mn removal from mine tailings was influenced for the citric acid concentration, the liquid/solid ratio, the current intensity and the extraction time. Different values for each of these parameters were tested in order to check their effects on the removal efficiency. The highest efficiency and smallest residual concentrations of contaminants were reached for concentrations of citric acid of 0.8 mol/L, liquid/solid ratio of 10, current intensity of 800 mA and extraction time of 6 h. Too high current intensities or too long extraction times caused corrosion problems in the steel parts of the system.

Low Intensity Focused tDCS Over the Motor Cortex Shows Inefficacy to Improve Motor Imagery Performance.

Transcranial direct current stimulation (tDCS) is a brain stimulation technique that can enhance motor activity by stimulating the motor path. Thus, tDCS has the potential of improving the performance of brain-computer interfaces during motor neurorehabilitation. tDCS effects depend on several aspects, including the current density, which usually varies between 0.02 and 0.08 mA/cm2, and the location of the stimulation electrodes. Hence, testing tDCS montages at several current levels would allow the selection of current parameters for improving stimulation outcomes and the comparison of montages. In a previous study, we found that cortico-cerebellar tDCS shows potential of enhancing right-hand motor imagery. In this paper, we aim to evaluate the effects of the focal stimulation of the motor cortex over motor imagery. In particular, the effect of supplying tDCS with a 4 × 1 ring montage, which consists in placing an anode on the motor cortex and four cathodes around it, over motor imagery was assessed with different current densities. Electroencephalographic (EEG) classification into rest or right-hand/feet motor imagery was evaluated on five healthy subjects for two stimulation schemes: applying tDCS for 10 min on the (1) right-hand or (2) feet motor cortex before EEG recording. Accuracy differences related to the tDCS intensity, as well as μ and β band power changes, were tested for each subject and tDCS modality. In addition, a simulation of the electric field induced by the montage was used to describe its effect on the brain. Results show no improvement trends on classification for the evaluated currents, which is in accordance with the observation of variable EEG band power results despite the focused stimulation. The lack of effects is probably related to the underestimation of the current intensity required to apply a particular current density for small electrodes and the relatively short inter-electrode distance. Hence, higher current intensities should be evaluated in the future for this montage.

Beam commission of the high intensity proton source developed at INFN-LNS for the European Spallation Source

At the Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud (INFN-LNS) the beam commissioning of the high intensity Proton Source for the European Spallation Source (PS-ESS) started in November 2016. Beam stability at high current intensity is one of the most important parameter for the first steps of the ongoing commissioning. Promising results were obtained since the first source start with a 6 mm diameter extraction hole. The increase of the extraction hole to 8 mm allowed improving PS-ESS performances and obtaining the values required by the ESS accelerator. In this work, extracted beam current characteristics together with Doppler shift and emittance measurements are presented, as well as the description of the next phases before the installation at ESS in Lund.

Towards the scale-up of bioelectrogenic technology: stacking microbial fuel cells to produce larger amounts of electricity

Experimental work carried out in this work has investigated the scale-up of microbial fuel cell (MFC) technology by studying the stacking of single microbial fuel cells, paying attention to the electric and hydraulic connections between each unit. To do this, the performance of three stacks (which were set up with different configurations) was studied for more than three months. The first stack (two hydraulically non-connected cells) was operated for 80 days without any electric connection between them, in order to determine the reproducibility of the performance of a single MFC, and then it was electrically connected in parallel for 20 days to determine if the electricity produced by each single cell was added when they were joined in the stack. The other two stacks (with five and ten cells, hydraulically connected) were connected electrically in series during the first 80 days and in parallel during the last 20 days. The results confirmed that connection in parallel allows higher current intensities and power to be obtained, and that the total electrode surface area attained with the stack is directly related to the production of electricity and to the removal of COD, although not in a linear way.

N-doped few-layered graphene-polyNi complex nanocomposite with excellent electrochromic properties

A new nanocomposite was obtained through the incorporation of N-doped few-layered graphene (N-FLG) into films of the electroactive polymer poly[Ni(3-Mesalen)] (poly[1]). The nanocomposite, N-FLG@poly[1], prepared by in situ electropolymerization, showed similar electrochemical responses to pristine poly[1], but with more well-defined redox peaks and higher current intensities, in compliance with larger electroactive surface coverage. N-FLG incorporation did not affect the electronic structure of poly[1], but decreased in 12% the molar extinction coefficient of the charge transfer band between metal and oxidized ligand, which is a promising advantage since this band is related to polymer degradation.The N-FLG@poly[1] showed multi-electrochromic behaviour (yellow in reduced state and green/russet in oxidized states) and revealed excellent improvement in electrochromic performance compared to original poly[1], specifically an increase of 71% in electrochemical stability (loss of 2.7% in charge after 10 000 switching cycles). Furthermore, nanocomposite formation decreased the switching time for oxidation (reduction) τ = 9 s (11 s) and improved the optical contrast (ΔT = 35.9%; increase of 38%) and colouration efficiency (η = 108.9 cm2 C−1; increase of 12%), for a representative film of coverage Γ = 296 nmol cm−2. The excellent electrochromic performance improvements are attributed to the alternative conducting pathways and to morphological modifications induced by N-FLG.

Electroacupuncture for Functional Constipation: A Multicenter, Randomized, Control Trial.

Background and Aim. To investigate the efficacy and safety of electroacupuncture (EA) with different current intensities for functional constipation (FC) and to assess whether the effects of EA with different current intensities are superior to the mosapride. Methods. Patients with FC were randomly divided into low current intensity group (LCI), high current intensity group (HCI), and mosapride group (MC). The primary outcome was three or more spontaneous bowel movements (SBMs) per week and an increase of one or more SBMs from baseline during at least 3 of the 4 weeks. Results. The primary outcome was reached by 53.45%, 66.15%, and 52.24% of the patients who received LCI, HCI, and mosapride, respectively. EA can significantly improve the weekly SBMs and stool consistency and reduce straining severity (p < 0.0001, all). HCI improved the quality of life better than mosapride (p < 0.05) and reduced the proportion of severe constipation more than LCI and mosapride (p < 0.05, both). Conclusions. EA is effective and safe at both current intensities for FC; therapeutic effects of LCI and HCI are not superior to mosapride. EA is superior to mosapride in improving patients' life quality and satisfaction level of treatment; EA has fewer adverse events than mosapride.

Parametric characterization of neural activity in the locus coeruleus in response to vagus nerve stimulation

Vagus nerve stimulation (VNS) has emerged as a therapy to treat a wide range of neurological disorders, including epilepsy, depression, stroke, and tinnitus. Activation of neurons in the locus coeruleus (LC) is believed to mediate many of the effects of VNS in the central nervous system. Despite the importance of the LC, there is a dearth of direct evidence characterizing neural activity in response to VNS. A detailed understanding of the brain activity evoked by VNS across a range of stimulation parameters may guide selection of stimulation regimens for therapeutic use. In this study, we recorded neural activity in the LC and the mesencephalic trigeminal nucleus (Me5) in response to VNS over a broad range of current amplitudes, pulse frequencies, train durations, inter-train intervals, and pulse widths. Brief 0.5s trains of VNS drive rapid, phasic firing of LC neurons at 0.1mA. Higher current intensities and longer pulse widths drive greater increases in LC firing rate. Varying the pulse frequency substantially affects the timing, but not the total amount, of phasic LC activity. VNS drives pulse-locked neural activity in the Me5 at current levels above 1.2mA. These results provide insight into VNS-evoked phasic neural activity in multiple neural structures and may be useful in guiding the selection of VNS parameters to enhance clinical efficacy.

Center Segregation with Final Electromagnetic Stirring in Billet Continuous Casting Process

With a multiphase solidification model built, the effect of F-EMS parameters on center segregation was investigated in 160 mm × 160 mm billet continuous casting process. In the model, the initial growth of equiaxed grains which could move freely with liquid was treated as slurry, while the coherent equiaxed zone was regarded as porous media. The results show that the stirring velocity is not the main factor influencing center segregation improvement, which is more affected by current intensity and stirring pool width. Because solute transport is controlled by solidification rate as stirring pool width is 73 mm, center segregation declines continuously with current intensity increasing. As liquid pool width decreases to 61 mm and less latent heat needs to dissipate in the later solidification, the center segregation could be improved more obviously by F-EMS. Due to center liquid solute enrichment and liquid phase accumulation in the stirring zone, center segregation turns to rise reversely with higher current intensity and becomes more serious with stirring pool width further decreasing to 43 mm. As the stirring pool width is 25 mm, the positive segregation has already formed and solute could still concentrate with weak stirring, leading to center segregation deterioration. With the optimized current intensity (400 A) and stirring pool width (61 mm) set for continuous mode, center segregation improvement is better than that of alternative mode.

PMo11V@N-CNT electrochemical properties and its application as electrochemical sensor for determination of acetaminophen

A polyoxometalate-nanocarbon composite, PMo11V@N-CNT, was prepared by a simple procedure which consisted of the immobilization of phosphovanadomolybdate (PMo11V) onto N-doped carbon nanotubes (N-CNT). The FTIR and XPS characterizations confirmed its successful synthesis. The cyclic voltammograms of glassy carbon electrode (GCE) modified with PMo11V and PMo11V@N-CNT showed four Mo-centred redox processes (MoVI/V) and a vanadium redox process (VV/IV). All were surface-confined redox processes. Additionally, PMo11V@N-CNT/GCE showed good stability and well-resolved redox peaks with high current intensities. The electrocatalytic sensing properties of PMo11V@N-CNT/GCE towards acetaminophen (AC) in the presence of tryptophan (TRP) were evaluated by square wave voltammetry. Under the conditions used, the peak current increased linearly with AC concentration in the presence of TRP, with a linear range from 1.5 × 10−6 to 3.9 × 10−4 mol dm−3 and a detection limit of 1.0 × 10−6 mol dm−3.

Novel simple method for preparing tailored polymer-titania nanotubes hybrid materials

A novel method for preparing hybrid polymer-titania nanotube (TNT) arrays with promising optical, catalytic and filtration applications is reported. The procedure is based on a one-step rapid galvanostatic anodization followed by the transfer of the TNT arrays to a polymer support by applying heat and pressure. The fraction of open-ended tubes can be controlled by changing the intensity of the current at the end of the anodization step. For example, completely open-ended or close-ended TNT arrays can be obtained by applying high or low current intensity, respectively at the end of the anodization process. The reported procedure allows the one-step simple and rapid preparation of flexible hybrid polymer-TNT materials which have great potential for photonic flow-through membranes.

Risk evaluation for needle-nerve contact related to electrical nerve stimulation in a porcine model.

For performing peripheral nerve blocks, the risk for needle-nerve contact (NNC) as an adverse event for low and high current thresholds has not yet been clearly defined when nerve stimulator guided techniques were applied. This experimental study aimed to investigate the risk of NNCs when applying stimulation currents between 0.1 and 2mA (in increments of 0.1mA). Brachial plexus nerves were exposed surgically in five anesthetized pigs. An insulated needle connected to a nerve stimulator was placed at 10mm distance to the targeted nerves. Current intensity was adjusted according to randomization (0.1-2.0mA, increments of 0.1mA). The needle tip was advanced toward the nerve until a motor response was elicited. The frequencies of NNCs for each of the adjusted current intensities were noted. Risks of NNCs were calculated according to the analysis of 95% confidence intervals (95% CI). We executed 2000 needle placements with stimulation currents ranging from 0.1 to 2.0mA. The risks for NNC at low current intensities were 0.85 (95% CI, 0.77-0.91) for 0.3mA and 0.5 (95% CI, 0.4-0.6) for 0.5mA, respectively. For high current intensities, risks of 0.13 (95% CI, 0.07-0.21) for 0.9mA and 0.01 (95% CI, 0-0.05) for 1.1mA were calculated. In this experimental animal study, a relevant reduction in the risk of NNCs could be observed when high current intensities (0.9-1.1mA) were applied compared to low current intensities (0.3-0.5mA).

Performance of microbial electrolysis cells with bioanodes grown at different external resistances.

Bioelectrochemical systems need an anode with a high abundance of exoelectrogenic bacteria for an optimal performance. Among all possible operational parameters for an efficient enrichment, the role of external resistance in microbial fuel cell (MFC) has gained a lot of interest since it indirectly poises an anode potential, a key parameter for biofilm distribution and morphology. Thus, this work aims at investigating and discussing whether bioanodes selected at different external resistances under MFC operation present different responses under both MFC and microbial electrolysis cell (MEC) operation. A better MEC performance (i.e. shorter start-up time, higher current intensity and higher H2 production rate) was obtained with an anode from an MFC developed under low external resistance. Quantitative real-time polymerase chain reaction (qPCR) confirmed that a low external resistance provides an MFC anodic biofilm with the highest content of Geobacter because it allows higher current intensity, which is correlated to exoelectrogenic activity. High external resistances such as 1,000 Ω led to a slower start-up time under MEC operation.

Exotic x-ray emission from dense plasmas

Exotic x-ray emission from dense matter is identified as the complex high intensity satellite emission from autoionizing states of highly charged ions. Among a vast amount of possible transitions, double K-hole hollow ion (HI) x-ray emission K0LX → K1LX−1 + hνhollow is of exceptional interest due to its advanced diagnostic potential for matter under extreme conditions where opacity and radiation fields play important roles. Transient ab initio simulations identify intense short pulse radiation fields (e.g., those emitted by x-ray free electron lasers) as possible driving mechanisms of HI x-ray emission via two distinct channels: first, successive photoionization of K-shell electrons, second, photoionization followed by resonant photoexciation among various ionic charge states that are simultaneously present in high density matter. We demonstrated that charge exchange of intermixing inhomogenous plasmas as well as collisions driven by suprathermal electrons are possible mechanisms to populate HIs to observable levels in dense plasmas, particularly in high current Z-pinch plasmas and high intensity field-ionized laser produced plasmas. Although the HI x-ray transitions were repeatedly identified in many other cases of dense optical laser produced plasmas on the basis of atomic structure calculations, their origin is far from being understood and remains one of the last holy grails of high intensity laser–matter interaction.