Strip Electrodes Research Articles

Cortical Potentials Evoked by Subthalamic Stimulation Demonstrate a Short Latency Hyperdirect Pathway in Humans.

A monosynaptic projection from the cortex to the subthalamic nucleus is thought to have an important role in basal ganglia function and in the mechanism of therapeutic subthalamic deep-brain stimulation, but in humans the evidence for its existence is limited. We sought physiological confirmation of the cortico-subthalamic hyperdirect pathway using invasive recording techniques in patients with Parkinson's disease (9 men, 1 woman). We measured sensorimotor cortical evoked potentials using a temporary subdural strip electrode in response to low-frequency deep-brain stimulation in patients undergoing awake subthalamic or pallidal lead implantations. Evoked potentials were grouped into very short latency (<2 ms), short latency (2-10 ms), and long latency (10-100 ms) from the onset of the stimulus pulse. Subthalamic and pallidal stimulation resulted in very short-latency evoked potentials at 1.5 ms in the primary motor cortex accompanied by EMG-evoked potentials consistent with corticospinal tract activation. Subthalamic, but not pallidal stimulation, resulted in three short-latency evoked potentials at 2.8, 5.8, and 7.7 ms in a widespread cortical distribution, consistent with antidromic activation of the hyperdirect pathway. Long-latency potentials were evoked by both targets, with subthalamic responses lagging pallidal responses by 10-20 ms, consistent with orthodromic activation of the thalamocortical pathway. The amplitude of the first short-latency evoked potential was predictive of the chronic therapeutic stimulation contact.SIGNIFICANCE STATEMENT This is the first physiological demonstration of the corticosubthalamic hyperdirect pathway and its topography at high spatial resolution in humans. We studied cortical potentials evoked by deep-brain stimulation in patients with Parkinson's disease undergoing awake lead implantation surgery. Subthalamic stimulation resulted in multiple short-latency responses consistent with activation of hyperdirect pathway, whereas no such response was present during pallidal stimulation. We contrast these findings with very short latency, direct corticospinal tract activations, and long-latency responses evoked through polysynaptic orthodromic projections. These findings underscore the importance of incorporating the hyperdirect pathway into models of human basal ganglia function.

Superposition of streamer and glow discharges in single pulse mode of sliding discharge burning in Ne

Numerical simulation of streamer development following the 1D ‘classic fluid model’ of ionization wave front propagation is applied to analyze the previously observed superposition of streamer- and glow-type discharges, in experiments with Ne using a single pulse sliding discharge setup at voltage amplitudes below the threshold of the spark gas breakdown. Experimental results are presented using single pulse images of spatial discharge plasma distribution between two parallel strip electrodes placed above the alumina ceramics substrate, at Ne pressures of 30 and 100 kPa and with the applied voltage rise time of 20–25 ns. A comparison of electron density values, calculated behind the wave front and estimated from the experiments, resulted in the conclusion that discharge formation in the gap begins from the development and propagation of the ionization wave. Its formation starts from the high voltage electrode at faster temporal dynamics as compared to the glow discharge, whose slower development begins from the cathode. The structure of the visual discharge plasma depends on the discharge voltage and polarity, as well as the gas pressure. In particular, at relatively low voltage the wave propagation may stop somewhere in the gap and then the rest of the gap is occupied by the glow discharge only, as was observed in positive polarity experiments at a gas pressure of 100 kPa.

Square‐wave Amplitude Effect in Cathodic and Anodic Stripping Square‐wave Voltammetry

AbstractIn this paper a theoretical study of stripping processes at planar electrodes under conditions of square‐wave voltammetry is presented. A mechanistic examination for cathodic stripping electrode mechanisms, a simple anodic striping mechanism, and anodic stripping mechanisms coupled with adsorption equilibrium of the analyte are discussed using varying square‐wave amplitudes. The methodologies described here use two typical features: the peak potential separation of square‐wave components and the amplitude‐based quasireversible maximum. Both methods can be applied at a constant frequency, i. e., constant scan rate. The received data are combined with the critical parameters of electrode reaction kinetics. Thus, the established methodologies allow for a simple kinetic characterization. The received diagnostic criteria are verified with experiments at a glassy carbon electrode for lead ions.

High-Speed Traveling-Wave Modulator Based on Graphene and Microfiber

The two-dimensional graphene has an extremely high carrier mobility that can potentially offer an electrical bandwidth of over 500 GHz. However, the bandwidth of the reported graphene-based modulators is only a few tens of gigahertz due to the limitation of the RC constant rather than the carrier transit time. In this paper, a high-speed traveling-wave electro-optic modulator based on a graphene/microfiber structure is proposed and investigated for the first time to the best of our knowledge. The all-in-fiber electro-optic modulation in the graphene/microfiber-modulator is achieved by changing the Fermi level of graphene during its interaction with the evanescent wave of the microfiber. The active length of the modulator is 1.372 mm with a V π of 4.9 V. The coplanar strip electrodes have a characteristic impedance of 54 Ω and a microwave attenuation of 0.967 dB/mm. The mismatch between the microwave and the optical group velocity is 7.38%. A very high speed of 82 GHz 3-dB bandwidth is achieved.

Safety and efficacy of stereoelectroencephalography in pediatric focal epilepsy: a single-center experience.

Patients with medically refractory localization-related epilepsy (LRE) may be candidates for surgical intervention if the seizure onset zone (SOZ) can be well localized. Stereoelectroencephalography (SEEG) offers an attractive alternative to subdural grid and strip electrode implantation for seizure lateralization and localization; yet there are few series reporting the safety and efficacy of SEEG in pediatric patients. The authors review their initial 3-year consecutive experience with SEEG in pediatric patients with LRE. SEEG coverage, SOZ localization, complications, and preliminary seizure outcomes following subsequent surgical treatments are assessed. Twenty-five pediatric patients underwent 30 SEEG implantations, with a total of 342 electrodes placed. Ten had prior resections or ablations. Seven had no MRI abnormalities, and 8 had multiple lesions on MRI. Based on preimplantation hypotheses, 7 investigations were extratemporal (ET), 1 was only temporal-limbic (TL), and 22 were combined ET/TL investigations. Fourteen patients underwent bilateral investigations. On average, patients were monitored for 8 days postimplant (range 3-19 days). Nearly all patients were discharged home on the day following electrode explantation. There were no major complications. Minor complications included 1 electrode deflection into the subdural space, resulting in a minor asymptomatic extraaxial hemorrhage; and 1 in-house and 1 delayed electrode superficial scalp infection, both treated with local wound care and oral antibiotics. SEEG localized the hypothetical SOZ in 23 of 25 patients (92%). To date, 18 patients have undergone definitive surgical intervention. In 2 patients, SEEG localized the SOZ near eloquent cortex and subdural grids were used to further delineate the seizure focus relative to mapped motor function just prior to resection. At last follow-up (average 21 months), 8 of 15 patients with at least 6 months of follow-up (53%) were Engel class I, and an additional 6 patients (40%) were Engel class II or III. Only 1 patient was Engel class IV. SEEG is a safe and effective technique for invasive SOZ localization in medically refractory LRE in the pediatric population. SEEG permits bilateral and multilobar investigations while avoiding large craniotomies. It is conducive to deep, 3D, and perilesional investigations, particularly in cases of prior resections. Patients who are not found to have focally localizable seizures are spared craniotomies.

Using subdural strip electrodes to define functional sensory nerves and the most inferior functional portion of the conus medullaris during detethering surgeries for tethered cord syndrome: a pilot study.

The aim of this study was to investigate the feasibility of using subdural strip electrodes, placed just rostral to the surgical field, to record sensory evoked potentials (SEPs) from the lumbosacral sensory nerves and define the most inferior functional portion of the conus medullaris during detethering surgery for spinal dysraphism and/or tethered cord syndrome (TCS). Six patients, 2 boys and 4 girls, aged 0.5 to 16 years, were enrolled in this study. One patient had lipomyelomeningocele-related, 4 had myelomeningocele-related, and 1 had diastematomyelia and lipomyelomeningocele-related TCS. In addition to the routine preparations that are needed for performing functional mapping and monitoring during surgery for spinal dysraphism and TCS, the patients had a 1 × 4 strip of electrodes placed rostral to the surgical field, where it was secured by a surgeon after opening the dura. With the patient under total intravenous anesthesia, the sensory nerves and conus medullaris were stimulated with a concentric bipolar electrode over the surgical field while SEPs were recorded with the strip electrodes to identify any possible sensory roots with remaining function and the most inferior functional portion of the conus medullaris. The SEP amplitudes that were recorded with the subdural strip electrodes ranged from 4 to 400 μV, and the responses to sensory nerve stimulation were frequently much larger than were those to conus stimulation. Use of the SEP recordings for sensory mapping along with the routine mapping and monitoring techniques allowed detethering to be completed such that none of the patients sustained any new functional deficit after surgery. Recording SEPs from the functional sensory nerves and conus medullaris through subdural strip electrodes proved to be a feasible and valuable tool during detethering surgery in young patients. This approach may help surgeons achieve maximal detethering while preserving important sensory functions, consequently retaining the patient's quality of life.

Language mapping using electrocorticography versus stereoelectroencephalography: A case series

Direct electrical stimulation (DES) is sometimes used in epilepsy surgery to identify areas that may result in language deficits if resected. Extraoperative language mapping is usually performed using electrocorticography (ECOG) — grids and strip electrodes; however, given the better safety profile of stereoelectroencephalogaphy (SEEG), it would be desirable to determine if mapping using SEEG is also effective. We report a case series of fifteen patients that underwent language mapping with either ECOG (5), SEEG (9), or both (1). Six patients in the SEEG group underwent resection or ablation with only mapping via SEEG. No patients in the SEEG group that underwent resective or ablative surgery experienced persistent language deficits. These results suggest that language mapping with SEEG may be considered as a clinically useful alternative to language mapping with ECOG.

Intracranial EEG for seizure focus localization: evolving techniques, outcomes, complications, and utility of combining surface and depth electrodes.

Intracranial electroencephalography (iEEG) provides valuable information that guides clinical decision-making in patients undergoing epilepsy surgery, but it carries technical challenges and risks. The technical approaches used and reported rates of complications vary across institutions and evolve over time with increasing experience. In this report, the authors describe the strategy at the University of Iowa using both surface and depth electrodes and analyze outcomes and complications. The authors performed a retrospective review and analysis of all patients who underwent craniotomy and electrode implantation from January 2006 through December 2015 at the University of Iowa Hospitals and Clinics. The basic demographic and clinical information was collected, including electrode coverage, monitoring results, outcomes, and complications. The correlations between clinically significant complications with various clinical variables were analyzed using multivariate analysis. The Fisher exact test was used to evaluate a change in the rate of complications over the study period. Ninety-one patients (mean age 29 ± 14 years, range 3-62 years), including 22 pediatric patients, underwent iEEG. Subdural surface (grid and/or strip) electrodes were utilized in all patients, and depth electrodes were also placed in 89 (97.8%) patients. The total number of electrode contacts placed per patient averaged 151 ± 58. The duration of invasive monitoring averaged 12.0 ± 5.1 days. In 84 (92.3%) patients, a seizure focus was localized by ictal onset (82 cases) or inferred based on interictal discharges (2 patients). Localization was achieved based on data obtained from surface electrodes alone (29 patients), depth electrodes alone (13 patients), or a combination of both surface and depth electrodes (42 patients). Seventy-two (79.1%) patients ultimately underwent resective surgery. Forty-seven (65.3%) and 18 (25.0%) patients achieved modified Engel class I and II outcomes, respectively. The mean follow-up duration was 3.9 ± 2.9 (range 0.1-10.5) years. Clinically significant complications occurred in 8 patients, including hematoma in 3 (3.3%) patients, infection/osteomyelitis in 3 (3.3%) patients, and edema/compression in 2 (2.2%) patients. One patient developed a permanent neurological deficit (1.1%), and there were no deaths. The hemorrhagic and edema/compression complications correlated significantly with the total number of electrode contacts (p = 0.01), but not with age, a history of prior cranial surgery, laterality, monitoring duration, and the number of each electrode type. The small number of infectious complications precluded multivariate analysis. The number of complications decreased from 5 of 36 cases (13.9%) to 3 of 55 cases (5.5%) during the first and last 5 years, respectively, but this change was not statistically significant (p = 0.26). An iEEG implantation strategy that makes use of both surface and depth electrodes is safe and effective at identifying seizure foci in patients with medically refractory epilepsy. With experience and iterative refinement of technical surgical details, the risk of complications has decreased over time.

Novel designs of dielectric barrier discharge hydride atomizers for atomic spectrometry

Eight designs of dielectric barrier discharge (DBD) atomizers have been constructed and optimized. Subsequently, their performance with atomic absorption (AAS), atomic fluorescence (AFS) and atomic emission (AES) detectors was investigated employing arsane as a model analyte. Although being all based on a planar shaped quartz body, the individual DBD designs differed from each other in the style of electrode attachment, electrode shape and area as well as electrode distance. All the designs studied were found compatible with AAS detection giving comparable sensitivity (between 0.38 and 0.47 s ng−1 As) and detection limit (around 0.2 ng ml−1 As) under optimum atomization conditions. However, significant differences in optimum conditions were found among the designs in terms of the applied voltage that strongly depends on the style of electrode attachment and electrode distance. The design with metal strip electrodes glued to a quartz body requires >14 kV to be operated. The design with sputtered electrodes of the same shape can reach the same sensitivity with 8.5 kV. These values can be further reduced to 6.5 kV, when decreasing the electrode distance from 3 to 1 mm. Selected DBD designs tested have been proven to be compatible with other spectrometric detectors such as AFS reaching detection limit 0.05 ng ml−1 As or AES with detection limit of 30 ng ml−1 As showing the universality of the planar DBD designs and its potential to further applications as well as mechanistic studies.

F118. Somatosensory evoked potential phase reversal for intraoperative localization of central sulcus: A simple technique can make a big difference

Introduction In their talks, neurosurgeons defend that the more aggressive the tumor resection is, longer will be the survival and quality of life. Their main concern in surgeries of the perirolandic tumors is to prevent new neurologic deficits. Among the neurophysiological techniques developed to identify the cortical functional landmarks, the somatosensory evoked potential phase reversal (SEP-PR) allows the intraoperative localization of the central sulcus (CS). The aim of this paper is to highlight the use of this simple technique describing our experience. Methods We studied 45 patients with perirolandic tumors (24 female), mean age of 46.6 y (4–76 y), submitted to tumor resection under total intravenous anesthesia (TIVA) and intraoperative neuromonitoring (IONM) with our standard protocol consisting of SEP-PR, cortical motor mapping (CMM), continuous direct cortical motor evoked potential (DC-MEP) and continuous subcortical motor evoked potential (SUBC-MEP). The SEP-PR was recorded with a strip electrode with 4 or 6 contacts positioned across the central sulcus. Both unipolar (referred to Fz) and bipolar assemblages were used. The median nerve was stimulated at the wrist or the tibial posterior nerve at the ankle, if the strip electrode was positioned between 3 to 8 cm or 0 to 3 cm laterally from the interhemispheric fissure, respectively. Results From the 45 cases, SEP-PR were recorded in 41 allowing the precise localization of the CS, and the start of the CMM. In other 4 patients SEP-PR were not obtained because of intense adhesion of the dura mater. In these cases, motor mapping was done as the first step to localize the motor area what, except for a well preserved cortical anatomy, in our experience seems to be more time-consuming than when it is done after SEP-PR. Interestingly, in 9 cases the CS seams to be outside the craniotomy limits. In these cases, the strip electrode was positioned posteriorly under the edge of the craniotomy trying to reach the CS under the bone, which can be more time consuming. These patients showed a SEP-PR recorded outside the limits of the craniotomy, assuring the surgeon that the CS is not visible. Conclusion The SEP-PR is a simple and easy to perform technique that allows the precise localization of the functional CS. With the CS identification it seems much easier to start the motor mapping. In few cases of reoperation, the placement of the strip can be difficult or even impossible. When the CS is outside the limits of the craniotomy, recording SEP-PR under the bone can confirm that it really is out of the surgical field.

F112. Continuous monitoring with direct cortical and subcortical stimulation for perirolandic tumor resection: The experience of a Brazilian group

Introduction Tumor resection should be maximal for a longer survival and quality of life but the main concern in surgeries of the perirolandic tumors is to prevent new neurologic deficits. Neurophysiologic intraoperative techniques to continuously monitor the motor function are desired to avoid this risk. Direct cortical stimulation (DC-MEP) and subcortical (SUBC-MEP) stimulation have been successfully used for this. The aim of this paper is to present our experience with this technique. Methods We studied 36 of 45 patients with perirolandic tumors (18 female), mean age of 46.6 y (4–76 y), submitted to tumor resection under total intravenous anesthesia (TIVA) and intraoperative neuromonitoring (IONM) with our standard protocol consisting of SEP-PR, cortical motor mapping (CMM), continuous direct cortical motor evoked potential (DC-MEP) and continuous subcortical motor evoked potential (SUBC-MEP). The DC-MEP was elicited using a strip electrode placed over the hand area of the precentral gyrus (anodic stimulation) and recorded with subdermal needle electrodes placed in the contralateral hemibody muscles. SUBC-MEP was elicited through a monopolar aspirator device (cathodic stimulation) and recorded in the same muscles. A train of 4 or 5 pulses with 0,5 ms duration and inter-stimulus interval of 3 ms is applied continuously at 1 Hz alternating between cortical and subcortical. Warning criteria was 50% amplitude decrease for DC-MEP and 3–5 mA for SUBC-MEP. Results From the 45 cases, DC-MEP and SUBC-MEP were recorded in 36 patients, allowing continuous monitoring of the motor pathways. In the remaining 9 cases the surgeons decided for the use of cortical mapping only because the strip electrode positioning would disturb the tumor resection; in these patients, subcortical stimulation was performed in 5 according to the surgeon decision, but not continuously, and in two of them transitory postoperative new neurologic deficits were observed. From the 36 patients monitored with simultaneous DC-MEP and SUBC-MEP, there were no consistent amplitude decrease for DC-MEP and the threshold for SUBC-MEP was above 11 mA in 19 cases, between 6 and 10 mA in 12 and between 3 and 5 mA in 3. Only one patient with 3 mA subcortical threshold had a transitory motor deficit (less than 24 h). Our results are comparable with the previously reported in the literature. Conclusion Despite the few studied cases, it seems for us that continuous monitoring is better than cortical motor mapping alone. The DC-MEP and SUBC-MEP are precise for intraoperative diagnostic and allow a better resection with preservation of the motor pathway. In one case, SUBC-MEP showed the lowest threshold of 3 mA and was followed by a transitory deficit. Simultaneous and continuous monitoring of the cortical and subcortical MEP must be encouraged.

Monitoring the Relationship Between Changes in Cerebral Oxygenation and Electroencephalography Patterns During Cardiopulmonary Resuscitation: A Feasibility Study.

To date, no studies have examined real-time electroencephalography and cerebral oximetry monitoring during cardiopulmonary resuscitation as markers of the magnitude of global ischemia. We therefore sought to assess the feasibility of combining cerebral oximetry and electroencephalography in patients undergoing cardiopulmonary resuscitation and further to evaluate the electroencephalography patterns during cardiopulmonary resuscitation and their relationship with cerebral oxygenation as measured by cerebral oximetry. Extended case series of in-hospital and out-of-hospital cardiac arrest subjects. Tertiary Medical Center. Inclusion criteria: Convenience sample of 16 patients undergoing cardiopulmonary resuscitation during working hours between March 2014 and March 2015, greater than or equal to 18 years. A portable electroencephalography (Legacy; SedLine, Masimo, Irvine, CA) and cerebral oximetry (Equanox 7600; Nonin Medical, Plymouth, MN) system was used to measure cerebral resuscitation quality. Real-time regional cerebral oxygen saturation and electroencephalography readings were observed during cardiopulmonary resuscitation. The regional cerebral oxygen saturation values and electroencephalography patterns were not used to manage patients by clinical staff. In total, 428 electroencephalography images from 16 subjects were gathered; 40.7% (n = 174/428) were artifactual, therefore 59.3% (n = 254/428) were interpretable. All 16 subjects had interpretable images. Interpretable versus noninterpretable images were not related to a function of time or duration of cardiopulmonary resuscitation but to artifacts that were introduced to the raw data such as diaphoresis, muscle movement, or electrical interference. Interpretable data were able to be obtained immediately after application of the electrode strip. Seven distinct electroencephalography patterns were identified. Voltage suppression was commonest and seen during 78% of overall cardiopulmonary resuscitation time and in 15 of 16 subjects at some point during their cardiopulmonary resuscitation. Other observed patterns and their relative prevalence in relation to overall cardiopulmonary resuscitation time were theta background activity 8%, delta background activity 5%, bi frontotemporal periodic discharge 4%, burst suppression 2%, spike and wave 2%, and rhythmic delta activity 1%. Eight of 16 subjects had greater than one interpretable pattern. At regional cerebral oxygen saturation levels less than or equal to 19%, the observed electroencephalography pattern was exclusively voltage suppression. Delta background activity was only observed at regional cerebral oxygen saturation levels greater than 40%. The remaining patterns were observed throughout regional cerebral oxygen saturation categories above a threshold of 20%. Real-time monitoring of cerebral oxygenation and function during cardiac arrest resuscitation is feasible. Although voltage suppression is the commonest electroencephalography pattern, other distinct patterns exist that may correlate with the quality of cerebral resuscitation and oxygen delivery.

Increased nationwide use of stereoencephalography for intracranial epilepsy electroencephalography recordings

Intracranial electroencephalography (iEEG) can be performed using minimally invasive stereo-electroencephalography (SEEG) or by implanting subdural electrodes via a craniotomy or multiple burr holes. There is anecdotal evidence that SEEG is becoming more common in the United States, though this has yet to be quantified. To address this question, all SEEG and burr hole/craniotomy subdural iEEG procedures were extracted from the Centers for Medicare and Medicaid Services Part B data files for the years 2000–2016. National trends were compared over time. In 2016, SEEG became the most frequently performed intracranial monitoring procedure in the Medicare population, increasing from 28.8% of total cases in 2000 to 43.1% in 2016 (p = 0.02). The proportion of strip electrode cases (through burr holes) significantly declined, while the frequency of craniotomies for subdural grid placement did not significantly change. These data are consistent with a nationwide increase in the utilization of SEEG with a concomitant decline in burr hole placement of subdural strip electrodes in the United States. The factors driving these changes are unknown, but are likely due in part to the desire for minimally invasive surgical options.

Heterogeneous Iron-Containing Carbon Gels As Catalysts for Oxygen and Carbon Dioxide Electroreductions – Rotating Ring-Disk Voltammetric Studies

There has been growing interest in the development of highly active catalysts for electroreduction of oxygen that could be effectively utilized in low-temperature fuel cells. The important practical issue is related to the need of lowering costs of catalysts by substituting the noble metals with inexpensive abundant elements. In this respect materials containing metallic moieties coordinated by nitrogen atoms embedded in the carbon matrix (M-N-C) are recognized as most suitable candidates to replace platinum catalysts. More recently, the approach of using such biomimetic centers has been considered for the carbon dioxide reduction, the reaction which permits generation of carbon-based chemicals, fuels or syngas. Since both reactions (O2 and CO2 reductions) are characterized by slow kinetics and may proceed through different pathways producing various products, their efficiency and selectivity still remain fundamental problems for practical applications. It is well established that the best performing M-N-C catalysts (with high specific surface area and large fraction of micropores) are produced from nitrogen-containing polymeric precursors. In these study we present a new type of self-supporting M-N-C materials, namely nitrogen and sulfur co-doped iron containing highly porous carbon gels (obtained through pyrolysis of organic gels) as efficient non-precious metal catalysts for both the oxygen and carbon dioxide electroreductions. The precursors of the catalysts were prepared via the sol-gel polycondensation (induced with iron(III) cations) of resorcinol together with the mixture of two heterocyclic aldehydes containing nitrogen and sulfur. The role of S is to produce carbon gels with high specific surface areas (e.g. when compared to carbon gels containing solely N heteroatom). It is commonly accepted that rotating ring(platinum)-disk(glassy carbon) electrode voltammetry can be effective diagnostic tool for elucidation of the performance and selectivity (towards water or hydrogen peroxide) of the oxygen electroreduction. We are going to demonstrate that a combination of the rotating ring-disk electrode methodology and stripping type voltammetry (at platinum ring) can be also used for the determination of the reaction mechanism, competitive formation (evolution) of hydrogen, and determination of CO-type adsorbates generated at the catalyst during the CO2 electroreduction.

Engineered fungus derived FAD-dependent glucose dehydrogenase with acquired ability to utilize hexaammineruthenium(III) as an electron acceptor

Fungal FAD-dependent glucose dehydrogenases (FADGDHs) are considered to be superior enzymes for glucose sensor strips because of their insensitivity to oxygen and maltose. One highly desirable mediator for enzyme sensor strips is hexaammineruthenium(III) chloride because of its low redox potential and high storage stability. However, in contrast to glucose oxidase (GOx), fungal FADGDH cannot utilize hexaammineruthenium(III) as electron acceptor. Based on strategic structure comparison between FADGDH and GOx, we constructed a mutant of Aspergillus flavus-derived FADGDH, capable of utilizing hexaammineruthenium(III) as electron acceptor: AfGDH-H403D. In AfGDH-H403D, a negative charge introduced at the pathway-entrance leading to the FAD attracts the positively charged hexaammineruthenium(III) and guides it into the pathway. The corresponding amino acid in wild-type GOx is negatively charged, which explains the ability of GOx to utilize hexaammineruthenium(III) as electron acceptor. Electrochemical measurements showed a response current of 46.0 μA for 10 mM glucose with AfGDH-H403D and hexaammineruthenium(III), similar to that with wild-type AfGDH and ferricyanide (47.8 μA). Therefore, AfGDH-H403D is suitable for constructing enzyme electrode strips with hexaammineruthenium(III) chloride as sole mediator. Utilization of this new, improved fungal FADGDH should lead to the development of sensor strips for blood glucose monitoring with increased accuracy and less stringent packing requirements.

Understanding Spreading Depression from Headache to Sudden Unexpected Death.

Spreading depression (SD) is a neurophysiological phenomenon characterized by abrupt changes in intracellular ion gradients and sustained depolarization of neurons. It leads to loss of electrical activity, changes in the synaptic architecture, and an altered vascular response. Although SD is often described as a unique phenomenon with homogeneous characteristics, it may be strongly affected by the particular triggering event and by genetic background. Furthermore, SD may contribute differently to the pathogenesis of widely heterogeneous clinical conditions. Indeed, clinical disorders related to SD vary in their presentation and severity, ranging from benign headache conditions (migraine syndromes) to severely disabling events, such as cerebral ischemia, or even death in people with epilepsy. Although the characteristics and mechanisms of SD have been dissected using a variety of approaches, ranging from cells to human models, this phenomenon remains only partially understood because of its complexity and the difficulty of obtaining direct experimental data. Currently, clinical monitoring of SD is limited to patients who require neurosurgical interventions and the placement of subdural electrode strips. Significantly, SD events recorded in humans display electrophysiological features that are essentially the same as those observed in animal models. Further research using existing and new experimental models of SD may allow a better understanding of its core mechanisms, and of their differences in different clinical conditions, fostering opportunities to identify and develop targeted therapies for SD-related disorders and their worst consequences.

Super flexible GaN light emitting diodes using microscale pyramid arrays through laser lift-off and dual transfer.

We demonstrated a method to obtain super flexible LEDs, based on high quality pyramid arrays grown directly on sapphire substrates. Laser lift-off (LLO) and dual transfer processes were applied to transfer pyramid arrays face up onto the flexible substrates, which is more efficient than back light emission. Ag grid and Ag nanowires were employed as the electrical connection. No significant performance reduction appeared until the device reached a curvature radius of 0.5 mm. The performance reduction results from cracks appearing at the junction of the Ag grid, which can be improved by replacing the Ag grid with a strip electrode.

Enhanced co-registration methods to improve intracranial electrode contact localization.

BackgroundElectrode contact locations are important when planning tailored brain surgeries to identify pathological tissue targeted for resection and conversely avoid eloquent tissue. Current methods employ trained experts to use neuroimaging scans that are manually co-registered and localize contacts within ~2 mm. Yet, the state of the art is limited by either the expertise needed for each type of intracranial electrode or the inter-modality co-registration which increases error, reducing accuracy. Patients often have a variety of strips, grids and depths implanted; therefore, it is cumbersome and time-consuming to apply separate localization methods for each type of electrode, requiring expertise across different approaches.New methodTo overcome these limitations, a computational method was developed by separately registering an implant magnetic resonance image (MRI) and implant computed tomography image (CT) to the pre-implant MRI, then calculating an iterative closest point transformation using the contact locations extracted from the signal voids as ground truth.ResultsThe implant MRI is robustly co-registered to the pre-implant MRI with a boundary-based registration algorithm. By extracting and utilizing ‘signal voids’ (the metal induced artifacts from the implant MRI) as electrode fiducials, the novel method is an all-in-one approach for all types of intracranial electrodes while eliminating inter-modality co-registration errors.Comparison with existing methodsThe distance between each electrode centroid and the brain's surface was measured, for the proposed method as well as the state of the art method using two available software packages, SPM 12 and FSL 4.1. The method presented here achieves the smallest distances to the brain's surface for all strip and grid type electrodes, i.e. contacts designed to rest directly on the brain surface.ConclusionWe use one of the largest reported sample sizes in localization studies to validate this novel method for localizing different kinds of intracranial electrodes including grids, strips and depth electrodes.

High resolution gamma-ray spectroscopy at high count rates with a prototype High Purity Germanium detector

High-resolution gamma-ray spectrometers are required for applications in nuclear safeguards, emergency response, and fundamental nuclear physics. To overcome one of the shortcomings of conventional High Purity Germanium (HPGe) detectors, we have developed a prototype device capable of achieving high event throughput and high energy resolution at very high count rates. This device, the design of which we have previously reported on, features a planar HPGe crystal with a reduced-capacitance strip electrode geometry. This design is intended to provide good energy resolution at the short shaping or digital filter times that are required for high rate operation and which are enabled by the fast charge collection afforded by the planar geometry crystal. In this work, we report on the initial performance of the system at count rates up to and including two million counts per second.

Fabrication of monolithic diamond photodetector with microlenses.

A monolithic diamond photodetector with microlenses is fabricated by etching microlens arrays (MLAs) on single crystal diamond surface and patterning tungsten electrode strips on the edge of these arrays. Firstly, compact MLAs are etched on half of diamond sample surface by thermal reflow method. Secondly, via magnetron sputtering technique, two sets of interdigitated tungsten electrodes are patterned on the sample surface, one set is on the edge of MLAs, the other set is on the planar area. The optoelectronic performances of photodetectors have been investigated and indicated that the photocurrent of microlens photodetector increases by 74.8 percent at 10 V under 220 nm UV light illumination by comparing with that in planar case. Simulations of photodetectors' electrical and optical properties have been carried out, illustrating an improvement of charge collection ability and light absorption efficiency in microlens case. Furthermore, the present device structure can be extended to other semiconductor photodetectors.