Transient Spike Research Articles

Biomarker evidence of algal-microbial community changes linked to redox and salinity variation, Upper Devonian Chattanooga Shale (Tennessee, USA)

AbstractLate Devonian marine systems were characterized by major environmental perturbations and associated biotic community changes linked to climate change and widespread oceanic anoxia. Here, we provide high-resolution lipid biomarker chemostratigraphic records from the Upper Devonian Chattanooga Shale (Tennessee, USA) to investigate algal-microbial community changes in the southern Illinois Basin that were related to contemporaneous shifts in marine redox (as proxied by trace metals, Fe-species, and Corg/P) and salinity conditions (as proxied by B/Ga, Sr/Ba, and S/total organic carbon). The Frasnian was characterized by dominantly bacterial lipids (high hopane/sterane), near-marine salinity, and a shift from oxic to increasingly reducing conditions in response to increasing organic carbon sinking fluxes. Aryl isoprenoids and aryl isoprenoid ratios reveal that the O2-H2S chemocline was unstable and intermittently shallow (i.e., within the photic zone). The Frasnian-Famennian boundary was marked by a shift in microalgal community composition toward green algal (e.g., prasinophyte) dominance (lower C27 and higher C28 and C29 steranes), a sharp reduction in watermass salinity, and a stable O2-H2S chemocline below the photic zone, conditions that persisted until nearly the end of the Famennian. We infer that changing watermass conditions, especially a sharp reduction in salinity to possibly low-brackish conditions (<10 psu), were the primary cause of concurrent changes in the microalgal community, reflecting tolerance of low-salinity conditions by green algae. Transient spikes in moretane/hopane (M/H) ratios may record enhanced terrestrial weathering at the Frasnian-Famennian and Devonian–Carboniferous boundaries, triggered by coeval glacio-eustatic falls and increased inputs of soil organic matter. High M/H and pristane/phytane, in combination with low chemical index of alteration and K/Al, record a decrease in chemical weathering intensity during the Famennian that may have been due to contemporaneous climatic cooling, and a concurrent reduction in silt content may reflect stabilization of land surfaces by vascular plants and resulting reduced sediment yields. This study demonstrates the effectiveness of combining organic and inorganic geochemical proxies (including novel paleosalinity indices) for determination of environmental controls on the composition and productivity of plankton communities in paleomarine systems.

T-type Calcium Channels in Health and Disease.

Low Voltage-Activated (LVA) T-type calcium channels are characterized by transient current and Low Threshold Spikes (LTS) that trigger neuronal firing and oscillatory behavior. Combined with their preferential localization in dendrites and their specific "window current", T-type calcium channels are considered to be key players in signal amplification and synaptic integration. Assisted by the emerging pharmacological tools, the structural determinants of channel gating and kinetics, as well as novel physiological and pathological functions of T-type calcium channels, are being uncovered. In this review, we provide an overview of structural determinants in T-type calcium channels, their involvement in disorders and diseases, the development of novel channel modulators, as well as Structure-Activity Relationship (SAR) studies that lead to rational drug design.

Is Carbon Dioxide Insufflation During Endoscopy in Children as Safe and as Effective as We Think?

Distension of the gastrointestinal lumen is crucial for visualization and advancement during endoscopic procedures. An increasing number of pediatric centers now use carbon dioxide (CO2) preferentially over air as many adult studies and a few pediatric studies have concluded that CO2 is better tolerated than air, especially for colonoscopy. The aim of the study was to determine if CO2 is as safe and as effective as air and if it reduces abdominal discomfort and distension in children undergoing upper endoscopy and colonoscopy. Double blinded, prospective, randomized clinical study. Patient- and nursing-reported outcomes of pain and distension were recorded. End tidal CO2 (EtCO2) was monitored continuously with a CO2-sampling nasal cannula for patients undergoing procedural sedation and via the endotracheal tube for those who were intubated. One hundred seventy-eight patients with 180 procedures were enrolled, 91 procedures were randomized to receive CO2, and 89 to air. Groups did not differ significantly with respect to nursing-assessed abdominal discomfort, change in girth from baseline, or endoscopist-perceived ease of inflation. Use of CO2 was associated with transient spikes in the EtCO2 (≥60 mmHg) in a significant number of patients during sedated upper endoscopy without endotracheal intubation. There was a reduction of bloating and flatulence for all procedures in the CO2 group. The benefits of using CO2 for insufflation were minimal in our patients. The observed transient elevations of EtCO2 during sedated upper endoscopy raise concerns of possible systemic hypercarbia. The wisdom of its routine use for all pediatric endoscopic procedures is questioned.

Language Consistency and Stock Market Trading Volume

An information-theoretic measure of language consistency is constructed from the text of 13 years of trade journal articles on the biotechnology industry. This measure is then related to the trading volume of a representative portfolio of biotechnology stocks. Findings indicate that language consistency and trading volume have a joint (positive) influence on each other over the long term; however, sharp drops in consistency are also predictive of transient spikes in trading volume. The significance of these findings is discussed in relation to modern theories of legitimation and the economics of surprise.

A volcanic scenario for the Frasnian–Famennian major biotic crisis and other Late Devonian global changes: More answers than questions?

Abstract Although the prime causation of the Late Devonian Frasnian–Famennian (F–F) mass extinction remains conjectural, such destructive factors as the spread of anoxia and rapid upheavals in the runaway greenhouse climate are generally accepted in the Earth-bound multicausal scenario. In terms of prime triggers of these global changes, volcanism paroxysm coupled with the Eovariscan tectonism has been suspected for many years. However, the recent discovery of multiple anomalous mercury enrichments at the worldwide scale provides a reliable factual basis for proposing a volcanic–tectonic scenario for the stepwise F–F ecological catastrophe, specifically the Kellwasser (KW) Crisis. A focus is usually on the cataclysmic emplacement of the Viluy large igneous province (LIP) in eastern Siberia. However, the long-lasted effusive outpouring was likely episodically paired with amplified arc magmatism and hydrothermal activity, and the rapid climate oscillations and glacioustatic responses could in fact have been promoted by diverse feedbacks driven by volcanism and tectonics. The anti-greenhouse effect of expanding intertidal–estuarine and riparian woodlands during transient CO2-greenhouse spikes was another key feedback on Late Devonian land. An updated volcanic press-pulse model is proposed with reference to the recent timing of LIPs and arc magmatism and the revised date of 371.9 Ma for the F–F boundary. The global changes were initiated by the pre-KW effusive activity of LIPs, which caused extreme stress in the global carbonate ecosystem. Nevertheless, at least two decisive pulses of sill-type intrusions and/or kimberlite/carbonatite eruptions, in addition to flood basalt extrusions on the East European Platform, are thought to have eventually led to the end-Frasnian ecological catastrophe. These stimuli have been enhanced by effective orbital modulation. An attractive option is to apply the scenario to other Late Devonian global events, as evidences in particular by the Hg spikes that coincide with the end-Famennian Hangenberg Crisis.

Microvascular changes in macula and optic nerve head after femtosecond laser-assisted LASIK: an optical coherence tomography angiography study

BackgroundTo measure the microcirculation change of macula and optic nerve head before and after femtosecond laser assisted laser in situ keratomileusis.MethodsIn total 45 eyes from 45 subjects, who underwent FS-LASIK during June 2017 to December 2017 in Guangdong Provincial People’s Hospital, were recruited in this study. Vessel density in macula and optic nerve head were measured by optical coherence tomography angiography before and after transient elevation in intraocular pressure caused by application of suction ring during surgery.ResultsVessel density (VD) at superficial (SCP) plexus of macular region did not differ after surgery (F(3,132) = 1.41, P = 0.24), while the deep (DCP) plexus of macular region significantly decreased 1 day after surgery (P = 0.001) but returned to its baseline value 1 month postoperatively (P = 0.1). Vessel density of optic nerve head region had no significant changes after surgery (F(2.51,95.18) = 0.6, P = 0.59).ConclusionsA short-term temporary decrease of vessel density at deep layer of macular region was observed in eyes undergoing FS-LASIK. However, the retinal capillary density went back to preoperative level 1 month after surgery. Therefore, transient IOP spike during FS-LASIK did not cause long-term decline of retinal microcirculation.

Different dynamical behaviors induced by slow excitatory feedback for type II and III excitabilities

Neuronal excitability is classified as type I, II, or III, according to the responses of electronic activities, which play different roles. In the present paper, the effect of an excitatory autapse on type III excitability is investigated and compared to type II excitability in the Morris-Lecar model, based on Hopf bifurcation and characteristics of the nullcline. The autaptic current of a fast-decay autapse produces periodic stimulations, and that of a slow-decay autapse highly resembles sustained stimulations. Thus, both fast- and slow-decay autapses can induce a resting state for type II excitability that changes to repetitive firing. However, for type III excitability, a fast-decay autapse can induce a resting state to change to repetitive firing, while a slow-decay autapse can induce a resting state to change to a resting state following a transient spike instead of repetitive spiking, which shows the abnormal phenomenon that a stronger excitatory effect of a slow-decay autapse just induces weaker responses. Our results uncover a novel paradoxical phenomenon of the excitatory effect, and we present potential functions of fast- and slow-decay autapses that are helpful for the alteration and maintenance of type III excitability in the real nervous system related to neuropathic pain or sound localization.

A low dropout voltage regulator with a transient voltage spikes reducer and improved figure of merit

An area efficient output capacitor-free low dropout [LDO] voltage regulator with an improved figure of merit is presented in this paper. The proposed LDO regulator consists of a novel, dynamically biased error amplifier that reduces overshoot and undershoot voltage spikes arising from abrupt load changes. Source bulk modulation is employed to enhance the current driving capability of the pass transistor. An adaptive biasing scheme is also used along with dynamic biasing to improve the current efficiency of the system. The on-chip capacitor required for proper working of the LDO regulator is only 35 pF. The proposed LDO regulator is designed and simulated in 180 nm standard CMOS technology. The LDO regulator exhibits a line regulation of 1.67 mV/V and a load regulation of 100 µV /mA. When load changes from 0 mA to 100 mA in 1 µs, an undershoot of 148 mV and an overshoot of 172 mV are observed. The measured power supply rejection ratio is 25 dB at 100 kHz. The working of the proposed LDO regulator has been tested under all process corners and Monte-Carlo statistical analysis reveals that it is robust against process variations and local mismatch.

Bioelectrical domain walls in homogeneous tissues.

Electrical signaling in biology is typically associated with action potentials, transient spikes in membrane voltage that return to baseline. Hodgkin-Huxley and related conductance-based models of electrophysiology belong to a more general class of reaction-diffusion equations which could, in principle, support spontaneous emergence of patterns of membrane voltage which are stable in time but structured in space. Here we show theoretically and experimentally that homogeneous or nearly homogeneous tissues can undergo spontaneous spatial symmetry breaking through a purely electrophysiological mechanism, leading to formation of domains with different resting potentials separated by stable bioelectrical domain walls. Transitions from one resting potential to another can occur through long-range migration of these domain walls. We map bioelectrical domain wall motion using all-optical electrophysiology in an engineered cell line and in human induced pluripotent stem cell (iPSC)-derived myoblasts. Bioelectrical domain wall migration may occur during embryonic development and during physiological signaling processes in polarized tissues. These results demonstrate that nominally homogeneous tissues can undergo spontaneous bioelectrical symmetry breaking.

Real-world efficacy of the Hydrus microstent in Black and Afro-Latinx patients with glaucoma: a retrospective study.

Purpose:The purpose was to determine the real-world efficacy of phacoemulsification cataract surgery and Hydrus microstent in Black and Afro-Latinx patients with glaucoma.Methods:A retrospective noncomparative single-center study of 76 Black and Afro-Latinx patients with glaucoma who underwent phacoemulsification cataract surgery and Hydrus microstent placement for treatment of glaucoma at single practice. Investigated parameters were intraocular pressure (IOP), number of medications, mean deviation on visual field test, and visual acuity. Patients were also subgrouped into mild, moderate, and advance glaucoma for further analysis.Results:We reviewed a total of 76 patients who had 6 months of follow up in the study. The mean number of medications decreased significantly from 2.6 ± 1.5 preoperatively to 0.72 ± 1.4 in 6 months (p < 0.0010), while IOP decreased from 14.7 ± 3.7 to 13.9 ± 4.3 (p = 0.25). At 6 months, 55 patients (74%) of all patients were medication free (n = 27, 84.4% mild glaucoma; n = 17, 70.8% moderate glaucoma; n = 10, 50% advance glaucoma). There was significant improvement in visual acuity (p < 0.00010) and stabilization of mean deviation on visual field test (baseline −9.2; 6 months −9.1; p = 0.22). The most common adverse effect was a transient IOP spike and transient corneal edema (n = 6, 7.9%; n = 6, 7.9%, respectively) with spontaneous resolution in all cases. No sight-threatening complications were reported at 6 months.Conclusion/clinical relevance:This 6-month retrospective study demonstrated the efficacy of phacoemulsification cataract surgery and Hydrus microstent in reducing the medication burden while maintaining lower IOP in Black and Afro-Latinx patients with glaucoma.

Processes of change in cognitive behavioral therapy for treatment-resistant depression: psychological flexibility, rumination, avoidance, and emotional processing

Recent clinical research suggests that facilitating psychological flexibility and emotional processing and decreasing rumination and avoidance are important tasks of treatment for disorders characterized by entrenched patterns of psychopathology, such as major depressive disorder. The current study examined these processes as predictors of treatment outcomes in a subsample of depressed adult patients (n = 49) who had not fully responded to antidepressant medication and were randomized to receive cognitive–behavioral therapy (CBT). Target variables were coded from session recordings at baseline and in the vicinity of two therapeutic transition points: a sudden gain (improvement) and a transient spike in depression symptoms, or at similar periods for those without such transitions. Results indicated that psychological flexibility during the pre-sudden gain period predicted less depression at 12-month follow-up, beyond baseline symptoms and other co-occurring processes. Interaction analyses revealed that when flexibility was low during the post-spike period, avoidance and rumination predicted higher depressive symptoms, whereas emotional processing predicted lower symptoms at the 12-month follow-up. When flexibility was high, none of these variables were associated with outcome. Together, these findings highlight psychological flexibility as a key therapeutic target in CBT for treatment-resistant depression and might have implications for relapse prevention.

Early transient intraocular pressure spike after cataract surgery in highly myopic cataract eyes and associated risk factors

PurposeTo investigate the incidence of the early transient intraocular pressure (IOP) spike after cataract surgery in eyes with highly myopic cataract (HMC) and associated risk factors.MethodsConsecutive patients treated with phacoemulsification...

A Sub-1-V 100-mA OCL-LDO Regulator With Process-Temperature-Aware Design for Transient Sustainability

In this article, an output-capacitorless low-dropout (OCL-LDO) regulator that features low-power, small-transient-spike, and process-temperature (PT)-aware design for transient sustainability is presented. The circuit architecture is based on the improved PT-aware current source for keeping stable bandwidth and the proposed PT-aware transistor biasing network in conjunction of dual fast local feedback (DFLF) loops in a single power transistor stage to yield both enhanced and sustained transient metrics under a sub-1-V supply. Fabricated in 40-nm CMOS technology, the regulator can deliver a full-load current of 100 mA at a 100-pF load under a 0.75-V supply. From the measured results of 12 samples, it consumes an average quiescent power of 19.5 $\mu \text{W}$ and quiescent current of 26 $\mu \text{A}$ . It displays an average settling time of 414 ns for a full-load current of 100 mA at room temperature. The average load transient voltage spike is 23.9 mV and small when compared to the reported works at a similar level of load current. Finally, the process corner simulations at different temperatures together with the 12 measured samples at temperature corners have validated the sustainability of transient metrics.

Modeling excitability in cerebellar stellate cells: Temporal changes in threshold, latency and frequency of firing

Cerebellar stellate cells are inhibitory molecular interneurons that regulate the firing properties of Purkinje cells, the sole output of cerebellar cortex. Recent evidence suggests that these cells exhibit temporal increase in excitability during whole-cell patch-clamp configuration in a phenomenon termed runup. They also exhibit a non-monotonic first-spike latency profile as a function of the holding potential in response to a fixed step-current. In this study, we use modeling approaches to unravel the dynamics of runup and categorize the firing behavior of cerebellar stellate cells as either type I or type II oscillators. We then extend this analysis to investigate how the non-monotonic latency profile manifests itself during runup. We employ a previously developed, but revised, Hodgkin–Huxley type model to show that stellate cells are indeed type I oscillators possessing a saddle node on an invariant cycle (SNIC) bifurcation. The SNIC in the model acts as a “threshold” for tonic firing and produces a slow region in the phase space called the ghost of the SNIC. The model reveals that (i) the SNIC gets left-shifted during runup with respect to Iapp=Itest in the current-step protocol, and (ii) both the distance from the stable limit cycle along with the slow region produce the non-monotonic latency profile as a function of holding potential. Using the model, we elucidate how latency can be made arbitrarily large for a specific range of holding potentials close to the SNIC during pre-runup (post-runup). We also demonstrate that the model can produce transient single spikes in response to step-currents entirely below ISNIC, and that a pair of dynamic inhibitory and excitatory post-synaptic inputs can robustly evoke action potentials, provided that the magnitude of the inhibition is either low or high but not intermediate. Our results show that the topology of the SNIC is the key to explaining such behaviors.

Cavitation erosion mechanisms in Co-based coatings exposed to seawater.

The cavitation erosion (CE) of most materials in seawater is more serious than in fresh water due to the onset of corrosion; however, in a previous study we reported results that contradict this widely accepted trend. In this research our objective is to provide fundamental insight into the mechanisms that may be responsible for these earlier results. To accomplish this objective, two types of Co-based coatings, prepared by high velocity oxygen fuel (HVOF) spraying system, were used to further investigate the underlying corrosion-mitigating CE mechanism in seawater. Accordingly, the influence of spraying parameters on microstructure, composition and mechanical properties of the coatings was analyzed on the basis of SEM, XRD, Raman spectroscopy, Vicker's hardness and nano-indentation results. Electrochemical corrosion tests were used to evaluate the corrosion behavior of the Co-based coatings. Their CE performances in seawater and deionized water were comparatively studied by a vibratory apparatus. Results demonstrated that a higher flame temperature facilitated the oxides formation with associated improvements in compactness, hardness and toughness of the coatings. The presence of alumina in combination with the oxides formed in-situ facilitated the formation of an oxidation film on surfaces, and effectively enhanced the charge transfer resistance of the coating, thereby significantly improving the corrosion resistance in seawater. Metallic Co was not only more easily oxidized but also more readily corroded than the alloyed Co. Compactness was identified as an important factor affecting CE resistance of coatings in deionized water, because defects facilitate the nucleation and eventual collapse of bubbles. Moreover, bubble collapse produced a transient high temperature spike in excess of 600 °C that also caused Co and Cr elements to oxidize. Because the CE tests were carried out in seawater, additional Co3O4 and Cr2O3 were generated owing to corrosion that more effectively increased the surface compactness and mechanical properties of the coatings. This behavior was particular notable for coatings with metallic Co and Cr, which should be why seawater corrosion could weaken the CE of Co-based coatings.

Provisioning Short-Term Traffic Fluctuations in Elastic Optical Networks

Transient traffic spikes are becoming a crucial challenge for network operators from both user-experience and network-maintenance perspectives. Different from long-term traffic growth, the bursty nature of short-term traffic fluctuations makes it difficult to be provisioned effectively. Luckily, next-generation elastic optical networks (EONs) provide an economical way to deal with such short-term traffic fluctuations. In this paper, we go beyond conventional network reconfiguration approaches by proposing the novel lightpath-splitting scheme in EONs. In lightpath splitting, we introduce the concept of SplitPoints to describe how lightpath splitting is performed. Lightpaths traversing multiple nodes in the optical layer can be split into shorter ones by SplitPoints to serve more traffic demands by raising signal modulation levels of lightpaths accordingly. We formulate the problem into a mathematical optimization model and linearize it into an integer linear program (ILP). We solve the optimization model on a small network instance and design scalable heuristic algorithms based on greedy and simulated annealing approaches. Numerical results show the tradeoff between throughput gain and negative impacts like traffic interruptions. Especially, by selecting SplitPoints wisely, operators can achieve almost twice as much throughput as conventional schemes without lightpath splitting.

A Family of Step-Up Series–Parallel Dual Resonant Switched-Capacitor Converters With Wide Regulation Range

In this paper, a family of new step-up series–parallel dual resonant switched-capacitor converters (SP-DRSCs) is proposed to extend the conversion ratio for high step-up applications. The converters feature a wide gain range, continuously adjustable, and enhanced light-load voltage regulation. All flying capacitors operate in resonance, eliminating high transient current spikes and charge sharing losses. Thus, zero-current-switching (ZCS) turn- on for all transistors and ZCS turn- off for all diodes are achieved. A comprehensive analysis of the operation principle, voltage-gain curves, stable regulation range, and voltage and current stress is given. An analytical method to quantify the passive component volume for the group of step-up dual resonance switched-capacitor converters is presented. Further design considerations to optimize the passive component volume of the proposed SP-DRSC and the effect of bulky bypass capacitors on the volume are discussed.

Multi-Resonance-Core-Based Dickson Resonant Switched-Capacitor Converters With Wide Regulation

The Cuk dual resonance core (DRC) realizes overlapped dual resonance to regulate its output voltage. However, the DRC configuration was only applied to the Fibonacci switched-capacitor converter (SCC), series–parallel SCC, and voltage doubler. In this paper, the Cuk DRC is modified and then is extended to the Dickson SCC to form a multi-resonance-core-based (MRC) Dickson resonant switched-capacitor converter. All charging and discharging loops achieve soft charging, and so the inherent capacitor charge sharing loss and the high current transient spikes are eliminated. The modular configuration makes the MRC Dickson easy to be extended to a higher voltage level. The on -time fixed frequency modulation is adopted, all transistors being turned on with zero-current-switching (ZCS) operation and all diodes being turned off with ZCS operation. Most importantly, the conversion ratio of the MRC Dickson can be regulated continuously, widely, and efficiently even at light load condition, which is a huge advantage over the traditional Dickson SCC with limited control headroom. A comprehensive analysis of the operation principle, voltage-gain curve, component stress analysis, and output characteristic is provided. The converter operation principle and regulation capability were verified by both simulation and experiment.

No Evidence for a Large Atmospheric CO2 Spike Across the Cretaceous‐Paleogene Boundary

AbstractCurrently, there is only one paleo‐CO2 record from plant macrofossils that has sufficient stratigraphic resolution to potentially capture a transient spike related to rapid carbon release at the Cretaceous‐Paleogene (K‐Pg) boundary. Unfortunately, the associated measurements of stomatal index are off‐calibration, leading to a qualitative interpretation of &gt;2,300‐ppm CO2. Here we reevaluate this record with a paleo‐CO2 proxy based on leaf gas exchange principles. We also test the proxy with three living species grown at 500‐ and 1,000‐ppm CO2, including the nearest living relative of the K‐Pg fern, and find a mean error rate of ~22%, which is comparable to other leading paleo‐CO2 proxies. Our fossils record a ~250‐ppm increase in CO2 across the K‐Pg boundary from ~625 to ~875 ppm. A small CO2 spike associated with the end‐Cretaceous mass extinction is consistent with many temperature records and with carbon cycle modeling of Deccan volcanism and the meteorite impact.

Excitable dynamics through toxin-induced mRNA cleavage in bacteria.

Toxin-antitoxin (TA) systems in bacteria and archaea are small genetic elements consisting of the genes coding for an intracellular toxin and an antitoxin that can neutralize this toxin. In various cases, the toxins cleave the mRNA. In this theoretical work we use deterministic and stochastic modeling to explain how toxin-induced cleavage of mRNA in TA systems can lead to excitability, allowing large transient spikes in toxin levels to be triggered. By using a simplified network where secondary complex formation and transcriptional regulation are not included, we show that a two-dimensional, deterministic model captures the origin of such toxin excitations. Moreover, it allows to increase our understanding by examining the dynamics in the phase plane. By systematically comparing the deterministic results with Gillespie simulations we demonstrate that even though the real TA system is intrinsically stochastic, toxin excitations can be accurately described deterministically. A bifurcation analysis of the system shows that the excitable behavior is due to a nearby Hopf bifurcation in the parameter space, where the system becomes oscillatory. The influence of stress is modeled by varying the degradation rate of the antitoxin and the translation rate of the toxin. We find that stress increases the frequency of toxin excitations. The inclusion of secondary complex formation and transcriptional regulation does not fundamentally change the mechanism of toxin excitations. Finally, we show that including growth rate suppression and translational inhibition can lead to longer excitations, and even cause excitations in cases when the system would otherwise be non-excitable. To conclude, the deterministic model used in this work provides a simple and intuitive explanation of toxin excitations in TA systems.