High Frequency Activity Research Articles

Oxygen-vacancy-rich Ru-clusters decorated Co/Ce oxides modifying ZIF-67 nanocubes as a high-efficient catalyst for NaBH4 hydrolysis

Designing a cost-effective and high-performance catalyst for NaBH4 hydrolysis is a significant step in developing a sustainable hydrogen source. Herein, we prepared a cost-effective Ru-clusters decorated cobalt-cerium oxides coating ZIF-67 (Ru/Co6Ce1@ZIF-67) catalyst via a facile reduction method, displaying high performance and exceptional reusability in alkaline NaBH4 solution. The optimized catalyst exhibits a high hydrogen generation rate (HGR, 5726.1 mL min−1 g−1), turnover frequency (TOF, 413.9 molH2 min−1molRu−1), and low activation energy (Ea, 53.0 kJ mol−1), surpassing most of the recently reported catalysts. Furthermore, the catalytic performance does not change considerably after five cycles, indicating the catalyst's multi-cycle reusability. Studies imply the uniquely synergistic effect of Ru, Co/Ce oxides, abundant oxygen vacancies, as well as the porous nanocube structure, enabling the catalysts to possess high metal dispersion, outstanding catalytic performance and exceptional reusability. This work will open light on using an oxygen vacancies-rich strategy to design a high-activity catalyst for promoting NaBH4 hydrolysis.

Distinct interacting cortical networks for stimulus-response and repetition-suppression

Non-invasive studies consider the initial neural stimulus response (SR) and repetition suppression (RS) – the decreased response to repeated sensory stimuli – as engaging the same neurons. That is, RS is a suppression of the SR. We challenge this conjecture using electrocorticographic (ECoG) recordings with high spatial resolution in ten patients listening to task-irrelevant trains of auditory stimuli. SR and RS were indexed by high-frequency activity (HFA) across temporal, parietal, and frontal cortices. HFASR and HFARS were temporally and spatially distinct, with HFARS emerging later than HFASR and showing only a limited spatial intersection with HFASR: most HFASR sites did not demonstrate HFARS, and HFARS was found where no HFASR could be recorded. β activity was enhanced in HFARS compared to HFASR cortical sites. θ activity was enhanced in HFASR compared to HFARS sites. Furthermore, HFASR sites propagated information to HFARS sites via transient θ:β phase-phase coupling. In contrast to predictive coding (PC) accounts our results indicate that HFASR and HFARS are functionally linked but have minimal spatial overlap. HFASR might enable stable and rapid perception of environmental stimuli across extended temporal intervals. In contrast HFARS might support efficient generation of an internal model based on stimulus history.

Market Quality and Short-Selling Ban during the COVID-19 Pandemic: A High-Frequency Data Approach

The recent emergence of COVID-19 and the subsequent short-selling restriction (SSR) imposed on some equity markets provide us with a unique framework to analyze the effects of this kind of measure on market quality in the context of increasingly automated equity markets. We contribute to the literature by analyzing the microstructure and quality parameters of the Spanish equity market during COVID-19 and SSR. We study four subperiods, namely pre-crisis, turmoil, SSR, and first de-escalation periods, by means of a tick-by-tick dataset and the complete limit order book (LOB). We observe the following impact of the SSR on the constituents of IBEX 35: (1) the SSR did comply partially with its aim at an intraday level regarding volatility, but liquidity was reduced; (2) liquidity deterioration affected more the sell than the buy side of the LOB; (3) high-frequency activity (HFT) diminished during SSR, reinforcing volatility; (4) negative effects on liquidity and HFT diminished and disappeared as the ban was lifted; (5) HFT unidirectionally Granger causes 1 min realized volatility while the natural logarithm of the slope of the LOB bidirectionally Granger causes 1 min realized volatility.

Anti-dissolution Pt single site with Pt(OH)(O3)/Co(P) coordination for efficient alkaline water splitting electrolyzer

As the most well-known electrocatalyst for cathodic hydrogen evolution in water splitting electrolyzers, platinum is unfortunately inefficient for anodic oxygen evolution due to its over-binding with oxygen species and excessive dissolution in oxidative environment. Herein we show that single Pt atoms dispersed in cobalt hydrogen phosphate with an unique Pt(OH)(O3)/Co(P) coordination can achieve remarkable catalytic activity and stability for oxygen evolution. The catalyst yields a high turnover frequency (35.1 ± 5.2 s−1) and mass activity (69.5 ± 10.3 A mg−1) at an overpotential of 300 mV and excellent stability. Mechanistic studies elucidate that the superior catalytic performance of isolated Pt atoms herein stems from optimal binding energies of oxygen intermediate and also their strong electronic coupling with neighboring Co atoms that suppresses the formation of soluble Ptx>4 species. Alkaline water electrolyzers assembled with an ultralow Pt loading realizes an industrial-level current density of 1 A cm−2 at 1.8 volts with a high durability.

Effects of an Overnight, 8-Hour Low Oxygen Exposure on Energy Intake and Resting Energy Expenditure in Healthy, Normal Weight Adults

ObjectivesIndividuals who travel to high altitude (≥5,000 ft) are exposed to hypobaric hypoxic (HH) conditions (i.e., low pressure, low oxygen). Extended exposure to HH conditions often results in body weight loss. This body weight loss is the result of an increase in resting metabolic rate (RMR) due to alterations in the sympathetic and parasympathetic nervous system (PNS), and a decrease in energy intake due to appetite suppression. However, it is unknown if an acute bout of normobaric hypoxic (NH) exposure (i.e., normal pressure, low oxygen) at sea level induces similar changes in energy expenditure and intake. The objective of the current study was to determine the effects of a single overnight exposure to NH on RMR, heart rate variability (HRV), and energy and macronutrient intake compared to an overnight exposure to normobaric normoxia (NN) in normal-weight adults. MethodsIn this randomized crossover trial, normal-weight adults (n = 20; 22.7 ± 1.7 kg/m2, 24.5 ± 3.9 y) slept 8 h in a tent maintained at either 15% oxygen (∼8500 ft) or 20% oxygen (∼1000 ft). The following morning, HRV was measured inside the tent using electrocardiography and RMR was measured outside the tent using indirect calorimetry. Energy and macronutrient intake were assessed in the morning outside the tent with an ad-libitum breakfast buffet and a self-reported dietary record kept for the remainder of the day. ResultsOvernight oxygen saturation was lower in NH (mean ± SD: 88 ± 2%) compared to NN (96 ± 1%; P < 0.0001). Following overnight exposure to NH, RMR was elevated (1537 ± 264 kcal/d) compared to NN (1491 ± 184 kcal/d; P = 0.018. Heart rate was higher in NH (64.2 ± 10.2 bpm) compared to NN (59.7 ± 10.9 bpm; P = 0.003). PNS activity [i.e., the root mean square of successive RR interval differences (RMSSD) and high frequency activity 0.15–0.4 hz (HF)] was lower following NH (47.7 ± 19.5 ms and 524 ± 335 ms2, respectively) compared to NN (58.3 ± 22.6 ms, P = 0.034 and 748 ± 476 ms2, P = 0.052, respectively). Energy and macronutrient intake did not differ between conditions. ConclusionsOne-night exposure to NH increases RMR and reduces PNS activity without impacting energy or macronutrient intake when compared to one-night NN exposure. Future studies should evaluate whether overnight NH exposure is an effective adjunct to traditional weight loss interventions. Funding SourcesInternal funds from FSU.

Time-dependent oxidation of graphite and cobalt oxide nanoparticles as electrocatalysts for the oxygen evolution reaction

• Co 3 O 4 /G OX was synthesized via a facile hydrothermal method for the OER. • Co 3 O 4 /G OX-10 catalyst showed the lowest overpotential of 250 mV at 10 mA cm −2 . • The optimal catalyst exhibited higher specific activity and turnover frequency. • Demonstrated improved electrical conductivity and small charge transfer resistance. • The optimal catalyst Exhibited excellent stability and durability. Water splitting is a promising way of producing hydrogen, but a highly efficient and durable electrocatalyst to accelerate the oxygen evolution reaction (OER) is required. In this study, we report cobalt oxide (Co 3 O 4 ) and oxidized graphite (G OX ) synthesized by a simple hydrothermal method to prepare a catalyst (Co 3 O 4 /G OX ) for the OER. Time-dependent oxidation of graphite (G) and Co 3 O 4 nanoparticles was observed by physical and electrochemical studies. The optimal catalyst (Co 3 O 4 /G OX-10 ) demonstrated the best catalytic OER performance with the lowest overpotential of 250 mV to reach 10 mA cm −2 and a small Tafel slope of 67 mV dec -1 , which is substantially smaller than that of pristine Co 3 O 4 and Co 3 O 4 /G. An efficient synergistic effect between Co 3 O 4 and G OX in the composite catalyst was observed compared to the individual catalysts. The optimal catalyst exhibited high specific activity (1.543 mA cm −2 ) and turnover frequency (0.474 s −1 ) compared to the other catalysts in this study. The high catalytic performance of the catalyst is attributed to the presence of oxygen functional groups, which induced a high electrochemical surface area, additional active site exposure, fast electron transfer, and enhanced dispersion of the catalyst. Thus, the synthesized Co 3 O 4 /G OX-10 catalyst can replace noble metals as an efficient OER electrocatalyst.

High-Frequency Ultrasound Activation of Perfluorocarbon Nanodroplets for Treatment of Glaucoma.

Elevated intraocular pressure (IOP) is the most prevalent risk factor for initiation and progression of neurodegeneration in glaucoma. Ocular hypertension results from increased resistance to aqueous fluid outflow caused by reduced porosity and increased stiffness of tissues of the outflow pathway. Acoustic activation and resulting bioeffects of the perfluorocarbon (PFC) nanodroplets (NDs) introduced into the anterior chamber (AC) of the eye could potentially represent a treatment for glaucoma by increasing permeability in the aqueous outflow track. To evaluate the potential of NDs to enter the outflow track, 100-nm diameter perfluoropentane (PFP) NDs with a lipid shell were injected into the AC of ex vivo pig eyes and in vivo rat eyes. The NDs were activated and imaged with 18- and 28-MHz linear arrays to assess their location and diffusion. NDs in the AC could also be visualized using optical coherence tomography (OCT). Because of their higher density with respect to aqueous humor, some NDs settled into the iridocorneal angle where they entered the outflow pathway. After acoustic activation of the NDs at the highest acoustic pressure, small gas bubbles were observed in the AC. After two days, no acoustic activation events were visible in the AC of the rats and their eyes showed no evidence of inflammation.

0147 Electrophysiologic Localization of Pathological Brain Tissue Is Accomplished with Intracranial Sleep Staging

0147 Electrophysiologic Localization of Pathological Brain Tissue Is Accomplished with Intracranial Sleep Staging

Systematic identification of low voltage-high frequency electrogram zones at sites of left atrial reentrant tachycardia termination

Abstract Funding Acknowledgements Type of funding sources: Private company. Main funding source(s): Abbott Background Localization of the narrow isthmus of conduction of left atrial local and macro reentrant tachycardia (LAMRT) circuits within scar tissue is challenging. (Panel A). Near-field (NF) electrograms are often obscured by and difficult to distinguish from far-field (FF) activation. The peak frequency (PF) associated with bipolar electrograms is a novel parameter which may distinguish between NF and FF signals. (Panel B). However, the potential value of PF for LAMRT ablation has never been evaluated. Purpose 1) To quantify the percentage of LA surface with low voltage (LV) and NF signals. 2) To study the proportion of LAMRT ablation sites which were located within a LV-NF region or in the vicinity of it (&amp;lt;10 mm away). Methods LART bipolar voltage and activation maps were generated with a 16-pole grid catheter (HD-Grid) during tachycardia. (Panels A,B). PF maps were retrospectively computed (Panels C,D). LV zones were defined according to a cutoff &amp;lt;0.3mV. Four different PF cut-off values (&amp;gt;250, &amp;gt;300, &amp;gt;350 and &amp;gt;400 Hz) were assessed in the delineation of overlapping LV-NF regions. (Panel E) Results 16 consecutive patients with 24 LAMRT’s targeted for ablation were prospectively enrolled. 21/24 LAMRT’s were terminated by radiofrequency application. (Panel F). The LV area represented 47.7±14% of the LA surface. The LV-NF area represented 8.2±6.2%, 5.2±5.4%, 3.4±7.4% and 3.3±4.1% of the LA surface by using 250, 300, 350, and 400 Hz PF cutoffs respectively. There were 2.1±1 (range 0-3), 0.9±0.8(range 0-3), 0.5±0.6 (range 0-2) and 0.5±0.6 (range 0-2) LV-NF areas per patient using 250, 300, 350 and 400 Hz PF cutoffs respectively. At the optimal PF cutoff &amp;gt; 250Hz and voltage &amp;lt; 0.3mV, the site of tachycardia termination by radiofrequency application was found inside of a LV-NF region in 13/21 LAMRTs (sensitivity 68.4%), and within 1cm of a LV-NF region in 19/21 LAMRTs (sensitivity 89.5%) respectively. Conclusion 1. Left atrial reentry termination sites by radiofrequency application are often within or nearby LV-NF areas as identified by the PF and voltage analysis of bipolar electrograms. 2. Beyond conventional substrate mapping, the systematic identification of high frequency activity within the low voltage zone holds promise for rapid identification of isthmus conduction critical to LAMRTs.

Seizure Forecasting by High-Frequency Activity (80-170 Hz) in Long-term Continuous Intracranial EEG Recordings.

Reliable seizure forecasting has important implications in epilepsy treatment and improving the quality of lives for people with epilepsy. High-frequency activity (HFA) is a biomarker that has received significant attention over the past 2 decades, but its predictive value in seizure forecasting remains uncertain. This work aimed to determine the utility of HFA in seizure forecasting. We used seizure data and HFA (80-170 Hz) data obtained from long-term, continuous intracranial EEG recordings of patients with drug-resistant epilepsy. Instantaneous rates and phases of HFA cycles were used as features for seizure forecasting. Seizure forecasts based on each individual HFA feature, and with the use of a combined approach, were generated pseudo-prospectively (causally). To compute the instantaneous phases for pseudo-prospective forecasting, real-time phase estimation based on an autoregressive model was used. Features were combined with a weighted average approach. The performance of seizure forecasting was primarily evaluated by the area under the curve (AUC). Of 15 studied patients (median recording duration 557 days, median seizures 151), 12 patients with >10 seizures after 100 recording days were included in the pseudo-prospective analysis. The presented real-time phase estimation is feasible and can causally estimate the instantaneous phases of HFA cycles with high accuracy. Pseudo-prospective seizure forecasting based on HFA rates and phases performed significantly better than chance in 11 of 12 patients, although there were patient-specific differences. Combining rate and phase information improved forecasting performance compared to using either feature alone. The combined forecast using the best-performing channel yielded a median AUC of 0.70, a median sensitivity of 0.57, and a median specificity of 0.77. These findings show that HFA could be useful for seizure forecasting and represent proof of concept for using prior information of patient-specific relationships between HFA and seizures in pseudo-prospective forecasting. Future seizure forecasting algorithms might benefit from the inclusion of HFA, and the real-time phase estimation approach can be extended to other biomarkers. This study provides Class IV evidence that HFA (80-170 Hz) in long-term continuous intracranial EEG can be useful to forecast seizures in patients with refractory epilepsy.

Frequency band coupling with high-frequency activities in tonic-clonic seizures shifts from θ to δ band

ObjectiveTo clarify variations in the relationship between high-frequency activities (HFAs) and low-frequency bands from the tonic to the clonic phase in focal to bilateral tonic-clonic seizures (FBTCS), using phase-amplitude coupling. MethodsThis retrospective study enrolled six patients with drug-resistant focal epilepsy who underwent intracranial electrode placement at Osaka University Hospital (July 2018–July 2019). We recorded 11 FBTCS. The synchronization index (SI) and receiver-operating characteristic (ROC) analysis were used to analyze the coupling between HFA amplitude (80–250 Hz) and lower frequencies phase. ResultsIn the tonic phase, the θ (4–8 Hz)-HFA coupling peaked, and the HFA power occurred at baseline (0 μV) of θ oscillations. In contrast, in the clonic phase, the δ (2–4 Hz)-HFA coupling peaked, and the HFA power occurred at the trough of δ oscillations. ROC analysis indicated that the δ-HFA SI discriminated well the clonic from the tonic phase. ConclusionsThe main low-frequency band modulating the HFA shifted from the θ band in the tonic phase to the δ band in the clonic phase. SignificanceNeurophysiological key frequency bands were implied to be the θ band and δ band in tonic and clonic seizures, respectively, which improves our understanding of FBTCS.

Adrenergic receptors control frequency-dependent switching of the exocytosis mode between “full-collapse” and “kiss-and-run” in murine motor nerve terminal

AimsNeurotransmitter release from the synaptic vesicles can occur through two modes of exocytosis: “full-collapse” or “kiss-and-run”. Here we investigated how increasing the nerve activity and pharmacological stimulation of adrenoceptors can influence the mode of exocytosis in the motor nerve terminal. MethodsRecording of endplate potentials with intracellular microelectrodes was used to estimate acetylcholine release. A fluorescent dye FM1–43 and its quenching with sulforhodamine 101 were utilized to visualize synaptic vesicle recycling. Key findingsAn increase in the frequency of stimulation led to a decrease in the rate of FM1–43 unloading despite the higher number of quanta released. High frequency activity promoted neurotransmitter release via the kiss-and-run mechanism. This was confirmed by experiments utilizing (I) FM1–43 dye quencher, that is able to pass into the synaptic vesicle via fusion pore, and (II) loading of FM1–43 by compensatory endocytosis. Noradrenaline and specific α2-adrenoreceptors agonist, dexmedetomidine, controlled the mode of synaptic vesicle recycling at high frequency activity. Their applications favored neurotransmitter release via full-collapse exocytosis rather than the kiss-and-run pathway. SignificanceAt the diaphragm neuromuscular junctions, neuronal commands are translated into contractions necessary for respiration. During stress, an increase in discharge rate of the phrenic nerve shifts the exocytosis from the full-collapse to the kiss-and-run mode. The stress-related molecule, noradrenaline, restricts neurotransmitter release in response to a high frequency activity, and prevents the shift in the mode of exocytosis through α2-adrenoceptor activation. This may be a component of the mechanism that limits overstimulation of the respiratory system during stress.

Electroencephalogram (EEG) With or Without Transcranial Magnetic Stimulation (TMS) as Biomarkers for Post-stroke Recovery: A Narrative Review.

Stroke is one of the leading causes of death and disability. Despite the high prevalence of stroke, characterizing the acute neural recovery patterns that follow stroke and predicting long-term recovery remains challenging. Objective methods to quantify and characterize neural injury are still lacking. Since neuroimaging methods have a poor temporal resolution, EEG has been used as a method for characterizing post-stroke recovery mechanisms for various deficits including motor, language, and cognition as well as predicting treatment response to experimental therapies. In addition, transcranial magnetic stimulation (TMS), a form of non-invasive brain stimulation, has been used in conjunction with EEG (TMS-EEG) to evaluate neurophysiology for a variety of indications. TMS-EEG has significant potential for exploring brain connectivity using focal TMS-evoked potentials and oscillations, which may allow for the system-specific delineation of recovery patterns after stroke. In this review, we summarize the use of EEG alone or in combination with TMS in post-stroke motor, language, cognition, and functional/global recovery. Overall, stroke leads to a reduction in higher frequency activity (≥8 Hz) and intra-hemispheric connectivity in the lesioned hemisphere, which creates an activity imbalance between non-lesioned and lesioned hemispheres. Compensatory activity in the non-lesioned hemisphere leads mostly to unfavorable outcomes and further aggravated interhemispheric imbalance. Balanced interhemispheric activity with increased intrahemispheric coherence in the lesioned networks correlates with improved post-stroke recovery. TMS-EEG studies reveal the clinical importance of cortical reactivity and functional connectivity within the sensorimotor cortex for motor recovery after stroke. Although post-stroke motor studies support the prognostic value of TMS-EEG, more studies are needed to determine its utility as a biomarker for recovery across domains including language, cognition, and hemispatial neglect. As a complement to MRI-based technologies, EEG-based technologies are accessible and valuable non-invasive clinical tools in stroke neurology.

Estimations of free fatty acid (FFA) as a reliable proxy for larval performance in Mediterranean octocoral species

The survival, behavior and competence period of lecithotrophic larvae depends not only on the energy allocation transferred by maternal colonies but also on the amount of energy consumed to sustain embryonic, larval, and post-larval development. The objective of the present work is to understand the effect of energy consumption on the performance of lecithotrophic larvae. To this aim, we analyzed free fatty acid (FFA) content and composition of the larvae of three Mediterranean octocorals (Corallium rubrum, Eunicella singularis and Paramuricea clavata) as a proxy for energy consumption. Results showed that C. rubrum larvae consume more FFA than P. clavata, whereas the energy consumed by E. singularis larvae is high but highly variable. These results are in accordance with the larval behavior of these three species since C. rubrum larvae are characterized by their high swimming activity frequency, P. clavata larvae are almost inactive, and the swimming activity frequency of E. singularis larvae is high, although variable. The differences in FFA composition of the larvae suggest contrasting energetic strategies that could explain the differences in survival and recruitment rates. In fact, high dispersal and recruitment capacities for E. singularis larvae can be inferred from the FFA composition, whereas the high spatial and temporal variability of recruitment observed in C. rubrum may be related to the non-selective transfer of fatty acid (FA) from maternal colonies. Finally, the high recovery rates after mass mortality events observed in P. clavata could be favored by the presence of a specific FA (22:6(n-3)) related to adaptation mechanisms under environmental stresses during the first developmental stages.

The biogenic silica-derived Ni-phyllosilicate catalyst with Ru modification: effect of the hydroxylation enhancement and reduction procedure

Ni-phyllosilicate is difficultly formed on the surface of biogenic silica (E) extracted from equisetum fluviatile after calcination, resulting in poor catalytic activity at low temperature (<400 °C). In this work, the hydroxylation treatment of E was carried out to address the problem of lack of the surface silanol group and difficult formation of Ni-phyllosilicate, and the second metal Ru was added using a special procedure to further improve the activity of the catalyst. The surface silanol group concentration of silica (HE) was increased from 0.5 to 0.7 mmol/g after hydroxylation treatment, resulting in formation of more Ni-phyllosilicate with Ni content increase from 11.3 to 17.0 wt%. Considering the great gap of reduction difficulty of Ni-phyllosilicate (>800 °C) and RuO2 species (190 °C), RuO2 species was doped onto the 750 °C-pre-reduced Ni-phyllosilicate via impregnation, and metallic Ru together with Ni could be obtained simultaneously after reduction at a low temperature of 400 °C. The obtained Ru-modified Ni-phyllosilicate catalyst showed high CO2 conversion of 77.3% and CH4 selectivity of 96.4% with high turnover frequency (1.22 s−1, 180 °C) and low activation energy (71.25 kJ/mol). In situ Diffused Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) results revealed that more active formate intermediates (m-HCOO- and m-CO32−) result in high catalytic activity of the Ru-modified Ni-phyllosilicate catalyst. In addition, this catalyst exhibited high anti-sintering property, long-term stability, and hydrothermal stability under severe conditions owing to the Ni-phyllosilicate–based structure.

A Long Time Constant May Endorse Sharp Waves and Spikes Over Sharp Transients in Scalp Electroencephalography: A Comparison of After-Slow Among Different Time Constants Concordant With High-Frequency Activity Analysis.

Objective: To clarify whether long time constant (TC) is useful for detecting the after-slow activity of epileptiform discharges (EDs): sharp waves and spikes and for differentiating EDs from sharp transients (Sts).Methods: We employed 68 after-slow activities preceded by 32 EDs (26 sharp waves and six spikes) and 36 Sts from 52 patients with partial and generalized epilepsy (22 men, 30 women; mean age 39.08 ± 13.13 years) defined by visual inspection. High-frequency activity (HFA) associated with the apical component of EDs and Sts was also investigated to endorse two groups. After separating nine Sts that were labeled by visual inspection but did not fulfill the amplitude criteria for after-slow of Sts, 59 activities (32 EDs and 27 Sts) were analyzed about the total area of after-slow under three TCs (long: 2 s; conventional: 0.3 s; and short: 0.1 s).Results: Compared to Sts, HFA was found significantly more with the apical component of EDs (p < 0.05). The total area of after-slow in all 32 EDs under TC 2 s was significantly larger than those under TC 0.3 s and 0.1 s (p < 0.001). Conversely, no significant differences were observed in the same parameter of 27 Sts among the three different TCs. Regarding separated nine Sts, the total area of after-slow showed a similar tendency to that of 27 Sts under three different TCs.Significance: These results suggest that long TC could be useful for selectively endorsing after-slow of EDs and differentiating EDs from Sts. These findings are concordant with the results of the HFA analysis. Visual inspection is also equally good as the total area of after-slow analysis.

Fast synthesis of Pt single-atom catalyst with high intrinsic activity for hydrogen evolution reaction by plasma sputtering

Platinum-based materials are identified as the most effective electrocatalysts for the hydrogen evolution reaction (HER) in acidic media. However, the scarcity and high cost of platinum (Pt) have limited its wide application. Therefore, catalysts with low loading but high intrinsic activity can promote the wide application of Pt. In this work, we creatively applied plasma sputtering to deposit Pt single atoms on TiO2−X as an efficient hydrogen evolution reaction (HER) catalyst. The catalyst shows high intrinsic activity and superior stability in acid media, with high turnover frequency (38.9H2 s−1) and mass-specific activity (39.1 A/mg Pt) at 50 mV (vs. RHE) overpotential in 0.5 M H2SO4 that are respectively 3.3 and 11.04 times greater than those of the commercial 20% Pt/C catalyst. In particular, the plasma sputtering method used in this work can shorten the synthesis period of the catalyst to ‘minutes’ or even ‘seconds.’ This work provides guidance and inspiration for the fast synthesis of catalysts with high intrinsic activity for various applications.

Independent dynamics of low, intermediate, and high frequency spectral intracranial EEG activities during human memory formation

A wide spectrum of brain rhythms are engaged throughout the human cortex in cognitive functions. How the rhythms of various frequency ranges are coordinated across the space of the human cortex and time of memory processing is inconclusive. They can either be coordinated together across the frequency spectrum at the same cortical site and time or induced independently in particular bands. We used a large dataset of human intracranial electroencephalography (iEEG) to parse the spatiotemporal dynamics of spectral activities induced during formation of verbal memories. Encoding of words for subsequent free recall activated low frequency theta, intermediate frequency alpha and beta, and high frequency gamma power in a mosaic pattern of discrete cortical sites. A majority of the cortical sites recorded activity in only one of these frequencies, except for the visual cortex where spectral power was induced across multiple bands. Each frequency band showed characteristic dynamics of the induced power specific to cortical area and hemisphere. The power of the low, intermediate, and high frequency activities propagated in independent sequences across the visual, temporal and prefrontal cortical areas throughout subsequent phases of memory encoding. Our results provide a holistic, simplified model of the spectral activities engaged in the formation of human memory, suggesting an anatomically and temporally distributed mosaic of coordinated brain rhythms.

Moment-by-moment tracking of naturalistic learning and its underlying hippocampo-cortical interactions

Humans form lasting memories of stimuli that were only encountered once. This naturally occurs when listening to a story, however it remains unclear how and when memories are stored and retrieved during story-listening. Here, we first confirm in behavioral experiments that participants can learn about the structure of a story after a single exposure and are able to recall upcoming words when the story is presented again. We then track mnemonic information in high frequency activity (70–200 Hz) as patients undergoing electrocorticographic recordings listen twice to the same story. We demonstrate predictive recall of upcoming information through neural responses in auditory processing regions. This neural measure correlates with behavioral measures of event segmentation and learning. Event boundaries are linked to information flow from cortex to hippocampus. When listening for a second time, information flow from hippocampus to cortex precedes moments of predictive recall. These results provide insight on a fine-grained temporal scale into how episodic memory encoding and retrieval work under naturalistic conditions.

Neural activity in the human anterior thalamus during natural vision

In natural vision humans and other primates explore environment by active sensing, using saccadic eye movements to relocate the fovea and sample different bits of information multiple times per second. Saccades induce a phase reset of ongoing neuronal oscillations in primary and higher-order visual cortices and in the medial temporal lobe. As a result, neuron ensembles are shifted to a common state at the time visual input propagates through the system (i.e., just after fixation). The extent of the brain’s circuitry that is modulated by saccades is not yet known. Here, we evaluate the possibility that saccadic phase reset impacts the anterior nuclei of the thalamus (ANT). Using recordings in the human thalamus of three surgical patients during natural vision, we found that saccades and visual stimulus onset both modulate neural activity, but with distinct field potential morphologies. Specifically, we found that fixation-locked field potentials had a component that preceded saccade onset. It was followed by an early negativity around 50 ms after fixation onset which is significantly faster than any response to visual stimulus presentation. The timing of these events suggests that the ANT is predictively modulated before the saccadic eye movement. We also found oscillatory phase concentration, peaking at 3–4 Hz, coincident with suppression of Broadband High-frequency Activity (BHA; 80–180 Hz), both locked to fixation onset supporting the idea that neural oscillations in these nuclei are reorganized to a low excitability state right after fixation onset. These findings show that during real-world natural visual exploration neural dynamics in the human ANT is influenced by visual and oculomotor events, which supports the idea that ANT, apart from their contribution to episodic memory, also play a role in natural vision.