Contributors: Maeike Zijlmans, Julia Jacobs, Rina Zelmann, François Dubeau, Jean Gotman

Date: 2009-08-01

frequency. We studied whether the same applies to patients with focal ...frequency per month and the number of channels with more than 1 ripple...frequency before implantation was compared to numbers of channels with...frequency oscillations (HFOs) have been associated with epileptogenicity...frequency, was not confirmed, though there might be a correlation for ...frequency compared to number of channels with higher rates of ripples ...frequency per month and number of channels with (A) ripples (>1/min), ...frequency was shown on a logarithmic scale, because of the distribution...frequency and more than 20 fast ripples per minute. ...frequency. There was a linear positive correlation between the number ... High frequency oscillations (HFOs) have been associated with epileptogenicity. In rats, the extent of HFOs (>200Hz) is correlated with seizure frequency. We studied whether the same applies to patients with focal epilepsy. Thirty-nine patients with intracerebral EEG sampled at 2000Hz were studied for interictal ripples (80–250Hz), fast ripples (FR, 250–500Hz) and spikes. Seizure frequency before implantation was compared to numbers of channels with HFOs (>1/min). Analyses were repeated for HFO rates of >5, >10 and >20. Separate analyses were done for 25 patients with temporal lobe epilepsy only and for a selection of similar unilateral temporal channels in 12 patients. No linear correlation or trend was found relating the number of channels with HFOs and seizure frequency. There was a linear positive correlation between the number of channels with more than 20 FRs/min and seizure frequency. The hypothesis that the more tissue generating HFOs, the higher the seizure frequency, was not confirmed, though there might be a correlation for high FR rates.

Contributors: Maeike Zijlmans, Julia Jacobs, Yusuf U. Kahn, Rina Zelmann, François Dubeau, Jean Gotman

Date: 2011-04-01

frequencies as well. If still in doubt, the signal was reviewed at a timescale...frequency artifact over channels that are potentially outside of the brain...frequency spectrum shows relatively more frequencies (Otsubo et al., 2008...frequency oscillations (HFOs) can be recorded with depth electrodes in...frequency oscillations ... High frequency oscillations (HFOs) can be recorded with depth electrodes in focal epilepsy patients. They occur during seizures and interictally and seem important in seizure genesis. We investigated whether interictal and ictal HFOs occur in the same regions and how they relate to epileptiform spikes.

Contributors: Cheemeng Tan, Faisal Reza, Lingchong You

Date: 2007-12-01

frequency (see Methods for more details). ...frequency domain. By modeling simple gene circuits, we analyze the impact...frequency-signal transmission. We find that transmission of frequency ...oscillating signals; that is, these signals can encode information in ...oscillations decreased with fin. fc was calculated as the intersection...oscillation amplitude” curve. (B) Calculations of fout for varying fin...frequency (fc). Signals with frequencies <fc are transmitted with high...oscillations compounded with noise. The mean and standard deviation of...frequency. ...frequencies >fc are severely corrupted or completely lost in transmission ... To maintain normal physiology, cells must properly process diverse signals arising from changes in temperature, pH, nutrient concentrations, and other factors. Many physiological processes are controlled by temporal aspects of oscillating signals; that is, these signals can encode information in the frequency domain. By modeling simple gene circuits, we analyze the impact of cellular noise on the fidelity and speed of frequency-signal transmission. We find that transmission of frequency signals is “all-or-none”, limited by a critical frequency (fc). Signals with frequencies fc are severely corrupted or completely lost in transmission. We argue that fc is an intrinsic property of a gene circuit and it varies with circuit parameters and additional feedback or feedforward regulation. Our results may have implications for understanding signal processing in natural biological networks and for engineering synthetic gene circuits.

Contributors: Hiroshi Kajiya, Fujio Okamoto, Tetsuomi Nemoto, Keiichiro Kimachi, Kazuko Toh-Goto, Shuji Nakayana, Koji Okabe

Date: 2010-01-01

oscillations has not yet been identified. Using a DNA microarray, we found...oscillations and activates the Nuclear Factor of Activated T cells 1 (...frequency of [Ca2+]i oscillations in cells before (0h) and 18h or 48h ...oscillations. Recordings were obtained from four cells. (B) Frequency ...Frequency (times per 1min) of transient inward currents (only counting...oscillations and a transient inward cation current in a time-dependent...frequency of Ca2+ oscillations and the transient inward currents in RANKL-treated...oscillations are an important trigger signal for osteoclastogenesis, however...frequency of [Ca2+]i oscillations (times per 10min) before (control; n...oscillations...Frequency (times per 1min) of the transiently activated inward currents ... The receptor activator of NFκB ligand (RANKL) induces Ca2+ oscillations and activates the Nuclear Factor of Activated T cells 1 (NFATc1) during osteoclast differentiation (osteoclastogenesis). Ca2+ oscillations are an important trigger signal for osteoclastogenesis, however the molecular basis of Ca2+ permeable influx pathways serving Ca2+ oscillations has not yet been identified. Using a DNA microarray, we found that Transient Receptor Potential Vanilloid channels 2 (TRPV2) are expressed significantly in RANKL-treated RAW264.7 cells (preosteoclasts) compared to untreated cells. Therefore, we further investigated the expression and functional role of TRPV2 on Ca2+ oscillations and osteoclastogenesis. We found that RANKL dominantly up-regulates TRPV2 expression in preosteoclasts, and evokes spontaneous Ca2+ oscillations and a transient inward cation current in a time-dependent manner. TRPV inhibitor ruthenium red and tetracycline-induced TRPV2 silencing significantly decreased both the frequency of Ca2+ oscillations and the transient inward currents in RANKL-treated preosteoclasts. Silencing of store-operated Ca2+ entry (SOCE) proteins similarly suppressed both RANKL-induced oscillations and currents in preosteoclasts. Furthermore, suppression of TRPV2 also reduced RANKL-induced NAFTc1 expression, its nuclear translocation, and osteoclastogenesis. In summary, Ca2+ oscillations in preosteoclasts are triggered by RANKL-dependent TRPV2 and SOCE activation and intracellular Ca2+ release. Subsequent activation of NFATc1 promotes osteoclastogenesis.

Contributors: Jingjing Wang, Da Chen, Yan Xu, Weihui Liu

Date: 2014-01-01

oscillator. ...frequency shift compared with the level without pesticides. The obtained...frequency profiles. ...frequency spectrum of the FBAR oscillator after the PBS was injected into...frequencies (fs and fp) of the FBAR before and after the immobilization...frequency profiles when the pure parathion MAb solution and the mixed ...frequency changes of the resonator. The presence of pesticides can be ... A highly sensitive label-free immunosensor based on film bulk acoustic resonator has been developed for the detection of pesticide residues. The film bulk acoustic resonator works at 2GHz as a mass-sensitive transducer for bio-sensing. Artificial antigens were immobilized on the sensing surface of the resonator through self-assembled method to employ a competitive format for the immunoassays. The competitive immunoreactions are observed in real time by measuring the frequency changes of the resonator. The presence of pesticides can be detected according to the diminution of the frequency shift compared with the level without pesticides. The obtained ultra low limit of detection for parathion was as low as 0.08μg/L. The fabricated device was further used to detect trace pesticide residues in vegetable samples. The results show that the proposed immunosensor is a rapid and convenient detection method with a high accuracy comparable to gas chromatography.

Contributors: Shibin Mathew, Ipsita Banerjee

Date: 2014-12-04

oscillations with a frequency greater than 0.05min−1 (or period less than...frequencies, we see a flat response, with a fixed but lower amplitude ...oscillations. ...frequency cut-off. Negative feedback contributes to signal attenuation...frequency on the output amplitude of p-AKT in the entire parameter space ... Robustness is a critical feature of signaling pathways ensuring signal propagation with high fidelity in the event of perturbations. Here we present a detailed quantitative analysis of robustness in insulin mediated PI3K/AKT pathway, a critical signaling pathway maintaining self-renewal in human embryonic stem cells. Using global sensitivity analysis, we identified robustness promoting mechanisms that ensure (1) maintenance of a first order or overshoot dynamics of self-renewal molecule, p-AKT and (2) robust transfer of signals from oscillatory insulin stimulus to p-AKT in the presence of noise. Our results indicate that negative feedback controls the robustness to most perturbations. Faithful transfer of signal from the stimulating ligand to p-AKT occurs even in the presence of noise, albeit with signal attenuation and high frequency cut-off. Negative feedback contributes to signal attenuation, while positive regulators upstream of PIP3 contribute to signal amplification. These results establish precise mechanisms to modulate self-renewal molecules like p-AKT.

Contributors: Tomoko Okada, Yuji Yamamoto, Tsubasa Shibuya, Hyen-Wook Kang, Hirotaka Miyachi, Isao Karube, Hiroshi Muramatsu, Jong Min Kim

Date: 2008-08-01

oscillation amplitude changes....oscillation of the microspheres owing to their surface charges. The oscillation...Oscillation amplitudes of Profilin-beads alone (a) and Profilin-beads ...oscillation amplitude of the microspheres, thus, suggesting a possible...oscillation amplitude (b). ...oscillation amplitudes of Biotin-IgG-beads (orange) without Sav (a) or...Oscillation amplitudes of Biotin-IgG-beads with or without Sav (a) and...oscillation amplitude of the profilin-modified microsphere increased by...oscillation amplitudes of IgG-beads (yellow-green) without (c) or with ... We have developed a new method for evaluating the affinity interactions between two different proteins by applying an alternating current (AC) voltage to a micro-flow channel. An AC voltage was applied to the protein-modified microspheres in the micro-flow channel, which resulted in the oscillation of the microspheres owing to their surface charges. The oscillation amplitude showed a linear relationship with the charge density of the microspheres. As an example for protein affinity measurement, the amplitude changes of a profilin-modified microsphere were measured by the addition of actin. In the same electrical condition, the oscillation amplitude of the profilin-modified microsphere increased by ≈175% by binding with actin. Similar results in the principle were obtained for the affinity interaction between biotin and streptavidin. The results showed that the higher the charge density of the microspheres induced by binding with different proteins, the higher the oscillation amplitude of the microspheres, thus, suggesting a possible application of the micro-flow channel and AC voltage on the protein property study, as well as on the biosensor application using the oscillation amplitude changes.

Contributors: Simone Guadagna, Christoffer Bundgaard, Nanna Hovelsø, Christiane Volbracht, Paul T. Francis, Jan Egebjerg, Florence Sotty

Date: 2012-01-01

frequency following vehicle (0.9% NaCl), MK-801 (a) and memantine (b) ...oscillations in the hippocampus of urethane anesthetized mice, a model...frequency of pedunculopontine-induced hippocampal theta in anesthetized...frequency before drug administration. Data are represented as mean±SEM...frequencies between 0 and 20 (Hz) (left panel) and on frequencies between ... Memantine is an uncompetitive, low-affinity NMDA receptor antagonist clinically used for the treatment of cognitive deficits in moderate to severe Alzheimer’s disease. Both neurophysiological and behavioral studies in rodents have suggested a beneficial effect of memantine on synaptic plasticity and learning performances. In the present study, we investigated the effect of memantine on pedonculopontine-elicited theta oscillations in the hippocampus of urethane anesthetized mice, a model shown to be sensitive to several pharmacological agents exhibiting cognitive-enhancing properties. We found that a low dose of memantine potentiated elicited theta power while a high dose was disruptive. The low dose of memantine used was shown to yield an unbound brain concentration well within the range of therapeutic concentrations reported in rodent brain extracellular fluid and human cerebrospinal fluid. For further comparison, the effect of another uncompetitive NMDA receptor antagonist with higher affinity, i.e. MK-801, was also investigated. MK-801 was at a low dose devoid of effect on elicited theta power, while a high dose, within the range of doses reported to induce cognitive deficits in a variety of hippocampal-dependent learning paradigms in mice, was found disruptive on elicited theta waves. Taken together, our results suggest that clinically relevant doses of memantine promote neuronal network synchronization in the hippocampus, which may represent an underlying mechanism for the reported cognitive-enhancing properties in both preclinical and clinical studies.

Contributors: Wiljan Smaal, Charlotte Kjellander, Yongbin Jeong, Ashutosh Tripathi, Bas van der Putten, Antonio Facchetti, Henry Yan, Jordan Quinn, John Anthony, Kris Myny

Date: 2012-09-01

frequency of 2.6kHz. ...oscillators as a function of frequency. Frequency was measured at 10V ...oscillators with 10μs stage delay operating at 20V....oscillators having different WN:WP channel width and different [PFBT]/...oscillators. (b) Stage delays of 19-stage complementary ring oscillators...oscillators. Under optimal processing conditions we realized complementary ... Complementary thin-film transistor circuits composed of 6,13-bis(triisopropyl-silylethynyl) pentacene (TIPS–PEN) and a rylene carboxylic diimide derivative for p- and n-channel thin-film transistors (TFTs) were fabricated on flexible foils. The so-called staggered TFT configuration is used, meaning that the semiconductors layers are deposited last. The work-function of the injecting gold electrodes were modified using several self-assembled monolayers (SAMs). For optimized contacts the mobility of the n- and p-channel TFTs was 0.5cm2/Vs and 0.2cm2/Vs, respectively. Strongly degraded performance is obtained when the n-channel material was printed on contacts optimized for the p-channel TFT, and vice versa. This illustrates that for CMOS circuits we need careful work-function engineering to allow proper injection for both electrons and holes. We show for the first time that by using a bimolecular mixture for the SAM we can systematically vary the work function, and demonstrate how this affects the performance of discrete n-type and p-type transistors, as well as CMOS inverters and ring oscillators. Under optimal processing conditions we realized complementary 19-stage ring oscillators with 10μs stage delay operating at 20V.

Contributors: Julian Antonio Valverde, Adriana Echavarría, Maria Filipa Ribeiro, Luz Amparo Palacio, Jean-Guillaume Eon

Date: 2012-09-30

oscillations in R and k spaces of the NiAlH_Cal. – observed spectrum, ...oscillations in R space, (b) V-K edges EXAFS oscillations in k spaces,...oscillations in R space, NiO contributions and (d) Ni-K edges EXAFS oscillations ... Two nickel–aluminum hydrotalcite type precursors were synthesized with molar ratio Ni/Al=3, using hydroxyl and carbonate as compensation anions. These precursors were intercalated by 30% (theoretical) decavanadate anion. The catalysts were obtained after calcination at 550°C and their performance was evaluated in propane oxidative dehydrogenation at 400°C using space velocities of 100, 150, 200 and 400mlg−1min−1 under conditions of oxygen deficiency and oxygen excess. Catalysts derived from nickel–aluminum-hydroxyl precursors attained an excellent performance under oxygen deficiency conditions promoting high propene selectivity and conversion. Under oxygen excess conditions the catalyst was more active but its selectivity was lower. Vanadium-containing catalysts showed improved selectivity under this operation condition. The formation of the hydrotalcite phase in precursors and mixed oxides in the catalysts was evidenced by X-ray diffraction (XRD). Analyses of textural and reduction properties were carried-out with nitrogen adsorption and temperature programmed reduction techniques respectively. Structural studies were performed by X-ray absorption spectroscopy for materials that showed best performance in the oxidative dehydrogenation reaction.