Burst Waveform Research Articles

The effects of pulsed electromagnetic fields on the cellular activity of SaOS‐2 cells

Although pulsed electromagnetic fields (PEMFs) have been used for treatments of nonunion bone fracture healing for more than three decades, the underlying cellular mechanism of bone formation promoted by PEMFs is still unclear. It has been observed that a series of parameters such as pulse shape and frequency should be carefully controlled to achieve effective treatments. In this article, the effects of PEMFs with repetitive pulse burst waveform on the cellular activity of SaOS-2 osteoblast-like cells were investigated. In particular, cell proliferation and mineralization due to the imposed PEMFs were assessed through direct cell counts, the MTT assay, tissue nonspecific alkaline phosphatase (ALP) and Alizarin Red S (ARS) staining. PEMF stimulation with repetitive pulse burst waveform did not affect metabolic activity and cell number. However, the ALP activity of SaOS-2 cells and mineral nodule formation increased significantly after PEMF stimulation. These observations suggest that repetitive pulse burst PEMF does not affect cellular metabolism; however, it may play a role in the enhancement of SaOS-2 cell mineralization. We are currently investigating cellular responses under different PEMF waveforms and Western blots for protein expression of bone mineralization specific proteins.

Matched filter analysis of burst waveform injections

Hardware injections provide us with a crucial tool for proving that we understand the response and performance of the LIGO detectors. Since we have complete knowledge of the injected waveform and detailed measurements of the detector response function, we are able to predict and confirm the instrument response. During the S5 science run of LIGO, various burst-type waveforms are being injected. We have analyzed the first seven months of these injections, using optimal matched filters derived from the injection waveforms. We have confirmed that most of the responses follow the predictions and have measured the accuracy of the estimated arrival time. In addition, we examined transients identified by the KleineWelle algorithm in auxiliary data channels at the time of hardware injections. Through this study, we could recognize couplings between auxiliary channels and the gravitational wave channels and assess the safety of the use of auxiliary channels as vetoes for gravitation wave candidates.

Peripheral estrogen receptor-α selectively modulates the waveform of GH secretory bursts in healthy women

Estradiol (E(2)) drives growth hormone (GH) secretion via estrogen receptors (ER) located in the hypothalamus and pituitary gland. ERalpha is expressed in GH releasing hormone (GHRH) neurons and GH-secreting cells (somatotropes). Moreover, estrogen regulates receptors for somatostatin, GHR peptide (GHRP, ghrelin), and GH itself, while potentiating signaling by IGF-I. Given this complex network, one cannot a priori predict the selective roles of hypothalamic compared with pituitary ER pathways. To make such a distinction, we introduce an investigative model comprising 1) specific ERalpha blockade with a pure antiestrogen, fulvestrant, that does not penetrate the blood-brain barrier; 2) graded transdermal E(2) administration, which doubles GH concentrations in postmenopausal women; 3) stimulation of fasting GH secretion by pairs of GHRH, GHRP-2 (a ghrelin analog), and l-arginine (to putatively limit somatostatin outflow); and 4) implementation of a flexible waveform deconvolution model to estimate the shape of secretory bursts independently of their size. The combined strategy unveiled that 1) E(2) prolongs GH secretory bursts via fulvestrant-antagonizable mechanisms; 2) fulvestrant extends GHRH/GHRP-2-stimulated secretory bursts; 3) l-arginine/GHRP-2 stimulation lengthens GH secretory bursts whether or not E(2) is present; 4) E(2) limits the capability of l-arginine/GHRP-2 to expand GH secretory bursts, and fulvestrant does not inhibit this effect; and 5) E(2) and/or fulvestrant do not alter the time evolution of l-arginine/GHRH-induced GH secretory bursts. The collective data indicate that peripheral ERalpha-dependent mechanisms determine the shape (waveform) of in vivo GH secretory bursts and that such mechanisms operate with secretagogue selectivity.

Estimation of the size and shape of GH secretory bursts in healthy women using a physiological estradiol clamp and variable-waveform deconvolution model

Because estrogen production and age are strong covariates, distinguishing their individual impact on hypothalamo-pituitary regulation of growth hormone (GH) output is difficult. In addition, at fixed elimination kinetics, systemic GH concentration patterns are controlled by three major signal types [GH-releasing hormone (GHRH), GH-releasing peptide (GHRP, ghrelin), and somatostatin (SS)] and by four dynamic mechanisms [the number, mass (size), and shape (waveform) of secretory bursts and basal (time invariant) GH secretion]. The present study introduces an investigative strategy comprising 1) imposition of an experimental estradiol clamp in pre- (PRE) and postmenopausal (POST) women; 2) stimulation of fasting GH secretion by each of GHRH, GHRP-2 (a ghrelin analog), and l-arginine (to putatively limit SSergic restraint); and 3) implementation of a flexible-waveform deconvolution model to estimate basal GH secretion simultaneously with the size and shape of secretory bursts, conditional on pulse number. The combined approach unveiled the following salient percent POST/PRE contrasts: 1) only 27% as much GH secreted in bursts during fasting (P < 0.001); 2) markedly attenuated burstlike GH secretion in response to bolus GHRP-2 (29%), bolus GHRH (30%), l-arginine (37%), constant GHRP-2 (38%), and constant GHRH (42%) (age contrasts, 0.0016 </= P </= 0.027); and 3) a 160% prolongation and 32% abbreviation of the time required to achieve maximal GH secretion after injection of l-arginine and bolus GHRP-2, respectively (both, P < 0.001). Accordingly, age selectively determines both the size (amount) and shape (waveform) of GH secretory bursts in healthy women independently of the short-term estrogen milieu.

Build-on Technology of Bidirectional Optical Communication System Using Bifunctional Organic Diodes

A bidirectional optical communication system using bi-functional organic diodes (BiORDs) has been investigated. The stacked structure used was a front transparent organic light emitting diode (TOLED) and a back organic photodiode (OPD). For a device structure of LiF (1 nm)/semitransparent AlNd (15 nm)/MoO3 (30 nm)/TPD (100 nm)/td-PTC (perylene derivative, 50 nm)/Al, a maximum luminance of 77,400 cd/m2 and a ratio of photo- to dark current of 1,100 were obtained. As a result, an excellent linearity range between the input TOLED current and the output OPD current was obtained at over three orders of magnitude. Cutoff frequencies of the TOLED and OPD were 1.4 MHz and 150 kHz, respectively. For an optical transmission experiment, random burst waveforms of return-to-zero and nonreturn-to-zero were applied to the BiORDs, and an operational frequency of 100 kbps was realized.

Analysis of Q burst waveforms

The electric field changes in ELF to VLF were observed with a ball antenna in fair weather at Kochi (latitude 33.3°N, longitude 133.4°E) during 2003–2004. Some 376 Q bursts were obtained, seven examples of which are analyzed in the present study. The continuous frequency spectra of the Q bursts and the background noises from 1.0 Hz to 11 kHz are compared, and it was found that the Q bursts prevail over the background in the frequency range from 1 to 300 Hz. The surplus is 20 dB (in amplitude) near the fundamental mode frequency. The “W”‐type changes found in the initial portion of the Q burst waveforms are interpreted as the combined electromagnetic waveform of direct and antipodal waves from the causative lightning strokes. From the time intervals between the two waves, the source‐receiver distances are estimated as far as 19 Mm. The pulses to excite the Schumann resonances in the Q bursts are clearly identified.

Coherent network analysis technique for discriminating gravitational-wave bursts from instrumental noise

The sensitivity of current searches for gravitational-wave bursts is limited by non-Gaussian, nonstationary noise transients which are common in real detectors. Existing techniques for detecting gravitational-wave bursts assume the output of the detector network to be the sum of a stationary Gaussian noise process and a gravitational-wave signal. These techniques often fail in the presence of noise nonstationarities by incorrectly identifying such transients as possible gravitational-wave bursts. Furthermore, consistency tests currently used to try to eliminate these noise transients are not applicable to general networks of detectors with different orientations and noise spectra. In order to address this problem we introduce a fully coherent consistency test that is robust against noise nonstationarities and allows one to distinguish between gravitational-wave bursts and noise transients in general detector networks. This technique does not require any a priori knowledge of the putative burst waveform.

Testosterone supplementation in healthy older men drives GH and IGF-I secretion without potentiating peptidyl secretagogue efficacy

Testosterone supplementation increases GH and IGF-I concentrations in healthy older men via unknown mechanisms. We examine the hypotheses that (i) testosterone amplifies stimulation of GH secretion by GH-releasing peptide (GHRP)-2 or GH-releasing hormone (GHRH) infused with l-arginine to limit somatostatin outflow (i.e. upregulates each agonistic pathway), (ii) testosterone augments the effect of both peptidyl secretagogues infused together (i.e. reduces opposition by hypothalamic somatostatin) and (iii) abdominal visceral fat (AVF) mass is a negative determinant of specific secretagogue-stimulated GH secretion. Randomized double-blind crossover design of placebo versus testosterone administration in healthy older men. Deconvolution analysis was used to estimate basal GH secretion and the mass (integral) and waveform (time-shape) of GH secretory bursts. Statistical contrasts revealed that administration of testosterone compared with placebo in seven men aged 60-77 years increased fasting concentrations of GH (P < 0.01) and IGF-I (P = 0.003), and basal (P < 0.005) and pulsatile (P < 0.01) GH secretion. Testosterone did not alter the absolute value or rank order of secretagogue efficacy: l-arginine/GHRP-2 (23-fold effect over saline) = GHRH/GHRP-2 (20-fold) > l-arginine/GHRH (7.5-fold). Waveform reconstruction indicated that each stimulus pair accelerated initial GH secretion within a burst (P < 0.01). Regression analysis disclosed a significant inverse association between GH secretory-burst mass and computer tomography-estimated AVF following stimulation with l-arginine/GHRH after testosterone supplementation (R(2) = 0.54, P = 0.015). Supraphysiological testosterone concentrations augment GH and IGF-I production in the elderly male without altering maximal somatotrope responses to single and combined GHRH and GHRP-2 drive, thus predicting multifactorial mechanisms of testosterone upregulation.

Photonic synthesis of broadband microwave arbitrary waveforms applicable to ultra-wideband communication

We demonstrate photonic synthesis of broadband radio-frequency (RF) waveforms suitable for ultra-wide bandwidth (UWB) systems via open-loop reflection-mode dispersive Fourier transform optical pulse shaping. Using this technique, we synthesize broadband burst, monocycle and pulsed waveforms with RF bandwidths ranging from /spl sim/1-8 GHz. Through appropriate optical waveform design, we demonstrate direct control over the shape of the RF spectrum - a capability that enables us to tailor our RF waveforms to conform to the low-power UWB spectral criteria.

A wavelet method for detection of gravitational wave bursts

In this paper, we describe a method for detection of gravitational wave bursts in data from gravitational wave interferometers. The method is based on wavelet transformations, which give a time–frequency representation of data. The bursts are identified by looking for regions in the wavelet domain with an excess of power inconsistent with stationary detector noise. The method is applied simultaneously for two or more gravitational wave detectors, resulting in the production of coincident burst triggers. To describe the statistical properties of the triggers, non-parametric statistics are used. This makes the method more robust against uncertainties in the detector noise. The excess power approach does not require an accurate knowledge of the burst waveforms allowing detection of signals from poorly modelled or unmodelled gravitational wave sources.

Performance of the WaveBurst algorithm on LIGO data

In this paper we describe the performance of the WaveBurst algorithm which was designed for detection of gravitational wave bursts in interferometric data. The performance of the algorithm was evaluated on the test dataset collected during the second LIGO Scientific run. We have measured the false alarm rate of the algorithm as a function of the threshold and estimated its detection efficiency for simulated burst waveforms.

Dendritic control of spontaneous bursting in cerebellar Purkinje cells.

We investigated the mechanisms that contribute to spontaneous regular bursting in adult Purkinje neurons in acutely prepared cerebellar slices. Bursts consisted of 3-20 spikes and showed a stereotypic waveform. Each burst developed with an increase in firing rate and was terminated by a more rapid increase in firing rate and a decrease in spike height. Whole-cell current-clamp recordings showed that each burst ended with a rapid depolarization followed by a hyperpolarization. Dual dendritic and somatic extracellular recordings revealed that each burst was terminated by a dendritic calcium spike. The contributions of T- and P/Q-type calcium current, large (BK) and small (SK) conductance calcium-activated potassium currents, and hyperpolarization-activated (I(H)) current to bursting were investigated with specific channel blockers. None of the currents, except for P/Q, were required to sustain spontaneous bursting or the stereotypic burst waveform. T-type calcium, BK, and SK channels contributed to interspike and interburst intervals. The effect of T-type calcium channel block was more pronounced after BK channel block and vice versa, indicating that these two currents interact to regulate burst firing. Block of I(H) current had no effect on bursting. Partial block of P/Q-type calcium channels concurrently eliminated dendritic calcium spikes and caused a switch from regular bursting to tonic firing or irregular bursting. Dendritic calcium spikes persisted in the presence of tetrodotoxin, indicating that their initiation did not require somatic sodium spikes. Our results demonstrate an important role for dendritic conductances in burst firing in intact Purkinje neurons.

First steps towards characterizing the hierarchical algorithm for curves and ridges pipeline

The hierarchical algorithm for curves and ridges is a variation of the burst gravitational wave search algorithm known as TFClusters. In this paper, we examine the detection efficiency of the hierarchical algorithm for curves and ridges by injecting sine-Gaussian burst waveforms with four different central frequencies into data acquired by the GEO600 gravitational wave detector during the S1 run. The fluctuation of the output signal-to-noise ratios was observed to be ∼5% for frequencies above 1.5 kHz and at least 15% for frequencies below 1.5 kHz. The uncertainty in the estimation of the arrival time is found to be less than 0.05 s.

Measurement of position offset in hard disk drive using dual frequency servo bursts

This paper presents a new scheme for encoding position information in hard disk drives (HDDs). Modern HDDs use embedded servo patterns where the servo sectors containing information related to the location of the tracks are placed interleaved with the data blocks. Reduced length of the servo sector, therefore, means availability of more space for storage of data. The scheme of dual-frequency servo burst used in this paper enables more than 50% reduction in the length of the servo bursts that encode the position error sensing signal (PES). Different methods suitable for decoding PES from the samples of these servo bursts are also discussed, and a detection technique based on the concepts of discrete Fourier transform (DFT) is proposed. High sensitivity and flexibility of the digital PES allows the tracks to be placed closer which, is required to meet the demands of future generation HDDs. The dual frequency servo bursts are written on a 2.5-in disk to create tracks at a spacing of 10 /spl mu/-in, and the PES is decoded from the samples of the burst waveforms using DFT-based algorithms. The linearity of the decoded position offset proves the effectiveness of the proposed encoding method and the decoding algorithm.

Divergent gonadotropin-gonadal dose-responsive coupling in healthy young and aging men.

The present study extends a recent composite model of in vivo interglandular signaling to assess the impact of age on 1) nonequilibrium exchange among diffusible and protein-bound testosterone (Te); 2) elimination of total and free Te; 3) basal and pulsatile Te secretion (sec); 4) the implicit feedforward function mediating luteinizing hormone (LH) concentration (con) drive of instantaneous Te sec; and 5) possible stochastic variability of the predicted LH con-Te sec dose-response linkage. To this end, we measured LH and Te con every 10 min for 24 h in healthy young (n = 13) and older men (n = 13). Statistical comparisons of analytic estimates revealed that elderly subjects manifest 1) reduced maximal burstlike LH-stimulated Te sec (impaired stimulus efficacy); 2) depressed half-maximally LH-stimulated Te sec (lower Leydig-cell responsivity); 3) decreased pulsatile and total Te sec; 4) elevated basal Te sec; 5) a prolonged half-life of total but not free Te con; and 6) delayed time evolution of LH and Te sec bursts. In contradistinction, age did not influence estimated LH-pulse potency (ED50), steroidogenic sensitivity (slope term), or stochastic variability of LH-Te coupling. On the basis of these data, we postulate that aging in the human male alters specific dose-response attributes linking LH con and Te sec and disrupts the time waveform of LH and Te sec bursts.

Ionic Mechanisms of Burst Firing in Dissociated Purkinje Neurons

Cerebellar Purkinje neurons have intrinsic membrane properties that favor burst firing, seen not only during complex spikes elicited by climbing fiber input but also with direct electrical stimulation of cell bodies. We examined the ionic conductances that underlie all-or-none burst firing elicited in acutely dissociated mouse Purkinje neurons by short depolarizing current injections. Blocking voltage-dependent calcium entry by cadmium or replacement of external calcium by magnesium enhanced burst firing, but it was blocked by cobalt replacement of calcium, probably reflecting block of sodium channels. In voltage-clamp experiments, we used the burst waveform of each cell as a voltage command and used ionic substitutions and pharmacological manipulations to isolate tetrodotoxin (TTX)-sensitive sodium current, P-type and T-type calcium current, hyperpolarization-activated cation current (Ih), voltage-activated potassium current, large-conductance calcium-activated potassium current, and small-conductance calcium-activated potassium (SK) current. Measured near the middle of the first interspike interval, TTX-sensitive sodium current carried the largest inward current, and T-type calcium current was also substantial. Current through P-type channels was large immediately after a spike but decayed rapidly. These inward currents were opposed by substantial components of voltage-dependent and calcium-dependent potassium current. Termination of the burst is caused partly by decay of sodium current, together with a progressive buildup of SK current after the first interspike interval. Although burst firing depends on the net balance between multiple large currents flowing after a spike, it is surprisingly robust, probably reflecting complex interactions between the exact voltage waveform and voltage and calcium dependence of the various currents.

Time Frequency Characteristics of the Vibroacoustic Signal of Hydrodynamic Cavitation

A theoretical analysis and experimental results are presented of the time-frequency characteristics of hydrodynamic cavitation signals. Because of the limitation of the frequency bandwidth of the data acquisition system and the random nature of cavity collapses, the signal consists of transient burst waveforms. The acoustic pulses from collapses in close time proximity mix together and form transient oscillatory bursts. The local oscillation frequency of a burst is related to either the time duration between burst collapses or the cut-off frequency of the system. These results enable the identification and detection of individual cavitation events by the time-frequency characteristics in the vibroacoustic signal.

Digital servo demodulation in a digital read channel

A technique is described which implements high-performance servo burst amplitude demodulation using the 6-bit analog-to-digital converter in a digital read channel. The use of digital circuits reduces the size of the channel chip as well as reducing the design time and variability compared to analog circuits. The performance of the digital area detect burst demodulator is compared to standard analog techniques. Simulation results show digital area detect performance better than peak detect and very close to optimal for a practical burst waveform.

The effect of pulsed electromagnetic fields on flexor tendon healing in the rabbit

A double-blind controlled trial of the effects of pulsed electromagnetic fields on flexor tendon healing in adult New Zealand White rabbits was performed. A pulse burst waveform, previously demonstrated to influence new vessel growth in the rabbit, was employed. No significant effect was observed on either the healed strength of the tendon repair or the adhesion formation between the repair and the surrounding tissues. The model used for examination of adhesion formation was reproducible and is recommended for further work on the adhesion formation of healing tendons.

Hereditary effects in gravitational radiation.

This paper derives the leading nonlinear hereditary effects in the generation of gravitational radiation, i.e., the terms in the wave form which depend in an irreducible manner on the entire past history of the source. At the quadratically nonlinear order there are two types of hereditary contributions. The first ones are due to the readiation of gravitational waves by the stress-energy distribution of (linear) gravitational waves, and give rise to a net cumulative change in the wave form of bursts (memory effect). The second ones come from the backscattering of (linear) gravitational waves emitted in the past onto the constant curvature associated with the total mass of the source (gravitational-wave tails). An extension of a previously proposed multipole-moment wave generation formalism allows us to compute explicitly the wave form, including hereditary contributions, up to terms of fractional order ${(\frac{v}{c})}^{4}$. Our results are derived for slow-moving systems of bodies, independently of the strength of their internal gravity. The tail contribution to the far wave-zone field is found to be fully consistent with a corresponding hereditary contribution to the gravitational radiation damping previously derived from a study of the near-zone field.