Millisecond Duration Research Articles

More safety with more energy

We report the first clinical case of ineffective high-voltage therapy with 36J and subsequent effective therapy with 40J in a patient with electrical storm who had previously received a high-energy implantable cardioverter defibrillator (ICD, Fortify VR, 1233-40Q St. Jude Medical, Sylmar, CA, USA). Using a combination of high energy and optimized fixed millisecond duration biphasic waveform shock, successful defibrillation could be achieved at 8J below the programmed maximum energy level.

Transient Suppression of Broadband Gamma Power in the Default-Mode Network Is Correlated with Task Complexity and Subject Performance

Task performance is associated with increased brain metabolism but also with prominent deactivation in specific brain structures known as the default-mode network (DMN). The role of DMN deactivation remains enigmatic in part because its electrophysiological correlates, temporal dynamics, and link to behavior are poorly understood. Using extensive depth electrode recordings in humans, we provide first electrophysiological evidence for a direct correlation between the dynamics of power decreases in the DMN and individual subject behavior. We found that all DMN areas displayed transient suppressions of broadband gamma (60-140 Hz) power during performance of a visual search task and, critically, we show for the first time that the millisecond range duration and extent of the transient gamma suppressions are correlated with task complexity and subject performance. In addition, trial-by-trial correlations revealed that spatially distributed gamma power increases and decreases formed distinct anticorrelated large-scale networks. Beyond unraveling the electrophysiological basis of DMN dynamics, our results suggest that, rather than indicating a mere switch to a global exteroceptive mode, DMN deactivation encodes the extent and efficiency of our engagement with the external world. Furthermore, our findings reveal a pivotal role for broadband gamma modulations in the interplay between task-positive and task-negative networks mediating efficient goal-directed behavior and facilitate our understanding of the relationship between electrophysiology and neuroimaging studies of intrinsic brain networks.

Mechanical Effects during Pulsed Laser and Metals Interaction in Neutral Solution

In order to investigate the mechanical effects during pulsed laser and metal target in neutral solution, a measuring part of stainless cantilever was developed. The vibration of the stainless cantilever was tested and analyzed based on the test mechanism of piezoelectric accelerometer. The impact pressure of the target in NaNO3 solution by pulsed lasers at wavelength of 532nm and 1064nm with millisecond pulse duration were obtained by the test with the measuring part. The results show that mechanical effect during pulsed laser and stainless target interaction in neutral solution is more than three times higher than in air. The pressure of the target with infrared laser is decreased with the distance of laser propagation in neutral solution. However, the effect with green laser is stable in the laser transmission range of 20mm. The green laser is more suitable for processing under neutral solution.

Size Effect during Ignition of a Condensed Material by a Light Pulse

The ignition of a semitransparent reactive material (thermite) by a light pulse of millisecond duration for various radii of the irradiation spot was investigated numerically and experimentally. The variation in the temperature field in the material is analyzed, and the limiting ignition energy parameters and the effect exerted on them by of the radial size of the irradiation spot are found. Results of numerical and experimental studies are compared which each other and with the results of approximate theoretical studies of other authors.

Detection of terrestrial gamma ray flashes up to 40 MeV by the AGILE satellite

We report the detection by the Astrorivelatore Gamma a Immagini Leggero (AGILE) satellite of terrestrial gamma ray flashes (TGFs) obtained with the minicalorimeter (MCAL) detector operating in the energy range 0.3–100 MeV. We select events typically lasting a few milliseconds with spectral and directional selections consistent with the TGF characteristics previously reported by other space missions. During the period 1 June 2008 to 31 March 2009 we detect 34 high‐confidence events showing millisecond durations and a geographical distribution peaked over continental Africa and Southeast Asia. For the first time, AGILE‐MCAL detects photons associated with TGF events up to 40 MeV. We determine the cumulative spectral properties of the spectrum in the range 0.5–40 MeV, which can be effectively described by a Bremsstrahlung spectrum. We find that both the TGF cumulative spectral properties and their geographical distribution are in good agreement with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) results.

Gadolinium blocks membrane permeabilization induced by nanosecond electric pulses and reduces cell death

It has been widely accepted that nanosecond electric pulses (nsEP) are distinguished from micro- and millisecond duration pulses by their ability to cause intracellular effects and cell death with reduced effects on the cell plasma membrane. However, we found that nsEP-induced cell death is most likely mediated by the plasma membrane disruption. We showed that nsEP can cause long-lasting (minutes) increase in plasma membrane electrical conductance and disrupt electrolyte balance, followed by water uptake, cell swelling and blebbing. These effects of plasma membrane permeabilization could be blocked by Gd(3+) in a dose-dependent manner, with a threshold at sub-micromolar concentrations. Consequently, Gd(3+) protected cells from nsEP-induced cell death, thereby pointing to plasma membrane permeabilization as a likely primary mechanism of lethal cell damage.

The millisecond radio sky: transients from a blind single-pulse search

We present the results of a search for transient radio bursts of between 0.125 and 32 millisecond duration in two archival pulsar surveys of intermediate galactic latitudes with the Parkes multibeam receiver. Fourteen new neutron stars have been discovered, seven of which belong to the recently identified "rotating radio transients" (RRATs) class. Here we describe our search methodology, and discuss the new detections in terms of how the RRAT population relates to the general population of pulsars. The new detections indicate (1) that the galactic z-distribution of RRATs in the surveys closely resembles the distribution of pulsars, with objects up to 0.86 kpc from the galactic plane; (2) where measurable, the RRAT pulse widths are similar to that of individual pulses from pulsars of similar period, implying a similar beaming fraction; and (3) our new detections span a variety of nulling fractions, and thus we postulate that the RRATs may simply be nulling pulsars that are only "on" for less than a pulse period. Finally, the newly discovered object PSR J0941-39 may represent a link between pulsars and RRATs. This bizarre object was discovered as an RRAT, but in follow-up observations often appeared as a bright (~10 mJy) pulsar with a low nulling fraction. It is obvious therefore that a neutron star can oscillate between being an RRAT and a pulsar. Crucially, the sites of the RRAT pulses are coincident with the pulsar's emission, implying that the two emission mechanisms are linked, and that RRATs are not just pulsars observed from different orientations.

Time estimation in mild Alzheimer's disease patients

BackgroundTime information processing relies on memory, which greatly supports the operations of hypothetical internal timekeepers. Scalar Expectancy Theory (SET) postulates the existence of a memory component that is functionally separated from an internal clock and other processing stages. SET has devised several experimental procedures to map these cognitive stages onto cerebral regions and neurotransmitter systems. One of these, the time bisection procedure, has provided support for a dissociation between the clock stage, controlled by dopaminergic systems, and the memory stage, mainly supported by cholinergic neuronal networks. This study aimed at linking the specific memory processes predicted by SET to brain mechanisms, by submitting time bisection tasks to patients with probable Alzheimer's disease (AD), that are known to present substantial degeneration of the fronto-temporal regions underpinning memory.MethodsTwelve mild AD patients were required to make temporal judgments about intervals either ranging from 100 to 600 ms (short time bisection task) or from 1000 to 3000 ms (long time bisection task). Their performance was compared with that of a group of aged-matched control participants and a group of young control subjects.ResultsLong time bisection scores of AD patients were not significantly different from those of the two control groups. In contrast, AD patients showed increased variability (as indexed by increased WR values) in timing millisecond durations and a generalized inconsistency of responses over the same interval in both the short and long bisection tasks. A similar, though milder, decreased millisecond interval sensitivity was found for elderly subjects.ConclusionThe present results, that are consistent with those of previous timing studies in AD, are interpreted within the SET framework as not selectively dependent on working or reference memory disruptions but as possibly due to distortions in different components of the internal clock model. Moreover, the similarity between the timing patterns of elderly and AD participants raises the important issue of whether AD may be considered as part of the normal aging process, rather than a proper disease.

OcuDrain-E™—A noninvasive technique for reduction of intraocular pressure

OcuDrain-E™ is a noninvasive technique in which electrical pulses are applied across the cornea to enhance the rate of transcorneal water evaporation (TCWE). In vitro studies were carried out with rabbit cornea mounted on a Franz diffusion cell. Application of 30 pulses each of 1 millisecond (ms) duration at ≥40 V/cm 2 decreased the corneal resistivity ∼80% indicating permeabilization of the cornea. The corneal resistivity was almost completely recovered within 6 h when the pulse voltage was <40 V/cm 2. The average TCWE at 40 V/cm 2 was significantly (∼39-fold) higher than the control ( t-test, p < 0.0001). Application of electrical pulses (40 V–30 pulses–1 ms–1 Hz) across the cornea resulted in significant decrease in the intraocular pressure (IOP) in rabbits. The electrical protocol was well tolerated by the rabbits. Microscopic studies revealed that the applied electrical protocol did not cause any edema or detachment of the epidermal layers. The results of current investigation suggest that OcuDrain-E™ could be developed as a potential technique for the treatment of glaucoma in patients who respond poorly to drugs.

Production of Millisecond Dips in Sco X‐1 Count Rates by Dead Time Effects

Chang and coworkers reported millisecond duration dips in the X-ray intensity of Sco X-1 and attributed them to occultations of the source by small trans-Neptunian objects (TNOs). We have found multiple lines of evidence that these dips are not astronomical in origin, but rather the result of high-energy charged particle events in the RXTE PCA detectors. Our analysis of the RXTE data indicates that at most 10% of the observed dips in Sco X-1 could be due to occultations by TNOs, and, furthermore, we find no positive or supporting evidence for any of them being due to TNOs. We therefore believe that it is a mistake to conclude that any TNOs have been detected via occultation of Sco X-1.

Improved Boron Activation with Reduced Preheating Temperature during Flash Annealing of Preamorphized Silicon

In flash lamp annealing, the entire wafer is uniformly preheated to an intermediate temperature before a millisecond duration flash of intense light is applied. This interaction of the preheating condition and final flash energy density on the properties of preamorphized boron-implanted silicon was studied. It was found that for a fixed flash energy density, an increase in sheet resistance was observed with higher preheating temperature. This sheet resistance degradation is attributed to the occurrence of solid-phase epitaxial regrowth (SPER) during preheating instead of during the high temperature flash step. When the preheating temperature is reduced, occurrence of SPER of the amorphous silicon during preheating is not possible due to the low temperature. As such, SPER has to take place during the high temperature flash anneal step. Since the solid solubilities attainable using SPER is higher than flash, by introducing SPER at a higher temperature, the amount of activated boron atoms that can be incorporated into the silicon lattice is increased and a sheet resistance improvement is observed.

Effects of high-temperature anneals and Co60 gamma-ray irradiation on strained silicon on insulator

Strained silicon on insulator was exposed to high-temperature annealing and high-dose Co60 gamma (γ)-ray irradiation to study the tenacity of the bond between the strained Si film and the underlying buried oxide. During the high-temperature anneals, the samples were ramped at a rate of 150°C/s to 850°C then ramped to 1200, 1250, and 1300°C at a rate of approximately 5×105°C∕s for millisecond duration anneals. For the irradiation experiments, the samples were irradiated with Co60 γ rays to a dose of 51.5kGy. All samples were characterized by ultraviolet (UV) Raman, pseudo metal-oxide-semiconductor field-effect transistor (Ψ-MOSFET) current voltage, Hall mobility, and photoluminescence (PL) to verify changes in strain. UV Raman, PL, and Ψ-MOSFET measurements show no strain relaxation for the high-temperature annealed samples and only very slight relaxation for the γ-ray irradiated samples.

A Bright Millisecond Radio Burst of Extragalactic Origin

Pulsar surveys offer a rare opportunity to monitor the radio sky for impulsive burst-like events with millisecond durations. We analyzed archival survey data and found a 30-jansky dispersed burst, less than 5 milliseconds in duration, located 3 degrees from the Small Magellanic Cloud. The burst properties argue against a physical association with our Galaxy or the Small Magellanic Cloud. Current models for the free electron content in the universe imply that the burst is less than 1 gigaparsec distant. No further bursts were seen in 90 hours of additional observations, which implies that it was a singular event such as a supernova or coalescence of relativistic objects. Hundreds of similar events could occur every day and, if detected, could serve as cosmological probes.

Achieving Sufficient Safety Margins with Fixed Duration Waveforms and the Use of Multiple Time Constants

There are several options to achieve a sufficient safety margin in a patient with a high defibrillation threshold (DFT), with varying and typically modest success. Programming fixed (millisecond) durations of both phases of a biphasic waveform in an implantable cardioverter defibrillator (ICD) has demonstrated utility. We established an informal multisite registry of ICD implanting facilities. Each facility agreed to attempt the use of fixed duration waveforms whenever there was an inadequate safety margin with tilt-based waveforms. A 3.5-ms-based fixed duration shock was tried first. If that failed to achieve a 10-J safety margin then a 2-ms-based shock was used. We also tabulated an HEDFT (high estimate DFT) as precise DFTs were not determined. Sixteen patients (15 M, 1 F) were entered into the registry (age 58.2 +/- 17.9 years) with ejection fractions of .30 +/-.11. Superior vena cava coils were used in 7 patients according to physician preference. The tilt-based HEDFTs were 35.4 +/- 3.2 J delivered and 35.8 +/- 3.3 J stored energy. The 3.5-ms based shocks were evaluated on 14 patients and the HEDFT fell to 23.4 +/- 6.3 J delivered (P < 0.0001) and 26.2 +/- 6.9 J stored energy (P < 0.0001). The 2-ms-based fixed duration shocks were then evaluated on 6 patients and the delivered energy HEDFT was 22.2 +/- 5.8 J (P = 0.001 vs. tilt-based shocks) while the stored energy HEDFT was 27.9 +/- 6.4 J (P = 0.01 vs. tilt-based shocks). Using the better of the two fixed duration waveforms, the mean safety margin was improved from -1.2 +/- 1.9 J to 9.5 +/- 5.9 J (P < 0.00001). Multivariate predictors of the safety margin improvement were the absence of the Superior Vena Cava (SVC) coil and absence of Ventricular fibrillation (VF) presentation. Four patients still required lead repositioning after the use of the fixed duration waveforms. No additional leads were implanted. The use of a selection of directly programmed fixed duration biphasic shocks had a striking impact on the HEDFT for these difficult patients. Adequate safety margins were obtained for 12 of 16 patients with no lead manipulation or other approaches.

A pulsed two-channel Nd:YAG laser with an improved spatial structure of IR radiation for prompt recording and development of photothermoplastic holograms

A two-channel Nd:YAG laser for high-speed recording and development of photothermoplastic holograms has been created. In two independent channels, the laser generates monopulse radiation of nanosecond duration (30 ns) at the second harmonic frequency (λ 2 = 0.532 μm) and IR radiation (λ 1 = 1.064 μm) produced by quasi-stationary free-running lasing of millisecond duration (4 ms). The radiations with wavelengths λ 2 and λ 1 are used, respectively, for exposure and development of photothermoplastic holograms. A method based on the use of a passive resonator is proposed to improve the spatial structure of IR radiation during lasing.

Size effects on the quenching to the normal state ofYBa2Cu3O7−δthin-film superconductors

To probe the quenching mechanisms under high current densities, current-voltage curves have been measured in $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ thin film microbridges with widths lower than the thermal diffusion length. This condition was obtained by using microbridge-widths under $100\phantom{\rule{0.3em}{0ex}}\ensuremath{\mu}\mathrm{m}$ and stepped ramps of one millisecond step duration. Whereas the flux-flow resistivity is found to be microbridge-width independent, strong width dependence of the quenching current density is observed. These results provide a direct experimental demonstration that for high current densities varying in the millisecond range the transition to a highly dissipative state is due to self heating driven by ``conventional'' (nonsingular) flux flow effects.

An investigation of the temperature dynamics in pulsed heating by the photoemission pyrometry method

An instrument for investigating temperature processes of 30–5000 µsec duration with a time resolution of 2 µsec is described and examples of its use are given.

Pyrometry in laser surface treatment

The pyrometers specially developed for laser machining were applied to analyse temperature fields in laser cladding. It is shown that 2D temperature mapping is useful to optimise the cladding parameters: zone of powder injection in relation to laser beam, temperature gradients and their evolution versus cladding parameters. Multi-wavelength pyrometer was applied to restore the value of true temperature that is useful to control melting/solidification when complex powder blends are used and when it is necessary to minimise thermal decomposition of certain compounds. The developed multi-wavelength pyrometer and the applied notch filters are appropriate instruments to measure the evolution of surface temperature produced by Nd:YAG laser pulses of millisecond duration. The variations of several characteristics of the thermal cycle, such as the maximum peak temperature, T max, the instant when melting starts, t m, the melt lifetime, τ lt, the duration of the solidification stage, τ s, with various energy inputs (in the range 10–33 J) and pulse durations (10–20 ms), have been determined for rectangular laser pulses. By appropriate modification of the laser pulse shape (keeping the same energy input and pulse duration), it is possible to realise rather different temperature profiles to vary the melt lifetime and the instant when melting starts. In order to minimise surface temperature variation, to minimise thermal decomposition of certain melt compounds and to increase the melt lifetime, it is necessary to apply higher energy density flux at the beginning of the laser pulse. To obtain a higher peak of the surface temperature, for the given energy input and pulse duration, it is necessary to apply higher energy density flux at the pulse end. This will minimise the melt lifetime as well. In general, it is possible to impose the instant when melt cooling starts and thus to realise an intensive melt cooling during laser irradiation. The above results correspond to the action of laser pulses in the millisecond range with relatively low energy density flux (4 · 10 8–10 9 W m − 2 ) on metallic materials, whose thickness is larger than the heat affected zone (i.e. semi-infinite body from the heat transfer point of view).

Benefit of millisecond waveform durations for patients with high defibrillation thresholds

Patients with a high defibrillation threshold (DFT) present an atypical but vexing problem with regard to implantable cardioverter-defibrillator (ICD) therapy. Their implant procedures are lengthy and involve more risk of complications. These patients often sustain a reduced safety margin that may compromise their survival. The purpose of this study was to evaluate the use of fixed millisecond duration model-optimized biphasic waveforms compared with conventional tilt-based waveforms in patients having a high DFT. We compared a 65%/65% tilt biphasic waveform to a millisecond duration biphasic waveform based on the biphasic burping theory using a 90-microF shock capacitor. Fifty-four patients were evaluated. Mean DFT with tilt was reduced from 11.0 +/- 5.5 J to 8.8 +/- 4.1 J, for a mean reduction of 20% (P < .0001). For the 13 patients with tilt-based DFTs > or = 15 J, DFT was reduced from 18.7 +/- 4.1 J to 13.4 +/- 3.5 J, for a mean DFT reduction of 28% (P = .009). The population peak DFT was reduced from 29.0 J to 17.5 J, for a 41% reduction (P = .03). Use of simple millisecond biphasic waveforms instead of conventional tilt-based waveforms can lead to substantial reductions in DFT, especially in patients with high DFT.

PULSATING NEUTRON STAR AS A SOURCE OF QUASISTATIC WAVES OF GRAVITY IN INTERSTELLAR MEDIUM

The hydrodynamic waves of gravity in the galactic interstellar medium generated by a pulsating neutron star are discussed in this paper. It is shown that the frequency of oscillations of interstellar gas–dust matter in this wave is proportional to that for the g-mode in the neutron star bulk. The corresponding periods are of the millisecond duration. The collective oscillations of charged species in the interstellar wave of gravity can produce electromagnetic radiation, and that the only radio waves of this radiation can freely travel through the galactic gas–dust clouds, suggests that this kind of interstellar waves can manifest itself in the radio range of spectra of a neutron star undergoing pulsations triggered by starquake. This inference is in line with the statement that quasiperiodic micropulses with a time scale of a few milliseconds located in the windows of the main pulse train of the radio pulsar spectra owe their origin to pulsations of neutron stars.