Twin Pulse Research Articles

Compensation of CdZnTe signals using a twin shaping filter technique

The performance of high Z solid state detectors has been significantly improved over the last decade: one of the most promising materials for X and gamma ray detectors is CdTe/CdZnTe, which combines high detection efficiency, no requirement for cooling to cryogenic temperatures, good spectroscopic performances, good time response and imaging capabilities. Unfortunately some important features of semiconductor detectors (pulse height, energy resolution, photopeak efficiency) are affected by the charge collection efficiency: the low mobility of the charge carriers (particularly the holes) and trapping/detrapping phenomena can degrade the CdTe/CdZnTe detectors' response, depending on the distance between the charge formation position and the collecting electrodes. The deterioration of the spectroscopic performances can be reduced by using either hardware or software techniques. The biparametric method herein described is based on a hybrid HW and SW technique that utilizes a twin pulse shaping active filter (one slow and one fast) to analyze the same signal. This technique could be particularly suitable for implementation in a readout integrated circuit for multipixel detectors. The experimental results obtained with the application of this biparametric technique with CdZnTe detectors are presented in order to assess the reliability and the efficiency of this compensation method as a function of bias voltage, primary photon energy and shaping time pairs.

Hemoperfusion using a portable dual pulsatile extracorporeal life support on paraquat intoxication

Study objectives: To remove toxic substances in the blood, nonpulsatile roller pumps usually have been used for hemoperfusion. We develop a portable extracorporeal life support using dual pulsatile electromechanical blood pump (Twin Pulse Life Support: T-PLS). The purpose of this study is to evaluate the efficacy of an alternative hemoperfusion using T-PLS after paraquat intoxication in dogs. Methods: Twelve dogs weighing 30 to 35 kg were randomly assigned to the T-PLS or roller pump group. An 11F double-lumen hemoperfusion catheter was inserted into the right femoral vein in each dog and connected to T-PLS or a roller pump. At 1 hour after the intramuscular administration of paraquat (30 mg/kg), T-PLS or roller pump was started. Hemodynamic and hematologic parameters, including blood pressure, SaO 2 , plasma hemoglobin, and paraquat levels, arterial blood gas, CBC count, electrolytes, blood urea nitrogen and creatinine, aspartate aminotransferase/alanine aminotransferase, and prothrombin time/partial thromboplastin time were measured at baseline and 60 minutes after paraquat administration and 30 minutes, 60 minutes, 120 minutes, 180 minutes, and 240 minutes after T-PLS or roller pumps supports. Results: Compared with the roller pump group, the T-PLS group showed similar or improved effects on hemodynamic and hematologic parameters, including plasma paraquat level. However, there were no significant differences between the groups. Conclusion: We suggest that hemoperfusion using T-PLS may be an alternative method for the removal of toxic substances in blood.

1882: Evaluation of Synchronous Twin Pulse Technique for Extra Corporeal Shock Wave Lithotripsy (SWL): Early Post-SWL Morphologic and Haemodynamic Renal Changes in Comparison to Standard Single Pulse Technique

1882: Evaluation of Synchronous Twin Pulse Technique for Extra Corporeal Shock Wave Lithotripsy (SWL): Early Post-SWL Morphologic and Haemodynamic Renal Changes in Comparison to Standard Single Pulse Technique

1679: Synchronous Twin Pulse Technique for Shock Wave Lithotripsy: Results of The First Prospective Clinical Study

1679: Synchronous Twin Pulse Technique for Shock Wave Lithotripsy: Results of The First Prospective Clinical Study

Evaluation of Synchronous Twin Pulse Technique for Shock Wave Lithotripsy: Determination of Optimal Parameters for In Vitro Stone Fragmentation

The Twinheads extracorporeal shock wave lithotriptor (THSWL) is composed of 2 identical shock wave generators and reflectors. One reflector is under the table and the other is over the table with a variable angle between the axes of the 2 reflectors. The 2 reflectors share a common second focal point, making it possible to deliver an almost synchronous twin pulse to the targeted stone. We studied the optimal parameters for in vitro stone fragmentation. Two types of 1 cm artificial stones were used, namely Bon(n)-stones of 3 compositions (75% calcium oxalate monohydrate [COM] plus 25% uric acid, struvite and cystine) and plaster of Paris. The parameters tested were shock wave number (100, 500 and 1,000), shock wave power (8, 11 and 14 kV) and angle between the reflector axes (67, 90 and 105 degrees). After the optimal parameters were determined we studied the disintegrative efficacy of THSWL for 3 types of human urinary calculi, including COM, calcium hydrogen phosphate (brushite) and cystine. Each stone received 1,000 twin shock waves at 14 kV with an angle of 90 degrees between the reflectors. All experiments were done using a rate of 60 twin shock waves per minute. Following lithotripsy stone fragments were processed and sized. The ratio of the weight of fragments greater than 2 mm-to-total weight of all fragments was calculated. Optimal stone fragmentation results for THSWL were obtained with the maximum number of shock waves (1,000) and full power (14 kV). There was no significant statistical difference in fragment size or the ratio of fragments greater than 2 mm with the use of different angles except for cystine and plaster of Paris calculi, for which the right angle was most effective. At application of the optimal parameters to human stones THSWL produced small fragment size for COM and cystine stones, while brushite stones were not fragmented to the same extent. The efficacy of synchronous twin pulse technology improves as the number of shock waves and power increase. A 90-degree angle between the shock wave reflectors is advantageous for certain stones (that is cystine and plaster of Paris) but it is not a factor for other stone compositions. THSWL has satisfactory disintegrative efficacy for human stones, especially COM and cysteine calculi.

Evaluation of synchronous twin pulse technique for shock wave lithotripsy: in vivo tissue effects

Objectives To study the in vivo tissue effects of synchronous twin pulse technology. Recently, the concept of a synchronous twin pulse technique for shock wave therapy has been introduced with the development of the Twinheads' unit. Methods In 10 pigs (20 kidneys), one of three sites was targeted: the renal pelvis (2 pigs), the mid-zone parenchyma (5 pigs), or the lower pole parenchyma (3 pigs). The treatment parameters were 1000 twin shock waves at 14 kV with a 90° angle between the shock wave reflectors using a rate of 60 shock waves/min in 17 kidneys and 120 shock waves/min in 3 kidneys. To study the effect of an increasing number of twin shock waves, 4 animals (8 kidneys) were used; the mid-zone parenchyma was subjected to 2000 and 3000 twin shock waves in 4 kidneys each, using a rate of 60 shock waves/min at 14 kV and a 90° angle in all of them. For comparison with the use of a single head, another 3 animals (6 kidneys) were treated with the use of the single under-table head; all of them received 2000 single shock waves at 14 kV focused on the mid zone of the kidney parenchyma. Within 1 hour of treatment, the treated kidneys were harvested, inspected, and sectioned at the focal site, as well as at 1 and 2 cm distant to the focal site. Results No gross lesions of the surrounding organs, subcapsular hemorrhage, or parenchymal damage were found at the outer surfaces of the kidneys undergoing twin head shock wave lithotripsy even after 3000 twin shocks. The coronal section revealed minimal gross lesions in 4 of 28 kidneys. Microscopically, the parenchymal changes were minimal. In vivo study of the use of the single under-table head revealed that 5 of 6 kidneys had large subcapsular hematomas at both anterior and posterior surfaces and on coronal section extending into the parenchyma. Microscopically, the changes were significant. Conclusions Synchronous twin pulse shock waves induced minimal damage compared with single pulse standard shock waves. Of note, even after 3000 twin pulses (ie, a total of 6000 shock waves), the renal damage remained minimal.

Experimental study of twin pulse jet engines for power plant application

The total efficiency of power plants depends on the energy conversion in a combustor and a turbine. Considerably higher energy transfer rates can be obtained from a pulsed combustion, but unsteady flow of a single jet combustor reduces the turbine efficiency. Therefore, two pulse combustors were set in parallel and connected to a settling chamber that supplies a flow with constant pressure to the turbine. The aim of investigations presented here is a demonstration of technical feasibility for industrial applications and to show the benefits obtained from the pulse combustors.

Evaluation of synchronous twin pulse technique for shock wave lithotripsy: Early results of the first prospective clinical study

Evaluation of synchronous twin pulse technique for shock wave lithotripsy: Early results of the first prospective clinical study

Speed limit of all-optical gate switches using cascaded second-order nonlinear effect in quasi-phase-matched LiNbO3 devices

In all-optical gate switches that employ the cascaded second-order nonlinear effect in quasi-phase-matched (QPM) LiNbO/sub 3/ devices, walkoff between the fundamental and second harmonic pulses is very large. The authors experimentally show that crosstalk of the switch induced by such walkoff limits the switching speed, but that the switching speed can significantly be enhanced by walkoff compensation. Using a 20-mm-long QPM LiNbO/sub 3/ waveguide device, the authors switch one of twin pulses separated by 6.25 ps without crosstalk, showing the possibility of switching a 160-Gb/s signal.

Trapped pulse generation by femtosecond soliton pulse in birefringent optical fibers

A novel phenomenon of trapped pulse generation by orthogonally polarized femtosecond soliton pulse is discovered in low birefringent optical fiber. As pulse propagation, wavelengths of soliton pulse and trapped pulse are shifted toward longer wavelength side due to effects of soliton selffrequency shift and pulse trapping. The energy of trapped pulse is increased exponentially through Raman gain of soliton pulse and orthogonally polarized and temporally overlapped two colored femtosecond twin pulses are generated. The spectrogram of output pulses is observed using crosscorrelation frequency resolved optical gating technique. The characteristics of this phenomenon are also analyzed numerically and numerical results are almost in agreement with experimental ones.

COMPARISON OF NONPULSATILE VERSUS PULSATILE ECLS (TPL-STM)

PURPOSE OF STUDY The study was designed to compare the safety and efficacy of Korean pulsatile ECLS (Twin Pulse Life Support system: TPLSTM) to those of nonpulsatile ECLS. METHODS USED An acute heart failure model was constructed in twelve piglets by using a pulmonary artery banding technique. The animals were divided into two groups: In group I, a centrifugal pump (Medtronic, co.) was used as a control (n = 6). In group II, a dual-pulse ECLS (TPLS) system was used as an experiment (n=6). The bypass circuit contained a membrane oxygenator, and the right atrium and the aorta were bypassed for two hours under 2 L/min of pump flow. SUMMARIZED RESULTS Pulmonary artery banding lowered systolic blood pressure to 60 mmHg or less. During the bypass, systolic pressure was maintained 103±20 mmHg in group I and 103±20 mmHg in group II (P=NS). Central venous pressure was 8±3 mmHg in group I and 7±5 mmHg in group II (p=NS). The plasma free hemoglobin level showed 19±9 mg% in group I and 15±2 mg% in group II. The peak pressure at the inlet of a membrane oxygenator was 190 mmHg in group I and 230 mmHg in group II. Systemic oxygenation throughout the bypass period was not different between the groups. We believe the Korean dual-pulsatile system (TPLSTM) can be safely applied as an ECLS for the treatment of acute heart failure.

T-PLS NEW PULSATILE BLOOD PUMP TECHNOLOGY FROM CARDIAC ARREST TO HEART RECOVERY

The conventioal non-pulsatile blood pump of the roller-type or the centrifugal pump are used for present ECMO application. We have developed the Twin Pulse Life Support (T- PLS) and performed animal experiments. As T- PLS is a portable device with small size, it can he used, sequencially, from the emergency care to the surgical operation and the patients recovery. The T- PLS system consists of two blood sac and oxygenator. The polypropylene hollow fiber membrane oxygenator (Univoxtm- IC, Baxter) was used. The polyurethane polymer valves are used at the inlet and outlet sides of the tubular blood sacs. Non- pulsatile ECMO system as centrifugal pump may generate negative pressure as high 2s − 200 to − 700 mmHg in the drainage circuit which may cause cavitation, and the pump output are independent upon the afterload However, T- PLS flow's pre-load dependency and after-load-independent pump output can make the system to he automatically controlled In animal experiments, the degree of the blood damages was lower than the other conventional pumps. These animal and in-vitro experimental results show that the pulsatile flow can be safely produced for physiological blood flows in the brain, heart, and the lung.

Experimental study of twin pulse jet engines

The total efficiency of power plants depends on energy conversion in a combustor and a turbine. Considerably higher energy transfer rates can be obtained from a pulsed combustion although unsteady flow of a single jet combustor reduces the turbine efficiency. Therefore, two pulse combustors were set in parallel and connected to a settling chamber that supplies a flow with constant pressure to the turbine. The aim of investigations presented here is a demonstration of technical feasibility for industrial applications and to show the benefits obtained from the pulse combustors.

Neurochemical and electrophysiological studies on the functional significance of burst firing in serotonergic neurons

We have previously described a population of 5-hydroxytryptamine neurons which repetitively fires bursts of usually two (but occasionally three or four) action potentials, with a short (<20 ms) interspike interval within a regular low-frequency firing pattern. Here we used a paradigm of electrical stimulation comprising twin pulses (with 7- or 10-ms inter-pulse intervals) to mimic this burst firing pattern, and compared the effects of single- and twin-pulse electrical stimulations in models of pre- and postsynaptic 5-hydroxytryptamine function. Firstly, we measured the effect of direct electrical stimulation (2 Hz for 2 min) of rat brain slices on efflux of preloaded [ 3H]5-hydroxytryptamine. In this in vitro model, twin-pulse stimulation increased the efflux of tritium by about twice as much as did single-pulse stimulation. This effect was evident in the medial prefrontal cortex (area under the curve: 2.59±0.34 vs 1.28±0.22% relative fractional release), as well as in the caudate–putamen (3.93±0.65 vs 2.17±0.51%) and midbrain raphe nuclei (5.42±1.05 vs 2.51±0.75%). Secondly, we used in vivo microdialysis to monitor changes in endogenous extracellular 5-hydroxytryptamine in rat medial prefrontal cortex in response to electrical stimulation (3 Hz for 10 min) of the dorsal raphe nucleus. In this model, twin-pulse stimulation of the dorsal raphe nucleus increased 5-hydroxytryptamine by approximately twice as much as did single-pulse stimulation at the same frequency (area under the curve: 50.4±9.0 vs 24.2±4.4 fmol). Finally, we used in vivo extracellular recording to follow the response of postsynaptic neurons in the rat medial prefrontal cortex to 5-hydroxytryptamine released by dorsal raphe stimulation. Electrical stimulation of the dorsal raphe nucleus (1 Hz) induced a clear-cut poststimulus inhibition in the majority of cortical neurons tested. In these experiments, the duration of poststimulus inhibition following twin-pulse stimulation was markedly longer than that induced by single-pulse stimulation (200±21 vs 77±18.5 ms). Taken together, the present in vitro and in vivo data suggest that in 5-hydroxytryptamine neurons, short bursts of action potentials will propagate along the axon to the nerve terminal and will enhance both the release of 5-hydroxytryptamine and its postsynaptic effect.

Time-space conversion of femtosecond light pulse by spatio-temporal joint transform correlator

A new method to obtain the auto-correlation of an ultrafast light pulse spatially and parallel is proposed. The method is based on a conventional optical computing technique, joint transform correlator, and a spectral filtering method to control ultrafast light pulses temporally. A simple experimental determination of the pulse-separation of twin pulses, is demonstrated. In the experiment, the optically addressable spatial light modulator is used as a spectrum-power spectrum conversion device, and the temporal accuracy of the system is 12.4 fs.

Importance of stimulation paradigm in determining facilitation and effects of neuromodulation

Evoked synaptic activity within the CNS and at the neuromuscular junction in most in vivo preparations studied occurs not with single isolated stimuli, but with trains, or bursts, of stimuli. Although for ease in studying the mechanisms of vesicular synaptic transmission one often uses single discrete stimuli, the true mechanisms in the animal may be far more complex. When repetitive stimuli are present at a nerve terminal, often a heightened (i.e., facilitated) postsynaptic potential can be as a result. Facilitation is commonly used as an index of synaptic function and plasticity induced by chronic stimulation or by neuromodulation. The mechanisms that give rise to facilitation are thought to be the same that may underlie short-term learning and memory [C.H. Bailey, E.R. Kandel, Structural changes accompanying memory storage. Annu. Rev. Physiol. 55 (1993) 397–426.]. Differences in short term facilitation (STF) are seen depending on the conventional stimulation paradigm (twin pulse, train, or continuous) used to induce facilitation. Thus, a battery of paradigms should be used to characterize synaptic function to obtain a closer understanding of the possible in vivo conditions.

Two components of transmitter release from the chick ciliary presynaptic terminal and their regulation by protein kinase C.

1. A study was made of the effects of phorbol ester (phorbol 12-myristate 13-acetate, PMA, 0.1 microM) on the two components of evoked transmitter release, namely the fast synchronous and the slow asynchronous components, from the giant presynaptic terminal of the chick ciliary ganglion. The excitatory postsynaptic currents (EPSCs) were recorded under whole-cell voltage clamp of the postsynaptic neuron. 2. The decay time constant of the slow component was prolonged by replacing Ca2+ with Sr2+. In 5 mM [Sr2+]o the fast component decayed with a time constant of 2.6 +/- 1.4 ms whereas the slow component decayed with a time constant of 19 +/- 7 ms. 3. When stimulated with twin pulses with a short interpulse interval, the fast component of the second EPSC was often depressed whereas the slow component was usually facilitated. Both components were positively dependent on [Sr2+]o in a saturable manner, but the fast component approached its maximum at a lower [Sr2+]o than the slow component. 4. PMA potentiated both the fast and slow components to a similar extent and with a similar time course. For each component, the effect of PMA was less potent at high [Sr2+]o than at low [Sr2+]o. For either the fast or the slow component the PMA-induced potentiation was accompanied by a reduction in the paired-pulse ratio (PPR). 5. Despite the different dissociation constant for dextran-conjugated fura-2, the fluorescent ratio for intraterminal [Sr2+] ([Sr2+]i) decayed to the baseline after the nerve-evoked increment with a time course similar to that for [Ca2+]i, suggesting that intraterminal Sr2+ is buffered less efficiently than Ca2+. PMA did not increase the [Sr2+]i transients produced by stimulation of the presynaptic oculomotor nerve. 6. It is suggested that protein kinase C (PKC) modulates both the fast and slow components through common molecular mechanisms that upregulate the Sr2+ sensitivity of the vesicle fusion probability.

Protein kinase C potentiates transmitter release from the chick ciliary presynaptic terminal by increasing the exocytotic fusion probability.

1. The giant presynaptic terminal of chick ciliary ganglion was used to examine how protein kinase C (PKC) modulates neurotransmitter release. Cholinergic excitatory postsynaptic currents (EPSCs) were recorded under whole-cell voltage clamp. 2. Although the EPSC was potentiated by phorbol ester (phorbol 12-myristate 13-acetate, PMA; 0.1 microM) in a sustained manner, the nicotine-induced current was unaffected. PMA increased the quantal content to 2.4 +/- 0.4 (n = 9) of control without changing the quantal size. 3. The inactive isoform of PMA, 4alpha-PMA, showed no significant effect on EPSCs. The PMA-induced potentiation was antagonized by two PKC inhibitors with different modes of action, sphingosine (20 microM) and bisindolylmaleimide I (10 microM). 4. When stimulated by twin pulses of short interval, the second EPSC was on average larger than the first EPSC (paired-pulse facilitation; PPF). PMA significantly decreased the PPF ratio with a time course similar to that of the potentiation of the first EPSC. 5. PMA did not affect resting [Ca2+]i or the action potential-induced [Ca2+]i increment in the giant presynaptic terminals. 6. The effect of PMA was less at 10 mM [Ca2+]o than at 1 mM [Ca2+]o. 7. When a train of action potentials was generated with a short interval, the EPSC was eventually depressed and reached a steady-state level. The recovery process followed a simple exponential relation with a rate constant of 0.132 +/- 0.029 s-1. PMA did not affect the recovery rate constant of EPSCs from tetanic depression. In addition, PMA did not affect the steady-state EPSC which should be proportional to the refilling rate of the readily releasable pool of vesicles. 8. These results conflict with the hypothesis that PKC upregulates the size of the readily releasable pool or the number of release sites. PKC appears to upregulate the Ca2+ sensitivity of the process that controls the exocytotic fusion probability.

Spinal inputs from lateral columns to reticulospinal neurons in lampreys

This study characterizes the inputs from the lateral columns of the spinal cord to reticulospinal neurons in the lampreys, using the in vitro isolated brainstem and spinal cord preparation. Synaptic responses to the electrical stimulation of the lateral columns were recorded in reticulospinal neurons of the posterior and middle rhombencephalic reticular nuclei. The responses consisted of a mixture of excitation and inhibition. They were markedly potentiated when using trains of two to five pulses, suggesting that the larger part of these synaptic responses was mediated via an oligosynaptic pathway. An early component, however, persisted when using twin pulses at 10–20 Hz on the ipsilateral side, suggesting the presence of an early mono- or disynaptic component. When increasing the stimulation strength, an early fast rising excitatory component appeared. It most likely resulted from an antidromic activation of vestibulospinal axons in the lateral tracts, which make en passant synaptic contacts with reticulospinal neurons. Responses were practically abolished by adding CNQX and AP5 to the Ringer's solution. The late component of excitatory responses was decreased by AP5, suggesting that NMDA receptors were activated. The NMDA receptor-mediated component was larger when using trains of stimuli or in Mg 2+-free Ringer's. The application of NMDA depolarized reticulospinal neurons. The glycinergic inhibitory component was markedly increased in Mg 2+-free Ringer's. Moreover, GABA B-receptor activation with (−)-baclofen abolished both excitatory and inhibitory responses. Taken together, the present results indicate that ascending lateral column axons generate large excitatory and inhibitory synaptic potentials in reticulospinal neurons. The possible role of these inputs in modulating the activity of reticulospinal neurons during locomotion is discussed.

Control of the calcium concentration involved in acetylcholine release and its facilitation: an additional role for synaptic vesicles?

2,5-Diterbutyl-1,4-benzohydroquinone, a specific blocker of Ca 2+-ATPase pumps, increased acetylcholine release from an identified synapse of Aplysia, as well as from Torpedo and mouse caudate nucleus synaptosomes. Because 2,5-diterbutyl-1,4-benzohydroquinone does not change the presynaptic Ca 2+ influx, the enhancement of acetylcholine release could be due to an accumulation of Ca 2+ in the terminal. This possibility was further checked by studying the effects of 2,5-diterbutyl-1,4-benzohydroquinone on twin pulse facilitation, classically attributed to residual Ca 2+. While preventing the fast sequestration of Ca 2+ by presynaptic organelles, 2,5-diterbutyl-1,4-benzohydroquinone magnified both twin pulse facilitation observed under low extracellular Ca 2+ concentration and twin pulse dysfacilitation observed under high extracellular Ca 2+ concentration. Thus, it is concluded that 2,5-diterbutyl-1,4-benzohydroquinone, by preventing Ca 2+ buffering near transmitter release sites, modulates acetylcholine release. As 2,5-diterbutyl-1,4-benzohydroquinone was also shown to decrease by 50% the uptake of 45Ca 2+ by isolated synaptic vesicles, we propose that synaptic vesicles can control the presynaptic Ca 2+ concentration triggering the release of neurotransmitter.