Quantitative evaluation of CTP derived time-density alterations versus CTP for collateral status prediction with stroke.

BACKGROUND AND OBJECTIVES: Collateral status is a pivotal determinant of clinical outcomes in acute ischemic stroke (AIS); however, its evaluation can be challenging. We investigated the predictive value of CT perfusion (CTP) derived time and density alterations versus CTP for collateral status prediction in AIS. METHODS: Consecutive patients with anterior circulation occlusion within 24 h were retrospectively included. Time-density curves of the CTP specified ischemic core, penumbra, and the corresponding contralateral unaffected brain were obtained. The collateral status was dichotomised into robust (4-5 scores) and poor (0-3 scores) using multiphase collateral scoring, as described by Menon et al.. Receiver operating characteristic curves and multivariable regression analysis were performed to assess the predictive ability of CTP-designated tissue time and density alterations, CTP for robust collaterals, and favourable outcomes (mRS score of 0-2 at 90 days). RESULTS: One-hundred patients (median age, 68 years; interquartile range, 57-80 years; 61 men) were included. A smaller ischemic core, shorter peak time delay, lower peak density decrease, lower cerebral blood volume ratio, and cerebral blood flow ratio in the CTP specified ischemic core were significantly associated with robust collaterals (PFDR ≤ 0.004). The peak time delay demonstrated the highest diagnostic value (AUC, 0.74; P < 0.001) with 66.7 % sensitivity and 73.7 % specificity. Furthermore, the peak time delay of less than 8.5 s was an independent predictor of robust collaterals and favourable clinical outcomes. CONCLUSIONS: Robust collateral status was significantly associated with the peak time delay in the ischemic core. It is a promising image marker for predicting collateral status and functional outcomes in AIS.

Exploring Hierarchical Information in Hyperbolic Space for Self-Supervised Image Hashing.

In real-world datasets, visually related images often form clusters, and these clusters can be further grouped into larger categories with more general semantics. These inherent hierarchical structures can help capture the underlying distribution of data, making it easier to learn robust hash codes that lead to better retrieval performance. However, existing methods fail to make use of this hierarchical information, which in turn prevents the accurate preservation of relationships between data points in the learned hash codes, resulting in suboptimal performance. In this paper, our focus is on applying visual hierarchical information to self-supervised hash learning and addressing three key challenges, including the construction, embedding, and exploitation of visual hierarchies. We propose a new self-supervised hashing method named Hierarchical Hyperbolic Contrastive Hashing (HHCH), making breakthroughs in three aspects. First, we propose to embed continuous hash codes into hyperbolic space for accurate semantic expression since embedding hierarchies in the hyperbolic space generates less distortion than in the hyper-sphere or Euclidean space. Second, we update the K-Means algorithm to make it run in the hyperbolic space. The proposed hierarchical hyperbolic K-Means algorithm can achieve the adaptive construction of hierarchical semantic structures. Last but not least, to exploit the hierarchical semantic structures in hyperbolic space, we propose the hierarchical contrastive learning algorithm, including hierarchical instance-wise and hierarchical prototype-wise contrastive learning. Extensive experiments on four benchmark datasets demonstrate that the proposed method outperforms state-of-the-art self-supervised hashing methods. Our codes are released at https://github.com/HUST-IDSM-AI/HHCH.git.

Ischemic stroke as an initial performance of polycythemia vera in young adults: A case report and literature review.

INTRODUCTION: As the second leading cause of death and disability worldwide, stroke is mainly caused by atherosclerosis and cardiac embolism, particularly in older individuals. Nevertheless, in young and otherwise healthy individuals, the causes of stroke can be more diverse and may include conditions such as patent foramen ovale, vasculitis, coagulopathies, genetic factors, or other undetermined causes. Although these other causes of stroke account for a relatively small proportion compared to ischemic stroke, they are becoming increasingly common in clinical practice and deserve attention. Here, we present a rare female patient with polycythemia vera (PV) who was admitted to the hospital as a stroke patient without any previous medical history. PATIENT CONCERNS: A 40-year-old young woman felt sudden dizziness and slow response. After 4 days of being admitted, she developed blurry vision on the right. DIAGNOSES: Cranial magnetic resonance imaging revealed aberrant signals in the left temporal and parietal lobe, as well as multiple small focal signal abnormalities were observed in the left frontal lobe. Magnetic resonance angiography revealed partial stenosis of the left internal carotid artery. The patient's blood routine examination revealed a significant elevation in complete blood counts, particularly the increase in red blood cells, as well as prolonged clotting time. An abdominal ultrasound and abdomen computed tomography showed splenomegaly. The outcome of the genetic testing was positive for the Janus kinase JAK2 exon V617F mutation (JAK2/V617F). The patient was diagnosed with PV-related stroke. INTERVENTIONS: The patient was treated with phlebotomy, cytoreductive therapy, and low-dose aspirin antiplatelet therapy and was regularly followed up in hematology and neurology clinics after discharge. OUTCOMES: The patient's red blood cell, leukocyte, and thrombocyte counts had fully normalized, with her hemoglobin level measuring at 146 g/L and hematocrit value at 43%. Furthermore, there had been a significant improvement in neurological symptoms. LESSONS: PV, a rare hematological disorder, can present with ischemic stroke as the initial performance, and the diagnosis mainly relies on routine blood tests, bone marrow biopsies, and genetic test. Therefore, clinicians should pay attention to PV, a low-prevalence disease, when encountering stroke in youth.

Tightly coupled arrays with time-domain beam scan for the radiation of high-power ultrawideband electromagnetic pulses.

In this paper, a kind of tightly coupled array (TCA) with time-domain beam scan is developed for the radiation of high-power ultrawideband (UWB) electromagnetic pulses, and the peak-power pattern is proposed to characterize the directivity. First, the active voltage standing wave ratio (AVSWR) bandwidth of the TCA is optimized, which is the precondition for the beam scan. It indicates that the lower-cutoff frequency (LCF) is inversely proportional to the total length of the whole array; an increase in the distance between the array and the ground plane could remarkably reduce the LCF; and an increase in the element number can also decrease the LCF because of the increase in length, but more elements would make the center elements difficult to match in the low-frequency range, so there is a limitation on the number of elements for a certain LCF. Based on these results, a six-element linear array is designed. Then, the definition of the peak-power pattern is proposed to characterize the directivity of the UWB pulsed antenna. Finally, the optimized six-element array is developed, and the measured working band is 276 MHz-6.4 GHz (AVSWR < 3). The effective potential gain is 1.76, and it improves by 51.7% with a reduction in the aperture area by 68.4% compared with the previous TCA, which means that the aperture efficiency is remarkably improved. The half-power beam width of the developed TCA with the scan angle of 0° is 45°. The time-domain beam scan could be performed with time-delay feeding lines, and the maximum scan angle is over ±30° in the E-plane. The developed TCA can be applied for the generation of high-power electromagnetic environments for the study of intentional electromagnetic interference.

Application of Sofia Plus catheter tip shaping in the treatment of acute middle cerebral artery occlusion: A case control study.

To explore the safety and efficacy of Sofia Plus distal access catheter tip shaping for treatment of acute middle cerebral artery embolism. This single-center retrospective study involved patients eligible for acute embolic middle cerebral artery occlusion from January 2020 to October 2021. They were divided into a shaping and non-shaping group according to whether the Sofia Plus catheter tip was shaped intraoperatively. Baseline data, preoperative Alberta Stroke Program Early Computed Tomography (ASPECT) score, National Institutes of Health Stroke Scale (NIHSS) score, onset-to-admission time, admission-to-puncture time, Sofia Plus-clot time, puncture-to-reperfusion time, surgical approach, and use of a stent for rescue thrombectomy were compared between the 2 groups. Postoperative symptomatic intracerebral hemorrhage and the modified Rankin scale score at the 90-day follow-up were observed. In total, 54 patients were enrolled in this study (shaping group, 26 patients; non-shaping group, 28 patients). Their mean age was 64.8 ±â€…14.6 years, and the proportion of men was 68.5% (37/54). Successful recanalization was achieved in all patients. There were no differences in the baseline data (age, sex, history, pre-admission ASPECT score, or NIHSS score) between the shaping and non-shaping groups. Patients treated with a shaped Sofia Plus catheter had a shorter Sofia Plus-clot time [median (25th, 75th percentile: 4 (4, 7) vs 10.5 (5.25, 14) min, P = .006] and puncture-to-reperfusion time [16.5 (12, 30.5) vs 26 (16.25, 38.25) min, P = .036]. There were significant differences in the surgical approaches between the 2 groups. The rates of a favorable outcome (57.7% vs 64.3%, P = .62) and postoperative symptomatic intracerebral hemorrhage (7.7% vs 3.6%, P = .60) were not significantly different between the groups. Sofia Plus catheter tip shaping improved catheter trafficability and reduced the operative time. It was safe and effective for treatment of acute middle cerebral artery thrombotic occlusion.

Development of a compact high-current repetitive pulsed x-ray system.

Pulsed x-rays are crucial for various applications such as radiography, biological effects, and the system-generated electromagnetic pulse effect. X rays with a higher dose rate and a higher total dose can generate more significant radiation effects and more effective radiography. However, most pulsed sub-100 keV x-ray systems with high dose rates operate in the single pulse mode with limited total dose, and most repetitive pulsed x-ray systems have a low dose rate. This paper develops a compact high-current repetitive pulsed x-ray system with a low-impedance diode to generate high dose rate pulsed x-rays with an average energy below 100 keV. A diode with a double-ring cathode is designed and tested to produce uniform pulsed x-rays. In order to investigate the x-ray intensity and the pulse number of repetitions for different anode thicknesses, five typical thicknesses are tested. The experimental results show that this system can operate stably at a repetitive rate of 0.2 Hz with a peak voltage of about 200 kV and a peak current of about 100 kA. The dose rate is about 2.4 × 105 Gy(LiF)/s, and the average x-ray energy is about 55 keV with the 40 µm thick tantalum anode. The x-ray uniformity is better than 2:1 over the measuring plane.

Prognostic Values of Prothrombin Time and Inflammation-Related Parameter in Acute Ischemic Stroke Patients After Intravenous Thrombolysis with rt-PA.

In previous studies, prothrombin time (PT), systemic inflammation response index (SIRI) and systemic immune inflammation Index (SII) levels might be the prognostic factors for patients with ischemic stroke. However, the association between these coagulation and inflammation biomarkers and prognosis in patients with acute ischemic stroke (AIS) who undergo intravenous thrombolysis (IVT) with recombinant tissue plasminogen activator (rt-PA) remains unclear and needs further study. Thus, this study aimed to investigate the relationship between these biomarkers and clinical prognosis after IVT in AIS patients. We included patients at the Hebei general hospital diagnosed with AIS who received standard-dose IVT with rt-PA from September 2017 to August 2022. Demographic information, vascular risk factors, laboratory test results, and other stroke-related data were collected for analysis. Clinical outcomes included short-term outcome at 24 h and functional outcome at 3 months. We enrolled 281 patients in this study. In total, 16 patients had END within 24 h, and 106 patients had an unfavorable outcome at the 3-month visit. In the multivariate analysis, PT level (OR = 1.833; 95% CI: 1.161-2.893; P = 0.009), SIRI level (OR = 2.166; 95% CI: 1.014-4.629; P = 0.046) and SII level (OR = 1.002; 95% CI: 1.000-1.003; P = 0.021) were independently associated with 3-month poor outcome in AIS patients with IVT. In conclusion, the higher PT, SIRI and SII levels were independently associated with poor prognosis in AIS patients after IVT. Additionally, PT, SIRI and SII all can be novel short-term prognostic biomarkers for AIS patients treated with IVT.

Effectiveness of Guiding Catheter Retrieval Balloon Technique in the Treatment of Acute Anterior Circulation Tandem Occlusion: A Retrospective Study.

BACKGROUND: Tandem occlusion accounts for 10%-20% of all large vessel occlusion strokes and often yields a poor recanalization rate. The endovascular treatment of tandem lesions is still controversial. This study uses an endovascular treatment strategy, "guided catheter recovery balloon (GRB)" for the treatment of acute anterior circulation tandem occlusion. METHODS: A retrospective design was adopted. The population included patients with acute tandem occlusion who received emergency GRB endovascular treatment. And the choice of stenting was made based on intraoperative radiography imaging. Recanalization was evaluated by the thrombolysis in cerebral infarction score after the operation. Three-month modified Rankin Scale follow-up results were recorded, and modified Rankin Scale ≤2 was considered favorable recovery. RESULTS: A total of 55 patients aged 66.9 ± 8.5 years were enrolled, 37 of whom received stenting. The mean overall recanalization time was 46 minutes. Fifty (90.9%) patients achieved successful recanalization with a thrombolysis in cerebral infarction score of 2b-3. At the 3-month follow-up, the number of patients with favorable functional recovery was 28 (50.9%). The presence of hypertension was correlated with a favorable recovery outcome: 82.1% of the favorable recovery population had hypertension, and 55.6% of the unfavorable outcome population had hypertension (P = 0.033). There was no statistically significant association between stent application and favorable recovery outcomes (P = 0.504). CONCLUSIONS: GRB technique showed a high recanalization rate when applied to the treatment of acute anterior circulation tandem occlusion.

A miniatured helical antenna based on the sinusoidal folding structure with exponential spacing.

An exponential spacing and sinusoidal folded helical (ESSFH) antenna backed with a cavity is developed in this paper. Compared with the conventional helical (CH) antenna, the proposed antenna not only has smaller dimension but also exhibits a wider working bandwidth, a higher gain, and a better circular polarization (CP) characteristic. To reduce the dimension of the helical antenna, a sinusoidal structure is adopted along the circumference of the helix. However, it deteriorates the CP characteristic of the antenna. Therefore, the structure of the exponential helix spacing is introduced into the sinusoidal folded helical (SFH) antenna. Then, to further improve the gain of the ESSFH antenna, its ground plane is replaced by an optimized cavity. Compared with the CH antenna, the helix diameter of the ESSFH antenna Dλ is reduced from 0.32 to 0.23, and its volume is reduced to 53%. The ESSFH antenna backed with a cavity has an impedance bandwidth of 0.43-1.02 GHz, which is much wider than 0.48-0.60 GHz of the CH antenna. Moreover, it has an axial ratio of 1.77, while the axial ratio of the CH antenna is 2.61. In addition, its effective potential gain is 0.56, which is 22% higher than that of the CH antenna.

A modularized high-power ultra-wideband radiation system based on the space-synthesis method.

In this paper, a high-power ultra-wideband radiation system, composed of multiply radiation modules, is developed based on the space-synthesis method. The radiation module mainly consists of a transistorized pulser, a 2 × 2 combined antenna array, and a power divider. To improve the out parameters [the amplitude, the pulse repetition frequency (PRF), and the rise time] of the transistorized pulser based on the Marx circuit, the influence of the traveling wave process on the output pulse must be concerned. Based on the theoretical analysis, the printed circuit board circuit parameters and the circuit structure of the pulser are optimized. To improve the power synthesis efficiency, the pulse jitter characteristic of the pulser is improved by replacing the conventional base triggering mode with the collector voltage ramp triggering mode for the first-stage avalanche transistor in the pulser. The previous optimized antenna array is utilized in this radiation system, which has a better radiation performance in the prescribed aperture area. In addition, based on the gradient microstrip structure, the power divider integrated with the pulser is designed, which has the advantages of wide bandwidth, low loss, and light weight. Experimental results show that the peak effective potential rEp of the radiation system of 20 radiation modules is 221.8 kV, the maximum PRF could reach 10 kHz, and the half-power radiation angles of its radiation field are about 5° in both the E plane and the H plane. More radiation modules could be integrated into the system to achieve a higher electric field in the future.

A broadband optical fiber transmission-based time domain measurement system for nanosecond-level transient electric field.

A novel nanosecond transient electric field (E-field) measurement system is developed in this paper to measure the E-field pulse caused by the operation of the high-voltage switch (switching E-field pulse) in the substation. An electrically small rod antenna is used as the receiving antenna and is matched by the operational amplifier with high input impedance to achieve broadband frequency response and stable working performance. A broadband analog optical fiber transmission system is further designed based on the high-frequency circuit model of the electronic components. Unlike the traditional frequency domain E-field measurement methods, the developed measurement system can directly output the time domain waveform of the switching E-field pulse. It also has the advantages of adjustable sensitivity, portability, and anti-electromagnetic interference. The calibrated measurement bandwidth ranges from 200 Hz to 680 MHz. Furthermore, the switching E-field pulse in an ultra-high voltage substation is measured and analyzed to verify the effectiveness of the fabricated measurement system.

A compact narrow-width combined antenna for the radiation of the UWB electromagnetic pulses.

In this article, a Narrow-Width Combined Antenna (NWCA) is proposed for the compact design of high-power ultra-wideband (UWB) systems. The dependence of performances on three dimensions of the combined antenna is investigated so as to minimize its size with a given excitation. It indicates that the working process of the combined antenna can be divided into two stages: (1) energy transmitted from the feeding point to the aperture by the TEM horn structure, and during this stage, the passband is determined by the effect of the impedance taper, which is related to the length and aperture impedance of the antenna, and (2) energy radiated to the free space from the aperture, during which the height of the aperture is the dominant factor. Therefore, the three dimensions of the combined antenna can be appropriately adjusted to make the antenna more compact. Thus, the NWCA is designed by reducing the width and making a slight compensation in height and/or length. Compared with the conventional cubic antenna, the aperture area of the developed NWCA is reduced by 47%, whereas the amplitude of the radiating field only reduces by 2.5% with the given pulsed excitation at the cost of a slight decrease in the pulse duration. It demonstrates that the NWCA is an effectively compact design for the combined antenna in the application of the radiation of the high-power UWB pulse.

A high-efficiency wideband coupler for nanosecond-level pulsed current injection.

Pulsed current injection (PCI), as a conducted vulnerability testing technique under nanosecond-level transient electromagnetic disturbance (TED), has gained great attention recently. Many kinds of TEDs, e.g., high-altitude electromagnetic pulse, very fast transient overvoltage, and electrical fast transients, have very fast rise time as well as pretty slow decay, whose frequency spectrum may cover a very wideband. Therefore, one of the challenges is that the existing inductive couplers cannot interact with the equipment under test (EUT) over the wideband efficiently, and consequently, they are inadequate to inject the proper disturbance at ports of EUT in PCI tests. To address this problem, a high-efficiency wideband PCI coupler is proposed in this paper. The coupling performance is analyzed theoretically based on the distributed-parameter model of an inductive coupler. By using the composited ferrites instead of the simplex Ni-Zn ferrites, the inductive coupling is enhanced. The capacitive coupling is also enhanced to improve the high-frequency performance by exploiting the distributed tubular winding. A PCI coupler with the dimension of 30 × 10 × 10 cm3 is built to be validated experimentally. The 3 dB bandwidth has been improved from 421 kHz-14 MHz to 77 kHz-39 MHz, which indicates that the coupler can be applied efficiently over the frequency range of interest for PCI tests.

A wideband picosecond pulsed electric fields (psPEF) exposure system for the nanoporation of biological cells.

The effects and mechanisms of ultrashort and intense pulsed electric fields on biological cells remain some unknown. Especially for picosecond pulsed electric fields (psPEF) with a high pulse repetition rate, electroporation or nanoporation effects could be induced on cell membranes and intracellular organelle membranes. In this work, the design, implementation, and experimental validation of a wideband psPEF exposure system (WPES) is reported, comprising picosecond pulser and wideband biochip, for the in vitro exposure of suspended cells to high-intensity psPEF. Excited by repetitive picosecond pulses (the duration of 200 ps and the amplitude of a few kilovolts), the proposed biochip adopts grounded coplanar waveguide (GCPW) for a wide working bandwidth, which was fabricated with 160 µm thick electrodes for uniform distribution of psPEF in the cross-section. To ensure that only psPEF is generated in the biological medium containing cells except for ionic current, this work proposes to install capillary tubes in the electrode gaps for electrical insulation and cells delivery. By electrical measurements in the time domain and frequency domain, the exposure system is adapted for local generation of extremely high-intensity psPEF with the 3 dB bandwidth up to 4.2 GHz. Furthermore, biological experiments conducted on the developed exposure system verified its capability to permeabilize biological cells under the exposure of high-intensity psPEF.

Neuroprotective effects of zonisamide on cerebral ischemia injury via inhibition of neuronal apoptosis.

It is known that neuronal apoptosis contributes to pathology of cerebral ischemia injury. Zonisamide (ZNS) has shown anti-apoptosis effects in recent studies. The present study investigated whether the anti-apoptotic effect can account for the neuroprotective action of ZNS on cerebral ischemia. Neuronal cells were maintained under oxygen-glucose deprivation conditions to simulate cerebral ischemia and treated with ZNS simultaneously. The apoptosis of the cells and expression of apoptosis-related proteins were investigated by flow cytometry and western blot analysis, respectively. A cerebral ischemia mouse model was created via middle cerebral artery occlusion, and the mice were treated with ZNS. Neurological deficit scores and infarct volumes of the cerebral ischemia mice were measured. The apoptosis status of the neuronal cells was evaluated by TUNEL staining. In vitro, the ZNS treatment inhibited both the apoptosis of the neuronal cells and apoptosis-related protein expression (caspase-3, caspase-8, and calpain-1) induced by the oxygen-glucose deprivation. The anti-apoptosis effect of ZNS could occur through the blocking of reactive oxygen species. Moreover, ZNS treatment significantly ameliorated neurological deficits and reduced infarct volumes in the cerebral ischemia mice model. In this study, ZNS exerted neuroprotective effects by inhibition of apoptosis in neuronal cells in cerebral ischemia. Therefore, ZNS might be a promising therapy for cerebral ischemia.

Development of a type of differential switched oscillator system for the radiation of mesoband high-power electromagnetic pulses.

In this Note, a type of Differential Switched Oscillator (DSWO) system is developed and compared with the conventional single-ended switched oscillator; the power capacity of the DSWO is twice with the same insulation level and twice total length. The DSWO system consists of a differential high-voltage pulsed source, a DSWO, and a pair of differential helical antennas. The differential pulsed source is based on the hydrogen thyratron and pulsed transformer whose peak voltage can theoretically reach ±100 kV to break down the high-pressure switch, whose limiting gas pressure is 25 atm; the DSWO is designed to generate a damped oscillation pulse with a central frequency of 300 MHz, which is also the central frequency of the differential helical antennas. Thus, a damped oscillation pulse can be produced and radiated to generate high-power mesoband circularly polarized electromagnetic fields, and the axial ratio is 1.98. According to the measured results, the central frequency of the developed DSWO is 284 MHz, the percent bandwidth of the radiating field is 11%, and the amplitude of the far-field effective potential is 105 kV.

Neuroprotective effects of zonisamide on cerebral ischemia injury via inhibition of neuronal apoptosis

It is known that neuronal apoptosis contributes to pathology of cerebral ischemia injury. Zonisamide (ZNS) has shown anti-apoptosis effects in recent studies. The present study investigated whether the anti-apoptotic effect can account for the neuroprotective action of ZNS on cerebral ischemia. Neuronal cells were maintained under oxygen-glucose deprivation conditions to simulate cerebral ischemia and treated with ZNS simultaneously. The apoptosis of the cells and expression of apoptosis-related proteins were investigated by flow cytometry and western blot analysis, respectively. A cerebral ischemia mouse model was created via middle cerebral artery occlusion, and the mice were treated with ZNS. Neurological deficit scores and infarct volumes of the cerebral ischemia mice were measured. The apoptosis status of the neuronal cells was evaluated by TUNEL staining. In vitro, the ZNS treatment inhibited both the apoptosis of the neuronal cells and apoptosis-related protein expression (caspase-3, caspase-8, and calpain-1) induced by the oxygen-glucose deprivation. The anti-apoptosis effect of ZNS could occur through the blocking of reactive oxygen species. Moreover, ZNS treatment significantly ameliorated neurological deficits and reduced infarct volumes in the cerebral ischemia mice model. In this study, ZNS exerted neuroprotective effects by inhibition of apoptosis in neuronal cells in cerebral ischemia. Therefore, ZNS might be a promising therapy for cerebral ischemia.

A transient electromagnetic disturbance testing system based on low-frequency-compensated symmetric TEM horn antenna.

A transient electromagnetic disturbance (TED) testing system with an adjustable direction of polarization is developed in terms of a low-frequency-compensated symmetric transverse electromagnetic (TEM) horn antenna in this paper. TEM horn antennas are deficient in the low-frequency radiation, which would lead to a very narrow pulse width and cannot be directly applied in radiation tests of TED, especially the TED with abundant low-frequency components such as fast transient overvoltage and high-altitude electromagnetic pulse. To address this problem, a theoretical radiation model and a design principle of the back-loading method are proposed to compensate for the low-frequency performance. After the optimization of the structure according to the simulated results, a TED testing system with the aperture width of 0.9 m and the length of 1.8 m is built. The rise time of the electric field measured at the center of the aperture is 2.39 ns, the pulse width is 27.65 ns, and the peak field is over 50 kV/m, which can meet the requirements of relative standards. The dimension of the working volume is estimated as 0.4 × 0.5 × 0.5 m3 according to the field distribution.

High power and high pulse repetition frequency transistorized pulser by time base stability improvement and power synthesis technique.

Output power of a transistorized pulser is usually limited by the power capacity of avalanche transistors. To improve the total output power, the power synthesis method is widely used, in which a single pulser with high output power and high time base stability is required. However, the time base stability tends to deteriorate as the output power increases. To improve the output power under the premise of high time base stability, from the perspective of carrier movement, the mechanisms of pulse jitter and pulse drift are investigated. It is found that the pulse jitter is caused by time dispersion of the ionization process in the collector depletion region, while the pulse drift is due to the decrement of the diffusion coefficient Dn and the electron mobility µn, which are both temperature-dependent. Based on the microscopic theoretical study, some macroscopic improvements on the time base stability are made. Some parameters of the trigger pulse and the circuit (e.g., charging capacitance) are optimized experimentally. Consequently, we achieved a pulser with an amplitude of 1.8 kV, pulse jitter of 25 ps, pulse drift of 100 ps/min at a pulse repetition frequency (PRF) of 100 kHz. Additionally, a new parameter k, the product of the highest PRF f and the peak power Ep, is defined to evaluate the output power. With almost the same time base stability, the proposed pulser has a k of 6.48 GHz W, which is improved significantly. Finally, a synthesized pulser with an amplitude of 2.5 kV and highest PRF of 100 kHz is achieved.

Development of a TEM-cell-integrated CO2 incubator for cell-based transient electromagnetic field bioeffect study.

To facilitate the cell-based experiment for pulsed electromagnetic field biological effect study, a novel TEM-cell-integrated CO2 incubator was developed. The integrated experimental system could simultaneously meet the requirement of standard cell culture condition and the various Transient Electromagnetic Field (TEF) exposure, which made it possible to study the relationship between different electromagnetic pulse exposure and the cellular responses in a reliable way. During the research, a comparison experiment was carried out to evaluate the necessity of the integrated incubator system: firstly, two different types of cell lines, which are the human prostate cancer cell line (PC3) and the pancreatic ß cell line (MIN6) were chosen and exposed in the TEM-cell which located in the open area and the integrated system, respectively, with the same EFT radiation conditions; then, the cells' viability, the cellular ROS level and the mitochondrial membrane potential (MMP) were detected, respectively. The results showed that in the same parameter of the EFT radiation, the processes of the cells had a significant difference and even opposite in the incubator and open area, and all the results could be reproducible. The phenomenon indicated the stability of the TEM-cell-integrated CO2 incubator, and also demonstrated the necessity to strictly control the cell culture condition when carrying out the precise mechanism study of the TEF bioresponse at the cellular levels.