Use Of High Voltage Research Articles

Effect of GA+ ion beam on the stability of retained austenite in high carbon steel

This paper presents studies concerning the influence of the Ga+ ion beam on the stability of retained austenite in K110 cold work tool steel (X155CrVMo12). The material was first austenitized at 1200 °C to dissolve a significant amount of the alloy's carbides to obtain the largest possible volume fraction of retained austenite, which was 93% after quenching in oil. Changes in the steel's crystal structure upon interaction with Ga+ ions were observed using a combination of SEM-FIB-EBSD techniques. Selected grains in the material were sputtered with Ga+ ions of various accelerating voltages (2 kV – 30 kV) using two different doses, namely 50 and 100 pC/μm2. It was found that the application of 5 kV Ga+ ion beam is enough to induce partial transformation of austenite to BCC phase. The use of higher voltages (8–30 kV) resulted in the complete transformation of austenite. Low acceleration voltages of 2 kV, even with a high dose of 500 pC/μm2, did not induce any phase transformation and only deformed austenite's crystal structure. Moreover, it was shown that the crystallographic orientation between austenite and the Ga+ ion beam induced BCC phase is not random.

Impact of voltage and pulse delivery mode on the efficacy of pulsed light for the inactivation of Listeria

Listeria innocua inactivation by pulsed light (PL) was evaluated at different settings and voltages, to establish the best treatment conditions and post-treatment handling for further implementation of PL in the food industry. Fluences up to 0.2 J/cm2 were applied to superficially inoculated TSA agar plates (4.5–5 log cfu/cm2). Inactivation was calculated, and log-linear and Weibull models were applied. A fluence of 0.2 J/cm2 applied in a single pulse inactivated 3.8 log cfu/cm2, while sequential application of this fluence yielded an inactivation between 1.5 and 2.5 log cfu/cm2 depending on the delivery mode (consecutive flashing or with 5 min-holding times under ambient light or in the dark). Data from consecutive PL treatment were fitted with the Weibull model. No photoreactivation following PL was observed after 120-min exposure to ambient light in any of the conditions assayed. This study showed that flashing with a single pulse at higher voltage would offer the highest inactivation of Listeria. Industrial relevanceThis study offered information of practical interest to establish pulsed light processing and post-processing conditions for the control of Listeria spp. in the food industry, for instance in ready-to-eat (RTE) products. The use of higher voltages provided higher inactivation and allowed to minimise the number of flashes. If sequential treatments are to be applied, the treatment is more effective if short holding times are kept between pulses. The post-processing illumination conditions do not influence the efficacy of PL treatment.

High-speed and high-efficiency shape memory alloy actuation

When standard voltage levels commonly adopted in industry are used to activate thermal shape memory alloy (SMA) wire actuators, they often result in very high electrical currents which may eventually damage or destroy the actuators. To improve performance of SMA wire actuators operating in industrial environments, in this paper we investigate a novel, fast and energy-efficient actuation strategy based on short pulses in the millisecond range. The use of higher voltages leads to a highly dynamic activation process, in contrast to commonly used quasi-static activation based on low-voltage. A test setup is designed to examine the effects of the control parameters (i.e., supply voltage, activation pulse duration, SMA wire pre-tension and wire diameter) on the measured displacement and force output of the SMA wire. It is shown that actuation times in the range of 20 ms and strokes of more than 10% of the SMA wire length can be reached. Additionally, energy savings of up to 80% with respect to conventional quasi-static actuation are achieved. Possible applications for this activation method are release mechanisms, switches or safety applications.

Real-time monitoring of cytotoxic effects of electroporation on breast and colon cancer cell lines

PurposeTo study the effects of electroporation on different cell lines. MaterialThe effects of electroporation on human breast cancer (MDA-MB-231), human colon cancer (SW-480 and HCT-116), human fibroblast cell line (MRC-5), primary human aortic smooth muscle cells (hAoSMC) and human umbilical vein endothelial cells (HUVEC) were studied. Real-time technology was used for cell viability monitoring. Acridine orange/ethidium bromide assay was applied for cell death type determination. A numerical model of electroporation has been proposed. ResultsElectroporation induced inhibition of cell viability on dose (voltage) dependent way. The electroporation treatment 375–437.5Vcm−1 caused irreversible electroporation of cancer cells and reversible electroporation of healthy cells. The application of lower voltage rating (250Vcm−1) led to apoptosis as the predominant type of cell death, whereas the use of higher voltage (500Vcm−1) mainly caused necrosis. ConclusionElectroporation represents a promising method in cancer treatment. Different cancer cell lines had different response to the identical electroporation treatment. Electroporation 375–437.5Vcm−1 selectively caused permanent damage of cancer cells (SW-480), while healthy cells (MRC-5, hAoSM and HUVEC) recovered after 72h. The type of cell death is dependent of electroporation conditions. The proposed numerical model is useful for the analysis of phenomena related to electroporation treatment.

Selective Imaging of Discrete Polyoxometalate Ions on Graphene Oxide under Variable Voltage Conditions.

Monosubstituted lacunary Keggin [CoSiW11O39](6-) ions on graphene oxide (GO) were used in a comparative imaging study using aberration corrected transmission electron microscopy at two different acceleration voltages, 80 and 200 kV. By performing a set of static and dynamical studies, together with image simulations, we show how the use of lower voltages results in better stability and resolution of the underlying GO support while the use of higher voltages permits better resolution of the individual tungsten atoms and leads to less kinetic motion of the cluster, thus leading to a more accurate identification of cluster orientation and better stability under dynamical imaging conditions. Applying different voltages also influences the visibility of both GO and the lighter Co at lower or higher voltages, respectively.

Optimisation of the number of IGBT devices in a series–parallel string

High-power semiconductor switches can be realised by connecting existing devices in series and parallel. The number of devices in series depends on the operating voltage of an application and the individual device voltage rating. For a given application, the use of higher voltage rated IGBTs leads to a fewer number of devices and vice versa. The total power loss of the series string equals to the sum of individual IGBT power losses and total loss increases with the increase in operating frequency. The level of increase in power loss depends on the device characteristics. For high current operation, the minimum number of devices depends on the current rating of individual device. In this paper, series IGBT string of six 1.2kV, four 1.7kV, two 3.3kV and a single 6.5kV IGBTs are simulated for a 4.5kV/100A application and power losses are analysed for different frequencies and duty cycles. This power loss analysis is extended for commercial IGBTs to compare the simulation results. The number of devices for minimum power loss depends on operating frequencies and power savings are significant both at low and high frequencies. In addition to the power losses, the other important issues in optimising the number of IGBTs are described in this paper. When IGBT modules are connected in parallel the principle of derating is applied to obtained reliable operation. This is explained with some examples.

Self-assembled coating for modification of the electro-osmotic flow in nonaqueous capillary electrophoresis using formamide

The use of pure nonaqueous solvents in capillary electrophoresis (CE) can alter the separation selectivity and enhance the solubility of hydrophobic compounds and enables the use of higher voltages. However, control of the electro-osmotic flow (EOF) is essential. In this work, we report the use of self-assembled coatings for EOF modification and elimination of analyte adsorptions onto silica capillaries in pure formamide. Bilayer capillary coatings derived from the double chain cationic surfactant dimethyldioctadecylammonium bromide (2C18DAB) reverses the EOF in buffers such as acetate, formate, and phosphate. Reversed EOF of >1.1 × 10–4 cm2/Vs enables the separation of the pharmaceutical drugs propranolol, metoprolol, chloroquine, and chloropheniramine in less than 5 min with efficiencies of 0.2–0.5 million plates/m (66 000 to 165 000 plates). Chemical and physical factors affecting the coating stability and their influence on separation speed and efficiency of the cationic drugs in formamide are also investigated.Key words: capillary electrophoresis, cationic surfactants, electro-osmotic flow, formamide, nonaqueous solvents.

Unconventional specimen preparation techniques using high resolution low voltage field emission scanning electron microscopy to study cell motility, host cell invasion, and internal cell structures in Toxoplasma gondii.

Apicomplexan parasites employ complex and unconventional mechanisms for cell locomotion, host cell invasion, and cell division that are only poorly understood. While immunofluorescence and conventional transmission electron microscopy have been used to answer questions about the localization of some cytoskeletal proteins and cell organelles, many questions remain unanswered, partly because new methods are needed to study the complex interactions of cytoskeletal proteins and organelles that play a role in cell locomotion, host cell invasion, and cell division. The choice of fixation and preparation methods has proven critical for the analysis of cytoskeletal proteins because of the rapid turnover of actin filaments and the dense spatial organization of the cytoskeleton and its association with the complex membrane system. Here we introduce new methods to study structural aspects of cytoskeletal motility, host cell invasion, and cell division of Toxoplasma gondii, a most suitable laboratory model that is representative of apicomplexan parasites. The novel approach in our experiments is the use of high resolution low voltage field emission scanning electron microscopy (LVFESEM) combined with two new specimen preparation techniques. The first method uses LVFESEM after membrane extraction and stabilization of the cytoskeleton. This method allows viewing of actin filaments which had not been possible with any other method available so far. The second approach of imaging the parasite's ultrastructure and interactions with host cells uses semithick sections (200 nm) that are resin de-embedded (Ris and Malecki, 1993) and imaged with LVFESEM. This method allows analysis of structural detail in the parasite before and after host cell invasion and interactions with the membrane of the parasitophorous vacuole as well as parasite cell division.

Molecular size determinations of DNA restriction fragments and polymerase chain reaction products using capillary gel electrophoresis

Commercially available capillary electrophoresis (CE) systems offer advantages over traditional slab gel methodologies. The capillary format allows the use of higher voltages (225 V/cm), which results in faster migration, higher resolution and greater efficiency without excessive heating. The ability to automate the system increases the unattended sample analysis throughput. For this study, the CE system was configured with a μ PAGE 3% T, 3% C polyacrylamide gel capillary with an effective length of 40 cm and μ PAGE Tris-borate urea buffer system. The analysis of DNA restriction fragments and polymerase chain reaction products, with an internal standard of Boehringer Mannheim DNA marker XI were completed in less than 70 min. All samples were analyzed at 260 nm. The data establishes automated capillary gel electrophoresis as a high-resolution, reproducible method for analysis of samples under 1000 base pairs.

Influence of age of in vitro matured oocytes and electrical stimulations on the development of cattle nuclear transfer embryos

High-power semiconductor switches can be realised by connecting existing devices in series and parallel. The number of devices in series depends on the operating voltage of an application and the individual device voltage rating. For a given application, the use of higher voltage rated IGBTs leads to a fewer number of devices and vice versa. The total power loss of the series string equals to the sum of individual IGBT power losses and total loss increases with the increase in operating frequency. The level of increase in power loss depends on the device characteristics. For high current operation, the minimum number of devices depends on the current rating of individual device. In this paper, series IGBT string of six 1.2 kV, four 1.7 kV, two 3.3 kV and a single 6.5 kV IGBTs are simulated for a 4.5 kV/100 A application and power losses are analysed for different frequencies and duty cycles. This power loss analysis is extended for commercial IGBTs to compare the simulation results. The number of devices for minimum power loss depends on operating frequencies and power savings are significant both at low and high frequencies. In addition to the power losses, the other important issues in optimising the number of IGBTs are described in this paper. When IGBT modules are connected in parallel the principle of derating is applied to obtained reliable operation. This is explained with some examples.

Low Magnitude, Non-Violent, Fault Clearing Devides for Use with Current Limiting Fuses

The use of higher voltages (e.g. 35kV) in underground distribution systems has introduced new problems in control of fault currents. These problems are especially evident in the higher ampacity load current ranges. This problem may be addressed by the use of a low current vacuum interrupter (under 2000 amps) coordinated with a backup current limiting fuse to give full-range fault protection without the operating violence and space requirements of conventional expulsion fuses and at a lower cost than conventional circuit breakers. This approach can provide a full-range, non-violent fault interrupter up through the full-rated load current of present load density requirements.

Prospects For Extending The Resolution Limit Of The Electron Microscope

The factors that limit the performance of present-day high-resolution electron microscopes include the source brightness, the temporal coherence of the illumination, and phase contrast 'artefacts' due to spherical aberration and defocus. Further advancement of the instrumental performance might be accomplished in different ways, including the use of high coherence conditions combined with image restoration; the use of higher accelerating voltages; the use of aberration correctors; or the use of conditions for incoherent image formation. Current efforts in each of these directions are reviewed, from which it is evident that the combined use of higher voltages and improved coherence is the direction that is presently leading to the greatest degree of progress.

EHV transmission in the Soviet Union

The total output of Soviet electric stations at the beginning of 1968 was 135 million kW; by 1970 it is expected to reach 180 million kW. There are ten interconnected power systems in the country. The European Power Grid unites six of the systems, with a total power output of 68.5 million kW and covering a territory of 6 million km2 with a population of 160 million. Plans for the period to 1980 call for the use of higher voltages; 1200 kV for ac and up to ± 1100 kV for dc transmission.

Economics of various secondary voltages

THE GENERAL USE OF HIGHER VOLTAGES for distribution of power in commercial areas has many facets, one of the most important being economics. This digest deals with the economic comparison of power distribution in congested commercial areas at 120/208 volts and 265/460 volts. These voltages are the nominal system voltages. The specific areas considered are in the borough of Manhattan, New York, N. Y., but are similar to those generally encountered in any large metropolitan area. Underground distribution systems only were studied.

Postcricoid carcinoma as a sequel to radiotherapy for laryngeal carcinoma.

DURING the past 20 years, scattered reports have appeared in the literature on the development of laryngeal, hypopharyngeal, and esophageal neoplasms occurring in patients previously treated with radiotherapy. For the most part, these have been late sequelae, occasionally as long as 32 years after completion of the initial course of radiation. All of these cases developed within the field of radiation following treatment for benign lesions, such as goiter or tuberculous adenitis. Discussion of this problem must include mention of the rationale of radiotherapy as it was practiced prior to the popularization of the Coutard method. It was then believed that the radiation should be given quickly and in the highest feasible dosage in order to eliminate the disease as rapidly as possible. With refinement in radiation dosage, the use of higher voltage, and the institution of protracted therapy, the complications have decreased. The cases previously cited in the literature

Power limits of transmission lines

THIS ARTICLE PRESENTS the results of studies of the factors which influence the power limits or design loadings of transmission lines. Recent investigations have shown the principal factors determining the loading of transmission circuits, particularly those for distances of 100 to 600 miles. Since there is a continuing trend toward the use of higher voltages, it is desirable to study their possibilities more completely over the entire range of distances expected for 230 kv and higher. Hence, the present investigation extends the earlier studies to include lines from 10 to 600 miles in length. The results are general as regards the stability limits (Base kva = 5.0 kv <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and may be applied to lines of any voltage level. The economic comparisons in this study pertain to the 287-kv voltage level, which is about in the middle of the range for 230 to 380 kv and fairly representative of the general economic picture for all voltages 230 kv and above.

Power Limits of Transmission Lines [includes discussion

THIS ARTICLE PRESENTS the results of studies of the factors which influence the power limits or design loadings of transmission lines. Recent investigations have shown the principal factors determining the loading of transmission circuits, particularly those for distances of 100 to 600 miles. Since there is a continuing trend toward the use of higher voltages, it is desirable to study their possibilities more completely over the entire range of distances expected for 230 kv and higher. Hence, the present investigation extends the earlier studies to include lines from 10 to 600 miles in length. The results are general as regards the stability limits (Base kva = 5.0 kv2) and may be applied to lines of any voltage level. The economic comparisons in this study pertain to the 287-kv voltage level, which is about in the middle of the range for 230 to 380 kv and fairly representative of the general economic picture for all voltages 230 kv and above.

The Roentgen Treatment of Acute Peritonitis and Other Infections with Mobile X-Ray Apparatus

IN 1928, under pressure of necessity, a case of gas gangrene was treated with the mobile x-ray unit, and recovered. The mobile unit was the ordinary unit designed for mobile diagnostic work in general hospitals and rated below 90 kilo-volts. In the first report (1) on the treatment of gas gangrene with the mobile unit, two cases out of eight died. Both of those dying had trunk involvement. In the six who recovered, the infection was entirely, or to a great extent, limited to the extremities. From the outcome of these cases it was thought that probably the mobile unit did not have sufficient kilovoltage to obtain the necessary depth dose to effect a cure in the trunk cases. This led to a recommendation for the use of higher voltages in treating deep-seated or trunk infections. Since the maximum kilovoltage obtainable from the mobile unit had been used in treating the two cases which died, it was apparent that in the future cases with trunk involvement must be moved to the x-ray department if they were to be treated successfully, or some apparatus producing a higher kilovoltage must be designed to enable the radiologist to treat at the bedside. Since no bedside apparatus was available, we started to move these patients to the x-ray department. This was done, on a few occasions, and, as these patients recovered promptly, we felt we were well rewarded for our efforts. In fact, we were so impressed with the results that we decided to treat other infections in the trunk. Peritonitis, following acute appendicitis and other intra-abdominal infections, is relatively common and was selected for a trial. The immediate difficulty encountered was that of obtaining the permission of the clinician to move the patient with peritonitis to the x-ray department, and we fully agreed with the clinician that the dangers involved in moving the patient seemed out of proportion to the chances of improving his condition. The whole thing then resolved itself into providing some means of treating the patient with peritonitis without disturbing him in any way, and, as no equipment was commercially available for this purpose, we felt that it was our duty to devise some means of providing x-ray treatment at the bedside, for those who were too sick to be moved. In a short tour of the local x-ray dealers' basements, we were able to select from the stock of obsolete and discarded x-ray equipment, a suitable transformer which was mounted upon a wooden base carrying a tube stand. We found two such units, and built two mobile units; they have served our purpose very well. They are not, we hope, the last word in this type of equipment, as we appreciate some deficiencies in this assembly, but we look for a real piece of apparatus to be developed in the near future for this type of work, as we are certain that the results will warrant its production.2

Notes on the Exhibition of Apparatus at the Third International Congress of Radiology

The exhibition of apparatus held during the Third International Congress of Radiology was of very considerable interest, and showed a high level of individual and collective excellence in keeping with other aspects of the Congress. The exhibition was well housed in the Palais des Congres, near the Porte de Versailles, the area available for the approximately sixty stands being sufficient if not ample. It is manifestly impossible to discuss the individual exhibits which, in any case, are probably destined to become familiar to us in time via the advertisements of the exhibitors, but it was clear that certain definite advances are being rapidly made in X-ray apparatus, and we may mention some of these, though little of a revolutionary character was shown. The tendency towards the use of higher voltages in therapy in order to obtain artificial gamma rays is very marked. There appears indeed to be at the moment no difficulty in persuading manufacturers to provide high-tension equipment for a million or more v...

Tests of losses on high tension lines

It is generally admitted that corona losses constitute the most serious objection to the use of higher voltages in transmission lines. For this reason a number of physicists and engineers have devoted and are devoting their attention to the study of corona phenomena. Their investigations can be divided into two classes.