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Understanding and improving obstetrical quality and safety is an important goal of professional societies, and many interventions such as checklists, safety bundles, educational interventions, or other culture changes have been implemented to improve the quality of care provided to obstetrical patients. Although many factors contribute to delivery decisions, a reduced workload has addressed how provider issues such as fatigue or behaviors surrounding impending shift changes may influence the delivery mode and outcomes.The objective was to assess whether intrapartum obstetrical interventions and adverse outcomes differ based on the temporal proximity of the delivery to the attending's shift change.This was a secondary analysis from a multicenter obstetrical cohort in which all patients with cephalic, singleton gestations who attempted vaginal birth were eligible for inclusion. The primary exposure used to quantify the relationship between the proximity of the provider to their shift change and a delivery intervention was the ratio of time from the most recent attending shift change to vaginal delivery or decision for cesarean delivery to the total length of the shift. Ratios were used to represent the proportion of time completed in the shift by normalizing for varying shift lengths. A sensitivity analysis restricted to patients who were delivered by physicians working 12-hour shifts was performed. Outcomes chosen included cesarean delivery, episiotomy, third- or fourth-degree perineal laceration, 5-minute Apgar score of4, and neonatal intensive care unit admission. Chi-squared tests were used to evaluate outcomes based on the proportion of the attending's shift completed. Adjusted and unadjusted logistic models fitting a cubic spline (when indicated) were used to determine whether the frequency of outcomes throughout the shift occurred in a statistically significant, nonlinear pattern RESULTS: Of the 82,851 patients eligible for inclusion, 47,262 (57%) had ratio data available and constituted the analyzable sample. Deliveries were evenly distributed throughout shifts, with 50.6% taking place in the first half of shifts. There were no statistically significant differences in the frequency of cesarean delivery, episiotomy, third- or fourth-degree perineal lacerations, or 5-minute Apgar scores of4 based on the proportion of the shift completed. The findings were unchanged when evaluated with a cubic spline in unadjusted and adjusted logistic models. Sensitivity analyses performed on the 22.2% of patients who were delivered by a physician completing a 12-hour shift showed similar findings. There was a small increase in the frequency of neonatal intensive care unit admissions with a greater proportion of the shift completed (adjusted P=.009), but the findings did not persist in the sensitivity analysis.Clinically significant differences in obstetrical interventions and outcomes do not seem to exist based on the temporal proximity to the attending physician's shift change. Future work should attempt to directly study unit culture and provider fatigue to further investigate opportunities to improve obstetrical quality of care, and additional studies are needed to corroborate these findings in community settings.

This work consists of a first investigation of materials that could be used as ESR dosimeters with doses up to 5 Gy aiming possible applications that would include retrospective dosimetry or dosimetry in specific applications. The characteristics considered were radiological properties close to that of soft tissues, evaluated through their effective atomic number and mass attenuation coefficient, ESR signal dependence on the irradiation dose, sensitivity to dose in the range of ∼5 Gy when exposed to a 50 kV x-ray source and signal stability over a 30-day period. A total of 16 compounds of lithium, potassium and sodium were analyzed, including the already known dosimeter material, lithium formate. Among them, lithium carbonate, lithium phosphate, sodium formate, sodium acetate, sodium citrate, sodium dithionite, sodium carbonate, showed eligible characteristics. After analyzing the ESR dose-response curves, the molecules that showed greater sensitivity to radiation in descending order are: sodium formate, sodium acetate, sodium citrate and sodium dithionite, however, lower than lithium formate. Sodium formate and sodium citrate presented ESR signals with high stability, similar to lithium formate, with fading of ∼3% in 30 days, different from sodium acetate, which showed a 19% reduction. Sodium citrate also presents radiological properties close to soft tissue. Therefore, considering all properties, in the set of the new materials studied in this work, sodium citrate is a promising material for ESR dosimetry.

Short cervix at midgestation, the presence of intraamniotic debris, and cervical funneling are risk factors for preterm birth; however, cervical length measurements and cutoffs are not well documented among pregnant patients of different gestational ages and self-reported races and ethnicities.This study aimed to describe the distribution of cervical length and frequency of funneling and debris at midgestation in nulliparous women by gestational age and race/ethnicity.This secondary analysis of screening data from a multicenter treatment trial of singleton nulliparous patients with short cervix was conducted at 14 geographically distributed, university-affiliated medical centers in the United States. Singleton nulliparous patients with no known risk factors for preterm birth were screened for trial participation and asked to undergo a transvaginal ultrasound to measure cervical length by a certified sonographer. The distribution of cervical length and the frequency of funneling and debris were assessed for each gestational age week (16-22 weeks) and stratified by self-reported race and ethnicity, which for this study were categorized as White, Black, Hispanic, and other. Patients enrolled in the randomized trial were excluded from this analysis.A total of 12,407 nulliparous patients were included in this analysis. The racial or ethnic distribution of the study participants was as follows: White, 41.6%; Black, 29.6%; Hispanic, 24.2%; and others, 4.6%. The 10th percentile cervical length for the entire cohort was 31.1 mm and, when stratified by race and ethnicity, 31.9 mm for White, 30.2 mm for Black, 31.4 mm for Hispanic, and 31.2 mm for patients of other race and ethnicity (P.001). At each gestational age, the cervical length corresponding to the tenth percentile was shorter in Black patients. The 25 mm value commonly used to define a short cervix and thought to represent the 10th percentile ranged from 1.3% to 5.4% across gestational age weeks and 1.0% to 3.8% across race and ethnicity groups. Black patients had the highest rate of funneling (2.6%), whereas Hispanic and Black patients had higher rates of intraamniotic debris than White and other patients (P.001).Black patients had shorter cervical length and higher rates of debris and funneling than White patients. The racial and ethnic disparities in sonographic midtrimester cervical findings may provide insight into the racial disparity in preterm birth rates in the United States.

BACKGROUND: While there are well-accepted standards for the diagnosis of arrested active-phase labor, the definition of a "failed" induction of labor remains less certain. One approach to diagnosing a failed induction is based on the duration of the latent phase. However, a standard for the minimum duration that the latent phase of a labor induction should continue, absent acute maternal or fetal indications for cesarean delivery, remains lacking. OBJECTIVE: The objective of this study was to determine the frequency of adverse maternal and perinatal outcomes as a function of the duration of the latent phase among nulliparous women undergoing labor induction. METHODS: This study is based on data from an obstetric cohort of women delivering at 25 U.S. hospitals from 2008-2011. Nulliparous women who had a term singleton gestation in the cephalic presentation were eligible for this analysis if they underwent a labor induction. Consistent with prior studies, the latent phase was determined to begin once cervical ripening had ended, oxytocin was initiated and rupture of membranes (ROM) had occurred, and was determined to end once 5 cm dilation was achieved. The frequencies of cesarean delivery, as well as of adverse maternal (e.g., cesarean delivery, postpartum hemorrhage, chorioamnionitis) and perinatal outcomes (e.g., a composite frequency of either seizures, sepsis, bone or nerve injury, encephalopathy, or death), were compared as a function of the duration of the latent phase (analyzed with time both as a continuous measure and categorized in 3-hour increments). RESULTS: A total of 10,677 women were available for analysis. In the vast majority (96.4%) of women, the active phase had been reached by 15 hours. The longer the duration of a woman's latent phase, the greater her chance of ultimately undergoing a cesarean delivery (P

Background Studies of early-term birth after demonstrated fetal lung maturity show that respiratory and other outcomes are worse with early-term birth (370–386 weeks) even after demonstrated fetal lung maturity when compared with full-term birth (390–406 weeks). However, these studies included medically indicated births and are therefore potentially limited by confounding by the indication for delivery. Thus, the increase in adverse outcomes might be due to the indication for early-term birth rather than the early-term birth itself. Objective We examined the prevalence and risks of adverse neonatal outcomes associated with early-term birth after confirmed fetal lung maturity as compared with full-term birth in the absence of indications for early delivery. Study Design This is a secondary analysis of an observational study of births to 115,502 women in 25 hospitals in the United States from 2008 through 2011. Singleton nonanomalous births at 37–40 weeks with no identifiable indication for delivery were included; early-term births after positive fetal lung maturity testing were compared with full-term births. The primary outcome was a composite of death, ventilator for ≥2 days, continuous positive airway pressure, proven sepsis, pneumonia or meningitis, treated hypoglycemia, hyperbilirubinemia (phototherapy), and 5-minute Apgar Results In all, 48,137 births met inclusion criteria; the prevalence of fetal lung maturity testing in the absence of medical or obstetric indications for early delivery was 0.52% (n = 249). There were 180 (0.37%) early-term births after confirmed pulmonary maturity and 47,957 full-term births. Women in the former group were more likely to be non-Hispanic white, smoke, have received antenatal steroids, have induction, and have a cesarean. Risks of the composite (16.1% vs 5.4%; adjusted odds ratio, 3.2; 95% confidence interval, 2.1–4.8 from logistic regression) were more frequent with elective early-term birth. Propensity scores matching confirmed the increased primary composite in elective early-term births: adjusted odds ratios, 4.3 (95% confidence interval, 1.8–10.5) for 1:1 and 3.5 (95% confidence interval, 1.8–6.5) for 1:2 matching. Among components of the primary outcome, CPAP use and hyperbilirubinemia requiring phototherapy were significantly increased. Transient tachypnea of the newborn, neonatal intensive care unit admission, and prolonged neonatal intensive care unit stay (>2 days) were also increased with early-term birth. Conclusion Even with confirmed pulmonary maturity, early-term birth in the absence of medical or obstetric indications is associated with worse neonatal respiratory and hepatic outcomes compared with full-term birth, suggesting relative immaturity of these organ systems in early-term births.

Although preterm birth37 weeks' gestation is the leading cause of neonatal morbidity and mortality in the United States, the majority of data regarding preterm neonatal outcomes come from older studies, and many reports have been limited to only very preterm neonates. Delineation of neonatal outcomes by delivery gestational age is needed to further clarify the continuum of mortality and morbidity frequencies among preterm neonates.We sought to describe the contemporary frequencies of neonatal death, neonatal morbidities, and neonatal length of stay across the spectrum of preterm gestational ages.This was a secondary analysis of an obstetric cohort of 115,502 women and their neonates who were born in 25 hospitals nationwide, 2008 through 2011. All liveborn nonanomalous singleton preterm (23.0-36.9 weeks of gestation) neonates were included in this analysis. The frequency of neonatal death, major neonatal morbidity (intraventricular hemorrhage grade III/IV, seizures, hypoxic-ischemic encephalopathy, necrotizing enterocolitis stage II/III, bronchopulmonary dysplasia, persistent pulmonary hypertension), and minor neonatal morbidity (hypotension requiring treatment, intraventricular hemorrhage grade I/II, necrotizing enterocolitis stage I, respiratory distress syndrome, hyperbilirubinemia requiring treatment) were calculated by delivery gestational age; each neonate was classified once by the worst outcome for which criteria was met.In all, 8334 deliveries met inclusion criteria. There were 119 (1.4%) neonatal deaths. In all, 657 (7.9%) neonates had major morbidity, 3136 (37.6%) had minor morbidity, and 4422 (53.1%) survived without any of the studied morbidities. Deaths declined rapidly with each advancing week of gestation. This decline in death was accompanied by an increase in major neonatal morbidity, which peaked at 54.8% at 25 weeks of gestation. As frequencies of death and major neonatal morbidity fell, minor neonatal morbidity increased, peaking at 81.7% at 31 weeks of gestation. The frequency of all morbidities fell32 weeks. After 25 weeks, neonatal length of hospital stay decreased significantly with each additional completed week of pregnancy; among babies delivered from 26-32 weeks of gestation, each additional week in utero reduced the subsequent length of neonatal hospitalization by a minimum of 8 days. The median postmenstrual age at discharge nadired around 36 weeks' postmenstrual age for babies born at 31-35 weeks of gestation.Our data show that there is a continuum of outcomes, with each additional week of gestation conferring survival benefit while reducing the length of initial hospitalization. These contemporary data can be useful for patient counseling regarding preterm outcomes.

Homopolar generator pulsed power systems have been workhorse facilities in the pulsed power community. In the 1960s the Tellahoma Pulsed Generators powered large wind tunnel facilities at Arnold Air Force Base, in the 1970s the Canberra Homopolar performed some of the modern day railgun experiments and in the 1980s and 1990s the homopolars at the University of Texas performed railgun experiments and a myriad of industrial application research efforts.[1] There are both commercial and Federal Government applications for the technology. In applications where stick welding is altering the chemistry of the Heat Affected Zone due to long time at temperature the HPG process due to its short welding time alleviates the problem. There are plans to install high speed rail in the Northeast corridor. This rail will have to be welded and the HPG process readily transitions to the field and in-situ welding of the track is feasible. With the large interest in hydraulic fracturing pipelines are being installed to transport shale oil and gas recovered from these fields. Homopolar welding should have a large role to play in this process. The Ho-mopolar has also been used to sinter metal powders. Xray targets in CT scanners are made from sintered molybdenum and tungsten. The ability to sinter these metals has already been demonstrated with pulsed compaction. An inexpensive generator would have a large role to play in this medical field. In transporting nuclear waste spent fuel rods have to be welded inside very robust containment. The Homopolar generator could be part of a welding robot that accomplishes this task without exposing personnel to the radiation. These are just a few of the applications envisioned for Homopolar welding and compaction.

Objective We sought to describe the prevalence of serious maternal complications following early preterm birth by gestational age (GA), delivery route, and type of cesarean incision. Study Design Trained personnel abstracted data from maternal and neonatal charts for all deliveries on randomly selected days representing one third of deliveries across 25 US hospitals over 3 years (n = 115,502). All women delivering nonanomalous singletons between 23-33 weeks' gestation were included. Women were excluded for antepartum stillbirth and highly morbid conditions for which route of delivery would not likely impact morbidity including nonreassuring fetal status, cord prolapse, placenta previa, placenta accreta, placental abruption, and severe and unstable maternal conditions (cardiopulmonary collapse, acute respiratory distress syndrome, seizures). Serious maternal complications were defined as: hemorrhage (blood loss ≥1500 mL, blood transfusion, or hysterectomy for hemorrhage), infection (endometritis, wound dehiscence, or wound infection requiring antibiotics, reopening, or unexpected procedure), intensive care unit admission, or death. Delivery route was categorized as classic cesarean delivery (CCD), low transverse cesarean delivery (LTCD), low vertical cesarean delivery (LVCD), and vaginal delivery. Association of delivery route with complications was estimated using multivariable regression models yielding adjusted relative risks (aRR) controlling for maternal age, race, body mass index, hypertension, diabetes, preterm premature rupture of membranes, preterm labor, GA, and hospital of delivery. Results Of 2659 women who met criteria for inclusion in this analysis, 8.6% of women experienced serious maternal complications. Complications were associated with GA and were highest between 23-27 weeks of gestation. The frequency of complications was associated with delivery route; compared with 3.5% of vaginal delivery, 23.0% of CCD (aRR, 3.54; 95% confidence interval (CI), 2.29–5.48), 12.1% of LTCD (aRR, 2.59; 95% CI, 1.77–3.77), and 10.3% of LVCD (aRR, 2.27; 95% CI, 0.68–7.55) experienced complications. There was no significant difference in complication rates between CCD and LTCD (aRR, 1.37; 95% CI, 0.95–1.97) or between CCD and LVCD (aRR, 1.56; 95% CI, 0.48–5.07). Conclusion The risk of maternal complications after early preterm delivery is substantial, particularly in women who undergo cesarean delivery. Obstetricians need to be prepared to manage potential hemorrhage, infection, and intensive care unit admission for early preterm births requiring cesarean delivery.

Objective We sought to evaluate whether the presence of condition-specific obstetric protocols within a hospital was associated with better maternal and neonatal outcomes. Study Design This was a cohort study of a random sample of deliveries performed at 25 hospitals over 3 years. Condition-specific protocols were collected from all hospitals and categorized independently by 2 authors. Data on maternal and neonatal outcomes, as well as data necessary for risk adjustment were collected. Risk-adjusted outcomes were compared according to whether the patient delivered in a hospital with condition-specific obstetric protocols at the time of delivery. Results Hemorrhage-specific protocols were not associated with a lower rate of postpartum hemorrhage or with fewer cases of estimated blood loss >1000 mL. Similarly, in the presence of a shoulder dystocia protocol, there were no differences in the frequency of shoulder dystocia or number of shoulder dystocia maneuvers used. Conversely, preeclampsia-specific protocols were associated with fewer intensive care unit admissions (odds ratio, 0.28; 95% confidence interval, 0.18–0.44) and fewer cases of severe maternal hypertension (odds ratio, 0.86; 95% confidence interval, 0.77–0.96). Conclusion The presence of condition-specific obstetric protocols was not consistently shown to be associated with improved risk-adjusted outcomes. Our study would suggest that the presence or absence of a protocol does not matter and regulations to require protocols are not fruitful.

Performance testing of the model-scale CPA was completed at the University of Texas Center for Electromechanics. A major part of the project was the development of design and simulation codes that would accurately represent the performance of pulsed alternators. This paper discusses the components of the system and its operational sequence. Details of the performance simulation model are presented along with test data. The test result is compared to the predicted data.

The flow resistance of electrorheological fluids (ER fluids) can be controlled by applying electric fields. Thus, ER fluids are suitable for the application in actuators, using high-voltage sources for the generation of the field. The behaviour of an ER fluid actuator not only depends on the properties of the individual actuator components (ER fluid, energy transducer and energy source) but especially on their combined efforts as a system. Based on a possible scheme for the design of ER fluid actuators, this paper presents important practice-relevant aspects of a systematic actuator construction. Here the behaviour of a commercial ER suspension is examined and compared to a homogeneous ER fluid without yield point using a rotational viscometer and a flow-mode damper realized at the Laboratory of Process Automation (LPA) of the University of Saarland.

Callus and cell suspension cultures were established from young leaves of Pilocarpus pennatifolius on Murashige & Skoog (MS) medium supplemented with 5.0 mg/L 2,4-dichlorophenoxyacetic acid (2,4-D) and 1.0 mg/L kinetine. The pilocarpine contents of callus and cell suspension cultures were quantitatively compared by HPLC.Culturas de calos e de células em suspensão foram estabelecidas a partir de folhas jovens de Pilocarous pennatifolius em meio Murashige & Skoog (MS) suplementado com 5 mg/L de ácido 2,4-diclorofenoxiacético e 1 mg/L de cinetina. O teor de pilocarpina nas culturas e suspensões celulares foi quantitativamente comparado por CLAE.

Background Cesarean delivery in the second stage of labor is common, whereas the frequency of operative vaginal delivery has been declining. However, data comparing outcomes for attempted operative vaginal delivery vs cesarean in the second stage are scant. Previous studies that examine operative vaginal delivery have compared it to a baseline risk of complications from a spontaneous vaginal delivery and cesarean delivery. However, when a woman has a need for intervention in the second stage, spontaneous vaginal delivery is not an option she or the provider can choose. Thus, the appropriate clinical comparison is cesarean vs operative vaginal delivery. Objective Our objective was to compare outcomes by the first attempted operative delivery (vacuum, forceps vs cesarean delivery) in patients needing second-stage assistance at a fetal station of +2 or below. Study Design We conducted secondary analysis of an observational obstetric cohort in 25 academically affiliated US hospitals over a 3-year period. A subset of ≥37 weeks, nonanomalous, vertex, singletons, with no prior vaginal delivery who reached a station of +2 or below and underwent an attempt at an operative delivery were included. Indications included for operative delivery were: failure to descend, nonreassuring fetal status, labor dystocia, or maternal exhaustion. The primary outcomes included a composite neonatal outcome (death, fracture, length of stay ≥3 days beyond mother's, low Apgar, subgaleal hemorrhage, ventilator support, hypoxic encephalopathy, brachial plexus injury, facial nerve palsy) and individual maternal outcomes (postpartum hemorrhage, third- and fourth-degree tears [severe lacerations], and postpartum infection). Outcomes were examined by the 3 attempted modes of delivery. Odds ratios (OR) were calculated for primary outcomes adjusting for confounders. Final mode of delivery was quantified. Results In all, 2531 women met inclusion criteria. No difference in the neonatal composite outcome was observed between groups. Vacuum attempt was associated with the lowest frequency of maternal complications (postpartum infection 0.2% vs 0.9% forceps vs 5.3% cesarean, postpartum hemorrhage 1.4% vs 2.8% forceps vs 3.8% cesarean), except for severe lacerations (19.1% vs 33.8% forceps vs 0% cesarean). When confounders were taken into account, both forceps (OR, 0.16; 95% confidence interval, 0.05–0.49) and vacuum (OR, 0.04; 95% confidence interval, 0.01–0.17) were associated with a significantly lower odds of postpartum infection. The neonatal composite and postpartum hemorrhage were not significantly different between modes of attempted delivery. Cesarean occurred in 6.4% and 4.4% of attempted vacuum and forceps groups ( P = .04). Conclusion In patients needing second-stage delivery assistance with a station of +2 or below, attempted operative vaginal delivery was associated with a lower frequency of postpartum infection, but higher frequency of severe lacerations.

The 9 MJ Range Gun system under construction at the Center for Electromechanics at The University of Texas at Austin is designed as a self-contained, field portable electromagnetic launch system to accelerate a salvo of three projectiles to a muzzle energy of 9 MJ at velocities ranging from 2.5 to 4.0 km/s. The Range Gun system will consist of a self-excited air-core compulsator, a 90 mm bore railgun launcher, prime power and auxiliary systems, solid state switches for field rectification and gun discharge, and the controls and data acquisition required to operate the system. The compulsator is designed to deliver 3.2 MA current pulses to the railgun launcher at a peak power rating of 10 GW. This paper describes some of the innovations incorporated into the design of the 9 MJ Range Gun system compulsator and presents the status of the fabrication and testing efforts. Initial performance of the 90 mm railgun during testing at the Electric Armaments Research Center will also be presented. >

Fabrication efforts have begun on a field-based compulsator for firing 9 MJ projectiles from a railgun launcher. The machine is designed to store 200 MJ kinetic energy and fire a salvo of nine rounds in three minutes at velocities between 2.5 and 4.0 km/s. Prime power required to meet this firing schedule is 1.865 kW, and will be supplied by a gas turbine engine. It is also possible to fire a burst of two shots in rapid succession, if desired. Operating speed of the machine is 8250 r/min and it has design ratings of 3.2 MA peak current and 20 GW peak power into a 9 MJ railgun load. A two-pole configuration is used for pulse-length considerations, and selectivity passive compensation is used to produced a relatively flat pulse and limit peak projectile acceleration to about 980000 m/s/sup 2/. Other distinguishing features include an air core magnetic circuit, separate rotor armature windings for self-excitation and railgun firing, ambient temperature field coils, and excitation field magnetic energy recovery capability. A detailed description of the machine as designed, and its auxiliary and control systems, is provided. Fabrication and assembly methods are reviewed, and the current status of the project is discussed. >

The autonomously replicating plasmid YEpSS1, containing the S. cerevisiae SOD1 and SRB1 genes, was highly unstable in a wild-type strain. When transformed into a fragile srb1-1 mutant host, the same plasmid displayed different characteristics depending on the growth medium used. Both batch and continuous culture experiments demonstrated that the plasmid was very unstable when the transformed strain SLU15 was grown in the presence of an osmotic stabiliser (10% w/v sorbitol). However, in the absence of the osmoticum, nearly 100% of the cells retained the plasmid and produced the Sod1 protein after 80 generations of growth.

The first homopolar-fired railgun system was operated in Canberra in 1972 [1,2]. Since that time two additional systems have been tested, the EMACK homopolar generator (HPG) built by Westinghouse and operated by Army Research and Development Center (ARDC) [3] and the joint effort by The Center for Electromechanics of The University of Texas (CEM-UT) and General Dynamics in 1982 [4]. This paper describes the homopolar railgun system operated by CEM-UT in 1985. The aspect that makes this system different from the previous experiments is the design of a fast opening switch (10 to 20 µs) that will allow operation of the HPG into hypervelocity launchers.

Homopolar generators (HPGs) are modern day energy stores (megajoules) capable of large currents (megamps). The generators are typically low voltage and large capacitance, disallowing loads requiring fast rise times to be driven directly by the HPG. An opening switch must be provided to first, in the closed state, transfer energy from the high current source to an inductive energy store and then open to commutate the current to the load. To charge an inductive energy store with large currents for long times (hundreds of milliseconds) indicates a massive switch with many low resistance contacts. At the same time the switch must commutate current to the load in a short time interval (tens of microseconds) indicating a light, fast-acting device. A two-stage opening switch addresses these two conflicting requirements. The first stage is a massive mechanical switch of coaxial geometry with many low resistance galvanic contacts, which commutates through a low inductance to an explosive element second stage. The second-stage switch is then interrupted explosively to provide the microsecond commutation. The design, manufacture, and testing of the two-stage opening switch were performed at the Center for Electromechanics at The University of Texas at Austin (CEM-UT) Taylor Hall facility in Austin, TX, using a compact homopolar generator (CHPG) and a five-turn coaxial, cryogenic inductor as the pulsed power supply. Initial testing included mechanical actuations and electrical measurements to verify fundamental operation and proper assembly. Testing continued with the CHPG charging the inductor through the switch statically (no commutation) to characterize the current carrying capability of the primary galvanic contacts. Next, tests to check the ability of the first stage to commutate to the second stage by sliding the primary contacts onto the armature insulator were conducted. The fourth phase of testing was a series of two-stage (double) commutations to a fixed load to characterize performance and timing of triggers, voltage hold-off capability, and fixed load commutation times. The fifth and last phase of testing involved the two-stage switch commutating current to a variable impedance (railgun) load.

The design of a lightweight, compulsator-driven 9-MJ electromagnetic (EM) launcher has been completed and is in the fabrication phase. Scheduled for initial field testing in early 1989, the system will be capable of firing a salvo of nine rounds in three minutes at muzzle velocities between 2.5 and 4.0 km/s. Prime power for the compulsator is supplied by a 5000-hp gas turbine engine through a gearbox and clutch arrangement, and auxiliary power is provided by a small 750-hp turbine. Electrical power generation and pulse conditioning for the launcher are performed by the compulsator, which features a self-excited, air-core magnetic circuit and selectively passive armature compensation designed to minimize peak projectile acceleration. Peak power from the machine is 27 GW, and a total of 30 MJ is extracted from the rotor during each firing of the gun. System mass, including gun, compulsator, prime power, and auxiliary systems, is less than 22 tons and will be mounted on a 36-ton concrete slab which simulates the mass of an armored vehicle on which the system will eventually be integrated. >

Tandem solar cells combining silicon and perovskite absorbers have the potential to outperform state-of-the-art high efficiency silicon single junction devices. However, the practical fabrication of monolithic silicon/perovskite tandem solar cells is challenging as material properties and processing requirements such as temperature restrict the device design. Here, we fabricate an 18% efficient monolithic tandem cell formed by a silicon heterojunction bottom-and a perovskite top-cell enabling a very high open circuit voltage of 1.78 V. The monolithic integration was realized via low temperature processing of the semitransparent perovskite sub-cell where an energetically aligned electron selective contact was fabricated by atomic layer deposition of tin oxide. The hole selective, transparent top contact was formed by a stack of the organic hole transport material spiro-OMeTAD, molybdenum oxide and sputtered indium tin oxide. The tandem cell design is currently limited by the photo-current generated in the silicon bottom cell that is reduced due to reflectance losses. Based on optical modelling and first experiments, we show that these losses can be significantly reduced by combining optical optimization of the device architecture including light trapping approaches.