A vacuum-compatible cylindrical inertial rotation sensor with picoradian sensitivity.

We describe an inertial rotation sensor with a 30-cm cylindrical proof-mass suspended from a pair of 14 µm thick BeCu flexures. The angle between the proof-mass and support structure is measured with a pair of homodyne interferometers, which achieve a noise level of ∼5prad/Hz. The sensor is entirely made of vacuum compatible materials, and the center of mass can be adjusted remotely.

A cryogenic torsion balance using a liquid-cryogen free, ultra-low vibration cryostat.

We describe a liquid-cryogen free cryostat with ultra-low vibration levels, which allows for continuous operation of a torsion balance at cryogenic temperatures. The apparatus uses a commercially available two-stage pulse-tube cooler and passive vibration isolation. The torsion balance exhibits torque noise levels lower than room temperature thermal noise by a factor of about four in the frequency range of 3-10 mHz, limited by residual seismic motion and by radiative heating of the pendulum body. In addition to lowering thermal noise below room-temperature limits, the low-temperature environment enables novel torsion balance experiments. Currently, the maximum duration of a continuous measurement run is limited by accumulation of cryogenic surface contamination on the optical elements inside the cryostat.

A low-frequency torsion pendulum with interferometric readout.

We describe a torsion pendulum with a large mass-quadrupole moment and a resonant frequency of 2.8 mHz, whose angle is measured using a Michelson interferometer. The system achieved noise levels of ∼200prad/Hz between 0.2 and 30 Hz and ∼10prad/Hz above 100 Hz. Such a system can be applied to a broad range of fields from the study of rotational seismic motion and elastogravity signals to gravitational wave observation and tests of gravity.

Implications of Dedicated Seismometer Measurements on Newtonian-Noise Cancellation for Advanced LIGO.

Newtonian gravitational noise from seismic fields will become a limiting noise source at low frequency for second-generation, gravitational-wave detectors. It is planned to use seismic sensors surrounding the detectors' test masses to coherently subtract Newtonian noise using Wiener filters derived from the correlations between the sensors and detector data. In this Letter, we use data from a seismometer array deployed at the corner station of the Laser Interferometer Gravitational Wave Observatory (LIGO) Hanford detector combined with a tiltmeter for a detailed characterization of the seismic field and to predict achievable Newtonian-noise subtraction levels. As was shown previously, cancellation of the tiltmeter signal using seismometer data serves as the best available proxy of Newtonian-noise cancellation. According to our results, a relatively small number of seismometers is likely sufficient to perform the noise cancellation due to an almost ideal two-point spatial correlation of seismic surface displacement at the corner station, or alternatively, a tiltmeter deployed under each of the two test masses of the corner station at Hanford will be able to efficiently cancel Newtonian noise. Furthermore, we show that the ground tilt to differential arm-length coupling observed during LIGO's second science run is consistent with gravitational coupling.

Injector design for liner-on-target gas-puff experiments.

We present the design of a gas-puff injector for liner-on-target experiments. The injector is composed of an annular high atomic number (e.g., Ar and Kr) gas and an on-axis plasma gun that delivers an ionized deuterium target. The annular supersonic nozzle injector has been studied using Computational Fluid Dynamics (CFD) simulations to produce a highly collimated (M > 5), ∼1 cm radius gas profile that satisfies the theoretical requirement for best performance on ∼1-MA current generators. The CFD simulations allowed us to study output density profiles as a function of the nozzle shape, gas pressure, and gas composition. We have performed line-integrated density measurements using a continuous wave (CW) He-Ne laser to characterize the liner gas density. The measurements agree well with the CFD values. We have used a simple snowplow model to study the plasma sheath acceleration in a coaxial plasma gun to help us properly design the target injector.

Digital holographic interferometry employing Fresnel transform reconstruction for the study of flow shear stabilized Z-pinch plasmas.

The ZaP-HD flow Z-pinch project provides a platform to explore how shear flow stabilized Z-pinches could scale to high-energy-density plasma (plasma with pressures exceeding 1 Mbar) and fusion reactor conditions. The Z-pinch is a linear plasma confinement geometry in which the plasma carries axial electric current and is confined by its self-induced magnetic field. ZaP-HD generates shear stabilized, axisymmetric Z-pinches with stable lifetimes approaching 60 µs. The goal of the project is to increase the plasma density and temperature compared to the previous ZaP project by compressing the plasma to smaller radii (≈1 mm). Radial and axial plasma electron density structure is measured using digital holographic interferometry (DHI), which provides the necessary fine spatial resolution. ZaP-HD's DHI system uses a 2 ns Nd:YAG laser pulse with a second harmonic generator (λ = 532 nm) to produce holograms recorded by a Nikon D3200 digital camera. The holograms are numerically reconstructed with the Fresnel transform reconstruction method to obtain the phase shift caused by the interaction of the laser beam with the plasma. This provides a two-dimensional map of line-integrated electron density, which can be Abel inverted to determine the local number density. The DHI resolves line-integrated densities down to 3 × 1020 m-2 with spatial resolution near 10 µm. This paper presents the first application of Fresnel transform reconstruction as an analysis technique for a plasma diagnostic, and it analyzes the method's accuracy through study of synthetic data. It then presents an Abel inversion procedure that utilizes data on both sides of a Z-pinch local number density profile to maximize profile symmetry. Error estimation and Abel inversion are applied to the measured data.

Impact of multiple organ system dysfunction and nosocomial infections on survival of children treated with extracorporeal membrane oxygenation after heart surgery.

OBJECTIVES: To evaluate whether cardiac and noncardiac variables may be used to predict survival in children treated with extracorporeal membrane oxygenation (ECMO) after cardiopulmonary bypass and to determine when to discontinue ECMO support. DESIGN: Retrospective review. SETTING: Neonatal and pediatric intensive care units of Kosair Children's Hospital. PATIENTS: Fifty-nine children treated with ECMO after cardiopulmonary bypass from 1987 through 1996. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Medical, nursing, operative, and perfusion records for each patient were reviewed. The primary outcome measure was survival to hospital discharge. Cardiac and noncardiac variables were recorded at serial times. Nineteen of 59 patients (32%) survived. No cardiac variable was a clinically useful predictor of survival or marker for when to discontinue ECMO. Among the noncardiac variables, progressive multiple organ system dysfunction and development of a nosocomial infection were significantly associated with nonsurvival. No patient with a positive blood culture (n = 3) within the first 24 hrs of ECMO survived, and 21 of 24 children with a positive culture from any site during ECMO died (p = .007). Despite their higher mortality, children with positive cultures were supported with ECMO significantly longer than those with negative cultures (275+/-168 vs. 135+/-108 hrs, respectively; p = .0004). For all patients, the longest duration of ECMO that resulted in survival was 256 hrs. For children with a positive culture, the longest duration of support that resulted in survival was 200 hrs. CONCLUSIONS: Support with ECMO beyond 256 hrs was not associated with survival. Progressive multiple organ system dysfunction and nosocomial infections have a negative impact on survival. Serious consideration should be given to discontinuing ECMO support whenever there is a progressive increase in the number of abnormally functioning organ systems, a nosocomial infection occurs, or native cardiac function has not improved significantly by 250 hrs of ECMO support.

Fatal ingestion of sodium hypochlorite bleach with associated hypernatremia and hyperchloremic metabolic acidosis.

Ingestion of sodium hypochlorite bleach is usually benign, leading most poison centers to advocate conservative, home management. We report a rare, fatal case of household bleach ingestion. A 66-y-old female ingested an unknown quantity of regular CLOROX bleach (5.25% sodium hypochlorite, pH = 11.4). Upon discovery, she was vomiting spontaneously, and had slurred speech and oral mucosal discoloration. On hospital arrival the patient became unresponsive with shallow respirations. Laboratory studies revealed hypernatremia (169 mEq Na/L), hyperchloremia (143 mEq Cl/L), and metabolic acidosis (5 mmol total CO2/L). Radiographic evaluation showed bilateral pneumothoraces and pneumoperitoneum. The patient was intubated and ventilated, hypotension was treated with fluid resuscitation, and metabolic acidosis corrected with sodium bicarbonate. Naloxone and flumazenil were given without effect, and thoracostomy tubes were placed. Rapid deterioration of vital signs and mental status ensued, with cardiorespiratory arrest from which she was resuscitated. A second cardiac arrest resulted in death. Autopsy revealed esophageal and gastric mucosal erosions, perforation at the gastroesophageal junction, and extensive necrosis of adjacent soft tissue. Stomach contents contained sodium hypochlorite, and pleural and peritoneal fluid had the aroma of bleach. Postmortem vitreous humor Na was 187 mEq/L and Cl was 169 mEq/L. Toxicologic analysis revealed meprobamate metabolites in the urine, and lidocaine in the blood. The literature regarding fatal bleach ingestion is reviewed.

Theoretical optimization of pulmonary-to-systemic flow ratio after a bidirectional cavopulmonary anastomosis.

A univentricle with parallel pulmonary and systemic circulations is inherently inefficient because mixing of pulmonary and systemic venous return occurs. Thus a cavopulmonary anastomosis is used as a staged palliative procedure to reduce volume overload in patients with cyanotic congenital heart disease. On the basis of oxygen uptake and consumption, an equation was derived that related cardiac output, pulmonary venous oxygen saturation, upper body oxygen consumption, and superior-to-inferior vena caval blood flow ratio (QSVC/QIVC) to oxygen delivery. The primary findings were as follows. 1) As QSVC/QIVC increases, total body oxygen delivery and arterial and superior vena caval oxygen saturations increase. 2) As QSVC/QIVC increases, lower body oxygen delivery and inferior vena caval oxygen saturation initially increase, then peak, and then decrease. 3) As the percentage of lower body oxygen consumption increases, oxygen delivery and saturation decrease. 4) A cavopulmonary anastomosis decreases the required cardiac output for a given oxygen delivery. Thus we concluded that a high systemic arterial oxygen saturation after cavopulmonary anastomosis requires a high percentage of upper body oxygen consumption and a high QSVC/QIVC and that the cavopulmonary anastomosis reduces the volume load on the single ventricle.

Modulation of an acquired coagulation factor V inhibitor with intravenous immune globulin.

PURPOSE: We report that treatment of an immune mediated postoperative Factor V (FV) deficiency with intravenous immune globulin (IVIg) resulted in serological and clinical disappearance of the inhibitor. PATIENTS AND METHODS: A 9-year-old girl was exposed to bovine thrombin during cardiovascular surgery and subsequently developed severe, refractory hemorrhage caused by acquired FV deficiency (FV activity < 5%). Despite blood product transfusions, hemorrhage continued, and the patient was given IVIg, 400 mg/kg daily, for 9 day. RESULTS: Prolonged clotting times immediately trended toward normal, and the hemorrhage ceased by the fifth IVIg treatment day, concomitant with increasing plasma FV activity and disappearance of human FV inhibitor activity. The patient's plasma initially had a much higher inhibitor titer against bovine FV (122-215 Bethesda units) than against human FV (3-4 Bethesda units). Circulating antibodies (IgM and IgG) to bovine and human thrombin and FV were detected by enzyme-linked immunosorbent assay (ELISA). After completion of IVIg treatment, IgG antibodies to bovine FV and thrombin persisted, as did high-titer inhibition of bovine FV, whereas the subpopulation of IgG and IgM antibodies reactive with human FV were undetectable. CONCLUSIONS: The inhibitor likely developed from a heterogenetic immune response to bovine FV contaminating the topical thrombin preparation used during surgery. To our knowledge, this is the first demonstration of immunological clearance of an acquired FV antibody associated with the use of IVIg. The data suggest an antiidiotypic mechanism of IVIg in modulating clearance of antihuman FV antibodies.

Delay among the general public in telephoning a poison center.

Delay in seeking treatment for poisonings can hinder patient recovery. Our study examined delay in notifying a poison center about green tobacco sickness (GTS), a form of nicotine poisoning resulting from dermal contact with tobacco leaves. We conducted a follow-up survey of 55 cases of GTS reported by telephone to the kentucky Regional Poison Center in 1993. The "delay" group (38.2% of the cases) was defined as those callers who stated in the follow-up report that they should have phoned the poison center sooner than they did. Characteristics of the callers who delayed and the GTS patients they reported were compared with characteristics of the "non-delay" group. Delay was associated with callers' awareness of the poison center's expertise in agricultural poisonings and with age and sex of the patient. Our findings point to the need to target groups such as farmers with an educational campaign to make them more aware of the extent of the poison center's services and to encourage timely reporting of occupational poisonings.

Age-related amrinone pharmacokinetics in a pediatric population.

OBJECTIVES: To measure the plasma concentrations of amrinone and N-acetyl-amrinone achieved using current pediatric dosing recommendations. To examine the pharmacokinetics of amrinone in an extended age range of pediatric patients. To examine any age-related differences in the relative contribution of hepatic metabolism vs. renal elimination of amrinone. DESIGN: Prospective study. SETTING: A pediatric intensive care unit in a tertiary care teaching hospital. PATIENTS: Thirty-one patients aged 4 days to 15 yrs who required a constant infusion of amrinone. INTERVENTIONS: Blood samples were obtained 15 mins after each 0.75 mg/kg loading dose, and every 6 hrs during a constant infusion of amrinone to measure plasma amrinone, N-acetyl-amrinone and N-glycolyl-amrinone concentrations by high-performance liquid chromatography. Blood samples to measure amrinone, N-acetyl-amrinone, and N-glycolyl-amrinone concentrations during elimination were also obtained at regular intervals after discontinuation of the infusion. Six-hour urine collections were obtained to measure amrinone renal clearance. MEASUREMENTS AND MAIN RESULTS: Plasma amrinone concentrations > or = 2 micrograms/mL were obtained in 13 of 14 patients after a 3-mg/kg loading dose. There was a six-fold variability in steady-state plasma amrinone concentrations in patients receiving the same ordered infusion rate. There was a significant (p = .001) difference between the ordered and measured amrinone infusion rates. Six (19.4%) of 31 patients had steady-state plasma amrinone concentrations of < or = 2 micrograms/mL. There was a large variability in the volume of distribution, clearance, and elimination half-life which did not appear to be age-related. Renal clearance of amrinone ranged between 0.4 and 2.18 mL/kg/min, and did not increase with age. There was no increase in the proportion of children with a high plasma steady-state N-acetyl-amrinone/amrinone ratio over time from 1 to 24 months of life. CONCLUSIONS: Administering a 3-mg/kg amrinone loading dose in four divided doses over 1 hr resulted in relatively rapid therapeutic plasma concentrations without excessively high concentrations and good clinical tolerance. The wide interindividual variation in clearance and volume of distribution resulted in a variable dose-concentration relationship; children receiving lower amrinone infusion rates may-have subtherapeutic plasma steady-state concentrations. There did not appear to be any age-related change in renal clearance or hepatic metabolism of amrinone in children aged 1 to 24 months.

Amrinone-associated thrombocytopenia: pharmacokinetic analysis.

Amrinone-associated thrombocytopenia is thought to result from nonimmune-mediated peripheral platelet destruction. Platelet destruction may be a concentration-dependent toxic effect of amrinone or its principal metabolite N-acetylamrinone. Eighteen children receiving amrinone after heart surgery were prospectively evaluated to correlate the pharmacokinetics of amrinone and N-acetylamrinone with thrombocytopenia. Amrinone and N-acetylamrinone plasma concentrations were determined by HPLC during loading, infusion, and terminal elimination, with concurrent monitoring of platelet counts. Thrombocytopenia developed in eight patients (platelet count, 66 +/- 17 x 10(9) platelets/L [mean +/- SD]). Peak and steady-state amrinone plasma concentration, amrinone total dose, duration of amrinone exposure, and amrinone area under curve (AUC) were similar between patients with and without thrombocytopenia. N-Acetylamrinone peak concentration, steady-state concentration, N-acetylamrinone AUC, and ratio of N-acetylamrinone to amrinone were greater in patients with thrombocytopenia. This association suggests that N-acetylamrinone, and not amrinone, may be the mediator of thrombocytopenia in children receiving amrinone.

Comparison of numerical calculations with phantom experiments and clinical measurements.

Three-dimensional models, while fundamentally desirable in hyperthermia treatment simulation, are only beginning to emerge and may take a number of years to perfect for routine clinical use. Two dimensional calculations, on the other hand, can be efficiently performed on today's inexpensive computer workstations; however, the accuracy of two-dimensional models in the pretreatment planning context is questionable. This paper investigates the ability of a general two-dimensional finite element model to predict power deposition patterns in phantoms and temperature distributions during actual clinical treatments. The experiments and simulations have been performed for an annular phased array (APA) operating at 70 MHz. Comparisons between model predictions and measurements show that quantitative agreement occurs in phantoms containing moderate complexities in heterogeneity, but that only qualitative agreement appears possible in clinical treatments. However, the results suggest that the lack of blood flow information may contribute as much, if not more, to the uncertainties in the clinical predictions than the two-dimensional nature of the model itself.

A randomized trial to develop criteria for administering erythrocyte transfusions to anemic preterm infants 1 to 3 months of age.

A randomized trial of erythrocyte transfusion vs no transfusion was performed in 16 preterm infants 1 to 3 months old with hematocrits of less than or equal to 0.29 L/L. To determine which (if any) such patients definitely benefit from transfusion, an analysis of outcome variables was performed. Factors that prospectively identified patients who would benefit from transfusions included a heart rate of greater than 152 beats per minute (P less than .01), apnea/bradycardia (heart rate less than 90/min) requiring intervention to increase the heart rate (P less than .01), and a blood lactate level above the reference range (P less than .02). Additional investigations were performed to determine the cause of the low hematocrits in the study patients. All had diminished, rather than accelerated, erythropoiesis. However, neither the anemia of chronic disorders nor iron deficiency anemia contributed to the diminished erythropoiesis. In all cases, serum erythropoietin levels were below the predicted range (P less than .001). Thus, at least some preterm infants aged 1 to 3 months with hematocrits less than or equal to 0.29 L/L definitely derive benefit from erythrocyte transfusion. The presence of tachycardia, apnea/bradycardia, or an elevated blood lactate may prospectively identify such patients.

Theoretical quantification of the effects of plastic wall thickness on phantom measurements in electromagnetic hyperthermia.

Phantom experiments are a staple of research and development in electromagnetic hyperthermia. Phantom containers and compartments are typically constructed from plastics which are readily available in a wide variety of thicknesses and material compositions. The perturbation effects of these plastics on the electric fields to be measured may be important, especially if one is trying to obtain quantitative results such as when comparing with a numerical model. This communication presents a theoretical investigation into the effects of plastic wall thickness on the computed electric field. Design curves are reported which aid in the selecting of an acceptable wall thickness given a maximum degree of wall perturbation that can be tolerated. Many other materials such as rubbers and polystyrenes also have electrical properties within the ranges considered herein; hence, the results should apply to a variety of commonly used phantom construction materials.

Responsiveness to recombinant human erythropoietin of marrow erythroid progenitors from infants with the "anemia of prematurity".

We used cells from marrow aspirations that had been performed on 10 infants with the "anemia of prematurity" and tested the responsiveness of their erythroid colony-forming units (CFU-E) to recombinant human erythropoietin. For comparison, we also tested marrow-derived CFU-E from five healthy adults, and circulating CFU-E from cord blood of five healthy neonates. CFU-E from the anemic infants had a 50% maximal response at 0.073 +/- 0.024 U erythropoietin per milliliter (mean +/- SD). They were therefore at least as responsive as were CFU-E from adults, which displayed a 50% maximal response at 0.118 +/- 0.076 U/ml, and as were circulating CFU-E of cord blood origin, which had a 50% maximal response at 0.109 +/- 0.047 U/ml. Because CFU-E from infants with the "anemia of prematurity" appeared highly sensitive to erythropoietin in vitro, we propose that its administration to these patients would likely result in a significant increase in erythrocyte production in vivo.