Implementation of sonopartogram: multicenter feasibility study

OBJECTIVES

Well-established clinical practice to assess progress in labor involves routine abdominal palpation and vaginal examination (VE). However, VE is subjective, poorly reproducible and painful for women. In this study, our aim is to evaluate the feasibility of systematically integrating transabdominal and transperineal ultrasound assessment of fetal position, psAOP, HPD and SCD to monitor labor progress in women undergoing induction of labor (IOL). We also aim at determining if ultrasound can reduce women's pain during examinations.

METHODS

Women were recruited as they presented for IOL in three maternity units. Ultrasound assessments were performed in 100 women between 37+0 and 41+6 weeks' gestation. A baseline combined transabdominal and transperineal scan was performed, including the assessment of fetal biometry, umbilical artery and middle cerebral artery Dopplers, amniotic fluid index (AFI), fetal spine and occiput positions, psAOP, HPD, SCD, and cervical length. Intrapartum scans were performed instead of VEs according to protocol. Participants were asked to indicate their level of pain by verbally giving a pain score from 0 - 10 (with 0 representing no pain) during assessment. The repeated measures data were analyzed by mixed effect models to identify the significant factors that affected the relationship between psAOP, HPD, SCD and mode of delivery.

RESULTS

223 intrapartum ultrasound scans with a median of 2 scans per participant (interquartile range (IQR) = 1 - 3), and 151 VEs were performed with a median of 1 per participant (IQR = 0 - 2). There were no adverse fetal or maternal outcomes. After excluding those with epidural anesthesia during examination, median pain score for intrapartum scan was 0 (IQR = 0 - 1) and 3 for VE (IQR = 0 - 6). Cesarean delivery and epidural anesthesia were significantly associated with slower rate of change in psAOP, HPD and SCD. Maternal height, parity and neonatal birth weight did not affect ultrasound measurements of labor progress.

CONCLUSIONS

Comprehensive transabdominal and transperineal ultrasound assessment can be successfully used to assess progress in labor and can reduce the level of pain experienced during examination. Ultrasound assessment may be able to replace some transabdominal and VE examinations during labor. This article is protected by copyright. All rights reserved.

Prediction of spontaneous preterm birth and preterm prelabor rupture of membranes using maternal factors, obstetric history and biomarkers of placental function at 11-13 weeks

OBJECTIVES

To determine whether first-trimester biomarkers of placental function can be used to screen for spontaneous preterm birth (sPTB), and to develop prediction models using maternal factors, obstetric history and biomarkers of placental function at 11-13 weeks for the calculation of patient-specific risk for sPTB.

METHODS

This was a retrospective secondary analysis of data derived from a prospective cohort study on first-trimester screening for pre-eclampsia in singleton pregnancies attending for routine Down syndrome screening at 11 + 0 to 13 + 6 weeks' gestation at a tertiary obstetric unit between December 2016 and September 2019. A split-sample internal validation method was used to explore and develop prediction models for all sPTB at < 37 weeks and for PTB at < 37 weeks after preterm prelabor rupture of membranes (PPROM) using maternal risk factors, uterine artery Doppler indices, serum placental growth factor (PlGF), pregnancy-associated plasma protein-A (PAPP-A) and β-human chorionic gonadotropin (β-hCG). Screening performance was assessed using receiver-operating-characteristics (ROC)-curve analysis, with calculation of the areas under the ROC curves (AUCs).

RESULTS

A total of 9298 singleton pregnancies were included in this study. sPTB at < 37 weeks occurred in 362 (3.89%) cases, including 231 (2.48%) cases of PPROM. sPTB at < 34 weeks occurred in 87 (0.94%) cases, including 39 (0.42%) cases of PPROM. Identified maternal risk factors for sPTB at < 37 weeks included chronic hypertension, conception using in-vitro fertilization and history of PTB. Maternal risk factors for PPROM at < 37 weeks included conception using in-vitro fertilization and history of PTB. Median PlGF multiples of the median (MoM) and PAPP-A MoM were significantly reduced in women with sPTB at < 37 weeks, as well as in those who had PPROM, compared to those who delivered at term. Screening by a combination of maternal risk factors, PAPP-A and PlGF achieved better performance in predicting sPTB at < 37 weeks (AUC, 0.630 vs 0.555; detection rate (DR), 24.8% vs 16.6% at a false-positive rate (FPR) of 10%; P ≤ 0.0001) and PPROM at < 37 weeks (AUC, 0.643 vs 0.558; DR, 28.1% vs 17.0% at a FPR of 10%; P ≤ 0.0001) than using maternal risk factors alone. Both models were successfully applied to the internal validation dataset, with AUCs of 0.628 and 0.650, respectively.

CONCLUSIONS

We demonstrated that low levels of maternal serum PAPP-A and PlGF in the first trimester are associated with increased risks of sPTB and PPROM at < 37 weeks. However, further research is needed to identify additional biomarkers to improve the screening performance of the combined model that includes maternal risk factors, PAPP-A and PlGF before clinical application. © 2022 International Society of Ultrasound in Obstetrics and Gynecology.

Multipactor experiments on an S-band coaxial test cell

Radio frequency vacuum electronics are prone to multipactor discharges. These electron discharges, driven by secondary electron emission, can disrupt and damage devices and are particularly important in satellite communication systems. We present results from a new S-band coaxial multipactor test cell which demonstrates scaling to much higher frequencies (3.05 GHz) than previous coaxial experiments (10-150 MHz). The multipactor breakdown threshold has been found to agree very well with our earlier simulated predictions. The significant effect from multipactor self-conditioning has also been demonstrated and characterized. Future experiments will use this test cell to investigate various multipactor mitigation strategies.

COVID-19 Crisis: Exploring Community of Inquiry in Online Learning for Sub-Degree Students

The COVID-19 pandemic has brought a tremendous impact on the pedagogy and learning experience of students in sub-degree education sector of Hong Kong. Online learning has become the "sole" solution to deal with student learning challenges during this chaotic period. In this study, we explore online learning for sub-degree students by using a community of inquiry (CoI). As such, confirmatory factor analysis (CFA) was conducted on survey data gathered from 287 sub-degree students from the business and engineering disciplines. Results indicated that the network speed for online education determines the perceived cognitive presence, social presence, and teaching presence of students, whereas gender and academic disciplines of students are not moderating factors that create a significant difference in perceived cognitive presence, social presence, and teaching presence of students. Our study findings for creating and sustaining a purposeful online learning community are highlighted.

Comparative analysis of Student's live online learning readiness during the coronavirus (COVID-19) pandemic in the higher education sector

Amid the coronavirus outbreak, many countries are facing a dramatic situation in terms of the global economy and human social activities, including education. The shutdown of schools is affecting many students around the world, with face-to-face classes suspended. Many countries facing the disastrous situation imposed class suspension at an early stage of the coronavirus outbreak, and Asia was one of the earliest regions to implement live online learning. Despite previous research on online teaching and learning, students' readiness to participate in the real-time online learning implemented during the coronavirus outbreak is not yet well understood. This study explored several key factors in the research framework related to learning motivation, learning readiness and student's self-efficacy in participating in live online learning during the coronavirus outbreak, taking into account gender differences and differences among sub-degree (SD), undergraduate (UG) and postgraduate (PG) students. Technology readiness was used instead of conventional online/internet self-efficacy to determine students' live online learning readiness. The hypothetical model was validated using confirmatory factor analysis (CFA). The results revealed no statistically significant differences between males and females. On the other hand, the mean scores for PG students were higher than for UG and SD students based on the post hoc test. We argue that during the coronavirus outbreak, gender differences were reduced because students are forced to learn more initiatively. We also suggest that students studying at a higher education degree level may have higher expectations of their academic achievement and were significantly different in their online learning readiness. This study has important implications for educators in implementing live online learning, particularly for the design of teaching contexts for students from different educational levels. More virtual activities should be considered to enhance the motivation for students undertaking lower-level degrees, and encouragement of student-to-student interactions can be considered.

Segmenting Cruise Consumers by Motivation for an Emerging Market: A Case of China

After around four decades of fast growth, the cruise industry has become the most profitable and dynamic segment in the entire global leisure and tourism sector. Behind this growth is a significant shift in the profile of cruise consumers/passengers/tourists, with growth rates twice as fast as those of other types of tourists. China has become a strategic emerging market for the global cruise industry, quickly developing their cruise reception business and holding about 10% of the market share of global cruisers. In this paper, we examine and categorize various travel motivations of Chinese cruise tourists by means of a questionnaire via factor analysis, mean analysis, and K-cluster analysis. The results of the study indicate that Chinese cruise tourists are primarily encouraged to participate in cruise tourism by the motivational dimensions of family leisure/relaxation, natural and cultural exploration, bond/communication, social respect, tourism shopping, and cruise-promotion information sources. The strongest motivations for Chinese cruise tourists were found to be family leisure/relaxation and natural/cultural exploration. We identify four types of cruisers using the K-means cluster method. We find that for all cruiser demographics, leisure/relaxation is the most important motivational factor. Based on these results, we propose some specific solutions for expanding the customer pool in the Chinese cruise market.

Survey data on the impact of COVID-19 on parental engagement across 23 countries

This data article describes the dataset of the International COVID-19 Impact on Parental Engagement Study (ICIPES). ICIPES is a collaborative effort of more than 20 institutions to investigate the ways in which, parents and caregivers built capacity engaged with children's learning during the period of social distancing arising from global COVID-19 pandemic. A series of data were collected using an online survey conducted in 23 countries and had a total sample of 4,658 parents/caregivers. The description of the data contained in this article is divided into two main parts. The first part is a descriptive analysis of all the items included in the survey and was performed using tables and figures. The second part refers to the construction of scales. Three scales were constructed and included in the dataset: 'parental acceptance and confidence in the use of technology', 'parental engagement in children's learning' and 'socioeconomic status'. The scales were created using Confirmatory Factor Analysis (CFA) and Multi-Group Confirmatory Analysis (MG-CFA) and were adopted to evaluate their cross-cultural comparability (i.e., measurement invariance) across countries and within sub-groups. This dataset will be relevant for researchers in different fields, particularly for those interested in international comparative education.

[The clinical advantage of using three dimensional visualization technology in hepatic surgery]

The three-dimensional body visible system is a further development of the three-dimensional CT reconstruction system. It has a lot of merits over the latter system. Clinical application of the three-dimensional body visible system in liver surgery showed the system to have the following merits: (1) The system can support the Couinaud classification of liver anatomy into two hemilivers, four sectors and eight segments. As the system can rotate the liver to any angle and it has the ability to make part or whole of the liver transparent thus making the internal blood vessels and bile ducts visible. Learning liver anatomy and liver surgery becomes easier. (2)The system can clearly localize liver tumors within the liver segment(s). (3)It can help clinicians to decide and to plan different operations on an individual. (4)By carrying out simulation partial hepatectomy using this system, it can help clinicians to estimate the difficulty and the risks involved in different options of liver resection and finally.(5)The system helps clinicians to identify anomalies in hepatic artery, portal vein, hepatic vein and bile duct, thus making the operation safer. In conclusion, this system significantly improves on the conventional three-dimensional CT reconstruction system. It is especially useful for inexperienced liver surgeons.

Therapeutic inertia in the management of hyperlipidaemia in type 2 diabetic patients: a cross-sectional study in the primary care setting

OBJECTIVES

To study the prevalence of therapeutic inertia in lipid management among type 2 diabetic patients in the primary care setting and to explore associated factors.

METHODS

This was a cross-sectional study involving type 2 diabetic patients with suboptimal lipid control followed up in all general out-patient clinics of Kowloon Central Cluster in Hong Kong from 1 October 2011 to 30 September 2013. Main outcome measures included prevalence of therapeutic inertia in low-density lipoprotein management among type 2 diabetic patients and its association with patient and physician characteristics.

RESULTS

Based on an agreed standard, lipid control was suboptimal in 49.1% (n=9647) of type 2 diabetic patients who attended for a regular annual check-up (n=19 662). Among the sampled 369 type 2 diabetic patients with suboptimal lipid control, therapeutic inertia was found to be present in 244 cases, with a prevalence rate of 66.1%. When the attending doctors' profiles were compared, the mean duration of clinical practice was significantly longer in the therapeutic inertia group than the non-therapeutic inertia group. Doctors without prior training in family medicine were also found to have a higher rate of therapeutic inertia. Patients in the therapeutic inertia group had longer disease duration, a higher co-morbidity rate of cardiovascular disease, and a closer-to-normal low-density lipoprotein level. Logistic regression analysis revealed that lack of family medicine training among doctors was positively associated with the presence of therapeutic inertia whereas patient's low-density lipoprotein level was inversely associated.

CONCLUSIONS

Therapeutic inertia was common in the lipid management of patients with type 2 diabetes in a primary care setting. Lack of family medicine training among doctors and patient's low-density lipoprotein level were associated with the presence of therapeutic inertia. Further study of the barriers and strategies to overcome therapeutic inertia is needed to improve patient outcome in this aspect of chronic disease management.

Technique for fabrication of ultrathin foils in cylindrical geometry for liner-plasma implosion experiments with sub-megaampere currents

In this work, we describe a technique for fabricating ultrathin foils in cylindrical geometry for liner-plasma implosion experiments using sub-MA currents. Liners are formed by wrapping a 400 nm, rectangular strip of aluminum foil around a dumbbell-shaped support structure with a non-conducting center rod, so that the liner dimensions are 1 cm in height, 6.55 mm in diameter, and 400 nm in thickness. The liner-plasmas are imploded by discharging ∼600 kA with ∼200 ns rise time using a 1 MA linear transformer driver, and the resulting implosions are imaged four times per shot using laser-shadowgraphy at 532 nm. This technique enables the study of plasma implosion physics, including the magneto Rayleigh-Taylor, sausage, and kink instabilities on initially solid, imploding metallic liners with university-scale pulsed power machines.

Absolute Instability near the Band Edge of Traveling-Wave Amplifiers

Applying the Briggs-Bers "pole-pinch" criterion to the exact transcendental dispersion relation of a dielectric traveling wave tube (TWT), we find that there is no absolute instability regardless of the beam current. We extend this analysis to the circuit band edges of a linear beam TWT by approximating the circuit mode as a hyperbola in the frequency-wave-number (ω-k) plane and consider the weak coupling limit. For an operating mode whose group velocity is in the same direction as the beam mode, we find that the lower band edge is not subjected to absolute instability. At the upper band edge, we find a threshold beam current beyond which absolute instability is excited. The nonexistence of absolute instability in a linear beam TWT and the existence in a gyrotron TWT, both at the lower band edge, is contrasted. The general study given here is applicable to some contemporary TWTs such as metamaterial-based and advanced Smith-Purcell TWTs.

Novel scaling laws for the Langmuir-Blodgett solutions in cylindrical and spherical diodes

It is found that the Langmuir-Blodgett solutions for the space charge limited current density, for both cylindrical and spherical diodes, may be approximated by Japp=(4/9)ε0sqrt[(2e/m)](Ec3/2/sqrt[D]) over a wide range of parameters, where Ec is the surface electric field on the cathode of the vacuum diode and D is the anode-cathode spacing. This dependence is valid whether Ra/Rc is greater than or less than unity, where Ra and Rc are, respectively, the anode and cathode radius. Minor empirical corrections to the above scaling yield fitting formulas that are accurate to within 5% for 3×10(-5)<Rc/Ra<500. An explanation of this scaling is given. An accurate transit time model yields the Langmuir-Blodgett solutions even in the Coulomb blockade regime for a nanogap, where the electron number may be in the single digits, and the transit time frequency is in the THz range.

Anisotropy and feedthrough in magneto-Rayleigh-Taylor instability

The magneto-Rayleigh-Taylor instability (MRT) of a finite slab is studied analytically using the ideal MHD model. The slab may be accelerated by an arbitrary combination of magnetic pressure and fluid pressure, thus allowing an arbitrary degree of anisotropy intrinsic to the acceleration mechanism. The effect of feedthrough in the finite slab is also analyzed. The classical feedthrough solution obtained by Taylor in the limit of zero magnetic field, the single interface MRT solution of Chandrasekhar in the limit of infinite slab thickness, and Harris' stability condition on purely magnetic driven MRT, are all readily recovered in the analytic theory as limiting cases. In general, we find that MRT retains robust growth if it exists. However, feedthrough may be substantially reduced if there are magnetic fields on both sides of the slab, and if the MRT mode invokes bending of the magnetic field lines.

Unstable spiral modes in disk-shaped galaxies: A general fluid dynamical theory with some preliminary results

A numerical scheme has been devised to calculate discrete spiral modes in a fluid-dynamical model of disk galaxies. The procedure is free from the usual restrictions imposed upon the asymptotic theory. A radiation condition has been formulated as one of the boundary conditions. For a test model galaxy with moderately low surface density, quantitative agreement is found between the asymptotic spiral modes and the corresponding ones obtained from the present scheme. The present scheme should find ready application to the study of open spiral modes.

Unstable spiral modes in disk-shaped galaxies: Enhancement of growth rate

An additional effect not considered in our earlier papers is found to enhance the rate of growth of spiral modes in disk-shaped galaxies. This enhanced growth appears to be attributable to the combined influence of differential rotation and tangential forces. For certain galaxy models, rapid temporal growths are possible (comparable to those found in numerical experiments), but in many real galaxies, these tendencies to extreme growth rates are probably reduced to lower levels by competing effects such as wave absorption at inner Lindblad resonance.

Unstable spiral modes in disk-shaped galaxies

The mechanisms for the maintenance and the excitation of trailing spiral modes of density waves in diskshaped galaxies, as proposed by Lin in 1969 and by Mark recently, are substantiated by an analysis of the gas-dynamical model of the galaxy. The self-excitation of the unstable mode in caused by waves propagating outwards from the corotation circle, which carry away angular momentum of a sign opposite to that contained in the wave system inside that circle. Specifically, a simple dispersion relationship is given as a definite integral, which allows the immediate determination of the pattern frequency and the amplification rate, once the basic galactic model is known.

Discrete spiral modes in disk galaxies: Some numerical examples based on density wave theory

Discrete growing spiral modes are calculated, on the basis of principles of stellar dynamics, according to the recently developed asymptotic theory of density waves for spiral structure in galaxies. From the growth rates obtained, it appears likely that several spiral modes coexist in a given disk galaxy. General properties of these modes are described for two galaxy models, and some of their important observational implications are discussed.

Microwave window breakdown experiments and simulations on the UM/L-3 relativistic magnetron

Experiments have been performed on the UM/L-3 (6-vane, L-band) relativistic magnetron to test a new microwave window configuration designed to limit vacuum side breakdown. In the baseline case, acrylic microwave windows were mounted between three of the waveguide coupling cavities in the anode block vacuum housing and the output waveguides. Each of the six 3 cm deep coupling cavities is separated from its corresponding anode cavity by a 1.75 cm wide aperture. In the baseline case, vacuum side window breakdown was observed to initiate at single waveguide output powers close to 20 MW. In the new window configuration, three Air Force Research Laboratory-designed, vacuum-rated directional coupler waveguide segments were mounted between the coupling cavities and the microwave windows. The inclusion of the vacuum side power couplers moved the microwave windows an additional 30 cm away from the anode apertures. Additionally, the Lucite microwave windows were replaced with polycarbonate windows and the microwave window mounts were redesigned to better maintain waveguide continuity in the region around the microwave windows. No vacuum side window breakdown was observed in the new window configuration at single waveguide output powers of 120+MW (a factor of 3 increase in measured microwave pulse duration and factor of 3 increase in measured peak power over the baseline case). Simulations were performed to investigate likely causes for the window breakdown in the original configuration. Results from these simulations have shown that in the original configuration, at typical operating voltage and magnetic field ranges, electrons emitted from the anode block microwave apertures strike the windows with a mean kinetic energy of 33 keV with a standard deviation of 14 keV. Calculations performed using electron impact angle and energy data predict a first generation secondary electron yield of 65% of the primary electron population. The effects of the primary aperture electron impacts, combined with multiplication of the secondary populations, were determined to be the likely causes of the poor microwave window performance in the original configuration.

Effect of soft metal gasket contacts on contact resistance, energy deposition, and plasma expansion profile in a wire array Z pinch

Soft metal gaskets (indium and silver) were used to reduce contact resistance between the wire and the electrode in an aluminum wire Z pinch by more than an order of magnitude over the best weighted contact case. Clamping a gasket over a Z-pinch wire compresses the wire to the electrode with a greater normal force than possible with wire weights. Average contact resistance was reduced from the range of 100-3000 Omega (depending on wire weight mass) to 1-10 Omega with soft metal gaskets. Single wire experiments (13 microm Al 5056) on a 16 kA, 100 kV Marx bank showed an increase in light emission (97%) and emission volume (100%) of the plasma for the reduced contact resistance cases. The measured increases in plasma volume and light emission indicate greater energy deposition in the ablated wire. Additionally, dual-wire experiments showed plasma edge effects were significantly decreased in the soft metal gasket contact case. The average height of the edge effects was reduced by 51% and the width of the edge effects was increased by 40%, thus the gasket contact case provided greater axial uniformity in the plasma expansion profile of an individual wire.

Metal-oxide-junction, triple point cathodes in a relativistic magnetron

Triple point, defined as the junction of metal, dielectric, and vacuum, is the location where electron emission is favored in the presence of a sufficiently strong electric field. To exploit triple point emission, metal-oxide-junction (MOJ) cathodes consisting of dielectric "islands" over stainless steel substrates have been fabricated. The two dielectrics used are hafnium oxide (HfO(x)) for its high dielectric constant and magnesium oxide (MgO) for its high secondary electron emission coefficient. The coatings are deposited by ablation-plasma-ion lithography using a KrF laser (0-600 mJ at 248 nm) and fluence ranging from 3 to 40 J/cm(2). Composition and morphology of deposited films are analyzed by scanning electron microscopy coupled with x-ray energy dispersive spectroscopy, as well as x-ray diffraction. Cathodes are tested on the Michigan Electron Long-Beam Accelerator with a relativistic magnetron, at parameters V=-300 kV, I=1-15 kA, and pulse lengths of 0.3-0.5 micros. Six variations of the MOJ cathode are tested, and are compared against five baseline cases. It is found that particulate formed during the ablation process improves the electron emission properties of the cathodes by forming additional triple points. Due to extensive electron back bombardment during magnetron operation, secondary electron emission also may play a significant role. Cathodes exhibit increases in current densities of up to 80 A/cm(2), and up to 15% improvement in current start up time, as compared to polished stainless steel cathodes.

Role of ions in a crossed-field diode

The effect of ions in a magnetically insulated crossed-field gap is studied using a single particle orbit model, shear flow model, and particle-in-cell simulation. It is found that, in general, the presence of ions in a crossed-field gap always increases the electrons' excursion toward the anode region, regardless of the location of the ions. Thus, the rate at which the electrons migrate toward the anode, which is a measure of the diode closure rate, is related to the rate at which ions are introduced into the crossed-field gap. This anode migration of electrons is unrelated to crossed-field ambipolar diffusion. The implications of these findings are explored, such as pulse shortening in relativistic magnetrons and bipolar flows in pulsed-power systems.

effect of OATP1B transporter inhibition on the pharmacokinetics of atorvastatin in healthy volunteers

The inhibition of hepatic uptake transporters, such as OATP1B1, on the pharmacokinetics of atorvastatin is unknown. Here, we investigate the effect of a model hepatic transporter inhibitor, rifampin, on the kinetics of atorvastatin and its metabolites in humans. The inhibitory effect of a single rifampin dose on atorvastatin kinetics was studied in 11 healthy volunteers in a randomized, crossover study. Each subject received two 40-mg doses of atorvastatin, one on study day 1 and one on study day 8, separated by 1 week. One intravenous 30-min infusion of 600 mg rifampin was administered to each subject on either study day 1 or study day 8. Plasma concentrations of atorvastatin and metabolites were above the limits of quantitation for up to 24 h after dosing. Rifampin significantly increased the total area under the plasma concentration-time curve (AUC) of atorvastatin acid by 6.8+/-2.4-fold and that of 2-hydroxy-atorvastatin acid and 4-hydroxy-atorvastatin acid by 6.8+/-2.5- and 3.9+/-2.4-fold, respectively. The AUC values of the lactone forms of atorvastatin, 2-hydroxy-atorvastatin and 4-hydroxy-atorvastatin, were also significantly increased, but to a lower extent. An intravenous dose of rifampin substantially increased the plasma concentrations of atorvastatin and its acid and lactone metabolites. The data confirm that OATP1B transporters represent the major hepatic uptake systems for atorvastatin and its active metabolites. Inhibition of hepatic uptake may have consequences for efficacy and toxicity of drugs like atorvastatin that are mainly eliminated by the hepatobiliary system.

Thomson scattering and ponderomotive intermodulation within standing laser beat waves in plasma

Electrons in a standing electromagnetic wave--an optical lattice--tend to oscillate due to the quiver and ponderomotive potentials. For sufficiently intense laser fields (Ilamda2 approximately < or = 5 x 10(17) W cm(-2) microm2) and in plasmas with sufficiently low electron densities (n approximately < or = 10(18) cm(-3)), these oscillations can occur faster than the plasma can respond. This paper shows that these oscillations result in Thomson scattering of light at both the laser and ponderomotive bounce frequencies and their harmonics as well as at mixtures of these frequencies. We term this mixing ponderomotive intermodulation. Here, the case of counterpropagating laser beams creating a one-dimensional (1D) optical lattice is analyzed. The near-equilibrium electron orbits and subsequent Thomson scattering patterns are computed in the single-particle limit. Scaling laws are derived to quantify the range of validity of this approach. Finally, collective plasma and laser focusing effects are included by using particle-in-cell (PIC) techniques. This effect resulting in light-frequency conversion has applications both as an infrared light source and as a means to diagnose high laser intensities inside dense plasmas.

New scaling of child-langmuir law in the quantum regime

This paper presents a consistent quantum mechanical model of Child-Langmuir (CL) law, including electron exchange-correlation interaction, electrode's surface curvature, and finite emitter area. The classical value of the CL law is increased by a larger factor due to the electron tunneling through the space-charge potential, and the electron exchange-correlation interaction becomes important when the applied gap voltage Vg and the gap spacing D are, respectively, on the order of Hartree energy level, and nanometer scale. It is found that the classical scaling of Vg(3/2) and D(-2) is no longer valid in the quantum regime, and a new scaling of Vg(1/2) and D(-4) is established. The smooth transition from the classical regime to the quantum regime is also demonstrated.

Suppression of third-order intermodulation in a klystron by third-order injection

The first observations and measurements are reported on suppression of the third-order intermodulation (IM3) product arising from nonlinear mixing of two drive frequencies in a klystron, by externally injecting a wave at the IM3 product frequency. Optimum amplitude and phase of the injected wave for maximum suppression are examined. Results indicate that suppression of the IM3 product by as much as 30 dB can be achieved. Experimental results compare favorably with predictions of a 1D simulation code that takes into account all kinematical and dynamical effects including charge overtaking and space charge forces.

Backscattering of an intense laser beam by an electron

We present a novel, simple asymptotic expansion for the spectrum of radiation that is backscattered from a laser by a counterpropagating (or copropagating) electron. The solutions are presented in such a way that they explicitly show the relative merit of using an intense laser and of an energetic electron beam in x-ray production in the single particle regime. Simple scaling laws are given.

Characterization of glucose microsensors for intracellular measurements

Ultrasmall glucose sensors have been constructed by using platinum-deposited carbon ring microelectrodes with glucose oxidase. Response times as low as 270 ms have been obtained with these sensors. Moreover, there is a linear relationship between sensor tip diameter and response times. The use of these sensors has been demonstrated in the detection of glucose in single-cell cytoplasm of the large dopamine cell of the pond snail Planorbis corneus. Current responses obtained at these sensors implanted into a cell increase following injection of 2 pL of glucose solution (3 M) into the cell. Results obtained from these experiments show that these sensors are suitable for glucose monitoring in ultrasmall environments. In addition, characterizations of these sensors have been investigated under different O2 concentrations. At atmospheric oxygen concentrations, glucose levels in the submillimolar range can be measured without oxygen interference; however, oxygen interference can be substantial at low oxygen concentrations.

Simple theory for the two-dimensional Child-Langmuir law

This paper presents, for the first time, a simple analytic theory for the two-dimensional (2D) Child-Langmuir law. For electron emission over a finite patch on a planar cathode, the limiting current density is derived approximately from first principles. The scaling laws are in excellent agreement with simulation results. They predict the onset of virtual cathode formation in a 2D geometry; they also indicate that electrons emitted from a cathode over only a restricted area may have a current density much exceeding the classical (1D) Child-Langmuir value.

Limiting current density in a crossed-field nanogap

Using a mean-field theory, we have studied the quantum extension on the limiting current density in a crossed-field nanogap. When the gap spacing is less than the electron wavelength, our results show that the limiting current density is increased by a large factor from the classical values due to the effects of electron tunneling. The effects of the external magnetic field diminish with a decrease of gap spacing. Smooth transition from the classical regime to the quantum regime is demonstrated.

Alcoholic carbowax prefixation and formal alcohol fixation. A new technique for urine cytology

OBJECTIVE

To compare the cellular yield and sensitivity of cancer detection by urine cytology using alcoholic carbowax as a prefixative and formal alcohol as a final fixative with the conventional centrifugation-and-smearing method.

STUDY DESIGN

Four hundred seventeen voided urine specimens were examined. Each specimen was divided into two equal portions. One portion was centrifuged and wet fixed (CS). The other was treated with alcoholic carbowax as a prefixative and then fixed in formal alcohol (CW). The smears were studied for cellular yield, morphology, cancer detection rate and typing.

RESULTS

The CW method yielded significantly more cells with excellent morphology. It detected 25 more abnormal cases out of a total of 86, including 5 more transitional cell carcinomas, as compared to the CS method. This finding was statistically significant (P < .0000003).

CONCLUSION

The CW method is simple and enhances cellular yield and the cancer detection rate as compared to the conventional centrifuge-and-smear technique.

Determination of pramipexole (U-98,528) in human plasma by high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

A highly sensitive and selective HPLC-MS-MS method was developed for the determination of pramipexole in human plasma. The analytes, pramipexole and BHT-920 (internal standard), were extracted from plasma at basic pH with methyl tert.-butyl ether (MTBE). MTBE was evaporated to dryness and reconstituted in 100 microliters of (95:5) methanol-water. Chromatographic separation was achieved on a Zorbax SB-CN column with a mobile phase of (15:5:80) water-0.1 M ammonium acetate-methanol. The analytes were detected utilizing HPLC in conjunction with atmospheric pressure chemical ionization (APCI) tandem mass spectrometry (MS-MS). The assay was linear in the concentration ranges of 50 to 5000 pg/ml. The analysis of pooled quality controls (150, 750, and 3000 pg/ml) demonstrated excellent precision with relative standard deviations (R.S.D.) (n = 18) of 7.2%, 5.3% and 5.2%, respectively. The method is accurate with all intra-day (n = 6) and overall (n = 18) mean values being less than 11.7% from theoretical.

Determination of pramipexole (U-98,528) in human plasma and urine by high-performance liquid chromatography with electrochemical and ultraviolet detection

A sensitive and selective high-performance liquid chromatographic (HPLC) method was developed for the determination of pramipexole in human plasma and urine. Plasma/urine is made alkaline before pramipexole and BHT-920 (internal standard) are extracted by ethyl ether and back-extracted with a solution that contains heptanesulfonic acid. Separation is achieved by ion-pair chromatography on a Zorbax Rx C8 column with electrochemical detection at 0.6 V for plasma and ultraviolet detection at 286 nm for urine. The retention times of pramipexole and internal standard are approximately 14.4 and 10.7 min, respectively. The assay is linear in concentration ranges of 50 to 15,000 pg/ml (plasma) and 10 to 10,000 ng/ml (urine). The correlation coefficients are greater than 0.9992 for all curves. For the plasma method, the analysis of pooled quality controls (300, 3000, and 10,000 pg/ml) demonstrates excellent precision with relative standard deviations (R.S.D.) (n = 18) of 1.1%, 2.3%, and 6.8%, respectively. For the urine method, quality control pools prepared at 30, 300, and 3000 ng/ml had R.S.D. values (n = 18) of 2.9%, 1.7%, and 3.0%, respectively. The plasma and urine controls were stable for more than nine and three months, respectively. The mean recoveries for pramipexole and internal standard from plasma were 97.7% and 98.2%, respectively. The mean recoveries for pramipexole and internal standard from urine were 89.8% and 95.1%, respectively. The method is accurate with all intra-day (n = 6) and overall (n = 18) mean values for the quality control samples being less than 6.4 and 5.8% from theoretical for plasma and urine, respectively.

Determination of rifampin in human plasma by high-performance liquid chromatography with ultraviolet detection

A simple, specific and sensitive high-performance liquid chromatographic (HPLC) method was developed for the determination of rifampin in human plasma. Rifampin and sulindac (internal standard) are extracted from human plasma using a C2 Bond Elut extraction column. A 100-microliter volume of 0.1 M HCl is added to the plasma before extraction to increase the retention of the compounds on the extraction column. Methanol (1 ml) is used to elute the compounds and 0.5 ml of 3 mg/ml ascorbic acid in water is added to the final eluate to reduce the oxidation of rifampin. Separation is achieved by reversed-phase chromatography on a Zorbax Rx C8 column with a mobile phase composed of 0.05 M potassium dihydrogen phosphate-acetonitrile (55:45, v/v). Detection is by ultraviolet absorbance at 340 nm. The retention times of rifampin and internal standard are approximately 4.4 and 7.8 min, respectively. The assay is linear in concentration ranges of 50 to 35 000 ng/ml. The quantitation limit is 50 ng/ml. Both intra-day and inter-day accuracy and precision data showed good reproducibility.

Determination of rifabutin in human plasma by high-performance liquid chromatography with ultraviolet detection

A simple, specific and sensitive high-performance liquid chromatographic (HPLC) method was developed for the determination of rifabutin in human plasma. Rifabutin and sulindac (internal standard) are extracted from human plasma using a C8 Bond Elut extraction column. Methanol (1 ml) is used to elute the compounds. The methanol is dried down under nitrogen and reconstituted in 250 microliters of mobile phase. Separation is achieved by HPLC on a Zorbax Rx C8 column with a mobile phase composed of 0.05 M potassium dihydrogen phosphate and 0.05 M sodium acetate at pH 4.0-acetonitrile (53:47, v/v). Detection is by ultraviolet absorbance at 275 nm. The retention times of rifabutin and internal standard were approximately 10.8 and 6.9 min, respectively. The assay is linear over the concentration range of 5-600 ng/ml. The quantitation limit was 5 ng/ml. Both intra-day and inter-day accuracy and precision data showed good reproducibility.

Sensitivity of sputum cytology after homogenization with dithiothreitol in lung cancer detection. Two years of experience

OBJECTIVE

To compare the sensitivity of sputum cytology using the dithiothreitol homogenization method (DTT) with that of the standard pick-and-smear (PS) method in lung cancer detection.

STUDY DESIGN

In a two-year period, 2,428 sputum specimens were examined. Standard PS smears were prepared as controls; the remainder of the specimens were homogenized with DTT before smears were prepared. The sensitivity of the two methods in detecting positive cases was compared.

RESULTS

Among 260 positive cases, the DTT method detected 256, while the PS method detected only 212, representing a difference of 17%. The DTT method also detected 28 more suspicious cases and permitted definitive typing of the tumor in a further 11 cases.

CONCLUSION

Homogenization of sputum with DTT is not only a simple and versatile method but also a more sensitive method as compared to the PS method in lung cancer detection.

Amphetamine redistributes dopamine from synaptic vesicles to the cytosol and promotes reverse transport

Whether amphetamine acts principally at the plasma membrane or at synaptic vesicles is controversial. We find that d-amphetamine injection into the Planorbis giant dopamine neuron causes robust dopamine release, demonstrating that specific amphetamine uptake is not required. Arguing for action at vesicles, whole-cell capillary electrophoresis of single Planorbis dopamine neurons shows that amphetamine reduces vesicular dopamine, while amphetamine reduces quantal dopamine release from PC12 cells by > 50% per vesicle. Intracellular injection of dopamine into the Planorbis dopamine neuron produces rapid nomifensine-sensitive release, showing that an increased substrate concentration gradient is sufficient to induce release. These experiments indicate that amphetamine acts at the vesicular level where it redistributes dopamine to the cytosol, promoting reverse transport, and dopamine release.

Capillary electrophoresis of single cells: observation of two compartments of neurotransmitter vesicles

Capillary electrophoresis has been used to directly identify and measure the neurotransmitter, dopamine, in two vesicular compartments in a single nerve cell of Planorbis corneus. Dopamine in the cytoplasm and in easily released transmitter vesicles was separated from dopamine in what are apparently non-functional storage vesicles. In this method, the two peaks in the electropherogram attributed to dopamine were differentiated based on cell lyse time in a non-physiological buffer. The measurements presented here suggest that of the total dopamine present in the cell: 24% is in the cytoplasmic and easily released compartments and 76% is more centrally located, perhaps in a reserve compartment, in the cell. This methodology provides the means to determine molecular species in subcellular compartments and should allow kinetic parameters associated with membrane lysing to be evaluated at single nerve cells.

Voltammetric measurement of oxygen in single neurons using platinized carbon ring electrodes

Naflon-coated ultrasmall platinum ring electrodes have been implanted in the giant dopamine neuron of the pond snail Planorbis corneus, and the oxygen concentration inside these single neurons has been estimated. Experimental data suggest that the intracellular oxygen level in the identified dopamine neuron of P. corneus is approximately 0.032 mM. The oxygen concentration immediately outside the cell (ca. 10 microns away from the cell) is 0.041 mM. Furthermore, staircase voltammetry can be used to monitor dynamic changes in oxygen concentration inside the cell after bathing with Ringer's solution saturated with air/oxygen. Data obtained for intracellular oxygen concentrations suggest that intracellular oxygen consumption is increased following potassium chloride-induced stimulation of these cells.

Dietary N-3 fatty acids do not affect induction of Ha-ras mutations in mammary glands of NMU-treated rats

The purpose of this study was to determine whether dietary n-3 polyunsaturates (PUFA) can affect the frequency of N-nitrosomethylurea (NMU)-induced Ha-ras mutations in virgin female F344 rat mammary glands. Two groups of 15 rats each were fed isocaloric diets containing either 23% w/w corn oil or corn oil plus menhaden oil (1:1) at starting 14 d before NMU administration (day 50 of age) and continuing for 13 wk. Mammary gland samples were taken serially at 3, 5, 9, and 13 wk post-NMU treatment. Total cellular DNA was isolated and analyzed by a newly devised enriched amplification procedure that involves predigestion of normal Ha-ras alleles at codon 12, amplification of the mutant alleles, and restriction fragment length polymorphism analysis. Selective amplification enabled the detection of Ha-ras mutations as early as 3 wk post-NMU treatment. Approximately 40-50% of all glands and 75% of all rats tested had the Ha-ras codon 12 mutation. No significant differences were found between the two dietary groups at any time point, indicating that the mammary tumor-inhibiting effect of n-3 PUFA is probably not exerted at the level of the Ha-ras activation step in NMU tumorigenesis.