George Papaioannou

Aspirin versus Placebo in Pregnancies at High Risk for Preterm Preeclampsia

Background Preterm preeclampsia is an important cause of maternal and perinatal death and complications. It is uncertain whether the intake of low‐dose aspirin during pregnancy reduces the risk of preterm preeclampsia. Methods In this multicenter, double‐blind, placebo‐controlled trial, we randomly assigned 1776 women with singleton pregnancies who were at high risk for preterm preeclampsia to receive aspirin, at a dose of 150 mg per day, or placebo from 11 to 14 weeks of gestation until 36 weeks of gestation. The primary outcome was delivery with preeclampsia before 37 weeks of gestation. The analysis was performed according to the intention‐to‐treat principle. Results A total of 152 women withdrew consent during the trial, and 4 were lost to follow up, which left 798 participants in the aspirin group and 822 in the placebo group. Preterm preeclampsia occurred in 13 participants (1.6%) in the aspirin group, as compared with 35 (4.3%) in the placebo group (odds ratio in the aspirin group, 0.38; 95% confidence interval, 0.20 to 0.74; P=0.004). Results were materially unchanged in a sensitivity analysis that took into account participants who had withdrawn or were lost to follow‐up. Adherence was good, with a reported intake of 85% or more of the required number of tablets in 79.9% of the participants. There were no significant between‐group differences in the incidence of neonatal adverse outcomes or other adverse events. Conclusions Treatment with low‐dose aspirin in women at high risk for preterm preeclampsia resulted in a lower incidence of this diagnosis than placebo. (Funded by the European Union Seventh Framework Program and the Fetal Medicine Foundation; EudraCT number, 2013‐003778‐29; Current Controlled Trials number, ISRCTN13633058.)

In vitro release of chlorpheniramine maleate from ointment bases

The in vitro release of chlorpheniramine maleate from ointments was studied using the Sartorius Absorption Simulator and its artificial epidermis barrier. The amount of drug released depended on the composition of the vehicle and the concentration of drug incorporated in it. The rate of release increased in the following order: ointment < o/w emulsion < w/o emulsion.

On the modeling of dielectric charging in RF-MEMS capacitive switches

The dielectric charging in RF MEMS capacitive switches is modeled. The modeling focus on charge injections processes and the calculations start from first principles. The calculations were performed on materials with uniform and exponential distribution of defects. The time and bias dependence of distribution of injected charges are derived. The dielectric charging/polarization build-up is derived and found to obey the stretched exponential law, a result being supported by experimental data in various dielectrics.

Preparation and Characterization of the Inclusion Complex of Furosemide with Hydroxypropyl-β-Cyclodextrin:

A highly hydrophobic drug, furosemide, was treated with 2-Hydroxypropyl-β-Cyclodextrin in an attempt to produce modified compounds with increased water solubility. Following a freeze-drying process, the interactions of furosemide and cyclodextrin led to the formation of an inclusion complex, whose dissolution rate in water was studied by the solubility method. Furthermore, mechanical mixtures of furosemide and cyclodextrin were also prepared and tested for their solubility. The reaction products were characterized in the solid state by differential scanning calorimetry (DSC), which provided some evidence about complexation. Additional evidence was obtained by recording the 1HNMR spectra of aqueous solutions of these same products. The study of phase solubility was based on the Higuchi & Connors method and showed an impressive enhancement of the miscibility of furosemide with water. In fact, a 11 fold increase of the drug solubility was recorded for the inclusion complex, in the first stages of dissolution. The experimental results of this work show that 2-Hydroxypropyl-β-Cyclodextrin isan efficient complexation agent for furosemide. Combination of those two substances can be carried out by simple techniques, providing easy control and the obtained inclusion complex is characterized by acceptable water solubility and increased dissolution rate.

Physics of Charging in Dielectrics and Reliability of Capacitive RF-MEMS Switches

The dielectric charging constitutes a major problem that still inhibits the commercial application of RF MEMS capacitive switches. The effect arises from the presence of the dielectric film (Fig.1a), which limits the displacement of the suspended electrode and determines the device pull-down state capacitance. Macroscopically, the dielectric charging is manifested through the shift (Fig.1b) (Rebeiz 2003, Wibbeler et al. 1998, Melle et al. 2003, Yuan et al. 2004) or/and narrowing (Czarnecki et al. 2006, Olszewski et al. 2008) of the pullin and pull-out voltages window thus leading to stiction hence the device failure. The first qualitative characterization of dielectric charging within capacitive membrane switches and the impact of high actuation voltage upon switch lifetime was presented by C. Goldsmith et al. (Goldsmith et al. 2001) who reported that the dependence of number of cycles to failure on the peak actuation voltage follows an exponential relationship. Particularly it was reported that the lifetime improves by an order of a decade for every 5 to 7 V decrease in applied voltage. The lifetime in these devices is measured in number of cycles to failure although experimental results have shown that this tests do not constitute an accurate figure of merit and the time the device spends in the actuated position before it fails is a much better specification to judge device reliability (Van Spengen et al. 2003). The aim to improve the reliability of capacitive switches led to the application of different characterization methods and structures such as the MIM (Metal-Insulator-Metal) capacitors that allowed to determine the charging and discharging times constants (Yuan et al. 2004, Lamhamdi 2008) as well as to monitor the various charging mechanisms (Papaioannou 2007a), since these devices marginally approximate the capacitive switches in the pull-down state. A method that approximates more precisely the charging process through asperities and surface roughness in MEMS and allows the monitoring of the discharging process is the Kelvin Probe Force Microscopy (Nonnenmacher 1991). This method has been recently employed for the investigation of the charging and discharging processes in capacitive switches (Herfst 2008, Belarni 2008). The charging of the dielectric film occurs independently of the actuation scheme and the ambient atmosphere (Czarnecki et al. 2006). Up to now the effect has been attributed to the charge injection during the pull-down state (Wibbeler et al. 1998, Melle et al. 2003, 14

Low‐temperature properties and phototransport in silicon‐on‐insulator films synthesized by oxygen implantation

Silicon‐on‐insulator material formed by oxygen implantation (SIMOX) is analyzed by comparing conductivity and Hall‐effect measurements performed at low temperature, under darkness, illumination, and substrate biasing. The quality of SIMOX films annealed at high temperatures above 1300 °C is found to be greatly enhanced in comparison with that obtained after conventional annealing at 1150–1200 °C. The analysis is fulfilled by discussing the carrier mobility and lifetime behavior, impurity ionization, doping compensation, film contamination, and scattering mechanisms. Hopping conduction is found to prevail below 60 K.

Charge collection mechanism in MEMS capacitive switches

The present paper investigates the effect of stressing bias magnitude and stressing time on the discharging process in MEMS capacitive switches. The calculation of discharge current through the dielectric film is based on monitoring the rate of shift of bias for up-state minimum capacitance. The data analysis shows that the discharge current lies in the range of femto-Amperes and the calculated discharge time constant depends directly on the time window of observation and on the stressing conditions. Moreover the analysis reveals an increase of trapped charge that remains in the bulk of the dielectric film for very long time as the stressing bias increases. The dominant discharge process, taking place under an intrinsic field of about 103 V/cm, is found to be the hopping effect.

Lipid peroxidation by Pseudomonas aeruginosa in the pathogenesis of nosocomial sepsis

BACKGROUND To study whether Pseudomonas aeruginosa may directly trigger peroxidation of polyunsaturated fatty acids, since lipid peroxidation is a mechanism involved in the pathogenesis of sepsis. METHODS Gamma-linolenic acid (GLA) was administered intravenously at a dose of 25mg/kg in an infusion time of 10 minutes to seven male rabbits. Blood samples were collected from the hepatic veins and from the carotid artery at regular time intervals. One clinical isolate was ex vivo incubated with the serum derived from the latter samples and concentrations of malondialdehyde (MDA) were determined during incubation in the growth medium by the thiobarbiturate assay. RESULTS Elevated concentrations of MDA compared to their basal levels were found over the first three hours of incubation in the presence of samples collected 30 to 60 minutes after the end of the infusion of GLA. After infusion of GLA concentrations of arachidonic acid in the serum increased to concentrations comparable to those detected in sepsis. CONCLUSION Direct triggering of lipid peroxidation by nosocomial isolates might be proposed as a pathogenetic mechanism of sepsis.

The Impact of Dielectric Material and Temperature on Dielectric Charging in RF MEMS Capacitive Switches

The present work attempts to provide a better insight on the dielectric charging in RF-MEMS capacitive switches that constitutes a key issue limiting parameter of their commercialization. The dependence of the charging process on the nature of dielectric materials widely used in these devices, such as SiO2, Si3N4, AlN, Al2O3, Ta2O5, HfO2, which consist of covalent or ionic bonds and may exhibit piezoelectric properties is discussed taking into account the effect of deposition conditions and resulting material stoichiometry. Another key issue parameter that accelerates the charging and discharging processes by providing enough energy to trapped charges to be released and to dipoles to overcome potential barriers and randomize their orientation is the temperature will be investigated too. Finally, the effect of device structure will be also taken into account.

Dielectric Discharging processes in RF-MEMS Capacitive Switches

The discharging processes in silicon nitride dielectric film of RF-MEMS capacitive switches are investigated for the first time. The study includes the dependence of discharging as a function of temperature that allows the detection of thermally activated mechanisms. The discharging time constants were found to depend only on temperature and not on the actuation bias polarity.