Changes in maternal middle cerebral artery blood flow velocity associated with general anesthesia in severe preeclampsia

In women with severe preeclampsia, significant increases in mean arterial pressures (MAP) are common after rapid induction of general anesthesia (GA) and tracheal intubation. The objectives of this prospective study were to assess the effects of the rapid induction-intubation technique on middle cerebral artery (MCA) flow velocity in severe preeclampsia and to examine the correlation between mean MCA flow velocity (Vm) and MAP. Eight women with severe preeclampsia (study group) and six normotensive women at term (control group) scheduled to undergo cesarean section under GA were studied. Before induction, patients in the study group received i.v. labetalol in divided doses to lower diastolic pressures to <100 mm Hg. Anesthesia was induced with pentothal 4-5 mg/kg, followed by succinylcholine 1.5 mg/kg to facilitate tracheal intubation. A transcranial Doppler was used to measure Vm. Both Vm and MAP were recorded before induction and every minute for 6 min after intubation. In the study group, after the administration of labetalol, MAP decreased from 129 +/- 9 to 113 +/- 9 mm Hg (P < 0.05), and Vm decreased from 59 +/- 11 to 54 +/- 10 cm/s (P < 0.05). After intubation, MAP increased from 113 +/- 9 to 134 +/- 5 mm Hg (P < 0.001), and Vm increased from 54 +/- 10 to 70 +/- 10 cm/s (P < 0.001). In the control group, while MAP increased significantly from 89 +/- 6 to 96 +/- 4 mm Hg (P < 0.05) after intubation, the concurrent increase in Vm from 49 +/- 5 to 54 +/- 7 cm/s was not significant. There was a significant positive pooled correlation between Vm and MAP (r = 0.5, P < 0.0006) in the study group but not in the control group (r = 0.24). After induction and intubation, both Vm and MAP values were significantly increased in the study group patients at all observation points compared with the control group patients. The findings indicate that Vm increases significantly after rapid-sequence induction of GA and tracheal intubation in women with severe preeclampsia, and there seems to be a direct relationship between MAP and Vm. Implications: In women with severe preeclampsia, rapid-sequence induction of general anesthesia and tracheal intubation can cause severe hypertension. Our results indicate that the increase in blood pressure is associated with a significant increase in maternal cerebral blood flow velocity and that there is a significant correlation between these two variables.     

Synthesis and characterization of one-dimensional flat ZnO nanotower arrays as high-efficiency adsorbents for the photocatalytic remediation of water pollutants

We report on facile fabrication of 1-D flat ZnO nanotower arrays on various substrates, including a metal, a semiconductor and an insulator. The nanotowers have a unique flat basal section near the substrate and taper in stages to wire-like at the tip. Electron microscopy and X-ray photoelectron spectroscopy are used to characterize these new nanostructures, revealing that their morphologies are significantly influenced by reaction temperature. A qualitative formation mechanism is proposed based on the experimental observations. A proof-of-concept demonstration shows that the ZnO nanotower arrays are highly effective at adsorbing and subsequently photo-remediating a model pollutant (Eosin B) from water. These observations could promote new applications of photocatalytic adsorbents for wastewater treatment utilizing oxide semiconductor nanostructures.     

Kenntnisstand und Untersuchungsergebnisse zur Wirkung von Ammoniak auf Holzspäne

The state of knowledge on the action of ammonia gas, ammonia solutions and liquid ammonia on wood and wood components is reviewed briefly. Results of experimental work on the effect of dilute ammonia solutions on the physical and chemical properties of beech and oak wood particles show that ammonia solutions increasse their nitrogen content and pH value, whereas the acetyl group content and buffering capacity towards alkali decrease. No remarkable changes take place in the lignin and pentosan content of wood on account of this treatment. IR-spectral analysis showed a decrease in the absorption intensity of wavenumber at about 1750cm^?1, whereas the x-ray diffractograms revealed no significant changes in the cellulose. Wood chips treated with ammonia solution exhibit an increase in the equilibrium moisture content at a relative humidity elose to 90%, and density in particleboard face alyers was raised.     

A post-growth processing methodology to achieve barium strontium titanate thin films with low dielectric loss and high tunability for reconfigurable tunable devices

Ba_0.60Sr_0.40TiO₃ (BST) thin films, grown via RF-sputtering and the metalorganic solution deposition (MOSD) techniques, were post-growth annealed via conventional thermal annealing (CTA) and UV-photon irradiation annealing. With respect to the conventional thermal annealed films the UV-photon irradiation annealed films possessed improved structural properties and dielectric response. The optimization of the UV-photon irradiation annealing process parameters (using RF-sputtered BST films) was achieved via a detailed set of iso-thermal/chronal annealing experiments. The optimized UV-process parameters, applied to MOSD synthesized BST films revealed further enhanced dielectric response, i.e., 23% reduction in tan δ with sustained tunability of 42%. The improvements in the material properties of the UV-photon irradiation annealed BST thin films are attributed to stoichiometry and structural changes enabled through the UV-photon irradiation annealing process.     

Quasi-static stress fields for a crack inclined to the property gradation in functionally graded materials

Summary.  Quasi-static stress fields for a crack inclined to the direction of property gradation in functionally graded materials (FGMs) are obtained through an asymptotic analysis coupled with Westergaard's stress function approach. The elastic modulus of the FGM is assumed to vary exponentially along the gradation direction. The mode mixity due to the inclination of the property gradient is accommodated in the analysis through superposition of opening and shear modes. The first four terms in the expansion of the stress field are derived to explicitly bring out the influence of nonhomogeneity on the structure of the stress field. Using these stress field contours of constant maximum shear stress, constant maximum principal stress, constant first stress invariant and constant out of plane displacement are generated, and the effect of inclination of the property gradation direction on these contours is discussed. Received September 22, 2002 Published online: May 20, 2003 The financial support of National Science Foundation (NSF) under grant no. CMS 99000138 is gratefully acknowledged.     

Cloud screening in IRS-P4 OCM satellite data: potential of spatial coherence method in the absence of thermal channel information

Cloud screening of satellite data for the remote sensing of atmospheric aerosols, ocean sediments, chlorophyll, and phytoplankton in the marine environment is a major problem in the absence of information from thermal channel. This is particularly the case with the data from some of the highly potential satellite sensors such as the Ocean Colour Monitor (OCM—on board the Indian Remote Sensing Satellite, IRS-P4) and the SeaWiFS. Two main tests conventionally used for cloud screening of data from such satellite sensors are the threshold method applied to visible and near-IR bands and the visible to near-IR channel ratio method. These methods do not have the potential to eliminate the pixels with small cloud fractions, leading to overestimation of the aerosol optical depth (AOD) derived from satellite data, and might also identify the pixels with high values of AOD as cloudy. The purpose of this paper is to study the potential of Spatial Coherence Test (SCT) applied to the data from the near-IR bands for cloud screening of satellite data over the oceanic environment. We use here the data from IRS-P4 OCM. Though more computationally intensive, the SCT does not suffer from the serious limitations of the threshold and channel ratio methods and is found to be superior in identifying the clear sky pixels that are not affected by clouds. Although the SCT applied to near-IR channel data may be overestimating the number of cloud affected pixels, it neither leads to overestimation of AOD nor identifies the pixels with high AOD values as cloudy.