Micro orientation and anisotropy of conductivity in liquid crystalline polymer films filled with carbon nanotubes.

In this communication we report the preferential orientation of single wall carbon nanotubes (SWNT) in a nematic liquid crystalline (LC) polymer matrix. The alignment of the nanotubes was characterized through anisotropy of electrical conductivity of the composite measured in directions parallel and perpendicular to the nematic director. The anisotropy of the nanocomposite films strongly depends on the nanotube concentration in the range from 1 to 10% and vanished at higher loads. The electrical conductivity of nanocomposites is related to their structural features revealed by atomic force microscopy and Raman spectroscopy experiments and is explained by a strong coupling between the nanotubes and the polymer matrix.

Apogeotropic roots in an Amazon rain forest.

Roots of some tropical trees grow vertically upward on the stems of neighboring trees. Apogeotropic roots occur in 12 species across five families. These roots, originating as fine roots in the mineral soil, grow upward as fast as 5.6 centimeters in 72 hours. Apogeotropic root growth may be an adaptation to extremely low soil nutrient availability in Amazon forests. In these forests upward-growing roots obtain nutrients via the predictable pathway of precipitation that flows down along the stem. Apogeotropic roots form a nutrient cycling pathway in which nutrients are absorbed and transported directly from plant to plant, without entering the soil solution.

Amazon rain-forest fires.

Charcoal is common in the soils of mature rain forests within 75 kilometers of San Carlos de Rio Negro in the north central Amazon Basin. Carbon-14 dates of soil charcoal from this region indicate that numerous fires have occurred since the mid-Holocene epoch. Charcoal is most common in tierra firme forest Oxisols and Ultisols and less common in caatinga and igapo forest soils. Climatic changes or human activities, or both, have caused rain-forest fires.

Prevention of acute aspirin-induced gastric mucosal injury by 15-R-15 methyl prostaglandin E2: an endoscopic study.

The deleterious effects of aspirin on gastric mucosa have been well documented in experimental and clinical studies. Prostaglandins offer a potential method by which this injury may be prevented. In these studies, we developed a single-dose endoscopic assay system of aspirin-induced gastric mucosal injury in normal volunteers. With this system, 27 of 30 volunteers (90%) demonstrated severe mucosal injury after ingestion of aspirin. Subsequently, we evaluated whether pretreatment with 15-R-15 methyl prostaglandin E2 prevented severe injury after ingestion of aspirin. Following an initial dose-response study, a double-blind crossover trial was performed using pretreatment with placebo or with 10-micrograms doses of 15-R-15 methyl prostaglandin E2 for 24 h before treatment with aspirin. The results of this trial indicate that prostaglandin pretreatment significantly prevented the occurrence of endoscopically visible severe gastric mucosal injury after single-dose aspirin administration.

Cumulative sum control charts for admixture quality control.

The use of cumulative sum control charts as a means of monitoring the sterility of i.v. admixtures produced by a centralized service is discussed. To create a sum control chart, acceptable and rejectable quality levels must be determined. Frequency of sampling will responsiveness and can be varied to affect the length of time necessary to detect an unacceptable shift in product quality. Cumulative sum control charts allow monitoring to be carried out on a cost versus benefit basis, and can be used to provide a basis for action on production of existing product and to maintain or improve product quality in the future.

Metabolism in rat lung tissue slices: technical factors.

We compared several sets of conditions used to estimate metabolism in rat lung slices. 14CO2 production from [14C]glucose, oxygen consumption, lactate production, and glucose consumption were used as measures of metabolic activity. The calculated results differed when we used 1) different techniques for estimating tissue weight, 2) tissue slices of 0.3-, 0.5-, 0.7-, and 1.0-mm thickness, 3) 95% air or 95% oxygen with 5% CO2 4) a delay after slice preparation and 4 degrees C and room temperature or periods of anoxia before incubation, 5) shaking rates of 60, 90, 120, or 150/min, 6) phosphate or bicarbonate buffers. Conditions of maximal activity were found using 95% O2 with 1.0-mm tissue slices, shaking at 120/min in phosphate buffer without periods of hypoxia or undue delays before incubation. Tissue weight should be obtained without exposure to aqueous solutions or dehydration by contact with cotton gauze or filter paper.