Antenna, load, and field effects on the bistatic scattering patterns from a linear dipole array

Scattering from a terminated antenna structure is studied and evaluated by modeling and computing its characteristics for linear dipole arrays and a variety of field, structure, and load conditions. Specific current distributions and effective load terminations are established that separate and compare the surface- and load-reflected contributions to the scattered field. The level and spatial distribution of the resulting fields and cross sections are determined as well as the relationship of these fields to the antenna gain pattern and their dependence on termination network effects that include waveguide phase delays and interdipole connections. The results presented illustrate the character of the bistatic scattering and its dependence on array structure, mutual coupling, conducting plates, incident field variations, and the internal and termination impedances.     

Metered dose inhalers III: Metaproterenol sulphate; particle size distribution and dose uniformity

Three American products and one Canadian product were examined for content uniformity and particle size distribution. The results showed that not all products performed equally well. Some of the products exhibited high sprays early in the canister lifetime and all products demonstrated loss of prime. The particle size distributions were determined using the Andersen cascade impactor (USP Induction Port) and the fine particle fraction was determined using the twin impinger. The results showed that three of the four products had similar particle size distribution profiles. Both the Andersen cascade impactor and the twin impinger yielded the same trends in the amount of drug substance delivered to the fine particle fraction.     

Classification of Simulated And Actual NOAA-6 AVHRR Data for Hydrologic Land-Surface Feature Definition

Current ground hydrology models (GHM's) require global distribution of bare soil and vegetation, the physical and thermal properties of soil, and the physiological and physical properties of plants to parameterize evaporation and the sensible heat flux from the land surfaces. Thus the ability to infer vegetative cover, and to some extent vegetation type, is hydrologically important because of the relationship between vegetation and evapotranspiration through the process of root-zone soil-moisture extraction. LANDSAT digital data degraded to approximately 1 km and NOAA-6 digital data have been used to study the capability and problems associated with the use of low-resolution data to provide land-surface information such as forest, grassland, agriculture, bare, urban, and water. Three LANDSAT scenes and a subscene from a NOAA-6 pass were classified using supervised and unsupervised techniques. The LANDSAT data were used initially to study classification techniques and ascertain problems associated with large-scale classification prior to the receipt of NOAA-6 data. Comparisons between the LANDSAT supervised classification (?ground truth?) and the unsupervised classification resulted in percentage differences between the cover types of generally less than 10 percent. The Advanced Very Hign Resolution Radiometer (AVHRR) results were similar to the LANDSAT. In both cases there was no statistical difference between the supervised and unsupervised results. The major problem encountered was consistent labeling of the various landcover categories derived by the classification methods.     

Effect of MWCNT addition on the thermal and rheological properties of polymethyl methacrylate bone cement

Multi-walled carbon nanotube (MWCNT)/polymethyl methacrylate (PMMA) composites with loadings ranging from 0.1 to 1.0 wt.% were prepared for use as bone cement. Unfunctionalised, carboxyl and amine functionalised MWCNT were used. Thermal properties were characterised in accordance with the International Standard for acrylic cements, ISO 5833:2002. The rate of reaction exotherm generated and thermal necrosis index (TNI) values were calculated. Polymerisation kinetics were characterised using parallel plate rheology and the exotherm during polymerisation was reduced by ≈4–34%, as a consequence of the MWCNT thermal conductivity. The rate of reaction was significantly altered, such that the setting times of the cements were extended (≈3–24%). Consequently, significant decreases in TNI values (ranging from 3% to 99%) were recorded, which could reduce the exothermic temperatures experienced in vivo and therefore prevent the likelihood of polymerising PMMA cement causing thermally-induced bone tissue necrosis. Thermal data was supported by the rheological characterisation results. Onset of polymerisation for PMMA cement exhibited a strong linear increase as a function of MWCNT loading, however, polymer gelation was not affected to the same degree. It is proposed that the chemically functionalised MWCNT altered PMMA bone cement polymerisation kinetics, reducing the rate of polymerisation, and hence, the reaction exotherm.     

Acute haloperidol attenuates the hypomotility induced with 7-hydroxy-DPAT

Dopamine D3 receptors have been implicated in pathophysiological substrates of schizophrenia, and neuroleptic drugs which are antagonists primarily at D2 receptors possess therapeutic activity in this disorder. In the present study, rats tested for hypomotility induced by 7-hydroxy-DPAT (7OH, a selective D3 agonist) were pretreated with the neuroleptic haloperidol. These animals showed an attenuated agonist-induced suppression of behavior compared with rats receiving 7OH alone. The drug combination also 'normalized' dopamine metabolism in the frontal cortex, as turnover ratios which are typically enhanced by acute neuroleptic administration were no longer significantly increased when 7OH was also given. These observations suggest that the effects of haloperidol in cortical regions regulating limbic locomotor systems may be important for therapeutic efficacy in schizophrenic symptoms generated from a D3 substrate.     

Long-term memory retrieval deficits of learned taste aversions are ameliorated by cortical fetal brain implants.

In this study, the effects that fetal brain implants have on the ability to retrieve the memory for a previously acquired conditioned taste aversion (CTA) in insular cortex (IC) lesioned rats were tested. Several groups of rats were trained for a CTA, were lesioned in the IC 4 days later, were implanted with different fetal cortical tissues, were treated or untreated with nerve growth factor (NGF), and then were tested for recall either 15 or 45 days later. Rats were then retrained and tested with a different taste and in the inhibitory avoidance (IA) task. All implanted animals recovered the retrieval of CTAs learned before IC lesions; however, only the homotopic IC implants at 45 days or NGF supplemented at 15 days induced recovery of the ability to learn CTA. The latter effect was also true for IA learning. The results suggest that the brain mechanisms for recovery of memory functions are different from those of learning abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Landsat digital analysis of the initial recovery of burned tundra at Kokolik River, Alaska

During late July and early August 1977, a wildfire burned 48km² of tundra in northwestern Alaska near the Kokolik River. The environmental effects of the fire were studied in the field and from aircraft and Landsat data. Three categories of burn severity were delineated using an August 1977 Landsat scene acquired shortly after the fire stopped. Measurable reflectance increased in all three categories by the following year as determined from a Landsat image acquired in August 1978. Regrowth of vegetation in the year following the fire was measured using Landsat digital data and compared with field measurements from selected portions of the burned area. Live vascular plant cover doubled in one of the severely burned portions of the area and increased 33% in a lightly burned portion as determined from field measurements. Landsat-derived measurements showed an increase of 62.5% in reflectance for the severely burned areas, and 53% for the lightly burned areas, which is attributed to regrowth of vegetation. Within the most severely burned portion, 9.6 out of a total of 13.3 km² showed minimal recovery based on the Landsat-derived spectral data. Within the lightly burned portion, 5.9 out of a total of 13.5 km² showed the same range of spectral values as did the control areas. Prefire terrain and vegetation conditions were found to influence burn severity. The drier high-relief areas generally burned more completely than lower-lying wet areas. Satellite data acquired after the fire confirmed this for much of the burned area.