Relation of computerized tomography Hounsfield unit measurements and internal components of fresh chestnuts (Castanea spp.)

Little is known about Chestnut (Castanea spp.) in vivo cultivar characterization and morphology, the effect of mechanical harvesting, peelability, postharvest mold, physiological kernel decay, and quality. Thus, there is a need to develop a nondestructive technique able to assess fresh chestnut internal components, especially disorders. In this study, a medical grade computed tomography (CT) was used to obtain transversal two-dimensional (2D) images from decayed and healthy fresh chestnuts, from the hybrid cultivar ‘Colossal’ and ‘Chinese seedlings’. Attenuation coefficients, referred to as Hounsfield-units (HU) or CT numbers, were acquired from different 2D CT image regions including air, and several chestnut components containing decayed tissue, healthy tissue, various imperfections such as pellicle invagination into healthy kernel, and void spaces. Results offer an in vivo accurate insight of fresh intact chestnuts, and suggest that CT technology is appropriate for inline sorting. HU measurements can be used as a nondestructive predictor of fresh chestnut internal components with a 90.6% overall accuracy rate.     

Survival of Sprouting Shrubs Following Summer Fire: Effects of Morphological and Spatial Characteristics

Efficacy of fire in reducing shrub density is low in plant communities where most woody plants resprout from stem bases and crowns following fire. Our objective was to determine the relationship of shrub mortality and recovery from summer fire to prefire shrub structural characteristics. A randomized, complete block design with two treatments (burned and control) and three blocks was used in the experiment. Within each block and treatment combination, we randomly selected 40 individuals each of brasil (Condalia hookeri M. C. Johnst.), huisache (Acacia farnesiana [L.] Willd.), and spiny hackberry (Celtis ehrenbergiana [Klotzsch] Liebm.). We estimated height, canopy diameter, number of stems, stem diameter, and distance to the nearest shrubs before ignition of fires. Fires were ignited during July and August 2001. Survival, sprout number, height, and total plant height were estimated 47–52 wk postburn. Mortality of brasil was 26 times greater on burned sites than on control sites, but mortality of huisache and spiny hackberry was negligible. Mortality of brasil varied from 0% to 68% among blocks. Postburn height and number of sprouts increased with preburn shrub height and number of stems, indicating that longer intervals of time between fires that allow shrub growth facilitate more rapid postfire recovery. Factors other than the preburn shrub structural characteristics we measured appear to influence postfire shrub survival most strongly, although these characteristics are useful in predicting postfire sprout production and shrub height.     

Elevated mitochondrial alternative oxidase activity in dsRNA-free, hypovirulent isolates of Cryphonectria parasitica

In Cryphonectria parasitica, the causal agent of chestnut blight, hypovirulence is commonly associated with the presence of cytoplasmically transmissible, double-stranded RNA (dsRNA). Recently, hypovirulent isolates of C. parasitica that do not have detectable levels of dsRNA have been obtained from healing cankers on chestnut trees. In these isolates, most of the respiratory activity is cyanide-resistant and salicylhydroxamate-sensitive, indicating that the mitochondrial alternative oxidase was induced. In contrast, the respiration of virulent isolates from the same trees and most of the dsRNA-containing hypovirulent isolates from a variety of geographical locations was cyanide sensitive. In all of these isolates, the alternative oxidase could be induced by growing them in the presence of chloramphenicol, an inhibitor of mitochondrial protein synthesis. The attenuated virulence and altered respiratory phenotypes could be transferred from the dsRNA-free hypovirulent isolates to virulent strains through hyphal anastomosis. Some of the dsRNA-free hypovirulent isolates grew more slowly than virulent strains. These results indicate that, in Cryphonectria, cytoplasmically transmitted hypovirulence may have more than one cause, and that mitochondrial mutations sometimes may be involved in the generation of this phenotype.     

Climatic Limits on Landscape Development in the Northwestern Himalaya

The interaction between tectonism and erosion produces rugged landscapes in actively deforming regions. In the northwestern Himalaya, the form of the landscape was found to be largely independent of exhumation rates, but regional trends in mean and modal elevations, hypsometry (frequency distribution of altitude), and slope distributions were correlated with the extent of glaciation. These observations imply that in mountain belts that intersect the snowline, glacial and periglacial processes place an upper limit on altitude, relief, and the development of topography irrespective of the rate of tectonic processes operating.     

Pathology of experimentally-induced, acute toxoplasmosis in macropods

SUMMARY Thirteen Tammar wallabies (Macropus eugenii) were dosed orally with 500, 1000 or 10 000 oocysts of Toxoplasma gondii, as part of a vaccination trial. Eleven animals died of acute toxoplasmosis 9 to 15 days after challenge. The lesions were similar in all animals, consisting of foci of necrosis and inflammation in the intestines, lymphoid tissue, adrenal cortex, heart, skeletal muscle and brain, and severe generalised pulmonary congestion and oedema. Free and intracellular tachyzoites of Toxoplasma were associated with the lesions. The remaining 2 animals had shown no signs of disease when euthanased four months after challenge. Small, focal, non-suppurative inflammatory lesions were seen in brain, heart and skeletal muscle of these animals and chronic Toxoplasma infection was confirmed by mouse inoculation.     

Estimating the mass of asteroid 253 mathilde from tracking data during the NEAR flyby

The terminal navigation of the Near Earth Asteroid Rendezvous (NEAR) spacecraft during its close flyby of asteroid 253 Mathilde involved coordinated efforts to determine the heliocentric orbits of the spacecraft and Mathilde and then to determine the relative trajectory of the spacecraft with respect to Mathilde. The gravitational perturbation of Mathilde on the passing spacecraft was apparent in the spacecraft tracking data. As a result of the accurate targeting achieved, these data could be used to determine Mathilde's mass as 1.033 (+/- 0.044) x 10(20) grams. Coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a low bulk density for Mathilde of 1.3 grams per cubic centimeter.     

Real-time quantitative PCR assays for evaluation of soybean varieties for resistance to the stem and root rot pathogen Phytophthora sojae

Phytophthora root and stem rot caused by Phytophthora sojae is one of the most destructive disease of soybeans in the world. Effective management of the disease depends on selection and use of soybean varieties resistant to the disease. Fast and reliable procedures are vital to screen soybean varieties against the pathogen. Novel real-time quantitative (qPCR) assays were developed for both absolute and relative quantification of P. sojae in infected root tissues. QPCR assays were based on the detection of the internal transcribed spacer (ITS) gene of the pathogen and 18S ribosomal gene of the host plant. Absolute qPCR allowed the detection of as low as 10 femtograms (fg) of P. sojae DNA in soybean roots. Relative qPCR, employing the comparative threshold cycle (Ct) method, was effective and reliable for quantification of P. sojae DNA normalized to plant DNA in infected soybean root tissues. P. sojae DNA quantities detected in both qPCR assays had high correlations with disease severity index (DSI) ratings of soybean varieties. QPCR assays developed in this study were useful for determination of the levels of P. sojae DNA in different varieties of soybean and for evaluation of them for relative resistance to the pathogen.     

Hydrogen radicals, nitrogen radicals, and the production of O3 in the upper troposphere

The concentrations of the hydrogen radicals OH and HO2 in the middle and upper troposphere were measured simultaneously with those of NO, O3, CO, H2O, CH4, non-methane hydrocarbons, and with the ultraviolet and visible radiation field. The data allow a direct examination of the processes that produce O3 in this region of the atmosphere. Comparison of the measured concentrations of OH and HO2 with calculations based on their production from water vapor, ozone, and methane demonstrate that these sources are insufficient to explain the observed radical concentrations in the upper troposphere. The photolysis of carbonyl and peroxide compounds transported to this region from the lower troposphere may provide the source of HOx required to sustain the measured abundances of these radical species. The mechanism by which NO affects the production of O3 is also illustrated by the measurements. In the upper tropospheric air masses sampled, the production rate for ozone (determined from the measured concentrations of HO2 and NO) is calculated to be about 1 part per billion by volume each day. This production rate is faster than previously thought and implies that anthropogenic activities that add NO to the upper troposphere, such as biomass burning and aviation, will lead to production of more O3 than expected.