Polar lightning and decadal-scale cloud variability on Jupiter     

Baines KH  Simon-Miller AA  Orton GS  Weaver HA  Lunsford A  Momary TW  Spencer J  Cheng AF  Reuter DC  Jennings DE  Gladstone GR  Moore J  Stern SA  Young LA  Throop H  Yanamandra-Fisher P  Fisher BM  Hora J  Ressler ME 《Science (New York, N.Y.)》2007,318(5848):226-229

Although lightning has been seen on other planets, including Jupiter, polar lightning has been known only on Earth. Optical observations from the New Horizons spacecraft have identified lightning at high latitudes above Jupiter up to 80 degrees N and 74 degrees S. Lightning rates and optical powers were similar at each pole, and the mean optical flux is comparable to that at nonpolar latitudes, which is consistent with the notion that internal heat is the main driver of convection. Both near-infrared and ground-based 5-micrometer thermal imagery reveal that cloud cover has thinned substantially since the 2000 Cassini flyby, particularly in the turbulent wake of the Great Red Spot and in the southern half of the equatorial region, demonstrating that vertical dynamical processes are time-varying on seasonal scales at mid- and low latitudes on Jupiter.  相似文献   

Girdling and summer pruning in apple increase soil respiration   总被引：1，自引：0，他引：1  

D.M. Glenn  E. Campostrini 《Scientia Horticulturae》2011

The root system of plants derives all its energy from photosynthate translocated from the canopy to the root system. Canopy manipulations that alter either the rate of canopy photosynthesis or the translocation of photosynthate are expected to alter dry matter partitioning to the root system. Field studies were conducted to evaluate the effect of trunk girdling (2008 and 2009) and summer pruning (2009) on soil respiration, maximum quantum yield efficiency of photosystem II and leaf carbohydrate content. In apple trees, following trunk girdling there was increased soil respiration in association with a significant rainfall event suggesting rapid release of organic matter and subsequent microbial decomposition of the carbon. Soil respiration rates returned to baseline levels over time. Reduction in midday maximum quantum efficiency of photosystem II (RPSII) was increased by girdling when crop load was low and this reduction was not related to leaf carbohydrate levels. Girdling reduced leaf sucrose and sorbitol levels in both years, however, total leaf carbohydrates were not affected by girdling. Summer pruning increased soil respiration within 2 weeks of treatment in association with a significant rainfall event, also suggesting a release of organic matter and microbial decomposition of the carbon. Cultural practices that severely affect canopy sink source relationships such as girdling and summer pruning increase soil respiration, however these effects appear to be very short lived, 3–10 days, followed by recovery of the soil/root system to similar levels of soil carbon dioxide efflux. These cultural practices do not likely pose a long-term detrimental effect on root system efficiency because the effects are of short duration with apparent recovery.  相似文献   

Effect of fermentation on Sweetpotato (Ipomoea batatas) toxicity in mice     

Thibodeau MS  Poore MH  Hagler WM  Rogers GM 《Journal of agricultural and food chemistry》2004,52(2):380-384

Unfortunate bovine fatalities occurring after ingestion of mold-damaged sweetpotatoes preclude the use of the culled tubers in livestock feed. In cattle, mold-damaged sweetpotatoes induce an acute respiratory distress syndrome resulting in asphyxiation. Because of this potential toxicity and the general abundance of culled sweetpotatoes, the detoxification efficacy of ensiling was explored since it is an easy and economically viable technique often applied to preserve livestock feed. Sweetpotato slices with or without mold damage were stored either frozen (to represent unfermented samples) or fermented for 6 weeks at room temperature. Following fermentation, organic extracts were generated for administration to mice. Thirty hours following administration of the extracts, mice were evaluated for gross and microscopic lesions affecting the lungs, liver, and kidneys. Fermentation of 6 weeks duration was observed to inadequately eliminate the lung, liver, and kidney toxicity caused by mold-damaged sweetpotatoes. In fact, fermentation exacerbated the hepatotoxicity of mold-damaged sweetpotatoes. This is also the first demonstration that sweetpotato regions lacking visible mold damage can induce lung and kidney injury, which, however, is preventable by fermentation.  相似文献   

Influence of disaccharide structure on prebiotic selectivity in vitro     

Sanz ML  Gibson GR  Rastall RA 《Journal of agricultural and food chemistry》2005,53(13):5192-5199

To obtain structure-function information of a range of carbohydrates, which are available only in very small quantities, an in vitro fermentation method using 7 mg of carbohydrate, 0.7 mL of basal medium, and 1% (w/v) of fecal bacteria was validated against a pH-controlled batch culture with 150 mL of basal medium and 1.5 g of test carbohydrate. This method was used to determine the influence of different glycosidic linkages and monosaccharide compositions of disaccharides on the selectivity of microbial fermentation. A prebiotic index (PI) was calculated for each disaccharide. Generally, disaccharides with linkages of 1-2, 1-4, and 1-6 generated a high PI score, with kojibiose and sophorose showing the greatest values (21.62 and 18.63, respectively). Apart from 6alpha-mannobiose, mannose-containing disaccharides gave a low PI due to low numbers of bifidobacteria and lactobacilli and an increase in bacteroides. The structure-function information obtained in this study may lead to a predictive understanding of how specific structures are fermented by the human gut microflora.  相似文献   

Forest loss with urbanization predicts bird extirpations in Vancouver     

Kenneth B.H. Er  John L. Innes  Kathy Martin 《Biological conservation》2005,126(3):410-419

Forest loss with accompanying urbanization is often permanent as forests are replaced by impervious concrete structures or surfaces. The remaining forest patches are usually isolated and too small to maintain viable populations of forest-dependent wildlife species. Consistent with the species-area function (S = cA^z), extirpation of species should follow forest loss. However, this has rarely ever been tested in the urban landscape. We determined whether the observed number of forest-dependent bird extirpations occurring after forest loss matches that predicted by the species-area function in Vancouver (study area ∼126.7 km²), British Columbia, Canada. Prior to European settlement in 1859, Vancouver was covered completely by coastal western hemlock forest. Based on published historical maps of forest cover and present Landsat imagery of Vancouver, we estimated that approximately 87% of the forest area in Vancouver has been converted to urban development. Using the species-area function, we then predicted that approximately 14 bird species closely associated with lowland forest should have been extirpated. This figure is significantly greater than the three bird species known to have been extirpated in Vancouver. When we constrained the comparison to bird species closely associated with lowland forest and restricted in their distribution in British Columbia, we found a close match between the observed and predicted number of extirpations, suggesting that bird species closely associated with lowland forest and restricted in their geographic distribution are most prone to extirpation as a result of forest loss. Given that urban areas are situated in productive habitats with inherently high species richness, it is important that local land-use plans incorporate the conservation of habitat fragments from the onset and place particular emphasis on the regionally restricted forest-dependent species.  相似文献   

Assessment of C budget for grasslands and drylands of the world   总被引：1，自引：0，他引：1  

Dennis S. Ojima  Bjørn O. M. Dirks  Edward P. Glenn  Clenton E. Owensby  Jonathan O. Scurlock 《Water, air, and soil pollution》1993,70(1-4):95-109

Intergovernmental Panel on Climate Change (IPCC) estimates indicate that potential changes in seasonal rainfall and temperature patterns in central North America and the African Sahel will have a greater impact on biological response (such as plant production and biogeochemical cycling) and feedback to climate than changes in the overall amount of annual rainfall. Simulation of grassland and dryland ecosystem responses to climate and CO₂ changes demonstrates the sensitivity of plant productivity and soil C storage to projected changes in precipitation, temperature and atmospheric CO₂. Using three different land cover projections, changes in C levels in the grassland and dryland regions from 1800 to 1990 were estimated to be ?13.2, ?25.5 and ?14.7 Pg, i.e., a net source of C due to land cover removal resulting from cropland conversion. Projections into the future based on a double-CO₂ climate including climate-driven shifts in biome areas by the year 2040 resulted in a net sink of +5.6, +27.4 and +26.8 Pg, respectively, based upon sustainable grassland management. The increase in C storage resulted mainly from an increase in area for the warm grassland sub-biome, together with increased soil organic matter. Preliminary modeling estimates of soil C losses due to 50 yr of regressive land management in these grassland and dryland ecoregions result in a 11 Pg loss relative to current conditions, and a potential loss of 37 Pg during a 50 yr period relative to sustainable land-use practices, an average source of 0.7 Pg C yr^?1. Estimates of the cost of a 20 yr rehabilitation program are 5 to 8×10⁹ US$ yr^?1, for a C sequestering cost of approximately 10 US$ per tC.  相似文献   

Mercury Concentrations in Largemouth BASS (Micropterus Salmoides) from Five South Carolina Reservoirs     

John D. Peles  Travis C. Glenn  Heather A. Brant  Angela K. Wall  Charles H. Jagoe 《Water, air, and soil pollution》2006,173(1-4):151-162

Mercury concentrations in largemouth bass (Micropterus salmoides) bass were compared among five reservoirs in South Carolina. Three of these reservoirs (Lake Russell, Lake Thurmond, and Lake Marion) are accessible to the public and two (L-Lake and Par Pond) are located on the U.S. Department of Energy's Savannah River Site (SRS), which is closed to public access. Age-adjusted mercury concentrations were significantly higher in SRS bass compared to the offsite reservoirs. In addition, mercury concentrations were significantly higher in bass from Par Pond compared to L-Lake and in bass from Lakes Russell and Thurmond compared to Lake Marion. No mercury concentrations in excess of the U.S. Food and Drug Administration action level (1.0 mg?kg^?1) were found in any bass from the public-accessible reservoirs. However, the majority of fish from these reservoirs had mercury concentrations that fall into or exceed the U.S. Environmental Protection Agency consumption category of “no more than one per week". In addition, most fish from these reservoirs had mercury levels in excess of those believed to be detrimental to sensitive avian species.  相似文献   

Effect of soil leachates on the release and motility of zoospores of Phytophthora cinnamomi rands     

H.J. Nesbitt  A.R. Glenn  N. Malajczuk 《Soil biology & biochemistry》1981,13(1):79-81

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Orthodromic Reciprocating Tachycardia and Heart Failure in a Dog With a Concealed Posteroseptal Accessory Pathway     

Clarke E. Atkins  Ronald Kanter  Kathy Wright  Ziad Saba  Catherine Baty  Cliff Swanson  Stephen Bai  Bruce W. Keene 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1995,9(1):43-49

A 4-month-old male Labrador Retriever was presented for recurrent bouts of pulmonary edema associated with tachycardia. Initial physical examination and echocardiography were unremarkable, and the electrocardiogram revealed only an intraventricular conduction disturbance. Subsequent recordings showed paroxysmal supraventricular tachycardia (SVT) (340 beats/min), which consistently produced pulmonary edema. The supraventricular tachycardia was unresponsive to adenosine, esmolol, and propranolol; was variably and transiently responsive to various vagal maneuvers and precordial thumps; and was always responsive to IV diltiazem. Multiple life-threatening episodes of SVT occurred, however, despite the chronic administration of oral diltiazem, propranolol, and procainamide. Diastolic cardiac dysfunction was documented by Doppler echocardiography and was thought to contribute to the development of pulmonary edema. A subsequent electrophysiologic study confirmed the presence of an atrioventricular posteroseptal accessory pathway that participated in orthodromic reciprocating tachycardia. This pathway was determined to conduct only in the retrograde direction ("concealed accessory pathway"). Intraoperative IV procainamide titration terminated the arrhythmia, which could not be reinduced when procainamide blood concentration approximated 20 μg/dL. Increasing the oral procainamide dose to achieve such plasma concentrations was successful in eliminating orthodromic reciprocating tachycardia, preventing heart failure, and returning Doppler indices of diastolic function to normal.  相似文献   

Splenic Infarction in 16 Dogs: A Retrospective Study   总被引：2，自引：0，他引：2  

Elizabeth M. Hardie  Shelly L. Vaden  Kathy Spaulding  David E. Malarkey 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1995,9(3):141-148

Sixteen dogs with splenic infarction due to causes other than splenic torsion were identified. Dogs with splenic infarction often had multiple concurrent diseases, and surgical management of splenic infarction was associated with high mortality. Splenic infarction occurred in dogs with hypercoagulable conditions associated with liver disease, renal disease, and hyperadrenocorticism, or as a consequence of uniform splenomegaly, neoplasia, or thrombosis associated with cardiovascular disease. Clinical signs and common laboratory findings generally reflected the underlying disease process. A variety of splenic abnormalities were detected by abdominal ultrasound in 15 dogs, with the ventral extremity of the spleen being most often abnormal. Four dogs were euthanized or died because of the presence of severe systemic disease, whereas 12 dogs underwent laparotomy. Complete splenectomy was performed in 9 dogs and partial splenectomy was performed in 2 dogs. Seven dogs died in the immediate postoperative period, 3 required chronic veterinary care, and 2 had uncomplicated long-term recoveries. Splenic infarction should be regarded as a sign of altered blood flow and coagulation, rather than as a primary disease, and surgical management should be reserved for patients with life-threatening complications such as hemoabdomen or sepsis.  相似文献