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121.
Parker JE Timm KI Smith BB Van Saun RJ Winters KM Sukon P Snow CM 《American journal of veterinary research》2002,63(7):948-953
OBJECTIVE: To evaluate temporal changes in bone mineral density associated with seasonal variation in serum vitamin D, calcium, and phosphorus concentrations in alpacas. ANIMALS: 5 healthy mature neutered male alpacas. PROCEDURE: Metacarpal bone mineral density was measured at 4 times during a year. Each time alpacas were weighed, blood was collected for determination of serum calcium, phosphorus, and vitamin D concentrations, and samples of feed were analyzed for nutrient content. Vitamin D status was determined by use of an assay that measured serum 25-hydroxycalciferol concentration. Effects of changes in serum vitamin D, calcium, and phosphorus concentration and body weight with season on bone mineral density were determined. RESULTS: Bone mineral density, body weight, and serum vitamin D and phosphorus concentrations varied with season. Bone mineral density, serum vitamin D concentration, and body weight also varied among individual alpacas. Serum vitamin D concentration was lower in January than the previous October and increased from May to the following September. The decrease in bone mineral density lagged behind the decrease in serum vitamin D concentration and was lower in May, compared with the previous October. Body weight was lower in May than the previous October or following September. Solar radiation was highest in July and lowest in December. CONCLUSIONS AND CLINICAL RELEVANCE: Seasonal changes in bone mineral density are associated with changes in serum vitamin D concentrations in alpacas. Changes in bone mineral density associated with a decline in serum vitamin D concentration may predispose some alpacas to developing fractures minimal trauma. 相似文献
122.
Jadwiga W. Płodowska Peter H. J. Jongebloed Pieter A. C. M. Van De Sanden Paul C. Struik 《Potato Research》1989,32(3):255-266
Summary Single-stemmed potato plants, cv. Bintje, were grown on a nutrient solution under controlled conditions. They were exposed
to a short drought stress, or remained untreated. Short-term changes in tuber volume and in specific leaf weight were measured
non-destructively.
Tubers from control plants increased rapidly in volume during the night and did not grow, or even shrivelled during the day.
Tubers of stressed plants did not show a uniform response; some tubers markedly declined in volume during the day. The patterns
of volume increase of stressed plants became erratic after the stress, mainly because some plants never fully recovered.
Patterns of diurnal fluctuation in tuber volume were similar to diurnal changes in specific leaf weight; tubers within the
same stressed plant sometimes reacted differently. In these cases the effects on the diurnal fluctuation partly reflected
the long-term effects, reported in an earlier paper. 相似文献
123.
W Zhou JM Thomas DS Shephard BFG Johnson D Ozkaya T Maschmeyer RG Bell Q Ge 《Science (New York, N.Y.)》1998,280(5364):705-708
The anionic ruthenium cluster carbonylates [Ru6C(CO)16]2- or [H2Ru10(CO)25]2- interspersed with bis(triphenylphosphino)iminium counterions (PPN+) are incorporated from solution into the pores of MCM-41 mesoporous silica (3 nanometers in diameter), where they form tightly packed arrays. These arrays were shown by high-resolution transmission electron microscopy, Fourier transform optical diffraction, and computer simulations to be well ordered both along and perpendicular to the axis of the cylindrical pores. In their denuded state produced by gentle thermolysis, the cluster carbonylates yield nanoparticles of ruthenium that are less well ordered than their assimilated precursors but show good activity as hydrogenation catalysts for hexene and cyclooctene. In both their as-prepared and denuded states, these encapsulated clusters are likely to exhibit interesting electronic and other properties. 相似文献
124.
Summary Based on visual inspection, discrimination between common scab (Streptomyces spp.) and powdery scab (Spongospora subterranea) can be difficult. Inspections are performed on unwashed samples, incidentally supported by microscopic examination.
During 1994–1996 surveys were performed in The Netherlands on tubers with symptoms resembling common scab. Under microscopic
assessment nearly all samples showed the presence of structures resembling cystosori (sporeballs) ofS. subterranea. At that time confirmation using alternative techniques was not possible.
In 2003 research was undertaken to clarify the situation with respect to scab on potato tubers in The Netherlands. One hundred
and eighteen scab samples were extensively tested forS. subterranea. All samples were digitally photographed, microscopically examinated and tested with real-time PCR and DAS-ELISA. Use of
these modern methods resulted in a clear picture of symptoms that can be attributed toS. subterranea. A lot of scab samples with structures resembling cystosori could not be confirmed as contaminated withS. subterranea. 相似文献
125.
Udayakantha W.A. Vitharana Marc Van Meirvenne David Simpson Liesbet Cockx Josse De Baerdemaeker 《Geoderma》2008,143(1-2):206-215
Recent advances in on-the-go soil sensing, terrain modelling and yield mapping have made available large quantities of information about the within-field variability of soil and crop properties. But the selection of the key variables for an identification of management zones, required for precision agriculture, is not straightforward. To investigate a procedure for this selection, an 8 ha agricultural field in the Loess belt of Belgium was considered for this study. The available information consisted of: (i) top- and subsoil samples taken at 110 locations, on which soil properties: textural fractions, organic carbon (OC), CaCO3 and pH were analysed, (ii) soil apparent electrical conductivity (ECa) obtained through an electromagnetic induction based sensor, and (iii) wetness index, stream power index and steepest slope angle derived from a detailed digital elevation model (DEM). A principal component analysis, involving 12 soil and topographic properties and two ECa variables, identified three components explaining 67.4% of the total variability. These three components were best represented by pH, ECa that strongly associated with texture and OC. However, OC was closely related to some more readily obtainable topographic properties, and therefore elevation was preferred. A fuzzy k-means classification of these three variables produced four potential management classes. Three-year average standardized yield maps of grain and straw showed productivity differences across these classes, but mainly linked to their landscape position. In the loess area with complex soil-landscape interactions pH, ECa and elevation can be considered as key properties to delineate potential management classes. 相似文献
126.
P. Dhert L.C. Lim P. Candreva H. Van Duffel P. Sorgeloos 《Aquarium Sciences and Conservation》1997,1(2):119-128
There has been rapid development in the marine foodfishlarviculture technology in Europe since the early eighties,especially in the flat fish, turbot and halibut, and the bass andbream species. The most significant improvements in the eightieswere the introduction of light control, artificial reproductiontechniques, appropriate water treatment and the use of rotifersand Artemia nauplii of specific sizes and in the late eightiesand early nineties the quality enhancement of live food organismsusing specific enrichment techniques. Present research is focusedon the implementation of several microbial techniques to improvethe hygiene of live prey and fish.Many of the modern larviculture techniques being used in marine foodfish could be adapted for application in the ornamental fish industry. For examples, research in the Onamental Fish Section, Primary Production Department, Singapore has demonstrated that the use of freshwater rotifers and Artemia nauplii would enable artificial rearing of Discus in the absence of the parent fish and improve the larval performance of Gouramis and Tetra larvae. The use of such small live food organisms is likely to facilitate breeding of new fish species with small larvae. Research has also indicated that the use of diets containing vitamin C and certain immuno-stimulants improved the stress resistance of guppy. Such techniques would have important application in the fish transport, an important aspect in the ornamental fish industry 相似文献
127.
Juvenile, 0.87 g Colossoma macropomum (Cuvier) were submitted to different ad libitum feeding regimes. Feeding frequency ranged from one to five meals per day and intervals between meals from 3 h to 24 h. Higher feeding frequencies resulted in higher feed uptake, a higher growth rate and a decreased feed utilization efficiency. Feed consumption was lower at 0700 h than at 1900 h. The amount of feed from different meals persisting in the digestive tract was determined with chromic-oxide-marked feed. This method revealed that with ad libitum feeding, about 21% of the feed remained uneaten. Feed losses did not differ significantly between feeding regimes. Feed accumulated in the digestive tract in the morning and early afternoon. In the late afternoon most feed rests disappeared from the digestive tract and feed consumption increased. It is suggested that feed uptake and growth of C. macropomum can be improved by extending the feeding period after 1900 h. 相似文献
128.
Gummy stem blight resistance of cucumbers (Cucumis sativus L.) 总被引:1,自引:0,他引:1
Summary A start was made with breeding for resistance to gummy stem blight in cucumber. A method has been development for screening plants in a young stage. Using this method a distinct level of resistance was found in plants of Leningradsky, Wjarnikovsky,a P.I. entry from Birma, Rheinische Vorgebirge and a P.I.entry from Turkey. Lines developed from this material show a higher level of resistance than Dutch slicing and pickling cucumber varieties. 相似文献
129.
We evaluated factors influencing the development of autumn red coloration in leaves of sugar maple (Acer saccharum Marsh.) by measuring mineral nutrient and carbohydrate concentrations, water content, and phenology of color development of leaves from 16 mature open-grown trees on 12 dates from June through October 1999. Mean foliar nutrient and carbohydrate concentrations and water content were generally within the range published for healthy sugar maple trees. However, foliar nitrogen (N) concentrations were near deficiency values for some trees. The timing and extent of red leaf coloration was consistently correlated with both foliar N concentrations and starch or sugar concentrations, which also varied with N status. Leaves of trees with low foliar N concentrations turned red earlier and more completely than those of trees with high foliar N concentrations. Low-N trees also had higher foliar starch concentrations than high-N trees. During the autumn development of red leaf coloration, foliar starch, glucose and fructose concentrations were positively correlated with red leaf color expression. At peak red expression, the concentrations of glucose, fructose, sucrose and stachyose were all positively correlated with red color expressed as a percent of total leaf area. 相似文献
130.
Bert Lambooij Karen Kloosterboer Marien A Gerritzen Geert André Martine Veldman & Hans Van De Vis 《Aquaculture Research》2006,37(1):61-70
The objective of this study was to assess neural and behavioural responses in farmed African catfish (Clarias gariepinus) upon electrical stunning in combination with decapitation or chilling. To assess the possibility of scaling up one or both experimental methods, two trials were performed in an experimental setting. The product quality of the collected samples was compared with the currently applied industrial method: live chilling. After electrical stunning in combination with decapitation, the fish showed spikes alternated with theta and delta waves on the EEG, followed by minimal brain activity after 20±10 s. The same traces on the EEGs were observed after electrical stunning in combination with chilling. Here, minimal brain activity occurred after 22±11 s. Within a confidence level of 95%, the percentage of African catfish that was effectively stunned after administration of an electrical current of 1.5 A dm−2, 300 V (50 Hz a.c.), followed by decapitation or chilling was above 91%. The analysis yield and evolution of liquid loss showed significant (P<0.05) differences among the batches, which could be explained by the stunning method used. The course values of the pH in the different batches were significantly (P<0.05) dependent on the stunning method, sex and location (visceral or skin side). It is concluded that African catfish can be stunned effectively using electrical stunning in a water tank, followed by decapitation or chilling in ice. Dutch commercial processors prefer to combine electrical stunning with chilling in flake ice in a rotating tumbler, as the outer slime layer is then removed, which facilitates further processing. 相似文献