Normal metallic point contacts     

Jansen AG  Mueller FM  Wyder P 《Science (New York, N.Y.)》1978,199(4333):1037-1040

The measured voltage derivative of the nonlinear resistance of tiny point contacts can be separated into a phonon-emission effect (alpha(2)F) and an analytic functional form (background effect). The alpha(2)F's show structure coincident with bulk phonon densities of states. Values of the integral of 2 alpha(2)F/omega are closely related to literature values. The background effect is related to the impurity concentration of the materials.  相似文献   

Comparison of the pig and feline models for full thickness corneal transplantation     

Brunette I  Rosolen SG  Carrier M  Abderrahman M  Nada O  Germain L  Proulx S 《Veterinary ophthalmology》2011,14(6):365-377

Purpose The goal of this study was to report on the advantages and limitations of the pig and feline models for experimental in vivo corneal transplantation. Methods Ten healthy domestic pigs and ten healthy cats were used. Full thickness penetrating keratoplasty was performed using autologous (eight cases), allogeneic (seven cases) or human xenogeneic (three cases) tissue. In two other cases, the inflammatory response to partial thickness trephination (without transplantation) was evaluated. Eyes were assessed daily before and after surgery by slit‐lamp, pachymetry, and tonometry. A transparency score ranging from 0 (opaque graft) to 4 (clear graft) was used, based on the slit‐lamp examination. Optical coherence tomography, histology, and electron microscopy were performed postmortem. Results In the pig, the mean (±SD) transparency score for the eight full thickness grafts was 0.88 ± 0.99, ranging from 0 to 3. In the feline model, the mean transparency score for the seven uncomplicated grafts was 3.93 ± 0.19, ranging from 3.5 to 4. Both negative controls without endothelium remained opaque at all time. Intraoperative tendency for iris incarceration into the wound, rapid corneal swelling, suture cheese wiring, and postoperative intraocular inflammation were the main factors jeopardizing the functional success of the corneal transplant in the pig model. Conclusion Suboptimal functional results were obtained after full thickness corneal transplantation in the pig model, while in the feline model, the same protocol yielded uneventful surgeries and clear transplants, with functional results similar to those achieved in human subjects.  相似文献   

Frog communities and wetland condition: relationships with grazing by domestic livestock along an Australian floodplain river     

Amy Jansen  Michael Healey 《Biological conservation》2003,109(2):207-219

Frogs are in decline worldwide, and are known to be sensitive indicators of environmental change. Floodplains of the Murray-Darling Basin in southeastern Australia have been altered in many ways by livestock grazing, by the introduction of exotic fish, and by changes to flooding regimes. These changes have led to declines in wetland condition and hence to the availability of habitat for wetland frogs. This study examined relationships between frogs, wetland condition and livestock grazing intensity at 26 wetlands on the floodplain of the Murrumbidgee River. Frog communities, species richness, and some individual species of frogs declined with increased grazing intensity. Wetland condition also declined with increased grazing intensity, particularly the aquatic vegetation and water quality components. There were clear relationships between frog communities and wetland condition, with several taxa responding to aquatic and fringing vegetation components of wetland condition. Thus, grazing intensity appeared to influence frog communities through changes in wetland habitat quality, particularly the vegetation. Reduced stocking rates may result in improved wetland condition and more diverse frog communities. River management to provide natural seasonal inundation of floodplain wetlands may also enhance wetland condition, frog activity and reproductive success.  相似文献   

Soil Microbial Community Structure of Coal Mine Discard Under Rehabilitation     

S. Claassens  P. J. Jansen Van Rensburg  L. Van Rensburg 《Water, air, and soil pollution》2006,174(1-4):355-366

Assessment of soil microbial diversity, in terms of the actively growing population, may be a sensitive indicator of ecological stress and restoration processes. During this study, the relationship between microbial community structure; vegetation cover; and physical and chemical characteristics of topsoil covers at seven coal discard rehabilitation sites in South Africa were evaluated. A positive association was observed between the microbial biomass, vegetation cover and the organic carbon, ammonium, nitrate and phosphorus contents. Although the seven coal discard sites had different rehabilitation ages (1–8 years), there was no statistically significant difference between these sites based on physical and chemical characteristics. The various rehabilitation sites could be differentiated based on the microbial community structure. The Hendrina site was characterised by the highest viable biomass, monounsaturated fatty acids, and high ground cover. Bethal and Ermelo sites were the youngest sites (1 and 3 years) in terms rehabilitation age. Both these sites were associated with higher abundances of fungi and Actinomycetes than the other sites. Ratios of trans- to cis-monoenoic fatty acids and cyclopropyl fatty acids to their monoenoic precursors indicated stress in all sites sampled.  相似文献   

Mobilization of dissolved organic matter, aluminium and iron in podzol eluvial horizons as affected by formation of metal-organic complexes and interactions with solid soil material   总被引：1，自引：0，他引：1  

B. Jansen  K. G. J. Nierop  & J. M. Verstraten 《European Journal of Soil Science》2004,55(2):287-297

Interactions with dissolved organic matter (DOM) are generally believed to play a crucial role in the translocation of Al and Fe in acid sandy soils. Binding of Al and Fe to DOM affects their mobility in soils by altering sorption equilibria of charged sites on solid soil material, inducing precipitation of organo‐metallic complexes and preventing the formation of inorganic Al and Fe phases. The relative importance of the different processes, especially with respect to the translocation of Al, Fe and organic matter in podzols, remains unresolved. We determined the effect of the presence of solid soil material from the eluvial (AhE and AE, respectively) horizons of a Fimic Anthrosol and a Haplic Podzol on the metal‐to‐organic carbon (M/C) ratio in solution and the formation of dissolved organic Al and Fe complexes. Furthermore, we assessed the resulting influence on the mobilization of Al, Fe and DOM. Even under considerable metal loading, the M/C ratios and ‘free’ metal fractions in solution remained low and relatively constant, due to an apparent buffering by the solid phase and the formation of organo‐metal complexes in solution. The M/C ratios remained so low that significant precipitation of organo‐metal complexes due to saturation with metals was not found. The apparent buffering by the solid phase can be explained by a strong release of organic matter from solid soil material and adsorption of non‐complexed Al and Fe on solid organic matter upon metal addition. Adsorption of organo‐metal complexes most likely played only a minor role. The observations confirm the expected mobilization of Al, Fe and DOM in eluvial horizons and seem to indicate that even under fluctuating input of Al, Fe and DOM the soil solution will have a constant composition with respect to M/C ratios and percentage of Al and Fe present in dissolved organo‐metal complexes.  相似文献   

Nonsurgical videolaparoscopy for determination of reproductive status of the Arctic charr.   总被引：2，自引：0，他引：2       下载免费PDF全文

A I Ortenburger  M E Jansen    S K Whyte 《The Canadian veterinary journal. La revue veterinaire canadienne》1996,37(2):96-100

The efficient commercial production of Arctic charr is hampered by the limited and subtle sexual dimorphism shown by this species. This project examined the feasibility of low-cost videoendoscopy through the genital pore to determine sex, stage of maturity, and safety for 80, randomly selected, anesthetized Arctic charr. The sensitivity and specificity for correct assignment of male sex were 90% and 100%, respectively, among 3 observers in a single-blind design. Sensitivity and specificity for relative sexual maturity in the same fish were 96% and 54%, respectively. The observed mortality rate of 7% at the end of 3 weeks was confounded by the presence of unrelated disease. We conclude that the technique holds promise for application by producers to improve production efficiency.  相似文献   

Prognostic Factors in Dogs with Lymphoma and Associated Hypercalcemia     

Mona P. Rosenberg DVM    Robert E. Matus DVM  MS  Amiya K. Patnaik BVSc  MVSc 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1991,5(5):268-271

Lymphoma and hypercalcemia were diagnosed in 37 dogs. Twenty-six of the dogs received chemotherapy. The association between some prognostic factors including clinical stage of disease, illness status, presence of bone marrow involvement, and presence of an anterior mediastinal mass and remission duration and survival time was evaluated. Statistical analysis of the prognostic factors showed that the presence of an anterior mediastinal mass had an adverse effect on remission duration (P less than 0.03). Calcium concentration was not significantly related to any of the prognostic factors evaluated. Dogs that received chemotherapy were more likely to be self-supporting than the dogs that were not treated (P less than 0.005). However, initial illness status was not significantly related to remission duration or survival time in the 26 dogs that were treated. Six dogs (25% of dogs treated) survived longer than 14 months. Five of these dogs were female. Overall mean and median remission times were 10.4 and 6 months, respectively.  相似文献   

The peri-parturient rise in sheep. Faecal worm egg counts in normal and late lambing ewes     

J Jansen 《The Veterinary quarterly》1987,9(2):97-102

The trichostrongylid and strongylid egg output in a group of ewes lambing in March, the middle of the usual lambing time in the Netherlands, was compared with counts in groups of older ewes and yearling ewes lambing in May-June and with counts in a group of barren ewes. The groups lambing in March showed only a rise related to parturition date as normally seen in the Netherlands. A few of the late lambing ewes showed a slight rise in spring, but all of them showed a peri-parturient rise related to parturition date. In the late lambing ewes and in the barren ewes egg counts due to reinfection were seen in summer. It is concluded that under the present circumstances a true spring rise, the calendar phenomenon, occurs very irregularly, while a peri-parturient rise related to the parturition date is a common phenomenon. The occurence of high egg counts in summer, excluding consideration on the barren ewes, in the late lambing ewes only, suggests that changing the traditional husbandry system may influence the epidemiological pattern of the trichostrongylid infections.  相似文献   

A Hypoderma diana (Diptera: Hypodermatidae) infection in a horse     

W M Hendrikx  J Jansen  T J de Vries 《The Veterinary quarterly》1989,11(1):56-57

An infection with second-stage larvae of the warble-fly H. diana in a horse is described. The second-stage larvae were incapable of developing into the third stage, because horses are unsuitable hosts and because the infected horse was treated with an insecticide. Since the horse was used for dragging trees in the forests, the infection was likely contracted via contact with H. diana, a normal parasite of roe deer in the Netherlands.  相似文献   

Risk assessment of dietary exposure to pesticides using a Bayesian method   总被引：2，自引：0，他引：2  

Paulo MJ  van der Voet H  Jansen MJ  ter Braak CJ  van Klaveren JD 《Pest management science》2005,61(8):759-766

Risk assessment of pesticides can be a statistically difficult problem because pesticides occur only occasionally, but they may occur on multiple components in the diet. A Bayesian statistical model is presented which incorporates multivariate modelling of food consumption and modelling of pesticide measurements which are for a large part below a measurement threshold. It is shown that Bayesian modelling is feasible for a limited number of food components, and that in a data-rich situation the model compares well with an empirical Monte Carlo modelling.  相似文献