Influence of pH and Zinc Concentration on Cadmium Sorption in Acid, Sandy Soils     

B. J. Wilkins  N. Brummel  J. P. G. Loch 《Water, air, and soil pollution》1998,101(1-4):349-362

Batch adsorption experiments were carried out with samples from an A-, Bh- and C-horizon of contaminated sandy soil of podzolic character from the Kempen region at the Dutch-Belgian border. Cadmium sorption was studied on 3 soil samples at 3 different pH-levels (3.6, 4.3 and soil buffered pH) and 3 different additions of zinc (0–40 mg l^-1). Adsorption of cadmium by acid sandy soils can be fitted by a Freundlich adsorption isotherm. Although zinc competes with cadmium for the sorption sites, we observe a two to three times stronger competition effect of the proton cation, which is explained by the chemical properties of both ions. The cadmium adsorption coefficient K_F decreases considerably by an increase of the proton activity used in the sorption experiments. Organic matter content explains for a large part the variation of KF of te three soil samples. Desorption data do not fit the proposed regression model for adssorption. Not all the cadmium, intitially present in the polluted soil, will fylly desorb reversibly. Thus, part of the cadmium may be irreversible bound.  相似文献   

Abrupt climate events 500,000 to 340,000 years ago: evidence from subpolar north atlantic sediments     

DW Oppo  JF McManus  JL Cullen 《Science (New York, N.Y.)》1998,279(5355):1335-1338

Subpolar North Atlantic proxy records document millennial-scale climate variations 500,000 to 340,000 years ago. The cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle. These findings suggest that such climate variations are inherent to the late Pleistocene, regardless of glacial state. Sea surface temperature during the warm peak of Marine Isotope Stage 11 (MIS 11) varied by 0.5 degrees to 1 degrees C, less than the 4 degrees to 4.5 degrees C estimated during times of ice growth and the 3 degrees C estimated for glacial maxima. Coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature.  相似文献   

Local food policy coalitions: Evaluation issues as seen by academics, project organizers, and funders     

Karen L. Webb  David Pelletier  Audrey N. Maretzki  Jennifer Wilkins 《Agriculture and Human Values》1998,15(1):65-75

Several different evaluation issuesare perceived as important by people involved withinnovative projects intended to improve local food andnutrition systems; particularly the establishment oflocal food policy coalitions. Several such coalitionshave been formed in North America, Europe, andAustralia with the goal of improving community foodsecurity and promoting sustainable local food systems.Pioneer coalitions have served as models, yet therehas been little systematic evaluation of thesemodels. A qualitative study was conducted to identifyfactors that may hinder evaluation efforts. In grouptelephone interviews, we sought the views ofacademics, project organizers, and funders, a total of24 key informants. Pressures to evaluate were assessed differently bythe three groups of key informants. Academics felt thefocus of evaluation should be on the effectiveness ofthe process used to discuss issues and formulatepolicies and plans. Project organizers and fundersperceived a need to assess project impact andoutcomes. A lack of suitable evaluation models andmethods was viewed as a formidable barrier. The use ofinappropriate methods and premature impact evaluationwere noted as potential threats to projectsustainability. External constraints and resourcelimitations were also said to inhibit evaluationefforts. It appears that several other factors may also beimpeding progress in conducting more (and more useful)evaluations including: (1) the apparent negativeconnotation of evaluation and the limited benefitsexpected from evaluation by stakeholders, (2) a lackof consensus about important evaluation questions,(3) insufficient evaluation expertise among projectorganizers, and (4) inadequate appreciation ofincreasing accountability pressures.  相似文献   

Lectin Histochemistry as a Tool to Identify Apoptotic Cells in the Seminiferous Epithelium of Syrian Hamster (Mesocricetus auratus) Subjected to Short Photoperiod     

V Seco‐Rovira  E Beltrán‐Frutos  C Ferrer  MM Sánchez‐Huertas  JF Madrid  FJ Saez  LM Pastor 《Reproduction in domestic animals》2013,48(6):974-983

Lectins have been widely used to study the pattern of cellular glycoconjugates in numerous species. In the process of cellular apoptosis, it has been observed that changes occur in the membrane sugar sequences of these apoptotic cells. The aim of our work was to identify which lectins, out of an extensive battery of the same (PNA, SBA, HPA, LTA, Con‐A, UEA‐I, WGA, DBA, MAA, GNA, AAA, SNA), show affinity for germinal cells in apoptosis, at what stage of cell death they do so and in which germinal cell types they can be detected. For this, we studied testis sections during testicular regression in Syrian hamster (Mesocricetus auratus) subjected to short photoperiod. Several lectins showed an affinity for the glycoconjugate residues of germ cells in apoptosis: Gal β1,3‐GalNAcα1, α‐d ‐mannose, N‐acetylgalactosamine and l ‐fucose. Furthermore, lectin specificity was observed for some specific germinal cells and in certain stages of apoptosis. It was also observed that one of these lectins (PNA) showed affinity for Sertoli cells undergoing apoptosis. Therefore, we conclude that the use of lectin histochemistry could be a very useful tool for studying apoptosis in the seminiferous epithelium because of the specificity shown towards germinal cells in pathological or experimentally induced epithelial depletion models.  相似文献   

Use of computerized interactive morphometry in the diagnosis of mammary adenoma and adenocarcinoma in dogs.     

D Ciurea  R J Wilkins  M Shalev  Z Liu  J Barba  J Gil 《American journal of veterinary research》1992,53(3):300-303

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Thoracic haemangiosarcoma in a 3-year-old horse     

JF FREESTONE  MM WILLIAMS  G NORWOOD 《Australian veterinary journal》1990,67(7):269-270

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Characterization of the toxicity of the mycotoxins aflatoxin, ochratoxin, and T-2 toxin in game birds. III. Bobwhite and Japanese quail.     

M D Ruff  W E Huff  G C Wilkins 《Avian diseases》1992,36(1):34-39

Bobwhite and Japanese quail were fed diets containing 1.25, 2.50, or 5.00 ppm aflatoxin; 1, 2, or 4 ppm ochratoxin A (OA); or 4, 8, or 16 ppm T-2 toxin. Aflatoxin induced mortality in bobwhites during the second and third week with 1.25 ppm (10%), 2.50 ppm (30%), and 5.00 ppm (40%), and during the same period with T-2 toxin at 8 ppm (20%) and 16 ppm (22.5%). Body weights of bobwhite quail were significantly decreased by the two higher levels of aflatoxin by 2 weeks of age, and by the two higher levels of T-2 toxin by 1 week of age. In Japanese quail, only the highest level of aflatoxin and T-2 toxin reduced body weight (by 3 weeks and by 1 week of age, respectively), and even then to a much lesser extent than in bobwhites (less than 10%). Aflatoxin did not affect feed-conversion ratio (FCR) in bobwhite quail, but the two higher levels of T-2 toxin increased FCR. None of the toxins induced mortality or increased the FCR in Japanese quail. Aflatoxin increased liver weight in both bobwhite and Japanese quail. OA increased kidney weight in 3-week-old Japanese quail but had no effect on the kidney weight of bobwhite quail. Mouth lesions were progressively more severe in bobwhite quail fed increasing levels of T-2 toxin, but lesions were far less severe in Japanese quail.  相似文献   

Patterns of ionizing radiation exposure among women veterinarians   总被引：1，自引：0，他引：1  

S A Moritz  W D Hueston  J R Wilkins 《Journal of the American Veterinary Medical Association》1989,195(6):737-739

Radiation detection devices (film badges) were distributed to a random sample of 118 women in Ohio, Indiana, and Michigan, who had graduated from a US veterinary school between 1970 and 1980, inclusive. Ionizing radiation exposure exceeded 15 mrem/mo in 17% of the women monitored. The maximal recorded whole-body dose was 44.2 mrem/quarter-year, which was well below the maximal permissible doses of 1,250 mrem/quarter-year for nonpregnant women and 500 mrem/quarter-year for pregnant women. Associations between the women's safety beliefs or behaviors and recorded exposure were not observed; however, the school from which the women graduated was an important determinant of safety behavior.  相似文献   

The isolation of nucleic acid sequences specific for Cowdria ruminantium     

S C Wilkins  R E Ambrosio 《The Onderstepoort journal of veterinary research》1989,56(2):127-129

Screening of a genomic library of Cowdria ruminantium has yielded twelve clones hybridizing to Cowdria DNA. These clones should be suitable for development into DNA probes specific for this organism.  相似文献   

Breakdown of self-incompatibility in perennial ryegrass at high temperature and its uses in breeding     

P. W. Wilkins  D. Thorogood 《Euphytica》1992,64(1-2):65-69

Summary The maximum temperature (34°C) at which perennial ryegrass plants from one breeding population successfully shed pollen was determined and the seed set of ten clones taken from the same population and self-pollinated both in an unheated glasshouse and at a constant 34°C during anthesis was compared. Seed set by selfing of all ten clones was markedly increased by heat treatment, from a mean of 2.3% to 30.7%. Heat treatment of anthers, but not stigmas, greatly enhanced pollen tube growth on stigmas from the same genotype. Germination of progeny was not affected by the heat treatment. Heat treatment of ten clones from a breeding population with contrasting morphology and growth rate was not so successful. Only one clone shed pollen freely at 34°C and showed a marked improvement in subsequent seed set. The advantages to the breeder of routinely producing full-sib families of elite perennial ryegrass parents by selfing are outlined.  相似文献