Plasma glucose levels in South Australian Merino ewes     

D O KLEEMANN  D H SMITH  S K WALKER  J R W WALKLEY 《Australian veterinary journal》1988,65(3):99-100

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Further studies of the enhanced biodegradation of some soil-applied herbicides   总被引：1，自引：0，他引：1  

A. WALKER  S. J. WELCH 《Weed Research》1992,32(1):19-27

In field experiments to investigate the effect of repeated application of eight herbicides on their persistence in the soil, the rates of loss of metribuzin, metolachlor and isoproturon were shown to be unaffected by up to three previous doses of the same herbicide. With linuron, there was a small but significant enhancement of biodegradation by two or more previous applications. The persistence of monolinuron, propyzamide and metamitron was shorter in plots that had been treated once, twice or three times previously than in plots treated for the first time, but the effects were often small. In the case of napropamide, rates of loss were considerably increased by a single previous dose. In laboratory experiments with soil from the field plots, there was again no evidence of enhanced biodegradation of metribuzin, metolachlor or isoproturon. However, the rate of linuron degradation was enhanced by a single application. This effect was most marked after 12 weeks, but had disappeared by 57 weeks after initial treatment of the soil in the field. Considerable enhancement of monolinuron, propyzamide and metamitron degradation rates was also observed. The effects were again most pronounced after 12 weeks; however, with these compounds, they were still apparent more than 1 year later. Enhancement of napropamide biodegradation was most stable when assessed in laboratory incubations; the effects from a single pretreatment were still apparent more than 12 months later. Etudes complementaires de la degradation accélerée de certains herbicides appliques au sol Dans des essais de plein champ conduits pour etudier 1'influence d'applications répetées de 8 herbicides sur leur persistance dans le sol, les taux de perte de métribuzine, métolachlor et isoproturon n'ont pas été affectés jusqu'à 3 applications précédentes du même herbicide. Avec le linuron, il y a eu une faible mais significative augmentation de la dégradation aprés 2 ou 3 applications. La persistance du monolinuron, de la propyzamide et de la métamitrone éiait plus courte dans les parcelles déjà traitées une, deux ou trois fois que dans celles traitées pour la premiére fois, mais les effets étaient souvent faibles. Avec la napropromide, les taux ont été considérablement accrus aprés une seule application. Dans des essais de laboratoire avec du sol venant des parcelles de plein champ, il n'y a pas eu de nouveau d'accélération de la biodégradation pour la métribuzine, le métolachlor ou 1'isoproturon. Cependant, la dégradation du linuron a été renforcée par une seule application. Cet effet a été plus fort qu'aprés 12 semaines, mais a disparu 57 semaines aprés le traitement du sol au champ. Un accroissement important de la dégradation du monolinuron, de la propyzamide et de la métamitrone a étéégalement observé Les effets étaient de nouveau maxima aprés 12 semaines; cependant avec ces produits, ils étaient encore apparent une année plus tard. L'accé1ération de la biodégradation de la napropromide était la plus stable dans les observations de laboratoire; les effets d'une seule application étaient encore apparents plus de 12 mois plus tard. Weitere Untersuchungen zum beschleunigten Abbau von Bodenherbiziden In Feldversuchen zur Persistenz von 8 Herbiziden bei wiederholter Ausbringung ging bei Metribuzin, Metolachlor und Isoproturon nach 3-maliger Ausbringung desselben Herbizids die Verlustrate nicht zurück. Bei Linuron war der mikrobielle Abbau nach 2 oder mehr Vorbehandlungen nur leicht, aber signifikant erhöht. Die Persistenz von Monolinuron, Propyzamid und Metamitron war bei l-, 2- oder 3-maliger Vorbehandlung geringer als bei erstmaliger Behandlung, doch waren die Wirkungen oft klein. Bei Napropamid erhöhte sich die Verlustrate bereits nach einer Vorbehandlung beträchtlich. Auch in Laborversuchen mit Böden aus den Freilandparzellen konnte bei Metribuzin, Metolachlor und Isoproturon kein verstärkter mikrobieller Abbau nachgewiesen werden. Bei Linuron dagegen erhöhte sich die Abbaurate schon nach einmaliger Applikation. Diese Wirkung war nach 12 Wochen am deutlichsten ausgeprägt, verschwand jedoch nach 57 Wochen nach dem Behandlungstermin. Eine erheblich größere Abbaurate wurde auch bei Monolinuron, Propyzamid und Metamitron beobachtet, am deutlichsten nach 12 Wochen, aber auch noch nach mehr als l Jahr. Bei Napropamid war die Verstärkung der Biodegradation im Labor am bestRaUndigsten; die Wirkungen einmaliger Vorbehandlungen bestanden noch nach mehr als 1 Jahr.  相似文献   

Enhanced degradation of some soil-applied herbicides   总被引：5，自引：0，他引：5  

A. WALKER  SARAH J. WELCH 《Weed Research》1991,31(1):49-57

In a field experiment involving repeated herbicide application, persistence of simazine was not affected by up to three previous doses of the herbicide. With propyzamide, there was a trend to more rapid rates of degradation with increasing number of previous treatments. Persistence of linuron and alachlor was affected only slightly by prior applications. In a laboratory incubation with soil from the field that had received four doses of the appropriate herbicide over a 12–month period, there was again no effect from simazine pretreatments on rates of loss. However, propyzamide, linuron and alachlor all degraded more rapidly in the previously treated than in similar untreated soil samples. Propyzamide, linuron, alachlor and napropamide degradation rates were all enhanced by a single pretreatment of soil in laboratory incubations, whereas degradation rates of isoproturon, metazachlor, atrazine and simazine were the same in pretreated and control soil samples.  相似文献   

The Volatility of ¹⁴C-Labelled Atrazine and Linuron from Aluminium Planchets     

A. WALKER 《Weed Research》1972,12(3):275-278

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EQUINE HERPESVIRUS TYPE 3 (EQUINE COITAL EXANTHEMA) IN NEW SOUTH WALES     

C. P. FEILEN  S. T. WALKER  M. J. STUDDERT 《Australian veterinary journal》1979,55(9):443-444

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Change in the Concentration of Employment in Computer Services: Spatial Estimation at the U.S. Metro County Level     

DONALD GRIMES  PENELOPE B. PRIME  MARY BETH WALKER 《Growth and change》2007,38(1):39-55

ABSTRACT This article models the concentration of computer services activity across the U.S. with factors that incorporate spatial relationships. Specifically, we enhance the standard home‐area study with an analysis that allows conditions in neighboring counties to affect the concentration of employment in the home county. We use county‐level data for metropolitan areas between 1990 and 1997. To measure change in employment concentration, we use the change in location quotients for SIC 737, which captures employment concentration changes caused by both the number of firms and the scale of their activity relative to the national average. After controlling for local demand for computer services, our results support the importance of the presence of a qualified labor supply, interindustry linkages, proximity to a major airport, and spatial processes in explaining changes in computer services employment concentration, finding little support for the influence of cost factors. Our enhanced model reveals interjurisdictional relationships among these metro counties that could not be captured with standard estimates by state, metropolitan statistical area (MSA), or county. Using counties within MSAs, therefore, provides more general results than case studies but still allows measurement of local interactions.  相似文献   

Simulation of the persistence of atrazine in soil at different sites in Portugal     

F. ROCHA  A. WALKER 《Weed Research》1995,35(3):179-186

The effects of soil temperature and soil moisture content on the rates of degradation of atrazine, were measured in the laboratory in soils from different sites in Portugal. Persistence of atrazine was measured in the same soils in the field during the spring and summer of 1984, 1985, 1986 and 1987. Weather records from the different sites, measured during the periods of the field experi ments, were used in conjunction with appropriate constants derived from the laboratory data in a computer program to simulate persistence in the field. The model generally overestimated the ob served soil residues, particularly during the first 7–14 days after application. The fit from the model was good from day 14 to the end of the experiments.  相似文献   

Correlation of Clinical, Radiographic, and Surgical Localization of Intervertebral Disc Extrusion in Small-Breed Dogs: A Prospective Study of 50 Cases     

KURT S. SCHULZ DVM  MS  Diplomate ACVS    MICHAEL WALKER DVM  Diplomate ACVR    MARTHA MOON DVM  Diplomate ACVR    DON WALDRON DVM  Diplomate ACVS    MARGARET SLATER DVM  PhD  DARRYL E. McDONALD DVM  MS  Diplomate ACVS 《Veterinary surgery : VS》1998,27(2):105-111

Objective —To compare prospectively clinical, radiographic, and surgical findings of intervertebral disc extrusion (IDE) localization in small-breed dogs and to determine the best means of lesion localization for the purpose of hemilaminectomy. Study Design —Clinical, radiographic, and surgical findings of small-breed dogs with thoracolumbar IDE were prospectively compared for agreement on lesion localization. Sample Population—50 small-breed dogs with IDE treated at the three participating veterinary hospitals were included in the study if no other confounding diseases were identified and if the owner gave permission for diagnostic tests and surgery. Methods —Clinical and surgical findings were recorded by the surgeon assigned to the case. Radiographic studies were evaluated independently by two radiologists blinded as to the clinical and surgical findings. values and 95% confidence intervals were calculated for agreement on lesion localization by clinical, radiographic, and surgical means and for agreement between radiologists. Results —K values for agreement of lesion localization were as follows: clinical versus surgical, 0.595; radiologist A versus radiologist B, 0.81; radiologist A versus surgical findings, 0.60; radiologist B versus surgical findings, 0.71. Both radiologists' interpretation of IDE localization agreed with surgical localization in 60% of cases. Conclusions —Clinical lateralization of IDE was found to be the least reliable factor of those studied for determining on which side the hemilaminectomy should be performed. Results of this study differ from those of previous studies examining the reliability of myelography to localize the site of IDE accurately. The results of this study further suggest that surgery may not be an absolute standard for determination of the localization of IDE in small-breed dogs. Clinical Relevance —Intervertebral disc extrusion in small-breed dogs frequently results in bilateral distribution of extruded material. Computed tomography or magnetic resonance imaging may be necessary to delineate completely the distribution of extruded disc material in IDE.  相似文献   

Measurement and simulation of the movement of thiazafluron, clopyralid and metamitron in soil columns     

L. COX  A. WALKER  M.C. HERMOSIN  J. CORNEJO 《Weed Research》1996,36(5):419-429

Adsorption and leaching of the herbicides thiazafluron (1,3-dimethyl-1(5-trifluoromethyl-1,3,4-thiadiazol-2-yl)urea), metamitron (4-amino-4,5-dihydro-3-methyl-6-phenyl-1,2,4-tri azin-5-one) and clopyralid (3,6-dichloropicolinic acid) were studied in one sandy and two silty-clay soils. Equilibrium adsorption coefficients (K_d) were measured using a batch equilibration procedure, and mobility was studied in repacked columns of the soils under fluctuating saturated/unsaturated flow conditions. Breakthrough curves (BTCs) were consistent with an inverse relationship between leaching and adsorption with greater mobility of the weakly-adsorbed clopyralid than the more strongly adsorbed thiazafluron or metamitron. The BTC data were used to evaluate the LEACHP simulation model. Following model calibration with respect to hydrological parameters and some of the herbicide degradation rates, the best fits between predicted and observed data were with the less adsorptive and highly mobile clopyralid. In general, the model gave acceptable predictions of the timing of the concentration maxima and the shapes of the BTCs, although earlier breakthrough than that observed was predicted with the less mobile herbicides, thiazafluron and metamitron, in the silty-clay soils. For metamitron, the total amounts leached were not predicted accurately, suggesting more rapid degradation of the herbicide in the soil columns than in the kinetic studies performed in a 1:1 soil:solution ratio shaken system.  相似文献   

The efficiency of herbicide incorporation into soil with different implements     

A. WALKER  D. M. FARRANT  †  J. H. BRYANT†  PAULINE A. BROWN 《Weed Research》1976,16(6):391-397

The distribution of trifluralin in soil was measured following its incorporation with the rotavator, rotary power harrow, reciprocating harrow, spring-tined harrow, tandem disc cultivator and drag harrow. A single pass with the rotavator gave an even distribution In the top 5 cm of soil and similar results were obtained by cross cultivations with the rotary power harrow, reciprocating harrow, spring-tined harrow and disc cultivator. A single cultivation with the spring-tined harrow, reciprocating harrow and rotary power harrow left much of the herbicide close to the soil surface as did both a single and cross cultivation with the drag harrow. With the tandem discs, although a single pass did incorporate the herbicide, a cross cultivation was necessary to ensure that incorporation was even enough across the treated area. A single pass of the rotavator gave a uniform mixing throughout its working depth, whereas cross cultivations with each of the other implements gave a relatively uniform mixing to about half of their working depth.  相似文献