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Graham F. White 《Pest management science》1993,37(2):159-166
Agricultural, industrial and domestic use of surfactants leads to the entry of these compounds into terrestrial and aquatic ecosystems. Synthetic surfactants vary significantly in structure, but most consist of alkyl or alkylphenol groups attached to nonionic or anionic hydrophilic moieties. Continued use of these compounds is usually justified on the basis that they do not cause pollution problems because they undergo biodegradation by micro-organisms present in soils and surface waters. In accomplishing biodegradation, micro-organisms, predominantly bacteria, are exploiting these potentially useful resources of reduced carbon to derive energy and support growth in situations which are otherwise frequently oligotrophic. This paper reviews aspects of surfactant biodegradation, especially in relation to alcohol and alkylphenol ethoxylates used extensively as adjuvants for agrochemicals. In principle, bacteria can employ two strategies to gain access to the aliphatic chains in alcohol ethoxylate surfactants: separation of the hydrophobic chain from the hydrophile (central fission), or direct attack on the -terminal of the alkyl chain of the intact surfactant. Direct exo-cleavage of ethylene glycol units from the polyethylene glycol (PEG) chain also provides a third route to assimilable carbon. In pure cultures of known degraders or in mined environmental samples, all three strategies are exploited, some even within the same organism. Central fission occurs predominantly at the alkyl-ether bond, but may also occur within the PEG chain itself, thus producing various glycol intermediates which accumulate in pure cultures but appear only transiently in mixed environmental samples. Against this background, the relative resistance of some alkylphenol ethoxylates to biodegradation can be assessed in mechanistic terms. The steric bulk of the aryl nucleus effectively eliminates the central fission pathway. Moreover, some alkyl phenol ethoxylates contain branched alkyl chains which restrict ω-β-oxidation. As a result, ethoxylate shortening appears to be the major course of biodegradation observed so far. Not surprisingly, these surfactants are observed to undergo extensive primary biodegradation (removal of surfactant properties) but relatively restricted ultimate degradation to carbon dioxide and normal cell components. 相似文献
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Matsas DJ Warnick LD Mechor GD Seib LN Fatone S White ME Guard CL 《Journal of the American Veterinary Medical Association》1999,214(6):826-828
OBJECTIVE: To determine whether a commercially available water hardness test kit could be used to measure total serum calcium concentration and diagnose hypocalcemia in dairy cows. DESIGN: Prospective study. ANIMALS: 30 dairy cows from 19 commercial herds. PROCEDURE: Serum calcium concentration was determined using a water hardness test kit and a standard, laboratory-based method. Simple linear regression was used to determine whether there was a linear relationship between results of the 2 methods, and Spearman's rank correlation was used to calculate correlation between measurements. Sensitivity, specificity, and predictive values of using test kit-derived values for diagnosis of hypocalcemia (laboratory value < 8 mg/dl) were calculated. RESULTS: There was a high correlation and significant linear relationship between results of the 2 methods. Sensitivity, specificity, predictive value of a positive test result, and predictive value of a negative test result were 100, 73, 86, and 100%, respectively. Accuracy was improved by using a test kit-derived calcium concentration of 7 mg/dl as the cut-off for determining hypocalcemia. CLINICAL IMPLICATIONS: Results indicate that a commercially available water hardness test kit can be used as a rapid, inexpensive method of estimating serum calcium concentrations and diagnosing hypocalcemia in dairy cattle. However, the test is not practical for cow-side use, because blood samples must be centrifuged to obtain serum for use in the test kit. 相似文献
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White RN 《The Journal of small animal practice》1999,40(2):84-87
A nine-year-old, spayed female crossbred dog sustained a traumatic skin lesion to the right proximal pelvic limb, extending to the extensor surface of the stifle. Surgical management of the wound included primary closure using a body skin flap fashioned from the right caudolateral abdominal wall. To achieve closure and prevent tension on the wound, the coxofemoral and stifle joints on the affected side needed to be immobilised in flexion. Flexion immobilisation of the stifle was achieved using the anatomical principle of muscle reciprocation. The ipsilateral tarsal joint was immobilised in flexion using a uniplanar-bilateral (type II) transarticular external skeletal fixator and this resulted in the automatic flexion of the stifle. The fixator was removed six weeks postoperatively when the wound had healed. There were no apparent complications associated with the fixator either during its use or in the longer term following its removal. 相似文献
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An outbreak of fibropapillomatosis following rectal examination for pregnancy and involving the anus and to a lesser extent the rectum in a herd of beef heifers in western Victoria is described. Almost half the herd were involved at one time; most lesions regressed with the following 16 weeks. Lesions varied from 0.2 mm diameter polyps up to large multiple lesions up to 7 x 5 x 2 cm with a broad base. The presence of lesions did not affect the body condition or health of the animals. 相似文献
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F H White F C Neal C F Simpson A F Walsh 《Journal of the American Veterinary Medical Association》1969,155(7):1057-1058