Oxygen Isotope Effect and Structural Phase Transitions in La2CuO4-Based Superconductors     

Crawford MK  Farneth WE  McCarronn EM  Harlow RL  Moudden AH 《Science (New York, N.Y.)》1990,250(4986):1390-1394

The oxygen isotope effect on the superconducting transition temperature (alpha(o)) varies as a function of x in La2-xSrxCuO(4) and La2-xBaxCuO(4), with the maximum alpha(o) values (alpha(o) >/= 0.5) found for x near 0.12. This unusual x dependence implies that the isotope effect is influenced by proximity to the Abma --> P4(2)/ncm structural phase transition in these systems. Synchrotron x-ray difaction measurements reveal little change in lattice parameters or orthorhombicity due to isotope exchange in strontium-doped materials where alpha(o) > 0.5, eliminating static structural distortion as a cause of the large isotope effects. The anomalous behavior of alpha(o) in both strontium- and barium-doped materials, in combination with the previously discovered Abma --> P4(2)/ncm structural phase-transition in La(1.88)B(0.12)CuO(4), suggests that an electronic contribution to the lattice instability is present and maximizes at approximately 1/8 hole per copper atom. These observations indicate a dose connection between hole doping of the Cu-O sheets, tilting instabilities of the CuO(6) octahedra, and superconductivity in La(2)CuO(4)-based superconductors.  相似文献   

Clinical outcome following pneumonectomy for management of chronic pyothorax in four cats     

Crawford AH  Halfacree ZJ  Lee KC  Brockman DJ 《Journal of Feline Medicine and Surgery》2011,13(10):762-767

Pneumonectomy is the resection of all lung lobes from one side of the thorax. The clinical findings, treatment and outcome of four cases of feline chronic pyothorax managed with exploratory thoracotomy and pneumonectomy are reported. All cases were initially medically managed with thoracic drain placement and antibiosis. However, resolution was not achieved with medical therapy and diagnostic imaging findings consistent with an area of abscessation or marked lung lobe consolidation were identified, supporting a decision for surgical management. Surgical exploration was performed via median sternotomy and, on the basis of gross inspection, non-functional lung was removed. A left-sided pneumonectomy was performed in three cats and a right-sided pneumonectomy in one. All cases survived to discharge and an excellent quality of life was reported on long-term follow-up. Pneumonectomy appears to be well tolerated in the cat.  相似文献   

Significance of earthworms in stimulating soil microbial activity   总被引：9，自引：0，他引：9  

F. Binet  L. Fayolle  M. Pussard  J. J. Crawford  S. J. Traina  O. H. Tuovinen 《Biology and Fertility of Soils》1998,27(1):79-84

 The stimulatory effect of earthworms (Lumbricus terrestris L.) on soil microbial activity was studied under microcosm-controlled conditions. The hypothesis was tested that microbial stimulation observed in the presence of a soil invertebrate would be due to the utilization of additional nutritive substances (secretion and excretion products) that it provides. Changes in microbial activity were monitored by measuring simultaneously CO₂ release and protozoan population density. The increase in CO₂ released in the presence of earthworms was found to result from both earthworm respiration and enhanced microbial respiration. The stimulation of microbial activity was confirmed by a significant increase in protozoan population density, which was 3–19 times greater in the presence of earthworms. The respiratory rate of L. terrestris was estimated to be 53 μl O₂ g^–1 h^–1. Earthworm respiration significantly correlated with individual earthworm weight, but there was no correlation between the increase in microbial respiration and earthworm weight. This finding does not support the hypothesis given above that enhanced microbial respiration is due to utilization of earthworm excreta. A new hypothesis that relationships between microbial activity and earthworms are not based on trophic links alone but also on catalytic mechanisms is proposed and discussed. Received: 26 August 1997  相似文献   

Relationship of strain 19 calfhood vaccination in beef herds and brucellosis reactor rates, duration of quarantine, and number of herd tests     

R A Dietrich  S H Amosson  R P Crawford  V C Beal 《Journal of the American Veterinary Medical Association》1991,198(1):78-80

Initial and cumulative reactor rates for strain 19 vaccinates and nonvaccinates were significantly (P less than 0.001) lower for beef herds containing variable proportions of vaccinates, compared with reactor rates in nonvaccinated herds. In addition, significant (P less than 0.005) reduction in cumulative incidence was observed in nonvaccinated and strain 19-vaccinated cattle as the proportion of vaccinates within the herd increased from 1 to 19%, 20 to 39%, 40 to 59%, and 60 to 100%. Duration of quarantine and number of herd tests were not reduced in herds with strain 19-vaccinated cattle. In herds released from quarantine, duration of quarantine and number of tests were positively correlated to proportion of the herd vaccinated. In nonvaccinated herds released from quarantine, effect of herd size was documented by strong positive (P = 0.042) correlation with duration of quarantine and slightly weaker correlation (P = 0.095) with number of tests.  相似文献   

Human infections associated with waterborne Leptospires, and survival studies on serotype pomona   总被引：4，自引：0，他引：4  

R P Crawford  J M Heinemann  W F McCulloch  S L Diesch 《Journal of the American Veterinary Medical Association》1971,159(11):1477-1484

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Guidelines for the future of equine locomotion research   总被引：1，自引：0，他引：1  

D H Leach  W H Crawford 《Equine veterinary journal》1983,15(2):103-110

This paper describes the major areas that require investigation in equine locomotion and outlines a plan for such research in both the Thoroughbred and Standardbred. Fifteen topics for future investigation have been selected and given an order of priority. These topics deal with characteristics of normal locomotion, factors which influence locomotion, the epidemiology and economics of lameness and the clinical identification of lameness.  相似文献   

Biotechnology's stock market blues     

M Crawford 《Science (New York, N.Y.)》1987,238(4833):1503-1504

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Court rules cells are the patient's property     

M Crawford 《Science (New York, N.Y.)》1988,241(4866):653-654

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Brucellosis in heifers weaned from seropositive dams     

R P Crawford  J D Huber  R B Sanders 《Journal of the American Veterinary Medical Association》1986,189(5):547-549

Fifty-six heifers were weaned from dams that were card-test positive for brucellosis. Forty-four dams were positive by rivanol and complement-fixation tests and Brucella abortus field strain was isolated from 14. Numbers of expected pregnancies following natural breeding and numbers of viable calves produced were not reduced in the heifers. Persistent B abortus infection was documented in 2 of 37 parturient heifers from reactor dams. The frequency of infection was 1 of 10 in strain 19-vaccinated heifers, and 1 of 27 in nonvaccinated heifers. The 2 persistently infected heifers had atypical serologic reaction patterns before normal parturitions.  相似文献   

Multiple organ metastasis of an aortic body tumor in a boxer     

J M Gliatto  M A Crawford  T G Snider  R Pechman 《Journal of the American Veterinary Medical Association》1987,191(9):1110-1112

A 9-year-old sexually intact male Boxer with a history of multiple episodes of syncope and various cardiac arrhythmias was determined radiographically to have a large mass in the heart-base region and was subsequently euthanatized upon worsening of clinical signs. Histologic and ultrastructural examination of tissue from the heart-base mass indicated that the tumor was most likely a chemodectoma derived from the aortic body (aortic body tumor, extra-adrenal paraganglioma). Macroscopic and/or microscopic evidence of metastasis of the tumor was seen in the lungs, myocardium, spleen, liver, kidneys, and dura mater over the cerebellum.  相似文献