The Burns leaching equation   总被引：1，自引：0，他引：1  

D. R. SCOTTER  R. E. WHITE  J. S. DYSON 《European Journal of Soil Science》1993,44(1):25-33

The simplicity and utility of Burns' leaching equation make it worthy of study. The equation may be written as where X is the fraction of initially surface-resident fertilizer leached below depth z by net rainfall I, in soil with a volumetric water content at ‘field capacity’ of θ. The equation is analysed using transfer functions. The analysis shows that Burns' equation is consistent with an ‘independent flow tube’ soil leaching model, rather than the soil solution being well-mixed at each soil depth as Burns suggested. The flux and resident soil solution soil concentration profiles are shown to be quite different. An alternative definition of θ is suggested. The behaviour of ‘a Burns soil’ for different initial and boundary conditions is discussed.  相似文献   

控制中国非点源污染的生物经济学战略   总被引：4，自引：0，他引：4  

WEI Yong-Ping  CHEN De-Li  B. DAVIDSON  R. E. WHITE 《土壤圈》2005,15(2):156-163

While non-point pollution from agriculture has become an increasingly serious problem in China, some progress has been made in studying the causal biophysical processes. However, few studies have assessed the economic consequences of non-point pollution in China or the policy options that could be employed to combat it. In this work a sustainable strategy to control non-point pollution from crop production, which involved taxing excessive inputs of irrigation water and fertilizer, was proposed. The approach taken to assess these measures combined biophysical and economic models,having a trade-off between economic returns and an improved environment. A proven and practical spatially referenced water and nutrient management model was used to determine the quantities of excessive irrigation water and fertilizer for specific soil and land use. Also, a set of indicators were proposed for evaluating the effects of agricultural economic output and agricultural practices on the environment.  相似文献   

A comparison of the convection-dispersion equation and transfer function model for predicting chloride leaching through an undisturbed, structured clay soil   总被引：2，自引：0，他引：2  

J.S. DYSON  R.E. WHITE 《European Journal of Soil Science》1987,38(2):157-172

The transfer function mode) (TFM) and convection-dispersion equation (CDE) were compared for predicting Cl ^? transport through a calcareous pelosol during steady, nearsaturated water flow. Large, undisturbed soil cores were used at constant irrigation intensities (q₀) between 0.3 and 3 cm h^?1, with a step-change in Cl^? concentration. The assumption of a lognormal distribution of travel times–characterized by the mean (μ) and variance (σ²)–permitted the flux-averaged breakthrough curves (BTCs) to be modelled very accurately by the TFM. The BTCs could be modelled equally well by the CDE when both the mean pore water velocity (v) and dispersion coefficient (D) were optimized simultaneously by the method of least squares, but not when v was put equal to q₀/_v, where _V was the mean volumetric water content. The best estimate of v was consistently > q₀/_v, which suggested that not all the pore water was effective in chloride transport. An operationally defined transport volume (θ_st) was calculated from the mean () or median (τ_m) travel times derived from the TFM. Chloride exclusion was not solely responsible for θ_st() being <_V: immobile water also contributed. The positive skewness of the travel time distributions meant that θ_st(τ_m) < θ_st(), indicating the effectiveness of macropore flow in solute transport. Dαv^1.42 (from the CDE), and σ²αv (from the TFM), confirmed that Cl^? dispersion increased as flow velocity increased. Flux-averaged concentrations were used to calculate the volume-averaged resident concentrations. They matched the measured Cl^? concentrations most closely when there was a gradual decrease in measured Cl ^? concentration with depth, but not when Cl ^? decreased sharply below c. 10 cm. Calculations assuming that all the water was effective in chloride transport gave less accurate results. Comparison of the measured and predicted concentrations of solute demonstrated that this must be a critical part of the evaluation of any model of solute transport.  相似文献   

Metacarpophalangeal Joint Synovial Pad Fibrotic Proliferation in 63 Horses     

ROBIN M. DABAREINER DVM  MS    NATHANIEL A. WHITE DVM  MS  Diplomate ACVS  KENNETH E. SULLINS DVM  MS  Diplomate ACVS 《Veterinary surgery : VS》1996,25(3):199-206

Medical records, radiographs, and sonograms of 63 horses with metacarpophalangeal joint synovial pad proliferation were examined retrospectively. All horses had lameness, joint effusion, or both signs associated with one or both metacarpophalangeal joints. Bony remodeling and concavity of the distodorsal aspect of the third metacarpal bone (Mc3) just proximal to the metacarpal condyles was identified by radiography in 71 joints (93%); 24 joints (32%) had radiographic evidence of a chip fracture located at the proximal dorsal aspect of the proximal phalanx. Fifty-four joints (71%) were examined by ultrasound. The mean ± SD sagittal thickness of the synovial pad was 11.3 ± 2.8 mm. Seventy-nine percent of the horses had single joint involvement with equal distribution between the right and left forelimbs. Sixty-eight joints in 55 horses were treated by arthroscopic surgery. Sixty joints (88%) had debridement of chondral or osteochondral fragmentation from the dorsal surface of Mc3 beneath the synovial pad and 30 joints (44%) had a bone chip fracture removed from the medial or lateral proximal dorsal eminence of the proximal phalanx. Complete or partial excision of both medial and lateral synovial pads was completed in 42 joints. Only the medial synovial pad was excised or trimmed in 21 joints, and 5 joints had only the lateral pad removed. Eight joints in eight horses were treated by stall rest, administration of intra-articular medication and systemic nonsteroidal anti-inflammatory drugs. Follow-up information was obtained for 50 horses treated surgically and for eight horses treated medically. Forty-three (86%) that had surgery returned to racing; 34 (68%) raced at an equivalent or better level than before surgery. Three (38%) of the medically treated horses returned to racing; only one horse raced better than the preinjury level. Horses that returned to racing at a similar or equal level of performance were significantly younger in age than horses returning at a lower level or not racing (P≤.05). Overall, horses with synovial pad proliferation treated by arthroscopic surgery had a good prognosis for return to racing at a level equal or better than before injury.  相似文献   

Clearance of penicillin G in the newborn calf     

CHARLES R. SHORT  MARY B. WHITE  KANWAL J. VARMA†  THOMAS E. POWERS†  JEAN D. POWERS† 《Journal of veterinary pharmacology and therapeutics》1984,7(1):45-48

Sodium penicillin G was administered intravenously (4545 IU/kg) to calves on the day of birth (12-24 h old) and at 5, 10, and 15 days of age. Serum was collected at varying intervals for 120 min after injection and analysed for penicillin G. The mean total body clearance (ClB) of penicillin G on the day of birth was 2.98 ml/min/kg compared to 4.83 ml/min/kg at 5 days, 3.11 ml/min/kg at 10 days and 4.65 ml/min/kg at 15 days of age. Clearances at 5 and 15 days were significantly (P less than or equal to 0.05) higher than on the day of birth. The half-life (t1/2 beta), however, did not change significantly over the 15-day period of the study. These results indicate that the newborn calf has an appreciable ability to excrete penicillin G before it is 24 h old, and that total body clearance of the antibiotic increases rapidly in the immediate postnatal period.  相似文献   

A Modified Cloward''s Technique for Arthrodesis of the Normal Metacarpophalangeal Joint in the Horse     

GREGORY R. CRAWLEY DVM  MS    BARRIE D. GRANT DVM  MS  DipiomateACVs    KARL K. WHITE DVM  DipiomateACVs    DAVID D. BARBEE DVM  MS  DiplomateACVR    ANTHONY M. GALLINA DVM  PhD  MARC H. RATZLAFF DVM  PhD 《Veterinary surgery : VS》1988,17(3):117-127

A modified Cloward's technique was performed for arthrodesis of one metacarpophalangeal (MCP) joint in eight horses. Dorsal arthrotomies were performed medial and lateral to the common digital extensor tendon and two 16 mm holes were drilled through the joint. A perforated cylindrical stainless steel basket filled with cancellous bone was impacted into each hole. The limbs were supported in casts for 8 weeks. The joints were examined and radiographed at 4 weeks, 8 weeks, 6 months, and 10 months. One horse was euthanatized at week 14 to assess the progress of the arthrodesis. In the other seven horses, there was clinical fusion at month 6. Dynamographic evaluations were performed 11 months after surgery at the walk and trot. The maximum vertical forces exerted during weight bearing by treated and control limbs were compared. No difference was detected at the walk; however, a significant difference was present at the trot (p less than 0.05). It was calculated that at the trot the horses placed 90% as much force on the treated limb as on the control limb. Eleven months after surgery, the baskets contained compact and cancellous bone. Ingrowth of bone occurred through all openings, completely filling the baskets and fusing the joints.  相似文献   

Bladder retroflexion in the dog     

R. A. S. WHITE  M. E. HERRTAGE 《The Journal of small animal practice》1986,27(11):735-746

In a series of 61 dogs examined for perineal hernia 12, (20 per cent) were found to have bladder retroflexion. Associated urinary signs were seen in only five dogs including one case with bladder rupture. Radiology was found to be the most consistently accurate means of diagnosis. Bladders were drained by catheterization, or by percutaneous or surgical cystocentesis before manipulative or surgical reduction. Conventional herniorrhaphy and castration were performed in all cases. Cystopexy was performed in only one case although recurrence of the retroflexion was not encountered in any dogs. Three dogs remained urinary incontinent after treatment.  相似文献   

Progression of Femoropatellar Osteochondrosis in Nine Young Horses Clinical, Radiographic and Arthroscopic Findings     

ROBIN M. DABAREINER dvm  MS    KENNETH E. SULLINS dvm  MS Diplomate ACVS  NATHANIEL A. WHITE II  dvm  MS  Diplomate ACVS 《Veterinary surgery : VS》1993,22(6):515-523

The clinical and radiographic progression, and arthroscopic findings for nine young horses (<1 year of age) with femoropatellar osteochondrosis (OCD) are presented. Horses had a 2 to 12 week history of bilateral (8 horses) or unilateral (1 horse) hindlimb lameness. The most consistent clinical signs included femoropatellar joint distention and bilateral hindlimb lameness. At the onset of clinical signs, radiographic lesions were not present (4 horses) or subtle (5 horses), but were easily identified on radiographs taken 4 to 24 weeks later. Arthroscopic surgery was delayed until radiographic changes became obvious. Surgical findings in 20 femoropatellar joints were most commonly osteochondral "flaps" located on the proximal lateral trochlear ridge of the femur and were larger than had been indicated by the radiographs. Eight horses were being used for their intended purpose, which was racing (3 horses were racing and 3 were in race training), dressage (1 horse) or pleasure riding (1 horse). One horse required a second surgery when similar lesions developed in the opposite stifle, and was euthanatized 2 months later because of persistent lameness. Once clinical signs are observed, osteochondrosis lesions of the distal femur can progress in foals younger than 9 months of age and the full extent of the radiographic lesion may take several weeks to develop.  相似文献   

Dystrophic (Dermolytic) Epidermolysis Bullosa in a Cat     

STEPHEN D. WHITE †  ROBERT W. DUNSTAN‡  THIERRY OLIVRY§  DIANE K. NAYDAN§  KEITH RICHTER| 《Veterinary dermatology》1993,4(2):91-95

Abstract— Dystrophic epidermolysis bullosa was diagnosed in an 8-month-old male domestic shorthaired cat. Lesions noted were paronychia, ulcers on the palate, oropharynx, gums and tongue, as well as ulceration and crusts on the metacarpal, metatarsal and digital pads. Histology of lesions showed dermal-epidermaj separation and ulceration. Immunohistochemistry showed collagen IV (characteristic of the lamina densa) located at the roof of the cleft at both the dermal-epidermal and follicular-dermal interfaces. Electron microscopy showed the dermal-epidermal cleft to be sublamina densa. Résumé— Une épidermolyse bulleuse dystrophíque a été diagnostiquée chez un chat européen à poils courts de huit mois. Les lésions étaient une paronychie, des ulcères du palai, de l'oropharynx, des gencives et de la langue ains que des ulcères et des croutes au niveau des métacarpes, métatarses et coussinets plantaires. L'examen histologique des lésions faiasait apparaitre des ulcérations et des disjonctions derme/épiderme. L'étude immunohistochimique a montré la présence de fibres de collagène IV (caractéristiques de la lamina densa) sur lew toit des bulles tant au niveau des interfaces derme/épiderme que derme/follicule. La microscopie électronique a montré que les séparations derme/épiderme se faisaient au niveau de la sublamina densa. Zusammenfassung— Eine dystrophe Epidermolysis bullosa wurde bei einer achtjährigen kurzhaarigen männlichen hauskatze diagnostiziert. Die beschriebenen Veränderungen bestanden in Paronychie, Ulzera an Gaumen, Oropharynx, Gingiva und Zunge sowie Ulzerationen und Krusten an den metacarpalen, metatarsalen und digitalen Ballen. Die Histologie der Veränderungen zeigte dermal-epidermale Trennungen und Ulzerationen. Mit der Immunhistochemie wurde Kollagen IV nachgewiesen (ein Kennzeichen der Lamina densa), das am Gewölbe der Spaltbildung sowohl an den derma-epidermalen als auch an den follikulär-dermalen Schnittstellen lokalisiert war. Die Elektronenmikroskopie zeigte, daß die dermal-epidermale Spaltbildung die Sublamina densa darstellte. Resumen En un gato macho de ocho meses doméstico de pelo corto se diagnóstico epidermolisis distrófica bullosa. Las lesiones presentes fueron paroniquia, úlceras del paladar, orofaringe, encías y lengua, así como ulceraciones y costras en las regiones del metacarpo, metatarso, y almohadillas plantares. Las lesiones histologicas consistieron de separación y ulceración a nivel de la dermis y epidermis. Exámenes inmunohistoquímicos demostraron la presencia de colágeno IV (característico de la lámina densa), localizado en el techo de las indentactiones en ambas interfases, epidermo-dérmica y foliculo-dérmica. Por medio de microscopía electrónica se comprobo que las indentaciones de la dermis y epidermis consistían de sublámina densa.  相似文献   

Vaginourethroplasty for Treatment of Urethral Obstruction in the Bitch   总被引：1，自引：0，他引：1  

R. N. WHITE BSc  BVetMed  CertVA  Diplomate ECVS    J. V. DAVIES BVetMed  PhD  DVR  Diplomate ECVS  S. P. GREGORY BVetMed  PhD  DVR 《Veterinary surgery : VS》1996,25(6):503-510

Vaginourethroplasty was performed in six bitches with infiltrative, obstructive urethral disease. The initial clinical signs included dysuria, hematuria, pollakiuria, and stranguria. Diagnosis was based on the clinical signs, plain radiography and contrast vagino-urethrogram examination, and urethral biopsy. Five dogs were diagnosed as having urethral neoplasia; the sixth dog had granulomatous urethritis. In all six dogs, up to 50% of the urethra and the urethral tubercle were resected to ensure adequate surgical margins. One dog was euthanatized 4 months after surgery for recurrence of a transitional cell carcinoma at the surgical site. Long-term resolution of the problem (minimum of 12 months) was achieved in the other five dogs. The frequency of serious complications, including urinary incontinence and ascending lower urinary tract infections, was low.  相似文献