Chemical control of marsh ragwort (Senecio aquaticus Huds.) in established grassland

Infestations of marsh ragwort, Senecio aquaticus Huds., in established ley grassland were sprayed at the rosette stage in April or May with MCPA, 2,4-D, asulam or a 2,4-D asulam mixture. All treatments gave better control in the year after spraying than in the year of spraying. The most effective herbicide was 2,4-D ester at 1–68 or 1–12 kg/ha with or without the incorporation of asulam at 1–12 kg/ha. MCPA at 1–68 kg/ha was less effective, especially in the year of spraying and asulam alone at 1-12 kg/ha gave consistently the poorest control of all treatments. Spraying in May gave better control in the year of spraying than April application, but in the year after spraying date of application made no difference to the degree of control. S. aquaticus at the various sites differed in general susceptibility to herbicides in the year of spraying, but in the year after spraying these differences disappeared.     

Square Pegs and Round Holes: Can the Economic Paradigm be Used to Value the Wilderness?

ABSTRACT This paper examines whether economic valuation methods are capable of meaningfully measuring the value of the wilderness in monetary terms. Although non-monetary valuation methods are often important in policy making arenas, this paper focuses on monetary methods. Three questions are examined to determine if these economic valuation methods can contribute to the development of wilderness policy. First, are the valuation methods which have been developed by economists capable of expressing in dollar terms the value of all the services which the wilderness supplies? Second, if these valuation methods are not capable of eliciting all the relevant values, are they still useful for public policy purposes? Third, can the valuation methods be modified or can new methods be developed which can measure some of the values which have not been captured by the previously employed methods? The paper reviews existing valuation methods according to these criteria and finds that the ability to value the wilderness is limited by the shortcomings of currently employed techniques. Refinements to existing methods and potential new methods are suggested to further the valuation process.     

THE EFFECT OF SEQUENCE SELECTION AND FIELD STRENGTH ON DETECTION OF OSTEOCHONDRAL DEFECTS IN THE METACARPOPHALANGEAL JOINT

Six cadaver forelimbs were imaged in two high‐field magnetic resonance (MR) systems and one low‐field MR system following the creation of osteochondral defects on the palmar distal aspect of the third metacarpal bone. The following sequences were performed using all three systems: proton density (PD) turbo spin echo, T2^* gradient echo (GRE), T2‐weighted fast spin echo, and short tau inversion recovery. In addition, 3D T1 GRE sagittal standard and motion insensitive sequences were obtained using the low‐field system. PD fat saturated and 3D T1‐weighted spoiled GRE images with and without fat suppression were acquired with the high‐field systems. Lesions were measured and assigned a confidence score. The images obtained using high‐field systems (1.0 and 1.5 T) more accurately represented the osteochondral defects when compared with low‐field system (0.27 T) images. The largest difference was observed when evaluating articular cartilage defects, which were not identified on the low‐field images. Sequence selection affected the appearance of the lesions. On all systems the turbo and fast spin echo sequences more accurately represented the lesion size and shape when compared with the GRE sequences. The T1 GRE sequence is the only sequence that appears to allow visualization of the articular cartilage on the low‐field images, but is limited in providing adequate cartilage visualization. Confidence scores were greater on the high‐field systems when compared with the low‐field system.     

MAGNETIC RESONANCE IMAGING APPARENT DIFFUSION COEFFICIENTS FOR HISTOLOGICALLY CONFIRMED INTRACRANIAL LESIONS IN DOGS

Diffusion‐weighted imaging is an advanced magnetic resonance imaging technique that is well established in the diagnosis of nonhemorrhagic infarction in people. However, recent investigations into intracranial neoplastic and inflammatory disease in people have identified variable and overlapping results. In this retrospective study of 37 dogs with histologically confirmed intracranial disease, we investigated whether histogram analysis of quantitative apparent diffusion coefficients (ADC) can differentiate specific disease processes. Disease categories included: meningiomas, glial cell tumors, choroid plexus tumors, pituitary tumors, inflammatory brain diseases, acute nonhemorrhagic infarcts, chronic nonhemorrhagic infarcts, and hemorrhagic infarcts. A wide range of ADC value distributions were identified within the disease groups, and there were overlapping ADC values between most groups. Low ADC values indicating restricted diffusion of water were identified in acute nonhemorrhagic infarcts as expected, but were also seen in meningiomas, glial cell tumors, and granulomatous meningoencephalitis. Based on this preliminary data it is unlikely that singular quantitative ADC values can be used to determine the histological type of canine intracranial disease.     

Partial Arytenoidectomy in the Horse with and without Mucosal Closure

Left-sided partial arytenoidectomy was performed in eight horses to evaluate healing. Four horses underwent conventional partial arytenoidectomy with suture apposition of the mucosa. In four horses, most of the arytenoid cartilage, including overlying mucosa, vocal fold, and laryngeal saccule, were excised en bloc without mucosal closure. The horses were monitored clinically by endoscopic examination. One horse from each group was euthanatized at weeks 2, 4, 8, and 16. Complete necropsies with gross and histologic examination of the arytenoidectomy sites were performed. Postoperative complications such as coughing, dysphagia, and aspiration pneumonia were not encountered and problems with wound healing were minimal in both groups. The defect created by partial arytenoidectomy without mucosal closure initially filled to the level of the luminal surface with granulation tissue, with a gradual transition to mature fibrous connective tissue. Grossly, the defect appeared to be healed and was completely epithelialized by week 16 without apparent narrowing of the laryngeal lumen. Partial arytenoidectomy sites with mucosal closure healed in a similar pattern by week 8. Partial dehiscence of the dorsal portion of the sutured mucosa occurred in three horses.