Modeling scour and deposition in ephemeral channels after wildfire

The area burned by wildfire in the states of Arizona and New Mexico in the southwestern US has been increasing in recent years. In many cases, high severity burns have caused dramatic increases in runoff and sediment yield from burned watersheds. This paper describes the potential and limitations of the HEC6T sediment transport model to describe changes in channel scour and deposition following the Cerro Grande fire near Los Alamos, New Mexico. Following the fire, Pueblo Canyon, near Los Alamos, was subject to a peak flow two orders of magnitudes higher than any discharge in the 7-year period of record, and twice the initial post-fire estimate of the 100-year event. HEC6T requires that the limits of scour and deposition on a cross-section be specified prior to application. This was achieved by using geomorphologic principles, predicted post-burn hydrology and long-term estimates of channel change derived from air photos, to estimate post-fire channel widths. Because significant quantities of silt and clay were present in the runoff, erosion shear stress and erosion rate parameters for cohesive sediments had to be obtained experimentally. After a sensitivity analysis, an optimization routine was used to estimate the optimal model parameter values for sensitive parameters. HEC6T was able to accurately model the change in cumulative sediment volume change derived from Airborne Laser Swath Mapping (ALSM, often called Lidar) taken before and after the large post-fire event. One discrepancy between the HEC6T model prediction and the ALSM-estimated change was that the ALSM-estimated change showed the greatest amount of deposition in a portion of the canyon with increasing slope, which the HEC6T model did not predict. Any sediment transport model will predict increased sediment transport capacity with increasing energy slope, so that it was considered to be beyond the capability of any sediment transport model to predict this deposition. Therefore, HEC6T simulated the overall changes in scour and deposition within reasonable expectation of the capabilities of physically-based sediment transport modeling indicating that it is capable of modeling sediment transport in ephemeral channels following wildfire.     

Anaesthesia with ketamine/medetomidine in the rabbit: influence of route of administration and the effect of combination with butorphanol

Objective To compare the characteristics of anaesthesia induced with ketamine/medetomidine administered by the subcutaneous and intramuscular routes and to assess the effects of the addition of butorphanol to this combination. Study design Prospective randomised study. Animals Six female New Zealand White rabbits. Methods Rabbits were given one of four combinations of ketamine and medetomidine (K/M) either subcutaneously (SC) or intramuscularly (IM) on four successive occasions with a 7‐day interval between treatments. The dose combinations were; 15/0.25 mg kg^?1 SC; 15/0.25 mg kg^?1 IM; 15/0.5 mg kg^?1 SC, and 15/0.25 mg kg^?1 together with 0.4 mg kg^?1 butorphanol (K/M/B) SC. The effects of anaesthesia on arterial blood gas values and cardiovascular variables were recorded at predetermined time points. Toe and ear pinch reflexes were judged to determine the duration of surgical anaesthesia. Loss of the righting reflex was used to measure the duration of sleep time. Analyses used repeated measures analysis of variance. Results All groups lost the righting reflex and ear pinch response. Three animals in the groups that received K/M alone lost their toe pinch reflex, whereas four lost this reflex when given K/M/B. Time of onset of loss of the righting, toe and ear pinch reflexes did not differ significantly among the groups. The higher dose combination of medetomidine with ketamine and the combination of K/M/B produced a greater duration of loss of the ear pinch response than the lower dose of K/M administered by either route. No significant differences were found among the groups in the duration of loss of the toe pinch reflex. All animals developed a moderate bradycardia (mean heart rate <166 beats minute^?1) and moderate hypoxaemia (mean P_aO₂ < 6.0 kPa). Animals given butorphanol showed the greatest reduction in respiratory rate (31 ± 13 breaths minute^?1, p < 0.05) but this was not reflected in any significant differences in arterial PCO₂, PO₂ or pH among the groups. Conclusions Administration of K/M by the SC route produced equivalent effects in comparison to intramuscular administration. The addition of butorphanol increased the duration of anaesthesia, but produced a slight increase in the degree of respiratory depression. All dose rates resulted in hypoxaemia so oxygen should be administered when these combinations are used in rabbits. Clinical relevance Subcutaneous administration is both technically simpler and may cause less discomfort to the animal than IM injection, and so is preferred. The combination of K/M with butorphanol has relatively minor effects on the depth and duration of anaesthesia, so offers little advantage to the use of K/M alone.     

AGEING OF HYDROLYSED IRON (III) SOLUTIONS1

Three 0.01m Fe(ClO₄)₃ Solutions of R= 0, 1, and 2, respectively, were studied over a period of 8 months, where R is referred to the HCO₃^?/Fe³⁺ mole ratio in preparation. The R= 0 solution was initially light yellow and clear but rapidly changed to a dense cloudy Suspension after a 9-day induction period. Hydrolysed species rapidly grew from <10 nm to >650 nm. Particles of intermediate size were not observed during the entire period of study. Settleable FeOOH precipi-tate was first observed in 5 weeks with 23 per cent of its iron noted as precipitate at the end of 5 months. The R= 1 and R= 2 Solutions were reddish-brown of low turbidity. Rapid hydrolysis and polymerization were observed immediately after preparation. The hydrolysed species gradually grew in size during ageing and no settleable FeOOH precipitate was observed for at least two years. A hypo-thesis based on Lamb and Jacques's model of Fe³⁺ hydrolysis is proposed to interpret the reactions taking place in these three Solutions. In the R= 0 solution, the initial number of nuclei for condensation is low, whereas the poten-tial supply of Fe(OH)₃ is abundant. In the R= 1 and R= 2 Solutions the number of nuclei initially formed is high, whereas a limited amount of mono-meric Fe(OH)₃ is available for condensation. The initial number of nuclei relative to the concentration of monomeric species is the key factor that governs the appearance and properties of these Solutions.     

Post-vaccinal distemper encephalitis in two Border Collie cross littermates

Abstract

CASE HISTORY: One 4.5-month-old male Border Collie cross presented with aggression and seizures in October 2006. A 16-month-old, female, spayed Border Collie cross presented with hypersalivation and a dropped jaw and rapidly became stuporous in September 2007. The dogs were littermates and developed acute neurological signs 5 and 27 days, respectively, after vaccination with different modified live vaccines containing canine distemper virus.

HISTOPATHOLOGICAL FINDINGS: Sections of brain in both dogs showed evidence of encephalitis mainly centred on the grey matter of brainstem nuclei, where there was extensive and intense parenchymal and perivascular infiltration of histiocytes and lymphocytes. Intra-nuclear and intra-cytoplasmic inclusions typical of distemper were plentiful and there was abundant labelling for canine distemper virus using immunohistochemistry.

DIAGNOSIS: Post-vaccinal canine distemper.

CLINCIAL RELEVANCE: Post-vaccinal canine distemper has mainly been attributed to virulent vaccine virus, but it may also occur in dogs whose immunologic nature makes them susceptible to disease induced by a modified-live vaccine virus that is safe and protective for most dogs.     

Gentamicin-associated acute renal failure in the dog

Gentamicin-associated acute renal failure was diagnosed in 10 dogs. The disease was characterized by a poor prognosis and lengthy hospitalization. Hypoalbuminemia, disorders of potassium homeostasis, proteinuria, hematuria, and cylindruria were common during therapy for renal failure. Fever and dehydration were the most commonly identified potential predisposing factors.     

A nephrotic-like syndrome with an associated mesangio-proliferative glomerulopathy in a cow

A 3-year-old Limousin cow was admitted to the University of Georgia Teaching Hospital with a history of chronic weight loss and diarrhea of more than 1 year's duration. Clinical laboratory findings included proteinuria and hypoproteinemia and were suggestive of a nephrotic-like syndrome. Necropsy findings included generalized edema of the visceral organs and diffuse red glistening foci on the capsular and cut surfaces of the cortex of both kidneys. Microscopically, the kidney had hypercellular and hypersegmented glomeruli, focal glomerulosclerosis, periglomerular fibrosis, and tubular nephrosis. The glomerular hypercellularity was confirmed by electron microscopy to be due to increased mesangial cells.     

Distal renal tubular acidosis and hepatic lipidosis in a cat

Clinical and laboratory evidence of hepatic failure was found in a chronically anorectic cat. Simultaneous blood and urine pH determinations established a diagnosis of distal renal tubular acidosis. The cat did not respond to treatment. Necropsy revealed distal tubular nephrosis and hepatic lipidosis. The finding of distal renal tubular acidosis in a cat with hepatic lipidosis emphasizes the importance of complete evaluation of acid-base disorders in patients.