Kinetic modeling of 2,4-dichlorophenoxyacetic acid (2,4-D) degradation in soil slurry by anodic fenton treatment

Anodic Fenton treatment (AFT) has been shown to be a promising technology in pesticide wastewater treatment. However, no research has been conducted on the AFT application to contaminated soils. In this study, the 2,4-D degradation kinetics of AFT in a silt loam soil slurry were investigated for the first time, and the effects of various experimental conditions including initial 2,4-D concentration, Fenton reagent delivery rate, amount of humic acid (HA) addition, and pH were examined. The 2,4-D degradation in soil slurry by AFT was found to follow a two-stage kinetic model. During the early stage of AFT (the first 4-5 min), the 2,4-D concentration profile followed a pseudo-first-order kinetic model. In the later stage (typically after 5 or 6 min), the AFT kinetic model provided a better fit. This result is most likely due to the existence of (*)OH scavengers and 2,4-D sorption on soil. The Fe(2+) delivery rate was shown to be a more significant factor in degradation rate than the H(2)O(2) delivery rate when the Fe(2+)/H(2)O(2) ratios were in the range of 1:2 to 1:10. The presence of HA in soil lowered the AFT rate, most probably due to the competition with 2,4-D for consumption of (*)OH and increased sorption of 2,4-D on soil. The optimal pH for 2,4-D degradation in soil slurry by AFT was observed to be in the range of pH 2-3.     

Impact of pH on the kinetics of acrylamide formation/elimination reactions in model systems

The effect of pH on acrylamide formation and elimination kinetics was studied in an equimolar (0.1 M) asparagine-glucose model system in phosphate or citrate buffer, heated at temperatures between 120 and 200 degrees C. To describe the experimental data, a simplified kinetic model was proposed and kinetic parameters were estimated by combined nonlinear regression and numerical integration on the data obtained under nonisothermal conditions. The model was subsequently validated in a more realistic potato-based matrix with varying pH. By increasing acidity, the reaction rate constants at T(ref) (160 degrees C) for both acrylamide formation and elimination can significantly be reduced, whereas the temperature dependence of both reaction rate constants increases. The introduction of a lyophilized potato matrix (20%) did not affect the acrylamide formation reaction rate constant at reference temperature (160 degrees C) as compared to the asparagine-glucose model system; the elimination rate constant at T(ref), on the contrary, was almost doubled.     

Care and use of feeding tubes in dogs and cats

Feeding tubes are an accepted way of providing nutritional support for animals unable or unwilling to consume adequate calories on their own. This article provides information on the indications for the use of feeding tubes in small animals, the types of tubes available, and ways to initiate nutritional support once the tubes are in place. The pros and cons of the various tubes are discussed, as well as potential complications.     

Influence of gastrointestinal tract disease on pharmacokinetics of lidocaine after intravenous infusion in anesthetized horses

OBJECTIVE: To determine the disposition of lidocaine after IV infusion in anesthetized horses undergoing exploratory laparotomy because of gastrointestinal tract disease. ANIMALS: 11 horses (mean +/- SD, 10.3 +/- 7.4 years; 526 +/- 40 kg). PROCEDURE: Lidocaine hydrochloride (loading infusion, 1.3 mg/kg during a 15-minute period [87.5 microg/kg/min]; maintenance infusion, 50 microg/kg/min for 60 to 90 minutes) was administered IV to dorsally recumbent anesthetized horses. Blood samples were collected before and at fixed time points during and after lidocaine infusion for analysis of serum drug concentrations by use of liquid chromatography-mass spectrometry. Serum lidocaine concentrations were evaluated by use of standard noncompartmental analysis. Selected cardiopulmonary variables, including heart rate (HR), mean arterial pressure (MAP), arterial pH, PaCO2, and PaO2, were recorded. Recovery quality was assessed and recorded. RESULTS: Serum lidocaine concentrations paralleled administration, increasing rapidly with the initiation of the loading infusion and decreasing rapidly following discontinuation of the maintenance infusion. Mean +/- SD volume of distribution at steady state, total body clearance, and terminal half-life were 0.70 +/- 0.39 L/kg, 25 +/- 3 mL/kg/min, and 65 +/- 33 minutes, respectively. Cardiopulmonary variables were within reference ranges for horses anesthetized with inhalation anesthetics. Mean HR ranged from 36 +/- 1 beats/min to 43 +/- 9 beats/min, and mean MAP ranged from 74 +/- 18 mm Hg to 89 +/- 10 mm Hg. Recovery quality ranged from poor to excellent. CONCLUSIONS AND CLINICAL RELEVANCE: Availability of pharmacokinetic data for horses with gastrointestinal tract disease will facilitate appropriate clinical dosing of lidocaine.     

Stress-related behaviors among horses used in a therapeutic riding program

OBJECTIVE: To determine whether therapeutic riding resulted in higher levels of stress or frustration for horses than did recreational riding and whether therapeutic riding with at-risk individuals was more stressful for the horses than was therapeutic riding with individuals with physical or emotional handicaps. DESIGN: Observational study. ANIMALS: 14 horses in a therapeutic riding program. PROCEDURE: An ethogram of equine behaviors was created, and horses were observed while ridden by 5 groups of riders (recreational riders, physically handicapped riders, psychologically handicapped riders, at risk children, and special education children). Number of stress-related behaviors (ears pinned back, head raised, head turned, head tossed, head shaken, head down, and defecation) was compared among groups. RESULTS: No significant differences in mean number of stress-related behaviors were found when horses were ridden by recreational riders, physically handicapped riders, psychologically handicapped riders, or special education children. However, mean number of stress-related behaviors was significantly higher when horses were ridden by the at-risk children. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that for horses in a therapeutic riding program, being ridden by physically or psychologically handicapped individuals is no more stressful for the horses than is being ridden in the same setting by recreational riders. However, at-risk children caused more stress to the horses, suggesting that the time horses are ridden by at-risk children should be limited both daily and weekly.     

Effects of a therapeutic riding program on at-risk and special education children

OBJECTIVE: To determine the effects of a therapeutic riding program on psychosocial measurements among children considered at risk for poor performance or failure in school or life and among children in special education programs. DESIGN: Observational study. POPULATION: 17 at-risk children (6 boys and 11 girls) and 14 special education children (7 boys and 7 girls). PROCEDURE: For the at-risk children, anger, anxiety, perceived self-competence, and physical coordination were assessed. For the special education children, anger and cheerfulness were measured, and the children's and their mothers' perceptions of the children's behavior were assessed. Measurements were made before and after an 8-session therapeutic riding program. RESULTS: For boys enrolled in the special education program, anger was significantly decreased after completion of the riding program. The boys' mothers also perceived significant improvements in their children's behavior after completion of the program. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that an 8-session therapeutic riding program can significantly decrease anger in adolescent boys in a special education program and positively affect their mothers' perception of the boys' behavior.     

Hemodynamic effects in dogs after intramuscular administration of a combination of dexmedetomidine-butorphanol-tiletamine-zolazepam or dexmedetomidine-butorphanol-ketamine

Objective-To evaluate hemodynamic effects in dogs after IM administration of dexmedetomidine (7.5 μg/kg, butorphanol (0.15 mg/kg), and tiletamine-zolazepam (3 mg/kg [DBTZ]) or dexmedetomidine (15 μg/kg), butorphanol (0.3 mg/kg), and ketamine (3 mg/kg [DBK]). Animals-5 healthy adult mixed-breed dogs. Procedures-Each dog received DBTZ and DBK in a randomized crossover study with a 48-hour interval between treatments. Anesthesia was induced and maintained with sevoflurane in 100% oxygen while instrumentation with Swan-Ganz and arterial catheters was performed. Following instrumentation, hemodynamic measurements were recorded at 3.54% (1.5 times the minimum alveolar concentration) sevoflurane; then sevoflurane administration was discontinued, and dogs were allowed to recover. Six hours after cessation of sevoflurane administration, baseline hemodynamic measurements were recorded, each dog was given an IM injection of DBTZ or DBK, and hemodynamic measurements were obtained at predetermined intervals for 70 minutes. Results-DBTZ and DBK induced hypoventilation (Paco(2), approx 60 to 70 mm Hg), respiratory acidosis (pH, approx 7.2), hypertension (mean arterial blood pressure, approx 115 to 174 mm Hg), increases in systemic vascular resistance, and reflex bradycardia. Cardiac output, oxygen delivery, and oxygen consumption following DBTZ or DBK administration were similar to those following sevoflurane administration to achieve a surgical plane of anesthesia. Blood l-lactate concentrations remained within the reference range at all times for all protocols. Conclusions and Clinical Relevance-In healthy dogs, both DBTZ and DBK maintained oxygen delivery and oxygen consumption to tissues and blood lactate concentrations within the reference range. However, ventilation should be carefully monitored and assisted when necessary to prevent hypoventilation.