Plasma-Catalysis of Nonoxidative Methane Coupling: A Dynamic Investigation of Plasma and Surface Microkinetics over Ni(111).

A heterogeneous catalytic microkinetic model is developed and implemented in a zero-dimensional (0D) plasma model for the dynamic study of methane nonoxidative coupling over Ni(111) at residence times and power densities consistent with experimental reactors. The microkinetic model is thermodynamically consistent and is parameterized based on the heats of chemisorption of surface species on Ni(111). The surface network explicitly accounts for the interactions of plasma species, namely, molecules, radicals, and vibrationally excited states, with the catalyst active sites via adsorption and Eley-Rideal reactions. The Fridman-Macheret model is used to describe the enhancement of the rate of the dissociative adsorption of vibrationally excited CH4, H2, and C2H6. In combination with a previously developed detailed kinetic scheme for nonthermal methane plasma, 0D simulation results bring insights into the complex dynamic interactions between the plasma phase and the catalyst during methane nonoxidative coupling. Differential turnover frequencies achieved by plasma-catalysis are higher than those of equivalent plasma-only and catalysis-only simulations combined; however, this performance can only be sustained momentarily. Hydrogen produced from dehydrogenation of ethane via electron collisions within the plasma is found to quickly saturate the surface and even promote the conversion of surface CH3* back to methane.

Nasopharyngeal Presentation of a Pharyngeal Cleft Cyst in a Dog.

A 2 yr old castrated male shih tzu was presented for assessment of worsening chronic snoring since first detected at 3 mo of age. An upper respiratory endoscopic examination and a computed tomographic scan showed a well-circumscribed, fluid-filled nasopharyngeal mass located in the median plane on the nasal side of the soft palate. This lesion was removed using a ventral approach to the nasopharynx by blunt-sharp dissection from the submucosal tissues of the soft palate. Histopathology revealed a cystic lesion lined by a single layer of a pseudostratified columnar ciliated epithelium, characteristic of a pharyngeal cyst. Follow-up 5 mo after surgery revealed complete resolution of the clinical signs with no evidence of local recurrence. Pharyngeal cysts are developmental abnormalities of the branchial apparatus. Most derive from the second branchial arch and cause cysts, sinuses, and fistulae to develop in the neck region. In our case, the lesion was located in the nasopharynx, leading to snoring and exercise intolerance. This condition should be included in the differential diagnosis of suspected nasopharyngeal obstruction.

Use of endoscopic-guided electrocautery ablation for treatment of tracheal liposarcoma in a dog.

CASE DESCRIPTION A 7-year-old 44-kg (97-lb) neutered male Great Pyrenees was referred for evaluation because of episodic dyspnea with cyanosis of 1 to 2 weeks' duration. Three days prior to evaluation, the clinical signs had worsened, including 1 episode of collapse. CLINICAL FINDINGS Thoracic radiography and CT revealed a well-delineated soft tissue mass, located approximately 1.5 cm cranial to the carina and occupying almost 90% of the tracheal lumen. A CBC and serum biochemical analysis were performed, and all results were within reference limits. TREATMENT AND OUTCOME Tracheoscopy confirmed the presence of a broad-based bilobate mass that was protruding from the right dorsal aspect of the trachea and occupied almost the entire tracheal lumen. The mass was successfully resected by endoscopic-guided electrocautery ablation. Findings of histologic evaluation were consistent with a diagnosis of liposarcoma. Immediately following the ablation procedure, the previously noted clinical signs of respiratory tract disease resolved. On follow-up examination 12 months later, no regrowth of the mass was evident on thoracic helical CT and tracheoscopy. CLINICAL RELEVANCE Endoscopic-guided electrocautery ablation of tracheal liposarcoma was a safe and effective minimally invasive treatment for the dog of this report. The procedure was brief and appeared to be well tolerated, resulting in immediate improvement of clinical signs.

Endoscope-assisted thoracolumbar lateral corpectomy.

OBJECTIVE: To report an endoscope-assisted lateral approach to expose the intervertebral foramen and disk and perform lateral corpectomy of thoracolumbar disks in dogs. STUDY DESIGN: Cadaver study. ANIMALS: Fresh canine cadavers (n=6). METHODS: A thoracic (T10-T11) and a lumbar (L3-L4) lateral approach were made on 6 fresh canine mixed breed cadavers. Through a limited skin incision, musculature was dissected and retracted using a neurosurgical self-retaining retractor and lateral corpectomy performed. The approach and bone removal, both performed under endoscopic control, were assessed. RESULTS: The foramen and intervertebral disk were clearly observed in all specimens without any iatrogenic injury of the ventral and dorsal nerve branches. Access to the foramen was possible in all specimens; in the thoracic area the head of the rib was always partially excised to observe the intervertebral disk medially. Lateral corpectomy was easily performed in all cadavers and spinal cord observation was good. Extension to foraminotomy or mini hemilaminectomy could easily be performed through the same limited approach. CONCLUSION: Endoscopic exploration provided a good viewing of the intervertebral disk and/or foramen. An endoscope-assisted thoracolumbar lateral corpectomy could effectively be performed through a limited approach to the thoracolumbar disks and allowed good ventral spinal cord assessment.

Radiographic assessment of the femorotibial joint of the CCLT rabbit experimental model of osteoarthritis.

BACKGROUND: The purposes of the study were to determine the relevance and validity of in vivo non-invasive radiographic assessment of the CCLT (Cranial Cruciate Ligament Transection) rabbit model of osteoarthritis (OA) and to estimate the pertinence, reliability and reproducibility of a radiographic OA (ROA) grading scale and associated radiographic atlas. METHODS: In vivo non-invasive extended non weight-bearing radiography of the rabbit femorotibial joint was standardized. Two hundred and fifty radiographs from control and CCLT rabbits up to five months after surgery were reviewed by three readers. They subsequently constructed an original semi-quantitative grading scale as well as an illustrative atlas of individual ROA feature for the medial compartment. To measure agreements, five readers independently scored the same radiographic sample using this atlas and three of them performed a second reading. To evaluate the pertinence of the ROA grading scale, ROA results were compared with gross examination in forty operated and ten control rabbits. RESULTS: Radiographic osteophytes of medial femoral condyles and medial tibial condyles were scored on a four point scale and dichotomously for osteophytes of medial fabella. Medial joint space width was scored as normal, reduced or absent. Each ROA features was well correlated with gross examination (p < 0.001). ICCs of each ROA features demonstrated excellent agreement between readers and within reading. Global ROA score gave the highest ICCs value for between (ICC 0.93; CI 0.90-0.96) and within (ICC ranged from 0.94 to 0.96) observer agreements. Among all individual ROA features, medial joint space width scoring gave the highest overall reliability and reproducibility and was correlated with both meniscal and cartilage macroscopic lesions (rs = 0.68 and rs = 0.58, p < 0.001 respectively). Radiographic osteophytes of the medial femoral condyle gave the lowest agreements while being well correlated with the macroscopic osteophytes (rs = 0.64, p < 0.001). CONCLUSION: Non-invasive in vivo radiography of the rabbit femorotibial joint is feasible, relevant and allows a reproducible grading of experimentally induced OA lesion. The radiographic grading scale and atlas presented could be used as a template for in vivo non invasive grading of ROA in preclinical studies and could allow future comparisons between studies.