EXPERIMENTAL INVESTIGATION OF CERTAIN INTERNAL CONDENSING AND BOILING FLOWS: THEIR SENSITIVITY TO PRESSURE FLUCTUATIONS AND HEAT TRANSFER ENHANCEMENTS

Space-based (satellite, scientific probe, space station, etc.) and millimeter – to – microscale (such as are used in high power electronics cooling, weapons cooling in aircraft, etc.) condensers and boilers are shear/pressure driven. They are of increasing interest to system engineers for thermal management because flow boilers and flow condensers offer both high fluid flow-rate-specific heat transfer capacity and very low thermal resistance between the fluid and the heat exchange surface, so large amounts of heat may be removed using reasonably-sized devices without the need for excessive temperature differences. However, flow stability issues and degradation of performance of shear/pressure driven condensers and boilers due to non-desirable flow morphology over large portions of their lengths have mostly prevented their use in these applications. This research is part of an ongoing investigation seeking to close the gap between science and engineering by analyzing two key innovations which could help address these problems. First, it is recommended that the condenser and boiler be operated in an innovative flow configuration which provides a non-participating core vapor stream to stabilize the annular flow regime throughout the device length, accomplished in an energy-efficient manner by means of ducted vapor re-circulation. This is demonstrated experimentally. Second, suitable pulsations applied to the vapor entering the condenser or boiler (from the re-circulating vapor stream) greatly reduce the thermal resistance of the already effective annular flow regime. For experiments reported here, application of pulsations increased time-averaged heat-flux up to 900 % at a location within the flow condenser and up to 200 % at a location within the flow boiler, measured at the heat-exchange surface. Traditional fully condensing flows, reported here for comparison purposes, show similar heat-flux enhancements due to imposed pulsations over a range of frequencies. Shear/pressure driven condensing and boiling flow experiments are carried out in horizontal mm-scale channels with heat exchange through the bottom surface. The sides and top of the flow channel are insulated. The fluid is FC-72 from 3M Corporation.

The Shelhigh No-React bovine internal mammary artery: a questionable alternative conduit in coronary bypass surgery?

BACKGROUND: Increasing age and comorbidities among patients undergoing coronary artery bypass surgery (CABG) stimulates the exhaustive research for alternative grafts. No-React treatment should render the tissue resistant against degeneration and reduce early inflammatory response. The aim of the present study was an invasive assessment of the patency of No-React bovine internal mammary artery (NRIMA grafts) used as bypass conduit in CABG surgery. PATIENTS AND METHODS: Nineteen NRIMA grafts were used in 17 patients (2.9%) out of a total of 572 patients undergoing CABG surgery within a 12-month period. All intraoperative data were assessed and in-hospital outcome was analysed. Follow-up examination was performed 7.0+/-4.0 months after initial surgery, including clinical status and coronary angiography to assess patency of the NRIMA grafts. RESULTS: Average perioperative flow of all NRIMA grafts was 71+/-60 ml/min. One patient died in hospital due to a multi-organ failure. Four patients refused invasive assessment. Follow-up was complete in 12 patients with overall 13 NRIMA grafts. Nine NRIMA grafts (69.2%) were used for the right coronary system, two NRIMA grafts (15.4%) on the LAD and two on the circumflex artery. Graft patency was 23.1% and was independent of the intraoperative flow measurement. CONCLUSIONS: NRIMA grafts show a very low patency and cannot be recommended as coronary bypass graft conduits. Patency was independent of the perioperative flow, assessed by Doppler ultrasound. Because of this unsatisfying observation, this type of graft should be utilised as a last resource conduit and used only to revascularise less important target vessels, such as the end branches of the right coronary artery.

Non-robotic thoracoscopic internal mammary artery preparation in the pig. A training model

Notwithstanding non-robotic, thoracoscopic preparation of the internal mammary artery (IMA) is a difficult surgical task, an appropriate experimental training model is lacking. We evaluated the young domestic pig for this purpose. Four domestic female pigs (30-40 kg body weight) were used for this study. Bilateral thoracoscopic preparation of the IMA was carried out under continuous, pressure controlled CO(2) insufflation. A 30 degrees rigid thoracoscope was inserted through a 10-mm port in the 5th/6th intercostal space (ICS) dorsally to the posterior axillary line. The dissection instrument (Ultracision Harmonic Scalpel) was inserted (5-mm port) in the 7th ICS at the posterior axillary line and the endo-forceps (5-mm port) in the 5th ICS at the posterior axillary line. Thoracoscopic IMA preparation in pig resulted more difficult than in man. A total of seven IMAs were prepared in their full intrathoracic length. A change in the preparation technique (lateral detachment of the endothoracic muscle) improved the safety of the procedure, allowing all four respective IMAs to be prepared safely, while the initial technique ensued an injury for 2 out of 3 vessels. The described young domestic pig model is suitable for experimental training of bilateral thoracoscopic IMA preparation.

Stability after bilateral sagittal split osteotomy advancement surgery with rigid internal fixation: a systematic review

PURPOSE: The purpose of this systematic review was to evaluate horizontal relapse and its causes in bilateral sagittal split advancement osteotomy (BSSO) with rigid internal fixation of different types. MATERIALS AND METHODS: A search of the literature was performed in the databases PubMed, Ovid, Cochrane Library, and Google Scholar Beta. From 488 articles identified, 24 articles were finally included. Six studies were prospective, and 18 were retrospective. The range of postoperative study records was 6 months to 12.7 years. RESULTS: The short-term relapse for bicortical screws was between 1.5% and 32.7%, for miniplates between 1.5% and 18.0%, and for bioresorbable bicortical screws between 10.4% and 17.4%, at point B. The long-term relapse for bicortical screws was between 2.0% and 50.3%, and for miniplates between 1.5% and 8.9%, at point B. CONCLUSIONS: BSSO for mandibular advancement is a good treatment option for skeletal Class II, but seems less stable than BSSO setback in the short and long terms. Bicortical screws of titanium, stainless steel, or bioresorbable material show little difference regarding skeletal stability compared with miniplates in the short term. A greater number of studies with larger skeletal long-term relapse rates were evident in patients treated with bicortical screws instead of miniplates. The etiology of relapse is multifactorial, involving the proper seating of the condyles, the amount of advancement, the soft tissue and muscles, the mandibular plane angle, the remaining growth and remodeling, the skill of the surgeon, and preoperative age. Patients with a low mandibular plane angle have increased vertical relapse, whereas patients with a high mandibular plane angle have more horizontal relapse. Advancements in the range of 6 to 7 mm or more predispose to horizontal relapse. To obtain reliable scientific evidence, further short-term and long-term research into BSSO advancement with rigid internal fixation should exclude additional surgery, ie, genioplasty or maxillary surgery, and include a prospective study or randomized clinical trial design with correlation statistics.

Human internal thoracic arteries from diabetic patients are resistant to endothelial dysfunction

The aim of this analysis was to compare vasoreactive properties of internal thoracic arteries (ITA) grafts from diabetic (DM) to those of non-diabetic (ND) patients. Ring segments of ITA, taken from patients undergoing coronary artery bypass grafting, were suspended in organ bath chambers filled with modified Krebs-Henseleit solution and contractile responses to potassium chloride (KCl), noradrenaline (NA), endothelin-1 (ET-l), and endothelium-dependent relaxant responses to acetylcholine (ACH) were recorded isometrically. The receptor-mediated agonists NA and ET-1 stimulated ITA from both groups within similar concentration ranges while ITA from DM patients proved to be significantly more sensitive to KCl than ITA from ND. Furthermore, maximal contractile responses indicated that KCl (3.79 +/- 0.30 g, n = 7 in DM and 2.50 +/- 0.23 g, n = 29 in ND, P < 0.05) evoked significantly higher responses in ITA from DM as compared to the ND control group while both NA and ET-l stimulated ITA from both groups with similar efficacies. Endothelium-dependent relaxant responses to ACH proved to be similar in both groups when expressed as percentages of the pre-existing tone. The present data support the contention that in comparison to ND controls arteries from DM patients are more sensitive to depolarization but endothelial dysfunction is less frequent in human ITA than expected from observations in systemic vascular beds.

Experience and attitudes towards CAM--a survey of internal and psychosomatic patients in a German university hospital

Complementary and alternative medicine (CAM) is popular in Germany. In a consecutive survey the experiences with CAM and the need for a CAM consultation among inpatients of the departments of cardiology (CL), gastroenterology (GE), oncology (OL) and psychosomatics (PS) of the University Hospital Freiburg (FUH) were questionned. Exclusion criteria were inability to understand the questions or a Karnofsky Index < 30%. Four hundred thirty-five patients were included. Three hundred and fifty patients, 100 each in the departments of CL, GE and OL, and 50 in PS answered the questionnaires. Eighty-five patients (20%) refused. Among the 350 patients 26% had previously visited a CAM physician and 19% had visited a CAM therapist (Heilpraktiker). Information about CAM was obtained mainly by television, radio and family members. Frequently used therapies for the current disease were physical training (21%), diet (19%), massage (19%), vitamins/trace elements (19%), herbs (13%), acupuncture (10%) and homeopathy (7%). The highest frequency of CAM use had PS patients, followed by GE, OL and CL patients. High effectivity (> or = 70%) for the current disease, rated on a scale of 4 degrees, had for CL patients physical exercise and massage, for GE patients herbal treatment and for OL patients diet. Physical exercise, diet, massage and herbal treatment generally had better ratings than homeopathy, acupuncture and vitamins. 65% would welcome a CAM center and 53% asked for a consultation about CAM at FUH. OL and GE patients had the strongest (58%), PS patients a lower (52%) and patients with cardiovascular diseases the lowest (43%) interest in a CAM consultation. Twenty-five percent believed, that CAM can help to cope better with their disease. Predictors for a positive attitude towards CAM were young age, aversion to chemical medications (Spearman correlation r = 0.22), desire to participate in therapeutic decisions (r = 0.29), motivation to change, if recommended, the life style (r = 0.31) and desire for a holistic treatment (r = 0.37).