Thermophysical properties for the solid and liquid phases of several Ni based superalloys (CMSX-4, CMSX-10, CM186LC, IN 738 and Rene 80) have been measured. The following properties were measured: heat capacity and enthalpy, thermal expansion coefficient and density, thermal diffusivity, viscosity and surface tension. Analysis of these measurements showed that that γ′ phase (Ni3Al) affected the values for the following properties; Cp, enthalpy, electrical resistivity, thermal diffusivity and conductivity. Relationships have been identified between properties and the γ′ phase content (which can be represented by mass% Al in the alloy). These relations were then used to calculate property values of the alloys from chemical composition. Other relations were developed to estimate the viscosities and surface tensions of Ni based superalloys. The predicted property values were found to be in good agreement with the measured values.

BACKGROUND:Metabolic bone disease is a potential complication of bariatric surgery. The aims of our study were to evaluate the effects of laparoscopic gastric bypass on calcium and vitamin D metabolism, and to identify patients at high risk to develop secondary hyperparathyroidism (HPT).METHODS:Serum calcium, alkaline phosphatase, intact parathyroid hormone (PTH), and 25-hydroxy (OH) vitamin D were measured at 3, 6, 12, and 24 months after laparoscopic gastric bypass in a cohort of morbidly obese women. Logistic regression was used in both univariate and multivariate models to identify independent preoperative variables associated with secondary HPT.RESULTS:The study enrolled 193 morbidly obese women. During the 2-year follow-up period, the incidence of elevated PTH levels (>65 pg/ml) was 53.3%. The mean time elapsed between surgery and detection of secondary HPT was 9.1 months (range, 3-24 months). Vitamin D deficiency was observed in 39 patients (20.2%). On univariate analysis, the preoperative factors associated with secondary HPT were race (high PTH levels were detected in 70% of African Americans versus 50% of Caucasians; p < 0.05), preoperative body mass index (BMI; high PTH: 52.5 +/- 10.8 versus normal PTH: 48.9 +/- 7.5 kg/m2; p < 0.01), and age (high PTH: 44.9 +/- 9.2 versus normal PTH: 42.3 +/- 9 years, p < 0.05). Race and age remained independent risk factors for secondary HPT in the multivariate logistic regression model after adjusting for the covariate Roux-limb length. African Americans were at more than 2.5 times greater risk to develop secondary HPT as Caucasian (RR 2.5; 95% CI: 1.03-6.17, p < 0.05). Patients older than 45 years were at 1.8 times higher risk of developing secondary HPT as their younger counterparts (RR 1.8; 95% CI: 1.01-3.32, p < 0.05).CONCLUSIONS:Morbidly obese women have a high incidence of elevated PTH levels after gastric bypass surgery. Low vitamin D levels did not constitute the only reason behind this finding. African-American women and women older than 45 years of age were at significantly higher risk of developing secondary HPT. In these populations, aggressive supplementation with calcium citrate and vitamin D should be implemented.

Background: Laparoscopic Roux-en-Y gastric bypass surgery (RYGB) was introduced at the authors' institution 5 years ago. The authors analyzed the short- and long-term results of this procedure compared with those for the same procedure using the laparotomy approach over the same period.Methods: Retrospective analysis of a prospectively collected bariatric database used the outcome end points used by the American Society of Bariatric Surgery (ASBS) and the American College of Surgeons (ACS) in their center of excellence programs.Results: From January 2001 to July 2005, 568 laparoscopic and 399 open gastric bypasses were performed at Vanderbilt University. The patients were from the same bariatric surgery program and therefore received the same pre- and postoperative care. The hospital length of stay in the laparoscopic group was significantly shorter (2.5 +/- 2.4 days) than in the open group (3.7 +/- 3.7 days; p = 0.001). The procedure time was significantly shorter in the laparoscopic group (164 +/- 50 min) than in the open group (195 +/- 50 min; p = 0.0001). The follow-up assessment response at 2 years was 76.6%. At 2 years, the excess weight loss (EWL) was significantly greater in the laparoscopic group (71.3% +/- 18.4%) than in the open group (67.3% +/- 15.3%; p = 0.03). The wound infection rate was significantly higher in open group (9.2%) than in the laparoscopic group (1.7%; p = 0.001). There was no significant difference in 30day mortality: open (0.50%) versus laparoscopic (0.17%; p = 0.371). There was no significant difference in the 30-day reoperation rate between the open (2.4%) and laparoscopic (2.6%; p = 0.705) groups. The 30-day readmission rate was similar in the open (5.0%) and laparoscopic (5.2%; p = 0.852) groups, as was the rate of leakage from the gastrojejunostomy in the open (0.50%) and laparoscopic (0.35%; p = 0.127) groups. The conversion rate from laparoscopic procedure to laparotomy was 1.7%.Conclusion: In the authors' institution, a laparoscopic bariatric surgery program with a very low rate of morbidity and mortality has been introduced. Operative time, hospital stay, and wound complications are reduced with the laparoscopic approach. The laparoscopic and open procedures are equally safe, with equivalent 30-day mortality, readmission, reoperation, and gastrojejunostomy leakage rates.

The optimization of a specimen design allowing the investigation of the biaxial strength of composite laminates over the full range of failure strain was the primary objective of this work. Multiaxial strength criteria are often found unreliable mainly as a result of the inherent complexity of biaxial tests and, in many cases, as a result of inefficient specimen designs. As a result of a development program combining numerical simulations and experimental measurements, a flat cruciform-shaped specimen has been developed for carbon fiber reinforced plastic (CFRP) laminates. The design fulfills the basic criteria for such a specimen, namely allowing for a uniform biaxial stress/strain state to exist in the gauge area and for testing the virgin material up to failure in both the tension-tension and tension-compression quadrants of the strain/stress space. The fabrication of the specimen is described and a three-step testing procedure for generating biaxial strength data is proposed. Typical results obtained from specimens of the proposed configuration tested in accordance with this procedure are presented. Results compare well with those obtained from tubular specimens, thus confirming the effectiveness of the proposed design. Experimental data obtained for the AS4/3501-6 carbon/epoxy composite system are finally compared against strength predictions of recognized failure theories.

Molding processes of fiber reinforced thermoplastic involve phase transformations of the matrix material under non-isothermal conditions. The rates and kinetics of these transformations control the final properties of the molded composites and affect the processing cycle time. Good understanding of these transformations would allow to optimize the composite properties while minimizing the process cycle. In this work, the effect of the addition of maleic anhydride modified polypropylene, mPP, on the crystallization behavior of polypropylene, PP, matrix in glass fiber/polypropylene composites was investigated.

Thermoplastic composite matrix material undergoes successive thermal phase transformations during the thermoforming process. The processing conditions control these transformations and hence are responsible for the final crystalline morphology, the inerface quality, the mechanical properties as well as for the residual stresses developed in the composites.The objective of this work was to develop a model in order to be able to predict the development of residual stresses during the molding process of the continuous glass fiber/polypropylene composites, PP/G. For this purposes, the classical lamination theory model was adapted in order to include temperature-dependent parameters and relaxation phenomena. Stress relaxation phenomena were taken into account by considering the viscoelastic behavior of the matrix and the transverse stress cracking in the composite plies. The model incorporates also the effect of thermal history and crystallization kinetics which are known to control the matrix microstructure and the interface quality of the composites.

Thermoplastic composite matrix material undergoes successive thermal phase transformations during the thermoforming process. The processing conditions control these transformations and hence are responsible for the final crystalline morphology, the interface quality, the mechanical properties as well as for the residual stresses developed in the composites.The objective of this work was to develop a model in order to be able to predict the development of residual stresses during the molding process of the continuous glass fiber/polypropylene composites, PP/G. For this purposes, process-induced residual stresses in thermoformed polypropylene/glass composite laminates have been experimentally evaluated by the measurement of cross-ply unsymmetric laminate curvatures. Two composite systems presenting different interfacial properties have been studied. Classical lamination theory model for residual stress prediction has been adapted to take into account the variation of the physical and mechanical properties of the matrix as a function of temperature and cooling rate and to account for stress relaxation either by the viscoelastic behavior of the matrix or by transverse cracking in the composite plies. This model incorporates the effect of the thermal history and processing kinetics (cooling rate) on the composite properties, particularly those controlled by the matrix microstructure and the interface quality.

The objective of this work was to characterize the microstructure, mechanical properties and residual stresses in glass fiber reinforced polypropylene (PP) composites with respect to the thermoforming parameters and as a function of the fiber-matrix interface quality. First, differential scanning calorimetry (DSC) was used to investigate the crystallization behavior of the PP matrix. Second, short beam shear tests and tensile tests in the ±45° directions have been conducted to characterize respectively the interfacial strength and the matrix properties in the composites. Finally, residual stresses were measured via the curvatures of unsymmetric cross-plied laminates. The cooling rate was found to be a critical parameter of the molding process since the matrix crystallization temperature, the interfacial strength as well as the residual stresses showed large variations with various cooling rates. At slow cooling, the crystallization process initiates at higher temperatures and covers longer time periods resulting in more spherulitical matrix structures. In this case, the composites becomes stiffer but also fragile indicating a decrease in the stress transfer efficiency at the interface level. This effect was also observed in the improved interface system, suggesting that the fiber-matrix interaction operates through the amorphous phase surrounding the fibers. The fiber-matrix interface improvement was accompanied by an increase in residual stresses, possibly due to the inhibition of some stress relief mechanism.

A technique of coronary surgical angioplasty is described. The long arteriotomy of the coronary artery over the stenosis is closed with the Internal Thoracic Artery (ITA) giving an enlargement patch effect. The majority of the atheromatous plaque is excluded from the lumen of the anastomosis and placed outside the suture line. The origin of the collateral arteries is preserved in the vascular lumen. The remodeled coronary artery is composed of a small gutter of native coronary artery and the whole surface of the ITA wall. In some cases, it is useful to associate a limited endarterectomy with the angioplasty. 66 surgical angioplasties have been performed in extensive coronary disease. Operative mortality was 5.4% with a myocardial infarction rate of 5.4%.

Reimplantation of the right internal thoracic artery, as a free graft, into the left in situ internal thoracic artery (Y procedure) has enabled us to bypass more distant marginal vessels, which was not possible by the bilateral technique alone. This prospective study was aimed at evaluating the clinical state of the patients and the degree of patency of grafts within 16 months of follow-up. All 80 patients who underwent the Y procedure between January 1988 and January 1992 were included. This group represented 10% of the 840 patients having coronary bypass during the same period. A total of 202 coronary anastomoses were performed in this series. Early postoperative (30 days) complications included three deaths (3.75%), eight myocardial infarctions (10%), one case of phrenic nerve paralysis (1.25%), two cases of respiratory failure (2.5%), and six wound infections (7.5%). At 3 months' follow-up, 96% of patients were free of symptoms. During the follow-up period, four patients died of noncardiac causes (lung, pancreatic, and brain cancer and rupture of an abdominal aortic aneurysm). At 1 year, 71 patients were free of symptoms (97%). Sixty-one patients underwent coronary angiography between 12 and 24 months. Six patients with peripheral arterial disease were not suitable for coronary angiography, and six refused to be tested. These 12 patients had normal thallium test results in the bypassed area (stress or dipyridamole test). The patency rate of the left internal thoracic artery was 98.3% (n = 60), occlusion rate 1.6% (n = 1), and incidence of threadlike arteries 4.9% (n = 3). Thus the rate of perfect patency was 93.4%. The patency rate of the right internal thoracic artery as a free graft was 93.4% (n = 57), occlusion rate 6.5% (n = 4), and the incidence of threadlike arteries 8% (n = 5). Thus the rate of perfect patency was 85.2%. A total of 169 anastomoses were studied. The rate of patency of the anastomoses to the left anterior descending coronary artery was 96% (n = 58) and the occlusion rate, 4% (n = 2). The patency rate of sequential anastomoses (side to side) to diagonal arteries was 100% (n = 16). Patency rate of anastomoses to obtuse marginal arteries was 95% (n = 58) and the rate of occlusion, 4.9% (n = 3). The patency rate of anastomoses to the posterior descending artery or distal branches of the right coronary artery was 80% (n = 4/5).(ABSTRACT TRUNCATED AT 400 WORDS)

A technique of coronary surgical angioplasty is described. The long arteriotomy of the coronary artery over the stenosis is closed with the Internal Thoracic Artery (ITA) giving an enlargement patch effect. The majority of the atheromatous plaque is excluded from the lumen of the anastomosis and placed outside the suture line. The origin of the collateral arteries is pre served in the vascular lumen. The remodeled coronary artery is composed of a small gutter of native coronary artery and the whole surface of the ITA wall. In some cases, it is useful to associate a limited endarterectomy with the angioplasty. 66 surgical angoplasties have been performed in extensive coronary disease. Operative mortality was 5.4% with a myocardial infarction rate of 5.4%.

A technique of coronary surgical angioplasty is described. At the level of the stenosis the arteriotomy of the coronary artery is closed with the internal thoracic artery giving an enlargement patch effect. The major surface of the atherome plaque is excluded from the lumen of the anastomosis and put outside the suture line. The origins of the collateral arteries are kept in the vascular lumel. So the new remodeled coronary artery is formed with a small gutter of native coronary artery and the whole surface of the internal thoracic artery wall. In some cases it is useful to associate a limited endarterectomy to the angioplasty. Sixty-six surgical angioplasties have been done in extensive coronary disease. Operative mortality was 5.4% and myocardial infarction 5.4%.

The optimization of a specimen design allowing the investigation of the biaxial strength of composite laminates over the full range of failure strain was the primary objective of this work.Multiaxial strength criteria are often unreliable mainly due to the inherent complexity of biaxial tests and to inefficient specimen designs.Guided by a combination of numerical simulations and experimental measurements, a flat cruciform-shaped specimen configuration has been fabricated with AS4/3501-6 laminates which fulfills three basic criteria namely, homogeneous stress/strain state in the gauge area, the possibility of allowing various biaxiality ratios to develop and the ultimate failure in the virgin material of the gauge area in the tension-tension and tension-compression quadrants of the strain/stress space.The results of a typical biaxial test are discussed to demonstrate the adequacy of the specimen design for strength data generation with composite laminates under biaxial loading conditions.