Estimation of the physical properties of nanocomposites by finite-element discretization and Monte Carlo simulation.

This paper reviews and enhances numerical models for determining thermal, elastic and electrical properties of carbon nanotube-reinforced polymer composites. For the determination of the effective stress-strain curve and thermal conductivity of the composite material, finite-element analysis (FEA), in conjunction with the embedded fibre method (EFM), is used. Variable nanotube geometry, alignment and waviness are taken into account. First, a random morphology of a user-defined volume fraction of nanotubes is generated, and their properties are incorporated into the polymer matrix using the EFM. Next, incremental and iterative FEA approaches are used for the determination of the nonlinear properties of the nanocomposite. For the determination of the electrical properties, a spanning network identification algorithm is used. First, a realistic nanotube morphology is generated from input parameters defined by the user. The spanning network algorithm then determines the connectivity between nanotubes in a representative volume element. Then, interconnected nanotube networks are converted to equivalent resistor circuits. Finally, Kirchhoff's current law is used in conjunction with FEA to solve for the voltages and currents in the system and thus calculate the effective electrical conductivity of the nanocomposite. The model accounts for electrical transport mechanisms such as electron hopping and simultaneously calculates percolation probability, identifies the backbone and determines the effective conductivity. Monte Carlo analysis of 500 random microstructures is performed to capture the stochastic nature of the fibre generation and to derive statistically reliable results. The models are validated by comparison with various experimental datasets reported in the recent literature.

Cardiovascular risk factor(s) prevalence in Greek hypertensives. Effect of gender and age.

The aim of this study was to determine cardiovascular (CV) risk factors (RFs) and target organ damage clustering in 21280 Greek hypertensives stratified by gender and age. Glycemic and lipid profile were determined, left ventricular mass index, estimated gromerular filtration rate (eGFR), 10-years CV risk according to Framingham risk score (FRS) and HeartScore (HS) were calculated. Only 10.2% of patients had no concomitant RFs, 53.1% had one (48.8% dyslipidemia, 3.4% smoking, 0.9% diabetes), 32.9% had two (26% dyslipidemia and smoking, 6.6% dyslipidemia and diabetes, 0.3% smoking and diabetes) and 3.7% had all four traditional RFs. Obesity was present in 30%, metabolic syndrome in 38%, low eGFR in 24% and left ventricular hypertrophy in 49%. Mean FRS risk was 35% for males, 24.1% for females whereas in high risk (>20%) were 68.7 and 50.7%, respectively (P<0.0001). Mean HS risk was 8.4% for males, 6.2% for females whereas in high risk (>5%) were 48.6 and 36.2%, respectively (P<0.0001). Age was correlated to pulse pressure, eGFR, left ventricular mass index and CV risk (P<0.0001). Ageing increased the risk difference between genders for total (P=0.001) but not for fatal events (P=nonsignificant). In conclusion, as RFs cluster in hypertensives, CV risk calculation should guide treatment decisions.

The effect of milrinone on metabolism after cardiopulmonary bypass.

AIM: The aim of this study was to examine the effects of milrinone on tissue metabolism perioperatively in cardiac surgery patients using extracorporeal circulation, in comparison to adrenaline and placebo. These effects were measured indirectly by measuring serum lactate, base excess and glucose levels at standard intervals. METHODS: Seventy-seven consecutive patients, who underwent elective cardiac surgery, were allocated in 3 groups. Inotropic support was initiated coming off CPB (cardiopulmonary bypass) if there was evidence of hypotension (mean arterial pressure [MAP] <60 mmHg), after adequate preload (pulmonary capillary wedge pressure [PCWP] >10 mmHg). Milrinone was used in patients with pulmonary hypertension (MPAP >20 mmHg). Group 1 (N.=26) received no inotropes, placebo. Group 2 (N.=32) received adrenaline. Group 3 (N.=19) received adrenaline + milrinone at 0.5 microg/kg/min infusion. Adrenaline was infused at a variable dose (0.01-0.02 microg/kg/min) to achieve a MAP >60 mmHg. The serum lactate, base excess and glucose levels were measured at standard intervals in all 3 groups. Diabetic, hepatic or renal failure patients (serum creatinine >2 mg/dL), were excluded from the study. Patient demographic and clinical characteristics were similar in all 3 groups. RESULTS: Repeated measure analysis of variance between groups showed significantly lower serum lactate levels and higher base excess in the milrinone group (P<0.05), after 2 to 4 hours of treatment. Serum glucose levels were higher in the adrenaline group (P=0.01). There were no immediate complications, morbidity or mortality in the study groups. CONCLUSION: These findings suggest that milrinone has a beneficiary effect on aerobic tissue metabolism after extracorporeal circulation, reflected on serum lactate, base excess and glucose levels, possibly due to a combination of positive inotropic and peripheral vasodilatory effect of the drug.

The supportive value of pre-bypass L-glutamate loading in patients undergoing coronary artery bypass grafting.

AIM: Experimental studies have demonstrated that an exogenous supply of glutamate improves mechanical function and recovery of ischemic myocardium. The aim of the present study was to investigate the effect of myocardial pre-bypass loading with glutamate on myocardial protection during global ischemia and reperfusion of patients undergoing coronary artery bypass grafting (CABG). METHODS: The study was double blinded. Twenty patients undergoing elective CABG were randomized to receive L-glutamate (n = 10) or normal saline (n = 10). Intracellular levels of glutamate, ATP and lactate were measured in left ventricular biopsies collected 10 min after aortic clamp release. Hemodynamic data, and postoperative release of CK-MB and troponin T were also measured. RESULTS: Pre-bypass administration of glutamate resulted in myocardial glutamate loading since glutamate levels were significantly higher in the glutamate group of patients than in controls (18.6 +/- 3.1 versus 8.7 +/- 1.2 microg/g tissue, P < 0.001). In the same group ATP levels were also significantly higher (2.4 +/- 0.7 versus 1.5 +/- 0.4 microg/g tissue, P < 0.05) and lactate levels significantly less than in controls (6.9 +/- 1.9 versus 12.0 +/- 2.1 microg/g tissue, P < 0.001). Glutamate patients had statistically significantly superior post-bypass hemodynamic performance (cardiac index, left ventricular stroke work index, systemic vascular resistance and pulmonary vascular resistance). Statistically significantly lower levels of CK-MB (6 h postoperative), total and peak CK-MB, troponin T (24 h postoperative), and total troponin T were found in the glutamate group. CONCLUSIONS: The results of this preliminary study indicate that pre-bypass intravenous administration of glutamate in patients undergoing CABG has a supportive effect on myocardial metabolism during global ischemia and reperfusion, improves patients' postoperative hemodynamic performance and reduces postoperative cardiac enzyme release.

A comprehensive approach to enhancing sexual health education in the Case Western Reserve University School of Medicine.

We report on the Sexual Health Curriculum Enhancement project at Case Western Reserve University School of Medicine. Using a US dollars 100000 grant from Pfizer Pharmaceuticals, Inc., we have developed and are in the process of implementing a comprehensive, cross-disciplinary and innovative curriculum that is based on three primary objectives for teaching sexual health: attitude change, behavior change, and knowledge acquisition. Five general strategies to incorporate specific sexual health content into the medical school curriculum have been implemented: (1). Faculty Development; (2). Additional Didactics; (3). Cased-Based Learning; (4). Testing and Assessment; and (5). Electronic (Computer/Web-Based Enhancements).

Constrictive pericarditis after coronary artery bypass surgery as a cause of unexplained dyspnea: a report of five cases.

Constrictive pericarditis after coronary artery bypass grafting (CABG) is rare and can present as unexplained dyspnea. We report five consecutive cases of post-CABG constrictive pericarditis seen within a period of 17 months at our institution. All patients presented with heart failure of unknown etiology within a period of 8-84 months after surgery. During the initial post-CABG period, two patients had developed postcardiotomy syndrome that was successfully treated with steroids. They were all assessed noninvasively and invasively. In all patients, the diagnosis of constriction was initially suspected clinically (symptoms, high jugular venous pressure with deep "X" and "Y" descents, pericardial knock). Echocardiography showed transmitral flow typical of constriction in all patients and hepatic venous flow in two. Two patients showed rapid left ventricular relaxation. In all patients, hemodynamic assessment showed diastolic equalization of pressures in all chambers, "W" shape waveform in right atrial pressure, and "dip and plateau" configuration in right and left ventricular pressure waveforms. Diagnosis was confirmed surgically in four patients who were subjected to pericardiectomy-pericardial stripping (three survived, one died). One patient refused surgery. We conclude that constrictive pericarditis, although rare, should be suspected in every case of unexplained dyspnea post CABG. It can appear early or late after surgery, and clinical examination plays an important role in its early recognition. It requires a full noninvasive and invasive assessment in case of clinical suspicion.

Pathogenesis of aortoenteric fistula. An experimental study.

The pathogenesis of aortoenteric fistulas was studied in the experimental laboratory. In 23 dogs patch of woven dacron was interposed in the anterior wall of the infrarenal abdominal aorta. In two groups (I and II), the serosa denuded duodenal wall was sutured to an opening of the proximal anastomosis--creating a pseudoaneurysm--, with induction of staphylococcal bacteremia, without (group I) and with simultaneous administration of methicillin (group II) pre and postoperatively. In the remaining two groups (III and IV), the serosa stripped duodenal wall, was simply attached to overlay the intact proximal anastomosis, with induction of staphylococcal bacteremia, without methicillin in group II and with administration of methicillin without bacteremia in group IV. Aortoduodenal fistulas developed in 100% of animals in group I, 80% in group II and 14% in group III. No aortoduodenal fistula was observed in group IV. We conclude that mechanical factors have the decisive role for the formation of aortoenteric fistulas, especially the development of a false aneurysm, which subsequently ruptures into the duodenum or the bowel.

Prophylactic treatment with cimetidine after renal transplantation.

17 consecutive patients who underwent renal transplantation during the period 1979-1981 and were at risk of gastrointestinal hemorrhage were treated prophylactically with the histamine H2-blocker cimetidine without antacids. The incidence of gastrointestinal bleeding, the number of rejection episodes and graft survival were compared with 17 patients, who had received renal transplant during the period 1976-1978 and had not received cimetidine. The incidence of gastrointestinal hemorrhage was not reduced in the cimetidine-treated patients. In addition, cimetidine treatment neither increased the total number of rejection episodes nor changed the long-term graft survival. The results of this study indicate that cimetidine does not appear to be superior to antacids in the prevention of gastrointestinal bleeding in renal transplant recipients.

The effects of canrenoate K on corticosteroid biosynthesis in nephrectomized dogs.

There is evidence from in vitro experiments that spironolactone not only antagonises the peripheral effects of aldosterone but also inhibits the production of corticosteroids by the adrenals. However relevant data from clinical studies are contradictory probably because spironolactone action on the kidneys also activates other mechanisms, such as renin secretion and potassium retention, which are potent stimulants of the adrenal cortex and thus tend to compensate for the inhibition. To determine the inhibitory effect of spironolactone on the adrenals in isolation, three groups of nephrectomized dogs were studied. Steroidogenesis was stimulated either by angiotensin II, potassium, or ACTH infusion. Potassium canrenoate was administered i.v. bolus at the beginning of the experiment. All the groups showed a similar marked decrease in plasma renin activity (PRA). Plasma aldosterone and cortisol were stimulated by the appropriate stimulus but their increase was blunted after the canrenoate K administration. The altered response between the subgroups was statistically significant (P less than 0.05). Plasma progesterone increased after the administration of canrenoate K. The response difference between the respective subgroups was again statistically significant (P less than 0.05). Canrenoate K was rapidly eliminated from the systemic circulation. These data indicate that canrenoate K causes a partial inhibition of aldosterone and cortisol stimulated secretion but augments the plasma levels of the precursor progesterone, as would be expected following inhibition of specific steps of corticosteroid biosynthesis.

Inferior vena cava thrombosis due to migration of retained functionless pacemaker electrode.

Thrombosis of the inferior vena cava due to migration of a pacing wire has not been published previously. We describe such a complication due to migration of a retained pacemaker electrode. The distal cut end of the wire was found looped at the level of thrombosis of the inferior vena cava. The patient was treated initially with heparin and placed later on coumadin. Currently, he is doing well without any evidence of thromboembolism.

[Surgery of pulmonary hydatid diseases in childhood]. / Zur Chirurgie des Echinococcus cysticus der Lunge im Kindesalter.

Fourteen cases of hydatid cysts of the lung in childhood are reported. The lung organ constitutes the most frequent site of the disease in childhood. The possible pathogenetic factors and the complications such as rupture and suppuration of the cyst are described. Conservative surgical procedures are recommended. The value of prophylaxis against the disease in infants and young children is emphasised.

The significance of intraoperative ventricular fibrillation during aortic valve replacement.

The effect of the spontaneous occurrence of ventricular fibrillation during aortic valve replacement and coronary arterial perfusion was studied in a consecutive series of 361 such operations. All operations were performed in a standard manner before 1972. One fourth of the patients experienced ventricular fibrillation,and the early mortality rate of this group was significantly (p less than 0.005) higher 7.3 per cent) than in the nonfibrillating group (1.5 per cent). The total mortality rate was 3 per cent. However, late results among survivors of the operations showed no effect of fibrillation. These findings indicate that ventricular fibrillation should be avoided in these patients. Whether or not countershock is advisable if and when fibrillation occurs remains an unanswered question.

Repair of atrioventricular canal associated with membranous subaortic stenosis.

The successful repair of associated atrioventricular canal anomaly and membranous subaortic stenosis is reported for the first time in two patients. Although subaortic stenosis associated with atrioventricular canal anomaly has been reported previously, it was caused by anomalous positioning of the atrioventricular valve, so that the discrete membranous type of stenosis in these two patients is the unique feature. Awareness of the possible association of these two deformities should enable accurate preoperative diagnosis and simultaneous correction at operation.

Pulmonary resection for metastatic osteogenic sarcoma.

A retrospective analysis of thirty patients who underwent pulmonary resection for metastatic osteosarcoma over a twenty-eight-year period revealed that most were young males with previous amputations for primary lesions of the lower extremity. In each, one to four thoracotomies had been performed, for a total of fifty-two chest operations with resection of 124 pulmonary metastatic lesions. At last follow-up, eleven of the thirty patients were alive and free of disease. At five years 28 per cent had survived: three of them were alive at more than nine years, and one was alive at nearly twenty years. Adverse survival factors identified were short tumor-free interval and multicentricity of pulmonary metastases. Long-term survival was associated with a tumor-free interval of more than two years and one to four thoracotomies at which few foci were present. As a group, patients selected for lung resection had significantly longer suvival than did patients whose pulmonary metastasis was untreated.

The management of infected abdominal aortic grafts and graft-enteric fistulas.

Seven cases of infected aortic grafts or aorto-enteric fistulas following resection of an abdominal aortic aneurysm are reviewed. All cases were treated with axillo-femoral bypass and graft removal. Patients had recurrent fever, chills, and abdominal pain (5 patients), or massive gastrointestinal hemorrhage (2 patients). The two patients with massive gastrointestinal hemorrhage died. Three of the 5 long-term survivors had a recurrence of the retroperitoneal abscess after graft removal; one of these died. One axillo-femoral bypass graft required early thrombectomy. There have been no subsequent problems with any of the grafts in the 2.5 to 4 year followup period. Axillo-femoral bypass immediately before graft removal is the treatment of choice for infected or fistulous aortic grafts. Any delay in graft removal after the onset of symptoms should be avoided.

Successful transplantation of ectopic kidneys from living related donors.

Two ectopic pelvic kidneys were transplanted from living donors into well matched recipients. Both kidneys have good function at two and four years post transplantation and there has been no evidence of infection post transplantation. Such kidneys can be utilized when there is no evidence of obstruction or infection in the donor and when the contralateral kidney is normal.