A SIMS study of cation and anion diffusion in tantalum oxide.

Ion transport in ceramics of the low-temperature phase of tantalum pentoxide, L-Ta2O5, was examined by means of diffusion experiments and subsequent analysis of diffusion profiles with time-of-flight secondary ion mass spectrometry (ToF-SIMS). 18O/16O isotope anneals were used to investigate oxygen diffusion, and oxygen tracer diffusion coefficients were obtained for the temperature range of 623 ≤ T/K ≤ 873 at an oxygen partial pressure of pO2 = 0.2 bar and for the oxygen partial pressure range of 10-2 ≤ pO2/bar ≤ 100 at a temperature of T = 723 K. Cation diffusion in Ta2O5 was probed by using chemically similar niobium as the diffusant (in the absence of stable tantalum isotopes). Thin films of Nb2O5 were deposited onto Ta2O5 ceramics; diffusion anneals yielded niobium diffusion coefficients for the temperature range of 1073 ≤ T/K ≤ 1223 at an oxygen partial pressure of pO2 = 0.2 bar. Comparison of the measured diffusion coefficients strongly suggests that oxygen is many orders of magnitude more mobile than niobium in L-Ta2O5 at these temperatures and at pO2 = 0.2 bar. The electrical conductivity was also determined in the range 950 ≤ T/K ≤ 1200 and 10-23 ≤ pO2/bar ≤ 10-2. Considered together with the measured diffusion coefficients, the conductivity data indicate that under oxidising conditions conduction is due to oxygen ions above T = 1090-1130 K and due to electron holes below this temperature range. Point-defect models are presented that are consistent with these transport data and with conductivity data in the literature. They suggest that under oxidising conditions oxygen interstitials are the majority ionic charge carriers in L-Ta2O5. The implications for resistive switching devices are discussed.

Thermodynamic Ground States of Complex Oxide Heterointerfaces.

The formation mechanism of 2-dimensional electron gases (2DEGs) at heterointerfaces between nominally insulating oxides is addressed with a thermodynamical approach. We provide a comprehensive analysis of the thermodynamic ground states of various 2DEG systems directly probed in high temperature equilibrium conductivity measurements. We unambiguously identify two distinct classes of oxide heterostructures: For epitaxial perovskite/perovskite heterointerfaces (LaAlO3/SrTiO3, NdGaO3/SrTiO3, and (La,Sr)(Al,Ta)O3/SrTiO3), we find the 2DEG formation being based on charge transfer into the interface, stabilized by the electric field in the space charge region. In contrast, for amorphous LaAlO3/SrTiO3 and epitaxial γ-Al2O3/SrTiO3 heterostructures, the 2DEG formation mainly relies on the formation and accumulation of oxygen vacancies. This class of 2DEG structures exhibits an unstable interface reconstruction associated with a quenched nonequilibrium state.

Genetic polymorphisms of TP53 and FAS promoter modulate the progression of coronary artery disease after coronary artery bypass grafting: a gender-specific view.

INTRODUCTION: Progression of coronary artery disease (CAD) after primary coronary artery bypass grafting (CABG) is frequent and may lead to recurrent symptoms. Various data indicate that apoptosis is the main event occurring during development and progression of atherosclerotic plaque. Plaque vascular smooth muscle cells (VSMCs) are more sensitive than regular VSMCs to TP53-mediated apoptosis. METHODS: We investigated EDTA blood of 192 patients (18% female, age 60.9 ± 7.4 years) who had primary CABG more than 5 years ago. CAD progression was defined as clinical endpoints: re-operation (n = 88; 46%), catheter re-intervention (n = 58; 30%), or angina at follow-up (n = 89; 46%). Apoptotic gene polymorphisms (Toll-like receptor 2 A753G, FAS ligand C-844T, FAS promoter G-670A, TP53 Arg72Pro, and CD14 C-260T) were investigated by PCR-RFLP and compared to healthy controls (n = 200, 24% female, age 63.4 ± 5.4). Gender-specific analysis was carried out. RESULTS: Heterozygous, homozygous and wild-type expression of all five genetic polymorphisms showed almost identical distribution between patients with CAD and healthy controls. Looking at clinical endpoints, with GG expression of Toll-like receptor 2 polymorphism and GG expression of FAS promoter polymorphism, results showed a relative increased risk (p = 0.09) for recurrent symptoms and re-intervention. Patients with FAS promoter polymorphism with AA expression had an increased risk of suffering from recurrent symptoms (n = 28, p = 0.04). We found that patients with homozygous expression of TP53 polymorphisms (n = 3, all male) were prone to needing re-intervention after prior CABG (p = 0.03), but not re-operation. Over a period up to 15 years, the re-intervention rate was significantly different in homozygous genotypes of FAS LG, FAS promoter and TP53. CONCLUSIONS: Patients presenting with polymorphisms of FAS LG, FAS promoter and TP53 have an increased risk of CAD progression, as they have a higher rate of re-interventions.

Omental flap for recurrent deep sternal wound infection and mediastinitis after cardiac surgery.

BACKGROUND: Unsuccessful surgical treatment of deep sternal wound infection (DSWI) and mediastinitis may lead to sepsis, multiorgan failure and death. Omental flap transposition (OFT) may, in this situation, be the only effective therapy. METHODS: Twenty-seven patients with DSWI and mediastinitis after one or more unsuccessful surgical attempts to cure the infection were treated by OFT. Forty-one interventions (1.5/patient) consisting of closed irrigation technique, bilateral pectoralis flap reconstruction and vacuum-assisted therapy were performed before carrying out OFT. RESULTS: Operative mortality was 0. Mean postoperative ventilation time was 1.38 days and mean time in the intensive care unit was 4.7 days. Hospital mortality was 7.4 % (n = 2). Mean follow-up time was 2 years. One patient (4 %) died one year after discharge. During follow-up, abdominal wall hernia occurred in one patient (4 %) and presternal fistula resection was necessary in another patient (4 %). CONCLUSION: OFT is, in our experience, the most effective procedure for the treatment of recurrent DSWI and mediastinitis after cardiac surgery. Early mortality is acceptable, morbidity is low and late results are very good.

Aberrant origin of the left main coronary artery arising from the right coronary artery associated with coronary artery disease: a case report.

Coronary artery anomalies are not frequent, nevertheless they are associated with increased and potentially lethal cardiac events. Recognition of these anomalies is fundamental in patients undergoing diagnostic or interventional coronary angiography. Most patients presenting with coronary anomalies are asymptomatic, but the risk of myocardial ischemia and sudden death requires the treatment of those patients. Different therapeutic options have been discussed, including surgery, conservative therapy, and interventional approaches. In this report, an aberrant origin of the left main coronary artery arising from the right coronary artery associated with coronary artery atherosclerosis and its surgical correction is described.

Contrast enhanced ultrasound and Dual Source CT of left atrial myxoma.

PURPOSE: Myxomas of the left atrial cavity of the heart are a rare occurrence. Incidental diagnosis is mostly based on transthoracic echocardiography. Contrast enhanced ultrasound (CEUS) seems to be a promising new diagnostic option for diagnosis and preoperative planning of treatment for patients with myxoma. It is an additional examination to baseline ultrasound and CT or MRT. MATERIALS AND METHODS: We report a case of a 63-year-old woman with myxoma of the left atrial cavity of the heart in which CEUS helped to define the location and its relation to the heart valve. RESULTS: In contrast enhanced ultrasound (CEUS), the oval mass in the left atrium was scanned in the 4-chamber view. Perfusion of the mass was examined by visualising gradual contrast enhancement. An involvement of the mitral valve could be excluded. The tumour base could be clearly depicted and differentiated from normal surrounding tissue. No thrombotic material was found in the left atrium (LA) or ventricle (LV). CONCLUSION: CEUS could detect the mass and offer additional information such as vascularity, mobility, attachment to the valve and possible thrombi. Dual Source CT (DSCT) confirmed the findings and provided a very clear morphological characterisation and dynamic evaluation of mobility and valve interference.

Arterial T-graft in coronary surgery: comparison of selective coronary angiography and multi-slice computed tomography.

BACKGROUND: The main aim of our study was to compare the results and value of angiography and multi-slice computed tomography (MSCT) after coronary artery bypass grafting using complex arterial conduit combinations. METHODS: Twenty-six patients underwent coronary surgery. In all patients, we utilized a T-graft (free arterial graft centrally implanted into the left internal thoracic artery IN SITU). Postoperative coronary angiography and MSCT were carried out prior to discharge. The results were interpreted separately by two different investigators. RESULTS: One hundred and thirteen distal anastomoses using 59 grafts for T-graft combinations were performed in 26 patients. A mean of 3.5 peripheral anastomoses was established per patient. Angiography showed a bypass graft patency rate of 94.6 % (56/59). In angiography, the patency rate of anastomoses was 96.5 % (109/113). All occlusions were identified in sequential anastomoses. The bypass patency rate measured by MSCT was 100 % and the patency rate of anastomoses 100 %. Based on these results, MSCT showed a sensitivity of 98.9 %. The specificity was 50.8 %, the positive predictive value was 94.6 % and the negative predictive value had a level of 99.9 %. CONCLUSION: MSCT is a simple, less invasive and useful method of monitoring results after coronary surgery including anastomosis and graft patency after complex arterial grafts. Its value may be restricted for sequential anastomoses and angiography should be preferentially used in these cases.

Minimally invasive off-pump pulmonary vein isolation to treat paroxysmal atrial fibrillation.

BACKGROUND: Minimally invasive off-pump pulmonary vein isolation to cure paroxysmal atrial fibrillation (PAF) may be an alternative to percutaneous catheter-based procedures. METHODS: Three patients with highly symptomatic lone PAF refractory to medical treatment and having undergone unsuccessful catheter-based ablation underwent pulmonary vein isolation using the Cardioblate BP device with a minimally invasive approach. RESULTS: There were no complications and all patients were discharged in sinus rhythm. Mean ablation time per lesion was 15.2 sec and mean operation time was 118 min. CONCLUSIONS: Irrigated bipolar radiofrequency ablation of the pulmonary veins is safe and can be performed off-pump in a minimally invasive manner.

Neurological and neuropsychological examination and outcome after use of an intra-aortic filter device during cardiac surgery.

Cerebral embolization of particles after cardiac surgery is frequently associated with neurological deficits. Aortic crossclamp manipulation seems to be the most significant cause of emboli release during cardiac surgery. The goal of this study was to demonstrate whether the use of an intra-aortic filter device has an effect on the magnet resonance imaging (MRI) and functional neurological outcome. Twenty-four patients undergoing cardiosurgical procedures using cardiopulmonary bypass (CPB) were selected: coronary artery bypass graft (CABG) surgery (n = 17), aortic valve replacement (AVR) surgery (n = 4) or combined procedures (n = 3). Patients were evaluated by diffusion weighted MRI of the brain, neurological examination and neuropsychological assessment regarding alertness as well as divided and selective attention before and five to seven days after surgery. The patients were divided into two groups. In group I, 12 patients received a filter through a modified 24 F arterial cannula immediately before the aortic crossclamp was released. Filters remained in the aorta until CPB was discontinued. Intraoperatively, bilateral middle cerebral artery transcranial Doppler (TCD) was monitored at baseline, at the beginning of CPB, at a timepoint when the aorta was crossclamped, when the filter was inserted and while the crossclamp was switched to partial clamping until the CPB was discontinued. TCD was used for detection of microembolic signals (MES). The captured material in the filter was examined histologically. Twelve patients served as controls without aortic filtration (group II). The MRI of the brain did not show any diffusion alterations in either group before or after surgery. No patient developed a focal neurological deficit or stroke. Intraoperative quantitative MES detection revealed a four to tenfold increase in patients of group I compared with group II (5-6 versus 0.5-1 MES/min) during the filter dwell time. There was no consistent pattern regarding the neurobehavioural sequelae. Filters showed arteriosclerotic debris in 75% of the patients. The use of the intra-aortic filter device did not show a positive effect on neurological, neuroradiographical and neuropsychological outcomes. The increase of the MES rate in group I patients may be due to microbubbles generated as microcavitations by the filter or the aortic filter cannula. The intra-aortic filter was able to capture atheromatous material in 75% of the patients.

Induced hypothermia during emergency department thoracotomy: an animal model.

BACKGROUND: Induced hypothermia is used clinically to prevent ischemic injury during elective procedures. We present an animal model of asanguinous hypothermic (10 degrees C) circulatory arrest, induced through a left anterior lateral thoracotomy after exsanguinating uncontrolled hemorrhage. METHODS: Through a left anterior thoracotomy, 26 swine (45-70 kg) sustained a laceration of the descending thoracic aorta, producing exsanguinating uncontrolled hemorrhage. After 5 minutes of severe hypotension (systolic BP <20 mm Hg), a 22 French Foley catheter was directed cephalad through the enlarged aortic wound. A solution (containing 42.5 mmol/L K+ and precooled to 1 degrees C) was infused to arrest/preserve the heart and brain. A second 24 French Foley catheter was then directed caudally through the same wound. The right atrium was opened to drain the venous system. The animal was cooled with a cardiopulmonary bypass pump (>5L/min) through the Foley catheters. Once 10 degree C was reached, a cannula was placed to the aortic root and the aortic laceration repaired. The animal was maintained at 10 degree C for a total of 90 minutes. Before the rewarming process, the circulation was rinsed with a solution containing normal levels of electrolytes followed by infusion of whole blood. Rewarming was performed by maintaining a 10-degree gradient on the heat exchanger. The first 16 animals were used in nonsurvival experiments to develop the technique and to record dural temperatures and electroencephalogram tracings. The last 10 animals were used to determine long-term survival and neurologic outcome. Group I: seven animals were kept at < 10 degrees C with flows less than 2L/min. Group II: three animals underwent 20, 30, and 40 minutes of no flow once they were cooled to 10 degrees C. After 6 weeks of survival and neurologic examinations, the brains were fixed for histologic evaluations. RESULTS: The average time to cool the head to 18 degrees C and 10 degrees C was 6 minutes and 12 minutes, respectively. The hematocrit fell below 2% by the end of the cooling period. A total of 7 of the 10 animals from the long-term study survived. Group I: five of seven animals survived. Four of the survivors had no appreciable neurologic deficits, were fully functional at 6 weeks, and had no evidence of histologic injury. One of the five survivors in this group had moderate neurologic disability. Of the two animals that died, one died from air embolism from the i.v. line. The second death was in an animal for which maximal cooling to 2.7 degrees C was attempted. Group II: The first two animals that had "no flow" for 20 and 30 minutes were fully functional and had normal neurologic examinations. However, the second animal was found to have brain injury on histologic examination. The last animal in this group died of accidental extubation during recovery. CONCLUSION: Induction of hypothermic arrest through the chest after exsanguination is possible. The further development of this technique may provide an extended state of "suspended animation" to allow for repairs of hemorrhaging injuries in trauma patients who require emergency department thoracotomy.

Prevalence of deep venous anomalies in congenital vascular malformations of venous predominance.

PURPOSE: The overall incidence of congenital vascular malformations in the general population is 1.5%. Approximately two thirds of them are malformations of venous predominance. Abnormalities of the deep venous trunks have been observed in association with large superficial compensatory varices in these type of malformations. Knowledge of the integrity of the deep venous system is important in their management because excision of the enlarged superficial veins may be deleterious if there is aplasia or hypoplasia of the deep venous trunks. The objective was to investigate the prevalence and nature of deep venous anomalies that occur in patients with congenital vascular malformations of venous predominance both in our series and in the series from the medical literature. METHODS: From the last 35 years of medical literature, we reviewed seven series of congenital vascular malformations that provided pertinent information on the subject of our study. We also reviewed our own series of 392 patients with congenital vascular malformations studied at Children's Hospital of Mexico City (1963-1983; n = 223 children) and at Walter Reed Army and National Naval Medical Centers (1984-1998; n = 169 children). Of 392 patients, 257 (65.5%) had malformations of venous predominance; these were the subject of our analysis. Prevalence of the following deep venous anomalies was recorded: phlebectasia, aplasia or hypoplasia of venous trunks, aneurysms, and avalvulia. Diagnosis was made by one or more of the following methods: Doppler scanning, duplex scanning, plethysmography, computerized tomography, magnetic resonance imaging, and angiography. RESULTS: At least one anomaly of the deep venous system was present in 47% of the congenital vascular malformations of venous predominance reviewed. Phlebectasia was recorded in 36% of the cases, and aplasia or hypoplasia of deep venous trunks was observed in 8% of the cases. Venous aneurysms also were present in 8% of the cases; avalvulia was recorded in 7% of the cases. CONCLUSION: Anomalies of the deep venous system occur in almost one half of congenital vascular malformations of venous predominance. The most common is the relatively innocuous phlebectasias that occur in over one third of cases. Aplasia/hypoplasia, venous aneurysms, and avalvulia were less frequent, each less than 10%; but failure to detect the latter three anomalies may lead to serious therapeutic errors.