Investigation of the changes in hydrogen bonding accompanying the structural reorganization at 103†K in ammonium iodate.

Neutron powder diffraction has been used to observe the changes in hydrogen bonding that occur as a function of temperature in ND4IO3 and, thus, determine the structural features that occur during the low-temperature (103 K) phase transition. It is shown that in the deuterated material the change is not a phase change per se but rather a structural reorganization in which the hydrogen bonding becomes firmly locked in at the phase transition temperature, and stays in this configuration upon further cooling to 4.2 K. In addition, both the differences and changes in the axial thermal expansion coefficients in the region 100-290 K can be explained by the changes involving both the hydrogen bonding and the secondary I...O halogen bonds.

New insights into the phase diagram of a magnetic perovskite, LaCo1/3Mn2/3O3.

We report the crystal structure of the orthorhombic perovskite LaCo1/3Mn2/3O3 as determined by neutron diffraction from 5-300 K. A high-temperature x-ray diffraction study is also reported from 290-900 K. At temperatures above 570 K, LaCo1/3Mn2/3O3 transforms to a rhombohedral structure with space group R3̄c. This rhombohedral phase is also observed in the material at high pressure and the crystal structure has been determined by in situ neutron diffraction at 4.7 GPa. Finally, the ferromagnetic behaviour has been determined by magnetometry and the magnetic structure has been determined using low temperature neutron diffraction at ambient pressure.

From quantum disorder to magnetic order in an s=1/2 kagome lattice: a structural and magnetic study of herbertsmithite at high pressure.

The structural and magnetic properties of deuterated herbertsmithite have been studied by means of neutron powder diffraction and magnetic susceptibility measurements in a wide range of temperatures and pressures. The experimental data demonstrate that a phase transition from the quantum-disordered spin-liquid phase to the long-range ordered antiferromagnetic phase with the Néel temperature T(N)=6 K is induced at P=2.5 GPa. The observed decrease of T(N) upon compression correlates with the anomalies in pressure behavior of Cu-O bond length and Cu-O-Cu bond angles. The reasons for the observed spin-freezing transition are discussed within the framework of the available theoretical models and the recent observation of the field-induced spin freezing.

High-pressure powder neutron diffraction study on lead scandium niobate.

The structural evolution of PbSc(0.5)Nb(0.5)O(3) (PSN) under pressure has been studied by in situ powder neutron diffraction. Rietveld refinements to the data show that the continuous phase transition detected by x-ray diffraction at p(c) = 4.1 GPa (Maier et al 2010 Phys. Rev. B 81 174116) is associated with long-range ordering of antiphase octahedral tilts and local ordering of ferroic Pb displacements. Similar to PbSc(0.5)Ta(0.5)O(3) (PST) (Maier et al 2010 Acta Crystallogr. 66 280-91), antiphase octahedral tilting even exists below the critical pressure in a regime in which the structure retains a cubic metric. In contrast to PST, in which the Pb atomic displacement parameters (DPs) form ellipsoids elongated along the cubic {111} directions, the atomic DPs of Pb in PSN form flattened discs parallel to the cubic {111}-planes. This indicates that in PST the Pb displacements are along the cubic {111} directions, whereas in PSN the local Pb displacements are randomly distributed along the cubic {110} directions. The latter can be explained by the abundance of underbonded oxygen atoms associated with the chemical B-site disorder.

The crystal structures of the low-temperature and high-pressure polymorphs of nitric acid.

A new high-pressure phase of pure nitric acid (HNO(3)) has been characterised at 1.6 GPa at room temperature by high-pressure neutron powder and X-ray single-crystal diffraction techniques. This is the first crystalline phase obtained upon compression of liquid nitric acid at room temperature and appears to be the stable phase up to pressures of at least 4 GPa. The crystal structure of this new phase shows some similarities to that of the low-temperature phase of nitric acid at ambient pressure, which has been redetermined as part of this study. Both structures share a herringbone packing of hydrogen-bonded molecular catemers, although the presence of disorder within the hydrogen bonds within one of the catemers of the low-temperature phase makes its structure comparatively more complex.

Electroporation-mediated delivery of a naked DNA plasmid expressing VEGF to the porcine heart enhances protein expression.

Gene therapy is an attractive method for the treatment of cardiovascular disease. However, using current strategies, induction of gene expression at therapeutic levels is often inefficient. In this study, we show a novel electroporation (EP) method to enhance the delivery of a plasmid expressing an angiogenic growth factor (vascular endothelial growth factor, VEGF), which is a molecule previously documented to stimulate revascularization in coronary artery disease. DNA expression plasmids were delivered in vivo to the porcine heart with or without coadministered EP to determine the potential effect of electrically mediated delivery. The results showed that plasmid delivery through EP significantly increased cardiac expression of VEGF compared with injection of plasmid alone. This is the first report showing successful intracardiac delivery, through in vivo EP, of a protein expressing plasmid in a large animal.

The compression mechanism of CrF3.

The structure of CrF3 has been studied in the pressure range from ambient to 9.12 GPa by time-of-flight neutron powder diffraction. Rietveld refinements of the crystal structure were performed in the space group R3 c for all the recorded data sets. It was found that volume reduction is achieved through rotation of the CrF6 octahedra and that the Cr-F-Cr bond angle decreases from 144.80 (7) to 133.9 (4) degrees within the investigated pressure range. Furthermore, a small octahedral strain was found to develop during compression. The octahedral strain reflects an elongation of the CrF6 octahedra along the c-axis direction. The zero-pressure bulk modulus Bo and its pressure derivative Bo' were determined to be Bo = 29.2 (4) GPa and Bo' = 10.1 (3).

Local and long-range order in ferroelastic lead phosphate at high pressure.

Pure lead phosphate, Pb(3)(PO(4))(2), undergoes a phase transition from C2/c to R(-)3m symmetry at a pressure of approximately 1.8 GPa and room temperature. Single-crystal X-ray diffraction measurements of the unit-cell parameters of a sample doped with 1.6% Ba(2+) for the Pb(2+) indicates that the doping reduces the transition pressure by approximately 0.1 GPa. The structural evolution of both samples through the phase transition has been determined by Rietveld refinement of neutron powder diffraction data collected to pressures of 6.3 and 3.3 GPa, respectively. There is no evidence for any significant change in the local structure at the phase transition at high pressures; the structure of the R(-)3m phase at pressures just above the phase transition includes disordered positions for several atoms. The observation of diffuse scattering from the R(-)3m phase at high pressure by single-crystal X-ray diffraction suggests that the disorder is static and arises from the presence of several orientations of the ordered microdomains of the monoclinic local structure. The macroscopic transition from monoclinic to trigonal symmetry therefore appears to correspond to the pressure at which the coherency strains between the locally monoclinic microdomains are sufficient to create a dimensionally trigonal lattice within which local displacements of atoms are still significant. A further pressure increase then decreases the magnitude of these displacements until at 3.5 GPa or higher they are not detectable by our current experimental probes, and the structure appears to have true local and global trigonal symmetry.

Toward further reducing wound infections in cardiac operations.

BACKGROUND: Serious wound infections such as mediastinitis still occur at a rate of 0.8% to 2.0%, according to the most recently published cardiac operative series. METHODS: Data from careful surveillance for infection have been collected prospectively during a 4.5-year period on 1,717 patients who underwent cardiac operations performed under direct ultraviolet C radiation. RESULTS: The rate for mediastinitis was 0.23%, and for deep incisional infection without mediastinitis, 0.12%; these rates are significantly lower than those for eight of nine of the most recently published cardiac series. When our infection rates were stratified using the National Nosocomial Infection Surveillance risk index, they were also significantly lower in the most important risk categories than the corresponding stratified rates collected from the participating hospitals of the Centers for Disease Control and Prevention National Nosocomial Infection Surveillance system. CONCLUSIONS: Though we lack the proof that only a large, randomized study might provide, certainly, one possible explanation for our lower wound infection rate was the use of bactericidal ultraviolet C radiation during operation. This is a simple and effective means of minimizing operating room airborne bacteria as one possible source of these infections.

Duplex scanning of the inferior epigastric artery.

PURPOSE: The inferior epigastric artery (IEGA) has been used as a conduit for coronary artery bypass grafting. Because of varying lengths, diameters, and depths, a method of determining vessel adequacy before operation was needed. METHOD: A BioSound Phase II scanner (BioSound, Indianapolis, Ind.) with a 10 MHz probe was used to image the IEGA in 40 patients. Beginning at the common femoral artery and moving superiorly, the external iliac artery is identified with its first branch, which is the IEGA. The IEGA is located deep in the rectus muscle, along the posterior rectus sheath. Frequent measurements of the diameter and depth are taken along the length of the IEGA. RESULTS: When comparing the group of patients in whom there was operative confirmation of the ultrasound findings, we found, on the right side, a mean length of 9.0 cm and mean diameter of 2.4 mm by ultrasonography and 10.5 mm and 2.4 mm at operation. On the left side the findings were 9.6 cm and 2.6 mm by ultrasonography and 11 cm and 2.6 mm at operation. There was one wound complication in an IEGA harvest site that had a body wall thickness of less than 4 cm (1/23; 4.2%), but all four sites with a body wall thickness of 4 cm or greater developed wound complications (4/4; 100%). CONCLUSION: The use of duplex scanning of the IEGA before operation provided excellent information about the length, diameter, depth, and patency of the vessel. Preoperative scanning prevented unnecessary dissection when the IEGA was not of adequate length or diameter. It was also very useful in providing information regarding risk of wound complications in obese patients.

Technique for visualization of the functioning mitral valve.

A technique is described for visualization of the mitral valve in the beating perfused heart to identify areas of abnormality in the valve apparatus before reconstruction. Risks of air embolus and myocardial ischemia are minimized.

Risks of bilateral internal mammary artery bypass grafting.

Although use of one internal mammary artery (IMA) for coronary artery bypass grafting does not appear to be associated with increased risk, the results with both IMAs are less certain; the potential for a higher incidence of sternal wound infection as a result of devascularization of the sternum is a major concern. During a 42-month interval ending July 1988, 1,566 patients had coronary artery bypass grafting alone or in combination with other procedures: 633 received only vein grafts, 687 had unilateral IMA grafting, and 246 had bilateral IMA grafting. The IMA patients were younger, were more often male, had better cardiac function, and underwent fewer emergent, urgent, or combined procedures than the patients receiving vein grafts (p less than 0.05). Thirty-day mortality was lower among the IMA patients (unilateral IMA group, 2.8%; bilateral IMA group, 3.7%; and vein graft group, 7.9%; p = 0.001). With the exception of sternal wound problems, occurrence rates for postoperative complications among the IMA patients did not differ significantly from or were lower (p less than 0.05) than those among the patients with vein grafts. Sternal infections occurred with greater frequency among the bilateral IMA patients (6.9%) than among the unilateral IMA (1.9%) or vein graft (1.3%) patients (p = 0.001). By univariate analysis, obesity, diabetes, bilateral IMA grafting, and need for prolonged (greater than 48 hours) mechanical ventilation were associated with a significantly higher incidence of sternal infection (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Avoidance of embolic complications by ultrasonic characterization of the ascending aorta.

Surgical manipulation of the atherosclerotic ascending aorta in elderly patients is often accompanied by serious complications. To reduce the risk of disrupting highly degenerated but nonpalpable plaques, we used quantitative ultrasonic techniques to intraoperatively image the ascending aorta in 33 patients (mean age, 71 years) as a guide to selection of cross-clamping or cannulation sites. Two-dimensional, integrated backscatter images (integration time, 1.6 mu sec) were obtained with a 5-MHz transducer wrapped in a sterile sheath and placed directly on the aorta. Significant atherosclerotic disease was detected in 18 patients. Calcified lesions were found in 13 patients, and fibrofatty lesions were found in five. In four patients undergoing repair of degenerative aneurysms, the extent and distribution of ultrasonically delineated regions of calcification and fibrosis were confirmed histologically. In eight (24%) patients, the composition, severity, and location of plaques delineated ultrasonically led to selection of alternate cannulation sites without resultant atheroembolism. Thus, ultrasonic tissue characterization sensitively delineates the extent of aortic atherosclerosis, and its use may decrease the risk of atheroembolism.

Intraoperative ultrasonic imaging of the ascending aorta.

Embolization of atherosclerotic material from the ascending aorta resulting from placement of cannulas or vascular clamps is a major cause of stroke during cardiac surgical procedures. In an effort to identify atherosclerotic disease of the ascending aorta which might predispose to embolization, intraoperative B-mode ultrasonography was performed in 50 patients. The aorta was imaged from the aortic annulus to the origin of the innominate artery in transverse and longitudinal views. The results were compared with visual and tactile examination of the aorta for the presence of atherosclerosis. Ultrasonic imaging demonstrated atherosclerotic disease in 29 patients (58%). Visual examination and palpation identified atherosclerosis in 12 patients (24%). The amount and location of plaque was sufficient to require a change in the site of arterial cannulation or the proximal vein graft anastomoses or the technique of cardiopulmonary perfusion in 12 of the 50 patients (24%). All 12 patients were 65 years of age or older. Palpation underestimates the presence of atherosclerotic disease in the ascending aorta. Intraoperative ultrasonography accurately identifies patients with atherosclerotic disease of the ascending aorta. This allows the surgeon to modify cannulation, perfusion, and operative techniques to reduce the risk of perioperative stroke due to the embolization of atherosclerotic debris from the ascending aorta.

Coronary artery bypass grafting for postinfarction angina pectoris.

The variables that predict increased operative risk and postoperative morbidity among patients who undergo coronary artery bypass grafting (CABG) early after myocardial infarction for persistent or recurrent ischemia are incompletely defined. In a recent 3-year interval (1985-1987), 240 patients underwent CABG within 30 days of a documented myocardial infarction. Thirty-day mortality was 3.3% (eight patients). Twenty variables were examined by univariate and multivariate analysis for their effects on early mortality. Left main coronary artery disease (p = 0.0003), female sex (p = 0.0059), and preoperative left ventricular dysfunction (increased left ventricular wall motion score) (p = 0.0135) were significant independent predictors of increased 30-day mortality. Postoperative inotropic support for low cardiac output was required for 55.6% of patients operated upon within 24 hours of infarction as compared with 11.6% of patients operated upon between 1 and 30 days (p less than 0.01). Significantly more patients undergoing emergent CABG required postoperative intra-aortic balloon pumping and inotropic support than those patients who underwent urgent or elective operation (23.8% vs. 4.6% and 52.4% vs. 10%, respectively) (p less than 0.01). Other studies confirm that preoperative left ventricular dysfunction, presence of cardiogenic shock, or intra-aortic balloon pumping are important predictors of operative risk. Other variables that may be important include advanced age, female sex, left main coronary artery disease, and anterior transmural infarction. The timing and urgency of operation have not been shown to be significant and independent determinants of increased operative risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased complications and prolonged hospital stay in elderly cardiac surgical patients with low serum albumin.

Cardiac surgery in elderly patients is associated with acceptable operative mortality but an increased complication rate. Malnutrition is common in the elderly and may adversely affect surgical outcome. To determine the effect of hypoalbuminemia on postoperative complications, 92 patients greater than or equal to 75 years (range 75 to 90) undergoing a variety of major cardiac surgical procedures were evaluated. Thirteen patients (14%) had a serum albumin level less than 3.5 g/dl preoperatively. Compared to patients with normal albumin, hypoalbuminemic patients had an increased frequency of postoperative confusion, congestive heart failure, low cardiac output, renal dysfunction and gastrointestinal complications (all p less than 0.05). Mean postoperative length of stay was markedly prolonged in these patients (27 vs 12 days; p less than 0.001), and mortality also tended to be higher (31 vs 13%; p = 0.11). Using multivariate analysis, albumin less than 3.5 g/dl was the most powerful predictor of postoperative renal dysfunction (p less than 0.01), and was also an independent predictor of increased length of stay (p less than 0.01) and gastrointestinal disorders (p less than 0.05). Thus, hypoalbuminemia is a powerful indicator of an increased risk of perioperative complications in elderly patients undergoing cardiac surgery. Increased attention to nutritional factors is warranted in these patients.

Morbidity and mortality of coronary bypass surgery in patients 75 years of age or older.

To determine factors associated with an increased risk of postoperative complications in elderly patients, 60 consecutive patients 75 years of age or older undergoing isolated coronary artery bypass grafting (CABG) were evaluated. Thirty-nine patients (65.0%) had at least one major postoperative complication, including 2 deaths (3.3%). Low body weight was the only univariate predictor (p less than 0.05) of an increased likelihood of complications overall. Prior cardiac operation, low serum cholesterol value, and prolonged cardiopulmonary bypass time were associated with increased bleeding. Electrocardiographic evidence of left ventricular hypertrophy was associated with prolonged postoperative confusion. Age of 80 years or more and increased cross-clamp time were predictive of pulmonary dysfunction. Low cardiac output occurred more frequently in patients with nonsinus rhythm, prior cardiac operation, recent congestive heart failure, or elevated level of blood urea nitrogen. Identification of risk factors for specific complications should prompt further studies to define ways of reducing morbidity and the resultant high cost associated with CABG in elderly patients.

Coronary artery bypass grafting in patients with a tracheostoma: use of a bilateral thoracotomy incision.

The performance of cardiac surgical procedures via median sternotomy in patients with a tracheostoma can present difficult problems, including stomal necrosis, mediastinitis, and inadequate operative exposure. Bilateral thoracotomy is an alternative approach in such patients. This approach separates the stoma from the operative field and provides satisfactory exposure for internal mammary artery dissection and performance of coronary artery bypass grafting.

Vasorelaxant effects of atriopeptins in human internal mammary artery.

The vasorelaxant effects of the atriopeptins, AP-(103-126) and AP-(103-123) were compared in human internal mammary artery (IMA) rings which had been contracted with norepinephrine. AP-(103-126) completely relaxed the IMA with an IC50 within the physiologically relevant range (15 nM). However, relaxation with AP-(103-123) was greatly reduced compared to AP-(103-126), with complete relaxation observed in only half of the vessels tested and only at concentrations of 10-50 microM. These results indicate that the atriopeptin (AP) receptor in human arteries may be more similar to the AP receptor in rabbit rather than rat arteries.

Carotid endarterectomy based on duplex scanning without preoperative arteriography.

Between July 1985 and September 1987, 25 patients underwent 26 carotid endarterectomies based on an abnormal duplex scan (B-mode ultrasonography and pulsed-Doppler sound spectral analysis) indicative of severe stenosis or ulceration. Arteriography was not performed because of severe unstable angina requiring coronary artery bypass grafting (23 patients) or patient preference (two). Twelve patients were symptomatic, and 13 were asymptomatic but had severe (greater than or equal to 75%) bilateral or unilateral carotid artery stenosis. Operative and pathological analyses confirmed the duplex-scan findings in all 25 cases. All 25 patients survived the operation. One patient had a transient ipsilateral neurological deficit, and one had a permanent contralateral neurological deficit. Five patients died of ventricular arrhythmias within 30 days of operation. Duplex scanning is an accurate method for determining the presence of clinically and hemodynamically significant carotid arterial occlusive disease. Duplex scanning also serves as an alternative method for evaluating patients for whom carotid arteriography may be associated with significant risk.