Heterogeneity in the Fragmentation of Ziegler Catalyst Particles during Ethylene Polymerization Quantified by X-ray Nanotomography.

Ziegler-type catalysts are the grand old workhorse of the polyolefin industry, yet their hierarchically complex nature complicates polymerization activity-catalyst structure relationships. In this work, the degree of catalyst framework fragmentation of a high-density polyethylene (HDPE) Ziegler-type catalyst was studied using ptychography X-ray-computed nanotomography (PXCT) in the early stages of ethylene polymerization under mild reaction conditions. An ensemble consisting of 434 fully reconstructed ethylene prepolymerized Ziegler catalyst particles prepared at a polymer yield of 3.4 g HDPE/g catalyst was imaged. This enabled a statistical route to study the heterogeneity in the degree of particle fragmentation and therefore local polymerization activity at an achieved 3-D spatial resolution of 74 nm without requiring invasive imaging tools. To study the degree of catalyst fragmentation within the ensemble, a fragmentation parameter was constructed based on a k-means clustering algorithm that relates the quantity of polyethylene formed to the average size of the spatially resolved catalyst fragments. With this classification method, we have identified particles that exhibit weak, moderate, and strong degrees of catalyst fragmentation, showing that there is a strong heterogeneity in the overall catalyst particle fragmentation and thus polymerization activity within the entire ensemble. This hints toward local mass transfer limitations or other deactivation phenomena. The methodology used here can be applied to all polyolefin catalysts, including metallocene and the Phillips catalysts to gain statistically relevant fundamental insights in the fragmentation behavior of an ensemble of catalyst particles.

Sternal reconstruction after post-sternotomy dehiscence and mediastinitis.

PURPOSE: Post-sternotomy dehiscence and mediastinitis remains a serious complication in cardiothoracic surgery. The aim of this work is to report our experience over a period of 8 years in the surgical treatment and risk factor analyses of post-sternotomy dehiscence and mediastinitis. METHODS: All patients treated for post-sternotomy dehiscence at our Thoracic Surgery Unit in the last 8 years were retrospectively collected. We identified 237 patients with post-sternotomy dehiscence/mediastinitis. Forty-two patients had simple fractures of the metal steel wires, 61 had an asymmetric sternotomy with multiple sternal fractures, 113 had a symmetric sternotomy with multiple sternal fractures, 14 had a failed Robicsek procedure, and 7 had sternal dehiscence with mediastinal abscess. RESULTS: Different surgical techniques and materials were used to repair the sternum. In 21 patients, the first revision failed and a second reoperation was required. At multivariate analyses, we have identified risk factors for revision failure and in-hospital mortality. Mortality rate was significantly higher in patients who underwent more than one surgical revision (8% vs 19%, p < 0.001). CONCLUSIONS: Patients with sternal dehiscence are very fragile due to multiple preoperative comorbidities as reflected by postoperative morbidity and risk factors for in-hospital mortality. A correct evaluation of the characteristics of sternal dehiscence is important to guide the most appropriate repair strategy. Patients who need repeated sternal revisions had a higher mortality. Further randomized studies are needed to evaluate different techniques and medical devices to define the gold standard procedure to reduce significantly sternal wound complications in high-risk patients as defined by well-known risk factors.

Correlated X-ray Ptychography and Fluorescence Nano-Tomography on the Fragmentation Behavior of an Individual Catalyst Particle during the Early Stages of Olefin Polymerization.

A combination of X-ray ptychography and X-ray fluorescence tomography (XRF) has been used to study the fragmentation behavior of an individual Ziegler-Natta catalyst particle, ∼40 µm in diameter, in the early stages of propylene polymerization with submicron spatial resolution. The electron density signal obtained from X-ray ptychography gives the composite phases of the Ziegler-Natta catalyst particle fragments and isotactic polypropylene, while 3-D XRF visualizes multiple isolated clusters, rich in Ti, of several microns in size. The radial distribution of Ti species throughout the polymer-catalyst composite particle shows that the continuous bisection fragmentation model is the main contributor to the fragmentation pathway of the catalyst particle as a whole. Furthermore, within the largest Ti clusters the fragmentation pathway was found to occur through both the continuous bisection and layer-by-layer models. The fragmentation behavior of polyolefin catalysts was for the first time visualized in 3-D by directly imaging and correlating the distribution of the Ti species to the polymer-catalyst composite phase.

Short-term effects on bone turnover markers of a single high dose of oral vitamin D3.

CONTEXT: Vitamin D deficiency is often treated or prevented by high intermittent doses of vitamin D to achieve a better treatment adherence, but treatment outcomes were contradictory, and even a transient increase in fracture and fall risk was reported. OBJECTIVE: The objective of the study was to investigate the short-term effects on bone turnover markers of a single bolus of vitamin D3. DESIGN, SETTING, PATIENTS, AND INTERVENTION: Twelve elderly subjects (eight women, four men; mean age 76 ± 3 yr) were given a single oral bolus of 600,000 IU vitamin D3. Blood samples were taken at baseline and 1, 3, 7, 14, 30, 60, and 90 d after vitamin D3 administration. Twenty-four subjects served as controls. MAIN OUTCOME MEASURES: Changes in serum levels of 25-hydroxyvitamin D (25OHD), 1,25-dihydroxyvitamin D, PTH, C-terminal-telopeptides of type I collagen, cross-linked N-telopeptide of type I collagen (sNTX), osteocalcin, and bone-specific alkaline phosphatase. RESULTS: No relevant changes in 25OHD and bone turnover markers were observed in the controls. In treated subjects, serum 25OHD attained a peak increment to 67.1 ± 17.1 ng/ml (P < 0.001) at d 3. Subsequently it slowly decreased to 35.2 ± 5.8 ng/ml (P <0.01 vs. a baseline value of 21.7 ± 5.6 ng/ml). Mean serum PTH concentration decreased by 25-50% and serum 1,25-dihydroxyvitamin D rose by 25-50%. Serum CTX and sNTX rose significantly at d 1 (P < 0.01), they attained a peak increment greater than 50% at d 3, and they subsequently decreased almost back to baseline values at d 90. Serum osteocalcin slightly rose within the first 3 d and then declined by d 60. No changes were observed in serum bone-specific alkaline phosphatase. CONCLUSIONS: Our results indicate that the use of large doses of vitamin D may be associated with acute increases in C-terminal-telopeptides of type I collagen and sNTX, which may explain the negative clinical results obtained by using intermittent high doses of vitamin D to treat or prevent vitamin D deficiency.

Efficacy of a new oxygenator-integrated fat and leukocyte removal device.

We evaluated the effectiveness of a new oxygenator-integrated device for removing lipid particles and leukocytes from shed mediastinal blood in 20 patients undergoing elective cardiac surgery under cardiopulmonary bypass. Another 20 patients undergoing cardiac surgery without the device served as controls. After filtration with the RemoveLL device, lipid particles, leukocytes, and fats were significantly reduced compared to preoperative levels. In the control group, blood fats and lipid particles at the end of cardiopulmonary bypass were significantly increased compared to preoperative levels. Leukocyte counts at the end of bypass were significantly lower in patients who had the filtration device compared to the control group. Platelets counts and hematocrit changes were not significantly different between the 2 groups.

Beating heart bentall procedure for late type A aortic dissection in a patient with in-situ bilateral mammary artery bypass grafts.

We report a case of a patient who had a type A aortic dissection after previous coronary bypass grafting. The in-situ right mammary artery had been anastomosed with the left anterior descending artery, the left mammary artery had been anastomosed to the obtuse marginal, and a vein graft had been used for the right coronary artery. All grafts were patent. The patients underwent a Bentall procedure on perfused heart.

Bariatric surgery improves atherogenic LDL profile by triglyceride reduction.

BACKGROUND: Small dense low-density lipoprotein (LDL) are atherogenic particles frequently observed in obese patients. Fatty acids modulate LDL. Objective of this study was to determine the relations between plasma phospholipid fatty acid composition and the presence of small dense LDL particles in morbidly obese patients treated with laparoscopic gastric banding (LAGB). METHODS: Small dense LDL, plasma lipids, lipoproteins, apoproteins, and phospholipid fatty acid composition (a marker of dietary fatty acid intake) were quantified before and 12 months after surgery in four men and 11 women who were morbidly obese and (BMI > 40 kg/m(2)) eligible for surgery, consecutively treated with LAGB at the Department of Medical and Surgical Sciences of the University of Padova. RESULTS: BMI was 48.3 +/- 4.8 kg/m(2) before and 36.1 +/- 5.5 kg/m(2) after LAGB. Plasma triglycerides and apoprotein E levels significantly decreased, while HDL cholesterol significantly increased after LAGB. A reduction of small dense LDL with an increase of LDL relative flotation (0.34 +/- 0.04 before vs 0.38 +/- 0.03 after LAGB, p < 0.001) was also observed. These modifications were neither related to weight reduction nor to changes in phospholipid fatty acid composition, but they were associated to triglyceride reduction, which explained 76.7% of the LDL relative flotation variation. CONCLUSION: Weight loss obtained by LAGB in morbidly obese subjects was accompanied by triglyceride reduction, high-density lipoprotein increase, and an improvement of the atherogenic LDL profile. Triglyceride reduction, but not the extent of weight loss or dietary fatty acid modifications, is the determinant of modifications of LDL physical properties in these patients.

Lipid and phospholipid profile after bowel resection for Crohn's disease.

BACKGROUND AND AIM: Chronic inflammation, impaired intestinal adsorption, and bowel resection may have an impact on lipid metabolism before and after intestinal surgery for Crohn's disease (CD). The aim of this prospective study was to define the impact of intestinal surgery for CD on plasma phospholipid fatty acid (FA) composition and of serum plasma lipoprotein concentrations and to investigate the role of CD recurrence on lipid parameters. MATERIALS AND METHODS: Twenty-four consecutive patients who had intestinal surgery for CD since December 2004 to March 2006 were enrolled in this prospective study. The total amount of calorie intake and the quality of the aliments, systemic inflammatory activity, and plasma lipoproteins and phospholipid fatty acid composition were determined at operation and at follow-up. Statistical analysis was performed with pair-matched tests. RESULTS: The median follow-up was 6 (4-20) months. During the follow-up, no significant modification of body mass index was observed. An increase of high-density lipoprotein (HDL) cholesterol (p=0.02) without other modifications in the plasma phospholipid FA composition were evidenced after surgery. The comparison between colectomy and ileo-colonic or ileal resection groups did not show any significant difference in the lipoprotein concentration and phospholipid FA profile. The length of resected bowel did not show any significant correlation with any relevant difference in lipid, phospholipid profile, or in inflammatory parameters. Patients who experienced a recurrence of CD reported significantly higher levels of total (p<0.01), HDL (p=0.01), and low-density lipoprotein cholesterol (p=0.01) were observed in patients in remission than in those with recurrent active disease. CONCLUSIONS: Patients who are submitted to intestinal resection for CD improve their inflammatory status as well as their lipid metabolism, and CD recurrence, but not the extent of bowel resection, is the main predictor of alteration of serum lipid concentration.

Metabolic syndrome and cardiovascular disease in the elderly: the Progetto Veneto Anziani (Pro.V.A.) study.

BACKGROUND AND AIMS: The prevalence of the metabolic syndrome increases with age, although only few data are available about its prevalence in the general elderly population. This study describes the prevalence of the metabolic syndrome in an elderly population, and its association with cardiovascular diseases. METHODS: The Progetto Veneto Anziani (Pro.V.A.) is an observational study of 3,099 subjects aged 65 and older, randomly selected from the general population of Northern Italy. Cardiovascular diseases and metabolic syndrome according to Adult Treatment Panel III were evaluated in 2,910 subjects. RESULTS: The metabolic syndrome was present in 25.6% of men and 48.1% of women. Its prevalence was mainly due to high blood pressure (93%) in both sexes, and to abdominal obesity in 73% of women. The prevalence of cardiovascular diseases was significantly higher among subjects with metabolic syndrome. Together with age and former smoking habits, the metabolic syndrome was significantly associated with cardiovascular diseases. High blood pressure and low HDL were independently associated with cardiovascular diseases in men, and with high fasting plasma glucose and waist circumference in women. CONCLUSIONS: The metabolic syndrome is frequent, and significantly but not independently associated with prevalent cardiovascular diseases in the elderly. In old people, rather than the metabolic syndrome per se, some of its components are independently associated with cardiovascular diseases.

Restorative proctocolectomy for ulcerative colitis: impact on lipid metabolism and adipose tissue and serum fatty acids.

The aim of this prospective study was to evaluate the changes of the metabolism of circulating and storage lipids in patients with ulcerative colitis after restorative proctocolectomy. Fifteen consecutive patients and 15 sex- and age-matched healthy controls were enrolled. Disease activity, diet, inflammatory parameters, plasma lipoprotein concentrations, and fatty acids (FA) of serum phospholipids and of the subcutaneous adipose tissue were assessed at colectomy and at ileostomy closure. In ulcerative colitis patients, total cholesterol and docosahexaenoic acid were lower than in healthy subjects (p < 0.01 and p < 0.05). The median interval between colectomy and ileostomy closure was 6 (range 2-9) months. During that interval, the inflammatory parameters improved, high-density lipoproteins (HDL) cholesterol increased (p < 0.01), and low-density (LDL) cholesterol decreased (p = 0.01). At ileostomy closure, serum arachidonic acid levels were increased (p = 0.04), whereas serum oleic acid level was decreased (p = 0.02). In this interval, no significant alteration, either in serum n-3 FA precursors or in the FA of subcutaneous adipose tissue, was observed. The increase of serum arachidonic acid after colectomy might suggest a lower utilization for inflammatory process. The reduction of LDL cholesterol is an index of malabsorption probably due to the accelerated transit and to the exclusion of the terminal ileum caused by the covering ileostomy.