Dynamics and Site Isolation: Keys to High Propane Dehydrogenation Performance of Silica-Supported PtGa Nanoparticles.

Nonoxidative dehydrogenation of light alkanes has seen a renewed interest in recent years. While PtGa systems appear among the most efficient catalyst for this reaction and are now implemented in production plants, the origin of the high catalytic performance in terms of activity, selectivity, and stability in PtGa-based catalysts is largely unknown. Here we use molecular modeling at the DFT level on three different models: (i) periodic surfaces, (ii) clusters using static calculations, and (iii) realistic size silica-supported nanoparticles (1 nm) using molecular dynamics and metadynamics. The combination of the models with experimental data (XAS, TEM) allowed the refinement of the structure of silica-supported PtGa nanoparticles synthesized via surface organometallic chemistry and provided a structure-activity relationship at the molecular level. Using this approach, the key interaction between Pt and Ga was evidenced and analyzed: the presence of Ga increases (i) the interaction between the oxide surface and the nanoparticles, which reduces sintering, (ii) the Pt site isolation, and (iii) the mobility of surface atoms which promotes the high activity, selectivity, and stability of this catalyst. Considering the complete system for modeling that includes the silica support as well as the dynamics of the PtGa nanoparticle is essential to understand the catalytic performances.

Lipid profile of immunocastrated, castrated male and female pigs / Perfil lipídico de suínos machos castrados e imunocastrados e fêmeas

A presente pesquisa foi realizada com o objetivo de avaliar os níveis de colesterol, extrato etéreo, perfil de ácidos graxos e o índice aterogênico e trombogênico da gordura intramuscular de suínos machos imunocastrados em relação às fêmeas e aos machos castrados cirurgicamente. Utilizaram-se 45 animais, com peso inicial de 25,2±2,8kg, distribuídos em delineamento inteiramente ao acaso, com três tratamentos (machos castrados, machos e fêmeas imunocastrados) e três repetições de cinco animais cada. Os animais foram abatidos a 90,3±2,7kg. As amostras de Longissimus dorsi foram coletadas, liofilizadas e analisadas quanto ao perfil de ácidos gordos, colesterol e extrato etéreo. Não foram observadas diferenças (P>0,05) para nenhuma das variáveis analisadas entre a gordura intramuscular de machos castrados cirurgicamente, machos imunocastrados e fêmeas. A imunocastração não alterou os níveis intramusculares de extrato etéreo, colesterol, composição de ácidos graxos ou o índice aterogênico e trombogênico do Longissimus dorsi.(AU)

Brief communication: smoking and duodenal blood flow.

Smoking promotes an increase in both the incidence and the recurrence of duodenal ulcers, but the mechanisms responsible for its adverse effects on the duodenal mucosa are still poorly understood. The aim of the present study was to investigate the effect of chronic cigarette smoking on duodenal blood flow. In 20 dyspeptic patients (10 non-smokers and 10 smokers) with endoscopically normal duodenum, mucosal blood flow was measured in the duodenal bulb by laser Doppler flowmetry during endoscopy. Basal bulbar perfusion was found to be significantly lower (P < 0.05) in smokers. Our results suggest that duodenal blood flow is reduced in heavy smokers. This may promote duodenal damage because of both local ischaemia and the reduced secretion of protective bicarbonate.

Surgical treatment of gastric adenocarcinoma: impact on survival and quality of life. A prospective ten year study.

BACKGROUND/AIMS: The objective of this prospective study was to compare the results of total (TG) versus subtotal (SG) gastrectomy in patients with adenocarcinoma of the lower two-thirds of the stomach. PATIENTS AND METHODS: Two hundred and twenty-seven patients underwent curative operation. Preoperative nutritional assessment, postoperative tumor stage, postoperative morbidity/mortality, five-year survival, postgastrectomy dietary intake and nutritional sequelae were recorded in all patients. RESULTS: Postoperative mortality rate was 2.8% in the TG group and 1.1% in the SG group. The number of reoperations, anastomotic dehiscence rate and the length of postoperative stay were higher in the TG group. Five-year survival was closely related to lymph node involvement and gastric wall invasion. The extent of gastric resection did not influence survival when patients were matched for cancer stage. In the SG group, no recurrence in the gastric stump was observed. SG group showed a higher dietary energy intake than the TG group (p < 0.01). This might explain the ability of the SG group to increase body weight more than the TG group (p < 0.01). Only the TG group needed a monthly parenteral vitamin B12 supplements starting 36 months after surgery. CONCLUSION: The results suggest that SG should be considered the treatment of choice of the gastric adenocarcinoma when a cancer-free proximal resection margin can be guaranteed.

Congestive gastropathy versus chronic gastritis: a comparison of some pathophysiological aspects.

In order to investigate some pathophysiological aspects of the two diseases, 15 patients with congestive gastropathy and 15 with chronic gastritis have been studied and compared with 15 healthy controls. Gastric blood flow as determined during endoscopy by means of laser Doppler flowmetry was found to be significantly increased (p < 0.001) in congestive gastropathy, whereas a significant reduction (p < 0.001) was noted in chronic gastritis. On the other hand, Helicobacter pylori was detected in 80% of cases in chronic gastritis, while the prevalence of the microorganism in congestive gastritis was similar to that in healthy controls. It is concluded that chronic gastritis and congestive gastropathy are related to different pathogenetic factors and require different therapeutic approaches.

Breakdown of mucosal defences in congestive gastropathy in cirrhotics.

The gastric mucus-bicarbonate barrier, the first line of mucosal defence, has been evaluated in patients with congestive gastropathy and cirrhosis of the liver. Fourteen cirrhotic patients of both sexes (Child's class A or B), with or without oesophageal varices, but with endoscopic signs of congestive gastropathy, and a matched group of healthy controls were studied. The amount of luminal mucoproteins, a Mucoprotective Index as a qualitative assessment of mucus secretion and the output of gastric bicarbonate were determined in basal conditions. In patients with congestive gastropathy a significant (p < 0.01) reduction in all the above parameters was observed, suggesting a substantial impairment of the gastric mucus-bicarbonate barrier. Whether this is an independent phenomenon or a consequence of altered local microcirculation remains to be determined.

[Malnutrition after total gastrectomy]. / Malnutrizione dopo gastrectomia totale.

We studied food intake and nutritional status of 28 patients who had undergone total gastrectomy for gastric cancer. At discharge, patients were instructed to keep a high protein, high calorie diet and to record food intake on a specific form, twice weekly. Nutritional follow-up, consisting in a computerized determination of dietary intake and nutritional assessment was performed monthly during the first postoperative year. The average calorie intake was 1,431.8 Kcal/day one month after operation and 2,225.4 Kcal/day one year after surgery (p less than 0.001). In particular, only one patient exceeded 2,000 Kcal/day one month after total gastrectomy, while 21 patients exceed 2,00 Kcal/day one year after operation. The evaluation of nutritional parameters in the postoperative course showed that a significant increase in body weight, serum albumin and total iron binding capacity was observed only in patients who exceed 2,000 Kcal/day one year after operation. These results indicate that malnutrition is not an inevitable consequence of total gastrectomy; in fact, a close relationship between calorie intake and the variations of nutritional parameters was observed.

Food intake and nutritional status after total gastrectomy: results of a nutritional follow-up.

We studied dietary intake and nutritional status of 23 patients for 6 months after total gastrectomy with Roux-en-Y reconstruction. At discharge, patients were instructed to keep to recommended dietary allowances (RDA) and to record food intake on a specific form twice weekly. Nutritional follow-up was performed monthly and consisted of a computerized determination of food intake and of a nutritional assessment. The average daily energy intake was 6.10 MJ (1457.9 kcal) in the first postoperative month and 8.87 MJ (2118.4 kcal) in the sixth (P less than 0.0005). In the first monthly follow-up no patient reached RDA. By the sixth month mean daily calorie intake was greater than or equal to RDA in 14 patients (group A), while 9 patients (group B) did not reach RDA. A significant increase in body weight, serum albumin, total iron binding capacity and arm muscular circumference was observed in group A, while a significant decrease in body weight and arm muscular circumference was noted in group B. Moreover, of the seven patients who showed weight loss at 6 months only one was group A. These data indicate that malnutrition is not an inevitable consequence of total gastrectomy and can be prevented by an adequate calorie intake. A close relationship between dietary intake and postoperative nutritional parameters was observed. In gastrectomized patients a strict nutritional follow-up is very important to obtain an adequate dietary intake.