Mohamed Mostafa

Effect of Chemical Composition on the Structure and Catalytic Behaviour of AlPO4 and Al2O3–AlPO4 Mixed Catalysts:

AlPO4 and Al2O3–AlPO4 mixed catalysts of different composition (Al/P > 1) were prepared and calcined in the temperature range 350–650°C. Such catalysts were characterized by DTA and X-ray diffraction methods, and by nitrogen adsorption studies at −196°C. Their acidity was determined using a calorimetric titration method while their catalytic activity towards the dehydration of isopropanol was determined using a pulse microcatalytic technique. The data obtained from XRD studies showed that pure AlPO4 when calcined at 650°C had a rather low crystallinity with its crystalline structure (which is of the α-cristobalite type) being characterized by poorly developed peaks. However, significant changes in the texture, surface acidity and catalytic activity were observed as a result of changing the chemical composition of the solid, with the surface area, total pore volume and surface acidity generally increasing with increasing alumina content. Sintering commenced above 550°C leading to a decrease in the surface area and to pore widening. Dehydration of isopropanol appeared to be insensitive to the structure of the catalysts investigated but was related to the surface acid density.

Characterization and Catalytic Activity of Cr2O3–Al2O3/AlPO4 Catalysts

Five samples of Al2O3/AlPO4 (Al/P = 1.75) and Cr2O3-loaded Al2O3/AlPO4 (wt% Cr2O3 = 5–25) were prepared. The catalysts were obtained by thermal treatment of the corresponding samples in air at 823 K and were characterized using XRD and DTA techniques. The textural properties (surface area, total pore volume and mean pore radius) were determined from nitrogen adsorption data obtained at 77 K. The acidic properties of all the samples were measured calorimetrically. The catalytic conversion of isopropanol was studied using a microcatalytic pulse technique. No spinel structure was detected by both XRD and DTA techniques and only Cr2O3 was detected for samples containing ≥ 15 wt% chromia. Loading Al2O3/AlPO4 with Cr2O3 led to significant changes in the texture, surface acidity and catalytic activity of the prepared catalysts. Al2O3/AlPO4 catalysts exhibit no dehydrogenation activity, whereas loading with Cr2O3 favoured the dehydrogenation of isopropanol to acetone.

Bile reflux measurement and its contribution to the severity of reflux esophagitis

BACKGROUND/AIMS Gastroesophageal reflux disease (GERD) may occur with acid, bile or in a mixed form. Endoscopic injury and mucosal metaplasia are a known sequelae to pathological GERD. The aim of the study was to determine the contribution of acid and duodenogastroesophageal reflux to endoscopic severity in patients with GERD and Barretts esophagus (BE). MATERIALS AND METHODS Ninety-one patients complaining of reflux symptoms were studied with upper gastrointestinal endoscopy and graded to nonerosive reflux disease (NERD), erosive reflux disease (ERD) and BE. Esophageal manometry and simultaneous ambulatory 24-h esophageal pH and bilirubin monitoring (Bilitec 2000) were performed in all patients. RESULTS Seventy-one patients (78.0%) had ERD (Savary-Miller (grade I-III), 11 patients (12.1%) had NERD and 9 patients (9.9%) had BE, which were suspected endoscopically and diagnosed by histological esophageal biopsy. Combined 24-h esophageal bilirubin and pH monitoring revealed the following: 39 patients (42.9%) had mixed acid and bile reflux, 16 (17.6%) had pathological acid reflux alone, 18 (19.8%) had bile reflux alone and 18 patients (19.8%) showed no evidences of abnormal reflux. The percentage of the total time of the bilirubin absorbance > 0.14 in 71 patients with ERD was (8.18+/-11.28%) and in 9 patients with BE was (15.48+/-30.48%), which was significantly greater than that in 11 patients with NERD (4.48+/-8.99%), P<0.05 and P=0.01 respectively. All the BE patients had abnormal esophageal bile reflux (bile alone (3 patients)); and mixed bile and acid (6 patients)); 44 of 71 patients (61.97%) with ERD had abnormal esophageal bile reflux (alone (13 patients) and mixed bile and acid (31 patients)); meanwhile, 15 of them (21.2%) had abnormal acid exposure alone. Despite 11 patients having NERD, four patients (36.4%) had abnormal esophageal bile reflux and two of them had mixed reflux of bile with acid. CONCLUSION We believe that the Bilitec method reliably identifies the presence of bilirubin and quantitatively detects the duodenogastroesophageal reflux of bile. Mixed reflux (acid and bile) is the chief pattern of reflux in our GERD patients. Bile reflux either alone or along with acid reflux contributes to the severity of erosive and nonerosive reflux diseases as well as in BE.

Hypertensive lower esophageal sphincter (HLES): Prevalence,symptoms genesis and effect of pneumatic balloon dilatation

Background: Summary and background data: The Hypertensive lower esophageal sphincter (HLES) is an unusual primary motor disorder of the esophagus. The significance of this motility disorder is still questionable. Objective: The objectives were: (a) identification of the prevalence of HLES in these patients, (b) identification of the common presenting symptoms of HLES, (c) study of the correlation of the symptoms with LESP and (d) study of the effectiveness of pneumatic balloon dilation in cases that fail to respond to medical treatment. Methods: A retrospective study that includes four thousand one hundred and seventy patients, who were subjected to esophageal manometry in the period from January 1994 to December 2003, among whom sixty-six patients with HLES (LESP >40 mmHg) were found. In addition to manometry, upper endoscopy was done to forty-nine patients, upper GI barium studies to thirtyeight patients and esophageal pH- metry to sixteen patients. Results: showed that most of our patients were females (45 females and 21 males), with a mean age of 36.6 ±±14 years. Patients with dysphagia (57.5%) had the highest LESP (52.1 ±±21, mmHg) while patients with chest pain (47%) had the highest distal esophageal contraction amplitude (153.9 ±± 93.2 mmHg). Endoscopy showed varying degrees of esophagitis in 17 patients (34%). Barium studies showed corkscrew esophagus in seven patients (18.4%) and dilated esophagus in nine patients (23.7%). LESP was highest in patients with dilated esophagus (57.5 ±± 33.4 mmHg). All our patients were subjected to medical treatment, of which twelve patients underwent pneumatic dilation with successfully reduced LESP and symptoms relief in 91% of patients. Conclusions: It was concluded that the prevalence of HLES is around 1.6, in which dysphagia and chest pain are the usual presenting symptom, and that pneumatic balloon dilatation is very effective when properly applied. It will probably occupy the same position it has in achalasia.

Hypertensive Lower Esophageal Sphincter (HLES): Prevalence, Symptoms genesis and effect of pneumatic balloon dilatation

BACKGROUND SUMMARY AND BACKGROUND DATA The Hypertensive lower esophageal sphincter (HLES) is an unusual primary motor disorder of the esophagus. The significance of this motility disorder is still questionable. OBJECTIVE The objectives were: (a) identification of the prevalence of HLES in these patients, (b) identification of the common presenting symptoms of HLES, (c) study of the correlation of the symptoms with LESP and (d) study of the effectiveness of pneumatic balloon dilation in cases that fail to respond to medical treatment. METHODS A retrospective study that includes four thousand one hundred and seventy patients, who were subjected to esophageal manometry in the period from January 1994 to December 2003, among whom sixty-six patients with HLES (LESP> 40 mmHg) were found. In addition to manometry, upper endoscopy was done to forty-nine patients, upper GI barium studies to thirty-eight patients and esophageal pH- metry to sixteen patients. RESULTS showed that most of our patients were females (45 females and 21 males), with a mean age of 36.6 +/- 14 years. Patients with dysphagia (57.5%) had the highest LESP (52.1 +/- 21, mmHg) while patients with chest pain (47%) had the highest distal esophageal contraction amplitude (153.9 +/- 93.2 mmHg). Endoscopy showed varying degrees of esophagitis in 17 patients (34%). Barium studies showed corkscrew esophagus in seven patients (18.4%) and dilated esophagus in nine patients (23.7%). LESP was highest in patients with dilated esophagus (57.5 +/- 33.4 mmHg). All our patients were subjected to medical treatment, of which twelve patients underwent pneumatic dilation with successfully reduced LESP and symptoms relief in 91% of patients. CONCLUSIONS It was concluded that the prevalence of HLES is around 1.6, in which dysphagia and chest pain are the usual presenting symptom, and that pneumatic balloon dilatation is very effective when properly applied. It will probably occupy the same position it has in achalasia.