ABSTRACT
In this work, dipole defects are investigated applying the thermally stimulated depolarisation currents (TSDC) technique. The TSDC spectra of Al2O3 doped with Mg and Cr show two bands centred at 230 K and 250 K, respectively. The maximum intensity of the bands increases linearly with the polarisation field, a typical behaviour of defects with dipole origin. An increase of the band at 250 K with gamma irradiation has been observed and a thermal decrease of the bands for heat treatments between 1000 K and 1400 K. Above this temperature the bands are partially recovered. Impurity neutron activation analysis shows that magnesium. chromium and iron content varies from 15 to 60 ppm. Optical absorption (AO) measurements show a broad band centred in 2.6 eV (21000 cm(-1)) associated with trapped holes localised on an O- ion adjacent to a cation site which is deficient in positive charge. It has been assumed that a substitutional Mg2+ ion occupies the cation site near a trapped hole on one of the six oxygen ions surrounding the magnesium impurity giving rise to the dipole responsible for the observed TSDC bands. Calculations carried out through defect simulation methods confirm that the probability of Al3+ being replaced by Mg2+ is higher than Mn2+, Co2+, Fe2+ and Cr2+.
Subject(s)
Aluminum Oxide/radiation effects , Thermoluminescent Dosimetry/methods , Aluminum Oxide/chemistry , Chromium/chemistry , Gamma Rays , Magnesium/chemistry , Models, Theoretical , RadiochemistryABSTRACT
The incidence of sudden death in children with congenital aortic stenosis (CAS) varies between 4 and 20%. In several syndromes sudden death is associated with a long QT interval in the electrocardiogram (ECG). The aim of the study was to evaluate the cardiac repolarization in CAS during stress. We included 40 children and young persons, 20 with CAS and 20 healthy controls. All underwent echocardiographic study and treadmill stress test. The QT and relative RR intervals were measured in leads II and V6 at rest and during exercise at preselected heart rates. Mean values of QT were compared by analysis of variance, Student's t-test, and linear regression method. No statistically significant differences in the resting ECG were found between the two groups, whereas during exercise the mean QT of the CAS group was significantly longer than in the controls (p < 0.05), except at a heart rate of 140 +/- 5. Our study demonstrates that patients with CAS have transiently altered cardiac repolarization when there are sudden variations in heart rate. Such a defect could predispose patients with CAS to fatal arrhythmias and sudden death.
Subject(s)
Aortic Valve Stenosis/congenital , Death, Sudden, Cardiac/etiology , Electrocardiography , Exercise/physiology , Heart Conduction System/physiopathology , Myocardial Contraction/physiology , Aortic Valve Stenosis/mortality , Aortic Valve Stenosis/physiopathology , Child , Death, Sudden, Cardiac/epidemiology , Echocardiography , Exercise Test , Heart Rate/physiology , Humans , Incidence , Regression AnalysisABSTRACT
This paper reports Authors' experience in 58 cases of early gastric cancer observed between 1972 and 1990. The diagnosis of E.G.C. was frequently obtained in patients with recent dyspeptic symptoms. The diagnostic importance of endoscopic procedures, upper gastrointestinal X-rays and endoscopic ultrasonography is underlined. The choice of total gastrectomy with the standardized dissection of regional lymph nodes in order to treat multicentric or upper gastric malignancies v.s. distal gastrectomy for antral lesions is discussed. The cumulative survival rate was 84.4%; local recurrence rate was 4.2%.
Subject(s)
Adenocarcinoma/surgery , Carcinoma/surgery , Stomach Neoplasms/surgery , Adenocarcinoma/mortality , Adenocarcinoma/pathology , Adult , Aged , Aged, 80 and over , Carcinoma/mortality , Carcinoma/pathology , Female , Follow-Up Studies , Gastrectomy , Humans , Lymphatic Metastasis , Male , Middle Aged , Neoplasm Recurrence, Local , Stomach/pathology , Stomach Neoplasms/mortality , Stomach Neoplasms/pathology , Time FactorsABSTRACT
The Mallory-Weiss syndrome is a more common cause of upper gastrointestinal bleeding than that previously recognised. Personal experience is reported of twelve cases of Mallory-Weiss tear, constituting 6.4% of all cases of upper gastrointestinal tract hemorrhage observed in the three year period from 1984 to 1986. History of alcoholism was present in 50% and hiatus hernia was associated in 41% of all the cases. Ten patients (84%) were managed nonoperatively, two patients underwent operation. None of the twelve patients in this series died. The literature of the last few years, is reviewed with particular reference to progress in the treatment of the syndrome.
