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At least 559 records · Page 31Linked to original sources
PubMed2000

Electric-octupole and pure-electric-quadrupole effects in soft-X-Ray photoemission

Second-order [ O(k(2)), k = omega/c] nondipole effects in soft-x-ray photoemission are demonstrated via an experimental and a theoretical study of angular distributions of neon valence photoelectrons in the 100-1200 eV photon-energy range. A newly derived theoretical expression for nondipolar angular distributions characterizes the second-order effects using four new parameters with primary contributions from pure-quadrupole and octupole-dipole interference terms. Independent-particle calculations of these parameters account for a significant portion of the existing discrepancy between experiment and theory for Ne 2p first-order nondipole parameters.

Journal Article↗
PubMed2004

Electric activity of the colon in irritable bowel syndrome: the 'tachyarrhythmic' electric pattern.

BACKGROUND AND AIM: The etiology of irritable bowel syndrome is unknown. It presents with crampy abdominal pain associated with alternating constipation and diarrhea but with no anatomic abnormality on diagnostic testing. Because the condition is related to motility disturbance, the hypothesis that a disorder of the colonic electromyographic activity is responsible for the colonic motile disorders in irritable bowel syndrome, was investigated. METHODS: The electromyographic activity of the sigmoid colon was recorded transcutaneously in 18 patients with irritable bowel syndrome (49.6 +/- 10.2 years, 12 women) and 14 healthy volunteers (47.2 +/- 9.9 years; eight women) by applying three electrodes to the abdominal skin below the umbilicus. The sigmoid colon pressure was measured by means of a saline-perfused tube connected to a pneumohydraulic capillary infusion system. RESULTS: Slow waves with a regular rhythm were recorded in the healthy volunteers exhibiting the same frequency, amplitude and conduction velocity from all three electrodes. Action potentials (AP) were not registered. The basal sigmoid colon pressure was interrupted by bouts of elevation. In irritable bowel syndrome, the electromyographic rhythm was irregular and the slow wave variables were higher than those of the normal volunteers and were not the same from the three electrodes; occasional AP were also recorded. The sigmoid colon basal pressure was significantly higher, and was interrupted by pressure bouts significantly higher, than those of the volunteers. CONCLUSIONS: Irritable bowel syndrome exhibited a 'tachyarrhythmic' pattern of electromyographic activity with higher slow wave variables than normal and occasional AP. The resulting elevated basal colonic pressure and tone may explain some of the irritable bowel syndrome symptoms. Because diagnostic testing of the irritable bowel syndrome shows no anatomic abnormalities, it is suggested that the cause of irritable bowel syndrome is related to an abnormal focus in one or more of the colonic pacemakers emitting these abnormal waves. However, further studies are required to verify these findings.

Adult↗
PubMed1999

Effect of volatile anaesthetics on the electrical activity and the coupling coefficient of weakly electrically coupled neurones.

1. The application of the volatile anaesthetics, halothane and isoflurane (1% v/v and 2% v/v), to the CNS of Lymnaea reduced the firing frequency of the small weakly coupled pedal A cluster (PeA) neurones, which eventually become quiescent. There was no change in their resting membrane potential. 2. Met-enkephalin significantly increased the coupling coefficient between PeA neurones. 3. The volatile anaesthetics decreased the coupling coefficient even in the presence of met-enkephalin. 4. These effects were dose dependent and the effects of halothane were more rapid than those of isoflurane, reflecting their different anaesthetic potencies.

Anesthetics, Inhalation↗