Collective excitations of the QED vacuum

Using relativistic Green’s-function techniques we examined single-electron excitations from the occupied Dirac sea in the presence of strong external fields. The energies of these excited states are determined taking into account the electron-electron interaction. We also evaluate relativistic transition strengths incorporating retardation, which represents a direct measure of correlation effects. The shifts in excitation energies are computed to be lower than 0.5%, while the correlated transition strengths never deviate by more than 10% from their bare values. A major conclusion is that we found no evidence for collectivity in the electron-positron field around heavy and superheavy nuclei

Nonlinear extensions of the Dirac equation and their implications in QED

We investigate the influence of additional nonlinear terms in the Dirac Lagrangian on strongly bound electron states in heavy and superheavy atoms. Upper bounds for the coupling constants are deduced by comparison with precision spectroscopy data in QED. We demonstrate that nonlinear interactions may cause significant modifications of electron binding energies in superheavy quasiatomic systems which would not be visible in ordinary atomic-physics measurements

SALIVARY PARAMETERS ALTERED IN SMOKERS AND POSSIBLE CORRELATIONS WITH THE CARIOGENIC ACTIVITY

Objectives. Our research team aimed to evaluate the effects smoking has on several salivary parameters and to assess if there are any correlations between smoking and the cariogenic activity. Material and method. The present research included a total of 35 participants. Saliva was collected from every participant to the study. Salivary chloride, calcium and potassium levels, as well as salivary flux and pH were determined for all subjects. Results. Our results showed significantly lower salivary flux and pH levels in smokers compared to nonsmokers (p < 0.01). Chloride, calcium and potassium we found to have higher concentrations in smokers compared to the control group. However, a statistical significance could be found only for calcium (p = 0.02). Moreover, we were able to find in the smokers group a positive correlation in smokers between salivary chloride levels and cariogenic activity as well as a negative correlation could be found in smokers between salivary calcium levels and the cariogenic activity Conclusions. The results of the present study show that smoking alters salivary parameters and that these modifications can favour the development of dental caries

Transplantul hepatic ortotopic de la donator decedat la adult. Experienţa Centrului de Chirurgie Generală şi transplant hepatic Fundeni

Studiul de faţă analizează experienţa Centrului de Chirurgie Generală şi Transplant Hepatic din Institutul Clinic Fundeni în transplantul hepatic ortotopic cu ficat întreg de la donator decedat la adult (THO), din aprilie 2000 până în aprilie 2006. În această perioadă au fost realizate 45 de THO – 20 femei şi 25 de bărbaţi, cu vârste cuprinse între 19-57 de ani (medie de 45 ani).Indicaţiile pentru transplantare au fost: ciroză VHB – 11, ciroză VHB VHD – 6, ciroză VHC – 13 (2 cu hepatocarcinom), ciroză VHB VHC – 2, ciroză VHB VHD etanol – 1, ciroză biliară primitivă – 5, boala Wilson – 2, ciroză toxic-nutriţională – 2, ciroza toxică non-alcoolică – 1, ciroză autoimună – 1, colangită sclerogenă primitivă – 1. Cu trei excepţii, la care s-a folosit tehnica clasică de transplantare, ficatul a fost grefat după tehnica Belghiti. Complicaţiile postoperatorii locale au survenit la 19 bolnavi (42,22%), iar generale la 19 (42,22%); complicaţiile tardive au fost înregistrate la 20 pacienţi (44,44%), iar recidiva bolii la 7 pacienţi (15,55%). Mortalitatea intraoperatorie şi postoperatorie imediată a fost de 6,66% (3 din 45 pacienţi). La peste 30 de zile de la TH, au decedat alţi cinci pacienţi (11,11%). Patru pacienţi (8,88%) au decedat la distanţă de momentul transplantului prin boală venoocluzivă, prin cancer bronho-pulmonar şi prin infarct miocardic -2. Patruzeci si doi de pacienţi au supravieţuit perioadei postoperatorii (93,33%) şi 33 peste un an (73,33%). THO reprezintă metoda principală de transplantare hepatică, cu o morbiditate şi mortalitate acceptabile

Die nichtlineare Dirac-Gleichung und die Untersuchung effektiver Vielteilchenwechselwirkungen in der QED

zugl.: Frankfurt/M., Univ., Diss., 198

Asymptotic analysis and scaling of friction parameters

International audienc

Asymptotic analysis and scaling of friction parameters

International audienc