Direct observation of long-lived isomers in 212Bi.

Long-lived isomers in (212)Bi have been studied following (238)U projectile fragmentation at 670 MeV per nucleon. The fragmentation products were injected as highly charged ions into a storage ring, giving access to masses and half-lives. While the excitation energy of the first isomer of (212)Bi was confirmed, the second isomer was observed at 1478(30) keV, in contrast to the previously accepted value of >1910 keV. It was also found to have an extended Lorentz-corrected in-ring half-life >30 min, compared to 7.0(3) min for the neutral atom. Both the energy and half-life differences can be understood as being due a substantial, though previously unrecognized, internal decay branch for neutral atoms. Earlier shell-model calculations are now found to give good agreement with the isomer excitation energy. Furthermore, these and new calculations predict the existence of states at slightly higher energy that could facilitate isomer deexcitation studies.

Schottky mass measurement of the 208Hg isotope: implication for the proton-neutron interaction strength around doubly magic 208Pb.

Time-resolved Schottky mass spectrometry has been applied to uranium projectile fragments which yielded the mass value for the 208Hg (Z=80, N=128) isotope. The mass excess value of ME=-13 265(31) keV has been obtained, which has been used to determine the proton-neutron interaction strength in 210Pb, as a double difference of atomic masses. The results show a dramatic variation of the strength for lead isotopes when crossing the N=126 neutron shell closure, thus confirming the empirical predictions that this interaction strength is sensitive to the overlap of the wave functions of the last valence neutrons and protons.

Isotope shift in the dielectronic recombination of three-electron ANd57+.

Isotope shifts in dielectronic recombination spectra were studied for Li-like (A)Nd(57+) ions with A=142 and A=150. From the displacement of resonance positions energy shifts deltaE(142 150)(2s-2p(1/2))=40.2(3)(6) meV [(stat)(sys)] and deltaE(142 150)(2s-2p(3/2))=42.3(12)(20) meV of 2s-2p(j) transitions were deduced. An evaluation of these values within a full QED treatment yields a change in the mean-square charge radius of (142 150)deltar(2)=-1.36(1)(3) fm(2). The approach is conceptually new and combines the advantage of a simple atomic structure with high sensitivity to nuclear size.

Radiative electron capture to the continuum and the short-wavelength limit of electron-nucleus bremsstrahlung in 90A MeV U88 + ((1s2)(2s2))+N2 Collisions.

We have measured the continuum momentum distribution for radiative electron capture to the continuum (RECC) cusp electrons in 90A MeV U88+ + N2-->U88+ + N2 +* + ecusp(0 degrees ) + hnu (RECC) collisions. We demonstrate that x rays coincident with RECC cusp electrons originate from the short-wavelength limit of the electron-nucleus bremsstrahlung and explain the asymmetric cusp shape by comparison with theory within the relativistic impulse approximation.

First measurement of the linear polarization of radiative electron capture transitions.

For radiative electron capture into the K shell of bare uranium ions, a study of the polarization properties has been performed. For this purpose a position sensitive germanium detector has been used as an efficient Compton polarimeter. This enabled us to measure the degree of linear polarization by analyzing Compton scattering inside the detector and to determine the orientation of the polarization plane. Depending on the observation angle and the beam energy used, the radiation is found to be linearly polarized by up to 80%. In all cases studied, the plane of polarization coincides with the collision plane. The results will be discussed in the context of rigorous relativistic calculations, showing that relativistic effects tend to lead to a depolarization of the radiation emitted.

Quantum electrodynamics in strong electric fields: the ground-state Lamb shift in hydrogenlike uranium.

X-ray spectra following radiative recombination of free electrons with bare uranium ions (U92+) were measured at the electron cooler of the ESR storage ring. The most intense lines observed in the spectra can be attributed to the characteristic Lyman ground-state transitions and to the recombination of free electrons into the K shell of the ions. Our experiment was carried out by utilizing the deceleration technique which leads to a considerable reduction of the uncertainties associated with Doppler corrections. This, in combination with the 0 degree observation geometry, allowed us to determine the ground-state Lamb shift in hydrogenlike uranium (U91+) from the observed x-ray lines with an accuracy of 1%. The present result is about 3 times more precise than the most accurate value available up to now and provides the most stringent test of bound-state quantum electrodynamics for one-electron systems in the strong-field regime.

Simultaneous measurement of beta- decay to bound and continuum electron states.

We report the first measurement of a ratio lambda(beta(b))/lambda(beta(c)) of bound-state ((lambda(beta(b))) and continuum-state (lambda(beta(c))) beta(-)-decay rates for the case of bare 207Tl81+ ions. These ions were produced at the GSI fragment separator FRS by projectile fragmentation of a 208Pb beam. After in-flight separation with the Brho-deltaE-Brho method, they were injected into the experimental storage-ring ESR at an energy of 400.5A MeV, stored, and electron cooled. The number of both the 207Tl81+ ions and their bound-state beta(-)-decay daughters, hydrogen-like 207Pb81+ ions, were measured as a function of storage time by recording their Schottky-noise intensities. The experimental result, lambda(beta(b))/lambda(beta(c)) = 0.188(18), is in very good agreement with the value of 0.171(1) obtained from theory employing spectra of allowed transitions.

Pathogenesis of degenerative joint disease produced by in vivo freezing of rabbit articular cartilage.

In vivo freezing of rabbit lateral femoral arterial cartilage with a cryoprobe produces an osteoarthritic-like condition in 12 months. Previous studies have established that the chondrocytes are killed by the freezing process. A loss of stainable mucopolysaccharide occurs. The collagen content of the lesional tissue does not change. The present study investigates the extracellular lysosomal enzyme content, collagen type (I or II), and histologic changes which produce chondrocyte cell clusters in the frozen tissue in response to freezing or articular cartilage. The results indicate that after the initial 30 days there is no significant rise in the extracellular lysosomal enzyme content of the experimental tissue compared with controls. Type II, or cartilage, collagen remains the major constituent of the lesional tissue. Histologic examination at six- to 12-month intervals suggests that chondrocyte clones are produced by invasion by the underlying viable subchondral bone. These results provide insight into the pathogenesis of degenerative joint disease and the rationale of treatment by the use of inhibitors of vascular invasion of articular cartilage.

Evaluation of a new instrument designed for directed cervical excision: cone biopsy excisor.

OBJECTIVE: Our objective was to compare a newly designed instrument, the Cone Biopsy Excisor (CBE; Apple Medical Corporation, Bolton, MA), with the standard loop electrosurgical excision procedure (LEEP) for providing a cervical conization specimen with the best achievable margin quality for histological evaluation. METHODS: Patients referred to the dysplasia clinics at Hartford Hospital, St. Francis/Mt. Sinai Hospital and the University of Connecticut Health Center/New Britain General Hospital were randomized to either the CBE procedure or LEEP. To be included in the study, patients had to meet at least one of the following criteria: biopsy-proven cervical intraepithelial neoplasia grade 2 or 3, unsatisfactory colposcopy, positive endocervical curettage, or one or more degrees of cytohistological discrepancy. Exclusion criteria included pregnancy, undiagnosed uterine bleeding, acute cervicitis, or biopsy-proven invasive carcinoma. Forty-seven patients were randomized to the CBE and 48 to LEEP. To obtain the cervical specimen, third- and fourth-year obstetricalgynecological residents used Force II Valley Lab Generators (Valley Lab, Boulder, CO) at a blend one setting (80/20 blend of cutting and coagulation). Wattage ranged from 25 to 45, according to the size of the instrument used. Pathological reports were reviewed by the author to determine the amount of fragmentation and for tissue diagnosis. Slides of the specimens were evaluated by two blinded gynecological pathologists. The slides were analyzed for margin quality and thermal damage. A thermal damage score was assigned, evaluating the number of cells affected and the depth of damage. This scoring system, designed by the pathologists, ranged from 3 (least thermal damage) to 9 (greatest thermal damage). RESULTS: Of 47 CBE cases and 48 LEEP cases, 41 (87%) and 8 (17%), were single specimens X (1) = 44.6; (p < .0001). The mean number of specimens submitted to pathology per case was 1.2 (+/- 0.6) in the CBE group and 2.3 (+/- 0.9) in the LEEP group (t - 6.89;p < .001). Margins obliterated by thermal artifact included 3 of 47 (6%) in the CBE group and 16 of 48 (33%) in the LEEP group (X (1) = 9.16;p < .003). Mean thermal damage score was 4.1 (± 0.9) in the CBE group and 6.1 (± 1.8) in the LEEP group (t = 6.77; p < .001). CONCLUSION: The Cone Biopsy Excisor provides a cervical specimen that exhibits less fragmentation and less thermal damage and has margins that are less likely to be indeterminate than that provided by standard LEEP.

Electron-electron interaction in strong electromagnetic fields: the two-electron contribution to the ground-state energy in He-like uranium.

Radiative recombination transitions into the ground state of cooled bare and hydrogenlike uranium ions were measured at the storage ring ESR. By comparing the corresponding x-ray centroid energies, this technique allows for a direct measurement of the electron-electron contribution to the ionization potential in the heaviest He-like ions. For the two-electron contribution to the ionization potential of He-like uranium we obtain a value of 2248+/-9 eV. This represents the most accurate determination of two-electron effects in the domain of high-Z He-like ions, and the accuracy reaches already the size of the specific two-electron radiative QED corrections.