Tracking ultrafast non-adiabatic dissociation dynamics of the deuterated water dication molecule.

We applied reaction microscopy to elucidate fast non-adiabatic dissociation dynamics of deuterated water molecules after direct photo-double ionization at 61 eV with synchrotron radiation. For the very rare D+ + O+ + D breakup channel, the particle momenta, angular, and energy distributions of electrons and ions, measured in coincidence, reveal distinct electronic dication states and their dissociation pathways via spin-orbit coupling and charge transfer at crossings and seams on the potential energy surfaces. Notably, we could distinguish between direct and fast sequential dissociation scenarios. For the latter case, our measurements reveal the geometry and orientation of the deuterated water molecule with respect to the polarization vector that leads to this rare 3-body molecular breakup channel. Aided by multi-reference configuration-interaction calculations, the dissociation dynamics could be traced on the relevant potential energy surfaces and particularly their crossings and seams. This approach also unraveled the ultrafast time scales governing these processes.

Atomic autoionization in the photo-dissociation of super-excited deuterated water molecules fragmenting into D+ + O+ + D.

We present the relaxation dynamics of deuterated water molecules via autoionization, initiated by the absorption of a 61 eV photon, producing the very rare D+ + O+ + D breakup channel. We employ the COLd target recoil ion momentum spectroscopy method to measure the 3D momenta of the ionic fragments and emitted electrons from the dissociating molecule in coincidence. We interpret the results using the potential energy surfaces extracted from multi-reference configuration interaction calculations. The measured particle energy distributions can be related to a super-excited monocationic state located above the double ionization threshold of D2O. The autoionized electron energy shows a sharp distribution centered around 0.5 eV, which is a signature of the atomic oxygen autoionization occurring in the direct and sequential dissociation processes of D2O+* at a large internuclear distance. In this way, an O+ radical fragment and a low-energy electron are created, both of which can trigger secondary reactions in their environment.

Efficiency of charge transfer in changing the dissociation dynamics of OD+ transients formed after the photo-fragmentation of D2O.

We present an investigation of the relaxation dynamics of deuterated water molecules after direct photo-double ionization at 61 eV. We focus on the very rare D+ + O+ + D reaction channel in which the sequential fragmentation mechanisms were found to dominate the dynamics. Aided by theory, the state-selective formation and breakup of the transient OD+(a1Δ, b1Σ+) is traced, and the most likely dissociation path-OD+: a1Δ or b1Σ+ → A 3Π â†’ X 3Σ- → B 3Σ--involving a combination of spin-orbit and non-adiabatic charge transfer transitions is determined. The multi-step transition probability of this complex transition sequence in the intermediate fragment ion is directly evaluated as a function of the energy of the transient OD+ above its lowest dissociation limit from the measured ratio of the D+ + O+ + D and competing D+ + D+ + O sequential fragmentation channels, which are measured simultaneously. Our coupled-channel time-dependent dynamics calculations reproduce the general trends of these multi-state relative transition rates toward the three-body fragmentation channels.

Resonance signatures in the body-frame valence photoionization of CF4.

We present a combined experimental and theoretical investigation of the electron dynamics and body-frame angular dependence of valence photo-single ionization of CF4 and subsequent dissociation into CF3+ and F. Ionization from a valence t2 orbital shows overlapping shape resonances close to threshold that couple to the same total symmetry, leading to striking changes in the photoelectron angular distributions when viewed in the body-frame.

VUV and XUV reflectance of optically coated mirrors for selection of high harmonics.

We report the reflectance, ~1° from normal incidence, of six different mirrors as a function of photon energy, using monochromatic vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) radiation with energies between 7.5 eV and 24.5 eV. The mirrors examined included both single and multilayer optical coatings, as well as an uncoated substrate. We discuss the performance of each mirror, paying particular attention to the potential application of suppression and selection of high-order harmonics of a Ti:sapphire laser.

On the occurrence of focal, occult in situ and invasive carcinoma in 250 mastectomy specimens.

In 1982, a total of 250 breasts were removed for cancer in the surgical departments of the Oslo City Health Department, comprising 81% of all new breast cancers reported in Oslo in 1982. Invasive ductal carcinoma (68%) and invasive lobular carcinoma (12.4%) were the predominant types. Special attention was given to the presence of occult in situ or invasive carcinomas more than 1 cm from the periphery of the main carcinoma. In 24.8% of the specimens, carcinoma in situ was found in such locations, and an additional 6.9% showed a second, occult invasive carcinoma. Carcinoma in situ was equally common in invasive ductal and invasive lobular carcinoma. Occult invasive carcinoma was predominantly found in specimens with invasive lobular carcinoma. There was a significantly increased number of lymph node metastases in patients with carcinoma in situ or second, occult primary carcinoma more than 1 cm from the periphery of the main carcinoma.

Development of the otolith organs and semicircular canals in the Japanese red-bellied newt, Cynops pyrrhogaster.

The sequence in which the otoliths and semicircular canals and their associated sensory epithelia appear and develop in the newt are described. Three-dimensional reconstruction of serial sections through the otic vesicle of newt embryos from stages 31 through 58 demonstrate the first appearance, relative position and growth of the otoliths. A single otolith is first seen in stage 33 embryos (approximately 9 days old); this splits into separate utricular and saccular otoliths at stage 40 (13 days). The lateral semicircular canal is the first to appear, at stage 41 (14 days). The anterior and posterior canals appear approximately one week later and the vestibular apparatus is essentially fully formed at stage 58 (approximately 5 weeks). The data reported here will serve as ground-based controls for fertilized newt eggs flown on the International Microgravity Laboratory-2 Space Shuttle flight, to investigate the influence of microgravity on the development of the gravity-sensing organs.

Location of a cytoplasmic epitope for monoclonal antibody HK 12.18 on H,K-ATPase alpha subunit.

The enzyme responsible for gastric acidification is a heterodimeric (alpha and beta subunit) P-type ATPase, an integral protein of parietal cell apical membranes, which promotes electroneutral exchange of exoplasmic K(+) for cytoplasmic H(3)O(+). The molecular mechanisms of the catalytic exchange reaction are imperfectly understood, and await clarification of the precise topology of the enzyme with respect to the secretory membrane. Antibodies directed against H,K-ATPase subunits have been useful in confirming hydropathy plot predictions of HKalpha and HKbeta secondary structure. The monoclonal antibody HK 12.18, which labels gastric mucosal parietal cells by immunocytochemistry, and which binds to a single M(r) approximately 94,000 polypeptide by SDS-PAGE immunoblot of gastric microsomes, has been widely used as a specific marker of parietal cells in clinical and cell biological studies of acid secretion, and as a specific HKalpha probe in biochemical studies. However, the uncertain location of the HK 12.18 epitope has limited the antibody's usefulness as a topology probe. In this study, HK 12. 18 immune reactivity with native H,K-ATPase tryptic peptides, HKalpha cDNA fragments expressed in bacteria, and overlapping synthetic HKalpha tridecapeptides, was used to identify the HK 12.18 epitope as seven consecutive amino acids (Asp(682)-Met-Asp-Pro-Ser-Glu-Leu(688)) in the cytoplasmic middle third of HKalpha.

H,K-ATPase alpha subunit C-terminal membrane topology: epitope tags in the insect cell expression system.

The H,K-ATPase responsible for gastric acidification is a heterodimeric (alpha and beta subunit) P-type ATPase, an integral protein of parietal cell apical membranes, which promotes the electroneutral exchange of K+ for protons, is stimulated by K+ and is inhibited by 2-methyl-8-(phenylmethoxy)imidazo[1, 2-alpha]pyridine-3-acetonitrile (SCH 28080). Hydropathy analysis of the catalytic alpha subunit has been interpreted in terms of four N-terminal transmembrane domains, a cytoplasmically oriented segment containing ATP binding and phosphorylation sites, and a C-terminal region with four or six putative transmembrane domains. Several lines of evidence implicate the C-terminal region of P-type ATPases in cation-binding and occlusion, conformational changes, and interactions with the beta subunit (HKbeta), making the definition of topology a prerequisite for understanding the structural basis of these functions. Influenza haemagglutinin epitopes (YPYDVPDYA; flu tag) were inserted in predicted hydrophilic segments of the alpha subunit (HKalpha) to establish the membrane orientation of two amino acids with different predicted topologies in the C-terminal four- and six-transmembrane models. Wild-type and mutated HKalpha and HKbeta cDNA species were expressed in insect cells (Sf9) via recombinant baculovirus infection, and expression of H,K-ATPase was verified by immunoblotting with HKalpha- and HKbeta-specific and flu-tag-specific antibodies. Functional assays showed K+-stimulated, SCH 28080-sensitive ATPase activity, confirming neo-native topology in H,K-ATPase heterodimers expressed in Sf9 cells. The topology of flu tags was determined by microsomal protease protection assays in Sf9 cells and immunolabelling of HKalpha and HKbeta in intact and permeabilized Sf9 cells. In addition, MS of native H,K-ATPase tryptic peptides identified cytoplasmically oriented HKalpha residues. The results indicated cytoplasmic exposure of Leu844 and Phe996, and luminal exposure of Pro898, leading to a revised secondary structure model of the C-terminal third of HKalpha.