A higher-than-predicted measurement of iron opacity at solar interior temperatures.

Nearly a century ago it was recognized that radiation absorption by stellar matter controls the internal temperature profiles within stars. Laboratory opacity measurements, however, have never been performed at stellar interior conditions, introducing uncertainties in stellar models. A particular problem arose when refined photosphere spectral analysis led to reductions of 30-50 per cent in the inferred amounts of carbon, nitrogen and oxygen in the Sun. Standard solar models using the revised element abundances disagree with helioseismic observations that determine the internal solar structure using acoustic oscillations. This could be resolved if the true mean opacity for the solar interior matter were roughly 15 per cent higher than predicted, because increased opacity compensates for the decreased element abundances. Iron accounts for a quarter of the total opacity at the solar radiation/convection zone boundary. Here we report measurements of wavelength-resolved iron opacity at electron temperatures of 1.9-2.3 million kelvin and electron densities of (0.7-4.0) × 10(22) per cubic centimetre, conditions very similar to those in the solar region that affects the discrepancy the most: the radiation/convection zone boundary. The measured wavelength-dependent opacity is 30-400 per cent higher than predicted. This represents roughly half the change in the mean opacity needed to resolve the solar discrepancy, even though iron is only one of many elements that contribute to opacity.

Systematic Study of L-Shell Opacity at Stellar Interior Temperatures.

The first systematic study of opacity dependence on atomic number at stellar interior temperatures is used to evaluate discrepancies between measured and modeled iron opacity [J. E. Bailey et al., Nature (London) 517, 56 (2015)NATUAS0028-083610.1038/nature14048]. High-temperature (>180 eV) chromium and nickel opacities are measured with ±6%-10% uncertainty, using the same methods employed in the previous iron experiments. The 10%-20% experiment reproducibility demonstrates experiment reliability. The overall model-data disagreements are smaller than for iron. However, the systematic study reveals shortcomings in models for density effects, excited states, and open L-shell configurations. The 30%-45% underestimate in the modeled quasicontinuum opacity at short wavelengths was observed only from iron and only at temperature above 180 eV. Thus, either opacity theories are missing physics that has nonmonotonic dependence on the number of bound electrons or there is an experimental flaw unique to the iron measurement at temperatures above 180 eV.

Electron impact ionization dynamics of para-benzoquinone.

Triple differential cross sections (TDCSs) for the electron impact ionization of the unresolved combination of the 4 highest occupied molecular orbitals (4b3g, 5b2u, 1b1g, and 2b3u) of para-benzoquinone are reported. These were obtained in an asymmetric coplanar geometry with the scattered electron being observed at the angles -7.5°, -10.0°, -12.5° and -15.0°. The experimental cross sections are compared to theoretical calculations performed at the molecular 3-body distorted wave level, with a marginal level of agreement between them being found. The character of the ionized orbitals, through calculated momentum profiles, provides some qualitative interpretation for the measured angular distributions of the TDCS.

Electron- and photon-impact ionization of furfural.

The He(i) photoelectron spectrum of furfural has been investigated, with its vibrational structure assigned for the first time. The ground and excited ionized states are assigned through ab initio calculations performed at the outer-valence Green's function level. Triple differential cross sections (TDCSs) for electron-impact ionization of the unresolved combination of the 4a″ + 21a' highest and next-highest occupied molecular orbitals have also been obtained. Experimental TDCSs are recorded in a combination of asymmetric coplanar and doubly symmetric coplanar kinematics. The experimental TDCSs are compared to theoretical calculations, obtained within a molecular 3-body distorted wave framework that employed either an orientation average or proper TDCS average. The proper average calculations suggest that they may resolve some of the discrepancies regarding the angular distributions of the TDCS, when compared to calculations employing the orbital average.

Bowel perforation in intestinal lymphoma: incidence and clinical features.

BACKGROUND: Perforation is a serious life-threatening complication of lymphomas involving the gastrointestinal (GI) tract. Although some perforations occur as the initial presentation of GI lymphoma, others occur after initiation of chemotherapy. To define the location and timing of perforation, a single-center study was carried out of all patients with GI lymphoma. PATIENTS AND METHODS: Between 1975 and 2012, 1062 patients were identified with biopsy-proven GI involvement with lymphoma. A retrospective chart review was undertaken to identify patients with gut perforation and to determine their clinicopathologic features. RESULTS: Nine percent (92 of 1062) of patients developed a perforation, of which 55% (51 of 92) occurred after chemotherapy. The median day of perforation after initiation of chemotherapy was 46 days (mean, 83 days; range, 2-298) and 44% of perforations occurred within the first 4 weeks of treatment. Diffuse large B-cell lymphoma (DLBCL) was the most common lymphoma associated with perforation (59%, 55 of 92). Compared with indolent B-cell lymphomas, the risk of perforation was higher with aggressive B-cell lymphomas (hazard ratio, HR = 6.31, P < 0.0001) or T-cell/other types (HR = 12.40, P < 0.0001). The small intestine was the most common site of perforation (59%). CONCLUSION: Perforation remains a significant complication of GI lymphomas and is more frequently associated with aggressive than indolent lymphomas. Supported in part by University of Iowa/Mayo Clinic SPORE CA97274 and the Predolin Foundation.

Evidence for a T-shape break-up pattern in the triple photoionization of Li.

We examine the angular distributions of all three electrons ionized from Li by a single photon near the triple ionization threshold using a fully quantum-mechanical treatment. We find strong evidence for a T-shape break-up pattern at a 5 eV excess energy as previously predicted by quasiclassical simulations [A. Emmanouilidou and J. M. Rost, J. Phys. B 39, 4037 (2006); A. Emmanouilidou, P. Wang, and J. M. Rost, Phys. Rev. Lett. 100, 063002 (2008)]. This finding is in conflict with the expected Wannier break-up dynamics of three electrons moving at mutual angles of 120°, which is expected to hold at energies a few eV above threshold. We use our quantum-mechanical approach to explore the physical mechanisms behind this unusual break-up configuration.

Ejection of quasi-free-electron pairs from the helium-atom ground state by single-photon absorption.

We investigate the single-photon double ionization of helium at photon energies of 440 and 800 eV. We observe doubly charged ions with close to zero momentum corresponding to electrons emitted back to back with equal energy. These slow ions are the unique fingerprint of an elusive quasifree photon double ionization mechanism predicted by Amusia et al. nearly four decades ago [J. Phys. B 8, 1248 (1975)]. It results from the nondipole part of the electromagnetic interaction. Our experimental data are supported by calculations performed using the convergent close-coupling and time-dependent close-coupling methods.

Exotic dense-matter states pumped by a relativistic laser plasma in the radiation-dominated regime.

In high-spectral resolution experiments with the petawatt Vulcan laser, strong x-ray radiation of KK hollow atoms (atoms without n = 1 electrons) from thin Al foils was observed at pulse intensities of 3 × 10(20) W/cm(2). The observations of spectra from these exotic states of matter are supported by detailed kinetics calculations, and are consistent with a picture in which an intense polychromatic x-ray field, formed from Thomson scattering and bremsstrahlung in the electrostatic fields at the target surface, drives the KK hollow atom production. We estimate that this x-ray field has an intensity of >5 × 10(18) W/cm(2) and is in the 3 keV range.

Angular distributions for the complete photofragmentation of the Li atom.

We explore the complete breakup of the Li atom after absorption of a single photon, the purest example of the so-called four-body Coulomb problem. The resulting strongly correlated three-electron continuum is investigated by calculating the angular distributions of the ionized electrons using advanced close-coupling techniques. We find that the distributions are dominated by the Coulomb interactions between the electrons, that multiple break-up processes can be identified, and that the complex dynamics of the fragmentation process are evident for most scattering geometries.

Strong molecular alignment dependence of H2 electron impact ionization dynamics.

Low-energy (E(0) = 54 eV) electron impact single ionization of molecular hydrogen (H(2)) has been investigated as a function of molecular alignment in order to benchmark recent theoretical predictions [Colgan et al., Phys. Rev. Lett. 101, 233201 (2008) and Al-Hagan et al., Nature Phys. 5, 59 (2009)]. In contrast to any previous work, we observe distinct alignment dependence of the (e,2e) cross sections in the perpendicular plane in good overall agreement with results from time-dependent close-coupling calculations. The cross section behavior can be consistently explained by a rescattering of the ejected electron in the molecular potential resulting in an effective focusing along the molecular axis.

Prominent radiative contributions from multiply-excited states in laser-produced tin plasma for nanolithography.

Extreme ultraviolet (EUV) lithography is currently entering high-volume manufacturing to enable the continued miniaturization of semiconductor devices. The required EUV light, at 13.5 nm wavelength, is produced in a hot and dense laser-driven tin plasma. The atomic origins of this light are demonstrably poorly understood. Here we calculate detailed tin opacity spectra using the Los Alamos atomic physics suite ATOMIC and validate these calculations with experimental comparisons. Our key finding is that EUV light largely originates from transitions between multiply-excited states, and not from the singly-excited states decaying to the ground state as is the current paradigm. Moreover, we find that transitions between these multiply-excited states also contribute in the same narrow window around 13.5 nm as those originating from singly-excited states, and this striking property holds over a wide range of charge states. We thus reveal the doubly magic behavior of tin and the origins of the EUV light.

Energy relaxation rates in dense hydrogen plasmas.

A comprehensive study is made of the energy relaxation rates between ions and electrons in a dense hydrogen plasma. Results of classical molecular dynamics (MD) simulations are compared with quantal calculations using the Fermi golden rule and using dimensional continuation. The rates from the molecular dynamics simulations employing a screened potential are found to be in reasonable agreement with the Landau-Spitzer relaxation rates, and are around 30% higher than the Fermi golden rule rates. By inverting the classical MD relaxation rate vs the quantal result, a semiclassical value for the screening length is suggested. We present energy relaxation rates relevant for radiation-hydrodynamic simulations of inertial confinement fusion devices.

The molecular basis of the folate-sensitive fragile site FRA11A at 11q13.

We report on the molecular basis of the rare, folate-sensitive fragile site FRA11A in chromosome band 11q13 in a family with cytogenetic expression. Five individuals express the fragile site and one was mentally retarded. Expansion of a polymorphic CGG-repeat located at the 5' end of the C11orf80 gene causes FRA11A. The CGG-repeat elongation coincides with hypermethylation of the adjacent CpG island and subsequent transcriptional silencing of the C11orf80 gene. This gene has no homology with known genes. A relationship between cytogenetic expression of the fragile site and the mental handicap seems unlikely, as FRA11A was found in a mentally retarded patient as well as in phenotypically normal carriers from the same family. However, incomplete penetrance cannot be entirely excluded.

A direct interaction between a glutamine-rich activator and the N terminus of TFIIB can mediate transcriptional activation in vivo.

Studies examining the mechanism by which transcriptional activators function have suggested that the general transcription factor IIB (TFIIB) can be a target for certain regulatory proteins. For example, we showed previously that expression of a mutant form of TFIIB can specifically inhibit activation in vivo mediated by the strong, glutamine-rich activator protein GAL4-ftzQ. Using transient cotransfection assays, we have defined the regions in both GAL4-ftzQ and TFIIB that are required for activity in vivo and provide evidence that a potential zinc finger structure at the N terminus of TFIIB is necessary for the observed functional interaction between the two proteins. Using a protein binding assay, we have demonstrated that GAL4-ftzQ can specifically interact with TFIIB in vitro. This interaction requires the same regions in both molecules necessary for function in vivo and is reduced or eliminated by mutations predicted to disrupt the zinc finger in TFIIB. These results support the idea that a direct interaction between a regulatory protein and TFIIB can be important for transcriptional activation in vivo and, combined with previous data of others, suggest that different activators can function by contacting distinct regions of TFIIB.

Multiple cis-acting sequence elements are required for efficient splicing of simian virus 40 small-t antigen pre-mRNA.

We have determined the effects of a number of mutations in the small-t antigen mRNA intron on the alternative splicing pattern of the simian virus 40 early transcript. Expansion of the distance separating the small-t pre-mRNA lariat branch point and the shared large T-small t 3' splice site from 18 to 29 nucleotides (nt) resulted in a relative enhancement of small-t splicing in vivo. This finding, coupled with the observation that large-T pre-RNA splicing in vitro was not affected by this expansion, suggests that small-t splicing is specifically constrained by a short branch point-3' splice site distance. Similarly, the distance separating the 5' splice site and branch point (48 nt) was found to be at or near a minimum for small-t splicing, because deletions in this region as small as 2 nt dramatically reduced the ratio of small-t to large-T mRNA that accumulated in transfected cells. Finally, a specific sequence within the small-t intron, encompassing the upstream branch sites used in large-T splicing, was found to be an important element in the cell-specific pattern of early alternative splicing. Substitutions within this region reduced the ratio of small-t to large-T mRNA produced in HeLa cells but had only minor effects in human 293 cells.

Functional interaction between p53, the TATA-binding protein (TBP), andTBP-associated factors in vivo.

The transcriptional activator p53 is known to interact with components of the general transcription factor TFIID in vitro. To examine the relevance of these associations to transcriptional activation in vivo, plasmids expressing a p53-GAL4 chimera and Drosophila TATA-binding protein (dTBP) were transfected into Drosophila Schneider cells. p53-GAL4 and dTBP displayed a markedly synergistic effect on activated transcription from a GAL4 site-containing reporter that was at least 10-fold greater than observed with other activators tested. A mutant p53 previously shown to be defective in both transcriptional activation in vivo and in binding to TBP-associated factors (TAFs) in vitro, although still capable of binding dTBP, did not cooperate with dTBP, suggesting that TAFs may contribute to this synergy. Providing further support for this possibility, transfected dTBP assembled into rapidly sedimenting complexes and could be immunoprecipitated with anti-TAF antibodies. While overexpression of any of several TAFs did not affect basal transcription, in either the presence or the absence of cotransfected dTBP, overexpression of TAFII230 inhibited transcriptional activation mediated by p53-GAL4 as well as by GAL4-VP16 and Sp1. Overexpression of TAFII40 and TAFII60 also inhibited activation by p53-GAL4 but had negligible effects on activation by GAL4-VP16 and Sp1, while TAFII110 did not affect any of the activators. TAF-mediated inhibition of activated transcription could be rescued by high levels of exogenous dTBP, which also restored full synergy. These data demonstrate for the first time that functional interactions can occur in vivo between TBP, TAFs, and p53.

Collisional heating and adiabatic expansion of warm dense matter with intense relativistic electrons.

Adiabatic expansion of a warm dense Ti plasma has been observed after isochoric heating of a 100-µm-thick Ti foil with an ∼100-ns-long intense relativistic electron bunch at an energy of 19.8 MeV and a current of 1.7 kA. The expansion fits well with the analytical point-source solution. After 10 J is deposited and the plasma rapidly expands out of the warm dense phase, a stable degenerate plasma (T∼1.2eV) with n_{e}>10^{17}cm^{-3} is measured for >100 ns. This is the first temporal measurement of the generation and adiabatic expansion of a large volume (3×10^{-4}cm^{3}) of warm dense plasma isochorically heated by intense monochromatic electrons. The suite of diagnostics is presented, which includes time-resolved plasma plume expansion measurements on a single shot, visible spectroscopy measurements of the emission and absorption spectrum, measurements of the beam distribution, and plans for the future.

Clinical correlates of distinct immunophenotypic and histologic subcategories of lymphocyte-predominance Hodgkin's disease.

Histologic and paraffin immunohistologic studies were carried out on 32 patients with lymphocyte-predominance Hodgkin's disease (LPHD) seen from 1970 through 1982. While nodular histology was accurately predictive of B-cell phenotype (Leu M1 -/L26+), diffuse histology corresponded to either B-cell or Hodgkin's (Leu M1 +/L26-) phenotype, not invariably predictable even when attention was paid to subtle paragranuloma cytology. Clinical characteristics were compared between histologic (diffuse v nodular) and immunophenotypic (Leu M1 +/L26-, Hodgkin's phenotype, v Leu M1 -/L26+, B-cell phenotype) subgroups. Ten patients have since died, and the median follow-up of the living patients was 14 years (range, 6 to 31). Of the several clinical parameters compared, only axillary nodal presentation was strongly associated with both B-cell phenotype and nodular histology, while male predominance related more to B-cell phenotype than nodular histology. No significant difference in overall survival or relapse rate was apparent among either the histologic or the immunophenotypic subgroups. However, very late but salvageable relapses were associated with nodular histology. The incidences of secondary malignancies and death from Hodgkin's disease (HD) were also comparable between the subgroups. Although difference in clinical presentation may exist, neither the histologic nor the immunophenotypic subcategories of LPHD could be demonstrated to correlate with differences in clinical outcome.

Patterns of failure in primary testicular non-Hodgkin's lymphoma.

Patterns of failure were analyzed in 30 patients with testicular non-Hodgkin's lymphoma: 16 had stage IE disease, ten had stage IIE, and four had stage IV. After orchiectomy, two of the 16 patients with stage IE disease received no additional therapy, one received multiagent chemotherapy, and 13 received pelvic and para-aortic radiation. Twelve patients with stage IE disease had progression, and the median time to progression was 12 months. Of the 14 patients with extratesticular involvement (stage IIE or IV), one (stage IV) received no treatment after orchiectomy, three (stage IIE) received para-aortic and pelvic radiation, and ten (seven stage IIE and three stage IV) received multiagent chemotherapy with or without radiation. Eight of the patients with stage IIE or IV disease had progression, and the median time to progression was 11 months. Widespread extranodal progression was observed in 17 of the 20 patients who had progression. The tendency of testicular lymphoma for early systemic progression suggests a need for multiagent chemotherapy in initial management.