Average-atom calculations of bound-free and free-free cross sections in dense plasmas.

Cross sections for photo-induced bound-free and free-free transitions in plasmas are evaluated in the average-atom approximation and applied to determine opacities of dense plasmas of light elements. Parameters characterizing the plasmas (chemical potential, average ionic charge, free electron density, bound and continuum wave functions, and occupation numbers) are obtained from the average-atom model. Lowest-order calculations of the free-free cross sections, which diverge in the low-frequency limit, are regularized by accounting for the finite electron-ion relaxation time. The resulting analysis provides the basis for average-atom studies of plasma opacities. Such studies are presented for dense lithium, beryllium, boron, and carbon. Applications are given to Rosseland mean opacities of dense hydrogen and deuterium plasmas and to comparisons of free-free to bound-free opacities in shock-compressed plasmas. Average-atom cross section and opacity calculations are extended to plasmas consisting of more than one ionic species, boron nitride, polystyrene, and a composite H, He, C plasma.

Determination of the Scalar and Vector Polarizabilities of the Cesium 6s

Using recent high-precision measurements of electric dipole matrix elements of atomic cesium, we make an improved determination of the scalar (α) and vector (ß) polarizabilities of the cesium 6s^{2}S_{1/2}→7s^{2}S_{1/2} transition calculated through a sum-over-states method. We report values of α=-268.82(30)a_{0}^{3} and ß=27.139(42)a_{0}^{3} with the highest precision to date. We find a discrepancy between our value of ß and the past preferred value, resulting in a significant shift in the value of the weak charge Q_{w} of the cesium nucleus. Future work to resolve the differences in the polarizability will be critical for interpretation of parity nonconservation measurements in cesium, which have implications for physics beyond the standard model.

Average-atom treatment of relaxation time in x-ray Thomson scattering from warm dense matter.

The influence of finite relaxation times on Thomson scattering from warm dense plasmas is examined within the framework of the average-atom approximation. Presently most calculations use the collision-free Lindhard dielectric function to evaluate the free-electron contribution to the Thomson cross section. In this work, we use the Mermin dielectric function, which includes relaxation time explicitly. The relaxation time is evaluated by treating the average atom as an impurity in a uniform electron gas and depends critically on the transport cross section. The calculated relaxation rates agree well with values inferred from the Ziman formula for the static conductivity and also with rates inferred from a fit to the frequency-dependent conductivity. Transport cross sections determined by the phase-shift analysis in the average-atom potential are compared with those evaluated in the commonly used Born approximation. The Born approximation converges to the exact cross sections at high energies; however, differences that occur at low energies lead to corresponding differences in relaxation rates. The relative importance of including relaxation time when modeling x-ray Thomson scattering spectra is examined by comparing calculations of the free-electron dynamic structure function for Thomson scattering using Lindhard and Mermin dielectric functions. Applications are given to warm dense Be plasmas, with temperatures ranging from 2 to 32 eV and densities ranging from 2 to 64 g/cc.

A cohort and database study of airway management in patients undergoing thyroidectomy for retrosternal goitre.

Patients undergoing thyroid surgery with retrosternal goitre may raise concerns for the anaesthetist, especially airway management. We reviewed a multicentre prospective thyroid surgery database and extracted data for those patients with retrosternal goitre. Additionally, we reviewed the anaesthetic charts of patients with retrosternal goitre at our institution to identify the anaesthetic induction technique and airway management. Of 4572 patients in the database, 919 (20%) had a retrosternal goitre. Two cases of early postoperative tracheomalacia were reported, one in the retrosternal group. Despite some very large goitres, no patient required tracheostomy or cardiopulmonary bypass and there were no perioperative deaths. In the subset of 133 patients managed at our institution over six years, there were no major adverse anaesthetic outcomes and no patient had a failed airway or tracheomalacia. In the latter cohort, of 32 (24%) patients identified as having a potentially difficult airway, 17 underwent awake fibreoptic tracheal intubation, but two of these were abandoned and converted to intravenous induction and general anaesthesia. Eleven had inhalational induction; two of these were also abandoned and converted to intravenous induction and general anaesthesia. Of those suspected as having a difficult airway, 28 (87.5%) subsequently had direct laryngoscopy where the laryngeal inlet was clearly visible. We found no good evidence that thyroid surgery patients with retrosternal goitre, with or without symptoms and signs of tracheal compression, present the experienced anaesthetist with an airway that cannot be managed using conventional techniques. This does not preclude the need for multidisciplinary discussion and planning.

Thomson scattering from a three-component plasma.

A model for a three-component plasma consisting of two distinct ionic species and electrons is developed and applied to study x-ray Thomson scattering. Ions of a specific type are assumed to be identical and are treated in the average-atom approximation. Given the plasma temperature and density, the model predicts mass densities, effective ionic charges, and cell volumes for each ionic type, together with the plasma chemical potential and free-electron density. Additionally, the average-atom treatment of individual ions provides a quantum-mechanical description of bound and continuum electrons. The model is used to obtain parameters needed to determine the dynamic structure factors for x-ray Thomson scattering from a three-component plasma. The contribution from inelastic scattering by free electrons is evaluated in the random-phase approximation. The contribution from inelastic scattering by bound electrons is evaluated using the bound-state and scattering wave functions obtained from the average-atom calculations. Finally, the partial static structure factors for elastic scattering by ions are evaluated using a two-component version of the Ornstein-Zernike equations with hypernetted chain closure, in which electron-ion interactions are accounted for using screened ion-ion interaction potentials. The model is used to predict the x-ray Thomson scattering spectrum from a CH plasma and the resulting spectrum is compared with experimental results obtained by Feltcher et al. [Phys. Plasmas 20, 056316 (2013)].

Thomson scattering in the average-atom approximation.

The average-atom model is applied to study Thomson scattering of x-rays from warm dense matter with emphasis on scattering by bound electrons. Parameters needed to evaluate the dynamic structure function (chemical potential, average ionic charge, free electron density, bound and continuum wave functions, and occupation numbers) are obtained from the average-atom model. The resulting analysis provides a relatively simple diagnostic for use in connection with x-ray scattering measurements. Applications are given to dense hydrogen, beryllium, aluminum, and titanium plasmas. In the case of titanium, bound states are predicted to modify the spectrum significantly.

Low-frequency plasma conductivity in the average-atom approximation.

Low-frequency properties of a plasma are examined within the average-atom approximation, which presumes that scattering of a conducting electron on each atom takes place independently of other atoms. The relaxation time tau distinguishes a high-frequency region omegatau>1 , where the single-atom approximation is applicable explicitly, from extreme low frequencies omegatau<1 , where, naively, the single-atom approximation is invalid. A proposed generalization of the formalism, which takes into account many-atom collisions, is found to be accurate in all frequency regions, from omega=0 to omegatau>1 , reproducing the Ziman formula in the static limit, results based on the Kubo-Greenwood formula for high frequencies and satisfying the conductivity sum rule precisely. The correspondence between physical processes leading to the conventional Ohm's law and the infrared properties of QED is discussed. The suggested average-atom approach to frequency-dependent conductivity is illustrated by numerical calculations for an aluminum plasma in the temperature range 2-10eV .

Relativistic electron correlation, quantum electrodynamics, and the lifetime of the 1s(2)2s(2)2p2p0(3/2) level in boronlike argon.

The lifetime of the Ar13+ 1s(2)2s(2)2p2p0(3/2) metastable level was determined at the Heidelberg Electron Beam Ion Trap to be 9.573(4)(5). The accuracy level of one per thousand makes this measurement sensitive to quantum electrodynamic effects like the electron anomalous magnetic moment (EAMM) and to relativistic electron-electron correlation effects like the frequency-dependent Breit interaction. Theoretical predictions, adjusted for the EAMM, cluster about a lifetime that is approximately shorter than our experimental result.

Nondipole effects in the photoionization of xe 4d5/2 and 4d3/2: evidence for quadrupole satellites.

Measurements of nondipole parameters in spin-orbit-resolved Xe 4d photoionization demonstrate dynamical differences arising from relativistic effects. The experimental data do not agree with relativistic random-phase approximation calculations of single ionization dipole and quadrupole channels. It is suggested that the discrepancy is due to the omission of multiple-excitation quadrupole channels, i.e., quadrupole satellite transitions.

Dramatic nondipole effects in low-energy photoionization: experimental and theoretical study of Xe 5s.

The Xe 5s nondipole photoelectron parameter gamma is obtained experimentally and theoretically from threshold to approximately 200 eV photon energy. Significant nondipole effects are seen even in the threshold region of this valence shell photoionization. In addition, contrary to previous understanding, clear evidence of interchannel coupling among quadrupole photoionization channels is found.

Vacuum-polarization corrections to the parity-nonconserving 6s-7s transition amplitude in (133)Cs.

The dominant one-loop radiative corrections to atomic wave functions, those associated with vacuum polarization in the nuclear Coulomb field, are evaluated for the 6s-7s parity-nonconserving transition amplitude in (133)Cs. These corrections increase the size of this amplitude by 0.4% and, correspondingly, increase the difference between the experimental value of the weak charge Q(W)((133)Cs) and the value predicted by the standard model.

Perceived overqualification and dimensions of job satisfaction: a longitudinal analysis.

The present study is an investigation of the effects of perceived overqualification on dimensions of job satisfaction. The data for this study came from a two-wave panel study of members of a midwestern American Postal Workers Union local. Job satisfaction was operationalized with 4 subscales from the Job Descriptive Index (P. Smith, L. Kendall, & C. Hulin, 1969). The following three hypotheses were tested: (a) Perceived overqualification will be negatively related to facets of job satisfaction; (b) there is stability in the test-retest correlations of facets of job satisfaction; and (c) the effects of perceived overqualification on facets of job satisfaction will not change from Time 1 to Time 2 because of adaptation. The cross-sectional results supported the hypotheses and suggested that perceived overqualification has a negative effect on job satisfaction. However, the relationships varied by dimension of perceived overqualification and dimension of job satisfaction. Future researchers of overqualification and dimensions of job satisfaction should consider relative deprivation as a source of work-related deprivations.

Perceived overqualification and health: a longitudinal analysis.

The authors examined the effects of perceived overqualification on health and health decline by means of a 2-wave panel study of members of a midwestern American Postal Workers Union local. The 1st hypothesis was that overqualification was negatively related to health at Time 2 (T2); the second hypothesis was that overqualification was positively related to perceived health decline at T2. Neither was supported by the data. However, the relationships were in the expected direction for perceived mismatch but not for the perceived no grow dimension of overqualification. The results imply that perceived no grow may have immediate threats to health, whereas perceived mismatch may have longer term implications for health. The stability of perceived health between Time 1 (T1) and T2 could overshadow a longitudinal effect of overqualification on health and health decline at T2.

Cosmesis following complete local excision of breast cancer.

BACKGROUND: With the establishment of the safety of breast conservation in early breast cancer, cosmesis has become an increasingly important end-point of treatment. The aim of the present study was to establish a model to assess breast cosmesis after complete local excision and to assess cosmesis achieved in patients who had surgery using the seroma technique. METHODS: A total of 42 patients were retrospectively reviewed and assessed by independent clinical assessment by a surgeon, structured questionnaire and clinical photography. RESULTS: A total of 86% of patients were rated by surgeon and patient as having a good or excellent cosmetic outcome. There was a high degree of concordance between independent clinical assessment and clinical photographic analysis. CONCLUSIONS: A model has been established for the assessment of breast cosmesis; the technique of seroma formation without reconstruction of the defect results in good or excellent cosmesis in the majority of patients.

Pre-operative histological diagnosis of breast cancer.

BACKGROUND: A concordant triple assessment (clinical, mammographic and cytological) diagnosis of breast malignancy allows for pre-operative planning of surgery and may also allow for one-stage surgery. However, while the accuracy of cytology is high, it is unable to distinguish invasive cancer from ductal carcinoma in situ (DCIS). A malignant mass may be due to pure in situ cancer and hence axillary dissection may be avoided if pre-operative histology is available. METHODS: A consecutive series of 300 cases of breast cancer treated over the last 5 years by the two authors was analysed to determine: the method of achieving pre-definitive operation histology; the number of stages of surgery required; and the number of cases of mass-forming DCIS which could be susceptible to over-treatment. RESULTS: Of 289 patients undergoing local definitive surgery for breast cancer, 12 (42%) had clinical masses predominantly due to DCIS and in most of these patients axillary dissection was avoided. Histology was obtained prior to definitive surgery in 272 (94.1%) patients, by intra-operative frozen section in 159 (55.0%), incisional biopsy in 37 (12.8%), needle localization biopsy in 62 (21.5%) and core biopsy in 14 (4.8%). A total of 189 patients (65.4%) underwent one-stage surgery only. Breast conservation was achieved in 210 (72.7%) patients. Those requiring mastectomy were significantly more likely to have required two stages of surgery as were those with lesions detected by screening. CONCLUSIONS: Mass-forming DCIS cannot be predicted pre-operatively by triple assessment alone; and therefore pre-operative histology is required to avoid axillary dissection. Pre-operative histology may be obtained by core biopsy or intra-operative frozen section to identify DCIS and distinguish it from invasive disease, but both allow a one-stage surgical procedure in the majority of cases.

Perceived overqualification and psychological well-being.

The relationship between perceived overqualification and psychological well-being was explored within the framework of stress-illness models, using multiple regression analysis. Data were collected from 179 male and 109 female members of a local midwestern chapter of the American Postal Workers Union. As expected, there was a significant, positive relationship between perceived overqualification and psychological well-being: The greater the perceived overqualification, the greater the psychological distress. The interaction between perceived overqualification and gender was not significant.

Modification of growth of desmoid tumours in tissue culture by anti-oestrogenic substances: a preliminary report.

BACKGROUND: Tamoxifen and toremifene have been used in patients with advanced desmoid tumours with response rates of 51%. METHODS: We developed an experimental model of desmoid tumour cells in tissue culture to study their effect. Four cell lines were established in tissue culture. All native and corresponding cultured tumours were oestrogen receptor negative. Tumour 1 was from a 22 year old with familial adenomatous polyposis (FAP) and recurrent abdominal wall desmoid tumours. She remains disease free on tamoxifen 4 years following surgery. Both her mother and sister also have shown regression of their FAP-associated desmoid tumours at the menopause and on tamoxifen, respectively. We assessed the effect of tamoxifen on desmoid tumours in tissue culture at 780 ng/mL. The results were assessed by cell density counting. RESULTS: Tumours 1 and 2 have responded with an approximately. 50% reduction in growth to tamoxifen at 780 ng/mL. CONCLUSIONS: This apparent growth inhibitory effect of tamoxifen on two desmoid tumour cell lines appears to be independent of oestrogen and correlates with the in vivo effect of tamoxifen on three desmoid tumours in an FAP family.

The effects of union membership on multiple work commitments among female public sector employees.

The effects of union membership on union, organizational, and dual commitment among 245 clerical employees at a midwestern state university represented by a Local of the American Federation of State, County, and Municipal Employees (AFSCME) were investigated. Based on the similarity hypothesis of the social identity theory, it was hypothesized that union membership would be positively related to union and dual commitment and negatively related to organizational commitment. The results of the regression analyses supported the similarity hypothesis, and union membership explained a significant amount of variance in union and dual commitment but not in organizational commitment. These findings are discussed in the context of applying social psychological approaches to understand attitudes toward unionization; industrial conflict; and union, organizational, and dual commitment.

Evaluation of an automated urine chemistry reagent-strip analyzer.

We evaluated the Miles Inc., Clinitek Atlas Automated Urine Chemistry Analyzer for 11 tests: bilirubin, color, glucose, ketones, leukocyte esterase, nitrite, occult blood, pH, protein, specific gravity, and urobilinogen. The instrument uses a roll of reagent strips affixed to a clear plastic support; urine specimens are automatically pipetted onto these strips. The instrument measures the pads' color using reflectance colorimetry. Specific gravity is measured using a fiberoptic refractive index method. Four hospitals participated in the evaluation, and tests were performed only on fresh urine samples. We found the instrument easy to use; it has walk-away capability with up to 40-specimen loading capacity plus spaces for STATs, calibrators and controls. We found good comparability with chemical tests and other nonreagent strip procedures, as well as good agreement with the Miles Inc. Clinitek 200+ urine chemistry analyzer and visual reading of the Miles Inc. Multistix Reagent Strips. The Clinitek Atlas is rugged and reliable, and is suitable for a high-volume urinalysis laboratory.