Measurement of the parity violating 6S-7S transition amplitude in cesium achieved within 2 \times 10^{-13} atomic-unit accuracy by stimulated-emission detection

We exploit the process of asymmetry amplification by stimulated emission which provides an original method for parity violation (PV) measurements in a highly forbidden atomic transition. The method involves measurements of a chiral, transient, optical gain of a cesium vapor on the 7S-6P_{3/2} transition, probed after it is excited by an intense, linearly polarized, collinear laser, tuned to resonance for one hyperfine line of the forbidden 6S-7S transition in a longitudinal electric field. We report here a 3.5 fold increase, of the one-second-measurement sensitivity, and subsequent reduction by a factor of 3.5 of the statistical accuracy compared with our previous result [J. Gu\'ena et al., Phys. Rev. Lett. 90, 143001 (2003)]. Decisive improvements to the set-up include an increased repetition rate, better extinction of the probe beam at the end of the probe pulse and, for the first time to our knowledge, the following: a polarization-tilt magnifier, quasi-suppression of beam reflections at the cell windows, and a Cs cell with electrically conductive windows. We also present real-time tests of systematic effects, consistency checks on the data, as well as a 1% accurate measurement of the electric field seen by the atoms, from atomic signals. PV measurements performed in seven different vapor cells agree within the statistical error. Our present result is compatible with the more precise Boulder result within our present relative statistical accuracy of 2.6%, corresponding to a 2 \times 10^{-13} atomic-unit uncertainty in E_1^{pv}. Theoretical motivations for further measurements are emphasized and we give a brief overview of a recent proposal that would allow the uncertainty to be reduced to the 0.1% level by creating conditions where asymmetry amplification is much greater.Comment: Article 21 pages, 6 figures, 3 tables Typos, addition of few comments and little more data (1 week) leading to a slight reduction of the error bar Accepted for publication in Phys.Rev.

Allergenicity and crossreactivity of buffalo grass (Stenotaphrum secundatum)

Background. In the subtropical climate of South Africa, grasses of the subfamily Panicoideae are predominant. Bermuda grass has previously been shown to be an important local allergen, and immunoglobulin E (IgE) epitopes of Bermuda grass extracts are known to be distinct from those of the Pooid pollen extracts. Following our demonstration of sensitivity in 43% of patients grass-allergic to the Panicoid, Kikuyu grass, we have studied the closely related buffalo grass, Stenotaphrurn secundaturn, indigenous to the Western Cape region, the east coast of Africa and the oceanic islands such as Mauritius; and Eragrostis, another common indigenous grass with a wide distribution.Objective. To partially characterise the allergens of buffalo pollen, and examine its immunological relationships with local common grasses such as Eragrostis and Kikuyu.Methods. Grass-allergic patients were evaluated clinically, and skin prick tests (SPTs) and radio-allergosorbent tests (RASTs) to Bermuda and grass mix were performed. Sera of timothy grass-sensitive patients from Belgium were also included in this study. Pollen extract from buffalo grass was characterised by specific IgE binding by means of immunoblotting and enzyme-linked immunosorbent assay (ELISA). Crossreactivity between the grasses was studied by means of inhibition of IgE binding.Results. More than 90% of grass-sensitive patients were found to have IgE antibodies to Buffalo and Eragrostis pollen. Inhibition of ELISA and immunoblots revealed that extracts of these grass pollens could significant inhibit IgE binding to the local grass pollens, Kikuyu, buffalo, Eragrostis and Bermuda on solid phase, but 100% inhibition was never achieved, indicating that cross-reactive but also unique epitopes are present. We also identified a subset of patients with negative RASTs to Bermuda, and minimal inhibition by Bermuda pollen extract.Conclusion. Buffalo and Eragrostis are important aeroallergens in the Cape, dispersed during the long dry, windy summer. Our data suggest that the local grasses are major  sensitisers, and that South African diagnostic panels should include extracts of buffalo and Eragrostis grasses

Is routine pathological examination required in South African children undergoing adenotonsillectomy?

Objective. We aimed to determine the incidence of abnormal pathological findings in the tonsils and/or adenoids of children undergoing tonsillectomy and/or adenoidectomy, and the incidence of tuberculosis of the tonsils and adenoids; suggest criteria to identify children at risk for adenotonsillar tuberculosis; and investigate the association between HIV and adenotonsillar abnormality, the cost-effectiveness of routine pathological examination of adenotonsillectomy specimens, and criteria to decide which specimens to send for histological examination. Methods. We undertook an 8-month prospective study on all children (≤12 years) undergoing consecutive tonsillectomy or adenotonsillectomy (T&A) at Red Cross War Memorial Children’s Hospital. Patients were assessed pre-operatively and tonsil sizes graded pre- and intra-operatively. Blood was taken for HIV testing, and all tonsils and adenoids were examined histologically. A cost-benefit analysis was done to determine the cost-effectiveness of adenotonsillectomy routine pathology. Results. A total of 344 tonsils were analysed from 172 children (102 boys, 70 girls); 1 patient had nasopharyngeal tuberculosis, and 1 lymphoma of the tonsils; 13 (7.6%) patients had clinically asymmetrically enlarged tonsils but no significant abnormal pathological finding. The average cost of detecting a clinically significant abnormality was R22 744 (R45 488 ÷ 2 abnormalities). Conclusions. The following criteria could improve cost-effectiveness of pathological examination of adenotonsillectomy specimens: positive tuberculosis contact at home, systemic symptoms of fever and weight loss, cervical lymphadenopathy >3 cm, suspicious nasopharyngeal appearance, HIV-positive patient, rapid tonsillar enlargement or significant tonsillar asymmetry. On our evidence, routine pathological investigation for South African children does not seem to be justified

Is diagnostic tonsillectomy indicated in all children with asymmetrically enlarged tonsils?

Objectives. The aims of the study were: (i) to determine the necessity for diagnostic tonsillectomy in children with asymmetrically enlarged tonsils; (ii) to determine the accuracy of clinical assessment of tonsillar asymmetry; and (iii) to determine how to manage children with clinical tonsillar asymmetry in a developing-world practice. Methods. A prospective study was carried out at Red Cross War Memorial Children's Hospital in Cape Town, over an 8-month period. All children undergoing tonsillectomy or adenotonsillectomy had a clinical assessment of tonsil symmetry done, and all tonsil and adenoid specimens were examined histologically. The maximum diameter and volume of the resected tonsils were measured. A comparison was done of true tonsil asymmetry in patients with asymmetrical tonsils and a subgroup of matched controls with symmetrical tonsils. Results. A total of 344 tonsils were analysed (172 patients). The 13 patients (7.6%) diagnosed as having clinically asymmetrically enlarged tonsils had no significant pathological diagnosis. In the patients with symmetrical tonsils there were 2 abnormal pathological findings (tuberculosis of the adenoids and T-cell lymphoma of the tonsils and adenoids). In the clinically asymmetrical tonsil group, true tonsillar asymmetry was 3 mm (maximum diameter), and 2.2 cm3 (volume), compared with 1.9 mm and 1.5 cm3 in the symmetrical tonsil group. When patients with clinical tonsillar asymmetry and symmetry were compared, the difference in maximum diameter (p = 0.62) and volume (p = 0.73) was not significantly different. Conclusions. Clinical tonsillar asymmetry is usually apparent rather than real. The incidence of significant pathology in children with asymptomatic, asymmetrical tonsils is low. Diagnostic tonsillectomy is indicated in children with asymmetrically enlarged tonsils associated with constitutional symptoms, cervical lymphadenopathy, rapid tonsil enlargement or significant tonsillar asymmetry

Indian monsoon variability in response to orbital forcing during the late Pliocene

The Asian monsoon is a major component of the global climate system and can be divided into two subsystems, the Indian monsoon and the East Asian monsoon. Insights into monsoon behaviour and dynamics can be gained through studying past warm intervals in Earth's history. One such interval is the Pliocene epoch, specifically the mid-Piacenzian Warm Period (mPWP; 3.264–3.025 Ma). This time is characterised as a period of sustained warmth, with annual mean temperatures 2–3 °C higher than the pre-industrial era. Studies have examined the East Asian monsoon during the mPWP from both a geological data and climate modelling perspective. However, there has been little investigation into the behaviour of the Indian monsoon. Using a coupled atmosphere-ocean global climate model (HadCM3), the Indian summer monsoon response to orbital forcing during the mPWP is studied. Of the simulated interglacial events (Marine Isotope Stages KM5c, KM3, K1 and G17), MIS KM5c is the only one with a near-modern orbital forcing. This experiment is compared to a pre-industrial simulation to determine the nature of the mPWP Indian summer monsoon in the absence of a different pattern if insolation forcing. The monsoon at MIS KM5c, is simulated to be stronger than pre-industrial, with higher surface air temperatures and precipitation over land due to higher levels of CO2. MIS G17, K1, and KM3 represent interglacial events of similar magnitude with different insolation forcing than MIS KM5c. The Indian summer monsoon is simulated to be significantly stronger for the interglacials K1 and KM3, compared to KM5c. This is due to stronger precession forcing causing an increase in summer surface air temperature and precipitation. When combined with Pliocene geological boundary conditions, these results highlight the significant effect of orbital forcing on the strength of the Indian summer monsoon. The sensitivity of the Indian monsoon to orbital forcing has important implications for any parallels drawn between Pliocene and future monsoon behaviour

Atomic Hydrogen Cleaning of Polarized GaAs Photocathodes

Atomic hydrogen cleaning followed by heat cleaning at 450$^\circ$C was used to prepare negative-electron-affinity GaAs photocathodes. When hydrogen ions were eliminated, quantum efficiencies of 15% were obtained for bulk GaAs cathodes, higher than the results obtained using conventional 600$^\circ$C heat cleaning. The low-temperature cleaning technique was successfully applied to thin, strained GaAs cathodes used for producing highly polarized electrons. No depolarization was observed even when the optimum cleaning time of about 30 seconds was extended by a factor of 100

Is diagnostic tonsillectomy indicated in all children with asymmetrically enlarged tonsil?

Objectives. The aims of the study were: (i) to determine the necessity for diagnostic tonsillectomy in children with asymmetrically enlarged tonsils; (ii) to determine the accuracy of clinical assessment of tonsillar asymmetry; and (iii) to determine how to manage children with clinical tonsillar asymmetry in a developing-world practice. Methods. A prospective study was carried out at Red Cross War Memorial Children’s Hospital in Cape Town, over an 8-month period. All children undergoing tonsillectomy or adenotonsillectomy had a clinical assessment of tonsil symmetry done, and all tonsil and adenoid specimens were examined histologically. The maximum diameter and volume of the resected tonsils were measured. A comparison was done of true tonsil asymmetry in patients with asymmetrical tonsils and a subgroup of matched controls with symmetrical tonsils. Results. A total of 344 tonsils were analysed (172 patients). The 13 patients (7.6%) diagnosed as having clinically asymmetrically enlarged tonsils had no significant pathological diagnosis. In the patients with symmetrical tonsils there were abnormal pathological findings (tuberculosis of the adenoids and T-cell lymphoma of the tonsils and adenoids). In the clinically asymmetrical tonsil group, true tonsillar asymmetry was 3 mm (maximum diameter), and 2.2 cm3 (volume), compared with 1.9 mm and 1.5 cm3 in the symmetrical tonsil group. When patients with clinical tonsillar asymmetry and symmetry were compared, the difference in maximum diameter (p = 0.62) and volume (p = 0.73) was not significantly different. Conclusions. Clinical tonsillar asymmetry is usually apparent rather than real. The incidence of significant pathology in children with asymptomatic, asymmetrical tonsils is low. Diagnostic tonsillectomy is indicated in children with asymmetrically enlarged tonsils associated with constitutional symptoms, cervical lymphadenopathy, rapid tonsil enlargement or significant tonsillar asymmetry

The Intrinsically X-ray Weak Quasar PHL 1811. I. X-ray Observations and Spectral Energy Distribution

This is the first of two papers reporting observations and analysis of the unusually bright (m_b=14.4), luminous (M_B=-25.5), nearby (z=0.192) narrow-line quasar PHL 1811, focusing on the X-ray properties and the spectral energy distribution. Two Chandra observations reveal a weak X-ray source with a steep spectrum. Variability by a factor of 4 between the two observations separated by 12 days suggest that the X-rays are not scattered emission. The XMM-Newton spectra are modelled in the 0.3--5 keV band by a steep power law with \Gamma = 2.3\pm 0.1, and the upper limit on intrinsic absorption is 8.7 x 10^{20} cm^{-2}. The spectral slopes are consistent with power law indices commonly observed in NLS1s, and it appears that we observe the central engine X-rays directly. Including two recent Swift ToO snapshots, a factor of ~5 variability was observed among the five X-ray observations reported here. In contrast, the UV photometry obtained by the XMM-Newton OM and Swift UVOT, and the HST spectrum reveal no significant UV variability. The \alpha_{ox} inferred from the Chandra and contemporaneous HST spectrum is -2.3 \pm 0.1, significantly steeper than observed from other quasars of the same optical luminosity. The steep, canonical X-ray spectra, lack of absorption, and significant X-ray variability lead us to conclude that PHL 1811 is intrinsically X-ray weak. We also discuss an accretion disk model, and the host galaxy of PHL 1811.Comment: 45 pages, 9 figures, accepted for publication in Ap

Cross-country differences in unemployment : fiscal policy, unions, and household preferences in general equilibrium

We develop a five period overlapping generations model with individuals who differ by ability and with an imperfect labour market (union wage setting) for the individuals of lower ability. The model explains human capital formation, hours worked and unemployment within one coherent framework. Its predictions match the differences in the unemployment rate across 12 OECD countries remarkably well. A Shapley decomposition of these differences reveals an almost equal role for fiscal policy variables and union preferences. As to fiscal policy, differences in unemployment benefits play a much more important role than tax differences. Differences in households’ taste for leisure are unimportant