15,693 research outputs found

    The Muon Anomalous Magnetic Moment in the Reduced Minimal 3-3-1 Model

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    We study the muon anomalous magnetic moment (g−2)μ(g-2)_{\mu} in the context of the reduced minimal 3-3-1 model recently proposed in the literature. In particular, its spectrum contains a doubly charged scalar (H±±H^{\pm \pm}) and gauge boson (U±±U^{\pm \pm}), new singly charged vectors (V±V^{\pm}) and a Z′Z^{\prime} boson, each of which might give a sizeable contribution to the (g−2)μ(g-2)_{\mu}. We compute the 1-loop contributions from all these new particles to the (g−2)μ(g-2)_{\mu}. We conclude that the doubly charged vector boson provides the dominant contribution, and by comparing our results with the experimental constraints we derive an expected value for the scale of SU(3)L⊗U(1)NSU(3)_L\otimes U(1)_N symmetry breaking vχ∼2v_{\chi} \sim 2 TeV. We also note that, if the discrepancy in the anomalous moment is resolved in the future without this model then the constraints will tighten to requiring vχ>2.7v_\chi > 2.7 TeV with current precision, and will entirely rule out the model if the expected precision is achieved by the future experiment at Fermilab.Comment: 19 pages, 4 figure

    Monitoring the Bi-Directional Relativistic Jets of the Radio Galaxy 1946+708

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    We report on a multi-frequency, multi-epoch campaign of Very Long Baseline Interferometry observations of the radio galaxy 1946+708 using the VLBA and a Global VLBI array. From these high-resolution observations we deduce the kinematic age of the radio source to be ∼\sim4000 years, comparable with the ages of other Compact Symmetric Objects (CSOs). Ejections of pairs of jet components appears to take place on time scales of 10 years and these components in the jet travel outward at intrinsic velocities between 0.6 and 0.9 c. From the constraint that jet components cannot have intrinsic velocities faster than light, we derive H_0 > 57 km s^-1 Mpc^-1 from the fastest pair of components launched from the core. We provide strong evidence for the ejection of a new pair of components in ~1997. From the trajectories of the jet components we deduce that the jet is most likely to be helically confined, rather than purely ballistic in nature.Comment: 20 pages, 8 figures, accepted to Ap

    Assessment of an ORION-based experimental platform for measuring the opacity of high-temperature and high-density plasma

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    The following provides an assessment of an experimental platform based on the ORION laser at AWE Aldermasten, England, for measuring the opacity of high-temperature and high-density LTE plasmas. The specific points addressed are (1) the range of electron density and temperature that can be achieved with short-pulse beams alone, as well as (2) by means of compression with a long-pulse beam; (3) the accuracy with which electron density, electron temperature, and absolute emissivity can be measured; (4) the use of pulse shaping to increase the sample density to above solid density; (5) the effect that target materials and target design have on maintaining spatial uniformity of the sample, and (6) the need for additional diagnostics to produce and characterize samples for decisive measurements

    The two sided parsec scale structure of the Low Luminosity Active Galactic Nucleus in NGC 4278

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    We present new Very Long Baseline Interferometry observations of the LINER galaxy NGC 4278. The observations were taken with the Very Long Baseline Array (VLBA) and a single antenna of the Very Large Array (VLA) at 5 GHz and 8.4 GHz and have a linear resolution of <0.1 pc. Our radio data reveal a two sided structure, with symmetric S-shaped jets emerging from a flat spectrum core. We fit the jet brightness with gaussian components, which we identify from a previous observation taken five years before. By comparing the positions of the components in the two epochs, we measure motions between 0.45 +/- 0.14 and 3.76 +/- 0.65 mas, corresponding to apparent velocities < 0.2c, and to ages in the range 8.3 - 65.8 years. Assuming that the radio morphology is intrinsically symmetric and its appearance is governed by Doppler beaming effects, we find that NGC4278 has mildly relativistic jets (beta ~ 0.75), closely aligned to the line-of-sight (2 degrees < theta < 4 degrees). Alternatively, the source could be oriented at a larger angle and asymmetries could be related to the jet interaction with the surrounding medium. We also present new simultaneous VLA observations between 1.4 and 43 GHz, and a 5 GHz light curve between 1972 and 2003. The radio spectrum can be fit by a relatively steep power-law (alpha = 0.54). We find significant variability at 5 GHz. All these arguments indicate that the radiation from NGC 4278 is emitted via the synchrotron process by relativistic particles accelerated by a supermassive black hole. Despite a much lower power, this is the same process that takes place in ordinary radio loud AGNs.Comment: 29 pages, 9 figures, ApJ accepte

    The incidence and risk factors for new onset atrial fibrillation in the PROSPER study

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    Aims Atrial fibrillation/flutter (AF) is the most common arrhythmia in older people. It associates with reduced exercise capacity, increased risk of stroke, and mortality. We aimed to determine retrospectively whether pravastatin reduces the incidence of AF and whether any electrocardiographic measures or clinical conditions might be risk factors for its development. Methods and results The PROspective Study of Pravastatin in the Elderly at Risk (PROSPER) was a randomized, double-blind controlled trial that recruited 5804 individuals aged 70-82 years with a history of, or risk factors for, vascular disease. A total of 2891 were allocated to pravastatin and 2913 to placebo; mean follow-up was 3.2 years. Electrocardiograms (ECGs), which were recorded at baseline, annually thereafter, and at run-out, were processed by computer and reviewed manually. In all, 264 of 2912 (9.1%) of the placebo group and 283 of 2888 (9.8%) of the pravastatin-treated group developed AF [hazard ratio 1.08 (0.92,1.28), P = 0.35)]. Multivariate analysis showed that PR and QTc intervals, age, left ventricular hypertrophy, and ST-T abnormalities were related to development of AF after adjustment for many variables including alcohol consumption, which itself was univariately predictive of developing AF. Previous myocardial infarction on the ECG was not a risk factor. A history of vascular disease was strongly linked with developing AF but not diabetes and hypertension. Conclusion Pravastatin does not reduce the incidence of AF in older people at risk of vascular disease, at least in the short-medium term. Risk factors for AF include older age, prolongation of PR or QTc intervals, left ventricular hypertrophy, and ST-T abnormalities on the EC

    Measurement of urinary beta core fragment of human chorionic gonadotrophin in women with vulvovaginal malignancy and its prognostic significance

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    Tumours of the vulva and vagina are rare and there are relatively few studies of circulating markers in these conditions. The urinary measurement of the core fragment of the beta-subunit of hCG has been proposed as a useful tumour marker in non-trophoblastic gynaecological malignancies. This study describe the measurement of urinary beta-core in 50 patients with vulvovaginal malignancy. In contrast to other studies corrections were made for both the effect of urine concentration and the age of the patient. Each patient was followed up for at least 24 months, and at this time their status was correlated with their initial level of urinary beta-core. The sensitivity of beta-core was only 38%, but of those patients with elevated levels 90% had died within 24 months, while only 32% of those with normal levels had died. For both patients at initial presentation and those with recurrent disease, there was a highly significant difference in the survival curve between those with elevated beta-core levels and those with normal levels. This is similar to findings in cervical carcinoma, and suggests that for lower genital tract cancer the measurement of urinary beta-core may be valuable as a prognostic indicator, allowing a more informed approach to treatment and follow-up

    The prognostic significance of beta human chorionic gonadotrophin and its metabolites in women with cervical carcinoma

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    AIMS: To examine long term survival of women with primary and recurrent cervical carcinoma in relation to (1) excretion of beta-core (a urinary metabolite of beta human chorionic gonadotrophin (beta hCG)) and (2) beta hCG immunostaining of the tumours, to determine the suitability of these markers for assessing prognosis. METHODS: This was a prospective observational study undertaken in a gynaecological oncology centre: 57 women with primary cervical cancer and 42 with recurrent disease were recruited between January 1990 and September 1992. Kaplan-Meier survival analysis with the log rank test was used to assess survival differences with survival rate given per year of follow up. RESULTS: In primary disease, the four year survival for the beta-core negative group was 79%, compared with 14% for the beta-core positive group (p = 0.001). This was still significant for early stage disease or squamous lesions alone. In recurrent disease, beta-core positivity was not prognostically significant. Immunohistochemistry was of no prognostic significance in either group. CONCLUSIONS: beta-core excretion appears to be useful in assessing prognosis of primary cervical cancer but not of recurrent disease. A large prospective study of urinary beta-core in early stage cervical cancer is needed to determine whether it can be used as an index for modifying treatment

    Absorption cross section at 3.39 µm of alkanes, aromatics and substituted hydrocarbons

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    The present study reports gas phase absorption cross sections at 3.39 μm of 21 liquid hydrocarbons. Measurements were performed in the temperature range 303–413 K using an infrared He–Ne laser. In addition to n-alkanes, a number of cyclo-alkane, aromatic, and substituted hydrocarbons were investigated. The results demonstrate that (i) the absorption cross sections are temperature independent in the studied range, and that (ii) the aromatic and substituted hydrocarbons exhibit much smaller cross sections than n-alkanes for an identical number of C–H bonds. A tentative empirical correlation has been developed and shown to accurately predicts the cross section
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