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We apply Weinberg's method of effective gauge theories to the study of light scalar masses and coupling constants, in a simplified model with two widely separated mass scales. No improvement of the unnaturalness in the Higgs sector is seen. 相似文献
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We propose a class of supergravity models coupled to matter in which the scales of supersymmetry breaking and of weak gauge symmetry breaking are both fixed by dimensional transmutation, not put in by hand. The models have a flat potential with zero cosmological constant before the evaluation of weak radiative corrections which determine . These models are consistent with all particle physi cs and cosmological constraints for top quark masses in the range 30 GeV < mt < 100 GeV. 相似文献
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Bächler J Bartke J Bialkowska H Bock R Brockmann R Buncic P Chase SI Derado I Eckardt V Eschke J Ferenc D Fleischmann B Foka P Fuchs M Gazdzicki M Gladysz E Harris JW Heck W Hoffmann M Jacobs PM Kabana S Kadija K Keidel R Kosiec J Kowalski M Kühmichel A Lahanas M Lee JY Ljubicic A Margetis S Morse R Nappi E Odyniec G Paic G Panagiotu AD Petridis A Piper A Posa F Poskanzer AM Pugh HG Pühlhofer F Rai G Rauch W Renfordt R Röhrich D Roland G Rothard H Runge K Sandoval A Schambach JJ Schmitz N 《Physical review letters》1994,72(10):1419-1422
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The recently proposed cosmologically acceptable N=1 supergravity models based on the SU(5) unification group define unambigously the minimal particle content of the theory. This fact allows us to determine quite precisely their low-energy behaviour. The SU(2)×U(1) breaking to U(1)e.m. is a consequence of radiative corrections of the supergravity induced soft breaking terms. The proposed mechanism (which is model independent) introduces naturally a hierarchy between the MW and MX scales. Calculating the low-energy effective potential we shot that a corrects SU(2)×U(1) breaking is obtained without any limit (except the experimental one) on the top-quark mass. The masses of the supersymmetric partners of mater and gauge fermions can be low and consequently accessible experimentally (sleptons, s quarks, gauginos ). A neutral Higgs is also predicted wirth a mass . In addition, we show that if mt?45 GeV, the gravitino and gluino masses are bounded from below by . The values of sin2θW (in the two-loop approximation) and the ratio predicted are in very good agreement with the experimentally measured values. 相似文献
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It is explicitly shown that in the SU(5) prototype for grand unified theories, the decoupling of superheavy gauge bosons as well as Higgses from the light gauge particles is complete and therefore a gauge interaction hierarchy is possible. 相似文献
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Amran AB Majid Aznan Fazli Ismail Muhamad Samudi Yasir Redzuwan Yahaya Ismail Bahari 《Journal of Radioanalytical and Nuclear Chemistry》2013,297(2):277-284
Previous studies have shown that the natural radioactivity contained in building materials have significantly influenced the dose rates in dwelling. Exposure to natural radiation in building has been of concerned since almost 80 % of our daily live are spend indoor. Thus, the aim of the study is to assess the radiological risk associated by natural radioactivity in soil based building materials to dwellers. A total of 13 Portland cement, 46 sand and 43 gravel samples obtained from manufacturers or bought directly from local hardware stores in Peninsular of Malaysia were analysed for their radioactivity concentrations. The activity concentrations of 226Ra, 232Th and 40K in the studied building materials samples were found to be in the range of 3.7–359.3, 2.0–370.8 and 10.3–1,949.5 Bq kg?1 respectively. The annual radiation dose rates (μSv year?1) received by dwellers were evaluated for 1 to 50 years of exposure using Resrad-Build Computer Code based on the activity concentration of 226Ra, 232Th and 40K found in the studied building material samples. The rooms modelling were based on the changing parameters of concrete wall thickness and the room dimensions. The annual radiation dose rates to dwellers were found to increase annually over a period of 50 years. The concrete thicknesses were found to have significantly influenced the dose rates in building. The self-absorption occurred when the concrete thickness was thicker than 0.4 m. Results of this study shows that the dose rates received by the dwellers of the building are proportional to the size of the room. In general the study concludes that concrete building materials; Portland cements, sands, and gravels in Peninsular of Malaysia does not pose radiological hazard to the building dwellers. 相似文献
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Sudharshan Prabhu Rekha PD Chiu-Chung Young Asif Hameed Shih-Yao Lin Arun AB 《Applied biochemistry and biotechnology》2013,171(4):817-831
Zeaxanthin carotenoids are class of commercially important natural products and diverse biomolecules produced by plants and many microorganisms. Bacteria often produce a cocktail of polar and nonpolar carotenoids limiting their industrial applications. Marine members of the family Flavobacteriaceae are known to produce potential carotenoids such as astaxanthin and zeaxanthin. A few bacterial species have been reported for the predominant production zeaxanthin. Here, we report the molecular identification of the zeaxanthin as a major carotenoid produced by two novel bacteria (YUAB-SO-11 and YUAB-SO-45) isolated from sandy beaches of South West Coast of India and the effect of carbon sources on the production of zeaxanthin. The strains were identified based on the 16S rRNA gene sequencing as a member of genus Muricauda. The closest relatives of YUAB-SO-11 and YUAB-SO-45 were Muricauda aquimarina (JCM 11811T) (98.9 %) and Muricauda olearia (JCM 15563T) (99.2 %), respectively, indicating that both of these strains might represent a novel species. The highest level of zeaxanthin production was achieved (YUAB-SO-11, 1.20?±?0.11 mg g?1) and (YUAB-SO-45, 1.02?±?0.13 mg g?1) when cultivated in marine broth supplemented with 2 % NaCl (pH 7) and incubated at 30 °C. Addition of 0.1 M glutamic acid, an intermediate of citric acid cycle, enhanced the zeaxanthin production as 18 and 14 % by the strains YUAB-SO-11 and YUAB-SO-45 respectively. The zeaxanthin showed in vitro nitric oxide scavenging, inhibition of lipid peroxidation, and 2,2-diphenyl-1-picryl hydrazyl scavenging activities higher than the commercial zeaxanthin. The results of this study suggest that two novel strains YUAB-SO-11 and YUAB-SO-45 belonging to genus Muricauda produce zeaxanthin as a predominant carotenoid, and higher production of zeaxanthin was achieved on glutamic acid supplementation. The pigment showed good in vitro antioxidant activity, which can be exploited further for commercial applications. 相似文献
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MR Eskildsen AB Abrahamsen PL Gammel DJ Bishop NH Andersen K Mortensen PC Canfield 《Pramana》2002,58(5-6):903-905
We compare the results of small angle neutron scattering on the flux line lattice (FLL) obtained in the borocarbide superconductor
LuNi2B2C with the applied field along the c- and a-axes. For H‖c the temperature dependence of the FLL structural phase transition from square to hexagonal symmetry was investigated. Above
10 K the transition onset field. H
2(T), rises sharply, bending away from H
c2(T) in contradiction to theoretical predictions of the two merging. For H‖a a first order FLL reorientation transition is observed at H
tr=3–3.5 kOe. Below H
tr the FLL nearest neighbor direction is parallel to the b-axis, and above H
tr to the c-axis. This transition cannot be explained using nonlocal corrections to the London model. 相似文献