Multiplicative Conservation of Baryon Number and Baryogenesis

In the canonical seesaw mechanism of neutrino mass, lepton number is only multiplicatively conserved, which enables the important phenomenon of leptogenesis to occur, as an attractive explanation of the present baryon asymmetry of the Universe. A parallel possibility, hitherto unrecognized, also holds for baryon number and baryogenesis. This new idea is shown to be naturally realized in the context of a known supersymmetric string-inspired extension of the Standard Model, based on E(6) particle content, and having an extra U(1)_N gauge symmetry. Within this framework, two-loop radiative neutrino masses are also possible, together with a new form of very long-lived matter.Comment: 9 pages, 4 figures, 3 table

Allowable Low-Energy E_6 Subgroups from Leptogenesis

There are only two viable low-energy $E_6$ subgroups: $SU(3)_C \times SU(2)_L \times U(1)_Y \times U(1)_N$ or $SU(3)_C \times SU(2)_L \times SU(2)'_R \times U(1)_{Y_L + Y'_R}$, which would not erase any preexisting lepton asymmetry of the Universe that may have been created by the decay of heavy singlet (right-handed) neutrinos or any other mechanism. They are also the two most favored $E_6$ subgroups from a recent analysis of present neutral-current data. We study details of the leptogenesis, as well as some salient experimental signatures of the two models.Comment: 12 page

Are UK E-waste recycling facilities a source of environmental contamination and occupational exposure to brominated flame retardants?

Investigations into the impacts of regulated electrical and electronic waste (e-waste) recycling activities on urban environments in Europe remain rather scarce. In this study, dust samples taken both inside and outside of five UK e-waste recycling facilities were analysed for concentrations of polybrominated diphenyl ethers (PBDEs), novel brominated flame retardants (NBFRs), and hexabromocyclododecane (HBCDD). Average concentrations of ∑BFRs in dust inside and outside UK e-waste recycling facilities were 12,000 ng/g and 180 ng/g, with median concentrations of 7500 ng/g and 85 ng/g, respectively. BDE-209 and decabromodiphenyl ethane (DBDPE) were the most abundant BFRs in both indoor and kerb dust, making a combined contribution to ∑BFRs of ~90 % on average. While four out of the five studied e-waste facilities showed a lack of significant impact on BFR contamination in surrounding environment, one of the studied e-waste recycling facilities was identified as a likely source of BFR contamination to UK urban environments, with industrial activities as another potential source of NBFRs. Occupational exposure of UK e-waste recycling workers to BFRs via dust ingestion was generally lower than that estimated for e-waste recyclers from other countries, but was comparable to BFR exposure via dust ingestion of UK office workers. Our estimates suggested that health burdens posed by dust ingestion of BFRs were minimal for UK e-waste recycling workers.</p

Leptogenesis from Neutralino Decay with Nonholomorphic R-Parity Violation

In supersymmetric models with lepton-number violation, hence also R-parity violation, it is easy to have realistic neutrino masses, but then leptogenesis becomes difficult to achieve. After explaining the general problems involved, we study the details of a model which escapes these constraints and generates a lepton asymmetry, which gets converted into the present observed baryon asymmetry of the Universe through the electroweak sphalerons. This model requires the presence of certain nonholomorphic R-parity violating terms. For completeness we also present the most general R-parity violating Lagrangian with soft nonholomorphic terms and study their consequences for the charged-scalar mass matrix. New contributions to neutrino masses in this scenario are discussed.Comment: 30 pages, 6 figure

Impact of Legislation on Brominated Flame Retardant Concentrations in UK Indoor and Outdoor Environments:Evidence for Declining Indoor Emissions of Some Legacy BFRs

Concentrations of polybrominated diphenyl ethers, hexabromocyclododecane (HBCDD), and novel brominated flame retardants (NBFRs) were measured in indoor dust, indoor air, and outdoor air in Birmingham, UK. Concentrations of ΣBFRs ranged from 490 to 89,000 ng/g, 46–14,000 pg/m3, and 22–11,000 pg/m3, respectively, in UK indoor dust, indoor air, and outdoor air. BDE-209 and decabromodiphenyl ethane (DBDPE) were the main contributors. The maximum concentration of DBDPE (10,000 pg/m3) in outdoor air is the highest reported anywhere to date. In contrast with previous studies of outdoor air in Birmingham, we observed significant correlations between concentrations of tri- to hepta-BDEs and HBCDD and temperature. This may suggest that primary emissions from ongoing use of these BFRs have diminished and that secondary emissions (e.g., evaporation from soil) are now a potentially major source of these BFRs in outdoor air. Conversely, the lack of significant correlations between temperature and concentrations of BDE-209 and DBDPE may indicate that ongoing primary emissions from indoor sources remain important for these BFRs. Further research to clarify the relative importance of primary and secondary sources of BFRs to outdoor air is required. Comparison with earlier studies in Birmingham reveals significant (p &lt; 0.05) declines in concentrations of legacy BFRs, but significant increases for NBFRs over the past decade. While there appear minimal health burdens from BFR exposure for UK adults, dust ingestion of BDE-209 may pose a significant risk for UK toddlers