We reconsider the strength of the electroweak phase transition in the singlet Majoron extension of the Standard Model, with a low ( < ∼ TeV) scale of the singlet VEV. A strongly first order phase transition, of interest for electroweak baryogenesis, is found in sizeable regions of the parameter space, especially when the cross-coupling λ hs |S| 2 |H| 2 between the singlet and the doublet Higgs is significant. Large Majorana Yukawa couplings of the singlet neutrinos, y i Sν c i ν i , are also important for strengthening the transition. We incorporate the LEP and Tevatron constraints on the Higgs masses, and electroweak precision constraints, in our search for allowed parameters; successful examples include singlet masses ranging from 5 GeV to several TeV. Models with a strong phase transition typically predict a nonstandard Higgs with mass in the range 113 GeV < ∼ m H < ∼ 200 GeV and production cross sections reduced by mixing with the singlet, with cos 2 θ significantly less than 1. We also find examples where the singlet is light and the decay H → SS can modify the Higgs branching ratios relative to Standard Model expectations. * current address: Barclays Capital Japan Limited

No abstract

An inversional-rotational isomeric state (IRIS) scheme including first-order to fourth-order intramolecular interactions has been developed and applied to conformational analysis of poly(trimethylene imine) (PTMI) and poly(N-methyltrimethylene imine) (PMTMI). Bond conformations and conformational energies of PTMI and PMTMI were evaluated from ab initio molecular orbital calculations at the MP2/6-311++G(3df, 3pd)//HF/6-31G(d) level and 1H and 13C NMR experiments for the monomeric model compounds, CH3NR1CH2CH2CH2NR2CH3 (R1 = R2 = H; R1 = H and R2 = CH3; R1 = R2 = CH3). The IRIS analysis yielded the following data on the polymers at 25 °C:  the characteristic ratio for the infinite chain, 3.5 (PTMI) and 4.2 (PMTMI); trans fractions of the C−C and C−N bonds, respectively, 0.29 and 0.77 (PTMI) and 0.40 and 0.65 (PMTMI); the meso-diad probability, 0.44 (PTMI) and 0.48 (PMTMI). Intramolecular hydrogen bonds were found in the polyimines:  PTMI, N−H···N (the interaction energy, −0.83 kcal mol-1) and C−H···N (−0.15 kcal mol-1); PMTMI, C−H···N (−0.40 kcal mol-1). The chain dimension, stereochemical configuration, and bond conformations of the polyimines are sensitive to the first-order interaction energy around the C−C bond and the hydrogen-bond energies. Polar solvents weaken the hydrogen bonds to increase the chain dimension and randomize the configuration.

No abstract

Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.