Detonation pulse engine

Exploratory experiments with an air-breathing propulsion device which uses detonative combustion to achieve high cycle pressures, are reported. In the first phase, detonation in a chamber containing ethylene and air was initiated by a detonation produced in a small tube containing ethylene and oxygen. An automobile spark system was used for ignition. In the second phase, a repetitive detonation process was sustained in a naturally-aspirated chamber at a frequency of 25Hz. Projections based on the present test results suggest that frequencies of 150Hz and specific impulse in the range 1000-1400 sec might be obtained in a practical engine.Office of Naval Research via Naval Postgraduate School Foundation Research Progra

Melanocytes and Langerhans Cells in Aged Versus Young Skin Before and After Transplantation onto Nude Mice

Previous studies have demonstrated decreased numbers of melanocytes and Langerhans cells (LC) in aged skin. In the present study, we employed dopa and indirect immunoperoxidase techniques in epidermal sheets to determine the fate of melanocytes and LC of aged versus young donors after skin transplantations onto nude mice. The detection of positive homologous leucocytic antibody reaction of degeneration (HLA-DR) of LC indicates an age-associated reduction in sun-protected thigh skin in aged versus young subjects (263 ± 63 versus 589.25 ± 142.643, p < 0.001). The mean number of LC four weeks after transplanation remained almost constant. Prior to skin engraftment, a decreased number of melanocytes was found in aged versus young epidermis (160.77 ± 51.7 versus 255.83 ± 81.2, respectively, p < 0.05). A significantly increased number of melanocytes was noted four weeks following engraftment in epidermis from aged (307.44 ± 174, p <0.05) and young human donors (402.16 ± l39,p < 0.02). The marked increase in density of dopa-positive melanocytes following engraftment onto nude mice may indicate the existence of circulating factors in nude mice that perhaps both stimulates and enhances proliferation and activity of these cells

Patterns of New Physics in B Decays

We show that any new physics (NP) which affects B decays with penguin contributions can be absorbed by redefinitions of the standard-model (SM) diagrammatic amplitudes. Hence, there are no clean signals of NP in such decays unless there is an accurate theoretical estimate of parameters or a justifiable approximation can be made. In all decays with penguin contributions, NP simultaneously affects pairs of diagrams. The evidence for a large C' from fits to B-> pi K data is naturally explained if NP contributes to P_EW, since NP affects the P_EW and C' diagrams as a pair. The weak phase gamma measured in B-> pi K decays will always agree with its SM value even in the presence of NP, if the NP contributes in such a way that the amplitudes retain the SM form after suitable redefinitions.Comment: 4 pages, revtex, no figures; Several changes made to highlight results obtaine

Signatures of HyperCharge Axions in Colliders

If in addition to the standard model fields, a new pseudoscalar field that couples to hypercharge topological number density, the hypercharge axion, exists, it can be produced in colliders in association with photons or Z bosons, and detected by looking for its decay into photons or Z's. For a range of masses below a TeV and coupling above a fraction of 1/TeV, existing data from LEP II and the Tevatron can already put interesting constraints, and in future colliders accessible detection range is increased significantly. The hypercharge axion can help in explaining the matter-antimatter asymmetry in the universe.Comment: 11 pages, 8 figures, uses axodraw.st

Detection of SUSY in the Stau-Neutralino Coannihilation Region at the LHC

We study the feasibility of detecting the stau neutralino (stau_1-neutralino_1)coannihilation region at the LHC using tau leptons. The signal is characterized by multiple low energy tau leptons from neutralino_2-->tau stau_1-->tau tau neutralino_1 decays, where the stau_1 and neutralino_1 mass difference (Delta M) is constrained to be 5-15 GeV by current experimental bounds including the bound on the amount of neutralino cold dark matter. Within the framework of minimal supergravity models, we show that if hadronically decaying tau's can be identified with 50% efficiency for visible pt >20 GeV the observation of such signals is possible in the final state of two tau leptons plus large missing energy and two jets. With a gluino mass of 830 GeV the signal can be observed with as few as 3-10 fb^-1 of data (depending on the size of Delta M). Using a mass measurement of the tau pairs with 10 fb^-1 we can determine dM with a statistical uncertainty of 12% for Delta M = 10 GeV and an additional systematic uncertainty of 14% if the gluino mass has an uncertainty of 5%.Comment: 15 pages. 9 Figures, Latex, Typing error in the title as it appeared in the web listing is corrected, paper is unchange

Minimally Fine-Tuned Supersymmetric Standard Models with Intermediate-Scale Supersymmetry Breaking

We construct realistic supersymmetric theories in which the correct scale for electroweak symmetry breaking is obtained without significant fine-tuning. We consider two classes of models. In one class supersymmetry breaking is transmitted to the supersymmetric standard model sector through Dirac gaugino mass terms generated by a D-term vacuum expectation value of a U(1) gauge field. In the other class the supersymmetry breaking sector is separated from the supersymmetric standard model sector in an extra dimension, and the transmission of supersymmetry breaking occurs through gauge mediation. In both these theories the Higgs sector contains two Higgs doublets and a singlet, but unlike the case for the next-to-minimal supersymmetric standard model the singlet field is not responsible for generating the supersymmetric or supersymmetry breaking mass for the Higgs doublets. These masses, as well as the mass for the singlet, are generated through gravitational-strength interactions. The scale at which the squark and slepton masses are generated is of order (1-100) TeV, and the generated masses do not respect the unified mass relations. We find that electroweak symmetry breaking in these theories is caused by an interplay between the top-stop radiative correction and the holomorphic supersymmetry breaking mass for the Higgs doublets and that the fine-tuning can be reduced to the level of 20%. The theories have rich phenomenology, including a variety of possibilities for the lightest supersymmetric particle.Comment: 24 pages, version to appear in Nucl. Phys.

An Estimate of \Lambda in Resummed Quantum Gravity in the Context of Asymptotic Safety

We show that, by using recently developed exact resummation techniques based on the extension of the methods of Yennie, Frautschi and Suura to Feynman's formulation of Einstein's theory, we get quantum field theoretic descriptions for the UV fixed-point behaviors of the dimensionless gravitational and cosmological constants postulated by Weinberg. Connecting our work to the attendant phenomenological asymptotic safety analysis of Planck scale cosmology by Bonanno and Reuter, we estimate the value of the cosmological constant \Lambda. We find the encouraging estimate \rho_\Lambda\equiv \frac{\Lambda}{8\pi G_N} \simeq (2.4\times 10^{-3}eV)^4. While this numerical value is close to recent experimental observations, we caution the reader that the estimate involves a number of model parameters that still possess significant levels of uncertainty, such as the value of the transition time between the Planck scale cosmology era and the Friedmann-Robertson-Walker radiation dominated era, where our current understanding allows for at least two orders of magnitude in its uncertainty and this would change our estimate of \rho_\Lambda by at least four orders of magnitude. We discuss such theoretical uncertainties as well. We show why GUT and EW scale vacuum energies from spontaneous symmetry breaking are suppressed in our approach to the estimation of \rho_\Lambda. As a bonus, we show how our estimate constrains susy GUTS.Comment: 11 pages, 1 figure; more systematic presentation; extended text, two new figures for self-containment - now 37 pages; corrected grammar, improved references to published version. arXiv admin note: text overlap with arXiv:hep-ph/060719

Lattice QCD Calculation for the Physical Equation of State

In this report we consider the numerical simulations at finite temperature using lattice QCD data for the computation of the thermodynamical quantities including the pressure, energy density and the entropy density. These physical quantities can be related to the equation of state for quarks and gluons. We shall apply the lattice data to the evaluation of the specific structure of the gluon and quark condensates at finite temperature in relation to the deconfinement and chiral phase transitions. Finally we mention the quantum nature of the phases at lower temperatures.Comment: 60 pages, 15 figure