On the population of remnant FRII radio galaxies and implications for radio source dynamics

The purpose of this work is two-fold: (1) to quantify the occurrence of ultra-steep spectrum remnant FRII radio galaxies in a 74 MHz flux limited sample, and (2) perform Monte-Carlo simulations of the population of active and remnant FRII radio galaxies to confront models of remnant lobe evolution, and provide guidance for further investigation of remnant radio galaxies. We find that fewer than 2$\%$ of FRII radio galaxies with S$_{ \rm74~MHz} > 1.5$ Jy are candidate ultra-steep spectrum remnants, where we define ultra-steep spectrum as $\alpha_{\rm 74~MHz}^{\rm 1400~MHz} > 1.2$. Our Monte-Carlo simulations demonstrate that models involving Sedov-like expansion in the remnant phase, resulting in rapid adiabatic energy losses, are consistent with this upper limit, and predict the existence of nearly twice as many remnants with normal (not ultra-steep) spectra in the observed frequency range as there are ultra-steep spectrum remnants. This model also predicts an ultra-steep remnant fraction approaching 10$\%$ at redshifts $z < 0.5$. Importantly, this model implies the lobes remain over-pressured with respect to the ambient medium well after their active lifetime, in contrast with existing observational evidence that many FRII radio galaxy lobes reach pressure equilibrium with the external medium whilst still in the active phase. The predicted age distribution of remnants is a steeply decreasing function of age. In other words young remnants are expected to be much more common than old remnants in flux limited samples. For this reason, incorporating higher frequency data $\gtrsim 5$ GHz will be of great benefit to future studies of the remnant population.Comment: 19 pages, 8 figures, 4 table

Dynamics and Decay of Heavy-Light Hadrons

Recent signals for narrow hadrons containing heavy and light flavours are compared with quark model predictions for spectroscopy, strong decays, and radiative transitions. In particular, the production and identification of excited charmed and cs states are examined with emphasis on elucidating the nature of $0^+$ and $1^+$ states. Roughly 200 strong decay amplitudes of $D$ and $D_s$ states up to 3.3 GeV are presented. Applications include determining flavour content in $\eta$ mesons and the mixing angle in $P$ and $D$ wave states and probes of putative molecular states. We advocate searching for radially excited $D_s^*$ states in B decays.Comment: 19 pages, 7 figures, revtex. A numerical error is corrected. Some strong decay rates have change

Development of the health and economic consequences of smoking interactive model

Objective-To describe the health and economic consequences of smoking model, a user friendly, web based tool, designed to estimate the health and economic outcomes associated with smoking and the benefits of smoking cessation. Results-An overview of the development of the model equations and user interface is given, and data from the UK are presented as an example of the model outputs. These results show that a typical smoking cessation strategy costs approximately pound 1200 per life year saved and pound 22 000 per death averted. Conclusions-The model successfully captures the complexity required to model smoking behaviour and associated mortality, morbidity, and health care costs. Furthermore, the interface provides the results in a simple and flexible way so as to be useful to a variety of audiences and to simulate a variety of smoking cessation methods

Hadronic Decays of Excited Heavy Mesons

We studied the hadronic decays of excited states of heavy mesons (D, D_s, B and B_s) to lighter states by emission of pi, eta or K. Wavefunctions and energy levels of these excited states are determined using a Dirac equation for the light quark in the potential generated by the heavy quark (including first order corrections in the heavy quark expansion). Transition amplitudes are computed in the context of the Heavy Chiral Quark Model.Comment: 4 pages (incl. figures), proceedings of the IV International Conference on "Hyperons, Charm and Beauty Hadrons", Valencia (Spain

Large‐scale structures and molecular mixing

Scalar mixing and chemical reactions in turbulent shear layers and jets are examined with emphasis on experimental results of high spatial and temporal resolution. Such measurements show that the notion of distinguishing fluids that are molecularly mixed from those that are simply stirred is valid and useful. Two models that seem especially suitable for implementing mixing analyses from this viewpoint are described and speculations on possible connections with the idea of chaotic advection offered

The political economy of self-help: Kenya's Harambee Institutes of Technology

Since mid 1971 local self-help committees throughout Kenya have been raising large sums of money for this establishment of harambee institutes of technology. By April 1973 such institutes had been proposed for Kiambu, Kirinyaga, Murang'a, Nyeri, Embu, Meru, Yatta, Mombasa, Kajiado, Kericho, Nakuru, Kihencha, Kisii, Kisumu, Kaimosi, Kakamega and Sang'alo. The plans of the proposed institutes vary a great deal, but most of them are aiming to provide some kind of technical training to those who have finished secondary school form TV. In this paper we try to place this fascinating fund-raising campaign in its political and economic background and to look forward at the possible effects that the establishment of such institutes might have on Kenya's economy and society

Quartz crystal microbalance use in biological studies

Design, development, and applications of quartz crystal microbalance are discussed. Two types of crystals are used. One serves as reference and other senses changes in mass. Specific application to study of bacterial spores is described

InP shallow-homojunction solar cells

Indium phosphide solar cells with very thin n-type emitters have been made by both ion implantation and metalorganic chemical vapor deposition. Air mass zero efficiencies as high as 18.8 percent (NASA measurement) have been achieved. Although calculations show that, as is the case with GaAs, a heterostructure is expected to be required for the highest efficiencies attainable, the material properties of InP give the shallow-homojunction structure a greater potential than in the case of GaAs. The best cells, which were those made by ion implantation, show open-circuit voltage (V sub oc) of 873 mV, short-circuit current of 357 A/sq m (35.7 mA/sq cm), and fill factor of 0.829. Improvements are anticipated in all three of these parameters. Internal quantum efficiency peaks at over 90 percent in the red end of the spectrum, but drops to 54 percent in the blue end. Other cells have achieved 74 percent in the blue end. Detailed modeling of the data indicates that a high front surface recombination velocity is responsible for the low blue response, that the carrier lifetime is high enough to allow good carrier collection from both the base and the emitter, and that the voltage is base-limited

Spin-Orbit and Tensor Forces in Heavy-quark Light-quark Mesons: Implications of the New Ds state at 2.32 GeV

We consider the spectroscopy of heavy-quark light-quark mesons with a simple model based on the non-relativistic reduction of vector and scalar exchange between fermions. Four forces are induced: the spin-orbit forces on the light and heavy quark spins, the tensor force, and a spin-spin force. If the vector force is Coulombic, the spin-spin force is a contact interaction, and the tensor force and spin-orbit force on the heavy quark to order $1/m_1m_2$ are directly proportional. As a result, just two independent parameters characterize these perturbations. The measurement of the masses of three p-wave states suffices to predict the mass of the fourth. This technique is applied to the $D_s$ system, where the newly discovered state at 2.32 GeV provides the third measured level, and to the $D$ system. The mixing of the two $J^P=1^+$ p-wave states is reflected in their widths and provides additional constraints. The resulting picture is at odds with previous expectations and raises new puzzles.Comment: 6 pages, 1 figur