Z -> b\bar{b} Versus Dynamical Electroweak Symmetry Breaking involving the Top Quark

In models of dynamical electroweak symmetry breaking which sensitively involve the third generation, such as top quark condensation, the effects of the new dynamics can show up experimentally in Z->b\bar{b}. We compare the sensitivity of Z->b\bar{b} and top quark production at the Tevatron to models of the new physics. Z->b\bar{b} is a relatively more sensitive probe to new strongly coupled U(1) gauge bosons, while it is generally less sensitive a probe to new physics involving color octet gauge bosons as is top quark production itself. Nonetheless, to accomodate a significant excess in Z->b\bar{b} requires choosing model parameters that may be ruled out within run I(b) at the Tevatron.Comment: LaTex file, 19 pages + 2 Figs., Fermilab-Pub-94/231-

A Search for Time Variation of the Fine Structure Constant

A method offering an order of magnitude sensitivity gain is described for using quasar spectra to investigate possible time or space variation in the fine structure constant, alpha. Applying the technique to a sample of 30 absorption systems, spanning redshifts 0.5 < z< 1.6, obtained with the Keck I telescope, we derive limits on variations in alpha over a wide range of epochs. For the whole sample Delta(alpha)/alpha = -1.1 +/- 0.4 x 10^{-5}. This deviation is dominated by measurements at z > 1, where Delta(alpha)/alpha = -1.9 +/- 0.5 x 10^{-5}. For z < 1, Delta(alpha)/alpha = -0.2 +/- 0.4 x 10^{-5}, consistent with other known constraints. Whilst these results are consistent with a time-varying alpha, further work is required to explore possible systematic errors in the data, although careful searches have so far not revealed any.Comment: 4 pages, 1 figure, accepted for publication in Physical Review Letter

Boolean versus continuous dynamics on simple two-gene modules

We investigate the dynamical behavior of simple modules composed of two genes with two or three regulating connections. Continuous dynamics for mRNA and protein concentrations is compared to a Boolean model for gene activity. Using a generalized method, we study within a single framework different continuous models and different types of regulatory functions, and establish conditions under which the system can display stable oscillations. These conditions concern the time scales, the degree of cooperativity of the regulating interactions, and the signs of the interactions. Not all models that show oscillations under Boolean dynamics can have oscillations under continuous dynamics, and vice versa.Comment: 8 pages, 10 figure

Fire and rescue service community safety initiatives: measuring impact

Purpose - The purpose of this paper is to discuss methods of capturing the impact of fire and rescue service (FRS) community safety work which directly aims to reduce the occurrence of specific incidents. Design/methodology/approach - The impact assessment method described focuses on addressing one of the major problems with regards to attributing outcomes to FRS community safety work; the influence of external factors. This paper looked to assess the incident trends within a case study UK FRS within the context of the following external data sets: first, incident trends within other UK FRSs; second, demographic trends; and third, incident data from other public services. Findings - There were instances, either across the whole region served by the case study FRS, or within specific districts, where evidence suggested a strong likelihood of the community safety work of the case study FRS contributing towards an observed reduction in incidents. These findings were established through filtering the impact of widespread external factors, which could impact upon incident figures. Research limitations/implications - The utility of this impact assessment relies upon FRS consistently recording the specific aims and focus of individual community safety activity, so that any positive outcomes can be attributed to a particular group of community safety initiatives. Originality/value - This paper discusses how an evaluation process, to deter mine the likelihood of community safety impacting upon incident numbers, can be practically applied to a FRS

Generalized Haldane Equation and Fluctuation Theorem in the Steady State Cycle Kinetics of Single Enzymes

Enyzme kinetics are cyclic. We study a Markov renewal process model of single-enzyme turnover in nonequilibrium steady-state (NESS) with sustained concentrations for substrates and products. We show that the forward and backward cycle times have idential non-exponential distributions: \QQ_+(t)=\QQ_-(t). This equation generalizes the Haldane relation in reversible enzyme kinetics. In terms of the probabilities for the forward ($p_+$) and backward ($p_-$) cycles, $k_BT\ln(p_+/p_-)$ is shown to be the chemical driving force of the NESS, $\Delta\mu$. More interestingly, the moment generating function of the stochastic number of substrate cycle $\nu(t)$, follows the fluctuation theorem in the form of Kurchan-Lebowitz-Spohn-type symmetry. When $\lambda$ = $\Delta\mu/k_BT$, we obtain the Jarzynski-Hatano-Sasa-type equality: $\equiv$ 1 for all $t$, where $\nu\Delta\mu$ is the fluctuating chemical work done for sustaining the NESS. This theory suggests possible methods to experimentally determine the nonequilibrium driving force {\it in situ} from turnover data via single-molecule enzymology.Comment: 4 pages, 3 figure

Stochastic thermodynamics of chemical reaction networks

For chemical reaction networks described by a master equation, we define energy and entropy on a stochastic trajectory and develop a consistent nonequilibrium thermodynamic description along a single stochastic trajectory of reaction events. A first-law like energy balance relates internal energy, applied (chemical) work and dissipated heat for every single reaction. Entropy production along a single trajectory involves a sum over changes in the entropy of the network itself and the entropy of the medium. The latter is given by the exchanged heat identified through the first law. Total entropy production is constrained by an integral fluctuation theorem for networks arbitrarily driven by time-dependent rates and a detailed fluctuation theorem for networks in the steady state. Further exact relations like a generalized Jarzynski relation and a generalized Clausius inequality are discussed. We illustrate these results for a three-species cyclic reaction network which exhibits nonequilibrium steady states as well as transitions between different steady states.Comment: 14 pages, 2 figures, accepted for publication in J. Chem. Phy

Economic and demographic issues related to deployment of the Satellite Power System (SPS)

Growth in energy consumption stimulated interest in exploitation of renewable sources of electric energy. One technology that was proposed is the Satellite Power System (SPS). Before committing the U.S. to such a large program, the Department of Energy and the National Aeronautics and Space Administration are jointly participating in an SPS Concept Development and Evaluation Program. This white paper on industrial and population relocation is part of the FY 78 preliminary evaluation of related socio-economic issues. Results of four preliminary assessment activities are documented

Stock assessment and management recommendations for Pacific sardine (Sardinops sagax) in 1997

The primary goal of sardine management as directed by the California Fish and Game Code is rehabilitation of the resource with an added objective of maximizing sustained harvest. Accordingly, the Code states that the annual sardine quota can be set at an amount greater than 1,000 tons, providing that the level of take allows for continued increase in the spawning population. We estimated the sardine population size to have been 464,000 short tons on July 1, 1997. Our estimate was based on output from a modified version of the integrated stock assessment model called CANSAR (Deriso et al. 1996). CANSAR is a forward-casting, age-structured analysis using fishery-dependent and fishery-independent data to obtain annual estimates of sardine abundance, year-class strength and age-specific fishing mortality for 1983 through the first semester of 1997. Non-linear least-squares criteria are used to find the best fit between model estimates and input data. Questions about stock structure and range extent remain major sources of uncertainty in assessing current sardine population biomass. Recent survey results and anecdotal evidence suggest increased sardine abundance in the Pacific Northwest and areas offshore from central and southern California. It is difficult to determine if those fish were part of the stock available to the California fishery. In an attempt to address this problem, the original CANSAR model was reconfigured into a Two-Area Migration Model (CANSAR-TAM) which accounted for sardine lost to the areas of the fishery and abundance surveys due to population expansion and net emigration. While the model includes guesses and major assumptions about net emigration and recruitment, it provides an estimate which is likely closer to biological reality than past assessments. The original CANSAR model was also used and estimates are provided for comparison. Based on the 1997 estimate of total biomass and the harvest formula used last year, we recommend a 1998 sardine harvest quota of 48,000 tons for the California fishery. The 1998 quota is a decrease of 11% from the final 1997 sardine harvest quota for California of 54,000 tons. (55pp.