General Set Of Parameters Research Articles

Mutual Constraints between Reionization Models and Parameter Extraction from Cosmic Microwave Background Data

Spectroscopic studies of high-redshift objects and increasingly precise data on the cosmic microwave background (CMB) are beginning to independently place strong complementary bounds on the epoch of hydrogen reionization. Parameter estimation from current CMB data continues, however, to be subject to several degeneracies. Here, we focus on those degeneracies in CMB parameter forecasts related to the optical depth to reionization. We extend earlier work on the mutual constraints that such analyses of CMB data and a reionization model may place on each other to a more general parameter set and to the case of data anticipated from the MAP satellite. We focus in particular on a semianalytic model of reionization by the first stars, although the methods here are easily extended to other reionization scenarios. A reionization model can provide useful complementary information for cosmological parameter extraction from the CMB, particularly for the degeneracies between the optical depth and either of the amplitude and index of the primordial scalar power spectrum, which are still present in the most recent data. Alternatively, by using a reionization model, known limits on astrophysical quantities can reduce the forecasted errors on cosmological parameters. Forthcoming CMB data also have the potential to constrain the sites of early star formation, as well as the fraction of baryons that participate in it, if reionization were caused by stellar activity at high redshifts. Finally, we examine the implications of an independent, e.g., spectroscopic, determination of the epoch of reionization for the determination of cosmological parameters from the CMB. This has the potential to significantly strengthen limits from the CMB on parameters such as the index of the power spectrum, while having the considerable advantage of being free of the choice of the reionization model.

Writing the Meal: Dinner in the Fiction of Early Twentieth-Century Writers by Diane McGee

REVIEWS Deconstructive readings of decadent texts throw a raking light over continual alterations of signification, the “perennial decay,” referred to in the book’s title: “Decadent textual strate­ gies interfere with the boundaries and borders (national, sexual, definitional, historical, to name but a few) that criticism nor­ mally relies upon to make its judgments, producing what we call a ‘perennial decay’ of those boundaries and borders” (11). This position implies that theory, at least in the form of decon­ struction, is likewise a mode of “perennial decay,” indeed, of decadence. In refraining from directing its attention backward (so to speak) upon its own theoretical premises and methods, Perennial Decay chooses not to name deconstruction itself as one of the latest and most potent articulations of Decadence, a truth that, from the mouths of academic humanists, has fre­ quently been hurled in the form of an accusation against deconstruction . Within the context of a volume such as this one, deconstruction needs to come out as decadent, even if doing so prevents it (and us) from ever safely exiting the purlieus of Decadence. Within this general set of parameters, readers with an inter­ est in literary and other modes of decadence will find a variety of items of interest in this collection: an essay on opera and disease by Marc A. Weiner; the art of posing in Latin American liter­ ature of the fin de siècle (Sylvia Molloy), and the connection between Dorian’s portrait and late Victorian and Edwardian portraiture practice (Dennis Denisoff). RICHARD DELLAMORA / Trent University Diane McGee. Writing the Meal: Dinner in the Fiction of Early Twentieth-Century Writers. Toronto: University of Toronto Press, 2001. 221. $60.00 cloth. Re-imagine Michelangelo’s Creation of Adam: instead of the masculine text of a finger-tip touch through which God dele­ gates authority to a lolling Adam, picture instead God’s ex­ tended arm in the act of handing over to a harried Eve the divine cooking pot so that she can assume responsibility for 539 ESC 28, 2002 whipping up mini-acts of Creation daily in order to re-vivify physically and spiritually all those gathered round the hearth for the dinner rites. A vision only slightly less ambitious is set up at the beginning of McGee’s study. The first chapter draws upon a variety of anthropological and sociological references to argue that meal preparation is not only a cultural text but also a site of origins: “Thus the roots of storytelling, art, and religion are linked to cooking,” and “Through this process of ordering and transforming the world, cooking can be viewed as the ba­ sis of thought” (13). Not only are food preparation practices “conveyers of meaning both to those within the group and to outsiders” (11), but also, “in that they create meaning, these activities are fundamental to thought and to language” (13). Before narrowing her scope to meals of various sorts (pri­ marily dinners because they are the most ritualized), McGee provides an overview of changing societal attitudes towards cooking and women’s domestic roles in the late nineteenth and early twentieth centuries. She thus establishes a historical con­ text for the argument to turn from the notion of origins to the specific time-frame of modernity. The dinner analyses that fol­ low are situated to be reflective of problems rooted not just in women’s social roles but also in western culture’s worried responses to a changing world. McGee’s approach to dinner as discourse concentrates on female characters acting in the broadly defined roles of host­ ess or guest in fiction by Edith Wharton, Katherine Mansfield, Virginia Woolf, and Kate Chopin (with the work of some other women writers mentioned in passing, along with that of an occa­ sional male author). Interactions of gender, class, and economics are convincingly examined in novels by Wharton, and Clarissa’s significance as hostess in Woolf’s Mrs. Dalloway gets a more sympathetic reading than is often the case. The chapters on Mansfield may be especially welcome to readers because, despite the steady growth in Mansfield studies over the last few years, there are fresh insights here. To close, McGee picks up on her...

Waiting-Time Distributions in Polling Systems with Simultaneous Batch Arrivals

We study the delay in asymmetric cyclic polling models with general mixtures of gated and exhaustive service, with generally distributed service times and switch-over times, and in which batches of customers may arrive simultaneously at the different queues. We show that (1−ρ)X i converges to a gamma distribution with known parameters as the offered load ρ tends to unity, where X i is the steady-state length of queue i at an arbitrary polling instant at that queue. The result is shown to lead to closed-form expressions for the Laplace–Stieltjes transform (LST) of the waiting-time distributions at each of the queues (under proper scalings), in a general parameter setting. The results show explicitly how the distribution of the delay depends on the system parameters, and in particular, on the simultaneity of the arrivals. The results also suggest simple and fast approximations for the tail probabilities and the moments of the delay in stable polling systems, explicitly capturing the impact of the correlation structure in the arrival processes. Numerical experiments indicate that the approximations are accurate for medium and heavily loaded systems.

POLLING SYSTEMS WITH SIMULTANEOUS BATCH ARRIVALS

We study the delay in polling systems with simultaneous batch arrivals. Arrival epochs are generated according to a Poisson process. At any arrival epoch, batches of customers may arrive simultaneously at the different queues, according to a general joint batch-size distribution. The server visits the queues in cyclic order, the service times and the switch-over times are generally distributed, and the service disciplines are general mixtures of gated and exhaustive service. We derive closed-form expressions for the expected delay at each of the queues when the load tends to unity (under proper scalings), in a general parameter setting. The results are strikingly simple and reveal explicitly how the expected delay depends on the system parameters, and in particular, on the batch-size distributions and the simultaneity of the batch arrivals. Moreover, the results suggest simple and fast-to-evaluate approximations for the expected delay in heavily loaded polling systems. Numerical experiments demonstrate that the approximations are highly accurate in medium and heavily loaded systems.

Polling systems with periodic server routing in heavy traffic

We consider polling systems with mixtures of exhaustive and gated service, and in which the server visits the queues according to a general polling table, in heavy traffic. We derive exact expressions for the expected delay at each of the queues (under heavy-traffic scalings), requiring the solution of a set of M — N linear equations, where M is the length of the polling table and N is the number of queues. The results lead to closed-form expressions for the scaled expected delay under the commonly used star and elevator routing schemes, in a general parameter setting. In addition, the results reveal several insensitivity properties of the scaled expected delay with respect to the system parameters, providing new insights into the behavior of periodic polling systems in heavy traffic. The results also suggest simple and fast-to-evaluate approximations for the expected delay at each of the queues in stable polling systems. Numerical examples show that the approximations are very accurate in practical heavy-traffic scenarios

Stability of a polyphenol oxidase from the white‐rot fungus Trametes versicolor in the presence of canola meal

AbstractThe stability of a polyphenol oxidase (PPO) preparation from the white‐rot fungus Trametes versicolor during a process for the enzymatic decrease of the phenolic content of commercial canola meal (CM) was investigated. The effects of temperature, pH, protein origin and concentration, and meal particles were considered. The results showed that the thermal stability of the enzyme preparation was significantly increased in the presence of CM. The half‐life times for the enzyme preparation, pre‐incubated with CM at 50, 60, 70 and 75°C, were 45, 10.5, 3.5 and 1.5 hours, respectively; this represents an increase in the thermal stability of the enzyme preparation of up to four times in the presence of CM compared to the stability in the absence of CM. This effect was caused by the protective actions of both the CM particles and CM proteins, with the former responsible for 90% of the observed effect. The thermal stability of the enzyme in the presence of CM, from which 20% of the extractable proteins was extracted, was 5% lower compared to the stability in the presence of untreated CM. Changes in pH level from 5.0 to 3.2 resulted in a loss of stability comparable to that observed when the pre‐incubation temperature was increased from 50 to 70°C.A semi‐empirical model describing the changes in the concentration of the active enzyme pre‐incubated in the presence and absence of CM at various incubation temperatures was proposed. A very good agreement between the model and experimental data was obtained. The proposed model, together with a general set of model parameters, can be used as a tool for the optimization of a process for the upgrade of CM by enzymatically decreasing the meal's phenolic content.

Modeling of the Exchange Repulsion Energy

The nonempirical force field model (NEMO) has been augmented with a new exchange repulsion model based on a different choice of expansion center. In the new repulsion model, the size of the atoms are estimated from the trace of the local second-order electron density tensor divided with the local valence charge. A set of general atom type dependent parameters are fitted from SCF calculations on different complexes. An exponential form is used to describe the interaction. The new expansion center is chosen as the point where the local electronic dipole is zero, i.e. the center of electronic charge. The model has been tested on a set of intermolecular complexes between the molecules water, ammonia, methylamine, formamide, and urea.

Steepening of Alfvén waves and its effect on the structure of slow shocks

The interaction between Alfvén/ion cyclotron (A/IC) waves and a slow shock is examined by means of hybrid simulations. It is shown that for a rather general set of parameters, slow shocks can generate A/IC waves which become group standing within the shock transition layer, and steepen into thin structures (∼4 ion inertial lengths). Each front is shocklike with finite jumps in the plasma parameters across it. In such cases, the transition from upstream to downstream conditions across the slow shock occurs over a number of layers. Following the jumps over the steepened front(s), the final transition to downstream is made over a much broader region more typical of slow shocks (≳60 ion inertial lengths). Other important effects of the steepened front are the local trapping of the plasma, generation of a coherent wavetrain and changes in the polarization of the slow shock. In particular, the first simulations of slow shocks with a right‐handed polarization and an upstream wavetrain are shown. Due to the unusually complicated structures of these slow shocks much care must be taken in the search and identification of slow shocks in the observations.

MODEL FOR EFFICIENT MONOPOLE ANNIHILATION AND BARYOGENESIS

We present a model for efficient annihilation of magnetic monopoles which is accomplished by breaking the electromagnetic gauge invariance for an appropriate range of temperature during the radiation dominated epoch of the early universe. Except for the brief period when electromagnetism is broken, the gauge-group symmetry is SU (3)c × SU (2)L × U (1)Y between the grand unification and electroweak transition temperature scales. The model consists of a standard Higgs doublet, a charged singlet and an uncharged singlet, and it is shown to work for a very general set of parameters with none of the scalar coupling constants being, necessarily, either too large or too small. The uncharged singlet can easily give adequately large Majorana mass to the right-handed neutrinos making baryogenesis possible through the decay of heavy right-handed neutrinos and sphaleron interactions.

Cure kinetics of dicyanate matrix polymers

AbstractThe cure kinetics of two dicyanate resins were investigated by differential scanning calorimetry under isothermal and nonisothermal conditions. An autocatalytic kinetic model was proposed and a set of general kinetic parameters was calculated from the isothermal experiments. Good agreement between experimental data and the kinetic model has been obtained under different processing conditions, which demonstrated the validity and the usefulness of the analytical procedure and of the kinetic expression employed. Consequently, in its current form, the modeling methodology is capable of describing the degree of cure during a typical processing cycle and has the potential for comparing different resin formulations as well as the manifestations of cure in property development. Specifically, in this work the modeling methodology was tested using two distinct dicyanate resin systems while the development of the cure was also observed through dielectric analysis (DEA).

General parameterized SCF model for free energies of solvation in aqueous solution

We present a new general parameterization for aqueous solvation free energies of molecules and ions in aqueous solution. It is obtained by extending a semianalytic treatment of solvation recently proposed for use with molecular mechanics and liquid simulations by Still et al. As extended here, the solvation terms are included in a Fock operator. The model incorporates reaction field polarization effects through the generalized Born functional with charges obtained by AMI molecular orbital calculations, and it includes cavitation, dispersion, and hydrophobic effects through an empirical function of solvent-accessible surface area. A general parameter set, including parameters for H, C, N, 0, F, S, CI, Br, and I, has been obtained by considering a data set consisting of 141 neutral molecules, 10 cations, and 17 anions. The neutral molecules include alkanes, cycloalkanes, alkenes, arenes, alkynes, ethers, heterocycles, carboxylic acids, esters, nitriles, aldehydes, ketones, alcohols, amines, nitro compounds, sulfides, thiols, halides, and polyfunctional compounds. The general parameterization is called Solvation Model 1, and it is particularly well suited for chemical reaction dynamics and reaction intermediates. We also discuss how the model may be refined for solvation free energies for stable neutral molecules.

Geometry optimization within a modified extended Hückel formalism: Modifications to the ASED program

Abstract The ASED program by Anderson and coworkers was modified to include a full geometry optimizer. It was discovered that, even with this modification, the ASED program could not be used to perform geometry optimizations on organic molecules without further modification. These modifications included changing the Wolfsberg-Helmholz equation used in the ASED program back to the original equation found in the FORTICON8 program as well as changing the Slater orbital exponents. A general parameter set for C, H, O and N has been developed, which has been used to perform geometry optimizations on selected organic molecules. The calculated geometries compared reasonably with the experimental values and with previously published AM1 geometries.

Steric Effects on Reaction Rates. Part IX. Force‐Field Parameters for Bridgehead and Rigid Tertiary Carbenium Ions

AbstractMolecular‐mechanics calculations for strain of carbenium ions are tested using Bentley's unified reactivity scale for bridgehead solvolysis as reference. Excellent correlations are obtained for solvolytic bridgehead reactivity with the calculated steric‐energy difference (ΔEst) between substrate (RH or ROH) and cation (R+). After adjustment of appropriate force‐field parameters, the approach is successfully extended to the rigid, but planar cations derived from structures 15–20; however, the general set of parameters cannot be applied to highly strained systems such as the cation formed from 17. With all of the 18 sets of parameters tested, the 2‐endo‐norbornyl derivative 16, is adequately correlated, while the exo isomer 15 exhibits enhanced reactivity by a factor of ca. 102 to 103.

Electronic absorption spectra and electron transport properties of 1-benzothiopyrylium ions

The electronic absorption spectra of a series of 1-benzothiopyrylium salts have been calculated by the variable β PPP method. The agreement between calculated and experimental data is satisfactory in most cases using a general parameter set. The calculated results show that the bathochromic effect of a methoxy group is essentially due to a HOMO-HOMO interaction, and the bathochromic effect of a benzothiopyran ring in the 2-position is due to raising of a HOMO. The electron transfer properties of 1-benzothiopyrylium salts were examined by means of cyclic voltammogram and xerographic discharge techniques. It was found that the reduction wave of thioflavylium ions is reversible.

Space charge fields in photorefractive materials

The periodic space charge field generated by two interfering light beams is calculated for a general set of parameters using a linearization method.

REVSPEC—A reverberation spectrum numerical model

The REVSPEC model provides a numerical evaluation of the reverberation spectrum for a general set of sonar system parameters and environmental conditions. The model is a numerical evaluation scheme based on the discretization approach of Ackerman for a general formulation of reverberation as developed by Fauer, Ol'shevskii, and Middleton. The model produces surface, volume, and/or bottom reverberation spectra and power levels as functions of the sonar system (transmit signal waveform and power level, sampling rate, transmit/receive and horizontal/vertical beampatterns), environment (spreading and absorption propagation losses, backscattering strengths, wind speed and direction, scatterer motion), and sonar platform (motion, depth, direction). The reverberation spectra at the receiver input and at the receiver output for a range‐gated and waveform‐weighted receiver are generated. The reverberation is nonstationary in that the spectra vary with time (and range) both in their spectral shape and power levels. Intrinsic assumptions include: primary scattering only (no secondary scattering), isovelocity ocean (straight line propagation paths), direct path (no boundary forward reflections), quasistationary narrowband transmit signals, backscattering from a large number of randomly distributed, weak, discrete scatterers, and radial velocity distributions of boundary and volume scatterers are uniform in space. The model formulation is presented and examples which illustrate its applicability for sonar systems analysis are given.

A validated high-voltage arrester model for transient network analyzer applications

This paper describes the development of a dynamic surge arrester model for use on a transient network analyzer to evaluate the arrester instantaneous voltage, current and total energy during conduction. Based on the results of duty-cycle tests, a model is proposed for which three sets of parameters were found to match three different makes of 72 kV arrester. The relative values of these parameters are discussed as well as a general set of parameters that could represent all three types of arrester.

A statistical version of the solution of the inverse problem for nonabsorbing transparent media

Numerous applications of light-scattering methods to the investigation of weakly absorbing transparent objects [I-4] reduce to the solution of the inverse problem with various versions of the regularization conditions. The idea behind the regularization conditions is to achieve by one method or another a unique solution to the inverse problem with the most general algorithm providing for stability of the computational scheme and of the results of reading and accidental errors in an experiment. As a rule, the generality of the solution algorithm is provided for by an a priori choice of the function describing the distribution of scattering centers (SC) with respect to one or another parameter, for example, size. Restrictions associated with the approximate notion of a scattering coefficient suggested by Van de Hulst [6] are imposed in solving the inverse problem from measurements of the transmission coefficients of two-phase objects [2, 5]. These restrictions are so severe that the problem is soluble, as a rule, only for two-phase objects of a polydispersed system of particles having a constant index of refraction (rap) differing insignificantly from the refractive index of the surrounding medium (me) , i.e., for relatively small average values of the dimensionless cross section/3 ("soft particles"). It is known that one can solve the inverse problem when the Van de Hulst approximation is rather little in error if m = mp/m e -< 1.45 in the case of exact solutions of the inverse problem [2] or m = mp/m e -< 1.25 for approximate solutions [5]. The methods of solving the inverse problems for two-phase objeets are applicable, in principle, to single-phase objects with density (or refractive index) fluctuations in the volume if the following conditions are fulfilled: take m e = I; apply the exact solutions for the scattering coefficients K(/3, m) over wide ranges of values of /3 and m; and assume that single-scatterin g occurs. The use of a well-known theorem from mathematical statistics, according to which one can determine for every general set of parameters representing particular solutions of the problem a finite-sized sample adequate to it and consisting of those same solutions, occupies a special place among the conditions for solution of the problem. This theorem permits a significant reduction in the number of solutions necessary for a complete description of the object being investigated and excludes the process of inverting an integral equation [2]. Upon fulfilling the enumerated conditions, one can obtain a solution of the inverse light-scattering problem from the transmission coefficients for a single-phase object with density fluctuations in its volume and negligibly small absorption after having solved the problem for a model representing a system of spheres localized within the object's geometrical boundaries whose diameters and refractive indices are varied within a rather large range of values. Taking the enumerated conditions into account, the transmission equation [7] [ 3 K(~'m)c~[] T = exp 2 D (i)