Relative Order Of Magnitude Research Articles

Decoupling the SU(N)2-homogeneous sine-Gordon model

We provide a systematic construction for all n-particle form factors of the SU(N)_2/U(1)^{N-1}-homogeneous Sine-Gordon model in terms of general determinant formulae for a huge class of local operators. The ultraviolet limit is carried out and the corresponding Virasoro central charge together with the conformal dimensions of various operators are identified. The renormalization group flow is studied and we find a precise rule, depending on the relative order of magnitude of the resonance parameters, according to which the theory decouples into new cosets along the flow.

Fault Diagnosis of an Induction Drive Using Residual Directional Properties

Fault diagnosis is mainly a decoupling problem that can be solved through the elimination and/or estimation of unknown variables. In this paper, an elimination and estimation scheme based on residual directional properties is proposed. It is applied to the diagnosis of an induction drive. The interest in using the directions is that they contain the information about the relative orders of magnitude.

Resonant Raman scattering and photoluminescence enhancement in ZnCdSe quantum wells

We have observed resonant Raman scattering (RRS) and photoluminescence (PL) enhancement due to resonant absorption of the exciting light in low temperature experiments on a 50 Å Zn0.74Cd0.26Se quantum well (QW) confined by ZnSe barriers. The spectra presents a sharp and very intense Stokes longitudinal optical (LO) phonon at 31.1 meV and also a weak 2LO mode. We show that the RRS is due to a double resonance: the first is produced by the matching of the exciting laser line (488 nm, 2.5407 eV) with the 1hh→1e absorption transition of the QW; the second is due to the coincidence of the exciton binding energy (determined as 32.6±2 meV) and the LO phonon energy. A selective increase of the intensity of one of the PL excitonic peaks takes place when islands of 50 Å thickness of the QW are resonantly excited with the 488 nm laser line; the relative intensity of this peak increases one order of magnitude in relation to other excitonic peak situated around 9 meV below.

On the Substrate Specificity of DNA Methyltransferases: ADENINE-N6 DNA METHYLTRANSFERASES ALSO MODIFY CYTOSINE RESIDUES AT POSITION N4

Methylation of DNA is important in many organisms and essential in mammals. Nucleobases can be methylated at the adenine-N6, cytosine-N4, or cytosine-C5 atoms by specific DNA methyltransferases. We show here that the M.EcoRV, M.EcoRI, and Escherichia coli dam methyltransferases as well as the N- and C-terminal domains of the M. FokI enzyme, which were formerly all classified as adenine-N6 DNA methyltransferases, also methylate cytosine residues at position N4. Kinetic analyses demonstrate that the rate of methylation of cytosine residues by M.EcoRV and the M.FokI enzymes is reduced by only 1-2 orders of magnitude in relation to methylation of adenines. This result shows that although these enzymes methylate DNA in a sequence specific manner, they have a low substrate specificity with respect to the target base. This unexpected finding has implications on the mechanism of adenine-N6 DNA methyltransferases. Sequence comparisons suggest that adenine-N6 and cytosine-N4 methyltransferases have changed their reaction specificity at least twice during evolution, a model that becomes much more likely given the partial functional overlap of both enzyme types. In contrast, methylation of adenine residues by the cytosine-N4 methyltransferase M.BamHI was not detectable. On the basis of our results, we suggest that adenine-N6 and cytosine-N4 methyltransferases should be grouped into one enzyme family.

The Installed Base Effect: Some Empirical Evidence From The Microcomputer Market

The penetration rate US network technologies is not only determined by the indigenous qualities of these technologies, but also by the adoption behaviour of other actors using the same network technology. This paper provides empirical evidence for the importance of network externalities and suggests that the econonmic consequences of network externalities - as they affect the diffusion speed of network technologies at an aggregate level - may be considerable.When the market offers incompatible network technologies, the relative share of previous adopters of the technologies plays a critical role in determining the diffusion speed of network technologies. This paper provides empirical evidence from the European microcomputer market between 1985 and 1994 which supports this hypothesis. Our analysis suggests that the diffusion speed of microcomputers at an aggregate level has varied with the relative order of magnitude of the network size of the two incompatible operating systems: a higher variation between the number of users of different microcomputers sold is positively relaled to a higher diffusion speed of microcomputers in general.

Modeling of chemical wear in ferrous alloys/ silicon nitride contacts during high speed cutting

The wear resistance of Si3N4 in machining of iron alloys can be surprisingly low due to chemical affinity for dissolution in the metal. This limits the use of Si3N4 inserts in high speed machining of steels, while Si3N4 retains the best performance of all cutting materials in turning of grey cast iron, a different ferrous alloy. The chemical wear of several ceramics has been investigated on the basis of dissolution in pure iron by Kramer and Suh. Nevertheless, the influence of alloy elements was not studied. In the present work, solid solution thermodynamics is applied to predict chemical wear of Si3N4 by setting the influence of interaction coefficients of the alloy elements in the Henrian activity of Si and N in austenite. The model predicts the relative order of magnitude of the crater wear of Si3N4 inserts in machining of tool steels, carbon steels and grey cast iron.

Pitfalls in pharmacokinetic multicompartment analysis.

When a pharmacokinetic (PK) two-compartment body model with first-order absorption is fitted to blood levels of a drug, the estimates of the PK parameters may have considerable errors and can cause wrong predictions in other features of the system. The objectives of this report were to illustrate this problem, to provide an easy way to prevent wrong estimation, and to investigate the origin of the mistake. A simple way to prevent wrong interpretation of the calculated PK parameters is to inspect the PK profiles visually. Without observing a clear biphasic profile, one should not apply the two-compartment model if the resulting parameters are to be interpreted and used for further simulations. We investigated the origin of this ambiguity in terms of the relative order of magnitude of microconstants (ka, k12, k21, and k10) and of hybrid constants (A and B). The observed parameter errors will not be of any relevance if the calculated parameters are used only to predict future blood levels over the same time-span. However, if these parameters are used to predict any other characteristic of the system, erroneous predictions may result.

Homogenization of a thermal problem in the plate of a heat exchanger

In this paper we study a thermal problem with the Fourier boundary conditions on the edges of the holes in a periodically perforated plate of a heat exchanger. This problem contains several reduced parameters which can be very small (the period ε of the distribution of the holes, the relative thickness e of the plate and the three Biot numbers connected with the different parts of the boundary). We use the homogenization technique to estimate the field of temperatures attainable in the upper plate, depending on the relative order of magnitude of the small parameters. We use a combined asymptotic method involving the technique of multiple scales and that of matching expansions to calculate a solution of boundary layer.

Comparability in Qualitative Models

Abstract A framework for reasoning with both absolute and relative orders of magnitude together is developed in this paper. Three binary relations in R, closely related with Qualitative Orders of Magnitude Algebras, which are built from specific partitions of the real line, are presented. The three relations formalize the ideas of “having the same order of magnitude”, “negligibility” and “being close”, in terms of qualitative labels. The study of the properties of these relations has allowed to construct a system of inference rules, compatible with the qualitative labels language, and constitutes a new mixed model between absolute and relative orders of magnitude.

The genetic component of copula duration in the yellow dung fly

The heritabilities of copula duration ( h 2=0.39, P<0.01), body size ( h 2=0.76, P<0.001) and development time ( h 2=0.23, P<0.05), plus their genetic covariances, in the yellow dung fly, Scathophaga stercoraria(L.), were assessed using full sibling analysis. The relative order of magnitude of the values agrees with that of other data: morphological>behavioural>life-history characters. Repeated measures of copula duration for each male revealed a general increase in copula duration with Julian date or age. The individual pattern of this change in copula duration (here termed ‘flexibility’), an expression of phenotypic plasticity, was itself marginally heritable ( h 2=0.19, P=0.065). Significant positive phenotypic and genetic covariance was evident only between flexibility of copula duration and body size. All other correlations were not different from zero, including those between development time and body size and between copula duration and body size. It is suggested that in S. stercoraria populations there is some averaging selection towards a mean optimal copula duration which can guide an individual's behaviour in a variety of environments. At the same time, there is selection for phenotypic plasticity which allows individuals to adapt their behaviour to their immediate environment. These effects together are consistent with both the assumptions of optimality models and the classic results on copula duration in yellow dung flies.

Economic impacts of East Coast Fever immunization on smallholder farms, Kenya: a simulation analysis

AbstractA whole farm simulation model, Technology Impact Evaluation System (TIES), was used to assess ex‐ante financial and economic impacts of immunization of dairy cattle against East Coast Fever (ECF) by the infection and treatment method (ITM) on smallholder farms from two sites in Kenya. Four alternative strategics of immunization in combination with different levels of acaricide use were compared with the current acaricide‐based method of control. The economic impacts were estimated using simulated net present values, present values of ending net worth, internal rates of return, benefit‐cost ratios, annual cash farm incomes, cash expenses, and net farm incomes. The results from the analysis indicate that ECF immunization strategics are financially and economically viable on smallholder farms. Based on the risk preference for risk averse producers, the most preferred strategy was to adopt ITM in combination with a 75% reduction in acaricidc use. The results obtained provide a good indication of the relative orders of magnitude of the farm level financial and economic effects of ECF immunization by ITM. The whole farm simulation model used for the analysis has the advantage of incorporating the risks involved in farm production. Whole farm simulation offers a flexible method for assessing the financial and economic impacts of alternative disease control methods on smallholder farms.

Economic impacts of East Coast Fever immunization on smallholder farms, Kenya: a simulation analysis

Abstract A whole farm simulation model, Technology Impact Evaluation System (TIES), was used to assess ex-ante financial and economic impacts of immunization of dairy cattle against East Coast Fever (ECF) by the infection and treatment method (ITM) on smallholder farms from two sites in Kenya. Four alternative strategies of immunization in combination with different levels of acaricide use were compared with the current acaricide-based method of control. The economic impacts were estimated using simulated net present values, present values of ending net worth, internal rates of return, benefit-cost ratios, annual cash farm incomes, cash expenses, and net farm incomes. The results from the analysis indicate that ECF immunization strategies are financially and economically viable on smallholder farms. Based on the risk preference for risk averse producers, the most preferred strategy was to adopt ITM in combination with a 75% reduction in acaricide use. The results obtained provide a good indication of the relative orders of magnitude of the farm level financial and economic effects of ECF immunization by ITM. The whole farm simulation model used for the analysis has the advantage of incorporating the risks involved in farm production. Whole farm simulation offers a flexible method for assessing the financial and economic impacts of alternative disease control methods on smallholder farms.

Hyperfine Interactions in the ν3 Band of Osmium Tetroxide: The Electric Quadrupole Interaction in 189OsO4

The quadrupolar structures observed in the ν3 band of 189OsO4 have been analyzed. These structures occur necessarily because of a breaking of the tetrahedral symmetry of the molecule induced by its internal dynamics. Three contributions to the quadrupolar interactions have been observed. Besides a vibrational term, these structures reveal the important role of the centrifugal distortion. A third, much weaker contribution of the Coriolis type is demonstrated. Systematic treatment of the high-order effects in the hyperfine Hamiltonian by a sequential method for the contact transformation has been proposed. When applied to this specific problem, it reproduces the relative order of magnitude of the three quadrupolar contributions and yields the expression of the effective quadrupolar constants as functions of molecular constants.

Bulk and surface modifications of insulating poly (paraphenylene sulphide) films by ion bombardment

Thin poly(paraphenylene sulphide) (PPS) films (2 μm thick), bombarded with He + (380 keV), B + (350 keV) and Ar 2+ (700 keV) at fluences ranging from 10 12 to 2 × 10 16 ions cm −2, were analysed by X-ray diffractometry, UV-visible absorption spectroscopy, electrical resistance measurements and solubility tests. The polymer gradually underwent an amorphization process indicated by the decrease in the main X-ray diffraction peak area and also lost its solubility with increasing ion fluence. This behaviour revealed the formation of cross-linking and amorphous structures. A red shift of the optical absorption threshold with increasing fluence was also observed by UV-visible spectroscopy. This trend is usually attributed to the conjugation of unsaturated carbon bonds which gives rise to non-localized π electrons. From these spectral data the gap between valence band and conduction band (optical gap E g) using a model for amorphous semiconductors can be obtained. The conjugation process increased with fluence resulting in a decrease in the optical gap. For Ar 2+ -bombarded samples the optical gap saturated at 0.9 eV for fluences around 10 15 cm −2. The decrease in E g with increasing fluence is a direct indication that a new group of conducting structures is being formed in the polymeric material. Electrical measurements made immediately after 2 × 10 16 Ar 2+ cm −2 bombardment revealed that the electrical resistivity decreased by 18 orders of magnitude in relation to the original PPS. When the bombarded samples were exposed to air the electrical conductivity decreased. This electrical instability was assigned to the free radicals present in the polymer chain after ion bombardment. This work shows that different hydrogenated amorphous carbon films can be obtained from one common polymeric matrix by judicious choice of the projectile ion stopping mechanism.

A Microcontinuum Model of Electrokinetic Coupling in the Extracellular Matrix: Perturbation Formulation and Solution

A microcontinuum model is formulated to describe electrokinetic transduction interactions and transport in the extracellular matrix (ECM) in terms of microscopic structural and compositional parameters. A unit cell technique is used in which the ECM is modeled as an ordered array of charged solid cylinders surrounded by a diffuse double layer. Under physiological conditions, the Debye length is on the order of the relevant microstructural dimensions of the ECM. Hence, the model includes the effects of overlapping diffuse double layers and the associated electrokinetic coupling within the bulk of the unit cell. A system of coupled differential equations is developed to describe electrokinetic coupling within the unit cell. This governing system is cast in dimensionless form, introducing two dimensionless groups whose relative order of magnitude suggests a perturbation analysis. The perturbation expansion of the governing system shows that the electromechanical coupling perturbs both the fluid flow and ion concentrations to the same order. The system is solved using the numerical grid generation technique in conjunction with the finite difference method. Model parameter values were chosen to describe the ECM of articular cartilage and similar connective tissues. Reasonable agreement between theory and experiment was found for the strain dependence of the hydraulic permeability k 11, the magnitude of k 22 , and the magnitude and ionic strength dependence of k e = k 21/ k 22

Relation between Aspect Ratio of Heated Body and Squeezing Force in Close-Contact Melting.

The problem of close-contact melting of a cylindrical solid body of a phase-change material is studied analytically. Relative orders of magnitude for various terms are examined using the dimensionless governing equation, taking into account the temperature distribution in the cylindrical heated body. It is found that the unsteady terms can be neglected. The governing equation approximated is solved using a Fourier series. The relationship between the squeezing force due to the weight of the phase-change material and the melting velocity is determined as a function of the aspect ratio of the heated body. The critical condition above which a steady melting phenomenon exists is shown in the plane of aspect ratio and dimensionless applied temperature difference. If the aspect ratio is very small, this relationship tends to that derived by Moallemi in which the temperature in the heated body is assumed to be constant. In the case that the aspect ratio is comparatively small, its effect on the melting velocity is very strong. Convection in the melting fluid layer makes the range of steady melting narrow.

Excitation electric field inhomogeneities in a cubic ion cyclotron resonance cell: ion motion for away from the cyclotron frequency

A theory of ion motion in a cubic ICR cell is presented for differential sinusoidal excitation that explains the observed stability, orders of magnitude, and resonance positions for excitation frequencies away from the cyclotron frequency. This is accomplished by transforming the equations of motion to an amplitude-phase representation where resonance is identified as terms with slowly varying phase. The assumption of isolated resonance reduces the analysis to a case-by-case study of individual resonances. Two classes of nonlinear resonances are identified: those dependent only on the excitation field inhomogeneities and those dependent also on the linear excitation. The latter resonances are negligible compared to the first class. For the strong resonances in the first class, resonance frequencies are predicted at 2ω z ± ω −, ω + ± 2ω z , ω + ± ω −, 2ω + ± ω −, 3ω +, and 3ω −, where ω +, ω z , and ω − are the cyclotron, z-axis, and magnetron frequencies characteristic of the unperturbed motion, respectively. The amplitude—phase equations show that the z-node coupling coefficients are proportional to (mass) − 1 2 while the radial modes are mass-independent in the low mass limit. Therefore, if the initial mode amplitudes are mass independent, mass discriminatory effects related to excitation inhomogeneities in quadrupolar traps are attributable to the z-mode. The coupling coefficient for the z-mode equation of motion has a relative order of magnitude approximately (ω + − ω −)/ω z greater than the corresponding radial mode coefficients, hence the resonances at 2ω z ± ω − and ω + ± 2ω z hve the strongest effect on ion motion. The stability of ion motion in the isolated resonance approximation is governed by a constant of motion relating the mode-amplitudes for the mode coupling resonances. The observed stability at ω + — 2ω z and instability at w + + 2ω z are explained by this invariant. Finally, FT-ICR double resonance experiments are used to show changes in the ICR signal for excitation near ω + ± 2ω z , 2ω z , 2ω +, and 3ω +. Experimental results agree qualitatively with theoretical predictions. Excitation at ω + − 2ω z shows a small increase in the FT-ICR signal due to reduction in the z-mode amplitudes. The resonances at ω + + 2ω z and near 2ω z show a decrease in the signal due to z-axis ejection. Excitation at 3ω + and near 2ω + gave changes in the FT-ICR signal consistent with radial mode excitation.

Determination of thermoelastic stresses in the plates which maintain the tube bundle of a heat exchanger

We study the thermoelastic behaviour of the upper plate in the tube bundle of a heat exchanger. After a dimensional analysis, we obtain a problem with several reduced parameters which can be very small. After stating the existence and uniqueness of the solution, we use asymptotic methods (in particular, homogenization techniques) to determine the different behaviours of the plate, depending on the relative order of magnitude of the small parameters.

1-Methyl-3-hydroxy-2-pyridinone and 1,4-dihydroxy-2-pyridinone complexes of the trivalent metal ions of Fe(III), Ga(III), Al(III), In(III) and Gd(III): potentiometric and spectrophotometric determination of stabilities

The trivalent metal ion stability constants for tris bidentate chelates of 1-methyl-3-hydroxy-2-pyridinone (MH2P) and 1,4-dihydroxy-2-pyridinone (DH2P) were determined by potentiometric and spectroscopic methods at 25.0 °C, 0.100 M KCI. The overall log stability constants for Fe(III) complexes (log βFeL 3=[FeL 3]/[Fe][L] 3) are 29.99 and 28.18, respectively, and are lower than that of 1,2-dimethyl-3-hydroxy-4-pyridinone (DMHP), published previously (35.88). The placement of the bidentate hydroxy oxygen donors relative to the pyridyl nitrogen atom of the ligand influences the 3:1 stabilities for each of the trivalent metal ions studied (i.e. Fe(III), Ga(III), Al(III), In(III) and Gd(III)), as the relative order of stability is DMHP>MH2P>DH2P. Among these ligands, the relative order of magnitude of metal ion stability is Fe(III)> Ga(III)>Al(III)>In(III)>Gd(III). Influences of structural and inductive effects (resulting from hydroxyl and methyl substitution of hydroxypyridinone ligands) are evaluated.

Qualitative/Quantitative Models Description Language

Abstract The aim of this research is to built a language for quantitative/qualitative representation in expert supervisory process control. The specification of such a language led to the definition of ALCMEN (Automaticians Language for Causal Modelisation of Expert kNowledge). Its purpose is to represent in a qualitative way imprecision and uncertainty, as well as classical numerical equations, in order to solve the communication problem between process experts and control engineers; it appears as a network of interconnected blocks and a list of structured variables. Two principal choices characterize the structure of ALCMEN: 1) A causal network is the underlying structure of any model represented using ALCMEN. 2) Qualitative variables have as semantic reference subsets of quantitative spaces connected to the physical variables: i.e. absolute referenced magnitudes, not relative order of magnitude. A first approach for the mixed (qualitative/quantitative) Knowledge representation has been programmed using the Real Time Expert system development tool G2. It has been applied to the modelization of a discontinuous process in the framework of the Esprit project IPCES (Intelligent Process Control by means of Expert Systems). The definition of qualitative operations as well as the organization of the different workspaces will be described on this example.