First-order Level Research Articles

Theoretical investigation of the dissociation of bridged disilyne

The dissociation potential energy surfaces of ground-state bridged disilyne ( 1A 1), the Si 2H 2 global minimum, is investigated using the state-averaged multi-configuration self-consistent field (SA-MCSCF) method. The dissociation energy of bridged disilyne into Si 2 ( 1Δ g+H 2( 1Σ + g) is predicted to be 42 kcal/mol. The very small calculated energy barrier (about 1 kcal/mol) given by the SA-MCSCF calculations disappears at the first-order configuration interaction level of theory. The spin-orbit coupling constant between the lowest 1A 1 and 3B 1 states is estimated to be about 60 cm −1 in the crossing region of their potential energy surfaces.

Agoraphobic, animal, death-injury-illness and social stimuli clusters as major elements in a four-dimensional taxonomy of self-rated fears: First-order level confirmatory evidence from an australian sample of anxiety disorder patients

In a recent review article, Arrindell, Pickersgill, Merckelbach, Ardon, and Cornet (1991) ( Advances in Behaviour Research and Therapy, 13, 73–130) proposed an a priori four-dimensional categorization system for the description of self-rated fears on the basis of suggestions from previous reviews and research. The categories were described as: (I) Interpersonal events or situations, (II) Death, injuries, illness, blood and surgical procedures, (III) Animals, and (IV) Agoraphobia. While it has proven to be feasible to categorize fear factors/components derived in different empirical studies reliably into each of these categories, no confirmatory evidence is as yet available to support the factorial validity of the relevant dimensional system. Using the multiple-group method, clear evidence was found at the primary level for such in a sample of 398 anxiety disorder patients. In addition, the corresponding component scales were demonstrated to be highly consistent internally and to be moderately to highly intercorrelated, with none of the intercorrelations exceeding or even approaching the internal consistencies in magnitude — thus clearly indicating that a reliable distinction can be made between the four fear dimensions. The findings are discussed in relation to other classes of fear reactions described in the clinical-theoretical literature and to Endler's interactional model of personality. Following the line of research from the area of personality testing, it is, among other things, suggested that psychobiological, developmental, and behavioral-social studies should, in the future, be organized around the now well-established dimensions of fear described above.

Temperature dependent carbon-13 and proton isotope shifts of some isotopomers of methane

The carbon-13 and proton isotope shifts of 13CH 3D, 13CHD 3 and 13CD 4 with respect to 13CH 4 have been measured over the temperature range 200–370 K. The isotope shifts increase with temperature in all cases, with the increase being more marked for the more heavily deuterated isotopomers. The variations are attributable entirely to intramolecular effects and the data have been fitted by weighted least-squares regression analyses to defined carbon-13 and proton shielding surfaces to obtain derivatives of the shielding with respect to internal coordinates. At the first-order level it is found for the carbon-13 shielding that σ r , the derivative with respect to the stretching of a single bond, is − 71.0 (±0.6) ppm Å −1; for the proton shielding σ r , the derivative with respect to the length of the bond involving the proton, is − 23.5 (±1.5) ppm Å −1 whilst σ s , the derivative with respect to the length of one of the other bonds is − 2.1(±0.5) ppm Å −1. The derivatives are used to predict the values of the nuclear motion corrections for 13CH 4 and to predict isotope shifts for 13CH 2D 2 which was not studied experimentally in this work.

A comparison of flux limited difference methods and characteristic galerkin methods for shock modelling

Abstract A comparison is made between flux-limited finite difference methods and characteristic Galerkin methods for approximating hyperbolic conservation laws. At the first-order level, the characteristic Galerkin scheme using piecewise constants is closely related to the difference schemes of Engquist, fisher, and Roe. Adaptive recovery techniques used to improve accuracy then have much in common with the flux limiters used with difference methods. These relationships are explored and comparisons made using the linear advection, inviscid Burgers and Euler equations. A new, simple formulation is given of the characteristic Galerkin method using piecewise constant elements with piecewise linear recovery: it reduces to the Engquist-Osher algorithm but with a modified flux function when the CFL number is no greater than one half.

Concurrent dynamic logic

In this paper concurrent dynamic logic (CDL) is introduced as an extension of dynamic logic tailored toward handling concurrent programs. Properties of CDL are discussed, both on the propositional and first-order level, and the extension is shown to possess most of the desirable properties of DL. Its relationships with the μ-calculus, game logic, DL with recursive procedures, and PTIME are further explored, revealing natural connections between concurrency, recursion, and alternation.

A twistor approach to the regularization of divergences

One object of the twistor programme, as developed principally by R. Penrose, is the production of a manifestly finite theory of scattering in quantum field theory. Earlier work has shown that progress towards this goal is obstructed even at the first-order level, by the appearance of an infrared divergence in the standard theory. New studies in many-dimensional contour integration now suggest a simple but very powerful modification to this branch of twistor theory, in which the full (as opposed to the projective) twistor space plays an essential role. In this modified theory there arise natural contour-integral expressions with the effect of eliminating the infrared divergence previously noted, and replacing it by a finite quantity. This regularization can be specified by using a formalism of ‘inhomogeneous twistor diagrams’. The interpretation of this new formalism is not yet wholly clear, but the inhomogeneity can be seen as a means of relinquishing the concept of space-time point, while preserving light-cone structure. It therefore suggests a quite fresh approach to the divergences of quantum field theory.

More on looping vs. repeating in dynamic logic

This paper is a natural continuation of recent research dealing with the relative power of the formulas loop(a) and repeat(a) in the framework of dynamic logic. These constructs were suggested as means for extending dynamic logic in order to enable reasoning about infinite computations. A formula of the form loop(a) (cf. [3,7]) expresses the fact that the program et can diverge, i.e., that it admits an infinite computation. However, this statement does not point out the exact subprogram of a 'responsible' for this behaviour. For instance, iool)([3) may hold either when 13 can be repeated indefinitely, or when, after some number of executions of 13, the next execution itself diverges. These two types are referred to in [3] as global and local looping, respectively. Global looping has since been formulated as the repeat construct; thus, repeat(a) is true whenever cx can be repeated indefinitely. Using repeat, the formula loop(a) can be easily defined inductively. The expressive power of loop and repeat has already been examined within different versions of (propositional and quantified) dynamic logic. A number of results on this matter are summarized in [4,1,8]. These results indicate generally that repeat is a stronger construct than loop, in several respects. In particular, it is shown in [4] that PDL, the propositional version of dynamic logic, is more expressive with repeat added than with loop. In this paper we present two results, both of which strengthen the general conclusion outlined above. They concern, respectively, expressiveness and validity on the first-order level. First, it is shown, analogously to [4], that QDL, the first-order version of dynamic logic, is more expressive with repeat than with loop. The same is shown to hold for QDL with arrays, context-free QDL, finite-test bounded-memory QDL and r.e. QDL. This answers a series of questions from [7,1,4]. The second result concerns the problem of deciding whether a program scheme in QDL might diverge under some precondition. That is, one is interested in deciding the validity problem for formulas of the form q~ D ~ioop(et) or q~ D ~repeat(ct). We show that for first-order q~ and regular et with first-order tests, the two problems differ greatly in their complexity. While both are undecidable, the first is X°-complete, i.e., recursively enumerable, and the second is highly undecidable, viz. II~-complete.

Analysis of Turbulent Gas-Solid Suspension Flow in a Pipe

The mixing length theory is extended to close the relevant momentum equations for two-phase turbulent flow at a first-order closure level. It is assumed that the mass fraction of the particles is on the order of unity, that the particle size is so small that the particles are fully suspended in the primary fluid, and that the relaxation time scale of the particles is sufficiently small compared with the time scale of the energy containing eddies so that the suspended particles are fully responsive to the fluctuating turbulent field. Bulk motion of the particles is treated as a secondary fluid flow with its own virtual viscosity. The proposed closure is applied to a fully developed gas-solid pipe flow in which the particles are assumed to be uniformly distributed across the pipe section. Predicted velocity profiles and the friction factors are in good agreement with available experimental data.

Vertical crustal movements in the Charleston, South Carolina-Savannah, Georgia area

First-order vertical level surveys (National Geodetic Survey) repeated between 1955 and 1975 suggest that modern vertical crustal movements have taken place in the Atlantic Coastal Plain between Charleston, South Carolina and Savannah, Georgia. The relative sense of these movements correlates with the sense of displacement of Tertiary strata on known geologic structures. Whereas regional dip of strata in most of the Atlantic Coastal Plain is southeasterly, the regional dip of Tertiary strata in this part of the Coastal Plain averages 2 m/km to the south or southwest. Positive structural features disturb this regional dip along a poorly defined zone, about 25 km wide, parallel to the coast between Savannah and Charleston. Structural relief on these features is as much as 20 m. Repeated level lines that cross the Atlantic Coastal Plain elsewhere generally show an increase in modern relative subsidence from west to east. However, in the Charleston—Savannah area, the amount of relative subsidence remains fairly constant or decreases from west to east across the structural highs. At two localities near Charleston, where Tertiary beds are offset by faults roughly on strike with one another, an abrupt break in a repeated level line occurs where the level line crosses the probable extensions of these faults. The average modern rates of relative uplift and subsidence (assuming they are constant) are compatible with rates noted throughout the Coastal Plain. Long-term extrapolation of modern rates appears unreasonable; episodic or oscillatory movements are much more likely.

The Yellowstone Park Earthquake of June 30, 1975

abstract The June 30, 1975 Yellowstone Park Earthquake (ML 6.1, Ms 5.9) occurred on the north-central boundary of the Yellowstone caldera. Intensity studies show the felt area north of the epicenter to be substantially larger than the felt area south of the epicenter. This asymmetry may be due to attenuation of seismic waves propagating through the caldera. Aftershocks define a 10-km northwest-trending zone of seismicity centered on the main shock. A second zone of seismicity (active since March 1974) located 5 km west of and subparallel to the zone containing the main shock, increased in length during the aftershock sequence. No faults are mapped in the region of either zone, but north to northwest trending normal faults are found north of the caldera boundary. Focal mechanisms indicate both normal and oblique-slip faulting, but normal faulting predominates. The T axes are oriented northeast (perpendicular to the two seismic zones) suggesting block faulting. Elevation changes of 12 cm (determined by first-order level lines) between Madison Junction (up) and Mammoth Hot Springs (down) between 1960 and August 1975 are interpreted as a long-term trend with a local perturbation in the Norris Junction area which may have been caused by the June 30 earthquake.

Probability density function approach for a turbulent axisymmetric heated jet. Centerline evolution

The equation describing the evolution of the probability density function of the temperature field in a turbulent axisymmetric heated jet is presented. A closure problem is present and some possible ways of attacking it are suggested. A closure at the first-order level is then tentatively tried and similarity arguments are exploited. A hyperbolic first-order variable-coefficient quasi-self-preserving partial differential equation is obtained. The constants appearing in those coefficients are evaluated from available experiments. Some questions are raised on the uncertainty of the computed constants due to the experimental scattering of the velocity-temperature correlation at the centerline. The probability density function is obtained analytically as a function of downstream location along the centerline if it is prescribed at a reference centerline position. In particular, the probability density function is taken as Gaussian at ten diameters downstream. The computed mean and variance are compared with existing experiments and display a reasonably good agreement. Values for the skewness and flatness factor tend to indicate that deviations from Gaussianity along the centerline are very small.

Evidence for postearthquake slip in the Fairview Peak, Dixie Valley, and Rainbow Mountain fault areas of Nevada

abstract The U.S. Coast and Geodetic Survey ran first-order level surveys in 1934, 1955, and 1967 across the fault zone associated with the 1954 sequence of earthquakes at Rainbow Mountain (M = 6.6 and 6.8), Dixie Valley (M = 6.8), and Fairview Peak (M = 7.1) in Nevada. The difference between the 1955 and 1967 surveys clearly shows distinct anomalies over distances of several kilometers at all but one of the fault scarps mapped after the 1954 earthquakes. The anomalies resemble deformation produced by normal faulting extending to a depth of at least several kilometers and, consequently, are interpreted as implying continued slip on the earthquake faults in a period beginning at least 6 months after the earthquake. At the Fairview Peak Fault, the inferred postearthquake slip is about 5 per cent of the displacement observed at the time of the earthquake. The difference between the 1955 and 1967 surveys suggests an overall tilt of 2 mm/km down to the west extending over a 90-km distance crossing the fault zone. The difference between the 1934 and 1955 surveys suggests an overall tilt of 0.8 mm/km down to the east extending over a 200-km section. However, these regional tilts might be due to unusually large systematic errors in the level surveys. Gravity and seismic-refraction surveys indicate that the region as a whole is isostatically compensated, although the mountain ranges and intervening basins are not individually compensated. Thus, the regional elevation changes, if they exist, cannot be accounted for by isostasy.

Study of factors influencing variation in size characteristics of fluvioglacial sediments

Factor analysis using promax oblique rotation was used in a study of fluvioglacial sediments of Late Weichsilian (Wurm) age. The use of oblique rotation allowed a more realistic interpretation of the factors and understanding of relationships between sedimentsize classes. At the second-order level, two factors are operatable, one producing variations in the coarse-size range, the other in the fine-size range. The factors are uncorrelated and mutally unrelated. At the first-order level are six factors, four representing aspects of the second-order factor of coarse size and two representing the fine size. The factor producing the variation in the coarse size is the most important one. At the lowest level in the hierarchy scale are the individual size variables. Results show that the number of factors required to account for the variation in a sediment-size data set is a function of the scale at which the problem is examined.

Double Perturbation Theory for He-like Systems

The He-like system is considered to be a spherical Harmonic oscillator with the electrons attracted to the nucleus by a Hooke's-law force, under two perturbations: (1) electronic repulsion, H(1,0), and (2) the difference between the harmonic oscillator potential and the actual nuclear Coulomb attraction, H(0,1). For the ground state, the first-order wavefunctions with respect to both perturbations are found in closed form. Exact expressions for both of the single perturbation energies through third order and the mixed perturbation energy ε(1,1) are derived. Calculations have been carried out on H−, He, Li+, and Be2+ for different choices of f, the Gaussian parameter of the zeroth-order harmonic oscillator wavefunction ψ(0,0). The choice f = (4 / 3π1/2) [Z − (1 / 2√2)] corresponding to the variational one-term Gaussian orbital of a He-like system gives the best total calculated energy, − 2.88210 a.u. for helium compared to the experimental and “exact” value of − 2.90372 a.u. From the study of the convergence of the perturbation energies, it is concluded that as far as correlation is concerned the first-order perturbation with respect to H(1,0) is accurate enough. Higher order perturbations with respect to the one-electron operator H(0,1) will be needed for highly accurate results. However, even at the first-order level the Gaussian character of ψ(0,0) is improved tremendously by the perturbation H(0,1). This is shown by the values of ε(0,2) + ε(0,3), of the order of − 0.4 to − 0.6 a.u.

Survey Control for Concrete Dam Construction

The development of survey controls for Morrow Point Dam, a double-curvature, concrete-arch structure, 465 ft in height, was required through the phases of reconnaissance, site investigation, and preconstruction to satisfy the specific needs of the designer, and to fit the rough terrain. Statistics for the dam and power plant are given. Procedures and equipment used in establishing a modified second-order triangulation scheme and a first-order level net are explained. The method used in adjusting the triangulation scheme is presented. Planning survey controls to encompass specific structures was completed early in the construction phase. A description of survey procedures to bring accurate control into the blocks of the dam for each 7-1/2-ft placement-lift is given. Methods devised and equipment used in establishing vertical control in each keyway are described. A brief evaluation of planning field surveys to utilize modern electronic computing equipment is presented.

Personality correlates of the Similes preference inventory.

Recently, Pearson, and Maddi (1966) presented evidence that the Similes Preference Inventory (SPI) may serve as a rapid screening device for assessing tendency toward variety. An inspection of the task posed by the SPI suggested the alternative hypothesis that preferential judgment for the ending to common similes (e.g., Hot as . . .) is linked to established traits within the personality sphere. Specifically, the purpose of the srudy was to investigate the relationship between performance on the SPI and the Sixteen Personality Factor (16 PF) Questionnaire. The SPI, 54 multiple-choice items, was administered to 162 (76 male, 86 female) undergraduates at Western Washington State College. Each item was scored on a fivepoint scale proposed by Pearson and Maddi (1966) yielding results whereby low total score indicated a tendency to select usual and common place endings to common similes, while a high total score indicated a tendency to select unusual and novel alternatives. A basic set of source traits in the personality sphere was measured with the 16 PF (Cattell & Eber, 1964) ; both Forms A and B were administered for maximum dependability of measurement (Meredith, 1966). At the first-order level, seven factors on the 16 PF correlated significantly with SPI total score. When these findings were ordered from most salient to least salient, tendency toward variety was associated with being imaginative (M+; r = .35, p < .01), assertive (E+; r = .27, p < .01), expedient (G-; r = -.25, p < .01), tender-minded (I+; r = .24, p < .01), sell-sufficient (Qcf; 7 = .19, p < .05), experimenting (QL+; r = .17, p < .05), and abstract-thinking (B+; r = .17, p < .05). In addition, standard weights for estimating S's endowment on the higher-order factors of the 16 PF were applied to transform Ss sten (standard 10-point) scores on the primaries to sten scores on the secondaries. In terms of the seven major higher-order factors, tendency toward variety was significantly relared to independence (r = .37, p < .01) and creativity (r = .28, p < .01). The remaining broad factors (anxiety, extraversion, tough poise, neurolicism, and leadership) were unrelated to SPI performance. The pattern of relationships suggests that preference for unusual simile endings is indicative of a self-directing, imaginative, flexible, and innovative type of person. However, the magnitude of the relationships portends caution in over-generalizing from the SPI to the real world. The present writer would concur with Pearson and Maddi (1966, p. 308) that a good deal of research is needed to support the clinical use of the instrument.

One-Electron Perturbations in Self-Consistent Field Theory

Self-consistent field equations perturbed by one-electron operators are examined, with the aim of justifying the use of uncoupled equations at the first-order level. The independent-orbital equations of Sternheimer for the first-order corrections are shown to differ from the exact first-order SCF equations by sums of pair-coupling functions Aij which bring perturbed orbital j into the differential equation determining the perturbed orbital i. It is shown that the off-diagonal Lagrangian multipliers εij0 and εij(1) that appear in the unperturbed and perturbed SCF equations can be chosen so that ∫ φi0Aijdv= ∫ φj0Ajidv=0and ∫ (Aij2+Aji2) dv=minimum,where the φi0 are the unperturbed SCF orbitals. Complete neglect of the functions Aij—the Sternheimer method—is thereby given a firm basis. Further analysis provides a perturbation—iteration method for determining residual coupling effects. An alternative analysis also is presented in which the Sternheimer equations are obtained directly from the perturbed SCF equations by treatment of the exchange operator, the change of the Coulomb-exchange operator, and the operator generating the off-diagonal εij as pseudoperturbations that act cojointly with the pure-field operator. Integrodifferential equations are given for both the pure-field corrections and the corrections evolved by the pseudoperturbations.