Absolute Parameter Research Articles

Study of nonstoichiometry in undoped semi-insulating GaAs using precise lattice parameter measurements

Nonstoichiometry in undoped semi-insulating GaAs grown by the liquid-encapsulated Czochralski technique has been evaluated by absolute lattice parameter measurements using the Bond method. The lattice parameter increases with increasing As atom fraction in the initial melt. The observed range of lattice parameters and the variation along the growth direction suggest that the solidus curve in the phase diagram extends to the As-rich side than to the Ga-rich side, and the congruent point is located on the stoichiometric point or the slightly As-rich side.

Venustatriol. A new, anti-viral, triterpene tetracyclic ether from Laurencia venusta

Venustatriol, a new tetracyclic ether derived from squalene, which has anti-viral activity, has been isolated from the red alga Laurencia venusta. Its structure and absolute configuration were determined by X-ray using the absolute structure parameter x. By comparison of their spectral properties, the absolute configuration of its congener, thyrsiferol, was deduced.

Timing of the quantitative recovery in the regenerating rat lung.

Growing rats 23 days of age were subjected to the resection of the upper and middle lobes of the right lung (25% of total lung volume). On postoperative days 1, 4, 6, 9, 12, 18, and 30, the lungs of 5 animals were fixed by intratracheal instillation of glutaraldehyde, their volumes measured by water displacement, and the lung tissue processed for quantitative light (LM) and electron microscopic (EM) investigations. For each group, 3 age-matched sham-operated, and 4 normal rats served as controls. Sham operation consisted in entering the pleural space, and collapsing and ventilating the lungs. In all animals, the following parameters were measured by means of point and intersection counting stereology at either LM or EM-levels: volume densities of lung parenchyma and of its components (airspaces, tissue, capillary blood) and surface densities of airspaces and of capillaries. From these data absolute parameter values were calculated for each lung. The results showed that after bilobectomy the remaining lung re-expanded rapidly first by an overinflation of the airspaces and after Day 4 by an increase in tissue mass and capillary volume. On Days 9 and 12 the operated lungs did not differ quantitatively from control lungs. Later, however, further sequels of the bilobectomy were detected: On Day 18, lobectomy-lungs were smaller than controls, and on Day 30 lungs, the left lung was significantly different in structure from the right lung and from control lungs.(ABSTRACT TRUNCATED AT 250 WORDS)

Absolute hardness of ground and hybridised states of atoms

First calculations of the absolute hardness parameter eta are reported for a large number of atoms in the ground electronic state using the relativistic local density functional which includes the effects due to electron correlation. The results are found to be in excellent agreement with experimental values and are more reliable than the non-relativistic estimates available in the literature. In the cases of B, C, N, Al, Si and P atoms, empirical estimates of eta corresponding to the hybridised sp, sp2 and sp3 states are found to differ significantly from the ground-state eta values.

Infrared and Far-Infrared Studies on the Nematogenic Homologous Series Trans-4-Alkyl-(4-Cyanophenyl) Cyclohexanes

Abstract Infrared (4000–650 cm−1) and far-infrared (650–20 cm−1) spectra of the nematogenic homologous series trans-4-alkyl-(4-cyanophenyl) cyclohexanes (ethyl, propyl, butyl, pentyl and heptyl) have been examined in the solid and liquid crystalline states. An attempt has been made to correlate the variation in the intensities and frequency shifts with the molecular structures. The gradual shift towards smaller wavelength in the —C≡N stretching vibration and the relative alternation in the intensity of this frequency as the chain length increases may be correlated with odd-even effects in homologous liquid crystals and with the increase in thermal stability, as the spectra reveal an increase in the dipole-dipole interaction between the neighbouring molecules. A strong feature centred around 90 cm−1 is assigned to hindered rotation about the long axis of the molecule. Absolute orientational order parameter S has been evaluated for the series by a study of the temperature variation of —C≡N vibration in home...

Absolute rate parameters for infrared photochemistry: CF3I→CF3+I

IR-photolysis yields are reported for CF3I irradiated with the R14 line of the (001→0200) transition of a pulsed TEA-CO2 laser (at 1074.65 cm−1) with unstable resonator optics providing a smooth and well defined fluence profile in the far field. The reaction products (CF3+I) of the primary reaction are scavenged by reactions with added NO, Br2, or ClNO in order to reliably establish the primary yields. A data treatment valid for arbitrary, smooth spatial fluence profiles is proposed for the evaluation of true yields and rate coefficients kI(st). The influence of collisions with buffer gas molecules on the evaluation of kI(st) is investigated in experiments and by model calculations. A steady state rate coefficient for the unimolecular decomposition of CF3I under irradiation with constant intensity I is obtained to be k(st) = 10(6.2±0.3) (I/MW cm−2)s−1 valid for intensities near and above 100 MW cm−2. This is consistent with a low a priori estimate of rate coefficients from a simple theoretical model involving only easily measurable molecular properties. The physical significance of this absolute rate parameter is discussed.

Correlations between relatives for acrocentric association frequency.

Acrocentric association was investigated in peripheral blood lymphocytes of twins (10 female monozygotic and 11 females dizygotic pairs), newborns and both parents (30 families), and spouses (51 pairs). Seventy two hour cultures were G-banded and scored for both absolute and relative acrocentric association frequency, except in the case of the spouse pairs where only the absolute frequency was measured. Both relative and absolute parameters of acrocentric association show positive correlations between relatives with the values being highest and most consistent in monozygotic twins, intermediate in parent and offspring, and most variable in dizygotic twins. Husband and wife pairs from our family collections show a positive correlation for the absolute parameter but not for relative parameters. The environmental factors responsible have not been identified. A rough estimate of broad sense heritability (0.81) has been made for the relative parameters. It probably contains a large component due to genetic dominance. Heritability of the absolute parameters is probably lower than for the relative parameters though estimation of its value is complicated by inconsistent results. A model is proposed to account for the variation in satellite association frequency which contains two elements: (i) The genotype determines the ratio of one chromosome type to another in the population of associated chromosomes (ii) All other environmental factors influence the absolute frequency of association without altering this basic ratio.

Investigation of sensitivity of the proprioceptor system of man to the changes of working place parameters

Sensitivity thresholds of the proprioceptor system of man were investigated in the case of changes of working place taken as a whole and of its separate elements (table, chair and foot support) heights and angles. The influence of the absolute parameter value, duration of its estimation, subject posture at the time of changing parameters on the threshold value has been determined. The experiments have shown that sensitivity threshold is independent upon the subject sex and is the same for the table, chair and foot support heights - 8±2 mm. Sensitivity threshold for the table angle changes is equal to 90±20 minutes, for the chair angle changes - to 45± 15 minutes, equally for man and women. Recommendations are given for the psycho-physiological investigations of working places.

A study of the degradation of daytime astronomical images due to turbulence in the lower atmosphere by measurement of the standard deviation of the angle of arrival

Fluctuations in the angle-of-arrival of a luminous wavefront are investigated by placing a narrow slit over the image of the solar limb, and observing the entrance pupil through this diaphragm. Measurement of the standard deviation σAA of these fluctuations, in a direction perpendicular to the solar limb, provides sufficient information to estimate an absolute parameter characterizing the seeing, i.e. Fried's parameter r0 or the equivalent parameter ∫LCN2(h) dh which gives the integral, over an atmosphere thickness L which depends on the spatial and angular filterings performed by the slit, of the structure constant CN2characterizing fluctuations in the air's refractive index. Simultaneous estimations of σAA2 and ∫LCN2(h) dh permit a linear relationship to be established between these two quantities. The result is interpreted theoretically by integration of the two-dimensional power spectrum for the angle-of-arrival fluctuations. The influence of filtering effects is discussed.

Infrared Spectroscopic Study of Orientational Order and Phase Transformations in Liquid Crystalline CBOOA

Abstract An infrared study of the different phases of liquid crystalline CBOOA (N-p-cyanobenzilidene p-n-octyloxyaniline) has been made in the range 30-3100 cm−1. From a study of the -C≡N vibration in aligned samples, the absolute orientational order parameter, S, is determined in the smectic A and nematic phases. The variation of S is compared with the relative values determined earlier from diamagnetic anisotropy, NMR and birefringence studies. The farinfrared spectrum of the solid (Phase I) exhibits a mode whose intensity decreases gradually as the crystal-smectic A transition is approached. Also, a band observed at 296 cm−1 in the solid (Phase I) practically disappears in the fluid phases. These results are discussed in terms of possible pretransition effects and intramolecular changes characteristic of crystal-mesophase transitions. Dichroic effects are evident in the far-infrared absorption of the liquid crystalline phases and these are considered in relation to the influence of molecular structure ...

π-Bonding and tetragonality in dchloro- and dibromo-tetrapyridinecobalt(II) and diacetylacetonatodipyridinecobalt(II)

Average and principal magnetic susceptibilities of [Co(py)4Cl2], [Co(py)4Br2], and [Co(acetylacetone)2(py)2] in the temperature range 80–300 K are reported. Interpretation within the low-symmetry angular overlap model, described recently, are characterized by fits describing an approximately linear relationship between the π-bonding parameters. The indeterminacy of absolute eπ parameter values is a consequence of the high symmetry in these molecules, actual or effective. The relative contributions of π-bonding between different ligands and with respect to different directions all appear compatible with otherwise established chemical criteria.

Usefullness of some pressure velocity parameters for evaluation of left ventricular contractility.

In order to evaluate the usefullness of pressure velocity data for the assessment of left ventricular contractility it is necessary to know how they depend on the haemodynamic conditions under which the heart operates. Thus one has to know how these indices are influenced by the diastolic filling (preload), by the aortic pressure, which is also responsible for the coronary perfusion pressure (afterload), and by the heart rate. On the other hand it must be guaranteed, that canges in the inotropic state are expressed precisely. Though an absolute parameter for myocardial contractility is not yet available, it is possible to find out different sensitivities of intropic indices by comparing the changes following the same inotropic intervention (application of CaC12 or Halothane) in the same heart.

A note on transforms of renewal and other models applied to the collective risk theory

Abstract 1. Renewal models applied to the risk theory In this note the interval between the (n—1)th, and the nth event in a random process—the interoccurrence time—will be denoted by τ n for n = 2, 3 ... , and the interval from the starting point of the process to the time point of the first event by τ1. τ has here been chosen for the notations, in order to differentiate from t, usually used for the expected number of claims; the mean of n in a renewal process is, for finite values of τ, different from τ, and for τ→∞ linear in τ; τ is not necessarily measured on the absolute parameter scale. The renewal process is based on the assumptions that τ n are mutually independent variables, equally distributed with the distribution function Prob [τ n ⩽ τ] = K(τ) , n = 1, 2 ... , where K(τ) shall be defined below. The complex Fourier transform of dK(τ) shall be designated by k(z).

A thermodynamic approach to problems of drug antagonism I. The “Charniere theory”

The presence in the receptor of two sites, a “specific” one especially designed to bind the active groups of the agonist, and an “unspecific” site to which the heavy cyclic radicals of the antagonist are attached mainly through van der Waals forces (hydrophobic bonds) may allow a competition of the agonist versus the antagonist of the “specific” site, while the latter would remain in place held in the “unspecific” site. This hinge effect or “Charnière Phenomenon” may explain why the agonist though unable to remove the antagonist from the receptor site is nonetheless able to compete with the latter according to the mass action law. By using the simple thermodynamic concept of Gibbs' free energy or enthalpy, the “overall affinity” of the antagonist as measured as function of the logarithm of the dissociation constant K i , could be separated in two parcels, one corresponding to the “affinity” toward the “specific” site and measured by an absolute parameter, as the logarithm of the ratio of slopes “with/without” of Lineweaver-Burk plot. A consequence of this thermodynamic approach is the almost total impossibility of the agonist removing the antagonist from its “unspecific” bindings with the receptor.

Mean fitness and the equilibria in multilocus polymorphisms

A precise theorem is given for the increase in fitness due to natural selection on diploids subject to random mating, non-overlapping generations and not more than two loci; the method of extension to more loci is given by Kojima & Kelleher, and a precise theorem is given here for any number of loci when there is no recombination. The increase is equal to the haploid (or genic) variance in fitness, multiplied by a factor which is equal to two in the absence of dominance, but which otherwise is a function of gene frequency and dominance. The theorem is compared with that of Kimura, which is more general but harder to apply, and to those of Kojima & Kelleher and Fisher, which are respectively restricted to slow selection and absence of epistasis. The new theorem is used to predict the equilibria in populations polymorphic for two loci, and to deal especially with the quasi-stable equilibrium, for which the critical value of recombination is formulated, and the through point, at which a stable and unstable equilibrium meet and annihilate each other. The effect of this in space is to produce a stepped cline, in which gene frequencies and gametic excess change suddenly over a short distance; in time, the through point brings a new slant to Wright’s multiple peak theory of evolution, as populations can move precipitately from peak to peak without the help of random processes. Mean fitness is related only indirectly to population density. By distinguishing carefully between mean absolute fitness (which is the rate of population growth) and mean relative fitness (which is more useful than the absolute parameter for predicting genetical equilibria) we can show the effects of various types of density control on the genetical composition of the population; density dependent selection may appear to be gene-frequency dependent. The fundamental law of evolution is probably a thermodynamic law of increasing matter energy, which is related only tenuously to the law of increasing genetical fitness.

Some convolution theorems for compound poisson processes

Abstract Previously the term compound Poisson processes in the wide sense (cPp i. w. s.) has by the present author in several papers (e.g. 1964) been used for a process for which the probability of the occurrence of m changes in the interval (0, τ) on the absolute parameter scale, is defined by the following relation: where s and t are real-valued, positive functions of τ with one-to-one correspondence between t and τ, s and τ respectively. If the size of a change is a random variable, with the conditional distribution for the size of a change known to have occurred at t = u, V(x, u) with zu = z(η, u) as corresponding characteristic function, the distribution functions, defining the process, F(x; t, s), and their corresponding characteristic functions, ϕ(η; t, s) are defined by the following relations, where V (x, t) denotes the integral and, consequently, the characteristic function ξ corresponding to V (x, t), under mild regularity conditions equal to the expressions for V (x, t) and ξ may easily be extended to the case, where V(x, u) is a discontinuous function of u by substituting for V(x, u)du and zudu respectively. Further, in (2a) and in the following context, the asterisk power m* of any distribution function denotes for m = 0, unity, and, for m > 0 the m times iterated convolution of the function with itself.

Frequency Modulation

The differential equation of a frequency modulated transmitter is considered and the expression of the current as a function of time is derived. Frequency analysis of this function is made for two specific cases, (A) sinusoidal frequency modulation (telephony) and (B), right-angle frequency modulation (telegraphy with "marking" and "spacing" wave). The distribution and amplitudes of the frequencies present are seen to depend upon the value of an absolute parameter, the "frequency modulation index," equal to the ratio of the maximum frequency deviation to the imposed modulating frequency. The overall width of the band occupied is found to be approximately double the highest of these two frequencies. In the case of high-speed frequency modulated telegraphy, however, side frequencies of noticeable amplitude may occur outside this band. Charts are included showing the derived frequency spectra.