Showing papers by "University of Warsaw published in 1977"

The time-dependent physical spectrum of light*

Abstract: We investigate the time-dependent spectrum of light from an observational point of view and define a time-dependent “physical spectrum” of light based on the counting rate of a photodetector. The tunable element, the filter, that allows observation of different spectral components of the light is shown to play an essential role in the time-dependent spectrum. Its bandwidth cannot be taken arbitrarily narrow. We establish the connection between our physical spectrum and other time-dependent spectra associated with Page, Lampard, Silverman, and Kolmogorov, as well as with the Wiener-Khintchine power spectrum. Also, we show the conditions under which these earlier definitions can be used as the first approximations to the complete physical spectrum, and give an expression for the correction terms.

Development of cytochalasin B-induced tetraploid and diploid/tetraploid mosaic mouse embryos

Abstract: By subjecting F1 (CBA × C57/BL) × A eggs at the time of 2nd cleavage to 10 μg/ml of cytochalasin B (CB), tetraploidy was produced in 52 % of 2-cell eggs and 35 % of 3-cell eggs. 2n/4n mosaic embryos were produced from 2-, 3- and 4-cell eggs and amounted to 20 % of all treated eggs. 80 % of tetraploid embryos developed in vitro into regular blastocysts with half the cell number of control diploids. The effectiveness of CB in producing tetraploid embryos is limited by the asynchrony of 2nd cleavage, both between eggs and between sister blastomeres. Two-cell presumed tetraploids were transplanted to recipients and examined between the 6th and 11th day of pregnancy. Up to 6½ days development is normal and most embryos form egg-cylinders. At 7½ days the embryonic part of the cylinders is underdeveloped and in later development fails to form an embryo. Development of foetal membranes is much less affected and in the most successfully developing egg-cylinders their formation can be fully accomplished. Failure of embryonic development appears to be due to subnormal activity of the primitive streak, resulting in shortage of mesoderm. Postimplantation development of 2n/4n mosaics was normal. While in embryos tetraploid cells were either absent or in very low proportion (below 4 %), their contribution to the foetal membranes amounted in some cases to up to 50 %. Elimination of tetraploid cells from mosaic embryos suggests that they have a lower proliferation rate than diploid cells.

Density-dependent magnetic shielding in gas phase 13C N.M.R.

Abstract: Density-dependent 13C nuclear magnetic shielding has been found for each of the pure gases CH4, C2H6, C2H4, CO and CO2, and for several binary mixtures of gases. For methane gas the density dependence is greater at higher temperatures in contrast to expectation and the observed temperature dependence of the shielding at zero density is attributable to nuclear motion. 13C magnetic shielding is considerably higher in the gas phase than in the liquid phase and the difference varies for chemically non-equivalent 13C nuclei by amounts which are well above the level of experimental error.

Relationships between food and cellulase activity in freshwater fishes

Abstract: The food and cellulase activity of five cyprinid and one salmonid species were examined. All Cyprinidae species showed cellulase activity. No activity was found in pelagic Coregonus albula (Salmonidae). Cellulase activity showed a positive correlation with the amount of highly processed plant detritus in the gut. No correlation was found between the activity level and the amount of fresh fragments of macrophytes and filamentous algae.

Exchange polarization effects in the interaction of closed-shell systems

Abstract: Explicit formulae for the calculation of the exchange polarization energy in the interaction of closed-shell atoms or molecules have been derived by assuming neglect of the electron correlation within the noninteracting systems The dispersion part of the exchange polarization energy has been represented as a sum of contributions arising from the interaction of two, three or four orbitals at a time Each of these contributions is given by an integral involving the orbitals engaged in the interaction and the pair functions describing the dispersion interaction between these orbitals The numerical calculations for the interaction of two ground-state beryllium atoms show that the exchange dispersion energy is positive and quenches about 5 to 10 per cent of the dispersion term This results in a decrease of the interaction energy, computed as a sum of the SCF and dispersion components, by 6 to 30 per cent for interatomic distances ranging from 10 to 7 bohrs Simplified formulae for estimating the exchange dispersion energy in the interaction of larger systems are also proposed and their accuracy is discussed

Iterative refinement implies numerical stability

Abstract: Suppose that a method ϕ computes an approximation of the exact solution of a linear systemAx=b with the relative errorq,q<1. We prove that if all computations are performed in floating point arithmeticfl and single precision, then ϕ with iterative refinement is numerically stable and well-behaved wheneverq∥A∥ ∥A −1∥ is at most of order unity.

The soliton connection

Abstract: It is pointed out that the linear scattering problem for a non-linear evolution equation which admits soliton solutions may be described in terms of a linear connection on a principal SL(2, ℝ). The equation in question is satisfied if and only if the curvature of this connection vanishes. Some other properties of the curvature are identified. The sine-Gordon, Korteweg-de Vries and modified Korteweg-de Vries equations are treated explicitly.

On the convergence properties of the Rayleigh–Schrödinger and the Hirschfelder–Silbey perturbation expansions for molecular interaction energies

Abstract: The Rayleigh–Schrodinger polarization and the Hirschfelder–Silbey (HS) perturbation theories are applied, through the 38th order, to the interaction of a ground-state hydrogen atom with a proton. The calculations were made with high precision using a large basis set of orbitals expressed in the confocal elliptic coordinates. The results obtained show that for small internuclear separations R the polarization series converges slowly in an oscillatory way to the energy of the ground 1sσg state of the H molecule. At large R, however, the polarization expansion reproduces only the Coulomb part of the interaction energy effectively. When the value of the Coulomb energy is reached, the rate of convergence deteriorates drastically so that the exchange energy is not reproduced practically. The HS method converges fast when applied to both the 1sσg and the 2pσu states, the rate of convergence being roughly independent of the internuclear distance. If the finite basis set employed to solve the perturbation equations is stable under the symmetry operations, the HS expansion is shown to converge to the energy obtained by minimizing the Rayleigh–Ritz functional within the space spanned by the functions used in the perturbation theory calculations.

Interpretability of Elementary Theories

Abstract: The word ‘theory’ is often understood as dependent on the language used to formalise it (cf. e.g. Henkin et al, 1971, p. 44). As a consequence, the theory of groups formalised without a neutral element symbol is a proper subtheory of that formalised in a language with a symbol for this element. We may observe an even more striking situation in geometry: the systems presented in Pieri (1908) and Tarski (1959) using different primitive notions are completely different theories, though they are intuitively closely related. The series of papers (e.g. Beth and Tarski, 1956; Scott, 1956; Tarski, 1956; R. Robinson, 1959; Royden, 1959) has been devoted to the study of possible systems of primitive notions of Euclidean geometry. Each of these systems may be used to express the same facts in a completely different manner. The difference may even be in the elements of the universes: Tarski (1959) uses points only, Hilbert (1930)-points, lines, planes and angles, Schwabhauser and Szczerba (1975)-lines only, and Tarski (1929) — open discs or balls. Each of these formalisations may be included in any other by means of proper definitions, the procedure used commonly by most mathematicians. In fact if a lecturer speaking about some mathematical topic needs a new definable notion, no matter whether relation or object, he usually just introduces it, not bothering to change the language; and from that moment he works with a different theory.

4-nitroquinoline-1-oxide: A good mutagen for Aspergillus nidulans

Abstract: Conditions for using 4-nitroquinoline-1-oxide as a mutagen for Aspergillus nidulans were established. High frequencies of mutations (about 0.5%) and a broad spectrum of mutants were obtained. The stability of NQO in solutions and safety precautions are described.

Physiological mechanisms of frost tolerance: Possible role of protein in plant adaptation to cold

Abstract: Studies performed on winter rape plants(Brassica nnpus var.oleifera, cv. ‘Gor-czanski’) revealed that cold treatment affected the cell membranes and led to the temporary increase in electrolytic leakage from a tissue. This was followed by the marked decrease of the electrolytic leakage in the course of hardening. Changes in membrane properties were accompanied by the promotion of soluble protein accumulation. Inhibition of protein accumulation by the cycloheximide treatment brought about wilting of plants under cold conditions. Possible role of soluble protein in protection of cells against secondary water stress caused by the coldinduced changes in membrane properties is suggested. Cold-induced changes in the electrophoretic pattern of soluble protein are described and discussed.

On basis set effects in SCF calculations of the interaction energy between closed-shell atoms

Abstract: The so-called “superposition error” is investigated for different Gaussian basis sets used in the SCF calculations of the interaction energy between neon atoms. The results show that unless the counterpoise method [1] is applied, a qualitatively wrong description of interaction can be obtained. This is observed even for the basis sets which give fairly accurate atomic energies. It is shown that, despite large super-position error, basis sets fitted to the exact density [2] can provide very reasonable results if the counterpoise method is applied.

Absorption and luminescence of V (d3) in II-VI compound semiconductors

Abstract: The absorption and luminescence spectra of the V (d3) in ZnS, ZnSe, CdSe, and CdTe are presented. Values of the crystal-field parameters Δ, B, and C are derived from the spectra and discussed. The infrared luminescence at about 5000 cm−1, characteristic for the V (d3) impurity in II–VI and III–V compound semiconductors, is shown to be due to the 4A2(F)-4T2(F) transition. Die Absorptions- und Lumineszenzspektren von V (d3) in ZnS, ZnSe, CdSe und CdTe werden mitgeteilt. Werte der Kristallfeldparameter Δ, B und C werden aus den Spektren abgeleitet und diskutiert. Es wird gezeigt, das die Infrarot-Lumineszenz bei etwa 5000 cm−1, die fur V (d3)-Storstellen in den II–VI- und III–V-Verbindungshalbleitern charakteristisch ist, durch den 4A2(F)–4T2(F)-Ubergang hervorgerufen wird.

On the mechanism of the carbon dioxide/propylene oxide alternating copolymerization in the presence of organozinc catalysts

Abstract: Carbon dioxide and propylene oxide were copolymerized in the presence of the catalytic systems diethylzinc/polyhydric phenols modified by pretreatment with one of the monomers. The mechanisms of initiation, propagation, termination, and chain-transfer reaction in the copolymerization are suggested and discussed.