Phytohormonal regulation of in vitro formation of wheat androgenic structures

This research is devoted to developing a method of phytohormonal regulation of in vitro formation of a certain type of wheat androgenic structures. Using the method of ELISA it was shown that the induction of certain sporophytic morphogenesis pathway in vitro of anther haploid cells - microspores depends on both the content of endogenous auxin IAA in anthers before inoculating them onto induction medium, and the concentration of exogenous auxin 2,4-D in this medium. The obtained data confirms the principle possibility of regulation of ways of getting androgenic regenerants in vitro by selecting the optimal balance of endogenous and exogenous auxin

Wage indexation and industrial relations: A comparison of recent experience in Israel and Australia

Australia and Israel both have centralised machinery for the determination of national wage policy. In Australia, the Conciliation and Arbitration Commission holds an annual national wage hearing. In Israel, a national framework agreement for determining wage levels is bargained and signed by the parties every two years. In addition, both countries have periodical arrangements for adjusting wages as a result of movement in the cost of living. This article compares the indexation arrangements of the two countries and analyses their impact on industrial relations

Diffusion-Limited Aggregation on Curved Surfaces

We develop a general theory of transport-limited aggregation phenomena occurring on curved surfaces, based on stochastic iterated conformal maps and conformal projections to the complex plane. To illustrate the theory, we use stereographic projections to simulate diffusion-limited-aggregation (DLA) on surfaces of constant Gaussian curvature, including the sphere ($K>0$) and pseudo-sphere ($K<0$), which approximate "bumps" and "saddles" in smooth surfaces, respectively. Although curvature affects the global morphology of the aggregates, the fractal dimension (in the curved metric) is remarkably insensitive to curvature, as long as the particle size is much smaller than the radius of curvature. We conjecture that all aggregates grown by conformally invariant transport on curved surfaces have the same fractal dimension as DLA in the plane. Our simulations suggest, however, that the multifractal dimensions increase from hyperbolic ($K0$) geometry, which we attribute to curvature-dependent screening of tip branching.Comment: 4 pages, 3 fig

Gravitational Lensing by Rotating Naked Singularities

We model massive compact objects in galactic nuclei as stationary, axially-symmetric naked singularities in the Einstein-massless scalar field theory and study the resulting gravitational lensing. In the weak deflection limit we study analytically the position of the two weak field images, the corresponding signed and absolute magnifications as well as the centroid up to post-Newtonian order. We show that there are a static post-Newtonian corrections to the signed magnification and their sum as well as to the critical curves, which are function of the scalar charge. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightingly for the weakly naked and vastly for the strongly naked singularities with the increase of the scalar charge. The point-like caustics drift away from the optical axis and do not depend on the scalar charge. In the strong deflection limit approximation we compute numerically the position of the relativistic images and their separability for weakly naked singularities. All of the lensing quantities are compared to particular cases as Schwarzschild and Kerr black holes as well as Janis--Newman--Winicour naked singularities.Comment: 35 pages, 30 figure

Kerr-Sen dilaton-axion black hole lensing in the strong deflection limit

In the present work we study numerically quasi-equatorial lensing by the charged, stationary, axially-symmetric Kerr-Sen dilaton-axion black hole in the strong deflection limit. In this approximation we compute the magnification and the positions of the relativistic images. The most outstanding effect is that the Kerr-Sen black hole caustics drift away from the optical axis and shift in clockwise direction with respect to the Kerr caustics. The intersections of the critical curves on the equatorial plane as a function of the black hole angular momentum are found, and it is shown that they decrease with the increase of the parameter $Q^{2}/M$. All of the lensing quantities are compared to particular cases as Schwarzschild, Kerr and Gibbons-Maeda black holes.Comment: 31 pages, 17 figures; V2 references added, some typos corrected, V3 references added, language corrections, V4 table added, minor technical correction

Limitation of energy deposition in classical N body dynamics

Energy transfers in collisions between classical clusters are studied with Classical N Body Dynamics calculations for different entrance channels. It is shown that the energy per particle transferred to thermalised classical clusters does not exceed the energy of the least bound particle in the cluster in its ``ground state''. This limitation is observed during the whole time of the collision, except for the heaviest system.Comment: 13 pages, 15 figures, 1 tabl

Shadows of rotating hairy Kerr black holes coupled to time periodic scalar fields with non-flat target space

We study the shadows cast by rotating hairy black holes with two non-trivial time-periodic scalar fields having a non-flat Gaussian curvature of the target space spanned by the scalar fields. Such black holes are a viable alternative to the Kerr black hole, having a much more complicated geodesic structure and resulting shadows. We investigate how a nontrivial Gauss curvature alters the pictures for different amounts of scalar hair around the black holes, quantified by a normalized charge. Our results show that for high values of this charge, close to a boson star limit, chaotic shadows are observed with multiple small disconnected components for all considered Gaussian curvatures. For moderately large amounts of scalar hair and corresponding normalized charge, although the shadows still exhibit chaotic behavior, a dominant shadow component emerges, the size and shape of which are substantially influenced by the Gaussian curvature. For instance, highly chaotic shadows for flat target space, start developing a large central shadow region with the increase of the Gauss curvature even for black holes with substantially heavy scalar hair. For lower values of the normalized charge, the shadows resemble qualitatively the Kerr black hole while the Gaussian curvature has a small impact on their properties.Comment: 29 pages, 11 figures; v2: Notations modified, graphics and references adde

The cross sections for different channels in heavy ion nuclear reactions

Estimates have been made for the critical value lc of the orbital angular momentum above which a complete fusion nucleus cannot be formed. The results have been obtained by measurements of cross sections for noncompound inelastic processes (inelastic scattering, transfer. reactions, α particle emission) when Ag targets were bombarded by 86 MeV 12C ions and by 78 and 113 MeV 14N ions. The average value of lc was found between 38 and 45 ħ. A short discussion is given on the range of angular momenta at which transfer reactions occur. It is shown that quasi elastic single and multi-nucleon transfer reactions are possible only for large values of l called lT. When the bombarding energy is high enough, theses values lT are larger than lc and there is a region of l between l c and lT where a very inelastic mechanism takes place. A model called « fusion prompt scission » process is proposed. It is suggested that a deformed shape for the two fissioning nuclei is temporarly formed and breaks off very shortly after.La valeur critique lc du moment angulaire au-delà duquel un noyau composé de fusion ne peut plus être formé, a été estimée. Les résultats ont été obtenus selon une nouvelle méthode qui consiste à mesurer la section efficace de tous les processus ne faisant pas intervenir le noyau composé (diffusion inélastique, réactions de transfert, émission de particules alpha vers l'avant). L'étude a été effectuée au moyen d'ions 12C de 86 MeV et d'ions 14N de 78 et 113 MeV bombardant des cibles d'argent. On a trouvé lc compris entre 38 et 45 ħ quelque soit l'ion incident et l'énergie. On discute ensuite brièvement pour quelle région de moments angulaires les réactions de transfert ont lieu. On montre que les cas de transferts quasi élastiques sont possibles seulement pour des l élevés, de valeur moyenne lT dépendant de l'énergie incidente. lT devient très supérieur à lc lorsque l'énergie croit et un mécanisme d'échange de nucléons très inélastique intervient dans la région comprise entre lc et l T. Un modèle est proposé qui consiste en une fusion de durée très brève des deux noyaux sous la forme d'une configuration très déformée

A New Class of Nonsingular Exact Solutions for Laplacian Pattern Formation

We present a new class of exact solutions for the so-called {\it Laplacian Growth Equation} describing the zero-surface-tension limit of a variety of 2D pattern formation problems. Contrary to common belief, we prove that these solutions are free of finite-time singularities (cusps) for quite general initial conditions and may well describe real fingering instabilities. At long times the interface consists of N separated moving Saffman-Taylor fingers, with ``stagnation points'' in between, in agreement with numerous observations. This evolution resembles the N-soliton solution of classical integrable PDE's.Comment: LaTeX, uuencoded postscript file