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ASPECTS OF THE BIOLOGY OF TILAPIA RENDALLI IN THE DOORNDRAAI DAM TRANSVAAL
Item type: Journal Article • Journal: Journal of the Limnological Society of Southern Africa • Authors: G.R. Batchelor --- Division of Nature Conservation, South AfricaScale studies indicated that the annulus is a reliable year mark. A linear relationship existed between scale radius and body growth enabling back calculations to be made. The growth rate of males in Doorndraai Dam were similar to findings in... -
Uniqueness and spectral variation in Banach algebras
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: G. Braatvedt --- Department of Mathematics, South Africa R. Brits --- Department of Mathematics, South AfricaLet A be a complex semisimple Banach algebra with identity. We explore the situation whereby a portion of the elements of A have the same spectrum under multiplication by a ∈ A, as under multiplication by b ∈ A; and... -
Radius, leaf number, connected domination number and minimum degree
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: P. Mafuta --- University of the Free State, South Africa S. Mukwembi --- University of The Witwatersrand, South Africa S. Munyira --- University of Zimbabwe,Let G be a simple, connected graph with minimum degree δ, radius r and leaf number L(G). We prove that -
Cross-section measures, radii, and Radon curves
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Horst Martini --- University of Technology Chemnitz, Germany Zokhrab Mustafaev --- University of Houston-Clear Lake, USAThe purpose of this paper is to study cross-section measures and their connections to Radon curves in two-dimensional Minkowski spaces. More precisely, we use results on cross-section measures to present, for nomed planes, inner and outer radii of the unit... -
Numerical radius inequalities for the off-diagonal parts of 2 × 2 operator matrices
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Aicha Ammar --- Mustapha Stambouli University, Algeria Abdelkader Frakis --- Mustapha Stambouli University, Algeria Fuad Kittaneh --- The University of Jordan, JordanWe give some new bounds for the numerical radii of the off-diagonal parts of 2 × 2 operator matrices. A refinement of the triangle inequality for the operator norm is also given. -
Upper bounds for the numerical radii of powers of Hilbert space operators
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Mohammed Al-Dolat --- Jordan University of Science and Technology, Jordan Fuad Kittaneh --- The University of Jordan, JordanWe present several upper bounds for the numerical radii of 2 × 2 operator matrices. We employ these bounds to improve on some known numerical radius inequalities for powers of Hilbert space operators. In particular, we show that if T... -
Idempotents in Banach Algebras II
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Rudi Brits --- University of Johannesburg, South Africa Muhammad Hassen --- University of Johannesburg, South Africa Francois Schulz --- University of Johannesburg, South AfricaLet A be a complex and unital Banach algebra, and let E denote the collection of idempotents of A. An old paper of J. Zemánek’s, which was really the starting point of studies of idempotents in general Banach algebras, exhibits... -
On A-normaloid d-tuples of operators and related questions
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Najla Altwaijry --- King Saud University, Saudi Arabia Silvestru Sever Dragomir --- Victoria University, Victoria, Australia Kais Feki --- University of Sfax, TunisiLet ß A (ℍ) denote the algebra of bounded linear operators on a complex Hilbert space ℍ that admit A-adjoint operators, where A is a non-zero positive semi-definite operator on ℍ. A commuting operator tuple T = (T 1... -
On p-numerical radius inequalities for commutators of operators
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Abdelkader Frakis --- Mustapha Stambouli University, Algeria Fuad Kittaneh --- The University of Jordan, JordanIn this work, we give some p-numerical radius inequalities for operators as well as for commutators of operators. As applications, when p = ∞, we improve some earlier numerical radius inequalities for operators. Also, we refine the triangle inequalities for... -
Complementary bounds for the numerical and spectral radii
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Fuad Kittaneh --- The University of Jordan, Jordan Hamid Reza Moradi --- Islamic Azad University, Iran Mohammad Sababheh --- Princess Sumaya University for Technology, JordanLet denote the C* –algebra of all bounded linear operators on a Hilbert space . Among other results, we show that if are nonzero, then -
Interpolating inequalities for unitarily invariant norms and numerical radii of matrices
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Ahmad Al-Natoor --- Isra University, Jordan Omar Hirzallah --- The Hashemite University, Jordan Fuad Kittaneh --- The University of Jordan, JordanIn this paper, which is a continuation of our works in [9] and [10], we prove several interpolating inequalities for norms and numerical radii of matrices. Special cases of our results present refinements of some known inequalities. Among other results,... -
Generalized A-numerical radius inequalities in semi-Hilbert spaces through the angle between two vectors
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Mojtaba Bakherad --- University of Sistan and Baluchestan, IranThis paper presents several inequalities related to the A-numerical radius in the context of semi-Hilbert space operators. By integrating modern techniques from operator theory and functional analysis, we derive new inequalities for the A-numerical radius that emphasize the unique characteristics... -
The Frank graph
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Efruz Özlem Mersin --- Aksaray University, Turkey Ayşe Dilek Maden --- Selcuk University, Turkey Mustafa Bahşi --- Aksaray University, TurkeyThis paper introduces the Frank graph, a special weighted digraph with self-loops whose adjacency matrix corresponds to the Frank matrix, a special Max matrix. We derive bounds for the spectral radius and energy of the graph and illustrate these results...