Search
Search results for
We found
39 results for you
-
Remote sensing applications for monitoring rangeland vegetation
Item type: Journal Article • Journal: Journal of the Grassland Society of Southern Africa • Authors: P.T. Tueller --- Department of Range, Wildlife and Forestry, United States of AmericaRemote sensing techniques hold considerable promise for the inventory and monitoring of natural resources on range‐lands. A significant lack of information concerning basic spectral characteristics of range vegetation and soils has resulted in a lack of rangeland applications. To use... -
Early detection of nitrogen deficiency in wheat at different times of N application by using spectral reflectance of crop canopy
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: P. Shaker --- Department of Soil Science, South Africa P.S. Fouché --- Department of Soil Science, South AfricaPhysiological changes resulting from nitrogen limitations can be translated into clear spectral differences between treatments, demonstrating the relationship between leaf reflectance and leaf chlorophyll and nitrogen concentrations. A wheat trial was conducted in which nitrogen (N) was applied in the... -
Estimation of thrips (Fulmekiola serrata Kobus) density in sugarcane using leaf-level hyperspectral data
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: ElfatihM Abdel-Rahman --- School of Environmental Sciences, South Africa Mike Way --- , South Africa Fethi Ahmed --- School of Environmental Sciences, South Africa Riyad Ismail --- School of Environmental Sciences, South Africa Elhadi Adam --- School of Environmental Sciences, South AfricaThe aim of this study was to investigate the potential use of leaf-level hyperspectral data to predict the density of sugarcane thrips Fulmekiola serrata (Kobus). A hand-held spectroradiometer was used to make the spectral measurements on spindle leaves of 4-... -
OBSERVATTVNS ON THE UNDERWATER LIGHT FIELD OF TWO HWERTROPHIC, SOUTH AFRICAN IMPOUNDMENTS
Item type: Journal Article • Journal: Journal of the Limnological Society of Southern Africa • Authors: R.D. Robarts --- , South Africa T. Zohary --- , South Africa F. Ojeda --- , Chile C. C.E. Lovengreen --- , Chile R.D. Walmsley --- ,The spectral composition of the underwater light field was examined in two hypertrophic South African Impoundments (Hartbeespoort and Roodeplaat Dams) under a range of inorganic turbidities and chlorophyll α concentrations. The data indicated that inorganic turbidity and gilvin were dominant... -
OBSERVATIONS ON THE UNDERWATER LIGHT FIELD OF TWO HYPERTROPHIC SOUTH AFRICAN IMPOUNDMENTS
Item type: Journal Article • Journal: Journal of the Limnological Society of Southern Africa • Authors: R.D. Robarts --- National Institute for Water Research, South Africa T. Zohary --- National Institute for Water Research, South Africa F. Ojeda --- Institute of Physics, Chile C. C.E. Lovengreen --- Institute of Physics, Chile R.D. Walmsley --- Foundation for Research and Development,The spectral composition of the underwater light field was examined in two hypertrophic South African impoundments (Hartbeespoort and Roodeplaat Dams) under a range of inorganic turbidities and chlorophyll a concentrations. The data indicated that inorganic turbidity and gilvin were dominant... -
Spectral theory and quotients in von Neumann algebras
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Graeme WestIn this note we consider to what extent the functional calculus and the spectral theory in von Neumann algebras are preserved by the taking of quotients relative to two-sided ideals of the von Neumann algebra. -
Spectral Mapping Theorems For Evolution Semigroups on Spaces of Almost Periodic Functions
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Walter Hutter Frank Räbiger. We show that the weak spectral mapping theorem holds for evolution semigroups on spaces of periodic functions. Furthermore, we prove the spectral mapping theorem for evolution semigroups on spaces of (weakly asymptotically) almost periodic functions. The results are applied... -
Derivations on ρ-banach Algebras
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Amir KhosraviLet A be a ρ-Banach algebra with radical R and let D be a derivation on A. We generalize Johnson's theorem, Sinclair's theorem and Thomas's theorem (Singer-Wermer's conjecture) to ρ-Banach algebras. If K = {x ∈ R: for every n... -
The canonical spectral measure and köothe function spaces
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Jos´e Bonet Susumu Okada WernerJ. RickerThe theme of this paper is the interaction between analytic properties of (Fréchet) Köthe function spaces X and measure/operator theoretic properties of the canonical spectral measure Q acting in X. For instance, Q is boundedly σ-additive iff X is Montel... -
ON THE SPECTRUM OF A SINGULAR HAMILTONIAN SYSTEM, II
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: D.B. Hinton --- Department of Mathematics, J.K. Shaw --- Department of Mathematics Virginia Tech,In this paper we connect the pole structure of the Titchmarsh-Weyl m-coefficients with the spectrum of a Hamiltonian system which is singular at each end of an interval. Characterizations are given for the resolvent set, point spectrum, continuous spectrum and... -
Quadratic Pencil of Difference Equations: Jost Solutions, Spectrum, and Principal Vectors
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Murat Adıvar --- Department of Mathematics, TurkeyIn this paper, a quadratic pencil of Schrodinger type difference operator Lλ is taken under investigation to provide a general perspective for the spectral analysis of non-selfadjoint difference equations of second order. Introducing Jost-type solutions, structure and quantitative properties of... -
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... -
Morphological and electrophysiological field observations on electric freshwater fish of the genus Mormyrops Müller 1843 (Teleostei: Mormyridae) from West and southern Africa
Item type: Journal Article • Journal: African Journal of Aquatic Science • Authors: B Kramer --- Zoological Institute of the University of Regensburg, GermanyDifferent specimens of Mormyrops anguilloides (Linnaeus 1758) were reported to display electric organ discharge (EOD) pulses of either initially head-positive or initially negative polarity, a hypothetical sex difference that has not been substantiated to date. The morphology and EODs of... -
Comparison of fish-community size spectra based on length frequencies and mean lengths: a note
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: D Yemane MH Griffiths JG FieldEstimates of fish-community size spectra are promising indicators of the impact of fishing on fish assemblages. Size spectra consist of logarithmic graphs of abundance plotted against fish body size. Size spectra may either be constructed from length frequency data or... -
Variation in foliar water content and hyperspectral reflectance of Pinus patula trees infested by Sirex noctilio
Item type: Journal Article • Journal: Southern Forests: a Journal of Forest Science • Authors: O Mutanga --- School of Environmental Sciences, South Africa R Ismail --- School of Environmental Sciences, South AfricaThe remote detection and quantification of symptoms associated with declining forest health is critical for the introduction of proper pest monitoring and control measures. Sirex noctilio, the Eurasian wood wasp, is one of the major pests responsible for declining forest... -
The potential of remote sensing technology for the detection and mapping of Thaumastocoris peregrinus in plantation forests
Item type: Journal Article • Journal: Southern Forests: a Journal of Forest Science • Authors: Z Oumar --- School of Environmental Sciences, South Africa O Mutanga --- School of Environmental Sciences, South AfricaThaumastocoris peregrinus is a sap-sucking insect that feeds on eucalyptus leaves. It poses a major threat to the forest sector by reducing the photosynthetic ability of the tree, resulting in stunted growth and even death of severely infested trees. The... -
The First Group (co)homology of a Group G with Coefficients in Some G–Modules
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: LucíliaD. Borsari DacibergL. GonçalvesLet G be a group. We give some formulas for the first group homology and cohomology of a group G with coefficients in an arbitrary G–module Ž. More explicit calculations are done in the special cases of free groups, abelian... -
Imaging spectroscopy of foliar biochemistry in forestry environments
Item type: Journal Article • Journal: Southern Forests: a Journal of Forest Science • Authors: B Majeke JAN van Aardt MA ChoRemote sensing estimates of leaf biochemicals provide valuable information on ecosystem functioning, vitality and state at local to global spatial scales. This paper aims to give an overview of the state of the art of foliar biochemistry assessment in general... -
Estimating plot-level forest structural attributes using high spectral resolution ASTER satellite data in even-aged Eucalyptus plantations in southern KwaZulu-Natal, South Africa
Item type: Journal Article • Journal: Southern Forests: a Journal of Forest Science • Authors: MT Gebreslasie FB Ahmed JAN van AardtThis study assessed the suitability of both visible and shortwave infrared of ASTER reflectance bands and various vegetation indices for estimating forest structural attributes of Eucalyptus species. The study was conducted in even-aged monoculture plantations of E. grandis and E... -
A comparison of EEG spectral entropy with conventional quantitative EEG at varying depths of sevoflurane anaesthesia
Item type: Journal Article • Journal: Southern African Journal of Anaesthesia and Analgesia • Authors: PR Bartel --- Department of Neurology, South Africa FJ Smith --- Department of Anaesthesiology, South Africa PJ Becker --- Biostatistics Unit, South African Medical Research Council, and Faculty of Health Sciences, South AfricaBackground and Aim: Recently an electroencephalographic (EEG) spectral entropy module (M-ENTROPY) for an anaesthetic monitor has become commercially available. We compared its performance as an indicator of the state of anaesthesia with that of an older conventional quantitative EEG (QEEG)... -
Water quality monitoring in sub-Saharan African lakes: a review of remote sensing applications
Item type: Journal Article • Journal: African Journal of Aquatic Science • Authors: T Dube --- School of Agricultural, Earth and Environmental Sciences, South Africa O Mutanga --- School of Agricultural, Earth and Environmental Sciences, South Africa K Seutloali --- School of Agricultural, Earth and Environmental Sciences, South Africa S Adelabu --- Department of Geography, South Africa C Shoko --- School of Bioresources Engineering and Environmental Hydrology, South AfricaWater quality deterioration in sub-Saharan Africa has attained a scale that requires scientific intervention. It is therefore important to devise appropriate and reliable techniques to investigate the water quality of lakes and reservoirs for the development of water resource management... -
Potential use of visible and near-infrared spectroscopy for pine species discrimination by examination of needles
Item type: Journal Article • Journal: Southern Forests: a Journal of Forest Science • Authors: Silvana Nisgoski --- Department of Forest Engineering and Technology, Brazil Mayara E Carneiro --- Department of Forest Engineering and Technology, Brazil Elaine C Lengowski --- Department of Forest Engineering and Technology, Brazil Felipe Z Schardosin --- Department of Forest Engineering and Technology, Brazil Graciela I Bolzon de Muñiz --- Department of Forest Engineering and Technology, BrazilThe correct identification of pine species is necessary for proper application of wood in forest‑based industries, since the quality of each species’ wood depends on factors intrinsic to the material. The aim of this study was to evaluate the potential... -
Predicting soil nitrogen content using narrow-band indices from Eucalyptus grandis canopies as proxy
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: Thamsanqa Mzinyane --- University of KwaZulu-Natal, South Africa Jan van Aardt --- Rochester Institute of Technology, UK Fethi Ahmed --- University of Witswatersrand, South Africa Michael Gebreslasie --- School of Agriculture, Earth and Environmental Science, South AfricaOptimal fertiliser applications for sustainable forest stand productivity management, whilst protecting the environment, is vital. This study estimated soil nitrogen content using leaf-level narrow-band vegetation indices derived from a hand-held 350-2 500 nm spectroradiometer. Leaf-level spectral data were collected and subjected... -
Applications of the growth characteristics induced by the spectral distance
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Rudi Brits --- Department of Mathematics, South AfricaLet A be a complex unital Banach algebra. Using a connection between the spectral distance and the growth characteristics of a certain entire map into A, we derive a generalization of Gelfand’s famous power boundedness theorem. Elaborating on these ideas,... -
Characterisation of a Tunisian coastal lagoon through hyperspectral underwater irradiance
Item type: Journal Article • Journal: African Journal of Aquatic Science • Authors: DH Nourisson --- Department of Biology, Italy F Scapini --- Department of Biology, Italy L Massi --- Department of Biology, Italy L Lazzara --- Department of Biology, ItalyNorth African coastal lagoons are unique ecosystems that often suffer degradation due to human activities. Therefore, monitoring methods are required to identify stressors and assist with the management of these valuable and often understudied ecosystems. A synthetic indicator of water... -
Estimating forest carbon stocks in tropical dry forests of Zimbabwe: exploring the performance of high and medium spatial-resolution multispectral sensors
Item type: Journal Article • Journal: Southern Forests: a Journal of Forest Science • Authors: Tawanda W Gara --- Department of Geography and Environmental Science, Zimbabwe Amon Murwira --- Department of Geography and Environmental Science, Zimbabwe Timothy Dube --- Discipline of Geography, School of Agricultural, Earth and Environmental Sciences, South Africa Mbulisi Sibanda --- Discipline of Geography, School of Agricultural, Earth and Environmental Sciences, South Africa Donald T Rwasoka --- Faculty of Geo-information Science and Earth Observation, The Netherlands Henry Ndaimani --- Department of Geography and Environmental Science, Zimbabwe Emmerson Chivhenge --- Department of Geography and Environmental Science, Zimbabwe Chipo M Hatendi --- Department of Geography and Environmental Science, ZimbabweEstimation and mapping of forest dendrometric characteristics such as carbon stocks using remote sensing techniques is fundamental for improved understanding of the role of forests in the carbon cycle and climate change. In this study, we tested whether and to... -
Forest health and vitality: the detection and monitoring of Pinus patula trees infected by Sirex noctilio using digital multispectral imagery
Item type: Journal Article • Journal: Southern Hemisphere Forestry Journal • Authors: R Ismail O Mutanga U BobThe Eurasian woodwasp, Sirex noctilio, causes considerable tree mortality in commercial pine plantations in southern KwaZulu-Natal, South Africa. Broad-scale visual assessments of infestation provided by forest managers are currently used to measure forest health and vitality. The effectiveness of visual... -
Forest structural assessment using remote sensing technologies: an overview of the current state of the art
Item type: Journal Article • Journal: Southern Hemisphere Forestry Journal • Authors: JW Roberts S Tesfamichael M Gebreslasie J. van Aardt FB AhmedThe Forestry and Forest Products Research Centre (CSIR), University of KwaZulu-Natal and MONDI Business Paper have recently embarked on a remote sensing cooperative. The primary focus of this cooperative is to explore the potential benefits associated with using remote sensing... -
Determining the optimal phenological stage for predicting common dry bean (Phaseolus vulgaris) yield using field spectroscopy
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: Perushan Rajah --- Discipline of Geography, School of Agricultural, Earth and Environmental Sciences, South Africa John Odindi --- Discipline of Geography, School of Agricultural, Earth and Environmental Sciences, South Africa Elfatih Abdel-Rahman --- Discipline of Geography, School of Agricultural, Earth and Environmental Sciences, South Africa Onisimo Mutanga --- Discipline of Geography, School of Agricultural, Earth and Environmental Sciences, South AfricaOn-farm crop productivity and yield prediction are valuable for, among others, designing food policies, on-farm and after-farm planning and pricing, and marketing. Whereas existing prediction approaches are generally reliable, these require extensive and tedious field surveys and adequate ancillary agrometeorological... -
The composition of the soil seedbank and its role in ecosystem dynamics and rehabilitation potential in the arid Tankwa Karoo Region, South Africa
Item type: Journal Article • Journal: African Journal of Range & Forage Science • Authors: Manam WB Saaed --- Higher Institute of Agricultural Techniques, Libya Shayne M Jacobs --- Department of Conservation Ecology and Entomology, South Africa Mmoto L Masubelele --- Cape Research Centre, South Africa Igshaan Samuels --- Agricultural Research Council–Animal Production, c/o Department of Biodiversity and Conservation Biology, South Africa Lesego Khomo --- Department of Environmental Sciences, South Africa Yacoub M El-Barasi --- Botany Department, Faculty of Science, LibyaVery few soil seedbank studies have been conducted in South Africa, especially in arid rangelands. Insight into the soil seedbank could therefore improve assessment of rangeland dynamics and enhance rehabilitation efforts. This study aimed to characterise the soil seedbanks in... -
Correlation between vitamin D serum levels and severity of diabetic retinopathy in patients with type 2 diabetes mellitus
Item type: Journal Article • Journal: Journal of Endocrinology, Metabolism and Diabetes of South Africa • Authors: Gauhar Nadri --- , India Sandeep Saxena --- , India Apjit Kaur --- , India Kaleem Ahmad --- , India Pragati Garg --- , India Abbas Ali Mahdi --- , India Levent Akduman --- , USA Katarina Gazdikova --- , Slovakia Martin Caprnda --- , Slovakia Pavol Vesely --- , Slovakia Peter Kruzliak --- , Czech Republic Vladimir Krasnik --- , SlovakiaPurpose: To study the correlation of serum vitamin D levels with quantitative (central subfield thickness [CST], cube average thickness [CAT]), cross-sectional (disorganisation of retinal inner layer [DRIL] and ellipsoid zone [EZ]) and topographic parameters (retinal pigment epithelium [RPE]) on spectral... -
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... -
Spectrum of the Cesàro-Hardy operator in rearrangement invariant spaces
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Meiram Akhymbek --- Institute of Mathematics and Mathematical Modeling, Kazakhstan Kanat Tulenov --- Institute of Mathematics and Mathematical Modeling, Kazakhstan Gulnur Zaur --- Institute of Mathematics and Mathematical Modeling, KazakhstanIn this paper, we investigate the spectrum of the Cesàro-Hardy operator in rearrangement invariant spaces over a finite interval and a half line, thereby extending Boyd’s and Leibowitz’s results for Lp(1 < p ⩽ 8) spaces. In particular, when our... -
Orbit spaces of free involutions on the product of three spheres
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Dimpi --- University of Delhi, India Hemant Kumar Singh --- University of Delhi, IndiaIn this paper, we have determined the orbit spaces of free involutions on a finitistic space having mod 2 cohomology of the product of three spheres . This paper generalizes the results proved by Dotzel et al. [7] for free... -
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... -
Tricomi problem for mixed parabolic-hyperbolic equation with dynamic-type boundary condition
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Bauyrzhan Derbissaly --- Institute of Mathematics and Mathematical Modeling, KazakhstanIn this paper, we study an analogue of Tricomi problem for a parabolichyperbolic equation of the first type. To solve the problem for the heat equation, we use properties of the spectral problem with a spectral parameter in the boundary... -
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 -
On uniqueness theorems for the inverse q-Sturm–Liouville problems
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: F.A. Gawish --- Benha University, Egypt Z.S. Mansour --- Cairo University, EgyptWe establish two theorems that illustrate the uniqueness of inverse q-Sturm-Liouville problems based on a specified set of spectral data. The first uniqueness theorem employs the method of transformation operators to provide a q-analog of the Levinson-Marchenko uniqueness theorem. The... -
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...