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An Evaluation of the Use of “Gentan” Probabilities in Forestry Planning
Item type: Journal Article • Journal: South African Forestry Journal • Authors: JohnH. Randall --- Department of Biometry, South Africa Klaus von Gadow --- Department of Forest Science, South AfricaAn evaluation of Suzuki's concept of Gentan probabilities is presented. Model fitting is discussed in some detail. It is shown that the Gentan method is suitable only for forests that are at least close to normality. -
An ocular technique for estimating utilization of karoo bushes
Item type: Journal Article • Journal: Journal of the Grassland Society of Southern Africa • Authors: F.O. Hobson --- Department of Agriculture, Republic of South AfricaA subjective technique for estimating utilization of karoo bushes is evaluated and guidelines for its use are proposed. Taking the average utilization from estimates on 30–40 bushes, 20% differences in utilization could be distinguished as significant ‐ even when different... -
Estimation of minimum temperature on a mesoscale
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: J. Myburgh --- ,Working relationships between mean minimum temperatures and environmental factors by means of regression techniques were established and used to estimate temperatures at gridpoints. These estimated temperatures were then used with a computer package program to map the isotherms on a... -
Evaluation of the coefficients of the Ångström formula for the estimation of solar radiation in South Africa
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: P. C.M. Reid --- Department of Water Affairs,The regression coefficients of a modified Ångström formula, initially postulated as being constant under all climatic conditions, have with widespread use been shown to vary not only spatially but also due to variable sunshine duration conditions. Daily sunshine duration and... -
Estimating Class A pan evaporation at locations with sparse climatic data
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: B. Clemence --- , Republic of South AfricaClass A pan evaporation was found to correlate closely with daylength-adjusted maximum daily air temperature (ATM), on a bimonthly basis. ATM and altitude were used as variables in a regression analysis to develop a series of evaporation-estimation equations for various... -
Comparison of methods for estimating cation exchange capacity of orchard soils
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: Marie Conradie --- , Republic of South Africa W. A.G. Kotze --- , Republic of South AfricaVarious methods for estimating soil cation exchange capacity (CEC) were compared. CEC obtained by the sum of extractable cations and the Adams-Evans buffer method were considerably higher than those obtained by saturation and displacement of either NH4 + or Na+... -
An attempt at estimating solar radiation at South African sites which measure air temperature only
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: B. S.E. Clemence --- , Republic of South AfricaDaily potential surface radiation values were calculated for selected South African weather stations. These were used, together with various air temperature parameters, to derive regression equations to estimate actual surface solar radiation at sites lacking the required instrumentation. A single... -
Estimation of soil water retention from clay content and cation exchange capacity values of soils
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: A. D.P. Botha --- , Republic of South Africa B.E. Eisenberg --- , Republic of South AfricaSoil water characteristics can be estimated accurately from the clay content and cation exchange capacity (CEC) values of soils. The clay with its very large adsorption surface and CEC which reflects the negative charge of clays, is jointly responsible for... -
Precision and accuracy of sward height distributions
Item type: Journal Article • Journal: African Journal of Range & Forage Science • Authors: C.D. Morris P.J.K. Zacharias J.F. DerryDouble normal distributions can be used to resolve many sward height frequency distributions into two components representing the 'short' (patches) and 'tall' (non∼patches) areas in the sward. The effect of sample size on the precision and accuracy of parameters of... -
Alternative Taper Curve Estimation Methods for Eucalyptus cloeziana (F. Muell.)
Item type: Journal Article • Journal: The Southern African Forestry Journal • Authors: K. P.A. Eerikäinen --- Faculty of Forestry, Finland D. Mabvurira --- , Zimbabwe J. Saramäki --- ,Three types of taper estimation methods for Eucalyptus cloeziana were applied and compared by using Zambian and Zimbabwean plantation data. The methods are: (1) Schumacher's taper equation, (2) diameter prediction method and (3) polynomial taper curve. The Schumacher's taper equation... -
The Optimism Bias: Is It Adaptive In Academic Settings?
Item type: Journal Article • Journal: Journal of Psychology in Africa • Authors: Caryl Ochse --- University of South Africa,This study investigated whether optimism was adaptive or maladaptive in an academic context. Participants were 715 psychology students with a large open and distance education university in South Africa (age range 20 to 61, average age 31 years, women =... -
Volume Regression Equations for Eucalyptus Grandis on the Coastal Plain of Zululand
Item type: Journal Article • Journal: South African Forestry Journal • Authors: B.V. Bredenkamp --- Natal Forestry Research Centre,Separate volume regression equations for pulpwood, sawtimber and over-mature Eucalyptus grandis are presented. An investigation of Schumacher and Hall's volume equation indicated that a better fit may be obtained by adding a constant to the dbh as predictor variable. The... -
Otoliths and vertebrae as potential hard structures for ageing South African yellowfin tuna Thunnus albacares
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: JD Filmalter --- Department of Ichthyology and Fisheries Science, South Africa OLF Weyl --- Department of Ichthyology and Fisheries Science, South Africa W Sauer --- Department of Ichthyology and Fisheries Science, South AfricaSagittal otoliths and vertebrae from 46 yellowfin tuna Thunnus albacares (118-175 cm fork length) collected off the west coast of South Africa were assessed for potential usefulness in age estimation. Growth increments were found on both structures. Comparisons of growth... -
A comparison of non-invasive versus invasive methods of haemoglobin estimation in patients undergoing intracranial surgery
Item type: Journal Article • Journal: Southern African Journal of Anaesthesia and Analgesia • Authors: Puneet Khanna --- Department of Anaesthesiology, India Vanitha Rajagopalan --- Department of Anaesthesiology, India Gyaninder Singh --- Department of Neuroanaesthesiology, India Hemanshu Prabhakar --- Department of Neuroanaesthesiology, IndiaBackground: Until recently, invasive monitoring techniques were the only ones available for the estimation of haemoglobin (Hb) in the blood. However, following the introduction of a new non-invasive monitor, Hb concentration could be non-invasively and continuously monitored. It allows immediate... -
A note on the estimation problems caused by thin-trading on the Johannesburg Stock Exchange
Item type: Journal Article • Journal: De Ratione • Authors: D. Bradfield --- University of Cape Town,The estimation problems caused by the effects of thin-trading are highlighted. In particular thin-trading is found to be the major cause of bias associated with the estimation of beta coefficients in smaller markets like the JSE. The empical study conducted... -
A Review of Systematic Risk Estimation on the JSE
Item type: Journal Article • Journal: De Ratione • Authors: D C Bowie --- University of Cape Town, D J Bradfield --- University of Cape Town,This paper reviews some recent developments in the area of beta estimation on the JSE. it turns out that the dual phenomena of extreme thin trading and mild segmentation between the industrial and mining boards on the JSE impact on... -
An investigation of investors’ estimates of returns earned and the effect of anchoring on these estimations
Item type: Journal Article • Journal: South African Journal of Accounting Research • Authors: G Dowie --- College of Accounting, South Africa G Willows --- College of Accounting, South AfricaThis study examines overconfidence and anchoring in an investing environment to determine if there is evidence of the phenomenon amongst a sample of academics at participating universities. -
Bird watching and estimation of bird diversity – not always corresponding: a reply to Hogg and Vande weghe
Item type: Journal Article • Journal: Ostrich: Journal of African Ornithology • Authors: Callixte Gatali --- Department of Wildlife and Aquatic Resources Management, Rwanda Kjell Wallin --- Department of Biological and Environmental Sciences, SwedenSome occurrences of rare or unusual bird species reported by us in a previous paper (Ostrich 86(3): 267–276, 2015) are considered to be doubtful by Hogg and Vande weghe (Ostrich 88(1): 83–88, 2017). We believe that some of the problems... -
Portfolio performance under reference-day risk
Item type: Journal Article • Journal: Investment Analysts Journal • Authors: Marcelo Gonzalez --- Universidad de Chile, Chile Arturo Rodriguez --- Universidad de Chile, Chile Roberto Stein --- College of Business Administration, USAReference-day risk has been previously identified as a type of sampling variation phenomenon, and its effect on the estimation of stock returns and their volatility and market betas has been documented. Using a dataset of daily equity mutual fund returns,... -
Univariate tests of momentum on the JSE
Item type: Journal Article • Journal: Investment Analysts Journal • Authors: Daniel Page --- Finance Division, School of Economic & Business Sciences, South Africa Christo Auret --- Finance Division, School of Economic & Business Sciences, South AfricaThis study intends to test whether medium-term price momentum is present on the cross-section of shares listed on the JSE. Using the methodology of Jegadeesh and Titman (1993; 2001), shares are sorted applying four estimation periods (E = 3, 6,... -
Home range and habitat use of Trumpeter Hornbills Bycanistes bucinator in an urban–forest mosaic, Eshowe, South Africa
Item type: Journal Article • Journal: Ostrich: Journal of African Ornithology • Authors: Moses Chibesa --- School of Life Sciences, South Africa Barry Taylor --- School of Life Sciences, South Africa Tharmalingam Ramesh --- School of Life Sciences, South Africa Colleen T Downs --- School of Life Sciences, South AfricaDespite the negative impacts of urbanisation, some species adapt to pressures of habitat loss and fragmentation. Trumpeter Hornbills Bycanistes bucinator are a large avian forest frugivore that uses urban environments in South Africa. Consequently, we used GPS/UHF transmitters to study... -
Estimated burden of aggregate anthropometric failure among Malawian children
Item type: Journal Article • Journal: South African Journal of Clinical Nutrition • Authors: M Ziba --- Faculty of Food and Human Sciences, Malawi AA Kalimbira --- Faculty of Food and Human Sciences, Malawi Z Kalumikiza --- Faculty of Food and Human Sciences, MalawiBackground: The prevalence and trends of undernutrition among children below the age of five in Malawi are well known from a conventional (stunting, wasting and underweight) but not aggregate indicator perspective. -
Programmatic mapping to determine the size and dynamics of sex work and injecting drug use in Mauritius
Item type: Journal Article • Journal: African Journal of AIDS Research • Authors: Amita Pathack --- National AIDS Secretariat, Mauritius Ahmed Saumtally --- National AIDS Secretariat, Mauritius Sarah Soobhany --- National AIDS Secretariat, Mauritius Carly A Comins --- National AIDS Secretariat, Mauritius Said A H Kinoo --- National AIDS Secretariat, Mauritius Faran Emmanuel --- Centre for Global Public Health, CanadaHIV in Mauritius is in a concentrated phase. Most HIV infection is among key populations (KPs) including female sex workers (FSW), people who inject drugs (PWID), men who have sex with men (MSM), and transgender sex workers (TGSW). The objective... -
Analyses of mathematical models for city population dynamics under heterogeneity
Item type: Journal Article • Journal: African Journal of Science, Technology, Innovation and Development • Authors: O.C. Collins --- Institute of Systems Science, South Africa T.S. Simelane --- Institute of Systems Science, South Africa K.J. Duffy --- Institute of Systems Science, South AfricaIn this study, a mathematical model which takes heterogeneity into account is presented to describe city population dynamics. Initial insight is gained by qualitative analyses of a homogeneous version of this model. To understand the population dynamics of South African... -
Risk-based portfolio sensitivity to covariance estimation
Item type: Journal Article • Journal: Investment Analysts Journal • Authors: Hannes du Plessis --- , Paul van Rensburg --- ,Risk-based portfolio construction methods focus on optimally extracting information from the covariance matrix of asset returns, as opposed to utilising forecasts of expected returns, in determining the portfolio allocation. This improves their robustness to estimation error in means, but this... -
Rural infrastructure and production efficiency of food crop farmers: Implication for rural development in Nigeria
Item type: Journal Article • Journal: African Journal of Science, Technology, Innovation and Development • Authors: Abeeb Babatunde Omotoso --- , Nigeria Saidat Adebola Daud --- , Nigeria Luke Okojie --- , Nigeria Abiodun Olusola Omotayo --- , South AfricaThis study investigated the impact of rural infrastructure on production efficiency of food crop rural farmers in Ogun State, Nigeria. A total of 160 farming households from 20 communities in Abeokuta and Ilaro in Ogun State Agricultural Development Programme (OGADEP)... -
Status and density of the threatened Kori Bustard Ardeotis kori in a woodland savanna
Item type: Journal Article • Journal: Ostrich: Journal of African Ornithology • Authors: Kathan Bandyopadhyay --- University of Wyoming, United States Bogdan Cristescu --- , Namibia Jeffrey L Beck --- University of Wyoming, United States John L Koprowski --- University of Wyoming, United States Laurie Marker --- , NamibiaMany grassland habitats have disappeared or undergone substantial change worldwide and many obligatory grassland animal species have populations that are at risk of extinction. The Kori Bustard Ardeotis kori is the largest flying bird native to Africa and an open... -
Estimation accuracy of bean bags as portion size estimation aids for amorphous foods
Item type: Journal Article • Journal: South African Journal of Clinical Nutrition • Authors: Friedeburg Anna Maria Wenhold --- University of Pretoria, South Africa Una Elizabeth MacIntyre --- University of Pretoria, South Africa -
Population growth of Daphnia magna cultured in manure-fertilised water under laboratory conditions
Item type: Journal Article • Journal: African Journal of Aquatic Science • Authors: Adamneh Dagne --- Ethiopian Institute of Agricultural Research (EIAR), National Fishery and other Aquatic Life Research Center, Ethiopia Getacher Beyene --- Ethiopian Institute of Agricultural Research (EIAR), National Fishery and other Aquatic Life Research Center, Ethiopia Alemayehu Wubie --- Ethiopian Institute of Agricultural Research (EIAR), National Fishery and other Aquatic Life Research Center, EthiopiaIn developing countries, mass production of Daphnia magna, used as a food in freshwater aquaculture, is a challenge. A fifteen-day laboratory experiment was conducted to examine the population growth and reproductive parameters for D. magna reared in green water fertilised...