bluuebunny/crossref_metadata_2025 huggingface dataset:
Etho-ecological aspects of the Natal (Francolinus natalensis) and the Swainson’s francolin (Francolinus swainsoni) in the Willem Pretorius Game Reserve, Orange Free State
Authors: Jubelius C. W. , Kok O. B.
Published: March 2014

Etho-ecological information on the Natal (Francolinus natalensis) and the Swainson’s francolin (F. swainsoni) was obtained in the Willem Pretorius Game Reserve, Orange Free State, for management purposes. Although captures of the two francolin species suggest population structures with unbalanced age and sex ratios, the phenomenon should perhaps be attributed to differential dominance at the constant food supply (cages with bait). Apart from the tail length of the Swainson’s francolin, the body dimensions of immatures are generally smaller than those of adults.
Nonlinear functional analysis
Authors: Fouché W. L.
Published: March 2014

In this article we discuss some aspects of nonlinear functional analysis. It included reviews of Banach’s contraction theorem, Schauder’s fixed point theorem, globalising techniques and applications of homotopy theory to nonlinear functional analysis. The author emphasises that fundamentally new ideas are required in order to achieve a better understanding of phenomena which contain both nonlinear and definite infinite dimensional features.
The influence of stack height on air pollutant concentrations in looping plumes
Authors: Fourie O. L.
Published: March 2014

A theoretical model is proposed which predicts the influence of stack height on air pollutant concentration during plume looping episodes. The dependence of concentration on stack height increases as the distance between the stack and the point of plume impingement on the ground decreases.
A review on statistical Bayes decision theory in the case of more than one individual
Authors: De Waal D. J.
Published: March 2014

A review on statistical Bayes decision theory in the case of more than one individual is given. Although several solutions are pointed out, special attention is given to the Nash solution as a good candidate to use in practical decision problems. Attention is given to a decision problem where the best decision out of a finite number of decisions has to be taken and there is also an estimation of a binomial parameter by several Bayesians.
Relative age determination of the skull of the chacma baboon (Papio ursinus)
Authors: Van Niekerk J. P. , Kok O. B. , Stoltz L. P.
Published: March 2014

Relative age determination was carried out on the skulls of 261 chacma baboons (Papio ursinus), 117 from the Loskopdam Nature Reserve and 144 from the Messina district in the Northern Transvaal. Seven age groups were distinguished, of which classes I-IV were based on the eruption and displacement of milk and permanent teeth. Adults with a complete set of permanent dentition were subdivided into three additional classes (V- VII), mainly on the basis of the degree of molar attrition. For comparative purposes the pattern of maturation of craniometric parameters which reflect the general size and shape of the skull, as well as the degree of closure of ectocranial sutures, were treated on the same basis. From this it is apparent that a most reliable estimate of relative age can be obtained by using all the above-mentioned criteria.
Desalination of brackish water and concentration of industrial effluents by electrodialysis
Authors: Schoeman J. J. , Botha G. R.
Published: March 2014

Electrodialysis (ED) is, at present, used mainly for the desalination of brackish drinking-water. Brackish water with a high scaling potential can be successfully treated, using the electrodialysis reversal (EDR) process without the addition of chemicals. The reliability of the ED process makes it very attractive for water treatment. Although used mainly for brackish water desalination, ED also has certain industrial applications. Plating wash waters, cooling tower recirculation water and glass etching effluents have been treated successfully with ED for water recovery and effluent volume reduction, while ED treatment of nickel plating wash waters is an established industrial process.
Application of the finite element method in the structural design of the main magnets, vacuum chambers and resonators of an open sector cyclotron
Authors: Strasheim J. A. , Du Preez R. J.
Published: March 2014

The central role played by finite element analysis in the structural design of the main magnets, vacuum chamber and resonator of a 200 MeV open sector cyclotron facility for the National Accelerator Centre at Faure, South Africa, is described. The design evolved through a series of conceptual layouts of the structures involved. A finite element model of a main magnet, a main magnet vacuum chamber, one of a resonator, three of a resonator vacuum chamber and three of a valley vacuum chamber have been drawn up so far.
Historiese oorsig oor die aktiwiteite van die Afdelings binne die Fakulteit Natuurwetenskap en Tegniek
Authors: Office Editorial
Published: March 2014

Veel meer gegewens as wat hier verstrek word, is deur die medewerkers beskikbaar gestel. Weens gebrek aan ruimte moes die bydraes ingekort word. Die volledige artikels word egter in die Akademie-argief bewaar.
The lanthanides. Oxidation states and some other features
Authors: Cruywagen J. J.
Published: March 2014

The stabilities of oxidation states +2, +3 and +4 of the lanthanides in solution and in the solid state are discussed in terms of energy cycles. The irregular variation of the third and fourth ionization energies is of decisive importance in determining the relative stabilities of the various oxidation states. Some other features such as electronic configurations and the variation of properties with atomic number and L quantum number are also discussed. Important uses of the elements are mentioned.
A respirometer for aquatic animals standardized against the Scholander respirometer
Authors: Van Aardt W. J. , Steyn H. S.
Published: March 2014

A reliable but slow functioning respirometer was compared with a newly designed Clark-electrode respirometer. The material used during the measurements was Labeo capensis, a fresh-water mudfish. The results were statistically analysed. It was found that the Clark-electrode respirometer gave, on average, about 2% higher readings compared with the manometric respirometer developed by Scholander.
The history of domestication
Authors: Osterhoff D. R.
Published: March 2014

During domestication animals are exposed to conditions which greatly changed their body proportions and performance - the reproduction of the animals is totally changed, the social structure of wild populations is upset and no natural selection whatsoever takes place. During domestication the animals diminish is size, the height at withers of bulls is reduced to 120 cm and that of cows to only 110 cm.
The fundamental importance of differential equations with three singularities in Mathematical Statistics
Authors: Steyn H. S.
Published: March 2014

It is well-known that the solution of a second order linear differential equation with at most five singularities plays a fundamental role in Mathematical Physics. In this paper it is shown that this statement also applies to Mathematical Statistics but with the difference that an equation with three singularities will suffice. Two wide classes of probability distributions are defined as solutions of such a differential equation, one for continuous distributions and one for discrete distributions. These two classes contain as members all the distributions which are normally considered as of importance in Mathematical Statistics. In the continuous case the probability functions are solutions of the relevant second order equation, while in the discrete case the probability generating functions are solutions there-of. By defining appropriate multidimentional extensions corresponding differential equations are obtained for continuous and discrete multivariate distributions.
The use of kriging in gravity-surveys
Authors: Van Tonder G. J. , Botha J. F. , Wiegmans F.
Published: March 2014

The present investigation is mostly concerned with the contribution that kriging can make towards reducing the number of observed gravity measurements necessary for a reliable estimate of the volume weathered dolomite in the dolomitic areas of South Africa. After a brief introduction, the method is applied to the Bouguer anomaly values of a part of the Zuurbekom Compartment. It is shown that by using kriging, the number of measuring stations can be reduced by op to 90 percent without affecting the accuracy of the calculation of the estimated volume of the weathered dolomite adversely.
The determination of sea level in the Southern Ocean
Authors: Lutjeharms J. R. E.
Published: March 2014

The importance of sea-level measurements for an understanding both of oceanology and of climate is increasingly stressed in the literature. This review of existing knowledge on the sea-level of the Southern Ocean reveals certain well-defined gaps and it points to a need for specific research projects to fill these gaps.
How Lodewicus Van der Waerde found God
Authors: Haarhoff P. C.
Published: March 2014

The following question is discussed, in the form of a narrative: Suppose a scientist accepts that the laws of nature are the rules according to which God acts in the physical world, and that God would not act inconsistently by suspending these rules from time to time. Can something outside the known physical science then nevertheless have meaning for him?
Inter basin water transfers
Authors: Van Robbroeck T. P. C.
Published: March 2014

Most economic development in South Africa has taken place on the dry plateau of the interior following the discovery of minerals. The much smaller wetter parts get most of the run-off and have generally limited possibilities for advantageous use of their water resources. Consequently, it is logical to transfer water between basins with a surplus to ones experiencing shortages. There is a body of opinion that such transfers should be stopped in the interest of the decentralistion policy, but such action is not considered in the national interest. The intricate system of inter-basin transfer from the Komati, the Usutu and the Vaal River to supply the Eastern Transvaal coalfields is described. This system has shown its flexibility during the recent drought. The most important inter-basin transfer scheme is the Tugeia- Vaal Project which is described in broad terms. The advantages of the principle of reserve storage and of co-operation with Escom are dealt with. Possible further projects to augment the Vaal River supplies are mentioned. Other inter-basin transfer schemes implemented by the Department of Water Affairs such as the Orange River Project, the Riviersonderend-Berg River Project and others of lesser importance are dealth with.
Education-oriented Physics-Chemistry for Universities
Authors: Spoelstra B.
Published: March 2014

The shortage of well-qualified Science teachers is discussed, and possible contributing factors are mentioned. The need for an education-oriented university education in Physics and Chemistry, parallel to the existing courses in Physics and Chemistry, is justified. At the University of Zululand a subject called “Physical Science” (“Natuurwetenskap”) was established, bearing in mind the specific requirements of a teaching career in Physical Science at secondary level. “Physical Science” is offered at second and third year level and the syllabus covers equal amounts of Chemistry and Physics. A less formal-mathematical and more descriptive approach is followed, and as wide a field as possible is covered which includes new developments in the physical sciences. We believe that this new course will enhance the training of well-prepared teachers of Physical Science for secondary schools, where a severe shortage prevails. Special reference is made here to the situation in Black schools.
The conflict between coastal environmental protection and development in the Rooi-Els-Bot River estuary area
Authors: Claasen P. E.
Published: March 2014

The conflict between coastal environmental protection and development in the Rooi-Els-Bot River estuary area has come under renewed attention after the Minister of Constitutional Development and Planning recently announced his intention to declare this area a “nature area”. However, no clear guidance has yet been given by the government on how this conflict can be resolved. In this article the above-mentioned area is used as an example to investigate these problems and to formulate solutions for the control of coastal zones in such a way that the conflict can be reduced to a large extent. The proposed introduction of a nature area is examined critically and suggestions are made for its control and financing.
The interaction between ocean and atmosphere: a review
Authors: Lutjeharms J. R. E.
Published: March 2014

The atmosphere and the ocean may, from a functional point of view, be regarded as forming a coupled entity. They interact on a wide spatial range, from the molecular to the global. The necessity of considering the ocean and the atmosphere as a coupled system is illustrated most effectively if the interaction between them is studied insofar as it affects climate. This is done here by discussing the problem of an increase in atmospheric carbon dioxide, the influence of sea surface temperatures on the weather and the global El Nino/Southern Oscillation phenomenon. In conclusion mention is made of South African research in this connection.
Utilization of water in agriculture: strategy for the future
Authors: Van der Merwe D. S.
Published: March 2014

A n exposition is given of the factors influencing future utilization of water in agriculture. These are the quantity of water available for agricultural purposes, the increasing mineralisation of irrigation water and the effect of energy demands on irrigation. To meet this situation, research is necessary. The recommendations of four irrigation research workshops in this regard are discussed. From these discussions a strategy for future water
Pollution of water supplies
Authors: Toerien D. F.
Published: March 2014

Water is used in agriculture for irrigation as well as for drinking water for man and beast. The pollution of water with salts, plant nutrients, organic material, pathogens and parasites, as well as toxic components, decreases its value for agricultural purposes. The rapid development of and the population growth in South Africa will increase water pollution, and agriculture will thus be influenced. Agriculture will also have to intensify in the future to meet the expected increased demand for food; the role of agriculture as a water polluter will thus also increase. South African agriculturists and water managers will have to meet unique challenges in the next decade. However, there are also unique opportunities to utilise.
The structure of the eggshell of the laughing dove Streptopelia senegalensis
Authors: Steyn P. J. , Reinecke A. J. , Hamilton-Attwell V. L.
Published: March 2014

The morphology of the eggshell of Streptopelia senegalensis was studied using scanning electron microscopy. Thirty eggs from various parts of southern Africa, dating from 1899 to 1983, were used in this study. Thickness of the eggshell was determined directly from the micrographs. The eggshell has a low pore density and no cuticula. The three-layered structure of the membranes appears to consist of a network of small tubes. The external layer is closely associated with the protein nucleus of the mammillary nodules of the eggshell, while the inner membrane borders on the albumine layer. The mean length, breath, thickness and mass of the eggshell of this species is 25,78 mm, 19,97 mm, 0,088 mm and 0,324 g respectively.
A pharmacochemic investigation of Gomphrena celosioides (Amaranthaceae)
Authors: Botha S. , Van der Vijver L. M.
Published: March 2014

A chemical and biological screen was performed on Gomphrena celosioides (Amaranthaceae) known as prostrate globe amaranth. Chemical tests showed the presence of saponins, steroids, phenolic substances, flavonoids, amino acids, sugars and betacyanins in the plant. The roots exhibited a weak antibacterial activity against three Gram positive bacteria. An action on the autonomic nervous system of rats was shown by all the plant parts, when tested by the method of Malone and Robichaud. Sympathetic and parasympathetic symptoms were observed.
A chemical and biological evaluation of Kanahia laniflora (Asclepiadaceae)
Authors: Kruger A. M. C. , Van der Vijver L. M.
Published: March 2014

A chemical as well as a biological screening was performed on fresh frozen plant material (root, stem, leaves, fruit) of Kanahia laniflora (Asclepiadaceae). The chemical tests were positive for cardiac glycosides, flavonoids, phenolic compounds, carbohydrates and amino acids. The plant showed no antimicrobial or phototoxic activity. The Hippocratic evaluation revealed a definite indication of sympathetic stimulation, CNS depression, diuretic activity and peripheral vasodilatation, and a slight indication of psychotropic activity and a metabolic poison.
Error detection in proofreading
Authors: Plug C.
Published: March 2014

Two methods that can be used to estimate the total number of typographic errors in a text from the numbers of errors detected by two independent proofreaders are discussed. One of these methods is new and can be applied when two proofreaders read the same copy.
Attainable priorities in health care for the year 2000
Authors: Wassermann H. P.
Published: March 2014

Today’s problems stem from yesterday’s solutions to those problems. After tracing the origins of today’s problems from the French Revolution, the evolutionary phases of health-care development (in any country) is outlined. We are, in the RSA. now entering the third phase where emphasis should be on management and organisation. The greatest scarcity is the Academic Physician. Cost benefit and cost effectiveness are considered, with an algorithm for time-advantageous choices, which are then considered. Finally some heuristic thoughts on educational management and control are presented.
Silting in the Richards Bay Nature Reserve, Natal
Authors: Cooks J. , Pretorius J. R. , Venter L.
Published: March 2014

An investigation into the rate of silting in the Richards Bay Nature Reserve indicates that accelerated silting in the reserve is due to a disturbance of the equilibrium during development of the harbour. The most important reasons are probably the construction of a berm which divides the estuary into two parts, the cutting of an artificial exit into the sea, and farming malpractices in the catchment area. The rate of silting has increased to such an extent that approximately 36,14 percent of the reserve had already been silted up during the first 11 years after construction of the berm. A projection of the present rate of silting suggests the possibility that the reserve may be completely silted up within about 29 years. A rapid increase in plant colonization indicates the same tendency.
The mechanical and physical properties of trabecular (cancellous) bone of the femur neck
Authors: Van Papendorp D. H.
Published: March 2014

The stress required to reach the breaking point of trabecular bone of the femur neck of patients who obtained a femur neck fracture, was found to be 60% less than that required to reach the same result in patients with hip osteoarthritis. The compression strength of trabecular bone showed a reasonable correlation (r = 0,58) with the relative density of this bone. Analyses of the inclination of the stress-strain curves, and the determination of the elasticity modulus of trabecular bone showed that the bone of the fracture group was 30-60% more elastic than that of the osteoarthritic group. Both strength and elasticity may thus play a role in the evolution of this fracture.
Guide to biological drawing - Part 1: Line drawings
Authors: Holm E.
Published: March 2014

The advantages of drawings above photographic illustrations are listed, and the difference between skills needed for technical rendering and artwork is explained. Materials and techniques for good line drawing are treated in progressive steps, followed by appropriate recommended exercises. The text is elucidated by 18 illustrations.
Mycotoxin problems in South African foodstuffs
Authors: Rabie C. J.
Published: March 2014

Problems concerning the contamination of foods by toxic fungi and mycotoxins are reviewed. Mycotoxin contamination of specific South African foodstuffs such as maize, sorghum, oats, chicory, imported foodstuffs and certain processed foods is discussed. Emphasis is placed on those toxic fungi where the toxic metabolites are unknown and which regularly contaminate staple foods. Law-enforcement problems concerning mycotoxin contamination of food commodities are discussed.
Analysis and optimization of linear regenerative snubbers
Authors: Steyn C. G.
Published: March 2014

In this article both the general linear regenerative turn-on and turn-off snubbers are analysed and optimized independently from one another, in terms of minimum energy losses. The dissipative snubber - which was up to now the only optimized snubber - now becomes merely a special case of this general regenerative snubber. Equations describing the most important parameters are presented in tables, while some energy versus snubber size graphs are also shown.
Hydrological cycle of natural veld in the Central Orange Free State
Authors: Snyman H. A. , Van Rensburg W. L. J.
Published: March 2014

The hydrological cycle, which determines the water balance of the grazing ecosystem, is discussed. This cycle can be separated into a number of intermediate processes, each of which influences the water balance. These intermediate processes include surface runoff, evapotranspiration, percolation, infiltration and the storage of water in the ecosystem. Practical guidelines to increase the effectivity of the available rainfall for aboveground phytomass production, in arid and semi-arid regions, are discussed.
Mental retardation: a new challenge
Authors: Op't Hof J.
Published: March 2014

Although the care of the mentally handicapped in the RSA has improved over the past decades, it has only recently been possible to accurately establish the causes of mental retardation (MR). According to the WHO, the average incidence of severe MR (IQ < 50) is approximately 3-4 per 1 000 of the general population, while mild MR (IQ 50-70) occurs in about 20-30 individuals per 1 000 of the population. Genetic diagnostic investigations by the Genetic Services Division of the Department of National Health and Population Development have shown that the causes of serious MR at a school for white mentally retarded individuals can be divided as: genetic: 46%; non-genetic: 17%; and unknown causes: 37%. Chromosome abnormalities are the most important cause (± 18%) of MR, with Down syndrome and the Martin-Bell syndrome being the most common examples.
Nature and origin of bipedalism in primates
Authors: Ryke P. A. J.
Published: March 2014

The differences and similarities characterizing apes and humans are the inevitable and predictable consequence of both groups having diverged from a common ancestor. An important question to ask is what prompted the change from quadrupedalism to bipedalism, probably at the time of the divergence of the ape and human lineages. Or did it occur before the split? What are the advantages and disadvantages of bipedal walking? An evaluation of the origin of bipedalism requires a knowledge of the distinctive skeletal and locomotor features of man as a biped in contrast to quadrupeds. Fossil hominid footprints give an indication of the bipedal plantigrade propulsive striding of the protohominids.
pH-regulation: the role of the hepatorenal system
Authors: Pitout M. J. , Willemse G. T.
Published: March 2014

The regulation of the acid-base balance is generally regarded as a well entrenched area. However, a number of confusing views on pH-homeostasis, especially with reference to the relationship between the kidney and the ammonium buffer system, appear regularly in textbooks. One reason is that the correct stoichiometry of acid-base regulation is not mentioned. Recently the rote of the liver in pH regulation by controlling the bicarbonate concentration through urea synthesis is proposed. In this paper the role of the liver and kidneys as a team is discussed.
Activity patterns and feeding behaviour of hyrax (Procavia capensis) in the Mountain Zebra National Park
Authors: Fourie L. J. , Horak I. G. , Perrin M. R.
Published: March 2014

The activity patterns of marked hyrax in the Mountain Zebra National Park were quantified by direct observations. Extended periods are spent on basking during winter (6,8 h) and summer (5,3 h) respectively. At least 80 % of each day is spent in an inactive phase. The more extended time spent on movement and time spent within refuges during summer (0,4 and 2,7 h), compared to winter (0,2 and 0,9 h), can possibly be interpreted in terms of behavioural thermoregulation. Distinct differences between the feeding behaviour of juveniles (< 6 months) and older hyrax were observed. Foraging of juveniles was limited to a distance of 40 m or less from refuges and took place under the surveilance of adults. Foraging of older hyrax frequently occurred for extended distances (up to 500 m) from refuges. These hyrax frequently visited riparian thickets. Foraging excursions of individual hyrax lasted for 0,5 - 8 h. The reported early and late afternoon group feeding sessions for hyrax older than 5 months could not be confirmed.
The dependence of heat transfer and friction on fin tip configuration
Authors: Steyn L. J. C. , Pretorius L. , Visser J.
Published: March 2014

The dependence of heat transfer and friction parameters on fin tip configuration is investigated. Experimental tests are performed on a double tube heat exchanger with transverse annular fins on the inner tube. Seven different fin configurations are investigated. A theoretical model is used to calculate the heat transfer and friction parameters from experimental results.
The chemical and ammo acid composition of the compost worm Eisenia fetida as potential protein source in animal feeds
Authors: Reinecke A. J. , Alberts J. N.
Published: March 2014

There is an increasing demand for protein rich materials in the animal feed industry in South Africa. Intensive cattle husbandry as well as abattoirs are producing large quantities of organic waste, the protein content of which is not utilized. The compost worm, Eisenia fetida, can be reared in large numbers on this waste. This opens up the possibility to recover waste protein if E. fetida could be used as a protein source in animal feeds. The value of the protein was therefore researched by determining the general chemical composition and amino acid composition. The earthworm meal contained all the essential amino acids required in poultry feeds, in favourable ratios. The methionine and lysine availability was higher than that of fish meal.
The computer as an aid in the teaching of stereochemistry
Authors: Van Ree T.
Published: March 2014

A drill-and-tutorial program which can generate a large variety of asymmetric structures, has been developed with the aim of affording students practice in determining configuration. The computer program takes students stepwise through a number of problems and provides an analysis of the students’ errors. Students’ comments on the program were obtained and will be used to improve the program with new technology becoming available.
Is interspecific competition a major structuring force in animal communities?
Authors: Ryke P. A. J.
Published: March 2014

Until recently the view that competition is the dominant ecological interaction was the prevailing one. Interspecific competition was widely regarded as a principal mechanism in determining community structure and organization and thus the distribution and abundance of species. The volume of literature that provides indirect evidence in favour of competition (observational approach) greatly exceeds the number of studies that provide direct evidence (experimental approach). In part for this reason the importance of competition in community ecology is questioned by some ecologists. The strongest evidence for competition is derived from controlled field experiments which manipulate the abundancies of putative competitor species. It is stressed that to be able to study competition in the field and to test its theories, interaction coefficients have to be measured. In community studies the question should be asked how important competition, relative to other processes, is. A mechanistic perspective could be a powerful heuristic tool for community ecologists.
The early history of the earth
Authors: Snyman C. P.
Published: March 2014

In view of the principle of actualism the early history of the earth must be explained on the basis of present-day natural phenomena and the basic Laws of Nature. The study of the solar system leads to the conclusion that the planets were formed as by-products when the sun developed from a rotating cloud of cosmic gas and dust. The protoplanets or planetesimals could have accreted as a result of mutual collisions, during which they could have become partly molten so that they could differentiate into a crust, a mantle and a core on the basis of differences in density.
The origin of the universe and nuclear synthesis
Authors: Sellschop J. P. F.
Published: March 2014

The origin of the universe and nuclear synthesis are discussed in this paper. The concept of the “Big Bang” is introduced in cosmology from observational evidence that the universe is expanding. The language of elementary particle physics is used to describe the evolution of the universe starting at a very small fraction of a second after the "Big Bang”. Various “Eras” are identified during which certain nuclear processes predominate. At a later stage the remarkable nuclear synthesis of carbon takes place, leading to the evolution of other elements. Neutrino measurements are important to validate physical theories in this field and some results of such measurements by the WITS-CSIR Schonland Research Centre are presented.
A characterization of bimatrix variate distributions with special cases
Authors: Bekker A. , Rautenbach H. M. , Roux J. J. J.
Published: March 2014

The compatibility of pairs of matrix variate conditional densities and the uniqueness of the resulting bimatrix variate densities are investigated. Examples are given involving the matrix variate beta and Wishart conditional densities. Attention is also given to the characterization of bivector variate and bivariate distributions.
Determination of the operating voltage for non-linear capacitors as turn-off snubbers in power electronic switches
Authors: Lutsch A. G. K. , Schoeman J. J. , Van Wyk J. D.
Published: March 2014

The use of non-linear capacitors improves the efficiency of turn-off snubbers for power electronic switches. The parameters for the determination of non-linear ferro-electric capacitors are discussed and a novel measuring method for the determination of the maximum operating voltage is suggested. The procedure to select ferro-electric capacitors is also discussed.
Maturity in technology
Authors: Alberts L.
Published: March 2014

The concept is developed that modern technology, because of its relationship with pure science, can never really become mature, but will always grow as the pool of scientific knowledge grows. Parameters indicating to some extent the degree of technological prowess in a society are compared for a spectrum of countries. It is clear that in spite of some internationally outstanding successes. South Africa must be regarded on average as a developing society.
Voltage prediction in a resonant transfer cycle pulse power supply with snubber regulation
Authors: Bredenkamp G. L.
Published: March 2014

This paper describes a first and second order predictor based on a truncated Taylor series approximation on a time varying function. The Laplace transform of the Taylor series is taken to obtain a transfer function for the predictor whereupon the predictor is synthesised with an active RC network. Practical waveforms obtained are presented.
A re-evaluation of the T-wave in primates
Authors: Bosman H. , Theron J. J.
Published: March 2014

T-wave inversion was observed in a large number of primates (Papio ursinus). This observation was not associated with myocardial ischaemia. Inversion of the T-wave in primates, and other mammals, can be explained by differences in the duration of the action potential in different areas of the myocardium and the control of the duration of the action potential by the autonomic nervous system.
Soft drinking water: no cause of cardiovascular disease?
Authors: Van Staden D. A. , Van der Walt E.
Published: March 2014

In contrast with numerous references in world literature linking soft drinking water with an increased prevalence of hypertension, degenerative vascular diseases and cardiovascular disease, research done by the Hans Snyckers Institute at Tshikundamalema in Venda would indicate the opposite. The drinking water in this remote area is extremely soft but the traditional living people of the area appear to be free of these diseases.
A glance back at the Quillen-Suslin theorem and the recent status o f the Bass-Quillen conjecture
Authors: Lemmer A. A. , Naudé G.
Published: March 2014

In his famous FAC-article J.P. Serre asked whether all finitely generated projective modules over K[X1,...,Xn] (K a field) are free. This question soon became known in the mathematical society as “Serre’s Conjecture”. This conjecture was proved independently in 1976 by A. A. Suslin and D. Quillen. Important further developments followed from the ideas in Quillen’s proof. In this article we discuss the geometric motivation of the original problem as well as certain aspects of Quillen’s proof. Then we discuss further developments, in particular a proof that finitely generated projective modules over R[X1,...,Xn], R a Bezout domain, are free. We also give attention to new results on the existence of free summands in projective modules. In the case of polynomial rings, this work strengthens Serre’s famous free summand theorem: if R is a Noetherian ring and P is a finitely generated projective R-module such that rank P > dim R, then there exists a free rank one summand in P. Finally we discuss the present status of the most important open problem in this field, namely the Bass-Quillen Conjecture: if R is a regular local ring, is every finitely generated projective R[X1,...,Xn] module free?
Learning and memory
Authors: Ryke P. A. J.
Published: March 2014

Under various circumstances and in different species the outward expression of learning varies considerably, and this has led to the classification of different categories of learning. Just as there is no generally agreed on definition of learning, there is no one system of classification. Types of learning commonly recognized are: Habituation, sensitization, classical conditioning, operant conditioning, trial and error, taste aversion, latent learning, cultural learning, imprinting, insight learning, learning-set learning and instinct. The term memory must include at least two separate processes. It must involve, on the one hand, that of learning something and on the other, at some later date, recalling that thing. What lies between the learning and (he remembering must be some permanent record — a memory trace — within the brain. Memory exists in at least two forms: memory for very recent events (short-term) which is relatively labile and easily disruptable; and long-term memory, which is much more stable. Not everything that gets into short-term memory becomes fixed in the long-term store; a filtering mechanism selects things that might be important and discards the rest.
The nature and character o f agricultural research
Authors: Potgieter D. J. J.
Published: March 2014

The sustained and sensational developments since the sixties in the field of molecular and cell biology are causing a revolution in agricultural research, the scope of which will be greater than that caused by the application of chemical science to agricultural practices more than a century ago. Simultaneously there has been a growing awareness of the social responsibilities of agricultural researchers. Teaching and research in tertiary institutions need to be continuously adapted to new technologies and the changing demands of the country and the consumers of agricultural products.
Mass transfer parameters in spray columns: 2. The system benzene-wash oil
Authors: Rautenbach A. J. , Kornelius G.
Published: March 2014

Spray columns are widely used in industry as a gas-liquid contacting apparatus because of the advantages of a high transfer area per unit volume and the tow gas side resistance. For a large number of systems, mass transfer parameters are not available and an experimental determination for the system benzene/wash oil was therefore carried out. The experimental technique and design are described. The variation in mass transfer coefficient as function of gas flow rate, liquid flow rate and column height agrees with those published elsewhere.
Errors in the measurement of the terrestrial magnetic field with a proton magnetometer
Authors: Hancke G. P.
Published: March 2014

Typical errors in the measurement of the precession frequency of the magnetic moment of protons when using the periodometer, are discussed and methods are proposed to minimize it’s influence. Important conclusions are made with regard to the time of measurement and polarization and the properties of the sensor fluid.
An electronic valve controller for current control during the recording of oxygen consumption in aquatic animals
Authors: Du Preez H. H. , Grobler E. , Bell J. M.
Published: March 2014

A control system is described which allows the automatic recording of the oxygen consumption of five aquatic organisms and one control. The electronic valve controller operates six three-way valves which permit water from each of the six respiration chambers to flow successively past the oxygen sensor. A 38.4 kHz quartz cristal oscillator ensures a ten minute period and is not affected by disturbances on the power circuit.
Important design parameters of the proton magnetometer sensor
Authors: Hancke G. P.
Published: March 2014

The performance of the proton magnetometer depends mainly on the characteristics of the sensor which are determined by some critical design parameters. The most important parameters and their relevance are discussed.
Global rise in sea level: a South African perspective
Authors: Lutjeharms J. R. E. , Swart D. H.
Published: March 2014

There is general scientific consensus that the increase in anthropogenic trace gases in the atmosphere is leading to an increase in global temperatures. This global perturbation of climate is causing a rise in mean sea-level. Such a rise has important implications for sensitive coastal areas. Research on the possible consequences for the South African coast-line is urgently required.
Tobacco or Health?
Authors: Wang Long-de
Published: March 2014

It’s no doubt that smoking causes severe impair to health, and China is the world’s number one country in terms of cigarette consumption. Based on the global situation of tobacco control and the enforcement status of the World Health Organization Frame work Convention on Tobacco Control in China, this paper proposed some measures to promote the comprehensive tobacco control, such as legislation and specification of the responsibilities of all levels of government in this respect.
Advances of studies on blood diseases and bone marrow microvessel
Authors: Wu Di-jiong , Zhou Yu-hong , Ye Bao-dong , Yu Qing-hong
Published: March 2014

Bone marrow microvessel plays an important role in the onset and progression of hematologic diseases whose genesis is regulated by a variety of regulatory factors. Since abnormal angiogenesis has been found in a number of malignant and non-malignant hematologic diseases, microvessel density can be a valuable prognostic indicator, and also a stratifying factor in some of these diseases. In some cases, inhibiting or stimulating angiogenesis with certain treatments may be very important in improving therapeutic outcomes. However, mechanisms underlying these effects are yet to be further investigated.
High incidence of malnutrition in elective vascular surgery patients: An observational auditing study
Authors: De Waele Elisabeth , Moerman Leslie , Van Bael Kobe , Aerden Dimitri , Debing Erik , Honoré Patrick M. , Van den Brande Pierre
Published: March 2014

Background:Malnutrition has been shown to have an adverse effect on the clinical outcome of surgical patients. A >10% body weight loss in the previous 6 months is a significant preoperative predictor of worse post-operative outcome. There are limited data on malnutrition in vascular surgery patients. The current study was designed to investigate the prevalence of malnutrition in elective vascular surgery patients. Materials and Methods: This is a prospective, observational, auditing study carried out in department of vascular surgery of a tertiary, university and teaching hospital. All patients scheduled to undergo vascular surgery in a 4-month period were screened for malnutrition using the Nutritional Risk Score 2002. Nutritional status was assessed by body weight, body mass index, serum albumin and physical examination by a member of the hospitals’ nutrition team. The body weight was determined daily until 30 days post-operatively. Statistical analysis was performed using SPSS Statistics, Release Version 20.0.0. Results: On admission, 14 of 23 patients (61%) were at risk of malnutrition (Nutritional Risk Score 2002 ≥ 3). Assessment revealed no false-positive results. The mean post-operative body weight declined until Day 9. Afterwards, it rose with a mean weight gain of 1.32 kg. Conclusions: Malnutrition remains a largely unrecognized problem in vascular surgery patients. Given its detrimental effect, screening for malnutrition should be implemented in the pre-operative workup and therapeutic flow charts should be made available. Clear guidelines should also been made available for the bedside clinician.
On Persistent Poverty in a Rich Country
Authors: Islam T. M. Tonmoy , Minier Jenny , Ziliak James P.
Published: March 2014

We examine differences in income within the United States, and the regions of persistent poverty that have arisen, using a newly assembled county‐level data set linking 19th century Census data with contemporary data. We identify the roles of current differences in aggregate production technologies and factor endowments, together with contributions of historical institutions, culture, geography, and human capital. We allow for possible cross‐county factor mobility via a correlated random effects GMM estimator and find evidence of significant regional differences in production technologies. Our decompositions of the poor/nonpoor income gap suggest that at least three‐fourths of the gap is explained by differences in productive factors. Persistently poor counties are different (and poorer) primarily because they have lower levels of factors of production, not because they use the factors they have less efficiently. Together, historical and contemporary human capital explain over half of the overall income gap between persistently poor and nonpoor counties.
Annual cycle of Antarctic baseline aerosol: controlled by photooxidation-limited aerosol formation
Authors: Fiebig M. , Hirdman D. , Lunder C. R. , Ogren J. A. , Solberg S. , Stohl A. , Thompson R. L.
Published: March 2014

Abstract. This article investigates the annual cycle observed in the Antarctic baseline aerosol scattering coefficient, total particle number concentration, and particle number size distribution (PNSD), as measured at Troll Atmospheric Observatory. Mie theory shows that the annual cycles in microphysical and optical aerosol properties have a common cause. By comparison with observations at other Antarctic stations, it is shown that the annual cycle is not a local phenomenon, but common to central Antarctic baseline air masses. Observations of ground-level ozone at Troll as well as backward plume calculations for the air masses arriving at Troll demonstrate that the baseline air masses originate from the free troposphere and lower stratosphere region, and descend over the central Antarctic continent. The Antarctic summer PNSD is dominated by particles with diameters <100 nm recently formed from the gas-phase despite the absence of external sources of condensible gases. The total particle volume in Antarctic baseline aerosol is linearly correlated with the integral insolation the aerosol received on its transport pathway, and the photooxidative production of particle volume is mostly limited by photooxidative capacity, not availability of aerosol precursor gases. The photooxidative particle volume formation rate in central Antarctic baseline air is quantified to 207 ± 4 μm3/(MJ m). Further research is proposed to investigate the applicability of this number to other atmospheric reservoirs, and to use the observed annual cycle in Antarctic baseline aerosol properties as a benchmark for the representation of natural atmospheric aerosol processes in climate models.
Methods for estimating uncertainty in factor analytic solutions
Authors: Paatero P. , Eberly S. , Brown S. G. , Norris G. A.
Published: March 2014

Abstract. The EPA PMF (Environmental Protection Agency positive matrix factorization) version 5.0 and the underlying multilinear engine-executable ME-2 contain three methods for estimating uncertainty in factor analytic models: classical bootstrap (BS), displacement of factor elements (DISP), and bootstrap enhanced by displacement of factor elements (BS-DISP). The goal of these methods is to capture the uncertainty of PMF analyses due to random errors and rotational ambiguity. It is shown that the three methods complement each other: depending on characteristics of the data set, one method may provide better results than the other two. Results are presented using synthetic data sets, including interpretation of diagnostics, and recommendations are given for parameters to report when documenting uncertainty estimates from EPA PMF or ME-2 applications.
Modes of zonal mean temperature variability 20–100 km from the TIMED/SABER observations
Authors: Jiang Y. , Sheng Z. , Shi H. Q.
Published: March 2014

Abstract. In this study we investigate the spatial variabilities of the zonal mean temperature (20–100 km) from the TIMED (Thermosphere, Ionosphere, Mesosphere, Energetics and Dynamics)/SABER (Sounding of the Atmosphere using Broadband Emission Radiometry) satellite using the empirical orthogonal functions (EOFs). After removing the climatological annual mean, the first three EOFs are able to explain 87.0% of temperature variabilities. The primary EOF represents 74.1% of total anomalies and is dominated by the north–south contrast. Patterns in the second and third EOFs are related to the semiannual oscillations (SAO) and mesospheric temperature inversions (MTI), respectively. The quasi-biennial oscillation (QBO) component is also decomposed into the seventh EOF with contributions of 1.2%. Last, we use the first three modes and annual mean temperature to reconstruct the data. The result shows small differences are in low latitude, which increase with latitude in the middle stratosphere and upper mesosphere.