250 research outputs found
The genus Hymenagaricus Heinem. in South Africa
No full textDuring an investigation of South African species of Agaricus L.: Fr, and allied genera, three species of Hymenagaricus Heinem, have been studied. H. caespitosus is described as a new species, With the exception of H. luteolosporus Heinem. & Little Flower, which was recently recorded by van der Westhuizen & Eicker (1994), the remaining species constitute new additions to the mycobiota of this country; both the genus and species are still unfamiliar to many. A generic description, a key to the South African species, and accounts of these taxa follow. Type and other collections studied have been deposited in PRUM.Tydens ‘n ondersoek van Suid-Afrikaanse spesies van Agaricus L.: Fr. en naverwartte genusse, is drie spesies van Hymenagaricus Heinem. bestudeer. H. caespitosus word as ‘n nuwe spesie beskryf, Met die uitsondering van H. luteolosporus Heinem. & Little Flower, wat onlangs deur Van der Westhuizen & Eicker (1994) aangeteken is, verteenwoordig die oorblywende spesies nuwe aanwinste vir die mikobiota van hierdie land; beide die genus en die spesies is tans nog algemeen onbekend. ‘n Generiese beskrywing, ‘n sleutel tot die Suid-Afrikaanse spesies en ‘n beskrywing van hierdie taksons volg. Tipes en ander versamelings wat bestudeer is word in PRUM gehou
Bayesian Estimation of Unknown Heteroscedastic Variances
No full textWe propose a Bayesian procedure to estimate possibly heteroscedastic variances of the regression error term, without assuming any structure on them. What we propose in this paper, may be construed as a Conditional Bayesian procedure that is conditioned upon the HCCM obtained from the OLS estimation of the original regression model. After we obtain the Eicker-White HCCM, we set up a Bayesian model and use an MCMC to simulate posterior pdf's of heteroscedastic variances whose structures are unknown. In addition to the numerical examples, we present an empirical investigation on the stock prices of Japanese pharmaceutical and biomedical companies.Eicker-White HCCM, orthogonal regressors, conditional Bayesian, MCMC, stock return variance estimation
Bayesian Estimation of Unknown Regression Error Heteroscedasticity
No full textWe propose a Bayesian procedure to estimate heteroscedastic variances of the regression error term, when the form of heteroscedasticity is unknown. We use prior information that is elicited from the well-known Eicker-White Heteroscedasticity Consistent Variance- CovarianceMatrix Estimator, and then useMarkov ChainMonte Carlo algorithm to simulate posterior pdf's of the unknown heteroscedastic variances. In addition to numerical examples, we present an empirical investigation of the stock prices of Japanese pharmaceutical and biomedical companies.Eicker-White HCCM, orthogonal regressors, informative prior pdf's, MCMC, stock return variance
n Taksonomiese studie van Transvaalse varswater Euglenophyceae en Chlorophyceae
No full textThesis (DSc (Botany))--University of Pretoria, 1982.Algmonsters is oor die hele Transvaal versamel. In 433 van die ongeveer 500 ondersoekte algmonsters is verteen= woord~gers van die Euglenophyceae en/of Chlorophyceae ge= vind. Hierdie 433 algmonsters is by 152 lokaliteit~ ver samel. In totaal kon 415 algsoorte (spesies, varieteite en formae geidentifiseer word waarvan 19 as moontlike nuwe taksons beskryf word. n Verdere 21 entiteite kon nie met sekerheid tot op spesifieke of infraspesifieke vlak geiden= tifiseer word nie en 35 algsoorte is nie heeltemal tipies vir die spesie of infraspesifieke takson waarin hulle geplaas is nie. Die algsoorte wat in hierdie werk opgeneem is, ressorteer onder die Euglenophyceae-genusse Astasia, Euglena, Lepocinclis, Phacus, Strombomonas en Trachelomonas en die Chlorophyceaegenusse Eudorina, Gonium, Pandorina, Pleodorina, Volvox, Asterococcus, Gloeocystis, Chlorococcum, Sphaerocystis, Ankistrodesmus, Chlorella, Closteriopsis, Glaucocystis, Kirchneriella, Monoraphidium, Nephrocytium, Oocystis, Dictyosphaerium, Dimorphococcus, Westella, Coelastrum, Crucigenia, Scenedesmus; Pediastrum, Sorastrum, Geminella, Ulothrix, Microspora, Chaetophora, Aphanochaete, Chaeto sphaeridium, Bulbochaete, Oedogonium, Debarya, Mougeotia, Spirogyra, Zygnema, Zygnemopsis, . Cylindrocystis, Mesotaenium, Netrium, Roya, Spirotaenia, Gonatozygon, Actinotaenium, Bambusina, Closterium, Cosmarium, Desmidium, Groenbladia, Hyalotheca, Micrasterias, Penium, Pleurotaenium, Sphaerozosma, Teilingia en Triplastrum. Hiervan was die genusse Cosmarium, met 128 taksons, en Closterium, met 59 taksons, die beste verteenwoordig. 'n Getal van 109 van die algsoorte wat geidentifiseer kon word, is volgens bestaande literatuur nog nie voorheen in Suid-Afrika gevind nie en verteenwoordig dus nuwe rekords. Met enkele uitsonderings word illustrasies van al die algsoorte wat met hierdie studie gevind is voorsien en in die opsig is van lyntekeninge, fotomikrograwe en aftaselektron mikrograwe gebruik gemaak. By sekere algsoorte, veral ver teenwoordigers van die familie Desmidiaceae, is die skulp= tuur van die selwand taksonomies belangrik. Om hierdie rede is aftaselektronmikroskoopstudies van onskatbare waarde gevind.Plant ScienceDSc (Botany
Use of Phase Change Material in a Building Wall Assembly: A Case Study of Technical Potential in Two Climates
No full textPhase change material (PCM), placed in an exterior wall, alters the temperature profile within the wall and thus influences the heat transport through the wall. This may reduce the net energy transport through the wall via interactions with diurnal temperature swings in the external environment or reduce the electricity needed to meet the net load through the wall by shifting the time of the peak load to a time when the cooling system operates more efficiently. This study covers a broad range of parameters that can influence the effectiveness of such a merged thermal storage-thermal insulation system. These parameters included climate, PCM location within the wall, amount of PCM, midpoint of the PCM melting and freezing range relative to the indoor setpoint temperature, temperature range over which phase change occurs, and the wall orientation. Two climates are investigated using finite difference and optimization analyses: Phoenix and Baltimore, with two utility rate schedules. Although potential savings for a PCM with optimized properties were greater when the PCM was concentrated near the inside wall surface, other considerations described here lead to a recommendation for a full-thickness application. An examination of the temperature distribution within the walls also revealed the potential for this system to reduce the amount of energy transported through the wall framing. Finally, economic benefits can exceed energy savings when time-of-day utility rates are in effect, reflecting the value of peak load reductions for the utility grid
More efficient tests robust to heteroskedasticity of unknown form
No full textIn the presence of heteroskedasticity of unknown form, the Ordinary Least Squares parameter estimator becomes inefficient and its covariance matrix estimator inconsistent. Eicker (1963) and White (1980) were the first to propose a robust consistent covariance matrix estimator, that permits asymptotically correct inference. This estimator is widely used in practice. % Cragg (1983) proposed a more efficient estimator, but concluded thattests based on it are unreliable. Thus, this last estimator has not been used in practice. This paper is concerned with finite sample properties of tests robust to heteroskedasticity of unknown form. Our results suggestthat reliable and more efficient tests can be obtained with the Cragg estimators in small samples.wild bootstrap; heteroskedasticity-robust test; regression model
Optimization of Urban Cooling Strategies for Parking Lots in Hot and Dry Climates: Case Study of Las Vegas and Adelaide
No full textUrban microclimates are distinguished by the balance between solar gain and heat lost from building envelope and ground surfaces, by convective heat exchange, and by the generation of anthropogenic heat within the city. Global climate change and the urban heat island (UHI) effect—whereby cities are up to 8 °C hotter than their surrounding countryside—carry growing threats to outdoor living, public health, and urban energy demand. Urban heat stress intensifies in cities with hot and dry summer climates such as Las Vegas (USA) and Adelaide (Australia), where the temperature goes frequently above 36 °C (97 °F). Both cities have a dry, hot, and arid climate. Possible adaptation countermeasures include cool surfaces, urban greenery, and active cooling with the consideration of higher demand for water and energy, and potential winter cooling penalties. Large open-air parking lots appear in many modern cities around shopping malls, hospitals and public venues and provide essential access to these public facilities. In this context, a comparative study of different cooling strategies informs more effective decision making for the design and implementation of UHI adaptation and mitigation strategies. This chapter compares urban cooling strategies for typical parking lots in Downtown Las Vegas, Adelaide CBD and the suburban context. Cool surface materials, tree canopy, evaporative cooling and shading scenarios are estimated, and cooling benefits and side effects of each intervention are discussed. The research shows that planting trees between car parking spaces is vital to most urban environments, especially for parking lots where it leads to 1–5 °C summer cooling.Ehsan Sharifi, Phillip Zawarus, Steffen Lehman
n Studie van verskillende deklaagmateriale in die kommersiele verbouing van Agaricus Brunnescens Peck
No full textDissertation (MSc)--University of Pretoria, 1984.An attempt was made to find an economic alternative for peat moss which is currently used as casing material in the commercial production of Agaricus brunnescens Peck. Substrates such as spent compost which is obtainable from various farms, and paper pulp, as well as additives like vermiculite and activated charcoal, were evaluated. Certain chemical, physical and microbiological aspects as well as the production of mushrooms and the average number of fruit bodies per unit area obtained on the various substrates, were compared with peat moss. The percentage water-holding capacity, percentage pore space, pH, conductivity, number of fungi and number of bacteria per gram dry mass of the materials were determined. Fungi were isolated from these materials and identified with the aim of tracing possible competitive and parasitising fungi. In addition fresh spent compost was allowed to mature for a period of one year in the veld and was artificially leached by regular watering. Any changes in the above mentioned aspects as well as changes in the production of mushrooms by using compost as casing material were noted. The production on spent compost that was spread out in the veld under South African weather conditions and artificially leached, compared favourably with that of peat moss. The conductivity and number of bacteria in the matured spent compost showed a drastic reduction during this period, while the production increased. Spent compost left in the veld for two years to leach but without spreading it, did not give such a high yield. An increase in production was achieved by adding 2,6% activated charcoal to the spent compost. The physical properties of the casing material do not necessarily improve by adding 15% and 30% of vermiculite. Production when paper pulp was used as casing material was quite significant initially but the paper pulp probably cannot maintain this level of production over a long time span of five breaks. Only three fungi which probably parasitise mushroom miselium were isolated from the evaluated material, namely Mycogone perniciosa from fresh used compost and Chrysosporiumcf. pannorum and Verticillium fungicola from the peat. Futhermore a number of green moulds (possibly could be in competition with the mushrooms) were isolated, namely species of Aspergillus, ciadosporium, PeniciZZium and Trichoderma. None of these fungi affected the mushroom growth adversely.Plant ScienceMScUnrestricte
Language between intentions and conventions
No full textTitelblatt und Inhaltsverzeichnis
Voranalytisches
Die sprachliche Handlung
Das Meinen
Zwischen Meinen und Verstehen: Die Äußerung
Das Verstehen
Im Netzwerk des Gebrauches: Bedeutungszirkulation
Nachanalytisches
LiteraturverzeichnisIn der Sprachphilosophie ist eine der zentralen Fragen, was sprachliche Be-
deutung ist. Damit verbunden ist die Frage wie Sprache funktioniert, ob es die
Sprache ist, die funktioniert oder nicht vielmehr, die Kommunikation, das
aktive Kommunizieren, die In-Gebrauch-Nahme der Sprache, in welche die
sprachliche Bedeutsamkeit gleichsam eingebettet zu sein scheint. Das
Dissertationsprojekt Über Bedeutung. Sprache zwischen Intentionen und
Konventionen beschäftigt sich mit eben diesen Fragen, indem es ver-sucht,
zwischen intentionalistischen und konventionalistischen Ansätzen zur Erklärung
sprachlicher Bedeutung eine Brücke zu schlagen. Damit ist die Arbeit bereits
in eine bestimmte Debatte um konventionalistische und intentionalistische
Sprachauffassungen eingefasst. Sie verfolgt also nicht die Absicht, zu
erklären, was sprachliche Bedeutung ist, sondern wie man sie innerhalb dieser
Debatte positionieren könnte. Die Kernanalysen der Arbeit betreffen die
Begrifflichkeiten des Meinens und des Verstehens. Um diese zu bearbeiten wird
ein Modell der Bedeutungstrias konzipiert, welches sich zwischen
Sprecherintentionen und Sprachkonven-tionen situiert und die Phänomene des
Meinens und des Verstehens ablichten möchte. An die Stelle der Bedeutung tritt
eine Bedeutungstrias von Sprecher-, Äußerungs- und Hörerbedeutung, welche die
unterschiedlichen und temporären Verdichtungen eines Zirkulationsprozesses
sprachlicher Bedeutung innerhalb interaktiver Kommunikationssituationen
beschreibt. Um das Modell der Bedeutungstrias aufzuspannen, wird eine Debatte
inner-halb der Philosophie der normalen Sprache untersucht, welche sich auf
den Sprechakt als Elementareinheit sprachlicher Kommunikation beruft und in
der sprachliche Bedeutung zwischen den beiden Polen des Intentionalismus und
des Konventionalismus diskutiert wird. Zentral für das Dissertations-projekt
sind die Autoren Grice, Searle und Savigny, welche in einer Synthese die
Eckpunkte des Modells der Bedeutungstrias markieren werden. Es stellt sich die
Frage, was in einem Kommunikationsmoment geschieht, in dem ein Sprecher etwas
meint und ein Hörer dieses versteht. Bei der Beant-wortung der Frage wird mit
einem sprechakttheoretischen Begriff sprachli-cher Bedeutung argumentiert,
verstanden als ein propositionaler Gehalt, der durch Regeln und Konventionen
in lexikalischen Einheiten abgefasst wird, phonetisch realisiert wird, und vor
dem Horizont der Interaktion in einen intentionalen Prozess des Meinens gerät,
der in einem Verstehen eben jenes Meinens mündet. Dieser noch statisch
anmutende Begriff sprachlicher Be-deutung soll durch das sich aufspannende
Modell der Bedeutungstrias zu-sehends dynamisiert werden. Innerhalb der
Kommunikation, in der es zu einer In-Gebrauch-Nahme der Sprache kommt,
verzahnen sich systematische und interaktive Aspekte auf eine so enge und
subtile Weise, dass die Frage nach Sprache als System oder Handlung nicht
gestellt werden kann. Das System dynamisiert sich in der Praxis eines Meinens
und Verstehens, gerät in den Fluss des Interagierens und verliert dort
jegliche feste, universale Kontur. Der Vorgang des Kommu-nizierens dargestellt
im Modell der Bedeutungstrias macht eine Ortung der sprachlichen Bedeutung
schließlich unmöglich. Allerdings ist Sprache als ein Fundus an
regelorientierten und konventionalen Musteranwendungen, auch wenn
Kommunikation jenseits davon existieren kann, dennoch eine operativ wirksame
Fiktion.A central question in the philosophy of language concerns the nature of lin-
guistic meaning. This question introduces the uncertainty about how lan-guage
functions, and whether it is language that functions and not rather
communication, the act of communicating, the usage of language in which
meaning happens. The thesis About Meaning. Language between Intentions and
Conventions treats these questions and attempts to bridge the gap between
intentional and conventional approaches to the explanation of linguistic
meaning. The thesis is embedded in the approach of speech act theory and its
effort to ex-plain linguistic meaning as far as it concerns speaker intentions
and conven-tions. It is not the aim of this project to explain what linguistic
meaning is but to explain how it is to be positioned in this debate. The
central analysis of the thesis concerns the concepts of meaning and un-
derstanding. To deal with these concepts a model is designed which con-cerns
the trias of meaning situated between speaker intentions and linguis-tic
conventions, to define the concepts to mean and to understand. Instead of
meaning, the trias of meaning implies speaker, hearer and utterance mean-ing,
which portray the different and temporal condensations of a circulating
process of linguistic meaning within interactive situations of communication.
To demonstrate the model of the trias of meaning a debate within ordinary
language philosophy is analysed. The speech act is seen as the fundamental
unit of linguistic communication and meaning is discussed between the poles of
intentionalism and conventionalism. The central philosophers dis-cussed are
Grice, Searle and Savigny which mark in a synthesis the three edges of the
model of the trias of meaning. The question addressed is, what exactly happens
in the moment of commu-nication, in which a speaker means something and a
hearer understands the intended meaning. To answer this question the concept
of linguistic meaning in accord with speech act theory is assumed, where
linguistic meaning is a propositional content, formed in lexical units which
follow rules and conven-tions, uttered in phonetical units, and which becomes,
in interaction with the process of meaning, something intended to be
understood by an ad-dressee. This more static concept of linguistic meaning
shall becomes dy-namic under the model of the trias of meaning which points
out the circulat-ing process of meaning and understanding. Within
communication where language is used, systematic and interactive aspects
become interlocked so that questions such as whether language is a system or
an action cannot be answered. The system of language flows within the dynamic
of the practice of meaning and understanding, and en-ters in a state of flux
of interaction where it loses its solid, universal outline. Communication seen
with reference to the model of the trias of meaning makes it impossible to
find the linguistic meaning. However language as a store of rule-governed and
conventional sample applications is an operative effective fiction, albeit
with communication existing beyond
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