129,825 research outputs found
Impact of acid atmosphere deposition on soils : field monitoring and aluminum chemistry
No full textThe effect of acid atmospheric deposition on concentrations and transfer of major solutes in acid, sandy soils was studied. Emphasis was given to mobilization and transport of potentially toxic aluminum. Data on solute concentrations and fluxes in meteoric water as well as soil solutions were obtained from intensive monitoring programmes conducted at a number of sites in northwestern Europe and North-America. Specific hypotheses were tested in laboratory experiments.Atmospheric acid inputs dominated total acid loads in nearly all soils studied. This was particularly true for forest soils in the Netherlands, due to an extreme dry deposition of (NH 4 ) 2 SO 4 in the forest canopy. Input of (NH 4 ) 2 SO 4 may acidify the soil, due to NH 4 assimilation, or nitrification of NH 4 and subsequent leaching of NO 3 .In soils rich in weatherable minerals, mobilization of base cations dominated acid neutralization, so that percolation water was buffered at relatively high pH values and the mobility of aluminum was low. In these soils the mobilization and transport of aluminum was mainly driven by organic acids, which is consistent with the podzolization theory. However, in soils depleted in weatherable minerals (e.g. most of the acid, sandy soils in the Netherlands), mobilization rates of base cations were too low for a substantial neutralization of atmospheric acidity, so that pH values of the percolation water were often low enough to cause a significant mobilization of aluminum. In these soils the atmospherically derived strong acid load was almost fully neutralized by aluminum dissolution. Much of this dissolved inorganic aluminum is currently lost to the groundwater.Although aluminum is abundant in soils only a minor fraction, largely consisting of non-silicate organically bound aluminum, formed in the course of soil development (podzolization), was readily dissolved. The current rapid and irreversible depletion of this fraction in many acid, sandy soils of the Netherlands constitutes a drastic change in soil genesis. Depletion may eventually also result in reduced acid neutralization, due to decreased dissolution of aluminum.The aluminum solubility control varied with soil depth. Surface soil solutions were highly undersaturated with respect to gibbsite solubility, whereas saturation was approached in the subsoil. Possibly, the low aluminum solubility in the surface soil was controlled by an exchange type equilibrium with organic soil aluminum. Insight in the aluminum solubility control in soils is not only relevant for improving our understanding of the aluminum chemistry in soils per se, but it may also help explaining the aluminum chemistry of surface water in mountainous catchments, where soil solutions may reach the stream via different flowpaths through the soil, depending on hydrological conditions
Trade Performance in Transport
No full textcommunication préparée par B. Chane Kune, N. Mulder et I. Rabaud (1998),présentée par N. Mulder au 14me PROGRESS Seminar on the Service Economy, Genève, 11-12 septembr
Trade Performance in Transport
No full textcommunication préparée par B. Chane Kune, N. Mulder et I. Rabaud (1998),présentée par N. Mulder au 14me PROGRESS Seminar on the Service Economy, Genève, 11-12 septembr
'n Wegblystem is 'n ANC-stem
No full text462.A.1.6(5).pdf created from original election material in the South African Elections Collection held in the Manuscripts Section of the Stellenbosch Library and Information Service.Campaign poster by the Freedom Front / Vryheidsfront (FF/VF) urging South Africans to use their vote to ensure FF/VF victory over the African National Congress (ANC) at the elections. The text is in dark blue against a white background with General Constand Viljoen's name in orange. The party logo appears in the bottom left-hand corner. The letters "NP" have been written on the poster in place of the ANC with a blue marker. The poster is compiled and issued by Dr. Pieter Mulder
Linguistic meta-theory the formal and empirical conditions of acceptability of linguistic theories and descriptions
No full textMost linguists acknowledge, explicitly or implicitly,
the relevance of epistemological questions in
linguistics but relatively few have given more than a
cursory, ad hoc or incomplete consideration to them.
The work of one of those few, Jan Mulder, forms the
starting point for much of the present discussion.
Epistemological considerations arise in many contexts
in linguistics and in many guises. It is an epistemological
matter whenever we test the adequacy of a
description or the acceptability of a theory. Epistemological
considerations are latent whenever we discuss
the form or the content of linguistic theories
and descriptions or their interrelations. The comparison
of different approaches to linguistics inevitably
raises epistemological questions concerning our
approach to linguistics or our presuppositions about it.
These questions are of a general nature and transcend
questions about particular linguistic theories and descriptions.
These epistemological questions force us to
consider what we take linguistics to be. In considering
questions of the type mentioned we are forced, for
example, to analyse what we mean by a "linguistic
theory", a "linguistic description" and what phenomena
we are aiming to understand. We are, furthermore,
forced to analyse the constraints which a scientific
attitude places upon linguistic theorising
and description-building. It is these questions concerning
the acceptability of linguistic theories and
descriptions which we call linguistic meta-theory.
This thesis falls into five main parts. Firstly,
in Chapter One, we consider the nature and scope of
linguistic meta-theory. Secondly, in Chapter Two, we
look at a number of previous approaches to the subject.
Other important contributions are discussed as they
arise in the text. Thirdly, in Chapters Three and
Four, we consider in detail the major meta-theoretical
distinctions in linguistics and their consequences.
In particular, we distinguish linguistic theories
from linguistic descriptions and discuss the nature of
linguistic phenomena. The view is put forward that
linguistics is a scientific subject. The meaning of
this assertion is analysed and the interrelations of
linguistic theories, descriptions and phenomena are
considered in the light of this analysis. The main
epistemological requirement that is put forward and
defended is that of the empiricism of linguistics.
Certain changes in our view of the philosophy of science
and in our view of the form of linguistic theories
and descriptions follow from the conjunction of
these major meta-theoretical positions.
Fourthly, we consider the main meta-theoretical
considerations concerning theories (Chapter Five) and
reject a widespread view of linguistic theory as a
non-empirical study (Chapter Six) and we consider the
main meta-theoretical conditions relating to linguistic
descriptions and some practical examples of description
-building consonant with the general positions adopted
in Chapter Seven. In Chapter Eight, we look at a concrete
example of theory-building in the light of the
meta-theoretical conditions of acceptability previously
set up. We are especially concerned to show how a
theory can meet the condition of being "applicable" or
"indirectly scientific" through the establishment of
acceptable empirical descriptions consonant with the
meta-theoretical conditions on descriptions considered
earlier.
The view that linguistics is a science implies
that we must be concerned with the empirical testing of
descriptions and, so, the fifth part of the work is
devoted to methodology. In Chapter Nine, we defend
the role and necessity of methodology in linguistics
and set up the logical framework of relations between
the methodology and theory descriptions and phenomena.
In Chapter Ten, we examine two of the known types of
empirical testing and their shortcomings. Finally, in
Chapter Eleven, we give an example of the successful
and correct application of a methodology in order to
bring out the nature of empirical testing and to demonstrate
its feasibility within a scientific linguistics
of the sort we imagine
Productivité et performance à l'exportation dans le transport : le cas de huit pays
No full textcommunication préparée par B. Chane Kune, N. Mulder et I. Rabaud (1998),présenté par I. Rabaud au LXVIIè Congrès annuel de l'AFSE, Paris, 24-25 septembr
Introduction
No full textDanjou-Flaux, De Mulder Walter. Introduction. In: Langue française, n°116, 1997. Indéfinis et références, sous la direction de Walter de Mulder et Nelly Flaux. pp. 3-7
Productivité et performance à l'exportation dans le transport : le cas de huit pays
No full textcommunication préparée par B. Chane Kune, N. Mulder et I. Rabaud (1998),présenté par I. Rabaud au LXVIIè Congrès annuel de l'AFSE, Paris, 24-25 septembr
Introduction
No full textDanjou-Flaux, De Mulder Walter. Introduction. In: Langue française, n°116, 1997. Indéfinis et références, sous la direction de Walter de Mulder et Nelly Flaux. pp. 3-7
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