293,186 research outputs found
NMR, water and plants
No full textThis Thesis describes the application of a non-destructive pulsed proton NMR method mainly to measure water transport in the xylem vessels of plant stems and in some model systems. The results are equally well applicable to liquid flow in other biological objects than plants, e.g. flow of blood and other body fluids in human and animals (Chapter 8). The method is based on a pulse sequence of equidistant πpulses in combination with a linear magnetic field gradient G.Following a general introduction and a survey of the properties of water in plants (Chapters 1 and 2), the basic NMR theory as well as reviews on the application of pulsed NMR to the determination of flow, diffusion and water content are presented in chapter 3.A mathematical treatment has produced analytical expressions for the shape of the signal S(t), based on a model in which the flowing fluid is thought to receive a ½π-τ-(π-τ-) n pulse train: a ½πpulse upon entering the r.f. coil followed by a sequence of equidistant πpulses until the fluid leaves the coil; simultaneously, this movement. of the fluid along a magnetic field gradient applied in the direction of flow produces a phase shift of the nuclear magnetization with respect to the rotating frame of reference (Chapter 4). Although this model does not lead to perfect agreement between the experimental and theoretical signal shape S(t), it correctly predicts the effects of experimental parameters on S(t) via analytical expressions. The main results from this theoretical treatment in combination with computer simulations, which have been experimentally verified in glass capillary systems, are:- as long as T 2≥ ½T 1 , the mean linear flow velocity v can be found from the time t max at which a maximum appears in the signal shape: v=C/t max , where C is a calibration constant, depending on G, τand the flow profile. If T 2 <½T 1 v can only be reliably determined when both T 1 and T 2 of the flowing fluid are known.- T 2 and the amount of flowing water in the coil V, and consequently the volume flowrate Q, can be determined from the height of the maximum S(t max ) and t max . Depending on the value of T 2 and the value of the ratio T 1 /T 2 , T 2 and V are found from a semilog plot of either S(t max ) vs. t max (T 1 >>T 2 ) or ∂[S(t max ) . t max ]/∂t max vs. t max (T 1≈ T 2 ).Based on flow measurements in plant stem segments (Chapter 5) it has been suggested that T 2 strongly depends on the vessel diameter for the narrow xylem capillaries. This behaviour of T 2 can explain negative results in plant stems with small vessel diameter. Under the present experimental conditions the method has been successfully applied to Cucurbitaceae (cucumber, gherkin, pumpkin) and tomato plants.T 2 measurements in wheat leaves have been shown to be insensitive to the presence of cell-bound paramagnetic ions (Chapter 7). The magnitude of T 2 of two separate water fractions (covering -90% of the total water content) has been found to be inversely proportional to water content. Measurements of flow and water content have been combined for an intact gherkin plant (Chapter 5), demonstrating that the combination of both NMR methods results in a powerful non-invasive method to study important parts of the plant water balance simultaneously. The results strongly suggest that the method can be used as an early warning for development of stress phenomena in plants, due to drought and other factors. From the flow measurements it has been shown how in a plant system the values of T 2 and T 1 of the water in the xylem vessels can be determined and estimated, respectively.A comparison between the results obtained with NMR, heat pulse and weight balance flow measurements is presented in Chapter 6. A linear relationship between the linear flow velocity obtained by NMR and the volume flowrate determined by the balance method yields an effective cross-sectional area available for flow of ~50% of the cross-sectional area of the xylem vessels measured by using a microscope. NMR measurements alone yield a slightly lower value of the effective cross-sectional area. Compared with the NMR method, the heat pulse method monitors only relative changes in the flow velocity. A plot of the flow velocity obtained by the heat pulse method versus the volume flowrate obtained by the balance method exhibits some unwanted experimental scatter.Chapter 8 suggests some applications of the pulsed NMR flow method, also to other systems than plants, and defines important instrumental requirements for these applications
Cultivated landscapes as new cathedrals
No full textCornelis van Eesteren plays an instrumental role in the history of urbanism education in the Netherlands. He is regarded as a modernist, as a counterpart to the more traditional M.J. Granpré Molière. His expansion plans for Amsterdam earned him a reputation even before World War II, but as well as focusing on the IJsselmeer polders, his post-war work also involved modernising urbanism education in Delft. Van Eesteren was the pioneer of a new approach.ArchitectureArchitecture and The Built Environmen
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Sporen van Susteren - archeologische vondsten uit een Karolingische abdij en een adellijk vrouwenstift - de basispublicatie
No full textDe opgraving van het klooster van Susteren is uitgevoerd in 1991-1993 door de toenmalige Rijksdienst voor het Oudheidkundig Bodemonderzoek. Het klooster is in 714 door de Austrasische hofmeier Pepijn II en zijn vrouw Plectrudis gesticht en is door hen geschonken aan Willibrord (missionaris en abt van Echternach). Aanvankelijk bedoeld voor de huisvesting van ‘broeders’, blijkt het klooster in de late 9e eeuw door nonnen bewoond te zijn. Op een onbekend moment tussen de 11e en 14e eeuw werd het klooster omgezet in een wereldlijk damesstift dat in 1802 is opgeheven en kort daarna is gesloopt. Alleen de 11e-eeuwse abdijkerk is bewaard gebleven. Deze lag aan de noordzijde van het klooster.
Susteren is een van de weinige vroegmiddeleeuwse kloosters in Europa, die geheel of voor een groot deel archeologisch onderzocht zijn. De opgraving is in opdracht van het Limburgs Museum te Venlo uitgewerkt van 2012 tot en met 2023. Een samenvatting van de opgravingsresultaten is in 2021 verschenen in de reeks Nederlandse Archeologische Rapporten (Stoepker, H., 2021: Het Klooster van Susteren (714 – 1802). Het volledige rapport (de ‘basispublicatie’) is – met uitzondering van de bijlage ‘catalogus van de structuren’ – verschenen in 2023 (Stoepker, H. (red.), 2023: Sporen van Susteren). Dit rapport is zowel in zijn geheel als in hoofdstukken te downloaden.
Het vroegmiddeleeuwse klooster was klein en zal niet meer dan twintig tot dertig mensen gehuisvest hebben. Bij de opgraving werden de sporen gevonden van de woongebouwen van het klooster, van een grafveld en van de waterlopen waaraan het klooster gelegen was. Bij de woongebouwen hoorden waterputten, beerputten en ambachtelijke structuren, waaronder een klokkengieterij. In de 8e en 9e eeuw waren er twee woongebouwen, een van hout en een van steen. Ze lagen op een rij op de oever van een waterloop, gescheiden van de kerk door een grafveld met daarop een oratorium met een ronde plattegrond. Er zijn meer houten gebouwen geweest, maar deze zijn niet volledig teruggevonden en lagen deels buiten de opgraving. Na een verwoesting in het einde van de 9e eeuw, waarschijnlijk door een Vikingaanval, is het klooster beperkt herbouwd. Vanaf het midden van de 11e eeuw echter is er een geheel nieuwe structuur ontstaan, bestaande uit stenen gebouwen met een kloostergang rond een hof. Het grafveld was in gebruik van de 8e tot en met de late 11e eeuw. Skeletten zijn gevonden van mannen, vrouwen en kinderen. De meeste vondsten zijn in de waterlopen aangetroffen. De ontwikkeling van de kloosterplattegrond is geschetst in de publicatie uit 2021. De vondsten zijn uitvoerig beschreven in ‘Sporen van Susteren’ (2023) met in het bijzonder aandacht voor het aardewerk, het glas (vensterglas, drinkglas, kralen), het metaal en het dierlijk bot. Ook de analyse van het menselijk skeletmateriaal is hierin opgenomen, evenals een overzicht van de historische gegevens en het kerkgebouw.
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From 1991 to 1993, the former State Service for Archaeological Investigations of the Netherlands (ROB) carried out an excavation in the town of Susteren in the Dutch province of Limburg. The purpose of the excavation was to investigate the remains of a monastery founded in 714 by the Austrasian maior domus Pepin II and his wife Plectrude. It was donated by them to the Northumbrian missionary Willibrord to accommodate pilgrim brothers (fratres peregrini). Later the monastery would be populated by nuns and later still it would be converted into a convent of secular canonesses.
The Susteren excavation is one of the very few in Europe where a significant part of an early medieval monastic area has been excavated. It was concluded that there is no evidence for the presence of a church and a monastery in Susteren before 714. The oldest abbey church is believed to have been built on the site of the present-day church which was constructed in the second half of the 11th century.
In the 8th and 9th century, the site comprised from south to north four parallel zones, consisting of a (1) church, (2) a burial ground with a circular oratory, (3) a habitation area with many pits and at least two residential buildings (one in stone and one in wood), and (4) an artificial watercourse derived from a natural watercourse. At the east was a craft zone with kilns (probably for lime burning) and two bell casting pits.
It is known from historical sources that Vikings plundered the Meuse valley in 881-882. It is highly plausible that the Carolingian monastery was also hit by an attack by Norsemen, because the site was redeveloped in the early 10th century and a large amount of settlement waste was dumped in the watercourse. Many finds derived from the fills of the watercourses: pottery shards, glass beads, vessel and window glass, bones of slaughtered animals, objects made of metal, animal bone and wood and metal slag.
In the 11th century we see a new, artificial, watercourse and the emergence of a stone-built monastic complex around a courtyard which replaced the graveyard. In the following centuries, the complex was enlarged and the moat was twice replaced. The convent of secular canonesses has been dissolved in 1802 and shortly afterwards the buildings were demolished. Only the church remained.
Opportunities for publication did not arise until 2012. In this year, due to a grant from the province of Limburg, thirty specialists were commissioned by the Limburgs Museum (Venlo) to write reports mostly dedicated to the small finds. Due to the large number of finds, not all could be studied, and priority was given to finds from the Early and High Middle Ages.
Thanks to the support of the Dutch Cultural Heritage Agency (RCE) a summarising publication (in Dutch with an English summary) could appear in 2021 under the aegis of this agency: Stoepker, H., 2021: Het Klooster van Susteren (714 – 1802). Archeologisch onderzoek van een Karolingische abdij en een adellijk vrouwenstift, Amersfoort, (Nederlandse Archeologische Rapporten – NAR- 73). This ‘NAR’-report contains a description of the buildings and other structures, of the watercourses and the cemetery as well as a synthesis of all the discoveries.
In the 2021 ‘NAR’-report, the specialist reports had to be summarised. The 2023 publication (‘Sporen van Susteren’, 2023) however contains the unabridged specialist reports on the various material groups. All texts are in Dutch with an English summary. The text can be downloaded as a whole or in separate chapters.
The introductory chapters 1 to 9 describe, among others, the church building and the archaeological and historical context.
Chapters 10, 11 and 12 in Sporen van Susteren are devoted to the finds from the Iron Age and the Roman period. Chapters 13, 14, 15 and 16 describe the plant and fish remains and animal bones in the context of food supply. The pottery from the period before 1000 is discussed in chapter 17. Of the pottery finds dating after 1000 a selection was studied (chapter 18). A range of small finds are described in chapter 19 (ceramic objects), chapter 20 (clay pipes), chapter 21 (objects made animal bone, antler, etc.) and chapter 22 (wooden objects). They give a varied picture of the material culture of the monastery.
Objects made of metal are discussed in chapter 24. The fibulae worn by women form a special category amongst the metal finds. Metal slag (chapter 25) indicates that iron processing and bell casting occurred. Chapters 26 to 32 are devoted to glass finds. The most notable glass finds are without doubt the large 9th century beads (chapter 30), which indicate that in the 9th century there were women in the monastery who could afford to wear such jewellery. A small number of finds indicate that glass working occurred in the monastery (chapter 29). The origin of the raw materials has been studied by means of chemical analyses (chapter 31). Locally worked glass may include the window glass found in some Carolingian contexts, which may have once graced the windows of the abbey church and possibly also of the monastic buildings (chapter 27). Other glass mainly consists of small fragments of drinking glasses, particularly Carolingian funnel beakers (chapter 26). Glass from contexts dating to after 1000 has not been studied, except for the remains of 17th century luxury drinking glasses from a cesspit (chapter 32). These testify to the prosperity of the inhabitants of the chapter at the time.
The last chapter dedicated to finds (chapter 34) contains an analysis of a small selection of the building material. Finally, chapter 37 recalls the main conclusions of the previous chapters and provides a general conclusion about the material culture
Referensialiteit binne die onderrigkonteks van Afrikaanse literatuur as tweedetaal
No full textEnglish: The root of this study lies in die changing socio-political situation together with the changes in the literary teaching arena. All texts should be approached from within a specific context. Only if literature is studied from such an angle, it becomes a medium through which the realisation of political and social spheres, as well as cultural differences transpire.
The text becomes an aid through which contextualised cultural cross references can be made. Uterature should be seen as a communicative network in which tuition should be functional and interactive in all relevant fields of use. For such an approach one needs a specific referencial framework whereby the pupil as reader can interpret any text. Words supply the reader with frames of reference through which he/she can understand and describe the world behind the text.
The emphasis is on a specific reader namely the second language pupil, and a distinct accentual transfer is perceptible form: textual studies to textual experience
This ratio between text, reader and reality is in fact a pragmatic relation. Within such a pragmatic system the stipulation of any linguistic expression in a specific context is of the utmost importance. This presumes the investigation of referencialities in the text, as well as the users thereof. In the literary text there is talk of problemsolving without a definite frame of absolute reference. Defining and determining underlying codes as the basis of interpretation and the indication of meaning, becomes a necessary qualification within a new model for the teaching of Afrikaans as second language. The essence of pragmatics lies in the following classification:
- the study of speech acts;
- the study of what is suggested or implied, in comparison to what is literaly
said; and
- the study of diectic expression.
The focus in this study falls on referenciality. Referenciality becomes the
foundation on which pragmatic systems are built, and pragmatics in turn becomes the foundation on which interpretation is built. Interpretation as consequence of pragmatic and referencial systems forms the basis of literary communication that is the central idea of this study.
Literature implies a relationship between language and man. Therefore, literature calls for an emotional and intellectual independence op each and every reader. The reader has to take an active part in the reading process. The study of literary pragmatics is to a great extend a process which demands referenciality.
An important diversion made in this study is that the reader's line of thought is
channelised by interpretation, and that literature is seen from whithin a
hermeneutic perspective in which the relation between object and subject, text and reader, plays a primary roll.Afrikaans: Hierdie studie vind sy grondslag in die veranderde sosio-politieke situasie in Suid-Afrika en die gepaardgaande veranderinge op die terrein van literatuuronderrig. Alle tekste behoort binne konteks benader te word. Vanuit so 'n invalshoek word literatuur 'n medium waardeur bewuswording plaasvind van politieke, sosiale werklikhede sowel as kulturele verskeidenheid.
Die teks word 'n hulpmiddel waardeur kontekstueel-kulturele kruisverwysings
gemaak kan word. Uteratuur behoort gesien te word as 'n kommunikatiewe
netwerk waarin onderrig funksioneel en interaktief moet plaasvind in relevante gebruiksituasies. Vir so 'n benadering is 'n bepaalde verwysingsraamwerk nodig waarvolgens leerlinge as lesers tekste kan interpreteer. Woorde voorsien die leser van verwysingsraamwerke waarmee die wêreld van die roman begryp en beskryf kan word.
Die fokus val op 'n spesifieke leser naamlik die tweedetaalleerling, en 'n duidelike klemverskuiwing is waarneembaar van: teksbestudering na tekservaring
Hierdie verband tussen teks, leser en werklikheid is in feite 'n pragmatiese
verhouding. In so 'n pragmatiese sisteem val daar sterk klem op betekenisbepaling van linguistiese uitdrukkings binne spesifieke kontekste. Dit veronderstel die ondersoek na verwysings in die teks én die gebruikers daarvan. In die literêre werk is daar sprake van die oplos van onduidelikhede sonder 'n definitiewe raam van verwysing. Die bepaling van onderliggende kodes as die basis van interpretasie en betekenisaanduiding word 'n vereiste binne 'n nuwe model vir die onderrig van Afrikaans as tweededetaal. Die kern van die pragmatiek lê dus in die volgende indeling:
- die ondersoek na taalhandelinge;
- die ondersoek na wat gesuggereer word of geïmpliseer word, teenoor wat
letterlik gesê word; en
- die ondersoek na deiktiese uitdrukkings.
Die fokus in hierdie studie val op referensialiteit. Referensialiteit word die grondslag waarop pragmatiese sisteme gebou word, en pragmatiek word op sy beurt weer die grondslag waarop interpretasie gebou word. Interpretasie as uitvloesel van pragmatiese en referensiële sisteme is die basis vir literêre
kommunikasie wat die kerngedagte van hierdie studie vorm.
Literatuur is 'n verhouding tussen taal en mens. Uteratuur verg daarom 'n
emosionele en intellektuele onafhanklikheid van elke leser. Die leser moet aktief deelneem aan die leesproses. Die bestudering van literêre pragmatiek is in 'n groot mate 'n proses wat verwysing noodsaak. 'n Belangrike afleiding wat uit hierdie studie gemaak is, is dat die totale gedagtegang van die mens gelei word deur die vertolkingskunde, en dat daar na die literatuur gekyk moet word deur 'n hermeneutiese bril waarin die verhouding tussen objek en subjek, teks en leser 'n primêre rol speel
Probing water motion in heterogenous systems : a multi-parameter NMR approach
No full textIn this Thesis a practical approach is presented to study water mobility in heterogeneous systems by a number of novel NMR sequences. The major part of this Thesis describes how the reliability of diffusion measurements can be improved using some of the novel NMR sequences. The reliability of the data can be further enhanced by combining different NMR characteristics in a single fit routine. In addition, a fast NMR sequence for flow measurements is shown. A wide variety of samples is used to demonstrate how the NMR sequences and the subsequent analysis work.Throughout this Thesis the term heterogeneous system is used whenever a sample contains different physical or chemical environments or compositions, each of which influence the NMR signal in a distinguishable way. One of the effects of such a heterogeneous system is the variation of the magnetic susceptibility within the sample causing so-called in situ magnetic field gradients. These gradients lower the NMR signal amplitude and may cause a substantial deviation of the real diffusion constant from the one measured by NMR using pulsed field gradient spin echo or stimulated echo sequences. In the second half of Chapter 2 an improved version of the PFG multiple spin echo sequence is introduced which minimises the degrading effects of in situ field gradients. While using additional r.f. pulses between the pulsed field gradients to reach the desired reliability no compromises with regard to flexibility were necessary.This flexibility is important to study the change of the apparent diffusion constant with the echo time. This phenomenon, superficially appearing as an artefact, arises because compartments, as for example a vacuole, not only have a characteristic diffusion constant but also a T 2 which may significantly differ from other T 2 's in the sample. In Chapter 3 it is shown how a T 2 difference can be used to separate diffusion constants (D) even if these have a similar magnitude. Using Diffusion Analysis by Relaxation Time Separation the diffusion constant for water in the vacuole, the cytoplasm and the extra cellular space, respectively, can be distinguished in apple parenchyma tissue. In the second half of Chapter 3 a fast implementation of DARTS PFG NMR is presented which is combined with NMR imaging. Here, spatially localised T 2 measurements are preceded by pulsed field gradients for diffusion weighting. In this way the diffusion constant and fractional amplitude of cerebral spinal fluid (CSF) and white and grey matter in cat brain can be measured. The validity of these measurements are supported by Monte Carlo simulations of computer generated 2D data sets.Chapter 4 deals primarily with improving the DARTS technique without imaging (DARTS PFG MSE Carr Purcell Meiboom Gill) and determining the best resolution (for discriminating diffusion constants) which can be obtained, using Monte Carlo simulations on 2D data sets. The use of the 2D fitting routine is extensively studied. Furthermore, existing theoretical models are mutually compared and confronted with the results obtained by the PFG MSE CPMG sequence for different samples. Four heterogeneous samples with different complexity are studied, i.e.:a- A sample consisting of two tubes with different fluids, between which exchange can be ignored.b- Whole Blood where diffusive exchange between the red blood cells (RBC's) and the plasma causes the apparent D of the RBC's to increase with increasing observation time.c-Apple parenchyma tissue where the membrane between the vacuole and the cytoplasm (the tonoplast) is shown to severely restrict, but not prevent, diffusive exchange between these compartments.d- A column with Sephadex beads (porous beads) where flow is introduced. The effect of this flow on the water displacement outside and inside the beads is described. Experiments demonstrated exchange between the flowing fraction and the stationary water in the beads.In all instances it is profitable to combine the diffusion and T 2 measurements and analyse the resulting 2D data set as a whole. In this way an intuitive understanding is obtained of diffusion in complex systems measured by NMR. By using the T 2 as a label, the resolving power of NMR to distinguish diffusion constants is greatly improved and a difference between the diffusion constants as small as 30 % is demonstrated to be resolvable. None of the presented theories can be used to quantitatively describe the data.In Chapter 5 the subject of flow in heterogeneous systems is studied in further detail. In the first half of this Chapter novel flow measurements in and around the buccal cavity of a Carp are described. These measurements are performed on a standard medical imager without special, fast NMR sequences. The described data can therefore only be used in a qualitative manner. In the second half the line scan flow measurement is introduced. A temporal resolution of 16 ms can be obtained with this sequence allowing accurate, real time flow measurements. The combination of this line scan sequence with displacement imaging yields NMR images which picture the distribution of flow velocities over a line. Demonstrations of displacement imaging are performed in a tube with glass beads and in a pipe with a glass bead filter. The presented data can be used quantitatively.The diffusion and flow measurements described in the Thesis all employ pulsed field gradients to encode for motion. Despite the obvious similarities between the measurements, the optimisation of the NMR sequences results in sequences which can be rather distinct. By careful tuning of the NMR sequences the range of displacements which can thus be measured lies between 5 μm and about 5 cm. This range and the fact that small differences in flow velocities and diffusion constants can be resolved, if necessary using other NMR characteristics, makes NMR a powerful tool to study water mobility in heterogeneous systems
Van wonen tot marketing : een sociaal-filosofische analyse van het moderne behoefte-georienteerd handelen
No full textIn modern western society the broadened concept of marketing covers a considerable part of the field of action. An example is the overlap of marketing with the domain of living. Here we find a development of society into a system, appearing as a multi-coloured totality of relations between organizations and consumers.From this point of view I have tried to reconstruct the social philosophical foundations of modern marketing by means of concepts derived from Jürgen Habermas's theory of human action, in particular the concept of reproduction of personal identity. This has lead to the thesis, that any model of a marketingoriented society, in its broadest sense, has a relatively weak capacity as regards problemsolving, when compared with the model of a society, in which the marketing-function is bounded to the economic sub-system and controlled through a 'public domain'.</p
Time Domain Measurements and High Resolution Spectroscopy are Powerful Nuclear Magnetic Resonance Approaches Suitable to Evaluate the In Vitro Digestion of Protein-rich Food Products
No full textThere are many challenges and problems in food science and magnetic resonance methods may be used to provide answers and deepen both fundamental and practical knowledge. This book presents the latest innovations in magnetic resonance and in particular new applications to understanding the functionality of foods, their processing and stability and their impact on health, perception and behaviour. Drawing on expert knowledge from academia and industry, coverage includes structure and function, emphasizing respectively applications of spectroscopy/relaxometry and imaging/diffusometry; high resolution NMR spectroscopy as applied to quality and safety and foodomics; and, for the first time, dedicated information on perception and behaviour demonstrating the progress that has been made in applications of fMRI in this field. Providing a resource for any newcomer to the field or for those in need of a rapid update of the latest developments, this title will be an indispensable reference tool
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