No / A proxy climate record from a raised bog in County Fermanagh, Northern Ireland, is presented. The record spans the interval between 2850 cal. yr BC and cal. yr AD 1000 and chronological control is achieved through the use of tephrochronology and 14C dating, including a wiggle-match on one section of the record. Palaeoclimatic inferences are based on a combination of a testate amoebae-derived water table reconstruction, peat humification and plant macrofossil analyses. This multiproxy approach enables proxy-specific effects to be identified. Major wet shifts are registered in the proxies at ca. 1510 cal. yr BC, 750 cal. yr BC and cal. yr AD 470. Smaller magnitude shifts to wetter conditions are also recorded at ca. 380 cal. yr BC, 150 cal. yr BC, cal. yr AD 180, and cal. yr AD 690. It is hypothesised that the wet shifts are not merely local events as they appear to be linked to wider climate deteriorations in northwest Europe. Harmonic analysis of the proxies illustrates statistically significant periodicities of 580, 423-373, 307 and 265 years that may be related to wider Holocene climate cycles. This paper illustrates how the timing of climate changes registered in peat profiles records can be precisely constrained using tephrochronology to examine possible climatic responses to solar forcing. Relying on interpolated chronologies with considerable dating uncertainty must be avoided if the climatic responses to forcing mechanisms are to be fully understood.

No / We have studied the performance of multidimensional signaling techniques using wavelets based modulation within an orthogonally multiplexed communication system. The discrete wavelets transform and wavelet packet modulation techniques have been studied using Daubechies 2 and 8, Biothogonal1.5 and 3.1 and reverse Biorthognal 1.5 and 3.1 wavelets in the presence of Rayleigh multipath fading channels with AWGN. Results showed that DWT based systems outperform WPM systems both in terms of BER vs. SNR performance as well as processing. The performances of two different equalizations techniques, namely zero forcing (ZF) and minimum mean square error (MMSE), were also compared using DWT. When the channel is modeled using Rayleigh multipath fading, AWGN and ISI both techniques yield similar performance.

É bem conhecido o fato de que todo grupo compacto tem sequências não triviais convergentes. A existência de grupos enumeravelmente compactos sem sequências não triviais convergentes, foi provada usando axiomas adicionais à axiomática usual ZFC: A. Hajnal e I. Juhász sob CH, E. K. van Douwen sob MA, A. H. Tomita sob MA(sigma-centrada) e R.E. Madariaga-Garcia e A. H. Tomita usando ultrafiltros seletivos. Neste trabalho, estudaremos algumas construções recentes relacionadas com as citadas acima, usando o Axioma de Martin, ultrafiltros seletivos e forcing. Essas construções estão relacionadas com algumas questões indicadas por A.D. Wallace, E. van Douwen, M. Tkachenko, D. Dikranjan e D. Shakhmatov / It is well known that every compact group has non-trivial convergent sequences. The existence of countably compact groups without non-trivial convergent sequences was proved using extra set-theoretical assumptions: A. Hajnal and I. Juhasz under CH, E. K. van Douwen under MA, A.H.Tomita under MA(centered) and R.E.Madariaga-Garcia and A.H. Tomita using a selective ultrafilter. I n this work, we study some recent constructions related to the ones given above using Martin Axiom, selective ultrafilters and forcing, related to questions raised by A.D. Wallace, E. van Douwen, M. Tkacenko, D. Dikranjan and D. Shakhmatov.

É bem conhecido o fato de que todo grupo compacto tem sequências não triviais convergentes. A existência de grupos enumeravelmente compactos sem sequências não triviais convergentes, foi provada usando axiomas adicionais à axiomática usual ZFC: A. Hajnal e I. Juhász sob CH, E. K. van Douwen sob MA, A. H. Tomita sob MA(sigma-centrada) e R.E. Madariaga-Garcia e A. H. Tomita usando ultrafiltros seletivos. Neste trabalho, estudaremos algumas construções recentes relacionadas com as citadas acima, usando o Axioma de Martin, ultrafiltros seletivos e forcing. Essas construções estão relacionadas com algumas questões indicadas por A.D. Wallace, E. van Douwen, M. Tkachenko, D. Dikranjan e D. Shakhmatov / It is well known that every compact group has non-trivial convergent sequences. The existence of countably compact groups without non-trivial convergent sequences was proved using extra set-theoretical assumptions: A. Hajnal and I. Juhasz under CH, E. K. van Douwen under MA, A.H.Tomita under MA(centered) and R.E.Madariaga-Garcia and A.H. Tomita using a selective ultrafilter. I n this work, we study some recent constructions related to the ones given above using Martin Axiom, selective ultrafilters and forcing, related to questions raised by A.D. Wallace, E. van Douwen, M. Tkacenko, D. Dikranjan and D. Shakhmatov.

La phénologie du débourrement est un caractère majeur d’adaptation des arbres à leurenvironnement en milieu tempéré. Notre objectif a été de caractériser les contraintes biotiques (oïdium) etabiotiques (températures hivernales et printanières / gels tardifs) s’exerçant sur le débourrement afind’expliquer les patrons de variation phénologique intra et inter populationnelle observés chez le chêne(Quercus petraea) le long d’un gradient altitudinal. Nous avons utilisé une approche combinantobservations in situ, expérimentation, et modélisation. Nous avons mis en évidence que l’évitement desgels tardifs printaniers est un caractère adaptatif majeur le long du gradient altitudinal. La tardiveté dudébourrement pourrait être due à des besoins plus importants en température de forcing. Par ailleurs, lechampignon n’est pas adapté localement à la phénologie de son hôte et les individus et les populationssont alors inégalement exposés à la maladie. En montant en altitude, les chênes sont de plus en plusexposés au champignon, mais les facteurs environnementaux sont défavorables à une plus forte infection.A basse altitude, l’oïdium et les gels tardifs favorisent des phénotypes phénologiques opposés(respectivement précoces vs. tardifs) ; la combinaison des deux contraintes pourrait donc contribuer aumaintien de la forte diversité phénologique observée. D’autre part, nous avons observé que l’infection parl’oïdium engendre une augmentation du polycyclisme chez les semis de chêne au cours de la saison decroissance, ce qui les rend moins résistants aux gels hivernaux. Nous montrons qu’il est important que lesmodèles phénologiques à visée prédictive intègrent la phase de chilling aboutissant à la levée dedormance. Le manque de chilling ne semble pas encore un facteur limitant, mais la tendance actuelle à undébourrement de plus en plus précoce sera probablement freinée voire inversée au milieu du siècle enbasse altitude, dans la marge sud de distribution de Q. petraea. / Budburst phenology is a major adaptive trait of trees to the environment in temperateclimate. Our aim was to characterize the biotic (powdery mildew) and abiotic (winter and springtemperatures / spring frost) constraints acting on budburst in view to explain the patterns of intra and interpopulations’ phenological variation observed in sessile oak (Quercus petraea) along an elevation gradient.We based our approach on in situ monitoring, experimentation and modeling. Our results highlight that theavoidance of late spring frosts is a major adaptive trait along the elevation gradient. The lateness inbudburst might be due to higher requirements in forcing temperatures. Otherwise, the fungus is not locallyadapted to its host phenology so oak individuals and populations are unequally exposed to the disease.With increasing elevation, oaks are more and more exposed to the fungus, but the environmental factorsare unfavorable to higher infection. At low elevation, powdery mildew and late spring frosts favor oppositephonological phenotypes (early-flushing vs. late-flushing trees, respectively); the combination of the twopressures may thus contribute to the maintenance of the observed high phenological diversity. We alsoshowed that powdery mildew infection induced an increased polycyclism during the growing season in oakseedlings, which made them less resistant to winter frosts. Predictive phenological models will have toinclude the chilling phase which conditions dormancy breaking. Although the lack of chilling is not yet alimiting factor, the current trend in increasingly advanced budburst will certainly be slowed or even reversedin the middle of the century at low elevation, in the southern margin of the distribution area of Q. petraea.

Neste trabalho estudamos o valor mínimo da entropia topológica para uma classe de aplicações isotópicas à identidade em superfícies orientáveis (sem bordo, não necessariamente compactas e possivelmente de tipo finito) sob um ponto de vista estritamente topológico. Este estudo é feito utilizando a nova teoria de forcing para trajetórias transversas de Le Calvez e Tal que se baseia na teoria de Brouwer equivariante, em que é possível folhear superfícies com folhas relacionadas a teoria de Brouwer no plano. O principal resultado deste trabalho é uma melhora na estimativa da entropia topológica obtida por Le Calvez e Tal em um recente trabalho em que os autores buscam ferraduras topológicas em superfícies orientáveis utilizando ferramentas similares apresentadas aqui. Uma aplicação deste resultado acima é feita utilizando aplicações em S^2 que possuam um ponto fixo cuja trajetória pela isotopia deste ponto não seja homotópica a um múltiplo de um loop simples. Com estas hipóteses, melhoramos a estimativa dada por Le Calvez e Tal em que é encontrado um valor mínimo estritamente positivo para a entropia topológica desta aplicação. / In this work we study the minimum topological entropy value for one class of maps isotopics to the identity in oriented surfaces (without border, not necessary compacts and possibly of finite type) under the point of view strictly topological. This study is done using the new forcing theory to transverse trajectories from Le Calvez and Tal which it is based to equivariant Brouwer Theory, on what it is possible to leaf surfaces with leaves related to plane Brouwer theory. The main result in this work is a improvement in the estimates from the topological entropy obtained by Le Calvez and Tal in one recent work where the authors seek topological horseshoes on oriented surfaces using tools very similar to that are shown here. One application of the above result is done using maps on S^2 that have a fixed point whose trajectory by the isotopy of this point do not be homotopic to a multiple of a simple loop. With these hypotheses, we improve the estimates given by Le Calvez and Tal on what is found a strictly positive minimum value to the topological entropy of this map.

Prouver l’équivalence de programmes écrits dans un langage fonctionnel avec références est un problème notoirement difficile. L’objectif de cette thèse est de proposer un système logique dans lequel de telles preuves peuvent être formalisées, et dans certains cas inférées automatiquement. Dans la première partie, une méthode générique d’extension de la théorie des types dépendants est proposée, basée sur une interprétation du forcing vu comme une traduction de préfaisceaux de la théorie des types. Cette extension dote la théorie des types de constructions récursives gardées, qui sont utilisées ensuite pour raisonner sur les références d’ordre supérieure. Dans une deuxième partie, nous définissons une sémantique des jeux nominale opérationnelle pour un langage avec références d’ordre supérieur. Elle marie la structure catégorique de la sémantique des jeux avec une représentation sous forme de traces de la dénotation des programmes, qui se calcule de manière opérationnelle et dispose donc de bonnes propriétés de modularité. Cette sémantique nous permet ensuite de prouver la complétude de relations logiques à la Kripke définit de manière directe, via l’utilisation de types récursifs gardés, sans utilisation de la biorthogonalité. Une telle définition directe nécessite l’utilisation de mondes omniscient et un contrôle fin des locations divulguées. Finalement, nous introduisons une logique temporelle qui donne un cadre pour définir ces relations logiques à la Kripke. Nous ramenons alors le problème de l’équivalence contextuelle à la satisfiabilité d’une formule de cette logique générée automatique, c’est à dire à l’existence d’un monde validant cette formule. Sous certaines conditions, cette satisfiabilité peut être décidée via l’utilisation d’un solveur SMT. La complétude de notre méthode devrait permettre d’obtenir des résultats de décidabilité pour l’équivalence contextuelle de certains fragment du langage considéré, en fournissant un algorithme pour construire de tels mondes. / Proving program equivalence for a functional language with references is a notoriously difficult problem. The goal of this thesis is to propose a logical system in which such proofs can be formalized, and in some cases inferred automatically. In the first part, a generic extension method of dependent type theory is proposed, based on a forcing interpretation seen as a presheaf translation of type theory. This extension equips type theory with guarded recursive constructions, which are subsequently used to reason on higher-order references. In the second part, we define a nominal game semantics for a language with higher-order references. It marries the categorical structure of game semantics with a trace representation of denotations of programs, which can be computed operationally and thus have good modularity properties. Using this semantics, we can prove the completeness of Kripke logical relations defined in a direct way, using guarded recursive types, without using biorthogonality. Such a direct definition requires omniscient worlds and a fine control of disclosed locations. Finally, we introduce a temporal logic which gives a framework to define these Kripke logical relations. The problem of contextual equivalence is then reduced to the satisfiability of an automatically generated formula defined in this logic, i.e. to the existence of a world validating this formula. Under some conditions, this satisfiability can be decided using a SMT solver. Completeness of our methods opens the possibility of getting decidability results of contextual equivalence for some fragments of the language, by giving an algorithm to build such worlds.

No description available.

[pt] Modulação Espacial com Pré-codificação Generalizada (Generalized Precoding Aided Spatial Modulation, GPSM) é uma estratégia de comunicação em sistemas MIMO em que o transmissor codifica a informação em duas entidades: a transmissão paralela de símbolos pertencentes à constelação de uma modulação digital, e os índices das posições do vetor de informação que transportam estes símbolos, denominada information bearing positions (IBP), enquanto as demais posições transportam zero. Além disto, o transmissor, previamente à transmissão dos dados pré-codifica o vetor de informação, possibilitando a redução da complexidade do nó receptor. Entre as vantagens desta estratégia destaca-se a concentração da energia transmitida apenas nas posições do vetor de informação que efetivamente contém símbolos, favorecendo o desempenho do sistema. Esta tese considera um sistema MIMO multiusuário (MU-MIMO) que emprega GPSM no enlace direto. O modelo de sinais desenvolvido para descrever este sistema evidencia a influência das matrizes que codificam as IBP no desempenho do sistema. Com base neste modelo, o sistema GPSM MU-MIMO é apresentado para três pré-codificadores lineares: Zero-Forcing, Block Diagonalization e Block Diagonalization de Duas Fases. Para cada um destes pré-codificadores são propostas estratégias de seleção das matrizes de codificação IBP, de acordo com a matriz que descreve o canal MU-MIMO corrente, a serem empregadas pelo transmissor visando melhorar o desempenho de detecção do sistema. As curvas de desempenho de detecção são comparadas a limitantes semianalíticos desenvolvidos. Por fim, considera-se o cenário em que existem mais antenas disponíveis na estação rádio-base e/ou nos usuários do que o número de cadeias de radiofrequência que os equipam. Esta tese apresenta estratégias ótimas e de complexidade reduzida de se explorar o uso das antenas mais favoráveis à transmissão e/ou recepção, em adição à escolha das matrizes de codificação IBP, com o objetivo de prover melhorias ao desempenho do sistema. / [en] Generalized Pre-coding Aided Spatial Modulation (GPSM) is a MIMO system communication strategy in which the transmitter encodes the information in two entities: the parallel transmission of symbols belonging to a digital modulation constellation, and the choice of the indices of the information vector elements that carries the informaiton symbols, denoted information bearing positions (IBP), while the remaing positions are set to zero. Besides, the transmitter precodes, prior to transmission, the information vector, which lets the receiver node benefit from complexity reduction. Among the advantages of this strategies, the concentration of the transmitted energy only on the information vector positions that transports modulated symbols, resulting in system performance improvement. This thesis considers a multiuser MIMO (MU-MIMO) that employs GPSM in the donwlink transmission. The presented signal model to describe this system evidences the influence of the IBP coding matrices on the system performance. Based on this model, GPSM MU-MIMO system is presented considering three linear precoders: Zero-Forcing, Block Diagonalization and Double-Stage Block Diagonalization. For each precoder, strategies to select the IBP encoding matrix, acording to the matrix that describes the current MU-MIMO channel, is proposed. These matrices are to be employed by the user, aiming at system detection performance improvement. Detection performance curves are compared to semianalytic lower bounds. Finally, a scenario in which that are a number of available antennas at the BS and/or at the users that exceed the number of radiofrequency chains. this thesis porposes optimal and reduced complexity strategies that exploit the use of the most favorable antennas for transmission and/or reception, in addition to the choice of the IBP enconding matrices, aiming at system performance improvement.

Thesis (DPhilAgric)--Stellenbosch University, 2002 / ENGLISH ABSTRACT: South Africa is one of the worlds leading producers of chicory (Cichorium intybus L.). Most of the chicory produced is used locally for the production of instant coffee. Witloof chicory, or Belgian endive, however, is a vegetable crop grown from the root of Cichorium intybus L. var. foliosum. This is done by placing the mature taproot in a controlled, dark environment after vernalization and supplying it with water and nutrients by means of hydroponics. Witloof chicory is new to the South African market and is only produced on a limited scale. Nonetheless, seeing that chicory is successfully grown on a large scale for the coffee industry it seemed reasonable to investigate the cultivation of this essentially unknown vegetable locally. The focus of this study was on the evaluation of new witloof production techniques during the second stage of witloof (chicon) cultivation, also called 'forcing'. To this end, locally grown witloof chicory roots were used in all trials. In order to establish the effects of several irrigation methods on lateral root formation and chicon quality, witloof chicory roots were forced using the conventional means of hydroponic irrigation as well as ebb-and-flood and aeroponic irrigation. Lateral root formation was significantly increased when either ebb-and-flood or aeroponic irrigation was applied compared to that obtained with the conventional method. This increase in lateral root formation was, however, to the detriment of chicon quality (QI), possibly as a result of competition for limited carbohydrate reserves. In an attempt to optimize the aeroponic irrigation method, roots were forced in non-vertical positions. Placing roots horizontally during forcing resulted in a significantly lower marketable chicon yield than where roots were placed vertically. The loss in yield was probably brought about by an increased fallout percentage rather than by a decrease in chicon production. Considering the pivotal role that sucrose plays in the development of the chicory head, sucrose was applied exogenously to the root before and/or during forcing. Dry matter chicon yield was negatively effected by exogenously applied sucrose. This could have been due to an increased incidence of fungal or bacterial infections or causative of roots absorbing less water resulting in the inability of the plant to utilize the applied sucrose during chicon development. Fungal and bacterial infections are known to have a detrimental effect on witloof chicory production. An environmentally friendly product for disease control, 'Desogerme SP®', was used to contain or reduce infection. Irrigation of roots with 'Desogerme SP®' containing nutrient solution increased chicon yield by 31%. From this study it became clear that some new production techniques applied had the potential of improving lateral root formation or quality during growth. However, the conventional way of irrigation remains the most effective compared to the other techniques applied, but could possibly be improved to some extent by incorporating 'Desogerme SP®' either as a pretreatment or in the nutrient solution. A breakthrough was made with the development of the quality index (QI). The ongoing limitation of statistically analyzing quality data of chicons sorted according to quality-classes was overcome by making use of this tool. Despite the fact that the index was developed specifically for use on witloof, it is has the potential of being applied to quality data of a wide variety of crops. / AFRIKAANSE OPSOMMING: Suid Afrika is een van die wêreld se grootste produsente van sigorei (Cichorium intybus L.). Die meeste plaaslik geproduseerde sigorei word vir die produksie van kitskoffie benut. Witloofsigorei, of Belgiese "endive", is egter 'n groentegewas wat vanaf die wortel van Cichorium intybus L. var. foliosum gekweek word. Dit word gedoen deur die volwasse penwortel na vemalisasie in 'n gekontroleerde, donker omgewing te plaas en met 'n hidrokultuurstelsel van water en voedingselemente te voorsien. Witloof is nuut op die Suid Afrikanse mark en word net op beperkte skaal geproduseer. Aangesien sigorei suksesvolop groot skaal vir die koffieindustrie geproduseer word, blyk dit logies om die moontlikhede te ondersoek om hierdie relatief onbekende groente plaaslik te kweek. Die fokus van hierdie studie was gerig op die evaluasie van nuwe produksietegnieke gedurende die tweede fase van witloofproduksie, wat ook as forsering bekend is. Plaaslik gekweekte witloof sigoreiwortels is vir alle eksperimente gebruik. Die invloed van 'n verskeidenheid besproeiingsmetodes is op sywortelproduksie en witloof krop-kwaliteit ondersoek. Witloofwortels is geforseer deur van 'n konvensionele hidrokultuur-stelsel gebruik te maak wat met 'n ebb-en-vloed en 'n lugsproei sisteem vergelyk is. Sywortel-produksie was betekenisvol hoër waar ebb-en-vloed of lugsproei sisteme toegepas is. Hierdie verbetering in sywortel-ontwikkeling was egter tot nadeel van krop-kwaliteit, vermoedelik as gevolg van die allokasie van koolhidrate na sywortels, eerder as na die groeipunt. In 'n poging om die lugsproei besproeiingsmetode te verbeter en om swamsiektes te verminder, is wortels in nie-vertikale posisies geforseer. Wortels wat gedurende forsering horisontaal ingetafel was, het 'n betekenisvol laer opbrengs van bemarkbare kroppe getoon as wortels wat vertikaal geplaas was. Die verlies aan opbrengs kon toegeskryf word aan 'n verhoging van afval, aangesien geen betekenisvolle afname in vars krop-gewig gevind is nie. Aangesien sukrose 'n belangrike rol in die ontwikkeling van die witloofkrop speel, is sukrose voor en tydens forsering aan die wortels toegedien. Droë materiaal krop-opbrengs is negatief deur die toediening van sukrose beïnvloed. Dit kon moontlik as gevolg van 'n verhoogde voorkoms van swam- of bakteriese infeksies gewees het of 'n aanduiding wees dat behandelde wortels minder water geabsorbeer het en die toegediende sukrose nie kon gebruik gedurende krop-ontwikkeling me. Swam- en bakteriese infeksies is bekend vir hul negatiewe uitwerking op witloofproduksie. 'n Omgewingsvriendelike middel, 'Desogerme SP®' is gebruik om siektes te beheer ofte verminder. Wortels wat met 'n 'Desogerme SP®' bevattende voedingsoplossing besproei is, het 'n 31% verhoging in krop-opbrengs getoon. Uit data wat gedurende hierdie studie ingesamel is, blyk dit duidelik dat sommige van die nuwe produksietegnieke wel die potensiaal het om sekere planteienskappe te verbeter. In geheel gesien bly die konvensionele metode van besproeiing die mees effektiewe, wanneer dit vergelyk word met die ander wat getoets is. Die konvensionele metode kan moontlik verbeter word as 'Desogerme SP®' as 'n vooraf-behandeling of as deel van die voedingsoplossing geïnkorporeer word. 'n Deurbraak is met die ontwikkeling van 'n kwaliteitsindeks (QI) gemaak. Ernstige beperkings word met statistiese ontledings van kwaliteitsdata ervaar waar kroppe volgens kwaliteitskiasse gesorteer word. Hierdie probleme is met behulp van die QI oorkom. Ongeag die feit dat die indeks spesifiek vir gebruik by witloof ontwikkel is, het dit die potensiaal om toepassing te vind by 'n wye reeks landboukundige produkte.