• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1257
  • 916
  • 329
  • 323
  • 143
  • 52
  • 43
  • 35
  • 26
  • 26
  • 26
  • 26
  • 26
  • 26
  • 24
  • Tagged with
  • 3790
  • 720
  • 400
  • 316
  • 247
  • 237
  • 235
  • 233
  • 201
  • 191
  • 161
  • 160
  • 145
  • 136
  • 135
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
271

Large-scale nutrient pattern in the Gulf of Bothnia with the hydrodynamic of its loads

Salawu, Lukman January 2006 (has links)
Eutrophication, which is the most important degradation in water bodies, has been traced to the imposed loading of nutrients. Of interest is the fact that the process is often accompanied with undesirable effects, one of which is primarily the increased algae production at the surface and accumulation of biomass at the bottom and the secondary responses, which include a., change in species composition b. change in the biogeochemical cycle c. shift in the seasonal pattern and magnitude variability. The biogeochemical cycle in response to hydrodynamic alterations may occur internally; however external loading often fosters the process over large spatial scales. In the quest of validating the above statement, we hypothesized that there is no difference in the mean concentration of nutrients in the Gulf of Bothnia from the overall mean concentration. The analysis was done with a probability mapping method, in which all stations were grouped into a lattice. The cells are constructed using a grid system, i.e. x and y axis (longitude and latitude). Basically the method statistically tested for variables deviating from the over mean concentration. The variables analyzed are DIN, DSi, DIP and DIN: DSi. Results of the analysis showed significant spatial variations in the nutrient distribution in the Gulf of Bothnia; such differences were observed in the coastal to the deep zones of the Gulf.
272

Characterization of the Bovine Cathelicidin Gene Family

Flores, Erin Gillenwaters 2011 August 1900 (has links)
Cathelicidins (CATHLs) are small, cationic antimicrobial peptides that establish an early innate immune defense against infections in mammals. Beyond their wide spectrum of antimicrobial activity, these peptides play important roles in wound repair, chemotactic activity, and apoptosis. Thus, comprehensive characterizing of bovine CATHLs could potentially identify underlying inherited differences in innate immunity and disease resistance in cattle. The purpose of the present study was to verify the placement of the CATHL cluster at the distal end of bovine chromosome 22 (BTA22), identify any single nucleotide polymorphisms (SNPs) and insertion-deletion (indel) polymorphisms within the gene family, explore copy number variation, and investigate the functional impact any of these variants may have in overall bovine innate immunity. A framework radiation hybrid map was constructed with 7 markers screened against the bovine 12,000 rad whole genome RH (12K WG-RH) panel, which when compared to the current genome assembly (Btau_4.0) confirmed current gene order. Comparative sequence analysis for 10 domestic cattle breeds representing both Bos taurus taurus and Bos taurus indicus revealed 60 SNPs, 7 of which were nonsynonymous, and 5 indel mutations. Data from array comparative genomic hybridization (aCGH) between four Angus and four Nelore animals showed a 2-fold increase in copy number of the CATHL4 locus, which was verified by quantitative PCR (qPCR) of genomic DNA. Nelore animals showed an approximate 2-fold increase in the CATHL4 gene. Subsequently, the expression of CATHL4 in Nelore neutrophils exhibited a range of 2- to 5-fold increases in CATHL4 gene expression. Finally, a colorimetric bactericidal assay was performed on the neutrophils of the same Angus and Nelore animals previously genotyped for copy number variations (CNVs). After in vitro challenges to Staphylococcus aureus, Salmonella typhimurium, Mannheimia haemolytica, and Pasteurella multocida, the killing capacity of Nelore neutrophils was approximately 20 percent greater than Angus neutrophils for M. haemolytica and 10 percent greater for P. multocida. Characterization of this antimicrobial gene family is central to developing a firm understanding regarding the effects CATHL variation has with respect to bovine innate immunity.
273

Intercomparaison de trois modèles dynamiques canadiens de prévision numérique saisonnière du climat

Yazidi, Hatem January 2006 (has links) (PDF)
Le principal objectif de ce mémoire consiste en l'évaluation de trois modèles dynamiques canadiens de prévision numérique saisonnière du climat. Ayant conscience de l'influence de l'océan sur la qualité des prévisions numériques saisonnières nous vérifierons au cours de ce travail l'hypothèse de base suivante: la persistance de l'anomalie de la température de la surface de l'océan Pacifique (SSTA) communique à l'atmosphère un certain degré de prévisibilité. Afin de vérifier cette hypothèse un ensemble de vingt-six années de simulations effectuées par chacun des modèles a été étudié. Ensuite, pour tenter d'améliorer la qualité des prévisions saisonnières, nous avons calculé la moyenne d'ensemble des trois modèles. Nous appellerons désormais cette technique multimodèle. Pour estimer la réponse de chacun des modèles aux effets du forçage de l'océan nous avons commencé par séparer les années prévues en deux catégories: les années caractérisées par une forte SSTA (années EPSO) et celles caractérisées par une faible SSTA (années NEPSO). Ensuite, nous avons étudié la prévision des modèles des deux derniers mois de la saison. Ceci nous permet de distinguer l'influence des conditions aux limites. Nos résultats montrent que durant les saisons d'hiver et printemps boréales les trois modèles ainsi que le multimodèle semblent bien reproduire les patrons de la circulation dynamique au sein de l'atmosphère (GZ500). On peut également y voir un potentiel pour l'amélioration de la qualité des prévisions à longue échéance. En outre, nous avons remarqué que la région tropicale est généralement mieux prévue par les modèles que les extra-tropiques. Enfin, nous avons remarqué que les modèles présentent une habileté à prévoir les champs atmosphériques au-dessus de certaines régions du globe en dehors des tropiques. Parmi ces régions nous citons le Pacifique Nord/Amérique du Nord dans le cas de GZ500 et la route des dépressions du Pacifique « Storm Track » dans le cas des précipitations. Le « Storm Track » du Pacifique influence le climat de l'est de l'Asie ainsi que celui de l'Amérique du Nord. L'habileté de nos modèles à prévoir le « Storm Track » du Pacifique n'avait pas été observée dans des études précédentes. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Prévision numérique saisonnière moyenne d'ensemble.
274

Study of genetic diversity in Puccinellia nuttalliana based on agronomic/morphological traits and AFLP molecular markers

2013 April 1900 (has links)
Native prairie grasses of western Canada have the potential for development as turf and forage grass cultivars for semiarid environments. Nuttall’s salt-meadow, or alkali grass (Puccinellia nuttalliana (Shultes) Hitchc.), is a native grass species in North America well known for its salt tolerance. Little information is available about the genetic diversity of natural populations of this species. Understanding the genetic diversity of this species is a prerequisite for developing populations for forage or turf use in western Canada. The objectives of this study were to assess the variation in agronomic/morphological characters and AFLP markers of collections of Puccinellia and identify promising populations and genotypes for turf and forage utilization. A four replicate randomized complete block field nursery of twenty-four collections from western Canada was established in 2010. Plant height, tiller number, crown diameter, dry matter yield, seed yield, and leaf related characters were measured for each collection in the summers of 2011 and 2012. Considerable phenotypic variation was detected among and within the twenty-four populations. Promising populations and genotypes were identified with respect to their superior turf and forage related characteristics. The amplified fragment length polymorphism (AFLP) technique was used to assess the comparative genetic diversity of the collections. Five AFLP primer pairs were employed to screen 15 genotypes from each population, and 185 polymorphic AFLP bands were scored for each sample. Their frequencies of occurrence ranged from 0.02 to 0.99 with a mean of 0.61. The analysis of molecular variance revealed more than 96% of the total AFLP variation resided within populations. Populations were not highly differentiated with only 4% of the total AFLP variation residing among populations. A Mantel test revealed a significant but low correlation between genetic and geographic distances (r=0.293; P=0.024) and non-significant correlation between genetic and phenotypic distances (r=0.070; P=0.282). Implications for P. nuttalliana conservation, germplasm sampling, and cultivar development are discussed.
275

Är 15 kulor fler än 15 legobitar? : En studie om vilka strategier barn använder när de räknar och om variation av antal, material och gruppering har betydelse när barn ska bestämma antal.

Ohlsson, Ann-Charlotte, Larsson, Lisbeth, Elgenkrona, Monia January 2008 (has links)
Syftet med examensarbetet var att undersöka vilka strategier barn använde sig av när de räknade samt om variation av antal, föremål och gruppering påverkade deras val av strategier. Undersökningen gjordes genom strukturerade observationer då femton barn, födda 2002, på tre olika förskolor räknade föremål där antal, gruppering och material varierades. I vårt teoriavsnitt bearbetades Gelman och Gallistels fem räkneprinciper och Martons variationsteori. Resultatet visade att barn använde sig av samtliga fem räkneprinciper på olika sätt och i olika ordning när de räknade samt att både antal, material och gruppering hade betydelse för barns val av strategier vid antalsbestämning. Barnen hade lättare att räkna legobitar än kulor och behärskade de olika principerna bättre då antalet var färre eller materialet grupperat i rader.
276

Motivera och variera : Ett utvecklingsarbete med fokus på språkutveckling

Rydstedt, Sandra January 2011 (has links)
Det här utvecklingsarbetet har som syfte att ta fram språkutvecklande aktiviteter som motiverar och väcker elevernas nyfikenhet. Aktiviteterna är tänkta att tilltala flera sinnen. Jag har planerat fem aktiviteter som på olika sätt ska bidra till elevernas språkutveckling. Av dessa har jag genomfört tre och observerat två. Eleverna har bland annat tränat på att tala, lyssna, skriva och fantisera. I utvärderingen av aktiviteterna kunde jag se att eleverna tyckte de var roliga och att de var medvetna om vad de tränade. Så slutsatserna av utvecklingsarbetet är att det är bra att variera sin undervisning och plocka in aktiviteter som motiverar och lockarfram elevernas nyfikenhet för att få ett större engagemang från elevernas sida.
277

Spatiotemporal distribution of larval fish assemblage in the coastal waters off Kaohsiung and Pingtung, Taiwan

Wu, Chia-Ching 12 September 2012 (has links)
To clarify the spatiotemporal distribution of the winter and spring larval fish assemblage in the coastal waters off Kaohsiung and Pingtung, Taiwan, larval fishes were collected during four research cruises by conducting 35 tows of the larval net in coastal waters off Zuoying, Linyuan, Linban and Fangliao in January and March 2009 and in coastal waters off Linyuan adjacent to the Kaoping River estuary in January and March 2010. Water temperature, salinity and dissolved oxygen were measured during the sampling of the fish larvae. Seawater samples were also collected for analyzing concentrations of nutrient salts. In 2009, a total of 2,023 fish larvae, representing 38 families and 74 species, were collected. The fish larvae assemblage exhibited seasonal variation in both abundance and species composition. The abundance (460 ind./1000m3) and the number of species (34 families and 66 species) of the fish larvae collected in March were higher than those (28 ind./1000m3, 14 families and 27 species) collected in January. Fish larvae also exhibited spatial variation in species composition. In January, the most dominant families of fish larvae were: Myctophidae off Linyuan, Sparidae off Linban and Nomeidae off Fangliao. In March, in the northward coastal waters off Linyuan Scombridae was the most dominant family, and in the southward coastal waters off Linyuan, Clupeidae and Sillaginidae were the dominant families. No significant differences existed in the abundance of fish larvae among the sampling areas, but the abundance of fish larvae in the sampling sites off Linyuan and Linban tended to be strongly influenced by tide. In 2010, a total of 1,959 fish larvae, representing 39 families and 59 species, were collected. These fish larvae showed diurnal and seasonal variations in abundance and in species composition. The abundance (767 ind./1000m3) and the number of species (39 families and 55 species) of the fish larvae in March were higher compared with those (26 ind./1000m3, 16 families and 25 species) in January. Moreover, the abundance of fish larvae in the nighttime was higher than that in the daytime. In March, the most dominant family in the daytime was Serranidae, whereas the most dominant family in the nighttime was Myctophidae, indicating the diurnal migration of Myctophidae these larvae. Cluster analysis indicated that the abundance and species composition of the fish larvae differed between January and March in 2009. The difference in species composition among the four sampling areas was only found significant for the fish larvae collected in the coastal waters off Fangliao in winter, and the most influenced families were Nomeidae and Myctophidae. In 2010, seasonal variations were found in the abundance and species composition of the fish larvae, and the abundance of the fish larvae showed the difference between nearshore and inshore sampling sites in the nighttime in winter. In spring, the fish larvae were all inshore fishes, but the species composition had annual variation. The temperature and salinity data obtained in the sampling sites conformed to the surface seawater of South China Sea, indicating that the occurrence of the dominant family Scombridae may be related to the seawater of South China Sea.
278

Design methodologies for variation-aware integrated circuits

Samanta, Rupak 15 May 2009 (has links)
The scaling of VLSI technology has spurred a rapid growth in the semiconductor industry. With the CMOS device dimension scaling to and beyond 90nm technology, it is possible to achieve higher performance and to pack more complex functionalities on a single chip. However, the scaling trend has introduced drastic variation of process and design parameters, leading to severe variability of chip performance in nanometer regime. Also, the manufacturing community projects CMOS will scale for three to four more generations. Since the uncertainties due to variations are expected to increase in each generation, it will significantly impact the performance of design and consequently the yield. Another challenging issue in the nanometer IC design is the high power consumption due to the greater packing density, higher frequency of operation and excessive leakage power. Moreover, the circuits are usually over-designed to compensate for uncertainties due to variations. The over-designed circuits not only make timing closure difficult but also cause excessive power consumption. For portable electronics, excessive power consumption may reduce battery life; for non-portable systems it may impose great difficulties in cooling and packaging. The objective of my research has been to develop design methodologies to address variations and power dissipation for reliable circuit operation. The proposed work has been divided into three parts: the first part addresses the issues related with power/ground noise induced by clock distribution network and proposes techniques to reduce power/ground noise considering the effects of process variations. The second part proposes an elastic pipeline scheme for random circuits with feedback loops. The proposed scheme provides a low-power solution that has the same variation tolerance as the conventional approaches. The third section deals with discrete buffer and wire sizing for link-based non-tree clock network, which is an energy efficient structure for skew tolerance to variations. For the power/ground noise problem, our approach could reduce the peak current and the delay variations by 50% and 51% respectively. Compared to conventional approach, the elastic timing scheme reduces power dissipation by 20% − 27%. The sizing method achieves clock skew reduction of 45% with a small increase in power dissipation.
279

Case Studies on Variation Tolerant and Low Power Design Using Planar Asymmetric Double Gate Transistor

Singh, Amrinder 2010 August 1900 (has links)
In nanometer technologies, process variation control and low power have emerged as the first order design goal after high performance. Process variations cause high variability in performance and power consumption of an IC, which affects the overall yield. Short channel effects (SCEs) deteriorate the MOSFET performance and lead to higher leakage power. Double gate devices suppress SCEs and are potential candidates for replacing Bulk technology in nanometer nodes. Threshold voltage control in planar asymmetric double gate transistor (IGFET) using a fourth terminal provides an effective means of combating process variations and low power design. In this thesis, using various case studies, we analyzed the suitability of IGFET for variation control and low power design. We also performed an extensive comparison between IGFET and Bulk for reducing variability, improving yield and leakage power reduction using power gating. We also proposed a new circuit topology for IGFET, which on average shows 33.8 percent lower leakage and 34.9 percent lower area at the cost of 2.8 percent increase in total active mode power, for basic logic gates. Finally, we showed a technique for reducing leakage of minimum sized devices designed using new circuit topology for IGFET.
280

Architecture Variations of ARM7 Microprocessors

Lai, Chi-Shaw 29 August 2001 (has links)
In this paper, we will explore architecture variations of ARM7 microprocessors. The ARM7TDMI is a 32-bit microprocessor developed by ARM Ltd. It used in embedded application such as mobile phones, pager and PDAs. However, as portable products grow in complexity more processing power is required. This paper focuses on the implementation of the architecture variations of ARM7 microprocessors. The evolutions from our RTL design to architecture variations are described and the trade offs between high performance and low gate count discussed.

Page generated in 0.0686 seconds