• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 343
  • 81
  • 35
  • 25
  • 8
  • 7
  • 4
  • 4
  • 3
  • 3
  • 3
  • 2
  • 2
  • 2
  • 1
  • Tagged with
  • 550
  • 302
  • 54
  • 53
  • 49
  • 47
  • 47
  • 47
  • 42
  • 42
  • 40
  • 36
  • 36
  • 29
  • 28
  • 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.
151

Ανάπτυξη μεθοδολογίας για τον καθορισμό της μεταμόρφωσης στα ψάρια και εφαρμογή της σε είδη της οικογένειας Sparidae

Νικολιουδάκης, Νικόλαος 04 December 2008 (has links)
Η μεταμόρφωση (metamorphosis), το πέρασμα δηλαδή των ψαριών από το στάδιο της ιχθυονύμφης στο στάδιο του ιχθυδίου (juvenile), συνδέεται με αλλαγές στη μορφολογία, την αύξηση, τη συμπεριφορά και το ενδιαίτημα, οι οποίες είναι καθοριστικές για την επιβίωση των ατόμων και συνεπώς για τη δομή και τη δυναμική του πληθυσμού στον οποίο πρόκειται να ενσωματωθούν. Στην παρούσα εργασία μελετήθηκε η φάση της μεταμόρφωσης σε τέσσερα είδη της οικογένειας Sparidae με την ταυτόχρονη εξέταση της μορφομετρίας και της μορφολογίας συγκεκριμένων χαρακτήρων. Τα είδη που εξετάστηκαν ήταν τα Oblada melanura (μελανούρι), Diplodus puntazzo (μυτάκι), Diplodus vulgaris (σαργόπαπας ή κακαρέλος) και Diplodus sargus (σαργός). Τα αποτελέσματα της μελέτης, έδειξαν πως με τη μεθοδολογία που ακολουθήθηκε, η φάση της μεταμόρφωσης μπορεί να προσδιοριστεί ικανοποιητικά και να οριστεί ένα μέσο μήκος μεταμόρφωσης. Αποκαλύφθηκαν επίσης διαφορές και ομοιότητες στην αλλομετρική αύξηση των ειδών που εξετάστηκαν, καθώς και ισχυρή συσχέτιση της αλλομετρικής αύξησης με την πρόσφατη θερμοκρασιακή ιστορία του περιβάλλοντος ανάπτυξής για το στάδιο πριν το εκτιμηθέν μέσο μήκος μεταμόρφωσης του κάθε είδους. Τα αποτελέσματα, συζητούνται σε σχέση με τις οικολογικές απαιτήσεις των ψαριών κατά τη μετάβαση από την πελαγική στη βενθική διαβίωση. / During metamorphosis, fish undergo major changes in morphology and growth followed by shifts in behavior and habitat use. In this study, metamorphosis was examined on the early life stages of four Sparidae species, by analyzing their allometric growth patterns concurrently with the evolution of specific morphological characters. The species examined were Oblada melanura (saddled seabream), Diplodus puntazzo (sharpsnout seabream), Diplodus vulgaris (common two-banded seabream) και Diplodus sargus (white seabream). Our results showed that metamorphosis can be adequately defined and an average length at metamorphosis can be estimated, with the use of the methodology proposed. Moreover, specific patterns of allometric growth were detected within each species, as well as, a strong correlation of allometric growth with recent environment temperature, for the stage before the estimated average metamorphosis length. Results are discussed in terms of the ecological demands of fish during their transition from the pelagic to the benthic/coastal existence.
152

Tauriųjų elnių (Cervus elaphus L.) auginimas aptvaruose / Breeding of Red Deers (Cervus elaphus L.) in Enclosures

Gavorka, Vaidotas 21 June 2010 (has links)
Magistro darbe tiriami tauriųjų elnių auginimo aptvaruose ypatumai Lietuvos sąlygomis. Darbo objektas - S.Petraičio privatus elnininkystės ūkis, esantis Joniškio rajone. Darbo tikslas - išaiškinti aptvaruose auginamų tauriųjų elnių augimo ir veisimosi ypatumus. Darbo uždaviniai – nustatyti tauriųjų elnių veisimosi, kūno ir ragų augimo ypatumus, užsikrėtimą ligomis bei parazitais. Išaiškinti ar šėrimo racionas tenkina tauriųjų elnių poreikius. Darbo metodai – vizualinis tauriųjų elnių stebėjimas visais metų laikais, nustatant elgsenos ypatumus. Helmintų tyrimas (helmintoovoskopija) – laboratorijoje tiriami sviežiai surinkti tauriųjų elnių ekskrementai. Šėrimo raciono išaiškinimas, pagal maisto medžiagų kiekius skirtingose pašaro rūšyse ir elnių poreikius nustatomas jo pakankamumas. Rujos, jauniklių vedimo bei įvairių kitų darbų ir operacijų stebėjimas tiesiogiai dalyvaujant jose (haremų tvarkymas, vakcinavimas, ženklinimas (numeravimas), ir kt.). Kūno morfometrijos duomenys surinkti iš jau sumedžiotų elnių. Numestų ragų matavimas pagal CIC sistemą. Darbo rezultatai – intensyviai ūkininkaujant ir esant labai dideliam tauriųjų elnių tankumui susiduriama su labai daug problemų. Joniškio rajone esančiame elnininkystės ūkyje paskutiniais duomenimis yra 800 tauriųjų elnių, kurie gyvena 150 ha senų obelų sodų ir natūralių pievų, t.y. 5,3 individo kiekviename hektare. Esant tokiam žvėrių tankiui ir nevykdant dehelmintizacijos absoliučiai visi jauni elniai, o ypač iki vienerių metų... [toliau žr. visą tekstą] / In the Master’s Thesis the peculiarities of breeding the red deers in enclosures under the conditions of Lithuania are investigated. Work object – private deers’ farm of S.Petraitis in Joniškis region. Work aim – to reveal the peculiarities of growing and breeding of red deers in the enclosures. Work objectives – to ascertain the peculiarities of breeding the red deers, body and antlers, infection with diseases and parasites. To find out whether the feeding ration is suitable for the needs of the red deers. Work methods – visual observation of the red deers during all seasons, when determining the behaviour peculiarities. Analysis of helminths (helminthovoscopy) – the freshly collected excrements of the red deers are analysed in the laboratory. The exploration of feeding ration – its sufficiency is estimated according to the nourishing quantities in the types of feed and the needs of deers. The observation of rut, calving and various works and operations is performed by taking part directly in them (arranging of harems, vaccination, marking (numbering), etc.). The body morphometry data are collected from the bagged deers. Metering of dropped antlers according to CIC system. Work results – when performing the intensive farming and when the big density of the red deers is estimated, a lot of problems arise. According to the recent data, in the farm of deers in Joniškis region 800 red deers live in the garden of old apple-trees and natural meadows of 150 ha, i.e. 5.3... [to full text]
153

Analyse de la variation intra- et inter-populationnelle : application de deux méthodes craniométriques sur des collections amérindiennes-canadiennes

Lettre, Josiane January 2009 (has links)
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal
154

Effets des facteurs biologiques hormonaux sur la performance langagière

Lamoureux, Charles January 2007 (has links)
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal
155

Cerebellar pathophysiology in a mouse model of Duchenne muscular dystrophy

Snow, Wanda Mae 13 November 2012 (has links)
This series of experiments investigated dystrophin localization in the normal cerebellum and examined Purkinje neuron function in normal and dystrophin-deficient mice to better understand the physiological basis for cognitive deficits associated with Duchenne muscular dystrophy (DMD), a common genetic disorder among children. Cognitive impairments are consistently reported in DMD, yet precise mechanisms for their occurrence are unknown. Dystrophin protein, which is absent in DMD, is normally localized to muscles and specific neurons in the brain. Purkinje neurons are rich in dystrophin, specifically in somatic and dendritic membranes. Studies demonstrate perturbed cerebellar function in the absence of dystrophin, suggesting that DMD should be regarded as a cerebellar disorder in addition to being considered a neuromuscular disorder. However, theory and evidence are not generated from overlapping information: research investigating cerebellar involvement in DMD has focused on the vermal region, associated with motor function. The lateral region, implicated in cognition, has not been explicitly examined in DMD. The first experiment revisited the issue of dystrophin distribution in the mouse cerebellum using immunohistochemistry to investigate qualitative and quantitative differences between cerebellar regions. Both regions showed dystrophin localized to Purkinje neuron somatic and dendritic membranes, but dystrophin density was 30% greater in the lateral than the vermal region. The second experiment examined intrinsic electrophysiological properties of vermal and lateral Purkinje neurons from wild-type (WT) mice and from the mdx mouse model of DMD which lack dystrophin. Significant differences in action potential firing frequency, regularity, and shape were found between cerebellar regions. Purkinje neurons from mdx mouse cerebellum exhibited membrane hyperpolarization and irregular action potential firing, regardless of region. Spontaneous action potential firing frequency was reduced in Purkinje neurons from lateral cerebellum in mdx mice relative to controls, demonstrating that a loss of dystrophin causes a potent dysregulation of Purkinje neuron function in the region associated with cognition. This research extends our understanding of cerebellar pathology in DMD and its potential relevance to cognitive deficits in the disorder. Moreover, this research further supports the role of the cerebellum as a structure important for cognition and contributes to our understanding of dystrophin’s role in the brain.
156

Interactive Effects of Geography and Host Plant Species on Genetic and Phenotypic Variation of Cotton Fleahopper Populations

Barman, Apurba 2011 December 1900 (has links)
The cotton fleahopper, Pseudatomoscelis seriatus (Reuter) is a widely distributed insect across the United States. Although, it feeds on several native wild hosts, its agricultural importance lies as an economic pest of cotton in several states in the southern United States. No studies have addressed intraspecific genetic and phenotypic variation of this insect pest at a large geographic scale. I examined genetic variation among cotton fleahopper populations associated with cotton in different geographic locations across the southern United States (Chapter II). Using dominant, neutral, nuclear molecular markers (AFLP, amplified fragment length polymorphism) and mitochondrial DNA sequences, I found that overall genetic differentiation among different geographic populations, collected from cotton in eleven cotton growing states, was low but significant. AFLP revealed the presence of three regional groups representing western (Arizona), central (Texas, Oklahoma, Arkansas, Louisiana, Mississippi and Alabama), and eastern (Florida, Georgia, South Carolina and North Carolina) populations. I examined if there were distinct lineages of cotton fleahoppers associated with three of its host plant species: cotton (Gossypium hirsutum), horsemint (Monarda punctata) and woolly croton (Croton capitatus) in five different locations of Texas by using AFLP markers (Chapter III). I found two distinct host-associated lineages at three locations and local panmixia in the other two locations. I tested if host preference of cotton fleahoppers were affected by geographic variation and prior experience. Conducting choice tests with a Y-tube olfactometer, I found that host preference in cotton fleahoppers for horsemint (one of its native host plants) is conserved and unaffected by individual?s prior experience with cotton (Chapter IV). Finally, I explored the role of host-plant species in morphological differentiation of the cotton fleahopper in two locations that differ in presence of distinct host-associated lineages. Using a geometric-morphometric approach, I detected significant effect of host plant and geography on body morphology and wing shape of cotton fleahopper populations (Chapter V). Length of antenna and rostrum were two important traits associated with morphological divergence of cotton and horsemint associated insect populations. Cotton associated individuals had relatively longer antenna and rostrum compared to individuals associated with horsemint.
157

Morphometric Characterization of Limbal Vasculature using Ultra-high Resolution Optical Coherence Tomography

Alabi, Emmanuel January 2013 (has links)
Purpose: The aim of the present study was to compare and investigate morphometric characteristics of limbal vasculature within the superior and inferior limbal regions using ultra-high resolution optical coherence tomography. Method: Cross-sectional images of the human corneo-scleral limbus were acquired with a research grade ultra-high resolution optical coherence tomographer (UHR-OCT) from 14 healthy subjects after manual retraction of the upper and lower eyelid. The UHR-OCT provides an axial and lateral resolution in biological tissue of ~3μm and ~18μm, respectively. 3D stacks of OCT images (1000 x 1024 x 256) were acquired of the transition from cornea to bulbar conjunctiva at the superior and inferior limbal region. All visible vessels within the limbal region were measured using an Image J circle or ellipse tool. Vessel depth and size measurements were repeated for the same vessel and the concordance correlation coefficient was computed. Quantitative differences in vessel size and depth in the limbal region were analyzed using repeated measured ANOVA. R and SPSS were used for all data analysis procedures. Results: The average vessel size for superior and inferior limbus were 29.28µm ± 17.649 µm (SD) and 23.68µm ± 18.118µm (SD) respectively. The average vessel depth for superior and inferior limbus were 176.76µm ± 108.698µm (SD) and 205.62µm ± 131.991µm (SD) respectively. The concordance correlation coefficient for superior and inferior limbal vessel size were 0.95 (95% CI, 0.935 to 0.964) and 0.994 (95% CI, 0.991 to 0.995) respectively, while that of vessel depth were 0.998 (95% CI, 0.997 to 0.999) and 0.998 (95% CI, 0.997 to 0.998) respectively. The vessels within the superior limbus were larger than the vessels found in the inferior limbus (RM-ANOVA POS p = 0.004), and the vessels within the inferior limbus were on average deeper than the vessels found within the superior limbus (RM-ANOVA POS p = 0.042). There was a positive linear relationship between limbal vessel depth and size within the superior and inferior limbus with a Pearson correlation coefficient of 0.803 and 0.754, respectively. There were on average 9 vessels per subject within the superior limbal region as compared to 13 vessels per subject with the inferior limbal region. Conclusion: This study provided evidence that the UHR-OCT was capable of imaging (and therefore measuring) morphometric characteristics such as the size and depth of vessels within the limbus in a repeatable manner. A positive linear association between vessel depth and size was identified in the superior and inferior limbal regions. The results of this study suggest a definite difference in the size and depth of vessels across different positions of the limbus, and this may be indicative of adaptations to chronic hypoxia caused by the constant covering of the superior limbus by the upper eyelid.
158

Cerebellar pathophysiology in a mouse model of Duchenne muscular dystrophy

Snow, Wanda Mae 13 November 2012 (has links)
This series of experiments investigated dystrophin localization in the normal cerebellum and examined Purkinje neuron function in normal and dystrophin-deficient mice to better understand the physiological basis for cognitive deficits associated with Duchenne muscular dystrophy (DMD), a common genetic disorder among children. Cognitive impairments are consistently reported in DMD, yet precise mechanisms for their occurrence are unknown. Dystrophin protein, which is absent in DMD, is normally localized to muscles and specific neurons in the brain. Purkinje neurons are rich in dystrophin, specifically in somatic and dendritic membranes. Studies demonstrate perturbed cerebellar function in the absence of dystrophin, suggesting that DMD should be regarded as a cerebellar disorder in addition to being considered a neuromuscular disorder. However, theory and evidence are not generated from overlapping information: research investigating cerebellar involvement in DMD has focused on the vermal region, associated with motor function. The lateral region, implicated in cognition, has not been explicitly examined in DMD. The first experiment revisited the issue of dystrophin distribution in the mouse cerebellum using immunohistochemistry to investigate qualitative and quantitative differences between cerebellar regions. Both regions showed dystrophin localized to Purkinje neuron somatic and dendritic membranes, but dystrophin density was 30% greater in the lateral than the vermal region. The second experiment examined intrinsic electrophysiological properties of vermal and lateral Purkinje neurons from wild-type (WT) mice and from the mdx mouse model of DMD which lack dystrophin. Significant differences in action potential firing frequency, regularity, and shape were found between cerebellar regions. Purkinje neurons from mdx mouse cerebellum exhibited membrane hyperpolarization and irregular action potential firing, regardless of region. Spontaneous action potential firing frequency was reduced in Purkinje neurons from lateral cerebellum in mdx mice relative to controls, demonstrating that a loss of dystrophin causes a potent dysregulation of Purkinje neuron function in the region associated with cognition. This research extends our understanding of cerebellar pathology in DMD and its potential relevance to cognitive deficits in the disorder. Moreover, this research further supports the role of the cerebellum as a structure important for cognition and contributes to our understanding of dystrophin’s role in the brain.
159

Morphometric, Mtdna And Microsatellite Analysis In Honeybee Populations (apis Mellifera L.) Of North And Northwest Iran

Jabbarifarhoud, Houman 01 September 2004 (has links) (PDF)
ABSTRACT MORPHOMETRIC, MtDNA AND MICROSATELLITE ANALYSIS IN HONEYBEE POPULATIONS (Apis mellifera L.) OF NORTH AND NORTHWEST IRAN Morphometric measurements, mitochondrial DNA analyses and 5 microsatellite loci were used to investigate variation in the honeybee populations of Iran and comparing it with the Turkish populations. Five honeybee populations were sampled from North and west north of Iran. In morphometric aspect of the study 23 characters were measured from left forewings and hindlegs of honey bee samples. The data were analysed by multivariate statistical analyses. By using mtDNA analyses length polymorphism of the intergenic region COI-COII of mitochondrial DNA was studied. After amplification of this region by the polymerase chain reaction, DraI enzyme was used for restriction of amplified region. Results of mtDNA studies show no diversity between four populations and all of them exhibit the same C1 pattern. Five microsatellite loci (A7, A24, A28, A43 and A113) were used in this studies.A high level of average heterozygosity changing between 0.611 and 0.709 was detected in Iranian honey bee populations, and a significant degree of polymorphism was observed. Although Urmia, Sarein and Viladereg populations are similar, Amol population which has located in northern Iran shows a significant difference from other populations. Result obtained form morphometric studies are supporting microsatellite analyses. By comparing data obtained form Iranian honey bee populations with Turkish population (Hakkari), western populations (Urmia, Sarein and Viladereg) are more similar to Hakkari population. It is found Amol is significantly different form other populations and better represents Iranian honeybee.
160

DENDROECOLOGIA DE Cedrela fissilis (Vell.) NA REGIÃO DE SANTA MARIA, RS / DENDROECOLOGY OF Cedrela fissilis (Vell.) IN THE SANTA MARIA REGION OF RS

Pereira, Lilian Daniel 28 February 2011 (has links)
Conselho Nacional de Desenvolvimento Científico e Tecnológico / Cedrela fissilis (Vell.) is a species that has a considerable growth and a high quality wood, and because of that it is a potential species for native forests management. However, for the proper handling of this species is necessary the knowledge about its self-ecology and its dynamic in the forest. In order to contribute to the advancement of forest management in Rio Grande do Sul, we sought to evaluate the influence of morphometry (Crown proportion- Pc; range index -IA; degree of slenderness- Hd; salience index - IS; crown formal- FC), of the climate, of the presence of lianas, of soil (granulometry) and the competition (density point of Spurr), in the growing of cedro. Information was collected as regards of: circumference at breast height; overall height , commercial high, insertion height of the canopy; and eight rays of the canopy of dominant cedro trees, besides information about ecological conditions of: density point of Spurr, presence or absence of stones in soil; position on the ground; depth, presence or absence of lianas; and collected soil for particle size analysis. The increment data were obtained by the analysis of two rolls of increments, collected with the use of Pressler borer from. The morphological relationships, of IA, Hd, DBH, and crown diameter explained satisfactorily the average increase in basal area in recent years. The hypsometric relationship and range index were correlated with measures of competition. The growth was not influenced by soil texture. While Liana presence affected the productivity of cedro, trees with presence of lianas yielded less than the others. The growth was influenced by rainfall in November/December to April. The cedro trees in free conditions and with less competition were more suited to the dendroclimatic analysis. The proposed methodology: correspondence of the trend interval, for the formation of dendrochronology average, was more efficient than the methodology for obtaining the dendrochronological series average of the bigger correlations between the baguettes, because the correspondence of the trend interval, beyond include more trees in the dendrochronology mean, had a higher correlation with rain period of November/December to April, improving the correlations of monthly rain, had significant correlation with monthly November, January, march, April, for Spearman correlation with level of significant of 0.05. / Cedrela fissilis (Vell.) é uma espécie de crescimento considerável e apresenta alta qualidade de madeira, por isso, é uma espécie potencial para o manejo de florestas nativas. Contudo, para o manejo adequado desta espécie é necessário o conhecimento de sua autoecologia e a dinâmica na floresta. Com intenção de contribuir com os avanços do manejo florestal no Rio Grande do Sul, buscou-se avaliar a influência da morfometria (proporção de copa - Pc; índice de abrangência IA; grau de esbeltez Hd; índice de saliência-IS; Formal de copa Fc), do clima, da presença de lianas, do solo (granulometria) e da competição (densidade pontual de Spurr) no crescimento do cedro. Foram coletadas informações referentes à: circunferência à altura do peito; altura total; altura comercial; altura de inserção de copa e oito raios de copa das árvores dominantes de cedro, além de informações referentes às condições ecológicas de: densidade pontual de Spurr; presença e ausência de pedregosidade; posição no terreno; profundidade; presença de cipós e lianas e coletado solo para a análise granulometrica. Os dados de incremento foram obtidos pela análise de duas baguetas, coletados com a utilização do trado de Pressler. As relações morfométricas, de IA, Hd, IS, e o próprio Dap, e diâmetro de copa explicaram satisfatoriamente o incremento médio em área basal dos últimos anos. A relação hipsométrica e o índice de abrangência foram correlacionados com medidas de competição. O crescimento não foi influenciado pela textura do solo. A presença de lianas influenciou na produtividade do cedro, árvores com presença de lianas demonstraram produtividade inferior às demais. O crescimento foi influenciado pela precipitação de novembro/dezembro a abril. As árvores de cedro em condições livres e com menor concorrência foram mais aptas para as análises dendrocronológicas. A metodologia proposta de correspondência de tendência de intervalo, para formação de série dendrocronológica média, foi mais eficiente que a metodologia de obtenção de série dendrocronológica média pelas maiores correlações entre as baguetas, pois a metodologia de correspondência de tendência de intervalo, além de incluir maior número de indivíduos na série dendrocronológica média, obteve maior correlação com a precipitação do período de novembro/dezembro a abril, melhorando inclusive a correlação com relação a precipitação mensal, sendo correlacionado positivamente e significativamente com os meses de novembro, janeiro março e abril, pela correlação de postos de Spearman ao nível de 0,05 de significância.

Page generated in 0.0513 seconds