• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 789
  • 228
  • 132
  • 83
  • 55
  • 45
  • 42
  • 40
  • 26
  • 22
  • 12
  • 8
  • 5
  • 5
  • 3
  • Tagged with
  • 1903
  • 674
  • 373
  • 343
  • 234
  • 198
  • 187
  • 156
  • 151
  • 136
  • 135
  • 128
  • 125
  • 122
  • 101
  • 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.
641

Tracking an elusive predator: Studying the Scandinavian lynx population by use of genetic markers

Berlin, Ingrid January 2007 (has links)
<p>Abstract</p><p>Gaining accurate population information is crucial for the conservation and management of species. The National Monitoring Program for Large Carnivores monitors the Swedish lynx population (species Lynx lynx) by surveying family groups, non-invasive sampling and genetic analysis. Ten microsatellite regions were used as genetic markers to retrieve unique individual genotypes, through polymerase chain reactions (PCR) with specific primer-pairs and capillary-electrophoresis. Complete genotypes were matched using an internal database. The aim of this degree project was to show how monitoring of lynx through genetic analysis is carried out at the Department of Evolutionary Biology at Uppsala University, and to evaluate how effective these methods are and how they might be improved.</p><p>Even though most of the methods used were fairly robust and reproducible, non-invasive sampling and microsatellite analysis posed some problems regarding DNA quality and quantity, and increased the risks of certain genotyping errors. These risks might be worth taking though, as genetic analysis, in combination with field observations, gives a more comprehensive picture of the Swedish lynx population.</p>
642

The Effect of Skin and Soft Tissue on Spinal Frequency Response Measurements

Decker, Colleen 11 1900 (has links)
Introduction: This study sought to investigate the effects of soft tissue on measurements of a spinal vibration response using skin-mounted accelerometers and a non-invasive contact tip. Methods: Vibration was applied to the spine of porcine and human cadavers. Measurements of the spinal vibration response were taken from needle, skin, and bone-mounted accelerometers. Several skin-mounted accelerometer placements dorsal to a spinous process were tested, and 6 different non-invasive contact tip shapes were used to explore sources of variance in the signals. Results: Vibration measured from skin-mounted accelerometers had altered signal patterns compared to bone-mounted accelerometers. The measured FRF was found to be sensitive to accelerometer positioning. No significant difference in skin-bone correlation was attributed to contact tip shape or vertebral level. Conclusion: The use of a non-invasive contact tip excites vibration in the soft tissues which overlay the spine, in addition to the vertebral column. This vibration interferes with skin sensor measurements of vertebral vibration response, with the effect diminishing as distance from the contact tip increases. Small changes in contact tip shape do not affect the correlation between skin and bone signals.
643

Dynamics of tritrophic interactions between solenopsis invicta, antonina graminis, and neodusmetia sangwani: do fire ants negatively impact the success of a biological control system?

Chantos, Jillian Marie 15 May 2009 (has links)
Solenopsis invicta, the red imported fire ant, has recently become associated with Antonina graminis, an invasive pest, and Neodusmetia sangwani, biological control agent, and maybe negatively affecting established biological control. A preliminary survey outlined the range of A. graminis and its parasitoids, and found N. sangwani was present at a reduced rate in South Texas and in the southeastern United States. A greenhouse experiment demonstrated that S. invicta decreased the rate of parasitism of A. graminis by N. sangwani, with S. invicta directly interfering with oviposition. Interactions between S. invicta and A. gaminis may be facilitating the spread and establishment of two invasive pests which has a negative impact on established classical biological control of A. graminis by N. sangwani.
644

Acupuncture - effects on muscle blood flow and aspects of treatment in the clinicla context

Sandberg, Margareta January 2004 (has links)
The overall aim of this thesis was to elucidate and investigate psychophysiological aspects and effects of acupuncture and needle stimulation. Within this framework emphasis was directed toward the effects of needle stimulation (acupuncture) on muscle blood flow in the tibialis anterior and trapezius muscles in healthy subjects and patients suffering from chronic muscle pain. This study also included evaluation of a new application of photoplethysmography in noninvasive monitoring of muscle blood flow. The evaluation was based on experiments known to provocate skin or muscle blood flow. The psychological aspects studied comprised the effects of manual acupuncture on pain in fibromyalgia patients and the effects of electro-acupuncture on psychological distress and vasomotor symptoms in postmenopausal women in the clinical context. The results showed that photoplethysmography have potential to noninvasively monitor muscle blood flow and to discriminate between blood flow in skin and muscle, although some considerations still have to be accounted for. It was further shown that muscle blood flow change in response to needle stimulation differed between healthy subjects and patients. Deep needle stimulation in the muscle of healthy subjects consistently increased muscle blood flow more than subcutaneous needle stimulation. In the painful trapezius muscle of FMS patients, however, subcutaneous needling was equal or even more effective in increasing muscle blood flow than deep intramuscular stimulation. Generally, needle stimuli had weak effect on blood flow in the trapezius muscle of the severely affected trapezius myalgia patients, possibly depending on older age and lesser number of patients included in the study. The different patterns of blood flow response to needle stimulation between healthy subjects and patients with chronic muscle pain might be a manifestation of altered somatosensory processing in the patients. The clinical studies showed that best pain relief of acupuncture in FMS patients was achieved in the neck-shoulder region, while the effect on the generalised symptoms was of short duration. Well-being and sleep was found to best predict treatment outcome. The results suggest that acupuncture treatment may be used for the alleviation of neck-shoulder pain, primarily, but it is not an alternative as the sole treatment. Electro-acupuncture, significantly decreased psychological distress and climacteric symptoms in postmenopausal women, but not better than a (near-) placebo control, implying pronounced non-specific effects. / Akupunktur ingår som en del i traditionell kinesisk medicin (TCM) och har använts i över 2000 år för att lindra sjukdom och symptom. I Sverige blev akupunktur godkänd som smärtlindringsmetod inom Hälso- och Sjukvården 1984. Sedan nästan 10 år är akupunktur jämställd med övrig behandling i sjukvården vilket innebär, att akupunktur kan användas även för behandling av annat än smärta. Förutsättningen är emellertid, att det finns tillräckligt med vetenskapliga belägg, s.k. evidens, för detta. I de allra flesta fall saknas det idag. För att säkerställa att evidens föreligger krävs omfattande forskning om effekter av akupunktur. Syftet med de olika studierna i avhandlingen var att belysa och studera psykologiska och fysiologiska aspekter och effekter av akupunktur och nålstimulering. Effekt på blodflöde i hud och muskel undersöktes på friska personer och på patienter med kronisk muskelsmärta. Normalt krävs ett mindre kirurgiskt ingrepp för att mäta blodflöde i muskel, men i dessa studier användes en mätmetod, som enkelt och utan ingrepp (icke-invasivt) i normala fall används för att mäta blodflöde i huden, s.k. fotopletysmografi (PPG, eng.). Med hjälp av ny teknik användes PPG i dessa studier för att mäta även muskelblodflöde. En studie för utvärdering av den nya PPG-tekniken ingick också i avhandlingen. Utvärderingen av mätmetoden visade goda möjligheter att mäta muskelblodflöde icke-invasivt med hjälp av PPG. Hos friska personer blev effekten på blodflödet störst vid djup stimulering i muskeln och där den s.k. DeQi-känslan framkallades (som vid klassisk akupunktur). Hos patienter med fibromyalgi var nålstimulering i huden lika, eller t.o.m. mer, effektiv att öka muskelblodflödet i skuldran än den djupa nålstimuleringen. De olika mönstren av blodflödesökning mellan de friska personerna och patienterna kan bero på ett förändrat reaktionssätt i nervsystemet som svar på smärtsam stimulering. I två kliniska studier studerades den smärtlindrande effekten av manuell akupunktur vid fibromyalgi och effekten av elektroakupunktur på stress och klimakteriebesvär hos kvinnor i övergångsåldern. Akupunktur vid fibromyalgi visade sig ha bäst smärtlindrande effekt i nack-skulderområdet, medan effekten på de generella symptomen var kortvarig. Patienter som mådde och sov relativt bra erhöll bäst effekt. Efter en behandlingsserie, bestående av elektroakupunktur, minskade stress och klimakteriebesvär påtagligt hos kvinnorna i övergångsåldern, men inte mer än hos en grupp kvinnor, som fick en kontrollbehandling bestående av mycket ytligt placerade nålar i huden. Detta tyder på att en betydlig del av behandlingsresultatet utgjordes av ospecifika effekter eller, s.k. eller placeboeffekter.
645

Tracking an elusive predator: Studying the Scandinavian lynx population by use of genetic markers

Berlin, Ingrid January 2007 (has links)
Abstract Gaining accurate population information is crucial for the conservation and management of species. The National Monitoring Program for Large Carnivores monitors the Swedish lynx population (species Lynx lynx) by surveying family groups, non-invasive sampling and genetic analysis. Ten microsatellite regions were used as genetic markers to retrieve unique individual genotypes, through polymerase chain reactions (PCR) with specific primer-pairs and capillary-electrophoresis. Complete genotypes were matched using an internal database. The aim of this degree project was to show how monitoring of lynx through genetic analysis is carried out at the Department of Evolutionary Biology at Uppsala University, and to evaluate how effective these methods are and how they might be improved. Even though most of the methods used were fairly robust and reproducible, non-invasive sampling and microsatellite analysis posed some problems regarding DNA quality and quantity, and increased the risks of certain genotyping errors. These risks might be worth taking though, as genetic analysis, in combination with field observations, gives a more comprehensive picture of the Swedish lynx population.
646

Maternal Phylogeography Of Brown Bears (ursus Arctos) And Testing The Utility Of Non-invasive Genetic Samples

Cilingir, Fatma Gozde 01 October 2012 (has links) (PDF)
The genetic diversity and phylogeography of brown bear maternal lineages have been studied extensively over the last two decades. In this study the genetic diversity and maternal phylogeography of non-invasively sampled 35 brown bears, including 5 captive individuals were reported from Turkey. In addition to the optimization of DNA extraction from hair, faeces and old skin samples and their PCRs, Bayesian phylogenetic analyses based on a 269 bp long piece of bear mitochondrial DNA were conducted and 14 novel haplotypes belonging to three major lineages were revealed. The most widespread lineage was found to be the &ldquo / Eastern&rdquo / clade 3a, while geographically more restricted &ldquo / Western&rdquo / and &ldquo / Middle Eastern&rdquo / lineages were reported for the country for the first time. A specimen from the Taurus range (southern Turkey) was shown to be closely related to the presumably extinct bears in Lebanon. Moreover, a unique novel lineage that appears to have split early within the Middle Eastern clade was defined. Despite limited sampling, this study demonstrates a high level of mitochondrial diversity in Turkish brown bears, extends the ranges of both European and Middle Eastern clades into Turkey, and identifies a new divergent lineage of possibly wider historical occurrence while demonstrating the significance of non-invasive genetic sampling for such analysis.
647

Particularités de l'athérosclérose du sujet non diabétique, diabétique de type 2, et/ou stéatosique non alcoolique : de la physiopathologie aux techniques d'imagerie non invasives

Loffroy, Romaric 15 December 2010 (has links) (PDF)
L'athérosclérose est un problème de santé publique majeur puisque elle représente aujourd'hui la principale cause de décès dans les pays occidentalisés. Il est donc important de comprendre les mécanismes participant à la progression et aux complications de cette entité anatomoclinique. Nous nous sommes attachés dans ce travail de thèse à démontrer la place et l'apport potentiel de l'imagerie non invasive non expérimentale dans la mise en exergue des particularités de l'athérosclérose carotidienne et/ou coronarienne, et dans la stratégie de dépistage de ses complications chez le sujet non diabétique et diabétique de type 2, en fonction de l'existence ou non d'une stéatose hépatique non alcoolique. Nous présentons notamment dans ce travail, issu en partie de l'exploitation des données cliniques, biologiques et radiologiques de trois protocoles hospitaliers de recherche clinique, les différentes publications scientifiques internationales auxquelles il a donné lieu.
648

Facilitative Interactions Among Native Perennial Shrubs and Native and Exotic Annuals in Recovering Coastal Sage Scrub

Miranda, Courtney Elizabeth 18 May 2013 (has links)
Facilitative interactions can have a powerful influence on the structure of plant communities and must be accounted for in efforts to restore disturbed and invaded habitats, such as the now rare coastal sage scrub (CSS) of California. In this study, I tested for evidence of facilitative effects by the native shrubs Eriogonum fasciculatum var. foliolosum and Artemisia californica on germination and survival of the CSS native annual forb Phacelia distans. P. distans seeds were planted near patches of native shrubs, both under the shrub canopy where any facilitative effects should be strongest, and 0.5 m away in the more exposed grassland. To determine whether the shrub-forb relationship was affected by the presence of invasive annuals, E. fasciculatum sites were assigned either invasive annual removal or non-removal control treatment; no removal treatments were carried out for A. californica. P. distans had significantly higher germination but lower survivorship under the canopy of E. fasciculatum. The results showed no overall effect of invasive removal, but there was a weak interaction effect with location; in shrub-canopy plots, invasive species further lowered survivorship. A. californica showed neither facilitative nor negative effects of this shrub species on either germination or survivorship of P. distans, in contrast with the results for E. fasciculatum. Although E. fasciculatum appears to facilitate the germination of native forbs under its canopy, it also seems to have a negative effect on survival. The weak interaction between location and removal to further decrease survival under the canopy when invasives are present, and the abundance of grasses growing under the canopy, suggest that native shrubs may facilitate the growth of invasive annuals as well as the germination of natives. Consequently, controlling invasive grass abundance may be necessary to capture the benefits of shrub facilitation for the restoration of native CSS herbs.
649

Comanipulation Série Dextre pour la chirurgie Mini Invasive

Hassan Zahraee, Ali 04 January 2012 (has links) (PDF)
Une chirurgie minimalement invasive (CMI), qui implique généralement une caméra endoscopique et des instruments de laparoscopie, peut sembler être la procédure chirurgicale idéale pour ses avantages apparents. Toutefois, en comparaison à la chirurgie ouverte, les limites spatiales et outils mécaniques posés sur les chirurgiens sont si élevés que, souvent, la CMI est abandonné pour des cas complexes et même quand elle est possible, la procédure nécessite une grande dextérité, calibre et expérience du chirurgien. Cette recherche a été motivée par la nécessité d'habiles instruments chirurgicaux qui offrent un contrôle intuitif et une interface ergonomique, avec l'objectif final de développer un instrument robotisé adapté aux interventions par laparoscopie. La recherche a été basée sur l'évaluation comparative des différentes interfaces, modes de contrôle et cinématiques, en utilisant un simulateur de réalité virtuelle, développée spécialement à cet effet. Les résultats montrent que: 1. l'interface optimale a un mode de contrôle WYSIWYD (ce que vous voyez est ce que vous faites) et est exploité par les doigt. 2. les mobilités distales motorisées de l'effecteur doivent produire deux degrés de liberté (DDL) indépendants pour la flexion et la rotation de l'effecteur. Ce qui est suffisant pour des gestes SIG complexes. 3. ajouter une libre articulation à la poignée de l'instrument permet au chirurgien d'avoir une posture ergonomique. 4. un trocart actif permettrait la rotation de l'arbre de l'instrument avec un joint libre. Cette recherche a également permis le développement d'un prototype de validation de concept. Le prototype a été testé avec succès, in vitro et in vivo sur un modèle porcin.
650

A Study of the Impact of an Introduced Herbivore on Pollinator-mediated Interactions and Female Fitness in 'Lythrum salicaria'

Russell-Mercier, Jake L. 09 April 2013 (has links)
Herbivory can have many effects on plant fitness, including altering plant-pollinator interactions and sexual reproduction in angiosperms. Pollinator-mediated interactions may be impacted when herbivores alter plant traits, such as floral display size, that can influence pollinator visitation rates, and, ultimately, the reproductive component of plant fitness. Here I describe an investigation into the indirect effects of feeding by beetles released as a biological control agent, Galerucella calmariensis and G. pusilla, on plant-pollinator interactions and reproductive output in the invasive plant Lythrum salicaria L. (purple loosestrife). During the summer of 2011, three treatments (low, ambient and mechanical herbivory) were applied to 105 plants during the pre-flowering period of growth. At the onset of flowering, a series of pollinator observations were conducted over the course of approximately 1.5 weeks. Several aspects of floral display were affected by the herbivory treatments, including increased inflorescence and flower production in the ambient and mechanical herbivory treatments, relative to the low herbivory treatment. Treatment type did not have a significant effect on the number of pollinator foraging bouts, but had marginally significant effects on the number of flowers probed per pollinator foraging bout and per 30-minutes. Moreover, treatment had a significant effect on the number of switches among the inflorescences on a single plant. I discuss the possibility that the differences in pollinator visitation were mediated by differences in the architecture and the size of floral display. There were no detectable differences in fruit or seed production (i.e., female fitness) among treatments. However, as I discuss, differences in pollinator visitation may affect other unmeasured aspects of fitness, such as the level of inbreeding or the number of seeds sired through male function.

Page generated in 0.0596 seconds