• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 135
  • 59
  • 16
  • 12
  • 11
  • 11
  • 9
  • 5
  • 3
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 306
  • 55
  • 46
  • 45
  • 35
  • 35
  • 34
  • 31
  • 30
  • 30
  • 29
  • 28
  • 26
  • 26
  • 23
  • 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.
161

Mechanism of Vein Pattern Formation in Arabidopsis Thaliana Leaves: testing the Canalization Hypothesis

Amin, Mira 22 August 2011 (has links)
Several mechanisms have been proposed to explain the process of vein pattern formation in plant tissues. The most widely accepted amongst biologists is the canalization hypothesis, derived from pea root and stem experiments. According to this hypothesis, a signal, thought to be the phytohormone auxin, is transported polarly from cell to cell from the shoot to the root and is canalized progressively into narrow channels of high auxin fluxes that later differentiate to become vascular tissue. In this project, we set out to test whether auxin canalization drives vein pattern formation, using Arabidopsis thaliana mutants with increased auxin transport (max4-1, max3-9, max2-1 and max1-1). We predicted that the mutants would have distinct vein patterns and especially different angles between the primary and secondary veins, compared to the wild type. First rosette leaves of 15 plants per genotype were harvested for analysis each day from 7 to 17 days after sowing, giving a total of eight hundred twenty-five leaf samples to analyze. Venation patterns were extracted and analyzed using custom-made software written with Matlab. Overall, compared with the wild type, mutants with the highest auxin transport (max4-1 and max3-9) had different vein patterns at early developmental stages, confirming a role for auxin transport in vein patterning. However, veins of mutants and wild type connected at similar angles, which is not consistent with the auxin canalization hypothesis, as originally formulated.
162

Post-paleogene Deformation In Northernmost Tip Of Tuzgolu Fault Zone (pasadag, South Of Ankara), Turkey

Celiker, Dilara Gulcin 01 December 2009 (has links) (PDF)
The research area is located to the northern tip of Tuzgolu fault zone in the junction of neotectonic structures, namely, EskiSehir-Cihanbeyli, Sungurlu-Kirikkale and Tuzg&ouml / l&uuml / fault zones (Central Anatolia). The study is carried out in Paleocene sequences of PaSadag group on the structural analysis of bed, gash vein, fault and fault plane slippage data. The method of study based on i) the rose and stereo analysis of the planar structure (beds, gash veins and faults) on ROCKWORKS 2009 software and ii) on fault slip analysis on ANGELIER 1979 software. The bed analyses done on 605 measurements manifest N10&deg / -20&deg / E bedding attitude. The analysis done on 64 gash veins shows a general trend of NNE-SSW (N15&deg / E). The final analysis done on 160 fault planes pointed out a general trend of NNWSSE (N20&deg / W). Analysis based on the fault plane slip data manifest two stages of faulting under almost NE-SW compression during post-Paleocene &ndash / pre-Miocene period and one stage of faulting under WNW-ESE extension most probably during post-Miocene. To conclude, the Paleocene sequences are deformed continuously under WNW-ESE directed compression which is followed by a NE-SW to N-S compression resulted in the development of a reverse to dextral strike slip faulting during post-Paleocene &ndash / pre-Miocene period.
163

Arteriovenöse Differenzierung humaner Endothelzellen: Einfluss von Wachstumsfaktoren, Hypoxie und Biomechanik

Gryczka, Corina 30 October 2008 (has links) (PDF)
Arterien und Venen sind aufgrund ihrer Funktion im Körper morphologisch, funktionell und genetisch unterschiedlich. Schon die großen Blutgefässe auskleidende Endothelzellen zeigen eine arteriovenöse Determinierung. Ausgehend von einer Mikroarray-Analyse der mRNA-Expression arterieller und venöser Endothelzellen der Nabelschnur wurde im Rahmen dieser Arbeit auf Moleküle des Notch-Signalwegs, Dll-4, Notch-4, Hey-1 und Hey-2 fokussiert, die präferenziell bis exklusiv arteriell exprimiert werden. Weitere Gene mit einem arteriellen Expressionsmuster, die im Rahmen der vorliegenden Arbeit analysiert wurden, sind Angiopoietin-2 und CD44s. Trotz der genetisch definierten Unterschiede ließ der Vergleich physiologisch relevanter Funktionen, wie Proliferation oder die Interaktion mit monozytären Zellen keinen vom endothelialen Zelltyp abhängigen Unterschied erkennen. Die im Matrigel ausgebildeten kapillar-ähnlichen Strukturen sind durch homogene, eng beieinander liegende Netzwerke charakterisiert. Studien über den Einfluss von Wachstumsfaktoren und Schubspannung auf die arteriovenöse Expression von Angiopoietin-2 deuten auf eine schubspannungsvermittelte Regulation der Gefäßstabilität und Differenzierung hin. Die in der Zellkultur durchgeführten Manipulationen, wie der Einfluss verschiedener Wachstumsfaktoren oder die Applikation unterschiedlicher Schubspannungen, erreichten in Bezug auf die Expression der untersuchten Markergene keine tiefer greifende Redifferenzierung des jeweiligen endothelialen Phänotyps. Der evolutionär hoch konservierte Notch-Signalweg ist präferenziell arteriell exprimiert, wobei Hey-2 ausschließlich arteriell exprimiert wird. In adulten Endothelzellen erfolgt die Hey-2-Regulation jedoch Notch-unabhängig. Die arteriovenöse Genexpression von Molekülen des Notch-Signalwegs ist unabhängig von der Schubspannung. Unter hypoxischen Bedingungen verringerte sich die Expression von Dll-4, Hey-1 / 2 dramatisch, ohne das jedoch physiologische Beeinträchtigungen zu beobachten waren. Die Expression des venösen COUP-TF II wird in arteriellen Endothelzellen nicht durch den Notch-Signalweg reguliert. Die Auswertung der Daten in der vorgelegten Arbeit lässt vermuten, dass die einmal festgelegte genetische Determinierung adulter Endothelzellen fixiert und äußeren Einflüssen gegenüber stabil und unumkehrbar ist. Dennoch ist eine gewisse Anpassungsfähigkeit der Endothelzellen an bestimmte Situationen möglich, die zwar die Ausprägung von Merkmalen des jeweilig anderen Phänotyps beinhaltet, jedoch nicht eine vollständige Redifferenzierung.
164

Biometrinės autentifikacijos modelio automobiliams sukūrimas ir tyrimas / Development and research of biometric authentication model for cars

Kulikauskas, Kristijonas 31 August 2011 (has links)
Automobilių apsauga visada buvo, yra ir bus aktuali. Esamos apsaugos priemonės nesunkiai apeinamos ir nesudaro didelių kliūčių, norint transporto priemonę pasisavinti. Reikalinga naujoviška vairuotojo autentifikavimo sistema, galinti sumažinti šią, pasisavinimo tikimybę. Tam tinka biometrija – asmens bruožų ar charakteristikų statistinė analizė ir nustatymas. Juos nustačius, gali būti naudojami asmens autentifikacijai. Tai daroma lyginant su anksčiau užfiksuotu šablonu. Naudojama šioms autentifikacijoms: kompiuteriuose tinklų, praėjimo kontrolės, bankomatuose, apsipirkimams kreditinėmis kortelėmis, mobiliuosiuose telefonuose, delniniuose kompiuteriuose, medicininių įrašų valdymui, nuotoliniame mokymesi ir t.t. Pirštų kraujagyslės – nauja biometrinės autentifikacijos forma. Kadangi kraujagyslės yra po oda, jos yra nematomos apšviečiant natūralia šviesa. Tačiau jos puikiai matomos apšvietus artima infraraudoniems spinduliams šviesa. Šiame tyrime buvo sukurtas ir ištirtas biometrinės autentifikacijos automobiliams modelis. Ištirtas trijų atvaizdų apdorojimo algoritmų tinkamums, nustatant kuris jų mažiausia jautrus raiškos ir triukšmo pasikeitimams. Jį ir siūlome naudoti šiame autentifikacijos modelyje. / Automobile security is always relevant. Existing security systems could be easily bypassed and are not a big barrier for thieves. So there is a necessity for a innovative authentication system. Biometrics consist of methods for uniquely recognizing humans based upon one or more intrinsic physical or behavioral traits. In computer science, in particular, biometrics is used as a form of identity access management and access control. It could be also used for automobile security. Finger vein comparison is a relatively new form of biometrics, which could also be used for authentication. Images of finger veins could be obtained illuminating fingers with near-infrared light. Those images are very unique and different for every person and every finger. In this research biometric authentication model for automobiles is developed and researched. Three image recognition algorythms were tested in the experiment, determining which one is less sensitive to resolution changes and noise. The results were given, proposing use of one algorythm, in our model of biometric authentication system for automobiles.
165

Thermal and Structural Constraints on the Tectonic Evolution of the Idaho-Wyoming-Utah Thrust Belt

Chapman, Shay Michael 16 December 2013 (has links)
The timing of motion on thrust faults in the Idaho-Wyoming-Utah (IWU) thrust belt comes from synorogenic sediments, apatite thermochronology and direct dating of fault rocks coupled with good geometrical constraints of the subsurface structure. The thermal history comes from the analyses of apatite thermochronology, thermal maturation of hydrocarbon source rocks and isotope analysis of fluid inclusions from syntectonic veins. New information from zircon fission track and zircon (U-Th)/He analysis provide constraints on the thermal evolution of the IWU thrust belt over geological time. These analyses demonstrate that the time-temperature pathway of the rocks sampled never reached the required conditions to reset the thermochronometers necessary to provide new timing constraints. Previous thermal constraints for maximum temperatures of IWU thrust belt rocks, place the lower limit at ~110°C and the upper limit at ~328°C. New zircon fission track results suggest an upper limit at ~180°C for million year time scales. ID-TIMS and LA-ICPMS of syntectonic calcite veins suggest that new techniques for dating times of active deformation are viable given that radiogenic isotope concentrations occur at sufficient levels within the vein material.
166

Transcriptional regulation of vascular patterning in Arabidopsis thaliana

Donner, Tyler James Unknown Date
No description available.
167

Mechanism of Vein Pattern Formation in Arabidopsis Thaliana Leaves: testing the Canalization Hypothesis

Amin, Mira 22 August 2011 (has links)
Several mechanisms have been proposed to explain the process of vein pattern formation in plant tissues. The most widely accepted amongst biologists is the canalization hypothesis, derived from pea root and stem experiments. According to this hypothesis, a signal, thought to be the phytohormone auxin, is transported polarly from cell to cell from the shoot to the root and is canalized progressively into narrow channels of high auxin fluxes that later differentiate to become vascular tissue. In this project, we set out to test whether auxin canalization drives vein pattern formation, using Arabidopsis thaliana mutants with increased auxin transport (max4-1, max3-9, max2-1 and max1-1). We predicted that the mutants would have distinct vein patterns and especially different angles between the primary and secondary veins, compared to the wild type. First rosette leaves of 15 plants per genotype were harvested for analysis each day from 7 to 17 days after sowing, giving a total of eight hundred twenty-five leaf samples to analyze. Venation patterns were extracted and analyzed using custom-made software written with Matlab. Overall, compared with the wild type, mutants with the highest auxin transport (max4-1 and max3-9) had different vein patterns at early developmental stages, confirming a role for auxin transport in vein patterning. However, veins of mutants and wild type connected at similar angles, which is not consistent with the auxin canalization hypothesis, as originally formulated.
168

Arterioveninių jungčių dializuojamiems pacientams funkcionavimo pailginimo galimybių tyrimas / Investigation of possibilities to extend functioning time of arteriovenous fistulas for hemodialysis patients

Kybartienė, Sondra 02 July 2012 (has links)
Darbo tikslas: nustatyti veiksnius, susijusius su arterioveninių jung¬čių (AVJ) dializuojamiems pacientams funkcionavimo trukme bei įvertinti jungčių funkcijos monitoravimo naudą jų funkcionavimo trukmei prail-ginti. Darbo uždaviniai: 1. Įvertinti AVJ funkcijos monitoravimo naudą jos funkcionavimo trukmei prailginti. 2. Nustatyti pirmosios hemodializės procedūros atlikimo būdo ryšį su paciento stacionarizavimo trukme. 3. Nustatyti veiksnius, susijusius su AVJ funkcionavimo trukme. 4. Nustatyti centrinės venos kateterio buvimo ir lokalizacijos reikšmę AVJ funkcionavimo trukmei. 5. Įvertinti AVJ „brandinimo“ trukmės ryšį su AVJ funkcionavimo trukme. 6. Įvertinti priešoperacinio kraujagyslių ultragarsinio ištyrimo reikšmę pirminių jungties disfunkcijų išsivystymui bei AVJ funkcionavimo trukmei. DARBO METODIKA Tyrimas atliktas Lietuvos sveikatos mokslų universiteto Nefrologijos klinikoje, gavus Kauno regioninio tyrimų etikos komiteto leidimą Nr. BE 2-20. Dalis duomenų buvo renkama retrospektyviai, naudojant medicinos dokumentaciją, kita dalis informacijos apie pacientų laboratorinių tyrimų duomenis bei HD procedūros parametrus buvo renkama viso tyrimo ei¬goje. Visos AVJ pagal buvo suskirstytos į tris grupes: 1. Istorinė grupė – monitoravimas taikytas nebuvo (187 pacientai, 260 AVJ); 2. Monitoruota grupė – AVJ buvo monitoruojamos nuo pirmosios per ją atliktos HD (29 pacientai, 31 AVJ); 3. Dalinai monitoruota grupė – AVJ naudojamos HD iki 2008 m. gruo-džio 31 d., o vėliau... [toliau žr. visą tekstą] / Patients to be treated with chronic hemodialysis (HD) must have blood vessel connection. There are three types of blood vessel connections: native arteriovenous fistula (AVF), synthetic prosthesis and permanent central venous catheter. Each connection has its strengths and weaknesses. Primary AVF dysfunction occurs in 7.5% of the whole population of patients receiving HD, and in up to 80% of high risk patients (those with diabetes, elderly patients, and women) [Mann et al 2005]. Compared to other blood vessel connections (permanent central venous catheter or synthetic prosthesis) function of properly formed AVF is the longest, and incurs the lowest incidence of infectious and thrombotic complications. All international guidelines on HD procedures recommend native AVF as the method of choice. Formation of blood vessel junctions and treatment of their complications account for up to 20% of all hospitalizations of patients with end stage renal failure in USA [Allon et al 2002], up to 30% in Canada [Mann et al 2005], and up to 25% in Europe [Pissoni et al 2002]. It should be stated that formation of AVF and treatment of their complications are very expensive, and therefore determining the causes of the development of AVF complications and their timely diagnosis and correction are extremely important. Various methods of monitoring of AVF function are used in many European and USA HD centers; however, the most important criterion of early diagnosis of AVF complications has not... [to full text]
169

Hemodynamic investigation of the liver using magnetic resonance imaging and computational fluid dynamics

George, Stephanie Marie 02 July 2008 (has links)
Cirrhosis is a leading cause of death in the United States and has severe and costly complications. Because of the clinical significance of cirrhosis, it is important that noninvasive methods be developed to detect cirrhosis early and to monitor its progression with advancing liver disease. Previous studies on portal venous hemodynamics have been performed mainly with ultrasound with mixed results. Magnetic Resonance Imaging offers several advantages over ultrasound including acquisition of both high quality anatomical and hemodynamic information. Phase-Contrast MR was used to gather velocity data for the portal venous system. Methods were developed to perform registration, segmentation and isolation of the portal vein geometries and velocity data. Computational Fluid Dynamics was also employed to further investigate the flow within the portal vein. Velocity data for the portal vein, superior mesenteric vein, splenic vein and the right or left portal vein was acquired in varying numbers for both data sets. Even with the limited number of subjects a few parameters were significant. Patients with cirrhosis had a significantly increased portal vein area and a significantly decreased average velocity per liver volume and velocity variance. Patients with cirrhosis had a significantly increased splenic vein area and average flow rate per liver volume. While these results are preliminary due to small sample size, they are promising and require further investigation and more subjects including varying stages of disease.
170

Comparação de eficácia e segurança no tratamento da insuficiência venosa crônica grave (CEAP 6) ablação endovenosa por radiofrequência versus ablação endovenosa por laser versus escleroterapia por espuma versus elastocompressão. /

Pimenta, Rafael Elias Farres January 2018 (has links)
Orientador: Marcone Lima Sobreira / Resumo: Introdução: A doença venosa em sua apresentação mais grave, úlcera venosa em atividade ou cicatrizada, afeta de 2 – 6 milhões de pessoas, se considerarmos a população acima de 70 anos. A terapia de compressão (EC) é considerada o tratamento clínico mais eficaz para úlcera venosa(UV), mas a recorrência deve ser prevenida com o tratamento da hipertensão venosa. Evidências sugerem que a recorrência da úlcera é diminuída com a cirurgia venosa superficial, com superioridade de intervenções endovenosas minimamente invasivas, como laser (EVLA) ou ablação por radiofrequência (RF), sobre o tratamento cirúrgico clássico. A escleroterapia com espuma (EE) tem demonstrado também eficácia na correção da hipertensão venosa, sendo seu uso cada vez mais difundido. Entretanto, ainda faltam evidências comparando as técnicas entre si com a terapia compressiva clássica. Objetivo: Comparar as técnicas endovenosas, como radiofrequência (RF) e endolaser (ELVA), com escleroterapia por espuma (EE) e o tratamento clínico por meio de elastocompressão em pacientes com insuficiência venosa crônica (IVC) avançada (CEAP 6). Casuística e Métodos: Estudo prospectivo, controlado e randomizado. Foram incluídos 126 (cento e vinte e seis) pacientes, num total de 139 (cento e trinta e nove) pernas com úlceras venosas ativas, randomizados de maneira independente em 4 grupos: Radiofrequência ou Laser ou Espuma ou Elastocompressão. A área da ferida foi determinada em cm2, com controle fotográfico das úlceras venosas ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: ABSTRACT: Introduction: Venous disease in its more serious presentation, healed or open venous ulcers, affects 2 – 6 million people worldwide. Compression therapy (EC) is considered the most effective clinical treatment for venous ulcers (VU) ; however, recurrence is prevented by treating underlying venous hypertension. Current evidence suggests that ulcer recurrence is reduced by superficial venous surgery. Minimally invasive endovenous treatment modalities, such as laser (EVLA) or radiofrequency ablation (RF) have shown superiority over the classic open surgical treatment. Foam sclerotherapy (EE) has also been shown to be effective in treating venous hypertension, Nonetheless, there isn’t enough evidence comparing all these techniques against classic compression therapy. Objective: To compare catheter-based endovenous techniques, such as radiofrequency (RF) and endolaser (ELVA) with foam sclerotherapy (EE) and clinical treatment using elastic compression in patients with advanced chronic venous disease (IVC) (CEAP 6). Methods: Randomized, open label, controlled trialy. One hundred twenty-six (N=126) patients in a total of 139 (one hundred thirty-nine) legs with active venous ulcers, were randomized and enrolled in an independent manner into 4 groups: RF, EVLA, EE or EC.. The wound area was measured in cm2. Photographic assessment of venous ulcer healing along with ultrasonography control. Major adverse events, such as deep vein thrombosis, pulmonary embolism, and death were... (Complete abstract click electronic access below) / Doutor

Page generated in 0.0396 seconds