• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 49
  • 5
  • 4
  • 4
  • 2
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 96
  • 23
  • 14
  • 12
  • 12
  • 11
  • 10
  • 9
  • 9
  • 8
  • 7
  • 7
  • 7
  • 7
  • 6
  • 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.
31

Study of the Transport of Odorants from Illicit Substances Using Direct Analysis in Real Time Mass Spectrometry

Zughaibi, Torki A 29 June 2017 (has links)
Canines have been employed in matters of law enforcement because of their keen sense of smell. Presently, law enforcement officials are utilizing trained canines in routine traffic stops to assess if the vehicle contains any illicit substances. Many believe that this is an infringement on an individual’s fourth amendment rights, which has garnered the attention of both the media and the courts. Many questions have been raised with respect to canines alerting to locations where illicit substances were no longer present. Thus, the purpose of this dissertation research is to evaluate the manner in which active odorants transport and persist onto various substrates. Direct Analysis in Real Time (DART) coupled to an accurate-mass time-of-flight (AccuTOF™) mass spectrometer was used to rapidly analyze the volatile organic compounds (VOC’s) from a variety of narcotic and explosive substances. The DART ion source is a soft ionization technique used in ambient conditions to sample liquids, solids or gases in real time. Thermal desorption of the VOC’s could thus be conducted in seconds. The present study found that the VOC’s from illicit substances transport from one location to another, in a short amount of time, through a process known as advection, which may contribute to canines producing unconfirmed alerts during their training and certifications. Three of the four odorants used in this study produced positive results, with the exception being 2-ethyl-1-hexanol, as it was not detected at any time when held at distances between 0.5 and 3 meters. In addition, the amount of time needed for an active odorant to contaminate an object in its immediate vicinity was explored and the results were determined to be inconclusive. Although they were observed following longer exposure times, it was still deemed to be inconclusive since it was still possible for these odorants to be present, albeit not in detectable amounts, at lower exposure times. Controlled odor mimic permeating systems (COMPS), patented technology by IFRI were tested to determine the possibility of cross-contamination between the training aids, and the results conclude that there was not any evidence of cross-contamination observed during any of the trials.
32

Design, synthèse et évaluation biologique de mimes du paclitaxel dérivés de la proline / Design, synthesis and biological evaluation of paclitaxel mimics based on proline derivatives

Lamotte, Yann 18 December 2015 (has links)
Parmi les nombreux agents thérapeutiques utilisés en oncologie, le paclitaxel (Taxol®) est sans doute celui qui a suscité le plus d'intérêt. Il est utilisé en clinique pour le traitement des cancers de l'ovaire, du sein et des poumons. Il agit comme poison du fuseau mitotique en favorisant l'assemblage de la tubuline en microtubules et en stabilisant le polymère formé. Initialement extrait de l'if du Pacifique (Taxus Brevifolia) puis obtenu par hémisynthèse à partir de la 10-déacétylbaccatine III, il est aujourd'hui produit par un procédé biotechnologique de fermentation de cellules végétales. Le paclitaxel possède une structure chimique complexe basée sur un squelette tétracyclique taxane. Une approche visant à remplacer ce squelette taxane par une structure chimique plus simple a été entreprise afin d'identifier des mimes du paclitaxel. L'identification d'un fragment chimique (fragment based drug design) dérivé de la proline par une étude de modélisation moléculaire a permis de développer de nouvelles séries de mimes du paclitaxel. Parallèlement, le remplacement du squelette taxane par une matrice peptidique cyclique utilisant des dérivés de la proline a été réalisé. Les études de modélisation moléculaire, la synthèse des mimes du paclitaxel et leur évaluation biologique seront présentées. / Among the many therapeutic agents used in oncology, paclitaxel (Taxol®) is probably the one that generated the most interest. It is used clinically for the treatment of ovarian, breast and lung cancers and acts as a mitotic spindle poison by promoting the assembly of tubulin into microtubules and stabilizing the polymer formed. Initially extracted from the Pacific yew (Taxus Brevifolia) and obtained by semi-synthesis from 10-deacetylbaccatin III, it is now produced by a biotechnological process of cell plant fermentation. Paclitaxel has a complex chemical structure based on a tetracyclic taxane skeleton. A process to replace the taxane skeleton with a simpler chemical structure was undertaken to identify paclitaxel mimics. The identification of a chemical fragment (fragment based drug design) derived from proline by a molecular modeling study has led to the design of a new series of paclitaxel mimics. Meanwhile, replacing the taxane skeleton by a cyclic peptide scaffold using proline derivatives was performed. Molecular modeling studies, synthesis of paclitaxel mimics and biological evaluation will be presented.
33

Organizational networking in business-to-business markets : construct conceptualization, operationalization and application

Thornton, Sabrina January 2014 (has links)
This thesis focuses on one key theme, which is to understand the construct of organizational networking behaviors in business-to-business markets. It is concerned with two main issues, which are built into the research program of three empirical studies. The first issue is concerned with a systematic understanding of organizational behaviors in response to the embeddedness and interconnectedness of the network of business relationships that every organization has to deal with. Study 1 of the research program explores the concept termed ‘organizational networking behaviors’. This study adopts an industrial network approach, the central tenet of which is that firms undertake a continuous process of interaction with their important partners in the embedding context of the business network. A multi-informant approach, using semi-structured interviews, was used to collect qualitative data from thirty-one executive managers (in fifteen manufacturing firms in the UK). This study identified information acquisition, opportunity enabling, strong-tie resource mobilization and weak-tie resource mobilization as four types of organizational networking behaviors, which are reflected by their respective sub-types. The resulting conceptualization of organizational networking forms the basis for the operationalization of the construct in Study 2. While Study 1 takes an exploratory qualitative approach, Study 2 deploys a confirmatory quantitative approach since it is necessary to confirm/refute the resulting conceptualization and its types from Study 1. A rigorous scale construction and validation process was followed in this study. The conceptualization of the measurement model was carefully considered based on its theoretical underpinning. A second-order formative measurement structure was conceptualized, which required the employment of a multiple indicators and multiple causes (MIMIC) model for the validation of such a measurement model. A dataset of 603 responses was collected and analyzed to confirm the structure of the four types of organizational networking behaviors, which is in line with the results of Study 1.The second issue that the thesis is concerned with is the influences of such organizational networking efforts, which are examined from a firm’s behavioral perspective. Study 3 examines how organizational networking behaviors serve as the driver of a firm’s customer-oriented, competitor-oriented and relationship-oriented behaviors due to the sensing and seizing aspects of networking. It was also hypothesized that a firm’s customer-oriented, competitor-oriented and relationship-oriented behaviors positively affect firm performance. The test of these hypotheses required survey data collection, which was done through an on-line questionnaire. A dataset of 354 responses was collected from UK managers, whose organizations operate in business-to-business markets in either the manufacturing or services sectors. The use of statistical modeling techniques is similar to that of Study 2. The research results indicate that a firm’s network-oriented behaviors positively impact on the development of customer-oriented and competitor-oriented behaviors. They also foster relationship coordination with its important business partners within the network. In addition, the effective management of the firm’s portfolio of relationships is found to mediate the positive impact of network-oriented behaviors on firm profitability.
34

Identifying and Reducing Variability, Improving Scaffold Morphology, and Investigating Alternative Materials for the Blood Vessel Mimic Lab Electrospinning Process

Dowey, Evan M 01 September 2017 (has links)
The work of the Cal Poly Tissue Engineering Lab is primarily focused on the fabrication, characterization, and improvement of “Blood Vessel Mimics” (BVMs), tissue engineered constructs used to evaluate cellular response to vascular medical devices. Currently, cells are grown onto fibrous, porous tubes made using an in-house electrospinning process from PLGA, a biocompatible co-polymer. The adhesion and proliferation of cells in a BVM is reliant on the micro-scale structure of the PLGA scaffold, and as such it is of great importance for the electrospinning process to consistently produce scaffolds of similar morphologies. Additionally, it has been shown that cell proliferation increases with scaffolds of smaller fibers and pores than the current electrospinning protocol can produce. Finally, the Tissue Engineering Lab has interest in testing devices in more tortuous BVM bioreactor designs, however the use of relatively rigid PLGA scaffolds has severely limited the ability to construct more complicated vessel geometries. The overall goal of this thesis was to improve fabrication and characterization of electrospun polymer scaffolds for BVM use. The specific aims of this thesis were to: 1) Improve scaffold characterization by comparing two techniques for fiber diameter measurement and implementing a technique for pore area measurement. 2) Reduce scaffold fiber diameter and pore area by investigating humidity and solvent composition electrospinning parameters. 3) Reduce process variability by developing a more specific electrospinning protocol. 4) Improve scaffold consistency and use by understanding and reducing PLGA scaffold shrinkage. 5) Identify and evaluate more flexible polymers as potential alternatives for electrospun BVM scaffolds. In order to accomplish these aims, first, several BVM and outside literature images were taken and evaluated with current and prospective fiber diameter techniques, and with 2 prospective pore area techniques to characterize accuracy and consistency of each method. It was found that the prospective fiber diameter measurement technique was not superior to the current method. The techniques developed for pore area measurement were found to produce results that differed significantly from each other and from the published value for a given image. Next, changes to environmental and solution composition parameters were made with the hopes of reducing fiber diameter and pore area of electrospun PLGA scaffolds. Changes in relative humidity did not appear to significantly affect scaffold fiber diameter while changes to solvent composition, specifically the use of acetone, resulted in fibers significantly smaller than those regularly achieved in the BVM lab. Next, several sources of variability in the electrospinning protocol were identified and subsequently altered to improve consistency and usability. Specifically, this included redefining the precision with which PLGA mass was measured, repositioning electrical equipment to reduce the effect of stray electrostatic forces on the polymer solution jet, attempting to control the temperature and humidity inside the electrospinning enclosure, and improving the ease with which scaffolds are removed from their mandrels through alternative mandrel surface treatments. In addition to overall process variability, the issue of scaffold shrinkage during BVM use was investigated and two possible treatments, exposure to either ethanol or elevated temperatures, were proposed based on previous electrospinning literature results. Each was tested for their effectiveness in mitigating shrinkage through exposure to BVM setup-mimicking conditions. It was found that both treatments reduced scaffold shrinkage compared to control samples when exposed to BVM setup-mimicking conditions. Finally, 3 flexible polymers were selected and electrospun to compare against typical PLGA results and to conduct a kink radius test as a metric for measuring flexibility as it pertains to the proposed BVM lab application. It was concluded that two types of thermoplastic polyurethane (tPU) were not acceptable electrospinning materials for use in the BVM lab. Additionally, while polycaprolactone (PCL) could be successfully electrospun it could not undergo the amount bending required for more tortuous BVM bioreactor designs without kinking. Overall, the work in this thesis provided insight into multiple scaffold characterization techniques, reduced overall electrospinning variability in the fabrication and use of PLGA scaffolds, and defined processing parameters that have been shown to yield scaffolds with smaller morphological features than all prior Tissue Engineering Lab work. By creating better, more effective scaffolds, researchers in the Tissue Engineering Lab can more accurately mimic the structure and properties of native blood vessels; this, in turn, will result in BVM cell responses that more closely resemble that of native tissue. Creating consistent and appropriate BVMs will then lead to impactful contributions to the existing body of tissue engineering research and to better preclinical device testing.
35

Konspirationsteorier, alternativmedicin, vidskepelse och rasism : En studie om trossystem i VoF-undersökningen

Wallström, Måns January 2022 (has links)
In this study, data from the survey Vetenskap- och Folkbildningsundersökningen 2021 on belief in conspiracy theories, alternative medicine, superstition and racist ideas was analyzed using a multiple causes, multiple indicators structural equation model. It was found that viewing stances on the selected survey questions as a manifestation of these 4 belief systems (belief in conspiracy theories, belief in alternative medicine, superstition, and racism) is supported by the data, and that the belief systems are statistically significantly correlated. Among other results, it was also found that, when controlling for background variables such as size of place of residence, gender, education level and age, persons with a university education believe in conspiracy theories, alternative medicine, superstition and racist ideas to a lesser extent than persons with lower formal education, while sympathizers of the Sweden Democrats hold these beliefs to a greater extent than sympathizers of other parties.
36

Development of an In-Vitro Tissue Engineered Blood Vessel Mimic Using Human Large Vessel Cell Sources

Delagrammaticas, Dimitri E 01 May 2009 (has links)
Tissue engineering is an emerging field that offers novel and unmatched potential medical therapies and treatments. While the vast aim of tissue engineering endeavors is to provide clinically implantable constructs, secondary applications have been developed to utilize tissue-engineered constructs for in-vitro evaluation of devices and therapies. Specifically, in-vitro blood vessel mimics (BVM) have been developed to create a bench-top blood vessel model using human cells that can be used to test and evaluate vascular disease treatments and intravascular devices. Previous BVM work has used fat derived human microvascular endothelial cells (EC) sodded on an ePTFE scaffold. To create a more physiologically accurate model, a dual layer of large vessel endothelial and smooth muscle cells (SMC) on an ePTFE tube is investigated throughout this thesis. Human umbilical vein endothelial cells (HUVEC) and human umbilical vein smooth muscle cells (HUVSMC) were chosen as the large vessel cell types and cultivated according to standard procedures. Before dual sodding, sodding density experiments with HUVSMC were performed to determine the number of cells required to create a confluent cell layer. HUVSMC sodded by trans-luminal pressure at densities ranging from 3.5x10^5 cells/cm^2 to 1.0x10^6 cells/cm^2 were run for one day to observe luminal coverage. After determining the desirable range for HUVSMC sodding, HUVSMC experiments with 5.0x10^5 cells/cm^2 and 7.5x10^5 cells/cm^2 were run over seven days to evaluate progression of the graft over time. Histology and SEM methods were used for analysis. A HUVEC study was next conducted over 7 days to confirm that the large vessel endothelial cell could be sodded and sustained on ePTFE in-vitro. Next, dual sodding was performed by pressure sodding HUVSMC at 7.5x10^5 cells/cm^2 followed by trans-luminal flow for 30 minutes. HUVECs were subsequently trans-luminally pressure sodded at 5.0x10^5 cells/cm^2 followed by an additional 30 minutes of trans-luminal flow; perfusion flow began following the final 30 minutes of trans-luminal flow. Experiments for the dual layered grafts were run for both one and seven days to evaluate and develop the dual sodding protocol as well as observe the co-culture over time. Analysis of the dual layered grafts was performed by SEM, histology, and fluorescence microscopy. HUVECs were incubated with Cell Tracker™ prior to dual sodding and both cell types with bisbenzimide after graft harvest to attempt to distinguish between cell types. Results from the thesis illustrate that large vessel smooth muscle and endothelial cells can be sodded onto ePTFE scaffolds and sustained within the in-vitro BVM system for up to 7 days. Furthermore, cost analysis demonstrates that the addition of a smooth muscle cell layer adds minimal costs to the BVM system. In conclusion, the studies contained within this thesis culminate in a protocol for the dual sodding of smooth muscle and endothelial cells with the aim of creating a physiologically representative co-culture blood vessel mimic.
37

Development and evaluation of novel structurally simplified sialyl LewisX mimic-decorated liposomes for targeted drug delivery to E-selectin-expressing endothelial cells. / E-セレクチン発現内皮細胞への標的指向化薬物送達を目的とした新規構造単純化シアリルルイスXミミック修飾リポソームの開発と評価

CHANTARASRIVONG, CHANIKARN 25 March 2019 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(薬科学) / 甲第21715号 / 薬科博第106号 / 新制||薬科||11(附属図書館) / 京都大学大学院薬学研究科薬科学専攻 / (主査)教授 山下 富義, 教授 髙倉 喜信, 講師 樋口 ゆり子 / 学位規則第4条第1項該当 / Doctor of Pharmaceutical Sciences / Kyoto University / DFAM
38

The Great Masquerade: Medical Conditions that Mimic Mental Illness

Rice, Judy A. 01 April 2001 (has links)
No description available.
39

Synthesis of 4'-Ester Resveratrol Analogues, Chromium Trioxide Oxidation of Terpenes, and Synthesis of Mimics of (-)-Englerin A

Acerson, Mark Jeffrey 01 August 2014 (has links) (PDF)
4’ -ester analogues of resveratrol were synthesized using reaction conditions developed to produce mono-ester products in the presence of two other unprotected phenols. Basic conditions were employed to deprotonate the most acidic 4’ phenol followed by addition of anhydrides or acid chlorides to give the ester product. The reaction favored 4’-ester formation in polar aprotic solvents with DMSO being the optimal solvent. (—)-Englerin A is a guaiane-type sesquiterpene containing two ester side chains. Mimics of (—)-englerin A were proposed that retained the ester side chains while replacing the non-polar core with less complicated structures. These proposed mimic cores would maintain the three-dimensional positioning of the esters which are responsible for the anti-cancer activity of (—)-englerin A. Three mimics were synthesized using the bicyclic terpenes borneol and fenchol. Installation of the second ester on the terpene core was accomplished throught the development and optimization of a unique methylene oxidation using chromium trioxide in glacial acetic acid. These mimics were screened against two kidney cancer cell lines. The compounds were shown to have IC50 (inhibitory concentration for 50 % of cells) values above 30 µM.
40

Characterization and Implementation of a Decellularized Porcine Vessel as a Biologic Scaffold for a Blood Vessel Mimic

Smith, Aubrey N 01 June 2011 (has links) (PDF)
Every 34 seconds, someone in the United States suffers from a heart attack. Most heart attacks are caused by atherosclerotic build up in the coronary arteries, occluding normal blood flow. Balloon angioplasty procedures in combination with a metal stent often result in successful restoration of normal blood flow. However, bare metal stents often lead to restenosis and other complications. To compensate for this problem, industry has created drug-eluting stents to promote healing of the artery wall post stenting. These stents are continually advancing toward better drug-eluting designs and methods, resulting in a need for fast and reliable pre-clinical testing modalities. Dr. Kristen Cardinal recently developed a tissue engineered blood vessel mimic, with the goal of testing intravascular devices. However, the scaffold component of this model exhibits several physiological limitations that must be addressed to create a truly biomemtic BVM. The current model uses expanded poly(terafluorethylene) [ePTFE] or poly(lactic-go-glycolide) [PLGA] as the choice material for the scaffold. EPTFE has several advantages as it is a widely recognized biomaterial. However, ePTFE is very expensive and lacks native mechanical properties. PLGA is another polymer that is created in-house to produce a uniquely tailored scaffold for use in the BVM; resulting in a cheaper alternative scaffold material. However, PLGA again lacks the necessary native mechanical properties to properly mimic an in-vivo artery. The creation of a biological scaffold will provide a unique biomimetic material to most accurately recapitulate the artery in-vitro. Decellularization is the process of removing all cellular components from a tissue, leaving an acellular structure of extracellular matrix. Understanding the clinical problem and the potential of the BVM, the aim of this thesis is to develop the decellularization process for the creation of a biologic scaffold as a replacement to the non-physiologic polymer scaffolds for the BVM. The first phase of this thesis was to develop and optimize an acceptable protocol for the decellularization of porcine arteries. The use of a 0.075% sodium dodecyl sulfate detergent was sufficient for complete removal of all vascular cell types, without significant degradation to the scaffold wall. In the second phase of this thesis, the decellularized scaffolds were mechanically tested to ensure retention of their native properties. The longitudinal and radial properties of the scaffold were found to be similar to the native artery, indicating the decellularized scaffold improves several physiologically aspects when compared to a polymer scaffold. These mechanical attributes improve the testing environment when evaluating sent deployment or new balloon angioplasty devices; as the decellularized scaffold has an phsyiolgical compliance. The final phase of this thesis examined the cellular adhesion capacities of the scaffold through recellularization with human umbilical vein endothelial cells (hUVECS). Fluorescent microscopy analysis suggests uniform attachment of cells along the length of the scaffold creating a monolayer. These results indicate this new scaffold type can develop an endothelium to complete the ideal, most physiologically relevant BVM system. Further optimization of the decellularization procedures could enhance the ability of the scaffold to be cultured for long-term interaction with intravascular devices.

Page generated in 0.0412 seconds