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  • 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.
11

Ultrastructure of the Primary Cell Wall of Softwood Fibres Studied using Dynamic FT-IR Spectroscopy

Stevanic Srndovic, Jasna January 2008 (has links)
The primary cell wall is a complex multipolymer system whose composite structure has been mostly determined from chemical and biochemical studies. Although the primary cell wall serves a central role, with regard to the connective properties of fibres, knowledge about the interactions among the polymers, when it comes to the mechanical properties, is very limited. The physical properties of the polymers, i.e. their elastic and viscous deformations, as well as the ultrastructure of the polymers, i.e. the interactions among the polymers in the outer fibre wall layers that lead to this behaviour, are still not fully understood. The aim of this study was to examine how the different wood polymers, viz. lignin, protein, pectin, xyloglucan and cellulose, interact in the outer fibre wall layers of the spruce wood tracheid. The initial objective was to separate an enriched primary cell wall material from a first stage TMP, by means of screening and centri-cleaning. From this material, consisting of the primary cell wall (P) and outer secondary cell wall (S1) materials, thin sheets were prepared and analysed using a number of different analytical methods. The major measuring technique used was dynamic Fourier transform infra-red (FT-IR) spectroscopy in combination with dynamic 2D FT-IR spectroscopy. This technique is based on the detection of small changes in molecular absorption that occur when a sinusoidally stretched sample undergoes low strain. The molecular groups affected by the stretching respond in a specific way, depending on their environment, while the unaffected molecular groups provide no response to the dynamic spectra, by producing no elastic or viscous signals. Moreover, the dynamic 2D FT-IR spectroscopy provides useful information about various intermolecular and intramolecular interactions, which influence the reorientability of functional groups in a polymer material. Measurements of the primary cell wall material, using dynamic FT-IR spectroscopy, indicated that strong interactions exist among lignin, protein and pectin, as well as among cellulose, xyloglucan and pectin in this particular layer. This was in contrast to the secondary cell wall, where interactions of cellulose with glucomannan and of xylan with lignin were dominant. It was also indicated that the most abundant crystalline cellulose in the primary cell wall of spruce wood fibres is the cellulose Iβ allomorph, which was also in contrast to the secondary cell wall, where the cellulose Iα allomorph is more dominant. The presence of strong interactions among the polymers in the primary cell wall and, especially, the relatively high content of pectin and protein, showed that there is a very good possibility of selectively attacking these polymers in the primary cell wall. The first selective reaction chosen was a low degree of sulphonation, applied by an impregnation pretreatment of chips with a very low charge of sodium sulfite (Na2SO3). This selective reaction caused some structural modification of the lignin, a weakening of the interactions between lignin;pectin, lignin;protein and pectin;protein, as well as an increased softening of the sulphonated primary cell wall material, when compared to the unsulphonated primary cell wall material. All this resulted in an increased swelling ability of the material. / QC 20101123
12

Desenvolvimento de métodos físicos e químicos para distinção de amostras autênticas e falsificadas de sibutramina

Knobloch, Jéssica Gil January 2015 (has links)
O comércio ilegal de medicamentos é um problema mundial que afeta milhões de pessoas todos os anos. A inclusão digital contribui para a ascensão das vendas, transformando-se no principal veículo de comércio de medicamentos falsificados no mundo. No Brasil, o número de medicamentos contrabandeados apreendidos pela Polícia Federal aumentou nos últimos anos, principalmente, nas regiões Sul e Sudeste. Sendo que grande parte destes, entraram pelo país pelo Paraguai. Os medicamentos falsificados que predominam no Brasil são para tratamento de disfunção erétil e para perda de peso. O objetivo deste trabalho foi comparar amostras de sibutramina de origens distintas a fim de detectar falsificações e agrupar amostras com propriedades semelhantes, através da quantificação por Cromatografia líquida acoplada à espectrometria de massas (CL-EM); da identificação por espectroscopia de infravermelho (IV) e do perfil físico (determinação do peso médio e exames físicos dos pós e cápsulas). Fez-se previamente o perfil físico das amostras, no qual foi possível identificar grupos com características semelhantes, mas adquiridos por diferentes vias. No entanto, o perfil físico sozinho não é definitivo para determinar uma falsificação e muito menos determinar uma origem comum para a mesma. Na espectroscopia de IV observou-se que quase todas as amostras apresentaram sinais nas regiões características dos grupamentos químicos da sibutramina. Nesta análise, foi possível identificar quatro grupos distintos. Em relação ao método de CL-EM validado, ele se mostrou específico, linear, exato, preciso e robusto. Os resultados da análise por CL-EM revelaram que apenas uma das amostras ilegais da faixa de 90-110%. Duas amostras apresentaram teor acima e sete abaixo. Por fim, das doze amostras analisadas, apenas as duas originais e uma das ilegas apresentaram teor adequado. Assim, pudemos verificar que é muito fácil obter sibutramina de fontes ilegais e que estes medicamentos não têm qualidade. A divulgação destes resultados é a melhor maneira de desencorajar as pessoas a não utilizarem estas fontes para a obtenção de medicamentos. / The illegal trade in drugs is a global problem that affects millions of people every year. Digital inclusion contributes to the rise of the sale of these drugs, making internet the main option in the world. In Brazil, the number of smuggled drugs seized by the Federal Police increased in recent years, mainly in the South and Southeast regions. Since most of them have entered Brazil via Paraguay. Counterfeit drugs that predominate in Brazil are those used to treat erectile dysfunction and to promote weight loss. The objective of this study was to compare samples of sibutramine with different origins in order to detect counterfeits and grouping samples with similar properties through quantification by liquid chromatography coupled to mass spectrometry (LC-MS) in previously developed and validated method; identification by infrared spectroscopy (IR) and physical profile (determination of average weight and physical examinations powders and capsules). In order to do so, 12 samples were examined, two original products acquired from local pharmacies and 10 from internet and street vendors. Based on visual examination at least three potential sources of capsules were identified, but acquired from different sources. However, the physical profile alone cannot be used to identify counterfeit drugs. Using infrared spectroscopy we found out that almost all samples showed signals that could be attributed to sibutramine functional groups. Based on IR spectra, four groups were identified, with six, three, two and one brand. Regarding the LC-MS method validated, it proved to be showed specific, linear, accurate, precise and robust. The results of LC-MS analysis revealed that only one of the illegally acquired samples were within the 90-110%. Two samples were above and the other seven were bellows those limits. Overall we found out that is very easy to buy sibutramine in the informal market and most of them are of poor quality and maybe the publication of these data coulb be the best way to discourage people to seek these sources.
13

Rapid classification and differentiation of bacteria by analytical techniques

Almasoud, Nagla January 2016 (has links)
Several traditional methods have been used to characterise bacteria, such as biochemical, morphological and molecular tests; however, these methods are time-consuming and not always reliable. Recently, modern analytical techniques have emerged as powerful tools offering high-throughput, reliable and rapid analysis in applications, such as clinical and microbiology studies. A variety of modern analytical techniques have been employed for bacterial characterisation, including matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF-MS), liquid chromatography-mass spectrometry (LC-MS), Fourier transform infrared (FT-IR) spectroscopy and Raman spectroscopy. This thesis focused on developing a robust MALDI-TOF-MS methodology to generate mass spectra profiles for the discrimination of clinically-significant bacteria. The data generated from MALDI-TOF-MS analysis are significantly influenced by a number of experimental factors, namely instrument settings, sample preparation, the choice of matrix, matrix additives and matrix preparation as well as sample-matrix deposition methods. The need to optimise experimental variables for bacterial analysis using MALDI-TOF-MS was evident despite the increased application of this analytical tool for clinical microbiology. Experimental optimisation revealed that the choice of matrix is the most important element in MALDI-TOF-MS analysis. Based on this study, a number of different matrices were used to obtain more reproducible mass spectra to classify bacterial samples using a rapid and effective approach. Studies in this thesis indicated that sinapinic acid (SA) is the best matrix for the analysis of proteins from intact bacteria, while 6-aza-2-thiothymine (ATT) and 2,5-dihydroxybenzoic acid (DHB) produced promising results for the analysis of lipid extracts from bacteria. Analytical techniques in combination with multivariate analysis, such as principal components analysis (PCA) and principal component-discriminant function analysis (PC-DFA), were used for bacterial discrimination. Classification was initially undertaken using MALDI-TOF-MS analysis, and subsequently FT-IR spectroscopy, Raman spectroscopy and LC-MS were performed to confirm the classification results. Two main types of bacteria were used for this analysis: 34 strains from seven Bacillus and Brevibacillus species and 35 isolates from 12 Enterococcus faecium strains. The findings showed that the four analytical techniques provide clear discrimination between bacteria at these different levels. Classification of different Bacillus and Brevibacillus bacteria using MALDI-TOF-MS analysis of extracted lipids was confirmed by LC-MS data. In addition, MALDI-TOF-MS data based on extracted lipids and intact bacterial cell proteins were very similar. MALD-TOF-MS analysis of intact enterococci cells produced successful classification with 78% correct classification rate (CCR) at the strain level. FT-IR and Raman spectroscopic data produced very similar bacterial classification with CCR of 89% and 69% at the strain level, respectively. However, classification based on MALDI-TOF-MS data and that based on spectroscopic data were slightly different (Procrustes distance of 0.81, p < 0.001, at the species level). Overall, the findings in this thesis indicate the potential of MALDI-TOF-MS as a rapid, robust and reliable method for the classification of bacteria based on different bacterial preparations.
14

Caracteriza??o anat?mica e f?sicoqu?mica do tegumento da semente de Araucaria angustifolia (Bert.) O. Ktze / Anatomical and physico-chemical characterization of the Araucaria angustifolia (Bert.) O. Ktze

Sampaio, Danielle Affonso 19 May 2016 (has links)
Submitted by Sandra Pereira (srpereira@ufrrj.br) on 2017-01-26T14:34:24Z No. of bitstreams: 1 2016 - Danielle Affonso Sampaio.pdf: 3006939 bytes, checksum: 839c5d77a13fd99ad3c749c33dc2530a (MD5) / Made available in DSpace on 2017-01-26T14:34:25Z (GMT). No. of bitstreams: 1 2016 - Danielle Affonso Sampaio.pdf: 3006939 bytes, checksum: 839c5d77a13fd99ad3c749c33dc2530a (MD5) Previous issue date: 2016-05-19 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico - CNPq / Seed integument plays an important role in the plant life cycle, monitoring the embryo development and germination. Informations about cell structure and physico-chemical characteristics of the Araucaria angustifolia seed coat are important to its correct functional interpretation. Thus, the aim of this study was the anatomical and physico-chemical characterization of the Araucaria angustifolia seed integument. Anatomical features were observed using different microscopy techniques (brightfield microscopy, fluorescence microscopy and scanning electron microscopy) and histochemical tests (Lugol, Wiesner, Sudan IV and potassium dichromate ? K2Cr2O7). Chemical analysis included the extractive, holocelulose and Klason lignin contents (untreated and treated with sodium hydroxide ? NaOH). Functional groups of the integument layers and lignin were observed by Fourier transformed infrared spectroscopy using a VARIAN 640-IR FT-IR spectrometer. Colour analyses were performed in CIE 1976 L*a*b* space colour according to ISO 11664-4:2008 standard using CM 2600d spectrometer. Wettability of the layers was evaluated by contact angle analysis with the drop shape analyser DSA 100. The Araucaria angustifolia seed integument is composed by three distinct layers: exotesta, mesotesta and endotesta. The layers have different chemical and anatomical characteristics. Lignin structure of the integument layers was classified as guayacil (G) type. The endotesta was the layer with higher chromaticity due to higher extractive content and phenolic substances. The wettability varied between layers according to ther strusture. The results of this study contribute to a better understanding of the functioning of the Araucaria angustifolia seed integument and corroborate to future studies on seed physiology / O tegumento de semente desempenha um papel importante no ciclo de vida do vegetal, controlando o desenvolvimento do embri?o e a germina??o. O conhecimento da estrutura celular e das caracter?sticas f?sico-qu?micas do tegumento da semente de Araucaria angustifolia ? importante para a correta interpreta??o funcional do mesmo. Sendo assim, o objetivo deste estudo consistiu na caracteriza??o anat?mica e f?sico-qu?mica do tegumento da semente de Araucaria angustifolia. As caracter?sticas anat?micas foram observadas atrav?s de diferentes t?cnicas de microscopia (microscopia de campo claro, microscopia de fluoresc?ncia e microscopia eletr?nica de varredura) e testes histoqu?micos (Lugol, Wiesner, Sudan IV e dicromato de pot?ssio ? K2Cr2O7). Nas an?lises qu?micas, determinou-se os teores de extrativos, holocelulose e lignina de Klason tratada e n?o-tratada com hidr?xido de s?dio ?NaOH. Os grupos funcionais das camadas do tegumento e da lignina foram observados por espectroscopia no infravermelho por transformada de Fourier atrav?s do espectr?metro VARIAN 640-IR FT-IR. As an?lises colorim?tricas foram realizadas no espa?o de cor L*a*b* CIE 1976 segundo a norma ISO 11664-4: 2008 utilizando o espectrofot?metro CM 2600d. A molhabilidade das camadas foi avaliada atrav?s de an?lises de ?ngulo de contato com o sistema de formato da gota DSA 100. O tegumento da semente de Araucaria angustifolia ? composto por tr?s camadas distintas: exotesta, mesotesta e endotesta. As camadas apresentam caracter?sticas qu?micas e anat?micas distintas. A estrutura da lignina das camadas do tegumento foi classificada como guaiac?lica (G). A endotesta foi a camada com maior cromaticidade devido ao maior teor de extrativos e subst?ncias fen?licas. A molhabilidade variou entre as camadas em fun??o da sua estrutura. Os resultados deste estudo contribuem para uma melhor compreens?o do funcionamento do tegumento da semente de Araucaria angustifolia, podendo corroborar com estudos futuros sobre a fisiologia da semente
15

Synthesis and modification of potential CO2 adsorbents : Amine modified silica and calcium carbonates

Aziz, Baroz January 2012 (has links)
The prospect of rapid changes to the climate due to global warming is subject of public concern. The need to reduce the emissions of atmospheric green house gases and in particular carbon dioxide is greater than ever. Extensive research is performed to find new solutions and new materials, which tackles this problem in economically benign way. This thesis dealt with two potential adsorbents for post combustion  carbon capture, namely, amine modified silica and calcium carbonates. We modified porous silica with large surface area by propyl-amine groups to enhance the carbon dioxide adsorption capacity and selectivity. Experimental parameters, such as reaction time, temperature, water content, acid and heat treatment of silica substrate were optimized using a fractional factorial design. Adsorption properties and the nature of formed species upon reaction of CO2 and amine-modified silica were studied by sorption and infrared spectroscopy. Physisorbed and chemisorbed amount of adsorbed CO2 were, for the first time, estimated directly in an accurate way. The effects of temperature and moisture on the CO2 adsorption properties were also studied. Crystallization of calcium carbonate as a precursor to calcium oxide, which can be used as carbon dioxide absorbent, was studied in the second part of this thesis. Structure of different amorphous phases of calcium carbonate was studied in detail. Crystallization of calcium carbonate with and without additives was studied. Parameters like stirring rate, temperature, pH and polymer concentration showed to be important in selection of phase and morphology. An aggregation mediated crystallization was postulated to explain the observed morphologies. / At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Accepted.
16

Why do Fermented Milk Products Stick to Packaging Material Surfaces?

Hansson, Kristina January 2011 (has links)
Today approximately 10 % of fermented milk products stick to the packaging material inner surface, and therefore it is not possible to pour all of the dairy product from the package. This is both an economical and environmental issue. The product loss is expensive for consumer and makes recycling of package less effective. As they do not yet exist the development of packaging materials to which fermented milk products stick less, it would make it possible to both save money and protect our environment. The aim of this work was to provide knowledge and understanding of the important factors involved in the phenomenon when fermented milk products adhere to the inner surface of a packaging material. Studies were done on materials having different surface properties, such as polarity and relative oxidation. They were incubated in fermented milk and other dairy products varying in fat concentration and protein type up to 168 h. The systems were investigated gravimetrically, with Fourier Transform Infra Red/Attenuated Total Reflectance Spectroscopy, Scanning Electron Microscopy and Contact Angle measurements. Fermented milk contains amphiphilic components and therefore can interact both with polar and non-polar surfaces, such that the relative oxidation of the surface does not contribute to the adhesion. The adhesion of fermented milk is an equilibrium reaction, which depend on the fat concentration before equilibrium as well as the protein concentration after equilibrium. The adhesion seems to follows the Vroman effect, with smaller molecules associating faster and thereby adhering to the surface initially, but are displaced by larger molecules that associates slower as times passes.
17

Radiacijos generuoti taškiniai defektai ir jų reakcijos / Point defects generated by radiation and their reactions

Stuknys, Vaidas 28 August 2009 (has links)
Šiame darbe nagrinėjami radiaciniai defektai bei jų tarpusavio reakcijos silicyje. Atlikti eksperimentai, kurių metu pasitelkus minkštąją Rentgeno spinduliuotę buvo generuojami defektai. Vėliau bandiniai buvo tiriami FT-IR spektroskopijos metodais. Darbo apimtis 52 puslapiai. Darbas susideda iš 5 dalių. Pirmoje dalyje apžvelgiami Rentgeno spinduliuotės šaltiniai ir spinduliuotės savybės. Antroje - dalyje radiaciniai defektai silicyje. Trečioje - defektų tyrimo metodai. Ketvirtoje - dalyje defektų reakcijos. Penktoje - eksperimento metodika ir eksperimento rezultatai. / In this work, we are researching radiation defects and their reactions in silicon. During experiments defects were generated using soft Rentgen radiance. Later samples were researched using FT-IR methods of spectroscopy. Work amount is 52 pages. Work consists from 5 parts. First part - overview of sources and features of Rentgen radiance. Second part – radiation defects in silicon. Third part – methods of defect researching. Fourth part – reactions of defects. Fifth part – Methods and results of experiment.
18

Größenselektive Untersuchungen zur Kristallisation und Struktur von Wasserclustern / A size resolved investigation on crystallization and structures of water clusters

Pradzynski, Christoph Czeslaw 06 February 2015 (has links)
IR-Spektren von neutralen Na(H2O)n-Clustern wurden im OH-Streckschwingungsbereich (2800 – 3800 cm-1) größenselektiv bis n=575±25 gemessen. Die Infrarot-anregungsmodulierte, durch chemische Vorionisation verstärkte Photoionisation beruht auf dem Effekt einer Signalverstärkung durch IR-Absorption bei schwellennaher Photoionisation. Die Strukturinformation kann anhand eines Vergleichs mit quantenchemischen Rechnungen gewonnen werden. Die mit dieser Methode erhaltenen IR-Spektren können für verschiedene Größenbereiche mit durch andere Verfahren generierten Spektren verglichen werden. Für mittlere Clustergrößen (~n=20-50) sind die erhaltenen IR-Signaturen sehr ähnlich zu RIDIR-Spektren von phenoldotierten Clustern. Die Spektren großer amorpher Cluster (n=250) sind vergleichbar mit denen ionischer Cluster. Die Variation der Expansionsbedingungen (z. B. die Änderung des Trägergases) beeinflusst nicht nur das Einsetzten der Kristallisation (beginnend zwischen n=200 und n=400), sondern auch die Isomerenzusammensetzung für kleinere Clustergrößen. Auf dieser Grundlage wurden Strukturen für die Größen (H2O)20, (H2O)25 und (H2O)32 untersucht.
19

The Effects Of Antioxidants On Some Rat Tissues And Membranes

Gorgulu, Guvenc 01 April 2004 (has links) (PDF)
High blood glucose levels induce metabolic disorders that initiate a sequence of events including renal, arterial, cardiac and retinal disorders. Diabetes mellitus increases oxidative stress in tissues of animals including humans. The resulting oxidative stress might play role in the development of diabetic complications. In the present study, 36 male Wistar rats (250-300g) were divided into 5 groups as Control (n=6), Diabetic (n=7), Diabetic + Vit C (n=7), Diabetic + &amp / #945 / -Lipoic acid (n=6) and Diabetic + Combination of Vit C and &amp / #945 / -Lipoic acid (n=10). From the livers of all groups cytoplasmic and microsomal membrane fractions were prepared from liver and antioxidant enzymes namely, superoxide dismutase, glutathione peroxidase, catalase and glutathione S-transferase activities were measured. Microsomal lipid peroxidation, total lipid, total protein, reduced glutathione levels of each group was determined and compared. Microsomal fractions were also analyzed by FT-IR spectroscopy. The total protein levels of diabetic rats were found to be decreased significantly (p&lt / 0.05) compared to controls and the &amp / #945 / -lipoic acid and vitamin C supplemented groups tend to compensate the decreased levels of total proteins. Decreased catalase activity in diabetic group compared to control was restored by &amp / #945 / -lipoic acid, vitamin C treatment and/or combination of both. Increased glutathione peroxidase activity was decreased to control levels by the treatement of both &amp / #945 / -lipoic acid and vitamin C. Superoxide dismutase activities of diabetic rats were increased (p&lt / 0.05) compared to control group. Whereas glutathione S-transferase activities though showed some fluctuations, the results were not statistically significant. Total glutathione levels decreased in all groups significantly (p&lt / 0.0.5) compared to control group but any of the agent failed to compensate the reduced levels of glutathione. As an index of lipid peroxidation, TBA-reactivity (MDA) levels increased significantly in all diabetic groups and only combination group&rsquo / s TBARS levels decreased significantly compared to diabetic group. FT-IR study of rat liver microsomal membranes was carried out in order to understand the effects of diabetes on membrane order, dynamics and lipid peroxidation status. For this purpose CH2 symmetric wavenumber, CH2 antisymmetric bandwidth, =CH olefinic band area were compared. In temperature dependent FT-IR studies microsomal membrane phase behavior, order and dynamics were analyzed. Diabetic samples showed apparent decrease in both frequency and bandwidth. =CH olefinic band integrated area was increased for diabetic samples compared to controls. Alpha-lipoic acid and vitamin C supplemented groups showed similar effects. They tend to restore decreased levels of band frequency and bandwidth. Additive effect between &amp / #945 / -lipoic acid and vitamin C was seen in some cases that only the combination group achieved to restore control values while &amp / #945 / -lipoic acid and vitamin C were failed to restore alone. In conclusion, STZ-induced diabetes mainly caused an increase in antioxidant enzyme activities. Also, increase in lipid peroxidation caused a decrease in the fluidity and order of the membrane resulting in more rigid membrane structures. The loss of cooperation between the antioxidant network may play a role in the secondary complications of diabetes.
20

A study of protein dynamics and cofactor interactions in Photosystem I

Bender, Shana Lynn 10 November 2008 (has links)
Previous research has underscored the importance of protein dynamics during light-induced electron transfer; however, specific interactions have not been well characterized. It is of particular importance to understand the role of protein dynamics and cofactor interactions in controlling electron transfer in oxygenic photosynthesis. These factors include hydrogen bonding, ð-stacking and electrostatic interactions. Reaction-induced FT-IR spectroscopy is sensitive to these interactions as well as isotopic incorporation, and is useful to probe protein dynamics associated with light-induced electron transfer in Photosystem I (PSI). Density functional theory (DFT) provides information concerning the vibrational frequencies of molecules as well as the amplitudes of the vibrations and sensitivity to isotope incorporation. Combining these approaches, protein dynamics associated with light-induced electron transfer in PSI were studied. The work presented here describes specific protein cofactor interactions and specific protein relaxation events associated with light-induced electron transfer. The results reported here are consistent with noncovalent protein cofactor interactions that modulate the redox potential of the secondary electron acceptor of PSI. Furthermore, the studies presented here describe novel protein dynamics associated with the oxidation of the terminal electron donor of PSI. These results characterize specific protein dynamics that may be associated with interactions of the soluble electron donors. These studies highlight the importance of protein dynamics in oxygenic photosynthesis.

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