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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.
91

Emprego da maceração a frio na extração e estabilização de compostos fenólicos em vinhos de Syrah cultivada em ciclo de outubro-inverno / Influence of cold maceration technique on extraction and stabilization of phenolic compounds in Syrah wines from grapevines cultivated in autumnwinter cycle

Dal'Osto, Marite Carlin 16 April 2012 (has links)
Na busca por vinhos tintos de grande cor, aroma, corpo e identidade, enólogos forçam a extração dos compostos fenólicos durante a maceração. Nesta etapa, que ocorre durante a fermentação do mosto, estes compostos são extraídos da casca e sementes e modificados em sua estrutura à formas mais estáveis ao longo do tempo. Fatores como sistema de encubagem e remontagem do mosto, tempo de contato entre o mosto e as partes sólidas da baga, e a temperatura são críticos neste processo. A alteração do ciclo da videira para colheita no período de inverno na região sudeste do Brasil permitiu avanço na maturação fenólica das bagas. As uvas colhidas neste período apresentam potencial para a elaboração de vinhos de guarda, entretanto faltam estudos para estabelecer as melhores técnicas de vinificação para este novo ciclo de produção. Este trabalho teve como objetivo avaliar o emprego de baixas temperaturas na extração e estabilidade de antocianinas, taninos e do precursor de aroma acetato de isoamila. Uvas da variedade Syrah colhidas no inverno foram submetidas a vinificação com maceração pré-fermentativa a frio (5 - 8°C) e posterior fermentação alcoólica na presença das cascas a baixa temperatura (15 °C), e também pelo método tradicional (maceração e fermentação alcoólica entre 20 e 23°C). Teores de polifenóis totais, antocianinas, intensidade e tonalidade de cor, compostos fenólicos, flavanóis, índice de pigmentos polimerizados e acetato de isoamila foram avaliados durante a maceração e nas etapas de fermentação malolática, engarrafamento e envelhecimento em garrafa. Os vinhos com 14 meses de envelhecimento foram submetidos a um painel sensorial. O método de maceração tradicional permitiu maior extração de antocianinas e, consequentemente, maior intensidade de cor. Entretanto, o emprego do frio preservou os tons azuis (OD 620%) durante o envelhecimento, o que indica menor oxidação do vinho. A concentração de compostos fenólicos também foi maior na maceração tradicional. O vinho submetido ao frio apresentou maior índice de pigmentos polimerizados e maior preservação de tons vermelhos e compostos fenólicos totais durante o envelhecimento, além de menores teores de acetato de isoamila. Não houve diferença estatística entre os descritores apresentados na análise sensorial; entretanto, a média do parâmetro de preferência global foi maior no método tradicional. Os resultados indicam potencial de preservação dos compostos fenólicos pelo uso do tratamento a frio, entretanto outras técnicas devem ser avaliadas para melhorar a extração desses compostos em uvas colhidas no inverno. / In an attempt to elaborate red wines of great color, aroma, body and identity, winemakers overextract phenolic compounds at maceration. At this step, which occurs during must fermentation, grape solids are extracted from skins and seeds and their structure are modified to more stable forms over time. Factors such as types of maceration, pumping-over, maceration time and temperature are critical in this red winemaking step. The modification of grapevine cycle in the southeastern region of Brazil to harvest grapes in the winter season has improved phenolic ripeness of the berries. Grapes harvested at this period have potential to ageing, however there are few studies to establish the best winemaking techniques for these berries. This study aimed to evaluate the use of low temperature in the extraction and stability of anthocyanins, tannins and flavor precursor isoamyl acetate. Syrah grapes harvested in winter season were processed with pre-fermentative cold maceration (5 - 8 °C) and then allowed to start alcoholic fermentation in the presence of pomace at low temperature (15 °C), and also processed by the conventional method (maceration and alcoholic fermentation between 20 and 23°C). Total polyphenols, anthocyanins, intensity and color hue, phenolic compounds, flavanols, polymerized pigments index and isoamyl acetate were evaluated during maceration, malolactic fermentation, bottling and bottle ageing steps. Wines aged in bottles for 14 months were subjected to a sensory panel. The conventional method allowed more anthocyanins extraction and consequently resulted in wines with more color intensity. However, the use of cold temperatures preserved the blue component (OD 620%) during ageing, which indicates less wine oxidation. The concentration of phenolic compounds was also higher in wines from the conventional method. Cold macerated wines showed higher polymerized pigments index and preservation of the red component of color and total phenolic compounds during ageing, and lower levels of isoamyl acetate. There was no statistical difference among sensory descriptors presented in the sensorial analysis; however, the parameter of overall preference was higher scored for the conventional method. Results showed potential for phenolic compounds stabilization by the use of cold treatment, but other techniques should be evaluated to improve the extraction of these compounds in grapes harvested in winter season.
92

Characteristics of typical pollutants in tannery site soil

Teng, Xu, Wen-hua, Zhang, Bi, Shi 26 June 2019 (has links)
Content: This paper briefly introduced the process of leather manufacture and the potential pollution sources of soil in tannery sites. Pollutants are mainly derived from the use of a large number of various chemicals and organic matter decomposed by raw skin. The characteristics of typical pollutants in tannery sites soil were summarized, including tannery site soil pH, organic and inorganic compounds, and heavy metals, etc., especially the status of chromium contamination were reviewed. The pH of soil in the tanning workshop (6.65-7.8) is generally lower than tannery sludge dumping site (7.94-8.40). The main organic pollutants contained in the tannery site soil include nitrogen compound, grease, petroleum hydrocarbon. In tannery sludge dumping site soil, the content of nitrogen compound (10cm depth) is 28400 mg/kg, which is similar to tannery sludge. The content of petroleum hydrocarbon is 5-700 mg/kg, which partially exceed the limits of China agricultural land quality standard(<500 mg/kg). In tanning workshop soil, the content of grease is 220-62000 mg/kg. The main inorganic pollutants contained in the tannery site soil include sulfide, high concentration of salt, lime. The high salt content of tannery sludge (99000 mg/kg) leads to high salt content in soil (5500-17500 mg/kg). Total hardness (>450mg/L), total dissolved solids (>1000mg/L), sulfate ions (>250mg/L), nitrite nitrogen (>0.02mg/L) partially exceed the limits of China groundwater quality standard, which are found in groundwater below the tannery site. Heavy metal pollutants in the tannery sites soil have many characteristics and large differences in content, due to the different tanning processes. Among them, chromium (Cr) is the most used heavy metal and the highest content of pollutants. Cr content in tanning process wastewater, dyeing process wastewater and chromiumcontaining sludge are about 2000-3000 mg/L, 30-40 mg/L and 8500-25800 mg/kg, respectively. Total Cr content in the partial tannery sites soil are higher than 800 mg/kg, which exceed the limits of China agricultural land quality standard(<150mg/kg). Surprisingly, Cr(VI) appears in tannery sites soil and the contents are partly higher than 40 mg/kg, which exceed the limits of China development land quality standard(<3.0mg/kg). Furthermore, the more effort needs to be directed toward the chemistry of chromium-organic complex pollutants, and an understanding of the speciation of Cr in highly organics contaminated tannery site soil is essential for the development of suitable remediation strategies for contaminated soil. Take-Away: 1. The pH of soil in the tanning workshop (6.65-7.8) is generally lower than tannery sludge dumping site(7.94-8.40). 2. Total Cr content in the partial tannery sites soil are higher than 800 mg/kg, which exceed the limits of China agricultural land quality standard(<150mg/kg). 3. Cr(VI) appears in tannery sites soil and the contents are partly higher than 40 mg/kg, which exceed the limits of China development land quality standard(<3.0mg/kg).
93

Ti (III)-tannin combination tanning technology based on microwave irradiation

Wu, Jiacheng, Ning, Guoqiang, Zhang, Jinwei, Chen, Wuyong 26 June 2019 (has links)
Content: Microwave is a fast, efficient and energy-saving thermal resource, hence an attempt has been made for applying this technology in the combination tanning using titanium (III) and tannin extracts. In this work, the microwave effects on the complex reaction of Ti (III) with tannin extracts and leather products properties were investigated. The precipitation condition was used to characterize the complexation degree between Ti (III) and tannin extracts. And the shrinkage temperature, tear strength, SEM, DSC, TG, FT-IR, and histological structure were used to characterize the changes in the physical and chemical properties of the combined tanned leather. Take-Away: The results showed that microwave irradiation can accelerate the complex reaction of Ti (III) with tannin extracts. At the room temperature, the mixture of tannin and titanous sulphate kept stable at pH 3-4. In addition, microwave could increase the shrinkage temperature, tear strength, thermal stability, and fibrage of Ti (III)-tannin tanned leather, and it would not change the combination mode of the skins with tanning agents as well as the hierarchical structure of collagen. Therefore, these results inferred that microwave could promote the reaction between Ti (III) and tannins and the combination of tannins with collagen, which may provide a theoretical basis for the application of microwave in Ti (III)-tannin combination tanning technology.
94

A review of substances reported to cause false positives and negatives in forensic blood identification tests

Novelli, Brittany Catherine 26 February 2021 (has links)
Forensic biology encompasses the examination of evidentiary items from crime scenes for biological fluids, often identifying the specific biological fluid present and developing a DNA profile that can be used to link a suspect to a crime. Blood identification consists of visual examination, presumptive tests based on the catalytic activity of hemoglobin, and confirmatory tests based on antigen-antibody interactions. Issues encountered in blood identification include the occurrence of false positive and false negative results. Many causes of these results are well-known but more recently three substances resulting in false negatives with catalytic color tests, chemiluminescent reagents, and immunoassays have been explored. Quebracho extract (a common leather tannin), sodium percarbonate (the main component of detergents containing active oxygen) and vitamin C-containing beverages were all found to produce false negative results at varying degrees with each of the tests mentioned. Increased knowledge of potential negative interfering agents by forensic investigators can help ensure that probative evidence is properly collected and thoroughly analyzed from a crime scene.
95

Tannins in Natural Soil Systems

Schmidt, Michael Afton 20 April 2012 (has links)
No description available.
96

Uncovering New Players and New Roles in Microbial Anoxic Carbon Transformations

Solden, Lindsey M. 25 July 2018 (has links)
No description available.
97

Bioraffinering av bark: En jämförelse mellan två extraktionsmetoder / Bark Biorefining: A Comparison between two extraction methods

Al-Bety, Salwa January 2021 (has links)
Intresset för användningen av material från förnybara råvaror ökar. Produktionen av vedmassa och material i skogsindustrin genererar dagligen stora mängder biprodukter, särskilt bark. Barken innehåller många värdefulla komponenter som kan förädlas och öka värdet för barken, men först måste de separeras. Målet med denna undersökning var att separera dessa genom att jämföra två olika typer av extraktionsmetoder. Den första metoden använde programmerbar utrustning som namnges accelerated solvent extraction (ASE) och den andra använde manuell teknik som namnges Soxhlet extraktion. Syftet med undersökningen var att avgöra vilken extraktionsmetod som kan användas till att utvinna bark komponenter mest effektivt. Metoden ASE omfattar acetonextraktion och varmvattenextraktion där trycket var 100 bar, temperaturen 100oC och tiden drygt en timme. Soxhletextraktion omfattade enbart acetonextraktion under atmosfäriskt tryck, kontinuerlig värme och tiden 90 minuter. ASE-metoden gav fyra extrakt; acetonextrakt vid 100oC samt varmvattenextrakt vid 100oC, 140oC och 160oC.  Barken som studerades var uppdelad i två fraktioner, fuktig bark och torr bark. En beräkning av utbyte % utfördes efter varje extraktion. Extrakten från fuktig bark hade mörkare färg än extrakten från torr bark. Det uppmätes pH-värden för alla vattenextrakt och den som gav lägst pH var vattenextrakt som erhölls vid 160oC. Slutligen visade utbyteresultaten inga stora skillnader mellan de utförda ASE vattenextraktionerna exklusive extraktfärgen som kan vara en indikation till skillnad i extraherade molekyler. Användningen av sand under varmvattenextraktionerna gav inga förbättringar i extraktionsmetoden. / Interest in the use of materials from renewable sources is increasing. The production of wood pulp and materials in the forest industry generates large amounts of by- products daily, especially tree bark. Bark contains many valuable components which if separated can be used in various types of applications. The aim of this study was to compare two extraction methods. The first method used programmable equipment and is named accelerated solvent extraction (ASE) and the second used manual technology and is named Soxhlet extraction.  The purpose of the study was to determine which extraction method can be used to extract bark components more efficiently. The ASE method included acetone extraction and hot water extraction where the pressure was 100 bar, the temperature 100oC and the time just over an hour. Soxhlet extraction involved only acetone extraction under atmospheric pressure, continuous heating, and a time of 90 minutes. The ASE method yielded four extracts: acetone extract at 100oC and hot water extract at 100oC, 140oC and 160oC.  The bark studied was divided into two parts, undried bark and dry bark. Total calculation of yield% was performed after each extraction. The extracts from undried bark had a darker color than the extracts from dry bark. The pH values were measured for all water extracts and the one that gave the lowest pH was obtained at 160oC. Finally, the extraction results did not show any major differences between the ASE water extractions performed excluding the extract color which may be an indication of difference in extracted molecules. The use of sand during the hot water extractions did not improve the extraction method.
98

Development of Polyphenolic Nanoparticles for Biomedical Applications

Cheng, Huaitzung Andrew January 2016 (has links)
Polymeric nanoparticles have a wide range of applications, particularly as drug delivery and diagnostic agents, and tannins have been regarded as a promising building block for redox and pH responsive systems. Tannins are a class of naturally occurring polyphenols commonly produced by plants and are found in many of our consumables like teas, spices, fresh fruits, and vegetables. Many of the health benefits associated with these foods are a result of their high tannin contents and the many different types of tannins found in various plants have demonstrated therapeutic potentials for conditions ranging from cardiovascular disease and diabetes to ulcers and cancer. Diets rich in tannins have been associated with lower blood pressure in patients with hypertension. The plurality of phenols in tannins also makes them powerful antioxidants and as a result, there is a lot of interest in taking advantage of their self-assembling abilities to make redox and pH responsive drug delivery systems. However, the benefit of natural tannins is limited by their instability in physiological conditions. Furthermore, there is limited control over molecular weight and reactivity of the phenolic content of plant extracts. Herein we report the novel synthesis of pseudotannins with control over molecular weight and reactivity of phenolic moieties. These pseudotannins have can form nanoscale interpolymer complexes under physiological conditions and have demonstrated antioxidative potential. Furthermore, pseudotannin IPCs have been shown to be responsive to physiologically relevant oxidation as well as the ability to easily incorporate cell targeting peptides, fluorescent tags, and MRI contrast agents. The work presented here describes how pseudotannins would be ideally suited to minimally invasive techniques for diagnosing atherosclerotic plaques and targeting triple negative breast cancer. We demonstrate that pseudotannin can very easily and quickly form nanoscale particles that are small enough to be uptaken into mammalian cells. Furthermore, by self-assembling with gadolinium, pseudotannins can effectively attenuate the signal of gadolinium based MRI contrast agents. This in conjunction with oxidation responsive decomplexation could be a viable option for diagnosing the severity and risk of rupture of atherosclerotic plaques. Also, we demonstrate that pegylated compounds can easily be incorporated into pseudotannin nanoparticles to impart cell targeting functionality. The subsequent uptake of pseudotannin nanoparticles into breast cancer cells demonstrated the ability to increase their sensitivity to UV radiation. The creation of synthetic tannin-like polymers leads to directly to making a variety of self-assembling, stimuli responsive, and bioactive nanoparticles well-suited for various biomedical applications. / Bioengineering
99

Modification et stabilisation de la réactivité de tanins traités chimiquement : applications à la préparation de résines adhésives et de mousses écosoutenables / Modification and stabilization of the reactivity of tannins chemically treated : the applications to adhesive resins and eco-sustainable foams preparation

Giovando, Samuele 14 November 2013 (has links)
L'objectif de ce travail de thèse a été de produire des matériaux expansés à partir de produits d'origine naturelle, en particulier à partir de tanins. Au moment où cette thèse a débuté, des études étaient publiées sur la possibilité d'élaborer ce type de matériaux avec des formulations qui comportaient du formaldéhyde. Cela allait à l'encontre du caractère naturel recherché puisqu'en fait, on utilisait des produits naturels et les faisait réagir avec un produit cancérogène. Il n'était donc pas possible de les présenter comme des matériaux « verts ». Aussi, nous avons voulu au cours de ce travail, élaborer des matériaux expansés uniquement à partir de produits naturels ou en découlant. Les tanins sont des substances naturelles chimiquement actives qui peuvent être utilisées afin de remplacer des produits homologues dérivés du pétrole comme le phénol par exemple qui présente des caractéristiques de réactivité chimique très similaires à celles des tanins condensés. Des formulations comportant des tanins condensés ont d'ailleurs déjà été étudiées pour élaborer des matériaux expansés. En considérant cela, ce travail de thèse s'est déroulé sous la forme de différents projets convergents vers un objectif commun: la production de mousses aux tanins plus naturelles et plus intéressantes pour l'industrie. Cinq projets ont ainsi été menés : 1. analyses de différents tanins, condensés, hydrolysables et synthétiques ; 2. production de mousses aux tanins sans utilisation de formaldéhyde ; 3. production de mousses aux tanins sans solvants ; 4. production de mousses aux tanins rigides ou élastiques ; 5. production de mousses aux tanins, sans acides, mais avec une catalyse alcaline / The aim of this thesis was to produce foamed materials from natural products, especially from tannins. At the time this thesis began, studies were published on the possibility of doing this type of materials with formaldehyde containing formulations. This was contrary to the desired natural character because in fact, were used natural products reacted with carcinogenic product. It was not possible to present them as "green" materials. During this thesis our aim was to develop expanded materials only from natural or bio-derived raw materials. Tannins are chemically active natural substances that can be used to replace homologous oil derivatives such as phenol which has characteristics of chemical reactivity very similar to those of condensed tannins. Formulations containing condensed tannins have already been studied to develop expanded materials. Considering this argument, this thesis takes place in the form of various projects converging towards a common goal: production of foams with more natural impact and interesting for tannins industry. Five projects have been completed: 1. analysis of various tannins, condensed, hydrolysable and synthetic ; 2. tannin foams production without the use of formaldehyde ; 3. tannin foams production without solvents ; 4. tannin foams production with rigid or elastic behavior ; 5. tannin foams production without acids, but with an alkaline catalysis
100

Raman spectroscopic studies of carbon-bonded alumina filters and their binders

Brehm, Simon 08 December 2023 (has links)
Carbon-bonded alumina filters and their binders, lactose, tannin and CarboresP, were investigated by Raman spectroscopy. Special emphasis was placed on the pyrolysis study of the binders. In situ measurements were performed on the tannins gallic acid, ellagic acid and tannic acid to determine the pyrolysis temperatures and products. Furthermore, the binder samples fired in a reducing atmosphere in a coke bed were analyzed by Raman spectroscopy and their transition from an amorphous carbon system to nanocrystalline graphite was observed. The influence of different binders on the carbon-bound alumina filters was studied, as well as the influence of different additives. However, no significant difference was observed between samples with different binder compositions or with additives. In addition, Raman measurements on the spinel MgAlON indicate an increased disorder of the structure due to the incorporated nitrogen.

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