8,625 research outputs found

    Roles of the ubiquitin ligase complex CRL5Ozz and its substrate Alix in skeletal muscle

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    Converging organoids and extracellular matrix::New insights into liver cancer biology

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    Designs of Blackness

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    Across more than two centuries Afro-America has created a huge and dazzling variety of literary self-expression. Designs of Blackness provides less a narrative literary history than, precisely, a series of mappings—each literary-critical and comparative while at the same time offering cultural and historical context. This carefully re-edited version of the 1998 publication opens with an estimation of earliest African American voice in the names of Phillis Wheatley and her contemporaries. It then takes up the huge span of autobiography from Frederick Douglass through to Maya Angelou. "Harlem on My Mind," which follows, sets out the literary contours of America’s premier black city. Womanism, Alice Walker’s presiding term, is given full due in an analysis of fiction from Harriet E. Wilson to Toni Morrison. Richard Wright is approached not as some regulation "realist" but as a more inward, at times near-surreal, author. Decadology has its risks but the 1940s has rarely been approached as a unique era of war and peace and especially in African American texts. Beat Generation work usually adheres to Ginsberg and Kerouac, but black Beat writing invites its own chapter in the names of Amiri Baraka, Ted Joans and Bob Kaufman. The 1960s has long become a mythic change-decade, and in few greater respects than as a black theatre both of the stage and politics. In Leon Forrest African America had a figure of the postmodern turn: his work is explored in its own right and for how it takes its place in the context of other reflexive black fiction. "African American Fictions of Passing" unpacks the whole deceptive trope of "race" in writing from Williams Wells Brown through to Charles Johnson. The two newly added chapters pursue African American literary achievement into the Obama-Trump century, fiction from Octavia Butler to Darryl Pinkney, poetry from Rita Dove to Kevin Young

    An Investigation into the Relationship Between Adenine Modification and Cobamide Lower Base Synthesis

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    Cobalamin, also known as vitamin B12 is a widely used cofactor in cellular metabolism but is only synthesized in a few species of prokaryotes. Interestingly, cobalamin in the large intestine is not bioavailable. But 25% of sequenced human intestinal bacteria have the capacity to produce corrinoids and 80% produce gene products that potentially require corrinoids, leading to some questions about the diversity of cobamides. This project specifically takes interest in adenine and 2-methyladenine as lower ligands in cobamides. Which are present in some biomes such as the large intestine and are even produced by the flora which reside there. Even though they appear frequently in samples, little is known about the precursors to these lower ligands. RlmN is a dual specificity methyl transferase which methylates adenine residues on tRNA and rRNA. In this project, we seek to investigate the effects of adenine supplementation and the deletion of this adenine methyltransferase on the lower ligands of cobamides synthesized by genetically modified E. coli. This project demonstrated that the deletion of the rlmN gene was possible via CRISPR Cas9 gene deletion facilitated by homology directed repair with donor DNA. Additionally, it was demonstrated that the deletion may affect the growth rate of the deletion strain but is ultimately non-lethal. Adenine supplementation appeared to impact the variety of lower ligand incorporated to form a cobamide in the absence of DMB. Without supplemented adenine, as an intracellular booster or externally with powder, 2-methyladenine appears to be the main preferred lower ligand to be incorporated into a cobamide and produces the highest ratio of cobamides. Contrastingly, when supplemented with adenine, with an intracellular booster or externally, adenine becomes the main lower ligand of the cobamides produced by ratio. Interestingly, the addition of an intracellular adenine booster results in the loss of GDP cobinimide production. This project demonstrates the that the precursors for 2-methyladenine as a lower base are of intracellular origin, possibly from rlmN methylated t-RNA. Additionally, we have demonstrated that cobamides are preferentially produced when supplemented with adenine, even in the absence of DMB

    Valorisation of rice straw by obtaining active compounds and cellulosic materials for the development of biodegradable food packaging systems

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    Tesis por compendio[ES] En esta tesis se obtuvieron fracciones celulósicas y extractos activos de paja de arroz mediante diferentes técnicas de extracción y purificación, utilizando agua como disolvente. Estas fracciones se incorporaron en películas de almidón y PLA, y en bicapas de almidón-PLA, para obtener materiales de envasado activos para extender la vida útil de diferentes alimentos. Los extractos obtenidos por combinación de ultrasonidos y calentamiento a reflujo (USHT) y con agua subcrítica (SWE) (a 160 °C (SWE-160) y 180 °C (SWE-180)) presentaron un alto contenido fenólico (37, 51 y 83 mg GAE.g-1 de extracto seco, respectivamente) y actividad antioxidante (6,3, 2,0 y 1,2 mg de extracto seco.mg-1 DPPH, respectivamente). Los extractos SWE fueron activos contra L. innocua y E. coli. Se aislaron fibras de celulosa (FC) del residuo insoluble de las diferentes extracciones. A pesar de las ligeras diferencias en el grado de purificación, los nuevos métodos dieron lugar a FCs con rendimientos más elevados que el método alcalino (35-39 % frente al 29 %), con cristalinidad (60-69 %), comportamiento térmico y relación de aspecto (20-60) similares. Se incorporaron fibras USHT al 1, 3 y 5 % (p/p) en películas termoprocesadas de almidón de maíz, y de almidón de maíz modificado térmicamente. La incorporación al 3 % dio lugar a películas con mejores propiedades funcionales. Los extractos activos (al 4, 6 y 8 % en peso) en la matriz de almidón, con o sin CF (3 %), dieron lugar a películas más extensibles y menos resistentes, con mayor capacidad de barrera al oxígeno. Las bolsas monodosis de aceite de girasol con estas películas activas y reforzadas redujeron eficazmente la oxidación. Las películas activas de PLA termoprocesado, con diferentes proporciones (2, 4 y 6 % p/p) del extracto USHT, presentaron color y propiedades mecánicas ligeramente peores, pero con mayor barrera al oxígeno. La cinética de liberación de los antioxidantes incorporados en simulantes alimentarios de diferente polaridad (A: productos acuosos; y D1: sistemas de aceite en agua), mostró que las películas con un 6% de extracto, tuvieron una capacidad antioxidante similar en simulantes con distinta polaridad. Se obtuvieron bicapas biodegradables laminando PLA, con y sin extracto USHT (6 %), y almidón termoplástico, con o sin FC USHT (3 %). Las bicapas mostraron mejor capacidad de barrera global que las monocapas. Sin embargo, la migración de compuestos entre capas dio lugar a películas menos rígidas y resistentes de lo esperado de la contribución del film de PLA. Las bicapas activas y reforzadas alargaron la vida útil de carne de cerdo refrigerada. Las películas de PLA con un 6 % (p/p) de los diferentes extractos (USHT, SWE-160 y SWE-180) presentaron menor resistencia mecánica y capacidad de barrera al vapor de agua, pero una mayor capacidad de barrera al oxígeno y a la luz UV. Además, estas películas, especialmente con el extracto SWE-180, alargaron la vida útil de la carne de cerdo refrigerada. Las FCs obtenidas con los diferentes métodos de purificación también se utilizaron para producir aerogeles de celulosa. Las diferencias composicionales afectaron a la microestructura de los aerogeles. La capacidad de absorción y de retención de agua de los aerogeles estuvo dentro de los rangos descritos para este tipo de materiales. Por tanto, fue posible obtener fracciones valorizadas de la paja de arroz, extractos activos y fibras celulósicas, útiles en el desarrollo de materiales biodegradables activos a base de almidón y PLA. Son necesarios más estudios para validar la seguridad alimentaria de los materiales, así como para el desarrollo de otras aplicaciones en el campo de la industria alimentaria o farmacéutica.[CA] En aquesta tesi doctoral es van obtenir fraccions cel·lulòsiques i extractes actius de palla d' arròs mitjançant l'aplicació de diferents tècniques d'extracció i purificació, utilitzant aigua com a dissolvent. Aquestes fraccions es van incorporar a pel·lícules de midó i PLA, i bicapes de midó-PLA, per obtenir materials d'envasament actius útils per allargar la vida útil de diferents aliments. Els extractes combinant ultrasons i escalfament a reflux (USHT) i amb aigua subcrítica (SWE) (a 160 °C (SWE-160) i 180 °C (SWE-180)) van mostrar un alt contingut fenòlic (37, 51 i 83 mg GAE.g-1 d'extracte sec, respectivament) i activitat antioxidant (6,3, 2,0 i 1,2 mg d'extracte sec.mg-1 DPPH, respectivament). Els extractes SWE van mostrar activitat antibacteriana contra L. innocua i E. coli. Es van aïllar fibres de cel·lulosa (FC) de les fraccions insolubles de l'extracció. Malgrat les lleugeres diferències en el grau de purificació, els nous mètodes van donar lloc a FCs amb rendiments més elevats que el mètode alcalí (35-39 % enfront del 29 %), amb cristal·linitat (60-69 %), comportament tèrmic i relació d'aspecte (20-60) similars. Es van incorporar fibres USHT a l'1, 3 i 5 % (p/p) en pel·lícules de midó de dacsa, i de midó de dacsa modificat per tractament tèrmic. La incorporació al 3 % va donar lloc a pel·lícules amb les millors propietats funcionals. Els extractes actius (al 4, 6 i 8 % en pes) a la matriu de midó, amb o sense CF (3 %), proporcionaren pel·lícules més extensibles i menys resistents, però amb més capacitat de barrera a l'oxigen. Les bosses monodosi de l'oli de gira-sol amb aquestes pel·lícules actives i reforçades van reduir eficaçment l'oxidació. Les pel·lícules actives de PLA amb diferents proporcions (2, 4 i 6 % p/p) de l'extracte USHT, presentaren color i propietats mecániques lleugerament pitjors, però amb major capacitat de barrera a l'oxigen. La cinètica d'alliberament dels antioxidants incorporats, en simulants alimentaris de diferent polaritat (A: productes aquosos; i D1: sistemes d'oli en aigua), va mostrar que les pel·lícules amb un 6% d'extracte, tenien una capacitat antioxidant similar en simulants amb diferent polaritat. Es van obtenir bicapes biodegradables laminant PLA, amb i sense extracte USHT (6 %), i midó termoplàstic, amb o sense FC USHT (3 %). Les bicapes van mostrar millor capacitat de barrera global que les monocapes. No obstant això, la migració de compostos entre capes va donar lloc a pel·lícules menys rígides i resistents respecte a l'esperat de la contribució de la pel·lícula de PLA. Les bicapes actives i reforçades van allargar la vida útil de carn de porc refrigerada. Les pel·lícules de PLA amb un 6 % (p/p) dels diferents extractes (USHT, SWE-160 i SWE-180) van presentar menor resistència mecànica i capacitat de barrera al vapor d'aigua, però una major capacitat de barrera a l'oxigen i a la llum UV. A més, aquestes pel·lícules, especialment amb l'extracte SWE-180, van allargar la vida útil de la carn de porc refrigerada. Les FCs obtingudes amb els diferents mètodes de purificació també es van utilitzar per produir aerogels de cel·lulosa. Les diferències composicionals van afectar la microestructura dels aerogels. La capacitat d' absorció i de retenció d'aigua dels aerogels va estar dins dels rangs descrits per a aquest tipus de materials. Per tant, va ser possible obtenir fraccions valoritzades de la palla d' arròs, extractes actius i fibres cel·lulòsiques, útils en el desenvolupament de materials biodegradables actius a base de midó i PLA. Són necessaris més estudis per validar la seguretat alimentària dels materials, així com per al desenvolupament d' altres aplicacions en el camp de la indústria alimentària o farmacèutica.[EN] This Doctoral thesis focused on obtaining cellulosic fractions and bioactive extracts from rice straw (RS) by applying different extraction and purification techniques, using water as a green solvent. These fractions were incorporated into starch and poly (lactic acid) (PLA)-based films, as well as into starch-PLA bilayers, to obtain active packaging materials useful for extending the shelf life of different food matrices. The extracts obtained by applying a combined ultrasound-reflux heating method (USHT) and subcritical water extraction (SWE) (at 160 °C (SWE-160) and 180 °C (SWE-180)) exhibited high phenolic content (37, 51, 83 mg GAE.g-1 dry extract, respectively) and antioxidant activity (6.3, 2.0, and 1.2 mg dry extract.mg-1 DPPH, respectively). The SWE extracts showed antibacterial activity against L. innocua and E. coli. Cellulose fibres (CF) were isolated from the extraction insoluble fractions and compared with those obtained from the traditional alkaline method. Despite slight differences in the degree of purification, the new methods gave rise to CFs with higher yields than the alkaline method (35-39% vs. 29%), with similar crystallinity (60-69%), thermal behaviour, and aspect ratios. USHT fibres were incorporated into corn starch (1, 3, and 5% wt.), and corn starch-modified by heat treatment, obtained by thermoprocessing. The incorporation of CF at 3% gave rise to films with the best functional properties. When active extracts were incorporated at different ratios (4, 6, and 8% wt.) into the starch matrix, with or without CF (3%), the films were more stretchable and less resistant, but with higher oxygen barrier capacity. Likewise, mono-dose bags of these active and reinforced films effectively reduced the oxidation of packed sunflower oil. Active, plasticised PLA films were produced, incorporating USHT extract (2, 4, and 6% wt.) by thermoprocessing, which exhibited colour and slightly worsened tensile behaviour, but with higher oxygen barrier capacity. The release kinetics of the incorporated antioxidant compounds in food simulants of different polarity (A: aqueous products; and D1: oil-in-water systems) showed that films containing 6% of extract delivered similar antioxidant capacity regardless of the food simulant polarity. Biodegradable bilayers were obtained by laminating plasticised PLA, with and without USHT extract (6%), and thermoplastic starch, with or without USHT CFs (3%). The bilayers exhibited improved overall barrier capacity with respect to the monolayers. However, the interlayer compound migration led to less stiff and resistant films with respect to that expected from the PLA film contribution. The active and reinforced bilayers were able to extend the shelf life of the packed pork meat during cold storage. PLA films with 6% wt. of the different extracts (USHT, SWE-160, and SWE-180) were produced, which exhibited lower mechanical resistance and water vapour barrier capacity, but improved oxygen barrier capacity and intense UV light-blocking effect. Furthermore, the active PLA films, especially with SWE-180 extract, extended the shelf life of cold storage pork meat. The CFs obtained with the different purification methods were also used to produce cellulose aerogels. The differences in the chemical composition of the CFs affected the aerogels' microstructure. The water absorption and retention capacity of the aerogels were within the previously reported ranges for this type of material. Thus, it was possible to obtain valorised fractions of rice straw, active extracts and cellulosic fibres, useful in developing active biodegradable materials based on starch and PLA. Further studies are needed to validate the food safety of the materials, as well as for developing other applications in the food or pharmaceutical industry.The authors thank the Agencia Estatal de Investigación (Spain) for the financial support through projects PID2019-105207RB-I00/AEI/10.13039/501100011033 and Generalitat Valenciana [grant number GrisoliaP/2019/115].Vieira De Freitas, PA. (2022). Valorisation of rice straw by obtaining active compounds and cellulosic materials for the development of biodegradable food packaging systems [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191380Compendi

    Torque-Transferring Characteristics of Offshore Tetrapod Piled Jacket Foundations in Dense Sand

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    Quality of explosively welded steel plates using demex explosive

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    Заваривање експлозивом се често користи када конвенционалне методе заваривања не могу да обезбеде заварени спој два различита материјала, али и када треба заварити неку специфичну геометрију или велике површине металних плоча. Остваривање споја код заваривања експлозивом се заснива на динамичком дејству великог притиска створеног екплозијом. У ту сврху најчешће се користе индустријски експлозиви ниских параметара детонације, а један од њих је DEMEX, произвођача TRAYAL, из Србије. У овом истраживању DEMEX је примењен за заваривање плоча две различите врсте челика. Пре експерименталног поступка заваривања одабраних металних плоча, експлозив добијен од произвођача је подвргнут улазној контроли квалитета: мерењу његове насипне густине и брзине детонације, коришћењем оптичких сонди и фотодетектора повезаног са електронским бројачем. Експериментална поставка за заваривање била је следећа: експлозив DEMEX у прашкастом стању нанесен је у равномерном слоју преко горње челичне плоче, која је хоризонтално постављена преко доње плоче од друге врсте челика, у паралелном положају, са малим дрвеним дистанцерима ивично постављеним између њих. Активација је извршена електродетонирајућом капислом и малим бустером од пластичног експлозива. Заварени спој је испитан применом метода ултразвучне дефектоскопије, течним пенетрантима и микроструктурне анализе завареног споја. Микроструктурне анализе попречног пресека заварених плоча урађене су на стерео и оптичом микроскопу како би се анализирала зона завареног споја.Explosion welding is often used when conventional welding methods cannot provide welded joint of two dissimilar materials, but also when some specific geometry should be welded, or large surfaces of metal plates. The formation of a joint in explosive welding is based on the dynamic effect of the high pressure created by the explosion. For this purpose, most often some industrial explosives of low detonation parameters are used, and one of them is DEMEX, produced by TRAYAL, Serbia. In this research DEMEX was applied to weld plates of two different types of steel. Prior to the experimental procedure of welding, the selected metal plates, the explosive obtained from the producer was subjected to initial quality control: measurement of its bulk density and detonation velocity, using optical probes and a photodetector connected with an electronic counter. The experimental setup for welding was as follows: explosive DEMEX in powdery state was applied in a uniform layer over the upper plate, which was horizontally placed over the lower plate, in parallel position, with small wooden spacers, marginally placed between them. Activation was performed by an electro-detonating cap and a small booster of plastic explosive. The welded joint was examined using methods of ultrasonic defectoscopy, liquid penetrants testing and microstructural analysis of the welded joint. Cross-sectional microstructural analyses of the welded plates were performed using a stereo and optical microscope to analyze the weld zone
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