196,357 research outputs found
Synthesis and characterization of vanillin methacrylate as a precursor for highly porous polymers
No full textV okviru diplomske naloge smo si zadali dva glavna cilja: sintetizirati vanilin metakrilat (VMA) in ga uporabiti kot monomer pri nadaljnji polimerizaciji za sintezo poroznega polimera. Vanilin metakrilat smo sintetizirali iz vanilina in anhidrida metakrilne kisline pri različnih reakcijskih pogojih, kjer smo spreminjali čas reakcije (48 ur in 120 ur) in jo izvajali v različnih atmosferah (na zraku in v dušikovi atmosferi). Nastali vanilin metakrilat smo okarakterizirali z infrardečo (FTIR) spektroskopijo, jedrsko magnetno resonanco (NMR) in elementno analizo (EA). Na podlagi analiz smo pri vseh pogojih potrdili nastanek vanilin metakrilata. Ugotovili smo, da je učinkovitost reakcije boljša pri daljšem reakcijskem času in v prisotnosti inertne atmosfere.
Nato smo iz VMA in etilen glikol dimetakrilata (EGDMA) pripravili kopolimer poli(VMA-ko-EGDMA) s polimerizacijo v raztopini in s polimerizacijo kontinuirane faze emulzije z visokim deležem notranje faze (HIP emulzije). V obeh primerih je polimerizacija potekala s fotoiniciatorjem Irgacure 819. Pri polimerizaciji v raztopini smo kot topilo uporabili različne deleže toluena, da bi raziskali vpliv topila na morfologijo polimera. Nastali poli(VMA-ko-EGDMA) smo okarakterizirali s FTIR spektroskopijo, elementno analizo, vrstičnim elektronskim mikroskopom (SEM) za preučevanje morfologije monolitov in porozimetrom po Brunauer-Emmett-Teller (BET) metodi za določevanje specifične površine materiala. Neporozen polimer smo dobili le pri najnižji vsebnosti toluena, medtem ko smo pri višjih vsebnostih dobili porozen material. Pri polimerizaciji HIP emulzije smo poleg VMA in EGDMA uporabili še surfaktant Hypermer B246 za stabilizacijo emulzije, kot notranjo fazo pa vodno raztopino kalcijevega klorida heksahidrata. Nastali poli(VMA-ko-EGDMA) monoliti so bili zelo krhki, zato smo v monomerno fazo dodali še monomer 2-etilheksil akrilat (EHA), ki poveča prosti volumen polimera in s tem elastičnost materiala, kar se je v našem primeru tudi potrdilo. Nastale poli(VMA-ko-EGDMA) in poli(VMA-ko-EGDMA-ko-EHA) monolite smo nato okarakterizirali s FTIR spektroskopijo, elementno analizo, vrstičnim elektronskim mikroskopom in porozimetrom. S FTIR spektroskopijo in elementno analizo smo dokazali vključitev monomerov v polimerno verigo, s SEM-om pa smo ugotovili, da imajo poli(VMA-ko-EGDMA) monoliti odprto celično strukturo, medtem ko je pri poli(VMA-ko-EGDMA-ko-EHA) morfologija bikontinuirna.In this work, we set two main goals: to synthesize vanillin methacrylate (VMA) and to use it as a monomer in further polymerization to synthesize a porous polymer. We synthesized vanillin methacrylate from vanillin and methacrylic anhydride under different reaction conditions, varying the reaction time (48 hours and 120 hours) and carrying out the reactions in different atmospheres (in air and nitrogen). The resulting vanillin methacrylate was characterized by infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and elemental analysis (EA). Based on the analyses, we were able to confirm the formation of vanillin methacrylate under all conditions. We found that the reaction efficiency was higher with a longer reaction time and in the presence of an inert atmosphere.
Next, we prepared the copolymer poly(VMA-co-EGDMA) from VMA and ethylene glycol dimethacrylate (EGDMA) by solution polymerization and high internal phase emulsion (HIPE) polymerization. In both cases, the polymerization was carried out with the photoinitiator Irgacure 819. In the solution polymerization, we used different proportions of toluene as a solvent to investigate the effects of the solvent on the morphology of the polymer. The resulting poly(VMA-co-EGDMA) was characterized by FTIR spectroscopy, elemental analysis, scanning electron microscopy (SEM) to study the morphology of the monoliths and a Brunauer-Emmett-Teller (BET) porosimeter to determine the specific surface area of the material. We obtained a non-porous polymer only at the lowest toluene content, while a porous material was formed at higher toluene contents. In the HIPE polymerization, in addition to VMA and EGDMA, we also used the surfactant Hypermer B246 to stabilize the emulsion, with an aqueous solution of calcium chloride hexahydrate as the inner phase. The resulting poly(VMA-co-EGDMA) monoliths were very brittle, which is why we added the monomer 2-ethylhexyl acrylate (EHA) to the monomer phase, which increases the free volume of the polymer and thus the elasticity of the material, which was also confirmed in our case. The resulting poly(VMA-co-EGDMA) and poly(VMA-co-EGDMA-co-EHA) monoliths were then characterized by FTIR spectroscopy, elemental analysis, scanning electron microscopy and porosimetry. FTIR spectroscopy and elemental analysis confirmed the incorporation of the monomers into the polymer chain, while SEM analysis revealed that the poly(VMA-co-EGDMA) monoliths have an open-cell structure, whereas the poly(VMA-co-EGDMA-co-EHA) morphology is bicontinuous
Binding site of MraZ transcription factor in Mollicutes
No full textAbstractMollicutes (mycoplasmas) feature a significant loss of known regulators of gene expression. Here, we identified the recognition site of the MraZ-family regulator of Mycoplasma gallisepticum, which is conserved in many species of different clades within class Mollicutes. The MraZ binding site is AAAGTG[T/G], in the promoter of mraZ gene it forms a series of direct repeats with a structure (AAAGTG[T/G]N3)k, where k = 3 most frequently. MraZ binds to a single repeat as an octamer complex. MraZ can also bind a single binding site or a series of repeats with different spacer lengths (2–4 nt); thus, it may play a role in the regulation of multiple operons in Mollicutes. In M. gallisepticum, MraZ acts as a transcriptional activator. The overexpression of MraZ leads to moderate filamentation of cells and the formation of aggregates, likely as a result of incomplete cytokinesis
Analysis of the influence of queue type on packet delay in computer networks
No full textV diplomski nalogi smo opredelili probleme zagotavljanja kakovosti storitve interaktivnih aplikacij, ki zahtevajo prenos podatkov v realnem času. Predstavili smo osnovne pojme strežbe ter se seznanili s problemom čakalne vrste. Z vidika teorije strežbe smo predstavili dva primera realnih izgubnih strežnih sistemov s končno čakalno vrsto. Problem čakalnih vrst rešujemo z razvrščevalnimi algoritmi. Poznamo več vrst razvrščevalnih algoritmov, ki jih lahko med seboj primerjamo na podlagi različnih meril. Izbrane algoritme smo uporabili na zgledu simulacije sistema M/M/1/s in jih podrobneje analizirali. Eksperimente smo izvedli v programskem okolju OMNeT++. Slednje nam omogoča postavitev simulacijskega modela, izvedbo simulacije in analizo pridobljenih rezultatov. Rezultate simulacij smo uporabili za analizo in primerjavo učinkovitosti izbranih razvrščevalnih algoritmov.In this thesis, we have identified the problems of ensuring the service quality of interactive applications, which require data transfer in real time. We realised basic concepts of network service and got acquainted with the problem of waiting queue. In view of network service theory, we introduced two examples of real loss service systems with final waiting queue. The problem of waiting queue is solved with scheduling algorithms. There are several kinds of scheduling algorithms, which can be compared by different criteria. Selected algorithms have been used in simulation of system M/M/1/s and analysed in more detail. The experiment was done in software environment OMNet++, which makes it possible to set up a simulation model, carry out the simulation and analyse the results. The results of the simulation have been used to analyse and compare the efficiency of the selected scheduling algorithms
Combination of rosemary extract and buffered vinegar inhibits Pseudomonas and Shewanella growth in common carp (Cyprinus carpio)
No full textBACKGROUND: Aquaculture is the fastest growing food-production sector, and common carp (Cyprinus carpio) is one of the most cultivated fish species in the world. Due to its intrinsic characteristics, fish meat is highly susceptible to microbiological spoilage. Pseudomonas and Shewanella are the primary and secondary occurring microbiota during storage of fish meat, with significant contribution to spoilage with the formation of hydrolytic enzymes (lipases and proteases). RESULTS: With in vitro testing, we show that rosemary extract (Inolens4), buffered vinegar and their combination (SyneROX) exhibit antimicrobial effects against P. fragi, P. psychrophila, S. putrefaciens and S. xiaemensis at concentrations of 3.13 and 1.56 mg mL−1. The combination was the most effective in inhibiting growth of selected bacteria in food model, and production of lipases and proteases during 9 days at 5 °C. In situ testing of antimicrobial dip treatment of carp meat determined that aerobic mesophilic, total psychrotrophic, Pseudomonas and hydrogen sulfide producer counts were reduced in all treatments, with the most prominent influence being shown by the combination and buffered vinegar. CONCLUSIONS: Our study highlights the importance of a multilevel assessment of the antimicrobial potential of biopreservatives under conditions comparable to those of the selected food. Investigation with bacteria and food model provided coherent and consistent data for the evaluation of the antimicrobial potential for carp meat. Combination of buffered vinegar (as active antimicrobial) and rosemary extract, with well-known and researched antioxidant properties but low in situ antimicrobial activity, represents a good potential for combined effect in preservation of fish meat. © 2020 Society of Chemical Industry
The occurrence of strawberry viruses and phytoplasmas in the Czech Republic
No full textSeveral symptoms of strawberry mottle, crinkle, vein banding, mild yellow edge as well of mixed virus infection were observed on F. vesca clones after leaf graft bioassay. Isometric virus-like particles ranging from 21 to 50 nm in diameter, slightly flexuous filamentous particles (12 x 600 - 1200 nm), rhabdovirus-like virions (45-60 x 285 -320 nm) and virus-like inclusions were observed by electron microscopy in several strawberry preparations. Dot blot hybridisation and PCR analyses confirmed the presence of Strawberry vein banding virus (SVBV) in several samples. Moreover, DNA was isolated from this material, amplified, sequenced, and it was found that the fragment from the middle part of the coat protein gene of the Czech SVBV isolates was nearly identical with the corresponding region of the American SVBV isolate. Isolates of Arabis mosaic virus, Strawberry latent ringspot virus and Tobacco necrosis virus - D strain were mechanically transmitted from strawberries to differential host plants, purified, characterised by electron microscopy and antisera against them were prepared. Phytoplasmas belonging to aster yellows group (16SrI) subgroup I-C were detected in many strawberry plants which showed different types of symptoms: green petals, flower phyllody and early leaf reddening with subsequent decline. Electron microscopic observation of ultrathin sections confirmed the presence of phytoplasma structures in phloem tissues of diseased plants
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
Dr. Glendon Swarthout
No full textHosted by Roger M. Busfield, MSU Assistant Professor of Speech and Theater, Meet the Author is designed to introduce a general audience to a contemporary author and their work through in-depth interviews. This episode features a conversation between Dr. Glendon Swarthout, prolific author and English professor at MSU, and assistant professors Sam S. Baskett and Theodore B. Strandness
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