Academic literature on the topic '039999 Chemical Sciences not elsewhere classified'
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Journal articles on the topic "039999 Chemical Sciences not elsewhere classified"
Brice, Kylie L., Pankaj Trivedi, Thomas C. Jeffries, Michaela D. J. Blyton, Christopher Mitchell, Brajesh K. Singh, and Ben D. Moore. "The Koala (Phascolarctos cinereus) faecal microbiome differs with diet in a wild population." PeerJ 7 (April 1, 2019): e6534. http://dx.doi.org/10.7717/peerj.6534.
Full textNesrine, Lenchi, Kebbouche Salima, Khelfaoui Mohamed Lamine, Laddada Belaid, BKhemili Souad, Gana Mohamed Lamine, Akmoussi Sihem, and Ferioune Imène. "Phylogenetic characterization and screening of halophilic bacteria from Algerian salt lake for the production of biosurfactant and enzymes." World Journal of Biology and Biotechnology 5, no. 2 (August 15, 2020): 1. http://dx.doi.org/10.33865/wjb.005.02.0294.
Full textAdmin, Admin, and Dr Mustafa Arslan. "Effect of dexmedetomidine on ischemia-reperfusion injury of liver and kidney tissues in experimental diabetes and hepatic ischemia-reperfusion injury induced rats." Anaesthesia, Pain & Intensive Care, May 9, 2019, 143–49. http://dx.doi.org/10.35975/apic.v0i0.641.
Full textDissertations / Theses on the topic "039999 Chemical Sciences not elsewhere classified"
(9187331), Elijah B. Roth. "STUDENT EXPERIENCES AND MOTIVATIONS IN A FLIPPED GENERAL CHEMISTRY II COURSE." Thesis, 2020.
Find full textStudent-centered pedagogies have become increasingly popular in higher education. Research on flipped learning, in particular, has shown that collaborative problem-solving environments are able to better support effective learning than lecture alone. However, the effects of this format on students’ interests and motivations in chemistry remain unknown. For this study, students and graduate teaching assistants who participated in a flipped learning, second-semester general chemistry course were selected to participate in a focus group discussion and individual interviews that explored their experiences and perceptions of the features of the course (affordances) that supported and thwarted their sense of motivation.
This phenomenographic study mapped eight students’ experiences of the course and used qualitative data from interviews with the graduate teaching assistants (TAs) to compare and contrast with students’ claims. Self-determination theory was used to frame these experiences and the results were discussed using other relevant theories of motivation, including, but not limited to expectancy-value theory and achievement goal theories.
It was found that there are several features of the course that support students’ motivations according to the basic psychological needs of relatedness, autonomy, and competency in self-determination theory. The study also revealed many features of the course that thwarted students’ motivations. Features that students described as motivating left them feeling connected to their peers and other agents in the course, capable of efficiently interacting with their environments as a result of the course tasks, and a sense that their performance was related to their efforts. Features that students’ described as demotivating left them feeling helpless, incompetent, alone, and without a sense of control over their performance in the course.
The results of this study shed light on students’ perceptions of the environment in a flipped learning chemistry course. These findings can be used to improve students’ experiences, and consequently their motivation when taking a flipped learning chemistry course. Specific assertions developed from these results and recommendations for these improvements are further discussed.
(10290917), Arianna D. Romero Marcia. "EFFECT OF GLUCAN CHEMICAL STRUCTURE ON GUT MICROBIOTA COMPOSITION AND FUNCTION." Thesis, 2021.
Find full textIt is well known that colonic microbiota is influenced by both intrinsic and extrinsic factors; out of all these, diet plays a major role. The traditional human diet has typically been high in overall dietary fiber intake, due its inherent presence in plant-derived foods. However, over the years, dietary patterns have transitioned into a low-fiber Westernized diet. This diet is increasingly implicated in colonic diseases. Dietary fiber consumption is known to increase microbial diversity, yet the mechanisms are still unclear. This is partially true because dietary fiber as a category is composed of a wide variety of structures, which may have divergent effects on the gut microbiome. The food industry has extracted, isolated, refined and purified non-digestible carbohydrates and, in some cases, modified them for improved function, which may influence their interaction with the gut microbiome. This study was developed in two phases: we first hypothesized that glucans produced by different processes were structurally distinct and that these fine structural differences in glucans would govern microbial responses to the polymers. To test this hypothesis, we first determined the structural characteristics of the glucans by gas chromatography and mass spectrometry, which revealed substantial structural differences among the glucans with respect to size and linkage patterns, consequently categorizing the glucans by structure (i.e., mixed linkage α-glucans, resistant maltodextrins, and polydextroses). The second study involved the in vitro fecal fermentation of these commercially available soluble glucans which are uniformly composed of glucose linked into different structural arrangements. We further hypothesized that each glucan would select for different microbiota and that there would be glucan-specific general responses across microbiomes. We were able to identify a variety of idiosyncratic metabolic patterns as well as differential organisms selecting for specific glucan structures. Although there were associations with glucan classes at the family level (e.g., Bacteriodaceae and Lachnospiraceae were discriminants of the resistant maltodextrins and polydextroses respectively), associations with glucans across individual species within these families varied. These findings suggest that microbiome responses to structurally distinct glucans depend upon both fine glucan structure and community context, and community metabolic phenotypes emerge from the interaction of the two. These findings are relevant to the food industry as they may enable optimization of synthesis to generate chemical structures that select for specific organisms and/or improve overall gut health.
(5930483), Xiaowei Zhang. "DIFFERENTIAL GUT MICROBIOTA AND FERMENTATION METABOLITE RESPONSE TO CORN BRAN ARABINOXYLANS IN DIFFERENT CHEMICAL AND PHYSICAL FORMS." Thesis, 2020.
Find full textAs a major part of the dietary fiber classification, plant polysaccharides often have chemically complex structures which may differ by genera and species, and perhaps even by genotype and growing environment. Arabinoxylans from cereal cell walls are known to differently impact human gut microbiota composition and fermentation metabolites due to variability in chemical structure, though specificities of structure to these functions are not known at the level of genotype ́ environment. In the first study, corn bran arabinoxylan (CAX) extracted from 4 genotypes ́ 3 growing years at the Purdue Agronomy Farm was compared in human fecal fermentations to test the hypotheses that, 1) CAXs extracted from brans from different corn genotypes and grown over different years (environments) show distinct structures, and 2) these cause differences in gut microbiota response and fermentation metabolites. Monosaccharides and linkage analysis revealed that CAXs had different structures and the differences were genotype-specific, but not significantly due to environment. PCA analysis revealed that both short chain fatty acid production and the microbial community shifted also in a genotype-specific way. Thus, small structural changes, in terms of sugar and linkage compositions, cause significant changes in fermentation response showing very high specificity of structure to gut microbiota function.
Insoluble fermentable cell wall matrix fibers have been shown to support beneficial butyrogenic Clostridia, but have restricted use in food products due to their insoluble character.
In the second study, a soluble fiber matrix was developed that exhibited a similar fermentation effect as fermentable insoluble fiber matrices. Low arabinose/xylose ratio CAX was extracted with two concentrations of sodium hydroxide to give soluble polymers with relatively low and high residual ferulic acid (CAX-LFA and CAX-HFA). After laccase treatment to make diferulate crosslinks, soluble matrices were formed with average size of 3.5 to 4.5 mer. In vitro human fecal fermentation of CAX-LFA, CAX-HFA, soluble crosslinked ~3.5 mer CAX-LFA (SCCAX- LFA), and ~4.5 mer SCCAX-HFA revealed that the SCCAX matrices had slower fermentation property and higher butyrate proportion in SCCAX-HFA. 16S rRNA gene sequencing showed that SCCAX-HFA promoted OTUs associated with butyrate production including Unassigned Ruminococcaceae, Unassigned Blautia, Fecalibacterium prausnitzii, and Unassigned Clostridium. This is the first work showing the fabrication of soluble crosslinked fiber matrices that favors growth of butyrogenic bacteria.
Moreover, these same SCCAXs exhibited an interesting gel forming property on simple pH reduction, which is similar in gelling property to low acyl gellan gum, though is differently readily soluble in water. Both of the SCCAXs formed gels at pH 2, with SCCAX-HFA forming the stronger gel. Gels showed shear-thinning behavior and a thermal and pH reversible property. A gel forming mechanism was proposed involving noncovalent crosslinking including hydrogen bonds and hydrophobic interaction among the SCCAX complexes. This mechanism was supported by structural characterization of SCCAX complexes using a Zeta-sizer and FT-IR spectroscopy. SCCAX-HFA could be used in low sugar gels and has the above property of promoting butyrogenic bacteria in the gut.
In conclusion, gut microbiota responds differentially to CAXs with various fine structures. This probably due to dietary fiber-gut microbiota relationships have been evolved over time to be highly specific. Forming soluble fiber matrices could be a good strategy to promote butyrogenic bacteria and improve gut health, in a readily usable form in beverages.
(9510965), Adrienne Lea Voelker. "Vitamin Stability and Water-Solid Interactions." Thesis, 2020.
Find full textThis dissertation investigates two major structure-function relationships important to food science: vitamin stability and water-solid interactions. Thiamine, vitamin B1, is an essential micronutrient in the human diet. While thiamine is found naturally and as a fortification supplement in many foods, it is chemically unstable on exposure to heat and some co-formulated ingredients, with degradation exacerbated in prolonged shelf-life products. The instability of thiamine is a concern for the development of dietary deficiencies, which are prevalent even in developed countries; however, thiamine stability is not widely studied in the food or pharmaceutical industries. Thiamine is commercially available in two salt forms: thiamine mononitrate (TMN) and thiamine chloride hydrochloride (TClHCl). This study focused on documenting the storage stability of thiamine in solution, considering the effects of which commercially available salt form of the vitamin was used, vitamin concentration, pH, and ions present in solution by monitoring chemical stability and degradation kinetics over a 6-month to 1-year period following storage at 25-80ºC, and expanded these studies into food systems (bread doughs). The results from these studies, including the reaction kinetics of thiamine degradation, the degradation pathway, and the sensory impacts of the degradation products formed, especially as affected by pH and food matrix, can be used to improve thiamine stability and delivery in foods.
The studies of water-solid interactions in this dissertation covered two topics: 1) the effects of formulating a variety of food-relevant additives on the crystallization tendency of amorphous sucrose; and 2) the effects of formulation on the moisture sorption behaviors and physical stability of spices, herbs, and seasoning blends. Sucrose lyophiles were co-formulated with a variety of additives and stored at 11-40% relative humidity (RH). The structural compatibility of sucrose with the additive, and related intermolecular interactions, dictated the tendency of the additive to either delay, prevent, or accelerate sucrose crystallization. Spices, herbs, and seasoning blends were exposed to increasing RH (23-75%) and temperature (20-50ºC) to determine the effect of storage and formulation on a variety of physical properties. In general, as complexity of blends increased, physical stability decreased. While this dissertation covers a wide variety of food chemistry and food materials science topics, including vitamin chemical stability, amorphous sucrose physical stability, and moisture sorption behaviors of spices, herbs, and seasoning blends, the findings provide valuable information on the chemical and physical stability of ingredient systems and how the structure-function relationships of the systems can be controlled for optimal ingredient functionality.
(5930339), Seda Tuncil. "Investigating Stability in Amorphous Solid Dispersions: A Study of the Physical and Chemical Stability of Two Salt Forms of Thiamine and the Physical Stability of Citric Acid." Thesis, 2019.
Find full text(10971108), Yangjie Li. "REACTION ACCELERATION AT INTERFACES STUDIED BY MASS SPECTROMETRY." Thesis, 2021.
Find full textVarious organic reactions, including important synthetic reactions involving C–C, C–N, and C–O bond formation as well as reactions of biomolecules, are known to be accelerated when the reagents are present in confined volumes such as sprayed or levitated microdroplets or thin films. This phenomenon of reaction acceleration and the key role of interfaces played in it are of intrinsic interest and potentially of practical value as a simple, rapid method of performing small-scale synthesis. This dissertation has three focusing subtopics in the field of reaction acceleration: (1) application of reaction acceleration in levitated droplets and mass spectrometry to accelerate the reaction-analysis workflow of forced degradation of pharmaceuticals at small scale; (2) fundamental understanding of mechanisms of accelerated reactions at air/solution interfaces; (3) discovery the use of glass particles as a `green' heterogeneous catalysts in solutions and systematical study of solid(glass)/solution interfacial reaction acceleration as a superbase for synthesis and degradation using high-throughput screening.
Reaction acceleration in confined volumes could enhance analytical methods in industrial chemistry. Forced degradation is critical to probe the stabilities and chemical reactivities of therapeutics. Typically performed in bulk followed by LC-MS analysis, this traditional workflow of reaction/analysis sequence usually requires several days to form and measure desirable amount of degradants. I developed a new method to study chemical degradation in a shorter time frame in order to speed up both drug discovery and the drug development process. Using the Leidenfrost effect, I was able to study, over the course of seconds, degradation in levitated microdroplets over a metal dice. This two-minute reaction/analysis workflow allows major degradation pathways of both small molecules and therapeutic peptides to be studied. The reactions studied include deamidation, disulfide bond cleavage, ether cleavage, dehydration, hydrolysis, and oxidation. The method uses microdroplets as nano-reactors and only require a minimal amount of therapeutics per stress condition and the desirable amount of degradant can be readily generated in seconds by adjusting the droplet levitation time, which is highly advantageous both in the discovery and development phase. Built on my research, microdroplets can potentially be applied in therapeutics discovery and development to rapidly screen stability of therapeutics and to screen the effects of excipients in enhancing formulation stabilities.
My research also advanced the fundamental understanding of reaction acceleration by disentangles the factors controlling reaction rates in microdroplet reactions using constant-volume levitated droplets and Katritzky transamination as a model. The large surface-to-volume ratios of these systems results in a major contribution from reactions at the air/solution interface where reaction rates are increased. Systems with higher surface-active reactants are subject to greater acceleration, particularly at lower concentrations and higher surface-to-volume ratios. These results highlight the key role that air/solution air/solution interfaces play in Katritzky reaction acceleration. They are also consistent with the view that reaction increased rate constant is at least in part due to limited solvation of reagents at the interface.
While reaction acceleration at air/solution interfaces has been well known in microdroplets, reaction acceleration at solid/solution interfaces appears to be a new phenomenon. The Katritzky reaction in bulk solution at room temperature is accelerated significantly by the surface of a glass container compared to a plastic container. Remarkably, the reaction rate is increased by more than two orders of magnitude upon the addition of glass particles with the rate increasing linearly with increasing amounts of glass. A similar phenomenon is observed when glass particles are added to levitated droplets, where large acceleration factors are seen. Evidence shows that glass acts as a ‘green’ heterogeneous catalyst: it participates as a base in the deprotonation step and is recovered unchanged from the reaction mixture.
Subsequent to this study, we have systematically explored the solid/solution interfacial acceleration phenomena using our latest generation of a high-throughput screening system which is capable of screening thousands of organic reactions in a single day. Using desorption electrospray ionization mass spectrometry (DESI-MS) for automated analysis, we have found that glass promotes not only organic reactions without organic catalysts but also reactions of biomolecules without enzymes. Such reactions include Knoevenagel condensation, imine formation, elimination of hydrogen halide, ester hydrolysis and/or transesterification of acetylcholine and phospholipids, as well as oxidation of glutathione. Glass has been used as a general `green' and powerful heterogeneous catalyst.
(11198013), Kevin Wee. "Creation, deconstruction, and evaluation of a biochemistry animation about the role of the actin cytoskeleton in cell motility." Thesis, 2021.
Find full textExternal representations (ERs) used in science education are multimodal ensembles consisting of design elements to convey educational meanings to the audience. As an example of a dynamic ER, an animation presenting its content features (i.e., scientific concepts) via varying the feature’s depiction over time. A production team invited the dissertation author to inspect their creation of a biochemistry animation about the role of the actin cytoskeleton in cell motility and the animation’s implication on learning. To address this, the author developed a four-step methodology entitled the Multimodal Variation Analysis of Dynamic External Representations (MVADER) that deconstructs the animation’s content and design to inspect how each content feature is conveyed via the animation’s design elements.
This dissertation research investigated the actin animation’s educational value and the MVADER’s utility in animation evaluation. The research design was guided by descriptive case study methodology and an integrated framework consisting of the variation theory, multimodal analysis, and visual analytics. As stated above, the animation was analyzed using MVADER. The development of the actin animation and the content features the production team members intended to convey via the animation were studied by analyzing the communication records between the members, observing the team meetings, and interviewing the members individually. Furthermore, students’ learning experiences from watching the animation were examined via semi-structured interviews coupled with post- storyboarding. Moreover, the instructions of MVADER and its applications in studying the actin animation were reviewed to determine the MVADER’s usefulness as an animation evaluation tool.
Findings of this research indicate that the three educators in the production team intended the actin animation to convey forty-three content features to the undergraduate biology students. At least 50% of the student who participated in this thesis learned thirty-five of these forty-three (> 80%) features. Evidence suggests that the animation’s effectiveness to convey its features was associated with the features’ depiction time, the number of identified design elements applied to depict the features, and the features’ variation of depiction over time.
Additionally, one-third of the student participants made similar mistakes regarding two content features after watching the actin animation: the F-actin elongation and the F-actin crosslink structure in lamellipodia. The analysis reveals the animation’s potential design flaws that might have contributed to these common misconceptions. Furthermore, two disruptors to the creation process and the educational value of the actin animation were identified: the vagueness of the learning goals and the designer’s placement of the animation’s beauty over its reach to the learning goals. The vagueness of the learning goals hampered the narration scripting process. On the other hand, the designer’s prioritization of the animation’s aesthetic led to the inclusion of a “beauty shot” in the animation that caused students’ confusion.
MVADER was used to examine the content, design, and their relationships in the actin animation at multiple aspects and granularities. The result of MVADER was compared with the students’ learning outcomes from watching the animation to identify the characteristics of content’s depiction that were constructive and disruptive to learning. These findings led to several practical recommendations to teach using the actin animation and create educational ERs.
To conclude, this dissertation discloses the connections between the creation process, the content and design, and the educational implication of a biochemistry animation. It also introduces MVADER as a novel ER analysis tool to the education research and visualization communities. MVADER can be applied in various formats of static and dynamic ERs and beyond the disciplines of biology and chemistry.