272 research outputs found
Synthese und Charakterisierung neuer metall-organischer GerĂźstverbindungen und deren Anwendung in der asymmetrischen Katalyse und Gasspeicherung
Ziel der durchgefßhrten Arbeiten war die Etablierung neuer Synthesestrategien zur Gewinnung chiraler metall-organischer Gerßstverbindungen (engl: Metal-Organic Frameworks, MOFs). Hierfßr wurden drei verschiedene Ansätze verfolgt. Zunächst sollte die Einbringung einer chiralen Dicarbonsäure mit einem 2,2´-Spirobiindan-Gerßst in ein MOF-Netzwerk untersucht werden. Im Rahmen einer Kooperation wurden neue mit chiralen Oxazolidinonen substituierte 4,4´,4´´-Benzol-1,3,5-triyl-tribenzoesäuren H3ChirBTB-n (n = 1, 2) entwickelt, die ebenfalls zur Synthese neuer chiraler MOFs dienten. Die Modifizierung bekannter nicht-chiraler metall-organischer Gerßstverbindungen mit koordinativ ungesättigten Metallatomen durch Anbindung chiraler Amine stellte die dritte Synthesestrategie dar.
Im Rahmen der letztgenannten Syntheseroute wurde fßr MIL-101 (MIL = MatÊrial Institut Lavoisier) eine sehr hohe katalytische Aktivität in der Cyanosilylierung von Benzaldehyd nachgewiesen. Die Umsetzung mit chiralen Aminen fßhrte jedoch nicht zu einem enantioselektiven Katalysator.
Im Gegensatz dazu konnten die ersten beiden Synthesewege zur Gewinnung neuer chiraler metall-organischer Gerßstverbindungen erfolgreich beschritten werden. Durch solvothermale Reaktion von (S)-2,2´-Spirobiindan-5,5´-dicarbonsäure ((S)-H2Spiro-BIDC) mit Zinknitrat in N,N-Dimethylformamid (DMF) wurde eine neue chirale metall-organische Gerßstverbindung namens DUT-7 (DUT = Dresden University of Technology) der Zusammensetzung Zn4O((S)-Spiro-BIDC)3 dargestellt. Neben einer unerwarteten, zweifach interpenetrierten Netzwerkstruktur mit hexagonalen Kanälen weist DUT-7 eine fßr MOFs bislang noch nicht beobachtete temperaturinduzierte, reversible Strukturänderung auf.
Die zweite neue Strategie zur Gewinnung chiraler MOFs beinhaltete die Umsetzung der chiralen Tricarbonsäuren H3ChirBTB-n, die entweder (S)-4-iso-Propyl- (n = 1) oder (S)-4-Benzyl-1,3-Oxazolidin-2-on-Substituenten (n = 2) tragen. Die beiden gewonnenen Verbindungen Zn3(ChirBTB-1)2 und Zn3(ChirBTB-2)2 weisen trotz gleicher Zusammensetzung vÜllig unterschiedliche Kristallstrukturen auf. Beide Materialien wurden erfolgreich in der Mukaiyama-Aldol-Reaktion von Benz- bzw. 1-Naphthaldehyd mit 1-Methoxy-2-methyl-1-(trimethylsiloxy)propen eingesetzt, wobei ihre katalytische Aktivität mit verschiedenen Referenzkatalysatoren verglichen wurde. Die erzielten Enantiomerenßberschßsse (ee) liegen zwischen 6 und 16%.
Auf der Suche nach neuen, fßr die Einbringung der ChirBTB-n-Liganden geeigneten MOF-Strukturen wurde auch die Umsetzung der reinen, nicht chiralen 4,4´,4´´-Benzol-1,3,5-triyl-tribenzoesäure (H3BTB) untersucht. Die Reaktion mit Nickelnitrat fßhrte zur Bildung einer neuen hochporÜsen Verbindung namens DUT-9 mit der Zusammensetzung Ni5O2(BTB)2(DEF,DMF)4(H2O)4. DUT-9 weist neben den auf dem Gebiet der MOF-Forschung bislang unbekannten Ni5O2-Clustern eine noch nicht beschriebene dreidimensionale (3,6)-Netzwerktopologie auf. Das neue Material zeigt zudem exzellente Speicherkapazitäten fßr Wasserstoff, Methan und Kohlenstoffdioxid.The present work aims on the search for new synthesis strategies towards chiral Metal-Organic Frameworks (MOFs). Three different approaches were pursued. Initially, the integration of a chiral dicarboxylic acid with a 2,2´-spirobiindane backbone into a MOF network was investigated. Within a cooperation, new 4,4´,4´´-benzene-1,3,5-triyl-tribenzoic acids H3ChirBTB-n (n = 1,2) with chiral oxazolidinone substituents were developed which were also used for the assembly of chiral MOFs. The third synthesis strategy involved the tethering of chiral amines to coordinatively unsaturated metal atoms of known non-chiral Metal-Organic Frameworks.
Within the last-mentioned approach, the very high catalytic activity of MIL-101 (MIL = MatĂŠrial Institut Lavoisier) towards the cyanosilylation of benzaldehyde was demonstrated. Treatment with chiral amines did not lead to an enantioselective catalyst.
In contrast, the first two synthesis strategies could be performed successfully. A new MOF named DUT-7 (DUT = Dresden University of Technology) with composition Zn4O((S)-Spiro-BIDC)3 was obtained by solvothermal reaction of (S)-2,2´-spirobiindane-5,5´-dicarboxylic acid ((S)-H2Spiro-BIDC) with zinc nitrate in N,N-dimethylformamide (DMF). Besides an unexpected, two-fold interpenetrated framework structure with hexagonal channels, DUT-7 shows a temperature induced, reversible structure transformation not yet observed.
The other new strategy to obtain chiral Metal-Organic Frameworks involved the conversion of the chiral tricarboxylic acids H3ChirBTB-n bearing either a (S)-4-iso-propyl- (n = 1) or a (S)-4-benzyl-1,3-oxazolidin-2-one substituent (n = 2). Though having the same framework composition, the new compounds Zn3(ChirBTB-1)2 and Zn3(ChirBTB-2)2 exhibit completely different crystal structures. Both materials were tested in the Mukaiyama aldol reaction between benzaldehyde or 1-naphthaldehyde, respectively, and 1-methoxy-2-methyl-1-(trimethylsiloxy)propene and their catalytic activity was compared to different reference catalysts. Enantiomeric excess values (ee) between 6 and 16% were obtained.
In search of new MOF structures being suitable for the integration of the ChirBTB-n linkers, the conversion of the pure, non chiral 4,4´,4´´-benzene-1,3,5-triyltribenzoic acid (H3BTB) was investigated. The reaction with nickel nitrate lead to the formation of a new, highly porous compound Ni5O2(BTB)2(DEF,DMF)4(H2O)4 named DUT-9. Besides Ni5O2 clusters which are a novelty in MOF chemistry, DUT-9 exhibits a three dimensional (3,6)-network topology not yet described. In addition, the new material shows excellent storage capacities for hydrogen, methane and carbon dioxide
Forensic Social Work: Practice and Vision
Forensic social work can bridge the gap between the criminal justice and mental health systems and serve clients who âfall between the cracks.â The authors describe theoretical and clinical issues, utilizing case examples and the literature to develop a conceptual paradigm for the role of social workers in this area
Ernährungsziele unserer Gesellschaft: die Beiträge der Ernährungsverhaltenswissenschaft. 22. Wissenschaftliche Jahrestagung der Arbeitsgemeinschaft Ernährungsverhalten e.V. (AGEV), 12.-13. Oktober 2000, Bonn
Ernährung und Raum: Regionale und ethnische Ernährungsweisen in Deutschland. 23. Wissenschaftliche Jahrestagung der Arbeitsgemeinschaft Ernährungsverhalten e.V. (AGEV), 11.-12. Oktober 2001, Freising/Weihenstephan
Functional Food - Forschung, Entwicklung und Verbraucherakzeptanz. 25. Wissenschaftliche Jahrestagung der AGEV, 23.-24.Mai 2003 in Giessen
Estimated physical activity in Bavaria, Germany, and its implications for obesity risk: Results from the BVS-II Study
BACKGROUND: Adequate physical activity (PA) is considered as a key factor in the fight against the obesity epidemic. Therefore, detailed description of the actual PA and its components in the population is necessary. Additionally, this study aims to investigate the association between PA and obesity risk in a representative population sample in Bavaria, Germany. METHODS: Data from 893 participants (age 13â80 years) of the Bavarian Food Consumption Survey II (BVS II) were used. In each participant, three computer-based 24-hour recalls were conducted by telephone assessing type and duration of PA in the domains occupation, sports, other strenuous leisure time activities (of mostly moderate intensity) as well as TV/PC use in leisure time and duration of sleeping. After assigning metabolic equivalents (METs) to each activity, estimates of energy expenditure (MET*h) and total daily PA level (PAL(est.)) were calculated. In a subgroup of adults (n = 568) with anthropometric measurements logistic regression models were used to quantify the impact of PA on obesity risk. RESULTS: Estimated average PA in women and men was 38.5 Âą 5.0 and 40.6 Âą 9.3 MET*h/d, respectively, corresponding to PAL(est. )values of 1.66 Âą 0.22 and 1.75 Âą 0.40. Obese subjects showed lower energy expenditure in the categories sports, occupation, and sleeping, while the time spent with TV/PC during leisure time was highest. This is confirmed in logistic regression analyses revealing a statistically significant association between obesity and TV/PC use during leisure time, while sports activity was inversely related to obesity risk. Overall, less than 1/3 of the study participants reached the recommended PAL of ⼠1.75. Subjects within the recommended range of PA had an about 60 % (odds ratio = 0.43; 95% CI: 0.21â0.85) reduced risk of obesity as compared to inactive subjects with a PAL(est. )<1.5. CONCLUSION: Based on the results of short-term PA patterns, a major part of the Bavarian adult population does not reach the recommendations (PAL>1.75; moderate PA of > 30 min/d). Despite the limitations of the study design, the existing associations between sports activity, TV/PC use and obesity risk in this population give further support to the recommendation of increasing sports activity and reducing sedentary behaviour in order to prevent rising rates of obesity
Theory-driven Visual Design to Support Reflective Dietary Practice via mHealth: A Design Science Approach
Design for reflection in human-computer interaction (HCI) has evolved from focusing on an abstract and outcome-driven design subject towards exposing procedural or structural reflection characteristics. Although HCI research has recognized that an individual\u27s reflection is a long-lasting, multi-layered process that can be supported by meaningful design, researchers have made few efforts to derive insights from a theoretical perspective about appropriate translation into end-user visual means. Therefore, we synthesize theoretical knowledge from reflective practice and learning and argue for a differentiation between time contexts of reflection that design needs to address differently. In an interdisciplinary design-science-research project in the mHealth nutrition promotion context, we developed theory-driven guidelines for âreflection-in-actionâ and âreflection-on-actionâ. Our final design guidelines emerged from prior demonstrations and a final utility evaluation with mockup artifacts in a laboratory experiment with 64 users. Our iterative design and the resulting design guidelines offer assistance for addressing reflection design by answering reflective practiceâs respective contextual requirements. Based on our user study, we show that reflection in terms of âreflection- in-actionâ benefits from offering actionable choice criteria in an instant timeframe, while âreflection-on-actionâ profits from the structured classification of behavior-related criteria from a longer, still memorable timeframe
Perspective: a conceptual framework for adaptive personalized nutrition advice systems (APNASs)
Nearly all approaches to personalized nutrition (PN) use information such as the gene variants of individuals to deliver advice that is more beneficial than a generic one-size-fits-all recommendation. Despite great enthusiasm and the increased availability of commercial services, thus far, scientific studies have only revealed small to negligible effects on the efficacy and effectiveness of personalized dietary recommendations, even when using genetic or other individual information. In addition, from a public health perspective, scholars are critical of PN because it primarily targets socially privileged groups rather than the general population, thereby potentially widening health inequality. Therefore, in this perspective, we propose to extend current PN approaches by creating adaptive personalized nutrition advice systems (APNASs) that are tailored to the type and timing of personalized advice for individual needs, capacities, and receptivity in real-life food environments. These systems encompass a broadening of current PN goals (i.e., what should be achieved) to incorporate individual goal preferences beyond currently advocated biomedical targets (e.g., making sustainable food choices). Moreover, they cover the personalization processes of behavior change by providing in situ, just-in-time information in real-life environments (how and when to change), which accounts for individual capacities and constraints (e.g., economic resources). Finally, they are concerned with a participatory dialogue between individuals and experts (e.g., actual or virtual dieticians, nutritionists, and advisors), when setting goals and deriving measures of adaption. Within this framework, emerging digital nutrition ecosystems enable continuous, real-time monitoring, advice, and support in food environments from exposure to consumption. We present this vision of a novel PN framework along with scenarios and arguments that describe its potential to efficiently address individual and population needs and target groups that would benefit most from its implementation
Effects and challenges of using a nutrition assistance system: results of a long-term mixed-method study
Healthy nutrition contributes to preventing non-communicable and diet-related diseases. Recommender systems, as an integral part of mHealth technologies, address this task by supporting users with healthy food recommendations. However, knowledge about the effects of the long-term provision of health-aware recommendations in real-life situations is limited. This study investigates the impact of a mobile, personalized recommender system named Nutrilize. Our system offers automated personalized visual feedback and recommendations based on individual dietary behaviour, phenotype, and preferences. By using quantitative and qualitative measures of 34 participants during a study of 2â3Â months, we provide a deeper understanding of how our nutrition application affects the usersâ physique, nutrition behaviour, system interactions and system perception. Our results show that Nutrilize positively affects nutritional behaviour (conditional R2=. 342) measured by the optimal intake of each nutrient. The analysis of different application features shows that reflective visual feedback has a more substantial impact on healthy behaviour than the recommender (conditional R2=. 354). We further identify system limitations influencing this result, such as a lack of diversity, mistrust in healthiness and personalization, real-life contexts, and personal user characteristics with a qualitative analysis of semi-structured in-depth interviews. Finally, we discuss general knowledge acquired on the design of personalized mobile nutrition recommendations by identifying important factors, such as the usersâ acceptance of the recommenderâs taste, health, and personalization
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