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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.
21

Microdialysis Sampling from Wound Fluids Enables Quantitative Assessment of Cytokines, Proteins, and Metabolites Reveals Bone Defect-Specific Molecular Profiles

Förster, Yvonne, Schmidt, Johannes R., Wissenbach, Dirk K., Pfeiffer, Susanne E. M., Baumann, Sven, Hofbauer, Lorenz C., von Bergen, Martin, Kalkhof, Stefan, Rammelt, Stefan 27 January 2017 (has links) (PDF)
Bone healing involves a variety of different cell types and biological processes. Although certain key molecules have been identified, the molecular interactions of the healing progress are not completely understood. Moreover, a clinical routine for predicting the quality of bone healing after a fracture in an early phase is missing. This is mainly due to a lack of techniques to comprehensively screen for cytokines, growth factors and metabolites at their local site of action. Since all soluble molecules of interest are present in the fracture hematoma, its in-depth assessment could reveal potential markers for the monitoring of bone healing. Here, we describe an approach for sampling and quantification of cytokines and metabolites by using microdialysis, combined with solid phase extractions of proteins from wound fluids. By using a control group with an isolated soft tissue wound, we could reveal several bone defect-specific molecular features. In bone defect dialysates the neutrophil chemoattractants CXCL1, CXCL2 and CXCL3 were quantified with either a higher or earlier response compared to dialysate from soft tissue wound. Moreover, by analyzing downstream adaptions of the cells on protein level and focusing on early immune response, several proteins involved in the immune cell migration and activity could be identified to be specific for the bone defect group, e.g. immune modulators, proteases and their corresponding inhibitors. Additionally, the metabolite screening revealed different profiles between the bone defect group and the control group. In summary, we identified potential biomarkers to indicate imbalanced healing progress on all levels of analysis.
22

Not Only Delicious: Papaya Bast Fibres in Biocomposites

Lautenschläger, Thea, Kempe, Andreas, Neinhuis, Christoph, Wagenführ, André, Siwek, Sebastian 01 February 2017 (has links) (PDF)
Previous studies have shown favourable properties for papaya bast fibres, with a Young's modulus of up to 10 GPa and a tensile strength of up to 100 MPa. Because the fibres remain as residues on papaya plantations across the tropics in large quantities, their use in the making of green composites would seem to be worthy of consideration. This study aims to show that such composites can have very suitable mechanical properties, comparable to or even better than the common wood plastic composites (WPCs), and as such, represent a promising raw material for composites and a low-cost alternative to wood.
23

Phosphorus in Preferential Flow Pathways of Forest Soils in Germany.

Julich, Dorit, Feger, Karl-Heinz 27 March 2017 (has links) (PDF)
The transport of nutrients in forest soils predominantly occurs along preferential flow pathways (PFP). This study investigated the composition of phosphorus (P) forms in PFPs and soil matrix in several temperate beech forests with contrasting soil P contents in Germany. The PFPs were visualized using dye tracer experiments. Stained and unstained soil was sampled from three profile cuts per plot and analyzed for P fractions. The results show that labile P concentrations were highest in the O-layer and had the same range of values at all sites (240–320 mg·kg−1), although total P (TP) differed considerably (530–2330 mg·kg−1). The ratio of labile P to TP was significantly lower in the P-rich soil compared to the medium and P-poor soils. By contrast, the ratio of moderately labile P to TP was highest at the P-rich site. The shifts in P fractions with soil depth were generally gradual in the P-rich soil, but more abrupt at the others. The contents of labile and moderately labile P clearly differed in PFPs compared to soil matrix, but not statistically significant. The studied soils are characterized by high stone contents with low potential for P sorption. However, indications were found that labile organically bound P accumulates in PFPs such as biopores.
24

Sulfated hyaluronan alters fibronectin matrix assembly and promotes osteogenic differentiation of human bone marrow stromal cells

Vogel, Sarah, Arnoldini, Simon, Möller, Stephanie, Hempel, Ute, Schnabelrauch, Matthias 28 March 2017 (has links) (PDF)
Extracellular matrix (ECM) composition and structural integrity is one of many factors that influence cellular differentiation. Fibronectin (FN) which is in many tissues the most abundant ECM protein forms a unique fibrillary network. FN homes several binding sites for sulfated glycosaminoglycans (sGAG), such as heparin (Hep), which was previously shown to influence FN conformation and protein binding. Synthetically sulfated hyaluronan derivatives (sHA) can serve as model molecules with a well characterized sulfation pattern to study sGAG-FN interaction. Here is shown that the low-sulfated sHA (sHA1) interacts with FN and influences fibril assembly. The interaction of FN fibrils with sHA1 and Hep, but not with non-sulfated HA was visualized by immunofluorescent co-staining. FRET analysis of FN confirmed the presence of more extended fibrils in human bone marrow stromal cells (hBMSC)-derived ECM in response to sHA1 and Hep. Although both sHA1 and Hep affected FN conformation, exclusively sHA1 increased FN protein level and led to thinner fibrils. Further, only sHA1 had a pro-osteogenic effect and enhanced the activity of tissue non-specific alkaline phosphatase. We hypothesize that the sHA1-triggered change in FN assembly influences the entire ECM network and could be the underlying mechanism for the pro-osteogenic effect of sHA1 on hBMSC.
25

Work-related exposures and disorders among physical therapists: experiences and beliefs of professional representatives assessed using a qualitative approach

Girbig, Maria, Freiberg, Alice, Deckert, Stefanie, Druschke, Diana, Kopkow, Christian, Nienhaus, Albert, Seidler, Andreas 31 March 2017 (has links) (PDF)
Background According to international study results, physical therapists are afflicted with work-related musculoskeletal, psychosocial and dermal disorders as well as infections. The few existing studies in German-speaking regions focus mainly on dermal and psychosocial exposures and resulting complaints. An overview of all relevant work-related exposures and complaints of physical therapists is currently lacking. We sought to identify work-related exposures based on the subjective experiences and beliefs of physiotherapeutic representatives, in order to identify relevant work-related complaints and diseases. Likewise we aimed to compare the international evidence with the actual situation of physical therapists in Germany. Methods Two complementary qualitative approaches were used: 1) a focus group discussion with representatives of professional physiotherapy associations as well as health and safety stakeholders and 2) qualitative semi-structured telephone interviews incorporating currently employed physical therapists. The group discussion was conducted applying a moderation technique, and interviews were analyzed using the content analysis approach by Mayring. Results The focus group discussion with five participants and the 40 semi-structured interviews with physical therapists identified comparable results. The main exposures of physiotherapeutic work were considered to be musculoskeletal (e.g., awkward body postures during treatment, patient transfers, passive mobilization), psychosocial (e.g., statutory audit of prescriptions and the associated conflicts with doctors and health insurance providers) and partly dermal and infectious (e.g., wet work and risk of infection) factors. Diseases of the spine, wrist or finger joints, burnout syndrome and infections were mentioned as possible consequences. Conclusions The subjective data generated by both groups (focus group discussion and interviews) were comparable and consistent with the current state of research. The results provide new insight regarding work-related exposures and diseases of physical therapists working in Germany. These findings aided the design of a German-wide representative survey of practicing physical therapists.
26

A peroxygenase from Chaetomium globosum catalyzes the selective oxygenation of testosterone

Kiebist, Jan, Schmidtke, Kai-Uwe, Zimmermann, Jörg, Kellner, Harald, Jehmlich, Nico, Ullrich, René, Zänder, Daniel, Hofrichter, Martin, Scheibner, Katrin 03 April 2017 (has links) (PDF)
Unspecific peroxygenases (UPO, EC 1.11.2.1) secreted by fungi open an efficient way to selectively oxyfunctionalize diverse organic substrates, including less-activated hydrocarbons, by transferring peroxide-borne oxygen. We investigated a cell-free approach to incorporate epoxy and hydroxyl functionalities directly into the bulky molecule testosterone by a novel unspecific peroxygenase (UPO) that is produced by the ascomycetous fungus Chaetomium globosum in a complex medium rich in carbon and nitrogen. Purification by fast protein liquid chromatography revealed two enzyme fractions with the same molecular mass (36 kDa) and with specific activity of 4.4 to 12 U mg−1. Although the well-known UPOs of Agrocybe aegerita (AaeUPO) and Marasmius rotula (MroUPO) failed to convert testosterone in a comparative study, the UPO of C. globosum (CglUPO) accepted testosterone as substrate and converted it with total turnover number (TTN) of up to 7000 into two oxygenated products: the 4,5-epoxide of testosterone in β-configuration and 16α-hydroxytestosterone. The reaction performed on a 100 mg scale resulted in the formation of about 90 % of the epoxide and 10 % of the hydroxylation product, both of which could be isolated with purities above 96 %. Thus, CglUPO is a promising biocatalyst for the oxyfunctionalization of bulky steroids and it will be a useful tool for the synthesis of pharmaceutically relevant steroidal molecules.
27

Towards an optimal contact metal for CNTFETs

Fediai, Artem, Ryndyk, Dmitry A., Seifert, Gotthard, Mothes, Sven, Claus, Martin, Schröter, Michael, Cuniberti, Gianaurelio 07 April 2017 (has links) (PDF)
Downscaling of the contact length Lc of a side-contacted carbon nanotube field-effect transistor (CNTFET) is challenging because of the rapidly increasing contact resistance as Lc falls below 20–50 nm. If in agreement with existing experimental results, theoretical work might answer the question, which metals yield the lowest CNT–metal contact resistance and what physical mechanisms govern the geometry dependence of the contact resistance. However, at the scale of 10 nm, parameter-free models of electron transport become computationally prohibitively expensive. In our work we used a dedicated combination of the Green function formalism and density functional theory to perform an overall ab initio simulation of extended CNT–metal contacts of an arbitrary length (including infinite), a previously not achievable level of simulations. We provide a systematic and comprehensive discussion of metal–CNT contact properties as a function of the metal type and the contact length. We have found and been able to explain very uncommon relations between chemical, physical and electrical properties observed in CNT–metal contacts. The calculated electrical characteristics are in reasonable quantitative agreement and exhibit similar trends as the latest experimental data in terms of: (i) contact resistance for Lc = ∞, (ii) scaling of contact resistance Rc(Lc); (iii) metal-defined polarity of a CNTFET. Our results can guide technology development and contact material selection for downscaling the length of side-contacts below 10 nm.
28

Crystallographic insights into (CH3NH3)3(Bi2I9): a new lead-free hybrid organic–inorganic material as a potential absorber for photovoltaics

Eckhardt, Kai, Bon, Volodymyr, Getzschmann, Jürgen, Grothe, Julia, Wisser, Florian M., Kaskel, Stefan 17 March 2017 (has links) (PDF)
The crystal structure of a new bismuth-based light-absorbing material for the application in solar cells was determined by single crystal X-ray diffraction for the first time. (CH3NH3)3(Bi2I9) (MBI) is a promising alternative to recently rapidly progressing hybrid organic–inorganic perovskites due to the higher tolerance against water and low toxicity. Single crystal X-ray diffraction provides detailed structural information as an essential prerequisite to gain a fundamental understanding of structure property relationships, while powder diffraction studies demonstrate a high degree of crystallinity in thin films.
29

Tuning the flexibility in MOFs by SBU functionalization

Bon, Volodymyr, Kavoosi, Negar, Senkovska, Irena, Müller, Philipp, Schaber, Jana, Wallacher, Dirk, Többens, Daniel M., Mueller, Uwe, Kaskel, Stefan 17 March 2017 (has links) (PDF)
A new approach for the fine tuning of flexibility in MOFs, involving functionalization of the secondary building unit, is presented. The "gate pressure" MOF [Zn3(bpydc)2(HCOO)2] was used as a model material and SBU functionalization was performed by using monocarboxylic acids such as acetic, benzoic or cinnamic acids instead of formic acid in the synthesis. The resulting materials are isomorphous to [Zn3(bpydc)2(HCOO)2] in the "as made" form, but show different structural dynamics during the guest removal. The activated materials have entirely different properties in the nitrogen physisorption experiments clearly showing the tunability of the gate pressure, at which the structural transformation occurs, by using monocarboxylic acids with varying backbone structure in the synthesis. Thus, increasing the number of carbon atoms in the backbone leads to the decreasing gate pressure required to initiate the structural transition. Moreover, in situ adsorption/PXRD data suggest differences in the mechanism of the structural transformations: from "gate opening" in the case of formic acid to "breathing" if benzoic acid is used.
30

Unusual dimer formation of cyclometalated ruthenium NHC p-cymene complexes

Schleicher, David, Tronnier, Alexander, Leopold, Hendrik, Borrmann, Horst, Strassner, Thomas 27 February 2017 (has links) (PDF)
We present the synthesis and structural characterization of novel ruthenium complexes containing C^C* cyclometalated N-heterocyclic carbene ligands, η6-arene (p-cymene) ligands and one bridging chlorine ion. Complexes of the general formula [Ru(p-cymene)(C^C*)Cl] were prepared via a one-pot synthesis using in situ transmetalation from the correspondent silver NHC complexes. These complexes react with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaBArF4) to form dinuclear complexes of the general structure [Ru(p-cymene)(C^C*)-μ-Cl-(p-cymene)(C^C*)Ru]+[BArF4]−. Solid-state structures confirm that the pseudo-tetrahedral coordination around the metal center with the η6-ligand aligned perpendicularly to the C^C* ligand and the i-Pr group “atop” is retained in the bimetallic complexes.

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