• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 340
  • 2
  • Tagged with
  • 342
  • 342
  • 333
  • 329
  • 230
  • 189
  • 188
  • 186
  • 186
  • 155
  • 153
  • 103
  • 103
  • 72
  • 68
  • 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.
91

Non-Motor Symptoms in Patients Suffering from Motor Neuron Diseases

Günther, Rene, Richter, Nicole, Sauerbier, Anna, Chaudhuri, Kallol Ray, Martinez-Martin, Pablo, Storch, Alexander, Hermann, Andreas 19 January 2017 (has links)
Background The recently postulated “disease spreading hypothesis” has gained much attention, especially for Parkinson’s disease (PD). The various non-motor symptoms (NMS) in neurodegenerative diseases would be much better explained by this hypothesis than by the degeneration of disease-specific cell populations. Motor neuron disease (MND) is primarily known as a group of diseases with a selective loss of motor function. However, recent evidence suggests disease spreading into non-motor brain regions also in MND. The aim of this study was to comprehensively detect NMS in patients suffering from MND. Methods We used a self-rating questionnaire including 30 different items of gastrointestinal, autonomic, neuropsychiatric, and sleep complaints [NMS questionnaire (NMSQuest)], which is an established tool in PD patients. 90 MND patients were included and compared to 96 controls. Results In total, MND patients reported significantly higher NMS scores (median: 7 points) in comparison to controls (median: 4 points). Dribbling, impaired taste/smelling, impaired swallowing, weight loss, loss of interest, sad/blues, falling, and insomnia were significantly more prevalent in MND patients compared to controls. Interestingly, excessive sweating was more reported in the MND group. Correlation analysis revealed an increase of total NMS score with disease progression. Conclusion NMS in MND patients seemed to increase with disease progression, which would fit with the recently postulated “disease spreading hypothesis.” The total NMS score in the MND group significantly exceeded the score for the control group, but only 8 of the 30 single complaints of the NMSQuest were significantly more often reported by MND patients. Dribbling, impaired swallowing, weight loss, and falling could primarily be connected to motor neuron degeneration and declared as motor symptoms in MND.
92

Influence of Calcium Phosphate and Apatite Containing Products on Enamel Erosion

Kensche, Anna, Pötschke, Sandra, Hannig, Christian, Richter, Gert, Hoth-Hannig, Wiebke, Hannig, Matthias 19 January 2017 (has links)
For the purpose of erosion prevention the present study aimed to compare the efficacy of two biomimetic products and a fluoride solution to optimize the protective properties of the pellicle. After 1 min of in situ pellicle formation on bovine enamel slabs, 8 subjects adopted CPP-ACP (GC Tooth Mousse), a mouthwash with hydroxyapatite microclusters (Biorepair), or a fluoride based mouthwash (elmex Kariesschutz) for 1 min each. Afterwards, samples were exposed in the oral cavity for 28 min. Native enamel slabs and slabs exposed to the oral cavity for 30 min without any rinse served as controls. After oral exposure, slabs were incubated in HCl (pH values 2, 2.3, and 3) for 120 s and kinetics of calcium and phosphate release were measured photometrically; representative samples were evaluated by SEM and TEM. The physiological pellicle reduced demineralization at all pH values; the protective effect was enhanced by fluoride. The biomimetic materials also reduced ion release but their effect was less pronounced. SEM indicated no layer formation after use of the different products. However, TEM confirmed the potential accumulation of mineral components at the pellicle surface. The tested products improve the protective properties of the in situ pellicle but not as effectively as fluorides.
93

Not Only Delicious: Papaya Bast Fibres in Biocomposites

Lautenschläger, Thea, Kempe, Andreas, Neinhuis, Christoph, Wagenführ, André, Siwek, Sebastian 01 February 2017 (has links)
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.
94

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)
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.
95

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)
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.
96

Phosphorus in Preferential Flow Pathways of Forest Soils in Germany.

Julich, Dorit, Feger, Karl-Heinz 27 March 2017 (has links)
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.
97

Silicon availability modifies nutrient use efficiency and content, C:N:P stoichiometry, and productivity of winter wheat (Triticum aestivum L.)

Neu, Silke, Schaller, Jörg, Dudel, E. Gert 28 March 2017 (has links)
Silicon (Si) is known as beneficial element for graminaceous plants. The importance of Si for plant functioning of cereals was recently emphasized. However, about the effect of Si availability on biomass production, grain yield, nutrient status and nutrient use efficiency for wheat (Triticum aestivum L.), as one of the most important crop plants worldwide, less is known so far. Consequently, we assessed the effect of a broad range of supply levels of amorphous SiO2 on wheat plant performance. Our results revealed that Si is readily taken up and accumulated basically in aboveground vegetative organs. Carbon (C) and phosphorus (P) status of plants were altered in response to varying Si supply. In bulk straw biomass C concentration decreased with increasing Si supply, while P concentration increased from slight limitation towards optimal nutrition. Thereby, aboveground biomass production increased at low to medium supply levels of silica whereas grain yield increased at medium supply level only. Nutrient use efficiency was improved by Si insofar that biomass production was enhanced at constant nitrogen (N) status of substrate and plants. Consequently, our findings imply fundamental influences of Si on C turnover, P availability and nitrogen use efficiency for wheat as a major staple crop.
98

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)
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.
99

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)
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.
100

Diabetes-linked transcription factor HNF4α regulates metabolism of endogenous methylarginines and β-aminoisobutyric acid by controlling expression of alanine-glyoxylate aminotransferase 2

Burdin, Dmitry V., Kolobov, Alexey A., Brocker, Chad, Soshnev, Alexey A., Samusik, Nikolay, Demyanov, Anton v., Brilloff, Silke, Jarzebska, Natalia, Martens-Lobenhoffer, Jens, Mieth, Maren, Maas, Renke, Bornstein, Stefan R., Bode-Böger, Stefanie M., Gonzalez, Frank, Weiss, Norbert, Rodionov, Roman N. 21 July 2017 (has links)
Elevated levels of circulating asymmetric and symmetric dimethylarginines (ADMA and SDMA) predict and potentially contribute to end organ damage in cardiovascular diseases. Alanine-glyoxylate aminotransferase 2 (AGXT2) regulates systemic levels of ADMA and SDMA, and also of beta-aminoisobutyric acid (BAIB)-a modulator of lipid metabolism. We identified a putative binding site for hepatic nuclear factor 4 α (HNF4α) in AGXT2 promoter sequence. In a luciferase reporter assay we found a 75% decrease in activity of Agxt2 core promoter after disruption of the HNF4α binding site. Direct binding of HNF4α to Agxt2 promoter was confirmed by chromatin immunoprecipitation assay. siRNA-mediated knockdown of Hnf4a led to an almost 50% reduction in Agxt2 mRNA levels in Hepa 1–6 cells. Liver-specific Hnf4a knockout mice exhibited a 90% decrease in liver Agxt2 expression and activity, and elevated plasma levels of ADMA, SDMA and BAIB, compared to wild-type littermates. Thus we identified HNF4α as a major regulator of Agxt2 expression. Considering a strong association between human HNF4A polymorphisms and increased risk of type 2 diabetes our current findings suggest that downregulation of AGXT2 and subsequent impairment in metabolism of dimethylarginines and BAIB caused by HNF4α deficiency might contribute to development of cardiovascular complications in diabetic patients.

Page generated in 0.092 seconds