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Materials derived from renewable resources are highly desirable in view of more sustainable manufacturing. Among the available natural materials, wood is one of the key candidates, because of its excellent mechanical properties. However, wood and wood-based materials in engineering applications suffer from various restraints, such as dimensional instability upon humidity changes. Several wood modification treatments increase water repellence, but the insertion of hydrophobic polymers can result in a composite material which cannot be considered as renewable anymore. In this study, we report on the grafting of the fully biodegradable poly(epsilon-caprolactone) (PCL) inside the wood cell walls by Sn(Oct)(2) catalysed ring-opening polymerization (ROP). The presence of polyester chains within the wood cell wall structure is monitored by confocal Raman imaging and spectroscopy as well as scanning electron microscopy. Physical tests reveal that the modified wood is more hydrophobic due to the bulking of the cell wall structure with the polyester chains, which results in a novel fully biodegradable wood material with improved dimensional stability.
Differential exhumation in the Puna Plateau and Eastern Cordillera of NW Argentina is controlled by inherited paleostructures and resulting paleotopography related to the Cretaceous Salta Rift paleomargins. The Ceno zoic deformation front related to the development of the Andean retro-arc orogenic system is generally associated with >4 km of exhumation, which is recorded by Cenozoic apatite fi ssion-track (AFT) and (U-Th-[Sm])/He ages (He ages) in the Eastern Cordillera of NW Argentina. New AFT ages from the top of the Nevado de Cachi document Oligocene (ca. 28 Ma) cooling, which, combined with existing data, indicates exhumation of this range between ca. 28 Ma and ca. 14 Ma. However, some of the highest ranges in the Eastern Cordillera preserve Cretaceous ages indicative of limited Cenozoic exhumation. Samples collected from an similar to 3-km-elevation transect along the northern part of the Sierra de Quilmes paleorift fl ank (Laguna Brava) show AFT ages between ca. 80 and ca. 50 Ma and He ages between ca. 45 and ca. 10 Ma. Another set of samples from an similar to 1-km-elevation transect farther to the southwest (La Quebrada) shows Cretaceous AFT ages between ca. 116 Ma and ca. 76 Ma, and mainly Cretaceous He ages, in agreement with AFT data. Analysis of existing AFT and He ages from the area once occupied by the Salta Rift reveals a pattern characterized by Cretaceous ages along paleorift highs and Cenozoic ages within paleorift hanging-wall basins and later foreland basin depocenters. This pattern is interrupted by the Sierras Pampeanas at similar to 28 degrees S, which record mid-Cenozoic ages. Our data are consistent with a complex inherited pattern of pre-Andean paleostructures, likely associated with paleotopography, which was beveled by the Cenozoic regional foreland basin and reactivated during the late Neogene (ca. <10 Ma), strongly controlling the magnitude of Cenozoic uplift and exhumation and thus cooling age distribution. This, combined with variable lithologic erodibility, resulted in an irregular distribution of themochronological ages.
Background: DNA-methylation is a common epigenetic tool which plays a crucial role in gene regulation and is essential for cell differentiation and embryonic development. The placenta is an important organ where gene activity can be regulated by epigenetic DNA modifications, including DNA methylation. This is of interest as, the placenta is the interface between the fetus and its environment, the mother. Exposure to environmental toxins and nutrition during pregnancy may alter DNA methylation of the placenta and subsequently placental function and as a result the phenotype of the offspring. The aim of this study was to develop a reliable method to quantify DNA methylation in large clinical studies. This will be a tool to analyze the degree of DNA methylation in the human placenta in relationship to clinical readouts. Methods: Liquid chromatography-electrospray ionization/multi-stage mass spectrometry (LC-ESI/MS/MS) technique was used for the quantification of the 5dmC/dG ratio in placentas from 248 healthy pregnancies. We were able to demonstrate that this method is a reliable and stable way to determine global placental DNA methylation in large clinical trials. Results/Conclusion: The degree of placental DNA methylation seen in our pilot study varies substantially from 2% to 5%. The clinical implications of this variation need to be demonstrated in adequately powered large studies.
Hemocompatible materials are needed for internal and extracorporeal biomedical applications, which should be realizable by reducing protein and thrombocyte adhesion to such materials. Polyethers have been demonstrated to be highly efficient in this respect on smooth surfaces. Here, we investigate the grafting of oligo- and polyglycerols to rough poly(ether imide) membranes as a polymer relevant to biomedical applications and show the reduction of protein and thrombocyte adhesion as well as thrombocyte activation. It could be demonstrated that, by performing surface grafting with oligo-and polyglycerols of relatively high polydispersity (>1.5) and several reactive groups for surface anchoring, full surface shielding can be reached, which leads to reduced protein adsorption of albumin and fibrinogen. In addition, adherent thrombocytes were not activated. This could be clearly shown by immunostaining adherent proteins and analyzing the thrombocyte covered area. The presented work provides an important strategy for the development of application relevant hemocompatible 3D structured materials.
Polyelectrolytes are macromolecules composed of charged monomers and exhibit unique properties due to the interplay of their flexibility and electrostatic interactions. In solution, they are attracted to oppositely charged surfaces and interfaces and exhibit a transition to an adsorbed state when certain conditions are met concerning the charge densities of the polymer and surface and the properties of the solution. In this review, we discuss two limiting cases for adsorption of flexible polyelectrolytes on curved surfaces: weak and strong adsorption. In the first case, adsorption is strongly influenced by the entropic degrees of freedom of a flexible polyelectrolyte. By contrast, in the strong adsorption limit, electrostatic interactions dominate, which leads to particular adsorption patterns, specifically on spherical surfaces. We discuss the corresponding theoretical approaches, applying a mean-field description for the polymer and the polymer-surface interaction. For weak adsorption, we discuss the critical adsorption behavior by exactly solvable models for planar and spherical geometries and a generic approximation scheme, which is additionally applied to cylindrical surfaces. For strong adsorption, we investigate various polyelectrolyte patterns on cylinders and spheres and evaluate their stability. The results are discussed in the light of experimental results, mostly of DNA adsorption experiments.
Photoinduced excitation energy transfer and accompanying charge separation are elucidated for a supramolecular system of a single fullerene covalently linked to six pyropheophorbide-a dye molecules. Molecular dynamics simulations are performed to gain an atomistic picture of the architecture and the surrounding solvent. Excitation energy transfer among the dye molecules and electron transfer from the excited dyes to the fullerene are described by a mixed quantum-classical version of the Forster rate and the semiclassical Marcus rate, respectively. The mean characteristic time of energy redistribution lies in the range of 10 ps, while electron transfer proceeds within 150 ps. In between, on a 20 to 50 ps time-scale, conformational changes take place in the system. This temporal hierarchy of processes guarantees efficient charge separation, if the structure is exposed to a solvent. The fast energy transfer can adopt the dye excitation to the actual conformation. In this sense, the probability to achieve charge separation is large enough since any dominance of unfavorable conformations that exhibit a large dye-fullerene distance is circumvented. And the slow electron transfer may realize an averaging with respect to different conformations. To confirm the reliability of our computations, ensemble measurements on the charge separation dynamics are simulated and a very good agreement with the experimental data is obtained.
Background: Research on language comprehension in aphasia has primarily focused on comprehension of isolated words and sentences. Even though previous studies have provided insights into comprehension abilities of individuals with aphasia at the word and grammatical level, our understanding of the nature and extent of their language comprehension (dis)abilities is not yet complete. In contrast to the highly restricted semantic and syntactic interpretation of sentences, discourse comprehension requires additional pragmatic and non-linguistic skills.Aims: The purpose of this study was to assess language comprehension in individuals with and without aphasia at the discourse level. In particular, it addressed the question of whether the use of direct speech, compared to indirect speech, affects comprehension of narrative discourse in Dutch aphasic and non-brain-damaged (NBD) listeners.Methods & Procedures: The Direct Speech Comprehension (DISCO) test was developed to examine the effects of manipulating direct vs. indirect speech on discourse comprehension. Twenty-three individuals with aphasia and 20 NBD participants were presented with spoken narratives that contained either direct or indirect speech reports. The narratives were presented audio-visually on an iPad, and comprehension was assessed with yes/no questions.Outcomes & Results: The performance of the participants with aphasia was significantly poorer than that of the NBD participants. Moreover, a main effect for condition type was found, indicating that narratives with direct speech reports were better understood than narratives with indirect speech reports by listeners with and without aphasia. There was no interaction between group and condition type indicating that this main effect held for both the aphasic and the NBD listeners. However, for the participants with aphasia, there was an interaction between condition and Token Test error score indicating that the positive effect of direct speech constructions diminishes for individuals with poorer comprehension.Conclusions: Direct speech constructions facilitate language comprehension in listeners with and without aphasia. One explanation for this finding is the occurrence of additional layers of communication, such as intonation and facial expression, often accompanying direct speech constructions. An alternative account is the degree of grammatical complexity: In Dutch, the syntactic construction of indirect speech requires embedding, whereas in direct speech the introductory sentence and the quote are both main clauses. The finding that the beneficial effect of direct speech on language comprehension diminishes for individuals with severe aphasia may indicate that the DISCO is too difficult for them to reveal an effect of a subtle manipulation such as that of condition type.
The standard procedure in the lab for plasmid isolation usually involves a 2-mL, 16 h over-night cultivation in 15-mL bioreaction tubes in LB medium. This is time consuming, and not suitable for high-throughput applications. This study shows that it is possible to produce plasmid DNA (pDNA) in a 1.5-mL microcentrifuge tube with only 100 L cultivation volume in less than 7 h with a simple protocol. Compared with the standard LB cultivation for pDNA production reaching a final pDNA concentration range of 1.5-4 mu g mL(-1), a 6- to 10-fold increase in plasmid concentration (from 10 up to 25 mu g mL(-1) cultivation volume) is achieved using an optimized medium with an internal substrate delivery system (EnBase (R)). Different strains, plasmids, and the applicability of different inoculation tools (i.e. different starting ODs) were compared, demonstrating the robustness of the system. Additionally, dissolved oxygen was monitored in real time online, indicating that under optimized conditions oxygen limitation can be avoided. We developed a simple protocol with a significantly decreased procedure time, enabling simultaneous handling of more samples, while a consistent quality and a higher final pDNA concentration are ensured.