Review of manufacturing methods for structural parts from short-fiber polymeric composites and methods for improving their mechanical properties

Krátkovlákenné polymerní kompozity jsou jednodušší na výrobu než dlouhovlákenné kompozity, ale za cenu horších mechanických vlastností (t.j. pevnosti v tahu a modulu pružnosti). Existuje mnoho způsobů výroby krátkovlákenných polymerních kompozitů. Většina metod nevyžaduje lidskou práci a metody výroby kompozitů a polymerů jsou stejné, nebo alespoň velice podobné. To vede k tomu, že krátkovlákenné kompozity jsou poměrně levné. Mechanické vlastnosti krátkovlákenných kompozitů mohou být zlepšeny zarovnáním vláken v matrici. Během posledních 60 let byla vyvinuta celá řada metod zarovnávání vláken, ale většina z nich se ukázala jako nepoužitelná pro komerční využití. Některé novější metody ovšem dosáhly výborných výsledků, a těm je v práci věnováno více prostoru. V práci je i návrh dvou nových metod k zarovnávání vláken, první pomocí elektrického proudu a druhé pomocí kombinace statického a oscilujícího magnetického pole.Short fibre polymeric composites are easier to manufacture than long fibre composites but this comes at the cost of worse mechanical properties (i.e. tensile strength and modulus). There are many ways to manufacture short fibre polymer composites. Most methods don’t require manual labour and the methods are the same or at least very similar to manufacturing polymers. This makes short fibre composites relatively cheap. The mechanical properties of short fibre composites can be improved by aligning the fibres. Throughout the last 60 years multiple methods for aligning the fibres in the matrix have been developed. Most of these proved not to be practical for commercial use, but some of the more recent methods have shown great results; special emphasis is put on those in the respective part of the thesis. Additional two methods for aligning fibres are proposed; one using electric current and the other one a combination of alternating and static magnetic fields.

High-contrast differentiation resolution 3D imaging of rodent brain by X-ray computed microtomography

The biomedically focused brain research is largely performed on laboratory mice considering a high homology between the human and mouse genomes. A brain has an intricate and highly complex geometrical structure that is hard to display and analyse using only 2D methods. Applying some fast and efficient methods of brain visualization in 3D will be crucial for the neurobiology in the future. A post-mortem analysis of experimental animals' brains usually involves techniques such as magnetic resonance and computed tomography. These techniques are employed to visualize abnormalities in the brains' morphology or reparation processes. The X-ray computed microtomography (micro CT) plays an important role in the 3D imaging of internal structures of a large variety of soft and hard tissues. This non-destructive technique is applied in biological studies because the lab-based CT devices enable to obtain a several-micrometer resolution. However, this technique is always used along with some visualization methods, which are based on the tissue staining and thus differentiate soft tissues in biological samples. Here, a modified chemical contrasting protocol of tissues for a micro CT usage is introduced as the best tool for ex vivo 3D imaging of a post-mortem mouse brain. This way, the micro CT provides a high spatial resolution of the brain microscopic anatomy together with a high tissue differentiation contrast enabling to identify more anatomical details in the brain. As the micro CT allows a consequent reconstruction of the brain structures into a coherent 3D model, some small morphological changes can be given into context of their mutual spatial relationships

Preparation and Characterisation of Highly Stable Iron Oxide Nanoparticles for Magnetic Resonance Imaging

Magnetic nanoparticles produced using aqueous coprecipitation usually exhibit wide particle size distribution. Synthesis of small and uniform magnetic nanoparticles has been the subject of extensive research over recent years. Sufficiently small superparamagnetic iron oxide nanoparticles easily permeate tissues and may enhance the contrast in magnetic resonance imaging. Furthermore, their unique small size also allows them to migrate into cells and other body compartments. To better control their synthesis, a chemical coprecipitation protocol was carefully optimised regarding the influence of the injection rate of base and incubation times. The citrate-stabilised particles were produced with a narrow average size range below 2nm and excellent stability. The stability of nanoparticles was monitored by long-term measurement of zeta potentials and relaxivity. Biocompatibility was tested on the Caki-2 cells with good tolerance. The application of nanoparticles for magnetic resonance imaging (MRI) was then evaluated. The relaxivities and ratio calculated from MR images of prepared phantoms indicate the nanoparticles as a promising -contrast probe

SMV-2013-07: Development and validation of a body of methods for imaging and analysis of an animal model of schizophrenia by 9.4-Tesla magnetic resonance, and analysis of a sample provided

A contract-based research with a specified mouse model of schizophrenia was carried out, examining the possibility of imaging relevant parameters of the structure and function of organs specified by the client. The options were assessed with respect to client's needs, suitable imaging methodology was identified and developed, animal experiment protocols were prepared and validated, and the proposed methodology was applied to a series of 60 animals according to valid animal use protocols. Original and statistically evaluated data were provided to the client

SMV-2015-37: Development of an animal model of septic encephalopathy for MR studies, execution and evaluation of a pilot study

Two animal models of septic encephalopathy in mice were tested: the induction by lipopolysaccharide, and the fecal model, whose objective was to test their applicability in the study of pathophysiology of septic encephalopathy by magnetic resonance in 9.4 Tesla field. Three MR imaging protocols were optimized: T2-weighted RARE for morphological imaging, protocols for native perfusion imaging ASL, and for contrast-enhanced perfusion imaging DCE applying Magnevist, whose main target was the detection of potential changes in the cerebral blood flow and alteration of the blood brain barrier function. Measurements were performed in Bruker Biospec 94/30 with a set of 27 mice anesthesized by isoflurane, whose physiological functions were continuously monitored. The original and analyzed data were provided to the client

Some comments on frequency selective excitation in newly proposed MRSI sequences

In many pathologies it is desirable to compare the metabolism inside a lesion, near the lesion, and in healthy tissue. The diagnostic value of MRS is enhanced by spectroscopic imaging (MRSI), permitting the simultaneous acquisition of spatially resolved spectra. In this way, assessing metabolic information about different brain regions within a single examination is possible. As with all in vivo spectroscopy, low signal-to-noise ratio (SNR) is the fundamental limiting factor in MRSI due to very low concentrations of metabolites of interest. Proton spectroscopic imaging, however, offers additional technical challenges as compared to single-voxel techniques, especially if acquisition of short echo time (TE<30 ms) is required. Critical to the success of proton MRSI studies of the human brain is the elimination of the very intense water and lipid signals arising from outside the volume of interest (VOI). Water suppression in MRSI can be very problematic in MRSI, in which the achievable degree of water suppression is limited by B.sub.0./sub. and B.sub.1./sub. inhomogeneities and water T.sub.1./sub. variations, invariably present throughout the larger VOIs. Suppression of liquid signals (from bone marrow and subcutaneous fat) is often severely complicated due to the fact that their relaxation behavior differs substantially from that of water. One of the basic approaches used to reduce the undesired contamination if the MRSI signals of interest consists in the use of the STEAM or PRESS selective excitation of the VOI. Both STEAM and PRESS techniques suffer from some drawbacks. STEAM reduces the sensitivity of measurement, PRESS has higher RF power requirements