Electrohydrodynamic printing as a method to micropattern large titanium implant surfaces with photocrosslinkable structures

Metallic implants are widely used in orthopaedic and orthodontic applications. However, generally surface treatment of the metallic surfaces is necessary to render them more biologically active. Herein, we describe a direct write printing method to modify metallic implant surfaces with biocompatible polymers with microscale precision. Application of polymeric micropatterns on metallic implant surfaces can (i) improve their interaction with the host tissue, (ii) enable the delivery of growth factors, antibiotics, anti-inflammatory cytokines etc from the implant surface and (iii) can control the immune responses to the implant via controlling the attachment of immune cells, such as macrophages. Surface patterns with a resolution of less than 50 μm can be created using an electro hydrodynamic (EHD) printing, a template-free and single-step process. We present a revised EHD printing method for the deposition of parallel strips of photocrosslinkable, cell adhesive polymeric composites with spacing of around 20 μm onto medical grade titanium substrates. Optimization of voltage, feeding rate and collection speed resulted in regular structures via very rapid movement of the grounded rotating collector driven to equivalent of the linear surface speed of above 100 cm s−1. In the experimental part a mixture of chemically modified PEG /gelatin was deposited onto a conductive titanium substrate with different surface pretreatments with an area of 400 mm2. Acid etched or UV treated titanium surfaces improved the stability of the printed structures. Polymeric lines induced temporary orientation of human monocytes (THP-1) and induced a thicker cell multilayer formation by 3T3 fibroblasts (p < 0.05). Staining of the monocytes for M1(CD80) and M2 (CD206) macrophage markers on the patterned surface showed mixed populations with higher anti-inflammatory cytokine secretion compared to tissue culture plastic control. The results demonstrate the suitability of this method for the preparation of biomaterials with structured surfaces on large areas and with desired chemical composition

Aligned nanofibres made of poly(3-hydroxybutyrate) grafted to hyaluronan for potential healthcare applications

In this work, a hybrid copolymer consisting of poly(3-hydroxybutyrate) grafted to hyaluronic acid (HA) was synthesised and characterised. Once formed, the P(3HB)-g-HA copolymer was soluble in water allowing a green electrospinning process. The diameters of nanofibres can be tailored by simply varying the Mw of polymer. The optimization of the process allowed to produce fibres of average diameter in the range of 100-150 nm and low polydispersity. The hydrophobic modification has not only increased the fibre diameter, but also the obtained layers were homogenous. At the nanoscale, the hybrid copolymer exhibited an unusual hairy topography. Moreover, the hardness and tensile properties of the hybrid were found to be superior compared to fibres made of unmodified HA. Particularly, this reinforcement was achieved at the longitudinal direction. Additionally, this work reports the use in the composition of a water-soluble copolymer containing photo cross-linkable moieties to produce insoluble materials post-electrospinning. The derivatives as well as their nanofibrous mats retain the biocompatibility of the natural polymers used for the fabrication

Probable neuroimmunological link between Toxoplasma and cytomegalovirus infections and personality changes in the human host

BACKGROUND: Recently, a negative association between Toxoplasma-infection and novelty seeking was reported. The authors suggested that changes of personality trait were caused by manipulation activity of the parasite, aimed at increasing the probability of transmission of the parasite from an intermediate to a definitive host. They also suggested that low novelty seeking indicated an increased level of the neurotransmitter dopamine in the brain of infected subjects, a phenomenon already observed in experimentally infected rodents. However, the changes in personality can also be just a byproduct of any neurotropic infection. Moreover, the association between a personality trait and the toxoplasmosis can even be caused by an independent correlation of both the probability of Toxoplasma-infection and the personality trait with the third factor, namely with the size of living place of a subject. To test these two alternative hypotheses, we studied the influence of another neurotropic pathogen, the cytomegalovirus, on the personality of infected subjects, and reanalyzed the original data after the effect of the potential confounder, the size of living place, was controlled. METHODS: In the case-control study, 533 conscripts were tested for toxoplasmosis and presence of anti-cytomegalovirus antibodies and their novelty seeking was examined with Cloninger's TCI questionnaire. Possible association between the two infections and TCI dimensions was analyzed. RESULTS: The decrease of novelty seeking is associated also with cytomegalovirus infection. After the size of living place was controlled, the effect of toxoplasmosis on novelty seeking increased. Significant difference in novelty seeking was observed only in the largest city, Prague. CONCLUSION: Toxoplasma and cytomegalovirus probably induce a decrease of novelty seeking. As the cytomegalovirus spreads in population by direct contact (not by predation as with Toxoplasma), the observed changes are the byproduct of brain infections rather than the result of manipulation activity of a parasite. Four independent lines of indirect evidence, namely direct measurement of neurotransmitter concentration in mice, the nature of behavioral changes in rodents, the nature of personality changes in humans, and the observed association between schizophrenia and toxoplasmosis, suggest that the changes of dopamine concentration in brain could play a role in behavioral changes of infected hosts

Origin and Dimension of Strange Nonchaotic Attractors

Several examples of strange nonchaotic attractors are collected. The route to a particular kind of strangeness without chaos is explained and common typical features necessary for a generation of this type of strangeness are discussed. The capacity dimension is calculated analytically and requirements are estimated for a numerical calculation of the dimension. The extreme difficulty of the numerical approach is explained. 1 Introduction Recently a number of examples of strange nonchaotic attractors in nonlinear dissipative dynamical systems have been studied both numerically [1-14] and experimentally [15]. The term strange means a nontrivial geometrical structure of the attractor whereas the term nonchaotic refers to dynamics of the system characterized by the absence of positive Lyapunov exponents. The route to strangeness without chaos and the possibility of computation (both analytical and numerical) of the dimension of the attractor is the purpose of this contribution. 2 Example..

On the Route to Strangeness without Chaos in the Quasiperiodically Forced van der Pol Oscillator

Non-chaotic strange attractor of a non-autonomous dissipative dynamical system with a 2-frequency-quasiperiodic forcing is studied. Following results from [1] numerical observations are refined and the route from torus to strange non-chaotic attractor is described in detail. Possible misinterpretations of experimental observations are discussed. 1 Introduction Numerous results in nonlinear dynamics have shown that deterministic chaos is a robust phenomenon and chaotic strange attractors have been accepted as typical behaviour of nonlinear dissipative systems [2, 3]. Here chaotic refers to exponential divergence of nearby trajectories (characterized by at least one positive Lyapunov exponent) and strange means non-trivial geometrical structure of the attractor [4]. The terms strange and chaotic are often used interchangeably in the literature. However, some recent results have documented the existence of strange attractors generated by non-chaotic dynamics. First examples appeared in..

Step-up voltage converter for mems actuators by piezoelectric transformers

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An Electrostatic Spinning Technology with Improved Functionality for the Manufacture of Nanomaterials from Solutions

The last decade has seen an extensive development of the field of nanomaterials which are currently being used in their first commercial applications. This rapid develop‐ ment is necessarily connected with certain technological demands. This paper describes a technology for the manufacture of nanomaterials from solutions by electro‐ static spinning or spraying. Although this method has been well known since the last century, there are still only a few high-quality devices that can be used for the research of new nanomaterials. The main reason for this is that the process of nanomaterials manufacturing is influenced by numerous processing parameters which need to be properly regulated, and furthermore all device compo‐ nents must be resistant to interference from high voltage. The technological requirements are thus stringent. More‐ over, such a device must be multifunctional, compact and affordable. This paper describes the technical aspects of a unique laboratory device, i.e., device modules and central control, measured processing parameters, and their effect on the produced materials. The developed laboratory device meets the most demanding criteria for a nanotech‐ nological laboratory device and helps facilitate and speed up the research and development of new nanomaterials produced in high electrostatic field

Effect of different emitter types on the production of nanofibrous tubular structures: Thickness uniformity and productivity

This contribution focuses on the effects of electrospinning process on the homogeneity of nanofibrous tubular structures caused by different emitters. Six types of emitters were used for the production of nanofibrous tubes. For all, the electric potential and the electric field were simulated. The quality of the produced tubes was verified by scanning electron microscopy, contact measurement of thickness and by a new digital image processing method based on transillumination. The analysis of the spun samples proved that the quality and therefore the parameters of the prepared tubes are significantly influenced by the choice of an emitter and its configuration. The use of the five-needle and needleless emitters resulted in a tenfold increase in production, however, image analysis revealed major thickness inhomogeneities. The highest thickness homogeneity and a high repeatability of the spinning process were achieved by using a moving double-needle emitter. The results will find use especially in the research of small-diameter vascular replacements and other applications in the field of tissue engineering requiring highly uniform tubular grafts

Microwave Catheter Navigation System for the Radiofrequency Liver Ablation

Thermal ablation is a well-known method used in interventional radiology to treat cancer. The treatment success is closely related to the exact catheter location in the treated area. Current navigation methods are based mostly on ultrasound or computed tomography. This work explores the possibility of tracking the catheter position during ablation treatment of hepatocellular carcinomas (HCC) using an ultra-wideband (UWB) antenna array and microwave radar imaging based on the “Delay and Sum” (DAS) algorithm. The feasibility was first numerically studied on a simple homogeneous liver model. A heterogeneous anthropomorphic 3D model of the treated region consisting of the main organs within the treated area was then used. Various standard radiofrequency ablation (RFA) catheters were placed virtually in the heterogeneous model. The location and orientation of the antenna elements of the developed imaging system and the applied frequency band were studied. Subsequently, an experimental setup consisting of a 3D printed homogeneous anthropomorphic model, eight UWB dipole antennas, and catheters was created and used in a series of measurements. The average accuracy determining the catheter position from simulated and experimental data was 3.88 ± 0.19 and 6.13 ± 0.66 mm, which are close to the accuracy of clinical navigation systems

Agroekologie: východiska pro udržitelné zemědělské hospodaření

Kniha ukazuje, že k dlouhodobému řešení problémů moderního zemědělství je možno dospět jedině restrukturalizací a takovou správou zemědělských systémů, která změní jejich podobu a fungování na základě agroekologie. Agroekologie je věděcká disciplína, která využívá ekologické teorie ke studiu, designu, managementu a hodnocení produktivních zemědělských systémů, jež současně chrání přírodní zdroje. Kniha se zaměřuje jak na tradiční obhospodařování pro praktické zemědělce tak sofistikované využití ekosystémových poznatků. Kniha slouží jako učebnice pro moderní zemědělský provoz tak pro akademickou obec