The scrape loading/dye transfer (SL/DT) technique is a simple functional assay for the simultaneous assessment of gap junctional intercellular communication (GJIC) in a large population of cells. The equipment needs are minimal and are typically met in standard cell biology labs, and SL/DT is the simplest and quickest of all the assays that measure GJIC. This assay has also been adapted for in vivo studies. The SL/DT assay is also conducive to a high-throughput setup with automated fluorescence microscopy imaging and analysis to elucidate more samples in shorter time, and hence can serve a broad range of in vitro pharmacological and toxicological needs.

• Klíčová slova
• Dye coupling, Dye transfer, Ex vivo assessment, Gap junctional intercellular communication assessment, High throughput, In vitro assay, Incision loading, Lucifer Yellow, Scalpel loading, Scrape loading, Tracers,
• MeSH
• dextrany metabolismus   MeSH
• fluorescenční barviva metabolismus   MeSH
• fluorescenční mikroskopie metody   MeSH
• isochinoliny metabolismus   MeSH
• kultivované buňky MeSH
• mezerový spoj metabolismus   ultrastruktura   MeSH
• mezibuněčná komunikace * MeSH
• myši MeSH
• rhodaminy metabolismus   MeSH
• Sertoliho buňky MeSH
• zvířata MeSH
• Check Tag
• mužské pohlaví MeSH
• myši MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, N.I.H., Extramural MeSH
• Názvy látek
• dextrany MeSH
• fluorescenční barviva MeSH
• isochinoliny MeSH
• lucifer yellow MeSH Prohlížeč
• rhodamine dextran MeSH Prohlížeč
• rhodaminy MeSH

Nafion possesses many interesting properties such as a high ion-conductivity, hydrophilicity, and thermal and chemical stability that make this material highly suitable for many applications including fuel cells and various (bio-)chemical and physical sensors. However, the mechanical properties of a Nafion membrane that are known to be affected by the viscoplastic characteristics of the material itself have a strong impact on the performance of Nafion-based sensors. In this study, the mechanical properties of Nafion under the cyclic loading have been investigated in detail. After cyclic tensile loading (i.e., maximum elongation about 25% at a room temperature and relative humidity about 40%) a time-dependent recovery comes into play. This recovery process is also shown being strain-rate dependent. Our results reveal that the recovery behavior weakens after performing several stress-strain cycles. Present findings can be of a great importance in future design of various chemical and biological microsensors and nanosensors such as hydrogen or glucose ones.

• Klíčová slova
• Nafion, cyclic loading, mechanical properties, mechanical tests, viscoplastic properties,
• Publikační typ
• časopisecké články MeSH

PURPOSE: Delayed achievement of target vancomycin serum concentrations may adversely affect clinical outcomes. The objective of this retrospective study was to explore the real frequency of loading dose use and to evaluate the impact of loading dose for the achievement of vancomycin PK/PD target in adult patients treated with intermittent vancomycin. As a secondary aim we determined optimal vancomycin loading dose based on individual pharmacokinetic calculations. METHODS: Vancomycin pharmacokinetic models were computed using two-compartmental analysis. Based on these models AUC24 were calculated. Unpaired t-test was used to compare AUC24 achieved in patients treated with and without vancomycin loading dose. RESULTS: Vancomycin loading dose was administered only in 17.8% patients. Volume of distribution and clearance median values (interquartile range) for vancomycin in whole study population (n = 45) were 0.69 (0.55-0.87) L/kg and 0.0304 (0.0217-0.0501) L/h/kg, respectively. The AUC24 was significantly higher in patients taking loading dose compared with the group without loading dose: mean (SD) AUC24 was 496 (101) vs. 341 (77) mg h/L. Proportion of patients reaching PK/PD goal was 87.5% and 24.3% with and without loading dose administration, respectively. Considering individual pharmacokinetic parameters optimal vancomycin loading dose was 27.5 mg/kg of body weight. CONCLUSIONS: Loading dose administration plays crucial part in rapid attainment of vancomycin PK/PD target in adult patient treated with intermittent vancomycin, although it is not frequently used in clinical practise. The optimal loading dose of 25-30 mg/kg of body weight should be routinely administered to adult patients treated with intermittent vancomycin.

• Klíčová slova
• Intermittent infusion, Loading dose, Pharmacokinetics, Therapeutic drug monitoring, Vancomycin,
• MeSH
• antibakteriální látky aplikace a dávkování   krev   farmakokinetika   farmakologie   MeSH
• infuzní pumpy MeSH
• kreatinin krev   MeSH
• lidé MeSH
• monitorování léčiv metody   MeSH
• plocha pod křivkou MeSH
• počítačová simulace MeSH
• retrospektivní studie MeSH
• senioři MeSH
• vankomycin aplikace a dávkování   krev   farmakokinetika   farmakologie   MeSH
• Check Tag
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• pozorovací studie MeSH
• Názvy látek
• antibakteriální látky MeSH
• kreatinin MeSH
• vankomycin MeSH

The fracture properties of five types of chocolate (dark, extra dark, milk, white, and ruby) were investigated using an indirect tensile test known as the Brazilian test. Two different loading rates of 0.0017 m/s and around 12 m/s were used through the universal testing machine TIRATEST and split Hopkinson pressure bar (SHPB) technique. Results show that the tensile fracture stress increases with the loading rate. The sensitivity of the fracture stress at low-loading rates is lower than that at the high-loading rates. The obtained results can be used in industry for the correct processing of chocolate products and their transport. The presented methods can be also used to detect defects in chocolate products.

• Klíčová slova
• Brazilian test, chocolate, fracture properties, loading rate, split Hopkinson pressure bar, tensile strength,
• MeSH
• čokoláda * analýza   MeSH
• kakaovník * MeSH
• manipulace s potravinami metody   MeSH
• mechanický stres * MeSH
• pevnost v tahu * MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Brazílie MeSH

The resistance of goose (Anser anser f. domestica) eggs to damage was determined by measuring the average rupture force, specific deformation and rupture energy during their compression at different compression speeds (0.0167, 0.167, 0.334, 1.67, 6.68 and 13.36 mm/s). Eggs have been loaded between their poles (along X axis) and in the equator plane (Z axis). The greatest amount of force required to break the eggs was required when eggs were loaded along the X axis and the least compression force was required along the Z axis. This effect of the loading orientation can be described in terms of the eggshell contour curvature. The rate sensitivity of the eggshell rupture force is higher than that observed for the Japanese quail's eggs.

• Klíčová slova
• Compression, Deformation, Eggshell curvature, Goose egg, Loading rate, Rupture force,
• MeSH
• biomechanika MeSH
• husy * MeSH
• pevnost v tlaku * MeSH
• povrchové vlastnosti MeSH
• testování materiálů * MeSH
• vaječná skořápka MeSH
• vejce * MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

This paper deals with a knee joint endoprosthesis finite element analysis. Based on a three dimensional geometric model of a lower extremity, a mechanical axis of the limb was designed. This axis is important for several reasons. Firstly, the endoprosthesis was positioned due to its direction, secondly, boundary conditions was defined on its proximal and distal end and finally, the axis enabled reasonable simplification of the model which led to the time saving analysis while preserving principal features of the model like the natural boundary conditions or knee joint's degrees of freedom . Having this, one leg stance was simulated. Results of the analysis were encouraging for future models. Especially the choice of the mechanical axis was suitable and enabled a better distribution of contact pressures and stress on both femoral and tibial component compared to our former models. Also their magnitudes correspond better the manufacturer's experience and our findings. The stresses did not exceeded 30MPa for the UHMWPE tibial plateau and 100MPa for the femoral component. The contact pressures were lower than 40MPa.

• MeSH
• biologické modely * MeSH
• femur anatomie a histologie   patofyziologie   MeSH
• kolenní kloub anatomie a histologie   patofyziologie   MeSH
• lidé MeSH
• mechanický stres MeSH
• protézy kolene * MeSH
• rozsah kloubních pohybů * MeSH
• tibie anatomie a histologie   patofyziologie   MeSH
• tlak MeSH
• zatížení muskuloskeletálního systému * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

As a light structure, composite sandwich panels are distinguished by their significant bending stiffness that is rapidly used in the manufacture of aircraft bodies. This study focuses on the mechanical behaviour of through-thickness polymer, pin-reinforced foam core sandwich panels subjected to indentation and low impact loading. Experimental and computational approaches are used to study the global and internal behaviour of the sandwich panel. The samples for experimental testing were made from glass/polyester laminates as the face sheets and polyurethane foam as the foam core. To further reinforce the samples against bending, different sizes of polymeric pins were implemented on the sandwich panels. The sandwich panel was fabricated using the vacuum infusion process. Using the experimental data, a finite element model of the sample was generated in LS-DYNA software, and the effect of pin size and loading rate were examined. Results of the simulation were validated through a proper prediction compared to the test data. The results of the study show that using polymeric pins, the flexural strength of the panel significantly increased under impact loading. In addition, the impact resistance of the pin-reinforced foam core panel increased up to 20%. Moreover, the size of pins has a significant influence on the flexural behaviour while the sample was under a moderate strain rate. To design an optimum pin-reinforced sandwich panel a "design of experiment model" was generated to predict energy absorption and the maximum peak load of proposed sandwich panels. The best design of the panel is recommended with 1.8 mm face sheet thickness and 5 mm pins diameter.

• Klíčová slova
• composite panel, energy absorption, finite element model, low impact loading, pin-reinforced sandwich panel,
• Publikační typ
• časopisecké články MeSH

Fatigue (Wöhler's or S-N) curves are usually represented by upper stress of loading cycle in dependence on the logarithm of numbers of cycles to fracture. Increasing mean stress of loading cycle causes a shift of these curves towards higher values of fatigue strength. A successful quantitative description of the high cycle shift was published by Walker. The aim of the paper consists in deriving and verifying the relations describing the shift of fatigue curves in the whole cycle region from ultimate tensile stress to permanent fatigue limit, for the Palmgren, the Kohout-Věchet and the logistic S-N models, using the high-cycle Walker approach.

• Klíčová slova
• Asymmetry of loading cycle, Fatigue modelling, Kohout-Věchet model, Logistic S–N model, Palmgren model, S-N curves,
• Publikační typ
• časopisecké články MeSH

Polyurethane foams are one of the most common auxetic structures regarding energy absorption enhancement. This present study evaluates the result reliability of two different numerical approaches, the H-method and the P-method, to obtain the best convergence solution. A polymeric re-entrant cell is created with a beam element and the results of the two different methods are compared. Additionally, the numerical results compare well with the analytical solution. The results show that there is a good agreement between converged FE models and the analytical solution. Regarding the computational cost, the P-method is more efficient for simulating the re-entrant structure subjected to axial loading. During the second part of this study, the re-entrant cell is used for generating a polymeric auxetic cellular tube. The mesh convergence study is performed on the cellular structures using the H- and P- methods. The cellular tube is subjected to tensional and compressive loading, the module of elasticity and Poisson's ration to calculate different aspect ratios. A nonlinear analysis is performed to compare the dynamic response of a cellular tube versus a solid tube. The crashworthiness indicators are addressed and the results are compared with equivalent solid tubes. The results show that the auxetic cellular tubes have better responses against compressive loading. The primary outcome of this research is to assess a reliable FE approach for re-entrant structures under axial loading.

• Klíčová slova
• axial loading, cellular structures, crashworthiness, finite element method, negative Poisson’s ratio,
• Publikační typ
• časopisecké články MeSH

High-frequency ultrasound is used in this study to measure noninvasively, by means of osmotic loading, changes in speed of sound and cartilage thickness caused by variations of the salt concentration in the external bath. Articular cartilage comprises three main structural components: Water, collagen fibrils and proteoglycan macromolecules carrying negative charges. The negatively charged groups of proteoglycans attract cations and water into tissue and govern its shrinkage/swelling behavior, which is a fundamental mechano-electrochemical function of cartilage tissue. In this study, the mechano-electrochemical behavior of cartilage is modeled by a diffusion model. The proposed model enables simulations of cartilage osmotic loading under various parameter settings and allows to quantify cartilage mechanical properties. This theoretical model is derived from the kinetic theory of diffusion. The objectives of the study are to quantify time dependent changes in cartilage thickness, and in speed of sound within tissue with help of the finite element based simulations and data from experiments. Experimental data are obtained from fresh and trypsinized ovine patella samples. Results show that the proposed diffusion model is capable to describe transient osmotic loading of cartilage. Mean values and their deviations of the relative changes of cartilage characteristics in response to chemical loading are presented.

• Klíčová slova
• articular cartilage, diffusion model, fixed charge density, high-frequency ultrasound, numerical simulations, osmotic loading, swelling behavior,
• MeSH
• biologické modely * MeSH
• kloubní chrupavka * diagnostické zobrazování   MeSH
• osmóza MeSH
• ovce MeSH
• proteoglykany MeSH
• ultrasonografie MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• proteoglykany MeSH