Coefficient of friction (COF) tests were conducted on 28-mm and 36-mm-diameter hip joint prostheses for four different material combinations, with or without the presence of Ultra High Molecular Weight Polyethylene (UHMWPE) particles using a novel pendulum hip simulator. The effects of three micro dimpled arrays on femoral head against a polyethylene and a metallic cup were also investigated. Clearance played a vital role in the COF of ceramic on polyethylene and ceramic on ceramic artificial hip joints. Micro dimpled metallic femoral heads yielded higher COF against a polyethylene cup; however, with metal on metal prostheses the dimpled arrays significantly reduced the COF. In situ images revealed evidence that the dimple arrays enhanced film formation, which was the main mechanism that contributed to reduced friction.

• MeSH
• keramika analýza   MeSH
• kloubní náhrada typu kov-kov MeSH
• kyčelní kloub MeSH
• kyčelní protézy * MeSH
• lidé MeSH
• polyethyleny analýza   MeSH
• rozhraní kost/implantát MeSH
• testování materiálů * MeSH
• tření * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND AND OBJECTIVES: Catheter ablation of ventricular tachycardia (VT) may include induction of VT and localization of VT-exit site. Our aim was to assess localization performance of a novel statistical pace-mapping method and compare it with performance of an electrocardiographic inverse solution. METHODS: Seven patients undergoing ablation of VT (4 with epicardial, 3 with endocardial exit) aided by electroanatomic mapping underwent intraprocedural 120-lead body-surface potential mapping (BSPM). Two approaches to localization of activation origin were tested: (1) A statistical method, based on multiple linear regression (MLR), which required only the conventional 12-lead ECG for a sufficient number of pacing sites with known origin together with patient-specific geometry of the endocardial/epicardial surface obtained by electroanatomic mapping; and (2) a classical deterministic inverse solution for recovering heart-surface potentials, which required BSPM and patient-specific geometry of the heart and torso obtained via computed tomography (CT). RESULTS: For the MLR method, at least 10-15 pacing sites with known coordinates, together with their corresponding 12-lead ECGs, were required to derive reliable patient-specific regression equations, which then enabled accurate localization of ventricular activation with unknown origin. For 4 patients who underwent epicardial mapping, the median of localization error for the MLR was significantly lower than that for the inverse solution (10.6 vs. 27.3 mm, P  =  0.034); a similar result held for 3 patients who underwent endocardial mapping (7.7 vs. 17.1 mm, P  =  0.017). The pooled localization error for all epicardial and endocardial sites was also significantly smaller for the MLR compared with the inverse solution (P  =  0.005). CONCLUSIONS: The novel pace-mapping approach to localizing the origin of ventricular activation offers an easily implementable supplement and/or alternative to the preprocedure inverse solution; its simplicity makes it suitable for real-time applications during clinical catheter-ablation procedures.

• MeSH
• anatomické modely MeSH
• katetrizační ablace metody   MeSH
• komorová tachykardie diagnostické zobrazování   patofyziologie   chirurgie   MeSH
• lidé MeSH
• mapování potenciálů tělesného povrchu přístrojové vybavení   metody   MeSH
• modely kardiovaskulární * MeSH
• zobrazování trojrozměrné přístrojové vybavení   metody   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Affinity-based biosensing systems have become an important analytical tool for the detection and study of numerous biomolecules. The merging of these sensing technologies with microfluidic flow cells allows for faster detection times, increased sensitivities, and lower required sample volumes. In order to obtain a higher degree of performance from the sensor, it is important to know the effects of the flow cell geometry on the sensor sensitivity. In these sensors, the sensor sensitivity is related to the overall diffusive flux of analyte to the sensing surface; therefore increases in the analyte flux will be manifested as an increase in sensitivity, resulting in a lower limit of detection (LOD). Here we present a study pertaining to the effects of the flow cell height H on the analyte flux J, where for a common biosensor design we predict that the analyte flux will scale as J ≈ H(-2/3). We verify this scaling behavior via both numerical simulations as well as an experimental surface plasmon resonance (SPR) biosensor. We show the reduction of the flow cell height can have drastic effects on the sensor performance, where the LOD of our experimental system concerning the detection of ssDNA decreases by a factor of 4 when H is reduced from 47 μm to 7 μm. We utilize these results to discuss the applicability of this scaling behavior with respect to a generalized affinity-based biosensor.

• MeSH
• jednovláknová DNA analýza   genetika   MeSH
• limita detekce MeSH
• mikrofluidní analytické techniky přístrojové vybavení   MeSH
• povrchová plasmonová rezonance přístrojové vybavení   MeSH
• sekvence nukleotidů MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

• MeSH
• fyzikální chemie MeSH
• Publikační typ
• monografie MeSH

• Konspekt
• Fyzikální chemie
• NLK Obory
• chemie, klinická chemie

PURPOSE: Geant4-DNA is used to calculate S-values for different subcellular distributions of low-energy electron sources in various cell geometries. METHOD: Calculations of cellular S-values for monoenergetic electron sources with energy from 1 to 100 keV and the Auger-electron emitting radionuclides Tc-99m, In-111, and I-125 have been made using the Geant4 Monte Carlo toolkit. The Geant4-DNA low-energy extension is employed for simulating collision-by-collision the complete slowing-down of electron tracks (down to 8 eV) in liquid water, used as a surrogate of human cells. The effect of cell geometry on S-values is examined by simulating electron tracks within different cell geometries, namely, a spherical, two ellipsoidal, and an irregular shape, all having equal cellular and nuclear volumes. Algorithms for randomly sampling the volume of the nucleus, cytoplasm, surface, and whole cell for each cell phantom are presented. RESULTS: Differences between Geant4-DNA and MIRD database up to 50% were found, although, for the present radionuclides, they mostly remain below 10%. For most source-target combinations the S-values for the spherical cell geometry were found to be within 20% of those for the ellipsoidal cell geometries, with a maximum deviation of 32%. Differences between the spherical and irregular geometries are generally larger reaching 100-300%. Most sensitive to the cell geometry is the absorbed dose to the nucleus when the source is localized on the cell surface. Interestingly, two published AAPM spectra for I-125 yield noticeable differences (up to 19%) in cellular S-values. CONCLUSION: Monte Carlo simulations of cellular S-values with Geant4-DNA reveal that, for the examined radionuclides, the widely used approximation of spherical cells is reasonably accurate (within 20-30%) even for ellipsoidal geometries. For irregular cell geometries the spherical approximation should be used with caution because, as in the present example, it may lead to erroneous results for the nuclear dose for the commonly encountered situation where the source is localized to the cell surface.

• MeSH
• absorpce radiace * MeSH
• biologické modely * MeSH
• dávka záření MeSH
• elektrony MeSH
• lidé MeSH
• metoda Monte Carlo MeSH
• počítačová simulace MeSH
• radiometrie metody   MeSH
• statistické modely * MeSH
• velikost buňky * MeSH
• viabilita buněk účinky léků   fyziologie   MeSH
• vztah dávky záření a odpovědi MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: The aim of this article is to present a new methodology for assessment of skin topology using a three-dimensional image (3D). METHODS: The measurement of the skin surface roughness is based on 3D scanning of silicone replicas by chromatic aberration length technique in a contactless manner, i.e. by a polychromatic light beam. Analysis of the skin surface reprints was performed using Talymap, Gold version. Results were analysed by fractal geometry, which allows to evaluate changes of the skin surface before and after application of cosmetics and instrumental cosmetological techniques. The methodology was applied for objective assessment of the effects of diamond microdermabrasion on the skin surface roughness. Measurements were performed on 23 volunteers in the age group of 31-67 years. RESULTS: Based on the results of skin surface scanning after the treatment with diamond microdermabrasion it may be concluded that inequalities of the skin surface are reduced immediately after exfoliation. However, this effect mostly diminishes within 14 days after treatment. The entire study ultimately suggests that the instrumental method used only leads to improvement of the skin surface immediately after its application. Thermo vision images of the skin surface temperature were obtained during the application of the abrasive method. The experimental results showed that the skin is rather cooled than heated by the treatment. CONCLUSION: This study is focused on the development of a methodology for objective measurement of changes in treated skin relief using 3D scanning. The results are evaluated using fractal dimension. The output may also include also an enlarged model of the skin surface made by 3D printer, which can serve for illustrative communication with the client.

• MeSH
• dermabraze metody   MeSH
• dermatochirurgické výkony MeSH
• dospělí MeSH
• kosmetické přípravky farmakologie   MeSH
• kůže diagnostické zobrazování   účinky léků   patologie   účinky záření   MeSH
• lidé středního věku MeSH
• lidé MeSH
• povrchové vlastnosti účinky léků   účinky záření   MeSH
• senioři MeSH
• stárnutí kůže patologie   MeSH
• výsledek terapie MeSH
• zobrazování trojrozměrné metody   MeSH
• Check Tag
• dospělí MeSH
• lidé středního věku MeSH
• lidé MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• srovnávací studie MeSH

The goal of the study was to design a model of cardiac ventricles with realistic geometry that enables simulation of the ventricular activation with normal conduction system functions, as well as with bundle branch blocks. In ventricles, electrical activation propagates from the His bundle to the left and right bundle branches and continues to the fascicles and branching fibers of the Purkinje system. The role of these parts of the conduction system is to lead the activation rapidly and synchronously to the left and right ventricle. The velocity of propagation in the conduction system is several times higher than in the surrounding ventricular myocardium. If the conduction system works normally, QRS duration representing the total activation time of the ventricles lies in the physiological range of about 80 to 120 ms but it is more than 120 ms in the case of bundle branch blocks. In our study, the realistic geometry of the ventricles was constructed on the base of a patient CT scan, defining epicardial and endocardial surfaces. The first part of the conduction system (fast-conducting bundle branches, fascicles in the left ventricle and initial parts of the Purkinje fibers) was modeled as polyline pathways isolated from the surrounding ventricular tissue. The remaining part of the Purkinje system was modeled as an endocardial layer with higher conduction velocity. The propagation of the electrical activation in the ventricular model was modeled using reaction-diffusion (RD) equations, except for the first part of the conduction system, where the activation times were evaluated algebraically with respect to predefined velocity of propagation and estimated distance between the His bundle and particular entry point to the layer with higher conduction velocity. Propagation of activation in cardiac ventricles was numerically solved in Comsol Multiphysics environment. Several configurations of the first part of the conduction system with different number of polyline pathways and entry points were proposed and tested to achieve realistic activation propagation. For the model with 9 starting points, realistic total activation time (TAT) of the whole ventricles of about 108 ms was obtained for the model with normal conduction system, and realistic TAT of 126 ms and 149 ms were obtained for the right and left bundle branch block (RBBB, LBBB), respectively. Very similar TAT was found also for the model with 7 starting points, but unrealistically long TAT was obtained in LBBB simulation for the model with only 5 starting points.

• MeSH
• anatomické modely MeSH
• biomedicínské technologie metody   MeSH
• biomedicínský výzkum přístrojové vybavení   trendy   MeSH
• blokáda Tawarova raménka * diagnostické zobrazování   patofyziologie   MeSH
• lidé MeSH
• modely kardiovaskulární MeSH
• počítačová simulace klasifikace   MeSH
• srdeční komory anatomie a histologie   MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• práce podpořená grantem MeSH
• přehledy MeSH

Na biomateriály jsou v dnešní době kladeny mnohé požadavky. Jedním z potenciálních biomateriálů nové generace je titan a jeho slitiny s nanotubulární povrchovou úpravou, kterou lze připravit poměrně levně a jednoduše metodou anodické oxidace za vhodných podmínek. Tato nanostruktura má osteoinduktivní a osteokonduktivní vlastnosti. Výběr nejvhodnější geometrie a přesný mechanismus působení teprve čeká na objasnění.

Biomaterials nowadays should meet various criteria. One of the promising biomaterials of the new generation is titanium and its alloys with a nanotubular surface modification prepared by anodic oxidation at appropriate conditions. This relatively inexpensive and simple method leads to the nanostructure with osteoinductive and osteoconductive properties. Selection of the most suitable geometry and exact mechanism of action has to be elucidated.

• MeSH
• biokompatibilní materiály MeSH
• biologické modely MeSH
• biomedicínské inženýrství MeSH
• buněčné linie MeSH
• extracelulární matrix MeSH
• fyziologie buňky účinky léků   MeSH
• kosti a kostní tkáň * účinky léků   MeSH
• krysa rodu rattus MeSH
• lidé MeSH
• mezenchymální kmenové buňky MeSH
• modely u zvířat MeSH
• myši MeSH
• nanostruktury MeSH
• nanotechnologie MeSH
• osteoblasty MeSH
• slitiny MeSH
• techniky in vitro MeSH
• titan * chemie   MeSH
• výzkum MeSH
• Check Tag
• krysa rodu rattus MeSH
• lidé MeSH
• myši MeSH

A set of single-tryptophan mutants of the Na(+)/K(+)-ATPase isolated, large cytoplasmic loop connecting transmembrane helices M4 and M5 (C45) was prepared to monitor effects of the natural cytoplasmic ligands (i.e., Mg(2+) and/or ATP) binding. We introduced a novel method for the monitoring of the changes in the electrostatic surface potential (ESP) induced by ligand binding, using the quenching of the intrinsic tryptophan fluorescence by acrylamide or iodide. This approach opens a new way to understanding the interactions within the proteins. Our experiments revealed that the C45 conformation in the presence of the ATP (without magnesium) substantially differed from the conformation in the presence of Mg(2+) or MgATP or in the absence of any ligand not only in the sense of geometry but also in the sense of the ESP. Notably, the set of ESP-sensitive residues was different from the set of geometry-sensitive residues. Moreover, our data indicate that the effect of the ligand binding is not restricted only to the close environment of the binding site and that the information is in fact transmitted also to the distal parts of the molecule. This property could be important for the communication between the cytoplasmic headpiece and the cation binding sites located within the transmembrane domain.

• MeSH
• adenosintrifosfát farmakologie   metabolismus   MeSH
• akrylamidy farmakologie   metabolismus   MeSH
• cytoplazma metabolismus   MeSH
• fluorescence MeSH
• hořčík farmakologie   metabolismus   MeSH
• jodidy farmakologie   metabolismus   MeSH
• konformace proteinů účinky léků   MeSH
• ligandy MeSH
• molekulární modely MeSH
• mutace MeSH
• myši MeSH
• povrchové vlastnosti MeSH
• sodíko-draslíková ATPasa genetika   chemie   metabolismus   MeSH
• statická elektřina MeSH
• zvířata MeSH
• Check Tag
• myši MeSH
• zvířata MeSH
• Publikační typ
• práce podpořená grantem MeSH