In situ observation of hyaluronan molecular weight effectiveness within articular cartilage lubrication

Degradation of the articular cartilage (AC) structure due to osteoarthritis significantly influences its friction and lubrication mechanisms. Injection with exogenous hyaluronic acid (HA) is one of the ways to slow down the progress of these changes. The present paper aims to determine the effect of HA on the friction and lubrication processes of the synovial joint model. The main emphasis is placed on the effect of HA molecular weight (MW) on the coefficient of friction (COF) and the interactions between HA and other constituents of synovial fluid (SF). Frictional measurements between the AC surface and the glass were performed with simultaneous in situ observation of the contact zone by fluorescence microscopy. Using this methodology, a decrease in AC COF with an increase in the fluorescence intensity emitted from contact with HA was observed, while the phenomenon was found to be MW-dependent. These findings demonstrate that high-MW HA is more effective within a resumption of healthy AC lubrication due to a better adhesion to the AC surface.Grantová Agentura České Republiky, GA ČRCzech Science Foundation [20-00483S

Raman analysis of chemisorbed tribofilm for metal-on-polyethylene hip joint prostheses

The biochemical reaction during the formation of lubricant film the in case of a cobalt-chromium ball on an ultrahigh-molecular weight polyethylene cup was studied. Three types of model synovial fluids and hyaluronic acid (HA) at physiologic concentrations were used in the experiment. The coefficient of friction was measured using a pendulum hip simulator, and Raman spectroscopy was used to perceive chemical reactions between the synovial fluid and implant material. Raman spectra evidenced that the three model fluids and HA chemisorbed onto the cobalt-chromium surface. An -helix structure of the model fluid components was detected on the surface of the prosthesis

Towards near-permanent CoCrMo prosthesis surface by combining micro-texturing and low temperature plasma carburising

This article will argue that the legal academy has much to learn by recording, transcribing and systematically studying student-client and attorney-client consultations. Clinical faculty can utilize conversation analysis and other social science techniques to do this. Social scientists and medical providers have studied doctor-patient conversations in this way over many years. Through this systematic study researchers have reached conclusions about effective doctor-patient consultations that form the basis for teaching these skills in medical school. This article will highlight some of these studies and their findings. Some have contended that attorney-client conversations simply cannot be recorded and studied in the same way as doctor-patient consultations due to attorney-client privilege. This article will lay out how a law clinic could obtain client informed consent to this procedure, protect client confidentiality and privilege, and gain the necessary approval of the Institutional Review Board. Finally, this article will suggest topics about client consultations that could merit study in the law clinic

The impact of surface and geometry on coefficient of friction of artificial hip joints

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

The phase diagram of water at high pressures as obtained by computer simulations of the TIP4P/2005 model: the appearance of a plastic crystal phase

In this work the high pressure region of the phase diagram of water has been studied by computer simulation by using the TIP4P/2005 model of water. Free energy calculations were performed for ices VII and VIII and for the fluid phase to determine the melting curve of these ices. In addition molecular dynamics simulations were performed at high temperatures (440K) observing the spontaneous freezing of the liquid into a solid phase at pressures of about 80000 bar. The analysis of the structure obtained lead to the conclusion that a plastic crystal phase was formed. In the plastic crystal phase the oxygen atoms were arranged forming a body center cubic structure, as in ice VII, but the water molecules were able to rotate almost freely. Free energy calculations were performed for this new phase, and it was found that for TIP4P/2005 this plastic crystal phase is thermodynamically stable with respect to ices VII and VIII for temperatures higher than about 400K, although the precise value depends on the pressure. By using Gibbs Duhem simulations, all coexistence lines were determined, and the phase diagram of the TIP4P/2005 model was obtained, including ices VIII and VII and the new plastic crystal phase. The TIP4P/2005 model is able to describe qualitatively the phase diagram of water. It would be of interest to study if such a plastic crystal phase does indeed exist for real water. The nearly spherical shape of water makes possible the formation of a plastic crystal phase at high temperatures. The formation of a plastic crystal phase at high temperatures (with a bcc arrangements of oxygen atoms) is fast from a kinetic point of view occurring in about 2ns. This is in contrast to the nucleation of ice Ih which requires simulations of the order of hundreds of ns

Monitoring of Slope Stability to the Water Reservoir in "Šance" Area

Import 26/06/2013Bakalářská práce se zabývá sledováním vodorovných a svislých posunů části lesní asfaltové vozovky blízko lokality vodní nádrže Šance. V první části je podrobně popsáno sledované území, jeho historie a geologie. V druhé části se zabýváme technickým vyhodnocením zadaného úkolu. V další části jsou detailně popsány použité geodetické metody a také všechny přístroje. Nakonec v poslední části vyhodnocujeme získaná data ze tří na sobě nezávislých pozorovacích měření a porovnáváme je.This thesis deals with monitoring of the horizontal and vertical displacements of the forest asphalt road near the dam site called Šance. In the first section, we describe in details the monitored area, its history and geology. The second part we deal with the technical evaluation of our task. The next section describes in detail the methods used in surveying and all devices. Finally, in the last section we evaluate the data obtained from three independent observational measurements and compare them.Prezenční544 - Institut geodézie a důlního měřictvívýborn