Characterization of Synovial Fluid Components: Albumin-Chondroitin Sulfate Interactions Seen through Molecular Dynamics.

The friction coefficient of articular cartilage (AC) is very low. A method of producing tailor-made materials with even similar lubrication properties is still a challenge. The physicochemical reasons for such excellent lubrication properties of AC are still not fully explained; however, a crucial factor seems to be synergy between synovial fluid (SF) components. As a stepping stone to being able to produce innovative materials characterized by a very low friction coefficient, we studied the interactions between two important components of SF: human serum albumin (HSA) and chondroitin sulfate (CS). The molecular dynamics method, preceded by docking, is used in the study. Interactions of HSA with two types of CS (IV and VI), with the addition of three types of ions often found in physiological solutions: Ca2+, Na+, and Mg2+, are compared. It was found that there were differences in the energy of binding values and interaction maps between CS-4 and CS-6 complexes. HSA:CS-4 complexes were bound stronger than in the case of HSA:CS-6 because more interactions were formed across all types of interactions except one-the only difference was for ionic bridges, which were more often found in HSA:CS-6 complexes. RMSD and RMSF indicated that complexes HSA:CS-4 behave much more stably than HSA:CS-6. The type of ions added to the solution was also very important and changed the interaction map. However, the biggest difference was caused by the addition of Ca2+ ions which were prone to form ionic bridges.

Resistance of 3D-Printed Components, Test Specimens and Products to Work under Environmental Conditions-Review.

The development of additive manufacturing methods known as "3D printing" started in the 1980s. In these methods, spatial models are created from a semi-finished product such as a powder, filament or liquid. The model is most often created in layers, which are created from the semi-finished product, which is most often subjected to thermal treatment or using light or ultraviolet rays. The technology of additive manufacturing has both advantages and disadvantages when compared to the traditionally used methods of processing thermoplastic materials, such as, for example, injection or extrusion. The most important advantages are low cost, flexibility and speed of manufacturing of elements with different spatial shapes. From the point of view of the user of the product, the most important disadvantages are the lower mechanical properties and lower resistance to environmental factors that occur during the use of the manufactured products. The purpose of this review is to present current information and a compilation of features in the field of research on the effects of the interactions of different types of environments on the mechanical properties of 3D-manufactured thermoplastic products. Changes in the structure and mechanical properties of the material under the influence of factors such as humidity, salt, temperature, UV rays, gasoline and the environment of the human body are presented. The presented article enables the effects of environmental conditions on common materials used in 3D printing technology to be collated in one place.

The assessment of lower extremity peripheral artery disease impact on body mass center disorders.

BACKGROUND: Lower extremity peripheral artery disease is a problem of contemporary medicine and along with the ischemic heart disease it is considered to be a civilization disease. The risk of the disease increases significantly within a group of people reaching the age of 55 years and is closely related to co-occurring hazardous factors, such as diabetes, hyperlipidemia, hypertension or tobacco smoking. The first symptom reported by patients is intermittent claudication. Such symptoms may indicate that lower extremity peripheral artery disease does have an impact on posture disorders and motor skills. METHODS: The study covered four stages. The first stage involved medical interviews to obtain information regarding anthropometry, age, motor organ surgery, concomitant diseases and the lifestyle. In the following stage the value of the ankle brachial index for both lower limbs were calculated. In case of symptomatic patients, additionally, the location of artery stenosis/aortoiliac section, was verified. The third stage involved using a dynamometric platform for determination of the body mass center position for both studied groups. In the fourth stage a treadmill walk test was used to assess the participants for intermittent claudication. FINDINGS: Based on the obtained results, an attempt was taken to observe the relationship between the clinical characteristics of the disease and the body mass center position deviations. INTERPRETATION: The attempt was undertaken to assess whether the measurement of body mass center position might be a diagnostic parameter to evaluate the patient's condition and thus an indication for taking a decision for surgical treatment or rehabilitation.

Fatigue Life for Different Stress Concentration Factors for Stainless Steel 1.4301.

This paper presents the results of the static tensile and fatigue life tests under rotating bending of round 1.4301 (AISI 304) steel samples. The fatigue tests were carried out on smooth and notched samples with three different rounding angles with a shape factor of 1.4, 2 and 2.6. A fatigue life was determined for samples with different shape factors subject to identical loads. The results showed that the scatter of fatigue test results decreases with an increase in shape factor. To evaluate the cracking properties (cracking mode and mechanism), microstructure and fractographic tests of the fractured samples were carried out.