Wear behavior of hydroxyapatite reinforced polymer composite for biomedical applications

In medical fields, hydroxyapatite (HA) is used for restoring the human bones and teeth. Nowadays, newer bio composites are being developed to replace the broken or removed teeth in human using hydroxyapatite. The original teeth may be removed from human, due to various reasons such as tooth decay, periodontal disease and gum diseases. Due to the bioactivity property of HA, it helps the tooth to grow. In this work, tribological properties of HA powder reinforced composite are investigated. Three most important factors that affect the properties of the composites were chosen and varied during wear testing of the composites. The HA powder weight %, applied load (P) and sliding distance (SD) were varied on the basis of Taguchi’s experimental design. Analysis of variance (ANOVA) and (Signal to Noise) SN ratio analysis was used to study the influence of each factor on the specific wear rate (SWR). It was concluded that the HA wt. % highly influences the SWR of the composite during pin on disc testing.

COMPARING ANALYSIS OF PRETREATMENT METHODS OF WOOD AND BONE MATERIALS FOR THE CHRONOLOGY OF PERIPHERAL BURIALS AT TUNNUG 1, TUVA REPUBLIC, RUSSIA

ABSTRACT Nine burials from Tunnug 1 site in Tuva Republic, which contained human and animal bones as well as remains of wood, were chosen for intercomparison study of preparation methods. Nine human bones, nine animal bones and 11 pieces of wood were prepared. Gelatin extracted from bones was purified using the UF method but the extraction from bones was modified with respect to acid and base treatment. Wood samples were treated as whole using acid-base-acid and cellulose was extracted for comparison. The results confirmed a highly consistent chronology of the sites centered at 200–400 CE, however, a few bones resulted in an offset between ages obtained by different methods. The extraction of cellulose was limited due to the poor preservation of wood. Our results highlight problems of dating poorly preserved bones and wood.

Comparison of the Morphological and Structural Characteristic of Bioresorbable and Biocompatible Hydroxyapatite-Loaded Biopolymer Composites

Calcium phosphate (CaP)-based ceramic–biopolymer composites can be regarded as innovative bioresorbable coatings for load-bearing implants that can promote the osseointegration process. The carbonated hydroxyapatite (cHAp) phase is the most suitable CaP form, since it has the highest similarity to the mineral phase in human bones. In this paper, we investigated the effect of wet chemical preparation parameters on the formation of different CaP phases and compared their morphological and structural characteristics. The results revealed that the shape and crystallinity of CaP particles were strongly dependent on the post-treatment methods, such as heat or alkaline treatment of as-precipitated powders. In the next step, the optimised cHAp particles have been embedded into two types of biopolymers, such as polyvinyl pyrrolidone (PVP) and cellulose acetate (CA). The pure polymer fibres and the cHAp–biopolymer composites were produced using a novel electrospinning technique. The SEM images showed the differences between the morphology and network of CA and PVP fibres as well as proved the successful attachment of cHAp particles. In both cases, the fibres were partially covered with cHAp clusters. The SEM measurements on samples after one week of immersion in PBS solution evidenced the biodegradability of the cHAp–biopolymer composites.

RITUAL PITS AT THE MIDDLE DON SETTLEMENTS OF THE SCYTHIAN PERIOD

На городищах и селищах скифоидной культуры, существовавших в VIIII вв. до н. э. в лесостепной части бассейна Дона, фактически не были известны сооружения культового назначения. Для выявления таковых были проанализированы имеющиеся поселенческие материалы. Оказалось, что не менее 16 ям, открытых на шести памятниках и считавшихся хозяйственными, необходимо интерпретировать как ритуальные комплексы. Основанием для этого послужили специфичные находки и стратиграфия. Семь ям содержали человеческие кости вместе с костями животных и фрагментами керамики. В другие в качестве вотивных приношений были помещены наконечники стрел и копья, орудия труда, глиняные поделки и сосуды, нередко преднамеренно разбитые. Есть немногочисленные ритуальные захоронения собак. Как правило, в ямах имеются следы костров или продукты горения. Более половины сооружений найдены на Семилукском городище. Они, несомненно, были связаны с размещавшимися там же массовыми захоронениями. С выделением серии культовых комплексов появилась совершенно новая информация о сакральной сфере жизни оседлого населения региона. In reality, religious constructions have not been found at Scythoid hillforts and unfortified settlements in the forest-steppe belt of the Don basin. Settlement materials were analyzed to identify such constructions. The analysis demonstrated that at least 16 pits (Figs. 1-3) discovered at six sites that were considered to be of household character are to be interpreted as ritual complexes. Specific finds and stratigraphy were used to justify this conclusion. Seven pits contained human bones along with animal bones and ceramic fragments. Arrowheads and spearheads, implements, clay objects and vessels which were, in many cases, deliberately broken (Figs. 4; 5) were placed into some pits as votive offerings. There are some ritual burials of dogs that are few in number. Pits tend to show traces of fire or combustion products. More than half of such constructions were found at Semiluki. They are definitely associated with mass burials located at this settlement. Now that a series of religious complexes has been singled out, we have absolutely new information on sacral life of the sedentary population living in this region

Environment and Archaeology in New Zealand

<p>This thesis deals mainly with central New Zealand. The writer's archaeological excavations are described in Appendices. Lists are prepared giving all archaeological radiocarbon dates on wood, charcoal, moa bones, human bones and marine shells, for New Zealand up to 1974. The dates are sorted according to material, and the dates and their standard errors corrected. A stratigraphic system based on soils and Loisels pumice and tied to the corrected radio carbon dates is set up for central New Zealand. Radiocarbon and stratigraphy provide dates for vegetation changes' Moahunter sites, cultivation sites, and for the artifact assemblages that are independently grouped as either Early or Late. Change from Early to Late is explained by cultural breakdown and an initial movement of culture from south to north, The sequence of events postulated is summarised in a Table at the end of the text.</p>

DOES CEMENT CURING CAUSE CONCERNING INCREASE OF THE TEMPERATURE WHEN DELIVERED IN THE HUMAN HUMERUS?

For the treatment of humeral fractures, numerous strategies exist to improve the clinical outcome of the reconstruction and to reduce the incidence of fixation failure. Injection of acrylic-based cements to reinforce the bone and/or augment the screws is one option. The heat generated during cement polymerization raises some concerns, as it could cause tissue damage. The first aim of this study was to measure the temperature over time during polymerization when acrylic cements are delivered inside the bone to treat fracture. The second aim was to assess if the ISO-5833:2002 standard can predict what happens in a real bone. Different tests were performed using two acrylic-based cements (Mendec and Cal-Cemex): (i) the ISO-5833:2002 standard (Annex C); (ii) tests on human bones (humeral diaphysis and humeral head) injected with cement to simulate fracture treatment. In the humeri, the highest temperature was measured in the diaphysis (68.6∘C for Mendec, 62.7∘C for Cal-Cemex). These values are comparable with the temperature reached in other consolidated applications (vertebroplasty). Exposure to high temperature was shorter for the diaphysis than for the head. For both cements, in both the diaphysis and the head, temperatures exceeded 48∘C for less than 10[Formula: see text]min. This is within the threshold for tissue necrosis. The ISO-5833:2002 yielded significantly different results in terms of maximum temperature (difference exceeding 15∘C) and exposure to temperature above 48∘C and 45∘C. This discrepancy is probably due to a combination of factors affecting the amount of heat produced and dissipated (e.g., amount and shape of the cement, thermal conductivity).