Interface reactions between biodegradable implants and avascular bone grafts or vascular host site in the porcine skull

Poly-L-lactide (PLLA) threaded pins and polydioxanon (PDS) woven bands were used to stabilize bone fragments in the reconstruction of the calvaria of 27 minipigs. The aim of the present study was to determine whether the rate of degradation of resorbable implants is low enough to maintain fixation until the bone has united and, at the same time, high enough to ensure that the implant material loses its strength and no longer interferes with bone growth and remodelling. The experiment lasted between 1 and 24 weeks. Staining in vivo and radiographs were performed throughout the experiment. The treated calvaria were cut into thin sections and examined microradiographically and histologically. The results confirmed that the form of the skull could be sufficiently maintained in the animal experiment over the given periods to warrant the use of such fixations in craniofacial surgery. The use of degradable material could eliminate the possible need for a second operation to remove implants and would reduce interference with the growth process.     

Interface microstructure between silicon and silver formed after eutectic brazing reaction

The interface structure between silicon and silver after the eutectic reaction at 950°C has been examined primarily by using high-resolution transmission electron microscopy. Silver almost became a single crystal and a unique interface structure was found, where a special orientation relationship across the interface was recognized. The dominant relationship was obtained as {111}_Ag {111_Si and [110]_Ag [110]_Si. The lattice arrangement model of the interface showed that the interface expressed by this relation has a good lattice match across the interface.     

Interface stress induced hardness enhancement and superelasticity in polytetrafluoroethylene/metal multilayer thin films

Polytetrafluoroethylene (PTFE)/Al, PTFE/Cu, and PTFE/Ti multilayer thin films have been deposited in order to investigate effects of interface energy on mechanical properties. PTFE, which has a low surface energy of 19.2 mJ/m², was used to introduce a large interface energy into multilayer thin films. PTFE thin film was deposited by rf magnetron sputtering using a PTFE sheet target. Al, Cu, and Ti were deposited by dc magnetron sputtering. The multilayer thin films were fabricated sequentially without breaking vacuum. Substrate used was aluminosilicate glass. The modulation period was changed from 6.7 to 200 nm. The total thickness was about 200 nm for all samples. The internal stress of metal layers changed from tensile to compressive and increased with decreasing modulation period for all of PTFE/Al, PTFE/Cu, and PTFE/Ti. Both hardness enhancement and superelasticity were observed in the results of nanoindentation measurements. The energy dissipated during nanoindentation process (one load and unload cycle) decreased with decreasing modulation period. The minimum value of the ratio of dissipated/loaded energy was < 40%, which is smaller than the values obtained for monolithic PTFE or metal films (about 73% for PTFE and 87% for Al, 72% for Cu, and 71% for Ti, respectively). This meant that the PTFE/metal nano-multilayer thin films became more elastic with decreasing modulation period. The tendency of change in the mechanical properties strongly correlated to internal stress. Mechanisms involved in anomalous behaviors in film hardness and elasticity were discussed based on the relationship to interface energy, interface stress, and internal stress, induced by multilayering of the films. It is concluded that a large compressive stress introduced in the thin films increased the energy needed to deform elastically or plastically the thin film during indentation, resulting in the increase in hardness and elasticity. The nanoindentation analysis of the multilayer thin films emphasized that in PTFE/metal multilayer thin films mechanical properties of the films depend on interface stress induced by the accumulated interface energy, being independent of bulk materials properties composing thin films, resulting in increase in hardness and elasticity.     

Early morphological changes in tissues when replacing abdominal wall defects by bacterial nanocellulose in experimental trials

Experimental trials were done on five dogs to explore if an anterior abdominal wall defect could be repaired using wet (99.9%), compact BNC membranes produced by the Мedusomyces gisevii Sa-12 symbiotic culture. The abdominal wall defect was simulated by middle-midline laparotomy, and a BNC membrane was then fixed to open aponeurotic edges with blanket suture (Prolene 4-0, Ethicon). A comparative study was also done to reinforce the aponeurotic defect with both the BNC membrane and polypropylene mesh (PPM) (Ultrapro, Ethicon). The materials were harvested at 14 and 60 days postoperative to visually evaluate their location in the abdominal tissues and evaluate the presence of BNC and PPM adhesions to the intestinal loops, followed by histologic examination of the tissue response to these prosthetics. The BNC exhibited good fixation to the anterior abdominal wall to form on the 14th day a capsule of loose fibrin around the BNC. Active reparative processes were observed at the BNC site at 60 days post-surgery to generate new, stable connective-tissue elements (macrophages, giant cells, fibroblasts, fibrin) and neocapillaries. Negligible intraperitoneal adhesions were detected between the BNC and the intestinal loops as compared to the case of PPM. There were no suppurative complications throughout the postsurgical period. We noticed on the 60^th day after the BNC placement that collagenous elements and new capillary vessels were actively formed in the abdominal wall tissues, generating a dense postoperative cicatrix whose intraperitoneal adhesions to the intestinal loops were insignificant compared to the PPM graft.

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Heat transfer between a liquid metal and the solid metal crust formed on a water-cooled copper wall

This paper describes the two-phase region at the interface of the solid and liquid phases. The effect of change in thickness of the crust on the heat transfer between the water-cooled copper wall and the liquid metal is examined.     

A quantitative comparison of the cell response to commercially pure titanium and Ti-6Al-4V implants in the abdominal wall of rats

Commercially pure (c.p.) titanium and Ti-6Al-4V implants were inserted in the abdominal wall of rats. The surrounding fluid space, inflammatory cells and fibrous capsule were evaluated after 1, 6 and 12 weeks. Light-microscopic morphometry demonstrated a fluid space around both implant materials which gradually decreased with time. Macrophages were preferentially distributed close to the implant surface in the innermost zone (0–25 µm from the surface). In contrast, fibroblasts and endothelial cells were located mainly in the outer three zones (25–100 µm from the surface). At all time periods studied and around both materials, lymphocytes were detected throughout the surrounding tissue. The outer border of the fibrous capsule, which consisted of macrophages, fibroblasts, endothelial cells and collagen, was difficult to define, in particular during the early phase of healing. At later time stages, 6 and 12 weeks, no difference in width (60–90 µm) was observed between the two materials. No major quantitative differences with respect to the number of different cells, fluid space width and fibrous capsule thickness were noted between the two materials studied. The observed mild inflammatory reaction and the absence of statistically significant differences between c.p. titanium and Ti-6Al-4V in soft tissue indicate that both materials could be suitable for use in soft tissues. In the context of previous comparative studies it may be concluded that the animal species as well as the different implantation locals play an important role in the determination of biocompatibility.     

Bioactive glass granules and polytetrafluoroethylene membrane in the repair of bone defects adjacent to titanium and bioactive glass implants

An experimental animal model was used to investigate the effect of bioactive glass (BG) granules and nonresorbable polytetrafluoroethylene (PTFE) membrane on the repair of cortical bone defects adjacent to titanium and BG implants. Thirty-two Astra® (diameter 3.5 mm) dental implants were inserted bicortically and 42 conical BG implants (diameter 2.5–3.0 mm) monocortically, into fitted holes of rabbit tibia. Before implantation, a standardized bone defect was created by drilling an extra hole (diameter 3.0 mm) adjacent to each implant site. Twenty-eight defects were filled with BG granules (diameter 630–800 m) (BG group) and 28 defects were left empty but covered with PTFE membrane (PTFE group). No material was used in 18 control defects (control group). Morphometrical evaluation with a digital image analysis system was used to measure bone repair as percentages of the defect area on scanning electron microscopy (SEM) and light microscopy pictures. Bone–implant contact was measured as percentages of the thickness of the cortical bone. At 6 and 12 wk, bone repair in defects in connection with titanium implants was 23.2% and 36.6% in the BG group, 23.2% and 32.4% in the PTFE group, and 47.2% and 46.2% in control defects. Corresponding figures for BG implants were 33.2% and 40.1% in the BG group, 16.6% and 33.5% in the PTFE group, and 25.7% and 54.9% in control defects, BG granules and new bone together filled 82.7% and 68.5% of the defect area adjacent to titanium implants, and 75.9% and 74.4% of the defect adjacent to BG implants at 6 and 12 wk, respectively. Better bone–implant contact was achieved at the defect side with BG than titanium implants (77.0% versus 45.0% at 12 wk). The results indicate that BG granules are useful in treatment of bone defects adjacent to dental implants. BG coating of the implant seems to improve osseointegration in the defect area.     

Interface structure between magnesium matrix and SiCp

The microstructure of magnesium matrix composite (MMC) was investigated by transmission electron microscopy, and fracture behaviour of composite by step-by-step tensile in the strain range of 0.8–2.0% has been determined using the dislocation and microcrack analysis. The results indicated that the interface between matrix and double-sized SiC particle (SiCp) showed a good combination. With increasing the strain from 0 to 2.0%, the dislocation density was gradually increased, especially in the interface of SiCp/matrix. Some microcracks can be found in the interface between micrometre-SiCp and matrix while no microcracks were observed around nano-SiCp.     

Interface between Sn-Sb-Cu solder and copper substrate

Influence of antimony and copper in Sn-Sb-Cu solder on the melting and solidification temperatures and on the microstructure of the interface between the solder and copper substrate after wetting the substrate at 623 K for 1800 s were studied. Microstructure of the interface between the solder and copper substrates in Cu-solder-Cu joints prepared at the same temperature for 1800 s was observed and shear strength of the joints was measured. Influence of the atmosphere - air with the flux and deoxidising N₂ + 10H₂ gas - was taken into account. Thermal stability and microstructure were studied by differential scanning calorimetry (DSC), light microscopy, scanning electron microscopy (SEM) with energy-dispersive spectrometry (EDS) and X-ray diffraction (XRD). Melting and solidification temperatures of the solders were determined. An interfacial transition zone was formed by diffusion reaction between solid copper and liquid solder. At the interface Cu₃Sn and Cu₆Sn₅ phases arise. Cu₃Sn is adjacent to the Cu substrate and its thickness decreases with increasing the amount of copper in solder. Scallop Cu₆Sn₅ phase is formed also inside the solder drop. The solid solution Sn(Sb) and SbSn phase compose the interior of the solder drop. Shear strength of the joints measured by push-off method decreases with increasing Sb concentration. Copper in the solder shows even bigger negative effect on the strength.     

Theoretical and experimental study of fibre attrition during extrusion of glass-fibre-reinforced polypropylene

On the basis of the experimental observations described in ref. 1, a model has been proposed to analyse the phenomenon of fibre breakage taking place when granules of short-fibre-reinforced thermoplastics are processed in an extruder. This model essentially determines the bending moment experienced by a single fibre, anchored at one end, due to drag forces produced by the flow of molten polymer past it. This model clearly brings out the effects of molten film thickness, screw speed, viscosity of the polymer melt and the fibre orientation relative to the flow direction. It is postulated that the model provides a mechanism for the breakage of fibres exposed by melting of polymer at the solid bed-molten polymer interface. For fibres which are free to move in the molten polymer, buckling introduced by the shearing motion of the molten polymer, as predicted by the Forgacs and Mason model² is responsible for their attrition. Using the extrusion data of ref. 1, the results of the combined use of the two models show good agreement with the experimental observations, in particular the fibre length distribution of various stages of extrusion. This agreement is observed in spite of several assumptions inherent in the model. Finally, the effect of fibre agglomeration on the attrition phenomenon is also studied.     

ICL7135与单片机接口电路

针对双积分式A／D转换器对信号转换速率的要求不是很高而对转换精度要求很高的特点,分析了双积分式A／D转换器ICL7135与单片机的几种接口电路。对并行与串行两种方式进行说明;并行接口电路中根据占用单片机I／O端口数量的不同给出了9线制接法和改进的6线制接法;在单片机的I／O端口特别紧张的情况下,则可以采用串行接口电路。设计了双积分A／D转换器ICL7135与单片机的几种接口电路,具有简单可行,有效灵活的特点。为从事单片机设计和智能仪表开发研制的人员提供了一定的参考。     

Characterization of multicomponent crystal formed between indomethacin and lidocaine

Purpose: Crystalline complex was formed between indomethacin (IDM) and lidocaine (LDC) at molar ratio 2:1 from ethanol solution. The purpose of this study was elucidation of an interactive manner between IDM and LDC in ethanol solution and mechanism of the complex formation through solid state as well as liquid state. Methods: The chemical and physical nature of the complex was clearly elucidated by the alliance of powder X-ray diffractometry, differential scanning calorimetry, and infrared spectroscopy. The complex was also formed via solid-state reaction by cogrinding and heating treatment without any solvent. Results: The complexation process was estimated to be as follows: (i) mixing and contact of two components, (ii) disorder of crystalline LDC by grinding or fusion, and then (iii) crystal growth by heating. In addition, 1H-NMR coupled with microchanneled cell for synthesis monitoring revealed that a primary interactive force between IDM and LDC molecule was coulomb energy.     

An experimental study on conversion of high-density polyethylene and polypropylene to liquid fuel

Clean Technologies and Environmental Policy - Pyrolysis of plastic material is a potential way for the conversion of plastic into hydrocarbon fuel. Thermal and catalytic pyrolysis of high-density...     

Hemodialysis‐associated soft tissue amyloidomas of the chest and abdominal wall

Amyloidoma is a highly unusual presentation of amyloidosis in tumoral or nodular form. Isolated soft tissue amyloidomas in individuals with end‐stage renal disease on chronic hemodialysis is exceedingly rare, particularly in the era of advanced dialysis technologies. We report the case of a 55‐year‐old male with end‐stage renal disease due to autosomal‐dominant polycystic kidney disease, on HD for over 30 years, who was found to have soft‐tissue, dialysis‐related (β₂‐microglobulin) amyloidomas (DRA). He presented with painful, palpable masses within the thoracic and abdominal walls. Serum β₂‐microglobulin level was only mildly elevated at 24.9 mg/L. Biopsy confirmed amyloidosis with positivity for Congo Red staining and apple‐green birefringence under polarized light. Amyloid subtyping with immunohistochemistry showed positive β₂‐microglobulin staining within the deposits. Conservative therapy involving pain management and close monitoring resulted in eventual improvement in symptoms and thus proved to be a viable option for treatment.     

Oxides formed between ZrO2 and Nb2O5

High-purity monoclinic ZrO₂ and monoclinic Nb₂O₅ powder samples were mixed in varying ratios, and heated at 1300°C for 24 h before furnace cooling. X-ray diffraction analysis showed that two compounds, Nb₂O₅-6ZrO₂ and Nb₂O₅·8ZrO₂ (or (Zr, Nb)₈O₁₇ and (Zr, Nb)₁₀O₂₁), were formed. Some of the reflections from the two compounds were overlapped and interfered with those from the zirconium oxide, especially the tetragonal ZrO₂. A thermodynamic analysis was used to demonstrate that it is possible to have ZrO₂ as well as Nb₂O₅ formed on Zr-Nb alloys in an oxidizing environment. The relevance of these results (experimental and calculated) to the corrosion of a Zr-Nb alloy in high temperature aqueous environments is discussed. It is suggested that the incorporation of niobium into the oxide during the corrosion of Zr-Nb alloys could be by the formation of compounds such as (Zr, Nb)₈O₁₇ and (Zr, Nb)₁₀O₂₁. Also, the tetragonal ZrO₂, which has been found to be a barrier layer oxide, could, in fact, be either of the ternary compounds Nb₂O₅·6ZrO₂ and Nb₂O₅·8ZrO₂ both of which are orthorhombic with lattice parameters very close to those of the tetragonal ZrO₂.     

Interface between zinc phosphate-deposited steel fibres and cement paste

In an attempt to protect steel fibre reinforcements from corrosion and improve their adherence to cement pastes, we deposited a zinc phosphate (ZnPh) conversion coating on the surface of the fibres. At the interfacial contact zones between the cement paste and ZnPh, alkali-induced dissolution caused the dissociation of abundant PO ₄ ^3– ions from the ZnPh. The interaction of PO ₄ ^3– ions with Ca²⁺ ions from the pastes led to the formation of hydroxyapatite and brushite in the vicinity of the dissolved ZnPh surface. Such intermediate calcium phosphate compounds played important roles in (1) improving the cement-fibre interfacial bonds, and (2) repairing the damage of the ZnPh surfaces dissolved by alkali. These processes protected the steel fibre from corrosion.     

Interface reaction between oxide glasses and Fe-Al-Si magnetic alloy

The interface reactions between oxide glasses and magnetic alloy, Fe-Al-Si (so-called Sendust), were analysed. The oxide glasses used were SiO₂-PbO, SiO₂-Na₂O, SiO₂-Li₂O and B₂O₃-Na₂O binary glasses. It was observed that the lattice constant of the alloy decreases and the saturation magnetic-flux density of the alloy increases on reaction with the glasses. It was found that the aluminium atoms in the alloy diffuse to the interface and dissolve into the glass melt as Al³⁺ ions, leading to the iron-rich composition of the alloy. On the other hand, Pb²⁺, Na⁺ and H⁺ ions in the molten glasses were reduced at the interface. Metallic lead particles about 20 m in diameter were found to be dispersed in the SiO₂-PbO melt. Reduced sodium was thought to evaporate from the SiO₂-Na₂O melt, and H₂ gas bubbles were observed at the interface between B₂O₃-Na₂O melt and the alloy. These reactions were analysed based on the standard free energy diagrams of oxidation-reduction reaction, and expressed as 3Pb _glass ²⁺ +2Al_alloy 3Pb+2Al _glass ³⁺ 3Na _glass ⁺ +Al_alloy 3Na+Al _glass ³⁺ 6H _glass ⁺ +2Al_alloy 3H₂+2Al _glass ³⁺     

Correlations between image-analysed morphology and mechanical properties of calcium carbonate-filled polypropylene

Calcium carbonate-filled polypropylene composites were processed on two different highintensity mixing devices. The resulting relationships between morphology, processing conditions and mechanical properties of these composites were studied using an electron microscope with an image-analysis system and impact and tensile testing. Only under more extreme conditions did the recently developed turbine mixer give as good a dispersion as the classical Banbury-style mixer. Relatively small additions of the filler resulted in small increases in absorbed impact energy. Semi-quantitative information about the randomness achieved in the mixing process was obtained using a dilation/counting procedure and computer-derived spatial images. Object-specific parameters such as the percentage of objects greater than 1 m in size give good correlation with the mechanical properties of the mixture.     

Titanium implants and BMP-7 in bone: an experimental model in the rabbit

This study evaluates the effect of rhBMP-7/OP-1 on the osseointegration of commercially pure titanium implants in an experimental implant model in rabbits. Threaded titanium implants with two transverse parallel canals were inserted in the femur and tibia of rabbits. The canals were filled with, 10 g of BMP-7/collagen carrier, pure collagen carrier or were left empty as a control. The stiffness of the implant fixation was evaluated by Resonance Frequency Analysis (RFA) at baseline and four weeks postoperativly. Percentage of bone ingrowth in the canals was measured on microradiographs. Histomorphometry along the threaded part of the implants was performed on 15 m thin sections. The results from the RFA demonstrated a higher mean value for the BMP-7 treated implants in the tibia than the carrier treated implants but not compared to the control implants. The control implants in the tibia demonstrated more bone ingrowth in the upper canal than to the carrier or the BMP-7 treated implants. Apart from these differences there were no significant effects of BMP. In this study BMP-7 did not contribute to any substantially improved bone anchorage of titanium implants.