Chemotaxis and the inhibition of chemotaxis of human neutrophils in reponse to metal ions

The possibility that three different types of metal ions, Cr(III), Co(II) and Ni(II), all relevant to metallic biomaterials, might influence chemotaxis has been investigated. Two new techniques, not previously used in biomaterials research involving the study of locomotor morphology of neutrophils and cell movement through agarose gels, were used in this study. Chromium ion concentrations from 0.05 to 10 p.p.m. and cobalt ion concentrations from 0.5 to 30 p.p.m. were not chemotactic for neutrophils under agarose and did not induce neutrophils to polarize. As neutrophils must take up a locomotor morphology before migrating, it is clear that cobalt and chromium ions in a protein-free environment are not chemotactic for human neutrophils. Concentrations of > 2.5 p.p.m. nickel ions did induce neutrophils to polarize, probably a result of the nickel ions causing depolarization of the neutrophil plasma membrane.     

PVC-Cu composites with chemically deposited ultrafine copper particles

PVC-Cu composites with chemically deposited ultrafine (0.1 to 0.3 m diameter) copper particles were prepared by hot-pressing copper-coated PVC powder (–106, +150 m) at 120° C. Metallic copper in fine-particle form was deposited on the PVC particles by reducing an ammoniacal cupric acetate solution with hydrazine at 85° C. The electrical resistivity (d.c.) and transverse rupture strength of these composites were measured. Measurement of electrical resistivity indicated that in these composites copper particle network formation was initiated at a copper content of about 0.2 vol%; with further increase of copper content the resistivity dropped sharply from about 10¹⁴ (for pure PVC) to about 10⁵ MN m^–2 cm at a copper content of about 0.5 vol%. Increase of copper loading beyond 0.5 vol% did not decrease resistivity significantly whereas the rupture strength increased continuously from 120 MN m^–2 (for pure PVC) to a value of about 300 MN m^–2 with 4 vol% copper loading. This high value of resistivity even after copper particle chain formation and the continuous increase of rupture strength, is thought to be due to formation of a thin layer of polymer film between the copper particles introducing a quasi-random character to the otherwise segregated network of copper particles.     

Corrosion-Electrochemical Behavior of M1 Copper in Aqueous Ethylene-Glycol Media

In aqueous ethylene-glycol media, M1 copper oxidizes to Cu⁺ ions. In the course of corrosion, dissolved oxygen oxidizes ethylene glycol and Cu⁺ ions to Cu^{2 +} ions, which, together with ethylene glycol and the products of its oxidation, form complex compounds. In the case of deep ion-exchange purification of a water-ethylene-glycol heat carrier (ρ = 100 kΩ · m), the maximum value of the coefficient of protective action is 70%. With decrease in the concentration of dissolved oxygen to 1 g/m³, under conditions of minimum purification ρ = 5 kΩ · m), this parameter constitutes 77% and grows to 97% for a specific electric resistance of the heat carrier of 50 kΩ · m. Combining both methods of the removal of corrosion-active admixtures (dissolved oxygen and the products of copper and ethylene glycol oxidation), one can enhance substantially the corrosion resistance of copper in water-ethylene-glycol heat carriers.__________Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 1, pp. 19 – 26, January – February, 2005.     

Chemiluminescent oxidative products generated by in vitro leukocyte-material interactions

The effect of different polymeric materials on leukocyte adhesion and their oxidative responses was investigated. Two commercial polymers: polyethylene (PE) and silicone rubber (SR) and two laboratory-synthesized polyurethanes were examined. The polyurethanes studied consisted of a polytetramethylene oxide (PTMO)-based polyurethane (PEU-base) and a sulfonated polyurethane (PEU-SO3). In vitro polymorphonuclear leukocyte (PMN) adhesion and respiratory burst activity measurements were studied using a radiolabelling technique and a chemiluminescence (CL) assay, respectively. An increased number of adherent PMNs and increased cell spreading were found on PEU-SO3 compared to the PEU-base, SR and PE. The largest CL response was also found on PEU-SO3, whereas on the other hydrophobic polymers the response was smaller. Additionally, on the PEU-SO3 surface the CL response was sustained indicating more prolonged production of oxygen radicals by PMNs on this material. Upon stimulation with opsonized zymosan (OZ), the PMNs on PEU-SO3 showed the lowest CL response, indicating a decreased respiratory burst differences among them in their CL response. The residual CL response was reduced by 30% for PEU-SO3 and by 10–15% for PE, SR and PEU-base compared to the control (luminometer polystyrene cuvette only, no disc). Upon addition of phorbol myristate acetate (PMA), all surfaces except SR showed a slightly reduced CL response. Along with PE, PEU-SO3 showed the lowest CL response. These results suggest that oxygen radicals are produced during early incubation of PMNs with biomaterials, and upon subsequent stimulation of these cells, fewer oxygen radicals are produced due to cellular exhaustion.     

Fracture characteristics of a burst tested maraging steel rocket motor case

A 0.3 m diameter, 2 m long and 0.0015 m thick, 18 nickel 1800 MNm^–2 grade maraging steel motor case was designed, fabricated and burst tested to gain experience for using the steel as booster case material in satellite launch vehicles. The bursting occurred at 15.2 MPa for which the effective hoop stress worked out to be 1754 MNm^–2 almost equal to the ultimate tensile strength (1764 MNm^–2) of the material in the solution treated and aged condition. The failure analysis revealed that the material failed due to normal tensile overload fracture. The burst test data was used to arrive at fracture mechanics parameters like crack size, gross section area stress and the stress for leak before bursting.     

Behavior of Np(VII,VI, V) in silicate solutions

Properties of Np(VII, VI, V) in silicate solutions were studied spectrophotometrically. In noncomplexing media, the Np(VII) cation transforms into the anionic species at pH 5.5–7.5. In the presence of carbonate ions, this rearrangement occurs at pH 10–11.5, and in silicate solutions, at pH 10.5–12.0. These data show that Np(VII) cation forms complexes with carbonate and silicate ions, the latter being stronger. From the competitive reactions of Np(VI) complex formation with carbonate and silicate ions, the stability of NpO₂SiO₃ complex was estimated (log = 16.5) using the known stability constant of NpO₂(CO₃) ₃ ^4– . Complexation of Np(V) with SiO ₃ ^2– ions was not detected by the methods used.Translated from Radiokhimiya, Vol. 46, No. 6, 2004, pp. 527–530.Original Russian Text Copyright © 2004 by Shilov, Fedoseev, Yusov, Delegard.     

Structure and Mechanical Properties of ZrCr2 Intermetallic Compound within the Temperature Range 20–1300°C

We studied the properties of ZrCr₂ intermetallic compound without crystallization cracks, obtained due to the introduction of excess zirconium (up to 2 at.%) with respect to the stoichiometric composition into the alloy. The melt was poured in a copper chill mold, and specimens for mechanical compression tests within the temperature range 900–1300°C were cut out of the castings. The short-term strength of intermetallic compound was _u = 665 and 140 MPa, and fracture took place mainly along the grain boundaries: below 1100°C, it was brittle, but, at higher temperatures (1200–1300°C), the plastic strain reached 5–7% prior to crack initiation and almost 30% before fracture. Plastic deformation is not accompanied by hardening. In the case of transcrystalline fracture, its type can be attributed to venous, which is characteristic of amorphous metallic materials.     

Corrosion behaviour of two stainless steels and a chromium cast iron in phosphoric acid contaminated with S2− ions

Various impurities such as Cl^–, F^–, SO ₄ ^2– and S^2– contained in natural phosphates or introduced by enrichment processes, lead to many corrosion problems in equipment during the production of phosphoric acid by a wet process. Little is known about the action of S^2– ions in acidic media. In an attemptto investigate the mechanism of action of S^2– ions on stainless steels, the corrosion behaviour of three types of steel 904 L (X1NiCrMoCu25-20-5), 316 L (X2CrNiMo17-12-2) and cast iron containing 32wt % Cr in industrial phosphoric acid contaminated with S^2– ions was studied, using polarization curve analysis. The characterization of the corrosion products formed on the sample surface has enabled the production of a hypothesis on the corrosion and depassivation mechanisms of steels in these media. The effect of copper and molybdenum on the corrosion resistance of the studied materials in phosphoric acid contaminated by S^2– ions is noted and discussed in detail.     

Magnetic hydrophobic affinity nanobeads for lysozyme separation

N-Methacryloyl-l-phenylalanine (MAPA) containing poly(2-hydroxyethylmethacrylate) based magnetic [mag-poly(HEMA–MAPA)] nanobeads was prepared for lysozyme purification form chicken egg white. MAPA was synthesized by reacting methacryloyl chloride with l-phenylalanine methyl ester and provided hydrophobic functionality to the nanobeads. Size of mag-poly(HEMA–MAPA) nanobeads was 386 nm and obtained by surfactant free emulsion polymerization of HEMA and MAPA having a specific surface area of 580 m²/g. Mag-poly(HEMA–MAPA) nanobeads were characterized by FTIR, AFM, TEM, ESR, and elemental analysis. Lysozyme adsorption experiments were investigated under different conditions in batch system (i.e., medium pH, protein concentration, temperature, salt type). Lysozyme adsorption capacity of mag-poly(HEMA) and mag-poly(HEMA–MAPA) nanobeads from aqueous solutions was estimated as 24 and 517 mg/g, respectively. Lysozyme molecules were desorbed with 50% ethylene glycol solution with 98% recovery. It was observed that mag-poly(HEMA–MAPA) nanobeads can be used without significant decrease in lysozyme adsorption capacity after ten adsorption–desorption cycles. Mag-poly(HEMA–MAPA) nanobeads was used for the purification of lysozyme from chicken egg white. Purity of lysozyme was estimated by SDS-PAGE.     

Evaluation of the potential of starch-based biodegradable polymers in the activation of human inflammatory cells

The inflammatory response resulting from the implantation of a medical device may compromise its performance and efficiency leading, in certain cases, to the failure of the implant. Thus, the assessment of the behavior of inflammatory cells in vitro, constitutes a key feature in the evaluation of the adverse potential, or not, of new promising biomaterials. The objectives of this study were to determine whether starch-based polymers and composites activated human neutrophils. Blends of starch with ethylene-vinyl alcohol, with cellulose acetate and polycaprolactone, as well as composites based on all these materials filled with hydroxyapatite have been studied. A lysozyme assay was adapted to examine enzyme secretion from human neutrophils incubated with different starch-based materials. Changes in the free radical and degranulation activity of the neutrophil were also determined by measuring the luminescent response of Pholasin®, a photoprotein that emits light after excitation by reactive oxygen species. The amount of lysozyme secreted by neutrophils incubated with the polymers did not exhibit significant differences between the tested materials. Results were in all cases similar to those obtained for the control (polypropylene) except for one of the starch blends (corn starch with polycaprolactone reinforced with 30% (w/w) of HA). The chemiluminescence experiments showed that polymers reduce the signal produced by activated neutrophils. Furthermore, for some polymers it was demonstrated that the phenomenon was due to an effect of the surface of the materials in cell adhesion or a simultaneous competition for the photoprotein in solution, which results in the decrease of the intensity of light emitted and detected.     

All-thin-film GeAu thermistors for particle detection

All-thin-film thermistors for thermal detection of nuclear radiation are described. Co-evaporated Ge _1–xAu_x films were deposited on 7.5·7.5·0.25 mm Si chips, along with highly interdigitated gold electrodes patterned using photolithography. Values of d(ln R)/d(lnT) greater than 6 were obtainable at any desired operating temperature by varying x. A device was tested at 0.019 K in which the 200-digit electrode pattern used gave a sensitive GeAu region 20 µm long in the bias field direction, 2000 Å thick and effectively 50 cm wide perpendicular to the bias field (L/A=2.0 cm^–1). The device had =6.5, G_e/ph=8·10^–12 W/K, heat capacity between 0.7 and 4.4·10^–12 J/K, and optimum bias power 1.5·10^–11 W. Thermal pulses from 60 KeV x-rays absorbed in the substrate at T0.07 K were easily detectible with this arrangement.     

Oxide impurity absorptions in Ge-Se-Te glass fibres

Oxide impurity absorptions in Ge-Se-Te glass fibres and the cause of the absorption loss around 943 cm^–1, the frequency of the CO² laser, have been investigated. The oxygen in the glass bounds preferentially to germanium and causes the absorptions due to Ge-O bond vibrations at 765 cm^–1 (band I) and 1230cm^–1 (band II). The excess absorptions due to these bands were determined as 0.228cm^–1/P.p.m. wt O₂ for band-I and 0.006cm^–1 /p.p.m. wt O₂ for band II. The loss of the fibre at 943cm^–1 increased with the oxygen content. It was, however, revealed from the deconvolution of the IR spectra into the independent absorption components that the absorption tails of band I and band II did not affect the loss at 943 cm^–1. The content of the impurities except oxygen analysed by a mass spectroscopy was too low to affect the loss at 943 cm^–1.     

Alloy softening in Ni3Al polycrystals

The alloying effect of boron on localized deformation in Ni₃Al polycrystals containing 24–26 at% AI was studied using microhardness indentation. Alloy softening was observed both along the grain boundaries and in the grain interior. The softening effect decreased as the aluminium concentration increased. For alloys of near-stoichiometric composition, the maximum effect occurred at about 0.23 at% (500 wt p.p.m.) boron. A softening mechanism based on cross slip of screw dislocations was proposed.     

EXAFS, magnetic, spectral, and thermal studies on a new polymeric copper mixed-valence compound with the 2-thioisoorotato bridging ligand

From the reaction, in aqueous medium, of 2-thioisoorotic acid and copper carbonate, an orange compound can be isolated. The formula unit contains only one copper and one 2-tioisoorotato anion. This compound has been studied by means of extended X-ray atomic force spectroscopy (EXAFS), magnetic measurements, spectral (infrared, electronic and electron paramagnetic resonance (EPR)) and thermal methods (thermogravimetry, differential scanning calorimetry, evolved gas infrared analysis). EXAFS measurements point out the existence of a first shell around the copper atoms formed by a sulphur atom (Cu–S 0.2209 nm) and two oxygen atoms (Cu–O 0.1947 nm). This coincides with the coordination mode proposed for the ligand from infrared data. The structure may be described as a chain-like structure in which the metal ions are bridged by 2-thioisoorotato anions through both oxygen atoms of the carboxylate group and the sulphur atom, (S2)]–Cu–[(O5,O5)–2-thioisoorotato–(S2)]–Cu–[(O5,O5). Also, the weak involvement of an endocyclic nitrogen atom in the four-membered chelate formation with the sulphur atom cannot be rejected except at distances Cu–N beyond 0.23 nm. Whereas EXAFS measurements detect the only presence of Cu(I), magnetic measurements indicate there is a mixture of valence states of copper atoms (10% CuII+90% CuI). On the other hand, the compounds exhibit an axial EPR spectrum which is typical from a magnetically diluted Cu(II) compound with a stronger ligand field in the equatorial plane. Finally, in order to determine the homogeneity of this compound, we have analysed this sample by electron microscopy. It is composed of spheres with radii ranging between 1.3 and 1.7 m and cylinders whose length ranges between 6 and 10 m and width between 1.2 and 1.6 m. Energy dispersive spectroscopic analysis was performed on several points and areas of this polymer. In all analyses, the ratio Cu : S was the expected 1 : 1 without any appreciable difference between spheres and cylinders. These results seem to indicate a similar composition in both morphologies, pointing to the presence of two polymorphic phases. This could be the reason for the unsuccessful attempts to obtain single crystals of this polymer to date. © 1998 Chapman & Hall     

Effect of environment on fatigue crack growth in ultrafine grain Al–Mg

The fatigue crack growth rates, obtained in high vacuum and in ambient air, of ultrafine grain (UFG) Al–7.5Mg (grain size  250 nm) at various load ratios were compared to those of powder-metallurgy (P/M) Al–7Mg (grain size  2 μm) and ingot-metallurgy (I/M) Al–7Mg (grain size  100 μm). In both vacuum and ambient air, fatigue crack growth rates at all stress ratios decrease with increasing grain size. The fatigue crack growth threshold (ΔK_th) follows the reverse order, increasing with increasing grain size. These trends are interpreted in terms of fracture surface roughness effects that are correlated with grain size. In vacuum, the thresholds of all three materials exhibit no load ratio dependency at load ratios from 0.1 to 0.5. In air, the threshold of UFG Al–7.5Mg exhibits weak load ratio dependency, while P/M and I/M Al–7Mg exhibit modest load ratio dependency. The environmental effect on the fatigue crack growth rates is assessed by determining the difference in crack growth driving force (ΔK) between air and vacuum. It was found that the environmental contribution to the driving force of all three materials is similar, nearly independent of grain size.     

Electrical conductivity of sol-gel derived metal nanoparticles

Electrically conducting films of thickness 2 m have been prepared on ordinary glass slides by growing ultra-fine particles of iron and copper, respectively, from a suitable precursor sol. The diameters of metal particles can be varied from 3–13 nm by controlling the heat-treatment schedule of the sol coating. Resistivity measurements (d.c.) have been carried out over the temperature range 80–300 K. The resistivity values in the range 0.0001–0.0039 cm have been obtained depending on the particle diameter and the type of metal used. The effective Debye temperature _D for the different nanoparticle systems have been estimated by fitting the experimental data to the Ziman equation. _D is found to vary from 346–408 K for iron with the particle size in the range 3.4–9.5 nm. The values obtained for copper are 243–307 K with particle diameters covering a range of 5.9–12.6 nm.     

Sputtering of two-phase AgxCux alloys

Elemental sputtering yields from two phase AgCu alloys were measured for 20, 40 and 50 at% Ag. Argon ion bombardment energies were in the range 35–55 keV and the ion dose was 1×10¹⁹ ions cm^–2. The sputtering yield for silver was found to be considerably below what was expected by simple selective sputtering of a two component alloy. Analysis by electron probe X-ray microanalysis and scanning electron microscopy of the eroded surface indicated that surface diffusion of copper from copper rich grains and geometrical constraints in the dense cone forest on Cu/Ag eutectic regions combine to reduce the sputtering yield for silver.     

Characterization of yttria-stabilized zirconia thin films deposited by electron beam evaporation on silicon substrates

Structure, phase composition and electrical conductivity of thin yttria-stabilized zirconia (YSZ) films deposited by electron beam evaporation on a silicon (1 0 0) substrate at different temperatures i.e. room temperature (r.t.), 700 and 830°C, as well as the quality of the YSZ–Si interface have been investigated. The phase composition was verified by Raman spectroscopy and by infrared (i.r.) transmission measurements. The structure of films changed in agreement with their electrical conductivity depending on the deposition temperature. Both structure and thereby electrical conductivity were influenced by the high concentration of Y2O3 stabilizer used and by the post-deposition thermal treatment of films. The deposition temperature was also important in determining the quality of the YSZ–Si interface and hence the accessible sweep of the surface potential. The capacitance–voltage characteristics of the metal–insulator–semiconductor (MIS) structures incorporating YSZ films measured at r.t. showed hysteresis and positive shifts of the flat-band voltages. © 1998 Chapman & Hall     

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.     

The preparation,characterization and electrical properties of copper manganite spinels,CuxMn3−xO4, 0 ⩽x ⩽ 1

Single-phase copper manganite spinels Cu _x Mn_3–x O₄ with 0x1 were prepared by a careful thermal processing of copper-manganese co-precipitated hydroxide precursors. Powder X-ray diffraction (XRD) analysis of these spinels revealed the presence of a tetragonally distorted single spinel phase, with tetragonal distortionc/a > 1 which decreases with copper content. Thermogravimetric analysis (TGA) curves, run in an oxygen atmosphere for all the compositions studied, are characterized by a stability step up to 250 to 300° C, followed by a domain of oxidation between 300 and 900° C and finally a domain of reduction that restores the initial stoichiometry of the samples. The oxidation is observed to occur in two successive steps. The phenomenon appearing at the low temperature is due to the oxidation of Cu⁺ ions, while that at higher temperature corresponds to the oxidation of Mn²⁺ ions in tetrahedral sites. Further, electrical resistivity measurements confirm the presence of Cu⁺ ions on the tetrahedral sublattice of spinel. Correlation of the results obtained by XRD, TGA and electrical resistivity measurements permits one to infer the cation distribution, given by Cu _x ⁺ Mn _1–x ²⁺ [Mn _2–x ³⁺ Mn _x ⁴⁺ ] O ₄ ^2– .