Human tissue allograft processing: impact on in vitro and in vivo biocompatibility

This work investigates the impact of chemical and physical treatments on biocompatibility for human bone/tendon tissues. Nontreated and treated tissues were compared. In vitro testing assessed indirect and direct cytotoxicity. Tissues were subcutaneously implanted in rats to assess the immunological, recolonization, and revascularization processes at 2–4 weeks postimplantation. No significant cytotoxicity was found for freeze-dried treated bones and tendons in comparison to control. The cellular adhesion was significantly reduced for cells seeded on these treated tissues after 24 h of direct contact. A significant cytotoxicity was found for frozen treated bones in comparison to freeze-dried treated bones. Tissue remodeling with graft stability, no harmful inflammation, and neo-vascularization was observed for freeze-dried chemically treated bones and tendons. Frozen-treated bones were characterized by a lack of matrix recolonization at 4 weeks postimplantation. In conclusion, chemical processing with freeze-drying of human tissues maintains in vitro biocompatibility and in vivo tissue remodeling for clinical application.     

Irregularity in NbTi filament area and electric field versus current characteristics

There is a correlation between irregularity in filament area (‘sausaging’) and the shape of a superconductor's electric field (E) versus current (I) relationship. The shape of the E−I characteristic is quantified in terms of the resistive transition parameter, n, defined by E∝Iⁿ. Low values of n less than about 20 correlate with a wide filament diameter distribution, while n values over 50 correspond to a distribution more than 2.5 times smaller. It is proposed that the low-field (constant) value of n be used as an index of filament quality in evaluating different superconductors for practical applications. A model is also suggested to explain this effect in terms of a locally depressed filament critical current, which forces current to transfer across the normal matrix material into neighbouring filaments. The relationship between n and the statistical distribution of filament diameters may be useful as an easy method of estimating the extent of sausaging in practical multifilamentary NbTi superconductors from measurements of n.     

Phonon generation in KCl:Li+ and KCl:OH− with pulsed electric fields

A pulsed electric field technique has been developed to explore the possibility of using electrically polarizable tunneling defects in crystals as generators of short pulses of phonons of discrete, tunable frequencies, and has been applied to KCl:Li⁺ and KCl:OH^–. Phonons generated by the application of highvoltage pulses to one end of an impurity-doped sample are studied using bolometric detection. By measuring defect-lattice relaxation times it is concluded that in both KCl:Li⁺ and KCl:OH^– at least half of the detected phonon energy is a result of generation at discrete frequencies. The remainder of the signal may be a result of panchromatic generation produced by other relaxation processes faster than could be resolved ( 1 nsec). Low-field relaxation times of 8 and 6.5 nsec were obtained for KCl:Li⁺ and KCl:OH^– respectively, in reasonable agreement with previous estimates obtained with other techniques. These times exhibit electric field and temperature dependences consistent with a single-phonon relaxation model. Scattering by the Li⁺ and OH^– impurities resulted in considerable temporal broadening of the phonon pulses.Work supported by the U.S. Atomic Energy Commission under Contract AT(11-1)-3151, Technical Report No. CH-3151-139. Additional support was received from the Advanced Research Projects Agency through the use of space and technical facilities of the Materials Science Center at Cornell University, MSC Report No. 1714.     

Role of Coexistence of Superconductivity and Paramagnetism in Magnetostriction of High-T c Superconductors

Total magnetostriction in the superconducting state for high T _c superconductors has been separated into critical state and paramagnetic components in terms of a H(x) dependent magnetic flux density. We show that the paramagnetic part is χ(2+χ)〈H(x)²〉, where χ is paramagnetic susceptibility. We have reproduced successfully ΔL/L−H _a curves measured by de la Fuente et al. (Phys. C 244:214, [1995]), in which they clearly observed coexistence of superconductivity and paramagnetism, employing the concepts presented in this work.      

Application of dispersion–solidification liquid–liquid microextraction for the determination of triazole fungicides in environmental water samples by high-performance liquid chromatography

A simple, rapid and environmentally friendly method has been developed for the determination of four triazole fungicides (myclobutanil, tebuconazole, triadimenol, hexaconazole) in water samples by dispersion–solidification liquid–liquid microextraction coupled with high performance liquid chromatography-diode array detection. Several variables that affect the extraction efficiencies, including the type and volume of the extraction solvent and dispersive solvent, extraction time, effect of pH and salt addition, were investigated and optimized. Under the optimum conditions, the proposed method is sensitive and shows a good linearity within a range of 0.5–200 ng mL⁻¹, with the correlation coefficients (r) varying from 0.9992 to 0.9998. High enrichment factors were achieved ranging from 190 to 450. The recoveries of the target analytes from water samples at spiking levels of 1.0, 5.0 and 50.0 ng mL⁻¹ were between 84.8% and 110.2%. The limits of detection (LODs) for the analytes were ranged in 0.06–0.1 ng mL⁻¹, and the relative standard deviations (RSD) varied from 3.9% to 5.7%. The proposed method has been successfully applied for the determination of the triazole fungicides in real water samples.     

Effect of high-density electric current pulses on precipitation and mechanical properties of a Cu–Zn alloy

ABSTRACT

By applying high-density electric current pulses (ECP) on the Cu–Zn alloy, the high-temperature precipitated phase is explored and the related mechanical properties are investigated. Results show that the nucleation rate of the high-temperature β precipitation can be greatly accelerated due to the ECP treatment. Especially, an obvious orientation relationship can be detected between the matrix α phase and the product β precipitation by increasing the electric current density. In addition, for the samples with a dense distribution of refined β precipitation, a slight decrease in the tensile strength and a great increase in the elongation-to-failure can be observed.

This paper is part of a themed issue on Materials in External Fields.     

Preparation of Cf/Cu–C contact strip and wear behaviour under electric current

A novel carbon and copper fibre knitted fabric (C_f/Cu) reinforced contact strip (C_f/Cu–C) was fabricated by pyrolytic carbon deposition and resin impregnation–carbonisation process. The interface characteristics of the composite were characterised by a scanning electron microscope and a metallographic microscope; resistivity, mechanical strength and wear properties with electric current were also investigated. The results indicated that the C_f/Cu–C material with density of 1.73?g?cm^??3 combined quite well between phase contacting areas for each interface. With resistivity of 10.16?μΩ?m and bending strength of 123?MPa, the as prepared composite outperformed the present AR129 carbon contact strip (density, 1.70?g?cm^??3, resistivity, 33?μΩ?m; bending strength, 40?MPa). The wear mechanisms of C_f/Cu–C with electric current were proved to be slightly arc erosion and abrasive wear.     

Effect of in situ phases on microstructure and properties in Al–Bi immiscible alloy

Al–Bi immiscible alloy is of particular interest as potential self-lubricating wear materials with a homogeneous distribution of minority phase. However, it is difficult to obtain a homogeneous microstructure by conventional casting methods due to liquid phase separation of Al–Bi immiscible alloy. We have developed a new strategy to restrain liquid phase separation and improve the properties of Al–Bi immiscible alloy by in situ phases. The in situ AlB₂ phase acts as heterogeneous nucleation site to accelerate the nucleation and slow down the velocity of the Bi-rich droplet, resulting in a significant size reduction and a homogeneous microstructure of Al–Bi immiscible alloy. The self-lubricating wear resistance of Al–Bi immiscible alloy can be further enhanced by in situ Al₂Cuphase.     

Evaluation of polyethersulfone highflux hemodialysis membrane in vitro and in vivo

A new hemodialysis membrane manufactured by a blend of polyethersulfone (PES) and polyvinylpyrrolidone (PVP) was evaluated in vitro and in vivo. Goat was selected as the experimental animal. The clearance and the reduction ratio after the hemodialysis of small molecules (urea, creatinine, phosphate) for the PES membrane were higher in vitro than that in vivo. The reduction ratio of β₂-microglobulin was about 50% after the treatment for 4 h. The biocompatibility profiles of the membranes indicated slight neutropenia and platelet adhesion at the initial stage of the hemodialysis. Electrolyte, blood gas, and blood biochemistry were also analyzed before and after the treatment. The results indicated that PES hollow fiber membrane had a potential widely use for hemodialysis.     

Biocompatibility of polyhydroxybutyrate microspheres: in vitro and in vivo evaluation

Microspheres have been prepared from the resorbable linear polyester of β-hydroxybutyric acid (polyhydroxybutyrate, PHB) by the solvent evaporation technique and investigated in vitro and in vivo. Biocompatibility of the microspheres has been proved in tests in the culture of mouse fibroblast cell line NIH 3T3 and in experiments on intramuscular implantation of the microspheres to Wistar rats for 3 months. Tissue response to the implantation of polymeric microspheres has been found to consist in a mild inflammatory reaction, pronounced macrophage infiltration that increases over time, involving mono- and poly-nuclear foreign body giant cells that resorb the polymeric matrix. No fibrous capsules were formed around polymeric microparticles; neither necrosis nor any other adverse morphological changes and tissue transformation in response to the implantation of the PHB microparticles were recorded. The results of the study suggest that polyhydroxybutyrate is a good candidate for fabricating prolonged-action drugs in the form of microparticles intended for intramuscular injection.     

Advance and Application of Thermal Spraying in Machinery Maintenance

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Pulse electric current sintering of hydroxyapatite/β-tricalcium phosphate composites

Hydroxyapatite (HA)/β-tricalcium phosphate (β-TCP) composites attract attentions as bone implant materials. As one of the fabrication method of HA/β-TCP is mixing of HA and β-TCP powder in advance of sintering. This method enables to control the ratio of content of β-TCP easier. However, it is difficult to obtain dense composites. In this study, we focused on pulse electric current sintering (PECS) to obtain dense HA/β-TCP composites. The sinterability is evaluated with relative density and grain size measurements. Composition of sintered body was also characterized by X-ray diffraction. In comparison with pressureless sintering, PECS increased relative density of the composites without grain growth. In HA/β-TCP sintered by PECS, the phase transformation from β-TCP to α-TCP was promoted. This is due to higher thermal energy by spark discharge during PECS. On the other hand, sintering additives (MgO) inhibited phase transformation. It was suggested that sinterability of HA/β-TCP composites was improved by PECS.     

Revealing molecular-level surface structure of amyloid fibrils in liquid by means of frequency modulation atomic force microscopy

We have investigated the surface structure of islet amyloid polypeptide (IAPP) fibrils and α-synuclein protofibrils in liquid by means of frequency modulation atomic force microscopy (FM-AFM). ?ngstr?m-resolution FM-AFM imaging of isolated macromolecules in liquid is demonstrated for the first time. Individual β-strands aligned perpendicular to the fibril axis with a spacing of 0.5?nm are resolved in FM-AFM images, which confirms cross-β structure of IAPP fibrils in real space. FM-AFM images also reveal the existence of 4?nm periodic domains along the axis of IAPP fibrils. Stripe features with 0.5?nm spacing are also found in images of α-synuclein protofibrils. However, in contrast to the case for IAPP fibrils, the stripes are oriented 30° from the axis, suggesting the possibility of β-strand alignment in protofibrils different from that in mature fibrils or the regular arrangement of thioflavin T molecules present during the fibril preparation aligned at the surface of the protofibrils.     

Spiral superconducting NbTi filaments: electric field and critical current

As a first step to a better understanding of the voltage—current characteristics of fine filament multifilamentary composite superconductors, the electric field and critical current along a single spiral-shaped filament were studied. When the spiral superconducting filament was carrying constant current and placed in a magnetic field, the local critical current and electric field vary due to the change of the angle between the magnetic field and filament axis. A theory is presented which enables us to calculate the mean and local values of the electric field and critical current of spiral samples for arbitrary orientation between the magnetic field and spiral axis. The presented experimental results are in good agreement with this theory.     

Application of gas chromatography mass spectrometry with preliminary dispersive liquid–liquid microextraction for the determination of low contents of rocket kerosene in water

A procedure for sensitive determination of rocket kerosene in water is described; it includes the dispersive liquid–liquid microextraction of analytes followed by their separation and determination by gas chromatography mass spectrometry in the mode of chromatogram registration against selected ions (m/z: 67, 81, 85, 95, 136, 137, 174, 183, and 193). The effect of the nature and volume of disperser and extraction solvents, salt additives, and the extraction duration on the efficiency of extraction of analytes is studied. The detectable concentration range is 0.005–0.05 mg/L. The detection limits (S/N = 3) of kerosene RG-1 and T-1 are 0.0015 and 0.0022 mg/L, respectively. The repeatability of the measurement results for the above range varies from 16 to 9% (n = 3); the intermediate precision varies from 20 to 12% (n = 5).     

The Application of Standardization System in Corporate Management and Administration

This paper briefly discusses three important components of corporate standardization system and their functions and how such a system can be used in corporate management and administration. It also offers certain solutions and suggestions to some of the existing problems in the process of implementing corporate standardization system.     

Dispersion-Induced Splitting of the Collective Mode Spectrum in Axial and Planar Phases of Superfluid 3He

The whole collective mode spectrum in axial and planar phases of superfluid ³He with dispersion corrections is calculated for the first time. In axial A-phase the degeneracy of clapping modes depends on the direction of the collective mode momentum k with respect to the vector l (mutual orbital moment of Cooper pairs), namely: the mode degeneracy remains the same as in case of zero momentum k for k‖l only. For any other directions there is a threefold splitting of these modes, which reaches maximum for k ⊥ l. In planar 2D-phase, which exists in the magnetic field (at H>H _C ) we find that for clapping modes the degeneracy depends on the direction of the collective mode momentum k with respect to the external magnetic field H, namely: the mode degeneracy remains the same as in case of zero momentum k for k‖H only. For any other directions different from this one (for example, for k ⊥ H) there is twofold splitting of these modes. The obtained results imply that new interesting features can be observed in ultrasound experiments in axial and planar phases: the change of the number of peaks in ultrasound absorption into clapping mode. One peak, observed for these modes by Ling et al. (J. Low Temp. Phys. 78:187, 1990), will split into two peaks in a planar phase and into three peaks in an axial phase under the change of ultrasound direction with respect to the external magnetic field H in a planar phase and with respect to the vector l in an axial phase. In planar phase, some Goldstone modes in the magnetic field become massive (quasi-Goldstone) and have a similar twofold splitting under the change of ultrasound direction with respect to the external magnetic field H. The obtained results as well will be useful under interpretation of the ultrasound experiments in axial and planar phases of superfluid ³He.     

Quasi‐static analysis of electric and magnetic fields in tem cell

Abstract

A method is presented whereby the electric and magnetic fields within a rectangular coaxial transmission line (TEM cell) can easily be obtained. The analysis is based on the variational technique in the space domain combined with the Green's function method. Numerical data are presented for the characteristic impedance and for the field distributions within the cell. The results calculated by the present method are found to be in good agreement with those in open literature.     

The controlling biodegradation of chitosan fibers by N-acetylation in vitro and in vivo

Aim In the present study, we investigated the biodegradation of the fibers of chitosan and its acetylated derivatives in vitro and in vivo. Methods A series of chitosan fibers, with acetylation degrees of 7.7%, 21.6%, 40.9%, 61.2%, 82.5% and 93.4%, were obtained by acetylating chitosan filament with acetic anhydride, and were investigated by FT-IR analysis, elemental analysis and scanning electron microscopy analysis. Results The in vitro experimental data indicated that the degradation rate of chitosan fiber was strongly dependent on the degree of acetylation, and the degradation rate increased with an enhancement of the acetylation degree of chitosan fibers. In vivo degradation experiment evaluated by light microscopy as well as scanning electron microscopy, was studied by implanting the fibers between the two nerve stumps of the rat sciatic nerve gap (6 months). The findings demonstrated that acetylation degree could influence the degradation rate of chitosan fibers in vivo. Conclusion These results suggested that acetylated chitosan (chitin) fibers were more biodegradable than chitosan and the biodegradation rate of chitin fiber can be controlled to desirable extent by the variation of acetylation degree.