Low friction total knee arthroplasty with the alumina ceramic condylar prosthesis

This paper evaluates the failure and wear properties of the alumina ceramic posterior cruciate condylar total knee prosthesis, and reports the preliminary clinical results of this prosthesis. Thirteen sets of the alumina ceramic prostheses were used for destruction and wear tests. The average ultimate load in the static destruction tests showed 2.63 x 10(4) Newtons in the femoral component, and 1.28 x 10(4) Newtons in the tibial component. The average ultimate energy in the impact destruction tests showed 22.1 Joules in the femoral components, and 20.3 Joules in the tibial components. The wear test demonstrated that the average depth of wear was 0.04 mm in the alumina ceramic prostheses, and 0.20 mm in the Vitallium prostheses. Observation of the UHMWPE wear surface with a scanning electron microscope indicated many deep scratches and a scooped concave lesion in the Vitallium prostheses; there were few deep scratches in the alumina ceramic prostheses. Thirty patients underwent 32 total knee arthroplasties using the alumina ceramic posterior cruciate condylar prosthesis between 1988 and 1990. The results were evaluated as excellent for 59%, good for 28%, fair for 10%, and poor for 3%. Critical roentgenographic review demonstrated no cases of loosening or sinking after arthroplasties using the alumina ceramic prosthesis. Radiolucent lines were observed only in 4 knees (12%) cases. All were observed around the tibial components, but were less than 1 mm in thickness. The frequency of the radiolucent lines is less than that observed in the Vitallium prosthesis at the same followup period. The alumina ceramic posterior cruciate condylar prosthesis may have sufficient durability and excellent wear properties for low friction total knee arthroplasty.     

Two novel oleanolic acid saponins having a sialyl Lewis X mimetic structure from Achyranthes fauriei root

Two novel triterpene glycosides, achyranthosides E and F, were isolated as methyl esters from the root of Achyranthes fauriei, an antiinflammatory medicinal plant. Their structures were characterized as oleanolic acid glucuronides having unique substituents composed of C6H9O5 and C9H15O7, respectively, at the C-3 position of glucuronic acid. These compounds are active components which can inhibit the excess recruiting of neutrophiles to injured tissues 1,000 times more potently than sialyl Lewis X.     

Phosphorylation of the G protein gamma12 subunit regulates effector specificity

Although the G protein betagamma dimer is an important mediator in cell signaling, the mechanisms regulating its activity have not been widely investigated. The gamma12 subunit is a known substrate for protein kinase C, suggesting phosphorylation as a potential regulatory mechanism. Therefore, recombinant beta1 gamma12 dimers were overexpressed using the baculovirus/Sf9 insect cell system, purified, and phosphorylated stoichiometrically with protein kinase C alpha. Their ability to support coupling of the Gi1 alpha subunit to the A1 adenosine receptor and to activate type II adenylyl cyclase or phospholipase C-beta was examined. Phosphorylation of the beta1 gamma12 dimer increased its potency in the receptor coupling assay from 6.4 to 1 nM, changed the Kact for stimulation of type II adenylyl cyclase from 14 to 37 nM, and decreased its maximal efficacy by 50%. In contrast, phosphorylation of the dimer had no effect on its ability to activate phospholipase C-beta. The native beta1gamma10 dimer, which has 4 similar amino acids in the phosphorylation site at the N terminus, was not phosphorylated by protein kinase C alpha. Creation of a phosphorylation site in the N terminus of the protein (Gly4 --> Lys) resulted in a beta1 gamma10G4K dimer which could be phosphorylated. The activities of this beta gamma dimer were similar to those of the phosphorylated beta1 gamma12 dimer. Thus, phosphorylation of the beta1 gamma12 dimer on the gamma subunit with protein kinase C alpha regulates its activity in an effector-specific fashion. Because the gamma12 subunit is widely expressed, phosphorylation may be an important mechanism for integration of the multiple signals generated by receptor activation.     

Morphological change in FePt nanogranular thin films induced by swift heavy ion irradiation

We have investigated morphology change of FePt nanogranular films (FePt)₄₇(Al₂O₃)₅₃ under irradiation with 210 MeV Xe ions. Here, electron tomography technique was extensively employed to clarify three-dimensional (3D) structure in irradiated specimens, in addition to conventional transmission electron microscopy (TEM) techniques such as bright-field observation and scanning TEM energy dispersive X-ray spectroscopy (STEM-EDX) analysis. The ion irradiation induces the coarsening of FePt nanoparticles with elongation along the beam direction. Electron tomography 3D reconstructed images clearly demonstrated that when the fluence achieves 5.0 × 10¹⁴ ions/cm², well-coarsened FePt balls have been formed on the irradiated surface, and the particles in the film interior have been deformed into rods along the ion trajectory. The alloy particles become inhomogeneous in composition after prolonged irradiation up to 1.0 × 10¹⁵ Xe ions/cm². The particle center is enriched with Pt, while Fe is slightly redistributed to the periphery.     

Plasma polymerization of tetrafluoroethylene. II. Capacitive radio frequency discharge

The plasma polymerization of tetrafluoroethylene (TFE) is studied in a capacitively coupled system with internal electrodes using radio frequency (13.56 MHz) power. The emphasis is on identifying conditions that are compatible with continuous coating of plasma polymer on a substrate moving through the center of the interelectrode gap. At high pressure (500 mTorr), deposition of plasma polymer is primarily on the electrodes rather than on a substrate placed midway between electrodes. Glow is observed in only part of the interelectrode gap at low powers and fills the gap only at high power levels. The use of a magnetic field effects barely discernible changes. Low-pressure (below 100 mTorr) operation is more favorable for deposition of a substantial portion of the plasma polymer on a substrate placed midway between electrodes. The plasma polymer deposited at low pressure is characterized by ESCA and deposition rate data and compared to that deposited in an inductively coupled system. The polymers formed in both systems are broadly similar and completely different from conventional poly(TFE). Subtle system-dependent differences are identified. The known susceptibility of fluorine-containing polymers (including plasma polymer) to a high-power plasma has been used as a probe of plasma power density within the interelectrode gap in the capacitively coupled system. Without magnets the most active zone of the plasma is in the center of the interelectrode gap. The use of a magnetic field moves this active zone closer to the electrodes and leads to a more efficient coupling of energy to a polymerizing glow discharge.     

Barrier coatings on cellulose fiber mat

Two techniques were used in the deposition of thin, pinhole-free vapor barriers upon a Kraft fiber mat without affecting its combustibility properties. One technique involved a collodion spray precoating followed by low pressure styrene plasma coating, and the other involved a collodion spray coating. In the formation of the above coatings, two functional steps are essential: (1) surface pore covering, and (2) nonporous barrier formation.     

New carbon composites containing ultrafine metal particles. 2. Synthesis by pyrolisis of pitch-organometallic blends

Air-stable new carbon composites containing uniformly dispersed ultrafine Fe, Co, Ni, Ru, Pd, Rh, or Ag particles were obtained by thermal degradation of coal pitches mixed homogeneously with 1–10% of poly(vinyl ferrocene), cobaltocene, nickelocene, (acenaphthylene) Ru₃(CO)₇, PdCl₂(COD), RhCp(COD), and AgC₆H₄CH₂NMe₂, respectively, at 400–1200°C in Ar. Carbonization yields are 45–55% and the size of metal particles varied from 5 to 65 nm depending upon the treatment temperature and identity of the metal. The carbon composites containing Fe particles showed high Vicat hardness and good electrical conductivity. Pd- and Rh-dispersed materials exhibited good catalysis in hydrogenation of 1-hexene. The composite containing ultrafine Ag particles showed excellent bacteriostatic activity forEscherichia coli, Pseudomonas aeruginosa, andBatchillus subtilis.     

Mass transfer through the deposited asbestos diaphragm in chlor-alkali cells

Electrolysis of saturated NaCl solution was carried out in laboratory cells to investigate mass transfer through the deposited asbestos diaphragm under operating conditions similar to those of practical cells. It was found that hydrogen bubbles generated on the cathode screen penetrated into the asbestos mat, and significantly disturbed the brine flow.     

Diffusive and bulk flow transport in polymers

The transport properties of polymer membranes in various forms which have a wide variety of practical applications, such as ultrafiltration, dialysis and blood oxygenation, depend upon the structure (homogeneous or heterogeneous) and the transport characteristics of the membrane material. Among many possible driving forces of transport, the pressure gradient and the concentration gradient are considered to be the most general forces encountered in practical use of polymer membranes. The transport of various permeants (gas, dissolved gas, liquid solvent, and solute) through porous and homogeneous (nonporous) polymer membranes under these driving forces is discussed. In the absence of a pressure gradient, the transport of permeants can be described as diffusion, regardless of the permeant phase and the membrane structure. In the presence of a pressure gradient, the transport of permeants may occur by diffusion and/or bulk flow of the permeants, depending upon the membrane structure and the nature of the permeant. In homogeneous membranes, many noninteracting permeants such as gases and nonsolvent vapors permeate by diffusion under applied pressure gradient: however, solvent in homogeneously swollen membranes moves by bulk flow and the diffusion depending on the degree of swelling of the membrane. In heterogeneous membranes under applied pressure, most permeants move by bulk flow.     

Polymerization in an electrodeless glow discharge. III. Organic compounds without olefinic doublebond

The rates of polymer deposition from various organic compounds which do not contain an olefinic doublebond in an electrodeless glow discharge were studied. The polymerization rates of these unconventional monomers are by and large similar to those of olefinic monomers reported in the previous study (part II). The rate of polymer deposition R₀ from pure monomer flow can be characterized, according to the analysis used in part II, by R_o = apM² and R₀ = kF_w, where pM is the vapor pressure of the monomer, F_w is the weight basis flow rate of the monomer. Type A monomers which predominantly polymerize and type B monomers which decompose in a glow discharge were also found with these unconventional monomers. The effects of structural factors on the values of a amd k and on the classification of types A and B were examined. These structures and groups—aromatic, heteroaromatic, nitrogen-containing (e.g., >NH,? NH₂,? CN), Si-containing, and olefinic doublebond—favor the polymerization. These structures and groups—oxygen-containing chlorine, aliphatic hydrocarbon chains, and cyclic hydrocarbon chains—favor the decomposition of the monomer in a glow discharge. It is postulated that the polymerization of organic compounds proceed by the recombination of excited species (probably free radicals) created by glow discharge and reexcitation followed by further recombinations in the vapor phase and at the interface.