Friction transfer and self-lubrication of polymers

Current research into the friction transfer mechanism and self-lubrication of polymers is analyzed. The main theoretical and experimental results that characterize friction transfer quantitatively and qualitatively are discussed. Analytical models based on the molecular-mechanical theory of friction and the adhesion-energetic mechanism of friction transfer are used to find the basic tribological characteristics of metal-polymer friction units. The nature of mass transfer is considered with account for the effect of the material composition, structure, and surface topography, and some other parameters of the transfer kinetics.     

Copolymers of aniline and o‐methoxyaniline: Synthesis and characterization

High‐conversion (HC) copolymers of aniline and o‐methoxyaniline (o‐anizidine) were synthesized for the first time by chemical oxidative copolymerization using various polymerization techniques (simultaneous or consecutive introduction of comonomers into the polymerizing system). Low‐conversion (LC) copolymers have also been synthesized for comparison. The polymers obtained were characterized using ¹H‐NMR, infrared, and electronic absorption spectroscopy, differential scanning calorimetry, and electrical conductivity measurements. Solubility characteristics and composition of different fractions of the copolymers were also determined. It was shown that in contrast to the LC copolymers, HC copolymers reveal relatively poor solubility. Electrical conductivity of copolymers and also of o‐methoxyaniline homopolymer is lower compared to polyaniline, which correlates with notable hypsochromic (blue) shift of the bands in electronic absorption spectra. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 75–81, 2006     

Potentiometric sensing of chemical warfare agents: surface imprinted polymer integrated with an indium tin oxide electrode

Rapid and specific recognition of methylphosphonic acid (MPA), the degradation product of nerve agents sarin, soman, VX, etc., was achieved with potentiometric measurements using a chemical sensor fabricated by a surface imprinting technique coupled with a nanoscale transducer, indium tin oxide (ITO). An octadecylsiloxane thin layer was covalently bound to the ITO-coated glass surface in the presence of MPA. After extraction of MPA, potentiometric measurements showed selective detection of MPA. The selectivity of the sensor has been tested on other alkylphosphonic acids, such as ethylphosphonic acid and propylphosphonic acid, as well as tert-butylphosphonic acid. The viability of the sensor in the presence of other chemical analogues, such as organophosphorus pesticides and herbicides, was investigated.     

Theoretical study and 2D computational modeling of middle-infrared radiation generation in the field of few-cycle laser pulse propagating in GaSe slab waveguide

We have performed the theoretical study and 2D finite-difference time-domain-based computational modeling of middle-infrared radiation generation in the field of few-cycle laser pulse propagating in GaSe slab waveguide. The interaction of linearly polarized pulse with 1.98 um central wavelength, 22.44 fs duration, and electric field amplitudes 100 MV/m, propagated along the [010] crystalline direction of GaSe crystal with polarization aligned along [100] is considered. The crystal length chosen is equal to 21.78 um. Symmetric GaSe slab waveguides with 6.336 um, 7.92 um, 11.88 um, and 15.84 um thicknesses excited by the Gaussian pump beams with 3.96 um, 5.94 um, 8.91 um, and 11.88 um diameters, respectively, are considered. The 2D distributions of the electric fields are obtained by numerical integration of Maxwell’s equations’ systems. The spatially spectral normalized distributions of the electric fields are obtained. The efficiency of generated infrared (IR) radiation vs. spatial transverse coordinate is obtained.     

High-frequency properties of high-T c Josephson junctions and mixing experiments in the W-band

We report on the high frequency properties of high-T_c superconductor (HTS) Josephson junctions using mixing experiments in the frequency range 78 GHz-119 GHz. Experiments with YBa₂Cu₃O₇ (YBCO) step-edge (SEJ) and bicrystal junctions on LaAlO₃ and MgO substrates have been performed. In order to achieve optimal junction properties we performed an oxygen plasma treatment. Junctions with RSJ-like current voltage characteristics were mounted into a heterodyne mixing setup. We obtained conversion efficiencies around-40 dB and heterodyne mixing response above 1 THz. For SEJs we observed mixing response related to a second junction in series. We also investigated self-mixing properties.     

Scheduling and Priority Mapping for Static Real-Time Middleware

This paperpresents a middleware real-time scheduling technique for static,distributed, real-time applications. The technique uses globaldeadline monotonic priority assignment to clients and the DistributedPriority Ceiling protocol to provide concurrency control andpriorities for server execution. The paper presents a new algorithmfor mapping the potentially large number of unique global prioritiesrequired by this scheduling technique to the restricted set ofpriorities provided by commercial real-time operating systems.This algorithm is called Lowest Overlap First Priority Mapping;we prove that it is optimal among direct priority mapping algorithms.This paper also presents the implementation of these real-timemiddleware scheduling techniques in a Scheduling Service thatmeets the interface proposed for such a service in the Real-TimeCORBA 1.0 standard. Our prototype Scheduling Service is integratedwith the commercial PERTS tool that provides schedulability analysisand automated generation of global and local priorities for clientsand servers.     

In vitro adhesion of staphylococci to diamond-like carbon polymer hybrids under dynamic flow conditions

This study compares the ability of selected materials to inhibit adhesion of two bacterial strains commonly implicated in implant-related infections. These two strains are Staphylococcus aureus (S-15981) and Staphylococcus epidermidis (ATCC 35984). In experiments we tested six different materials, three conventional implant metals: titanium, tantalum and chromium, and three diamond-like carbon (DLC) coatings: DLC, DLC–polydimethylsiloxane hybrid (DLC–PDMS-h) and DLC–polytetrafluoroethylene hybrid (DLC–PTFE-h) coatings. DLC coating represents extremely hard material whereas DLC hybrids represent novel nanocomposite coatings. The two DLC polymer hybrid films were chosen for testing due to their hardness, corrosion resistance and extremely good non-stick (hydrophobic and oleophobic) properties. Bacterial adhesion assay tests were performed under dynamic flow conditions by using parallel plate flow chambers (PPFC). The results show that adhesion of S. aureus to DLC–PTFE-h and to tantalum was significantly (P < 0.05) lower than to DLC–PDMS-h (0.671 ± 0.001 × 10⁷/cm² and 0.751 ± 0.002 × 10⁷/cm² vs. 1.055 ± 0.002 × 10⁷/cm², respectively). No significant differences were detected between other tested materials. Hence DLC–PTFE-h coating showed as low susceptibility to S. aureus adhesion as all the tested conventional implant metals. The adherence of S. epidermidis to biomaterials was not significantly (P < 0.05) different between the materials tested. This suggests that DLC–PTFE-h films could be used as a biomaterial coating without increasing the risk of implant-related infections.     

X-Ray Visualized Sensors for Peritoneal Dialysis Catheter Infection

Peritonitis is a common complication for patients with end-stage renal disease undergoing peritoneal dialysis (PD) and is a direct cause or contributor in >15% deaths in PD patients. Since early detection is key to treatment, patients and their care teams need rapid, on-site diagnostics. A hydrogel-based peritoneal fluid pH sensor attached to a peritoneal dialysis catheter is developed to measure local acidosis indicative of peritoneal infections for early detection and monitoring of infections using X-ray imaging. The sensor comprises a polyacrylic acid hydrogel with embedded radiopaque markers enclosed in a polymer casing; contraction of the hydrogel in response to acidic pH is evident from the radiographically measured marker position. The sensor has a pH 4–8 response range; between pH 6.5 and 7.5 it responds linearly with a slope of 14% pH 7 length per pH unit, and about 1% length precision. The sensor is attached to a catheter and implanted in a rat peritoneum. Results in awake rats show a rapid pH drop during infection not observed in systemic C-reactive proteins (CRP) levels nor in the uninfected control animal, with negligible drift over 2 weeks. To our knowledge, this is the first report of an in vivo chemically responsive hydrogel sensor.     

Experimental facility for the study of acoustic emission registered in the primary circuit components of WWER power units

This paper is dedicated to the creation of a facility for the experimental study of a phenomenon of background acoustic emission (AE), which is detected in the main circulation loop (MCL) of WWER power units. The analysis of the operating principle and the design of a primary feed-and-blow down system (FB) deaerator of NPP as the most likely source of continuous acoustic emission is carried out. The experimental facility for the systematic study of a phenomenon of continuous AE is developed. A physical model of a thermal deaerator is designed and constructed. A thermal monitoring system is introduced. An automatic system providing acoustic signal registration in a low frequency (0.03–30 kHz) and high frequency (30–300 kHz) bands and study of its spectral characteristics is designed. Special software for recording and processing of digitized electrical sensor signals is developed. A separate and independent principle of study of the most probable processes responsible for the generation of acoustic emission signals in the deaerator is applied. Trial series of experiments and prechecks of acoustic signals in different modes of the deaerator model are conducted. Compliance of basic technological parameters with operating range of the real deaerator was provided. It is shown that the acoustic signal time-intensity curve has several typical regions. The pilot research showed an impact of various processes that come about during the operation of the deaerator physical model on the intensity of the AE signal. The experimental results suggest that the main sources of generation of the AE signals are the processes of steam condensation, turbulent flow of gas-vapor medium, and water boiling.