On an isotropic and centrifugal force invariant layout of a conically shaped gas-lubricated high-speed spiral-groove bearing

The following elaboration discusses the analytically complete layout of a self-acting gas-lubricated high-speed conically shaped spiral-groove bearing as well as suggestions for practical realization. The simple conically shaped bearing is separated into two conical main bearings, which are situated at the ends of the cone-stump. Both have an identical angle size, but otherwise differ with regard to their bearing geometries and bearing gap sizes. The isotropic layout of the two bearings in radial direction, i.e. the determination of the bearing geometries for the same load angle, the same load capacity and the same stiffness at the same nominal operating conditions, is determined analytically in an iterative way and has the goal of providing dynamically benign behavior. The radial expansion of the rotor which occurs at the nominal rotation, and therefore the occurrence of distortions of the bearing gaps due to enormous centrifugal forces that affect the rotor masses, is rendered ineffective by means of a centrifugal force invariant inner outline of the rotor. For this purpose, the outer contour of the rotor is designed in such a manner that the conically shaped inner contour expands congruently to itself and therefore causes a parallel increase in the bearing gap. The autonomous regulation of the bearing following the gap increase subject to the decrease in load capacity as a result of the decrease of the expanded rotor to the nominal bearing gap sizes restores the nominal state independent of the rotor speed. The half-frequency whirl which is dependent on natural frequencies and detrimental to self-acting, gas-lubricated bearings requires an investigation of the dynamic behavior of the bearing system. It will be shown that natural frequencies will be reached while passing through the turning frequency range. However, the suspension of the “rotor–stator” system in defined additional stiffnesses will show that the natural frequencies of the original system can be displaced upwards so that the turning frequency will no longer reach a natural frequency at any operating point. This prevents the occurrence of the half-frequency whirl. The realization of the described bearing system is supported by suggestions for a non-self-acting start-up assistance at low rotation speeds as well as by suggestions for actuation, pre-stressing, sensor and measurement devices as well as system regulation. It lays the foundation for high-speed bearings in spindle construction, laser and dental technology as well as for precision gyroscopes.     

Unsaturated fatty acids from food and in the growth medium improve growth of Bacillus cereus under cold and anaerobic conditions

In a chemically defined medium and in Luria broth, cold strongly reduced maximal population density of Bacillus cereus ATCC 14579 in anaerobiosis and caused formation of filaments. In cooked spinach, maximal population density of B. cereus in anaerobiosis was the same at cold and optimal temperatures, with normal cell divisions. The lipid containing fraction of spinach, but not the hydrophilic fraction, restored growth of B. cereus under cold and anaerobiosis when added to the chemically defined medium. This fraction was rich in unsaturated, low melting point fatty acids. Addition of phosphatidylcholine containing unsaturated, low melting point, fatty acids similarly improved B. cereus anaerobic growth at cold temperature. Addition of hydrogenated phosphatidylcholine containing saturated, high melting point, fatty acids did not modify growth. Fatty acids from phospholipids, from spinach and from hydrogenated phosphatidylcholine, although normally very rare in B. cereus, were inserted in the bacterium membrane. Addition of phospholipids rich in unsaturated fatty acids to cold and anaerobic cultures, increased fluidity of B. cereus membrane lipids, to the same level as those from B. cereus normally cold adapted, i.e. grown aerobically at 15 °C. B. cereus is therefore able to use external fatty acids from foods or from the growth medium to adapt its membrane to cold temperature under anaerobiosis, and to recover the maximal population density achieved at optimal temperature.     

Human brain activity related to speed discrimination tasks

This study examined the ionic mechanism of ibutilide, a class III antiarrhythmic in clinical use, on freshly isolated human atrial cells. Cells had resting potentials of -71.4 +/- 2.4 mV, action potentials with overshoot of 36.8 +/- 1.8 mV, duration of 265 +/- 89 msec at 90% repolarization and slow repolarization (n = 16). Ibutilide, at 10(-7) M, markedly increased action potential duration. Four types of outward currents were detected: Ito, Iso, a delayed rectifier and IK1. Ibutilide had no inhibitory effect on these outward currents at 10(-7) M (n = 28). In K(+)-free solutions and -40 mV holding potential, mean peak inward current at 20 mV was -1478 +/- 103 pA (n = 12). Ibutilide increased this current to -2347 +/- 75 pA at 10(-7) M, with half maximal effect (Kd) of 0.1 to 0.9 nM between -10 and +40 mV (n = 21). At similar concentrations, the drug increased APD, with Kd of 0.7 and 0.23 nM at 70 and 90% repolarization, respectively (n = 8). Ibutilide shifted the mid-point of the steady-state inactivation curve from -21 to -12.2 mV (n = 6), and reduced current decline during repetitive depolarization (n = 5). The drug induced inward current was carried by Na+o through a nifedipine inhibited inward channel because Na+o removal eliminated the effect, and nifedipine abolished the inward current and the drug induced APD prolongation. We propose that a Na+ current through the L-type Ca++ channel mediates ibutilide's potent clinical class III antiarrhythmic action.     

Control of structured white textiles

The aim of this article was to study the instrumental measurement of whiteness related specifically to structured textiles. Both brightened and unbrightened white textiles have been investigated. A method of controlling the acceptability of whites is proposed specifically for highly structured textiles.     

Skin Development during the Film Formation of Waterborne Acrylic Pressure-Sensitive Adhesives Containing Tackifying Resin

Tackifying resins (TR) are often used to improve the adhesive properties of waterborne pressure-sensitive adhesives (PSAs) derived from latex dispersions. There is a large gap in the understanding of how, and to what extent, the film formation mechanism of PSAs is altered by the addition of TR. Herein, magnetic resonance profiling experiments show that the addition of TR to an acrylic latex creates a coalesced surface layer or “skin” that traps water beneath it. Atomic force microscopy of the PSA surfaces supports this conclusion. In the absence of the TR, particles at the surface do not coalesce but are separated by a second phase composed of surfactant and other species with low molecular weight. The function of the TR is complex. According to dynamic mechanical analysis, the TR increases the glass transition temperature of the polymer and decreases its molecular mobility at high frequencies. On the other hand, the TR increases the molecular mobility at lower frequencies and thereby promotes the interdiffusion of latex particles to create a skin layer. In turn, the skin layer is a barrier that prevents the exudation of surfactant to the surface. The TR probably enhances the coalescence of the latex particles by increasing the compatibility between the acrylic copolymer and the solids in the serum phase.     

Cytochrome P4502E1 inducibility and hydroxyethyl radical formation among alcoholics

BACKGROUND/AIMS: Animal studies have shown that the induction of cytochrome P4502E1 (CYP2E1) modulates oxidative damage induced by ethanol. Since CYP2E1 activity varies substantially in humans, we have investigated whether differences in CYP2E1 activity might influence the formation of hydroxyethyl free radicals and the stimulation of lipid peroxidation among alcohol abusers. METHODS: Chlorzoxazone oxidation, an index of CYP2E1 activity, and the levels of antibodies reacting with hydroxyethyl radical and malonyldialdehyde protein adducts were investigated in 51 alcoholic patients. RESULTS: We observed that in 40 out of 51 (78%) alcoholics, chlorzoxazone oxidation was increased over the control levels, consistently with CYP2E1 induction by ethanol. However, in the remaining 22% of the patients, in spite of a similar alcohol intake, chlorzoxazone oxidation was within the control range, indicating a lack of CYP2E1 inducibility. IgG reacting with hydroxyethyl free radical-protein adducts were absent in subjects without CYP2E1 induction, while they were significantly increased in alcoholics with induced CYP2E1 activity. IgG against malonyldialdehyde protein-adducts were increased in all patients, irrespective of CYP2E1 inducibility. Moreover, chlorzoxazone oxidation was significantly lower in alcoholics without clinical and biochemical signs of liver disease as compared to patients with alcoholic liver disease. CONCLUSIONS: These results indicate that CYP2E1 activity greatly influences the formation of hydroxyethyl radicals in humans, and suggest a possible role of CYP2E1 in the development of alcoholic liver disease.     

Invasive pulmonary infection due to Scedosporium apiospermum in two children with chronic granulomatous disease

The aim of this study was to investigate of the relationship of ovarian stromal volume, measured using three-dimensional ultrasound, to serum androgen concentrations in patients with polycystic ovaries. Serum gonadotrophin, oestradiol and androgen concentrations and ovarian volume measurements were obtained in the early follicular phase from 100 women undergoing assisted conception treatment cycles. Group 1 contained 50 women with regular menstrual cycles and normal ovarian morphology, group 2 contained 24 women with regular menstrual cycles and polycystic ovaries seen on ultrasound scan and group 3 contained 26 women with polycystic ovary syndrome. Statistical analysis included analysis of variance, Scheffé's procedure and Pearson's correlation. Total ovarian volume (15.7-16.1 versus 11 ml, P < 0.05), stromal volume (14.5 versus 9.4 ml, P < 0.05) and thecal steroid concentrations were significantly greater in groups 2 and 3. Stromal volume was positively correlated with serum androstenedione concentrations (r = 0.45, P = 0.0019 in group 3) but was not correlated with any other endocrine parameter. It was concluded that polycystic ovaries are characterized by increased ovarian stroma with associated overproduction of theca-derived steroids, particularly androstenedione.     

Round-robin analysis of the RILEM TC 162-TDF beam-bending test: Part 2—Approximation of δ from the CMOD response

A round robin test programme was carried out using the beam-bending test recommended by RILEM TC 162-TDF [1]. The test programme included both plain and steel fibre reinforced concrete (SFRC) beams. A detailed analysis was carried out to investigate the influence of different test configurations on measurements of the crack mouth opening displacement (CMOD). Linear elastic fracture mechanics (LEFM) and non-linear fracture mechanics (NLFM) methods were utilised to investigate the problem analytically. From the analytical studies carried out, it is proposed that the CMOD should not be measured at a distance more than 5mm from the bottom fibre of the beam. A larger distance than 5mm will cause the deviation between the measured CMOD and the true CMOD to reach an unacceptable level. A simple rigid body model has been proposed to relate the CMOD to the mid-span deflection. The NLFM analysis and experimental results were compared for both the plain and SFRC beam results and it was found that results based on the basis of CMOD can be compared to those based on deflections, for practical purposes, using the simple rigid body model. The experimental results strongly suggest that the rigid body model could be effectively applied for all the types of materials tested in the round robin test programme. In addition it was found that the conversion from CMOD to the equivalent mid-span deflection, δ_c, revealed good agreement between the load-average mid-span deflection (P-δ) curve and the load-equivalent mid-span deflection (P-δ) curve especially for the SFRC specimens. It is proposed that the load-CMOD (P-CMOD) curve be used to calculate the proposed RILEM design parameters (as opposed to the P-δ curve) via the use of a correction factor determined using the simple rigid body model.     

The 13C-urea breath test in Helicobacter pylori gastric infection in children

Helicobacter pylori gastric infection in children is a public health problem. Classical diagnostic tools such as endoscopy are excessively invasive in the usual clinical context. Serology at this age has multiple drawbacks. The urea-13C breath test seems today the most appropriate alternative method. The principle of the test relies upon the indirect detection of H pylori through its high urease activity. The test uses a stable (ie, non radioactive) isotope, which allows its repeated use. The main indications are the detection and the follow-up of H pylori infection.