Computer-aided design in mechanisms

The man-machine dialog is very important for the design process. In this paper a program system, based on the minicomputer KRS 4201 (ROBOTRON), is demonstrated by using an interactive graphical screen. This program system provides the opportunity to analyze and synthesize mechanisms up to 16 links. The application is demonstrated by designing a front-loader-system for a truck. Real-time animation of seven-bar linkages and coupler curves, including velocity and acceleration, are shown.     

Peripheral noxious stimulation induces CREM expression in dorsal horn: involvement of glutamate

Thermal washout curves have been proposed as noninvasive tools for analysing lower airway dimensions and pulmonary blood flow, but how upper airway heat transfer affects these washout curves is unclear. The present study was designed to compare extrathoracic and tracheobronchial contributions to thermal washout curves. Respiratory frequency, air ambient temperature, and body core temperature (tc) were varied in six male subjects before and after immersion in cold (1.1 degrees C) water for up to 2 h under three conditions: 1) control: ambient temperature (tamb) = 25 degrees C, rectal temperature change (delta tre) = 0 degrees C; 2) pre-immersion: tamb = 4 degrees C, delta tre = 0 degrees C; and 3) post-immersion: tamb = 25 degrees C, delta tre = -0.7 degrees C. Both peak expiratory nasal (tpn) and oral (tpo) airstream temperatures were measured. Each subject was tested twice. Expiratory tpo was generally higher than tpn in all conditions. Increasing breathing rates lowered tpn and tpo in the control and cold air environments. Orifice temperatures, which are presumed to reflect upper airway blood temperatures, correlated with both tpn and tpo. Lowering tc had no effect on washout curves during quiet breathing and affected only tpn during rapid breathing. The results suggest that while tracheobronchial conditions may contribute to thermal washout curves, extrathoracic conditions predominate. Strong correlations between orifice temperatures, peak expiratory nasal temperatures and peak expiratory oral temperature demonstrate the dominant role of upper airway heat exchange in determining thermal washout curves.     

Identification of N,N'-dicyclohexylcarbodiimide-reactive glutamic and aspartic acid residues in Escherichia coli transhydrogenase and the exchange of these by site-specific mutagenesis

Pyridine nucleotide transhydrogenase (EC 1.6.1.1) from Escherichia coli was investigated with respect to the role of glutamic and aspartic acid residues reactive to N,N'-dicyclohexylcarbodiimide (DCCD) and potentially involved in the proton-pumping mechanism of the enzyme. The E. coli transhydrogenase consists of an alpha (510 residues) and a beta (462 residues) subunit. DCCD reacts with the enzyme to inhibit catalytic activity and proton pumping. This reagent modifies Asp alpha 232, Glu alpha 238, and Glu alpha 240 as well as amino acid residue(s) in the beta subunit. Using the cloned and overexpressed E. coli transhydrogenase genes (Clarke, D. M., and Bragg, P. D. (1985) J. Bacteriol. 162, 367-373), Asp alpha 232 and Glu alpha 238 were replaced independently by site-specific mutagenesis. In addition, Asp alpha 232, Glu alpha 238, and Glu alpha 240 were replaced to generate triple mutants. The specific catalytic activities of the mutant transhydrogenases alpha D232N, alpha D232E, alpha D232K, alpha D232H, alpha E238K, and alpha E238Q as well as of the triple mutants alpha D232N, alpha E238Q, alpha E240Q and alpha D232H, alpha E238Q, alpha E240Q were in the range of 40-90% of the wild-type activity. Proton-pumping activity was present in all mutants. Examination of the extent of subunit modification by [14C]DCCD revealed that the label was still incorporated into both alpha and beta subunits in the Asp alpha 232 mutants, but that the alpha subunit was not labeled in the triple mutants. Catalytic and proton-pumping activities were nearly insensitive to DCCD in the triple mutants. This suggests that loss of catalytic and proton-pumping activities is associated with modification of the aspartic and glutamic acid residues of the alpha subunit. In the presence of the substrate NADPH, the rate of modification of the beta subunit by [14C]DCCD was increased, and there was a greater extent of enzyme inactivation. By contrast, NADH and 3-acetylpyridine-NAD+ protected the catalytic activity of the transhydrogenase from inhibition by DCCD. The protection was particularly marked in the E238Q and E238K mutants. It is concluded that the Asp alpha 232, Glu alpha 238, and Glu alpha 240 residues are not essential for catalytic activity or proton pumping. The inactivation by DCCD is likely due to the introduction of a sterically hindering group that reacts with the identified acidic residues close to the NAD(H)-binding site.     

High dietary calcium level decreases colonic phytate degradation in pigs fed a rapeseed diet

The degradation of phytate (inositol hexaphosphate) in rapeseed meal diet not containing phytase activity was studied in 15 growing ileum-fistulated pigs. Stomach and small intestinal degradation and total gastrointestinal degradation were compared. The effect of addition of calcium carbonate to the rapeseed meal diet at two levels (9.2 and 18.5 g/kg diet) was investigated. A commercial barley-wheat-soybean diet with intrinsic phytase activity was used as reference. Phytate and its hydrolysis products in diets, ileal digesta and feces were determined by HPLC ion-pair chromatography. Hydrolysis of phytate in the stomach and small intestine was 35-45% in pigs fed the rapeseed meal diet independent of calcium addition, and 65% in pigs fed the reference diet. Total gastrointestinal degradation of phytate in pigs fed the rapeseed diet was 97, 77 and 42% (P < 0.001) when calcium intakes were 4.5, 9.9 and 15 g/d, respectively; total gastrointestinal degradation was 72% in pigs fed the reference diet. The intestinal phytate degradation pattern, when rapeseed diet was fed, indicated the activity of an unspecific phosphatase, whereas that of the reference diet indicated intrinsic dietary phytase activity. We conclude that dietary supplementation of calcium carbonate decreases the phytate degradation in the colon of pigs, but not in the stomach and small intestine.     

Student acceptance of unique meals

Students (N = 167) from the 4th, 8th, and 11th grades sorted meals, listed on individual cards, according to whether they would or would not eat them. Students were told to either consider eating the meals at home or at school. Forty-two different meals were selected from a pool of unique meals created by students in a previous study. The meals differed in head component, the presence or absence of vegetables, and the number of different foodstuffs. On average, approximately half of the meals were deemed acceptable, but older students accepted more meals than younger ones, boys accepted more meals than girls, and meals to be consumed at home were accepted more than those to be consumed at school. In addition, students tended to accept meals comprised of a small number of foodstuffs that did not contain vegetables. The also chose more meat-based meals over those containing fish or soup. These results suggest that students have rather unique food preferences that do not correspond well with nutritional standards. In order to address this problem we recommended that students be given more good choices in the school cafeteria through the introduction of a two-meal system and salad bars.     

Formation of droplets on Si surfaces bombarded by In from a capillary type liquid metal ion source

Droplet formation on Si surfaces bombarded by 10 keV beams from a liquid metal indium ion source has been observed. It has been verified that excess indium is transported in the ion beam, probably in the form of charged droplets. SIMS, SEM and RBS techniques have been used to study the distribution of droplets at the surface. At the specified ion source operating conditions, equilibrium droplet coverage is of the order of 25%. Individual droplets have an average diameter of 0.35 ωm and an average height of 2.2 nm. At a bombardment current density of 0.1 mA cm^?2, equilibrium coverage is reached in about 1 s.     

The influence of NaCl and CO2 on the atmospheric corrosion of magnesium alloy AZ91

The influence of NaCl and CO₂ on the atmospheric corrosion of magnesium alloy AZ91 is studied in the laboratory. Samples were exposed under carefully controlled air and flow conditions; the relative humidity was 95%, the temperature was 22.0°C and the concentration of CO₂ was < 1 ppm or 350 ppm. Different amounts of sodium chloride (0–70 μg/cm²) were added before exposure. The corrosion products were analyzed by gravimetry, ion chromatography, X‐ray diffraction and scanning electron microscopy. Mass gain and metal loss results are reported. The combination of high humidity and NaCl is very corrosive towards AZ91. However, the NaCl‐induced corrosion is inhibited by ambient concentrations of CO₂. Exposure in the absence of CO₂ gives rise to heavy pitting, with brucite, Mg(OH)₂, being the dominant corrosion product. In the presence of CO₂ a layer of hydrated magnesium hydroxy carbonate, Mg₅(CO₃)₄(OH)₂ · 5 H₂O forms. A tentative corrosion mechanism is presented that explains the behavior in the two environments.     

Windenergieausbau als Teil der Ökostromentwicklung

The new law for the support of electricity produced by renewable sources in Austria (Ökostromgesetz) which came into force with the beginning of 2003, shows its impacts already after the first months. Investments into wind power have increased considerably. These will be accompanied by activities for electricity production by biomass and biogas. The 4%-target quota will probably be reached earlier than the 2008 target period of the law.