The possibility to use a vibration signal to estimate friction processes in sliding couplings

In the article the results of the preliminary vibroacustic research and the stereometry examination of the surface of ball bearings used in the timing belt tensioner pulley of cars were presented. For comparative purposes the research was performed for the group of newly manufactured bearings and for the group of bearings after 110 thousand km mileage of the car. The analysis of the wear process of the rolling bearing elements was showed and also the theoretical study of the vibrations generated during a work of bearing-shaft coupling was discussed. The vibration signal components characteristic for the shaft and the elements of a bearing were described and estimated according to a review of literature. In the article the research program and experimental details of the preliminary signal vibration measurements were explained. The vibration tests (curves of instantaneous values of vibration acceleration during time) were carried out with industrial unit CSI 2130 by Emerson and with accelerometer A0760GP for new bearings and bearings after long operation. The amplitude-frequency signal spectrums were recorded for both group of bearings at the same work conditions, than compared between each other and with calculated characteristic theoretical signal components. During the project the laboratory investigation of the rolling bearings surface stereometry was also conducted. The results revealed the occurrence of the following wear processes: abrasive wear, adhesion-abrasive wear, pitting on the surface of the rollers mating with the bearing race, corrosion wear and also fretting in place of permanent connection. Based on the preliminary research of the rolling bearings used in the timing belt tensioner pulley it was assumed that vibrations spectrum for new bearings and after operation were significantly differed. It confirmed the used test equipment and the methodology of the laboratory tests had sufficient sensitivity and could be applied to the reliability research of other types of rolling bearings at the test stand and could be also used to estimate a key goal and range of the further research projects

Automated analyser for monitoring the contents of hydrocarbons in gas emitted from exploratory bore-holes in the gas and oil industry

An automated analyser for total hydrocarbon contents and hydrocarbon composition (from methane to pentanes) was constructed and tested in both laboratory and field exploitation. It used two-channel analysis: continuous measurements of total hydrocarbon contents and periodic (90 or 150 s) composition analysis after separation of hydrocarbons on a gas chromatographic column. Flame ionization detectors were used in both channels. A simple 16-bit analogue-to-digital converter was used (4.8, practically four orders of magnitude), while the full measuring range (six orders of magnitude) was ensured by automatic dilution of the sample (or standard) with clean air. Full control of the operating (calibration/analyses) cycle was performed by microcomputer. An external programme, based on a computer provided with full information on the instrument operating conditions, presents the results of calibrations/analyses and enables them to be archived in a standard database used in the oil/gas drilling industry (N-LAB) by providing a suitable link. The instrument measuring range was 1 ppm to 100% with precision not worse than 5% at the detection limit. The analyser can operate autonomously for two months, recalibrating itself daily

Bioactive nanocomposite PLDL/nano-hydroxyapatite electrospun membranes for bone tissue engineering

New nanocomposite membranes with high bioactivity were fabricated using the electrospinning. These nanocomposites combine a degradable polymer poly(L/DL)-lactide and bone cell signaling carbonate nanohydroxyapatite (n-HAp). Chemical and physical characterization of the membranes using scanning electron microscopy, Fourier transform infrared spectroscopy and the wide angle X-ray diffraction evidenced that nanoparticles were successfully incorporated into the fibers and membrane structure. The incorporation of the n-HAp into the structure increased significantly the mineralization of the membrane in vitro. It has been demonstrated that after a 3-day incubation of composite membrane in the Simulated Body Fluid a continuous compact apatite layer was formed. In vitro experiments demonstrated that the incorporation of n-HAp significantly improved cell attachment, upregulated cells proliferation and stimulated cell differentiation quantified using Alkaline Phosphatase and OsteoImage tests. In conclusion, the results demonstrated that the addition of n-HAp provided chemical cues that were a key factor that regulated osteoblastic differentiation

Automated analyser for monitoring trace amounts of volatile chloro-organic compounds in recirculated industrial water

An automated analyser of volatile chloro-organic compounds in water was constructed and tested using standard mixtures of dichloromethane and dichloroethane. It was based on continuous, countercurrent gas stripping of the liquid sample followed by periodic trapping of the analytes on two traps alternately connected to the bubbler outlet, and thermal desorption. When one trap performed adsorption, the other underwent desorption and cooling. Analytes were detected by an ECD detector. Integration, calibration, calculations and overall operating cycle control was performed by a microcomputer. The instrument guarantees a 0.02 ppm Cl (w/w) detection limit, a 0—2 ppm detection range and 2 months of autonomous operation. Results are reported every 13 min

Interactions between bioactive components determine antioxidant, cytotoxic and nutrigenomic activity of cocoa powder extract

Numerous studies have shown, rather disappointingly, that isolated bioactive phytochemicals are not as biologically effective as natural plant products. Such a discrepancy may be explained by the concept of food synergy, which was verified in this research for cocoa extract versus its major components with regard to cancer chemoprevention. The evaluation embraced the relationship between redox properties evaluated in cell-free systems with the aid of free radicals scavenging method and differential pulse voltammetry, and redox associated anticarcinogenic activities (cellular antioxidant activity, cytotoxicity, nutrigenomic activity) in human colon adenocarcinoma cell line exposed to either cocoa powder extract or artificial mixtures of cocoa bioactives at matching concentrations. In contrast to expectations, our results showed that the stepwise enrichment with antioxidants caused no gradual increase in the antioxidant activity of the model mixtures; also, these model mixtures did not reach the reducing potential of cocoa in the cell-free systems or cellular model employed. Further, the biological activities examined in colon adenocarcinoma cells did not alter in a stepwise manner that could reflect the gradual changes in composition of bioactive ingredients. In conclusion, the experiments presented here showed that the growing complexity of a mixture of phytochemicals seems to create a new redox bioactive substance rather than enrich the mixture with new activities, characteristic of the compound added. It follows that no simple, predictable relationship can be expected between the chemopreventive potential and the composition of real food items containing a complicated set of non-toxic redox active ingredients. Our observations suggest that the interactions between different bioactive compounds and food matrix components are cooperating factors determining the final bioactivity of foods

Effect of exogenously added rhamnolipids on citric acid production yield

The influence of a biosurfactant (rhamnolipids) on the effectiveness of citric acid production by Yarrowia lipolytica from sunflower oil was studied. The surfactant-mediated solubilization of the hydrophobic substrate was assessed by particle size distribution characteristics with and without the presence of sunflower oil hydrolization products. The presence of rhamnolipids contributed to a decrease of the oil droplet size, most notably for samples containing sunflower oil and its hydrolization products. The citric acid yield for cultures not supplemented with rhamnolipids was at 82.9 g/l, with a 1:0.04 citric acid to isocitric acid ratio (CA:ICA). The addition of rhamnolipids at 1 g/l resulted in a 5% increased citric acid yield (87.1 g/l), however a decrease (79.0 g/l) was observed for samples containing 5 g/l of rhamnolipids. The rhamnolipids-induced emulsification of sunflower oil did not seem to influence the citric acid production efficiency. Additional research revealed that the biosurfactant was degraded by yeast cells during the bioconversion process. The possible explanations of this phenomenon include the utilization of rhamnolipids as an alternative carbon source or microbial destabilization of micelles formed by this biosurfactant due to potential bioavailability issues.Keywords: Yarrowia lipolytica, citric acid, rhamnolipids, sunflower oilAfrican Journal of Biotechnology Vol. 12(21), pp. 3313-332

A reversible fluorescent probe for monitoring Ag(I) ions

Silver-containing nanomaterials are of interest for their antibiotic properties, for a wide range of applications from medicine to consumer products. However, much remains to be learnt about the degradation of such materials and their effects on human health. While most analyses involve measurement of total silver levels, it is important also to be able to measure concentrations of active free Ag(I) ions. We report here the preparation of a coumarin-based probe, thiocoumarin silver sensor 1 ( ), that responds reversibly to the addition of silver ions through the appearance of a new fluorescence emission peak at 565 nm. Importantly, this peak is not observed in the presence of Hg(II), a common interferent in Ag(I) sensing. To establish the utility of this sensor, we prepared silver-doped phosphate glasses with demonstrated bactericidal properties, and observed the Ag(I) release from these glasses in solutions of different ionic strength. is therefore a useful tool for the study of the environmental and medical effects of silver-containing materials

Interactions between polyphenolic antioxidants quercetin and naringenin dictate the distinctive redox-related chemical and biological behaviour of their mixtures

Food synergy concept is suggested to explain observations that isolated antioxidants are less bioactive than real foods containing them. However, mechanisms behind this discrepancy were hardly studied. Here, we demonstrate the profound impact of interactions between two common food flavonoids (individual: aglycones quercetin—Q and naringenin—N− or their glycosides rutin—R and naringin—N+ vs. mixed: QN− and RN+) on their electrochemical properties and redox-related bioactivities. N− and N+ seemed weak antioxidants individually, yet in both chemical and cellular tests (DPPH and CAA, respectively), they increased reducing activity of mixtures synergistically. In-depth measurements (differential pulse voltammetry) pointed to kinetics of oxidation reaction as decisive factor for antioxidant power. In cellular (HT29 cells) tests, the mixtures exhibited properties of a new substance rather than those of components. Pure flavonoids did not influence proliferation; mixtures stimulated cell growth. Individual flavonoids tended to decrease global DNA methylation with growing concentration; this effect was more pronounced for mixtures, but not concentration-dependent. In nutrigenomic studies, expression of gene set affected by QN− differed entirely from common genes modulated by individual components. These results question the current approach of predicting bioactivity of mixtures based on research with isolated antioxidants

Quantum Dot Nanomedicine Formulations Dramatically Improve Pharmacological Properties and Alter Uptake Pathways of Metformin and Nicotinamide Mononucleotide in Aging Mice

Orally administered Ag2S quantum dots (QDs) rapidly cross the small intestine and are taken up by the liver. Metformin and nicotinamide mononucleotide (NMN) target metabolic and aging processes within the liver. This study examined the pharmacology and toxicology of QD-based nanomedicines as carriers of metformin and NMN in young and old mice, determining if their therapeutic potency and reduced effects associated with aging could be improved. Pharmacokinetic studies demonstrated that QD-conjugated metformin and NMN have greater bioavailability, with selective accumulation in the liver following oral administration compared to unconjugated formulations. Pharmacodynamic data showed that the QD-conjugated medicines had increased physiological, metabolic, and cellular potency compared to unconjugated formulations (25× metformin; 100× NMN) and highlighted a shift in the peak induction of, and greater metabolic response to, glucose tolerance testing. Two weeks of treatment with low-dose QD-NMN (0.8 mg/kg/day) improved glucose tolerance tests in young (3 months) mice, whereas old (18 and 24 months) mice demonstrated improved fasting and fed insulin levels and insulin resistance. High-dose unconjugated NMN (80 mg/kg/day) demonstrated improvements in young mice but not in old mice. After 100 days of QD (320 μg/kg/day) treatment, there was no evidence of cellular necrosis, fibrosis, inflammation, or accumulation. Ag2S QD nanomedicines improved the pharmacokinetic and pharmacodynamic properties of metformin and NMN by increasing their therapeutic potency, bypassing classical cellular uptake pathways, and demonstrated efficacy when drug alone was ineffective in aging mice