ISPITIVANJE ŠIRENJA ZAGAĐIVAČA ZRAKA NA RADNOM MJESTU

This paper presents results of research on air pollutants dispersion within a working room. The tests were performed in a woodworking shop room, posing the hazard of exposure to hard wood (oak or beech) dust. The characteristic parameters for evaluation of pollutants dispersion from a machine equipped with a local exhaust ventilation were specified for the room. Three measurement methods (flow visualisation, anemometric, and tracer gases methods) were applied for the tests, enabling determination of air flow directions, air velocity distribution, and variation in concentration of a tracer gas, simulating the real pollution in characteristic points of the working room. The research indicates that air velocity values achieved their maximum within the breathing zone of the employees present at the circular saw and local exhaust ventilation operation area, and amounted from 0.35 m/s up to 0.45 m/s. Moreover, the air flow resulting from the circular saw and the local exhaust ventilation system operation was causing a quicker tracer gas dispersion within the employees’ breathing zone. Tracer gas concentration in the employees’ breathing zone amounted from 1.56 ppm up to 1.81 ppm.Članak opisuje rezultate ispitivanja širenja zagađivača zraka u radnoj prostoriji. Ispitivanje je provedeno u drvnoj radionici s ciljem istraživanja opasnosti od izlaganja hrastovoj ili bukovoj drvnoj prašini. Navedeni su tipični parametri za izračun širenja zagađivača iz stroja s ugrađenom ispušnom ventilacijom za određenu prostoriju. Primijenjene su tri metode mjerenja (vizualizacija protoka, anemometrijska metoda i metoda ispitnih plinova kako bi se ustanovili smjerovi gibanja zraka, distribucija brzine zraka i varijacije u koncentraciji ispitnog plina i to simuliranjem stvarnog zagađenja u karakterističnim točkama radne prostorije. Ispitivanje pokazuje da su vrijednosti za brzinu zraka bile najveće unutar zone disanja radnika na kružnoj pili i u zoni lokalne ispušne ventilacije, a kretale su se od 0,35 m/s do 0,45 m/s. Nadalje, protok zraka proizveden radom pile i lokalnog ispušnog sustava uzrokovao je brže širenje ispitnog plina u zoni disanja. Koncentracija ispitnog plina u zoni disanja bila je od 1,56 ppm do 1,81 ppm

PRINCIPAL COMPONENT ANALYSIS AND CLUSTER ANALYSIS IN MULTIVARIATE ASSESSMENT OF WATER QUALITY

This paper deals with the use of multivariate methods in drinking water analysis. During a five-year project, from 2008 to 2012, selected chemical parameters in 11 water supply networks of the Siedlce County were studied. Throughout that period drinking water was of satisfactory quality, with only iron and manganese ions exceeding the limits (21 times and 12 times, respectively). In accordance with the results of cluster analysis, all water networks were put into three groups of different water quality. A high concentration of chlorides, sulphates, and manganese and a low concentration of copper and sodium was found in the water of Group 1 supply networks. The water in Group 2 had a high concentration of copper and sodium, and a low concentration of iron and sulphates. The water from Group 3 had a low concentration of chlorides and manganese, but a high concentration of fluorides. Using principal component analysis and cluster analysis, multivariate correlation between the studied parameters was determined, helping to put water supply networks into groups according to similar water quality

Molecular characterization of the PhiKo endolysin from Thermus thermophilus HB27 bacteriophage phiKo and its cryptic lytic peptide RAP-29

IntroductionIn the era of increasing bacterial resistance to antibiotics, new bactericidal substances are sought, and lysins derived from extremophilic organisms have the undoubted advantage of being stable under harsh environmental conditions. The PhiKo endolysin is derived from the phiKo bacteriophage infecting Gram-negative extremophilic bacterium Thermus thermophilus HB27. This enzyme shows similarity to two previously investigated thermostable type-2 amidases, the Ts2631 and Ph2119 from Thermus scotoductus bacteriophages, that revealed high lytic activity not only against thermophiles but also against Gram-negative mesophilic bacteria. Therefore, antibacterial potential of the PhiKo endolysin was investigated in the study presented here.MethodsEnzyme activity was assessed using turbidity reduction assays (TRAs) and antibacterial tests. Differential scanning calorimetry was applied to evaluate protein stability. The Collection of Anti-Microbial Peptides (CAMP) and Antimicrobial Peptide Calculator and Predictor (APD3) were used to predict regions with antimicrobial potential in the PhiKo primary sequence. The minimum inhibitory concentration (MIC) of the RAP-29 synthetic peptide was determined against Gram-positive and Gram-negative selected strains, and mechanism of action was investigated with use of membrane potential sensitive fluorescent dye 3,3′-Dipropylthiacarbocyanine iodide (DiSC3(5)).Results and discussionThe PhiKo endolysin is highly thermostable with melting temperature of 91.70°C. However, despite its lytic effect against such extremophiles as: T. thermophilus, Thermus flavus, Thermus parvatiensis, Thermus scotoductus, and Deinococcus radiodurans, PhiKo showed moderate antibacterial activity against mesophiles. Consequently, its protein sequence was searched for regions with potential antibacterial activity. A highly positively charged region was identified and synthetized (PhiKo105-133). The novel RAP-29 peptide lysed mesophilic strains of staphylococci and Gram-negative bacteria, reducing the number of cells by 3.7–7.1 log units and reaching the minimum inhibitory concentration values in the range of 2–31 μM. This peptide is unstructured in an aqueous solution but forms an α-helix in the presence of detergents. Moreover, it binds lipoteichoic acid and lipopolysaccharide, and causes depolarization of bacterial membranes. The RAP-29 peptide is a promising candidate for combating bacterial pathogens. The existence of this cryptic peptide testifies to a much wider panel of antimicrobial peptides than thought previously

PRINCIPAL COMPONENT ANALYSIS AND CLUSTER ANALYSIS IN MULTIVARIATE ASSESSMENT OF WATER QUALITY

This paper deals with the use of multivariate methods in drinking water analysis. During a five-year project, from 2008 to 2012, selected chemical parameters in 11 water supply networks of the Siedlce County were studied. Throughout that period drinking water was of satisfactory quality, with only iron and manganese ions exceeding the limits (21 times and 12 times, respectively). In accordance with the results of cluster analysis, all water networks were put into three groups of different water quality. A high concentration of chlorides, sulphates, and manganese and a low concentration of copper and sodium was found in the water of Group 1 supply networks. The water in Group 2 had a high concentration of copper and sodium, and a low concentration of iron and sulphates. The water from Group 3 had a low concentration of chlorides and manganese, but a high concentration of fluorides. Using principal component analysis and cluster analysis, multivariate correlation between the studied parameters was determined, helping to put water supply networks into groups according to similar water quality

Transmission from group II muscle afferents is depressed by stimulation of locus coeruleus/subcoeruleus, Kölliker-Fuse and raphe nuclei in the cat

The effects of brief trains of electrical stimuli applied within the locus coeruleus and subcoeruleus, the Kölliker-Fuse nucleus and the raphe magnus, obscurus and pallidus nuclei were tested on transmission from group I and group II muscle afferent fibres in mid-lumbar spinal segments of chloralose anaesthetized cats. Changes in the effectiveness of transmission from these afferents were assessed from changes in the size of monosynaptic extracellular field potentials evoked by them. The depression of group II field potentials occurred at conditioning-testing intervals of 20-400 ms, and was maximal at intervals of 40-100 ms and 30-60 ms for potentials recorded in the intermediate zone and dorsal horn, respectively. At intervals up to about 30 ms it was combined with the depression of group I components of the intermediate zone field potentials. However, at longer intervals the conditioning stimuli depressed group II components of these potentials as selectively as monoamines applied ionophoretically at the recording site (Bras et al., 1989a, 1990). Thus, only the late depressive actions are considered as being possibly mediated by impulses in descending noradrenergic and/or serotonergic fibres. No major differences were found in the relative degree of depression of transmission from group II afferents by stimulation of the locus coeruleus/subcoeruleus, Kölliker-Fuse or raphe nuclei, either in the dorsal horn or in the intermediate zone. Since field potentials at these locations are preferentially depressed by ionophoretic application of serotonin and noradrenaline (Bras et al., 1990), and since the locus coeruleus/subcoeruleus, Kölliker-Fuse and raphe nuclei are interconnected, the study leads to the conclusion that both noradrenergic and serotonergic descending pathways can be activated by stimuli applied within either of them. Selective depression of field potentials of group II origin was also evoked by stimulation at other sites, e.g. the periaqueductal grey and medullary reticular formation, when conditioning-testing intervals were sufficiently long. Such a depression is considered to be secondary to activation of neurones of the locus coeruleus/subcoeruleus, Kölliker-Fuse or raphe nuclei and attributed to the spread of current or transsynaptic activation of these neurones, or to stimulation of their axon collaterals outside the nuclei rather than to other descending medullo-spinal systems. The non-selective depression of field potentials evoked by group I and group II afferents at shorter conditioning-testing intervals is proposed to be due to actions of reticulo-spinal pathways. © 1992 Springer-Verlag