Reliability of railway traffic personnel

The paper describes an analysis of reliability of railway traffic personnel. The human tasks critical to system safety are identified. Human error probability is chosen as a measure of human reliability in performing these tasks. The probabilities of some critical errors are estimated using the field data collected in the Slovenian railway traffic system. As stress conditions strongly affect the human performance, a simple model of the dependence of human error probability on stress levels is proposed.     

Development of a solid self-microemulsifying drug delivery system (SMEDDS) for solubility enhancement of naproxen

Context: Comparative evaluation of liquid and solid self-microemulsifying drug delivery systems (SMEDDS) as promising approaches for solubility enhancement.

Objective: The aim of this work was to develop, characterize, and evaluate a solid SMEDDS prepared via spray-drying of a liquid SMEDDS based on Gelucire® 44/14 to improve the solubility and dissolution rate of naproxen.

Material and methods: Various oils and co-surfactants in combination with Gelucire® 44/14 were evaluated during excipient selection study, solubility testing, and construction of (pseudo)ternary diagrams. The selected system was further evaluated for naproxen solubility, self-microemulsification ability, and in vitro dissolution of naproxen. In addition, its transformation into a solid SMEDDS by spray-drying using maltodextrin as a solid carrier was performed. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and X-ray diffraction (XRD) were used to evaluate the physical characteristics of the solid SMEDDS obtained.

Results: The selected formulation of SMEDDS was comprised of Miglyol 812®, Peceol?, Gelucire® 44/14, and Solutol® HS 15. The liquid and solid SMEDDS formed a microemulsion after dilution with comparable average droplet size and exhibited uniform droplet size distribution. In the solid SMEDDS, liquid SMEDDS was adsorbed onto the surface of maltodextrin and formed smooth granular particles with the encapsulated drug predominantly in a dissolved state and partially in an amorphous state. Overall, incorporation of naproxen in SMEDDS, either liquid or solid, resulted in improved solubility and dissolution rate compared to pure naproxen.

Conclusion: This study indicates that a liquid and solid SMEDDS is a strategy for solubility enhancement in the future development of orally delivered dosage forms.     

Characterization of steel mill electric-arc furnace dust

In order to make a complete characterization of electric-arc furnace (EAF) dust, as hazardous industrial waste, and to solve its permanent disposal and/or recovery, bearing in mind both the volumes formed in the Croatian steel industry and experiences of developed industrial countries, a study of its properties was undertaken. For this purpose, samples of EAF dust, taken from the regular production process in the Zeljezara Sisak Steel Mill between December 2000 and December 2001, were subjected to a series of tests. The chemical composition of EAF dust samples was investigated by means of a several different analytical methods. The results from the chemical analysis show that the approximate order of abundance of major elements in EAF dusts is as follows: Fe, Zn, Mn, Ca, Mg, Si, Pb, S, Cr, Cu, Al, C, Ni, Cd, As and Hg. Granular-metric composition of single samples was determined by applying sieve separation. Scanning electron micro-structural examination of EAF dust microstructure was performed and results indicated that all twelve EAF dusts were composed of solid spherical agglomerates with Fe, Zn, Pb, O, Si and Ca as the principal element. The investigation of grain morphology and the mineralogical composition of EAF dust were taken by combination of high resolution Auger electron spectroscopy (HR AES), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction analysis. The analysis of XPS-spectra determined the presence of zinc in the form of ZnO phase and the presence of lead in the form of PbO phase, i.e. PbSO3/PbSO4 forms. The results of the X-ray diffraction phase analysis show that the basis of the examined EAF dust samples is made of a mixture of metal oxides, silicates and sulphates. The metal concentration, anions, pH value and conductivity in water eluates was determined in order to define the influence of EAF dust on the environment.     

AES investigation of the stainless steel surface oxidized in plasma

Auger electron spectroscopy (AES) depth profiling was used to study the oxidation phenomena of AISI316L stainless steel during treatment with oxygen plasma. Samples were exposed to low-pressure RF plasma with a high dissociation degree, so that the flux of oxygen atoms onto the sample surface exceeded 10²⁴ m⁻² s⁻¹. A set of samples was oxidized 4 min at different temperatures up to 1300 K during plasma treatment. AES measurements showed that the oxide film thickness increased with the increasing temperature. The thickness of the oxide film on the samples oxidized in plasma at 300 K was nearly the same as for the untreated sample. The thickness of the oxide film of the samples which were oxidized at 1000 K was about 170 nm and it consisted of iron oxide. The thickest oxide film of about 350 nm was found on the samples heated in oxygen plasma to 1300 K. Depth profiling showed the uppermost layer of manganese oxide, followed by a mixture of chromium oxide and iron oxide. The scanning electron microscope analyses showed a dramatic increase of the surface roughness.     

Improvement of adhesion of fucoidan on polyethylene terephthalate surface using gas plasma treatments

Attachment of polysaccharide fucoidan to the polyethylene terephthalate (PET) polymer surface was studied by X-ray photoelectron spectroscopy (XPS). Fucoidan has antithrombogenic and anticoagulant properties and is therefore a promising coating for vascular graft implants for improving their hemocompatibility. Samples of PET polymer were first modified by nitrogen plasma treatment in order to change the surface wettability and to introduce amino groups to the surface, which act as a linker for further binding of fucoidan. Plasma treated samples were then incubated for 30 min in fucoidan solution. The presence of fucoidan layer on the polymer surface was demonstrated by appearance of S2p signal in the XPS spectra of the coated PET samples. The procedure for immobilization of fucoidan on PET surface was optimized by varying pH value of fucoidan solution from 5 to 7.4. The best results were obtained when using lower pH value pH = 5. At these conditions the thickness of the fucoidan coating was estimated to about 7 nm.     

Interaction of highly dissociated low pressure hydrogen plasma with W-C thin film deposits

Thin film deposits of carbon and tungsten on stainless steel substrate were prepared by RF sputtering of a tungsten target in acetylene atmosphere. At the target bias of − 1700 V and the target current of 30 mA cm^− 2, a rather uniform film containing 50 at.% of C and 50 at.% of W was deposited. The thickness of the deposited film was about 1 μm. Samples were exposed to highly dissociated hydrogen plasma created by a microwave discharge at the power of 1000 W. Some samples were heated additionally by concentrated solar radiation. After plasma treatment, the samples were characterized by X-Ray Diffraction and Auger Electron Spectroscopy. The results showed that aggressive hydrogen plasma allows for the removal of carbon from the deposits at moderated temperatures. Prolonged treatment showed formation of highly crystalline pure tungsten, and finally the tungsten film interacted with the substrate forming a thin film rich of Fe₇W₆ compound. The range of temperature and/or treatment time for the removal of carbon from the W-C film was found very narrow.     

Fluoride in teas of different types and forms and the exposure of humans to fluoride with tea and diet

Human exposure to the fluoride (F) from commercial teas was assessed. The efficacy of the F leaching was determined from the total F (F_t) contents in the teas (53–435 mg/kg) and the F concentrations in tea infusions (0.31–3.55 mg/l of free F available to human organism). Both were determined with a fluoride ion selective electrode. The efficacies of F leaching from the green, oolong and black teas were 55–90% with continuous, and 74–100% by repeated infusions, and were not affected by the type or the manufactured form. Lower efficacies were observed from Pu’erh teas, 21–38% with continuous, and 37–59% by repeated infusions. The daily intake of F with daily consumption of five cups of tea can represent 9–101% of the adequate intake (AI) for an adult person with 70 kg, and with tea and diet 25–173% of the AI in non-fluoridated and 35–210% of AI in fluoridated areas. The upper limits of these intakes can be already associated with a risk of developing F-related adverse effects.     

Stability of a chitosan layer deposited onto a polyethylene surface

A two‐step procedure was applied to obtain antimicrobial films; this procedure involved a corona treatment of the polyethylene (PE) surface and its chemical activation with 1‐ethyl‐3‐[3‐dimethylaminopropyl] carbodiimide hydrochloride and N‐hydroxysuccinimide, and this led to the covalent bonding of chitosan on the PE surface. Electrochemical methods were used to investigate the stability of the deposited chitosan layer. The potentiometric and polyelectrolyte titrations showed that some amount of chitosan desorbed faster from the surface until equilibrium was reached and also that the grafted chitosan layer was more stable than the physically adsorbed one. The chitosan immobilized on the PE surface exhibited the expected antibacterial activity when tested against three bacteria, which included two Gram‐negative bacteria, Salmonella enteritidis and Escherichia coli, and one Gram‐positive bacterium, Listeria monocytogenes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2444–2457, 2013     

Hydrogen atom density in a solar plasma reactor

A density of neutral hydrogen atoms was systematically measured in the MESOX solar plasma reactor at different MW powers and flow rates. The H-atom density was measured by a gold fibre optics catalytic probe. The H-atom density was in general increasing with increasing MW power. At a pressure of 40 Pa and a power of 500 W it was about 3.5 × 10²¹ m⁻³ and at a power of 1000 W it was about 4.1 × 10²¹ m⁻³. A degree of dissociation of hydrogen molecules was between 3% and 20% depending on pressure and power. A maximum degree of dissociation was obtained at a pressure of 40 Pa and 1000 W, while the lowest one at 130 Pa and 500 W.