Rapid and selective determination of hydrogen peroxide residues in milk by batch injection analysis with amperometric detection

We report a highly rapid, precise, selective and sensitive analytical method for the determination of hydrogen peroxide in milk using a batch-injection analysis (BIA) with amperometric detection at a Prussian-blue bulk modified graphite-composite electrode. An electronic micropipette injected 100 μL aliquots of 10-fold diluted samples (high and low-fat milk) directly onto the modified electrode immersed in the BIA cell. The analytical features of our proposed method includes low RSD between injections (0.76%, n = 9), low detection limit (10 μmol L⁻¹), elevated analytical frequency (up to 80 h⁻¹) and satisfactory recovery values for spiked samples. A fresh and highly reproductive electrode surface can be easily obtained by simple mechanical polishing (RSD = 1.6%, n = 5). The storage stability of the PB-modified graphite-composite surpassed 1 year keeping equivalent performance as initially presented. The association of BIA with an improved amperometric detector provides great promise for routine monitoring of hydrogen peroxide in milk and other beverages.     

Molecular diversity of Staphylococcus aureus and the role of milking equipment adherences or biofilm as a source for bulk tank milk contamination

Staphylococcus aureus is one of the most frequent pathogens causing intramammary infections in dairy herds. Consequently, virulence factors, pathobiology, and epidemiology of Staphylococcus aureus strains have been widely assessed through the years. Nevertheless, not much has been described about the epidemiology of Staph. aureus strains from bulk tank milk (BTM) and adherences on milking equipment (AMES), even when these strains may play a role in the quality of milk that is intended for human consumption. The objective of this study was to assess the strain diversity of 166 Staph. aureus isolates collected from 3 consecutive BTM samples, and from AMES in contact with milk from 23 Chilean dairy farms. Isolates were analyzed and typed using pulsed-field gel electrophoresis. Diversity of strains, both within and among farms, was assessed using Simpson's index of diversity (SID). On farms where Staph. aureus was isolated from both AMES and BTM (n = 8), pulsotypes were further analyzed to evaluate the role of AMES as a potential source of Staph. aureus strains in BTM. Among all Staph. aureus analyzed by pulsed-field gel electrophoresis, a total of 42 pulsotypes (19 main pulsotypes and 23 subtypes) were identified. Among dairy farms, strain diversity was highly heterogeneous (SID = 0.99). Within dairy farms, Staph. aureus strain diversity was variable (SID = 0 to 1), and 18 dairy operations (81.8%) had one pulsotype that was shared between at least 2 successive BTM samples. In those farms where Staph. aureus was isolated in both AMES and BTM (n = 8), 7 (87.5%) showed a clonal distribution of Staph. aureus strains between these 2 types of samples. The overlapping of certain Staph. aureus strains among dairy farms may point out common sources of Staph. aureus among otherwise epidemiologically unrelated farms. Indistinguishable Staph. aureus strains between AMES and BTM across dairy farms suggest that Staph. aureus–containing AMES may represent a source for BTM contamination, thus affecting milk quality. Our study highlights the role of viable Staph. aureus in AMES as a source for BTM contamination on dairy farms, and also describes the overlapping and presence of specific BTM and AMES pulsotypes among farms.     

MICROSCOPIC CHARACTERIZATION OF OIL SANDS PROCESSING EMULSIONS

ABSTRACT

Microscopic characterization of oil sands emulsions can be important in the prediction of processing characteristics and process yields in the extraction of oil from oil sands. The size distribution of the emulsion can determine how efficiently the oil can be separated from the water and by what means: mechanically or chemically. In addition, it is possible to characterize the nature of the dispersed phase by using fluorescence behaviour under an optical microscope or via x-ray analysis with a scanning electron microscope. In certain cases it is also possible to characterize the interface between the dispersed and the continuous phases. This paper presents results from our laboratory using microscopic techniques and illustrates their utility, not only for determining the morphology of these economically important emulsions, but also to characterize the composition of the interface itself.     

Optimized interpolator filters for timing error correction in DMTsystems for xDSL applications

Discrete multitone (DMT) modulation is a multicarrier technique that allows the transmission of high speed data over band limited channels. This type of system is very sensitive to synchronization errors when used in digital subscriber loop applications (xDSL), due to the high number of carriers and high density constellations involved. This paper addresses the topic of all-digital timing error correction in a DMT system for xDSL applications, where the timing error correction procedure is based entirely on signal interpolation. An analytical study of the interpolator filter performance is carried out, arriving at an expression for the signal-to-distortion ratio (SDR) at the output of the receiver, as a merit figure. In this derivation, the fixed frequency domain equalizer (FEQ) plays an important role since it compensates for a great part of the distortion introduced by the interpolator. From this study, the design of the optimal interpolator filter in terms of SDR, based on a multirate approach with Kaiser window, is presented. Specific designs for ASIC and for DSP-based implementations are obtained. Performance results are excellent, yielding SDR values above 50 dB for all carriers while keeping the computational cost low     

Safety and cost-effectiveness of outpatient total body irradiation in pediatric patients undergoing stem cell transplantation

Political changes in Poland in 1989 initiated a transition period for country's economy into a free market. This new situation prompted the pharmaceutical sector to apply for marketing authorization of a huge number of drugs. Subsequently, the availability, supply and variety of drugs was changing to resemble the one existing on the European Union market. We have analyzed the pattern of adverse drug reactions reported in Poland during the past 10 years. Subsequently we compared our data for years 1991-1995 with the reports received by the Belgian National Center for Monitoring of Adverse Drug Reactions over period 1990-1994. It was found that the number of reports increased in parallel with the number of drugs available. Also the variety of reported reactions was greater. Spontaneous reporting by individual physicians increased and the number of reports from the pharmaceutical inspection diminished. Comparison with the patterns of reporting in Belgium showed the range of drugs included in the reports to be similar in both countries during the studied period. In conclusion: we found that the increase in range and availability of drugs changed substantially the patterns of reporting of adverse drug reactions in Poland. It became similar to that observed in EU countries.     

Which ethics will survive in our technological society?

Today, in our technical civilization, every kind of human activity and production is heavily and increasingly tied to or surrounded by technology and technical schemes. Ethics is not an exception to this dramatic change. Under these circumstances the traditional role of ethics becomes even more difficult because the technological environment also has transformed human beings. Humans are often seen as just another element in a technological system, which has to adapt themselves to requirements imposed on them by the system. Therefore, before formulating any general or applied ethics (bioethics, computer ethics,...) it makes sense to ask to what extent traditional ethical arguments are still possible, not to say useful.     

Inhibitory activity of cigarette-smoke condensate on the mutagenicity of heterocyclic amines

Cigarette-smoke condensate (CSC) is a complex mixture containing over 3800 identified chemicals including nicotine, water, mutagens, antimutagens, cytotoxins and inert chemicals. Although CSC is mutagenic in the Ames test, its effect on the activity of other mutagens has not been characterized. Using the Ames Salmonella bacterial mutagenesis assay, we found CSC exerts a significant inhibitory effect on mutagens requiring bioactivation. Those studied included heterocyclic amines (Glu-P-1, Glu-P-2, IQ, MeIQ, Trp-P-1 and Trp-P-2), benzo[a]pyrene (B[a]P) and aflatoxin B1. However, CSC had no effect on the activity of direct-acting mutagens (2-nitrofluorene, sodium azide, 4-nitro-1,2-phenylenediamine, 4-nitroquinoline N-oxide and methyl methanesulfonate). With indirect-acting mutagens, the reduced number of revertants observed in the presence of CSC was not attributable to cytotoxicity. CSC exhibited a potent inhibitory effect on the cytochrome P-450 dependent monooxygenases, ethoxyresorufin O-deethylase and B[a]P hydroxylase. This suggests inhibition of the cytochrome P-450 isozymes as one possible mechanism for the antimutagenicity of CSC. Fractionation studies of CSC revealed that the neutral, weakly acidic (phenolic) and basic fractions are all effective as antimutagens against Glu-P-1, a representative heterocyclic amine. This indicates that several classes of chemicals contribute to the inhibitory effect of CSC on the mutagenicity of the heterocyclic amines.     

Automatic measurement of permittivity and permeability at microwavefrequencies using normal and oblique free-wave incidence with focusedbeam

A free-wave method for determining the dielectric and magnetic properties of materials from reflection measurements made at normal incidence and transmission measurements made at normal and oblique incidence is proposed. The method combines frequency domain measurements and time domain (TD) analysis and uses polarization to avoid typical ambiguities in the results. Varying the incident angle and the polarization, measurements were made in the X-band. The technique was validated by comparing the results obtained with those from well-established waveguide techniques. A focusing assembly makes it possible to measure relatively small samples, thus avoiding diffraction problems. It also improves the ambiguity-solving procedure proposed for the technique. The measurement procedure is fully automated by using the HP8510 network analyzer controlled by an HP362 computer, which also processes the data. Results for low-loss dielectrics such as teflon, nylon, and polymethyl methacrylate (PMMA) and for microwave-absorbing materials are reported     

Infections due to nontuberculous mycobacteria in children with leukemia

We reviewed the spectrum of infections due to nontuberculous mycobacteria (NTM) in children with leukemia. Three children acquired such infections. One patient developed pneumonia after the cessation of chemotherapy when Mycobacterium xenopi was identified in his lung biopsy specimen. He required 2 years of treatment with antituberculous agents and clarithromycin. Cultures of central and peripheral blood specimens from two patients yielded Mycobacterium fortuitum and Mycobacterium chelonae, respectively. Broviac catheters were likely the source of infection. Removal of the catheters and antibiotic treatment resulted in cure. Central venous catheters in leukemic children are potential sources of infection. For febrile neutropenic children with leukemia who do not respond to antibiotic therapy, cultures positive for diphtheroids or negative routine bacterial and fungal cultures should raise a suspicion for infections due to NTM. Systemic infections may require up to 2 years of therapy. Removal of the infected catheters during persistent or recurrent infections in necessary for control of the infection.