Sources and behavior of technetium in the environment

Technetium is a man-made element produced in increasing amounts during the last decades. The chemical and physical properties of some technetium compounds are considered, and a discussion of possible source terms is included. Literature on the environmental behavior of technetium is reviewed to evaluate its transfer and equilibrium distribution in aquatic and terrestrial ecosystems. Considerable effort has been expended in the last years in order to understand the biogeochemical processes responsible for the long-term behavior of technetium in the environment and its transfer through food chains as well as to identify critical pathways of the long-lived radioisotope Tc-99 from the environment to man.     

The Role of Scale Stresses in the Sulfidation of Steels

Several high-temperature processes in chemical,petrochemical, and energy-processing industry arecharacterized by H₂S-containing atmospheres,confronting engineers with severe corrosion attack ofthe metallic components. Sulfidation is observed onmaterials used for heat exchangers within theheat-recovery zones. The damage is originated not onlyby the relatively fast growth rates of the sulfidescales, but is also due to the loss of their limitedprotective effect by cracking. Scale failure, as aconsequence of stresses generated during scale growthand by temperature changes, was investigated on a carbon steel, a low-chromium steel (1Cr-0.4Mo, T12),a ferritic-chromium steel (12Cr-1Mo), and on austeniticsteel (18Cr-9Ni, AISI 321). The experiments in thetemperature range 400-600°C (700°C), withsubsequent cooling to ambient temperature, wereaccompanied by acoustic-emission measurements in orderto detect scale cracking. Critical parameters for scalefailure are presented.     

Mapping the structure of a liquid spray by means of neural networks

This paper presents the results of a study aimed at mapping the structure of a liquid spray system along the spray cone. Experimental results obtained by phase-Doppler anemometry (PDA) consisted of the number distributions of droplet size, velocity, and interparticle arrival time at different locations within the spray cone. The experimental data were analyzed by means of multivariate statistical techniques, in order to identify different regimes in the spray. Neural network models (NN) were fitted to the experimental data, resulting in good agreement between experimental and calculated results for most locations within the spray cone. However, in some parts of the cone the agreement was poor, and the general trends could not be well predicted by the NN models. The mismatch is due to unsteady spray conditions or incomplete atomization (e.g. existence of non-spherical particles). This fact was adopted as a criterion to identify the regions where the spray is fully established, corresponding to the regions of the spray where PDA measurements can be successfully performed. This criterion has been applied along the spray cone for different operating conditions, and can be used as a tool to map the fluid dynamic characteristics in liquid sprays.     

Easily made and handled carbon nanocones for scanning tunneling microscopy and electroanalysis

Well-formed carbon nanocones at the ends of micrometer-diameter carbon fibers (CFs) were fashioned into functional tips for scanning tunneling microscopy (STM) and miniaturized voltammetric sensors. Sharpening of single graphite filaments was achieved by simple DC electrochemical etching in 0.1 N NaOH. Operated as STM tips, pointed CFs resolved in air the contour and surface morphology of a nanoscopic Au line pattern and imaged in vacuum a Si (1 1 1) surface with clear atomic resolution. Subjecting already etched CFs to tip-sparing insulation with electrodeposited paint produced conical carbon ultramicroelectrodes (UMEs) with effective radii down to about 900 nm. Comparative cyclic voltammetry trials in alkaline, neutral and acidic solutions showed that the conical carbon UME’s had a wider practical potential window for electroanalytic applications than, for instance, Pt disk UMEs. The CF-based conical sensors described here are exceptionally easy to make with simple laboratory equipment and perform well in STM topography imaging and voltammetry. The inherent simplicity of sensor production widens the field of potential users, and offers clear advantages over existing types of UMEs, in particular those based on carbon nanotubes, which are especially hard to handle in an optical microscope setting.     

Magnetic resonance butterfly coils: Design and application for hyperpolarized C studies

Hyperpolarized ¹³C magnetic resonance spectroscopy in pig models enables cardiac metabolism assessment and provides a powerful tool for heart physiology studies, although the low molar concentration of derivate metabolites gives rise to technological limitations in terms of data quality. The design of dedicated coils capable of providing large field of view with high Signal-to-Noise Ratio (SNR) data is of fundamental importance.     

Flow injection with chemical reaction interface-isotope ratio mass spectrometry: an alternative to off-line combustion for detecting low levels of enriched 13C in mass balance studies

Current methods to assess voice outcomes in patients with unilateral vocal cord paralysis (UVCP) are limited by expense, reliability, or lack of a true patient-relevant focus. The purpose of this study was to develop and validate a patient-based, disease-specific instrument, the Voice Outcome Survey (VOS), that is brief, reliable, and sensitive to real clinical change in patients with UVCP. Fifty-six consecutive patients with uncompensated UVCP and without complicating comorbid illness received the VOS, the Medical Outcome Study Short Form 36-Item Health Survey (SF-36), and a voice laboratory analysis before and 6 months after type I thyroplasty. Overall, reliability of the VOS was excellent (r = 0.87, P < 0.0001). The VOS index was significantly (P < 0.05) correlated to subscales of the SF-36 including social functioning (SF) (r = 0.56) and physical role functioning (r = 0.35), as well as changes in objective voice measures such as phonation time (r = 0.51) and average intensity (r = 0.44). The VOS index was the most sensitive measure to clinical change after surgery (standardized response means: VOS, 1.92; phonation time, 0.68; SF, 0.58; physical role functioning, 0.53; intensity, 0.51). The VOS is a brief, valid, reliable, and highly sensitive measure of disease-specific health status in patients with UVCP.     

Economical micromethod for determination of polar components in frying fats

The polar components, formed in fats during deep‐frying, comprise a multitude of different artifacts. Their content is a suited indicator of fat quality. As an alternative to the time‐ and chemicals‐consuming official methods a simplified micromethod is described. The method employs general laboratory equipment and disposable consumables. The eluent mixture of petroleum ether + diethyl ether (90 + 10) was substituted by a mixture of isohexane + diisopropyl ether (85 + 15), because the high volatility of the former eluent caused problems at elevated ambient temperatures, e.g. during hot summers.