Marangoni heat transfer in subcooled nucleate pool boiling

The liquid motion induced by surface tension variation, termed the Marangoni effect, and its contribution to boiling heat transfer has been an issue of much controversy. Boiling heat transfer theory, although acknowledging its existence, considers its contribution to heat transfer to be insignificant in comparison with buoyancy induced convection. However, recent microgravity experiments have shown that although the boiling mechanism in a reduced gravity environment is different, the corresponding heat transfer rates are similar to those obtained under normal gravity conditions, raising questions about the validity of the assumption. An experimental investigation was performed in which distilled water was gradually heated to boiling conditions on a copper heater surface at four different levels of subcooling. Photographic investigation of the bubbles appearing on the surface was carried out in support of the measurements. The results obtained indicate that Marangoni convection associated with the bubbles formed by the air dissolved in the water which emerged from solution when the water was heated sufficiently, significantly influenced the heat transfer rate in subcooled nucleate pool boiling. A heat transfer model was developed in order to explain the phenomena observed.     

Complexity Reduction in SISO Decoding of Block Codes

SISO decoding for block codes can be carried out based on a trellis representation of the code. However, the complexity entailed by such decoding is most often prohibitive and thus prevents practical implementation. This paper examines a new decoding scheme based on the soft-output Viterbi algorithm (SOVA) applied to a sectionalized trellis for linear block codes. The computational complexities of the new SOVA decoder and of the conventional SOVA decoder, based on a bit-level trellis, are theoretically analyzed and derived for different linear block codes. These results are used to obtain optimum sectionalizations of a trellis for SOVA. For comparisons, the optimum sectionalizations for Maximum A Posteriori (MAP) and Maximum Logarithm MAP (Max-Log-MAP) algorithms, and their corresponding computational complexities are included. The results confirm that the new SOVA decoder is the most computationally efficient SISO decoder, in comparisons to MAP and Max-Log-MAP algorithms. The simulation results of the bit error rate (BER) performance, assuming binary phase -- shift keying (BPSK) and additive white Gaussian noise (AWGN) channel, demonstrate that the performance of the new decoding scheme is not degraded. The BER performance of iterative SOVA decoding of serially concatenated block codes shows no difference in the quality of the soft outputs of the new decoding scheme and of the conventional SOVA.     

Effect of high hydrostatic pressure on mortality and allergenicity of Anisakis simplex L3 and on muscle properties of infested hake

BACKGROUND: High pressure (HP) ranging from 100 to 350 MPa (1–15 min) was applied to Anisakis simplex larvae and parasitised hake (Merluccius merluccius) muscle. The aim of the study was to kill the larvae to prevent human anisakidosis, to evaluate the effect on A. simplex allergens and to minimally alter fish muscle quality. RESULTS: The larvae were killed at pressures ≥ 200 MPa and times ≥ 1 min, producing alterations in the larva body and ruptures in the cuticle when observed by scanning electron microscopy. Nevertheless, Ani s 4 and A. simplex crude antigens were recognised by immunoblotting and immunohistochemistry at all HPs assayed. Small changes in colour and texture were observed in fish muscle under all pressure/time conditions. Major changes were observed visually at 300 MPa, where the muscle appeared as slightly cooked. Apparent viscosity of muscle homogenates decreased significantly at longer times or higher applied pressure. No changes were detected at 200 MPa in the electrophoretic pattern of proteins treated with or without β‐mercaptoethanol, suggesting that disulfide bonds were not formed. CONCLUSION: Application of HP at 200 MPa for up to 5 min would kill A. simplex larvae, avoiding infestation of the consumer and causing small changes in the hake muscle perceived sensorially. However, HP‐treated A. simplex‐parasitised fish would still be a potential hazard for consumers allergic to the larvae. Copyright © 2009 Society of Chemical Industry     

Changes in kinetic parameters of decomposition of MgH2 destabilized by irradiation with C ions

In attempt to improve desorption behaviour of MgH₂, the influence of well-defined structural changes induced within a thin surface layer of MgH₂ have been investigated. The defects were induced by 30 keV C²⁺ ions irradiation using different fluencies ranging from 10¹²–10¹⁶ ions/cm². The hydrogen desorption properties were investigated by thermal desorption spectroscopy analysis (TDS), while kinetics parameters were deduced using non-isothermal kinetic approach. The existence of multiple TDS peaks and different curve shapes indicate difference in desorption mechanism. To understand changes in the rate limiting step, shapes of all desorption peaks have been analyzed using different kinetic models. Regarding the irradiated sample, the function based on Avrami–Erofeev model with n=4$n=4$ gives the best fit over θ   range from 0.3 to 0.8 while for untreated sample the best fit is obtained for Avrami–Erofeev model with n=3$n=3$. The change in mechanism can be attributed to the different way of nuclei growth.     

Aqua regia extracted metals in sediments from the industrial area and surroundings of Pančevo, Serbia

Surface and buried sediments were analyzed for Ba, Ca, Cd, Co, Cr, Cu, Mn, Ni, Pb, Zn and V, as well as for total carbon and hydrogen to assess the distribution of sediment pollution due to the vicinity of the petrochemical complex. The samples, collected from 20 locations within the petrochemical complex and from 16 locations outside the complex, were aqua regia extracted and analyzed by ICP/OES. Metals were determined with an acceptable accuracy for certified metals of 82-113%. The precision for the aqua regia extraction was satisfactory, less than 20%, except for Cd where it was 28%. Comparison of the data from the petrochemical with those from the non-petrochemical areas showed different distributions of the metals. Metals that exceeded the baseline range; Ba, Cd, Cu, Zn and Pb, were detected in higher concentrations in sediments that were under the influence of the chlor-alkali plant within the petrochemical complex. Comparison with data from the petrochemical complex and its surroundings and their distribution demonstrated that the metal compositions of the sediments were modified by anthropogenic activities.     

Atrazine in groundwater of Vojvodina Province

The objective of this study was to investigate concentrations of atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine), deethylatrazine (DEA) (2-amino-4-chloro-6-isopropylamino-1,3,5-triazine), deisopropylatrazine (DIA) (2-amino-4-chloro-6-ethylamino-1,3,5-triazine) and deethyldeisopropylatrazine (DEIA) (6-chloro-2,4-diamino-1,3,5-triazine) in groundwaters of Vojvodina Province. A study was conducted during April 2001. Some 110 samples of groundwater were taken from near surface aquifers. The water samples were first passed through a disk containing solid matrix coated with a chemically bonded C-18 organic phase. The disk was then eluted with supercritical carbon dioxide to remove compounds from the sorbent. Finally the extract was injected into capillary gas chromatograph. Average concentrations were 0.198 μg L⁻¹ for atrazine, 0.116 μg L⁻¹ for DEA, 0.043 μg L⁻¹ for DIA and 0.077 μg L⁻¹ for DEIA.