Toxin composition and toxicity dynamics of marine gastropod Nassarius spp. collected from Lianyungang, China

Consumption of nassariid gastropods often leads to poisoning incidents in some coastal provinces in China. To elucidate the pattern of toxicity dynamics and origin of toxins, samples of gastropod Nassarius spp. were collected from late May to early August 2007 from Lianyungang, Jiangsu province, where the poisoning incidents have been frequently reported. Toxicity was first screened with the mouse bioassay method, and tetrodotoxin and its analogues (TTXs) were analysed with high-performance liquid chromatography coupled with an ion-trap mass spectrometer (HPLC-MS(n)). The toxicity of nassariid N. semiplicatus showed an 'M'-shaped pattern of fluctuation during the sampling season. Two peaks of toxicity appeared in late May and late July. The maximum toxicity was recorded on 24 May, with the value of 846 mouse unit (MU) g(-1) of tissue (wet weight). TTX and its analogues trideoxyTTX, 4-epiTTX, anhydroTTX and oxoTTX were detected in the nassariid samples. TrideoxyTTX but not TTX was the major toxin in all the samples. No paralytic shellfish poison (PSP) was detected in the sample with the maximum toxicity by HPLC-FLD analysis. Variation of TTX content in the tissue of nassariid gastropods correlates well with the dynamics of toxicity. It is suggested that TTXs are the major toxins corresponding to the toxicity of the nassariids, and May and July are the high-risk seasons for consumption of nassariids, which is critical for the management of poisoning incidents.     

The dyeing and colour characteristics of alkali–treated polyester fibres dyed with disperse dyes

Alkali–treated and untreated polyester fabrics were dyed for up to 6 h at 100°C with a series of six disperse dyes of different chemical structures. The alkali–treated polyester samples adsorbed more dye and were dyed to deeper depths of shade and slightly different shades than was the untreated polyester. The greatest differences were observed for the alkali–treated polyester with the most outer surface or skin removed. Dye structure and molecular size also affected the amount of dye adsorbed on the fibres, but did not delineate the nature of differences between skin and core morphology. This study shows that significant differences exist between the molecular structure of the skin and core of melt–spun polyester fibres.     

Measurement of ionic calcium in milk

There are many reports in the literature regarding the effects of ionic calcium on reactions related to casein micelle stability, such as heat stability, ethanol stability and susceptibility to gelation, sediment formation and fouling. However, experimental evidence supporting these assertions is much less readily available.
This paper evaluates three selective ion electrode systems for measuring ionic calcium directly in milk as well as looking at the effects on pH reduction and addition of calcium chloride.
The best electrode system was the Ciba Corning 634 system, which was designed for blood but has been modified for milk. This was found to be reproducible and stable when calibrated daily and allowed direct measurements to be taken on milk in 70 s. This has been found to perform well now for 3 years. The other systems were not so useful, as they took longer to stabilize, but may be useful for higher ionic calcium concentrations, which are found in acidified milk products.
Reducing the pH increased ionic calcium and reduced ethanol stability. Calcium chloride addition reduced pH, increased ionic calcium and reduced the ethanol stability. Readjusting the pH to its value before calcium addition reduced the ionic calcium, but not back to its original value. Milks from individual cows showed wide variations in their ionic calcium concentrations.
This establishes the methodology for a more detailed investigation on measurement of ionic calcium in milks from individual cows and from bulk milks, to allow a better understanding of its role in casein micelle stability.     

Persistent toxic substance inputs to the river Seine basin (France) via atmospheric deposition and urban sludge application

Paris constitutes a major direct and indirect source of persistent toxic substances (PTS) to the river Seine, its tributaries and its basin, by atmospheric depositions and sewage sludge land-filling. The contaminant cycle and transfer pathways were investigated from 1999 to 2003 at local and inter regional scales in order to determine the respective importance of the main input and diffusion processes (wastewater, rainwater and runoff) from urban to rural areas. Paris constitutes an atmospheric emission hot spot for PAHs and PCBs. For example, for 2002, atmospheric concentrations ranged from 0.5 to 3 ng m(-3) for PAHs (Sigma 6 WHO) and from 0.06 to 0.69 ng m(-3) for PCBs (Sigma 7, EEC) and concentrations in bulk deposition ranged from 6.6 to 647 ng L(-1) for PAHs (Sigma 14) and from 0.6 to 8.1 ng L(-1) for PCBs. At Paris, annual atmospheric deposition inputs of PAHs (Sigma 6) and PCBs (Sigma 7) reached 104 g km(-2) and 35 g km(-2), respectively. PAHs followed a marked seasonal cycle in relation with winter domestic heating and bulk deposition concentrations were 5 to 15 times lower in remote areas. No seasonal cycle was observed for PCBs which varied little according to the area considered. PCB deposition fluxes were ruled by the rainfall amount, while for PAHs, the fluxes depended on local anthropogenic characteristics. At the scale of the Seine-Aval treatment plant comparison of annual inputs of PTS in wet period indicated that PCBs essentially come from atmospheric sources whereas PAHs are derived from both atmospheric and urban runoff sources. At the scale of the sub-basin, atmospheric inputs to the soil (Sigma 3 PAHs: 14-25 g km(-2), Sigma 7 PCBs: 5.6-25 g km(-2)) represent the prevailing source for PAHs and PCBs, as compared to that from the disposal of urban sludge on agricultural plots (Sigma 3 PAHs: 3-8 g km(-2), Sigma 7 PCBs: 0.5-2 g km(-2)).     

Preparation of Polymer Composite Membrane Reinforced by Natural Fibers (Fiber and Stem of Date Palm) for Treatment of Industrial Waste Water Residue

Theoretical Foundations of Chemical Engineering - The developed industries are utilized natural waste fibers as a clean criteria device. This work utilized natural composite membranes in the...     

Simultaneous high gain and wide dynamic range in a model of bacterial chemotaxis

Mathematical modelling and sensitivity analysis of the signal transduction pathway underlying chemotaxis in Escherichia coli suggests a mechanism for high sensitivity over a dynamic range of five orders of magnitude. The analysis reveals that the enhancement in sensing ability occurs in the signal receiving module that is comprised of ligand binding, change of occupancy and change of receptor activities. The clustering of receptors contributes to the signal capability by exploiting interactions between receptors for the activity change. The role of the autophosphorylation of the histidine kinase CheA and the phosphotransfer to the response regulator protein CheY is to relay the signal to the cell's motor apparatus at little expense to the sensitivity at low stimuli. The results also provide insight on the values of kinetic parameters that maximise the efficiency of the signalling pathway.     

Identification of lactic acid bacteria in Taiwanese ropy fermented milk and evaluation of their microbial ecology in bovine and caprine milk

The purpose of this study was to identify species of lactic acid bacteria in Taiwanese ropy fermented milk and to study their microbial dynamics during the fermentation process through conventional microbiological cultivation and PCR-denaturing gradient gel electrophoresis. Identification results indicated that Lactococcus lactis ssp. cremoris and Leuconostoc mesenteroides ssp. mesenteroides were the major lactic acid bacteria in Taiwanese ropy fermented milk. Interestingly, 3 groups were identified as Lc. lactis ssp. cremoris using 16S rDNA sequencing, but they showed different denaturing gradient gel electrophoresis patterns and assimilation of carbohydrates. In addition, the microbial dynamics study in different fermentation stages demonstrated that Lc. lactis ssp. cremoris was the most dominant bacterial species in the samples, followed by Leu. mesenteroides ssp. mesenteroides with no differences among the fermentation stages. Finally, the microbial distribution profiles showed that the microbial ecology was different in bovine, caprine, and reconstituted milk, which might further affect the characteristics of the product.     

Thermal transpiration correction in capacitance manometers

Capacitance manometers with sensors maintained at temperatures above ambient show a non-linearity in their pressure response. It is shown that the magnitude of this effect is consistent with the thermal transpiration effect calculated from simple kinetic theory. In addition, good agreement is found with the empirical model of Takaishi and Sensui⁵. This model provides a simple method of calculating the response of a capacitance manometer, for a given gas, from a previous calibration with any gas.     

New green coatings made from fatty acid dispersions: improvement in barrier properties of biodegradable thermoplasticized-starch substrate

This work was aimed at developing new coatings on biodegradable substrates for possible use in food packaging. In order to study barrier properties of these coatings made from fatty acid dispersions, oxygen permeability, water vapor permeability and also contact angle measurements were carried out. The coatings made from a fatty acid exhibited good barrier properties towards oxygen gas. Moreover, these coatings presented a higher contact angle value than the one obtained directly for the substrate without coating; this can be likely due to the hydrophobic nature of fatty acid and the recrystallization of fatty acid during the drying process.     

Fracture toughness and crack growth mechanism for multiphase polymers

The fracture behavior of acrylonitrile-butadiene-styrene (ABS) was investigated using the J-integral method under monotonic loading. Two ways were used to monitor the onset of crack growth: the dyeing method and the length of craze region ahead of initial notch. The blunting at the crack tip and crack growth mechanism for ABS Was observed using a scanning electron microscope. Before the onset of crack growth, the energy put into material was dissipated to create crazes ahead of the initial notch and to deform the material at the crack tip. A part of the energy was released to create a new crack surface after the onset, of crack growth.