Study of Starch Granules Swelling by the Blue Dextran Method and by Microscopy

The evolution of corn and wheat starch granules swelling at different temperatures was determined by two techniques: the blue dextran method (which measures the swelling factor) and by optical (light) microscopy. The graphical results obtained using the blue dextran technique showed curves indicating the swelling of corn and wheat starch dispersions (at 64%, w/w, moisture content) characterized by an initial phase of slight swelling, a second phase of fast swelling and a final phase of maximum swelling. The concentrated solutions (42% and 47%, w/w, moisture content) showed a slight swelling with the increase in temperature. The effect of temperature on the shape of the granules was evaluated by the optical microscopy. The shape of the type A wheat starch granules was deformed at high temperatures. The corn and type B wheat granules had a spherical form. In the case of corn starch, a good correlation (r²= 0.929) was obtained between the results of optical microscopy and blue dextran techniques.     

Ulva lactuca is poorly fermented but alters bacterial metabolism in rats inoculated with human faecal flora from methane and non-methane producers

In vivo fermentation of Ulva lactuca was studied in previously germ-free rats inoculated with human flora obtained from non-, low- and high-methane producers (groups NMP, LMP and HMP, respectively), in comparison to germ-free rats. Rats were fed either a control diet or a diet containing 4% of dried Ulva lactuca. Production of metabolites varied according to the flora and diet. Ulva lactuca induced a specific high production of methane in the HMP group. With the three human flora, Ulva diet induced a similar increase in caecal pH. In the NMP and HMP groups, this increase was associated with a fall of lactic acid caecal concentration. In the LMP group it was related to a decrease in the concentration of short-chain fatty acids. Ulva lactuca appeared to be able to regulate the β-glucuronidase and β-glucosidase activities, reducing the relatively high levels observed in groups NMP and HMP and increasing the low levels obtained in the LMP group. Results show that, although it was poorly fermented, Ulva induced significant effects on the gut microflora metabolism. The methanogenic status of the human donor appeared to be an important factor. © 1998 SCI.     

Physiological parameters of Bacillus cereus marking the end of acid-induced lag phases

During lag phases microbial cells adapt to their environment and prepare to proliferate. Physiological parameters of B. cereus cells upon exposure to near-growth-boundary acid stress were investigated and markers for the transition between lag phase and growth were identified using fluorescent probes combined with flow cytometry. Determination of cell counts and optical density revealed lag phases of 1 h, 2 h and 5 h, in cultures shifted to pH 7, pH 5.3 (set with lactic acid) and pH 4.9 (set with sulfuric acid), respectively. The obtained lag phases fitted the trends in ATP levels, which were constant during the lag phase and increased after the onset of growth. Both the percentage of PI-stained cells and cells with a significant membrane potential decreased during the lag phase. This points to repair of membrane damage and the loss of membrane potential. However, both trends extended in the growth phase, thus not suitable to mark the onset of growth. The activity of the electron transfer chain and esterases did allow for assessment of transition between lag and growth phase. These activities were generally low during the lag phase and increased after the onset of growth. Our results show that, independent of the duration of the lag phase, for different conditions the same physiological trends could be observed. The change in signal of selected probes can be used as a marker for transition from lag phase to the growth phase and may aid in identification of novel targets interfering with bacterial exit from lag phase.     

Correlations, partitioning and bioaccumulation of heavy metals between different compartments of Lake Balaton

Correlations between trace metals in dissolved and particulate phases, zooplankton, mussels and sediments in Lake Balaton were investigated. The degree of correlation between the various metals was different in each of the investigated compartments. Particulate metal concentrations (microg g(-1)) were anti-correlated with suspended particulate matter (SPM) (mg l(-1)), indicating a dilution effect, while total metal concentrations in the water column (microg l(-1)) were highly correlated with SPM, implying a major influence of the turbidity on the total metal concentrations. Between compartments, not many significant correlations were recognized. Only Ba, Ca, Sr and Mg are correlated in the sediments and in the particulate phase, suggesting common sources for both compartments. Partitioning coefficients (Kd) of trace metals between dissolved and particulate phases are generally low, typical for natural water and fairly stable over the lake. Most of the trace metals (Zn, Co, Cd and Pb) exist in the particulate phase (for about 70% of the total metal load). Cu and Ni are exceptions, showing a more equal distribution. Bioconcentration factors (BCF) of zooplankton and mussels were comparable to those of other natural waters. A negative biomagnification from suspended particulate matter to zooplankton and from sediment to mussel was recognized for all trace metals, except a small enrichment of Zn in zooplankton and Cd in mussel. Four factors were recognized in SPM and in sediments but they did not contain the same group of metals. Cluster analysis showed that metal accumulations in the sediments were different between northern and southern shores and in SPM between western and eastern areas.     

Phthalate removal throughout wastewater treatment plant: Case study of Marne Aval station (France)

The fate of six phthalates: dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), butyl benzyl phthalate (BBP), bis (2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DnOP) was investigated throughout wastewater treatment processes in the wastewater treatment plant (WWTP) of Marne Aval (France). That plant treats wastewater from a highly populated area and was used as a pilot station for development of nitrification processes.In wastewater, at each step of treatment, DEHP was always the major compound (9 to 44 µg L^− 1), followed by DEP (1.6 to 25 µg L^− 1). Other phthalates averaged 1 µg L^− 1 and DnOP remained close to the detection limit in nearly all cases.In sludge, the prevailing compound was also DEHP (72 µg g^− 1) which is consistent with its tendency to get sorbed upon suspended matter (SM). DnOP came in third, in relation with its resistance to biodegradation.For the studied period, the removal efficiency of DEHP from wastewater was about 78%. That removal seemed to proceed rather from particle settling than from biodegradation. A highly significant correlation (p < 0.001) was found between DEHP and SM concentrations throughout treatment processes. The other compounds: DMP, DEP, DnBP and BBP, displayed satisfactory efficiencies ranging from 68 to over 96% for the lighter ones obviously more easily degraded.Under rainy periods, the plant discharge impact upon Marne River quality in terms of phthalate fluxes, appeared to be minor as compared to the amount brought by the storm overflows in the same area. Downstream of the WWTP discharge, DEHP concentration remained under the European norm for surface water (NQE: 1.3 µg L^− 1).Our study documents the behaviour of phthalate esters throughout a WWTP which treatment device is used by 55% of the WWTP in the river Seine basin.     

α-Al2O3 (0001) Surfaces: Atomic and Electronic Structure

New results on the     R ± 9° reconstructed α-Al₂O₃ (0001) surface, which can be obtained after heating at high temperature (1400°C) under vacuum, are presented. The atomic structure has been studied by combining low-energy electron diffractometry and grazing incidence X-ray scattering. The surface structure is found to be perfectly commensurable with the underlying bulk lattice. The surface consists of hexagonal zones of two, nearly perfect, close-packed Al (111) planes separated by a defect of hexagonal periodicity with a parameter of 26.44 Å. This model is consistent with previous surface studies of this reconstruction. The electronic structure has been investigated using valence band photoemission spectroscopy, X-ray absorption spectroscopy at the O K edge, electron energy loss spectroscopy, and X-ray-induced Auger electron spectroscopy. Interpretation of these experimental data in the frame of a self-consistent, tight-binding calculation leads to the conclusion that the     R ± 9° reconstructed surface is more covalent than the (1 × 1) surface. Significant changes in the; Al-O hybridizations are observed; these are likely due to a difference in the interatomic distances along the [0001] axis (relaxations). The increase of covalent character is mainly due to a strong decrease of the Madelung field on the reconstructed surface.     

Simultaneous determination of the main molecular species of soybean phosphatidylcholine or phosphatidylethanolamine and their corresponding hydroperoxides obtained by lipoxygenase treatment

A method for the simultaneous determination of the main molecular species of soybean phosphatidylcholine or phosphatidylethanolamine and their corresponding hydroperoxides is described. Hydroperoxides were formed by incubation of phospholipids with lipoxygenase at pH 9.2. Silicic acid column chromatography (silica Sep-Pak column) was used to separate the phospholipids into phosphatidylcholine and phosphatidylethanolamine. A single C−18 reverse-phase column was employed to separate the main molecular species of soybean phosphatidylcholine or phosphatidylethanolamine and their hydroperoxides by high-performance liquid chromatography. The mobile phase consisted of 5% 10 mM ammonium acetate at pH 5 and 95% methanol. The molecular species of phosphatidylcholine and phosphatidylethanolamine were detected at 205 nm; the eluate was mixed with a chemiluminescence reagent (isoluminol and microperoxidase) and monitored by fluorometry. Under the experimental conditions used, three individual molecular species of both soybean phosphatidylethanolamine and phosphatidylcholine (18∶3/18∶2, 18∶2/18∶2 and 16∶0/18∶2), together with their corresponding hydroperoxides, were identified and quantitated.     

Surface functionalization with phosphazenes. V. Surface modification of plasma-treated polyamide 6 with fluorinated alcohols and azobenzene derivatives through chlorinated phosphazene intermediates

In this article, we describe the synthesis and characterization of surface-modified polyamide-6, using polydichlorophosphazene and hexachlorocyclophosphazene as coupling agents. The solid surface of this polymer was modified first by the introduction of polar functions (CO, OH, OR, COOH, COOR, etc.) with a cold plasma technique, then by the treatment of the alcoholic groups on the surface with (NPCl₂)_n and (NPCl₂)₃ to graft these substrates through the formation of strong covalent P O C bonds, and eventually by the substitution of the residual chlorines on the polyamide-6 surface with different types of fluorinated alcohols (2,2,2-trifluoroethanol and heptadecafluorononanol) and with 4-hydroxyazobenzene. Contact-angle measurements, together with X-ray photoelectron spectroscopy and ultraviolet–visible spectroscopy techniques, support the occurrence of these surface-functionalization reactions. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Charging and discharging phenomena in electrostatically-driven single-crystal-silicon MEM resonators: DC bias dependence and influence on the series resonance frequency

This paper presents a first study concerned with charging and discharging phenomena in single crystal silicon MEM resonators. It is shown that the DC voltage required for the device operation induces a residual voltage between the resonator and its driving electrode, which is attributed to dielectric charging. The residual voltage can affect the device series resonance frequency and is determined from the measurements. The residual voltage maximum amplitude and the charging rate depend not only on the stressing voltage amplitude but also on the polarization.