Evaluation of 28 marine algae from the Qingdao coast for antioxidative capacity and determination of antioxidant efficiency and total phenolic content of fractions and subfractions derived from Symphyocladia latiuscula (Rhodomelaceae)

The extracts obtained from 28 species of marine algae were evaluated for their antioxidant activity (AA) versus the positive controls butylated hydroxytoluene (BHT), gallic acid (GA), and ascorbic acid (AscA). Most of the tested samples displayed antioxidant activity to various degrees. Among them, the extract of Symphyocladia latiuscula exhibited the strongest AA, which was comparable to BHT, GA, and AscA in radical scavenging activity, as shown in the DPPH (alpha,alpha-diphenyl-beta-picrylhydrazyl) assay, and higher than those of the positive controls in beta-carotene-linoleate assay system. In addition, the ethyl acetate-soluble fraction isolated from the crude extract of S. latiuscula exhibited the highest antioxidant activity in both assay systems. This fraction was further fractionated into seven subfractions (F1-F7) by vacuum liquid chromatography (VLC). F1 and F4 were found to be the most effective subfractions in scavenging DPPH radical assay and in the beta-carotene-linoleate assay, respectively. The total phenolic content (TPC) and reducing power (RP) for all of the extracts, fractions, and subfractions (F1-F7) were also determined. The TPC of the 28 extracts ranged from 0.10 to 8.00 gallic acid equivalents (mg/g seaweed dry weight) while the RP ranged from 0.07 to 11.60 ascorbic acid equivalents (mg center dot g(-1) seaweed dry weight). Highly positive relationships between AA and TPC as well as between AA and RP were found for the extracts and fractions, while for the subfractions F1-F7 only weak or no such relations were found. The results obtained from this study indicate that further analysis is needed of those marine algal species that contain the most antioxidant activity in order to identify the active principles.

Growth characters and photosynthetic capacity of Gracilaria lemaneiformis as a biofilter in a shellfish farming area in Sanggou Bay, China

Experiments on growth characters and ecological functions of the macroalgae Gracilaria lemaneiformis, collected from south China, were conducted in polyculture areas of kelp and filter-feeding bivalve in Sanggou Bay in Weihai City, Shandong, in north China from May 2002 to May 2003. The results of 116 days cultivation showed that the average wet weight of alga increased 89 times from 0.1 to 8.9 kg rope(-1), with an average specific growth rate ( based on wet weight) of 3.95% per day. The most favorable water layer for its growth was 1.0 - 1.8 m below the surface in July and August, with an average specific growth rate of 8.2% per day in 30-day experiments. Photosynthetic activity changed seasonally, with an average of 7.3 mg O-2 g dw(-1) h(-1). The maximum rate (14.4 mg O-2 g dw(-1) h(-1)) was recorded in July, or 19.3 mg CO2 g dw(-1) h(-1), while the minimum (0.40 mg CO2 g dw(-1) h(-1)) was in April. This study indicated that the culture of G. lemaneiformis is an effective way to improve water quality where scallops are cultivated intensively.

Capacity of soil to protect organic carbon and biochemical characteristics of density fractions in Ziwulin Haplic Greyxems soil

Physical protection is one of the important ways to stabilize organic carbon in soils. In order to understand the role of soils as a carbon sink or source in global climatic change and carbon cycles and properly manage soils as a carbon sink, we ought to know how many organic carbon (OC) in a given soil could be protected. By a density fractionation approach and ultrasonic technique, each soil sample was divided into three fractions: free light fraction (free-LF), occluded fraction (occluded-LF) and heavy fraction (HF). The obtained fractions were analyzed for total OC content, carbohydrate content and recalcitrant OC content. The results showed: (i) In the whole soil profile, dominance of OC consistently decreased in the following order: HF, free-LF, occluded-LF. This suggested that OC in soils were mostly protected. From 0-10 to 60-80 cm horizons, the OC in free-LF decreased from 25.27% to 3.72%, while OC in HF they were increased from 72.57% to 95.39%. The OC in occluded-LF was between 2.16% and 0.89%. (ii) Organic carbon recalcitrance in free-LF was similar to that in HF, and was even higher than that in HF below the surface horizon. This suggested that free-LF was not always the most fresh and non-decomposed fraction. OM quality of HF was higher than that of free-LF in the surface 10 cm below, namely the protected OM had higher quality than free OM in these horizons.

Heat capacity enhancement and thermodynamic properties of nanostructured amorphous SiO2

The heat capacity of nanostructured amorphous SiO2 (na-SiO2) has been measured by adiabatic calorimetric method over the temperature range 9-354 K. TG and differential scanning calorimeter (DSC) were also employed to determine the thermal stability. Glass transition temperature (T-g) for the two same grain sizes with different specific surface of naSiO(2) samples and one coarse-grained amorphous SiO2 (ca-SiO2) sample were determined to be 1377, 1397 and 1320 K, respectively. The low temperature experimental results show that there are significant heat capacity (C-P) enhancements among na-SiO2 samples and ca-SiO2. Entropy, enthalpy, Gibbs free energy and Debye temperature (theta (D)) were obtained based on the low temperature heat capacity measurement of na-SiO2. The Cp enhancements of na-SiO2 were discussed in terms of configurational and vibrational entropy. (C) 2001 Elsevier Science B.V. All rights reserved.

Enhancement of molar heat capacity of nanostructured Al2O3

The nanosized alumina prepared by the hydrolysis method with an average particle size of 20 nm was characterized by X-ray diffraction. The heat capacity measurements of the prepared sample were carried out using an adiabatic calorimeter in the temperature range from 78 to 370 K. Enhancement of heat capacity was observed in the nanostructured materials as the heat capacity data were compared with those of the corresponding coarse-grained materials. The enhanced heat capacity was discussed on the basis of experiments. Differential scanning calorimetry and thermogravimetry were used to determine the thermal stability of the nanostructured alumina.

Heat capacity and thermochemical study of trifluoroacetamide (C2H2F3NO)

The low-temperature heat capacities of trifluoroacetamide were precisely determined with a small sample precision automated adiabatic calorimeter over the temperature range from 78 to 404 K. A solid-to-solid phase transition, a fusion and a phase transition from a liquid crystalline phase to fully liquid phase have been observed at the temperatures of 336.911+/-0.102, 347.622+/-0.094 and 388.896+/-0.160 K, respectively. The molar enthalpies of these phase transitions as well as the chemical purity of the substance were determined to be 5.576+/-0.004, 11.496+/-0.007, 1.340+/-0.005 kJ mol(-1) and 99.30 mol%, respectively, on the basis of the heat capacity measurements. The molar entropies of the three phase transitions were calculated to be 16.550+/-0.012, 33.071+/-0.029 and 3.447+/-0.027 J mol(-1) K-1, respectively. Further researches of the thermochemical properties for this compound have been carried out by means of TG and DSC techniques. (C) 2000 Elsevier Science B.V. All rights reserved.

Determination of total iron binding capacity of serum by capillary electrophoresis

A capillary electrophoresis (CE) technique for determining total iron binding capacity (TIBC) of serum has been developed. The optimum serum pretreatment involves the following major steps: at first, saturate serum transferrin with Fe+3; then, dissociate them completely after removing excess unbound Fe. Finally, complex the released iron with phenanthroline, a chromophore, to make suitable for the CE analysis. Ammonium acetate (pH = 5.0) was used as CE background electrolyte solution. In this system, a good linear correlation coefficient was maintained over the range 0.5 similar to 10 mu M (r = 0.9979, n =12). Seven adult serum samples were studied and the TIBC parameters measured. In the present system, 10 similar to 30 mu L serum is sufficient for determination. The study shows that the CE technique described is a powerful method for rapid, efficient, sensitive and reliable analysis and hence particularly suitable for clinical application.

Low-temperature heat capacity and phase transition of n-hexatriacontane

The heat capacities of crystalline and liquid n-hexatriacontane were measured with an automatic adiabatic calorimeter over the temperature range of 80-370 K. Two solid-to-solid phase transitions at the temperatures of 345.397 and 346.836 K, and a fusion at the temperature of 348.959 K have been observed. The enthalpies and entropies of these phase transitions as well as the chemical purity of the substance were determined on the basis of the heat capacity measurements. Thermal decomposition temperatures of the compound were measured by thermogravimetric analysis. (C) 1999 Elsevier Science B.V. All rights reserved.