A batch kinetic study on decolorization and inhibition of Reactive Black 5 and Direct Brown 2 in an anaerobic mixed culture

Decolorization and inhibition kinetic characteristics of two azo dyes namely Reactive Black 5 (RB 5) and Direct Brown 2 (DB 2) were investigated with partially granulated anaerobic mixed culture using glucose (3000 mg l(-1) COD) as carbon source and electron donor during batch incubation. Monod, zero-, first-, and second-order reaction kinetic models were tested in order to determine the most suitable rate model of substrate and color removal kinetic. The course of the decolorization and substrate removal process approximates to first-order kinetic model under batch conditions. Decolorization, and substrate removal were achieved effectively under test conditions but ultimate removal of azo dyes and substrate were not observed at high dye concentrations. Aromatic amine and volatile fatty acid accumulation were observed proportionally at a higher azo dye concentration. A competitive kinetic model that describes the anaerobic co-metabolism of increasing RB 5 and DB 2 dye concentrations with glucose as co-substrate has been developed based on the experimental data.     

Growth,mortality and shell morphology of cultivated mussel (Mytilus edulis) stocks cross-planted between two Scottish sea lochs

One-year-old rope-grown blue mussels (Mytilus edulis L.) were held in experimental lantern nets and cross-transplanted between two sea lochs (Lochs Etive and Leven) on the west coast of Scotland. Growth and mortality were monitored from May 1991 to May 1992, as well as shell morphology in native and transplanted mussels. There were highly significant differences (P0.001) in growth rates between lochs; both native and transplanted mussels performed better in all shell and tissue growth-parameters in Loch Etive than in Loch Leven. Stock also had a significant (P0.05) influence on shell length and live weight, but its contribution to total variance was considerable only in the latter case. Wet and ash-free dry meat weights were governed mainly by site and to some extent by site x stock interaction. Mortality rates were quite low (6 to 7% yr^-1) and did not show any significant variation either between sites or stocks. There were significant morphological differences (ratios of shell length, height and width) between the Loch Etive and Loch Leven populations (P0.001) which persisted for one year after transfer. Stock appeared to be the main factor affecting shell morphology, as opposed to site. Linear regressions of shell height and width on length were significantly different between the native stocks, but became indistinguishable from those of the recipient populations one year after reciprocal transfer. This did not, however, conceal the effect of stock origin on dimensional ratios. It is concluded that site differences related to environmental factors, notably chlorophyll a levels and currents, and also possible stress caused by high levels of Zn and Cu, are major determinants of growth, which are of main interest to aquaculture, while morphological differences most probably result from genotypic variation.     

Evaluating the seasonal changes of water quality of the Değirmendere and Galyan Rivers (Trabzon, Turkey)

The De?irmendere and Galyan (De?irmendere tributary) Rivers that discharge their water into the Black Sea are important watersheds in the northeastern part of Turkey. Water quality parameters were sampled from 1997 through 2001 for each year at five sites (three for Galyan, two for Degirmendere) along 29 and 42 km gradients, respectively covering all seasons. Surface water was collected from the sites and analyzed for temperature, total alkaline (MAAL), total dissolved solids (TDS), dissolved oxygen (DO), pH, conductivity (EC), nitrate (NO3), nitrite (NO2), total hardness (TH), phenolphthalein alkalinities (PAL) and organic matter (PV). Seasonal changes of water quality were analyzed statistically for both Rivers and evaluated according to the TS 266, EU and WHO standards. The analysis of variance results showed that Ca, Mg, MAL, NO3, pH, TDS and TH parameters of the De?irmendere River and Ca, DO, EC, MAL, NO3, pH and TH parameters of the Galyan River showed seasonal differences (p<0.05). The maximum values of the water pollution parameters for the two Rivers were below the threshold values throughout the study period. When both Rivers were compared, the mean values of the pollution parameters of the Degirmendere River were higher than those of the Galyan River and very close the limits. The results indicate that both Rivers can be used for the production of potable water during all seasons but only with an advanced treatment in the De?irmendere and a moderate treatment in the Galyan River, and for indirect and non-contact recreational activities.     

Response of the microbial food web to manipulation of nutrients and grazers in the oligotrophic Gulf of Aqaba and northern Red Sea

The control mechanisms within the pelagic microbial food web of the oligotrophic Gulf of Aqaba and the northern Red Sea were investigated in the spring of 1999. Nutrient conditions and potential grazer impact were manipulated in a series of dilution experiments. Ambient nutrient concentrations and autotrophic biomass were very low (0.23–1.21 µmol NO₃ l^–1, 0.06–0.98 µmol NH₄ l^–1, 1.08–1.17 µmol Si l^–1, 0.08–0.12 µmol P l^–1, 0.15–0.36 µg chlorophyll a l^–1). The planktonic community was characterized by low abundances [3.0–5.5×10⁵ heterotrophic bacteria ml^–1, 0.58–7.2×10³ ultraphytoplankton <8 µm ml^–1 (small eukaryotic photoautotrophs and Prochlorococcus sp., excluding Synechococcus sp.), 0.45–4.4×10⁴ Synechococcus sp. ml^–1, 0.32–1.2×10³ heterotrophic nanoflagellates ml^–1, 1.3–3.8×10³ phytoplankton >8 µm l^–1, 0.93–5.4×10² microzooplankton l^–1] and dominated by small forms (0.2–8 µm). Dinoflagellates and oligotrichous ciliates were the most common groups in initial samples among the phytoplankton >8 µm and microzooplankton, respectively. Results show that bottom-up and top-down control mechanisms operated simultaneously. Small organisms were vulnerable to grazing, with maximum grazing rates of 1.1 day^–1 on heterotrophic bacteria and 1.3 day^–1 on ultraphytoplankton. In contrast, algae >8 µm showed stronger signs of nutrient limitation, especially when the final assemblages were dominated by diatoms. Synechococcus sp. were not grazed and only showed moderate to no response to nutrient additions. The high spatial and temporal variation of our results indicates that the composition of the planktonic community determines the prevailing control mechanisms. It further implies that, at this transitional time of the year (onset of summer stratification), the populations fluctuate about an equilibrium between growth and grazing.Communicated by O. Kinne, Oldendorf/Luhe     

Bigger testes do work more: experimental evidence that testis size reflects testicular cell proliferation activity in the marine invertebrate,the free-living flatworm<Emphasis Type="Italic"> Macrostomum</Emphasis> sp.

Evolutionary theory predicts that more resources are allocated to sperm production when sperm competition is high. This prediction is supported by both comparative and experimental data on static measures of male allocation, such as testis and ejaculate size. However, resource allocation is a dynamic process, and it is therefore important to evaluate if the static measures reflect this. Such an evaluation has to our knowledge never been done. Immunocytochemical labelling with bromodeoxyuridine (BrdU) allows visualisation of cells in S-phase. BrdU becomes incorporated into cells if, and only if, they are actively undergoing DNA duplication, which is a dynamic process. The number of BrdU-positive cells in the testis can hence serve as a dynamic measure of male allocation, i.e. testicular activity. We evaluate the relationship between testis size and testicular activity in the marine flatworm Macrostomum sp. In a previous study, we showed that testis size is phenotypically plastic in this species, and that worms make larger testes when they are raised in larger groups. We use this plasticity to experimentally produce variation in testis size, and demonstrate that larger testes are associated with higher testicular activity. Moreover, testis size and testicular activity were related linearly. We have thus, for the first time, shown that testis size is a good measure of resource allocation to the male function. Moreover, increased testicular activity is probably one of the first steps in the upregulation of sperm production. It is thus expected that testicular activity is a more sensitive measure of short-term variation in male allocation than the commonly used static measures.Communicated by N. Wedell     

Life history of the red mullet Mullus surmuletus from the bottom-trawl fishery off the Island of Majorca (north-west Mediterranean)

The red mullet Mullus surmuletus is one of the main target species of the trawling fishery along the continental shelf off the Island of Majorca. The size distribution of the catches, and the reproduction, age and growth of this species have been studied based on sampling carried out from 1990 to 1992. The length range of the catches was between 10 and 32 cm, with a main distribution between 15 and 20 cm, but this included small specimens (recruits of 10 to 11 cm) from August. In the >19 cm length-class, females clearly dominated. Monthly variations in the gonadosomatic index (GSI) and in the percentage of mature specimens showed that males spawn from December to June, whereas the reproductive activity of the females centres around spring. Fifty percent of males and females mature at 15 and 16.8 cm, respectively, corresponding to 1 yr of age. Otolith age-readings indicate that the population exploited in the trawl fishery consists of six age-groups, including a very high proportion of individuals between 0 and 4 yr old. Population growth curves revealed that females grow comparatively slowly over a longer period of time and attain greater asymptotic sizes than males. The growth parameters for the whole population are: asymptotic length, L =31.28 cm; growth coefficient, K=0.211 yr^-1; theoretical age when length is zero, t ₀=-2.348 yr.     

砖红壤添加铜对作物生长和残留的影响

本文对广东湛江地区砖红壤性水稻土,进行铜(CuCl_2)的不同添加浓度对水稻和花生作物生长发育和残留影响的盆栽试验研究。结果表明,在玄武岩成土母质发育的较高铜背景土壤上(46.5mg/kg),添加金属铜浓度在200mg/kg范围内,无论对水稻或花生,仍未出现对产量的不良影响,反而有一定的促进作用。从作物食用部分的残留量与土壤浓度的相关性来看,花生显著,而水稻不明显。最后建议277mg/kg土壤铜浓度作为砖红壤性水稻土的临界浓度。     

金属塑性变形有限元模拟中的约束处理算法

此文提出了适用于金属体积成形过程有限元模拟的约束处理算法.该算法分为三部分.首先,将整个变形域上的节点分为潜在接触节点和非接触节点,分别建在立以节点位移为变量的子系统刚度方程.然后,以潜在接触节点的子系统为对象,确定每个节点与模具的接触状态,对实际接触摸具节点施加位移约束和摩擦条件,并求解耦合了位移约束和摩擦条件的刚度方程.第三,将上述求解的位移结果回代到非接触节点的子系统中,得到剩余节点的位移值.因此,整个系统的位移场以及应变、应力分布亦可确定.该算法的优点在于,将大系统分解为小系统分开求解,使每次求解的变量数目减少,从而可以处理较大规模的工程问题;只对含接触节点的子系统施行坐标变换、约束处理等,提高了有限元计算的效率;将位移约束、摩擦条件直接耦合到子系统中求解,当N—R迭代收剑时,力平衡条件与几何约束条件同时得到满足,从而保证了各控制方程之间的相容性,有利于提高迭代收敛速度和计算稳定性.     

磁性纳米颗粒对不同模式生物的毒性研究

磁性纳米颗粒在生物医学等领域应用广泛,而其毒性研究尚未深入,对生物的影响及作用机制仍未阐明。本文综述了磁性纳米颗粒近年来对于细胞、鼠、家兔和秀丽隐杆线虫的毒理学研究,为磁性纳米颗粒的应用提供参考。