Effect of parental care and aggregation on population dynamics

Behavioral changes of animal species can influence the consequence of population dynamics. One of the most remarkable behaviors of animal species is the aggregation by which species can reduce predation risk as a consequence of dilution or the other effects by forming a group. Empirical studies have demonstrated that an incompatibility exists in aggregation since resource competition might become severe at the cost of reducing predation pressure from predatory species. Parental care by supplying the food consumed by adults to their juveniles would reduce the mortality of juvenile due to starvation, but it would reduce the reproduction rate at the same time. In this paper, we study a class of stage-structured resource-consumer models to investigate the effect of behavioral changes on population dynamics. It is shown that under the presence of trade-off in parental care, moderate degrees of parental care will be favored as maximizing the equilibrium density of consumers. For consumer species having a long maturation period, consumer species might get benefit from dilution effects as a result of aggregation despite the elevated resource competition. Aggregation gives rise to two different outcomes in consumer extinction. Resource exhaustion as a consequence of over-exploitation can induce extinction of consumers due to Allee effects if aggregation strongly mediates juvenile survival.     

Ferrocenesuccinate-bridged lanthanide polymeric complexes: Syntheses, structures and properties

One-dimensional lanthanide-ferrocenesuccinate polymeric complexes [M(η²-FcCOC₂H₄COO)(μ₂-η²-FcCOC₂H₄COO)₂(H₂O)₂]_n (Fc = (η⁵-C₅H₄)Fe(η⁵-C₅H₄), M = Pr, 1; Ce, 2; La, 3) have been synthesized and structurally characterized by single-crystal X-ray crystallography. The three polymers are isomorphous, in which each Ln(III) ion is 10-coordinated and connects with two water molecules and eight oxygen atoms from ferrocenesuccinate units in two kinds of coordination modes: bidentate-chelating mode and tridentate-bridging mode. The variable-temperature magnetic susceptibility in the temperature range 5-300 K for 1 and 2 shows that both of them display weak antiferromagnetic interaction. In addition, the redox and fluorescent properties have been investigated. The redox properties are different from the previous results of transition metal compounds containing ferrocenyl systems. Compared with sodium ferrocenesuccinate, polymers 1 and 3, the fluorescent intensities of 2 are markedly enhanced in the solid state.     

Effect of Aluminium on Lipid Peroxidation of Human High Density Lipoproteins

We investigated the effect of aluminium (Al 3+ ) on lipid peroxidation and physico-chemical properties of high density lipoproteins (HDL) isolated from human plasma. Our results demonstrated that Al 3+ enhances lipid peroxidation of human HDL as shown by the significant increase in lipid hydroperoxides in Al-treated HDL with respect to control HDL. The oxidative effect was higher at acid pH (pH 5.5) with respect to pH 7.4. Moreover, a stimulating effect of Al 3+ on iron-induced lipid peroxidation of HDL was demonstrated. The study of the effect of Al 3+ on the physico-chemical properties of HDL, using the fluorescence polarization (Pf) of the probes TMA-DPH (1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene iodide) and DPH (1,6-diphenyl-1,3,5-hexatriene), showed a significant decrease of Pf in Al-treated HDL with respect to control. These results suggest that Al 3+ induces a decrease of molecular order at the lipoprotein surface. Moreover, the study of tryptophan (Trp) fluorescence demonstrated that aluminium induces structural modifications of HDL apoproteins and on HDL physico-chemical properties. The effect of Al 3+ on lipid peroxidation of HDL was observed at aluminium concentrations similar to those observed in the brain of patients affected by neurological diseases. Aluminium-induced oxidative damage of HDL could be involved in the development of neurological diseases.     

A method for demonstrating genetic principles using an imaginary organism

The use of an imaginary organism to illustrate principles of genetics is described. The organism is easily drawn, and is well suited to simple printing techniques. It has been used to show independent segregation of genes, partial dominance, linkage in both sex chromosomes and in autosomes, as well as the inheritance of an autosomal gene lethal in the homozygous state. Additional exercises for students are suggested.     

Influence of silicone oil modification on properties of ramie fiber reinforced polypropylene composites

This paper focused on the analyses of the composition, microstructure, thermal stability and mechanical behavior of modified ramie fiber and its reinforced polypropylene composites. Ramie fiber (RF) was treated with epoxy-silicone oil (ESO) at 160 °C in argon gas. The FTIR and XRD analyses indicated that some silicone molecular chains were bonded on the surface of modified RF, which decreased the crystallinity of the fiber without changing the crystalline type of cellulose. The SEM results of fracture surface showed that the modified RF/PP composite had better interfacial bonding between RF and PP. The mechanical tests showed that the impact strength and the elongation at break of RF/PP were increased by 17.0% and 196% after modification, respectively. The tensile strength of 30RF/PP was improved from 18.95 MPa to 25.96 MPa compared to pure PP. The results of TGA showed that fiber treatment could improve the degradation temperature of RF/PP composites.     

Assessment of the Effect of Mesh Density on the Material Property Discretisation Within QCT Based FE Models: A Practical Example Using the Implanted Proximal Tibia

A three-dimensional, quantitative computed tomography based finite element model of a proximal implanted tibia was analysed in order to assess the effect of mesh density on material property discretisation and the resulting influence on the predicted stress distribution. The mesh was refined on the contact surfaces (matched meshes) with element sizes of 3, 2, 1.4, 1 and 0.8 mm. The same loading conditions were used in all models (bi-condylar load: 60% medial, 40% lateral). Significant variations were observed in the modulus distributions between the coarsest and finest mesh densities. Poor discretisation of the material properties also resulted in poor correlations of the stresses and risk ratios between the coarsest and finest meshes. Little difference in Young's modulus, von Mises stress and risk ratio distributions were observed between the three finest models; hence, it was concluded that for this particular case an element size of 1.4 mm on the contact surfaces was enough to properly describe the stiffness, stress and risk ratio distributions within the bone. Poor convergence of the material property distribution occurred when the element size was significantly larger than the pixel size of the source CT data. It was concluded that unless there is convergence in the Young's modulus distribution, convergence of the stress field or of other parameters of interest will not occur either.     

毛节缬草的粉末鉴别

目的:研究黑龙江省毛节缬草Valeriana alternifolia Bunge var.stolonifera Bar.et Skv.的粉末鉴别特征.方法:性状鉴别、显微鉴别.结论:毛节缬草根、根茎、茎和叶的粉末均有明显的鉴别特征,可作为鉴别毛节缬草的依据.     

芽孢杆菌WS-3L淀粉酶的纯化和特性的研究

芽孢杆菌WS-3L产生的a-淀粉酶AmyL经过多步纯化, 酶的回收率为15.5%, 比活提高了345倍。该淀粉酶能够有效水解淀粉生成麦芽寡糖。酶的最适反应温度为45℃, 最适反应pH为6.5, 在pH 7.0~8.0, 40℃以下酶活较稳定; 离子Cu2+、NH4+、Ag+、Hg+ 和EDTA、SDS对酶活力有显著抑制作用, 而其他一些常见金属离子如Na+、K+则对酶活影响不大。AmyL对可溶性淀粉、直链淀粉、支链淀粉的Km值和Vmax分别为2.81 mg/mL、8.37 mg/mL、1.80 mg/mL和11.67 mmol/（min·mL）、10.00mmol/（min·mL）、13.33 mmol/（min·mL）, 表明支链淀粉是该酶的理想水解底物。玉米淀粉对AmyL有很高的吸附率, 预示这可以作为酶快速固定的一个简易方法应用到实际生产中。     

Mechanical and Barrier Properties of Avenin, Kafirin, and Zein Films

Biodegradable and renewable materials can be manufactured from prolamins, which are the major storage protein fraction of cereals. This paper investigates the material properties of oat prolamin (avenin), corn prolamin (zein), and sorghum prolamin (kafirin). Glass transition temperature, dry solid content, stress at break, strain at break, oxygen permeability, and water vapor permeability were analyzed at different plasticizer contents. Avenin was plasticized with glycerol, and kafirin and zein were plasticized with a mixture of polyethylene glycol, glycerol, and lactic acid. Avenin displayed potential, although it did not exhibit the mechanical qualities of gluten, which resembles avenin at the molecular level. Compared to kafirin and zein, avenin was more extensible at low plasticizer contents, while kafirin and especially zein were more extensible at the highest plasticizer content. Avenin was far weaker than the other two at all plasticizer contents. Kafirin and zein displayed similar barrier properties, whereas avenin was notably more permeable.     

假单胞杆菌D-海因酶的纯化及酶学性质

D-海因酶是工业上生产D-型氨基酸的关键酶,用热变性,硫酸铵沉淀及Sepharose Q fast flow,Phenyl-Sepharose fast flow,Superose 12等柱层析步骤从pseudomonas2262菌体中分离纯化了该酶,纯化倍数约为60,活力回收约为16%.该酶为同源二聚体,分子量约为109kD,亚基分子量约为53.7kD,反应最适pH为8.0,最适温度为70℃,在pH6.0～10.0和温度60℃以下稳定,该酶对巯基试剂敏感,大多数二价金属离子如镁、锰离子等能促使酶活提高,但高浓度锌离子能抑制酶活,以二氢尿嘧啶为底物的米氏常数Km=2.5×10-2mol/L.该酶的N末端10个氨基酸残基依次为MDKLIKNGTI.