灭活酵母对Sr2+的吸附行为及其受γ辐照的影响

以灭活面包酵母为原料,利用原子吸收光谱(AAS)、X射线能谱仪(EDS)等手段,研究吸附剂加入量、pH值等因素对其吸附效果的影响,并分析了γ辐照条件下灭活面包酵母菌对Sr2+的吸附动力学过程。结果显示,不同温度下酵母菌对Sr2+的吸附均是快速进行的反应过程,整个吸附过程中单位吸附量qt均存在30℃>20℃>10℃。不同温度下面包酵母菌对Sr2+的动力学二级吸附速率方程拟合程度非常好(R>0.999),其吸附反应过程中限速步骤是化学吸附过程。EDS分析进一步证明Sr2+被吸附到面包酵母细胞上。辐照后酵母菌对Sr2+的吸附效果要比相同温度条件下辐照前实验组略好。     

Risky attitudes towards road use in pre-drivers

Motor vehicle accidents are one of the principal causes of adolescent disability or mortality and male drivers are more likely to be involved in road accidents than female drivers. In part such associations between driver age and sex have been linked to differences in risky behaviour (e.g. speed, violations) and individual characteristics (e.g. sensation seeking, deviant behaviour). The aim of this research is to determine whether associations between risky road user behaviour and individual characteristics are a function of driver behaviour or whether they are intrinsic and measurable in individuals too young to drive.

Five hundred and sixty-seven pre-driver students aged 11–16 from three secondary schools completed questionnaires measuring enthusiasm for speed, sensation seeking, deviant behaviour and attitudes towards driver violations. Boys reported more risky attitudes than girls for all measures. Associations between sensation seeking, deviant behaviour and attitudes towards risky road use were present from early adolescence and were strongest around age 14, before individuals learn to drive.

Risky attitudes towards road use are associated with individual characteristics and are observed in adolescents long before they learn to drive. Safe attitudes towards road use and driver behaviour should be promoted from childhood in order to be effective.     

Dynamics of a heat transformer working with the mixture NaOH---H2O

The model described in the paper is based on the balance equations for mass and energy for the different apparatus such as absorber, generator, evaporator, condenser and solution heat exchanger. It simulates a heat transformer process and ensures calculations not too time-consuming and much faster than in real time. With the aid of the model the transient behaviour of a heat transformer working with the mixture NaOH---H₂O is examined. For steady state operation the simulations agree well with experiments on a pilot plant. With NaOH---H₂O as working substances high COPS up to 0.49 were obtained with this heat transformer. For unsteady state operation the deviations between experiments and simulations were slightly higher than those for steady state. The model nevertheless predicts the transient behaviour with a satisfying accuracy. Also the startup and shutdown behaviour of a heat transformer was investigated under different conditions.     

Dynamics of a heat transformer working with the mixture NaOHH2O

The model described in the paper is based on the balance equations for mass and energy for the different apparatus such as absorber, generator, evaporator, condenser and solution heat exchanger. It simulates a heat transformer process and ensures calculations not too time-consuming and much faster than in real time. With the aid of the model the transient behaviour of a heat transformer working with the mixture NaOHH₂O is examined. For steady state operation the simulations agree well with experiments on a pilot plant. With NaOHH₂O as working substances high COPS up to 0.49 were obtained with this heat transformer. For unsteady state operation the deviations between experiments and simulations were slightly higher than those for steady state. The model nevertheless predicts the transient behaviour with a satisfying accuracy. Also the startup and shutdown behaviour of a heat transformer was investigated under different conditions.     

Rheological research of partially-solidified dendritic Sn–14.8wt%Pb alloy by two backward extrusion methods

Two different backward extrusion methods were compared to study the rheological behaviour of partially-solidified Sn–14.8wt%Pb alloy for strip casting. For this work, the partially-solidified alloys were dendritic, as opposed to globular semi-solid slurries which have been studied more intensively. The first method was a constant-velocity experiment operating at constant extrusion-velocity of 3.5?mm?s^?1 and four different extrusion ratios. The second method was a varying-velocity experiment with unchanged extrusion ratio and four different extrusion velocities.

Both backward extrusion experiments were carried at different temperatures ranging from 183 to 208°C. The two experiments obtained quite different results, which are discussed accordingly. Moreover, an unreported abnormal shear thinning behaviour was the main characteristic of the rheological behaviour of the partially-solidified alloys. Finally, the applicability of these two different methods of measuring the viscosity of partially-solidified alloys at different solid fractions is compared and discussed.     

Can road traffic law enforcement permanently reduce the number of accidents?

In this paper it is argued that conventional analyses of road user adaptation to traffic law enforcement, based on parametric rational-choice theory, are flawed. Such analyses only consider road-user actions as a response to enforcement level and penalty size and do not simultaneously consider enforcement as a response to road-user behaviour. If each party is considered a rational agent who adapts to the other's behaviour, the proper way to analyze the outcomes is by the way of game theory. A game-theoretic model is presented and the main implications are: (i) most attempts at enforcing road traffic legislation will not have any lasting effects, either on road-user behaviour or on accidents; (ii) imposing stricter penalties (in the form of higher fines or longer prison sentences) will not affect road-user behaviour; (iii) imposing stricter penalties will reduce the level of enforcement; (iv) implementing automatic traffic surveillance techniques and/or allocating enforcement resources according to a chance mechanism, and not according to police estimates of violation probability, can make enforcement effects last, but both alternatives are difficult to implement. Relevant empirical studies are reviewed, and they seem to support the conclusions arrived at by the game-theoretic model.     

Paul Konitzer (1894–1947): Hygieniker,Amtsarzt, Sozialmediziner,Gesundheitspolitiker

Paul Konitzer was one of the outstanding and well-known physicians in the years after the World War II in East-Germany. THe paper describes his professional way as hygienist, social medical, municipal physician and last but not least as health politician in the times of four different political regimes: the imperial era in Germany till 1918, the time of "Weimarer Republic" till 1933, the Nazi dictatorship till 1945 and the early years in the Soviet occupation zone of Germany. The life of Konitzer is a typical example of the fate of a German doctor in the first half of the 20th century. Konitzer was arrested in February 1947 by the Soviet Military Government in Berlin in connection with some political troubles and reproach with a typhus epidemic in a German camp for Russian Prisoners of War in the Nazi era. On April 22nd 1947 he died in prison of Dresden by suicide without condemnation.     

Fracture behaviour and morphology of PC/ABS blends

The toughness behaviour of polycarbonate (PC)/acrylnitrile-butadiene-styrene (ABS) blends under dynamical loading (1 ms^–1) based on the J-integral concept was studied. For this the multiple specimen R-curve method was used. A special experimental technique of a stop block method was developed. It was shown that the materials exhibit a very different toughness behaviour depending on temperature and ABS content. The reasons for this material behaviour are discussed with the help of scanning and transmission electron microscopical (SEM and TEM) investigation methods. It can be shown that a combination of fracture mechanics and electron microscopy allows a toughness optimization to be made on the basis of quantitative morphology-toughness correlations.     

Effect of Strain Rate,Adiabatic Heating and Phase Transformation Phenomena on the Mechanical Behaviour of Stainless Steel

Abstract: The influence of strain rate on the stress–strain behaviour of an AISI 304 austenitic stainless steel sample was investigated. For this purpose, uniaxial tensile tests were performed at room temperature for different strain rates. Microstructural measurements of transformed martensitic phase as a function of plastic strain, and thermal analyses of the specimens were carried out as well. It was found that increasing the strain rate from 10^?4 to 10^?1 s^?1 leads to a 25% improvement in uniform elongation. Moreover, a ‘curve‐crossing’ phenomenon was observed for the hardening behaviour measured at different strain rates. These results were rationalized in terms of martensitic phase transformation suppressed by a temperature increase in the specimens deformed with high strain rates.     

Comparison of the Mechanical Behaviour of Standard and Auxetic Foams by X‐ray Computed Tomography and Digital Volume Correlation

The tensile behaviour of standard and auxetic polyurethane foams are contrasted by digital volume correlation of 3D images collected by in situ X‐ray computed tomography (CT). It was found that subset sizes of 32 and 64 voxels for the auxetic and standard foams were optimal for strain resolutions in the order of 0.1%. For the standard foam, good uniformity of strain was observed at low strains giving a tangent Poisson's ratio of 0.5. Some heterogeneity of strain was observed at higher strains, which may be related to the fixtures. The behaviour of the auxetic foam was totally different, with strain being spatially heterogeneous with transverse strains both positive and negative but giving a negative Poisson's ratio on average. This suggests that the unfolding tendency of some groups of cells was higher than others because of the complex frozen starting microstructure. Further different methods of deriving Poisson's ratio gave different results. Besides revealing interesting microstuctural mechanisms of transverse straining, the study also shows digital volume correlation of tomography sequences to be the perfect tool to study complex mechanical behaviour of cellular materials.     

Roles of detwinning in strain hardening and ultimate elongation in extruded Mg–3Al–1Zn alloy

Abstract

For extruded magnesium alloy, prior compression along extrusion direction has great influences in the flow stress during subsequent tension. Detwinning plays an important role for these influences. In the present study, the effects of different prestrains on strain hardening behaviour during subsequent tension were examined in an extruded magnesium alloy AZ31. The results showed that the existence of detwinning decreased the tensile yield stress. Samples with different prestrains exhibited different strain hardening behaviour during subsequent tension. The reorientation due to detwinning had a great effect on strain hardening during tension. In addition, the effect of detwinning on ultimate elongation was investigated. The results showed that the sample with higher prestrain always has higher ultimate elongation due to the contribution of detwinning on macroscopic strain.     

An application of the theory of planned behaviour to truck driving behaviour and compliance with regulations

A questionnaire study was conducted with truck drivers to help understand driving and compliance behaviour using the theory of planned behaviour (TPB). Path analysis examined the ability of the TPB to explain the direct and indirect factors involved in self-reported driving behaviour and regulation compliance. Law abiding driving behaviour in trucks was related more to attitudes, subjective norms and intentions than perceived behavioural control. For compliance with UK truck regulations, perceived behavioural control had the largest direct effect. The differing results of the path analyses for driving behaviour and compliance behaviour suggest that any future interventions that may be targeted at improving either on-road behaviour or compliance with regulations would require different approaches.     

A tribute to Claude Bathias – Highlights of his pioneering work in Gigacycle Fatigue

Current fundamental academic research in the field of Gigacycle Fatigue, now frequently referred to as Very High Cycle Fatigue (VHCF), is strongly related to the pioneering work of Professor Claude Bathias during the last two decades. Claude Bathias passed away in April 2015. In the present paper, dedicated to his memory, his most important contributions in conducting and initiating fatigue studies in the area of Gigacycle Fatigue are highlighted. In light of what is known today about the details of fatigue behaviour in the range of up to 10¹⁰ cycles and more, the pivotal role of Claude Bathias cannot be overestimated. He was among the first to demonstrate, in painstaking ultrasonic fatigue studies, that a fatigue limit in the traditional sense does not exist in the Gigacycle regime. In his subsequent work on different materials, he substantiated his earlier findings experimentally and, in close collaboration with Paul Paris, quantitatively described the mechanisms of subsurface and surface VHCF failures, originating from inclusions. Together they showed that, in the VHCF range, most of the fatigue life is spent in crack initiation and not in propagation. Claude Bathias’ work stimulated worldwide research and was instrumental in the emergence and development of the current new field of Very High Cycle Fatigue.     

Is surface chemical composition important for orthopaedic implant materials?

Ti-6Al-7Nb (NS) in its ‘standard’ implant form has been previously shown to be detrimental to fibroblast growth and colonisation on its surface. Specific aspects of the NS topography have been implicated, however, the contribution of its unique surface chemistry to the cell behaviour was unknown. By evaporating either gold or titanium on the surface of standard NS, two different model surface chemistries could be studied with the same characteristic standard NS topography. Two other ‘standard’ orthopaedic topographies, that of stainless steel (SS) and of ‘commercially pure’ titanium (TS) were also treated in a similar manner. All materials elicited behaviour similar to their uncoated counterparts. For coated SS and TS, cell proliferation was observed, cells were well spread and displayed mature focal adhesion sites, and associated cytoskeletal components. For coated NS, cell proliferation was compromised, cells remained rounded, filopodia attached and seemed to probe the surface, especially the β -phase particles, and both the focal adhesion sites and the microtubule network were disrupted by the presence of these particles. These results confirmed, that in the instance of NS, the topography was the primary cause for the observed stunted cell growth. For biomaterials studies, the standardisation of surface chemistry used here is a valuable tool in allowing vastly different materials and surface finishes to be compared solely on the basis of their topography.     

CLOSURE BEHAVIOUR OF SURFACE CRACKS

Abstract— The fatigue crack closure response was investigated for a surface crack in BS4360 50B structural steel, subjected to (1) constant amplitude loading and (2) constant amplitude loading interrupted by a single peak overload. A variety of compliance techniques was employed to determine closure behaviour. The crack mouth gauge measured the bulk, plane strain closure load, while the near tip strain gauge indicated the surface, plane stress closure response. For constant amplitude loading it was found that the surface regions of a surface crack are closed for a greater portion of the load cycle than the maximum depth point. A single peak overload caused different closure and growth rate transients at the surface of the thumbnail crack and at the maximum depth point. For growth rates above 10^-6 mm/cycle, such behaviour agrees with the response of a through crack when subjected to constant amplitude loading, and a single peak overload.     

Modelling and analysis of a symbiotic waste management system

A municipal solid waste management system is symbiotic when there exists physical exchange of material or by-products between different treatment units. We propose a mathematical model for studying the interactive behaviour of different waste treatment operators in a symbiotic environment. Each operator is a self-interested entity, who sets his gate fee charge to maximise his own payoff. We study the properties and gate fee strategies of the operators, and also perform sensitivity analysis on various model parameters to discuss the local operator behaviour and the effects of various intervention strategies. We also propose a numerical algorithm to solve the model, yielding the optimal equilibrium gate fee charges, payoff and market share levels of different operators. Finally, computational studies based on a two-unit scenario in a case study of organic waste recycling is performed to demonstrate the interactive and dynamic behaviours of different operators. Our results strongly suggest that, to improve new treatment technology utilisation, subsidising the operating cost of the new treatment unit is more effective in the long-run than exerting control on the gate fee upper bounds of the operators by the system regulator. Furthermore, providing residual post-treatment discounts for treatment units can benefit the service users, rather than the waste treatment operators.     

Grain-size dependence of the mechanical properties of an age-hardening Fe-1 % Cu-alloy

The contribution of grain size and precipitation hardening to the yield stress and other mechanical properties was investigated. An alloy of iron with 1 % copper was prepared as supersaturated solid solution with grain sizes between 12 and 140 μm. By ageingat 500 and 600° C different precipitation hardening conditions were produced. For small particle sizes an additive behaviour of grain-boundary and precipitation hardening was found (particle radiusr < 50 Å). For large particle sizes the yield stress is independent of grain size (r > 150 Å). A transition is found for intermediate particle sizes with grain size dependence for small and independence for large grain sizes (50 Å <r < 150 Å). The effect of grain boundaries and particles on the formation and motion of dislocations is used to explain this behaviour.     

Cracking diagnostics of brake pedals during press forming operations

In this work a study of the cracking problems arising in manufacturing of steel brake pedals by press forming is presented. Cracks were detected in critical zones of the part revealing a possible lack of ductility in the constitutive material. In order to overcome this problem, a detailed study of the behaviour of the steel used has been carried out. In this way, mechanical characterization as well as microstructural analysis were performed over both cracked and uncracked pedals. The results obtained from this comparative analysis showed different microstructural features and, consequently, the dissimilar mechanical behaviour can be justified.