Fungal degradation of poly(ethylene succinate)

Twenty fungi, which all formed a clear zone around the colony on a poly(ethylene succinate) (PESu)-containing medium, were isolated from various environmental samples. Mesophilic strain NKCM1003, with the highest PESu hydrolytic activity among all the isolates, degraded a PESu film at the rate of 21 ± 2 μg/cm²/h when it was aerobically incubated at 30 °C on a medium containing PESu as the sole carbon source. SEM observations showed that the strain gradually degraded the film starting from the amorphous regions of the surface. Phylogenetic analysis revealed that the strain was closely related to the species Aspergillus clavatus. Zymogram analysis suggested that the secreted enzyme with PESu hydrolytic activity is a P(3HB) depolymerase. The strain also utilized the enzymatic products of PESu, permitting it to grow well. These results indicate that the strain NKCM1003 plays an important role in the PESu-degrading process in the field.     

微型氧弹热量计和C60及C70的燃烧焓

富勒烯是新发现的一类碳的稳定单质，其分子骨架中含有多个五员环及非平面球壳状大力键.与全为六员环的平面大r键的石墨结构相比，这些张力提高了分子能量.通过富勒烯的生成焰的测定，对了解这些分子的稳定性和反应性，它们的生成机理，以及研究分子的结构与能量的规律是很有意     

一类具有二次感染和接种的两病株流行病模型

本文考虑了一类具有二次感染和接种的两病株流行病模型，通过定义每一病株的基本再生数和侵入再生数，我们分析了非负平衡态的稳定性并获得了这样结论：对于较低的接种水平，病株一感染者处于支配地位而病株二感染者将从易感人群中消失，对于非常高的接种水平，疾病将均被消除。     

Parameter identification of advanced plastic strain rate potentials and impact on plastic anisotropy prediction

In the work presented in this paper, several strain rate potentials are examined in order to analyze their ability to model the initial stress and strain anisotropy of several orthotropic sheet materials. Classical quadratic and more advanced non-quadratic strain rate potentials are investigated in the case of FCC and BCC polycrystals. Different identifications procedures are proposed, which are taking into account the crystallographic texture and/or a set of mechanical test data in the determination of the material parameters.     

Local electrochemical studies of the microstructural corrosion of AlCu4Mg1 as-cast aluminium alloy and influence of applied strain

The microstructure of AlCu4Mg1 as-cast aluminium alloy was first determined by means of field emission-scanning electron microscope with an integrated electron dispersion spectrometer, secondary ion mass spectroscopy and atomic force microscopy. Large precipitates (Al₂Cu, Al–Si–Mn–Fe–Cu, oxides) were located at grain boundaries, whereas small particles (aluminium, magnesium and copper) were present in grains. The electrochemical response and pitting susceptibility of sites containing precipitates were then investigated after polishing using the electrochemical microcell technique. After straining, big scattering was observed in the electrochemical response. The most active places corresponded to the sites containing wide microcracks and severe damages in the matrix. In this case, the corrosion potential was around −1,000 mV vs. Ag/AgCl, and the current in the passive domain was five times higher than on the strained matrix. In the absence of severe damage in the matrix or wide microcracks, the corrosion potential was more anodic and the current density in the passive range was around 0.5 mA cm⁻². Local polarisation curves carried out in sites containing large precipitates and no defects induced by straining were very close to those obtained in grains far from precipitates.     

Temperature-insensitive strain measurement using differential double Bragg grating technique

A novel differential double Bragg grating sensor for temperature-insensitive strain measurement is presented. The sensor consists of two identical weak measuring and reference gratings separated by some distance. The reference grating is placed inside the silica capillary that made it almost strain insensitive. The basic idea in differential double Bragg grating sensor is to measure the energy of the oscillating term in the reflection spectrum of double Bragg grating structure. The normalized energy of the interference term depends on the pitch difference of the two gratings and does not change when pitch variations of both gratings are equal with temperature variation. Therefore, the normalized energy of the interference term can be used for the temperature-insensitive strain measurement.     

The projected first-grade component of a structured medium

A systematic procedure to extract a projected first-grade constitutive equation from a given second-grade one is proposed and proven to be independent of the reference configuration used. The symmetry group of the projected material is shown to contain the first-grade projection of the symmetry group of the original material. The proposed method is illustrated by means of an example.     

Strain fields in arbitrary shaped quantum wires

The intent of this work is to develop a more generalized approach towards strain field calculations in embedded quantum wires (QWRs). Higher degree polynomials are used to achieve better discretization of QWR in arbitrary shapes and to avoid some of the singular points in the strain field calculations. Calculations are performed for simpler geometries such as triangular and square shaped QWRs to verify the validity of the approach. The same approach is tested for more complicated shapes such as crescent shaped QWRs with and without lateral quantum wells. The strain field distributions, are observed to be similar to those obtained from the analytical expressions. However, in the case of crescent shaped QWRs, the strain distribution is different in the region above the QWR. The difference is the result of the better discretization and of the removed singular points. The use of higher degree polynomials provides better discretization for shapes of interest.     

Evidence of Cooperative Rearranging Region size anisotropy for drawn PET

In this work, we determined the Cooperative Rearranging Region (CRR) average sizes at the glass transition temperature according to Donth’s approach. From Temperature Modulated Differential Scanning Calorimetry (TMDSC) and Dynamical Mechanical Analysis (DMA) investigations, the CRR average size has been estimated for drawn poly(ethylene terephthalate) (PET) with various draw ratios ranging from λ = 1 to λ = 4. We show that the CRR size becomes anisotropic as a function of a specific molecular orientation induced by drawing effect.     

A novel Galerkin-like weakform and a superconvergent alpha finite element method (SαFEM) for mechanics problems using triangular meshes

A carefully designed procedure is presented to modify the piecewise constant strain field of linear triangular FEM models, and to reconstruct a strain field with an adjustable parameter α. A novel Galerkin-like weakform derived from the Hellinger–Reissner variational principle is proposed for establishing the discretized system equations. The new weak form is very simple, possesses the same good properties of the standard Galerkin weakform, and works particularly well for strain construction methods. A superconvergent alpha finite element method (SαFEM) is then formulated by using the constructed strain field and the Galerkin-like weakform for solid mechanics problems. The implementation of the SαFEM is straightforward and no additional parameters are used. We prove theoretically and show numerically that the SαFEM always achieves more accurate and higher convergence rate than the standard FEM of triangular elements (T3) and even more accurate than the four-node quadrilateral elements (Q4) when the same sets of nodes are used. The SαFEM can always produce both lower and upper bounds to the exact solution in the energy norm for all elasticity problems by properly choosing an α. In addition, a preferable-α approach has also been devised to produce very accurate solutions for both displacement and energy norms and a superconvergent rate in the energy error norm. Furthermore, a model-based selective scheme is proposed to formulate a combined SαFEM/NS-FEM model that handily overcomes the volumetric locking problems. Intensive numerical studies including singularity problems have been conducted to confirm the theory and properties of the SαFEM.