The exponentiated Hencky strain energy in modelling tire derived material for moderately large deformations

This work presents a hyper-viscoelastic model based on the Hencky-logarithmic strain tensor to model the response of a Tire Derived Material (TDM) undergoing moderately large deformations. TDM is a composite made by cold forging a mix of rubber fibers and grains, obtained by grinding scrap tires, and polyurethane binder. The mechanical properties are highly influenced by the presence of voids associated with the granular composition and low tensile strength due to the weak connection at the grain-matrix interface. For these reasons, TDM use is restricted to applications concerning a limited range of deformations. Experimental tests show that a central feature of the response is connected to highly nonlinear behavior of the material under volumetric deformation which conventional hyperelastic models fail in predicting. The strain energy function presented here is a variant of the exponentiated Hencky strain energy proposed by Neff et al., which for moderate strains is as good as the quadratic Hencky model and in the large strain region improves several important features from a mathematical point of view. The proposed form of the exponentiated Hencky energy possesses a set of parameters uniquely determined in the infinitesimal strain regime and an orthogonal set of parameters to determine the nonlinear response. The hyperelastic model is additionally incorporated in a finite deformation viscoelasticity framework that accounts for the two main dissipation mechanisms in TDMs, one at the microscale level and one at the macroscale level. The model is capable of predicting different deformation modes in a certain range of frequency and amplitude with a unique set of parameters with most of them having a clear physical meaning. Moreover, by comparing the predictions from the proposed constitutive model with experimental data we conclude that the new constitutive model gives accurate prediction

Cation-induced changes in the circular dichroism spectrum of chloroplasts

Llimona Bruguera, Josep; Vilaseca, Josep (arquitecte)Primeríssim primer pla de: La Recompensa, fris de l'Arc de Triomf, situat al Passeig Lluís Companys. Realitzat amb pedra artificial de ciment portland. Representa el repartiment de recompenses als participants a l'Exposició Universal de 1888

The evolution of photosynthesis and chloroplasts

This review focuses on what has been learned about the evolution of photosynthesis in the past five years, and omits evolution of CO2 assimilation. Oxygenic photosynthesis (using both photosystems I and II) has evolved from anoxygenic photosynthesis. The latter occurs in different variants, using either a type 1 photosystem resembling photosystem I, or a type 2 photosystem resembling photosystem II. Opinions differ as to how two types of photosystem came to be combined in the same organism, whether by gene transfer between bacteria, by fusion of bacteria, or as a result of gene duplication and evolution within one kind of bacterium. There are also different opinions about when oxygenic photosynthesis arose, in conjunction with the Great Oxygenation Event, 2.3 billion years before the present, or more than a billion years before that. Cyanobacteria were the first organisms to carry out oxygenic photosynthesis. Some of them gave rise to chloroplasts, while others continued to evolve as independent organisms, and the review outlines both lines of evolution. At the end we consider the evolution of photosynthesis in relation to the evolution of our planet

The performance of initial public offerings on the JSE

Includes abstract.Includes bibliographical references.This study examined the performance 60 initial public offerings listing on the JSE main board between 1 January 2000 and 31 December 2011. Significant underpricing of 10.1% and 8.5% was found to exist on the first day and during first week subsequent to the IPO. Underperformance of 14.17% was found using abnormal returns and 12.91% underperformance was found when holding period returns were calculated one year after the IPO

Bicarbonate is a key regulator but not a substrate for O2 evolution in Photosystem II

Photosystem II (PSII) uses light energy to oxidize water and to reduce plastoquinone in the photosynthetic electron transport chain. O2 is produced as a byproduct. While most members of the PSII research community agree that O2 originates from water molecules, alternative hypotheses involving bicarbonate persist in the literature. In this perspective, we provide an overview of the important roles of bicarbonate in regulating PSII activity and assembly. Further, we emphasize that biochemistry, spectroscopy, and structural biology experiments have all failed to detect bicarbonate near the active site of O2 evolution. While thermodynamic arguments for oxygen-centered bicarbonate oxidation are valid, the claim that bicarbonate is a substrate for photosynthetic O2 evolution is challenged

Adventures with Cyanobacteria: A Personal Perspective

Cyanobacteria, or the blue-green algae as they used to be called until 1974, are the oldest oxygenic photosynthesizers. We summarize here adventures with them since the early 1960s. This includes studies on light absorption by cyanobacteria, excitation energy transfer at room temperature down to liquid helium temperature, fluorescence (kinetics as well as spectra) and its relationship to photosynthesis, and afterglow (or thermoluminescence) from them. Further, we summarize experiments on their two-light reaction – two-pigment system, as well as the unique role of bicarbonate (hydrogen carbonate) on the electron-acceptor side of their photosystem II, PSII. This review, in addition, includes a discussion on the regulation of changes in phycobilins (mostly in PSII) and chlorophyll a (Chl a; mostly in photosystem I, PSI) under oscillating light, on the relationship of the slow fluorescence increase (the so-called S to M rise, especially in the presence of diuron) in minute time scale with the so-called state-changes, and on the possibility of limited oxygen evolution in mixotrophic PSI (minus) mutants, up to 30 min, in the presence of glucose. We end this review with a brief discussion on the position of cyanobacteria in the evolution of photosynthetic systems

Integrated MEMS metrology device using complementary measuring combs

The present invention provides a device for in-situ monitoring of material, process and dynamic properties of a MEMS device. The monitoring device includes a pair of comb drives, a cantilever suspension comprising a translating shuttle operatively connected with the pair of comb drives, structures for applying an electrical potential to the comb drives to displace the shuttle, structures for measuring an electrical potential from the pair of comb drives; measuring combs configured to measure the displacement of the shuttle, and structures for measuring an electrical capacitance of the measuring combs. Each of the comb drives may have differently sized comb finger gaps and a different number of comb finger gaps. The shuttle may be formed on two cantilevers perpendicularly disposed with the shuttle, whereby the cantilevers act as springs to return the shuttle to its initial position after each displacement

Freedom of religion of children in private schools

This article argues against the interpretation that the right to establish private schools includes the right to require religious conformity from non-adherent learners by way of a waiver of their religious freedom. Despite the importance of respecting the rights of religious communities to protect and preserve their faith in private schools, it is submitted that this right cannot be exercised without regard for the religious freedom, dignity and best interests of non-adherent children. As a result, it is submitted that the waiver of the freedom of religion of non-adherent children is not consistent with the values which South African society reveres and, therefore, cannot be enforced. This article suggests that there is a way for the rights of private schools and the rights of the non-adherent child to co-exist in harmony through the application of the reasonable accommodation principle in private schools