Deformation-induced martensitic transformation behavior in cold-rolled and cold-drawn type 316 stainless steels

We investigate deformation-induced martensitic transformation behavior in cold-rolled and cold-drawn specimens of type 316 stainless steel. Deformation-induced martensite preferentially nucleates at the twin boundary between the austenite matrix and a deformation twin. In the cold-rolled specimen, martensite formed at the twin boundary has a Kurdjumov–Sachs (K–S) relationship with both the austenite matrix and the deformation twin (“double K–S relationship”). In the cold-drawn specimen, two kinds of deformation twins with different twin planes are typically formed, and therefore deformation-induced martensites are formed where the deformation twin boundaries intersect: martensite thus has an imperfect “triple K–S relationship” with the austenite matrix and the two deformation twins. The complicated crystallographic orientation relationship between austenite and martensite grains strongly restricts the formation of some variants of deformation-induced martensites. Because of the difference in number of nucleation sites in the cold-drawn and cold-rolled specimens, martensitic transformation is more enhanced in the former than in the latter.     

Effect of chloride ions on leaching rate of chalcopyrite

The effect of chloride on chalcopyrite leaching has been investigated by performing batch leaching tests with three kinds of leaching solutions and using Hiroyoshi’s model, which suggests that a zone of rapid leaching exists between the critical potential (E_c, equilibrium redox potential for the reduction of CuFeS₂ to Cu₂S) and the oxidation potential (E_ox, equilibrium redox potential for the oxidation of Cu₂S). The results of the leaching tests show that the leaching rate in hydrochloric acid solution is the fastest and that the relationship between the Cu leaching rate and oxidation–reduction potential (ORP) follows Hiroyoshi’s model. Thermodynamic calculations indicate that, with an increase in the chloride concentration, the concentration of cuprous ions increases as the chlorocuprate(I) complex ions are formed and the contribution of cuprous ions to the critical potential is greater than that of cupric ions, even though the concentration of cuprous ions is lower than that of cupric ions. This fact suggests that the formation of chlorocuprate(I) ions in a chloride solution may improve the chalcopyrite leaching rate by increasing the critical potential.     

An Investigation of Capacitors for Flying Capacitor Converters

Multilevel converters can essentially reduce harmonics even when their switching frequency is low. Among the various topologies of the multilevel converters, flying capacitor converters are considered to be promising converters for realizing high power density. However, the main circuit of the flying capacitor converters has many capacitors. Therefore, in this study, the volume of the capacitors in the flying capacitor converters is determined by taking into consideration the allowable ripple voltage and temperature rise in the capacitor. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(4): 81–91, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22361     

Improvement of both adsorption performance of silica gel and heat transfer characteristics by means of heat exchange modulation for a heat pump

In order to provide high performance silica gel for an adsorption heat pump (AHP), gels were synthesized using the sol-gel process modified with a new method of controlling the primary gel particle growth by the addition of aluminum ion. In this process, the pores of the silica gel synthesized became smaller when aluminum ion was added in the washing process. Furthermore, this silica gel adsorbed more water at a low region of water vapor pressure and its adsorption ability did not change after 100 repetitive times of adsorping/desorping water vapor. The experimental results from the water vapor adsorption on the silica gel agreed well with theoretical results obtained under the Lump model for heat transfer and intraparticle diffusion model for mass transfer. A new direct heat exchange silica gel module (DS-module) for the AHP was provided, and the heat transfer characteristics during the operation for the adsorption of water vapor were both experimentally and theoretically determined. The period of the adsorption for the DS-module was shorter than that for a silica gel/tube module. Therefore, with the addition of the DS-module the heat transfer in the AHP adsorber was sufficiently enhanced and the maximum heat generation power for the 2-mm-thick DS-module was obtained. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(7): 420–433, 1996     

Peptides before and during the nucleotide world: an origins story emphasizing cooperation between proteins and nucleic acids

Recent developments in Origins of Life research have focused on substantiating the narrative of an abiotic emergence of nucleic acids from organic molecules of low molecular weight, a paradigm that typically sidelines the roles of peptides. Nevertheless, the simple synthesis of amino acids, the facile nature of their activation and condensation, their ability to recognize metals and cofactors and their remarkable capacity to self-assemble make peptides (and their analogues) favourable candidates for one of the earliest functional polymers. In this mini-review, we explore the ramifications of this hypothesis. Diverse lines of research in molecular biology, bioinformatics, geochemistry, biophysics and astrobiology provide clues about the progression and early evolution of proteins, and lend credence to the idea that early peptides served many central prebiotic roles before they were encodable by a polynucleotide template, in a putative ‘peptide-polynucleotide stage’. For example, early peptides and mini-proteins could have served as catalysts, compartments and structural hubs. In sum, we shed light on the role of early peptides and small proteins before and during the nucleotide world, in which nascent life fully grasped the potential of primordial proteins, and which has left an imprint on the idiosyncratic properties of extant proteins.     

A molten metal jet impingement on a flat spreading surface

ABSTRACT

In the event of a severe accident, past experiences such as Three Mile Island and Fukushima Daichi have shown that the reactor core of a light-water nuclear reactor, if not properly safeguarded, could go through a meltdown. This will be followed by the formation of a corium, a mix of molten fuel elements, and liquid metals from the Reactor Pressure Vessel (RPV). In the worst-case scenario, a melt through from the RPV can occur and lead to the spreading of the corium, in the form of a molten element’s jet impinging on a flat concrete structure of the Primary Containment Vessel (PCV). To enhance the decommissioning and the safety procedure, scope of the present article is to deepen the understanding of the phenomena involved in the mentioned scenario, mainly jet-instability and molten material spreading. In the present study, experiments were carried out, by using corium simulant materials such as Copper and Tin, to investigate the link between the instability of the gravity-driven molten metal jet and the impinging followed by its spreading over a flat area.     

Compositional Dependence of Normal Spectral Emissivity of Molten Cu-Fe Alloy

Metallurgical and Materials Transactions B - Normal spectral emissivity of molten Cu-Fe alloy with different compositions was measured at the wavelength of 807 nm using an electromagnetic...     

Dynamic Changes in Reactive Oxygen Species in the Shoot Apex Contribute to Stem Cell Death in Arabidopsis thaliana

In monocarpic plants, stem cells are fated to die. However, the potential mechanism of stem cell death has remained elusive. Here, we reveal that the levels of two forms of reactive oxygen species (ROS), superoxide anion free radical (O2·−) and hydrogen peroxide (H₂O₂), show dynamic changes in the shoot apex during the plant life cycle of Arabidopsis thaliana. We found that the level of O2·− decreased and disappeared at four weeks after bolting (WAB), while H₂O₂ appeared at 3 WAB and showed a burst at 5 WAB. The timing of dynamic changes in O2·− and H₂O₂ was delayed for approximately three weeks in clv3-2, which has a longer lifespan. Moreover, exogenous application of H₂O₂ inhibited the expression of the stem cell determinant WUSCHEL (WUS) and promoted the expression of the developmentally programmed cell death (dPCD) marker gene ORESARA 1 (ORE1). These results indicate that H₂O₂ triggers an important signal inducing dPCD in stem cells. Given that O2·− plays roles in maintaining WUS expression and stem cell activity, we speculate that the dynamic shift from O2·− to H₂O₂ in the shoot apex results in stem cell death. Our findings provide novel insights for understanding ROS-mediated regulation during plant stem cell death.     

Physicochemical properties of monosodium glutamate-compounded tapioca starch exceeds those of simple heat-moisture treated starch

Monosodium glutamate (GluNa)-compounded starch was prepared by heat-moisture treating a mixture of tapioca starch and GluNa. GluNa-compounded starch exhibited a higher gelatinization temperature and reduced swelling and solubility, essentially lower hardness of the granule center, and paste viscosity than those of the heat-moisture treated tapioca starch and the untreated starch. However, its appearance, unit chain length distribution, and α-amylase digestibility were similar to those of the heat-moisture treated tapioca. It is thus concluded that GluNa compounding is useful for providing a unique type of starch that possesses a less swollen and viscous texture than that produced with simple heat-moisture treatment.