A review of accelerated carbonation technology in the treatment of cement-based materials and sequestration of CO2

Moist calcium silicate minerals are known to readily react with carbon dioxide (CO2). The reaction products can cause rapid hardening and result in the production of monolithic materials. Today, accelerated carbonation is a developing technology, which may have potential for the treatment of wastes and contaminated soils and for the sequestration of CO2, an important greenhouse gas. This paper reviews recent developments in this emerging technology and provides information on the parameters that control the process. The effects of the accelerated carbonation reaction on the solid phase are discussed and future potential applications of this technology are also considered.     

TEM and molecular simulation studies on the hydroxylapatite structure with Si and Mg impurities

Transmission electron microscopy (TEM) and molecular simulation studies of traces of chemical elements such as Mg, Si, and OH in the hydroxylapatite (CaHAP) crystal structure obtained from the sand dollar were carried out. Two different types of CaHAP crystal morphologies in the samples synthesized by the hydrothermal method used were observed. Reflections with regular intensity in the experimental electron diffraction patterns obtained from these morphologies were observed. However, when these results were compared with a simulated electron diffraction pattern (which was obtained using the crystalline structure proposed for the hydroxylapatite) some forbidden reflections in the experimental pattern were observed. Then, in order to reproduce the experimental patterns Si and Mg atoms in the crystalline lattice were introduced. These elements in the elemental chemical analysis carried out by X-ray energy dispersive spectroscopy (EDS) in the typical CaHAP morphologies were detected. The positions of these atoms in the asymmetric unit were obtained using molecular simulation and during the relaxation process, the structure did not show changes in the lattice parameters. Subsequently, the crystalline structure was reproduced and matched the electron diffraction patterns simulated resulting in the experimental electron diffraction pattern. Experimental and simulated X-ray diffraction spectra were also matched.     

Towards cooperative frameworks for modeling and integrating biological processes knowledge

Data organization has become a strategic target for biologists due to the increasing volume of genomic data available for them. For this purpose, we need a complete knowledge model for representing biological system. In this paper, we deal with both processes for the creation and integration of shareable, reusable domain models within biology, which is a critical issue. In particular, this work introduces a new cooperative development approach for biology ontologies. This approach is based on the integration of the ontologies supplied by different human experts. Two experiments in biological domains are presented and their results discussed.     

Polyynes Production in a Solvent-Submerged Electric Arc Between Graphite Electrodes. III. Chemical Reactivity and Stability Toward Air, Ozone, and Light

Since polyynes are easily accessible with the submerged electric arc synthesis between graphite electrodes, the chemical behavior of polyynes solutions in different solvents has been explored. It has been found that surprisingly the polyynes solutions, with polyynes having up to 16 carbon atoms arranged in a chain, are stable in air over 1 week time in the dark. These solutions react relatively slowly with ozone while add rapidly and completely bromine. The polyynes solutions are instead quite easily photolyzed under the action of UV radiation both in air and under N₂. Two different light sources were used in the study: a low pressure mercury lamp emitting almost a monochromatic radiation at 254 nm and an high pressure mercury lamp emitting in a broad wavelength range in the ultraviolet. With the former monochromatic light source, it has been demonstrated the possibility to perform a selective photolysis of selected polyynes in a mixture of homologous series.     

Structural properties and stability of metastable phases in the Zr-Nb system: Part II. Aging of bcc (β) alloys and assessment of β-Zr

The lattice parameters (LPs) of the bcc (β) phase occurring metastably in a series of Zr-rich Zr-Nb alloys have been determined at and above room temperature (T _R ) using neutron diffraction techniques. LP values at T = T _R were determined in alloys with Nb contents in the range 8.4 ≤ at. pct Nb ≤ 23 using both standard and high-resolution neutron diffractometry. These results support the applicability of Vegard’s law at T _R . In addition, a neutron thermodiffractometric technique is used to establish the LP vs T relation of the β phase in two Zr-Nb alloys with 18 and 23 at. pct Nb up to 700 K. Such high-temperature data are used in a generalized Vegard’s law approach to gain insight into the LP vs T relation of the β phase in pure Zr, which is metastable in this temperature range. With these new LP values, an assessment is performed of the thermal expansion coefficient of β-Zr covering both stable and metastable states. As a direct application of the present findings, the results of an aging experiment are discussed, which provide information on the composition of the β phase taking part in the bcc-hcp equilibrium in the Zr-Nb phase diagram at 900 K. Such composition has been the subject of contradictory reports in recent literature. The composition value arrived at in the present analysis agrees well with the results of a thermodynamic calculation of the Zr-Nb phase diagram (A. Fernández Guillermet: Z. Metallkd., 1991, vol. 82, p. 478)     

Impairment in long-term retention but not short-term performance on a water maze reversal task following hippocampal or mediodorsal striatal n-methyl-d-aspartate receptor blockade.

Male Long-Evans rats were injected with 32 ng/μl of the N-methyl-D-aspartate (NMDA) receptor antagonist 3-(2-carboxypiperazin-4-yl) propyl-1-phosphonic acid (CPP) or vehicle and trained to locate a hidden platform in a different location (reversal training) than used on the initial 4 days of training. Rats treated with vehicle or CPP into the dorsal hippocampus, basolateral amygdala, or mediodorsal striatum had similar latencies to locate the platform on the reversal day. Rats infused with CPP into the dorsal hippocampus or mediodorsal striatum failed to search preferentially in the novel location during a 24-hr, drug-free retention test, whereas all other groups searched preferentially in this location. Therefore, blocking dorsal hippocampal or mediodorsal striatal NMDA receptors selectively blocked long-term spatial retention without producing short-term performance deficits. (PsycINFO Database Record (c) 2010 APA, all rights reserved)