Incubation-based hydroxyapatite synthesis method using shells as Ca2+ source

Hydroxyapatite, the well-known calcium phosphate, was obtained on the surface of shells fragments by partial conversion of the latter, which served both as template and also provided the calcium ions required for synthesis. Confirmation of hydroxyapatite formation was acquired by recording and analyzing X-ray diffraction patterns. The degree to which the phosphate ions were consumed during the incubation-based synthesis was determined using a phosphate minicolorimeter, and the results indicate that a nucleation process takes place in the first 4 hours

Non-ambient FTIR study of thermally treated seashells

A large quantity of waste seashells (millions of tons) is discarded annually after mollusc consumption, which becomes a problem for the environment worldwide as these shells are a habitat for microbes which could turn into a public health issue [1]. On the other hand, waste shell biomaterials need a small amount of energy for recycling and processing into useful products for various applications. Calcium carbonate is essential in biomineralization, where it is the primary constituent of mollusc shells, crustacean cuticles, corals etc. In its pure form, it occurs naturally, under normal temperature and pressure conditions, in three anhydrous crystalline forms, namely calcite, aragonite and vaterite [2]. At high pressures, two further forms, namely calcite II and calcite III, are formed. The most stable form of calcium carbonate at atmospheric pressure and room temperature is calcite. The presence of both calcite and aragonite is very frequent in biologically produced calcium carbonate minerals. Though aragonite is metastable in aqueous solution, it can nucleate [3]. Aragonite is found in the nacre of the shells of bivalve molluscs, which provide a protection for these animals [4]. From the study of the marine bivalve species Mercenaria mercenaria and Crassostrea gigas, Weiner et al. [5] have shown that amorphous calcium carbonate is a precursor phase of aragonite. The present study, which is part of our efforts to convert seashells into useful products like hydroxyapatite, investigates the temperature influence on the calcite and aragonite in a processed shell sample by using Fourier-transform infrared spectroscopy (FTIR)

DESIGNING A WEBSITE FOR A RECRUITMENT AGENCY WITH PMBOK METHODOLOGY

Project management refers to a set of activities that contribute to to achieve a successful project: defining the objectives, establishing the team, planning the tasks and providing the resources and deadlines for completing them, continuous assessing the performance and making adjustments when is necessary. The case study used the PMBOK methodology and software tools to design a website for a recruitment agency. The project was accomplished by a group of master students guided by a teacher, at Software for Project Management class. As future work, the authors of this paper aim to continue this experience by enlarging the research study to other projects and by using different project management methodologies

Influence of nucleation centers upon solvothermal growth of silver nano/microcrystals

Silver nano/microcrystals were obtained at medium pressure in a microwave field by using the solvothermal synthesis. In order to evaluate the nucleation centers’ influence upon the formed crystals’ morphology, investigations were conducted using scaffolds to stimulate their heterogeneous nucleation. Therefore, besides the silver and chloride nanocrystals used as nucleation centers, SiOx type spheres were used. The results indicate that the presence of the heterogeneous nucleation centers on the SiOx scaffolds plays a crucial role in the silver nano/microcrystals morphology

Metal content of seashells from black sea's Romanian coast

The main metals from various species of seashells, commonly found on the Black Sea’s Romanian coast, were determined by using microwave plasma atomic emission spectroscopy (MP-AES) and energy-dispersive X-ray spectroscopy (EDX). As expected, calcium was the main component, followed by magnesium, aluminum, iron and manganese

Dimensional distribution of PM2.5 and PM10 in the road proximity

The particulate matter (PM) is comprised of two kinds of particles, classified after their dimensions, the PM2.5 which encompasses particles with sizes smaller than 2.5 µm and the PM10 with particles ranging in size from 2.5 µm to 10 µm. As previous studies have shown, PMs have an undeniable influence, dependent on the exposure time, upon the health of the human cardiopulmonary system. In this study we focused on the dimensional distribution of PMs and the influence of altitude on their numbers. Our detailed investigation lead us to the conclusion that the particle number is increasing at higher altitudes and also that PM2.5, which represents a greater health risk factor, is much more abundant than PM10