Lluís Casas

Self-assembled multifunctional Fe/MgO nanospheres for magnetic resonance imaging and hyperthermia

UNLABELLED A one-step process for the production of nanoparticles presenting advanced magnetic properties can be achieved using vapor condensation. In this article, we report on the fabrication of Fe particles covered by a uniform MgO epitaxial shell. MgO has a lower surface energy than Fe, which results in a core-shell crystal formation. The particles satisfy a few of technical requirements for the practical use in real clinics, such as a high biocompatibility in living cells in-vitro, an injection through blood vessels without any clothing problems in murine model, a high absorption rate for magnetic hyperthermia at small particle concentration, and the potential to be used as contrast agent in the field of diagnostic magnetic imaging. They are also able to be used in drug delivery and magnetic-activated cell sorting. FROM THE CLINICAL EDITOR In this paper, the authors report on the synthesis of Fe particles covered by a uniform MgO epitaxial shell resulting in a core-shell crystal formation. The particles are proven to be useful as contrast agents for magnetic resonance imaging and have the potential to be useful as heating mediators for cancer therapy through hyperthermia. They also might be used in drug delivery and magnetic-activated cell sorting.

Rock magnetic property and paleointensity determination on historical Santorini lava flows

Eight historical dacitic lava flows from Santorini with ages between 46 A.D. and 1950 A.D. (four of them within the past century) have been subjected to detailed rock magnetic analyses and various experiments of absolute paleointensity. Thermomagnetic measurements and acquisition of isothermal magnetization have revealed the presence of two physically distinct magnetic phases with Curie temperatures of 280°C and 500°C. In most of the samples, the second phase does not play a prominent role for the characteristic remanent magnetization, which is dominated by titanomagnetite. Magnetostatic interaction is very limited and does not considerably change upon heating. Back-field curve spectra indicate a good thermochemical stability of these dacitic lava samples, which is also supported by the absence of noticeable changes in the remanent coercive force prior heating to 450°C. Hysteresis measurements show typical pseudo-single-domain behavior without noticeable superparamagnetism. Such characteristics were favorable to conduct and to test the most widely used experimental approaches for absolute paleointensity determination. Despite a success rate of 38%, the microwave technique has provided rather scattered within-flow determinations. The results obtained from approaches involving alternating field demagnetization were biased by considerable differences between the NRM and the TRM coercive force spectra. We have also noticed that most determinations obtained by microwave heating differ from the historical field value at the site for the most recent flows. Last, techniques involving double-heating protocols were successful due to a dominant low Curie temperature phase with a narrow grain size distribution. The results were characterized by low dispersion and were found in good agreement with the historical field.

Interactive PDF files with embedded 3D designs as support material to study the 32 crystallographic point groups

Crystallography and X-ray diffraction techniques are essential topics in geosciences and other solid-state sciences. Their fundamentals, which include point symmetry groups, are taught in the corresponding university courses. In-depth meaningful learning of symmetry concepts is difficult and requires capacity for abstraction and spatial vision. Traditionally, wooden crystallographic models are used as support material. In this paper, we describe a new interactive tool, freely available, inspired in such models. Thirty-two PDF files containing embedded 3D models have been created. Each file illustrates a point symmetry group and can be used to teach/learn essential symmetry concepts and the International Hermann-Mauguin notation of point symmetry groups. Most interactive computer-aided tools devoted to symmetry deal with molecular symmetry and disregard crystal symmetry so we have developed a tool that fills the existing gap. Display Omitted PDF is a self-contained format that supports 3D designs and multi-layer structure.We use embedded 3D designs in PDF files to illustrate point groups.We use crystallographic notation to set a structure of interactive buttons in PDF files.

Three-dimensional-printing aids in visualizing the optical properties of crystals

Crystal optics is an essential topic in mineralogy and is also relevant at postgraduate level in solid-state chemistry and physics. The emergence of low-cost three-dimensional-printing technologies makes possible the creation of tangible objects for multiple educational purposes. Within the field of crystallography and chemistry, some examples of applications of such educational objects have been recently published. These were intended for teaching and learning of crystal and molecular symmetry concepts. In this paper, three-dimensional-printing applications have been extended to crystal optics. A number of tangible models of optical indicatrices have been designed and printed. These models were conceived as dissection puzzles and allow students to actively work on assembling them and analyzing their geometrical features and relevant sections. The STL files of the presented models are made available with this paper.