Animations, videos and 3D models for teaching space-group symmetry.

A series of animations, videos and 3D models that were developed, filmed or built to teach the symmetry properties of crystals are described. At first, these resources were designed for graduate students taking a basic crystallography course, coming from different careers, at the National Autonomous University of Mexico. However, the COVID-19 pandemic had the effect of accelerating the generation of didactic material.

Tooth acellular extrinsic fibre cementum incremental lines in humans are formed by parallel branched Sharpey's fibres and not by its mineral phase.

In humans, the growth pattern of the acellular extrinsic fibre cementum (AEFC) has been useful to estimate the age-at-death. However, the structural organization behind such a pattern remains poorly understood. In this study tooth cementum from seven individuals from a Mexican modern skeletal series were analyzed with the aim of unveiling the AEFC collagenous and mineral structure using multimodal imaging approaches.

Theoretical method for a radiopacifier proportion calculation in MTA type cements.

This article deals with the problem of determining the proportion by weight of radiopacifying material needed to add to a cement clinker of mineral trioxide aggregated (CE) to comply with ISO 6876/2001 and ANSI-ADA 57 regulations for radiopacity. With this aim, CE was synthesized and mixed experimentally with 5, 10, 15, and 20 wt% of ZrO as radiopacifying material. Radiographic images were taken so that radiographic density was obtained and related to the mmAl scale by using an aluminum step wedge.

Thermal degradation and lifetime of β-chitin from Dosidicus gigas squid pen: Effect of impact at 9.7 GPa and a comparative study with α-chitin.

The kinetics of thermal degradation of β-chitin extracted from Dosidicus gigas squid pen, was studied at normal conditions as well as after being subjected to the action of high-pressure impact of 9.7 GPa. The integral iso-conversional procedure of Kissinger-Akahira-Sunose (KAS) recommended by the ICTAC kinetics committee was applied to the non-isothermal data obtained from thermogravimetry (TGA).

Compositionally induced phase transitions and symmetry relations between space groups in the layered system FeInYGeO.

Symmetry reduction in the basic structure of thortveitite-type compound FeInGeO-mC22 (C12/m1, No. 12) promoted by the incorporation of yttrium in the formula FeInYGeO gives rise to a derivative structure called thortveitite-like AA'GeO-mP44, with symmetry described by the space group P12/m1 (No. 11) for x = 0.

Piezoelectric Ceramics of the (1 - x)BiNaTiO₃-xBaCaTiO₃ Lead-Free Solid Solution: Chemical Shift of the Morphotropic Phase Boundary, a Case Study for x = 0.06.

Research and development of lead-free piezoelectric materials are still the hottest topics in the field of piezoelectricity. One of the most promising lead-free family of compounds to replace lead zirconate-titanate for actuators is that of BiNaTiO₃ (BNT) based solid solutions. The pseudo-binary (1 - )BiNaTiO₃-BaCaTiO₃ system has been proposed for high temperature capacitors and not yet fully explored as piezoelectric material.

Hydroxyapatite crystallization in shrimp cephalothorax wastes during subcritical water treatment for chitin extraction.

The extraction of calcareous chitin from shrimp cephalothorax was successfully achieved using a subcritical water treatment to attain a deproteinization up to 96%. The treatments also increased the crystalline domain size in the α-chitin fibers. An experimental design of Taguchi allowed the optimization of experiments.

Phase composition of ProRoot mineral trioxide aggregate by X-ray powder diffraction.

Introduction: Composition and crystalline phases of the endodontic material mineral trioxide aggregate (MTA) is of fundamental importance for understanding its physical and chemical properties. This research was done to determine the composition of crystalline phases for ProRoot MTA.

Methods: For phase identification, powder of ProRoot MTA was analyzed by x-ray diffraction (XRD), comparing the MTA peaks with the data contained in the Powder Diffraction File of the International Centre for Diffraction Data (ICDD).

A synchrotron study of Na(2.27)Ho(7.73)(SiO(4))(6)O(0.72).

A well crystallized powder sample of sodium holmium orthosilicate oxyapatite, Na(2.27)Ho(7.73)(SiO(4))(6)O(0.

Y(0.76)Ho(0.24)FeGe(2)O(7): a new member of thortveitite-like layered compounds.

Y(0.76)Ho(0.24)FeGe(2)O(7) (yttrium holmium iron digermanate) was synthesized by solid-state reaction at 1573 K.

Rietveld refinement of the mixed boracite Fe(1.59)Zn(1.41)B(7)O(13)Br.

The structural characterization of the new iron-zinc hepta-borate bromide with composition Fe(1.59)Zn(1.41)B(7)O(13)Br, prepared by chemical transport is reported.

In1.06Ho0.94Ge2O7: a thortveitite-type compound.

A new indium holmium digermanate, In(1.06)Ho(0.94)Ge(2)O(7), with a thortveitite-type structure, has been prepared as a polycrystalline powder material by high-temperature solid-state reaction.

In1.08Gd0.92Ge2O7: a new member of the thortveitite family.

Indium gadolinium digermanium heptaoxide, In(1.08)Gd(0.92)Ge(2)O(7), with a thortveitite-type structure, has been prepared as a polycrystalline powder material by a high-temperature solid-state reaction.

gamma-Sodium gallate: a Rietveld refinement using X-ray powder diffraction.

Tetrahedrally coordinated oxides usually present polymorphism, but for NaGaO(2), only the beta polymorph has been reported. In this work, the synthesis and structural characterization of gamma-sodium gallate, gamma-NaGaO(2), are presented. The crystal structure belongs to the orthorhombic system, space group Pbca (No.