Lauro Bucio - Academia.edu (original) (raw)

Papers by Lauro Bucio

Acta Crystallographica Section A, 2017

Pharmaceutical solids are able to exist in several forms: polymorphic crystalline and amorphous a... more Pharmaceutical solids are able to exist in several forms: polymorphic crystalline and amorphous arrangements. They present differences in their physicochemical properties, for instance, melting point, density, morphology, solubility and color. These characteristics may have an impact on the stability (physical and chemical), bioavailability and bioequivalence1; e.g. amorphous substances are unstable than crystalline substances. Differences in degrees of drug crystallization affect chemical and physical stability, rather than crystalline polymorphism of the substance.

Antiferromagnetic polycrystalline FeTbGe 2O7 compound presents an ordered magnetic phase when its... more Antiferromagnetic polycrystalline FeTbGe 2O7 compound presents an ordered magnetic phase when its temperature decreases below the Néel temperature T N = 42 K. By mean of Rietveld refinement of collected neutron diffraction data, the broadened part of the magnetic peaks was modeled in order to analyze the effect of average size of magnetic domains on the evolution of magnetic structure with temperature. The rise of the magnetic structure was found to be sensitive to the shortening of distances along the b-axis between the magnetic atoms located in thebc-sheets of the layered structure. When the magnetic structure is generated, chains along the b-axis of Tb-Tb atoms are antiferromagnetically coupled. At the same time, ferromagnetic coupling along the c-axis between Tb -Fe atoms located in contiguous chains, couples all the chains along a sheet in the layered structure. The three-dimensional magnetic structure is reached by the ferromagnetic coupling between the set of sheets parallel ...

Acta Crystallographica Section A Foundations and Advances, 2017

Pharmaceutical solids are able to exist in several forms: polymorphic crystalline and amorphous a... more Pharmaceutical solids are able to exist in several forms: polymorphic crystalline and amorphous arrangements. They present differences in their physico-chemical properties, for instance, melting point, density, morphology, solubility and color. These characteristics may have an impact on the stability (physical and chemical), bioavailability and bioequivalence 1 ; e.g. amorphous substances are unstable than crystalline substances. Differences in degrees of drug crystallization affect chemical and physical stability, rather than crystalline polymorphism of the substance. Tablets are solids preparations of active pharmaceutical ingredients and additives, many of the additives commonly used are poorly crystalline or amorphous, determining the final solubility in the drug.

Ceramics International, 2020

Journal of Solid State Chemistry, 2017

In this work, we present both structural and magnetic (DC magnetization and AC susceptibility) st... more In this work, we present both structural and magnetic (DC magnetization and AC susceptibility) studies of the Dy 3−x Y x TaO 7 solid solution. The structural characterization of samples was performed by Rietveld refinements of the X-ray diffraction data. All compounds crystallized in a weberite-related structure in the orthorhombic C222 1 space group (No. 20); the variations of the lattice parameters obey the Vegard´s law in the whole range of composition. DC magnetic measurements of the Dy 3−x Y x TaO 7 system showed a Curie-Weiss paramagnetic behaviour, with antiferromagnetic interactions at T > 150 K. Below 3 K a spin glass behaviour in the 0 ≤ x ≤ 1 range of the solid solution was observed. The stoichiometric Dy 3 TaO 7 compound showed spin glass behaviour although there is no evidence of structural disorder. For some Y 3+ doped compounds (x = 0.33, 0.66 and 1.0), chemical disorder reduced the freezing temperature (T g) values with a × 1/3 dependence. Cole-Cole analysis of the AC magnetic field response showed similar phenomenological parameters for the stoichiometric (x = 0) and the Y 3+ doped compounds with spin glassiness, suggesting an analogous mechanism for these compounds. For the Dy 3−x Y x TaO 7 system, in which the spin glass behaviour seems to exhibit a critical concentration, a magnetic phase diagram is proposed.

Acta Crystallographica Section A Foundations of Crystallography, 2008

Voltage Electron Microscope). EF-PED data resulted in the basic crystallographic information of Z... more Voltage Electron Microscope). EF-PED data resulted in the basic crystallographic information of ZnS nano-crystals: P63mc, a = 3.83Å and c = 6.26Å; F-43m, a = 5.41Å, respectively. As a result of HREM analysis, their crystallite shapes were turned out to be nano-rods and nano particles, respectively and the nano-rod structure was elongated to the [001] direction. The size and shape dependency related to crystal structures of ZnS nano-crystals has been discussed.

Acta Crystallographica Section A Foundations of Crystallography, 2011

Materials Science Forum, 1996

... 172, 159 (1985). [4] AA Kaminskii, BV Mill, AV Butashin, EL Belokoneva and K. Kurbanov, Phys.... more ... 172, 159 (1985). [4] AA Kaminskii, BV Mill, AV Butashin, EL Belokoneva and K. Kurbanov, Phys. Stat. Sol.(a), 103, 575 (1987) [5] ZA Kazei, IA Kuyanov, RZ Levitin, AS Markosyan, BV Mill, SIReiman, VV Snegirevand SA Tamazyan, Sov. Phys. Solid State 31, 233 (1989). ...

Acta Crystallographica Section A Foundations of Crystallography, 2008

Microsymposia compound semiconducters such as Cu(In,Ga)Se2 as absorbers. Since the availability o... more Microsymposia compound semiconducters such as Cu(In,Ga)Se2 as absorbers. Since the availability of indium is an object of concern regarding solar cell large scale production, its replacement with Zn and Sn is beneficial in this sense. The alternative compound kesterite (Cu2ZnSnS4) has promising characteristic optical properties. The structure of kesterite consists of a ccp array of sulfur atoms, with metal atoms occupying one half of the tetrahedral voids. In literature an ordered distribution of Cu + , Zn 2+ and Sn 4+ is described. A disordered distribution may cause site defects and hence influences the electronic properties of the material. Thus the degree of cation order plays a crucial role and was therefore the focus of the presented investigations. Combined neutron and X-ray diffraction experiments revealed that the degree of cation order depends on the thermal history of the kesterite. In quenched samples Cu + and Zn 2+ are disordered, whereas in samples where a controlled cooling was applied, a certain degree of cation order is achieved. To shed more light into the formation process of kesterite, in-situ high temperature synchrotron X-ray diffraction experiments on stochiometric mixtures of binary and ternary sulfides were perfomed. Structural phase transitions and formation of new phases, resulting in kesterite formation, can be observed in detail by mapping the diffractograms and Rietveld analysis. The variation of the kesterite lattice parameter with temperature, especially during the kesterite nascency, indicates changes in the cation distribution. Completing the presentation, first promising results of kesterite thin film solar cells will be shown.

Coatings, 2021

A study on the physical and mechanical properties of beeswax (BW), candelilla wax (CW), paraffin ... more A study on the physical and mechanical properties of beeswax (BW), candelilla wax (CW), paraffin wax (PW) and blends was carried out with the aim to evaluate their usefulness as coatings for cheeses. Waxes were analyzed by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), differential scanning calorimetry (DSC), permeability, viscosity, flexural and tensile tests and scanning electron microscopy. Cheeses were coated with the waxes and stored for 5 weeks at 30 °C. Measured parameters were weight, moisture, occurrence and degree of fractures, and dimensional changes. The crystal phases identified by XRD for the three waxes allowed them to determine the length of alkanes and the nonlinear compounds in crystallizable forms in waxes. FTIR spectra showed absorption bands between 1800 and 800 cm−1 related to carbonyls in BW and CW. In DSC, the onset of melting temperature was 45.5 °C for BW, and >54 °C for CW and PW. Cheeses coated with BW did not show cracks afte...

Revista Mexicana De Fisica, 2017

Microcrystalline powders of the nonstoichiometric Ge_(0.74) V_(0.21) □_(0.05) O_(2)compound were ... more Microcrystalline powders of the nonstoichiometric Ge_(0.74) V_(0.21) □_(0.05) O_(2)compound were prepared by conventional high temperature solidstate reactions. The powders were characterized by X-ray diffraction (XRD); scanning electron microscopy (SEM); X-ray photoelectron spectroscopy (XPS); diffuse reflectance ultraviolet-visible spectroscopy (DRUV-VIS) and electron spin resonance (ESR) spectroscopy. From the analysis performed on compound, it was found that: The powders showed a rutile type crystalline structure with a rectangular prismatic crystalline habit. The XPS analysis, confirm the presence of V^(4+) and V^(5+) vanadium ions, the DRUV-VIS spectra show absorption bands in the 200-800 nm wave length interval and the ESR analysis confirms that the V^(4+) ions are within microcrystals, hosted as VO^(2+) at sites of rhombic (C_(2v)) symmetry.

Ceramics International

Abstract The mineral trioxide aggregate (MTA) is Portland type cement whose main application in d... more Abstract The mineral trioxide aggregate (MTA) is Portland type cement whose main application in dentistry is retrograde filling. The purpose of this study was to analyze hydration reactions and physicochemical properties of a new tricalcium-dicalcium silicate-based cement containing nanocrystalline hydroxyapatite (nHAp) and calcite. The new formulation was compared with Biodentine™ and MTA-Angelus™ as control samples. Hydration reactions were monitored by Raman spectroscopy, X-ray diffraction, radiopacity, pH, setting time, and compressive strength. The compressive strength reaches its higher value at 7 days following the sequence: Biodentine™ (104.8 MPa) > Cement + 5% nHAp (59 MPa) > MTAAngelus™ (27.3 MPa), in agreement with the pH values measured at 24 h: Biodentine™, Cements + nHAp or + calcite (10.6–11.6) > MTA-Angelus™ (9.7). Mean setting times was around 30 min and no significative differences (p = 0.0001) were observed. In the Biodentine™ control samples, Ca 3 SiO 5 diminishes until disappear at 28 days of hydration. On their turn, calcium silicate hydrate (CSH) increases continuously in the range of time analyzed. The present results suggest that the physicochemical properties were improved for the new cement with nanosized hydroxyapatite nanoparticles and relevant information on chemical properties is of valuable importance for testing predictive models for Biodentine™ and MTA-Angelus™.

Materials Research Express, 2021

Tricalcium silicate-based cements (TCS-BC) have reached great relevance in modern dentistry, wher... more Tricalcium silicate-based cements (TCS-BC) have reached great relevance in modern dentistry, where they are used in root-end filling or perforation repair treatments, and also for restoring deep and/or voluminous coronary carious lesions, among other applications. In some TCS-BC such as BiodentineTM, the physical and chemical properties, e.g. high compressive strength, have led to consider this cement as a dentine substitute. One of the drawbacks of BiodentineTM is its very high washout; which refers to the tendency of disintegrate at initial stage of hydration upon early contact with blood or other fluids, just at the moment after it is still as a freshly prepared paste. The present research was focused to compare properties related to workability and hardening at early stages of hydration of experimentally synthetized nano-sized tricalcium silicate (nTCS) and BiodentineTM (BIOD). Both pastes were tested for hardening at 0, 1, 2 and 3 h of hydration, using a penetration test adapte...

In this article we report the phase transitions induced by shock-compression on a sample of gypsu... more In this article we report the phase transitions induced by shock-compression on a sample of gypsum mineral. The shock experiment was performed in a light gas gun until a pressure close to 14 GPa. The experimental technique employed to analyze the shock effects on the `` recovered sample '' was the Micro-Raman Spectroscopy (MRS). The results indicate the partial dehydration of gypsum as a result of impact. The MRS analysis also suggests the presence of micro-mixtures of gypsum, bassanite and anhydrite heterogeneously distributed throughout the `` recovered sample ''.

Acta Crystallographica Section A Foundations and Advances

Catalysis Today, 2011

Nanocrystals of FAU(Y) and MFI(ZSM5) zeolites were synthesized from clear solutions at 80–95°C un... more Nanocrystals of FAU(Y) and MFI(ZSM5) zeolites were synthesized from clear solutions at 80–95°C under autogen and atmospheric pressures, respectively. The X-ray diffraction (XRD) patterns confirm the structural features reported for FAU(Y) and MFI(ZSM5). Similarly, Fourier transform infrared spectroscopy (FTIR) with KBr shows the bands arising from typical structural groups of FAU(Y) and MFI(ZSM5), i.e., 455–462cm−1 and 555–560cm−1. The mean crystallites size was measured by transmission electron microscopy (TEM) and it was determined also by Rietveld's method using Scherrer's equation; with similar results between 20 and 40nm. Also, a cubic morphology for FAU(Y) crystallites and a disk-like habit for MFI(ZSM5) were verified together with the typical dimensions of the pore system and symmetry, i.e., pore diameters were between 0.74 and 0.56nm for FAU(Y) and MFI(ZSM5). Theoretical images were calculated using HRTEM (Cerius2) program and these were compared with the experimental ones, thus matching the corresponding typical structural parameters. The textural properties were determined by N2 adsorption–desorption (BET) and typical surface areas of 658 and 495m2/g were obtained for the nanosized materials. After ion-exchanging NH4NO3 ammonia was removed by calcination (i.e., 550°C) and the total acidity was measured, i.e. 1190 and 1084μmol(Py)/g (cat) at 25°C and 84 and 34μmol(Py)/g (cat) at 400°C for FAU(Y) and MFI(ZSM5), respectively. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) in air and N2 atmospheres showed a thermal stability of these materials up to about 1000°C. The catalytic activity of FAU(Y) and MFI(ZSM5) was tested by means of the cracking of 1,3,5-triisopropylbenzene (1,3,5-TIPBz) in a CREC Riser Simulator Reactor at 350°C; the cracking of 1,3,5-TIPBz increased to about 0.6 and 1.3 times from big (108.9 and 82.8nm) to small (18 and 20.7nm) crystallites of FAU(HY) and MFI(HZSM5), respectively, while diffusivity increased to about 3 and 4.6 times, which demonstrates a correlation between the mean crystallite size of these zeolites with cracking activity from the external crystallite surface and the diffusivity of large reactive molecules, i.e., 1,3,5-TIPBz.

Acta Crystallographica Section A Foundations and Advances

Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials

Symmetry reduction in the basic structure of thortveitite-type compound FeInGe2O7–mC22 (C12/m1, N... more Symmetry reduction in the basic structure of thortveitite-type compound FeInGe2O7–mC22 (C12/m1, No. 12) promoted by the incorporation of yttrium in the formula FeIn1−xYxGe2O7gives rise to a derivative structure called thortveitite-likeAA′Ge2O7–mP44, with symmetry described by the space groupP121/m1 (No. 11) forx= 0.50, 0.75 and 0.90. The structure remains unchanged within the structural type of thortveitite whenx= 0.25. In order to establish structural models for performing a Rietveld refinement to the derivative structure, symmetry relations between space groups connecting the basic and derivative structures were used. The higher contrast to X-rays of Fe3+, In3+and Y3+as well as by the behaviour during the refinements of the isotropic thermal displacements, the values of interatomic distances and calculated bond-valence sums for each atom in the asymmetric unit, were helpful for elucidating the relocation of cations in the different available crystallographic sites generated by the...

Revista Mexicana de Ortodoncia

To characterize radiographically the periodontal ligament thickness (PLT) and pain perception (PP... more To characterize radiographically the periodontal ligament thickness (PLT) and pain perception (PP) at the beginning of orthodontic treatment by activating and applying infrared laser of 810 nm each month for three months. Methodology: It was a quasi-experimental, descriptive and longitudinal study with a nonprobabilistic sample consisting of 10 patients from the clinic of Orthodontics and Orthopedics at the Autonomous University of Sinaloa. Two hundred measurements were performed in teeth #11 and 12 (laser-treated); and 21 and 22 (non-treated control). To measure the PLT periapical radiographs were analyzed with Motic software 3V Advance. For PP determination, visual analog scale (VAS) was used. Descriptive statistical analysis was performed with SPSSv-19 (confidence interval of 95%). Results: In laser-treated teeth, PLT increased significantly 0.719 μm from the first to the second measurement and decreased 0.648 μm in the third measurement. In non-treated control teeth, PLT increased averaging 1.011 μm without significant change in the third measurement. PP in control teeth averaged 3.7 ± 3.2 on the VAS scale in the first measurement and 2.3 ± 2.3 in the second; while in the irradiated zone they averaged 2.9 ± 2.8 in the first month and 1.4 ± 1.2 in the second. Conclusion: With laser treatment, PLT is significantly reduced in comparison to the group that did not receive the treatment. At one and two months of treatment, average of PP decreased both in teeth where the laser is applied as in those without. Palabras clave: Terapia por láser de baja intensidad, ortodoncia, escala visual analógica.

Acta Crystallographica Section A, 2017

Pharmaceutical solids are able to exist in several forms: polymorphic crystalline and amorphous a... more Pharmaceutical solids are able to exist in several forms: polymorphic crystalline and amorphous arrangements. They present differences in their physicochemical properties, for instance, melting point, density, morphology, solubility and color. These characteristics may have an impact on the stability (physical and chemical), bioavailability and bioequivalence1; e.g. amorphous substances are unstable than crystalline substances. Differences in degrees of drug crystallization affect chemical and physical stability, rather than crystalline polymorphism of the substance.

Antiferromagnetic polycrystalline FeTbGe 2O7 compound presents an ordered magnetic phase when its... more Antiferromagnetic polycrystalline FeTbGe 2O7 compound presents an ordered magnetic phase when its temperature decreases below the Néel temperature T N = 42 K. By mean of Rietveld refinement of collected neutron diffraction data, the broadened part of the magnetic peaks was modeled in order to analyze the effect of average size of magnetic domains on the evolution of magnetic structure with temperature. The rise of the magnetic structure was found to be sensitive to the shortening of distances along the b-axis between the magnetic atoms located in thebc-sheets of the layered structure. When the magnetic structure is generated, chains along the b-axis of Tb-Tb atoms are antiferromagnetically coupled. At the same time, ferromagnetic coupling along the c-axis between Tb -Fe atoms located in contiguous chains, couples all the chains along a sheet in the layered structure. The three-dimensional magnetic structure is reached by the ferromagnetic coupling between the set of sheets parallel ...

Acta Crystallographica Section A Foundations and Advances, 2017

Pharmaceutical solids are able to exist in several forms: polymorphic crystalline and amorphous a... more Pharmaceutical solids are able to exist in several forms: polymorphic crystalline and amorphous arrangements. They present differences in their physico-chemical properties, for instance, melting point, density, morphology, solubility and color. These characteristics may have an impact on the stability (physical and chemical), bioavailability and bioequivalence 1 ; e.g. amorphous substances are unstable than crystalline substances. Differences in degrees of drug crystallization affect chemical and physical stability, rather than crystalline polymorphism of the substance. Tablets are solids preparations of active pharmaceutical ingredients and additives, many of the additives commonly used are poorly crystalline or amorphous, determining the final solubility in the drug.

Ceramics International, 2020

Journal of Solid State Chemistry, 2017

In this work, we present both structural and magnetic (DC magnetization and AC susceptibility) st... more In this work, we present both structural and magnetic (DC magnetization and AC susceptibility) studies of the Dy 3−x Y x TaO 7 solid solution. The structural characterization of samples was performed by Rietveld refinements of the X-ray diffraction data. All compounds crystallized in a weberite-related structure in the orthorhombic C222 1 space group (No. 20); the variations of the lattice parameters obey the Vegard´s law in the whole range of composition. DC magnetic measurements of the Dy 3−x Y x TaO 7 system showed a Curie-Weiss paramagnetic behaviour, with antiferromagnetic interactions at T > 150 K. Below 3 K a spin glass behaviour in the 0 ≤ x ≤ 1 range of the solid solution was observed. The stoichiometric Dy 3 TaO 7 compound showed spin glass behaviour although there is no evidence of structural disorder. For some Y 3+ doped compounds (x = 0.33, 0.66 and 1.0), chemical disorder reduced the freezing temperature (T g) values with a × 1/3 dependence. Cole-Cole analysis of the AC magnetic field response showed similar phenomenological parameters for the stoichiometric (x = 0) and the Y 3+ doped compounds with spin glassiness, suggesting an analogous mechanism for these compounds. For the Dy 3−x Y x TaO 7 system, in which the spin glass behaviour seems to exhibit a critical concentration, a magnetic phase diagram is proposed.

Acta Crystallographica Section A Foundations of Crystallography, 2008

Voltage Electron Microscope). EF-PED data resulted in the basic crystallographic information of Z... more Voltage Electron Microscope). EF-PED data resulted in the basic crystallographic information of ZnS nano-crystals: P63mc, a = 3.83Å and c = 6.26Å; F-43m, a = 5.41Å, respectively. As a result of HREM analysis, their crystallite shapes were turned out to be nano-rods and nano particles, respectively and the nano-rod structure was elongated to the [001] direction. The size and shape dependency related to crystal structures of ZnS nano-crystals has been discussed.

Acta Crystallographica Section A Foundations of Crystallography, 2011

Materials Science Forum, 1996

... 172, 159 (1985). [4] AA Kaminskii, BV Mill, AV Butashin, EL Belokoneva and K. Kurbanov, Phys.... more ... 172, 159 (1985). [4] AA Kaminskii, BV Mill, AV Butashin, EL Belokoneva and K. Kurbanov, Phys. Stat. Sol.(a), 103, 575 (1987) [5] ZA Kazei, IA Kuyanov, RZ Levitin, AS Markosyan, BV Mill, SIReiman, VV Snegirevand SA Tamazyan, Sov. Phys. Solid State 31, 233 (1989). ...

Acta Crystallographica Section A Foundations of Crystallography, 2008

Microsymposia compound semiconducters such as Cu(In,Ga)Se2 as absorbers. Since the availability o... more Microsymposia compound semiconducters such as Cu(In,Ga)Se2 as absorbers. Since the availability of indium is an object of concern regarding solar cell large scale production, its replacement with Zn and Sn is beneficial in this sense. The alternative compound kesterite (Cu2ZnSnS4) has promising characteristic optical properties. The structure of kesterite consists of a ccp array of sulfur atoms, with metal atoms occupying one half of the tetrahedral voids. In literature an ordered distribution of Cu + , Zn 2+ and Sn 4+ is described. A disordered distribution may cause site defects and hence influences the electronic properties of the material. Thus the degree of cation order plays a crucial role and was therefore the focus of the presented investigations. Combined neutron and X-ray diffraction experiments revealed that the degree of cation order depends on the thermal history of the kesterite. In quenched samples Cu + and Zn 2+ are disordered, whereas in samples where a controlled cooling was applied, a certain degree of cation order is achieved. To shed more light into the formation process of kesterite, in-situ high temperature synchrotron X-ray diffraction experiments on stochiometric mixtures of binary and ternary sulfides were perfomed. Structural phase transitions and formation of new phases, resulting in kesterite formation, can be observed in detail by mapping the diffractograms and Rietveld analysis. The variation of the kesterite lattice parameter with temperature, especially during the kesterite nascency, indicates changes in the cation distribution. Completing the presentation, first promising results of kesterite thin film solar cells will be shown.

Coatings, 2021

A study on the physical and mechanical properties of beeswax (BW), candelilla wax (CW), paraffin ... more A study on the physical and mechanical properties of beeswax (BW), candelilla wax (CW), paraffin wax (PW) and blends was carried out with the aim to evaluate their usefulness as coatings for cheeses. Waxes were analyzed by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), differential scanning calorimetry (DSC), permeability, viscosity, flexural and tensile tests and scanning electron microscopy. Cheeses were coated with the waxes and stored for 5 weeks at 30 °C. Measured parameters were weight, moisture, occurrence and degree of fractures, and dimensional changes. The crystal phases identified by XRD for the three waxes allowed them to determine the length of alkanes and the nonlinear compounds in crystallizable forms in waxes. FTIR spectra showed absorption bands between 1800 and 800 cm−1 related to carbonyls in BW and CW. In DSC, the onset of melting temperature was 45.5 °C for BW, and >54 °C for CW and PW. Cheeses coated with BW did not show cracks afte...

Revista Mexicana De Fisica, 2017

Microcrystalline powders of the nonstoichiometric Ge_(0.74) V_(0.21) □_(0.05) O_(2)compound were ... more Microcrystalline powders of the nonstoichiometric Ge_(0.74) V_(0.21) □_(0.05) O_(2)compound were prepared by conventional high temperature solidstate reactions. The powders were characterized by X-ray diffraction (XRD); scanning electron microscopy (SEM); X-ray photoelectron spectroscopy (XPS); diffuse reflectance ultraviolet-visible spectroscopy (DRUV-VIS) and electron spin resonance (ESR) spectroscopy. From the analysis performed on compound, it was found that: The powders showed a rutile type crystalline structure with a rectangular prismatic crystalline habit. The XPS analysis, confirm the presence of V^(4+) and V^(5+) vanadium ions, the DRUV-VIS spectra show absorption bands in the 200-800 nm wave length interval and the ESR analysis confirms that the V^(4+) ions are within microcrystals, hosted as VO^(2+) at sites of rhombic (C_(2v)) symmetry.

Ceramics International

Abstract The mineral trioxide aggregate (MTA) is Portland type cement whose main application in d... more Abstract The mineral trioxide aggregate (MTA) is Portland type cement whose main application in dentistry is retrograde filling. The purpose of this study was to analyze hydration reactions and physicochemical properties of a new tricalcium-dicalcium silicate-based cement containing nanocrystalline hydroxyapatite (nHAp) and calcite. The new formulation was compared with Biodentine™ and MTA-Angelus™ as control samples. Hydration reactions were monitored by Raman spectroscopy, X-ray diffraction, radiopacity, pH, setting time, and compressive strength. The compressive strength reaches its higher value at 7 days following the sequence: Biodentine™ (104.8 MPa) > Cement + 5% nHAp (59 MPa) > MTAAngelus™ (27.3 MPa), in agreement with the pH values measured at 24 h: Biodentine™, Cements + nHAp or + calcite (10.6–11.6) > MTA-Angelus™ (9.7). Mean setting times was around 30 min and no significative differences (p = 0.0001) were observed. In the Biodentine™ control samples, Ca 3 SiO 5 diminishes until disappear at 28 days of hydration. On their turn, calcium silicate hydrate (CSH) increases continuously in the range of time analyzed. The present results suggest that the physicochemical properties were improved for the new cement with nanosized hydroxyapatite nanoparticles and relevant information on chemical properties is of valuable importance for testing predictive models for Biodentine™ and MTA-Angelus™.

Materials Research Express, 2021

Tricalcium silicate-based cements (TCS-BC) have reached great relevance in modern dentistry, wher... more Tricalcium silicate-based cements (TCS-BC) have reached great relevance in modern dentistry, where they are used in root-end filling or perforation repair treatments, and also for restoring deep and/or voluminous coronary carious lesions, among other applications. In some TCS-BC such as BiodentineTM, the physical and chemical properties, e.g. high compressive strength, have led to consider this cement as a dentine substitute. One of the drawbacks of BiodentineTM is its very high washout; which refers to the tendency of disintegrate at initial stage of hydration upon early contact with blood or other fluids, just at the moment after it is still as a freshly prepared paste. The present research was focused to compare properties related to workability and hardening at early stages of hydration of experimentally synthetized nano-sized tricalcium silicate (nTCS) and BiodentineTM (BIOD). Both pastes were tested for hardening at 0, 1, 2 and 3 h of hydration, using a penetration test adapte...

In this article we report the phase transitions induced by shock-compression on a sample of gypsu... more In this article we report the phase transitions induced by shock-compression on a sample of gypsum mineral. The shock experiment was performed in a light gas gun until a pressure close to 14 GPa. The experimental technique employed to analyze the shock effects on the `` recovered sample '' was the Micro-Raman Spectroscopy (MRS). The results indicate the partial dehydration of gypsum as a result of impact. The MRS analysis also suggests the presence of micro-mixtures of gypsum, bassanite and anhydrite heterogeneously distributed throughout the `` recovered sample ''.

Acta Crystallographica Section A Foundations and Advances

Catalysis Today, 2011

Nanocrystals of FAU(Y) and MFI(ZSM5) zeolites were synthesized from clear solutions at 80–95°C un... more Nanocrystals of FAU(Y) and MFI(ZSM5) zeolites were synthesized from clear solutions at 80–95°C under autogen and atmospheric pressures, respectively. The X-ray diffraction (XRD) patterns confirm the structural features reported for FAU(Y) and MFI(ZSM5). Similarly, Fourier transform infrared spectroscopy (FTIR) with KBr shows the bands arising from typical structural groups of FAU(Y) and MFI(ZSM5), i.e., 455–462cm−1 and 555–560cm−1. The mean crystallites size was measured by transmission electron microscopy (TEM) and it was determined also by Rietveld's method using Scherrer's equation; with similar results between 20 and 40nm. Also, a cubic morphology for FAU(Y) crystallites and a disk-like habit for MFI(ZSM5) were verified together with the typical dimensions of the pore system and symmetry, i.e., pore diameters were between 0.74 and 0.56nm for FAU(Y) and MFI(ZSM5). Theoretical images were calculated using HRTEM (Cerius2) program and these were compared with the experimental ones, thus matching the corresponding typical structural parameters. The textural properties were determined by N2 adsorption–desorption (BET) and typical surface areas of 658 and 495m2/g were obtained for the nanosized materials. After ion-exchanging NH4NO3 ammonia was removed by calcination (i.e., 550°C) and the total acidity was measured, i.e. 1190 and 1084μmol(Py)/g (cat) at 25°C and 84 and 34μmol(Py)/g (cat) at 400°C for FAU(Y) and MFI(ZSM5), respectively. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) in air and N2 atmospheres showed a thermal stability of these materials up to about 1000°C. The catalytic activity of FAU(Y) and MFI(ZSM5) was tested by means of the cracking of 1,3,5-triisopropylbenzene (1,3,5-TIPBz) in a CREC Riser Simulator Reactor at 350°C; the cracking of 1,3,5-TIPBz increased to about 0.6 and 1.3 times from big (108.9 and 82.8nm) to small (18 and 20.7nm) crystallites of FAU(HY) and MFI(HZSM5), respectively, while diffusivity increased to about 3 and 4.6 times, which demonstrates a correlation between the mean crystallite size of these zeolites with cracking activity from the external crystallite surface and the diffusivity of large reactive molecules, i.e., 1,3,5-TIPBz.

Acta Crystallographica Section A Foundations and Advances

Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials

Symmetry reduction in the basic structure of thortveitite-type compound FeInGe2O7–mC22 (C12/m1, N... more Symmetry reduction in the basic structure of thortveitite-type compound FeInGe2O7–mC22 (C12/m1, No. 12) promoted by the incorporation of yttrium in the formula FeIn1−xYxGe2O7gives rise to a derivative structure called thortveitite-likeAA′Ge2O7–mP44, with symmetry described by the space groupP121/m1 (No. 11) forx= 0.50, 0.75 and 0.90. The structure remains unchanged within the structural type of thortveitite whenx= 0.25. In order to establish structural models for performing a Rietveld refinement to the derivative structure, symmetry relations between space groups connecting the basic and derivative structures were used. The higher contrast to X-rays of Fe3+, In3+and Y3+as well as by the behaviour during the refinements of the isotropic thermal displacements, the values of interatomic distances and calculated bond-valence sums for each atom in the asymmetric unit, were helpful for elucidating the relocation of cations in the different available crystallographic sites generated by the...

Revista Mexicana de Ortodoncia

To characterize radiographically the periodontal ligament thickness (PLT) and pain perception (PP... more To characterize radiographically the periodontal ligament thickness (PLT) and pain perception (PP) at the beginning of orthodontic treatment by activating and applying infrared laser of 810 nm each month for three months. Methodology: It was a quasi-experimental, descriptive and longitudinal study with a nonprobabilistic sample consisting of 10 patients from the clinic of Orthodontics and Orthopedics at the Autonomous University of Sinaloa. Two hundred measurements were performed in teeth #11 and 12 (laser-treated); and 21 and 22 (non-treated control). To measure the PLT periapical radiographs were analyzed with Motic software 3V Advance. For PP determination, visual analog scale (VAS) was used. Descriptive statistical analysis was performed with SPSSv-19 (confidence interval of 95%). Results: In laser-treated teeth, PLT increased significantly 0.719 μm from the first to the second measurement and decreased 0.648 μm in the third measurement. In non-treated control teeth, PLT increased averaging 1.011 μm without significant change in the third measurement. PP in control teeth averaged 3.7 ± 3.2 on the VAS scale in the first measurement and 2.3 ± 2.3 in the second; while in the irradiated zone they averaged 2.9 ± 2.8 in the first month and 1.4 ± 1.2 in the second. Conclusion: With laser treatment, PLT is significantly reduced in comparison to the group that did not receive the treatment. At one and two months of treatment, average of PP decreased both in teeth where the laser is applied as in those without. Palabras clave: Terapia por láser de baja intensidad, ortodoncia, escala visual analógica.