We report the synthesis, crystal structure, IR, Raman and luminescence studies of four metal-organic frameworks of the following formulas: CH
CH
NH
Y
Yb
Er
(HCOO)
(x = 1, y = 0; x = 0.2, y = 0.8; x = ...0.02, y = 0.07) and CH
CH
NH
Y
Eu
(HCOO)
. All the compounds are isostructural and crystallize in a polar and non-centrosymmetric monoclinic system (P2
space group). They have been characterized by single crystal and powder X-ray diffraction methods as well as by vibrational spectroscopy (IR and Raman). The assignment of the external and internal modes has been discussed and presented. Furthermore, the optical properties of the Er
and Eu
ions have been assessed using diffuse absorption, excitation and emission spectra. The site symmetry of the Eu
ions has been analyzed using the emission spectrum and the luminescence decay of the red emission.
We report on the experimental observation of confinement-induced new phase appearance in acetylsalicylic acid (ASA)–porous glass (PG) composites. In this study, ASA was embedded in PG host matrices ...of various pore widths (15–200 nm). The Raman spectra and positron annihilation lifetime measurements exhibit the existence of ASA nanocrystals in the PG matrix. The DSC data revealed that the melting temperature
T
M
and excess specific heat decrease with decreasing the size of embedded ASA nanocrystals. The close inspection of the
T
M
dependence versus diameter of filled pores has shown that the ASA crystallizes in polymorph II in confined matrix. Moreover, it was demonstrated that the ASA spatial confinement results in the appearance of new polymorphic phase in the investigated composites—highly likely form ASA III. Both the changes in ASA melting temperatures due to the volume constraints and the decrease in specific heat may be crucial for the bioavailability of the drug.
Extensive temperature-dependent phonon studies and low-temperature magnetic measurements of CoCr2−xFexO4 (for x=0.5, 1 and 2) and Co0.9Ni0.1Cr2O4 polycrystalline powders are presented. The main aim ...of these studies was to obtain information on phonon and structural properties of these compounds as well as strength of spin–phonon coupling in the magnetically ordered phases. IR and Raman spectra show that doping of CoCr2O4 with Fe(III) ions leads to broadening of bands and appearance of new bands due to the formation of inverted spinel structure. In contrast to this behavior, doping with 10mol% of Ni(II) ions leads to weak increase of band width only. Magnetization measured as a function of temperature and external magnetic field showed that magnetic properties of Co0.9Ni0.1Cr2O4 sample are similar to those reported for pure CoCr2O4, i.e., partial substitution of Ni(II) for Co(II) leads to slight shift of the ferrimagnetic phase transition at TC and spiral spin order transition at TS towards lower values. The change of crystallization preference induced by incorporation of increasing concentration of Fe(III) ions in the spinel lattice causes significant increase of TC and decrease of TS. The latter transition disappears completely for higher concentrations of Fe(III). The performed temperature-dependent IR studies revealed interesting anomalous behavior of phonons below TC for CoCr1.5Fe0.5O4 and Co0.9Ni0.1Cr2O4, which was attributed to spin–phonon coupling.
Visualization of normal spinel-type AB2O4 structure, where blue octahedrons denote BO6 and red tetrahedrons AO4 units as well as IR and Raman spectra of Co0.9Ni0.1Cr2O4 powder. Display omitted
•TC (TS) increases (decreases) with increasing Fe(III) concentration.•Ni(II) ions doping up to 10mol% does not change remarkably TC and TS.•Doping with Fe(III) ions causes increase of spinel inversion parameter.•Spin–phonon interactions in Co0.9Ni0.1Cr2O4 and CoCr1.5Fe0.5O4 were evidenced.
Pre-Eruptive Intracoronal Resorption (PEIR) is a rare yet significant phenomenon in which an abnormal, well-circumscribed, radiolucent area develops in the tooth prior to eruption. This case report ...outlines the treatment of a 12 year old Hispanic female who was referred for endodontic evaluation of tooth #31 and subsequently diagnosed with PEIR.
The patient’s chief complaint was recorded as “spontaneous pain” in the lower right quadrant of her jaw. Clinical examination revealed a partially erupted tooth #31 with no visible decay. Radiographic examination, including a cone beam computed tomography scan, led to the detection of a radiolucent area surrounding the pulp chamber on the mesial aspect of tooth #31. Radiographically, the enamel appeared intact with no signs of perforation. Based on the clinical and radiographic evaluation, tooth #31 was determined to have PEIR, with the pulpal and periapical diagnosis of “Symptomatic Irreversible Pulpitis” and “Normal Apical Tissue,” respectively.
The Orthodontic consultation obtained for this patient recommended that tooth #31 be maintained at least until tooth #32 appeared in the oral cavity and could be used as a replacement. Therefore, a treatment plan involving vital pulp therapy and gingivectomy was selected. During the procedure, granulation tissue was excavated and sent for histological evaluation, which concluded the presence of “granulation tissue with acute and chronic inflammation”. No caries were detected.
Following the procedure, the tooth was found to be asymptomatic with continued root development. A positive response to Electric Pulp Test was achieved after 3.5 years of follow up.
The compounds Bi2MoO6 (m = 1), Bi2WO6 (m = 1), Bi3NbTiO9 (m = 2), Bi4Ti3O12 (m = 3) and CaBi4Ti4O15 (m = 4) (Aurivillius phases with the general formula Аm–1Bi2BmO3m+3) have been synthesized by solid ...state reaction method. Using the high-temperature X-ray diffraction, the phase transition and melting temperatures have been determined for these compounds and their thermal expansion coefficients have been calculated. It has been established that composition and structure of Aurivillius phases have significant influence on the Curie temperature. We have also measured room temperature Raman and infrared spectra, and all observed bands have been assigned to respective motions of atoms in the unit cell. The spectra of the synthesized Auriviliius phases are in good agreement with reported in literature results of the lattice dynamics calculations. We also compare and discuss how the spectra change with increasing thickness of the perovskite-like layer.
Temperature dependence of unit-cell parameters for Bi4Ti3O12. Display omitted
•The compounds Bi2MoO6, Bi2WO6, Bi3NbTiO9, Bi4Ti3O12and CaBi4Ti4O15have been synthesized by solid state reactions.•The phase transition and melting temperatures have been determined using the high-temperature X-ray diffraction.•It has been established that composition and structure of Aurivillius phases have influence on the Curie temperature.•We have measured room temperature Raman and infrared spectra.
•The IR and Raman spectra of studied compounds were recorded.•The IR and Raman wavenumbers were calculated from the optimized geometry of molecule.•IR, Raman and DFT methods confirm the existence of ...an intramolecular HBs.•The vibrational characteristics of OH compounds were analyzed.
Molecular structures of quercitin and quercitin sulfonic acid have been determined by DFT quantum chemical calculations. FT-IR and FT-Raman spectra have been measured in the solid state and discussed in terms of B3LYP/6-311G(2d,2p) approach. The role of the hydrogen bonds in stabilization of their structures has been analyzed. The IR spectra were measured in the temperature range 5–300K and the observed effects were used in the discussion of the hydrogen bond behavior.
Accident reconstructions and numerical simulations are used to evaluate and improve protective systems. Virtual testing and numerical methods can assist in the improvement safety of vulnerable road ...users. This work presents the tremendous potential of using computer-aided engineering by describing the development of a windshield numerical model and its damage and fracture validation. The motivation behind this study is the possibility of using such a model in the reconstruction of road accidents involving vulnerable road users. The main goal is the development and validation of a finite element model of an automobile windshield in order to use it in further studies regarding the reconstruction of road traffic accidents. In order to validate it according to experimental studies available in the literature, the 4.8
kg standard adult headform from the European Enhanced Vehicle Safety Committee is also developed and validated. A total of eight impacts at six different locations and carried at two different impact velocities (6
m/s and 11.1
m/s) were simulated. The validation of the windshield model, and consequently the damage model employed to simulate glass cracking initiation and propagation, were accomplished by comparing the acceleration at the headform's centre of gravity and the windshield's fracture pattern against experimental data.
IR and Raman spectra of Ca2MgSi2O7, Ca2ZnSi2O7 and Sr2MgSi2O7 oriented single crystals and powders have been measured. The temperature dependence of phonons has been established in the 4–650K range. ...Discussion of the results has been performed on the basis of factor group approach for the tetragonal P4̄21m (D2d3) space group with Z=2. The assignment of the bands observed to the internal and external modes has been made on their polarization behaviour, phonon energy calculations and literature data. The evidences of the LO–TO splitting and commensurate (C) to incommensurate (IC) as well as incommensurate (IC) to normal (N) phase transitions have been found. As a representative example, the results obtained for the spontaneous Raman scattering have also been used in the discussion of the stimulated Raman spectra of Ca2ZnSi2O7.
Raman and IR spectra of Ca2MgSi2O7, Ca2ZnSi2O7, Sr2MgSi2O7 have been measured. The temperature dependence of phonons has been established in the 4–650K range. The evidences of the LO-TO splitting and commensurate (C) to incommensurate (IC) as well as incommensurate (IC) to normal (N) phase transitions have been found. Display omitted
► Polarized IR and Raman spectra of pyrosilicates single crystals have been studied. ► Temperature dependence of the phonon bands and LO–TO splitting have been analysed. ► Commensurate to incommensurate and to normal phase have been evidenced in the spectra. ► Phonon calculations have been used in assignment of the normal modes. ► Stimulated Raman spectra of Ca2ZnSi2O7 crystal have been measured and analysed.
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