Endothermic Events Research Articles

Revisiting the methodology for asphaltenes precipitation

The world increase in energy demand has directed the petroleum industry to exploit unconventional oil reserves such as the Brazilian Pre-Salt reservoirs. Production conditions verified in those reservoirs enhance the occurrence of asphaltene precipitation as well as the correlated problems. Asphaltenes are well known as a solubility class. Such classification makes tough the determination of consistent chemical properties for these compounds. In this scenario, this study aims to analyze the influence of the standard precipitation methodologies upon the asphaltene characteristics. Three oils were selected, which are hereinafter called BR1, BR2, and BR3. Oil BR1 was produced from a Post-Salt reservoir while oils BR2 and BR3 are originated from a Post-Salt one. The asphaltenes were extracted through precipitation by n-heptane according to the ASTM 2007, ASTM 6560 (IP-143), the so-called ASTM 6560 SOHXLET, and the NUESC methodology. Asphaltene fractions were characterized regarding their chemical composition (FTIR) and thermal stability (DSC). The results showed that endothermic events typically registered for compounds which are strange to the commonly accepted asphaltene composition were verified. Also, the degradation temperature varied according to the precipitation method. In turn, the FTIR spectra detected a peak which is usually associated with naphthenic acids (3500 cm−1). Therefore, the FTIR analysis confirmed what was indicated by the thermograms. In summary, it was concluded that the asphaltene fractions that were extracted through the commonly used ASTM 2007 methodology from the Pre-Salt oils were a precipitated complex composed by asphaltenes and wax of naphthenic acids. Thus, the present work results are suggested as a starting point for the analyses of asphaltene properties and their implications on the crude oil behavior.

Thermal profile of 4,4′-dinitrocarbanilide determined by thermogravimetry–differential scanning calorimetry–mass spectrometry (TG–DSC–MS) and pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS)

Nicarbazin is an anticoccidial used in poultry production. Its residue of concern left in chicken meat is 4,4′-dinitrocarbanilide (DNC) whose content can be reduced through meat thermal processing. Thermal analysis techniques can be considered to elucidate how DNC degradation proceeds. This study aimed to investigate the thermal behavior of DNC using TG–DSC–MS and Py–GC–MS. TG–DSC–MS data showed that DNC decomposition occurs in a single step (252–280 °C) as an endothermic event (ΔH of 670 J g−1). Fragments detected at m/z 43, 44 and 65 indicated the release of isocyanic acid, carbon dioxide and 4-nitroaniline as breakdown products. In addition, Py–GC–MS analysis confirmed that DNC is thermally degraded above 250 °C generating 4-nitrophenyl isocyanate and 4-nitroaniline as the major pyrolysis products. Findings obtained from thermal analysis herein are useful to better comprehend the DNC disappearance after submitting chicken meat to heat processing.

Natural deep eutectic solvents for sample preparation prior to elemental analysis by plasma-based techniques

Natural deep eutectic solvents (NADES) based on xylitol, citric acid, and malic acid were synthesized and were then characterized using infrared spectroscopy, thermogravimetry (TG), differential scanning calorimetry (DSC), also density and viscosity were measurements. The deep eutectic solvents were used as solvent in ultrasound-assisted extraction (DES-UAE) of plant samples prior to elemental analysis. Inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-optical emission spectrometry (ICP OES) were employed for the determination of As, Ca, Cd, Cu, Fe, K, Mg, Mn, Na, P, and Zn in the extracts. The infrared analyses of the NADES revealed bands characteristic of the initial reagents, with the presence of hydrogen bonds, which confirmed the formation of a NADES. The thermal analyses showed decomposition temperatures of around 170 °C and endothermic events related to degradation of the NADES. The viscosity and density parameters were found to be related to the presence of hydrogen bonds. The extraction recoveries ranged from 80% to 120%, with some analytes presenting poor recoveries. There were no significant differences between the NADES, in terms of the concentrations of the analytes found in the extracts. However, there were differences between the analyte concentrations obtained using the NADES extraction method and the concentrations obtained using microwave-assisted acid digestion (MW-AD), possibly due to the different types of interactions between the solvents and the analytes. Plant tissues are complex matrices containing substantial amounts of silica, so some elements may be tightly bound and consequently difficult to release. The results indicated that UAE using NADES is a promising technique for the elemental extraction of plant samples.

Characterization and Kinetic Studies of the Thermal Degradation of Mebendazole Polymorphs A and C

Mebendazole is an anthelmintic drug of low solubility, which exhibits three polymorphic forms (A, B, and C) with different thermodynamic stability (A > C > B). Form C is the most appropriate for pharmaceutical development due to its adequate bioavailability and lower toxicity. This form is stable between room temperature ± 180 °C. The aim of this work was to characterize and study the thermal degradation kinetics of Mebendazole polymorphs A and C by isothermal and non-isothermal (Ozawa method) thermogravimetric methods. Thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), Fourier-transform infrared spectroscopy (FTIR), and elementary analysis (EA) were used to identify Mebendazole polymorphs A and C. Isothermal and non-isothermal thermogravimetric methods were used to study the thermal degradation kinetics of Mebendazole polymorphs. The results showed that form C converts to the polymorphic form A after heating at 200 °C, exhibiting both exothermic and endothermic events before the first mass loss. Subsequent to this transformation, CO2 was released and the formation of a solid product occurred, which was characterized by EA and FTIR. These results suggested the presence of a Mebendazole impurity. The degradation kinetics studies of polymorphs A and C obtained by both methods indicated activation energy (Ea) values greater for polymorph C. In fact, part of the energy provided to the polymorph C was used for the transformation to polymorph A, which explains its greater thermal stability. This indicates that polymorph C is very stable under ambient conditions, but at high temperatures (above 180 °C) the stability of polymorph A predominates.

Crude Fat Analysis from Some Meat Products by Differential Scanning Calorimetry

This paper presents the thermal analysis of crude fat from salami samples which were reformulated by their lipid profile differentiation using the differential scanning calorimetry (DSC) method. Salami samples were manufactured by partial substitution of the back fat with vegetable oils and walnuts. Thermal curves profile of the crude fat was correlated with the lipids profile determined by gas-chromatography/mass spectrometry (GC/MS) method. The addition of lipids from vegetable sources determined a decrease of the ratio of saturated/unsaturated fatty acids from 0.639 (control) to 0.283 (salami with oil) and 0.218 (salami with oil and walnuts). The thermal curves obtained were different between the samples. For each sample, the crystallization profile showed an exothermic event for the reformulated samples and two events for the control sample, for different onset temperatures: 15.410C (control sample), 1.730C (salami with oil) and -5.120C (salami with oil and walnuts). The same profile was observed for two different heat flow rates: 100C/min and 200C/min, respectively. The melting profile showed three endothermic events for the reformulated samples and two events for the control sample. The samples were different regarding the onset temperature of the last endothermic event which was 11.820C for the control sample, 18.730C for salami with oil and 15.150C for salami with oil and walnuts, respectively, for both heat flow rates. DSC showed the physical properties and thermal behaviour for each chemical composition of the fat. DSC is a promising and rapid method for assessing the thermal fingerprint of a meat product by analyzing the crude fat.

Rheological and thermal study of structured oils: avocado (Persea americana) and sacha inchi (Plukenetia volubilis L.) systems.

Rheological and thermal characterization was performed in emulsions formulated from avocado oil and sacha inchi oil structured with soy lecithin, glyceryl monostearate and shortening (palm oil). For oleogel formulations, a completely randomized factorial design was considered to study the effect of the type of emulsifier and the proportions of avocado and sacha inchi oils. The rheological results indicated pseudoplastic behavior with semisolid characteristics. Additionally, the phase change studies showed two endothermic events corresponding to melting points from - 20.15 to - 18.94°C and from 40.25 to 61.04°C. The formulation with a ratio of avocado oil to sacha inchi oil of 80/20 and prepared using glyceryl monostearate as an emulsifier was evaluated as the best treatment and had an increased consistency coefficient and an increased loss tangent (δ < 0.5).

Phase-change behavior of hot-pressed methylammonium lead bromide hybrid perovskites

The investigation of hot-pressed methylammonium lead bromide (MAPbBr3) is reported. The as-prepared materials consisted of microcrystallites (30–500 μm size) with a non-centrosymmetric pseudo-cubic tetragonal crystalline structure (P4 mm space group). The thermal analysis under air showed a thermal stability of MAPbBr3 perovskite till T = 250 °C and a broad endothermic event at T = 371 °C (melting point of solid PbBr2). Under increasing pressure at room temperature, the MA–Pb–Br system retained the pseudo-cubic tetragonal structure, the optical adsorption spectra displayed a strong absorption edge between 570 and 572 nm, and the Tauc plots revealed a direct semiconducting behavior with band energy gaps around 2.20(± 0.01) eV. The steady-state emission (PL) photoluminescence spectra (excitation wavelengths λexc = 380 nm) showed an emission band at ~ 574 nm. With increase in the temperature (under constant pressure and treatment time), the MA–Pb–Br system turned into the higher cubic symmetry (space group $$Pm\, \bar{3} m$$ ), the absorption edges shifted to 571–575 nm, and at T = 120 °C, the absorbance profile begins to increase at higher wavelengths (> 600 nm). By increasing the pressure at constant temperature, the perovskite adopted the cubic structure and a slight decrease in the energy band gap (2.17 eV for T = 150 °C and P = 15 MPa) was recorded. With increase in the hot-pressing time at T = 150 °C and P = 20 MPa, the optical absorption edges remained at ~ 575 nm; however, the decrease in the absorbance can indicate a degradation of the materials. The changes in the emission mechanism(s) of the hot-pressed materials can be related to the observed change in the crystalline structure and morphology.

Phase Diagrams of Polymer-Dispersed Liquid Crystal Systems of Itraconazole/Component Immiscibility Induced by Molecular Anisotropy

Liquid crystalline (LC) materials and their nonmedical applications have been known for decades, especially in the production of displays; however, the pharmaceutical implications of the LC state are inadequately appreciated, and the misunderstanding of experimental data is leading to possible errors, especially in relation to the physical stability of medicines. The aim of this work was to study LC phases of itraconazole (ITZ), an azole antifungal active molecule, and for the first time, to generate full thermodynamic phase diagrams for ITZ/polymer systems, taking into account isotropic and anisotropic phases that this drug can form. It was found that supercooled ITZ does not form an amorphous but a vitrified smectic (vSm) phase with a glass transition temperature of 59.35 °C (determined using a 10 °C/min heating rate), as is evident from X-ray diffraction and thermomicroscopic (PLM) experiments. Two endothermic LC events with the onset temperature values for a smectic to nematic transition of 73.2 ± 0.4 °C and a nematic to isotropic transformation at 90.4 ± 0.35 °C and enthalpies of transition of 416 ± 34 J/mol and 842 ± 10 J/mol, respectively, were recorded. For the binary supercooled mixtures, PLM and differential scanning calorimetry showed a phase separation with birefringent vSm persistent over a wide polymer range, as noticed especially for the hypromellose acetate succinate (HAS) systems. Both, smectic and nematic, phases were detected for the supercooled ITZ/HAS and ITZ/methacrylic acid-ethyl acrylate copolymer (EUD) mixtures, while geometric restrictions inhibited the smectic formation in the ITZ/poly(acrylic acid) (CAR) systems. The Flory-Huggins lattice theory coupled with the Maier-Saupe-McMillan approach to model anisotropic ordering of molecules was successfully utilized to create phase diagrams for all ITZ/polymer mixtures. It was concluded that in a supercooled ITR/polymer mix, if ITZ is present in a LC phase, immiscibility as a result of molecule anisotropy is afforded. This study shows that the LC nature of ITZ cannot be disregarded when designing stable formulations containing this molecule.

MODIFICATION OF EXPANDED PERLITE WITH ORTHOPHENANTHROLINE FOR FORMATION OF ACTIVE SITES FOR ACID DYES: PREPARATION AND CHARACTERIZATION

The expanded perlite (aluminosilicate naturally acid) has been modified with orthophenanthroline (Lewis base). The material was characterized by TG/DTA, XRD and IR. The thermogravimetric curve of the modified expanded perlite presented a lower thermal stability due to the orthophenanthroline and showed 13,6% of mass loss total. However, pure expanded perlite presented only 2,3% of the mass loss. The DTA curve showed endothermic event characteristic of the presence of orthophenanthroline. For XRD analysis is visualized, the presence of reflections in the diffractogram relating to the modified material of orthophenanthroline peaks of crystallinity since no modification perlite is an amorphous material. The band regarding absorption vibration of Si-O group appears at lower wavenumbers than in the unmodified material. So there was an interaction between the OH groups of silanols of perlite groups with unshared electron pairs of nitrogen atoms and C=C bonds (also rich in electrons) in the chemical structure of orthophenanthroline as a result of a hydrogen bond between these groups. thus perlite was modified through the interaction of its acid sites (Si-OH) with Lewis basic sites of orthophenanthroline.

Thermal-alteration interphase transformations in natural and synthetic arsenic sulfide polymorphs

Abstract Thermal-alteration interphase transformations in natural (realgar α-As4S4 of two mineral origins) and synthetic (commercial powdered high-temperature β-As4S4 modification synthesized from elemental constituents and subjected to high-energy mechanical ball milling) arsenic monosulfide polymorphs are studied exploring temperature-modulated DSC TOPEM® method. Specific heat capacity and non-reversing heat flow variations in realgar α-As4S4 demonstrate two endothermic events, these being ascribed to interphase α → β transformation at ∼(540–550) K, and melting of this newly-formed high-temperature β-As4S4 phase at 581–582 K. This polymorph originated from thermal alteration of mineral realgar possesses congruent melting in contrast to synthetic β-As4S4 polymorph, which shows non-equilibrium melting due to accompanied generation of compositionally-authentic amorphous phase. Calorimetric studies on synthetic β-As4S4 in powdered coarse-grained and milled states demonstrate complicated non-equilibrium melting in principally different crystalline-amorphous environments along with crystal-to-glass transformation. Structural-chemical heterogeneity of β-As4S4 crystallites results in incongruent double-peak melting through two endothermic events at ∼578 K and ∼588 K. The amorphous phase formed under high-energy milling of synthetic β-As4S4 possesses a dual nature due to stabilization of As-rich glassy substances with low- and high-temperature glass transition mid-points. This process in the powdered synthetic β-As4S4, identified as re-amorphization of initial amorphous phase and direct vitrification from β-As4S4 crystallites, was parameterized as compared to calorimetric thermal-alteration events in orpiment As2S3 mineral.

Mangosteen pericarp extract embedded in electrospun PVP nanofiber mats: physicochemical properties and release mechanism of α-mangostin.

Backgroundα-Mangostin is a major active compound of mangosteen (Garcinia mangostana L.) pericarp extract (MPE) that has potent antioxidant activity. Unfortunately, its poor aqueous solubility limits its therapeutic application. Purpose: This paper reports a promising approach to improve the clinical use of this substance through electrospinning technique.MethodsPolyvinylpyrrolidone (PVP) was explored as a hydrophilic matrix to carry α-mangostin in MPE. Physicochemical properties of MPE:PVP nanofibers with various extract-to-polymer ratios were studied, including morphology, size, crystallinity, chemical interaction, and thermal behavior. Antioxidant activity and the release of α-mangostin, as the chemical marker of MPE, from the resulting fibers were investigated.ResultsIt was obtained that the MPE:PVP nanofiber mats were flat, bead-free, and in a size range of 387–586 nm. Peak shifts in Fourier-transform infrared spectra of PVP in the presence of MPE suggested hydrogen bond formation between MPE and PVP. The differential scanning calorimetric study revealed a noticeable endothermic event at 119°C in MPE:PVP nanofibers, indicating vaporization of moisture residue. This confirmed hygroscopic property of PVP. The absence of crystalline peaks of MPE at 2θ of 5.99°, 11.62°, and 13.01° in the X-ray diffraction patterns of electrospun MPE:PVP nanofibers showed amorphization of MPE by PVP after being electrospun. The radical scavenging activity of MPE:PVP nanofibers exhibited lower IC50 value (55–67 µg/mL) in comparison with pure MPE (69 µg/mL). The PVP:MPE nanofibers tremendously increased the antioxidant activity of α-mangostin as well as its release rate. Applying high voltage in electrospinning process did not destroy the chemical structure of α-mangostin as indicated by retained in vitro antioxidant activity. The release rate of α-mangostin significantly increased from 35% to over 90% in 60 minutes. The release of α-mangostin from MPE:PVP nanofibers was dependent on α-mangostin concentration and particle size, as confirmed by the first-order kinetic model as well as the Hixson–Crowell kinetic model.ConclusionWe successfully synthesized MPE:PVP nanofiber mats with enhanced antioxidant activity and release rate, which can potentially improve the therapeutic effects offered by MPE.

Characterization of scale deposits formed in sanitary hot water pipelines in the northern tourist zone of Agadir city

The formation of scale on surfaces in contact with water is due to many reasons as the hardness of water and its temperature. Therefore, this phenomenon of scale in water pipelines is a common and inevitable problem in the regions that exploit or use groundwater with high rigidity. The circuits fed by hot water are easily reached by hard water scaling. The deposition of encrusting curst at the level of walls in touch with water is due to many technical, economic and environmental problems. It causes a reduction in water flow and a decrease in the efficiency of heating systems.In this study, we are particularly interested in studying the phenomenon of hard water scaling caused by sanitary hot water in a tourist unit situated in the north of the seaside in the city of Agadir. First, we have evaluated the physico-chemical quality of water in use in this tourist unit. Secondly, we conducted a qualitative and quantitative analysis of the scale found in the circuits that transport sanitary hot water. Several analytical techniques were used to reach this goal namely: X-ray fluorescence (XRF) which shows that 85.50% of scale is represented by Calcium Carbonate. Whereas infrared spectrometry (IR) demonstrates the existence of the Carbonate anion CO32-. In addition, due to thermogravimetric analysis (TGA) and differential thermal analysis (DTA) we found that the endothermic event shows the decomposition of Calcium Carbonate of CaO and CO2 in the temperature range of 660 C° to 820 C°. For scanning electron microscopy (SEM), it indicates that the scale takes the form of needle-like aragonite crystals. At last, the X-ray diffraction (XRD) shows that the scale is composed essentially of Calcium Carbonate of the type aragonite.The results of the different techniques of characterisation are in concordance in the scaling of the circuits of sanitary hot water in the tourist unit under study.

Proton Conductivity and Thermal Properties of Ba(H2PO4)2

We have grown single crystals of barium dihydrogen phosphate and studied its thermal transformations during heating to 500°C and its electrotransport properties. Ba(H2PO4)2 (Pccn) has been shown to undergo no phase transitions up to its dehydration temperature. The thermal decomposition of Ba(H2PO4)2, accompanied by dehydration, involves two steps, with maximum rates at ~265 and 370°C, and results in the formation of barium dihydrogen pyrophosphate and barium metaphosphate, respectively. The total enthalpy of the endothermic dehydration events is–244.6 J/g. Using impedance spectroscopy, we have studied in detail the proton conductivity of polycrystalline and single-crystal Ba(H2PO4)2 samples in a controlled atmosphere. Adsorbed water has been shown to have a significant effect on the proton conductivity of Ba(H2PO4)2 up to 130°C. The proton conductivity of the Ba(H2PO4)2 single crystals has been shown to be anisotropic. The conductivity anisotropy correlates with specific structural features of the salt. Higher conductivity values, 3 × 10–9 to 2 × 10–7 S/cm in the range 60–160°C, have been observed in the [100] crystallographic direction, exceeding the conductivity along [010] by an order of magnitude. The activation energy for proton conduction is 0.80 eV.

Physical–chemical characterization studies of ketoprofen for orodispersible tablets

The development of orodispersible tablets containing ketoprofen (KTP) offers versatility in administration to patients with swallowing difficulties. The rational development of a medication requires characterization studies for the solid state of the active ingredient and compatibility with excipients to thus ensure a high-quality, safe and effective pharmaceutical form. Therefore, compatibility studies were performed by differential scanning calorimetry (DSC) and thermogravimetry/derivative thermogravimetry (TG/DTG), spectroscopy techniques (DRIFT, DRX, Raman), and morphological analysis by scanning electron microscopy in order to obtain thermal characterization of the drug. The DSC curve demonstrated an endothermic, symmetrical and evident fusion event (Tpeak = 96.37 °C, ΔH = −120.92 J g−1) and the TG/DTG curve showed mass loss of Δm = 92.45% relative decomposition. For stability analysis, the non-isothermal kinetic study was carried out. The granulate KTP showed higher Ea = 77.30 ± 0.25 kJ mol−1, hence being more stable than pure KTP (Ea = 54.69 ± 1.53 kJ mol−1). Regarding the compatibility study, a displacement of the drug’s melting point to lower temperatures was observed. However, a more significant interaction was evident with magnesium stearate. Further studies were performed using spectroscopic techniques of DRIFT, Raman, X-ray diffraction and by scanning electron microscopy, which demonstrated that there was no change in physicochemical properties of pure KTP. Therefore, through this study it is possible to produce orodispersible tablets by compression and freeze-drying methods containing ketoprofen.

Structural Insight into Chitosan Supports Functionalized with Nanoparticles

The incorporation of suspensions of nanoparticles functionalized with gallic acid (GA) was used as a strategy to obtain nanocomposite active films with different both chitosan : tripolyphosphate (CH : TPP) and nanoparticles:chitosan (N : CH) ratios. The thermal analysis carried out by modulated differential scanning calorimetry (MDSC) allowed observing the shift of an endothermic event towards higher temperatures with a greater N : CH ratio. Analyzing ATR‐FTIR spectra through principal component analysis (PCA) can be inferred that the incorporation of the nanoparticles produced a discrimination of the samples into clusters when the region 1400–1700 cm−1 was considered. The decrease in crystalline size with the inclusion of nanoparticles (NA and NB) proved the existence of interactions among CH, TPP, and GA, resulting in a more amorphous structure. The positron annihilation lifetime spectroscopy (PALS) technique was adequate to correlate the glass transition temperatures (Tg) obtained by using the MDSC technique with parameters τ2 and I2 ascribed to the annihilation of positrons in the interface. The cross section of nanocomposites obtained by scanning electron microscopy (SEM) clearly showed a homogeneous distribution of the nanoparticles without aggregation, suggesting their compatibility with the CH matrix. By virtue of the obtained results, the nanocomposites with the greatest nanoparticle proportion and the highest TPP concentration attained significant modifications in relation to CH matrices because of the crosslinking of the biopolymer with GA and TPP.

Microencapsulation by lyophilization of carotenoids produced by Phaffia rhodozyma with soy protein as the encapsulating agent

Abstract Carotenoids are pigments that can be applied to food but they are unstable towards certain food intrinsic conditions, as well as processing ones. Microencapsulation is an alternative to increasing their stability. This study aimed to produce carotenoids by Phaffia rhodozyma crops and promote their microencapsulation by lyophilization with soy protein as the wall material, in different proportions. High process yield of 96% and encapsulation efficiency of around 65% were observed at the ratios under study. Well-defined and separate micrometer-scale particles with different shapes and sizes were formed and the protection of the compounds of interest was confirmed by differential scanning calorimetry which showed that the endothermic event – typical of the free extract after encapsulation – did not occur.

Thermal property study of keratin from industrial residue by extraction, processing and application

The Brazilian productive chain of poultry meat is one of the most important of the agro-industrial complex in the country. However, this production generates large amounts of residue, causing environmental impacts. After its processing, poultry industry waste can be considered a great potential by-product and a sustainable alternative for animal food and to applications in the cosmetics industry. It can be estimated that the number of produced feathers in Brazil reaches up to around 670 thousand tons annually. This study aimed to obtain keratin from chicken feathers and their characterization by thermal analysis, as well as adding the product into shampoo formulation as well its application on hair samples and compare it to commercial shampoo. Thermal analytical study was performed for all samples by TG/DTG, DTA and DSC. Rheology and FTIR analyses of extracted keratin samples and commercial keratin solution were also performed. Results showed that the extraction process used was efficient, once the TG curves of the samples presented one decomposition stage referring to proteins and DSC curves showed endothermic events suggesting protein denaturation. The shampoo formulations with keratin applied to hair samples showed satisfactory results, such as increased brightness, smoothness and reduced frizz.

Effect of conventional and laser sintering on the (micro)structural and dielectric properties of Bi2/3Cu3Ti4O12 synthesized through a polymeric precursor route

This work explores a polymeric synthesis route for Bi2/3Cu3Ti4O12 (BCTO) and analyses the effect of both conventional and laser sintering on the (micro)structural and dielectric properties of the processed ceramics. The physico-chemical reactions taking place during the heat treatment of BCTO powders were investigated through differential thermal analysis (DTA), in which an endothermic event (at about 990 °C) was identified and ascribed to a liquid phase formation. Dense ceramics were achieved, with the observation of a slight increase in average grain size (AGS) from 1.1 μm to 2.1 μm while raising the sintering temperature from 960 °C to 1000 °C. The laser-sintered ceramics presented an AGS of 1.0 μm, which is comparable to that found for the ceramic conventionally sintered at 960 °C. It is shown, using energy dispersive analysis of X-rays (EDAX), that a Cu-rich phase segregates at the grain boundaries in BCTO ceramics, irrespective of the considered sintering technique. The dielectric response from such ceramics displays a remarkable dependence on the processing approach. We show that the grains of BCTO laser-sintered ceramics can be highly resistive, with room temperature (RT) resistivity of 2 MΩ cm and activation energy of 0.3 eV. In this case, a predominant bulk dielectric response (ε′ < 102) was verified at RT. When conventional sintering was applied, a semiconducting phase, with activation energy of 0.06 eV, develops into the grains (RT resistivity of 140 Ω cm) in agreement with the results typically reported in the literature. This latter electrical microstructure, which is consistent with the well-known internal barrier layer capacitance (IBLC) mechanism, results in the manifestation of interfacial polarization (grain-grain and material-electrode interfaces) effects at RT and, consequently, in a high effective permittivity (ε′ > 103).

Thermal properties of compacted pharmaceutical excipients

Thermal properties of powders are critical material attributes that control temperature rise during tableting and roll compaction. In this study, various analytical methods were used to measure the thermal properties of widely used pharmaceutical excipients including microcrystalline cellulose (MCC) of three different grades (Avicel PH 101; Avicel PH 102 and Avicel DG), lactose and mannitol. The effect of relative density on the measured thermal properties was investigated by compressing the powders into specimen of different relative densities. Differential thermal analysis (DTA) was employed to explore endothermic or exothermic events in the temperature range endured during typical pharmaceutical manufacturing processes, such as tabletting and roll compaction. Thermogravimetric analysis (TGA) was performed to analyse the water/solvent content, either in the form as solvates or as loosely bound molecules on the particle surface. Thermal conductivity analysis (TCA) was conducted to measure thermal conductivity and volumetric heat capacity. It is shown that, for the MCC powders, almost no changes in morphology or structural changes were observed during heating to temperatures up to 200°C. An increase in relative density or temperature leads to a high thermal conductivity and the volumetric heat capacity. Among all MCC powders considered, Avicel DG showed the highest increase in thermal conductivity and the volumetric heat capacity, but this heat capacity was not sensitive to the measurement temperature. For lactose and mannitol, some endothermic events occurred during heating. The thermal conductivity increased with the increase in temperature and relative density. A model was also developed to describe the variation of the thermal conductivity and the volumetric heat capacity with the relative density and the temperature. It was shown that the empirical model can well predict the dependency of the thermal conductivity and the volumetric heat capacity on the relative density and the temperature.

D-limonene exhibits superior antihyperalgesic effects in a β-cyclodextrin-complexed form in chronic musculoskeletal pain reducing Fos protein expression on spinal cord in mice

Chronic musculoskeletal pain is one of the main symptoms found in Fibromyalgia with unclear etiology and limited pharmacological treatment. The aim of this study was to complex LIM in β-cyclodextrin (LIM-βCD) and then evaluate its antihyperalgesic effect in an animal model of chronic musculoskeletal pain. Differential scanning calorimetry and scanning electron microscopy was used for the characterization of the inclusion complex. Male Swiss mice were used for experimental procedures where mechanical hyperalgesia, thermal hyperalgesia, muscular strength, Fos immunofluorescence was studied after induction of hyperalgesia. Mechanism of action was also investigated through tail flick test and capsaicin-induced nociception. Endothermic events and morphological changes showed that the slurry complex method was the best method for the complexation. After induction of hyperalgesia, the oral administration of LIM-βCD (50mg/kg) significantly increased the paw withdrawal threshold compared to uncomplexed limonene. Fos immunofluorescence showed that both compounds significantly decreased the number of Fos-positive cells in the dorsal horn. In nociceptive tests, FLU was able to reverse the antinociceptive effect of LIM-βCD. After intraplantar administration of capsaicin, LIM was able to significantly decrease time to lick. LIM-βCD has antihyperalgesic action superior to its uncomplexed form, with possible action in the dorsal horn of the spinal cord. These results suggest the possible applicability of LIM, uncomplexed or complexed with βCD, in conditions such as FM and neuropathic pain, for which there are currently only limited pharmacological options.