Microstructural and flexural strength of various CAD-CAM lithium disilicate ceramics.

PURPOSE: To analyze the microstructural and mechanical properties of various commercial trademarks of lithium disilicate ceramics for CAD-CAM systems. MATERIALS AND METHODS: Specimens of different lithium disilicate ceramics were obtained and randomized into 5 groups (n = 14): EM: e.max CAD; RT: Rosetta SM; EV: Evolith; PM: Smile-Lithium CAD; and, HS: HaHaSmile. The microstructural analysis was performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM); for flexural strength, the three-point bending flexure test was used. XRD and SEM data were qualitatively evaluated. Data from flexural strength were assessed with one-way ANOVA test (α = 0.05) and Weibull analysis. RESULTS: High peaks corresponding to the lithium metasilicate and lithium disilicate pattern with similar intensities were observed in all ceramics in the XRD analysis. SEM images showed similar patterns of crystalline structure in the EM and RT ceramics, while the other three groups presented different crystal morphologies than the previous ones and were similar to each other. No differences were found in flexural strength among the groups (p = 0.28). CONCLUSIONS: The CAD-CAM lithium disilicate ceramics showed comparable crystalline intensities. The microstructure of the EM and RT ceramics were different from the other groups. Flexural strength was similar among all ceramics.

Evaluation of Antibacterial Activity of Bismuth Ferrites Nanoparticles in the inhibition of E. coli and S. aureus bacteria.

In this work, bismuth ferrites (BFO) nanoparticles were produced in the form of using sol-gel technique, followed by annealing in a tube furnace in temperatures from 400 °C to 650 ºC. X-ray diffraction (XRD) results showed the formation of small sizes nanoparticles (NPs) with high purity. Structural analysis displayed that annealing at 600 ºC could make BFO NPs be fitted to rhombohedral space group (R3c), with small quantity of spurious phases. The sizes of the BFO nanoparticles determined by transmission electron microscopy (HRTEM) are between 50 to 100 nm. To evaluate the efficiency of BFO in antimicrobial susceptibility tests, the nanoparticles were dispersed through nanoemulsion and tested agar diffusion method and dilution in a 96 well plate using a Gram positive strains (Staphylococcus aureus) and Gram negative strain (Escherichia coli). The antibacterial activity of the BFO NPs was partially tested at concentrations of 2 mg/mL with MIC greater than 60 µg/mL for both bacteria.

Sustainable Hybrid Lightweight Aggregate Concrete Using Recycled Expanded Polystyrene.

Global concrete production, reaching 14×1013m3/year, raises environmental concerns due to the resource-intensive nature of ordinary Portland cement (OPC) manufacturing. Simultaneously, 32.7×109 kg/year of expanded polystyrene (EPS) waste poses ecological threats. This research explores the mechanical behavior of lightweight concrete (LWAC) using recycled EPS manufactured with a hybrid cement mixture (OPC and alkali-activated cement). These types of cement have been shown to improve the compressive strength of concrete, while recycled EPS significantly decreases concrete density. However, the impact of these two materials on the LWAC mechanical behavior is unclear. LWAC comprises 35% lightweight aggregates (LWA)-a combination of EPS and expanded clays (EC) - and 65% normal-weight aggregates. As a cementitious matrix, this LWAC employs 30% OPC and 70% alkaline-activated cement (AAC) based on fly ash (FA) and lime. Compressive strength tests after 28 curing days show a remarkable 48.8% improvement, surpassing the ACI 213R-03 standard requirement, which would allow this sustainable hybrid lightweight aggregate concrete to be used as structural lightweight concrete. Also obtained was a 21.5% reduction in density; this implies potential cost savings through downsizing structural elements and enhancing thermal and acoustic insulation. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy reveal the presence of C-S-H, C-(A)-S-H, and N-A-S-H gels. However, anhydrous products in the hybrid LWAC suggest a slower reaction rate. Further investigation into activator solution dosage and curing temperature is recommended for improved mechanical performance on the 28th day of curing. This research highlights the potential for sustainable construction incorporating waste and underscores the importance of refining activation parameters for optimal performance.

Synthesis and evaluation of the antimicrobial activity of purified and unpurified multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were purified and unpurified in this study to obtain hybrid materials with improved activity. The production stage comprised a chemical purification of the produced sample. Raman spectroscopy analyzed the structural composition of purified and unpurified samples. The disc diffusion assay, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and time-kill assessment analyzed antimicrobial activity. MWCNT performed well against the tested bacteria (Klebsiella pneumoniae, Pseudomonas aeruginosa, Enterobacter aerogenes, Staphylococcus aureus, and Streptococcus sp. Staphylococcus epidermidis). The disc diffusion assay revealed inhibition zone differences caused by purified and unpurified MWCNTs. MIC and MBC values of purified and unpurified MWCNTs were similar. The purified and unpurified nanotubes of Staphylococcus epidermidis (ATCC 35985) exhibited inhibition zone diameters of approximately 8 mm and 9 mm, respectively. The microdilution method revealed a MIC of 1.23 mg/ml for the purified nanotube and 0.156 mg/ml for the unpurified nanotube against the same microorganism. The killing curve analysis demonstrated that unpurified carbon nanotubes were more effective against all tested microorganisms. MWCNTs represent a promising method for microbiology, but studies on the toxicity of these materials remain scarce.

Development and properties of biodegradable film from peach palm (Bactris gasipaes).

Formulations of biodegradable films using macrocarpa peach palm flour (low amylose starch), chitosan and glycerol, were developed and the effects of the drying temperature on films by assessing their physicochemical, mechanical, barrier, optical, structural, antioxidant properties, and the biodegradability in soil were evaluated. Chitosan enhanced the mechanical properties of the films, but they showed no antimicrobial activity against the tested food-borne pathogens, except for Listeria monocytogenes, for which the inhibition zone was from 0.1 to 0.6 cm. Films with higher concentrations of peach palm flour are opaquer, with better antioxidant characteristics and content of phenolic compounds compared to films made with lower concentrations of flour. The films presented a yellowish color because of the carotenoids found in peach palm flour, 29.63 µg 100 g-1, and exhibited a C-type X-ray pattern, characteristic peak of materials where amylose and amylopectin are present. After 15 days in soil, the films lost 30% of their initial weight. Therefore, these results suggest that the development of films as food preservative is a promising field and that the material used in the study are suitable for their formulation.

Babassu Coconut Fibers: Investigation of Chemical and Surface Properties (Attalea speciosa.).

To complement previous results, an analysis of the chemical and morphological properties of babassu fibers (Attalea speciosa Mart. ex Spreng.) was conducted in order to evaluate their potential as reinforcements in the production of composites with epoxy matrix. The diameter distribution was analyzed in a sample of one hundred fibers, allowing the verification of its variation. The determination of the chemical properties involved experimental analyses of the constituent index and X-ray diffraction. The diffractogram was used to calculate the crystallinity index and the microfibril angle, which are crucial parameters that indicate the consistency of the mechanical properties of babassu fibers and the feasibility of their use in composites. The results revealed that babassu fiber has a chemical composition, with contents of 28.53% lignin, 32.34% hemicellulose, and 37.97% cellulose. In addition, it showed a high crystallinity index of 81.06% and a microfibril angle of 7.67°. These characteristics, together with previous results, indicate that babassu fibers have favorable chemical and morphological properties to be used as reinforcements in composites, highlighting its potential as an important material for applications in technology areas.

In situ Raman spectroscopy and synchrotron X-ray diffraction studies on maleic acid under high pressure conditions.

Maleic acid was studied by Raman spectroscopy and powder synchrotron X-ray diffraction (XRD) under high pressure conditions by using a diamond anvil cell. The Raman spectroscopy measurements were performed from ambient pressure up to 9.2 GPa in the 100-3200 cm-1 spectral range. While the XRD measurements were performed up to 10.1 GPa. Here we present the pressure-dependence behavior from both the Raman modes and cell parameters. Maleic acid lattice parameters decrease anisotropically as a function of pressure and a reduction of 27% in the volume of the unit cell was observed. Modifications in the material's compressibility were observed at around 2 and 6 GPa.

Lipid exchange in crystal-confined fatty acid binding proteins: X-ray evidence and molecular dynamics explanation.

Fatty acid binding proteins (FABPs) are responsible for the long-chain fatty acids (FAs) transport inside the cell. However, despite the years, since their structure is known and the many studies published, there is no definitive answer about the stages of the lipid entry-exit mechanism. Their structure forms a ß -barrel of 10 anti-parallel strands with a cap in a helix-turn-helix motif, and there is some consensus on the role of the so-called portal region, involving the second α -helix from the cap ( α 2), ß C- ß D, and ß E- ß F turns in FAs exchange. To test the idea of a lid that opens, we performed a soaking experiment on an h-FABP crystal in which the cap is part of the packing contacts, and its movement is strongly restricted. Even in these conditions, we observed the replacement of palmitic acid by 2-Bromohexadecanoic acid (Br-palmitic acid). Our MD simulations reveal a two-step lipid entry process: (i) The travel of the lipid head through the cavity in the order of tens of nanoseconds, and (ii) The accommodation of its hydrophobic tail in hundreds to thousands of nanoseconds. We observed this even in the cases in which the FAs enter the cavity by their tail. During this process, the FAs do not follow a single trajectory, but multiple ones through which they get into the protein cavity. Thanks to the complementary views between experiment and simulation, we can give an approach to a mechanistic view of the exchange process.

Thick layer drying and storage of rice grain cultivars in silo-dryer-aerator: Quality evaluation at low drying temperature.

Drying rice in a single layer in a silo-dryer-aerator allows uniform drying. The objective of this study was to evaluate the physical, physicochemical, and morphological quality of rice grain cultivars (IRGA 424, BRS Pampeira, and Guri INTA) in the lower (initial time) and upper (final time) layers in a silo-dryer-aerator, employing single-layer loading at low temperatures, using the methods of near-infrared spectroscopy, X-ray diffraction analysis, scanning electron microscopy, and multivariate statistical analysis. Drying rice in silo-dryer-aerator attenuated the moisture diffusivity in the grains, minimizing its effects on the physical, physicochemical, and morphological properties of the grains. However, the physicochemical constituents and morphology of starch were preserved by the low drying temperatures, mainly in the lower layers throughout the 2-month drying. The rice grains of the Guri INTA and BRS Pampeira cultivars were the most resistant to drying and showed greater uniformity on the final quality.

Cyclo-hexane plastic phase I: single-crystal diffraction images and new structural model.

The plastic phase of cyclohexane (polymorph I) was studied by Kahn and co-workers, without achieving a satisfactory determination of the atomic coord-inates [Kahn et al. (1973). Acta Cryst. B29, 131-138]. The positions of the C atoms cannot be determined directly as a consequence of the disorder in a high-symmetry space group, an inherent feature of plastic materials. Given this situation, the building of a polyhedron describing the disorder was the main tool for determining the molecular structure in the present work. Based on the shape of reflections {111}, {200} and {113} in space group Fm 3 m, we assumed that cyclohexane is disordered through the action of rotation group 432. The polyhedral cluster of disordered molecules is then a rhombic dodecahedron centred on the nodes of an fcc Bravais lattice. The vertices of this polyhedron are the positions of C atoms for the cyclohexane molecule, which is disordered over 24 positions. With such a model, the asymmetric unit is reduced to two C atoms placed on special positions, and an acceptable fit between the observed and calculated structure factors is obtained.

Extraction, Purification and Electrical Characterization of Gross Galactomannan and Purified Galactomannan Obtained from Adenanthera pavonina L. Seeds.

Aiming of self-sustainable production, the search for biodegradable and biocompatible materials has brought with it the need to know the physicochemical and dielectric characteristics of polysaccharide-based composite structures, which can be used as important and promising raw materials for biotechnology and electronic industries. Galactomannans are polysaccharides, extracted from seeds and microbiological sources, consisting of mannose and galactose. In this context, this work aimed to extract, purify and characterize by XRD, FTIR and impedance spectroscopy galactomannan obtained from seeds of Adenanthera pavonina L. The purification process was made with ethyl alcohol at concentrations of 70, 80 and 90 %. Polymeric films were prepared by solvent slow evaporation at low temperatures. XRD measurements revealed that Galactomannan from Adenanthera pavonina L., after purification, has a semi-crystalline structure due to the identification of two peaks the first between 5.849° and 6.118° and the second between 20.011° and 20.247°. FTIR spectra showed the functional groups associated with monosaccharides of the galactomannan from Adenanthera pavonina L. seeds, as well as the typical polysaccharide bands and peaks, confirmed by literature data. The impedance results give an increment on the state-of-the-art of this biomaterial by showing the existence of dielectric relaxations, independent of the degree of purification, using the dielectric modulus formalism. The permittivity analysis reveals the presence of water in the structure of the film, whose dipoles contribute to the relatively high value of the dielectric constant. From the results obtained, it can be concluded that purified galactomannan has the potential for possible applications in the electronics industry as a green and eco-friendly dielectric material.

Bromination of eudesmin isolated from araucaria araucana induces epimerization and give bromine derivatives with loss of anti-Candida activity.

Furofuran lignanes show important biological activities for the treatment of infectious diseases, inflammatory and metabolic pathologies. They have been isolated from leaves and barks of many plants. In Chile the native conifer Araucaria araucana produces eudesmin, matairesinol, secoisolariciresinol and lariciresinol in stemwood, branchwood and knotwood. These compounds were previously isolated by laborious flash chromatography on silica gel. Here we report the easy isolation of eudesmin by soxhlet extraction from milled knots of Araucaria araucana with hexane, followed by cryo-crystallization at -20 °C. Upon bromination of the isolated eudesmin epimerization at one benzylic position occurs, giving epieudesmin and the corresponding mono and di-brominated derivatives. The structures were determined by 1D, 2D NMR and X-ray diffraction. The analysis of products against Candida yeast showed that eudesmin has a moderate activity against different strains of Candida from 62.5 to 500 µg/mL. This activity decreases for epieudesmin, while bromine derivatives are not active.

Soybean residue (okara) modified by extrusion with different moisture contents: Physical, chemical, and techno-functional properties.

To increase hydration properties and soluble fiber content, okara with different moisture contents (30, 35, and 40%) was extruded in single-screw equipment, keeping the temperature (120 °C) and screw speed (115 rpm) fixed. The physical, chemical, and techno-functional properties of extruded and non-extruded okara (control) were evaluated. The microstructure, color, chemical composition, and techno-functional properties of okara were altered after extrusion. The extruded samples showed general microstructure aspects similar between them, with an irregular and rough surface, striated parts, orifices, and some agglomerated particles with distorted, compact, and amorphous appearance, different from control. Among the modified samples, okara extruded with 30% moisture showed more intense changes in relation to the samples extruded with 35 and 40% moisture. Based on the results, it can be inferred that okara extruded with 35% moisture is the most suitable. Under this condition, there was an increase of 80% in soluble fiber content, 45% in water absorption and holding capacity and 11% in solid stability in water, the maintenance of swelling and oil absorption and holding capacities and the reduction of protein solubility in water. X-ray diffraction analysis showed that crystalline phase was affected by extrusion.

Selectivity of soil constituents by termites in the construction of Brazilian termite mounds

Termites can create structures that alter the physical and chemical properties of soils. In this process, termites are selective about the soil constituents they will use to construct their mounds. Considering the common occurrence of termite mounds in Brazilian soils, this study aimed to investigate the selective action of termites in the mound building process. Samples were collected from six termite mounds and control soils (at a distance of 15 to 30 m from the termite mound) in different regions in Brazil to analyze the fine earth fraction. The content of clay fraction, organic C and Fe in pedogenic iron oxides increased in the mounds resulting in specific surface area increments. X-ray diffraction indicated a selectivity of termites by clay-sized particles such as kaolinite, gibbsite and iron oxides (hematite and goethite) rather than larger particles such as quartz. The proportion of low-crystalline iron oxides and the maghemite amount decreased in the mounds. The change of color parameters in the termite mounds was due to a combination of increase in clay fraction, organic carbon and iron oxides. The techniques used were sensitive, indicating changes and similarities between the control soils and the termite mounds.(AU)

Preformulation screening of lipids using solubility parameter concept in conjunction with experimental research to develop ceftriaxone loaded nanostructured lipid carriers

Abstract Development of ceftriaxone loaded nanostructured lipid carriers to increase permeability of ceftriaxone across uninflamed meninges after parenteral administration. Lipids were selected by theoretical and experimental techniques and optimization of NLCs done by response surface methodology using Box-Behnken design. The Δδt for glyceryl monostearate and Capryol90 were 4.39 and 2.92 respectively. The drug had maximum solubility of 0.175% (w/w) in glycerol monostearate and 2.56g of Capryol90 dissolved 10mg of drug. The binary mixture consisted of glyceryl monostearate and Capryol90 in a ratio of 70:30. The optimized NLCs particle size was 130.54nm, polydispersity index 0.28, % entrapment efficiency 44.32%, zeta potential -29.05mV, and % drug loading 8.10%. In vitro permeability of ceftriaxone loaded NLCs was 5.06x10-6 cm/s; evidently, the NLCs pervaded through uninflamed meninges, which, was further confirmed from in vivo biodistribution studies. The ratio of drug concentration between brain and plasma for ceftriaxone loaded NLCs was 0.29 and that for ceftriaxone solution was 0.02. With 44.32% entrapment of the drug in NLCs the biodistribution of ceftriaxone was enhanced 7.9 times compared with that of ceftriaxone solution. DSC and XRD studies revealed formation of imperfect crystalline NLCs. NLCs improved permeability of ceftriaxone through uninflamed meninges resulting in better management of CNS infections.

Use of Fourier Series in X-ray Diffraction (XRD) Analysis and Fourier-Transform Infrared Spectroscopy (FTIR) for Estimation of Crystallinity in Cellulose from Different Sources.

Cellulose crystallinity can be described according to the crystal size and the crystallinity index (CI). In this research, using Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) methods, we studied the crystallinity of three different types of cellulose: banana rachis (BR), commercial cellulose (CS), and bacterial cellulose (BC). For each type of cellulose, we analyzed three different crystallization grades. These variations were obtained using three milling conditions: 6.5 h, 10 min, and unmilled (films). We developed a code in MATLAB software to perform deconvolution of the XRD data to estimate CI and full width at half-maximum (FWHM). For deconvolution, crystalline peaks were represented with Voigt functions, and a Fourier series fitted to the amorphous profile was used as the amorphous contribution, which allowed the contribution of the amorphous profile to be more effectively modeled. Comparisons based on the FTIR spectra and XRD results showed there were no compositional differences between the amorphous samples. However, changes associated with crystallinity were observed when the milling time was 10 min. The obtained CI (%) values show agreement with values reported in the literature and confirm the effectiveness of the method used in this work in predicting the crystallization aspects of cellulose samples.

Crystal growth, crystal structure determination, and computational studies of a new mixed (NH4)2Mn1-xZnx(SO4)2(H2O)6 Tutton salt.

Tutton salts have been extensively explored in recent decades due to their attractive physical and chemical properties, which make them potential candidates for thermochemical heat storage systems and optical technologies. In this paper, a series of new mixed Tutton salts with the chemical formula (NH4)2Mn1-xZnx(SO4)2(H2O)6 is reported. Crystals are successfully grown by the solvent slow evaporation method and characterized by powder X-ray diffraction (PXRD) with Rietveld refinement. In particular, the crystal structure of the mixed (NH4)2Mn0.5Zn0.5(SO4)2(H2O)6 crystal is solved through PRXD data using the DICVOL06 algorithm for diffraction pattern indexing and the Le Bail method for lattice parameter and spatial group determination. The structure is refined using the Rietveld method implemented in TOPAS® and reported in the Cambridge Structural Database file number 2104098. Moreover, a computational study using Hirshfeld surface and crystal void analyses is conducted to identify and quantify the intermolecular interactions in the crystal structure as well as to determine the amount of free space in the unit cell. Furthermore, 2D-fingerprint plots are generated to evaluate the main intermolecular contacts that stabilize the crystal lattice. Density functional theory is employed to calculate the structural, thermodynamic, and electronic properties of the coordination [Zn(H2O)6]2+ and [Mn(H2O)6]2+ complexes present in the salts. Molecular orbitals, bond lengths, and the Jahn-Teller effect are also discussed. The findings suggest that in Mn-Zn salts several properties dependent on the electronic structure can be tuned up by modifying the chemical composition.

Green Route to Produce Silver Nanoparticles Using the Bioactive Flavonoid Quercetin as a Reducing Agent and Food Anti-Caking Agents as Stabilizers.

In previous work, the isolated polyphenolic compound (PPC) quercetin was used as a reducing agent in the formation of silver nanoparticles (AgNPs), testing two types of quercetin. This PPC is a bioactive molecule that provides the electrons for the reduction of silver ions to zerovalent silver. The results demonstrated that quercetin in dietary supplement presentation was better than reagent grade quercetin for the synthesis of AgNPs, and the difference between them was that the dietary supplement had microcrystalline cellulose (CM) in its formulation. Therefore, this dietary anti-caking agent was added to the reagent-grade quercetin to validate this previously found improvement. AgNPs were obtained at neutral pH by a green route using quercetin as a reducing agent and microcrystalline cellulose and maltodextrin as stabilizing agents. In addition, different ratios were evaluated to find the optimum ratio. Ultraviolet-Visible spectroscopy (UV-VIS), Atomic Force Microscope (AFM), Z-potential, Dynamic Light Scattering (DLS) and X-ray Powder Diffraction (XRD) were used for characterization. The antibacterial activity of the S. aureus and E. coli agent was tested by the disk diffusion and microdilution method. According to the results, this green synthesis needs the use of food stabilizer when working at pH 7 to maintain AgNPs in the long term. The ideal ratio of reducing the agent:stabilizing agent was 1:2, since with this system stable AgNPs are obtained for 2 months and with improved antimicrobial activity, validating this method was ecologically and economically viable.

Staphylococcus aureus Exfoliative Toxin E, Oligomeric State and Flip of P186: Implications for Its Action Mechanism.

Staphylococcal exfoliative toxins (ETs) are glutamyl endopeptidases that specifically cleave the Glu381-Gly382 bond in the ectodomains of desmoglein 1 (Dsg1) via complex action mechanisms. To date, four ETs have been identified in different Staphylococcus aureus strains and ETE is the most recently characterized. The unusual properties of ETs have been attributed to a unique structural feature, i.e., the 180° flip of the carbonyl oxygen (O) of the nonconserved residue 192/186 (ETA/ETE numbering), not conducive to the oxyanion hole formation. We report the crystal structure of ETE determined at 1.61 Å resolution, in which P186(O) adopts two conformations displaying a 180° rotation. This finding, together with free energy calculations, supports the existence of a dynamic transition between the conformations under the tested conditions. Moreover, enzymatic assays showed no significant differences in the esterolytic efficiency of ETE and ETE/P186G, a mutant predicted to possess a functional oxyanion hole, thus downplaying the influence of the flip on the activity. Finally, we observed the formation of ETE homodimers in solution and the predicted homodimeric structure revealed the participation of a characteristic nonconserved loop in the interface and the partial occlusion of the protein active site, suggesting that monomerization is required for enzymatic activity.

Nitrogen Fertilizers Technologies for Corn in Two Yield Environments in South Brazil.

Improvements in nitrogen use efficiency (NUE) in corn production systems are necessary, to decrease the economic and environmental losses caused by loss of ammonia volatilization (NH3-N). The objective was to study different nitrogen (N) fertilizer technologies through characterization of N sources, NH3-N volatilization losses, and their effects on the nutrient concentration and yield of corn grown in clayey and sandy soils in south Brazil. The treatments consisted of a control without N application as a topdressing, three conventional N sources (urea, ammonium sulfate, and ammonium nitrate + calcium sulfate), and three enhanced-efficiency fertilizers [urea treated with NBPT + Duromide, urea formaldehyde, and polymer-coated urea (PCU) + urea treated with NBPT and nitrification inhibitor (NI)]. The losses by NH3-N volatilization were up to 46% of the N applied with urea. However, NI addition to urea increased the N losses by NH3-N volatilization by 8.8 and 23.3%, in relation to urea alone for clayey and sandy soils, respectively. Clayey soil was 38.4% more responsive than sandy soil to N fertilization. Ammonium sulfate and ammonium nitrate + calcium sulfate showed the best results, because it increased the corn yield in clayey soil and contributed to reductions in NH3-N emissions of 84 and 80% in relation to urea, respectively.