Correlations between trabecular bone score, measured using anteroposterior dual-energy x-ray absorptiometry acquisition, and 3-dimensional parameters of bone microarchitecture: an experimental study on human cadaver vertebrae.

Developing a novel technique for the efficient, noninvasive clinical evaluation of bone microarchitecture remains both crucial and challenging. The trabecular bone score (TBS) is a new gray-level texture measurement that is applicable to dual-energy X-ray absorptiometry (DXA) images. Significant correlations between TBS and standard 3-dimensional (3D) parameters of bone microarchitecture have been obtained using a numerical simulation approach. The main objective of this study was to empirically evaluate such correlations in anteroposterior spine DXA images. Thirty dried human cadaver vertebrae were evaluated. Micro-computed tomography acquisitions of the bone pieces were obtained at an isotropic resolution of 93μm. Standard parameters of bone microarchitecture were evaluated in a defined region within the vertebral body, excluding cortical bone. The bone pieces were measured on a Prodigy DXA system (GE Medical-Lunar, Madison, WI), using a custom-made positioning device and experimental setup. Significant correlations were detected between TBS and 3D parameters of bone microarchitecture, mostly independent of any correlation between TBS and bone mineral density (BMD). The greatest correlation was between TBS and connectivity density, with TBS explaining roughly 67.2% of the variance. Based on multivariate linear regression modeling, we have established a model to allow for the interpretation of the relationship between TBS and 3D bone microarchitecture parameters. This model indicates that TBS adds greater value and power of differentiation between samples with similar BMDs but different bone microarchitectures. It has been shown that it is possible to estimate bone microarchitecture status derived from DXA imaging using TBS.

An experimental and theoretical study of multiphase flow in a circulating fluidized bed

A systematic averaging procedure has been derived in order to obtain an integral form of conservation equations for dispersed multiphase flow, especially applicable to fluidized beds. A similar averaging method is applied further to formulate macroscopic integral equations, which can be used in one-dimensional and macroscopic multi dimensional models. Circulating fluid bed hydrodynamics has been studied experimentally and both macroscopic and microscopic flow profiles have been measured in a cold model. As an application of the theory, the one dimensional model has been used to study mass and momentum conservation of gas and solid in a circulating fluid bed. Axial solid mixing has also been modelled by the one dimensional model and mixing parameters have been evaluated.

Experimental and discrete element simulation studies of bell-less charging of blast furnace

This thesis presents an experimental study and numerical study, based on the discrete element method (DEM), of bell-less charging in the blast furnace. The numerical models are based on the microscopic interaction between the particles in the blast furnace charging process. The emphasis is put on model validation, investigating several phenomena in the charging process, and on finding factors that influence the results. The study considers and simulates size segregation in the hopper discharging process, particle flow and behavior on the chute, which is the key equipment in the charging system, using mono-size spherical particles, multi-size spheres and nonspherical particles. The behavior of the particles at the burden surface and pellet percolation into a coke layer is also studied. Small-scale experiments are used to validate the DEM models.

Experimental study applied to an industrial robot by using variable structure controllers and friction compensation

Control of an industrial robot is mainly a problem of dynamics. It includes non-linearities, uncertainties and external perturbations that should be considered in the design of control laws. In this work, two control strategies based on variable structure controllers (VSC) and a PD control algorithm are compared in relation to the tracking errors considering friction. The controller's performances are evaluated by adding an static friction model. Simulations and experimental results show it is possible to diminish tracking errors by using a model based friction compensation scheme. A SCARA robot is used to illustrate the conclusions of this paper.

EXPERIMENTAL AND THEORETICAL STUDY OF SHYNTESIS OF N-ALKYL-NITROIMIDAZOLES.

In this work we realized and experimental and theoretical study of the N-alkylation of nitroimidazoles. The N-alkyl-2-methyl-nitroimidazoles correspond to biologically active molecules, obtained by reaction of 2-methyl-5-nitroimidazole and different alkyl halides. This reaction showed the formation of a mixture of isomeric products in different proportions, denominated like N-alkyl-2-methyl-4-nitroimidazole and N-alkyl-2-methyl-5-nitroimidazole, respectively. The reaction suggestes the formation of a tautomeric equilibrium, which generates two nucleophilic sites susceptible to electrophilic attack by the alkyl halide. The local nucleophilic reactivity of the nitroimidazole nng is determined using local reactivity indices such as the Fukui function and the electrostatic potential, besides the electronic localization function (ELF). The Fukui function was integrated for each atom using partition schemes based on analysis of Mulliken charges and natural bond orbital (NBO). Finally the reaction profiles were assessed. The results show a minor difference in the local reactivity. Nevertheless a significant difference in energy barriers is observed explaining the formation of an isomeric product over another. These results agree quite well with the experimental data.

Re-examination of the anion derivatives of isoflavones by radical fragmentation in negative electrospray ionization tandem mass spectrometry: experimental and computational studies

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Combined experimental and theoretical study to understand the photoluminescence of Sr1-xTiO3-x

A joint experimental and theoretical study has been carried out to rationalize the results of visible photoluminescence measurements at room temperature on Sr1-xTiO3-x (ST) perovskite thin films. From the experimental side, ST thin films, x = 0 to 0.9, have been synthesized following soft chemical processing, and the corresponding photoluminescence properties have been measured. First principles quantum mechanical techniques, based on density functional theory at the B3LYP level, have been employed to study the electronic structure of a crystalline, stoichiometric (x = 0) ST-s model and a nonstoichiometric (SrO-deficient, x not equal 0) and structurally disordered ST-d model. The relevance of the present theoretical and experimental results of the photoluminescence behavior of ST is discussed. The optical spectra and the calculations indicate that the symmetry-breaking process on going from ST-s to ST-d creates electronic levels in the valence band. Moreover, an analysis of the Mulliken charge distribution reveals a charge gradient in the structure. These combined effects seem to be responsible for the photoluminescence behavior of deficient Sr1-xTiO3-x.

Short-term movement and retreat sites of Leptodactylus labyrinthicus (Anura : Leptodactylidae) during the breeding season: A spool-and-line tracking study

Capture/recapture studies significantly increase our knowledge of the natural history of anuran amphibians. Many different methods have been employed in these studies, but a number of new techniques still require experimental validation. During two reproductive seasons in a Cerrado remnant in southeastern Brazil, we investigated the movement patterns and habitat use of the pepper frog, Leptodactylus labyrinthicus, using a spool-and-line device. This low-cost device did not appear to interfere with the activities of the frogs and allowed for constant monitoring, showing precise routes of movement and great predictability of relocations. Both sexes were active at night. During the day, males and females made use of retreat sites under vegetation or in burrows constructed by small- and medium-sized mammals. Males and females did not use standardized routes; there were no significant differences between their movements, and movements were not correlated with body size or environmental conditions. Individuals are able to move further than 100 m per day, a characteristic that may enable this species to colonize or recolonize open areas.

Room-temperature photoluminescence of BaTiO3: Joint experimental and theoretical study

Strong photoluminescent emission has been measured at room temperature for noncrystalline BaT'O-3 (BT) perovskite powders. A joint experimental and theoretical study has been carried out to rationalize this phenomenon. From the experimental side, BT powder samples have been synthesized following a soft chemical processing, their crystal structure has been confirmed by x-ray data and the corresponding photoluminescence (PL) properties have been measured. Only the structurally disordered samples present PL at room temperature. From the theoretical side, first-principles quantum-mechanical techniques, based on density-functional theory at the B3LYP level, have been employed to study the electronic structure of crystalline (BT-c) and asymmetric (BT-a) models. Theoretical and experimental results are found to be consistent and their confrontation leads to an interpretation of the PL apparition at room temperature in the structurally disordered powders.

Heparin, heparin plus ASA and dipyridamole, and arteriovenous fistula as adjuvant methods to prevent rethrombosis after venous thrombectomy. Experimental study in rabbits

Venous rethrombosis following thrombectomy is a common event. The aim of the present study was to verify the action of heparin, heparin plus acetyl salicylic acid (ASA) and dipyridamole, and of an arteriovenous fistula (AVF) in the prevention of this complication. Thrombosis was induced in 48 male rabbits by the injection of thrombin in a segment of the left jugular vein, in which the blood flow was arrested for 10 minutes. After 48 hours, the animals were randomly allocated into one of 4 groups of treatment: (1) control, (2) subcutaneous heparin (600 S.I. Units/kg - 8/8 hours), (3) heparin, in the same dose, plus ASA (10 mg/kg/once a day), and dipyridamole (0.5 mg/kg thrice a day), (4) an AVF was surgically constructed between the left carotid after and the left maxillar vein. After 30 minutes, thrombectomy was performed. The venous blood flow, the hematocrit, activated partial thromboplastin time and thrombin time tests were performed before, right after the thrombectomy and 48 hours after thrombectomy. Venography was performed after thrombectomy and at the end of the experiment. The animals were killed 48 hours after thrombectomy and the veins were examined macroscopically. Venous rethrombosis was significantly prevented only in the AVF group (9/12), when compared to control group (0/12), heparin group (1/12) and heparin plus antiaggregating agents group (2/12). These results validate further clinical and experimental investigations with the use of AVF to prevent rethrombosis after venous thrombectomy, when a reduction of venous flow is present.

Toward an Understanding of the Growth of Ag Filaments on alpha-Ag2WO4 and Their Photoluminescent Properties: A Combined Experimental and Theoretical Study

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Hard and soft tissue changes around implants installed in regular-sized and reduced alveolar bony ridges. An experimental study in dogs

Objective: To study bony and soft tissue changes at implants installed in alveolar bony ridges of different widths.Material and methods: In 6 Labrador dogs, the mandibular premolars and first molars were extracted, and a buccal defect was created in the left side at the third and fourth premolars by removing the buccal bone and the inter-radicular and interdental septa. Three months after tooth extraction, full-thickness mucoperiosteal flaps were elevated, and implants were installed, two at the reduced (test) and two at the regular-sized ridges (control). Narrow or wide abutments were affixed to the implants. After 3 months, biopsies were harvested, and ground sections prepared for histological evaluation.Results: A higher vertical buccal bony crest resorption was found at the test (1.5 +/- 0.7 mm and 1.0 +/- 0.7 mm) compared to the control implants (1.0 +/- 0.5 mm and 0.7 +/- 0.4 mm), for both wide and narrow abutment sites. A higher horizontal alveolar resorption was identified at the control compared to the test implants. The difference was significant for narrow abutment sites. The peri-implant mucosa was more coronally positioned at the narrow abutment, in the test sites, while for the control sites, the mucosal adaptation was more coronal at the wide abutment sites. These differences, however, did not reach statistical significance.Conclusions: Implants installed in regular-sized alveolar ridges had a higher horizontal, but a lower vertical buccal bony crest resorption compared to implants installed in reduced alveolar ridges. Narrow abutments in reduced ridges as well as wide abutments in regular-sized ridges yielded less soft tissue recession compared to their counterparts.

Freezing Distortions and Photoluminescence Property in PbMoO4 Micro Octahedrons: An Experimental and Theoretical Study

In this paper, we report a detailed structural and electronic characterization of PbMoO4 crystals by using a conventional hydrothermal (CH) method. The samples were characterized by X-ray diffraction (XRD), Fourier transform Raman (FT-Raman), field-emission gun scanning electron microscopy (FEG-SEM) and photoluminescence (PL) measurements. In addition, first-principles quantum mechanical calculations based on the density functional theory were employed in order to understand the band structure and density of states for the PbMoO4. Analysis of both theoretical and experimental results allows to rationalize the role of order-disorder effects in the observed green PL emissions in these ordered powders.

Fingerprints of short-range and long-range structure in BaZr1-xHfxO3 solid solutions: an experimental and theoretical study

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Experimental and theoretical study on the structure, optical properties, and growth of metallic silver nanostructures in Ag3PO4

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)