Fracture characterization of human cortical bone under mode II loading using the end-notched flexure test.

Fracture characterization of human cortical bone under mode II loading was analyzed using a miniaturized version of the end-notched flexure test. A data reduction scheme based on crack equivalent concept was employed to overcome uncertainties on crack length monitoring during the test. The crack tip shear displacement was experimentally measured using digital image correlation technique to determine the cohesive law that mimics bone fracture behavior under mode II loading. The developed procedure was validated by finite element analysis using cohesive zone modeling considering a trapezoidal with bilinear softening relationship. Experimental load-displacement curves, resistance curves and crack tip shear displacement versus applied displacement were used to validate the numerical procedure. The excellent agreement observed between the numerical and experimental results reveals the appropriateness of the proposed test and procedure to characterize human cortical bone fracture under mode II loading. The proposed methodology can be viewed as a novel valuable tool to be used in parametric and methodical clinical studies regarding features (e.g., age, diseases, drugs) influencing bone shear fracture under mode II loading.

Mixed-mode I+II fracture characterization of human cortical bone using the Single Leg Bending test.

Mixed-mode I+II fracture characterization of human cortical bone was analyzed in this work. A miniaturized version of the Single Leg Bending test (SLB) was used owing to its simplicity. A power law criterion was verified to accurately describe the material fracture envelop under mixed-mode I+II loading. The crack tip opening displacements measured by digital image correlation were used in a direct method to determine the cohesive law mimicking fracture behavior of cortical bone. Cohesive zone modeling was used for the sake of validation. Several fracture quantities were compared with the experimental results and the good agreement observed proves the appropriateness of the proposed procedure for fracture characterization of human bone under mixed-mode I+II loading.

Bone fracture characterization under mixed-mode I+II loading using the single leg bending test.

Fracture under mixed-mode I+II was induced in bovine cortical bone tissue using a developed miniaturized version of the single leg bending test (SLB). Due to the difficulty in crack length monitoring in the course of the test, an equivalent crack method based on specimen compliance and beam theory was adopted as a data reduction scheme. The method was applied to the experimental results in order to obtain the Resistance curves in each loading mode. The determined fracture energy is well described by an energetic power law whose exponent is below one, which means that the linear energetic criterion is not applicable to this material. The proposed procedure was numerically validated by means of a cohesive mixed-mode I+II damage model with bilinear softening. It was concluded that the miniaturized version of the SLB test is adequate for mixed-mode I+II fracture characterization of bone for a constant mode ratio.

Bone fracture characterization using the end notched flexure test.

A miniaturized version of the end notch flexure test was used in the context of pure mode II fracture characterization of bovine cortical bone. To overcome the difficulties intrinsic to crack length monitoring during its propagation an equivalent crack method was employed as data reduction scheme. The proposed method was validated numerically by means of a finite element analysis including a cohesive zone modeling and subsequently applied to experimental results to determine the fracture energy of bone under pure mode II loading. Finally, a cohesive law representative of fracture behavior of each specimen was determined employing an inverse method, considering a trapezoidal shape for the softening law. The consistency of the obtained results leads to the conclusion that the trapezoidal law is adequate to simulate fracture behavior of bone under mode II loading. The proposed testing setup and the employed data reduction scheme constitute powerful tools in which concerns fracture characterization of bone under pure mode II loading and can be viewed as the main outcomes of this work.

Fracture characterization of bone under mode II loading using the end loaded split test.

Fracture energy release rate under mode II loading of bovine cortical bone is determined using a miniaturized testing device of the end loaded split test. The energy release rate is evaluated by means of a data reduction scheme based on specimen compliance, beam theory and crack equivalent concept. Experimental tests were carried out to evaluate the Resistance curve which provides a successful method to characterize fracture behavior of quasi-brittle materials like bone. A numerical analysis including a cohesive damage model was used to validate the procedure. It was demonstrated that the end loaded split test and proposed data reduction scheme provide a valuable solution for mode II fracture characterization of bone.

First Report of Shallot latent virus in Garlic in Brazil.

Garlic (Allium sativum L.) can be infected by several viruses of the genera Allexivirus, Carlavirus, and Potyvirus (3). Garlic common latent virus (GarCLV) and Shallot latent virus (SLV) are the most important Carlavirus species infecting garlic, but only GarCLV has been described on garlic in Brazil. Seven hundred thirty-one samples of garlic showing mosaic symptoms and chlorotic streaking were collected from the states of São Paulo (São Manuel), Minas Gerais (Santa Juliana and São Gotardo), Goiás (Campo Alegre and Ipameri), and Paraná (Guarapuava and Piraquara) from April 2008 to July 2009 and analyzed by double-antibody sandwich (DAS)-ELISA for the presence of GarCLV and SLV using specific antiserum for SLV and GarCLV according to the manufacturer's protocol (Agdia Inc., Elkhart, IN). Cultivars sampled were Caçador, Chonan, Ito, Jonas, Quitéria, and Tropical. Fifty-five samples (7.5% of 731) tested positive for GarCLV, and none of the samples tested positive for SLV. Total RNA was extracted (2) from 15 samples that represented different states of production and used with primers SLV 7044 (5'-CTTTTGGTTCACTTTAGG-3') and SLV 8004 (5'-GCACGCAATAGTCTACGG-3'), designed in this study, to detect SLV in a one-step reverse transcription (RT)-PCR assay. Only 3 of the 15 samples, two from São Paulo and one from Paraná State, produced a 960-bp fragment covering the putative coat protein gene (ORF 5) (1) of SLV. The amplicons of the three isolates were sequenced. A nucleotide sequence identity of 91 to 92% was detected in comparison with two strains of SLV (GenBank Accession Nos. AB004567 and DQ520093), indicating the presence of two isolates of SLV in São Manuel (São Paulo State) and one in Piraquara, Paraná State (submitted to GenBank as Accession Nos. GU120176, HQ128602, and GU120175, respectively). To confirm identity of the virus, another pair of primers was constructed and tested (SLV 6737: 5'-YCCSGCCARGAAYTTCCC-3', and SLV 7060: 5'-TTAGAGCGCTGTWAACC-3'), from which a 340-bp fragment covering a portion of TGB2 (ORF 3) and TGB3 (ORF 4) (1) was amplified using the two isolates from São Paulo (GenBank Accession Nos. HQ123181 and HQ123182, respectively). The amplicon sequences shared 87% identity with that of an SLV isolate (Accession No. AJ292226), which confirmed the presence of SLV. The low titer of SLV in garlic might account for the false negative results by DAS-ELISA. The source of cultivated garlic bulbs in these regions of Brazil is unknown. Garlic cloves have been cultivated in São Manuel for approximately 15 years, indicating that SLV may have been present in Brazil for many years. To our knowledge, this is the first report of SLV in Brazil. References: (1) M. J. Adams et al. Virus Taxonomy: 8th Report of the International Committee on Taxonomy of Viruses. Elsevier Academic Press, 2005. (2) Y. D. Bertheau et al. Methods for the Detection and Quantification of Erwinia carotovora subsp. atroseptica on Potatoes. M. C. N. Perombelon and J. M. van der Wolff, eds. Scottish Crop Research Institute, Dundee, U.K., 1998. (3) T. V. M. Fajardo et al. Fitopatol. Bras. 26:619, 2001.

The double cantilever beam test applied to mode I fracture characterization of cortical bone tissue.

The primary objective of this work was to analyse the adequacy of the Double Cantilever Beam (DCB) test in determining fracture toughness under pure mode I loading of cortical bone tissue. A new data reduction scheme based on specimen compliance and the crack equivalent concept was used to overcome the difficulties inherent in crack monitoring during its growth. It provides a complete resistance curve, which is fundamental in estimating the fracture energy. A cohesive zone model was used to simulate damage initiation and propagation, thus assessing the efficacy of the proposed testing method and data reduction scheme. Subsequently, the DCB test was applied to evaluate the mode I fracture energy of hydrated and thermally dehydrated cortical bone tissue from young bovine femur, in the tangential-longitudinal propagation system. The results obtained demonstrate the efficacy of the DCB test and the proposed data reduction scheme on the bone fracture characterization under mode I loading.

[Different therapies in the treatment of obesity in hypertensive patients]. / Diferentes terapias no tratamento da obesidade em pacientes hipertensos.

PURPOSE: To evaluate the efficacy and tolerability of different therapies associated with diet in the treatment of hypertensive obese patients. METHODS: In a clinical study we randomly evaluated 39 hypertensive obese patients (body mass index (BMI) > or = 30 kg/m2). After 45 days of diet the patients were again randomly distributed in 3 groups and received in double blind way: group 1-hypocaloric diet+placebo; group 2-hypocaloric diet+dexfenfluramine; group 3-hypocaloric diet+spiruline+fucus+gelatin. We followed their progress during 12 weeks under medication and further 24 weeks without. We evaluated the groups comparing: weight, BMI, blood pressure and side-effects. RESULTS: Twenty seven patients completed the observation. In those patients from groups 1 and 3 no changes in any of parameters were observed. In group 2 we observed a clear loss of weight (-3.8 Kg) and a fall in BMI. Blood Pressure changes were only observed in group 2 (-9.6%). The only patients to maintain weight loss after the termination of use of medicines were those from group 2. We did not observe any side-effects. CONCLUSION: In hypertensive obese patients, when isolated diet is not enough to control weight loss, dexfenfluramine could be useful in association with a controlled diet. The drug assists in weight loss, does not promote side-effects and does not interfere in the treatment of blood pressure.