fracture and microstructural study of bovine bone under mixed mode i ii loading

Abstract Understanding the fracture behavior and associated crack growth mechanism in bone material is an important issue for biomechanics and biomaterial researches. Fracture of bone often takes place due to complex loading conditions which result in combined tensile-shear (i.e. mixed mode) fracture mechanism. Several parameters such as loading type, applied loading direction relative to the bone axis, loading rate, age and etc., may affect the mixed mode fracture resistance and damage mechanism in such materials. In this research, a number of mixed mode I/II fracture experiments are conducted on bovine femur bone using a sub-sized test configuration called "compact beam bend (CBB)" specimen to investigate the fracture toughness of bone under different mode mixities. The specimen is rectangular beam containing a mid-edge crack that is loaded by a conventional three-point bend fixture. The results showed the dependency of bone fracture toughness on the state of mode mixity. The fracture surfaces of broken CBB specimens under different loading conditions were studied via scanning electron microscopy (SEM) observations. Fracture surface of all investigated cases (i.e. pure mode I, pure mode II and mixed mode I/II) exhibited smooth patterns demonstrating brittle fracture of bovine femur. The higher density of vascular channels and micro-cracks initiated in the weakened area surrounded by secondary osteons were found to be the main cause of the decreased bone resistance against crack growth and brittle fracture

Classification and Lateralization of Temporal Lobe Epilepsies with and without Hippocampal Atrophy Based on Whole-Brain Automatic MRI Segmentation

Brain images contain information suitable for automatically sorting subjects into categories such as healthy controls and patients. We sought to identify morphometric criteria for distinguishing controls (n = 28) from patients with unilateral temporal lobe epilepsy (TLE), 60 with and 20 without hippocampal atrophy (TLE-HA and TLE-N, respectively), and for determining the presumed side of seizure onset. The framework employs multi-atlas segmentation to estimate the volumes of 83 brain structures. A kernel-based separability criterion was then used to identify structures whose volumes discriminate between the groups. Next, we applied support vector machines (SVM) to the selected set for classification on the basis of volumes. We also computed pairwise similarities between all subjects and used spectral analysis to convert these into per-subject features. SVM was again applied to these feature data. After training on a subgroup, all TLE-HA patients were correctly distinguished from controls, achieving an accuracy of 96 ± 2% in both classification schemes. For TLE-N patients, the accuracy was 86 ± 2% based on structural volumes and 91 ± 3% using spectral analysis. Structures discriminating between patients and controls were mainly localized ipsilaterally to the presumed seizure focus. For the TLE-HA group, they were mainly in the temporal lobe; for the TLE-N group they included orbitofrontal regions, as well as the ipsilateral substantia nigra. Correct lateralization of the presumed seizure onset zone was achieved using hippocampi and parahippocampal gyri in all TLE-HA patients using either classification scheme; in the TLE-N patients, lateralization was accurate based on structural volumes in 86 ± 4%, and in 94 ± 4% with the spectral analysis approach. Unilateral TLE has imaging features that can be identified automatically, even when they are invisible to human experts. Such morphometric image features may serve as classification and lateralization criteria. The technique also detects unsuspected distinguishing features like the substantia nigra, warranting further study

Comparison between pulpotomy with MTA (made in Iran) and formocresol in primary molars of 3-6 years old children attending the department of pediatric dentistry, School of Dentistry, Medical Sciences/ University of Tehran in 2004

Background and Aim: Formocresol (FC) has been a popular pulpotomy medicament for primary dentition in recent decades. Concerns have been raised about the toxicity and potential carcinogenicity of FC, and alternatives have been proposed. Recently, the physical and biological properties of mineral trioxide aggregate (MTA) have been described in many studies. The aim of this study was to compare the success rate of pulpotomy with MTA (made in Iran) and FC in primary molars."nMaterials and Methods: In this clinical trial, 30 primary molars needing pulpotomy treatment were selected and randomly divided into two groups: (15 teeth in FC and 15 in MTA group). The teeth were then pulpotomized and restored. Clinical and radiographic results were recorded at 1-3-6-9 and 12 months and success rates of two groups were compared using Fisher’s exact test with p<0.05 as the level of significance. "nResults: After 12 months, there was no statistical significant difference between MTA group (85.8%) and FC group (93.3%) (P 1.0). The only observed radiographic failure was internal resorption. "nConclusion: Based on the results of this study, MTA can be used as an alternative to formocresol in primary teeth pulpotomy

The Comparison of the Risk Factors in the Term and Preterm Delivery

BACKGROUND AND OBJECTIVE: Premature delivery is the presence of progressive uterine contractions before reaching 37 weeks of pregnancy. Since it is associated with perinatal complications and high costs, this study aimed to study the risk factors for premature delivery. METHODS: This cross-sectional study was conducted on 377 pregnant women with preterm labor (23-37 weeks) and 423 pregnant women of term delivery referring to Ayatollah Rohani Hospital of Babol city, Iran. We extracted and investigated the subjects&rsquo; demographic data, history of infertility, smoking habits, use of drugs, fast food consumption, history or presence of maternal illnesses and surgery, Urinary Tract Infections (UTI), Oligohydramnios, intrauterine growth restriction (IUGR), embryonic anomalies, premature rupture of membranes, vaginal bleeding as well as the neonatal data. FINDINGS: As observed in the two groups of preterm and term delivery respectively, there was employment during pregnancy in 83 (22%) and 51 (12%) cases, a history of preterm labor in 41 (10.9%) versus 21 (5%) cases, bleeding during the first trimester in 118 (31.3%) versus 61 (14.4%) cases, fast food consumption in 34 (9%) versus 14 (3.3%) cases, UTI in 150 (39.8%) versus 111 (26.2%) cases, anemia in 62 (16.4%) versus 29 (6.9%) cases, hypertension in 72 (19.1%) versus 13 (3.1%) cases and finally, smoking habits in 22 (5.8%) versus 5 (1.2%) subjects. There was a statistically significant association between the aforementioned variables (p<0.05). CONCLUSION: According to the results of this study, the most significant risk factors for premature delivery could be managed and controlle

GSTM1 and GSTP1 polymorphisms and glutathione S-transferase activity: Iranian infertile men

&quot;nBackground: Pi-GST and Mu-GST are subclasses of glutathione S-transferase that present on human sperm surface and play an important role against oxidative stress. Therefore, any defects in the enzyme activity may be associated with male infertility.In this study the polymorphisms of GSTM1 and GSTP1 in association with enzyme activity and sperm parameters were studied. &quot;nMethods: This case-control study involved 95 men with oligoastenoteratozoospermia and 26 controls with normozoospermia. Semen analyses were carried out according to WHO guidelines. Blood DNA was extracted using salting out procedures. GSTM1 and GSTP1 polymorphisms gene were determined through PCR-RFLP and multiplex PCR, respectively. Finally, Glutathione S-transferase activity was measured. &quot;nResults: Frequencies of GSTM1 null genotype in oligoastenoteratospermic and normospermic groups were 52.1% and 53.8% respectively. There were no statistically significant differences in sperm parameters and enzyme activity between GSTM1 null and positive genotypes in two groups. There were no statistically significant differences in glutathione S-transferase activity between oligoastenoteratospermia and normospermic groups (p&amp;gt;0.05). All the 121 men in this study had Ile/Ile genotypes at 105 codon of GSTP1. Frequency of normal homozygote (114Ala/Ala), heterozygote (114Ala/Val) and mutant homozygote (114Val/Val) genotypes in oligoastenoteratospermic group were 81.1%, 17.9% and 1.1% respectively but in the control group they were 88.5%, 11.5% and null. &quot;nConclusions: Total glutathione S-transferase activity and sperm parameters were not affected by deficient Glutathione S-transferase activity in GSTM1 null genotype. Compensate activity of other sperm surface glutathione S-transferase isozymes, like GSTP1, may justify the cause

Fracture and microstructural study of bovine bone under mixed mode I/II loading

Understanding the fracture behavior and associated crack growth mechanism in bone material is an important issue for biomechanics and biomaterial researches. Fracture of bone often takes place due to complex loading conditions which result in combined tensile-shear (i.e. mixed mode) fracture mechanism. Several parameters such as loading type, applied loading direction relative to the bone axis, loading rate, age and etc., may affect the mixed mode fracture resistance and damage mechanism in such materials. In this research, a number of mixed mode I/II fracture experiments are conducted on bovine femur bone using a sub-sized test configuration called "compact beam bend (CBB)" specimen to investigate the fracture toughness of bone under different mode mixities. The specimen is rectangular beam containing a mid-edge crack that is loaded by a conventional three-point bend fixture. The results showed the dependency of bone fracture toughness on the state of mode mixity. The fracture surfaces of broken CBB specimens under different loading conditions were studied via scanning electron microscopy (SEM) observations. Fracture surface of all investigated cases (i.e. pure mode I, pure mode II and mixed mode I/II) exhibited smooth patterns demonstrating brittle fracture of bovine femur. The higher density of vascular channels and micro-cracks initiated in the weakened area surrounded by secondary osteons were found to be the main cause of the decreased bone resistance against crack growth and brittle fracture