Stereological measurement and error estimates for three-dimensional fiber orientation

A method is presented for measuring three-dimensional fiber orientation in fiber-reinforced polymers and placing confidence limits on the results. The orientations of individual fibers are determined from the elliptical intersections between the cylindrical fibers and a polished section. This can be done using either manual digitization or automated image analysis. Volume averages for the sample are computed using an orientation-dependent weighting function that corrects for the bias of an area-based sample. Equations are developed for nonuniform fiber lengths, using both number-average and weight-average measures of orientation. Sources of systematic, measurement, and sampling error are discussed and equations for sampling error and the propagation of measurement error are derived. The results use a second-rank tensor to characterize fiber orientation, but the error analysis can be applied to any type of orientation parameter. We implement the technique using manual digitization of optical micrographs. Our implementation accurately measures samples with known orientation, and produces identical results from two perpendicular sections of a glass fiber/nylon injection-molded sample.     

Biomechanical consequences of anterior column fracture of the acetabulum

We conducted a prospective randomized controlled study on the prophylactic effects of short-term intravesical instillation of pirarubicin (THP) against recurrence to determine the effective administration schedule. All patients gave their informed consent. The subjects included bladder cancer patients who had pTa or pT1, and G1 or G2 cancer, and became tumor-free after transurethral resection of the bladder tumor (TUR-BT). After dissolving 30 mg of THP into 5 ml of distilled water, physiological saline was added to adjust the total volume to 50 ml, which was then instilled into the bladder, and was retained for 5 minutes. The schedule of instillation was for daily for 7 consecutive days from the day of TUR-BT and subsequently once a week for 10 weeks, 17 times in total for Group I, and once every two weeks for 6 months (12 times) starting 2 weeks after TUR and subsequently once a month until one year had passed after surgery (6 times), 18 times in total for Group II. The total number of cases was 69 (36 in Group I, 33 in Group II). The tumor-free ratios determined by the Kaplan-Meier analysis were 93.9% in Group I and 72.7% in Group II for one year, and 86.8% in Group I and 59.5% in Group II for two years. There was a statistically significant difference in the tumor-free ratios between the two groups by the generalized Wilcoxon test and the Log rank test (p = 0.0145 and 0.0107, respectively). Multivariated analysis using Cox's comparison hazard model produced p-values of 0.0002, 0.0007, 0.0009 and 0.0040 in the order of therapeutic mode, initial onset/recurrence, stage and number of tumor. Adverse events that forced discontinuation of the therapy for a while occurred in 4.3%. These results demonstrated that short-term intensive intravesical instillation of THP immediately after TUR-BT was a safe and effective therapy.     

Seventh International Workshop on Ataxia-Telangiectasia

Ataxia-telangiectasia (A-T) is a rare hereditary syndrome involving cerebellar degeneration, immunodeficiency, cancer risk, and radiosensitivity. Since the cloning of the A-T gene, ATM, in 1995, research on this pleiotropic disease and its molecular basis has expanded tremendously. ATM is a large protein kinase that appears to be one of the primary sensors of DNA strand-break damage. The vast majority of mutations in ATM result in truncation and destabilization of the protein, but certain missense and splicing errors have been shown to result in a less severe phenotype. A-T heterozygotes have been shown to have a slightly increased risk of cancer, but their increased in vitro radiosensitivity does not seem to result in any in vivo sensitivity. ATM does seem to act as a classic tumor suppressor gene in T-prolymphocytic leukemia, and LOH at the ATM locus is a common event in some tumor types, suggesting a general role for ATM in cancer. Recent work has shown the interaction of ATM with proteins involved in cell cycle control, and the direct phosphorylation of some of these interactors by ATM. ATM knockout mice have been created by several groups, and recapitulate the immunodeficiency, radiosensitivity, cancer risk, and fertility defects of A-T, although the effect on the cerebellum is slight. These diverse topics, and their integration into a global understanding of A-T, were the basis of the 7th International A-T Workshop.     

Recrystallization in Commercially Pure Aluminum

Recrystallization behavior in commercial aluminum with a purity of 99.4 pct was studied by techniques such as high voltage electron microscopy, 100 kV transmission electron microscopy, and light microscopy. Sample parameters were the initial grain size (290 and 24 microns) and the degree of deformation (5 to 30 pct reduction in thickness by cold-rolling). It was found that the original grain boundary region is the preferred site for nucleation. A few intragranular nuclei were, however, also observed. The effectiveness of the nucleation sites is enhanced by the presence of intermetallic particles (FeAl₃), which start to become operative when the degree of deformation is raised from 15 to 30 pct. The temperature of nucleation and of recrystallization decreases when the degree of deformation is increased and the initial grain size is decreased. The recrystallized grain size follows the same trend and it is observed that the refinement of the recrystallized grain size caused by an increasing degree of deformation and decreasing initial grain size is enhanced by the FeAl₃ particles (when the degree of deformation is raised from 15 to 30 pct). Finally, the structural and kinetic observations are discussed and compared with results from an earlier study¹ covering the recrystallization behavior of commercial aluminum of the same purity deformed at higher degrees of deformation (50 to 90 pct reduction in thickness by cold-rolling).     

The effect of boundary conditions on experimentally measured trabecular strain in the thoracic spine

Vertebral bodies are the primary structural entities of the spine, and trabecular bone is the dominant material from which vertebral bodies are composed. Understanding the mechanical characteristics of vertebral trabecular bone, therefore, is of critical importance in the many clinical conditions that affect the spine. Numerous studies have loaded vertebral bodies to investigate the influence of trabecular bone characteristics on deformation and failure patterns, but the methods of load application have been inconsistent. These differences in the method of load application are a potential confounding factor in the interpretation of the experimental results. We investigated this problem by measuring the distribution of minimum principal strain and maximum shear strain magnitude within 6.35 mm thick samples cut from thoracic spine segments (T8-T10) and loaded to simulate three common experimental configurations. Measurements were made using the texture correlation technique, which extracts deformation patterns from digitized contact radiographs of samples under load. The three loading configurations examined were a three-body construct, a single vertebral body loaded through sectioned intervertebral discs, and polymethylmethacrylate molded directly to the endplates. Results indicate that from both probability and spatial distribution standpoints the best simulation of in vivo loading generates the least uniform strains. Loading through disc remnants or through plastic molded to the endplates causes increasing degrees of strain homogenization. This result has implications not only for the design of experiments involving spinal loading, but also for theories concerning the adaptation of trabecular bone to functional loads.     

Initial stages of recrystallization in aluminum of commercial purity

In commercial aluminum with a purity of 99.4 pct, the formation and growth of recrystallization nuclei were studied by techniques such asin-situ annealing in a high voltage electron microscope, transmission electron microscopy and light microscopy. Sample parameters were the initial grain size (370 and 19 microns) and the degree of deformation (50 and 90 pct reduction in thickness by cold-rolling). It was found that the initial grain boundaries and high angle boundaries within the original grains are preferential sites for recrystallization nuclei, and that the effect of such sites is enhanced by the FeAl₃ particles present in the commercial aluminum as impurities. The nucleation temperatures determined by high voltage electron microscopy and transmission electron microscopy decrease markedly when the initial grain size is decreased both after 50 and 90 pct cold rolling; a less pronounced temperature decrease is obtained by increasing the degree of deformation. The size of the recrystallization nuclei, the recrystallization temperature and the recrystallized grain size are reported for the four sample states, and finally the structural and kinetic observations are discussed.     

AODVCS,a new bio-inspired routing protocol based on cuckoo search algorithm for mobile ad hoc networks

Mobile ad hoc networks (MANETs) are becoming an emerging technology that offer several advantages to users in terms of cost and ease of use. A MANET is a collection of mobile nodes connected by wireless links that form a temporary network topology that operates without a base station and centralized administration. Routing is a method through which information is forwarded from a transmitter to a specific recipient. Routing is a strategy that guarantees, at any time, the connection between any two nodes in a network. In this work, we propose a novel routing protocol inspired by the cuckoo search method. Our routing protocol is implemented using Network simulator 2. We chose Random WayPoint model as our mobility model. To validate our work, we opted for the comparison with the routing protocol ad hoc on-demand distance vector, destination sequence distance vector and the bio-inspired routing protocol AntHocNet in terms of the quality of service parameters: packet delivery ratio and end-to-end delay (E2ED).