Residual Strength Prediction of Aluminum Panels with Multiple Site Damage Using Artificial Neural Networks

Multiple site damage (MSD) cracks are small fatigue cracks that may accumulate at the sides of highly loaded holes in aging aircraft structures. The presence of MSD cracks can drastically reduce the residual strength of fuselage panels. In this paper, artificial neural networks (ANN) modeling is used for predicting the residual strength of aluminum panels with MSD cracks. Experimental data that include 147 unique configurations of aluminum panels with MSD cracks are used. The experimental dataset includes three different aluminum alloys (2024-T3, 2524-T3, and 7075-T6), four different test panel configurations (unstiffened, stiffened, stiffened with a broken middle stiffener, and bolted lap-joints), many different panel widths and thicknesses, and the sizes of the lead and MSD cracks. The results presented in this paper demonstrate that a single ANN model can predict the residual strength for all materials and configurations with high accuracy. Specifically, the overall mean absolute error for the ANN model predictions is 3.82%. Furthermore, the ANN model residual strength predictions are compared to those obtained using the most accurate semi-analytical and computational approaches from the literature. The ANN model predictions are found to be at the same accuracy level of these approaches, and they even outperform the other approaches for many configurations.     

High-Resolution Strain/Stress Measurements by Three-Axis Neutron Diffractometer

Resolution properties of the unconventional high-resolution neutron diffraction three-axis setup for strain/stress measurements of large bulk polycrystalline samples are presented. Contrary to the conventional two-axis setups, in this case, the strain measurement on a sample situated on the second axis is carried out by rocking the bent perfect crystal (BPC) analyzer situated on the third axis of the diffractometer. Thus, the so-called rocking curve provides the sample diffraction profile. The neutron signal coming from the analyzer is registered by a point detector. This new setup provides a considerably higher resolution (at least by a factor of 5), which however, requires a much longer measurement time. The high-resolution neutron diffraction setting can be effectively used, namely, for bulk gauge volumes up to several cubic centimeters, and for plastic deformation studies on the basis of the analysis of diffraction line profiles, thus providing average values of microstructure characteristics over the irradiated gauge volume.     

Minimalna choroba resztkowa w ostrych białaczkach u dzieci i dorosłych

Biological and genetic heterogeneity of acute leukemias is a major cause of therapeutic difficulties. Response to chemotherapy is one of the most important prognostic factors in this group of diseases. In acute lymphoblastic leukemia (ALL), and progressively more in acute myeloid leukemia (AML), the best parameter of that response is the presence of minimal residual disease (MRD). MRD monitoring is performed based on the flow cytometer analysis of leukemic immunophenotypes or detection of gene rearrangement by PCR. Both methods are characterized by high sensitivity and specificity, which clearly distinguishes them from the standard morphologic examination. This review presents the current state of knowledge of the importance and use of MRD in children and adults, in ALL and AML, emphasizing similarities and differences. Current opinions show that the MRD is the most important prognostic factor in ALL and an important factor in AML. Based on current data in children and adults, it seems that in acute lymphoblastic leukemia, presence of MRD is a continuous variable; the older the patient, the higher the risk of MRD and therapy failure. This paper presents also a new insight to the concept of MRD, because of the presence of leukemic stem cells that survive chemotherapy in AML and any of the maturational stages of leukemia-propagating cells in ALL. This idea combines the phenomenon of drug resistance of tumor stem cells and the presence of residual cells undetectable by methods of optical microscopy after applied chemotherapy. The concept of leukemic stem cells explains the occurrence of resistant clones both in ALL and AML. Based on studies of genetic profiles, there is growing evidence to suggest that acute leukemia is a highly heterogeneous disease, which goes hand in hand with the hierarchy of leukemic stem cells and leukemia initiating cells. In the light of the current knowledge based on MRD, it seems necessary to review the concept of complete remission in MRD-positive leukemic patients.     

Current incidence and residual risk of HIV, HBV and HCV at Canadian Blood Services

Estimates of the viral residual risk should be updated to reflect current incidence of infection in blood donors. Incidence rates were estimated for allogeneic whole‐blood donations made to Canadian Blood Services from 2006 to 2009 based on transmissible disease conversions of repeat donations within a 3‐year period. Residual risk was estimated as the incidence multiplied by the window period. The residual risk of HIV was 1 per 8 million donations, HCV 1 per 6·7 million donations and HBV 1 per 1·7 million donations. The residual risk remains low and has decreased for HCV since our previous estimates due to reduced incidence.     

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义齿树脂基托是全口义齿及局部义齿的重要组成部分,由于其具有吸水性和溶解性,加之释放一些残留单体,影响了材料的综合性能,降低了材料的使用寿命,并给患者的健康造成一定的危害。本文就义齿树脂基托的吸水性和溶解性机制及相关问题做一综述。     

Investigating the prevalence of complex fiber configurations in white matter tissue with diffusion magnetic resonance imaging

It has long been recognized that the diffusion tensor model is inappropriate to characterize complex fiber architecture, causing tensor‐derived measures such as the primary eigenvector and fractional anisotropy to be unreliable or misleading in these regions. There is however still debate about the impact of this problem in practice. A recent study using a Bayesian automatic relevance detection (ARD) multicompartment model suggested that a third of white matter (WM) voxels contain crossing fibers, a value that, whilst already significant, is likely to be an underestimate. The aim of this study is to provide more robust estimates of the proportion of affected voxels, the number of fiber orientations within each WM voxel, and the impact on tensor‐derived analyses, using large, high‐quality diffusion‐weighted data sets, with reconstruction parameters optimized specifically for this task. Two reconstruction algorithms were used: constrained spherical deconvolution (CSD), and the ARD method used in the previous study. We estimate the proportion of WM voxels containing crossing fibers to be ～90% (using CSD) and 63% (using ARD). Both these values are much higher than previously reported, strongly suggesting that the diffusion tensor model is inadequate in the vast majority of WM regions. This has serious implications for downstream processing applications that depend on this model, particularly tractography, and the interpretation of anisotropy and radial/axial diffusivity measures. Hum Brain Mapp 34:2747–2766, 2013. © 2012 Wiley Periodicals, Inc.