Modeling growth paths of interacting crack pairs in elastic media

The problem of predicting the growth of a system of cracks, each crack influencing the growth of the others, arises in multiple fields. We develop an analytical framework toward this aim, which we apply to the 'En-Passant' family of crack growth problems, in which a pair of initially parallel, offset cracks propagate nontrivially toward each other under far-field opening stress. We utilize boundary integral and perturbation methods of linear elasticity, linear elastic fracture mechanics, and common crack opening criteria to calculate the first analytical model for curved En-Passant crack paths. The integral system is reduced under a hierarchy of approximations, producing three methods of increasing simplicity for computing crack paths. The last such method is a major highlight of this work, using an asymptotic matching argument to predict crack paths based on superposition of simple, single-crack fields. Within the corresponding limits of the three methods, all three are shown to agree with each other. We provide comparisons to exact results and existing experimental data to verify certain approximation steps

Lifshitz Interaction between Dielectric Bodies of Arbitrary Geometry

A formulation is developed for the calculation of the electromagnetic--fluctuation forces for dielectric objects of arbitrary geometry at small separations, as a perturbative expansion in the dielectric contrast. The resulting Lifshitz energy automatically takes on the form of a series expansion of the different many-body contributions. The formulation has the advantage that the divergent contributions can be readily determined and subtracted off, and thus makes a convenient scheme for realistic numerical calculations, which could be useful in designing nano-scale mechanical devices

Study of Hydraulic Properties and Design Criteria for a River Subsurface Intake without Cut Off

Experimental Studie

Use of an Observational Coding System with Families of Adolescents: Psychometric Properties among Pediatric and Healthy Populations

Objective: To examine reliability and validity data for the Family Interaction Macro-coding System (FIMS) with adolescents with spina bifida (SB), adolescents with type 1 diabetes mellitus (T1DM), and healthy adolescents and their families.Methods: Sixty-eight families of children with SB, 58 families of adolescents with T1DM, and 68 families in a healthy comparison group completed family interaction tasks and self-report questionnaires. Trained coders rated family interactions using the FIMS.Results: Acceptable interrater and scale reliabilities were obtained for FIMS items and subscales. Observed FIMS parental acceptance, parental behavioral control, parental psychological control, family cohesion, and family conflict scores demonstrated convergent validity with conceptually similar self-report measures.Conclusions: Preliminary evidence supports the use of the FIMS with families of youths with SB and T1DM and healthy youths. Future research on overall family functioning may be enhanced by use of the FIMS

Characterizing the spiking dynamics of subthalamic nucleus neurons in Parkinson's disease using generalized linear models

Accurately describing the spiking patterns of neurons in the subthalamic nucleus (STN) of patients suffering from Parkinson's disease (PD) is important for understanding the pathogenesis of the disease and for achieving the maximum therapeutic benefit from deep brain stimulation (DBS). We analyze the spiking activity of 24 subthalamic neurons recorded in Parkinson's patients during a directed hand movement task by using a point process generalized linear model (GLM). The model relates each neuron's spiking probability simultaneously to factors associated with movement planning and execution, directional selectivity, refractoriness, bursting, and oscillatory dynamics. The model indicated that while short-term history dependence related to refractoriness and bursting are most informative in predicting spiking activity, nearly all of the neurons analyzed have a structured pattern of long-term history dependence such that the spiking probability was reduced 20–30 ms and then increased 30–60 ms after a previous spike. This suggests that the previously described oscillatory firing of neurons in the STN of Parkinson's patients during volitional movements is composed of a structured pattern of inhibition and excitation. This point process model provides a systematic framework for characterizing the dynamics of neuronal activity in STN

Identification of transcription-factor genes expressed in the Arabidopsis female gametophyte

Dongfang Wang, Changqing Zhang, David J. Hearn, Il-HO Kang, megan I. Skaggs, Karen S. Schumaker, and Ramin Yadegari are with the School of Plant Sciences, University of Arizona, Tucson, Arizona 85721-0036, USA -- Il-Ho Kang, Jayson A. Punwani, and Gary N. Drews are with the Department of Biology, University of Utah, Salt Lake City, Utah 84112-0840, USA -- Changqing Zhang is with The Section of Molecular, Cell and Developmental Biology, University of Texas at Austin, Austin, Texas 78712-0159, USA -- David J. Hearn is with the Department of Biological Sciences, Towson University, Towson, Maryland 21252-0001, USA -- Il-Ho Kang is with the Department of Horticulture, Iowa State University, Ames, Iowa 50011-1100, USA --Jayson A. Punwani is with the Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280, USABackground In flowering plants, the female gametophyte is typically a seven-celled structure with four cell types: the egg cell, the central cell, the synergid cells, and the antipodal cells. These cells perform essential functions required for double fertilization and early seed development. Differentiation of these distinct cell types likely involves coordinated changes in gene expression regulated by transcription factors. Therefore, understanding female gametophyte cell differentiation and function will require dissection of the gene regulatory networks operating in each of the cell types. These efforts have been hampered because few transcription factor genes expressed in the female gametophyte have been identified. To identify such genes, we undertook a large-scale differential expression screen followed by promoter-fusion analysis to detect transcription-factor genes transcribed in the Arabidopsis female gametophyte. Results Using quantitative reverse-transcriptase PCR, we analyzed 1,482 Arabidopsis transcription-factor genes and identified 26 genes exhibiting reduced mRNA levels in determinate infertile 1 mutant ovaries, which lack female gametophytes, relative to ovaries containing female gametophytes. Spatial patterns of gene transcription within the mature female gametophyte were identified for 17 transcription-factor genes using promoter-fusion analysis. Of these, ten genes were predominantly expressed in a single cell type of the female gametophyte including the egg cell, central cell and the antipodal cells whereas the remaining seven genes were expressed in two or more cell types. After fertilization, 12 genes were transcriptionally active in the developing embryo and/or endosperm. Conclusions We have shown that our quantitative reverse-transcriptase PCR differential-expression screen is sufficiently sensitive to detect transcription-factor genes transcribed in the female gametophyte. Most of the genes identified in this study have not been reported previously as being expressed in the female gametophyte. Therefore, they might represent novel regulators and provide entry points for reverse genetic and molecular approaches to uncover the gene regulatory networks underlying female gametophyte development.Cellular and Molecular [email protected]

Electronic States of Magnetic Quantum Dots

We study quantum states of electrons in magnetically doped quantum dots as a function of exchange coupling between electron and impurity spins, the strength of Coulomb interaction, confining potential, and the number of electrons. The magnetic phase diagram of quantum dots, doped with a large number of magnetic Mn impurities, can be described by the energy gap in the spectrum of electrons and the mean field electron-Mn exchange coupling. A competition between these two parameters leads to a transition between spin-unpolarized and spin-polarized states, in the absence of applied magnetic field. Tuning the energy gap by electrostatic control of nonparabolicity of the confining potential can enable control of magnetization even at the fixed number of electrons. We illustrate our findings by directly comparing Mn-doped quantum dots with parabolic and Gaussian confining potential.Comment: 5 pages, 5 figures, Part of Focus on Spintronics in Reduced Dimension