Thermally-stable, syntactic pyrrone foams

Foam formulations may be readily emplaced in honeycomb structures after heating to soft, doughlike consistency and forcing heated mixture into honeycomb cells. Final cure can be accomplished by simple oven cure, with no need for containment or restriction of foam formulation during cure

Development of dielectric windows for space- craft antennas third quarterly report, 1 jan. - 31 mar. 1964

Dielectric windows for spacecraft antennas - screening tests of reinforced plastic

Library Materials For Children

Library materials for children cannot be considered alone, because the term library has long implied more than a collection of books. It is fitting that this topic follows papers discussing goals, facilities, staff, services, and children themselves. A collection of materials is a means, not an end. There is evidence that the isolation of materials from the concept of service is not a new problem. Jesse Shera notes that the development in the nineteenth century of the American public library began with collections of books donated by successful businessmen and philanthropists to uplift the minds of the young. When the Boston Public Library opened its doors in 1854, however, those under eighteen were not admitted. The mere fact that collections of materials for youth existed and had encouraged library development did not mean that children were actually given service. 1 This paper will attempt to raise questions about materials for children in today's public library, their characteristics and availability; and to discuss the relation of materials to other elements of library service.published or submitted for publicatio

Preparation and characterization of the Pyrrones as thermal structural materials

Development of technique for preparing foam materials to be used as thermal structural components in spacecraft constructio

Primary neurons that express the L2/HNK-1 carbohydrate during early development in the zebrafish

In zebrafish, many nerve pathways in both the CNS and periphery are pioneered by a small and relatively simple set of ‘primary’ neurons that arise in the early embryo. We now have used monoclonal antibodies to show that, as they develop, primary neurons of several functional classes express on their surfaces the L2/HNK-1 tetrasaccharide that is associated with a variety of cell surface adhesion molecules. We have studied the early labeling patterns of these neurons, as well as some non-neural cells, and found that the time of onset and intensity of immunolabeling vary specifically according to cell type. The first neuronal expression is by Rohon-Beard and trigeminal ganglion neurons, both of which are primary sensory neurons that mediate touch sensitivity. These cells express the epitope very strongly on their growth cones and axons, permitting study of their development unobscured by labeling in other cells. Both types initiate axogenesis at the same early time, and appear to be the first neurons in the embryo to do so. Their peripheral neurites display similar branching patterns and have similar distinctive growth cone morphologies. Their central axons grow at the same rate along the same longitudinal fiber pathway, but in opposite directions, and where they meet they appear to fasciculate with one another. The similarities suggest that Rohon-Beard and trigeminal ganglion neurons, despite their different positions, share a common program of early development. Immunolabeling is also specifically present on a region of the brain surface where the newly arriving trigeminal sensory axons will enter the brain. Further, the trigeminal expression of the antigen persists in growth cones during the time that they contact an individually identified central target neuron, the Mauthner cell, which also expresses the epitope. These findings provide descriptive evidence for possible roles of L2/HNK-1 immunoreactive molecules in axonal growth and synaptogenesis

Development and optimization of pyrrone polymers, June 1966 - June 1967

Development and optimization of pyrrone polymer

Improving the Functional Control of Aged Ferroelectrics using Insights from Atomistic Modelling

We provide a fundamental insight into the microscopic mechanisms of the ageing processes. Using large scale molecular dynamics simulations of the prototypical ferroelectric material PbTiO3, we demonstrate that the experimentally observed ageing phenomena can be reproduced from intrinsic interactions of defect-dipoles related to dopant-vacancy associates, even in the absence of extrinsic effects. We show that variation of the dopant concentration modifies the material's hysteretic response. We identify a universal method to reduce loss and tune the electromechanical properties of inexpensive ceramics for efficient technologies.Comment: 6 pages, 3 figure

Dynamic and sequential patterning of the zebrafish posterior hindbrain by retinoic acid

AbstractA prominent region of the vertebrate hindbrain is subdivided along the anterior–posterior axis into a series of seven segments, or rhombomeres. The identity of each rhombomere is specified by the expression of conserved transcription factors, including Krox-20, vHnf1, Val (Kreisler, Mafb) and several Hox proteins. Previous work has shown that retinoic acid (RA) signaling plays a critical role in regulating the expression of these factors and that more posterior rhombomeres require higher levels of RA than more anterior rhombomeres. Models to account for RA concentration dependency have proposed either a static RA gradient or increasing time periods of RA exposure. Here, we provide evidence against both of these models. We show that early zebrafish rhombomere-specification genes, including vhnf1 in r5–r6 and hoxd4a in r7, initiate expression sequentially in the hindbrain, each adjacent to the source of RA synthesis in paraxial mesoderm. By knocking down RA signaling, we show that progressively more posterior rhombomeres require increasingly higher levels of RA signaling, and vhnf1 and hoxd4a expression are particularly RA-dependent. RA synthesis is required just at the time of initiation, but not for maintenance, of vhnf1 and hoxd4a expression. Furthermore, a premature RA increase causes premature activation of vhnf1 and hoxd4a expression. Our results support a new model of dynamic RA action in the hindbrain, in which a temporally increasing source of RA is required to sequentially initiate progressively more posterior rhombomere identities

Adult Barriers To Higher Education: A Comparison Of Gender, Age, And Ethnicity In Faith-Based Colleges

The study compares the responses of students in nontraditional undergraduate and graduate degree programs from three faith-based institutions and multiple campuses to determine what barriers exist for adult students. Nontraditional, in this case, refers to degree programs offered within the context of night classes and accelerated programs of study that cater primarily to working adults