Structural dynamic testing of composite propfan blades for a cruise missile wind tunnel model

The Naval Weapons Center at China Lake, California is currently evaluating a counter rotating propfan system as a means of propulsion for the next generation of cruise missiles. The details and results of a structural dynamic test program are presented for scale model graphite-epoxy composite propfan blades. These blades are intended for use on a cruise missile wind tunnel model. Both dynamic characteristics and strain operating limits of the blades are presented. Complications associated with high strain level fatigue testing methods are also discussed

Effects of orientation and meaning on mental rotation

Reading is a complex ability, for the most part, and performed automatically, especially when the visual stimulus is upright. The present study examined the contribution of mental rotation to reading; participants were timed as they read lists of consonant-vowel-consonant trigrams (CVCs) of varying orientations and meaning. An ANOVA revealed a significant interaction between orientation and meaning, F(3,126)=8.41, MSE=8238 77.99. CVCs misoriented by 180 required the longest response time in the low-meaning condition. However, in the high-meaning condition, CVCs misoriented by 270 ° required a longer response time than those misoriented by 180 o. These paradoxical results may be due to biases produced by previously viewed CVC lists. For lists misoriented by 270 °, participants appeared to rotate the CVCs through a longer (counterclockwise) rather than a shorter clockwise distance in order to read them

Drosophila nuclear proteins bind to regions of alternating C and T residues in gene promoters

Proteins from Drosophila nuclei that bind to regions of alternating C and T residues present in the promoters of the heat shock genes hsp70 and hsp26 and the histone genes his3 and his4 have been purified. These proteins bind to isolated linear DNA, and genomic footprinting analyses indicate that they are bound to DNA in nuclei. In supercoiled plasmids at low pH, some of these DNA sequences adopt triple-helical structures which, if they form in vivo, could significantly affect chromatin structure. The nuclear proteins described here, and not necessarily the deformed conformation of the DNA, may be responsible for maintaining a potentially inducible promoter structure before transcriptional activation

Lessons learned from the development and manufacture of ceramic reusable surface insulation materials for the space shuttle orbiters

Three ceramic, reusable surface insulation materials and two borosilicate glass coatings were used in the fabrication of tiles for the Space Shuttle orbiters. Approximately 77,000 tiles were made from these materials for the first three orbiters, Columbia, Challenger, and Discovery. Lessons learned in the development, scale up to production and manufacturing phases of these materials will benefit future production of ceramic reusable surface insulation materials. Processing of raw materials into tile blanks and coating slurries; programming and machining of tiles using numerical controlled milling machines; preparing and spraying tiles with the two coatings; and controlling material shrinkage during the high temperature (2100-2275 F) coating glazing cycles are among the topics discussed

Characterization of sequences associated with position-effect variegation at pericentric sites in Drosophila heterochromatin

In a variety of organisms, euchromatic genes brought into juxtaposition with pericentric heterochromatin show position-effect variegation (PEV), a silencing of gene expression in a subset of the cells in which the gene is normally expressed. Previously, a P-element mobilization screen identified transgenic Drosophila stocks showing PEV of an hsp70-white+ reporter gene; transgenes in many of these stocks map to the chromocenter of polytene chromosome. A screen at an elevated temperature identified two stocks that under standard culture temperatures show complete repression of the hsp70-white+ transgene. The transgenes in both cases map to the chromocenter of polytene chromosomes. Different types of middle repetitive elements are adjacent to seven pericentric transgenes; unique sequences are adjacent to two of the perimetric transgenes. All of the transgenes show suppression of PEV in response to a mutation in the gene encoding heterochromatin protein 1 (HP1). This suppression correlates with a more accessible chromatin structure. The results indicate that a pericentric transgene showing PEV can be associated with different types of DNA sequences, while maintaining a common association with the chromosomal protein HP1

A Drosophila melanogaster H3.3 cDNA encodes a histone variant identical with the vertebrate H3.3

A cDNA encoding an H3.3 histone variant in Drosophila melanogaster predicts a protein with an amino acid (aa) sequence identical with that in vertebrates. The D. melanogaster H3.3 nucleotide (nt) sequence has diverged significantly from that of both the H3.3 gene of vertebrates and the H3.1 gene of D. melanogaster, largely through third nt changes in its codons. The perfect H3.3 aa sequence conservation between organisms as phylogenetically divergent as vertebrates and flies suggests that the H3.3 histone variant itself is an important structural component of chromatin, apart from the value of its replication-independent expression pattern. Keywords: Conserved proteins, amino acid sequence homologies, chromatin, bacteriophage λ library, invertebrat

A Course-Based Research Experience: How Benefits Change with Increased Investment in Instructional Time

There is widespread agreement that science, technology, engineering, and mathematics programs should provide undergraduates with research experience. Practical issues and limited resources, however, make this a challenge. We have developed a bioinformatics project that provides a course-based research experience for students at a diverse group of schools and offers the opportunity to tailor this experience to local curriculum and institution-specific student needs. We assessed both attitude and knowledge gains, looking for insights into how students respond given this wide range of curricular and institutional variables. While different approaches all appear to result in learning gains, we find that a significant investment of course time is required to enable students to show gains commensurate to a summer research experience. An alumni survey revealed that time spent on a research project is also a significant factor in the value former students assign to the experience one or more years later. We conclude: 1) implementation of a bioinformatics project within the biology curriculum provides a mechanism for successfully engaging large numbers of students in undergraduate research; 2) benefits to students are achievable at a wide variety of academic institutions; and 3) successful implementation of course-based research experiences requires significant investment of instructional time for students to gain full benefit