Space telescope phase B definition study. Volume 2A: Science instruments, astrometer

The analysis and design of an astrometer instrument for the space telescope are discussed. The design concepts utilize the astrometric multiplexing area scanner and the OTA fine guidance sensor

Real-time sensing of optical alignment

The Large Deployable Reflector and other future segmented optical systems may require autonomous, real-time alignment of their optical surfaces. Researchers have developed gratings located directly on a mirror surface to provide interferometric sensing of the location and figure of the mirror. The grating diffracts a small portion of the incident beam to a diffractive focus where the designed diagnostics can be performed. Mirrors with diffraction gratings were fabricated in two separate ways. The formation of a holographic grating over the entire surface of a mirror, thereby forming a Zone Plate Mirror (ZPM) is described. Researchers have also used computer-generated hologram (CGH) patches for alignment and figure sensing of mirrors. When appropriately illuminated, a grid of patches spread over a mirror segment will yield a grid of point images at a wavefront sensor, with the relative location of the points providing information on the figure and location of the mirror. A particular advantage of using the CGH approach is that the holographic patches can be computed, fabricated, and replicated on a mirror segment in a mass production 1-g clean room environment

Study of alternate optical and fine guidance sensor designs for the space infrared telescope facility (SIRTF)

A unique optical design was developed that compensates for the coma degraded images caused by field chopping in SIRTF. The conic constants of a Cassegrain telescope were altered to compensate for the coma induced by the secondary mirror tilt. The modulation transfer function is essentially independent of secondary mirror tilt, and diffraction limited image quality is maintained over a several arcminute field during chopping. With an untilted secondary mirror, the coma compensated (CC) design has a smaller field than the unchopped Ritchey-Chretien design; but use of relay optics, such as the inverted Cassegrain design developed for the fine guidance sensor (FGS), can increase the CC telescope's field size. A reactionless secondary mirror chopper mechanism that uses superconducting magnets was studied. The heart producing elements are confined to a reaction plate that is not directly viewed by the IR focal plane. A design was also developed for a low moment of inertia, reticulated HIP beryllium secondary mirror consistent with blank fabrication technology and optical finishing requirements

Informing Workers of the Right to Workplace Representation: Reasonably Moving From the Middle of the Highway to the Information Superhighway

The National Labor Relations Act gives American workers the right to workplace representation, yet many workers do not exercise this right because they lack the information necessary to make an informed decision during a union\u27s organizing campaign and subsequent election. The rules of union access to employer property prevent organizers from reaching workers with meaningful information. In an effort to balance a union\u27s access to workers, unions are given the names and addresses of the workers they seek to organize. Although achieving balance was a goal of introducing home visits to the representation campaign, unions are nonetheless still at a clear disadvantage in reaching workers with information. This Article recommends technology as a partial remedy to the imbalance in representation campaigns through the use of e-mail and Internet web sites. It recommends that employers provide un- ions with e-mail addresses of workers who have access to e-mail and it suggests that employers post notices of union Internet web sites. Through the use of technology more employees can receive the information necessary to effectuate their right to organize in the workplace

Computational analysis of space transfer vehicle engine turbopump diffuser design for deep-throttling

Space Transfer Vehicles (STV) are expected to perform missions (orbital transfer, Lunar/Mars transfer and descents) which will require deep-engine throttling thrust capability. To accomplish this, turbopumps which can efficiently provide a wide range of flow outputs are needed. The current state-of-the-art cryogenic fuel and oxidizer turbopump designs do not perform efficiently at off-design flow rates mainly due to stall and flow separation in the diffuser. This thesis examines how boundary layer control techniques can be used to control, reduce or eliminate diffuser flow separation. A finite element based code, FIDAP, was used to study flow in a diffuser by developing a 2-D diffuser model and establishing conditions for flow separation. Various rates of suction (removing decelerating fluid particles) and blowing (reenergizing decelerating fluid particles) were tested for their effectiveness in suppressing or eliminating the flow separation at an off-design flow rate. The results showed that FIDAP can be used effectively to model boundary layer control by suction and blowing in a diffuser operating at 60% of design flow. Suction was implemented at various flow rates through the top of the diffuser and shown to be effective at a rate of 15% in counteracting the incidence effects at the inlet of the diffuser and reduce the region of flow separation. Blowing was also shown to be effective in reenergizing the boundary layer to reduce the region of flow separation

Using Argumentative Discussion to Enhance the Written Arguments of Middle School Students in Social Studies Classrooms

The purpose of this study was to explore the effects of Walton, Reed, and Macagno's (2008) dialectical framework on middle school students' historical discussions and written arguments. To do this,151 middle school students from six classrooms were randomly assigned to one of two conditions and asked to participate in a three-week intervention that featured: (a) examining three controversial topics in history, (b) primary source documents, (b) argumentative discussions, and (c) constructing argumentative essays. Because students were taught in small groups, the average performance of 12 groups of students who were assigned to the experimental condition was compared to the average performance of 12 groups of students who were assigned to the comparison conditions. Students in the experimental condition learned argumentative schemes and asked critical questions during discussions. Students in the comparison condition participated in the same historical investigations, received the same materials for instruction, engaged in discussions, and learned about text structure for writing argumentative essays in ways comparable to the experimental group, but used a traditional set of questions during discussions. The findings indicated a significant relationship between teaching students to use argumentative schemes and to ask critical questions during discussions and performance on students' resulting content knowledge. Main effects were also evident regarding students' historical thinking, a writing outcome that reflected use of evidence, ability to write from an author's perspective, use of contextual information, and the inclusion of rebuttals in their essays. While significant differences were not present between conditions on three outcome measures (i.e., reading comprehension, length of essays, or overall writing quality) students' in both sets of groups averaged moderate-to-high scores for reading comprehension and constructed essays that were considered proficient or advanced on the PSSA writing rubric. Taken together, the results of the study were encouraging and align with many of those in the existing literature, which emphasize the positive effects of integrating discussion in classroom activities

Theoretical efficiency of the Princeton two-element echelle spectrograph

Echelle spectrometer for use with spaceborne stellar telescope in Advanced Princeton Satellite Stud

Mapping of transcription start sites of human retina expressed genes

BACKGROUND: The proper assembly of the transcriptional initiation machinery is a key regulatory step in the execution of the correct program of mRNA synthesis. The use of alternative transcription start sites (TSSs) provides a mechanism for cell and tissue specific gene regulation. Our knowledge of transcriptional initiation sequences in the human genome is limited despite the availability of the complete genome sequence. While genome wide experimental and bioinformatic approaches are improving our knowledge of TSSs, they lack information concerning genes expressed in a restricted manner or at very low levels, such as tissue specific genes. RESULTS: In this study we describe the mapping of TSSs of genes expressed in human retina. Genes have been selected on the basis of their physiological or developmental role in this tissue. Our work combines in silico analysis of ESTs and known algorithm predictions together with their experimental validation via Cap-finder RACE. We report here the TSSs mapping of 54 retina expressed genes: we retrieved new sequences for 41 genes, some of which contain un-annotated exons. Results can be grouped into five categories, compared to the RefSeq; (i) TSS located in new first exons, (ii) splicing variation of the second exon, (iii) extension of the annotated first exon, (iv) shortening of the annotated first exon, (v) confirmation of previously annotated TSS. CONCLUSION: In silico and experimental analysis of the transcripts proved to be essential for the ultimate mapping of TSSs. Our results highlight the necessity of a tissue specific approach to complete the existing gene annotation. The new TSSs and transcribed sequences are essential for further exploration of the promoter and other cis-regulatory sequences at the 5'end of genes

Suppression of spin-state transition in epitaxially strained LaCoO_{3}

Epitaxial thin films of LaCoO_{3} (E-LCO) exhibit ferromagnetic order with a transition temperature T_c = 85 K, while polycrystalline thin LaCoO_{3} films (P-LCO) remain paramagnetic. The temperature-dependent spin-state structure for both E-LCO and P-LCO was studied by x-ray absorption spectroscopy at the Co L_{2,3} and O K edges. Considerable spectral redistributions over temperature are observed for P-LCO. The spectra for E-LCO, on the other hand, do not show any significant changes for temperatures between 30 K and 450 K at both edges, indicating that the spin state remains constant and that the epitaxial strain inhibits any population of the low-spin (S = 0) state with decreasing temperature. This observation identifies an important prerequisite for ferromagnetism in E-LCO thin films.Comment: 5 pages, 5 figures, submitted to Physical Review

Identification of a novel CRYBB2 missense mutation causing congenital autosomal dominant cataract

Purpose: To identify the genetic defect in a four-generation Croatian family presenting with autosomal dominant cataract. Methods: Genome-wide linkage analysis with 250K single nucleotide polymorphism (SNP) arrays was performed using DNA from one unaffected and seven affected individuals. Mutation screening of candidate genes was performed by bidirectional Sanger sequencing. Results: Evidence for linkage was observed for eight genomic regions. Among these was a locus on chromosome 22 which encompasses the β-crystallin gene cluster. This cluster includes four genes, namely beta-crystallin B1 (CRYBB1), beta-crystallin B2 (CRYBB2), beta-crystallin B3 (CRYBB3), and beta-crystallin A4 (CRYBA4). A novel sequence variant was found in the CRYBB2 gene (p.Arg188His). This variant cosegregated with the disease phenotype in all affected individuals but was not present in the unaffected family members and 100 healthy control subjects. Conclusions: We report a novel missense mutation, p.Arg188His, in CRYBB2 associated with congenital cataract in a family of Croatian origin. This variant is the most COOH-terminal missense mutation in CRYBB2 that has been identified so far. Congenital cataracts occur with a frequency of 30:100,000 in developed countries and most of them are caused by mutations in genes that are associated with the len