Evaluation of feasibility of measuring EHD film thickness associated with cryogenic fluids

The feasibility of measuring elastohydrodynamic (EHD) films as formed with a cryogenic (LN2) fluid is evaluated. Modifications were made to an existing twin disk EHD apparatus to allow for disk lubrication with liquid nitrogen. This disk apparatus is equipped with an X-ray system for measuring the thickness of any lubricant film that is formed between the disks. Several film thickness experiments were conducted with the apparatus which indicate that good lubrication films are filmed with LN2. In addition to the film thickness studies, failure analyses of three bearings were conducted. The HPOTP turbine end bearings had experienced axial loads of 36,000 to 44,000 N (8,000 to 10,000 lb). High continuous radial loads were also experienced, which were most likely caused by thermal growth of the inner race. The resulting high internal loads caused race spalling and ball wear to occur

Investigation of instability, dynamic forces, and effect of dynamic loading on strength of cages for the bearings in the high pressure oxygen turbopumps for the space shuttle main engine

Experiments were performed to determine the effect of cyclic loading on bearing cage strength. A long term working tensile load of approximately 1300 N (300 lbs) was found to be the likely maximum. Higher loads caused a decrease in cage tensile strength after the 125,000 cycle testing period. Poisson's ratio in compression was found to be highly dependent upon the direction of the fiberglass plies. At room temperature the value was 0.15 with the plies and 0.68 across the plies. At -196 C (-321 F), the value with the plies was 0.20. The results of the analyses conducted have again demonstrated the critical need for improved lubrication in the high pressure oxygen turbopump bearings. Lubricant films with low shear strength and low friction coefficients promote cage stability and decrease ball/cage forces during marginal operating conditions. The analysis of the effect of combined bearing loads on ball/cage loads has identified a radial load of 3600 N (800 lbs) as the maximum for the current clearance of the balls and cage pockets. Liquid oxygen impinging on the cage in the direction of rotation was found to enhance cage stability

DNA double strand breaks but not interstrand crosslinks prevent progress through meiosis in fully grown mouse oocytes

There is some interest in how mammalian oocytes respond to different types of DNA damage because of the increasing expectation of fertility preservation in women undergoing chemotherapy. Double strand breaks (DSBs) induced by ionizing radiation and agents such as neocarzinostatin (NCS), and interstrand crosslinks (ICLs) induced by alkylating agents such as mitomycin C (MMC), are toxic DNA lesions that need to be repaired for cell survival. Here we examined the effects of NCS and MMC treatment on oocytes collected from antral follicles in mice, because potentially such oocytes are readily collected from ovaries and do not need to be in vitro grown to achieve meiotic competency. We found that oocytes were sensitive to NCS, such that this ionizing radiation mimetic blocked meiosis I and caused fragmented DNA. In contrast, MMC had no impact on the completion of either meiosis I or II, even at extremely high doses. However, oocytes treated with MMC did show ?-H2AX foci and following their in vitro maturation and parthenogenetic activation the development of the subsequent embryos was severely compromised. Addition of MMC to 1-cell embryos caused a similarly poor level of development, demonstrating oocytes have eventual sensitivity to this ICL-inducing agent but this does not occur during their meiotic division. In oocytes, the association of Fanconi Anemia protein, FANCD2, with sites of ICL lesions was not apparent until entry into the embryonic cell cycle. In conclusion, meiotic maturation of oocytes is sensitive to DSBs but not ICLs. The ability of oocytes to tolerate severe ICL damage and yet complete meiosis, means that this type of DNA lesion goes unrepaired in oocytes but impacts on subsequent embryo quality

Measurements of elastohydrodynamic film thickness, wear and tempering behavior of high pressure oxygen turbopump bearings

The reusable design of the Space Shuttle requires a target life of 7.5 hours for the turbopumps of the Space Shuttle main engine (SSME). This large increase from the few hundred seconds required in single-use rockets has caused various problems with the bearings of the turbopumps. The berings of the high pressure oxygen turbopump (HPOTP) were of particular concern because of wear, spalling, and cage failures at service time well below the required 7.5 hours. Lubrication and wear data were developed for the bearings. Since the HPOTP bearings operate in liquid oxygen, conventional liquid lubricants cannot be applied. Therefore, solid lubricant coatings and lubricant transfer from the polytetrafluorethylene (FTFE) cage were the primary lubrication approaches for the bearings. Measurements were made using liquid nitrogen in a rolling disk machine to determine whether usable elastohydrodynamic films could be generated to assist in the bearing lubrication

Evaluation of outer race tilt and lubrication on ball wear and SSME bearing life reductions

Several aspects of the SSME bearing operation were evaluated. The possibility of elastohydrodynamics (EHD) lubrication with a cryogenic fluid was analyzed. Films as thick as .61 microns were predicted with one theory which may be thick enough to provide hydrodynamic support. The film formation, however, is heavily dependent on good surface finish and a low bulk bearing temperature. Bearing dynamics to determine if the radial stiffness of a bearing which are dependent on bearing misalignment were analyzed. Four ball tests were conducted at several environmental conditions from an LN2 bath to 426 C in air. Surface coatings and ball materials are evaluated. Severe wear and high friction are measured for all ball materials except when the balls have surface lubricant coatings

A bioinformatics workflow for detecting signatures of selection in genomic data

The detection of “signatures of selection” is now possible on a genome-wide scale in many plant and animal species, and can be performed in a population-specific manner due to the wealth of per-population genome-wide genotype data that is available. With genomic regions that exhibit evidence of having been under selection shown to also be enriched for genes associated with biologically important traits, detection of evidence of selective pressure is emerging as an additional approach for identifying novel gene-trait associations. While high-density genotype data is now relatively easy to obtain, for many researchers it is not immediately obvious how to go about identifying signatures of selection in these data sets. Here we describe a basic workflow, constructed from open source tools, for detecting and examining evidence of selection in genomic data. Code to install and implement the pipeline components, and instructions to run a basic analysis using the workflow described here, can be downloaded from our public GitHub repository: http://www.github.com/smilefreak/selectionTools

Reduced chromosome cohesion measured by interkinetochore distance is associated with aneuploidy even in oocytes from young mice

It is becoming clear that reduced chromosome cohesion is an important factor in the rise of maternal age-related aneuploidy. This reduction in cohesion has been observed both in human and mouse oocytes, and it can be measured directly by an increase with respect to maternal age in interkinetochore (iKT) distance between a sister chromatid pair. We have observed variations in iKT distance even in oocytes from young mice and wondered if such differences may predispose those oocytes displaying the greatest iKT distances to be becoming aneuploid. Therefore, we used two methods, one pharmacological (Aurora kinase inhibitor) and one genetic (Fzr1 knockout), to raise aneuploidy rates in oocytes from young mice (age, 1-3 mo) and to examine if those oocytes that were aneuploid had greater iKT distances. We observed that for both Aurora kinase inhibition and Fzr1 knockout, iKT distances were significantly greater in those oocytes that became aneuploid compared to those that remained euploid. Based on these results, we propose that individual oocytes undergo loss in chromosomal cohesion at different rates and that the greater this loss, the greater the risk for becoming aneuploid.Supported by an NHMRC project grant (569202) to K.T.J., S.M., and E.A.M. J.E.H. is supported by an Australian Research Council DECRA Fellowship. I.G.-H. and S.M. are supported by grants BFU2007-67464, BFU2008-01808, Consolider CSD2007-00015, and Junta de Castilla y León Grupo de Excelencia GR 265.Peer Reviewe

Dioctahedral mixed K-Na-micas and paragonite in diagenetic to low-temperature metamorphic terrains: bulk rock chemical, thermodynamic and textural constraints

Abstract Metamorphic mineral assemblages in low-temperature metaclastic rocks often contain paragonite and/or its precursor metastable phase (mixed K-Na-white mica). Relationships between the bulk rock major element chemistries and the formation of paragonite at seven localities from Central and SE-Europe were studied, comparing the bulk chemical characteristics with mineral assemblage, mineral chemical and metamorphic petrological data. Considerable overlaps between the projection fields of bulk chemistries of the Pg-free and Pg-bearing metaclastic rocks indicate significant differences between the actual (as analyzed) and effective bulk chemical compositions. Where inherited, clastic, inert phases/constituents were excluded, it was found that a decrease in Na/(Na+Al*) and in K/(K+Al*) ratios of rocks favors the formation and occurrence of Pg and its precursor phases (Al* denotes here the atomic quantity of aluminum in feldspars, white micas and “pure” hydrous or anhydrous aluminosilicates). In contrast to earlier suggestions, enrichment in Na and/or an increase in Na/K ratio by themselves do not lead to formation of paragonite. Bulk rock chemistries favorable to formation of paragonite and its precursor phases are characterized by enrichment in Al and depletion in Na, K, Ca (and also, Mg and Fe2+). Such bulk rock chemistries are characteristic of chemically “mature” (strongly weathered) source rocks of the pelites and may also be formed by synand post-sedimentary magmatism-related hydrothermal (leaching) activity. What part of the whole rock is active in determining the effective bulk chemistry was investigated by textural examination of diagenetic and anchizone-grade samples. It is hypothesized that although solid phases act as local sources and sinks, transport of elements such as Na through the grain boundaries have much larger communication distances. Sodium-rich white micas nucleate heterogeneously using existing phyllosilicates as templates and are distributed widely on the thin section scale. The results of modeling by THERMOCALC suggest that paragonite preferably forms at higher pressures in low-T metapelites. The stability fields of Pg-bearing assemblages increase, the Pg-in reaction line is shifted towards lower pressures, while the stability field of the Chl-Ms-Ab-Qtz assemblage decreases and is shifted towards higher temperatures with increasing Al* content and decreasing Na/(Na+Al*) and K/(K+Al*) ratios

Contradictions of slate formation resolved?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62973/1/392348a0.pd

PTPN22 R620W minor allele is a genetic risk factor for giant cell arteritis

Published online 7 April 2016.Giant cell arteritis (GCA) is one of the commonest forms of vasculitis in the elderly, and may result in blindness and stroke. The pathogenesis of GCA is not understood, although environmental, infectious and genetic risk factors are implicated. One gene of interest is PTPN22, encoding lymphoid protein tyrosine phosphatase (Lyp), expressed exclusively in immune cells, which is proposed to be an 'archetypal non-HLA autoimmunity gene'. The minor allele of a functional PTPN22 single nucleotide polymorphism (rs2476601, R620W), which disrupts an interaction motif in the protein, was originally reported to be associated with biopsy-proven GCA in Spanish patients, with supporting data from three replicate Northern European studies. Recently, this observation was extended with additional patients and controls, and studies encompassing European, Scandinavian, UK and American patients. The aim of our study was to determine the association between PTPN22 rs2476601 (R620W) and biopsy-proven GCA in an Australian case cohort.Susan Lester, Alex W Hewitt, Carlee D Ruediger, Linda Bradbury, Elisabeth De Smit, Michael D Wiese, Rachel Black, Andrew Harrison, Graeme Jones, Geoffrey O Littlejohn, Tony R Merriman, Bain Shenstone, Malcolm D Smith, Maureen Rischmueller, Matthew A Brown, Catherine L Hil