Aluminum runway surface as possible aid to aircraft braking

Several concepts are described for use singly or in combination to improve aircraft braking. All involve a thin layer of aluminum covering all or part of the runway. Advantage would derive from faster heat conduction from the tire-runway interface. Heating of tread surface with consequent softening and loss of friction coefficient should be reduced. Equations are developed indicating that at least 99 percent of friction heat should flow into the aluminum. Preliminary test results indicate a coefficient of sliding friction of 1.4, with predictably slight heating of tread. Elimination of conventional brakes is at least a remote possibility

Comparative chromosome band mapping in primates byin situ suppression hybridization of band specific DNA microlibraries

A DNA-library established from microdissected bands 8q23 to 8q24.1 of normal human chromosomes 8 (Lüdecke et al., 1989) was used as a probe for chromosomal in situ suppression (CISS-) hybridization to metaphase chromosomes of man and primates including Hylobates lar and Macaca fuscata. Comparative band mapping as first applied in this study shows the specific visualization of a single subchromosomal region in all three species and thus demonstrates that synteny of the bulk sequences of a specific human chromosome subregion has been conserved for more than 20 million years

Fluorescence in situ hybridization of YAC clones after Alu-PCR amplification

Alu-PCR protocols were optimized for the generation of human DNA probes from yeast strains containing yeast artificial chromosomes (YACs) with human inserts between 100 and 800 kb in size. The resulting DNA probes were used in chromosome in situ suppression (CISS) hybridization experiments. Strong fluorescent signals on both chromatids indicated the localization of specific YAC clones, while two clearly distinguishable signals were observed in ≥90% of diploid nuclei Signal intensities were generally comparable to those observed using chromosome-specific alphoid DNA probes. This approach will facilitate the rapid mapping of YAC clones and their use in chromosome analysis at all stages of the cell cycle

Sorting of chromosomes by magnetic separation

Chromosomes were isolated from Chinese hamster x human hybrid cell lines containing four and nine human chromosomes. Human genomic DNA was biotinylated by nick translation and used to label the human chromosomes by in situ hybridization in suspension. Streptavidin was covalently coupled to the surface of magnetic beads and these were incubated with the hybridized chromosomes. The human chromosomes were bound to the magnetic beads through the strong biotin-streptavidin complex and then rapidly separated from nonlabeled Chinese hamster chromosomes by a simple permanent magnet. The hybridization was visualized by additional binding of avidin-FITC (fluorescein) to the unoccupied biotinylated human DNA bound to the human chromosomes. After magnetic separation, up to 98% of the individual chromosomes attached to magnetic beads were classified as human chromosomes by fluorescence microscopy

Delineation of individual human chromosomes in metaphase and interphase cells by in situ suppression hybridization using recombinant DNA libraries

A method of in situ hybridization for visualizing individual human chromosomes from pter to qter, both in metaphase spreads and interphase nuclei, is reported. DNA inserts from a single chromosomal library are labeled with biotin and partially preannealed with a titrated amount of total human genomic DNA prior to hybridization with cellular or chromosomal preparations. The cross-hybridization of repetitive sequences to nontargeted chromosomes can be markedly suppressed under appropriate preannealing conditions. The remaining single-stranded DNA is hybridized to specimens of interest and detected with fluorescent or enzymelabeled avidin conjugates following post-hybridization washes. DNA inserts from recombinant libraries for chromosomes 1, 4, 7, 8, 13, 14, 18, 20, 21, 22, and X were assessed for their ability to decorate specifically their cognate chromosome; most libraries proved to be highly specific. Quantitative densitometric analyses indicated that the ratio of specific to nonspecific hybridization signal under optimal preannealing conditions was at least 8:1. Interphase nuclei showed a cohesive territorial organization of chromosomal domains, and laserscanning confocal fluorescence microscopy was used to aid the 3-D visualization of these domains. This method should be useful for both karyotypic studies and for the analysis of chromosome topography in interphase cells

Rapid interphase and metaphase assessment of specific chromosomal changes in neuroectodermal tumor cells by in situ hybridization with chemically modified DNA probes

Repeated DNAs from the constitutive heterochromatin of human chromosomes 1 and 18 were used as probes in nonradioactive in situ hybridization experiments to define specific numerical and structural chromosome aberrations in three human glioma cell lines and one neuroblastoma cell line. The number of spots detected in interphase nuclei of these tumor cell lines and in normal diploid nuclei correlated well with metaphase counts of chromosomes specifically labeled by in situ hybridization. Rapid and reliable assessments of aneuploid chromosome numbers in tumor lines in double hybridization experiments were achieved, and rare cells with bizarre phenotype and chromosome constitution could be evaluated in a given tumor cell population. Even with suboptimal or rare chromosome spreads specific chromosome aberrations were delineated. As more extensive probe sets become available this approach will become increasingly powerful for uncovering various genetic alterations and their progression in tumor cells

Adrift upon a salinity-stratified sea

The structure and variability of upper-ocean properties in the Bay of Bengal (BoB) modulate air-sea interactions, which profoundly influence the pattern and intensity of monsoonal precipitation across the Indian subcontinent. In turn, the bay receives a massive amount of freshwater through river input at its boundaries and from heavy local rainfall, leading to a salinity-stratified surface ocean and shallow mixed layers. Small-scale oceanographic processes that drive variability in near-surface BoB waters complicate the tight coupling between ocean and atmosphere implicit in this seasonal feedback. Unraveling these ocean dynamics and their impact on air-sea interactions is critical to improving the forecasting of intraseasonal variability in the southwest monsoon. To that end, we deployed a wave-powered, rapidly profiling system capable of measuring the structure and variability of the upper 100 m of the BoB. The evolution of upper-ocean structure along the trajectory of the instrument’s roughly two-week drift, along with direct estimates of vertical fluxes of salt and heat, permit assessment of the contributions of various phenomena to temporal and spatial variability in the surface mixed layer depth. Further, these observations suggest that the particular “barrier-layer” stratification found in the BoB may decrease the influence of the wind on mixing processes in the interior, thus isolating the upper ocean from the interior below, and tightening its coupling to the atmosphere abov

Multicolour interphase cytogenetics: 24 chromosome probes, 6 colours, 4 layers

From the late 1980s onwards, the use of DNA probes to visualise sequences on individual chromosomes (fluorescent in-situ hybridisation - FISH) revolutionised the study of cytogenetics. Following single colour experiments, more fluorochromes were added, culminating in a 24 colour assay that could distinguish all human chromosomes. Interphase cytogenetics (the detection of chromosome copy number in interphase nuclei) soon followed, however 24 colour experiments are hampered for this application as mixing fluorochromes to produce secondary colours produces images that are not easily distinguishable from overlapping signals. This study reports the development and use of a novel protocol, new fast hybridising FISH probes, and a bespoke image capture system for the assessment of chromosome copy number in interphase nuclei. The multicolour probe sets can be used individually or in sequential hybridisation layers to assess ploidy of all 24 human chromosomes in the same nucleus. Applications of this technique are in the investigation of chromosome copy number and the assessment of nuclear organisation for a range of different cell types including human sperm, cancer cells and preimplantation embryos