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  • 1
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 177 (1956), S. 1175-1176 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The experiments to be described were carried out with spark circuits of a type and power-level widely used in spectrographic analysis. In each of the circuits shown, Gx represents the control gap determining the striking voltage, while Gz represents the analysis gap which, for convenience in ...
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 37 (1933), S. 495-504 
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 203-207 
    ISSN: 1573-4862
    Keywords: ultrasonics ; synthetic aperture ; spatial frequency ; interior imaging ; acoustic microscopy ; defect detection ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new acoustic synthetic aperture geometry is demonstrated in which the image field is sampled in the spatial frequency domain. This means the sampled field is recorded in a particularly convenient form for presentation to the back propagation algorithms used to reconstruct the field at the object plane. The method has applications in interior visualization. It is difficult to image the interior of solid objects using lens based imaging systems because a different lens geometry must be used for each distinct object material. The system presented here overcomes such problems since both the angular variation of the transmission coefficient at the object-water interface and the aberrations introduced by the velocity mismatch at the object surface may be readily compensated for in the back propagation routine. Experimental results are presented illustrating the detection of four half wavelength diameter defects, spaced by three wavelengths, at a depth of eight wavelengths below the surface of an aluminum block.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1617-4623
    Keywords: Key words Cleavage and polyadenylation specificity factor ; Cleavage stimulation factor ; Drosophila melanogaster ; mRNA processing ; Additional sex combs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Processing of the 3′ end of mRNA precursors depends on several proteins. The multisubunit cleavage and polyadenylation specificity factor (CPSF) is required for cleavage of the mRNA precursor as well as polyadenylation. CPSF interacts with the cleavage stimulatory factor complex (CstF), and this interaction increases the specificity of binding. Following cleavage downstream of the AAUAAA site, CPSF and poly(A) polymerase (PAP) are required for efficient polyadenylation. Recently, it has been shown that 160-kDa subunit of CPSF interacts directly with the 77-kDa subunit of CstF, which is homologous to the product encoded by the Drosophila gene su(f), and with PAP. Here we report the cloning and characterization of a Drosophila homologue of CPSF-160. The 1329-amino acid dCPSF protein exhibits about 45% and 20% sequence identity, respectively, to its mammalian and yeast counterparts over its entire length. We show that the CPSF homologue is expressed throughout development and that CPSF is essential for viability. Mutations in the cpsf gene did not alter the phenotype of homozygous su(f) mutations, suggesting that, for most genes, processing of 3′ termini is not sensitive to small changes in cpsf and su(f) dosage.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1617-4623
    Keywords: Key words Polycomb group ; Trithorax group ; Homeotic mutations ; Drosophila melanogaster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The protein products of Polycomb group (PcG) and trithorax group (trxG) genes are required for the maintenance of the transcriptionally repressed and active states, respectively, of the homeotic genes. Mutations in PcG genes produce gain-of-function (posterior) homeotic transformations, while mutations in trxG genes produce loss-of-function (anterior) homeotic transformations. Double mutant combinations between a PcG gene and a trxG gene suppress the homeotic transformations seen with either mutation alone, suggesting that PcG and trxG genes act antagonistically. The PcG gene Additional sex combs (Asx) is interesting because one mutant allele, Asx P1 , causes both anterior and posterior homeotic transformations. Asx P1 and other Asx mutations were crossed to mutations in the PcG gene Polycomb (Pc) and the trxG gene trithorax (trx). Asx alleles enhance both PcG and trxG homeotic transformations, showing that Asx is required for both the activation and the repression of homeotic loci. Asx also shows strong allele-specific interactions with the PcG genes Pc and super sex combs (sxc). Together, these data indicate that there are functional interactions between Asx, Pc and sxc in vivo. ASX may interact with a PcG complex containing PC and SXC and mediate activation versus repression at target loci, perhaps by interacting directly with the TRX protein.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 287 (1980), S. 580-582 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A recent conference* showed that new types of scanning microscope which promise unique imaging capabilities are rapidly being developed. As well as improved optical microscopes, X rays and acoustic waves are being used for high resolution scanned imaging and energy conversion techniques are ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 56 (1999), S. 807-816 
    ISSN: 1420-9071
    Keywords: Key words. Yeast; aging; senescence; helicase; silencing; nucleolus; metabolism; retrograde signaling.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. The molecular mechanisms of aging are most fully understood for the budding yeast Saccharomyces cerevisiae. Recent advances in our understanding of aging in this organism have enabled researchers to answer some fundamental questions about the aging process. Is aging due to a multitude of ‘mechanisms’ or can there be a key few? Can we design single-gene mutations that will prolong life? Can we prolong life whilst maintaining health and fecundity? The various contributing factors to yeast longevity, uncovered thus far, fall into three classes: DNA metabolism, heterochromatin, and metabolic activity. However, these separate classes may actually represent different aspects of the same aging mechanism based on genome stability. This review examines the recent advances in our understanding of yeast aging and discusses their relevance, if any, to the human condition.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 170 (1979), S. 219-224 
    ISSN: 1617-4623
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We demonstrate that male recombination (MR) second chromosomes, known to act as mutators and recombination inducers in males, function in an equivalent manner in females. We suggest such chromosomes are more properly designated as mutation-recombination chromosomes.
    Type of Medium: Electronic Resource
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