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  • 1
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: It is known that an increase in plasma density in sources of multicharged ions leads to a substantial increase of ion current and slightly improves the ion distribution over charge states. The validity of this statement was verified in experiments with plasma densities not exceeding several units of 1012 cm−3. In the present work it is demonstrated experimentally that, for the electron densities exceeding 1013 cm−3, the regime of plasma confinement in a trap changes significantly and the quasigasdynamic regime of plasma confinement is realized. Comparison of numerical simulations and experimental data showed the essential influence of the anisotropy of electron velocity distribution in a plasma on the ion charge state distribution. This allows looking for the optimal conditions for the creation of highly charged ions in plasma. In this article we also address problems of plasma stability in an axisymmetric mirror trap under powerful microwave pumping. First experiments on ion extraction from a dense plasma pumped by millimeter wave radiation are described. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An essential increase of operation efficiency of electron cyclotron resonance (ECR) multiply charged ion (MCI) sources (that is the increase of the average charge number and current of ion beams) is related to the possibility of achieving more dense plasma and transferring to the so-called quasi-gas dynamic regime of the plasma confinement in mirror traps by pumping with higher frequency. The first results of this experimental investigation of ion charge state distribution in a pulsed ECR source of MCI with pumping by millimeter wave radiation of a powerful gyrotron are presented in the article. Millimeter wave radiation with maximum power W=130 kW, frequency f=37.5 GHz, and pulse duration up to 1.5 ms is used for the experiments. The charge state distribution maximum corresponded to argon charge (+11)-(+12). Total ion saturation current density of the probe achieved 2 A/cm2. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1090-6533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract An experimental investigation is made of x-ray bremsstrahlung in the 2–10 keV range of a pulsed discharge under electron cyclotron resonance conditions in a straight magnetic mirror system pumped by a high-power millimeter radiation beam. The plasma temperature and density were determined from the spectrum and intensity of the x-rays. The results indicate that a quasi-gasdynamic plasma confinement regime is achieved.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1090-6533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The soft X-ray line emission from a pulsed electron-cyclotron resonance discharge in argon, maintained by a high-power millimeter-wavelength beam in a magnetic mirror trap, was studied using a multilayer mirror X-ray monochromator. The X-ray spectrum was measured, and the absolute spectral intensity of emission was determined in a 6–17 nm wavelength range. The discharge can be used as an effective source of soft X-rays with an efficiency of the microwave to X-ray power conversion on a level of 10% and a maximum spectral power density of 7.3 kW/nm at a wavelength of 9 nm.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1090-6533
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Measurements have been made of the ion charge-state distribution in a high-power, pulsed, electron-cyclotron discharge in argon sustained by millimeter radiation. It has been observed that the maximum of the distribution is shifted toward higher charge states compared with the distributions in conventional cw sources of multiply charged ions pumped by centimeter radiation. This shift of the distribution maximum evidently occurs because a so-called quasigasdynamic plasma confinement regime can be established in a magnetic trap when higher-power, shorter-wavelength gyrotron radiation is used, and in this regime, an increase in plasma density is accompanied by an increase in the confinement parameter Nτ, which determines the ion charge distribution.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 101 (1991), S. 115-124 
    ISSN: 1573-4919
    Keywords: DNA topoisomerase I ; camptothecin ; αA-globin gene ; c-Ha-ras gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary Two molecular forms of topoisomerase I differing in size and sensitivity to camptothecin were isolated from calf thymus. Mapping of topo I cleavage sites of the cloned chicken αA-globin and human c-Ha-ras genes was carried out. Camptothecin was shown to affect site specificity of the topoisomerases.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Molecular and cellular biochemistry 40 (1981), S. 29-48 
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary This article covers research work in this laboratory on the structure and function of chromatin. Early studies have led to discovery of skeletal fibrills (nucleonemas) within the nuclei and showed the specific role of histone H1 in chromatin condensation and in restriction of transcription. More recently with the aid of a novel DNP electrophoresis technique the relation of histone HI and non-histone proteins to nucleosomes was studied. Three types of mononucleosomes and a number of subnucleosomes were identified in chromatin digests. The complexes of certain HMG proteins with short DNA segments were isolated and found to originate from transcriptionally active chromatin. Different forms of SV40 minichromosome were characterized. A method for the analysis of nucleosome distribution along the DNA sequence was elaborated and used to show non-random (phased) location of nucleosomes on SV40 DNA. The attachment of DNA to skeletal elements of interphase nuclei and metaphase chromosomes was shown to be a non-random, probably sequence-specific process.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Radiophysics and quantum electronics 38 (1995), S. 817-820 
    ISSN: 1573-9120
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract We describe shaper cavities for the production of ultrashort microwave pulses with a minimum duration of one period of the high-frequency field and a power of several tens of megawatts. Experimental results are presented.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 242 (1994), S. 649-652 
    ISSN: 1617-4623
    Keywords: α-Globin domain ; Hypersensitive sites ; Locus control region ; Chromatin structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distribution of DNase I hypersensitive sites upstream of the chicken α-globin gene cluster was studied. A group of hypersensitive sites with a complex pattern of tissue specificity, including erythroid-specific elements, was found at a distance of 11.5–14.5 kb upstream of the π gene, the first gene in the cluster. The observations indicate that this area, located upstream of the block of AT-rich sequences and MAR sites (at −8 kb) and upstream of the site of permanent DNA attachment to the nuclear matrix (−3 kb), still belongs to the domain of the α-globin genes.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1617-4623
    Keywords: Key words Chicken alpha-globin gene domain ; Northern analysis ; In situ hybridisation ; ggPRX gene ; -14 gene ; pre-mRNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A novel gene transcribed in the direction opposite to that of the globin genes was found in the chicken α-globin gene domain. Northern hybridisation with single-stranded riboprobes revealed that a 4.5-kb poly(A)+ RNA is transcribed in antisense polarity with respect to the globin genes. The transcription unit encoding this RNA seems to overlap the entire cluster of alpha-globin genes and extends at least 15 kb upstream from π, the first of the α-globin genes. This new transcript shows partial sequence homology with that encoded by the human “-14” gene. An oligonucleotide based on part of a restriction fragment of chicken DNA that is 80% homologous to exon 4 of the human “-14” gene hybridises with a 4.5-kb RNA molecule. In situ hybridisation of globin-antisense probes, that detect polyribosomal mRNAs of 1.7 and 2.5 kb on Northern blots, shows these “antisense” transcripts to be present in the cytoplasm. The 4.5-kb RNA is absent in polyribosomal poly(A)+ RNA and may, hence, represent a nuclear pre-mRNA transcribed from the chicken gene that is homologous to the human “-14” gene. The expression of this gene is not specific to erythroid cells; analogous transcripts were also detected in poly(A)+ RNA extracted from a chicken lymphoblastoma cell line (HP50). Taken together, these data allow us to postulate the existence in the chicken genome of a novel gene, for which we suggest the name “ggPRX” in analogy to the murine mProx1, a gene identified in the upstream region of the α-globin gene domain in mice.
    Type of Medium: Electronic Resource
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