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  • Articles  (97)
  • Other Sources  (162)
  • GEOPHYSICS  (162)
  • Amino Acid Sequence  (57)
  • Biochemistry and Biotechnology
  • Physics
  • 1995-1999
  • 1990-1994  (259)
  • 1980-1984
  • 1994  (259)
Collection
  • Articles  (97)
  • Other Sources  (162)
Years
  • 1995-1999
  • 1990-1994  (259)
  • 1980-1984
Year
  • 1
    Publication Date: 2019-07-13
    Description: Auroral hiss is observed to propagate over distances comparable to an Earth radius from its source in the auroral oval. The role of Landau damping is investigated for upward propagating auroral hiss. By using a ray tracing code and a simplified model of the distribution function, the effect of Landau damping is calculated for auroral hiss propagation through the environment around the auroral oval. Landau damping is found to be the likely mechanism for explaining some of the one-sided auroral hiss funnels observed by Dynamics Explorer 1. It is also found that Landau damping puts a lower limit on the wavelength of auroral hiss. Poleward of the auroral oval, Landau damping is found in a typical case to limit omega/k(sub parallel) to values of 3.4 x 10(exp 4) km/s or greater, corresponding to resonance energies of 3.2 keV or greater and wavelengths of 2 km or greater. For equatorward propagation, omega/k(sub parallel) is limited to values greater than 6.8 x 10(exp 4) km/s, corresponding to resonance energies greater than 13 keV and wavelengths greater than 3 km. Independent estimates based on measured ratios of the magnetic to electric field intensity also show that omega/k(sub parallel) corresponds to resonance energies greater than 1 keV and wavelengths greater than 1 km. These results lead to the difficulty that upgoing electron beams sufficiently energetic to directly generate auroral hiss of the inferred wavelength are not usually observed. A partial transmission mechanism utilizing density discontinuities oblique to the magnetic field is proposed for converting auroral hiss to wavelengths long enough to avoid damping of the wave over long distances. Numerous reflections of the wave in an upwardly flared density cavity could convert waves to significantly increased wavelengths and resonance velocities.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A2; p. 2471-2488
    Format: text
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  • 2
    Publication Date: 1994-09-02
    Description: As a step toward developing poliovirus as a vaccine vector, poliovirus recombinants were constructed by fusing exogenous peptides (up to 400 amino acids) and an artificial cleavage site for viral protease 3Cpro to the amino terminus of the viral polyprotein. Viral replication proceeded normally. An extended polyprotein was produced in infected cells and proteolytically processed into the complete array of viral proteins plus the foreign peptide, which was excluded from mature virions. The recombinants retained exogenous sequences through successive rounds of replication in culture and in vivo. Infection of animals with recombinants elicited a humoral immune response to the foreign peptides.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Andino, R -- Silvera, D -- Suggett, S D -- Achacoso, P L -- Miller, C J -- Baltimore, D -- Feinberg, M B -- AI22346/AI/NIAID NIH HHS/ -- AI35545/AI/NIAID NIH HHS/ -- RR00169/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1994 Sep 2;265(5177):1448-51.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Microbiology and Immunology, University of California, San Francisco.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8073288" target="_blank"〉PubMed〈/a〉
    Keywords: Amino Acid Sequence ; Animals ; Antibodies, Bacterial/biosynthesis ; Antibodies, Viral/biosynthesis ; Antigens, Bacterial/genetics/immunology ; Antigens, Viral/genetics/immunology ; Base Sequence ; Cloning, Molecular ; *Genetic Engineering ; Genetic Vectors ; HeLa Cells ; Humans ; Macaca fascicularis ; Mice ; Mice, Transgenic ; Molecular Sequence Data ; Poliovirus/*genetics/immunology/physiology ; Poliovirus Vaccine, Oral/*genetics ; *Protein Biosynthesis ; Proteins/metabolism ; Recombinant Proteins/biosynthesis/metabolism ; Vaccines, Synthetic/genetics/*immunology ; Virus Replication
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2011-08-24
    Description: High-energy electrons have been measured systematically in a low-altitude (520 x 675 km), nearly polar (inclination = 82 deg) orbit by sensitive instruments onboard the Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX). Count rate channels with electron energy thresholds ranging from 0.4 MeV to 3.5 MeV in three different instruments have been used to examine relativistic electron variations as a function of L-shell parameter and time. A long run of essentially continuous data (July 1992 - July 1993) shows substantial acceleration of energetic electrons throughout much of the magnetosphere on rapid time scales. This acceleration appears to be due to solar wind velocity enhancements and is surprisingly large in that the radiation belt 'slot' region often is filled temporarily and electron fluxes are strongly enhanced even at very low L-values (L aprroximately 2). A superposed epoch analysis shows that electron fluxes rise rapidly for 2.5 is approximately less than L is approximately less than 5. These increases occur on a time scale of order 1-2 days and are most abrupt for L-values near 3. The temporal decay rate of the fluxes is dependent on energy and L-value and may be described by J = Ke-t/to with t(sub o) approximately equals 5-10 days. Thus, these results suggest that the Earth's magnetosphere is a cosmic electron accelerator of substantial strength and efficiency.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 6; p. 409-412
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  • 4
    Publication Date: 2019-06-28
    Description: We investigate the possibility of perpendicular heating of electrons and the generation of '90 deg -electron conics' by particle diffusion in velocity space due to wave-particle interaction with intense auroral kilometric radiation. This interaction is made possible by the downward shift in the R-X cutoff below the electron cyclotron frequency that occurs in the presence of warm plasma. We stimulate this condition and solve the diffusion equation using a finite difference algorithm. The results show strong perpendicular electron heating and indicate that the main characteristics of an electron conic distribution can be reproduced under these conditions.
    Keywords: GEOPHYSICS
    Type: NASA-198815 , NAS 1.26:198815
    Format: application/pdf
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  • 5
    Publication Date: 2019-07-13
    Description: The respose of ClO concentrations to changes in NO2 concentrations has been inferred from simultaneous observations of (ClO), (NO), (NO2) and (O3) in the midlatitude lower stratosphere. This analysis demonstrates that (ClO) is inversely correlated with (NO2), consistent with formation and photolysis of (ClONO2). A factor of ten range in the concentration if NO2 was sampled (0.1 to 1 x 10(exp 9) mol/cu cm), with a comparable range in the ratio of (ClO) to total available inorganic chlorine (1% less than or equal to (ClO)/(Cl(sub y)) less than or equal to 5%. This analysis leads to an estimate of (ClONO2)/(Cl(sub y)) = 0.12 (x/2), in the mid-latitude, lower-stratospheric air masses sampled.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 21; 23; p. 2543-2546
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  • 6
    Publication Date: 2019-07-13
    Description: Analyses are presented for the first high-time resolution multisatellite study of the spatial and temporal characteristics of a relativistic electron enhancement event with a rapid onset. Measurements of MeV electrons were made from two low-altitude polar orbiting satellites and three spacecraft at synchronous altitude. The electron fluxes observed by the low-altitude satellites include precipitating electrons in both the bounce and drift loss cones as well as electrons that are stably trapped, whereas the observations at geosynchronous altitude are dominated by the trapped population. The fluxes of greater than 1 MeV electrons at low-satellite altitude over a wide range of L shells tracked very well the fluxes greater than 0.93 MeV at synchronous altitude.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A9; p. 17,421-17,426
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  • 7
    Publication Date: 2019-08-28
    Description: Using IMP 6, 7, and 8 magnetic field and plasma data, we have determined statistical occurrance properties of bulk flow and magnetic field orientation near the midtail neutral sheet. Characteristics of bulk plasma flow and magnetic field significantly change according to the radial distance down the tail. High-speed flow events (v greater than 300 km/s) are essentially restricted to the region tailward of X = -2.5 R(sub E) and are predominatly sunward or tailward. The low-speed flows were nearly equally likely to be in any direction, with the occurace rate of dustward and sunward flow being larger than that of tailward and dawnward flow. Dustward flow occurrence is highest in the region Earthward of X = -2.5 R(sub E), while sunward flow occurrence is highest in the region tailward of X = -2.5 R(sub E). The significance of the dawn-to-dust flow in the near-Earth region obtained in our study supports the idea that there exists a very effective mechanism to accelerate ions in the dawn-to-dust direction and hence the relief of pressure buildup in the near-Earth region. During high-speed flow events the relationship between B(sub Z) polarity and plasma flow direction is largely consistent with that expected from the magnetic reconnenection processes associted with substorms. There are also significant numbers of negative B9sub Z) events that are not associated with tailward flow. Mechanism other than substorm neutral line should therefore also taken into account to explain general B(sub Z) polarity in the midtail region.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 99; A12; p. 23,591-23,601
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  • 8
    ISSN: 0006-3592
    Keywords: monoclonal antibody ; glycosylation ; cell culture ; fed-batch ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many mammalian cell fed-batch processes rely on maintaining the cells in a viable and productive state for extended periods of time in order to reach high final concentrations of secreted protein. In the work described herein, a nonamplified NSO cell line was transfected with a vector expressing a recombinant human anti-HIV gp 120 monoclonal antibody (Mab) and a selectable marker, glutamine synthetase. A fed-batch process was developed which improved product yields tenfold over the yields reached in batch culture. In this case, the clone was cultured for a period of 22 days and produced 0.85 g Mab/L. To gauge the effect of extended culture lifetime on product quality, biochemical characteristics of MAb isolated from different time points in the fed-batch culture were determined. The apparent molecular weight of the MAb was constant throughout the course of the culture. Isoelectric focusing revealed four major charged species, with a fifth more acidic species appearing later in the culture. The antigen binding kinetics were constant for MAb isolated throughout the culture period. Glycosylation analysis, on the other hand, revealed that MAb produced later in the culture contained greater percentages of truncated N-acetylglucosamine and highmannose N-glycans. Possible contributions to this underglycosylated material from either cell lysis or synthesis from noviable cells were found to be negligible. Instead, the viable cells appeared to be secreting more truncated and high mannose MAb glycoforms as the culture progressed. © 1994 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 1362-1366 
    ISSN: 0006-3592
    Keywords: Saccharomyces cerevisiae ; bioaccumulation ; gel immobilization ; cross-flow microfiltration ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cross-flow microfiltration was shown to retain Saccharomyces cerevisiae biomass utilized for heavy metal bioaccumulation. The passage of metal-laden influent through a series of sequential bioaccumulation systems allowed for further reductions in the levels of copper, cadmium, and cobalt in the final effluent than that afforded by a single bioaccumulation process. Serial bioaccumulation systems also allowed for partial separation of metals from dual metal influents. More than one elemental metal cation could be accumulated simultaneously and in greater quantities than when a single metal was present in the effluent (Cu2+ 0.43 mmol, Cu2+ + Cd2+ 0.67 mmol, and Cu2+ + Co2+ 0.83 mmol/g yeast dry mass when the initial concentration of each of the metal species was 0.2 mmol·L-1). Co-accumulation of two different metal cations allowed higher total levels of bioaccumulation than found with a single metal. The flux rate was 2.9 × 102 L·h-2μm-2 using a polypropylene microfiltration membrane (0.1 μm pore size) at 25°C. © 1994 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 297-302 
    ISSN: 0006-3592
    Keywords: cell walls ; metal binding ; polymers ; yeast ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Isolated cell walls of the yeast Saccharomyces cerevisiae were treated by either chemical (alkali and acid) or enzymatic (protease, mannanase or β-glucuronidase) processes to yield partially purified products. These products were partially characterized by infrared analysis. They were subsequently reacted with heavy metal cation solutions and the quantity of metal accumulated by the cell wall material determined. The Cu2+ ion (0.24, 0.36, 1.12, and 0.60 μmol/mg) was accumulated to a greater extent than either Co2+ (0.13, 0.32, 0.43, and 0.32 μmol/mg) or Cd2+ (0.17, 0.34, 0.39, and 0.32 μmol/mg) by yeast cell walls, glucan, mannan, and chitin, respectively The isolated components each accumulated greater quantities of the cations than the intact cell wall. Removal of the protein component of the yeast cell walls by Pronase caused a 29.5% decrease in metal accumulation by yeast cell walls per mass, indicating the protein is a heavy metal accumulating component. The data indicate that the outer mannan-protein layer of the yeast cell wall is more important than the inner glucan-chitin layer in heavy metal action accumulation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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