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  • 1
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    Event Horizon Telescope imaging of the archetypal blazar 3C 279 at an extreme 20 microarcsecond resolution (2020)
    EDP Sciences
    Details
    Publication Date: 2020-08-01
    Description: 3C 279 is an archetypal blazar with a prominent radio jet that show broadband flux density variability across the entire electromagnetic spectrum. We use an ultra-high angular resolution technique – global Very Long Baseline Interferometry (VLBI) at 1.3 mm (230 GHz) – to resolve the innermost jet of 3C 279 in order to study its fine-scale morphology close to the jet base where highly variable γ-ray emission is thought to originate, according to various models. The source was observed during four days in April 2017 with the Event Horizon Telescope at 230 GHz, including the phased Atacama Large Millimeter/submillimeter Array (ALMA), at an angular resolution of ∼20 μas (at a redshift of z = 0.536 this corresponds to ∼0.13 pc  ∼ 1700 Schwarzschild radii with a black hole mass MBH = 8 × 108 M⊙). Imaging and model-fitting techniques were applied to the data to parameterize the fine-scale source structure and its variation. We find a multicomponent inner jet morphology with the northernmost component elongated perpendicular to the direction of the jet, as imaged at longer wavelengths. The elongated nuclear structure is consistent on all four observing days and across different imaging methods and model-fitting techniques, and therefore appears robust. Owing to its compactness and brightness, we associate the northern nuclear structure as the VLBI “core”. This morphology can be interpreted as either a broad resolved jet base or a spatially bent jet. We also find significant day-to-day variations in the closure phases, which appear most pronounced on the triangles with the longest baselines. Our analysis shows that this variation is related to a systematic change of the source structure. Two inner jet components move non-radially at apparent speeds of ∼15 c and ∼20 c (∼1.3 and ∼1.7 μas day−1, respectively), which more strongly supports the scenario of traveling shocks or instabilities in a bent, possibly rotating jet. The observed apparent speeds are also coincident with the 3C 279 large-scale jet kinematics observed at longer (cm) wavelengths, suggesting no significant jet acceleration between the 1.3 mm core and the outer jet. The intrinsic brightness temperature of the jet components are ≲1010 K, a magnitude or more lower than typical values seen at ≥7 mm wavelengths. The low brightness temperature and morphological complexity suggest that the core region of 3C 279 becomes optically thin at short (mm) wavelengths.
    Print ISSN: 0004-6361
    Electronic ISSN: 1432-0746
    Topics: Physics
    Published by EDP Sciences
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  • 2
    Electronic Resource
    Electronic Resource
    The V amylose-H2O system: Structural changes resulting from hydration (1974)
    New York : Wiley-Blackwell
    Biopolymers 13 (1974), S. 779-790 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: X-ray diffraction and stereochemical analyses were used to study the hydrated structure of the helical amylose polymorph having a fiber repeat spacing of 8 Å. Intensity calculations using computer models confirmed six as the number of residues per turn and supported the space group P212121. Both diffraction intensity and stereochemical methods indicate the suitability of residue G3 from the potassium acetate complex of cyclohexaamylose as opposed to residues with longer O(4)-O(1) vectors. Comparison of the present results with those obtained for V amylose dehydrate indicated no major conformational differences between the two helix skeletons. A net helical rotation of approximately 30° accompanied the hydrate-dehydrate transition and the rotational position in the hydrate allowed packing that was less close. Hydration water molecules were not located; noncarbohydrate peaks on the electron density maps were primarily due to Fourier series termination errors.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1974.360130413
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  • 3
    Electronic Resource
    Electronic Resource
    Naegeli amylodextrin and its relationship to starch granule structure. II. Role of water in crystallization of B-starchJournal Paper No. J-7181 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Proj. 1847. Supported in part by a grant from the Corn Refiners Association and by grant GM 08822 from the National Institutes of Health. (1972)
    New York : Wiley-Blackwell
    Biopolymers 11 (1972), S. 2241-2250 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Although native B-type starch loses its sharp X-ray pattern on strong drying, the wet Nägeli amylodextrin prepared from such starch gives a sharp B-pattern, that is only slightly reduced in sharpness by complete drying. Nägeli amylodextrin dried admixed with a noncrystalline “filler” (e.g., starch sirup) gives an X-ray pattern essentially identical to that of the wet amylodextrin, except that the 16-Å (No. 1) ring is greatly reduced in sharpness and intensity. Failure of the B-structure to collapse during drying indicates that water is not intercalated between turns of a helix or otherwise required to maintain the geometry and packing arrangement of the starch molecular chains. Rather, for native starch granules or amylose fibers, water relieves intercrystallite strains and consequent crystallite distortion induced by strong drying. For Nägeli amylodextrin, the small molecules of starch sirup can penetrate the interstices between crystallites and prevent strain build-up during drying. For native starch granules, the interstitial regions are gel-like in character and less permeable to starch sirup molecules. A model for B-starch is proposed, that employs intertwined (double) helices.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1972.360111105
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  • 4
    Electronic Resource
    Electronic Resource
    Circular dichroism of nucleic acid monomers. I. Calculated adenosine and 2′-deoxyadenosine CD spectra (1980)
    New York : Wiley-Blackwell
    Biopolymers 19 (1980), S. 1017-1038 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A combination of the DeVoe and Kirkwood polarizability concepts is developed to calculate CD spectra of nucleic acid monomers. The method is perfectly general and applies to any system where the constituents have absorption properties which are widely separated in terms of frequency. The theory is applied to calculate the CD spectra of adenosine and 2′-deoxyadenosine conformers. Bond polarizabilities are evaluated for the ribosyl moiety of adenosine, as a function of glycosidic rotational angles and polarizability anisotropies. It is found that a wide range of C-C and C-O bond polarizabilities give similar CD results. Isotropic atom polarizabilities are also evaluated. It is found that the CD results using these polarizabilities do not differ significantly from those obtained with bond polarizabilities. The CD spectra of adenosine and 2′-deoxyadenosine are calculated for three x-ray diffraction determined geometries: A-form RNA, B-form DNA, and C-form DNA. The results indicate that the monomer CD spectra are strongly dependent on the precise geometry and appear to be of importance in understanding the spectra of oligomers and polymers. The deoxyadenosine conformers are found to have calculated CD spectra which are less intense than those of the ribosyl conformers. These results indicate that the measured differences between the CD magnitudes of ribo- and deoxyriboadenosine are due to the presence or absence of the 2′-hydroxyl. Weighted averaged adenosine CD spectra are calculated with the aid of probability distributions from conformational energy calculations. The results suggest a new method for obtaining empirical monomer parameters for use in optical calculations. The calculations in this paper indicate for the first time that DeVoe theory, in combination with the Kirkwood theory, provides a useful method for the calculation of the CD spectra of nonpolymeric molecules.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1980.360190507
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  • 5
    Electronic Resource
    Electronic Resource
    Single cell proteins from cellulosic wastes (1974)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 16 (1974), S. 869-880 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Conventional sources of protein cannot meet the present or projected needs for human consumption. Single cell proteins from fermentation of petroleum and cellulosic wastes are likely sources of additional protein. The volume of cellulosic wastes is sufficient to supply all additional protein needs on a continuing basis for cellulose is a renewable resource. Both mesophilic and thermophilic microorganisms utilize cellulose at reasonable rates. Biodegradation of lignin and lignin-cellulose complexes constitutes a major obstacle to commercial utilization of cellulosic wastes. Thermophilic actinomyces appear to be the most effective organisms for single cell protein production from cellulosic wastes.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260160702
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  • 6
    Electronic Resource
    Electronic Resource
    Cellular interactions between 3T3 cells and interleukin-3-dependent multipotent haemopoietic cells: A model system for stromal-cell-mediated haemopoiesis (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 139 (1989), S. 301-312 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: With the aid of a multipotent stem cell line (FDCP-mix cells) co-cultured with either normal or irradiated Swiss 3T3, cellular interactions between stromal cells and haemopoietic stem cells were studied by electron microscopy and time-lapse video microscopy. When cultured in the presence of interleukin 3 (IL-3) but in the absence of stromal cells, the FDCP-mix cells have a characteristic blast morphology. In the absence of IL-3, the cells die unless they are co-cultured with marrow stromal cells or 3T3 cells. In the latter case, they attach, proliferate, and differentiate on both normal and irradiated Swiss 3T3 cell layers without the addition of extrinsic growth factor (IL-3). At the initial attachment sites of these two cell lines, cellular recognition seemed to be mediated by the formation of microvillus cytoplasmic projections and extracellular matrix. These areas may well be the sites of plasma-membrane-bound signalling/adhesional molecules between the interacting cells.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041390212
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  • 7
    Electronic Resource
    Electronic Resource
    Nägeli amylodextrin and its relationship to starch granule structure. I. Preparation and properties of amylodextrins from various starch types (1971)
    New York : Wiley-Blackwell
    Biopolymers 10 (1971), S. 1673-1680 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nägeli-type amylodextrins were prepared from various starch types: native starch granules from potato, waxy maize, wrinkled pea, and high-amylose maize, and from a commercial amylose (“Superlose”). The granular starches and retrograded amylose were treated with 15% sulfuric acid at 22°-25° for 3 months, the undissolved residues were washed free of acid and air dried. X-ray diffraction patterns showed that amylodextrin from waxy maize starch (A-type) and potato starch (B-type) retain the same diffraction type as that of the parent starch. On conversion of a starch to an amylodextrin, the sharpness and intensity of the diffraction patterns are either retained (waxy maize starch), improved (slightly with potato, significantly with high-amylose maize, and very markedly with wrinkled pea) or developed (amylose). The results indicate that the crystalline regions of a native starch granule, retrograded amylose, or amylodextrin are exceedingly resistant to acidic hydrolysis at room temperature. In contrast to the parent starches, native amylodextrins stain little if at all with dilute iodine solution. The iodine stains of dissolved amylodextrins were red (waxy maize), red-purple (potato), or purple (amylose, high-amylose maize, and wrinkled pea).
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360100920
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  • 8
    Electronic Resource
    Electronic Resource
    Origins of the differences between the circular dichroism of DNA and RNA: Theoretical calculations (1973)
    New York : Wiley-Blackwell
    Biopolymers 12 (1973), S. 201-221 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Theoretical calculations of the circular dichroism of double-helical DNA and RNA by the method of Johnson and Tinoco were performed in order to investigate the origins of the optical activity spectral differences between these polynucleotides. Calculations were performed using transition moment directions arising from molecular orbital calculations as well as a transition moment directions in agreement with experimental directions. The results of these calculations indicate that the conservative circular dichroism spectrum of B-form DNA and the nonconservative spectrum of RNA (and A-form DNA) arise as a consequence of the distance between the paired bases and the helix axis. The negative nonconservative spectrum of C-form DNA was calculated and shown also to result from the distance of the paired bases from the helix axis. Several other conspicuous geometric parameters of DNA and RNA were investigated and were found to be less significant in their effects upon the spectral differences. Theoretical calculations on a four-stranded DNA model which has paired bases similarly related to the helix axis as RNA and A-form DNA was found to yield a low intensity, nonconservative circular dichroism spectrum.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1973.360120119
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  • 9
    Electronic Resource
    Electronic Resource
    The structure of V amylose dehydrate: A combined X-ray and stereochemical approach (1975)
    New York : Wiley-Blackwell
    Biopolymers 14 (1975), S. 1487-1501 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Visually integrated, flat-plate film data were collected from oriented filaments of V amylose dehydrated made from dimethyl sulfoxide-amylose; and X-ray diffraction and stereochemical methods were used to search a multidimensional parameter space for the most satisfactory description of the crystal and molecular structure. Results indicate that the helical chains are left-handed and that they pack into the unit cell in an antiparallel arrangement conforming to space group P212121. Packing is very compact with several O …. O contacts in the range 2.70-2.85 Å between both parallel and antiparallel pairs of chains. Other characteristics of the final model are residue geometry similarity to residue 3 from potassium acetate-cyclohexamylose, O(2)i-O(3)i+1 distance of 2.75 Å, O(6) gg, and O(6)i-O(2)i-6 distance of 2.84 Å. Proton magnetic resonance studies of dried, crystalline V amylose dehydrate powder showed only 0.15 water per glucose residue.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1975.360140714
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  • 10
    Electronic Resource
    Electronic Resource
    Circular dichroism of nucleic acid monomers. II. Derivation and application to polymers of a consistent set of guanine and cytosine transition parameters (1983)
    New York : Wiley-Blackwell
    Biopolymers 22 (1983), S. 755-786 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An approximate semiempirical procedure has been developed in order to derive nucleic acid monomer π → π* electronic transition moment parameters. Using the approximate procedure, guanine (G) and cytosine (C) transition moment parameters have been derived from agreement found between calculated weight-averaged and measured CD spectra of cyclic-GMP and cyclic-CMP. The derived base transition moment parameters have been assessed in CD spectral calculations on some G- and C-containing nucleic acids for which reasonably good structural information exists. An attempt was also made at evaluating the likely CD spectral contributions of G and C electric n → π* transition moments whose magnitudes were taken to be the maximum expected. Overall, the results indicate that the derived G and C π → π* transition moment parameters are more successful in nucleic acid CD spectral calculations than those used in previous DeVoe theory CD calculations. In addition, the results indicate that electric n → π* transitions may be of importance in understanding nucleic acid monomer CD spectra but appear to be relatively unimportant in understanding nucleic acid polymer CD spectra. It is concluded that the derived G and C π → π* parameters are more useful in DeVoe theory CD calculations than parameters used previously.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360220214
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