ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
Collection
Keywords
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    Structure and Molecular Mobility at Free Surfaces of an n-Alkane Crystal: A Monte Carlo Simulation (1994)
    s.l. : American Chemical Society
    Macromolecules 27 (1994), S. 1466-1472 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00084a029
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    The Present and Future of Hardness Standard Blocks (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 118 (Dec. 2006), p. 457-462 
    Details
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: Looking at the current status of hardness standards, we occasionally come across the view that itis sufficient that hardness measurements can be matched somewhat forcibly to the hardness values ofstandard blocks. However, if the direct accuracy of a hardness tester and indenter and loading conditions arewell managed and appropriate testing procedures are taken, the measurement of hardness should naturallyagree with the value indicated on a standard block, and “hardness” should be an industrial quantity obtainedin that way. Therefore, we should recognize anew the original purpose of a hardness standard block as astandard tool, such as the daily inspection (indirect verification) of a tester and/or whether testing practicesare under proper management, as well as to make a comparison between testers and/or between indenters.From this standpoint, we, in the capacity of a dedicated test-block manufacturer, discuss the principles ofhardness test methods, the uniformity, durability and trends of hardness standard blocks, and future hardnessstandards relative to the ISO standards, based on our past results from testing and experiments with a numberof standard blocks
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/23/transtech_doi~10.4028%252Fwww.scientific.net%252FSSP.118.457.pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Computer simulation study of the conformational statistics of long chain hydrocarbons in cylindrical potentials (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 5990-5997 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The Monte Carlo method is applied to the study of disordered conformations of polymethylene chains confined in cylindrical mean-field potentials. It is assumed that the molecule, which is composed of 30 united atoms (methylene groups), has fixed bond length and bond angle, and makes quasicontinuous bond rotations. Various statistical properties of the molecule, such as dihedral angle distributions, dihedral angle pair correlations, transverse fluctuations, etc., are calculated vs strength of the mean-field potential. The dihedral angle distributions calculated exhibit the marked reduction of the gauche peaks with increasing potential; it implies the increasing inaccuracy of the usual rotational isomeric model. The dihedral angle pair correlations reveal novel characteristics of the dihedral angle fluctuation: the fluctuation has approximate period of four bonds with marked tendency for the next nearest bonds to counter-rotate. The characteristics are more conspicuous under weaker potential constraint. There are large transverse fluctuations of the chain, the average linear form of the chain being still maintained. These characteristic dihedral angle fluctuation and the transverse deviation of the chain are found to be well understood by a small scale kink model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459484
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    X-ray and thermal studies on the rotator phases of normal higher alcohols C17H35OH, C18H37OH, and their mixtures (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 631-641 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The structure of the rotator phase and the phase transitions in n-alcohols C17, C18, and their mixtures are studied by differential scanning calorimetry (DSC) and by x-ray diffraction. Both the heating and cooling phase diagrams of the binary system are determined. During cooling, a new intermediate phase α' is observed under a temperature region of the usual rotator phase α. These α and α' phases are found to correspond to the rotator-II phase and the rotator-I phase, respectively, of n-paraffins. The dynamical crystal structure in the α phase is revealed by investigation of the diffuse scattering from the single crystal. The characteristic diffuse scattering observed originates from molecular fluctuations due to the translation along and the rotation around the molecular axes. Both modes of the molecular motions are studied separately from the diffuse scattering on the first and on the second layer lines. The translational disorder is described by the averaged relative translation between the nearest neighbor molecules; it is found to be as much as 20% of the repeat period 2.55 A of the polymethylene chain. On the other hand, it is found that the rotational disorder of the molecules is much smaller than the translational. The molecules are found to have a tendency to make their molecular planes parallel. It is suggested that the crystal in the rotator phase consists of domains, within which the molecules are ordered with respect to the orientations of their molecular planes but are making fairly active translations. Such structural model of the rotator phase is found to be quite consistent with that obtained in our recent computer simulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458414
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Monte Carlo simulation of the crystal structure of the rotator phase of n-paraffins. II. Effects of rotation and translation of the rigid molecules (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 89 (1988), S. 2356-2365 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Structures and molecular motions in the rotator phases of n-paraffins are simulated by use of the Monte Carlo method—both rotational and translational degrees of freedom of the molecules being taken into account. Molecules of rigid trans-planar structure are assumed to be placed in a two-dimensional orthorhombic or orthohexagonal lattice with lattice parameters a and b. A model of the nearly continuous molecular motion is adopted in this work; each molecule is assumed to have 36 discrete orientations (in 10° intervals) and 10 discrete translations (in 0.128 A(ring) intervals) around and along the molecular axis, respectively. Molecular packing modes in various lattice systems of different a/b values are examined ranging from that of the ordinary orthorhombic phase (a/b=1.50) to that of the rotator-II (R-II) phase (a/b=31/2). It is found that the crystals in the rotator phases are generally composed of many domains within which molecules are packed more or less in order. In the rotator-I (R-I) phase, fairly large structural changes are observed with the change in a/b value; the structure of the R-I phase reported in our previous MC work should be slightly modified. The structure of the R-II phase, on the other hand, is found to be essentially the same as that of our previous MC work. Modes of the molecular motion in the R-II phase are studied by monitoring the time evolution of the rotational and translational states of all molecules in the system. It is found that the molecules are making fairly active rotational oscillation around one of the six equivalent directions connecting nearest neighbor molecular pairs. The molecules are also making sporadic large rotations to the different directions. The translational motion of the molecules is found to be very active and evidently independent of the rotational motion. The overall molecular motions in the rotator phase are found to be described in terms of the movement of the boundaries of the ordered domains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.455079
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    The surface-ordered phase of n-nonadecane: A molecular dynamics simulation (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 114 (2001), S. 5774-5780 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Behavior of realistic n-nonadecane, C19H40, on the free surface of the melt is investigated by the molecular dynamics simulation. A crystalline thin film made of three layers of lamellas is constructed and used as an initial state of the heating simulation, where we devise a special heating scheme in order to accelerate the rate of convergence to the thermal equilibrium. By very slow heating we find a temperature range (385–410 K) where the middle layer prefers to be in the melt state with both surface layers remaining crystalline; this observation is considered to correspond to the surface freezing recently found in n-alkanes. It is found that the molecules in the surface monolayer align their axes nearly perpendicular to the surface and form well-defined hexagonal packing. It is also found that the molecules in the surface monolayer show large center-of-mass fluctuations, translational and transverse, along the surface normal and parallel to the surface, respectively. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1351162
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Melting and crystallization in thin film of n-alkanes: A molecular dynamics simulation (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 3351-3359 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Recent discovery of the anomalous crystallization in n-alkanes and n-alcohols at the free surfaces of melts has revealed the necessity for much deeper understanding of the molecular mechanism of crystallization. With the aid of large-scale molecular simulation, and by use of a simplified molecular model of bead spring, the molecular processes of melting and crystallization in a thin film of n-alkane are directly observed. It is found that melting of the thin film is greatly influenced by its surface state. The film is more stable when the surface chains are lying perpendicular to the surface, on which the chain ends have marked preference. Crystallization by both rapid and slow cooling of the melt is shown to give rise to a formation of monolayers on the free surfaces. By slow stepwise cooling, the layer-by-layer growth of stacked lamellae is clearly reproduced. Detailed inspection of the molecular processes involved shows that there are considerable differences in the molecular mechanisms of monolayer formation and 3D crystallization. Furthermore, the molecular mobility and diffusivity in the surface monolayer are discussed. It is shown that longitudinal displacements of the chains along their axes are much larger in the monolayer than in the crystals, and that the calculated rate of transverse diffusion in the monolayer shows good comparison with experimental values. The interchanges of the molecules between the melt and the surface monolayers are observed directly; dynamical stability of the surface monolayer is clearly demonstrated. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1287062
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Monte Carlo simulation of the crystal structure of the rotator phase of n-paraffins (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 3790-3794 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Structures of two rotator phases of n-paraffin, orthorhombic and hexagonal rotator phases recently found by Doucet et al., are simulated by use of the Monte Carlo method. Only subcell structures are considered; a layer structure and effects of chain ends are neglected. The molecules of n-paraffin are assumed to take a rigid trans-planar structure, and they are assumed to be packed in an orthorhombic or orthohexagonal lattice, with each molecule having 36 possible orientations around the chain axis. Interactions between nearest-neighbor chains are calculated from van der Waals interactions between nonbonded C–C, C–H, and H–H atom pairs. A Monte Carlo calculation, similar to that used in our previous work on the structure of the low temperature phase of PTFE, is applied to disordered packings of the molecules in the rotator phases. It is found that the crystals in the rotator phases are composed of many ordered domains within which the chains tend to parallel their zigzag planes. The average size of the ordered domains is calculated to be about 30 A(ring) at 400 K. It is shown that this structure explains various experimental results which are not yet well understood.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448891
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of polymer ordering. II. Crystallization from the melt (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 8675-8680 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Detailed microscopic image of polymer crystallization from the melt is searched for by molecular dynamics simulation. In order to accelerate crystallization, a simple model of polymethylene chain is devised; the polymer chain is made of 100 beads (CH2 united atoms) connected by harmonic springs and the lowest energy conformation is a linear stretched sequence of the beads with a slight bending stiffness being imposed. A system of polymer melt, made of 80 chains of C100, is placed between two parallel substrates that represent the growth surface of the lamellae. Initial melt at 600 K is rapidly cooled down to various crystallization temperatures, and the molecular process of crystallization is investigated. We first notice a marked layer structure in the melt near the substrate. We find that the layer structure leads to growing lamellae when cooled below the melting point. It is shown that the growing lamellae have a definite tapered shape and show thickening growth along the chain axis as well as normal growth. The molecular trajectory of the crystallizing chain at the growth front is demonstrated to be a sequence of processes of local adsorption to the growth front followed by stretching along the chain axis and the final fold into crystalline conformation. The chains are found to be very mobile showing active diffusion in the melt and also in the crystal. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1410377
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Solid–solid phase transitions in n-alkanes C23H48 and C25H52: X-ray power diffraction study on new layer stacking in phase V (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 5762-5766 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The solid–solid phase transitions and the crystal structures of odd n-alkanes, n-C23H48, and n-C25H52, were investigated by x-ray powder diffraction. The phase transitions, I→V→RI for n-C23H48 and I→V→IV→RI for n-C25H52, were observed, where phases I, V, IV are the low-temperature ordered phases, and the phase RI is the rotator phase. The crystal structure of phase V was determined by the Rietveld profile refinement method. Phase V is orthorhombic (Pbnm). New molecular layer stacking appears in phase V, while the lamellar structure and the lateral packing of molecules are same as those in phase I and phase IV. The solid–solid phase transitions below the rotator phase transition of odd n-alkanes found to be characterized by the changes in molecular layer stacking are considered to be caused by the increased disorder in the layer surface. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470456
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...