Library

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
  • 1
    Electronic Resource
    Electronic Resource
    Erratum: "Effects of local reactant concentration perturbations in oscillatory catalysis" [J. Chem. Phys. 108, 5565 (1998)] (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1619-1619 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.480659
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Effects of local reactant concentration perturbations in oscillatory catalysis (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 5565-5570 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reaction-rate oscillations in CO oxidation over heterogeneous platinum thin-film catalysts were studied at atmospheric pressure where spatial coupling is due to gas-phase diffusion of reactant concentration gradients. The catalyst was perturbed locally by the introduction of CO directly above the surface, while the resulting spatiotemporal behavior was monitored using infrared imaging. The transient response of the system was studied in both the steady-state and oscillatory regimes, and comparisons are made between the observed behavior and predictions from models for the oscillations. Using these perturbations, global behavior was initiated using a localized effect. Similarities and differences between the induced oscillations and those occurring naturally are discussed, as are tests to vary the phase of the oscillatory cycle. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475946
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Spatial coupling in heterogeneous catalysis (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 8209-8215 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Spatial coupling mechanisms are studied in the heterogeneous catalytic oxidation of carbon monoxide over platinum at atmospheric pressure under oscillatory conditions. Experiments are conducted in a continuous flow reactor, and the reaction rate is monitored using both infrared imaging and thermocouples. The catalysts are in the form of platinum annular thin films on washer-shaped quartz substrates, and they provide highly repeatable oscillatory behavior. Oscillations are typically spatially synchronized with the entire catalyst "flashing'' on and off uniformly. Spatial coupling is investigated by introducing various barriers which split the annular ring in half. Infrared images show that coupling through the gas phase dominates coupling via the diffusion of CO on the surface or heat diffusion through the substrate. The introduction of a localized heat perturbation to the catalyst surface does not induce a transition in the reaction rate. Thus, it is likely that the primary mode of communication is through the gas-phase diffusion of reactants. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.470185
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Spatio-temporal dynamics of oscillatory heterogeneous catalysis: CO oxidation on platinum (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 8614-8625 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Reaction-rate oscillations in the oxidation of carbon monoxide on the surface of platinum catalysts are studied in a continuous flow reactor at atmospheric pressure using infrared imaging. Small-amplitude temperature oscillations (0.2–8 K) result in approximately isothermal conditions, where changes in rate constants, for typical activation energies and temperatures, are small. The catalysts are in the form of platinum thin films on quartz substrates and provide highly repeatable oscillatory behavior. The platinum films are fabricated in the form of annular rings which provide a quasi-one-dimensional geometry in order to simplify comparison to theoretical models. Time-series measurements by means of thermocouples are used to characterize the oscillations. The infrared images show that most oscillations are spatially synchronized to within the 0.25 s time resolution of the experiment. The images also show that "fine structure'' oscillations (i.e., small-amplitude, high frequency oscillations superimposed on larger-amplitude waveforms) are associated with spatially desynchronized patterns. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468963
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Thermal relaxation of the pinned layer magnetization in NiO spin valves (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 5036-5038 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A variation of the switching field of the pinned layer (PL) magnetization in NiO based spin valves was observed as a function of the rate of variation of the applied field. This phenomenon was characterized at low frequencies (0.4–120 Hz) using quasistatic magnetoresistance (MR) transfer curve testing and measurements of the relaxation of the resistance around the quasistatic switching field of the pinned layer (10−1–105 s). The influence of temperature was investigated between room temperature and 125 °C. The relaxation data were fit using a model based on an Arrhenius law thermal activation with a single relaxation time. The variation in the switching field of the pinned layer as a function of the applied field rate was compared to the Kurkijärvi model. The fit parameters in both models are the energy barrier height and the thermally activated volume of nucleation. The parameters derived from both types of experiments agree remarkably well. The understanding of this low frequency magnetic behavior of spin valves allows one to gain insight into the long-term relaxation of the magnetization of the PL in MR readback heads, as well as into the magnetic response of this layer to very short (ns) pulses of field or high frequency (100 MHz) excitations. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370083
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Fabrication and characterization of nanoscale arrays of nickel columns : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4730-4732 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have fabricated arrays of high aspect ratio nickel columns in both PMMA and SiO2, and we have characterized their structure using transmission electron microscopy and scanning electron microscopy. We have also characterized the magnetics of the columns with magnetic force microscopy. Such characterization of high aspect ratio perpendicular magnetic particles is only rarely found in the literature. This work lays a foundation for further studies to test the viability of lithographically defined arrays of magnetic particles as an alternative high density storage medium. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365444
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Scanning magnetoresistance microscopy (SMRM): Imaging with a MR head : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 4696-4698 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a new scanning magnetic microscopy that uses commercial magnetoresistive (MR) record/playback heads as sense probes. A high-resolution, linearized positioning stage is used to raster scan a magnetic sample with respect to the MR head while the head is in physical contact with the sample. An upper bound on the spatial resolution of the scanning magnetoresistance microscope (SMRM) is 100 nm in the "downtrack" direction and 1–2 μm in the "crosstrack" direction of the head. Magnetic force microscopy has better spatial resolution than SMRM, but SMRM gives a more quantifiable signal since the MR head response can be calibrated in a uniform external field. Furthermore, SMRM has the unique ability to apply localized fields to the sample via the inductive write element. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.365530
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    The role of mixing in traveling-wave convection (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1468-1468 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In binary fluid mixtures with negative separation ratio, the conduction state has a vertical concentration gradient, due to the Soret effect, which opposes the destabilizing effect of the vertical temperature gradient. The first convective states are traveling waves (TW) with a phase velocity which is much lower than that of the linear instability. Recent perturbation theory calculations and numerical simulations of this nonlinear, traveling-wave state predict that the linear concentration gradient in the conduction state is eliminated in the interior of the fluid by convective mixing, and the concentration gradient remains only in the boundary layers. It is the persistence of the concentration gradient in these boundary layers which leads to the small but nonzero wave speed. As the Rayleigh number R is increased, convective stirring of the mixture decreases the concentration boundary layers, and the TW phase speed goes continuously to zero. We report experimental studies of these nonlinear, traveling-wave states in ethanol/water mixtures in an annular geometry. The measured TW phase speed as a function of R is in excellent agreement with the theoretical predictions over the entire TW branch. The experiments also confirm that this transition to stationary convection is not hysteretic. The role of mixing and the transport of concentration in the dynamics of nonlinear fronts and pulses observed in this system will also be discussed. [Work supported by DARPA URI Contract No. N00014-86-K-0758.]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.858002
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Scanning magnetoresistance microscopy (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 3263-3265 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a new scanning magnetic microscopy which uses commercial magnetoresistive (MR) record/playback heads as sense probes. Two-dimensional magnetic images are constructed by bringing the MR head into physical contact with the sample, and then acquiring MR voltage while the head is raster scanned using a high resolution (∼1 nm), linearized positioning stage. With currently available MR heads, an upper bound on the spatial resolution is 0.1×2.0 μm. This technique has broad applications beyond the magnetic storage media for which these heads were designed. In addition to magnetic imaging, this instrument can also be used to evaluate contact record and playback processes. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118030
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Pinning and long-time-scale behavior in traveling-wave convection (1991)
    Springer
    Journal of statistical physics 64 (1991), S. 903-912 
    Details
    ISSN: 1572-9613
    Keywords: Convection ; traveling waves ; pattern formation and dynamics ; binary fluid mixtures
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study nonlinear traveling-wave (TW) and stationary states of convection in experiments in ethanol-water mixtures. While the TW phase velocity as a function of Rayleigh number has been recently shown to be in agreement with the predictions of theory and numerical calculations, we find that this velocity is temporally modulated at frequencies corresponding to the travel time of a single convection roll and of a roll pair past a point stationary in the convection cell. This modulation could be due to the pinning of the convection pattern by experimental inhomogeneities. For large Rayleigh numbers where stationary overturning convection is expected, we sometimes observe extremely slow unidirectional TW states. For larger Rayleigh numbers, this slow TW state starts and stops intermittently on a characteristic time scale of several days. The possible origin of these phenomena and their potential utility are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048803
    Library Location Call Number Volume/Issue/Year 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...