715 research outputs found
Response of a Model of CO Oxidation with CO Desorption and Diffusion to a Periodic External CO Pressure
We present a study of the dynamical behavior of a Ziff-Gulari-Barshad model
with CO desorption and lateral diffusion. Depending on the values of the
desorption and diffusion parameters, the system presents a discontinuous phase
transition between low and high CO coverage phases. We calculate several points
on the coexistence curve between these phases. Inclusion of the diffusion term
produces a significant increase in the CO_2 production rate. We further applied
a square-wave periodic pressure variation of the partial CO pressure with
parameters that can be tuned to modify the catalytic activity. Contrary to the
diffusion-free case, this driven system does not present a further enhancement
of the catalytic activity, beyond the increase induced by the diffusion under
constant CO pressure.Comment: 5 pages, RevTe
Quantum radiation pressure on a moving mirror at finite temperature
We compute the radiation pressure force on a moving mirror, in the
nonrelativistic approximation, assuming the field to be at temperature At
high temperature, the force has a dissipative component proportional to the
mirror velocity, which results from Doppler shift of the reflected thermal
photons. In the case of a scalar field, the force has also a dispersive
component associated to a mass correction. In the electromagnetic case, the
separate contributions to the mass correction from the two polarizations
cancel. We also derive explicit results in the low temperature regime, and
present numerical results for the general case. As an application, we compute
the dissipation and decoherence rates for a mirror in a harmonic potential
well.Comment: Figure 3 replaced, changes mainly in Sections IV and V, new appendix
introduced. To appear in Physical Review
Homologous Flares and Magnetic Field Topology in Active Region NOAA 10501 on 20 November 2003
We present and interpret observations of two morphologically homologous
flares that occurred in active region (AR) NOAA 10501 on 20 November 2003. Both
flares displayed four homologous H-alpha ribbons and were both accompanied by
coronal mass ejections (CMEs). The central flare ribbons were located at the
site of an emerging bipole in the center of the active region. The negative
polarity of this bipole fragmented in two main pieces, one rotating around the
positive polarity by ~ 110 deg within 32 hours. We model the coronal magnetic
field and compute its topology, using as boundary condition the magnetogram
closest in time to each flare. In particular, we calculate the location of
quasiseparatrix layers (QSLs) in order to understand the connectivity between
the flare ribbons. Though several polarities were present in AR 10501, the
global magnetic field topology corresponds to a quadrupolar magnetic field
distribution without magnetic null points. For both flares, the photospheric
traces of QSLs are similar and match well the locations of the four H-alpha
ribbons. This globally unchanged topology and the continuous shearing by the
rotating bipole are two key factors responsible for the flare homology.
However, our analyses also indicate that different magnetic connectivity
domains of the quadrupolar configuration become unstable during each flare, so
that magnetic reconnection proceeds differently in both events.Comment: 24 pages, 10 figures, Solar Physics (accepted
Study of flare energy release using events with numerous type III-like bursts in microwaves
The analysis of narrowband drifting of type III-like structures in radio
bursts dynamic spectra allows to obtain unique information about primary energy
release mechanisms in solar flares. The SSRT spatially resolved images and a
high spectral and temporal resolution allow direct determination not only the
positions of its sources but also the exciter velocities along the flare loop.
Practically, such measurements are possible during some special time intervals
when the SSRT (about 5.7 GHz) is observing the flare region in two high-order
fringes; thus, two 1D scans are recorded simultaneously at two frequency bands.
The analysis of type III-like bursts recorded during the flare 14 Apr 2002 is
presented. Using-muliwavelength radio observations recorded by SSRT, SBRS,
NoRP, RSTN we study an event with series of several tens of drifting microwave
pulses with drift rates in the range from -7 to 13 GHz/s. The sources of the
fast-drifting bursts were located near the top of the flare loop in a volume of
a few Mm in size. The slow drift of the exciters along the flare loop suggests
a high pitch-anisotropy of the emitting electrons.Comment: 16 pages, 6 figures, Solar Physics, in press, 201
PROPOSITION AND EVALUATION OF NATIVE VEGETATION RECOVERING INDEX (NVRI) OF RURAL PROPERTY
Monoketonic Curcuminoid Lidocaine Co Deliver Using Thermosensitive Organogels From Drug Synthesis to Epidermis Structural Studies
Organogels ORGs are remarkable matrices due to their versatile chemical composition and straightforward preparation. This study proposes the development of ORGs as dual drug carrier systems, considering the application of synthetic monoketonic curcuminoid m CUR and lidocaine LDC to treat topical inflammatory lesions. The monoketone curcuminoid m CUR was synthesized by using an innovative method via a NbCl5 acid catalysis. ORGs were prepared by associating an aqueous phase composed of Pluronic F127 and LDC hydrochloride with an organic phase comprising isopropyl myristate IPM , soy lecithin LEC , and the synthesized m CUR. Physicochemical characterization was performed to evaluate the influence of the organic phase on the ORGs supramolecular organization, permeation profiles, cytotoxicity, and epidermis structural characteristics. The physico chemical properties of the ORGs were shown to be strongly dependent on the oil phase constitution. Results revealed that the incorporation of LEC and m CUR shifted the sol gel transition temperature, and that the addition of LDC enhanced the rheological G amp; 8242; G amp; 8243; ratio to higher values compared to original ORGs. Consequently, highly structured gels lead to gradual and controlled LDC permeation profiles from the ORG formulations. Porcine ear skin epidermis was treated with ORGs and evaluated by infrared spectroscopy FTIR , where the stratum corneum lipids were shown to transition from a hexagonal to a liquid crystal phase. Quantitative optical coherence tomography OCT analysis revealed that LEC and m CUR additives modify skin structuring. Data from this study pointed ORGs as promising formulations for skin deliver
Evaluation of the concentration of allergens from mites in fur and households dust of dogs with atopic dermatitis
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