8,153 research outputs found
Determinations of upper critical field in continuous Ginzburg-Landau model
Novel procedures to determine the upper critical field have been
proposed within a continuous Ginzburg-Landau model. Unlike conventional
methods, where is obtained through the determination of the smallest
eigenvalue of an appropriate eigen equation, the square of the magnetic field
is treated as eigenvalue problems so that the upper critical field can be
directly deduced. The calculated from the two procedures are
consistent with each other and in reasonably good agreement with existing
theories and experiments. The profile of the order parameter associated with
is found to be Gaussian-like, further validating the methodology
proposed. The convergences of the two procedures are also studied.Comment: Revtex4, 8 pages, 4 figures, references modified, figures and table
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Anomalous thermopower and Nernst effect in : entropy-current loss in precursor state
The heavy-electron superconductor CeCoIn exhibits a puzzling precursor
state above its superconducting critical temperature at = 2.3 K. The
thermopower and Nernst signal are anomalous. Below 15 K, the entropy current of
the electrons undergoes a steep decrease reaching 0 at .
Concurrently, the off-diagonal thermoelectric current is
enhanced. The delicate sensitivity of the zero-entropy state to field implies
phase coherence over large distances. The prominent anomalies in the
thermoelectric current contrast with the relatively weak effects in the
resistivity and magnetization.Comment: 5 figures, 4 page
Improvement of dielectric loss of doped Ba0.5Sr0.5TiO3 thin films for tunable microwave devices
Al2O3-Ba0.5Sr0.5TiO3 (Al2O3-BST) thin films, with different Al2O3 contents,
were deposited on (100) LaAlO3 substrate by pulsed laser deposition (PLD)
technique. The Al2O3-BST films was demosnstrated to be a suitable systems to
fabricate ferroelectric thin films with low dielectric loss and higher figure
of merit for tunable microwave devices. Pure BST thin films were also
fabricated for comparison purpose. The films' structure and morphology were
analyzed by X-ray diffractiopn and scanning electron microscopy, respectively;
nad showed that the surface roughness for the Al2O3-BST films increased with
the Al2O3 content. Apart from that, the broadening in the intensity peak in XRD
result indicating the grain size of the Al2O3-BST films reduced with the
increasing of Al2O3 dopant. We measured the dielctric properties of Al2O3-BST
films with a home-made non-destructive dual resonator method at frequency ~ 7.7
GHZ. The effect of doped Al2O3 into BST thin films significantly reduced the
dielectric constant, dielectric loss and tunability compare to pure BST thin
film. Our result shows the figure of merit (K), used to compare the films with
varied dielectric properties, increased with the Al2O3 content. Therefore
Al2O3-BST films show the potential to be exploited in tunable microwave
devices.Comment: 8 pages, 4 figures, 1 table. Accepted & tentatively for Feb 15 2004
issue, Journal of Applied Physic
Visual Observation and Quantitative Measurement of the Microwave Absorbing Effect at X band
We have setup a simple field mapping measure system to describe graphically
the 2D quasi-free-space electromagnetic wave in a parallel plate waveguide at
the X-band frequencies. Our apparatus illustrates a potential application in
characterizing the microwave absorbing materials. The visual demonstration
about the physical process and quantitative measurement of reflectivity
coefficients can be achieved. This simple apparatus has have an advantage over
with conventional testing methods which usually involve huge, expensive
anechoic chambers and demand samples of large size.Comment: 24 pages, 8 figure
Growth hormone receptor and IGF-1 receptor immunoreactivity during orthodontic tooth movement in the prednisolone-treated rat
Bone remodeling during tooth movement is regulated by local and systemic factors. Two regulators of bone metabolism are growth hormone (GH) and insulin-like growth factor-I (IGF-1). Their effects are mediated via binding to GH receptor (GHR) and IGF-I receptor (IGF-IR) in target tissues. Corticosteroids may affect the activity of these growth factors. This study examined the effect of prednisolone on GHR and IGF-IR expression in dental tissues following orthodontic tooth movement. The corti ticosteroid-treated group (N = 6) was administered prednisolone ( 1 mg/kg,) daily and the control group (N = 6) received equivalent volumes of saline. An orthodontic force (30 g) was applied to the maxillary first molar. Animals were sacrificed 12 days postappliance insertion. Sagittal sections of the first molar were stained for GHR and IGF-IR immunoreactivity. GHR and IGF-IR cell counts were elevated following appliance-treatment. Orthodontic tooth movement appeared to up-regulate GHR and IGF-IR immunoreactivity, but this up-regulation was reduced following prednisolone treatment. The suppression of GHR and IGF-I immunoreactivity in steroid-treated animals infers the mechanism whereby bone resorption and deposition, necessary for orthodontic tooth movement, may be inhibited by prednisolone. However, at 12 days postappliance insertion. no difference in orthodontic tooth movement was observed following low-dose prednisolone treatment
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