3,776 research outputs found
The Effect of Transfer Printing on Pentacene Thin-Film Crystal Structure
The thermal deposition and transfer Printing method had been used to produce
pentacene thin-films on SiO2/Si and plastic substrates (PMMA and PVP),
respectively. X-ray diffraction patterns of pentacene thin films showed
reflections associated with highly ordered polycrystalline films and a
coexistence of two polymorph phases classified by their d-spacing, d(001): 14.4
and 15.4 A.The dependence of the c-axis correlation length and the phase
fraction on the film thickness and printing temperature were measured. A
transition from the 15.4 A phase towards 14.4 A phase was also observed with
increasing film thickness. An increase in the c-axis correlation length of
approximately 12% ~16% was observed for Pn films transfer printed onto a PMMA
coated PET substrate at 100~120 C as compared to as-grown Pn films on SiO2/Si
substrates. The transfer printing method is shown to be an attractive for the
fabrication of pentacene thin-film transistors on flexible substrates partly
because of the resulting improvement in the quality of the pentacene film.Comment: 5 pages, 5 figure
A Large Mass of H2 in the Brightest Cluster Galaxy in Zwicky 3146
We present the Spitzer/IRS mid-infrared spectrum of the infrared-luminous
(L_{IR}=4e11 L_sun) brightest cluster galaxy (BCG) in the X-ray-luminous
cluster Z3146 (z=0.29). The spectrum shows strong aromatic emission features,
indicating that the dominant source of the infrared luminosity is star
formation. The most striking feature of the spectrum, however, is the
exceptionally strong molecular hydrogen (H2) emission lines, which seem to be
shock-excited. The line luminosities and inferred warm H2 gas mass (~1e10
M_sun) are 6 times larger than those of NGC 6240, the most H2-luminous galaxy
at z <~ 0.1. Together with the large amount of cold H2 detected previously
(~1e11 M_sun), this indicates that the Z3146 BCG contains disproportionately
large amounts of both warm and cold H2 gas for its infrared luminosity, which
may be related to the intracluster gas cooling process in the cluster core.Comment: 13 pages, 3 figures, 1 table; Accepted for publication in ApJ
Nanotransfer Printing of Organic and Carbon Nanotube Thin-Film Transistors on Plastic Substrates
A printing process for high-resolution transfer of all components for organic
electronic devices on plastic substrates has been developed and demonstrated
for pentacene (Pn), poly (3-hexylthiophene) and carbon nanotube (CNT) thin-film
transistors (TFTs). The nanotransfer printing process allows fabrication of an
entire device without exposing any component to incompatible processes and with
reduced need for special chemical preparation of transfer or device substrates.
Devices on plastic substrates include a Pn TFT with a saturation, field-effect
mobility of 0.09 cm^2 (Vs)^-1 and on/off ratio approximately 10^4 and a CNT TFT
which exhibits ambipolar behavior and no hysteresis.Comment: to appear in Applied Physics Letter
Infinite-range Ising ferromagnet in a time-dependent transverse field: quench and ac dynamics near the quantum critical point
We study an infinite range ferromagnetic Ising model in the presence of a
transverse magnetic field which exhibits a quantum paramagnetic-ferromagnetic
phase transition at a critical value of the transverse field. In the
thermodynamic limit, the low-temperature properties of this model are dominated
by the behavior of a single large classical spin governed by an anisotropic
Hamiltonian. Using this property, we study the quench and AC dynamics of the
model both numerically and analytically, and develop a correspondence between
the classical phase space dynamics of a single spin and the quantum dynamics of
the infinite-range ferromagnetic Ising model. In particular, we compare the
behavior of the equal-time order parameter correlation function both near to
and away from the quantum critical point in the presence of a quench or AC
transverse field. We explicitly demonstrate that a clear signature of the
quantum critical point can be obtained by studying the AC dynamics of the
system even in the classical limit. We discuss possible realizations of our
model in experimental systems.Comment: Revtex4, 10 pages including 10 figures; corrected a sign error in Eq.
32; this is the final published versio
In Vitro Methane Production from Heifers Offered Four Bermudagrass Cultivars
Though bermudagrass (Cynodon dactylon [L.] Pers.) is one of the predominant warm-season perennial forage supporting the southeastern United States livestock production systems, little is known about its influence on parameters of ruminal metabolism, including carbon loss as methane. With the multitude of cultivars of this grass that have been developed and released, one may question whether the physiological cultivar differences will manifest varying results in digestive efficiency and subsequent methane emissions. Thus, the objective of this study was to evaluate in vitro methane (CH4) production as influenced by four bermudagrass cultivars. Ruminally-fistulated heifers (n = 4) were assigned randomly to one of four bermudagrass cultivars (Coastal [COS], Russell [RUS], Tifton 44 [T44], or Tifton 85 [T85]) for four 30-d in vivo periods in a Latin square design. On d 28 of each period, rumen fluid was collected from each heifer for use in CH4 production evaluation. Samples of each bermudagrass, corresponding to the cultivar fed, were weighed into duplicate 10-mL serum bottles and incubated at 39°C for 0, 2, 4, and 24 h. Following incubation, headspace samples were assayed for CH4 concentrations by gas chromatography. There was an interaction of cultivar and time (P \u3c 0.01). There was no difference among cultivars (P \u3c 0.05) at 0, 2, or 4 h of incubation. After 24 h of incubation, however, CH4 concentrations were greater (P \u3c 0.05) from T44 and T85 (7.7 and 6.2 mmol/L, respectively) than from RUS and COS (3.4 and 3.0 mmol/L, respectively). Results are interpreted to mean that cultivar type has an influence on the potential CH4 production of bermudagrass
The Vega Debris Disk -- A Surprise from Spitzer
We present high spatial resolution mid- and far-infrared images of the Vega
debris disk obtained with the Multiband Imaging Photometer for Spitzer (MIPS).
The disk is well resolved and its angular size is much larger than found
previously. The radius of the disk is at least 43" (330 AU), 70"(543 AU), and
105" (815 AU) in extent at 24, 70 and 160 um, respectively. The disk images are
circular, smooth and without clumpiness at all three wavelengths. The radial
surface brightness profiles imply an inner boundary at a radius of 11"+/-2" (86
AU). Assuming an amalgam of amorphous silicate and carbonaceous grains, the
disk can be modeled as an axially symmetric and geometrically thin disk, viewed
face-on, with the surface particle number density following an r^-1 power law.
The disk radiometric properties are consistent with a range of models using
grains of sizes ~1 to ~50 um. We find that a ring, containing grains larger
than 180 um and at radii of 86-200 AU from the star, can reproduce the observed
850 um flux, while its emission does not violate the observed MIPS profiles.
This ring could be associated with a population of larger asteroidal bodies
analogous to our own Kuiper Belt. Cascades of collisions starting with
encounters amongthese large bodies in the ring produce the small debris that is
blown outward by radiation pressure to much larger distances where we detect
its thermal emission. The dust production rate is >~10^15 g/s based on the MIPS
results. This rate would require a very massive asteroidal reservoir for the
dust to be produced in a steady state throughout Vega's life. Instead, we
suggest that the disk we imaged is ephemeral and that we are witnessing the
aftermath of a large and relatively recent collisional event, and subsequent
collisional cascade.Comment: 13 pages, 17 figures, accepted for publication in ApJ. (Figures 2,
3a, 3b and 4 have been degraded to lower resolutions.
Cascade Failure in a Phase Model of Power Grids
We propose a phase model to study cascade failure in power grids composed of
generators and loads. If the power demand is below a critical value, the model
system of power grids maintains the standard frequency by feedback control. On
the other hand, if the power demand exceeds the critical value, an electric
failure occurs via step out (loss of synchronization) or voltage collapse. The
two failures are incorporated as two removal rules of generator nodes and load
nodes. We perform direct numerical simulation of the phase model on a
scale-free network and compare the results with a mean-field approximation.Comment: 7 pages, 2 figure
Extremely Red Objects in The Lockman Hole
We investigate Extremely Red Objects (EROs) using near- and mid-infrared
observations in five passbands (3.6 to 24 micron) obtained from the Spitzer
Space Telescope, and deep ground-based R and K imaging. The great sensitivity
of the IRAC camera allows us to detect 64 EROs in only 12 minutes of IRAC
exposure time, by means of an R-[3.6] color cut (analogous to the traditional
red R-K cut). A pure infrared K-[3.6] red cut detects a somewhat different
population and may be more effective at selecting z > 1.3 EROs. We find 17% of
all galaxies detected by IRAC at 3.6 or 4.5 micron to be EROs. These
percentages rise to about 40% at 5.8 micron, and about 60% at 8.0 micron. We
utilize the spectral bump at 1.6 micron to divide the EROs into broad redshift
slices using only near-infrared colors (2.2/3.6/4.5 micron). We conclude that
two-thirds of all EROs lie at redshift z > 1.3. Detections at 24 micron imply
that at least 11% of 0.6 1.3 EROs are
dusty star-forming galaxies.Comment: to appear in the special Spitzer issue of the ApJ
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