1,353 research outputs found
Fluence and polarisation dependence of GaAs based Lateral Photo-Dember terahertz emitters
We characterise THz output of lateral photo-Dember (LPD) emitters based on semi-insulating (SI), unannealed and annealed low temperature grown (LTG) GaAs. Saturation of THz pulse power with optical fluence is observed, with unannealed LTG GaAs showing highest saturation fluence at 1.1 ± 0.1 mJ cm-2. SI-GaAs LPD emitters show a flip in signal polarity with optical fluence that is attributed to THz emission from the metal-semiconductor contact. Variation in optical polarisation affects THz pulse power that is attributed to a local optical excitation near the metal contact
The Effect of a Mycotoxin Deactivation Product on Growth of Juvenile Rainbow Trout Fed Distillers Dried Grains
Distillers dried grains (DDG) with solubles (DDGS) is a product that has shown potential as a protein source for some fish species, but high inclusion rates of DDGS have not always been successfully achieved for Rainbow Trout Oncorhynchus mykiss. Our objective was to determine whether inclusion of a mycotoxin deactivation product (Biofix Plus) could improve the ability of high-protein DDG (HPDDG) to replace a portion of the fish meal in diets for Rainbow Trout. The 2 à 2 factorial feeding trial examined protein source (menhaden fish meal [MFM] or HPDDG) with or without Biofix Plus. A control diet (42% digestible protein, 20% crude lipid, 25% MFM) was compared to a test diet in which HPDDG replaced 12% of the total MFM on a digestible-protein basis (24% HPDDG inclusion). Diets were fed to juvenile Rainbow Trout (initial weight: mean ± SE = 30.5 ± 1.6 g) in four replicate tanks per treatment for 9 weeks in a 15°C recirculating system. At the conclusion of the feeding trial, we observed no negative effects of fish meal replacement on growth or feed conversion ratio; no benefit of Biofix Plus supplementation was observed. These data indicate that when Rainbow Trout diets containing a high-quality DDGS product are balanced for digestible protein, lysine, methionine, and threonine, dietary fish meal levels can be successfully reduced to 13% without compromising growth and without the need for mycotoxin deactivator inclusion
Diquark-Antidiquark with open charm in QCD sum rules
Using the QCD sum rule approach we investigate the possible four-quark
structure of the recently observed charmed scalar mesons
(BELLE) and (FOCUS) and also of the very narrow
, firstly observed by BABAR. We use diquak-antidiquark
currents and work to the order of in full QCD, without relying on
expansion. Our results indicate that a four-quark structure is acceptable for
the resonances observed by BELLE and BABAR: and
respectively, but not for the resonances observed by FOCUS:
.Comment: 6 pages, 5 eps figures; Contribution to the 'Workshop on Light-Cone
QCD and Nonperturbative Hadron Physics 2005 (LC2005)', Cairns-Australi
Classical Cepheids: Yet another version of the Baade-Becker-Wesselink method
We propose a new version of the Baade--Becker--Wesselink technique, which
allows one to independently determine the colour excess and the intrinsic
colour of a radially pulsating star, in addition to its radius, luminosity, and
distance. It is considered to be a generalization of the Balona approach. The
method also allows the function F(CI) = BC + 10 log (Teff) for the class of
pulsating stars considered to be calibrated. We apply this technique to a
number of classical Cepheids with very accurate light and radial-velocity
curves and with bona fide membership in open clusters (SZ Tau, CF Cas, U Sgr,
DL Cas, GY Sge), and find the results to agree well with the reddening
estimates of the host open clusters. The new technique can also be applied to
other pulsating variables, e.g. RR Lyrae and RV Tauri.Comment: 6 pages, 2 figures, 1 table; Submitted to Astrophysical Bulletin,
201
Quantum railroads and directed localization at the juncture of quantum Hall systems
The integer quantum Hall effect (QHE) and one-dimensional Anderson
localization (AL) are limiting special cases of a more general phenomenon,
directed localization (DL), predicted to occur in disordered one-dimensional
wave guides called "quantum railroads" (QRR). Here we explain the surprising
results of recent measurements by Kang et al. [Nature 403, 59 (2000)] of
electron transfer between edges of two-dimensional electron systems and
identify experimental evidence of QRR's in the general, but until now entirely
theoretical, DL regime that unifies the QHE and AL. We propose direct
experimental tests of our theory.Comment: 11 pages revtex + 3 jpeg figures, to appear in Phys. Rev.
Terahertz emission by diffusion of carriers and metal-mask dipole inhibition of radiation
Terahertz (THz) radiation can be generated by ultrafast photo-excitation of
carriers in a semiconductor partly masked by a gold surface. A simulation of
the effect taking into account the diffusion of carriers and the electric field
shows that the total net current is approximately zero and cannot account for
the THz radiation. Finite element modelling and analytic calculations indicate
that the THz emission arises because the metal inhibits the radiation from part
of the dipole population, thus creating an asymmetry and therefore a net
current. Experimental investigations confirm the simulations and show that
metal-mask dipole inhibition can be used to create THz emitters.Comment: 9 pages, 5 figures; Fixed figure
The Effect of a Mycotoxin Deactivation Product on Growth of Juvenile Rainbow Trout Fed Distillers Dried Grains
Finite size and temperature effects in the AF Heisenberg model
The low temperature and large volume effects in the d=2+1 antiferromagnetic
quantum Heisenberg model are dominated by magnon excitations. The leading and
next-to-leading corrections are fully controlled by three physical constants,
the spin stiffness, the spin wave velocity and the staggered magnetization.
Among others, the free energy, the ground state energy, the low lying
excitations, staggered magnetization, staggered and uniform susceptibilities
are studied here. The special limits of very low temperature and infinite
volume are considered also.Comment: 44 pages, LATEX, no figure
Interplay of quantum magnetic and potential scattering around Zn or Ni impurity ions in superconducting cuprates
To describe the scattering of superconducting quasiparticles from
non-magnetic (Zn) or magnetic (Ni) impurities in optimally doped high T
cuprates, we propose an effective Anderson model Hamiltonian of a localized
electron hybridizing with -wave BCS type superconducting
quasiparticles with an attractive scalar potential at the impurity site. Due to
the strong local antiferromagnetic couplings between the original Cu ions and
their nearest neighbors, the localized electron in the Ni-doped materials is
assumed to be on the impurity sites, while in the Zn-doped materials the
localized electron is distributed over the four nearest neighbor sites of the
impurities with a dominant symmetric form of the wave function.
With Ni impurities, two resonant states are formed above the Fermi level in the
local density of states at the impurity site, while for Zn impurities a sharp
resonant peak below the Fermi level dominates in the local density of states at
the Zn site, accompanied by a small and broad resonant state above the Fermi
level mainly induced by the potential scattering. In both cases, there are no
Kondo screening effects. The local density of states and their spatial
distribution at the dominant resonant energy around the substituted impurities
are calculated for both cases, and they are in good agreement with the
experimental results of scanning tunneling microscopy in
BiSrCaCuO with Zn or Ni impurities, respectively.Comment: 24 pages, Revtex, 8 figures, submitted to Physical Review B for
publication. Sub-ject Class: Superconductivity; Strongly Correlated Electron
A diode-laser-pumped, Er<sup>3+</sup>-doped fibre laser operating at 1.57”m
Erbium-doped fibers show promise as stable narrow-linewidth laser sources and optical amplifiers operating in the third telecommunications window around 1.55”m Diode laser pumping is possible using the weak pump-band located at 807nm, although this band suffers severely from excited-state absorption (ESA), which reduces gain and pump efficiency. At the low pump power available from diode lasers the Er3+ behaves as a quasi four-level system. However, by codoping the core glass heavily with Yb3+, it is possible to excite the Er3+ ions indirectly using energy transfer. The Yb3+ provides an intense broad pump-band centered at 900nm, which reduces the effect of ESA. As a consequence of the resulting higher pump efficiency, the laser will oscillate at the required shorter wavelengths
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