315 research outputs found
Gallium oxide and gadolinium gallium oxide insulators on Si δ-doped GaAs/AlGaAs heterostructures
Test devices have been fabricated on two specially grown GaAs/AlGaAs wafers with 10 nm thick gate dielectrics composed of either Ga<sub>2</sub>O<sub>3</sub> or a stack of Ga<sub>2</sub>O<sub>3</sub> and Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub>. The wafers have two GaAs transport channels either side of an AlGaAs barrier containing a Si delta-doping layer. Temperature dependent capacitance-voltage (C-V) and current-voltage (I-V) studies have been performed at temperatures between 10 and 300 K. Bias cooling experiments reveal the presence of DX centers in both wafers. Both wafers show a forward bias gate leakage that is by a single activated channel at higher temperatures and by tunneling at lower temperatures. When Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> is included in a stack with 1 nm of Ga<sub>2</sub>O<sub>3</sub> at the interface, the gate leakage is greatly reduced due to the larger band gap of the Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> layer. The different band gaps of the two oxides result in a difference in the gate voltage at the onset of leakage of ~3 V. However, the inclusion of Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> in the gate insulator introduces many oxide states (≤4.70Ã�Â�10<sup>12</sup> cm<sup>âÂ�Â�2</sup>). Transmission electron microscope images of the interface region show that the growth of a Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> layer on Ga<sub>2</sub>O<sub>3</sub> disturbs the well ordered Ga<sub>2</sub>O<sub>3</sub>/GaAs interface. We therefore conclude that while including Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> in a dielectric stack with Ga<sub>2</sub>O<sub>3</sub> is necessary for use in device applications, the inclusion of Gd decreases the quality of the Ga<sub>2</sub>O<sub>3</sub>/GaAs interface and near interface region by introducing roughness and a large number of defect states
Monte Carlo simulations of high-performance implant free In<sub>0.3</sub>Ga<sub>0.7</sub> nano-MOSFETs for low-power CMOS applications
No abstract available
Is Cycle 24 the Beginning of a Dalton-Like Minimum?
The unexpected development of cycle 24 emphasizes the need for a better way
to model future solar activity. In this article, we analyze the accumulation of
spotless days during individual cycles from 1798-2010. The analysis shows that
spotless days do not disappear abruptly in the transition towards an active
sun. A comparison with past cycles indicates that the ongoing accumulation of
spotless days is comparable to that of cycle 5 near the Dalton minimum and to
that of cycles 12, 14 and 15. It also suggests that the ongoing cycle has as
much as 20 \pm 8 spotless days left, from July 2010, before it reaches the next
solar maximum. The last spotless day is predicted to be in December 2012, with
an uncertainty of 11 months. This trend may serve as input to the solar dynamo
theories.Comment: 10 pages, 5 figures. The final publication is available at
http://www.springerlink.co
Exact perturbative solution of the Kondo problem
We explicitly evaluate the infinite series of integrals that appears in the
"Anderson-Yuval" reformulation of the anisotropic Kondo problem in terms of a
one-dimensional Coulomb gas. We do this by developing a general approach
relating the anisotropic Kondo problem of arbitrary spin with the boundary
sine-Gordon model, which describes impurity tunneling in a Luttinger liquid and
in the fractional quantum Hall effect. The Kondo solution then follows from the
exact perturbative solution of the latter model in terms of Jack polynomials.Comment: 4 pages in revtex two-colum
Internal amplification controls have not been employed in fungal PCR hence potential false negative results
Polymerase chain reaction (PCR) is subject to false negative results. Samples of
fungi with the genes of interest (e.g. a disease or mycotoxin) may be categorized
as negative and safe as a consequence. Fungi are eukaryotic organisms that are involved in many fields of human activity such as antibiotic, toxin and food production. Certain taxa are implicated in human, animal and plant diseases.
However, fungi are difficult to identify and PCR techniques have been proposed increasingly for this purpose. Internal amplification controls (IACs)
will ameliorate the situation and need to become mandatory. These are nucleic
acids that posses a sequence which will provide a PCR product (i) using the
same primers employed for the target gene, and (ii) that will not coincide on
the gel with the product of the target gene. Only one group of workers employed an IAC, to respond to potential inhibition, which was reported in 1995 from this present assessment of numerous reports. Inhibitors in cultures need to be minimized, and secondary metabolites are an obvious source. The
fields reviewed herein include medical mycology, mycotoxicology, environmental
mycology and plant mycology. The conclusion is that previous reports are compromised because IACs have not been employed in fungal PCR; future research must include this control at an early stage.Fundação para a Ciência e a Tecnologia (FCT
Jack vertex operators and realization of Jack functions
We give an iterative method to realize general Jack functions from Jack
functions of rectangular shapes. We first show some cases of Stanley's
conjecture on positivity of the Littlewood-Richardson coefficients, and then
use this method to give a new realization of Jack functions. We also show in
general that vectors of products of Jack vertex operators form a basis of
symmetric functions. In particular this gives a new proof of linear
independence for the rectangular and marked rectangular Jack vertex operators.
Thirdly a generalized Frobenius formula for Jack functions was given and was
used to give new evaluation of Dyson integrals and even powers of Vandermonde
determinant.Comment: Expanded versio
Physics Opportunities with the 12 GeV Upgrade at Jefferson Lab
This white paper summarizes the scientific opportunities for utilization of
the upgraded 12 GeV Continuous Electron Beam Accelerator Facility (CEBAF) and
associated experimental equipment at Jefferson Lab. It is based on the 52
proposals recommended for approval by the Jefferson Lab Program Advisory
Committee.The upgraded facility will enable a new experimental program with
substantial discovery potential to address important topics in nuclear,
hadronic, and electroweak physics.Comment: 64 page
Logarithmic and complex constant term identities
In recent work on the representation theory of vertex algebras related to the
Virasoro minimal models M(2,p), Adamovic and Milas discovered logarithmic
analogues of (special cases of) the famous Dyson and Morris constant term
identities. In this paper we show how the identities of Adamovic and Milas
arise naturally by differentiating as-yet-conjectural complex analogues of the
constant term identities of Dyson and Morris. We also discuss the existence of
complex and logarithmic constant term identities for arbitrary root systems,
and in particular prove complex and logarithmic constant term identities for
the root system G_2.Comment: 26 page
(Borel) convergence of the variationally improved mass expansion and the O(N) Gross-Neveu model mass gap
We reconsider in some detail a construction allowing (Borel) convergence of
an alternative perturbative expansion, for specific physical quantities of
asymptotically free models. The usual perturbative expansions (with an explicit
mass dependence) are transmuted into expansions in 1/F, where
for while for m \lsim \Lambda,
being the basic scale and given by renormalization group
coefficients. (Borel) convergence holds in a range of which corresponds to
reach unambiguously the strong coupling infrared regime near , which
can define certain "non-perturbative" quantities, such as the mass gap, from a
resummation of this alternative expansion. Convergence properties can be
further improved, when combined with expansion (variationally improved
perturbation) methods. We illustrate these results by re-evaluating, from
purely perturbative informations, the O(N) Gross-Neveu model mass gap, known
for arbitrary from exact S matrix results. Comparing different levels of
approximations that can be defined within our framework, we find reasonable
agreement with the exact result.Comment: 33 pp., RevTeX4, 6 eps figures. Minor typos, notation and wording
corrections, 2 references added. To appear in Phys. Rev.
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