The array of chemiresistors made of individual pristine SnO2, surface doped (Ni)-SnO2 nanowires, and TiO2 and In2O3 mesoscopic whiskers was fabricated on a Si/SiO2 wafer. Their conductance was measured under pulses of H2 and CO reducing gases in oxygen as background gas. The nanostructures were shown to be n-type semiconductors possessing high sensitivity to the target gases. Following the "electronic nose" concept, correlation analysis of response of three-chemiresistor array is shown to be sufficient to discriminate between H2 and CO signals.
We show that the near horizon regime of a Kerr–Newman AdS (KNAdS) black hole, given by its two-dimensional analogue a là Robinson and Wilczek (Phys. Rev. Lett.95, 011303 (2005)), is asymptotically AdS2 and dual to a one-dimensional quantum conformal field theory (CFT). The s-wave contribution of the resulting CFT's energy–momentum tensor together with the asymptotic symmetries, generate a centrally extended Virasoro algebra, whose central charge reproduces the Bekenstein–Hawking entropy via Cardy's formula. Our derived central charge also agrees with the near extremal Kerr/CFT correspondence (Phys. Rev. D80, 124008 (2009)) in the appropriate limits. We also compute the Hawking temperature of the KNAdS black hole by coupling its Robinson and Wilczek two-dimensional analogue (RW2DA) to conformal matter.
The transport properties and gas-sensing performance of chemiresistors based on quasi-1D, single-crystal,
SnO2
nanostructures with deliberately synthesized (encoded) segmented morphology are
explored. Such nanostructures were obtained using programmable modulation of the gas
supersaturation ratio during their growth. Using hydrogen and oxygen as model
reducing and oxidizing gases, we show that the responsiveness of these structurally
modulated nanowires to gases is improved over that of straight nanowires of the same
average diameter. This is due to the presence of small-diameter segments, which
dominate the nanostructure’s transport properties and to the better tolerance of such
nanostructures towards contact effects. The narrow segments approximate the
excellent responsiveness of ‘necks’ between particles in traditional thin film gas
sensors but with the significant advantage of greater morphological integrity and
stability.
We compute the full asymptotic symmetry group of the four dimensional nearextremal Kerr-Sen black hole within an AdS 2 /CF T 1 correspondence. We do this by performing a Robinson-Wilczek two dimensional reduction and construct an effective quantum theory of the remaining field content. The resulting energy momentum tensor generates an asymptotic Virasoro algebra, to s-wave, with a calculable central extension. This center in conjunction with the proper regularized lowest Virasoro eigen-mode yields the nearextremal Kerr-Sen entropy via the statistical Cardy formula. Finally we analyze quantum holomorphic fluxes of the dual CF T giving rise to a finite Hawking temperature weighted by the central charge of the near-extremal Kerr-Sen metric.
We investigate a holographic description of k-strings in higher representations via D5 branes with worldvolume fluxes. The D-brane configurations are embedded in supergravity backgrounds dual to confining field theories in 3 and 4 dimensions. We compute the tensions and find qualitative agreement for the totally symmetric and totally anti-symmetric representations with the results of other methods such as lattice as well as the Hamiltonian approach of Karabali and Nair. A one-loop computation on the D-brane configurations yields the Lüscher term and allows us to confirm a previously proposed universal expression following from holography.
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