Classical realization of two-site Fermi-Hubbard systems

A classical wave optics realization of the two-site Hubbard model, describing the dynamics of interacting fermions in a double-well potential, is proposed based on light transport in evanescently-coupled optical waveguides.Comment: 4 page

Visualization of Coherent Destruction of Tunneling in an Optical Double Well System

We report on a direct visualization of coherent destruction of tunneling (CDT) of light waves in a double well system which provides an optical analog of quantum CDT as originally proposed by Grossmann, Dittrich, Jung, and Hanggi [Phys. Rev. Lett. {\bf 67}, 516 (1991)]. The driven double well, realized by two periodically-curved waveguides in an Er:Yb-doped glass, is designed so that spatial light propagation exactly mimics the coherent space-time dynamics of matter waves in a driven double-well potential governed by the Schr\"{o}dinger equation. The fluorescence of Er ions is exploited to image the spatial evolution of light in the two wells, clearly demonstrating suppression of light tunneling for special ratios between frequency and amplitude of the driving field.Comment: final versio

Effect of water adsorption on conductivity in epitaxial Sm0.1Ce0.9O2-δ thin film for micro solid oxide fuel cells applications

Water adsorption, splitting, and proton liberation were investigated on Sm0.1Ce0.9O2-δ thin films by scanning probe microscopy. An irreversible volume expansion was observed by applying a positive bias with increased temperature. The volume expansion is also linearly dependent on the relative humidity. A reversible water adsorption process and its effect on the conductivity were also investigated by electrochemical strain microscopy and first order reversal curve under a number of experiment conditions. The presence of a Ce3+ along with OH groups, detected by hard x-ray photoemission spectroscopy established a clear correlation between the water incorporation and the valence state of C

imaging the coupling of terahertz radiation to a high electron mobility transistor in the near field

We used AlGaN/GaN high electron mobility transistors as room-temperature direct detectors of radiation at 0.15 THz from a free electron laser, hence 5 times higher than their cutoff frequency of 30 GHz. By near-field active mapping we investigated the antenna-like coupling of the radiation to the transistor channel. We formulate a model for the detection based on self-mixing in the transistor channel. The noise equivalent power is found in the range of 10^{-7} W/Hz^{0.5} without any optimization of the device responsivity. Present day AlGaN/GaN fabrication technology may provide operation at higher frequency, integration of amplifiers for improved responsivity and fast switches for multiplexing, which make the detector here described the basic element of a monolithic terahertz focal plane array

Hysteretic characteristics of a double stripline in the critical state

Analytical investigations of the critical state are carried out for a superconducting stripline consisting of two individual coplanar strips with an arbitrary distance between them. Two different cases are considered: a stripline with transport current and strips exposed to a perpendicular magnetic field. In the second case, the obtained solutions correspond to "fieldlike" (for unclosed strips) and "currentlike" (for a long rectangular superconducting loop) states in an isolated strip to which both a transport current and a magnetic field are applied with constant ratio.Comment: 8 pages, 6 figures. accepted by SS

Drosophila Histone Deacetylase-3 Controls Imaginal Disc Size through Suppression of Apoptosis

Histone deacetylases (HDACs) execute biological regulation through post-translational modification of chromatin and other cellular substrates. In humans, there are eleven HDACs, organized into three distinct subfamilies. This large number of HDACs raises questions about functional overlap and division of labor among paralogs. In vivo roles are simpler to address in Drosophila, where there are only five HDAC family members and only two are implicated in transcriptional control. Of these two, HDAC1 has been characterized genetically, but its most closely related paralog, HDAC3, has not. Here we describe the isolation and phenotypic characterization of hdac3 mutations. We find that both hdac3 and hdac1 mutations are dominant suppressors of position effect variegation, suggesting functional overlap in heterochromatin regulation. However, all five hdac3 loss-of-function alleles are recessive lethal during larval/pupal stages, indicating that HDAC3 is essential on its own for Drosophila development. The mutant larvae display small imaginal discs, which result from abnormally elevated levels of apoptosis. This cell death occurs as a cell-autonomous response to HDAC3 loss and is accompanied by increased expression of the pro-apoptotic gene, hid. In contrast, although HDAC1 mutants also display small imaginal discs, this appears to result from reduced proliferation rather than from elevated apoptosis. The connection between HDAC loss and apoptosis is important since HDAC inhibitors show anticancer activities in animal models through mechanisms involving apoptotic induction. However, the specific HDACs implicated in tumor cell killing have not been identified. Our results indicate that protein deacetylation by HDAC3 plays a key role in suppression of apoptosis in Drosophila imaginal tissue

Micromachined capacitive ultrasonic transducers fabricated using silicon on insulator wafers

In this paper we present the fabrication process of capacitive micromachined ultrasonic transducers by means of surface micromachining techniques using silicon on insulator (SOI) substrates as starting material. The use of SOI substrates provides a structural layer, in which the free-standing membranes are fabricated, of crystal silicon with excellent mechanical properties, and a sacrificial layer of buried oxide that can be etched selectively with respect to silicon. The process we developed has allowed to obtain transducers with resonance frequency at 6 MHz in air

Building CMUTs for imaging applications from top to bottom

This paper focuses on an innovative fabrication process of a capacitive micromachined ultrasonic transducer (CMUT) array for medical imaging. Our approach consists in inverting the function of each layer to build the CMUT capacitive cell starting from the membrane, made of silicon nitride, up to the bottom electrode, which is supported by an appropriate acoustic backing to absorb any ultrasound energy transmitted towards the backside of the array and to prevent the ringing of the pulse-echo signal. The fabricated devices exhibited a large bandwidth (>100%) and an increased sensitivity, in respect to the classical CMUT devices. Using the fabricated devices as linear probes, echographic images are obtained

Investigations on the response to humidity of an interdigitated electrode structure coated with iodine doped polyphenylacetylene

The sensitivity to relative humidity of a sensor based on I-2-doped polyphenylacetylene thin film membranes has been investigated. The sensor geometry allows its application in miniature devices. The response to humidity variations (20%-80%) is fast and reproducible for long times (months). The I/V characteristics suggest that ionic type conductivity is prevailing. Current intensity measurements performed on films of different thicknesses show that surface conductivity is mainly responsible for the sensor's electrical response