Low field magnetotransport in strained Si/SiGe cavities

Low field magnetotransport revealing signatures of ballistic transport effects in strained Si/SiGe cavities is investigated. We fabricated strained Si/SiGe cavities by confining a high mobility Si/SiGe 2DEG in a bended nanowire geometry defined by electron-beam lithography and reactive ion etching. The main features observed in the low temperature magnetoresistance curves are the presence of a zero-field magnetoresistance peak and of an oscillatory structure at low fields. By adopting a simple geometrical model we explain the oscillatory structure in terms of electron magnetic focusing. A detailed examination of the zero-field peak lineshape clearly shows deviations from the predictions of ballistic weak localization theory.Comment: Submitted to Physical Review B, 25 pages, 7 figure

Conductance quantization in etched Si/SiGe quantum point contacts

We fabricated strongly confined Schottky-gated quantum point contacts by etching Si/SiGe heterostructures and observed intriguing conductance quantization in units of approximately 1e2/h. Non-linear conductance measurements were performed depleting the quantum point contacts at fixed mode-energy separation. We report evidences of the formation of a half 1e2/h plateau, supporting the speculation that adiabatic transmission occurs through 1D modes with complete removal of valley and spin degeneracies.Comment: to appear in Physical Review

Study of the Fabrication Process for a Dual Mass Tuning Fork Gyro

AbstractThe fabrication process of a dual mass tuning for gyroscope presents many different challenges: the aspect ratio of the sidewalls, the Aspect Ratio Dependent Etch (ARDE) which causes different gaps to be etched in different etching time [1], the stiction during the release of the free structures, the notching effect that occurs with a dielectric etch stop layer [2], the thermal contact during the etch process. In this paper are presented different processes and studies of the etching characteristics in order to avoid or minimize these problems

Gate-source distance scaling effects in H-terminated diamond MESFETs

In this paper, an analysis of gate-source and gate-drain scaling effects in MESFETs fabricated on hydrogen-terminated single-crystal diamond films is reported. The experimental results show that a decrease in gate-source spacing can improve the device performance by increasing the device output current density and its transconductance. On the contrary, the gate--drain distance produces less pronounced effects on device performance. Breakdown voltage, knee voltage, and threshold voltage variations due to changes in gate-source and drain-source distances have also been investigated. The obtained results can be used as a design guideline for the layout optimization of H-terminated diamond-based MESFETs

Controlling the Cassie-to-Wenzel Transition: an Easy Route towards the Realization of Tridimensional Arrays of Biological Objects

In this paper we provide evidence that the Cassie-to-Wenzel transition, despite its detrimental effects on the wetting properties of superhydrophobic surfaces, can be exploited as an effective micro-fabrication strategy to obtain highly ordered arrays of biological objects. To this purpose we fabricated a patterned surface wetted in the Cassie state, where we deposited a droplet containing genomic DNA. We observed that, when the droplet wets the surface in the Cassie state, an array of DNA filaments pinned on the top edges between pillars is formed. Conversely, when the Cassie-to-Wenzel transition occurs, DNA can be pinned at different height between pillars. These results open the way to the realization of tridimensional arrays of biological objects

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

A pilot study of IL-1 inhibition by anakinra in acute gout

Monosodium urate crystals stimulate monocytes and macrophages to release IL-1β through the NALP3 component of the inflammasome. The effectiveness of IL-1 inhibition in hereditary autoinflammatory syndromes with mutations in the NALP3 protein suggested that IL-1 inhibition might also be effective in relieving the inflammatory manifestations of acute gout. The effectiveness of IL-1 inhibition was first evaluated in a mouse model of monosodium urate crystal-induced inflammation. IL-1 inhibition prevented peritoneal neutrophil accumulation but TNF blockade had no effect. Based on these findings, we performed a pilot, open-labeled study (trial registration number ISRCTN10862635) in 10 patients with gout who could not tolerate or had failed standard antiinflammatory therapies. All patients received 100 mg anakinra daily for 3 days. All 10 patients with acute gout responded rapidly to anakinra. No adverse effects were observed. IL-1 blockade appears to be an effective therapy for acute gouty arthritis. The clinical findings need to be confirmed in a controlled study

Clinical utility of dual energy computed tomography in gout: Current concepts and applications

Summary. Gout is the most common inflammatory arthritis and is increasing in prevalence and incidence in many countries worldwide. Dual Energy Computed Tomography (DECT) has a high diagnostic accuracy in established gout, but its diagnostic sensitivity is low in subjects with recent-onset gout. A meta-analysis of 17 studies showed a pooled sensitivity and specificity of 0.85 and 0.88, respectively. DECT is a useful diagnostic tool for patients with contraindications for joint aspiration or for those who refuse joint aspiration. This article aims to give an up to date review and summary of existing literature on the role and accuracy of DECT in the imaging of gout. (www.actabiomedica.it)

Accurate large-signal equivalent circuit of surface channel diamond FETs based on the Chalmers model

The paper presents a large-signal nonlinear circuit-oriented model for polycrystalline and single-crystal H-terminated diamond MESFETs implemented within the Agilent ADS design suite. The DC characteristics of such devices suggest that the channel free charge control law may be modeled using the same strategy adopted for III-V HEMTs. For this reason, the well-known nonlinear Chalmers (Angelov) circuit model was chosen as the starting point for the development of the present non-linear diamond MESFET model. Model fitting was performed against DC and multibias small signal measurements, with good agreement. Model validations versus large-signal (power) measurements point out the accuracy of the proposed approach to simulate the behavior of H-terminated diamond MESFETs under large-signal operatio