1,721,078 research outputs found
Niobium Dayem nano-bridge Josephson gate-controlled transistors
No full textWe report on the realization of Nb-based all-metallic Dayem nano-bridge gate-controlled transistors (Nb-GCTs). These Josephson devices operate up to a temperature of ∼ 3 K and exhibit full suppression of the supercurrent thanks to the application of a control gate voltage. The dependence of the kinetic inductance and of the transconductance on gate voltage promises a performance already on par with so far realized metallic Josephson transistors and leads us to foresee the implementation of a superconducting digital logic based on the Nb-GCT. We conclude by showing the practical realization of a scheme implementing an all-metallic gate-tunable half-wave rectifier to be used for either superconducting electronics or photon detection applications
Gate control of superconductivity in mesoscopic all-metallic devices
Full text linkThe possibility to tune, through the application of a control gate voltage, the supercon-ducting properties of mesoscopic devices based on Bardeen–Cooper–Schrieffer metals was recently demonstrated. Despite the extensive experimental evidence obtained on different materials and geometries, a description of the microscopic mechanism at the basis of such an unconventional effect has not been provided yet. This work discusses the technological potential of gate control of superconductivity in metallic superconductors and revises the experimental results, which provide information regarding a possible thermal origin of the effect: first, we review experiments performed on high-critical-temperature elemental superconductors (niobium and vanadium) and show how devices based on these materials can be exploited to realize basic electronic tools, such as a half-wave rectifier. Second, we discuss the origin of the gating effect by showing gate-driven suppression of the supercurrent in a suspended titanium wire and by providing a comparison between thermal and electric switching current probability distributions. Furthermore, we discuss the cold field-emission of electrons from the gate employing finite element simulations and compare the results with experimental data. In our view, the presented data provide a strong indication regarding the unlikelihood of the thermal origin of the gating effect
Electrostatic Control of Phase Slips in Ti Josephson Nanotransistors
No full textThe investigation of the switching-current probability distribution of a Josephson junction is a conventional tool to gain information on the dynamics of the phase slips as a function of the temperature. Here we adopt this well-established technique to probe the impact of an external static electric field on the occurrence of phase slips in gated all-metallic titanium (Ti) Josephson weak links. We show, in a temperature range between 20 and 420 mK, that the evolution of the dynamics of the phase slips as a function of the electrostatic field starkly differs from that observed as a function of the temperature. This fact demonstrates, on the one hand, that the electric field suppression of the critical current is not simply related to a conventional thermal-like quasiparticle overheating in the weak-link region. On the other hand, our results may open the way to operate an electrostatic-driven manipulation of phase slips in metallic Josephson nanojunctions, which can be pivotal for the control of decoherence in superconducting nanostructures
Vernon Clare Mary, Visual culture in Norman Puglia c.1030-1130
No full textVernon Clare Mary, Visual culture in Norman Puglia c.1030-1130, Thèse de doctorat soutenue en 2015 (University of Cambridge) [Source : http://ethos.bl.uk/OrderDetails.do?did=1&uin=uk.bl.ethos.708775
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
In-vitro and in-vivo evaluation of oligoethylene esters as dermal prodrugs of 18-b-glycirrethic acid.
No full textNew Strategies for the Delivery of Some Natural Anti-oxidants with Therapeutic Properties
No full textNature offers tremendous potential in the medicine field. Natural antioxidant molecules inhibit or quench free radical reactions and delay or inhibit cellular damage. In the last few years, researchers have been focusing on the health benefits of natural products. Particularly some dietary nutrients, such as curcumin, crocin, resveratrol, quercetin, coenzyme Q10, vitamin C, as well as some polysaccharides have been evaluated for their numerous and unique therapeutic properties. This review focuses on examples of pharmaceutical applications of natural anti-oxidants, with special regards to their encapsulation in micro-and nano-delivery systems. In vitro and in vivo studies have been conducted to investigate the physicochemical and pharmacological properties of different delivery systems containing antioxidant molecules. For instance, ethosomes, organogels, monoolein aqueous dispersions and solid lipid nanoparticle have been considered. It was found that micro and nanoencapsulation strategy can improve the solubility of lipophilic molecules and the chemical stability of labile antioxidants, thus prolonging their efficacy. In vitro and in vivo studies have highlighted that antioxidant encapsulation prolongs release kinetics, bioavailability and antioxidant effects. Noticeably, some encapsulated antioxidants effectively inhibit cancer cell proliferation, cell migration and colony formation, thus suppressing cancer progression
Josephson Field-Effect Transistors Based on All-Metallic Al/Cu/Al Proximity Nanojunctions
Full text linkWe demonstrate proximity-based all-metallic mesoscopic superconductor-normal metal-superconductor (SNS) field-effect controlled Josephson transistors (SNS-FETs) and show their full characterization from the critical temperature Tc down to 50 mK in the presence of both electric and magnetic fields. The ability of a static electric field - applied by means of a lateral gate electrode - to suppress the critical current Is in a proximity-induced superconductor is proven for both positive and negative gate voltage values. Is reached typically about one-third of its initial value, saturating at high gate voltages. The transconductance of our SNS-FETs obtains values as high as 100 nA/V at 100 mK. On the fundamental physics side, our results suggest that the mechanism at the basis of the observed phenomenon is quite general and does not rely on the existence of a true pairing potential, but rather the presence of superconducting correlations is enough for the effect to occur. On the technological side, our findings widen the family of materials available for the implementation of all-metallic field-effect transistors to synthetic proximity-induced superconductors
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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