Andreev levels spectroscopy of topological three-terminal junctions

We calculate the differential conductance at a probe inserted in the weak link of a topological Josephson junction, consisting of a semiconducting nanowire deposited on top of two separated superconductors. Our aim is to understand how the peculiar features in the spectrum of Andreev bound states, arising due to the presence of Majorana bound states at the ends of the two topological superconducting wires defining the junction, can be determined through a measurement of the differential conductance. We find that when the probe allows a single propagating mode, the differential conductance presents a dip at zero voltage of zero conductance close to the position where the spectrum exhibits the topologically protected crossing. This can be viewed as a signature of the presence of Majorana states, which does not require fermion parity conservation and is robust against parameters' changes, as well as disorder. On the contrary, when the probe allows two or more propagating modes the differential conductance resembles the spectrum of Andreev bound states. This has been established making use of both numerical and analytical methods.Comment: 10 pages, 10 figures, published versio

Finite-frequency noise in a topological superconducting wire

In this paper we study the finite-frequency current cross-correlations for a topological superconducting nanowire attached to two terminals at one of its ends. Using an analytic 1D model we show that the presence of a Majorana bound state yields vanishing cross-correlations for frequencies larger than twice the applied transport voltage, in contrast to what is found for a zero-energy ordinary Andreev bound state. Zero cross-correlations at high frequency have been confirmed using a more realistic tight-binding model for finite-width topological superconducting nanowires. Finite-temperature effects have also been investigated.Comment: Contribution for the special issue of Physica E in memory of Markus B\"uttiker. 9 pages, 7 figure

Thermopower of three-terminal topological superconducting systems

We study the thermopower of a three-terminal setup composed of a quantum dot attached to three electrodes, one of which is a topological superconductor. In the model, superconductivity is explicitly taken into account. We compare the results for s-wave (trivial) and p-wave (topological) superconductors and observe that for small temperatures the thermopower has different sign in the two cases. This behavior is strongly dependent on temperature and we estimate an energy scale that controls the sign in the p-wave case, which results proportional to the square root of the gap and the coupling to superconductor. The analytical results obtained with a simple 1D model are confirmed by a more realistic tight-binding model.Comment: 10 pages, 15 figures, published versio

ASASSN-18aan revisited

The light curve of the cataclismic variable ASASSN-18aan is studied using recent observations of the MC589 Observatory, giving an orbital Period and Epoch fully consistent with the data obtained after the discovery flare in 2018. Archival data from ASASSN, ZTF and Gaia were used to check if its flares have a quasi-periodic behaviour. A recurrency time scale of about 11 months is found, confirming a previous tentative result using the historic plate archive of the Asiago Observatory. The next outbursts are expected by April 2023 and March 2024.Comment: 7 pages, 2 figures, published on OEJ

Vetigastropoda and Neritimorpha from the Lower Bajocian of Luxembourg and palaeobiogeography of Aalenian\u2013Bajocian (Middle Jurassic) gastropods of western Europe

Vetigastropod and neritimorph species from Lower Bajocian (Middle Jurassic) sediments of south-western Luxembourg are described. Eighteen species are recognized. Two new genera \u2013 Szabotomaria gen. nov. and Fabercapulus gen. nov. \u2013 and four new species \u2013 Szabotomaria ziqquratiformis sp. nov., Colpomphalus thuyi sp. nov., Colpomphalus tigratus sp. nov. and Fabercapulus semisculptus sp. nov. \u2013 are erected. These species, together with other species recently described from the same strata, are part of a diverse assemblage consisting of 32 species belonging to 14 genera in six families and five superfamilies, representing the richest vetigastropod-neritimorph fauna currently known from Bajocian and sub-coeval deposits of western Europe. An analysis of the palaeoecological and palaeobiogeographical relationships of this fauna and those from other areas of the western European shelf was performed using cluster analysis and by comparison of the respective taxonomic structures. The former detected a major cluster composed of two distinct branches: the faunas of the northern Paris-Wessex Basin, including Luxembourg, and those of the southern Germany basin. These faunas have similar taxonomic structures and occur mainly in facies represented by condensed iron ooid-rich marls and limestones deposited in lower offshore to upper offshore-shoreface settings. The close relationship between the Luxembourg and other faunas of the Paris-Wessex Basin reflects free faunal exchange and facies similarities. Slight differences in the sedimentary context could explain the separation of the southern German from the Anglo-Paris branch, whereas similarities between Swabian and Franconian faunas most probably reflect the geographical continuity of these areas. The Early Bajocian fauna of the East Midlands Shelf comes from sediments deposited in a shallow-water, oolitic barrier complex and is different from other western European faunas in both species composition and taxonomic structure

Normalization of oligonucleotide arrays based on the least-variant set of genes

<p>Abstract</p> <p>Background</p> <p>It is well known that the normalization step of microarray data makes a difference in the downstream analysis. All normalization methods rely on certain assumptions, so differences in results can be traced to different sensitivities to violation of the assumptions. Illustrating the lack of robustness, in a striking spike-in experiment all existing normalization methods fail because of an imbalance between up- and down-regulated genes. This means it is still important to develop a normalization method that is robust against violation of the standard assumptions</p> <p>Results</p> <p>We develop a new algorithm based on identification of the least-variant set (LVS) of genes across the arrays. The array-to-array variation is evaluated in the robust linear model fit of pre-normalized probe-level data. The genes are then used as a reference set for a non-linear normalization. The method is applicable to any existing expression summaries, such as MAS5 or RMA.</p> <p>Conclusion</p> <p>We show that LVS normalization outperforms other normalization methods when the standard assumptions are not satisfied. In the complex spike-in study, LVS performs similarly to the ideal (in practice unknown) housekeeping-gene normalization. An R package called lvs is available in <url>http://www.meb.ki.se/~yudpaw</url>.</p

Separation of heat and charge currents for boosted thermoelectric conversion

In a multi-terminal device the (electronic) heat and charge currents can follow different paths. In this paper we introduce and analyse a class of multi-terminal devices where this property is pushed to its extreme limits, with charge $and$ heat currents flowing in different reservoirs. After introducing the main characteristics of such $heat-charge$ $current$ $separation$ regime we show how to realise it in a multi-terminal device with normal and superconducting leads. We demonstrate that this regime allows to control independently heat and charge flows and to greatly enhance thermoelectric performances at low temperatures. We analyse in details a three-terminal setup involving a superconducting lead, a normal lead and a voltage probe. For a generic scattering region we show that in the regime of heat-charge current separation both the power factor and the figure of merit $ZT$ are highly increased with respect to a standard two-terminal system. These results are confirmed for the specific case of a system consisting of three coupled quantum dots.Comment: 12 pages, 8 figure

Electronic Quantum Interference-Diffraction Effects

The thesis work is set in the framework of quantum imaging, an area of quantum optics that exploits quantum correlations (such as quantum entanglement) to reconstruct images of object, with resolution or other characteristics that exceed the limits of classical optics. Recently, several experiments demonstrated the possibility of implementing ghost imaging and ghost diffraction schemes with photonic fields. The goal of this thesis is to analyze diffraction effects and to reconstruct images in the case of electronic sources. The basic idea is to observe ghost diffraction effects exploiting the quantum correlation of a Cooper pair emitted by a superconductive source in such a way that one electron goes in opposite direction with respect to the other. This idea originates from a formal analogy with systems having biphotonic correlated sources (twin-beams). After a brief review of the relevant experiments about ghost imaging, ghost interference and electron field emission, an effective model for the emission of Cooper pairs in the vacuum is introduced. This model exploits the matrix element formalism; a perturbation approach is exploited in the hypothesis of weak coupling. The dynamics of the system in the presence of an object (e.g. a single- or double-slit aperture) is studied, focusing on the non equilibrium steady state and on the far field limit. A gedanken-experiment is proposed in different configurations, aiming to reconstruct the image or the diffraction pattern through coincidence counting measurements of particles from different directions. The fundamental aspect is that one moves only the second detector, the one that detects particles that do not ``see'' the object, while the other is held fix. The first obtained result is just formal: various contributions, depending on the parameters of the system, are isolated and analyzed one by one. Then, some limit cases are discussed.The first one is the one with a planar infinite source. The ghost diffraction/interference effect is verified by numerical simulations and the direct analytic calculation of the point-like case, both showing patterns similar to that of classical optics, with the exception of the object-second detector distance being the relevant one. The result is totally analogous to the photonic case.The second setup is the one with a space-limited spherical-symmetric superconductive source. Interference fringes are not observed; instead, in case of not too small objects, one can reconstruct the image of the aperture. The specific cases of single and double slits are discussed

Pleomorphic adenoma rehabilitative treatment in growing up patient: a 20-years follow-up

OBJECTIVE: Although tumors of minor salivary glands are rare, the pleomorphic adenoma is the most common pathology among the benign neoplasm and can be found with high prevalence in the junction between hard palate and soft palate. Most of the maxillary tumors are surgically treated through either a total or partial maxillectomy. However, surgical defects lead to both clinical and psychologic disorders for the patient. A postoperative obturator prosthesis is a good option in patients who underwent maxillectomy. It allows to restore both masticatory and speaking functions, as well as aesthetic appearance. When reconstruction of the surgical site is possible, an implant-supported prosthesis can be considered to guarantee a better function and aesthetic's rehabilitation. CASE REPORT: This clinical report presents the prosthetic rehabilitation of a patient who underwent maxillectomy because of a pleomorphic adenoma of hard palate minor salivary glands. The patient was treated with a palatal obturator prosthesis first and with an implant-supported prosthesis after surgical site's reconstruction and complete healing. CONCLUSIONS: The rehabilitation of the patient after maxillectomy through both these devices was an excellent option and provided clinical benefits, improving the patient's quality of life, allowing the patient's reinsertion into societ