A Ballistic Graphene Cooper Pair Splitter

We report an experimental study of Cooper pair splitting in an encapsulated graphene based multiterminal junction in the ballistic transport regime. Our device consists of two transverse junctions, namely the superconductor/graphene/superconductor and the normal metal/graphene/normal metal junctions. In this case, the electronic transport through one junction can be tuned by an applied bias along the other. We observe clear signatures of Cooper pair splitting in the local as well as nonlocal electronic transport measurements. Our experimental data can be very well described by using a modified Octavio-Tinkham-Blonder-Klapwijk model and a three-terminal beam splitter model

Nonlinear thermoelectric effects in high-field superconductor-ferromagnet tunnel junctions

Thermoelectric effects result from the coupling of charge and heat transport, and can be used for thermometry, cooling and harvesting of thermal energy. The microscopic origin of thermoelectric effects is a broken electron-hole symmetry, which is usually quite small in metal structures, and vanishes at low temperatures. We report on a combined experimental and theoretical investigation of thermoelectric effects in superconductor/ferromagnet hybrid structures. We investigate the depencence of thermoelectric currents on the thermal excitation, as well as on the presence of a dc bias voltage across the junction. Large thermoelectric effects are observed in superconductor/ferromagnet and superconductor/normal-metal hybrid structures. The spin-independent signals observed under finite voltage bias are shown to be reciprocal to the physics of superconductor/normal-metal microrefrigerators. The spin-dependent thermoelectric signals in the linear regime are due to the coupling of spin and heat transport, and can be used to design more efficient refrigeratorsComment: 11 pages, submitted to Beilstein Journal of Nanotechnolog

BeppoSAX observations of the quasar Markarian 205

We present the first BeppoSAX observation (0.1 to 220 keV) of the quasar Mrk 205. We have searched for the unusual Fe line profile claimed in the XMM-Newton spectrum which has been widely discussed in recent literature. We find no evidence for a broad, ionized Fe line component in our data. We detect for the first time a Compton hump in this object. Besides, when this component is included in the fit, the line strength diminishes, in agreement with a recent re-analysis of the XMM-Newton data, but with better constraints on the reflection component thanks to the PDS instrument (15-220 keV). We interpret this fact as another indication for illumination of a distant and cold material rather than reprocessing in the highly ionized inner parts of an accretion disk. We cannot constrain the presence of a high energy cutoff but we confirm the existence of a variable soft excess (one year timescale).Comment: 13 pages, 12 figures, accepted for publication in A&

O značenju i nekim kontekstima termina ‘autonomija’. Konceptualno istraživanje

The paper aims to analyse conceptually the meaning of the term ‘autonomy’ and to examine critically its relations with other ethical norms. The question posed is whether autonomy is a right, or an ability, or a capacity, or an achievement, and whether it ought to be distinguished from self-determination. It is shown that autonomy is an anthropological principle, and that self-determination as its manifestation is a human right. As to its relation with other ethical norms, it is shown that there are possible conflicts between a patient’s and his doctor’s autonomies, as well as between autonomy and the duty to protect life, and between autonomy and care, so that trust plays an important role. The author concludes that man is autonomous not if and only if he is able to determine himself, but rather that he has the right to determine himself because he is autonomous. This holds for everybody from their beginning to their end, irrespective of what they are able to do and the situation they may be in. Since every human being is autonomous, autonomy entails self-limitation, and so it does not mean independence, but interdependence. As to trust, autonomy is to be acknowledged, while trust is to be practiced, since autonomy is of people, while trust is in people.Cet article tente d’analyser de manière conceptuelle la signification du terme d’autonomie et de questionner ses rapports avec d’autres normes éthiques. La question est de savoir si l’autonomie est un droit, une faculté ou une possibilité, et s’il faut la différencier de l’autodétermination. Il est montré que l’autonomie est un principe anthropologique et que l’autodétermination, qui en est sa manifestation, est un droit humain. En ce qui concerne ses rapports avec d’autres normes éthiques, il est montré que d’autres conflits sont possibles, des conflits entre l’autonomie du patient et l’autonomie du médecin, entre l’autonomie et les devoirs de protection de la vie, mais aussi entre l’autonomie et les soins. Ainsi, un rôle important revient à la confiance. L’auteur conclut que l’homme n’est pas autonome, si et seulement si, il est capable d’autodétermination, mais c’est bien parce qu’il a un droit à l’autodétermination qu’il est autonome. Cela vaut pour chacun depuis ses débuts jusqu’à ses fins, indépendamment de ce dont il est capable de faire et de la situation dans laquelle il peut se trouver. Étant donné que chaque être humain est autonome, l’autonomie entraîne à ses côtés l’autolimitation, de telle manière qu’il ne s’agit pas d’indépendance mais d’interdépendance. En ce qui concerne la confiance, l’autonomie doit être reconnue, et la confiance doit être pratiquée, car ce dont il s’agit c’est d’autonomie des personnes, et c’est bien en la personne que l’on a confiance.Der Beitrag gilt einer Analyse der Bedeutung des Terminus ‚Autonomie’ sowie einer kritischen Prüfung seiner Beziehungen zu anderen ethischen Normen. Zu klären ist, ob Autonomie ein Recht, eine Fähigkeit, ein Vermögen oder eine Errungenschaft darstellt und ob man zwischen Autonomie und Selbstbestimmung unterscheiden muss. Es wird gezeigt, dass Autonomie ein anthropologisches Prinzip ist und Selbstbestimmung als Manifestation von Autonomie ein menschliches Recht. Was die Beziehungen zu anderen ethischen Normen angeht, so zeigen sich mögliche ethische Konflikte zwischen Patienten- und Arztautonomie, zwischen Autonomie und der Pflicht zum Lebensschutz und zwischen Autonomie und Fürsorge, was der Norm des Vertrauens eine wichtige Rolle zuweist. Der Autor gelangt zu dem Ergebnis, dass der Mensch nicht deswegen noch dann autonom ist, wenn er sich selbst zu bestimmen in der Lage ist, sondern dass er das Recht zur Selbstbestimmung besitzt, weil er autonom ist. Dies gilt für jedermann, unabhängig von seinem Können oder seiner Lebenssituation, vom Anfang bis zum Ende seines Lebens. Da jedes menschliche Wesen in diesem Sinne autonom ist, impliziert Autonomie Selbstbegrenzung und somit nicht Unabhängigkeit, sondern Interdependenz. Was die Norm des Vertrauens angeht, so muss Autonomie anerkannt, Vertrauen hingegen praktiziert werden. Denn: Autonomie gehört untrennbar zum Menschen, Vertrauen gilt dem Menschen.Članak nastoji konceptualno analizirati značenje termina ‘autonomija’ i kritički ispitati njegove odnose s drugim etičkim normama. Postavlja se pitanje je li autonomija pravo ili sposobnost ili mogućnost te da li bi ju trebalo razlikovati od samoodređenja. Pokazuje se da je autonomija antropološki princip te da je samoodređenje kao njezina manifestacija ljudsko pravo. Što se tiče njezina odnosa s drugim etičkim normama, pokazuje se da su mogući sukobi između autonomije pacijenta i autonomije liječnika, kao i između autonomije i dužnosti zaštite života te između autonomije i skrbi, tako da važnu ulogu igra povjerenje. Autor zaključuje da čovjek nije autonoman ako i samo ako je sposoban za samoodređenje nego da ima pravo na samoodređenje zato što je autonoman. To važi za svakoga od njegova početka do njegova kraja, bez obzira na to što je sposoban učiniti i situaciju u kojoj se može naći. Budući da je svako ljudsko biće autonomno, autonomija za sobom povlači samoograničavanje, tako da ne znači nezavisnost, nego međuzavisnost. Što se tiče povjerenja, autonomiju treba priznavati, a povjerenje treba prakticirati zato što se radi o autonomiji ljudi, a povjerenje se ima u ljude

Compton processes in the bright AGN MCG+8-11-11

We present preliminary results on the hard X-ray emission properties of the Seyfert 1.5 galaxy MCG+8-11-11 as observed by INTEGRAL and SWIFT. All the INTEGRAL IBIS/ISGRI data available up to October 2009 have been analyzed together with two SWIFT/XRT snapshot observations performed in August and October 2009, quasi-simultaneously to INTEGRAL pointed observations of MCG+8-11-11. No correlation is observed between the hard X-ray flux and the spectral slope, while the position of the high-energy cut-off is found to have varied during the INTEGRAL observations. This points to a change in the temperature of the Comptonising medium from a minimum value of kT = 30-50 keV to values larger than 100-150 keV. There is no significant detection of Compton reflection, with a 3 sigma upper limit of R < 0.2, and no line has been detected at 112 keV, as previously claimed from HEAT observations (112 keV flux F < 2.4e-4 ph/cm^2/s). The variability behaviour of MCG+8-11-11 is found to be similar to that shown by IC 4329A, with different temperatures of the electron plasma for similar flux levels of the source, while other bright Seyfert galaxies present different variability patterns at hard X-rays, with spectral changes correlated to flux variations (e.g. NGC 4151).Comment: 6 pages, 4 figures. Accepted for publication on PoS (contribution PoS(INTEGRAL 2010)077), proceedings of the 8th INTEGRAL Workshop "The Restless Gamma-ray Universe" (September 2010, Dublin, Ireland

High-energy emission from NGC 5506, the brightest hard X-ray Narrow Line Seyfert 1 galaxy

We present results on the hard X-ray emission of NGC 5506, the brightest narrow line Seyfert 1 galaxy above 20 keV. All the recent observations by INTEGRAL, Swift and Suzaku have been analysed and spectral analysis during nine separated time periods has been performed. While flux variations by a factor of 2 were detected during the last 7 years, only moderate spectral variations have been observed, with the hint of a hardening of the X-ray spectrum and a decrease of the intrinsic absorption with time. Using Suzaku observations it is possible to constrain the amount of Compton reflection to R = 0.6-1.0, in agreement with previous results on the source. The signature of Comptonisation processes can also be found in the detection of a high-energy cut-off during part of the observations, at Ec = 40-100 keV. When a Comptonisation model is applied to the Suzaku data, the temperature and the optical depth of the Comptonising electron plasma are measured at kT = 60-80 keV and tau = 0.6-1.0, respectively. The properties inferred for NGC 5506 in this study agree with those based on other data sets for the same AGN, and fit the picture of NLS1 having in general lower high-energy cut-offs at hard X-rays than their broad line equivalent.Comment: 8 pages, 3 figures, 1 table. Proceedings of the Workshop "Narrow-Line Seyfert 1 Galaxies and Their Place in the Universe", Milano, April 4-6, 2011 (Proceedings of Science, http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=126

On the evolutionary behaviour of BL Lac objects

We present a new well defined sample of BL Lac objects selected from the ROSAT All-Sky Survey (RASS). The sample consists of 39 objects with 35 forming a flux limited sample down to f_X = 8 x 10^{-13} cgs, redshifts are known for 33 objects (and 31 of the complete sample). X-ray spectral properties were determined for each object individually with the RASS data. The luminosity function of RASS selected BL Lac objects is compatible with results provided by objects selected with the Einstein observatory, but the RASS selected sample contains objects with luminosities at least tenfold higher. Our analysis confirms the negative evolution for X-ray selected BL Lac objects found in a sample by the Einstein observatory, the parameterization provides similar results. A subdivision of the sample into halves according to the X-ray to optical flux ratio yielded unexpected results. The extremely X-ray dominated objects have higher redshifts and X-ray luminosities and only this subgroup shows clear signs of strong negative evolution. The evolutionary behaviour of objects with an intermediate spectral energy distribution between X-ray and radio dominated is compatible with no evolution at all. Consequences for unified schemes of X-ray and radio selected BL Lac objects are discussed.We suggest that the intermediate BL Lac objects are the basic BL Lac population. The distinction between the two subgroups can be explained if extreme X-ray dominated BL Lac objects are observed in a state of enhanced X-ray activity.Comment: 14 pages incl. 8 figures, accepted by A&