Over-Bias Light Emission due to Higher Order Quantum Noise of a Tunnel Junction

Understanding tunneling from an atomically sharp tip to a metallic surface requires to account for interactions on a nanoscopic scale. Inelastic tunneling of electrons generates emission of photons, whose energies intuitively should be limited by the applied bias voltage. However, experiments by Schull et al. [Phys. Rev. Lett. 102, 057401 (2009)] indicate that more complex processes involving the interaction of electrons with plasmon polaritons lead to photon emission characterized by over-bias energies. We propose a model of this observation in analogy to dynamical Coulomb blockade, originally developed for treating the electronic environment in mesoscopic circuits. We explain the experimental finding quantitatively by the correlated tunneling of two electrons interacting with an LRC circuit modeling the local plasmon-polariton mode. To explain the over-bias emission, the non-Gaussian statistics of the tunneling dynamics of the electrons is essential.Comment: 5 pages, 4 figure

Josephson current through a quantum dot coupled to a molecular magnet

Josephson currents are carried by sharp Andreev states within the superconducting energy gap. We theoretically study the electronic transport of a magnetically tunable nanoscale junction consisting of a quantum dot connected to two superconducting leads and coupled to the spin of a molecular magnet. The exchange interaction between the molecular magnet and the quantum dot modifies the Andreev states due to a spin-dependent renormalization of the quantum dot's energy level and the induction of spin-flips. A magnetic field applied to the central region of the quantum dot and the molecular magnet further tunes the Josephson current and starts a precession of the molecular magnet's spin. We use a non-equilibrium Green's function approach to evaluate the transport properties of the junction. Our calculations reveal that the energy level of the dot, the magnetic field and the exchange interaction between the molecular magnet and the electrons occupying the energy level of the quantum dot can trigger transitions from a 0 to a $\pi$ state of the Josephson junction. The redistribution of the occupied states induced by the magnetic field strongly modifies the current-phase relation. The critical current exhibits a sharp increase as a function of either the energy level of the dot, the magnetic field or the exchange interaction.Comment: 10 pages, 7 figure

Emergence of a negative charging energy in a metallic dot capacitively coupled to a superconducting island

We consider the hybrid setup formed by a metallic dot, capacitively coupled to a superconducting island S connected to a bulk superconductor by a Josephson junction. Charge fluctuations in S act as a dynamical gate and overscreen the electronic repulsion in the metallic dot, producing an attractive interaction between two additional electrons. As the offset charge of the metallic dot is increased, the dot charging curve shows positive steps ($+2e$) followed by negative ones ($-e$) signaling the occurrence of a negative differential capacitance. A proposal for experimental detection is given, and potential applications in nanoelectronics are mentioned.Comment: Revised version, 4 pages, 4 figure

Spin-precession-assisted supercurrent in a superconducting quantum point contact coupled to a single-molecule magnet

The supercurrent of a quantum point contact coupled to a nanomagnet strongly depends on the dynamics of the nanomagnet's spin. We employ a fully microscopic model to calculate the transport properties of a junction coupled to a spin whose dynamics is modeled as Larmor precession brought about by an external magnetic field and find that the dynamics affects the charge and spin currents by inducing transitions between the continuum states below the superconducting gap edge and the Andreev levels. This redistribution of the quasiparticles leads to a non-equilibrium population of the Andreev levels and an enhancement of the supercurrent which is visible as a modified current-phase relation as well as a non-monotonous critical current as function of temperature. The non-monotonous behavior is accompanied by a corresponding change in spin-transfer torques acting on the precessing spin and leads to the possibility of using temperature as a means to tune the back-action on the spin.Comment: 11 pages, 5 figure

Security governance and the private military industry in Europe and North America

Even before Iraq the growing use of private military contractors has been widely discussed in the academic and public literature. However, the reasons for this proliferation of private military companies and its implications are frequently generalized due to a lack of suitable theoretical approaches for the analysis of private means of violence in contemporary security. As a consequence, this article contends, the analysis of the growth of the private military industry typically conflates two separate developments: the failure of some developing states to provide for their national security and the privatisation of military services in industrialized nations in Europe and North America. This article focuses on the latter and argues that the concept of security governance can be used as a theoretical framework for understanding the distinct development, problems and solutions for the governance of the private military industry in developed countries.The United States Institute of Peace and the German Academic Exchange Service

PINCH is an independent prognostic factor in rectal cancer patients without preoperative radiotherapy - a study in a Swedish rectal cancer trial of preoperative radiotherapy

<p>Abstract</p> <p>Background</p> <p>The clinical significance between particularly interesting new cysteine-histidine rich protein (PINCH) expression and radiotherapy (RT) in tumours is not known. In this study, the expression of PINCH and its relationship to RT, clinical, pathological and biological factors were studied in rectal cancer patients.</p> <p>Methods</p> <p>PINCH expression determined by immunohistochemistry was analysed at the invasive margin and inner tumour area in 137 primary rectal adenocarcinomas (72 cases without RT and 65 cases with RT). PINCH expression in colon fibroblast cell line (CCD-18 Co) was determined by western blot.</p> <p>Results</p> <p>In patients without RT, strong PINCH expression at the invasive margin of primary tumours was related to worse survival, compared to patients with weak expression, independent of TNM stage and differentiation (<it>P </it>= 0.03). No survival relationship in patients with RT was observed (<it>P </it>= 0.64). Comparing the non-RT with RT subgroup, there was no difference in PINCH expression in primary tumours (invasive margin (<it>P </it>= 0.68)/inner tumour area (<it>P </it>= 0.49). In patients with RT, strong PINCH expression was related to a higher grade of LVD (lymphatic vessel density) (<it>P </it>= 0.01)</p> <p>Conclusions</p> <p>PINCH expression at the invasive margin was an independent prognostic factor in patients without RT. RT does not seem to directly affect the PINCH expression.</p

Nutritional regulation of oligodendrocyte differentiation regulates perineuronal net remodeling in the median eminence

The mediobasal hypothalamus (MBH; arcuate nucleus of the hypothalamus [ARH] and median eminence [ME]) is a key nutrient sensing site for the production of the complex homeostatic feedback responses required for the maintenance of energy balance. Here, we show that refeeding after an overnight fast rapidly triggers proliferation and differentiation of oligodendrocyte progenitors, leading to the production of new oligodendrocytes in the ME specifically. During this nutritional paradigm, ME perineuronal nets (PNNs), emerging regulators of ARH metabolic functions, are rapidly remodeled, and this process requires myelin regulatory factor (Myrf) in oligodendrocyte progenitors. In genetically obese ob/ob mice, nutritional regulations of ME oligodendrocyte differentiation and PNN remodeling are blunted, and enzymatic digestion of local PNN increases food intake and weight gain. We conclude that MBH PNNs are required for the maintenance of energy balance in lean mice and are remodeled in the adult ME by the nutritional control of oligodendrocyte differentiation

Deep Eyedentification: Biometric Identification using Micro-Movements of the Eye

We study involuntary micro-movements of the eye for biometric identification. While prior studies extract lower-frequency macro-movements from the output of video-based eye-tracking systems and engineer explicit features of these macro-movements, we develop a deep convolutional architecture that processes the raw eye-tracking signal. Compared to prior work, the network attains a lower error rate by one order of magnitude and is faster by two orders of magnitude: it identifies users accurately within seconds

Understanding Interorganizational Learning Based on Social Spaces and Learning Episodes

Different organizational settings have been gaining ground in the world economy, resulting in a proliferation of different forms of strategic alliances that translate into a growth in the number of organizations that have started to deal with interorganizational relationships with different actors. These circumstances reinforce Crossan, Lane, White and Djurfeldt (1995) and Crossan, Mauer and White (2011) in exploring what authors refer to as the fourth, interorganizational, level of learning. These authors, amongst others, suggest that the process of interorganizational learning (IOL) warrants investigation, as its scope of analysis needs widening and deepening. Therefore, this theoretical essay is an attempt to understand IOL as a dynamic process found in interorganizational cooperative relationships that can take place in different structured and unstructured social spaces and that can generate learning episodes. According to this view, IOL is understood as part of an organizational learning continuum and is analyzed within the framework of practical rationality in an approach that is less cognitive and more social-behavioral