Two-Twenty

The sixth hour of hogs was rolling by me. Men were working on hogs all around me. The single track that held the hogs suspended curved in front of me and in back of me..

The Naked Chain

It is not often that I think of this. Only when I am alone, as out on the southwester plains, standing beside the gray pavement stretching deep into the horizon which is my life..

Non-ideal artificial phase discontinuity in long Josephson 0-kappa-junctions

We investigate the creation of an arbitrary $\kappa$-discontinuity of the Josephson phase in a long Nb-AlO_x-Nb Josephson junction (LJJ) using a pair of tiny current injectors, and study the formation of fractional vortices formed at this discontinuity. The current I_inj, flowing from one injector to the other, creates a phase discontinuity kappa ~ I_inj. The calibration of injectors is discussed in detail. The small but finite size of injectors leads to some deviations of the properties of such a 0-kappa-LJJ from the properties of a LJJ with an ideal kappa-discontinuity. These experimentally observed deviations in the dependence of the critical current on I_inj$ and magnetic field can be well reproduced by numerical simulation assuming a finite injector size. The physical origin of these deviations is discussed.Comment: Submitted to Phys. Rev. B (12 figures). v 2: refs updated, long eqs fixed v 3: major changes, fractional vortex dynamics exclude

Kongenitale Nävi im Kindesalter

Zusammenfassung: Nävi stellen kongenitale hamartomatöse Fehlbildungen unterschiedlicher Bestandteile der Haut dar. Am häufigsten treten kongenitale melanozytäre Nävi (CMN) auf, gefolgt von Nävi epithelialen Ursprungs (epidermale und organoide Nävi). Insbesondere große CMN können zu schwerwiegenden Komplikationen führen, und das Management der Betroffenen stellt ab Geburt eine Herausforderung dar. Entgegen früheren Annahmen ist das Risiko einer malignen Entartung von CMN insgesamt als eher gering anzusehen, steigt jedoch in speziellen Situationen relevant an. Nicht zu vernachlässigen sind mögliche extrakutane Symptome im Falle einer ZNS-Beteiligung, und frühe bildgebende Untersuchungen gehören heute zur Routinediagnostik. Chirurgische Maßnahmen haben noch immer einen hohen Stellenwert in der Behandlung von CMN, die Indikation dazu ist jedoch von Fall zu Fall individuell abzuwägen. Nicht zuletzt leiden die Patienten häufig stark an der ästhetischen Beeinträchtigung durch ihr Muttermal, sodass in der Behandlung auch diesem Punkt Rechnung getragen werden muss. Der Naevus sebaceus ist der häufigste Vertreter der epithelialen Nävi. In 2-13% treten darin Zusatztumoren auf, und eine frühe chirurgische Exzision ist in den meisten Fällen nicht zuletzt auch aus ästhetischen Überlegungen sinnvoll. Epidermale Nävi erfordern bei generalisierter Ausdehnung Zusatzuntersuchungen zum Ausschluss von assoziierten ophthalmologischen, kardialen oder neurologischen Fehlbildunge

High-pressure phases and transitions of the layered alkaline earth nitridosilicates SrSiN2 and BaSiN2

We investigate the high-pressure phase diagram of SrSiN2 and BaSiN2 with density-functional calculation. Searching a manifold of possible candidate structures, we propose new structural modifications of SrSiN2 and BaSiN2 attainable in high-pressure experiments. The monoclinic ground state of SrSiN2 transforms at 3 GPa into an orthorhombic BaSiN2 type. At 14 GPa a CaSiN2-type structure becomes the most stable configuration of SrSiN2. A hitherto unknown Pbcm modification is adopted at 85 GPa and, finally, at 131 GPa a LiFeO2-type structure. The higher homologue BaSiN2 transforms to a CaSiN2 type at 41 GPa and further to a Pbcm modification at 105 GPa. Both systems follow the pressure-coordination rule: the coordination environment of Si increases from tetrahedral through trigonal bipyramidal to octahedral. Some high-pressure phases are related in structure through simple group–subgroup mechanisms, indicating displacive phase transformations with low activation barriers

Active control of the aerodynamic performance and tonal noise of axial turbomachines

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Two projects on axial fans are presented in this paper. The first aims at improving the aerodynamic performance and reducing the tip clearance noise caused by the rotating instability. This is achieved by injecting air into the radial gap between the impeller blade tips and the fan casing. Steady air injection with small mass flows results in remarkable reductions in the noise level along with improved aerodynamic performance. Larger injected mass flows give significant improvements in the aerodynamic performance at the expense of an increased overall noise level. The second project uses flow control actively to reduce the blade passage frequency (BPF) level. Experimental results are presented for steady jets injected into the main flow and cylindrical rods at axial positions downstream of the impeller blades. The method is successful for higher-order mode sound fields where the BPF level is reduced by up to 20.5 dB.DFB, SFB 557, Beeinflussung komplexer turbulenter Scherströmunge

Classical and Quantum Annealing in the Median of Three Satisfiability

We determine the classical and quantum complexities of a specific ensemble of three-satisfiability problems with a unique satisfying assignment for up to N=100 and N=80 variables, respectively. In the classical limit we employ generalized ensemble techniques and measure the time that a Markovian Monte Carlo process spends in searching classical ground states. In the quantum limit we determine the maximum finite correlation length along a quantum adiabatic trajectory determined by the linear sweep of the adiabatic control parameter in the Hamiltonian composed of the problem Hamiltonian and the constant transverse field Hamiltonian. In the median of our ensemble both complexities diverge exponentially with the number of variables. Hence, standard, conventional adiabatic quantum computation fails to reduce the computational complexity to polynomial. Moreover, the growth-rate constant in the quantum limit is 3.8 times as large as the one in the classical limit, making classical fluctuations more beneficial than quantum fluctuations in ground-state searches

Synthesis for Polynomial Lasso Programs

We present a method for the synthesis of polynomial lasso programs. These programs consist of a program stem, a set of transitions, and an exit condition, all in the form of algebraic assertions (conjunctions of polynomial equalities). Central to this approach is the discovery of non-linear (algebraic) loop invariants. We extend Sankaranarayanan, Sipma, and Manna's template-based approach and prove a completeness criterion. We perform program synthesis by generating a constraint whose solution is a synthesized program together with a loop invariant that proves the program's correctness. This constraint is non-linear and is passed to an SMT solver. Moreover, we can enforce the termination of the synthesized program with the support of test cases.Comment: Paper at VMCAI'14, including appendi

On the formation/dissolution of equilibrium droplets

We consider liquid-vapor systems in finite volume $V\subset\R^d$ at parameter values corresponding to phase coexistence and study droplet formation due to a fixed excess $\delta N$ of particles above the ambient gas density. We identify a dimensionless parameter $\Delta\sim(\delta N)^{(d+1)/d}/V$ and a \textrm{universal} value \Deltac=\Deltac(d), and show that a droplet of the dense phase occurs whenever \Delta>\Deltac, while, for \Delta<\Deltac, the excess is entirely absorbed into the gaseous background. When the droplet first forms, it comprises a non-trivial, \textrm{universal} fraction of excess particles. Similar reasoning applies to generic two-phase systems at phase coexistence including solid/gas--where the ``droplet'' is crystalline--and polymorphic systems. A sketch of a rigorous proof for the 2D Ising lattice gas is presented; generalizations are discussed heuristically.Comment: An announcement of a forthcoming rigorous work on the 2D Ising model; to appear in Europhys. Let