Deriving the term structure of banking crisis risk with a compound option approach: The case of Kazakhstan

We use a compound option-based structural credit risk model to infer a term structure of banking crisis risk from market data on bank stocks in daily frequency. Considering debt service payments with different maturities this term structure assigns a separate estimator for short- and long-term default risk to each maturity. Applying the Duan (1994) maximum likelihood approach, we find for Kazakhstan that the overall crisis probability was mainly driven by short-term risk, which increased from 25% in March 2007 to 80% in December 2008. Concurrently, the long-term default risk increased from 20% to only 25% during the same period. --Banking crisis,bank default,option pricing theory,compound option,liability structure

Classical many-body time crystals

Discrete time crystals are a many-body state of matter where the extensive system's dynamics are slower than the forces acting on it. Nowadays, there is a growing debate regarding the specific properties required to demonstrate such a many-body state, alongside several experimental realizations. In this work, we provide a simple and pedagogical framework by which to obtain many-body time crystals using parametrically coupled resonators. In our analysis, we use classical period-doubling bifurcation theory and present a clear distinction between single-mode time-translation symmetry breaking and a situation where an extensive number of degrees of freedom undergo the transition. We experimentally demonstrate this paradigm using coupled mechanical oscillators, thus providing a clear route for time crystals realizations in real materials.Comment: 23 pages, 5 figures, comments are welcom

The role of fluctuations in quantum and classical time crystals

Discrete time crystals (DTCs) are a many-body state of matter whose dynamics are slower than the forces acting on it. The same is true for classical systems with period-doubling bifurcations. Hence, the question naturally arises what differentiates classical from quantum DTCs. Here, we analyze a variant of the Bose-Hubbard model, which describes a plethora of physical phenomena and has both a classical and a quantum time-crystalline limit. We study the role of fluctuations on the stability of the system and find no distinction between quantum and classical DTCs. This allows us to probe the fluctuations in an experiment using two strongly coupled parametric resonators subject to classical noise.Comment: 11 pages, 5 figure

The impact of the AO foundation on fracture care : an evaluation of 60 years AO foundation

Objectives Sixty years ago, the Association of Osteosynthesis (AO) was founded with the aim to improve fracture treatment and has since grown into one of the largest medical associations worldwide. Aim of this study was to evaluate AO's impact on science, education, patient care and the MedTech business. Design/methods Impact evaluations were conducted as appropriate for the individual domains: Impact on science was measured by analyzing citation frequencies of publications promoted by AO. Impact on education was evaluated by analyzing the evolution of number and location of AO courses. Impact on patient care was evaluated with a health economic model analyzing cost changes and years of life gained through the introduction of osteosynthesis in 17 high-income countries (HICs). Impact on MedTech business was evaluated by analyzing sales data of AO-associated products. Results Thirty-five AO papers and 2 major AO textbooks are cited at remarkable frequencies in high ranking journals with up to 2000 citations/year. The number of AO courses steadily increased with a total of 645'000 participants, 20‘000 teaching days and 2‘500 volunteer faculty members so far. The introduction of osteosynthesis saved at least 925 billion Swiss Francs [CHF] in the 17 HICs analyzed and had an impact on avoiding premature deaths comparable to the use of antihypertensive drugs. AO-associated products generated sales of 55 billion CHF. Conclusion AO's impact on science, education, patient care, and the MedTech business was significant because AO addressed hitherto unmet needs by combining activities that mutually enriched and reinforced each other

FcγReceptors IIa on Cardiomyocytes and Their Potential Functional Relevance in Dilated Cardiomyopathy

ObjectivesThe purpose of this study was to investigate how cardiac autoantibodies might contribute to cardiac dysfunction in patients suffering from dilated cardiomyopathy (DCM).BackgroundIn the majority of DCM patients, it is possible to detect antibodies with negative inotropic effect on cardiomyocytes. The manner in which these antibodies impair cardiac function is poorly understood.MethodsImmunoglobulin (Ig)G was prepared from plasma of 11 DCM patients containing antibodies that induced a negative inotropic effect on cardiomyocytes. We analyzed the effects of antibodies/IgG fragments on calcium transients and on systolic cell shortening of adult rat cardiomyocytes and investigated the dependency of these effects on potential cardiomyocyte Fc receptors.ResultsIn contrast to control subjects, intact IgG from DCM patients reduced calcium transients and cell shortening of cardiomyocytes. The F(ab′)2fragments of these antibodies did not induce these effects but inhibited the functional effects of DCM-IgG of the respective patients’ IgG. These effects were also inhibited by Fc fragments of normal IgG. Reconstitution of the Fc part by incubation of cardiomyocytes with DCM-F(ab′)2fragments followed by goat-anti-human-F(ab′)-IgG again induced reduction of cell shortening and of calcium transients. In rat and human ventricular cardiomyocytes, Fcγreceptors IIa (CD32) were demonstrated by immunofluorescence.ConclusionsOur findings indicate that DCM-IgG-F(ab′)2bind to their cardiac antigen(s), but the Fc part might trigger the negative inotropic effects via the newly detected Fcγreceptor on cardiomyocytes. These results point to a novel potential mechanism for antibody-induced impairment of cardiac function in DCM patients

Ghost in the Ising machine

Coupled nonlinear systems have promise for parallel computing architectures. En route to realizing complex networks for Ising machines, we report an experimental and theoretical study of two coupled parametric resonators (parametrons). The coupling severely impacts the bifurcation topology and the number of available solutions of the system; in part of the stability diagram, we can access fewer solutions than expected. When applying noise to probe the stability of the states, we find that the switching rates and the phase-space trajectories of the system depend on the detuning in surprising ways. We present a theoretical framework that heralds the existence of 'ghost bifurcations'. These bifurcations involve only unstable solutions and lead to avoided zones in phase space. The emergence of such ghost bifurcations is an important feature of parametron networks that can influence their application for parallel logic operations

Rapid flipping of parametric phase states

Since the invention of the solid-state transistor, the overwhelming majority of computers followed the von Neumann architecture that strictly separates logic operations and memory. Today, there is a revived interest in alternative computation models accompanied by the necessity to develop corresponding hardware architectures. The Ising machine, for example, is a variant of the celebrated Hopfield network based on the Ising model. It can be realized with artifcial spins such as the `parametron' that arises in driven nonlinear resonators. The parametron encodes binary information in the phase state of its oscillation. It enables, in principle, logic operations without energy transfer and the corresponding speed limitations. In this work, we experimentally demonstrate flipping of parametron phase states on a timescale of an oscillation period, much faster than the ringdown time \tau that is often (erroneously) deemed a fundamental limit for resonator operations. Our work establishes a new paradigm for resonator-based logic architectures.Comment: 6 pages, 3 figure

GHz nanomechanical resonator in an ultraclean suspended graphene p-n junction

We demonstrate high-frequency mechanical resonators in ballistic graphene p-n junctions. Fully suspended graphene devices with two bottom gates exhibit ballistic bipolar behavior after current annealing. We determine the graphene mass density and built-in tension for different current annealing steps by comparing the measured mechanical resonant response to a simplified membrane model. We consistently find that after the last annealing step the mass density compares well with the expected density of pure graphene. In a graphene membrane with high built-in tension, but still of macroscopic size with dimensions 3 $\times$ 1 $\mu m^{2}$, a record resonance frequency of 1.17 GHz is observed after the final current annealing step. We further compare the resonance response measured in the unipolar with the one in the bipolar regime. Remarkably, the resonant signals are strongly enhanced in the bipolar regime. This enhancement is caused in part by the Fabry-Perot resonances that appear in the bipolar regime and possibly also by the photothermoelectric effect that can be very pronounced in graphene p-n junctions under microwave irradiation.Comment: 16 pages, 4 figures, 1 tabl

Spatially resolved surface dissipation over metal and dielectric substrates

We report spatially resolved measurements of static and fluctuating electric fields over conductive (Au) and non-conductive (SiO2) surfaces. Using an ultrasensitive `nanoladder' cantilever probe to scan over these surfaces at distances of a few tens of nanometers, we record changes in the probe resonance frequency and damping that we associate with static and fluctuating fields, respectively. We find that the two quantities are spatially correlated and of similar magnitude for the two materials. We quantitatively describe the observed effects on the basis of trapped surface charges and dielectric fluctuations in an adsorbate layer. Our results provide direct, spatial evidence for surface dissipation in adsorbates that affects nanomechanical sensors, trapped ions, superconducting resonators, and color centers in diamond