Dimensionality-Driven Photoproduction of Massive Dirac Pairs near Threshold in Gapped Graphene Monolayers.

Generation of quasiparticle-hole pairs in gapped graphene monolayers in the combined field of two counterpropagating light waves is studied. The process represents an analog of electron-positron pair production from the vacuum of quantum electrodynamics (QED) by the Breit-Wheeler effect. We show, however, that the two-dimensional structure of graphene causes some striking differences between both scenarios. In particular, contrary to the QED case, it allows for nonzero pair production rates at the energy threshold when the Breit-Wheeler reaction proceeds nonlinearly with absorption of three photons.

Weak Measurement Protocols for Majorana Bound State Identification.

We propose a continuous weak measurement protocol testing the nonlocality of Majorana bound states through current shot noise correlations. The experimental setup contains a topological superconductor island with three normal-conducting leads weakly coupled to different Majorana states. Putting one lead at finite voltage and measuring the shot noise correlations between the other two (grounded) leads, devices with true Majorana states are distinguished from those without by strong current correlations. The presence of true Majorana states manifests itself in unusually high noise levels or the near absence of noise, depending on the chosen device configuration. Monitoring the noise statistics amounts to a weak continuous measurement of the Majorana qubit and yields information similar to that of a full braiding protocol, but at much lower experimental effort. Our theory can be adapted to different platforms and should allow for the clear identification of Majorana states.

Giant Shot Noise from Majorana Zero Modes in Topological Trijunctions.

The clear-cut experimental identification of Majorana bound states in transport measurements still poses experimental challenges. We here show that the zero-energy Majorana state formed at a junction of three topological superconductor wires is directly responsible for giant shot noise amplitudes, in particular at low voltages and for small contact transparency. The only intrinsic noise limitation comes from the current-induced dephasing rate due to multiple Andreev reflection processes.

First reported implementation of a German-language progress test in an undergraduate dental curriculum: A prospective study.

INTRODUCTION: Progress testing is a special form of longitudinal and feedback-oriented assessment. Even though well established in human medical curricula, this is not the case in dental education. The aim was the prospective development and implementation of the first reported German-language Dental Progress Test (DPT) for the undergraduate dental curriculum at the Medical University of Graz, Austria. MATERIAL AND METHODS: Participation in DPT was compulsory for all dental students in terms 7-12 (years 4-6). Three tests, each consisting of 100 items out of a pool of 375, were administered within 3 consecutive terms in 2016 and 2017. Rasch analyses were used to evaluate the questionnaire and identify misfitting items. RESULTS: In the item responses, 59.7% were "correct," 27.0% were "false" and 13.3% were answered with "don't know," with similar results at all 3 time points. The assumption of parallel ICC was met (T1: χ2  = 51.071, df = 74, P = .981; T2: χ2  = 57.044, df = 67, P = .802; T3: χ2  = 58.443, df = 72, P = .876) and item difficulties for the thematic fields were similarly distributed across the latent dimensions. CONCLUSION: The newly introduced DPT is appropriate for testing dental students and is well balanced for the tested target group.

6π Josephson Effect in Majorana Box Devices.

We study Majorana devices featuring a competition between superconductivity and multichannel Kondo physics. Our proposal extends previous work on single-channel Kondo systems to a topologically nontrivial setting of a non-Fermi liquid type, where topological superconductor wires (with gap Δ) represent leads tunnel coupled to a Coulomb-blockaded Majorana box. On the box, a spin degree of freedom with Kondo temperature T_{K} is nonlocally defined in terms of Majorana states. For Δ≫T_{K}, the destruction of Kondo screening by superconductivity implies a 4π-periodic Josephson current-phase relation. Using a strong-coupling analysis in the opposite regime Δ≪T_{K}, we find a 6π-periodic Josephson relation for three leads, with critical current I_{c}≈eΔ^{2}/ℏT_{K}, corresponding to the transfer of fractionalized charges e^{*}=2e/3.

Towards Realistic Implementations of a Majorana Surface Code.

Surface codes have emerged as promising candidates for quantum information processing. Building on the previous idea to realize the physical qubits of such systems in terms of Majorana bound states supported by topological semiconductor nanowires, we show that the basic code operations, namely projective stabilizer measurements and qubit manipulations, can be implemented by conventional tunnel conductance probes and charge pumping via single-electron transistors, respectively. The simplicity of the access scheme suggests that a functional code might be in close experimental reach.

Multichannel Kondo impurity dynamics in a Majorana device.

We study the multichannel Kondo impurity dynamics realized in a mesoscopic superconducting island connected to metallic leads. The effective "impurity spin" is nonlocally realized by Majorana bound states and strongly coupled to lead electrons by non-Fermi liquid correlations. We explore the spin dynamics and its observable ramifications near the low-temperature fixed point. The topological protection of the system raises the perspective to observe multichannel Kondo impurity dynamics in experimentally realistic environments.

Majorana single-charge transistor.

We study transport through a Coulomb blockaded topologically nontrivial superconducting wire (with Majorana end states) contacted by metallic leads. An exact formula for the current through this interacting Majorana single-charge transistor is derived in terms of wire spectral functions. A comprehensive picture follows from three different approaches. We find Coulomb oscillations with universal halving of the finite-temperature peak conductance under strong blockade conditions, where the valley conductance mainly comes from elastic cotunneling. The nonlinear conductance exhibits finite-voltage sidebands due to anomalous tunneling involving Cooper pair splitting.

Genotypes and antibiotic resistance of Campylobacter coli in fattening pigs.

Campylobacter coli is a food-borne zoonotic pathogen causing human gastroenteritis worldwide. The organism is a commensal in the intestine of many food production animals including fattening pigs. The role of the pig as a potential reservoir for C. coli affecting human either directly or via poultry has hardly been investigated and genetic characterization of porcine strains is needed to address this question. For this aim multilocus sequence typing (MLST) and flaB typing was applied to 256 C. coli isolates from faeces of fattening pig collected during 2009 at different slaughterhouses in Switzerland. In addition genotypic resistances towards macrolides and quinolones based on point mutations in the 23S rRNA and gyrA genes, respectively, were determined. Of the 67 sequence types (STs) obtained by MLST, 37 were found for the first time. flaB typing revealed 46 different types with 14 of them being novel and was useful to further differentiate strains with an identical ST. Quinolone resistance was detected in 33.6% and macrolide resistance was found in 10.6% of isolates. Comparison with 99 C. coli pig isolates from 2001 revealed a significant decrease in antibiotic resistance towards both groups of antibiotics and there was high overlap between genotypes of 2001 and 2009. Little overlap of porcine genotypes was found with 97 C. coli isolates from poultry collected 2008, however, macrolide resistance was significantly higher in pig isolates. In conclusion, C. coli from Swiss pig are heterogeneous containing many novel STs, findings that could reflect the partitioned Swiss pig production with almost no international breed exchange. The antibiotic resistance echoes the use of corresponding drugs in the Swiss livestock production and indicates the efficacy of restrictive application of antibiotics in order to reduce resistances.

Helical Luttinger liquid in topological insulator nanowires.

We derive and analyze the effective low-energy theory for interacting electrons in a cylindrical nanowire made of a strong topological insulator. Three different approaches provide a consistent picture for the band structure, where surface states forming inside the bulk gap correspond to one-dimensional bands indexed by total angular momentum. When a half-integer magnetic flux pierces the nanowire, we find a strongly correlated helical Luttinger liquid topologically protected against weak disorder. We describe how transport experiments can detect this state.

Anomalous Josephson current through a spin-orbit coupled quantum dot.

For a general model of a mesoscopic multilevel quantum dot, we determine the necessary conditions for the existence of an anomalous Josephson current with spontaneously broken time-reversal symmetry. They correspond to a finite spin-orbit coupling, a suitably oriented Zeeman field, and the dot being a chiral conductor. We provide analytical expressions for the anomalous supercurrent covering a wide parameter regime.

Josephson-current-induced conformational switching of a molecular quantum dot.

We discuss the behavior of a two-level system coupled to a quantum dot contacted by superconducting source and drain electrodes, representing a simple model for the conformational degree of freedom of a molecular dot or a break junction. The Josephson current is shown to induce conformational changes, including a complete reversal. For small bias voltage, periodic conformational motions induced by Landau-Zener transitions between Andreev states are predicted.

Spin transport and bipolaron density in organic polymers.

We present a theory for spin-polarized transport through a generic organic polymer connected to ferromagnetic leads with arbitrary angle θ between their magnetization directions, taking into account the polaron and bipolaron states as effective charge and spin carriers. Within a diffusive description of polaron-bipolaron transport including polaron-bipolaron conversion, we find that the bipolaron density depends on the angle θ. This is remarkable, given the fact that bipolarons are spinless quasiparticles, and opens a new way to probe spin accumulation in organic polymers.

Interaction-induced harmonic frequency mixing in quantum dots.

We show that harmonic frequency mixing in quantum dots coupled to two leads under the influence of time-dependent voltages of different frequency is dominated by interaction effects. This offers a unique and direct spectroscopic tool to access correlations, and holds promise for efficient frequency mixing in nanodevices. Explicit results are provided for an Anderson dot and for a molecular level with phonon-mediated interactions.

Magnetic confinement of massless Dirac fermions in graphene.

Because of Klein tunneling, electrostatic potentials are unable to confine Dirac electrons. We show that it is possible to confine massless Dirac fermions in a monolayer graphene sheet by inhomogeneous magnetic fields. This allows one to design mesoscopic structures in graphene by magnetic barriers, e.g., quantum dots or quantum point contacts.

Tomonaga-Luttinger liquid and Coulomb blockade in multiwall carbon nanotubes under pressure.

We report that the conductance of macroscopic multiwall nanotube (MWNT) bundles under pressure shows power laws in temperature and voltage, as corresponding to a network of bulk-bulk connected Tomonaga-Luttinger liquids (LLs). Contrary to individual MWNTs, where the observed power laws are attributed to Coulomb blockade, the measured ratio for the end and bulk obtained exponents, approximately 2.4, can be accounted for only by LL theory. At temperatures characteristic of interband separation, it increases due to thermal population of the conducting sheets unoccupied bands.

Nonlinear magnetotransport in interacting chiral nanotubes.

Nonlinear transport through interacting single-wall nanotubes containing a few impurities is studied theoretically. Extending the Luttinger liquid theory to incorporate trigonal warping and chirality effects, we derive the current contribution Ie even in the applied voltage V and odd in an orbital magnetic field B, which is nonzero only for chiral tubes and in the presence of interactions.

Four-body problem and BEC-BCS crossover in a quasi-one-dimensional cold fermion gas.

The four-body problem for an interacting two-species Fermi gas is solved analytically in a confined quasi-one-dimensional geometry, where the two-body atom-atom scattering length a(aa) displays a confinement-induced resonance. We compute the dimer-dimer scattering length a(dd) and show that this quantity completely determines the many-body solution of the associated BEC-BCS crossover phenomenon in terms of bosonic dimers.

Hospital health care resource utilization and costs of colorectal cancer during the first 3-year period following diagnosis in Switzerland.

BACKGROUND: In industrialized countries, colorectal cancer is a leading cause of morbidity and mortality. Decisions on colorectal cancer screening are based on cost-effectiveness analyses that rely on colorectal cancer cost studies. Additionally, the study of the resource utilization pattern may lead to cost-saving strategies in the care of colorectal cancer. AIM: To estimate hospital resource utilization, the use of various therapy modalities and costs of colorectal cancer cases undergoing surgery during the first 3 years following the diagnosis at a Swiss university hospital. METHODS: Consecutive colorectal cancer patients from 1997 to 1998 were identified using the surgery database of the University Hospital of Basel and followed for a period of 3 years. In-hospital resource utilization and costs were retrieved from the computerized administrative records. Treatment outside of the hospital during the study period constituted an exclusion criterion. RESULTS: Eighty-three (94%) of 89 patients undergoing surgery for colorectal cancer were included in the study, 58 with colon cancer and 25 with rectal cancer. The average ages were 70.3 and 63.6 years, respectively. Overall, 59% of the patients were treated with surgery alone, 27% also had chemotherapy and 15% received additional chemoradiotherapy. These percentages and resource utilization varied broadly between the two colorectal cancer groups. On average, patients were admitted to the hospital 2.7 times and the hospital length of stay amounted to 35 days. They were visited by doctors 69 times, and examined with colonoscopy, ultrasonography and computerized tomography 2.7, 3.2 and 2.4 times, respectively. Mean costs incurred for rectal cancer (US dollars 40,230) were about 22% higher than for colon cancer patients (US dollars 33,079). Hospitalization and surgical therapy generated the greatest costs. Expenses were highest for the first year and with more severe disease stages at diagnosis. CONCLUSIONS: Colorectal cancer is an expensive disease. Economic analyses on screening should take into account the large resource utilization and cost variability by performing sensitivity analysis on broad cost ranges. Furthermore, they should consider stage shifting at diagnosis and include stage-specific costs.

Exact results for one-dimensional disordered bosons with strong repulsion.

We study one-dimensional disordered bosons with strong repulsive interactions. A Bose-Fermi mapping expresses this problem in terms of noninteracting Anderson-localized fermions, whereby known results for the distribution function of the local density of states, the spectral statistics, and density-density correlations can be transferred to this new domain of applicability. We show that disorder destroys bosonic quasi-long-range order by calculating the momentum distribution, and comment on the experimental observability of these predictions in ultracold atomic gases.