Observing Majorana bound states of Josephson vortices in topological superconductors

In recent years there has been an intensive search for Majorana fermion states in condensed matter systems. Predicted to be localized on cores of vortices in certain non-conventional superconductors, their presence is known to render the exchange statistics of bulk vortices non-Abelian. Here we study the equations governing the dynamics of phase solitons (fluxons) in a long Josephson junction in a topological superconductor. We show that the fluxon will bind a localized zero energy Majorana mode and will consequently behave as a non-Abelian anyon. The low mass of the fluxon, as well as its experimentally observed quantum mechanical wave-like nature, will make it a suitable candidate for vortex interferometry experiments demonstrating non-Abelian statistics. We suggest two experiments that may reveal the presence of the zero mode carried by the fluxon. Specific experimental realizations will be discussed as well.Comment: 10 pages, 3 figures, published version (title modified

Emergency Medicine Research—A Time to Celebrate, Contemplate, and Propagate

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72332/1/j.1553-2712.2001.tb00167.x.pd

Resident Perception of Academic Skills Training and Impact on Academic Career Choice

Objectives: 1) To evaluate residents' perceptions of the quality of training in basic academic skills and the availability and quality of research resources during residency; 2) to evaluate the association between these attitudes and choice of an academic career; and 3) to assess residents' attitudes toward the importance of postgraduate fellowship training for success in an academic career. Methods: A 15-item survey was administered to all U.S. emergency medicine (EM) residents in conjunction with the February 1997 American Board of Emergency Medicine (ABEM) In-service Examination. The survey assessed resident interest in a career in academic EM, and resident perception of the general quality of training in academic (research and teaching) skills. Residents were also asked to rate the quality of their training in the following specific academic skills: medical and grant writing, bedside teaching, lecturing, the use of computers, study design, statistics, and the use of audiovisual aids. Resident perceptions of the availability of the following resources were also assessed: teaching and research role models, data collection and analysis support, laboratory facilities, financial support of research, research fundamentals lectures, and computers. Results: The response rate was 93%. Forty-four percent of the respondents were interested in academic EM, 36.6% were undecided, and 19.6% were not interested in an academic career. On a scale of 1 (unprepared) to 5 (well prepared), the residents rated their overall preparedness for an academic career fairly high (3.97 [0.86]). In contrast, they perceived the quality of their training in the specific academic skill areas assessed and research resource availability to be only fair. Despite resident perception of relatively inadequate training in basic academic skills, only 24% of the respondents indicated that they believed fellowship training was important for success in an academic career. Logistic regression analyses demonstrated that participation in a research project in medical school, the length of the training program (4- vs 3-year), being a first-year resident, and a better perception of one's overall academic skill preparation were factors independently associated with having a greater interest in an academic career. Conclusions: A relatively high percentage of residents initially express an interest in an academic career, but this interest wanes as residency progresses. A minority of residents believe that their training provides them with the specific skills needed to succeed in academics, or with adequate exposure to research resources or mentors. Emergency medicine may be able to increase the number of qualified academic faculty by recruiting medical students with prior research experience, and providing residents with better research training and role models.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72196/1/j.1553-2712.2000.tb00499.x.pd

Sarcoidosis of the hypothalamus and pituitary stalk

We report a rare case of sarcoidosis of the hypothalamic and suprasellar region, with clinical course and the magnetic resonance imaging follow-up

Local Thermometry of Neutral Modes on the Quantum Hall Edge

A system of electrons in two dimensions and strong magnetic fields can be tuned to create a gapped 2D system with one dimensional channels along the edge. Interactions among these edge modes can lead to independent transport of charge and heat, even in opposite directions. Measuring the chirality and transport properties of these charge and heat modes can reveal otherwise hidden structure in the edge. Here, we heat the outer edge of such a quantum Hall system using a quantum point contact. By placing quantum dots upstream and downstream along the edge of the heater, we can measure both the chemical potential and temperature of that edge to study charge and heat transport, respectively. We find that charge is transported exclusively downstream, but heat can be transported upstream when the edge has additional structure related to fractional quantum Hall physics.Comment: 24 pages, 18 figure

Experimental and statistical reevaluation provides no evidence for Drosophila courtship song rhythms

From 1980 to 1992, a series of influential papers reported on the discovery, genetics, and evolution of a periodic cycling of the interval between Drosophila male courtship song pulses. The molecular mechanisms underlying this periodicity were never described. To reinitiate investigation of this phenomenon, we previously performed automated segmentation of songs but failed to detect the proposed rhythm [Arthur BJ, et al. (2013) BMC Biol 11:11; Stern DL (2014) BMC Biol 12:38]. Kyriacou et al. [Kyriacou CP, et al. (2017) Proc Natl Acad Sci USA 114:1970–1975] report that we failed to detect song rhythms because (i) our flies did not sing enough and (ii) our segmenter did not identify many of the song pulses. Kyriacou et al. manually annotated a subset of our recordings and reported that two strains displayed rhythms with genotype-specific periodicity, in agreement with their original reports. We cannot replicate this finding and show that the manually annotated data, the original automatically segmented data, and a new dataset provide no evidence for either the existence of song rhythms or song periodicity differences between genotypes. Furthermore, we have reexamined our methods and analysis and find that our automated segmentation method was not biased to prevent detection of putative song periodicity. We conclude that there is no evidence for the existence of Drosophila courtship song rhythms

Imaging Coulomb Islands in a Quantum Hall Interferometer

In the Quantum Hall regime, near integer filling factors, electrons should only be transmitted through spatially-separated edge states. However, in mesoscopic systems, electronic transmission turns out to be more complex, giving rise to a large spectrum of magnetoresistance oscillations. To explain these observations, recent models put forward that, as edge states come close to each other, electrons can hop between counterpropagating edge channels, or tunnel through Coulomb islands. Here, we use scanning gate microscopy to demonstrate the presence of quantum Hall Coulomb islands, and reveal the spatial structure of transport inside a quantum Hall interferometer. Electron islands locations are found by modulating the tunneling between edge states and confined electron orbits. Tuning the magnetic field, we unveil a continuous evolution of active electron islands. This allows to decrypt the complexity of high magnetic field magnetoresistance oscillations, and opens the way to further local scale manipulations of quantum Hall localized states

Moduli Space and Wall-Crossing Formulae in Higher-Rank Gauge Theories

We study the interplay between wall-crossing in four-dimensional gauge theory and instanton contributions to the moduli space metric of the same theory on $\mathbb{R}^{3}\times S^{1}$. We consider $\mathcal{N}=2$ SUSY Yang--Mills with gauge group SU(n) and focus on walls of marginal stability which extend to weak coupling. By comparison with explicit field theory results we verify the Kontsevich--Soibelman formula for the change in the BPS spectrum at these walls and check the smoothness of the metric in the corresponding compactified theory. We also verify in detail the predictions for the one instanton contribution to the metric coming from the non-linear integral equations of Gaiotto, Moore and Nietzke.Comment: 26 pages, no figure

Neurolymphomatosis mimicking neurosarcoidosis: a case report

<p>Abstract</p> <p>Introduction</p> <p>Both neurosarcoidosis and central nervous system lymphoma can be very difficult to diagnose. We describe the case of a patient in whom neurosarcoidosis was strongly suspected, but who was eventually found to have lymphoma. We believe the case to be of interest and practical value to neurologists, oncologists and internists with an interest in inflammatory diseases.</p> <p>Case presentation</p> <p>A diagnosis of neurosarcoidosis was considered in a 49-year-old Caucasian man on the basis of the following symptoms and indications: a cough, bilateral hilar lymphadenopathy confirmed by thoracic computed tomography, the development of an S1 radiculopathy, cerebrospinal fluid abnormalities (raised protein level), bilateral lung hilar and lachrymal gland uptake on a gallium scan, and erythema nodosum confirmed with skin biopsy. These were followed by the development of multiple cranial neuropathies, including seventh nerve palsy. Exhaustive further investigations yielded no evidence for an alternative diagnosis. Treatments with steroids, cyclophosphamide, intravenous immunoglobulin and finally infliximab were of no benefit. He eventually developed cutaneous nodules, a biopsy of which revealed lymphoma that proved resistant to therapy.</p> <p>Conclusion</p> <p>Constant diagnostic vigilance is required in disorders such as neurosarcoidosis.</p

Fractional quantum Hall effect in a quantum point contact at filling fraction 5/2

Recent theories suggest that the excitations of certain quantum Hall states may have exotic braiding statistics which could be used to build topological quantum gates. This has prompted an experimental push to study such states using confined geometries where the statistics can be tested. We study the transport properties of quantum point contacts (QPCs) fabricated on a GaAs/AlGaAs two dimensional electron gas that exhibits well-developed fractional quantum Hall effect, including at bulk filling fraction 5/2. We find that a plateau at effective QPC filling factor 5/2 is identifiable in point contacts with lithographic widths of 1.2 microns and 0.8 microns, but not 0.5 microns. We study the temperature and dc-current-bias dependence of the 5/2 plateau in the QPC, as well as neighboring fractional and integer plateaus in the QPC while keeping the bulk at filling factor 3. Transport near QPC filling factor 5/2 is consistent with a picture of chiral Luttinger liquid edge-states with inter-edge tunneling, suggesting that an incompressible state at 5/2 forms in this confined geometry