Spin Rotations in a Bose-Einstein Condensate Driven by Counterflow and Spin-independent Interactions

We observe spin rotations caused by atomic collisions in a non-equilibrium Bose-condensed gas of $^{87}$Rb. Reflection from a pseudomagnetic barrier creates counterflow in which forward- and backward-propagating matter waves have partly transverse spin directions. Even though inter-atomic interaction strengths are state-independent, the indistinguishability of parallel spins leads to spin dynamics. A local magnetodynamic model, which captures the salient features of the observed spin textures, highlights an essential connection between four-wave mixing and collisional spin rotation. The observed phenomenon has previously been thought to exist only in nondegenerate gases; our observations and model clarify the nature of these effective-magnetic spin rotations.Comment: 13 pages, 7 figure

Preferred Interaction Ranges in Neutral-Atom Arrays in the Presence of Noise

Successful execution of a quantum information processing (QIP) task on a quantum processing device depends on the availability of high-quality entangling gates. Two important goals in the design and implementation of any entangling gate are low error rates and high connectivity. The former minimizes unintended perturbations to the quantum state during application of that gate, while the latter maximizes the set of qubits that can interact directly without remapping the QIP task through intermediary qubits -- a step that can require many additional gates. Unfortunately, these goals can sometimes conflict, necessitating a careful trade-off. In this work, we study that trade-off in two-dimensional (2D) arrays of neutral atoms interacting through two-qubit gates mediated by the Rydberg blockade effect. The connectivity associated with Rydberg mediated gates on a 2D array is limited by the strength of the Rydberg blockade shift, which decays with distance. Whereas a common strategy to improving connectivity is to use Rydberg levels with larger dipole moments, doing so also leaves the atom more susceptible to electric field noise. Here, we simulate the performance of various logical QIP operations under realistic noise sources and for a variety of Rydberg levels in order to evaluate the connectivity versus gate error trade-off. We find that under many noise regimes, a preferred range of interaction emerges that best satisfies that trade-off. While the exact optimum interaction range depends closely on the details of the atomic implementation, we present simple scaling arguments with broad applicability that should inform future hardware and compiler design choices

Can Birds Perceive Rhythmic Patterns? A Review and Experiments on a Songbird and a Parrot Species

Article / Letter to editorInstituut Biologie Leide

Characterization of antigen-presenting properties of tumour cells using virus-specific cytotoxic T lymphocytes

Immunotherapy of tumours by induction of tumour-specific cytotoxic T-lymphocytes (CTLs) will only be effective for tumours with a functional antigen processing and presentation machinery. However, many tumours are known to down-regulate expression of major histocompatibility complex (MHC) class I molecules and/or to impair antigen processing. It is therefore desirable to evaluate the ability of a given tumour to present antigenic epitopes before developing an immunotherapy protocol. In this study we have used influenza virus as a tool to determine the antigen-presenting capacities of the murine neuroblastoma C1300 cell line NB41A3, a frequently used model for human neuroblastoma. Immunofluorescence analyses revealed low and moderate expression of MHC class I molecules Ddand Kkrespectively. Nevertheless, infected NB41A3 cells were lysed efficiently by influenza-specific CTLs. These results demonstrate that all steps of the antigen-processing pathway function properly in the NB tumour cells, and that the limited MHC class I expression suffices for efficient recognition by CTLs. In addition, lysis of the NB tumour cells shows that the cells are susceptible to CTL-induced apoptosis, a pathway that is often impaired in tumour cells. These characteristics make neuroblastoma a suitable target for immunotherapy. The presented assay allows evaluation of various immunological properties of tumour cells and, thus, represents a valuable tool to assess whether a given tumour will be susceptible to immunotherapy or not. Copyright 2000 Cancer Research Campaign. © 2000 Cancer Research Campaig

Budgerigars and zebra finches differ in how they generalize in an artificial grammar learning experiment

Animal science

Zebra Finches As a Model Species to Understand the Roots of Rhythm

Animal science

Microstructure and oxide particle stability in a novel ODS γ-TiAl alloy processed by spark plasma sintering and laser additive manufacturing

In this work, a novel oxide dispersion strengthened titanium aluminide alloy (Ti-45Al-3Nb-<0.2Y2O3 at.%) was developed for powder-based processing technologies with a focus on spark plasma sintering and additive manufacturing. Titanium aluminides are promising structural intermetallics for weight reduction and an increased performance of high temperature components. The alloy design and selection process was supported by computational thermodynamics based on the CALPHAD approach, taking into account requirements for processing as well as long term alloy behavior under service conditions. Processing trials using spark plasma sintering, direct metal deposition and selective laser melting were conducted to study the alloy behavior, microstructure formation and introduction as well as stability of the ODS particles. Additionally, thermal annealing on the sintered and laser consolidated material was performed. Conventional dual phase α2-Ti3Al and γ-TiAl duplex and near-lamellar microstructures were obtained from the processed material. The ODS particles were homogeneously distributed in the alloy matrix after processing in the liquid state. For the direct metal deposition process, the novel alloy was compared to the established GE48-2-2 alloy (Ti-48Al-2Cr-2Nb) in terms of phases, microstructure and texture after processing. A significantly reduced texture formation was observed with the novel alloy. The hardness of the consolidated material shows superior properties for ODS-containing TiAl compared to ODS-free material. This work provides a first step towards tailored alloys for AM and the production of ODS TiAl alloys

Rapid Responders to Frovatriptan in Acute Migraine Treatment: Results from a Long-Term, Open-Label Study

Background. the Chronic Nature of Migraine and the Reliance on Acute Treatment Constitute the Basis of the Present Long-Term, Open-Label Study. Objectives. First, Assessment of the Tolerability and Safety of Frovatriptan, 2.5-7.5 Mg Taken Orally over 24 Hours, for the Acute Treatment of Migraine, Repeatedly over a 12-Month Period. Second, Assessment of the Efficacy and Tolerability of a Second, Double-Blind Dose of 2.5-Mg Frovatriptan, Compared with Placebo, for Nonresponse at 2 Hours after Treatment of Moderate or Severe Headache with 2.5-Mg Frovatriptan. Results. with Regard to the First Attack Treated, 173 (36%) of the 486 Subjects in the Study Did Not Take a Second Dose at 2 Hours for Nonresponse. at 2 Hours and 4 Hours, These Rapid Responders Experienced a Decrease in Headache Intensity from Moderate or Severe to Mild or No Pain in 84% and 98%, Respectively ( Headache Response ). Six Percent of Them Experienced Recurrence of Moderate or Severe Headache within 24 Hours Following a Response at 4 Hours and 12% Took Rescue Medication. the Response, Measured in Terms of Median Time to Complete Migraine Relief, Was Maintained over 30 Subsequent Migraine Attacks, Treated from Attack 2 Onwards over the Course of 12 Months. Conclusion. Frovatriptan Provides a Remarkably Fast and High Headache Response in a Subgroup of More Than One-Third of Migraineurs, with a Very Low 24-Hour Headache Recurrence and Low Rescue Medication Intake. © 2009 American Academy of Pain Medicine

Construction of Strand-seq libraries in open nanoliter arrays

Single-cell Strand-seq generates directional genomic information to study DNA repair, assemble genomes, and map structural variation onto chromosome-length haplotypes. We report a nanoliter-volume, one-pot (OP) Strand-seq library preparation protocol in which reagents are added cumulatively, DNA purification steps are avoided, and enzymes are inactivated with a thermolabile protease. OP-Strand-seq libraries capture 10%-25% of the genome from a single-cell with reduced costs and increased throughput