Quantum marking and quantum erasure for neutral kaons

Entangled K0 anti-K0 pairs are shown to be suitable to discuss extensions and tests of Bohr's complementarity principle through the quantum marking and quantum erasure techniques suggested by M. O. Scully and K. Druehl [Phys. Rev. A 25, 2208 (1982)]. Strangeness oscillations play the role of the traditional interference pattern linked to wave-like behaviour, whereas the distinct propagation in free space of the K_S and K_L components mimics the two possible interferometric paths taken by particle-like objects.Comment: 4 RevTeX page

Does Social Presence or the Potential for Interaction reduce Social Gaze in Online Social Scenarios? Introducing the "Live Lab" paradigm.

Research has shown that people’s gaze is biased away from faces in the real-world but towards them when they are viewed onscreen. Non-equivalent stimulus conditions may have represented a confound in this research however, as participants viewed onscreen stimuli as pre-recordings where interaction was not possible, compared to real-world stimuli which were viewed in real-time where interaction was possible. We assessed the independent contributions of online social presence and ability for interaction on social gaze by developing the “live lab” paradigm. Participants in three groups (N = 132) viewed a confederate either as a) a live webcam stream where interaction was not possible (one-way), b) a live webcam stream where an interaction was possible (two-way) or c) as a prerecording. Potential for interaction, rather than online social presence, was the primary influence on gaze behaviour: Participants in the pre-recorded and one-way conditions looked more to the face than those in the two-way condition, particularly when the confederate made “eye contact”. Fixation durations to the face were shorter when the scene was viewed live, particularly during a bid for eye contact Our findings support the dual function of gaze, but suggest that online social presence alone is not sufficient to activate social norms of civil inattention. Implications for the reinterpretation of previous research are discussed

Differential cross section for electron impact excitation of metastable helium measured by the atomic time-of-flight method

The authors have measured the differential cross section for the inelastic process He(11S0)+e- to He(23S1)+e- just above threshold by bombarding a beam of helium atoms with electrons from a pulsed electron gun and measuring the times of flight of the excited metastable atoms to a distant detector. Since each time of flight corresponds to a definite value of the electron scattering angle, the angular distribution of electrons scattered over the entire range 0-180 degrees is deduced from the data.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/48848/2/jbv10i2pL43.pd

Group risk-taking under various group decision schemes

This study examined individual choice behavior when it occurs in groups engaged in joint decision-making. Ninety-six subjects made binary choices between "risky" and "conservative" alternatives acting alone and acting as members of three-man groups in a series of 360 trials. The groups operated under the majority rule, unanimity, and the so-called "minimal quorum" rule. It was found that under unanimity and the minimal quorum rule there were strong pressures toward uniformity. However, individual members in these groups did not succumb to these pressures by modifying their overall choice preferences. Instead they arranged their sequences of choices so that the joint choice of all members would be congruent with their acceptable level of risk-taking. The findings also indicated that there was a slight shift toward conservatism when individuals joined groups. The results on individual risk-taking supported a parameter-free model, and the model also accommodated the present group data when some new assumptions were made about the effects of pressures toward uniformity.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34182/1/0000471.pd

Unique Interplay between Sugar and Lipid in Determining the Antigenic Potency of Bacterial Antigens for NKT Cells

Structural and biophysical studies reveal the induced-fit mechanism underlying the stringent specificity of invariant natural killer T cells for unique glycolipid antigens from the pathogen Streptococcus pneumoniae

Observation of off-diagonal geometric phase in polarized neutron interferometer experiments

Off-diagonal geometric phases acquired in the evolution of a spin-1/2 system have been investigated by means of a polarized neutron interferometer. Final counts with and without polarization analysis enable us to observe simultaneously the off-diagonal and diagonal geometric phases in two detectors. We have quantitatively measured the off-diagonal geometric phase for noncyclic evolutions, confirming the theoretical predictions. We discuss the significance of our experiment in terms of geometric phases (both diagonal and off-diagonal) and in terms of the quantum erasing phenomenon.Comment: pdf, 22 pages + 8 figures (included in the pdf). In print on Phys. Rev.

Structural basis for CD1d presentation of a sulfatide derived from myelin and its implications for autoimmunity

Sulfatide derived from the myelin stimulates a distinct population of CD1d-restricted natural killer T (NKT) cells. Cis-tetracosenoyl sulfatide is one of the immunodominant species in myelin as identified by proliferation, cytokine secretion, and CD1d tetramer staining. The crystal structure of mouse CD1d in complex with cis-tetracosenoyl sulfatide at 1.9 Å resolution reveals that the longer cis-tetracosenoyl fatty acid chain fully occupies the A′ pocket of the CD1d binding groove, whereas the sphingosine chain fills up the F′ pocket. A precise hydrogen bond network in the center of the binding groove orients and positions the ceramide backbone for insertion of the lipid tails in their respective pockets. The 3′-sulfated galactose headgroup is highly exposed for presentation to the T cell receptor and projects up and away from the binding pocket due to its β linkage, compared with the more intimate binding of the α-glactosyl ceramide headgroup to CD1d. These structure and binding data on sulfatide presentation by CD1d have important implications for the design of therapeutics that target T cells reactive for myelin glycolipids in autoimmune diseases of the central nervous system

IEDB-3D: structural data within the immune epitope database

IEDB-3D is the 3D structural component of the Immune Epitope Database (IEDB) available via the ‘Browse by 3D Structure’ page at http://www.iedb.org. IEDB-3D catalogs B- and T-cell epitopes and Major Histocompatibility Complex (MHC) ligands for which 3D structures of complexes with antibodies, T-cell receptors or MHC molecules are available in the Protein Data Bank (PDB). Journal articles that are primary citations of PDB structures and that define immune epitopes are curated within IEDB as any other reference along with accompanying functional assays and immunologically relevant information. For each curated structure, IEDB-3D provides calculated data on intermolecular contacts and interface areas and includes an application, EpitopeViewer, to visualize the structures. IEDB-3D is fully embedded within IEDB, thus allowing structural data, both curated and calculated, and all accompanying information to be queried using multiple search interfaces. These include queries for epitopes recognized in different pathogens, eliciting different functional immune responses, and recognized by different components of the immune system. The query results can be downloaded in Microsoft Excel format, or the entire database, together with structural data both curated and calculated, can be downloaded in either XML or MySQL formats

Collective emotions online and their influence on community life

E-communities, social groups interacting online, have recently become an object of interdisciplinary research. As with face-to-face meetings, Internet exchanges may not only include factual information but also emotional information - how participants feel about the subject discussed or other group members. Emotions are known to be important in affecting interaction partners in offline communication in many ways. Could emotions in Internet exchanges affect others and systematically influence quantitative and qualitative aspects of the trajectory of e-communities? The development of automatic sentiment analysis has made large scale emotion detection and analysis possible using text messages collected from the web. It is not clear if emotions in e-communities primarily derive from individual group members' personalities or if they result from intra-group interactions, and whether they influence group activities. We show the collective character of affective phenomena on a large scale as observed in 4 million posts downloaded from Blogs, Digg and BBC forums. To test whether the emotions of a community member may influence the emotions of others, posts were grouped into clusters of messages with similar emotional valences. The frequency of long clusters was much higher than it would be if emotions occurred at random. Distributions for cluster lengths can be explained by preferential processes because conditional probabilities for consecutive messages grow as a power law with cluster length. For BBC forum threads, average discussion lengths were higher for larger values of absolute average emotional valence in the first ten comments and the average amount of emotion in messages fell during discussions. Our results prove that collective emotional states can be created and modulated via Internet communication and that emotional expressiveness is the fuel that sustains some e-communities.Comment: 23 pages including Supporting Information, accepted to PLoS ON