Search for Patterns in Sequences of Single-Photon Polarization Measurements

Sequences of random binary numbers created from polarization measurements of single photons were subjected to a comprehensive runs analysis. Photon pairs from a spontaneous parametric downconversion source were detected in coincidence, with one photon acting as a trigger while the other was analyzed for horizontal or vertical polarization. The resulting sequences of polarization measurements were tested for runs of consecutive vertical or horizontal outcomes against a theory of nonoverlapping runs, without numerical unbiasing. The sequences produced no statistically significant discrepancies with the predicted numbers of runs, even with multiphoton events retained

Granger causality and transfer entropy are equivalent for Gaussian variables

Granger causality is a statistical notion of causal influence based on prediction via vector autoregression. Developed originally in the field of econometrics, it has since found application in a broader arena, particularly in neuroscience. More recently transfer entropy, an information-theoretic measure of time-directed information transfer between jointly dependent processes, has gained traction in a similarly wide field. While it has been recognized that the two concepts must be related, the exact relationship has until now not been formally described. Here we show that for Gaussian variables, Granger causality and transfer entropy are entirely equivalent, thus bridging autoregressive and information-theoretic approaches to data-driven causal inference.Comment: In review, Phys. Rev. Lett., Nov. 200

Charm Leptonic and Semileptonic Decays

Experimental results for the pseudoscalar decay constants f_{D} and f_{D_s} are reviewed. Semileptonic form factor results from D -> (pseudoscalar) l nu and D -> (vector) l nu decays are also reviewed.Comment: 8 pages, 4 figures, presented at the 11th International Conference on B-Physics at Hadron Machines (BEAUTY 2006) Sept. 25-29, Oxford, England; corrected typo

111In-Labeled Cystine-Knot Peptides Based on the Agouti-Related Protein for Targeting Tumor Angiogenesis

Agouti-related protein (AgRP) is a 4-kDa cystine-knot peptide of human origin with four disulfide bonds and four solvent-exposed loops. The cell adhesion receptor integrin αvβ3 is an important tumor angiogenesis factor that determines the invasiveness and metastatic ability of many malignant tumors. AgRP mutants have been engineered to bind to integrin αvβ3 with high affinity and specificity using directed evolution. Here, AgRP mutants 7C and 6E were radiolabeled with 111In and evaluated for in vivo targeting of tumor integrin αvβ3 receptors. AgRP peptides were conjugated to the metal chelator 1, 4, 7, 10-tetra-azacyclododecane- N, N′, N″, N‴-tetraacetic acid (DOTA) and radiolabeled with 111In. The stability of the radiopeptides 111In-DOTA-AgRP-7C and 111In-DOTA-AgRP-6E was tested in phosphate-buffered saline (PBS) and mouse serum, respectively. Cell uptake assays of the radiolabeled peptides were performed in U87MG cell lines. Biodistribution studies were performed to evaluate the in vivo performance of the two resulting probes using mice bearing integrin-expressing U87MG xenograft tumors. Both AgRP peptides were easily labeled with 111In in high yield and radiochemical purity (>99%). The two probes exhibited high stability in phosphate-buffered saline and mouse serum. Compared with 111In-DOTA-AgRP-6E, 111In-DOTA-AgRP-7C showed increased U87MG tumor uptake and longer tumor retention (5.74 ± 1.60 and 1.29 ± 0.02%ID/g at 0.5 and 24 h, resp.), which was consistent with measurements of cell uptake. Moreover, the tumor uptake of 111In-DOTA-AgRP-7C was specifically inhibited by coinjection with an excess of the integrin-binding peptidomimetic c(RGDyK). Thus, 111In-DOTA-AgRP-7C is a promising probe for targeting integrin αvβ3 positive tumors in living subjects

Hubble Space Telescope and Ground-Based Observations of the Type Iax Supernovae SN 2005hk and SN 2008A

We present Hubble Space Telescope (HST) and ground-based optical and near-infrared observations of SN 2005hk and SN 2008A, typical members of the Type Iax class of supernovae (SNe). Here we focus on late-time observations, where these objects deviate most dramatically from all other SN types. Instead of the dominant nebular emission lines that are observed in other SNe at late phases, spectra of SNe 2005hk and 2008A show lines of Fe II, Ca II, and Fe I more than a year past maximum light, along with narrow [Fe II] and [Ca II] emission. We use spectral features to constrain the temperature and density of the ejecta, and find high densities at late times, with n_e >~ 10^9 cm^-3. Such high densities should yield enhanced cooling of the ejecta, making these objects good candidates to observe the expected "infrared catastrophe," a generic feature of SN Ia models. However, our HST photometry of SN 2008A does not match the predictions of an infrared catastrophe. Moreover, our HST observations rule out a "complete deflagration" that fully disrupts the white dwarf for these peculiar SNe, showing no evidence for unburned material at late times. Deflagration explosion models that leave behind a bound remnant can match some of the observed properties of SNe Iax, but no published model is consistent with all of our observations of SNe 2005hk and 2008A.Comment: 20 pages, 15 figure

The XMM Cluster Survey: Active Galactic Nuclei and Starburst Galaxies in XMMXCS J2215.9-1738 at z=1.46

We use Chandra X-ray and Spitzer infrared observations to explore the AGN and starburst populations of XMMXCS J2215.9-1738 at z=1.46, one of the most distant spectroscopically confirmed galaxy clusters known. The high resolution X-ray imaging reveals that the cluster emission is contaminated by point sources that were not resolved in XMM observations of the system, and have the effect of hardening the spectrum, leading to the previously reported temperature for this system being overestimated. From a joint spectroscopic analysis of the Chandra and XMM data, the cluster is found to have temperature T=4.1_-0.9^+0.6 keV and luminosity L_X=(2.92_-0.35^+0.24)x10^44 erg/s extrapolated to a radius of 2 Mpc. As a result of this revised analysis, the cluster is found to lie on the sigma_v-T relation, but the cluster remains less luminous than would be expected from self-similar evolution of the local L_X-T relation. Two of the newly discovered X-ray AGN are cluster members, while a third object, which is also a prominent 24 micron source, is found to have properties consistent with it being a high redshift, highly obscured object in the background. We find a total of eight >5 sigma 24 micron sources associated with cluster members (four spectroscopically confirmed, and four selected using photometric redshifts), and one additional 24 micron source with two possible optical/near-IR counterparts that may be associated with the cluster. Examining the IRAC colors of these sources, we find one object is likely to be an AGN. Assuming that the other 24 micron sources are powered by star formation, their infrared luminosities imply star formation rates ~100 M_sun/yr. We find that three of these sources are located at projected distances of <250 kpc from the cluster center, suggesting that a large amount of star formation may be taking place in the cluster core, in contrast to clusters at low redshift.Comment: Accepted for publication in ApJ, 16 pages, 10 figure

Type Ia Supernova Rate Measurements To Redshift 2.5 From CANDELS: Searching For Prompt Explosions In The Early Universe

dThe Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) was a multi-cycle treasury program on the Hubble Space Telescope (HST) that surveyed a total area of -0.25 deg2 with -900 HST orbits spread across five fields over three years. Within these survey images we discovered 65 supernovae (SNe) of all types, out to z 2.5. We classify -24 of these as Type Ia SNe (SNe Ia) based on host galaxy redshifts and SN photometry (supplemented by grism spectroscopy of six SNe). Here we present a measurement of the volumetric SN Ia rate as a function of redshift, reaching for the first time beyond z =- 2 and putting new constraints on SN Ia progenitor models. Our highest redshift bin includes detections of SNe that exploded when the universe was only -3 Gyr old and near the peak of the cosmic star formation history. This gives the CANDELS high redshift sample unique leverage for evaluating the fraction of SNe Ia that explode promptly after formation ( 40 Myr. However, mild tension is apparent between ground-based low-z surveys and space-based high-z surveys. In both CANDELS and the sister HST program CLASH (Cluster Lensing And Supernova Survey with Hubble), we find a low rate of SNe Ia at z > 1. This could be a hint that prompt progenitors are in fact relatively rare, accounting for only 20% of all SN Ia explosions-though further analysis and larger samples will be needed to examine that suggestion. Key words: infrared: general - supernovae:Astronom

European Financial Market Integration: A Closer Look at Government Bonds in Eurozone Countries

The European Union made a number of steps not least of them the introduction of a common currency to foster the integration of the European financial markets. A number of papers have tried to gauge the degree of integration for various financial markets looking at the convergence of interest rates. A common finding is that government bond markets are quite well integrated. In this paper stochastic Kernel density estimates are used to take a closer look at the dynamics that drive the process of interest rate convergence. The main finding is that countries with large initial deviations from the mean interest rate do indeed converge. Interestingly the candidates least suspected namely the countries initially with interest rates at the mean level show a pattern of slight divergence