Extended search for point sources of neutrinos below and above the horizon: Covering energies from TeV to EeV with IceCube

Point source searches with neutrino telescopes like IceCube are normally restricted to one hemisphere, due to the selection of up-going events as a way of rejecting the atmospheric muon background. In this work we show that the down-going region above the horizon can be included in the search by suppressing the background through energy-sensitive selection procedures. This approach increases the reach to the EeV regime of the signal spectrum, which was previously not accessible due to the absorption of neutrinos with energies above a PeV inside the Earth. We present preliminary results of this analysis, which for the first time includes up-going as well as down-going muon events in a combined approach. We used data collected with IceCube in a configuration of 22 strings. No significant excess above the atmospheric background is observed. While other analyses provided results for the Northern hemisphere, this new approach extends the field of view to a large part of the Southern sky, which was previously not covered with IceCube.Comment: 4 pages, 1 figure. To be published in the proceedings of the 2nd Heidelberg workshop "High-Energy Gamma-rays and Neutrinos from Extra-Galactic Sources", 2009 (Journal of Modern Physics D

New VLT observations of the Fermi pulsar PSR J1048-5832

PSR J1048-5832 is a Vela-like (P=123.6 ms; tau~20.3 kyr) gamma-ray pulsar detected by Fermi, at a distance of ~2.7 kpc and with a rotational energy loss rate dot{E}_{SD} ~2 x 10^{36} erg/s. The PSR J1048-5832 field has been observed with the VLT in the V and R bands. We used these data to determine the colour of the object detected closest to the Chandra position (Star D) and confirm that it is not associated with the pulsar. For the estimated extinction along the line of sight, inferred from a re-analysis of the Chandra and XMM-Newton spectra, the fluxes of Star D (V~26.7; R~25.8) imply a -0.13 < (V-R)_0 < 0.6. This means that the PSR J1048-5832 spectrum would be unusually red compared to the Vela pulsar.Moreover, the ratio between the unabsorbed optical and X-ray flux of PSR J1048-5832 would be much higher than for other young pulsars. Thus, we conclude that Star D is not the PSR J1048-5832 counterpart. We compared the derived R and V-band upper limits (R>26.4; V>27.6) with the extrapolation of the X and gamma-ray spectra and constrained the pulsar spectrum at low-energies. In particular, the VLT upper limits suggest that the pulsar spectrum could be consistent with a single power-law, stretching from the gamma-rays to the optical.Comment: 5 pages, 2 figures, accepted for publication on Monthly Notices of the Royal Astronomical Society Main Journa

Do semantic features capture a syntactic classification of compounds? Insights from compositional distributional semantics

Classifying compound words has been the ultimate goal of much research in for- mal linguistics. A popular, cross-linguistically applicable classification (Bisetto & Scalise 2005) distinguishes three main types of compounds, namely Subordinate, Attributive, and Coordinate on the basis of the underlying syntactic relation be- tween the compound elements. Similar tripartitions have also been proposed in cognitive psychology by works exploring conceptual combination. Focusing on the type of semantic interpretation assigned to novel combinations, three main classes have been traditionally described, namely Relation-linking, Property-mapping, and Hybrid or Conjunctive (see Wisniewski 1996). Based on these commonali- ties, we conjecture that syntax-based compound types might also be explained by means of the semantic properties of the compound and its constituents. Using a compositional model of distributional semantics (cDSM), we show that (a) the con- tribution of each constituent in determining the meaning of the compound and (b) the semantic similarity between the two constituent words are significant pre- dictors of these classes. These findings suggest that the various compound types identified by syntactic criteria can also be predicted by means of semantic features. On the one hand, this confirms the validity of the proposed linguistic categoriza- tion. On the other hand, we bring further evidence proving the effectiveness of cDSMs in describing linguistic phenomena

Classification and Ranking of Fermi LAT Gamma-ray Sources from the 3FGL Catalog using Machine Learning Techniques

We apply a number of statistical and machine learning techniques to classify and rank gamma-ray sources from the Third Fermi Large Area Telescope (LAT) Source Catalog (3FGL), according to their likelihood of falling into the two major classes of gamma-ray emitters: pulsars (PSR) or Active Galactic Nuclei (AGN). Using 1904 3FGL sources that have been identified/associated with AGN (1738) and PSR (166), we train (using 70% of our sample) and test (using 30%) our algorithms and find that the best overall accuracy (>96%) is obtained with the Random Forest (RF) technique, while using a logistic regression (LR) algorithm results in only marginally lower accuracy. We apply the same techniques on a sub-sample of 142 known gamma-ray pulsars to classify them into two major subcategories: young (YNG) and millisecond pulsars (MSP). Once more, the RF algorithm has the best overall accuracy (~90%), while a boosted LR analysis comes a close second. We apply our two best models (RF and LR) to the entire 3FGL catalog, providing predictions on the likely nature of {\it unassociated} sources, including the likely type of pulsar (YNG or MSP). We also use our predictions to shed light on the possible nature of some gamma-ray sources with known associations (e.g. binaries, SNR/PWN). Finally, we provide a list of plausible X-ray counterparts for some pulsar candidates, obtained using Swift, Chandra, and XMM. The results of our study will be of interest for both in-depth follow-up searches (e.g. pulsar) at various wavelengths, as well as for broader population studies.Comment: Accepted by Ap

Consistency measures individuate dissociating semantic modulations in priming paradigms: A new look on semantics in the processing of (complex) words

In human language the mapping between form and meaning is arbitrary, as there is no direct connection between words and the objects that they represent. However, within a given language, it is possible to recognize systematic associations that support productivity and comprehension. In this work, we focus on the consistency between orthographic forms and meaning, and we investigate how the cognitive system may exploit it to process words. We take morphology as our case study, since it arguably represents one of the most notable examples of systematicity in form-meaning mapping. In a series of three experiments, we investigate the impact of form-meaning mapping in word processing by testing new consistency metrics as predictors of priming magnitude in primed lexical decision. In Experiment 1, we re-analyse data from five masked morphological priming studies and show that Orthography-Semantics-Consistency explains independent variance in priming magnitude, suggesting that word semantics is accessed already at early stages of word processing and that crucially semantic access is constrained by word orthography. In Experiment 2 and 3, we investigate whether this pattern is replicated when looking at semantic priming. In Experiment 2, we show that Orthography-Semantics-Consistency is not a viable predictor of priming magnitude with longer SOA. However, in Experiment 3, we develop a new semantic consistency measure based on the semantic density of target neighbourhoods. This measure is shown to significantly predict independent variance in semantic priming effect. Overall our results indicate that consistency measures provide crucial information for the understanding of word processing. Specifically, the dissociation between measures and priming paradigms shows that different priming conditions are associated with the activation of different semantic cohorts

Novel nucleic acid molecules

The inventors have engineered novel DNA constructs for the expression of the tRNApyl genes in eukaryotic cells, especially mammalian cells, under new and improved promoter systems. The tRNApyl gene sequence possesses two internal regions that resemble an eukaryotic A box and B box, with the B box-like region more closely resembling a functional B box. Although previous attempts at reconstituting a consensus A- Box and B-box were unsuccessful as reported in Hancock et al (2010) and Mukai et al. (US 8,168,407), the inventors have now surprisingly found that the tRNApyl sequence can be altered to enable a functioning intragenic promoter and obtain a tRNApyl able to mediate efficient amber suppression in combination with WT pylRS. Such new tRNApyl gene can be used to generate highly active and stable cell lines for the incorporation of nnAAs into cells. The inventors have also found that the new modified tRNApyl gene containing a functional intragenic promoter element can be further improved by placing them downstream of the 5’ regulatory elements of genes expressed under type 4 promoters, thereby reconstituting a functional type 4 promoter element containing both extragenic and intragenic elements. The inventors have also surprisingly found that the WT tRNApyl gene can be expressed under transcriptional control of a tRNAglu gene and/or a tRNAasp gene, when said tRNAglu gene and/or tRNAasp gene is placed upstream of the tRNApyl gene and altered to lack the transcription termination sequence in order to effectively form a bicistronic message. DNA constructs bearing tandem repeats of novel tRNApyl genes of the invention have shown to lead to increased amber suppression

The fruitless effort of growing a fruitless tree: Early morpho.orthographic and morpho-semantic effects in sentence reading

In this eye-tracking study, we investigated how semantics inform morphological analysis at the early stages of visual word identification in sentence reading. We exploited a feature of several derived Italian words, that is, that they can be read in a \u201cmorphologically transparent\u201d way or in a \u201cmorphologically opaque\u201d way according to the sentence context to which they belong. This way, each target word was embedded in a sentence eliciting either its transparent or opaque interpretation. We analyzed whether the effect of stem frequency changes according to whether the (very same) word is read as a genuine derivation (transparent context) vs. as a pseudo-derived word (opaque context). Analysis of the first fixation durations revealed a stem-word frequency effect in both opaque and transparent contexts, thus showing that stems were accessed whether or not they contributed to word meaning, that is, word decomposition is indeed blind to semantics. However, while the stem-word frequency effect was facilitatory in the transparent context, it was inhibitory in the opaque context, thus showing an early involvement of semantic representations. This pattern of data is revealed by words with short suffixes. These results indicate that derived and pseudo-derived words are segmented into their constituent morphemes also in natural reading; however, this blind- to-semantics process activates morpheme representations that are semantically connote

Radio-quiet and radio-loud pulsars: similar in Gamma-rays but different in X-rays

We present new Chandra and XMM-Newton observations of a sample of eight radio-quiet Gamma-ray pulsars detected by the Fermi Large Area Telescope. For all eight pulsars we identify the X-ray counterpart, based on the X-ray source localization and the best position obtained from Gamma-ray pulsar timing. For PSR J2030+4415 we found evidence for an about 10 arcsec-long pulsar wind nebula. Our new results consolidate the work from Marelli et al. 2011 and confirm that, on average, the Gamma-ray--to--X-ray flux ratios (Fgamma/Fx) of radio-quiet pulsars are higher than for the radio-loud ones. Furthermore, while the Fgamma/Fx distribution features a single peak for the radio-quiet pulsars, the distribution is more dispersed for the radio-loud ones, possibly showing two peaks. We discuss possible implications of these different distributions based on current models for pulsar X-ray emission.Comment: Accepted for publication in The Astrophysical Journal; 12 pages, 3 figures, 2 table