Identification of activity peaks in time-tagged data with a scan-statistics driven clustering method and its application to gamma-ray data samples

The investigation of activity periods in time-tagged data-samples is a topic of large interest. Among Astrophysical samples, gamma-ray sources are widely studied, due to the huge quasi-continuum data set available today from the FERMI-LAT and AGILE-GRID gamma-ray telescopes. To reveal flaring episodes of a given gamma-ray source, researchers make use of binned light-curves. This method suffers several drawbacks: the results depends on time-binning, the identification of activity periods is difficult for bins with low signal to noise ratio. I developed a general temporal-unbinned method to identify flaring periods in time-tagged data and discriminate statistically-significant flares: I propose an event clustering method in one-dimension to identify flaring episodes, and Scan-statistics to evaluate the flare significance within the whole data sample. This is a photometric algorithm. The comparison of the photometric results (e.g., photometric flux, gamma-ray spatial distribution) for the identified peaks with the standard likelihood analysis for the same period is mandatory to establish if source-confusion is spoiling results. The procedure can be applied to reveal flares in any time-tagged data sample. The study of the gamma ray activity of 3C 454.3 and of the fast variability of the Crab Nebula are shown as examples. The result of the proposed method is similar to a photometric light curve, but peaks are resolved, they are statistically significant within the whole period of investigation, and peak detection capability does not suffer time-binning related issues. The method can be applied for gamma-ray sources of known celestial position. Furthermore the method can be used when it is necessary to assess the statistical significance within the whole period of investigation of a flare from an unknown gamma-ray source.Comment: 17 pages, 10 figures Accepted for publication in A&

Improved Constraints on Cosmic Microwave Background Secondary Anisotropies from the Complete 2008 South Pole Telescope Data

We report measurements of the cosmic microwave background (CMB) power spectrum from the complete 2008 South Pole Telescope (SPT) data set. We analyze twice as much data as the first SPT power spectrum analysis, using an improved cosmological parameter estimator which fits multi-frequency models to the SPT 150 and 220 GHz bandpowers. We find an excellent fit to the measured bandpowers with a model that includes lensed primary CMB anisotropy, secondary thermal (tSZ) and kinetic (kSZ) Sunyaev-Zel'dovich anisotropies, unclustered synchrotron point sources, and clustered dusty point sources. In addition to measuring the power spectrum of dusty galaxies at high signal-to-noise, the data primarily constrain a linear combination of the kSZ and tSZ anisotropy contributions at 150 GHz and ℓ = 3000: D^(tSZ) ^(3000) + 0.5 D_(kSZ)^(3000) = 4.5 ± 1.0 μK^2. The 95% confidence upper limits on secondary anisotropy power are D ^(tSZ)_(3000) < 5.3 μK^2 and D^(kSZ)_(3000) < 6.5 μK^2. We also consider the potential correlation of dusty and tSZ sources and find it incapable of relaxing the tSZ upper limit. These results increase the significance of the lower than expected tSZ amplitude previously determined from SPT power spectrum measurements. We find that models including non-thermal pressure support in groups and clusters predict tSZ power in better agreement with the SPT data. Combining the tSZ power measurement with primary CMB data halves the statistical uncertainty on σ8. However, the preferred value of σ8 varies significantly between tSZ models. Improved constraints on cosmological parameters from tSZ power spectrum measurements require continued progress in the modeling of the tSZ power

HerMES: deep galaxy number counts from a P(D) fluctuation analysis of SPIRE Science Demonstration Phase observations

Dusty, star-forming galaxies contribute to a bright, currently unresolved cosmic far-infrared background. Deep Herschel-Spectral and Photometric Imaging Receiver (SPIRE) images designed to detect and characterize the galaxies that comprise this background are highly confused, such that the bulk lies below the classical confusion limit. We analyse three fields from the Herschel Multi-tiered Extragalactic Survey (HerMES) programme in all three SPIRE bands (250, 350 and 500 μm); parametrized galaxy number count models are derived to a depth of ~2 mJy beam^(−1), approximately four times the depth of previous analyses at these wavelengths, using a probability of deflection [P(D)] approach for comparison to theoretical number count models. Our fits account for 64, 60 and 43 per cent of the far-infrared background in the three bands. The number counts are consistent with those based on individually detected SPIRE sources, but generally inconsistent with most galaxy number count models, which generically overpredict the number of bright galaxies and are not as steep as the P(D)-derived number counts. Clear evidence is found for a break in the slope of the differential number counts at low flux densities. Systematic effects in the P(D) analysis are explored. We find that the effects of clustering have a small impact on the data, and the largest identified systematic error arises from uncertainties in the SPIRE beam

Detection of Gravitational Lensing in the Cosmic Microwave Background

Gravitational lensing of the cosmic microwave background (CMB), a long-standing prediction of the standard cosmolgical model, is ultimately expected to be an important source of cosmological information, but first detection has not been achieved to date. We report a 3.4 sigma detection, by applying quadratic estimator techniques to all sky maps from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, and correlating the result with radio galaxy counts from the NRAO VLA Sky Survey (NVSS). We present our methodology including a detailed discussion of potential contaminants. Our error estimates include systematic uncertainties from density gradients in NVSS, beam effects in WMAP, Galactic microwave foregrounds, resolved and unresolved CMB point sources, and the thermal Sunyaev-Zeldovich effect.Comment: 27 pages, 20 figure

A programmable BIST architecture for clusters of Multiple-Port SRAMs

This paper presents a BIST architecture, based on a single microprogrammable BIST processor and a set of memory wrappers, designed to simplify the test of a system containing many distributed multi-port SRAMs of different sizes (number of bits, number of words), access protocol (asynchronous, synchronous), and timin

Molecular footprint of drug-selective pressure in a human immunodeficiency virus transmission chain

Known human immunodeficiency virus (HIV) transmission histories are invaluable models for investigating the evolutionary and transmission dynamics of the virus and to assess the accuracy of phylogenetic reconstructions. Here we have characterized an HIV-1 transmission chain consisting of nine infected patients, almost all of whom were treated with antiviral drugs at later stages of infection. Partial pol and env gp41 regions of the HIV genome were directly sequenced from plasma viral RNA for at least one sample from each patient. Phylogenetic analyses in pol using likelihood methods inferred an evolutionary history not fully compatible with the known transmission history. This could be attributed to parallel evolution of drug resistance mutations resulting in the incorrect clustering of multidrug-resistant virus. On the other hand, a fully compatible phylogenetic tree was reconstructed from the env sequences. We were able to identify and quantify the molecular footprint of drug-selective pressure in pol using maximum likelihood inference under different codon substitution models. An increased fixation rate of mutations in the HIV population of the multidrug-resistant patient was demonstrated using molecular clock modeling. We show that molecular evolutionary analyses, guided by a known transmission history, can reveal the presence of confounding factors like natural selection and caution should be taken when accurate descriptions of HIV evolution are required.status: publishe

Influence of the sebaceous gland density on the stratum corneum lipidome

The skin surface lipids (SSL) result from the blending of sebaceous and epidermal lipids, which derive from the sebaceous gland (SG) secretion and the permeability barrier of the stratum corneum (SC), respectively. In humans, the composition of the SSL is distinctive of the anatomical distribution of the SG. Thus, the abundance of sebum biomarkers is consistent with the density of the SG. Limited evidence on the influence that the SG exerts on the SC lipidome is available. We explored the differential amounts of sebaceous and epidermal lipids in areas at different SG density with lipidomics approaches. SC was sampled with adhesive patches from forearm, chest, and forehead of 10 healthy adults (8F, 2M) after mechanical removal of sebum with absorbing paper. Lipid extracts of SC were analysed by HPLC/(-)ESI-TOF-MS. In the untargeted approach, the naïve molecular features extraction algorithm was used to extract meaningful entities. Aligned and normalized data were evaluated by univariate and multivariate statistics. Quantitative analysis of free fatty acids (FFA) and cholesterol sulfate (CHS) was performed by targeted HPLC/(-)ESI-TOF-MS, whereas cholesterol and squalene were quantified by GC-MS. Untargeted approaches demonstrated that the relative abundance of numerous lipid species was distinctive of SC depending upon the different SG density. The discriminating species included FFA, CHS, and ceramides. Targeted analyses confirmed that sebaceous FFA and epidermal FFA were increased and decreased, respectively, in areas at high SG density. CHS and squalene, which are biomarkers of epidermal and sebaceous lipid matrices, respectively, were both significantly higher in areas at elevated SG density. Overall, results indicated that the SG secretion intervenes in shaping the lipid composition of the epidermal permeability barrier. © 2018, The Author(s)

A Measurement of the Cosmic Microwave Background Damping Tail from the 2500-square-degree SPT-SZ survey

We present a measurement of the cosmic microwave background (CMB) temperature power spectrum using data from the recently completed South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. This measurement is made from observations of 2540 deg$^2$ of sky with arcminute resolution at $150\,$GHz, and improves upon previous measurements using the SPT by tripling the sky area. We report CMB temperature anisotropy power over the multipole range $650<\ell<3000$. We fit the SPT bandpowers, combined with the seven-year Wilkinson Microwave Anisotropy Probe (WMAP7) data, with a six-parameter LCDM cosmological model and find that the two datasets are consistent and well fit by the model. Adding SPT measurements significantly improves LCDM parameter constraints; in particular, the constraint on $\theta_s$ tightens by a factor of 2.7. The impact of gravitational lensing is detected at $8.1\, \sigma$, the most significant detection to date. This sensitivity of the SPT+WMAP7 data to lensing by large-scale structure at low redshifts allows us to constrain the mean curvature of the observable universe with CMB data alone to be $\Omega_k=-0.003^{+0.014}_{-0.018}$. Using the SPT+WMAP7 data, we measure the spectral index of scalar fluctuations to be $n_s=0.9623 \pm 0.0097$ in the LCDM model, a $3.9\,\sigma$ preference for a scale-dependent spectrum with $n_s<1$. The SPT measurement of the CMB damping tail helps break the degeneracy that exists between the tensor-to-scalar ratio $r$ and $n_s$ in large-scale CMB measurements, leading to an upper limit of $r<0.18$ (95%,C.L.) in the LCDM+$r$ model. Adding low-redshift measurements of the Hubble constant ($H_0$) and the baryon acoustic oscillation (BAO) feature to the SPT+WMAP7 data leads to further improvements. The combination of SPT+WMAP7+$H_0$+BAO constrains $n_s=0.9538 \pm 0.0081$ in the LCDM model, a $5.7\,\sigma$ detection of $n_s < 1$, ... [abridged]Comment: 21 pages, 10 figures. Replaced with version accepted by ApJ. Data products are available at http://pole.uchicago.edu/public/data/story12