Exploring the “Middle Earth” of network spectra via a Gaussian matrix function

We study a Gaussian matrix function of the adjacency matrix of artificial and real-world networks. We motivate the use of this function on the basis of a dynamical process modeled by the time-dependent Schrodinger equation with a squared Hamiltonian. In particular, we study the Gaussian Estrada index - an index characterizing the importance of eigenvalues close to zero. This index accounts for the information contained in the eigenvalues close to zero in the spectra of networks. Such method is a generalization of the so-called "Folded Spectrum Method" used in quantum molecular sciences. Here we obtain bounds for this index in simple graphs, proving that it reaches its maximum for star graphs followed by complete bipartite graphs. We also obtain formulas for the Estrada Gaussian index of Erdos-Renyi random graphs as well as for the Barabasi-Albert graphs. We also show that in real-world networks this index is related to the existence of important structural patters, such as complete bipartite subgraphs (bicliques). Such bicliques appear naturally in many real-world networks as a consequence of the evolutionary processes giving rise to them. In general, the Gaussian matrix function of the adjacency matrix of networks characterizes important structural information not described in previously used matrix functions of graphs

Spitzer Space Telescope Measurements of Dust Reverberation Lags in the Seyfert 1 Galaxy NGC 6418

We present results from a fifteen-month campaign of high-cadence (~ 3 days) mid-infrared Spitzer and optical (B and V ) monitoring of the Seyfert 1 galaxy NGC 6418, with the objective of determining the characteristic size of the dusty torus in this active galactic nucleus (AGN). We find that the 3.6 $\mu$m and 4.5 $\mu$m flux variations lag behind those of the optical continuum by $37.2^{+2.4}_{-2.2}$ days and $47.1^{+3.1}_{-3.1}$ days, respectively. We report a cross-correlation time lag between the 4.5 $\mu$m and 3.6 $\mu$m flux of $13.9^{+0.5}_{-0.1}$ days. The lags indicate that the dust emitting at 3.6 $\mu$m and 4.5 $\mu$m is located at a distance of approximately 1 light-month (~ 0.03 pc) from the source of the AGN UV-optical continuum. The reverberation radii are consistent with the inferred lower limit to the sublimation radius for pure graphite grains at 1800 K, but smaller by a factor of ~ 2 than the corresponding lower limit for silicate grains; this is similar to what has been found for near-infrared (K-band) lags in other AGN. The 3.6 and 4.5 $\mu$m reverberation radii fall above the K-band $\tau \propto L^{0.5}$ size-luminosity relationship by factors $\lesssim 2.7$ and $\lesssim 3.4$, respectively, while the 4.5 $\mu$m reverberation radius is only 27% larger than the 3.6 $\mu$m radius. This is broadly consistent with clumpy torus models, in which individual optically thick clouds emit strongly over a broad wavelength range.Comment: 13 pages, 9 figure

Disease prevention versus data privacy : using landcover maps to inform spatial epidemic models

The availability of epidemiological data in the early stages of an outbreak of an infectious disease is vital for modelers to make accurate predictions regarding the likely spread of disease and preferred intervention strategies. However, in some countries, the necessary demographic data are only available at an aggregate scale. We investigated the ability of models of livestock infectious diseases to predict epidemic spread and obtain optimal control policies in the event of imperfect, aggregated data. Taking a geographic information approach, we used land cover data to predict UK farm locations and investigated the influence of using these synthetic location data sets upon epidemiological predictions in the event of an outbreak of foot-and-mouth disease. When broadly classified land cover data were used to create synthetic farm locations, model predictions deviated significantly from those simulated on true data. However, when more resolved subclass land use data were used, moderate to highly accurate predictions of epidemic size, duration and optimal vaccination and ring culling strategies were obtained. This suggests that a geographic information approach may be useful where individual farm-level data are not available, to allow predictive analyses to be carried out regarding the likely spread of disease. This method can also be used for contingency planning in collaboration with policy makers to determine preferred control strategies in the event of a future outbreak of infectious disease in livestock

Energy return on investment of major energy carriers: Review and harmonization

Net energy, that is, the energy remaining after accounting for the energy “cost” of extraction and processing, is the “profit” energy used to support modern society. Energy Return on Investment (EROI) is a popular metric to assess the profitability of energy extraction processes, with EROI > 1 indicating that more energy is delivered to society than is used in the extraction process. Over the past decade, EROI analysis in particular has grown in popularity, resulting in an increase in publications in recent years. The lack of methodological consistency, however, among these papers has led to a situation where inappropriate comparisons are being made across technologies. In this paper we provide both a literature review and harmonization of EROI values to provide accurate comparisons of EROIs across both thermal fuels and electricity producing technologies. Most importantly, the authors advocate for the use of point-of-use EROIs rather than point-of-extraction EROIs as the energy “cost” of the processes to get most thermal fuels from extraction to point of use drastically lowers their EROI. The main results indicate that PV, wind and hydropower have EROIs at or above ten while the EROIs for thermal fuels vary significantly, with that for petroleum oil notably below ten

Triggered Star Formation in Galaxy Pairs at z=0.08-0.38

We measure the strength, frequency, and timescale of tidally triggered star formation at redshift z=0.08-0.38 in a spectroscopically complete sample of galaxy pairs drawn from the magnitude-limited redshift survey of 9,825 Smithsonian Hectospec Lensing Survey (SHELS) galaxies with R<20.3. To examine the evidence for tidal triggering, we identify a volume-limited sample of major (|\Delta M_R|1/5) pair galaxies with $M_R < -20.8 in the redshift range z=0.08-0.31. The size and completeness of the spectroscopic survey allows us to focus on regions of low local density. The spectrophotometric calibration enables the use of the 4000 Ang break (D_n4000), the H\alpha specific star formation rate (SSFR_{H\alpha}), and population models to characterize the galaxies. We show that D_n4000 is a useful population classification tool; it closely tracks the identification of emission line galaxies. The sample of major pair galaxies in regions of low local density with low D_n4000 demonstrates the expected anti-correlation between pair-wise projected separation and a set of star formation indicators explored in previous studies. We measure the frequency of triggered star formation by comparing the SSFR_{H\alpha} in the volume-limited sample in regions of low local density: 32 +/-7% of the major pair galaxies have SSFR_{H\alpha} at least double the median rate of the unpaired field galaxies. Comparison of stellar population models for pair and for unpaired field galaxies implies a timescale for triggered star formation of ~300-400 Myr.Comment: 25 pages, 15 figures. Accepted to A

Evaluation of the INCREMENT-CPE, Pitt Bacteremia and qPitt Scores in Patients with Carbapenem-Resistant Enterobacteriaceae Infections Treated with Ceftazidime–Avibactam

Background The aim of this study was to evaluate the predictive performance of the INCREMENT-CPE (ICS), Pitt bacteremia score (PBS) and qPitt for mortality among patients treated with ceftazidime–avibactam for carbapenem-resistant Enterobacteriaceae (CRE) infections. Methods Retrospective, multicenter, cohort study of patients with CRE infections treated with ceftazidime–avibactam between 2015 and 2019. The primary outcome was 30-day all-cause mortality. Predictive performance was determined by assessing discrimination, calibration and precision. Results In total, 109 patients were included. Thirty-day mortality occurred in 18 (16.5%) patients. There were no significant differences in discrimination of the three scores [area under the curve (AUC) ICS 0.7039, 95% CI 0.5848–0.8230, PBS 0.6893, 95% CI 0.5709–0.8076, and qPitt 0.6847, 95% CI 0.5671–0.8023; P > 0.05 all pairwise comparisons]. All scores showed adequate calibration and precision. When dichotomized at the optimal cut-points of 11, 3, and 2 for the ICS, PBS, and qPitt, respectively, all scores had NPV > 90% at the expense of low PPV. Patients in the high-risk groups had a relative risk for mortality of 3.184 (95% CI 1.35–8.930), 3.068 (95% CI 1.094–8.606), and 2.850 (95% CI 1.016–7.994) for the dichotomized ICS, PBS, and qPitt, scores respectively. Treatment-related variables (early active antibiotic therapy, combination antibiotics and renal ceftazidime–avibactam dose adjustment) were not associated with mortality after controlling for the risk scores. Conclusions In patients treated with ceftazidime–avibactam for CRE infections, mortality risk scores demonstrated variable performance. Modifications to scoring systems to more accurately predict outcomes in the era of novel antibiotics are warranted

Can the Mechanism for π1→ηπ,η′π\pi_1\to \eta\pi,\eta'\pi Hybrid Decays be Detected?

Two mechanisms for the $\pi_1$ ($J^{PC}=1^{-+}$) hybrid meson decay processes $\pi_1\to\eta\pi,\eta'\pi$ are investigated. These mechanisms are applied to $\phi\to\eta\gamma,\eta'\gamma$ and $J/\psi\to\eta\gamma,\eta'\gamma$ decays to illustrate the validity of the decay mechanisms and to obtain independent information on the coupling of $\eta,\eta'$ to quark and gluonic operators. From this information, we find that $\Gamma(\pi_1\to\eta\pi)/\Gamma(\pi_1\to\eta'\pi)$ is substantially different in the two decay mechanisms, and hence future experimental measurements of this ratio will provide valuable information for substantiating the hybrid nature of these states and for determining the mechanism for these hybrid decays.Comment: 5 pages, revtex, 1 eps figure embedded in manuscript. Analysis and references extended in v

CD32 is expressed on cells with transcriptionally active HIV but does not enrich for HIV DNA in resting T cells

The persistence of HIV reservoirs, including latently infected, resting CD4+ T cells, is the major obstacle to cure HIV infection. CD32a expression was recently reported to mark CD4+ T cells harboring a replication-competent HIV reservoir during antiretroviral therapy (ART) suppression. We aimed to determine whether CD32 expression marks HIV latently or transcriptionally active infected CD4+ T cells. Using peripheral blood and lymphoid tissue of ART-treated HIV+ or SIV+ subjects, we found that most of the circulating memory CD32+ CD4+ T cells expressed markers of activation, including CD69, HLA-DR, CD25, CD38, and Ki67, and bore a TH2 phenotype as defined by CXCR3, CCR4, and CCR6. CD32 expression did not selectively enrich for HIV- or SIV-infected CD4+ T cells in peripheral blood or lymphoid tissue; isolated CD32+ resting CD4+ T cells accounted for less than 3% of the total HIV DNA in CD4+ T cells. Cell-associated HIV DNA and RNA loads in CD4+ T cells positively correlated with the frequency of CD32+ CD69+ CD4+ T cells but not with CD32 expression on resting CD4+ T cells. Using RNA fluorescence in situ hybridization, CD32 coexpression with HIV RNA or p24 was detected after in vitro HIV infection (peripheral blood mononuclear cell and tissue) and in vivo within lymph node tissue from HIV-infected individuals. Together, these results indicate that CD32 is not a marker of resting CD4+ T cells or of enriched HIV DNA–positive cells after ART; rather, CD32 is predominately expressed on a subset of activated CD4+ T cells enriched for transcriptionally active HIV after long-term ART