The catalysis of nucleic acid, as well as nucleobases, metals and other cofactors, is examined, focusing on metal-ion-assisted catalysis in ribozymes. Characteristics of RNA are also addressed.
We present the transient source detection efficiencies of the Palomar Transient Factory (PTF), parameterizing the number of transients that PTF found versus the number of similar transients that ...occurred over the same period in the survey search area but were missed. PTF was an optical sky survey carried out with the Palomar 48 inch telescope over 2009-2012, observing more than 8000 square degrees of sky with cadences of between one and five days, locating around 50,000 non-moving transient sources, and spectroscopically confirming around 1900 supernovae. We assess the effectiveness with which PTF detected transient sources, by inserting million artificial point sources into real PTF data. We then study the efficiency with which the PTF real-time pipeline recovered these sources as a function of the source magnitude, host galaxy surface brightness, and various observing conditions (using proxies for seeing, sky brightness, and transparency). The product of this study is a multi-dimensional recovery efficiency grid appropriate for the range of observing conditions that PTF experienced and that can then be used for studies of the rates, environments, and luminosity functions of different transient types using detailed Monte Carlo simulations. We illustrate the technique using the observationally well-understood class of type Ia supernovae.
ABSTRACT
Many scientific investigations of photometric galaxy surveys require redshift estimates, whose uncertainty properties are best encapsulated by photometric redshift (photo-z) posterior ...probability density functions (PDFs). A plethora of photo-z PDF estimation methodologies abound, producing discrepant results with no consensus on a preferred approach. We present the results of a comprehensive experiment comparing 12 photo-z algorithms applied to mock data produced for The Rubin Observatory Legacy Survey of Space and Time Dark Energy Science Collaboration. By supplying perfect prior information, in the form of the complete template library and a representative training set as inputs to each code, we demonstrate the impact of the assumptions underlying each technique on the output photo-z PDFs. In the absence of a notion of true, unbiased photo-z PDFs, we evaluate and interpret multiple metrics of the ensemble properties of the derived photo-z PDFs as well as traditional reductions to photo-z point estimates. We report systematic biases and overall over/underbreadth of the photo-z PDFs of many popular codes, which may indicate avenues for improvement in the algorithms or implementations. Furthermore, we raise attention to the limitations of established metrics for assessing photo-z PDF accuracy; though we identify the conditional density estimate loss as a promising metric of photo-z PDF performance in the case where true redshifts are available but true photo-z PDFs are not, we emphasize the need for science-specific performance metrics.
An approach for the time dependent evolution of the local chemical environment during the initial stage of localised corrosion for aluminium alloys has been developed. The approach was applied to ...study anodic dissolution of S phase in sodium chloride, where both metallic species, Al3+ and Mg2+, were taken into consideration. The developed model includes hydrolysis products of aluminium and species obtained as a result of homogeneous reactions between chloride and Al3+ and Mg2+ ions and Al hydrolysis products. The model does not assume the equilibrium state in solution: all terms in the homogeneous reactions are treated explicitly using kinetic constants either taken from the literature or derived using the Eigen mechanism for complex formation. It was shown that for an active dissolution process, the time needed for chemical species to achieve their steady state concentrations ranges from minutes (for solution potential and the pH value) to hours or even days. Thus, modelling predictions obtained with the steady state approximation can give inaccurate values for species concentrations. Two modelling examples are discussed: the dissolution of a large S phase and small isolated S phase particle in Al alloys. Input data for the models are supplied by microcapillary measurements.
To identify the impact of deep sternal wound infection (DSWI) on long-term survival after coronary artery bypass grafting (CABG).
DSWI following CABG is an infrequent, yet devastating complication ...with increased morbidity and mortality. However, little has been published regarding the impact of DSWI on long-term mortality.
We studied 3,760 consecutive patients who underwent isolated CABG between 1992 and 2002. Patients with CABG and no DSWI were compared with those in whom DSWI developed. Long-term survival data (mean follow-up, 5.2 years) were obtained from the National Death Index. Groups were compared by Cox proportional hazard models and Kaplan-Meier survival plots. The propensity for DSWI was determined by logistic regression analysis, and each patient with DSWI was then matched to 10 patients without DSWI.
DSWI developed in 40 of 3,760 patients (1.1%). Independent predictors for DSWI were diabetes (odds ratio OR, 5.5; 95% confidence interval CI, 2.7 to 11.6; p < 0.001), hemodynamic instability preoperatively (OR, 4.0; 95% CI, 1.2 to 13.9; p = 0.026), preoperative renal failure on dialysis (OR, 3.4; 95% CI, 1.0 to 13.6; p = 0.049), use of bilateral internal thoracic arteries (OR, 2.6; 95% CI, 1.3 to 5.3; p = 0.010), and sepsis and/or endocarditis after CABG (OR, 29.9; 95% CI, 11.7 to 76.4; p < 0.001). Patients with DSWI had prolonged length of stay (35.0 days vs 16.4 days; p < 0.001); however, there was no difference in early mortality between matched groups. After adjustment for preoperative, intraoperative, and postoperative factors, the adjusted hazard ratio of long-term mortality for patients with DSWI was 2.44 (95% CI, 1.51 to 3.92; p < 0.001). Patients without DSWI had a better 5-year survival rate (72.8 ± 2.4% vs 50.8.6 ± 8.5% mean ± SE; p = 0.0007 between matched groups).
We found that DSWI following CABG was associated with increased long-term mortality during a 10-year follow-up study.
We present spectroscopic observations of the host galaxies of 82 low-redshift Type Ia supernovae (SNe Ia) discovered by the Palomar Transient Factory. We determine star formation rates, ...gas-phase/stellar metallicities, and stellar masses and ages of these objects. As expected, strong correlations between the SN Ia light-curve width (stretch) and the host age/mass/metallicity are found: fainter, faster declining events tend to be hosted by older/massive/metal-rich galaxies. There is some evidence that redder SNe Ia explode in higher metallicity galaxies, but we found no relation between the SN colour and host galaxy extinction based on the Balmer decrement, suggesting that the colour variation of these SNe does not primarily arise from this source. SNe Ia in higher mass/metallicity galaxies also appear brighter after stretch/colour corrections than their counterparts in lower mass hosts, and the stronger correlation is with gas-phase metallicity suggesting this may be the more important variable. We also compared the host stellar mass distribution to that in galaxy-targeted SN surveys and the high-redshift untargeted Supernova Legacy Survey (SNLS). SNLS has many more low-mass galaxies, while the targeted searches have fewer. This can be explained by an evolution in the galaxy stellar mass function, coupled with an SN delay-time distribution proportional to t
−1. Finally, we found no significant difference in the mass–metallicity relation of our SN Ia hosts compared to field galaxies, suggesting any metallicity effect on the SN Ia rate is small.
ABSTRACT
Wide-field imaging surveys such as the Dark Energy Survey (DES) rely on coarse measurements of spectral energy distributions in a few filters to estimate the redshift distribution of source ...galaxies. In this regime, sample variance, shot noise, and selection effects limit the attainable accuracy of redshift calibration and thus of cosmological constraints. We present a new method to combine wide-field, few-filter measurements with catalogues from deep fields with additional filters and sufficiently low photometric noise to break degeneracies in photometric redshifts. The multiband deep field is used as an intermediary between wide-field observations and accurate redshifts, greatly reducing sample variance, shot noise, and selection effects. Our implementation of the method uses self-organizing maps to group galaxies into phenotypes based on their observed fluxes, and is tested using a mock DES catalogue created from N-body simulations. It yields a typical uncertainty on the mean redshift in each of five tomographic bins for an idealized simulation of the DES Year 3 weak-lensing tomographic analysis of σΔz = 0.007, which is a 60 per cent improvement compared to the Year 1 analysis. Although the implementation of the method is tailored to DES, its formalism can be applied to other large photometric surveys with a similar observing strategy.
The cosmological utility of galaxy cluster catalogues is primarily limited by our ability to calibrate the relation between halo mass and observable mass proxies such as cluster richness, X-ray ...luminosity or the Sunyaev-Zeldovich signal. Projection effects are a particularly pernicious systematic effect that can impact observable mass proxies; structure along the line of sight can both bias and increase the scatter of the observable mass proxies used in cluster abundance studies. In this work, we develop an empirical method to characterize the impact of projection effects on redMaPPer cluster catalogues. We use numerical simulations to validate our method and illustrate its robustness. We demonstrate that modeling of projection effects is a necessary component for cluster abundance studies capable of reaching $\approx 5\%$ mass calibration uncertainties (e.g. the Dark Energy Survey Year 1 sample). Specifically, ignoring the impact of projection effects in the observable--mass relation --- i.e. marginalizing over a log-normal model only --- biases the posterior of the cluster normalization condition $S_8 \equiv \sigma_8 (\Omega_{\rm m}/0.3)^{1/2}$ by $\Delta S_8 =0.05$, more than twice the uncertainty in the posterior for such an analysis.
A multi ion transport and reaction model has been developed with the intent to improve via simulation the understanding of the first steps of localized corrosion (pitting) of aluminum alloys at the ...microscale. However, the onset of pitting could not be predicted, but the simulation of all parts of a micropolarization curve, excluding the pitting regime, was possible. Unlike previous models, the model does not use the assumption that the system is at all times in a state of chemical equilibrium. In order to model localized corrosion initiation on Al alloys, one has to consider their complex microstructure which normally has a high number of structural inhomogeneities. We have considered localized corrosion initiation on the aluminum alloy AA2024 in sodium chloride solution. The intermetallic particles found in this widely used alloy can be divided into three major types based upon their composition: AlCuFeMnSi (2nd phase) intermetallics and Al2Cu (θ phase) precipitates, which are more noble than the Al matrix (areas of the alloy without constituent microscale particles), and Al2CuMg (S phase) precipitates, which are the preferential initiation sites for localized corrosion. It was expected that the results from this microscopic model would provide input data for a macroscopic corrosion model. Such a macroscopic model could then be used to simulate the behavior of sensitive assemblies, such as two overlapping aluminum alloy sheets, that can generate an occluded electrochemical cell. It turned out that this modeling approach has value, but requires very careful consideration of the input data.
Risk factors for post-operative conduction disturbances after cardiac valve surgery requiring a permanent pacemaker (PPM) are poorly characterized.
The aim of this study was to investigate the timing ...and risk factors for PPM implantation after mitral or aortic valve surgery.
All patients who underwent open aortic or mitral valve surgery between January 1996 and December 2014 were reviewed using New York State’s mandatory hospital discharge database. Patients with prior cardiac surgery or pre-existing PPM were excluded. The primary endpoint was PPM implantation within 1 year.
Among 77,882 patients, 63.8% (n = 49,706) underwent aortic valve replacement (AVR), 18.9% (n = 14,686) underwent mitral valve replacement (MVR), 10.5% (n = 8,219) underwent mitral valve repair (MVr), 5.4% (n = 4,202) underwent AVR plus MVR, and 1.4% (n = 1,069) underwent AVR plus MVr. The 1-year PPM implantation rate was 4.5% after MVr, 6.6% after AVR, 9.3% after AVR plus MVr, 10.5% after MVR, and 13.3% after AVR plus MVR (p < 0.001). Across all groups, the majority of PPMs were implanted during the index hospitalization (79.9%). MVr was associated with the lowest risk for PPM and AVR plus MVR with the highest risk. Older age, history of arrhythmias, pre-operative conduction disturbances, and concomitant index procedures were associated with increased risk for PPM during the index hospitalization. Conversely, beyond 30 days, chronic comorbidities were associated with increased risk for PPM.
Conduction disturbances requiring PPM remain a common adverse event after valve surgery. Identifying patients at risk for PPM will help facilitate perioperative planning and inform clinical decision making regarding post-operative rhythm surveillance.
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