Averaged Curves Research Articles

Seismic Damage Assessment of Reinforced Concrete Grain Silos

This paper deals with seismic performance and damage assessment of concrete grain silos. An existing large silo is taken as a case study to conduct the numerical analyses. A global damage index based on target displacement is proposed to quantify numerically different damage states of the structure. To this aim, the classical N2 method is extended to adaptive multimodal to evaluate seismic performance of the structure for increasing pic ground acceleration levels with taking into account degradation of stiffness and modification of modal characteristics. The seismic capacity of the silo is evaluated, as an averaged curve, by conducting pushover and several incremental dynamic analyses using artificial and recorded accelerograms. The seismic demand is derived from the design spectrum of the Algerian seismic code (RPA 2003). The target displacement is determined by taking into account both the participation of the dominant modes, and the degradation of the structure’s modal characteristics. The nonlinear behavior of the structure’s walls is modeled by using nonlinear multilayered shell elements. The effect of the stored granular material is included through distributed equivalent masses. It is found that when the structure modal characteristics are updated as its stiffness is degraded, the target displacement is correctly computed. Whereas, it wrongly grows indefinitely, with increasing PGA, when constant modal characteristics of the intact structure are assumed, as usually done. The proposed global damage index is compared to three existing reliable indices. It better reflects the different damage states of studied silo.

Correlation of gravitational wave background noises and statistical loss for angular averaged sensitivity curves

Gravitational wave backgrounds generate correlated noises to separated detectors. This correlation can induce statistical losses to actual detector networks, compared with idealized noise-independent networks. Assuming that the backgrounds are isotropic, we examine the statistical losses specifically for the angular averaged sensitivity curves, and derive simple expressions that depend on the overlap reduction functions and the strength of the background noises relative to the instrumental noises. For future triangular interferometers such as ET and LISA, we also discuss preferred network geometries to suppress the potential statistical losses.

ГИДРОЛОГИЧЕСКИЕ УСЛОВИЯ В РАЙОНЕ ЮЖНЫХ КУРИЛЬСКИХ ОСТРОВОВ ПО ДАННЫМ СПУТНИКОВЫХ И СУДОВЫХ ИЗМЕРЕНИЙ

The materials of satellite observations of the sea surface temperature in the study area (1998–2020) were also analyzed by statistical methods and by decomposition according to the EOF. The amplitude of the averaged curve of the annual variation of the ocean surface temperature (SST) as a whole for the region was estimated, which was 7° (the contribution of the semiannual component with an amplitude of 1°С is small), as well as the most significant anomalies that reached 4°С in cold August 2002 and 3°С in warm September 2012. A quasiperiodic course of the envelope of summer maximums with a period of 5–6 years was revealed. It is shown that there is negligible trend in the thermal regime in the study area. Based on the analysis of materials from 10 oceanological surveys, seasonal variations in hydrological conditions in the area of South Kuril Islands were studied. It is shown that the areas of the Kunashirsky and Yuzhno-Kurilsky Straits in the warm season are filled with warm and salty waters of the Soya Current, and in winter and spring - with freshened modified water from the Amur River runoff transported by the East Sakhalin Current. Annual salinity variations exceed 1.5 psu here.

Catalog of averaged magnetic phase curves of stars

Some stars show variability of the longitudinal components of their global magnetic fields, mainly resulting from rotation. Recently, a lot of new observational data have accumulated for various types of stars. To summarize information about magnetic variability, we present the second version of the catalog of average magnetic phase curves. The curves are obtained from literary data and as a result of observations from SAO RAS telescopes. A total of 357 stars of various spectral types were studied based on data that was published before the end of August 2020. Magnetic Ap and Bp stars make up the most numerous subset in the catalog (224 objects). The phase curves were obtained by least-squares fit of the simple sine wave or double sine wave, which are presented in uniform form. The parameters of variability of these objects are presented in tabular form; the upper limits of observed magnetic fields of various types are indicated. The information is presented in a convenient form for verification of various kinds of theoretical models. For clarity and ease of use, phase dependences are presented in graphic form in 514 figures. Periods of variability are defined or refined for a number of stars. The created catalog allows the estimation of the limits of the observed magnetic field variability for various types of stars and the estimation of the energy of the magnetic fields of stars. The catalog will be useful for the development of observation programs. The catalog facilitates the study of the orientation of the axes of rotation of stars in space, the investigation of the interactions of magnetic fields of stars with the interstellar medium, and the “magnetic braking” mechanism. This catalog also permits the study of the orientation of the orbits of planets for some stars with planets and planetary systems.

Estimation of thunderstorms occurrence from lightning cluster recorded by WWLLN and its comparison with the ‘universal’ Carnegie curve

Continuous global monitoring of lightning has been important in recent years to study a possible relationship with global warming. Consequently, several networks to detect lightning have been installed at various spatial scales (regional and global). One of these networks is the World Wide Lightning Location Network (WWLLN), which has been monitoring lightning since 2003. It is also important to monitor the occurrence of thunderstorms and this can be roughly archived by detecting lightning clusters. In this work, we propose a lightning grouping methodology, in order to estimate the global number of thunderstorms. Our methodology consists of grouping the WWLLN data into a density matrix with a spatial resolution of 0.1° x 0.1° (1 pixel) and a temporal resolution of one hour, then the algorithm identifies the pixels with lightning and groups these pixels with the adjacent pixels to form the thunderstorm. Then, we calculate monthly, seasonal and annual averaged daily curves of the number of thunderstorms. The data set under study includes years 2012 and 2013. Our methodology is validated by calculating the linear correlation coefficient (R) between the annual daily thunderstorm curve and the “universal” Carnegie curve (R = 0.97) and with the Vostok electric field measurements (R = 0.98). Additionally, we found higher correlation in September–October–November months (R = 0.98) compared with June–July–August months (R = 0.75) for Carnegie and for Vostok station (R=0.99 and R=0.88, respectively).

SIMULATION OF THE AUTUMN-WINTER RUNOFF OF THE ANADYR RIVER

. Runoff during the autumn-winter low-water period is of great importance in the life of river ecosystems. In this work, the goal is to construct a mathematical model of the curves of daily water discharge during the autumn-winter low-water period (September-April) on the Anadyr River near the village Snezhny (catchment area 106 000 km2 ). Anadyr River is the largest waterway of the Chukotka. The river is used by public utilities, river transport in summer and road transport in winter. Pacific salmon spawn in this river every year. The conditions for the survival of salmon eggs in winter are influenced by the water content of the rivers. The basin under consideration is located in a zone of subarctic climate and continuous permafrost. Therefore, the autumn-winter low-water period on the Anadyr River lasts from September to April during this period, 4–6 % of the annual runoff occurs. Based on the average annual monthly water discharges for September-April, the averaged runoff depletion curve was calculated in relative ordinates, which is approximated by an exponential function. Based on this curve, you can predict daily water discharges from September 15th to April 15th of the following year. Verification calculations for the years of winters with different water content showed that the mathematical model works satisfactorily. Based on the data on the runoff of other hydrological stations in the Anadyr catchment, the study can be continued to derive a basin formula, which can be used to predict the daily water discharges of the autumn-winter low-water period on any unexplored river.

A Wideband Current Transducer Based on an Array of Magnetic Field Sensors for Rectangular Busbar Current Measurement

Recently, the current transducer based on an array of magnetic field sensors has attracted a lot of attention. For busbars of circular cross section, many studies have been conducted and many results have been obtained. However, for the rectangular cross section busbar, the skin effect causes the frequency response curve of the magnetic flux density $B$ generated by the current-carrying conductor to appear nonlinear, which brings challenges to the wideband current measurement of the rectangular busbar. This article presents a wideband current transducer based on the array of magnetic field sensors for the current measurement of the rectangular busbar. First, according to the rectangular busbar, select reasonable magnetic field detection points to arrange the sensor array. Then, the frequency response curve of the magnetic flux density $B$ at each detection point around the rectangular busbar is obtained by simulation. After that, all frequency response curves are averaged, and the proper digital filter is designed according to the averaged frequency response curve to perform frequency compensation. The compensated frequency response curve is basically flat, so the wideband current measurement of the rectangular busbar can be realized. The bandwidth and overall performance of the designed wideband current transducer are verified through experiments, and experimental results show that the designed transducer can meet the requirements of relevant standards for the class 0.5 current transducer.

Prediction of COVID-19 Mortality in Patients with Cancer

Background: Coronavirus disease 2019 (COVID-19) is associated with an increased mortality rate in patients with cancer. Machine learning approaches have been used successfully to predict mortality in infected patients from the general population. We aimed to devise an algorithm to estimate the risk of death in the first 45 days after COVID-19 diagnosis for patients with cancer.Methods: As a first step we used the ensemble learning method random survival forests. Computations were performed with R packages randomForestSRC, ROCR and cvAUC. The cohort consisted of Memorial Sloan Kettering patients diagnosed with COVID-19 before June 12, 2020 (n=820). The primary endpoint was mortality at 45 days after diagnosis of COVID-19. Patients were included in the study regardless of whether or not they were admitted to the hospital. Predictors assessed at the time of COVID-19 diagnosis and retained for the model include: cancer type (thoracic, hematologic or other), metastatic status, age, sex, smoking, presence of a comorbidity (any of hypertension, diabetes, hyperlipidemia, chronic hepatic or renal disease, coronary artery disease, asthma, thromboembolism, chronic obstructive lung disease, congestive heart failure, valvular heart disease, stroke, HIV and peripheral arterial disease), body mass index (BMI), presence of hypoxia (defined as need to use supplemental oxygen 2 L/min or more), blood glucose, total bilirubin, total white blood count (WBC), hemoglobin, red cell distribution width (RDW), platelet count, absolute neutrophil count (ANC), absolute lymphocyte count, serum albumin, blood urea nitrogen (BUN) , creatinine, aspartate transaminase (AST), alanine transaminase (ALT), ferritin, lactate dehydrogenase (LDH), prothrombin time (PT), activated partial thromboplastin time (aPTT), D-dimers, race and smoking history. Model performance was assessed with repeated 10-fold cross-validation.Results: 11% (n=91) of patients had died by day #45 of observation. The prevalence of hematologic malignancy in the cohort at large was 26% (n=210), compared with 9% (n=74) for primary thoracic neoplasms. Metastatic solid cancer was present in 40% (n=332) of individuals. Information on cell counts and RDW was complete for 51% of patients, compared to 43% for liver function tests, 54% for renal function measurements, 23% for PT, 22% for PTT and 7% for D-dimers. Records were manually reviewed and assessed successfully in all patients for cancer type, metastatic status, presence of a comorbidity, presence of hypoxia and smoking history. Only 23% of patients were admitted at the time of COVID-19 diagnosis. The mean cross-validated area under the receiver operating characteristic (ROC) curve for a model including all available covariates was 0.81 (95% confidence interval = 0.80-0.82). The averaged ROC curve is shown in Figure A. Comorbidities, BUN, serum albumin, age, hypoxia, cancer type, RDW, hemoglobin, platelet count, metastatic status and smoking history all contributed significantly to the model, as measured with the Ishwaran-Kogalur Variable Importance (VIMP). Scaled VIMP values are reported in Figure B.Conclusions: COVID-19 is associated with substantial mortality in patients with cancer. As observed in prior reports of patients from the general population, the presence of comorbidities, age, BUN and hypoxia at presentation are highly predictive of mortality in this setting. Interestingly, serum albumin appears to be an important predictor in patients with cancer, as are cancer-specific covariates including tumor type and metastatic status. The latter suggests that optimal predictive models of COVID-19 mortality in oncology patients will differ substantially from those trained on more general medical cohorts. Additional work remains to be done in order to validate this model before its application in clinical practice.DisclosuresMantha:MJH Associates: Honoraria; Physicians Education Resource: Honoraria. Jee:MDSeq Inc.: Patents & Royalties. Soff:Bristol-Myers Squibb, Pfizer: Honoraria; Dova Pharmaceuticals: Research Funding; Amgen: Research Funding; Janssen Scientific Affairs: Research Funding; Dova Pharmaceuticals: Honoraria; Janssen Scientific Affairs: Honoraria; Amgen: Honoraria.

Search for giant planets around seven white dwarfs in the Hyades cluster with the Hubble Space Telescope

ABSTRACT Only a small number of exoplanets have been identified in stellar cluster environments. We initiated a high angular resolution direct imaging search using the Hubble Space Telescope (HST) and its Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) instrument for self-luminous giant planets in orbit around seven white dwarfs in the 625 Myr old nearby (≈45 pc) Hyades cluster. The observations were obtained with Near-Infrared Camera 1 (NIC1) in the F110W and F160W filters, and encompass two HST roll angles to facilitate angular differential imaging. The difference images were searched for companion candidates, and radially averaged contrast curves were computed. Though we achieve the lowest mass detection limits yet for angular separations ≥0.5 arcsec, no planetary mass companion to any of the seven white dwarfs, whose initial main-sequence masses were >2.8 M⊙, was found. Comparison with evolutionary models yields detection limits of ≈5–7 Jupiter masses (MJup) according to one model, and between 9 and ≈12 MJup according to another model, at physical separations corresponding to initial semimajor axis of ≥5–8 au (i.e. before the mass-loss events associated with the red and asymptotic giant branch phase of the host star). The study provides further evidence that initially dense cluster environments, which included O- and B-type stars, might not be highly conducive to the formation of massive circumstellar discs, and their transformation into giant planets (with m ≥ 6 MJup and a ≥6 au). This is in agreement with radial velocity surveys for exoplanets around G- and K-type giants, which did not find any planets around stars more massive than ≈3 M⊙.

Observational statistics analysis of seismoelectric effects in a gas condensate reservoir

The article considers the observational statistics analysis of seismoelectric effects of the second kind at the Bystryanskoye gas condensate reservoir in Krasnoyarsk Territory. The measurements were carried out by the passive method from 2014 to 2019 on one exploration profile. The authors obtained an averaged profiling curve. Its analysis showed that there exists the repeatability of measurement results, as well as the convergence with the results of mathematical modeling. The collected statistics on the observation points shows the possibility of this method application in carrying out industrial field work in conjunction with the standard seismic exploration.

Variations in shape among observed Lyman-α spectra due to intergalactic absorption

Lyman-α (Lyα) spectra provide insights into the small-scale structure and kinematics of neutral hydrogen (HI) within galaxies as well as the ionization state of the intergalactic medium (IGM). The former defines the intrinsic spectrum of a galaxy, which, in turn, is modified by the latter. These two effects are degenerate. Using the IllustrisTNG100 simulation, we studied the impact of the IGM on Lyα spectral shapes between z ∼ 0 and 5. We computed the distribution of the expected Lyα peaks and of the peak asymmetry for different intrinsic spectra, redshifts, and large-scale environments. We find that the averaged transmission curves that are commonly applied give a misleading perception of the observed spectral properties. We show that the distributions of peak counts and asymmetry can lift the degeneracy between the intrinsic spectrum and IGM absorption. For example, we expect a significant number of triple-peaked Lyα spectra (up to 30% at z ∼ 3) if the galaxies’ HI distribution become more porous at higher redshift, as predicted by cosmological simulations. We provide a public catalog of transmission curves for simulations and observations to allow for a more realistic IGM treatment in future studies.

Detection rates of chemosensory evoked Potenzials with healthy andanosmic subjects

The detection rate of olfactory chemosensory event-related EEG Potentials (oCSERP) and trigeminal chemosensory event-related EEG Potentials (tCSERP) is also dependent on the stimulants and the evaluator of the averaged EEG curves. In 45 subjects with age-appropriate normal olfactory capacity (NP) and 20 anosmics (AN), oCSERP (stimulation by hydrogen sulphide, H2S 6 ppm and phenylethyl alcohol, PEA 30 % v/v,) and tCSERP (irritation with CO2 20-60 % v/v, intensity standardized) were derived by default. Two investigators categorized the averaged EEG curves in: CSERP recognizable, no CSERP recognizable and artefact. Investigator 1 knew whether the subject was a NP or an AN, and which stimulants was used, whereas investigator 2 lacked this information. AN needed higher trigeminal stimulus concentrations but showed same intensity ratings compared to NP. The attention (tracking game) did not deteriorate in the course of test. The detection rate of H2S-CSERP was higher than that of PEA-CSERP. The match of H2S-CSERP detection rates between the two investigators was higher than that of PEA-CSERP and CO2-CSERP. For the standard derivation of oCSERP, stimulation with H2S is usually sufficient. Stimulation with PEA and CO2 as well as a blinded investigator is not necessary.

Characterization of Sagittal Spine Alignment With Reference to the Gravity Line and Vertebral Slopes: An Analysis of Different Roussouly Curves.

Prospective study. To map the healthy standing alignment of the adult spine, grouped according to Roussouly curve types, using both horizontal offset distance from the gravity line (GL), as well as vertebral slope measurements. Spinal sagittal realignment requires a reference posture, and this has been defined in the literature via horizontal offsets from the GL. While useful, this does not provide information on the orientation of each vertebral segment, or distinguish between the various physiological curve types. A total of 169 consecutive young adult subjects with healthy spines were recruited over a year. (EOS Imaging, Paris, France) whole body radiographs were performed. Radiographic measurements collected included sagittal vertical axis (SVA), T1-slope, global cervical angle (GCA), global thoracic angle (GTA), global lumbar angle (GLA), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), apical and inflection vertebrae. Outcome measures comprised slope measurements, and distance offsets relative to the GL for individual vertebrae from T3 to S1. GLA, PI, PT, SS, apex of lordosis, and inflection vertebra were significantly different across groups, while SVA, T1-slope, GCA, GTA, and apex of kyphosis were not. Mean PI to LL discrepancy for Type I to IV groups were 8.0°, 2.3°, 4.8°, and 3.0°, respectively. Between groups, T3, T7 to T12, and L2 to S1 slopes and T9 to L3 offset distances from GL were significantly different, while the distance of the hip center from the GL was not. GLA was significantly different between curve types except between Type 1 and 2 curves, while the inflection vertebrae were not significantly different between Type 1 and 2 curves, as well as Type 3 and 4 curves. This study demonstrates normative sagittal spatial orientation of each vertebra in healthy adults, for each Roussouly type. Comparison across groups suggests the possibility of further refining the sagittal curve patterns described by Roussouly. 3.

ВПЛИВ ЕЛІПТИЧНОСТІ ДЖЕРЕЛА НА КРИВІ БЛИСКУ В ПОЗАГАЛАКТИЧНИХ ГРАВІТАЦІЙНО-ЛІНЗОВИХ СИСТЕМАХ

In extragalactic gravitational lens system (GLS) several macro-images of a remote source (quasar) are observed. Gravitational microlensing leads to uncorrelated brightness variations of the macro-images. These variations can be separated from proper brightness changes of the source, which are repeated in each image with some relative delay. In most papers the gravitational microlensing effects in extragalactic GLS typically deal with centrally symmetric sources, though the real form of the source can be more complicated. In this paper we consider statistical signals of the source ellipticity in light curves of microlensed objects, which arise as a result of observations of many high amplification events. As a first step, we consider a qualitative version of the problem, when an elliptic source with Gaussian brightness distribution is crossed by a number of simple (fold) caustics with different orientations. Also we assume that the caustic network is isotropic, that is all orientations of the caustics and directions of their velocities are equally possible. We use the linear fold caustic approximation for the amplification of a small point source, when two critical images appear/disappear after the caustic crossing. For a rough estimate, the strength and velocity of the caustic are fixed by certain characteristic values. We estimate the averaged light curve after many caustic crossing events and compare maxima of brightness on the light curves for different eccentricities of the source. The ellipticity signal in the light curves is noticeable for a considerable oblateness of the source. Though we expect that the effect will be smeared out after taking into account the distribution of the caustic velocities and caustic strengths. Possible complications of the problem are indicated due to interplay of effects due to velocity distribution of stars in the lensing galaxy and bulk motion of the lensing galaxy as a whole.

Pharmacokinetics of Verapamil and Hemodynamic Indices during Head-down Bed Rest

The purpose of this work was to study the pharmacokinetics of the Ca ion antagonist verapamil (a single dose of 80 mg) and hemodynamics in nine volunteers with normal life activities (experiment 1) and on the second day of head-down (–8°) bed rest (experiment 2). The plasma concentration of verapamil was measured using high-performance liquid chromatography with fluorometric detection. Heart rate (HR), cardiac output (CO), stroke volume (SV) and general peripheral vascular resistance (GPVR) were measured using integral rheography according to Tishchenko (Mingograf-410, Russia); blood pressure (BP) was measured by Korotkoff sounds. Analysis of verapamil pharmacokinetics in both experiments showed identity of the averaged curve profiles that did not differ significantly. The pharmacokinetic parameters were comparable. Based on hemodynamics analysis, HR elevation 1 h after verapamil administration was the most common reaction in both experiments; a short CO rise and GPVR decrease were observed in experiment 2 1 h after administration. These hemodynamic shifts were not pathologic and did not deviate from the physiological range in healthy people; changes in verapamil pharmacokinetics were also not detected. These findings provide the grounds to recommend verapamil for rational pharmacotherapy of cardiovascular diseases that may develop in piloted space missions.

Development of the recipe for matrix compositions of 2-ethyl-3-methyl-6-hydroxymethylpyridine succinate for tablets of prolonged action based on polymeric bondin

The kinetics of the release of 2-ethyl-3-methyl-6-hydroxypyridine succinate from extended-release tablets obtained using K4M, K15M, K100M and K200M hydroxypropyl methylcellulose polymers was studied. The hypothesis about the possibility of accepting for the samples the normal distribution of response - the degree of release of the drug was tested. A weak effect of the nature of the polymer on the kinetics of release was revealed — the maximum relative difference between the average values for each polymer does not exceed 15%. A series of experimental studies in buffer solutions at pH 1.2; 4.5 and 6.8 to identify the effect of pH on the kinetics of release. A significant effect of pH on the release rate was revealed - at pH 1.2 a faster release is observed. Dissolution curves at pH 4.5 and 6.8 practically coincide. Using the substance of 2-ethyl-3-methyl-6-hydroxypyridine succinate as an example, a mathematical model of the kinetics of in vivo release has been developed, which reflects the effect of pH on the rate of release of ionized drugs from matrix tablets in aqueous media. The model is based on a statistical study of in vitro release kinetics data at pH 1.2; 4,5; 6.8, with the subsequent construction on their basis of cubic splines for the averaged curves and revealing the presence of the influence of pH. These data are used at the in vivo modeling stage, taking into account the degree of release at pH in the gastrointestinal tract preceding the current one. A condition for the application of the model is the presence of a normal distribution of in vitro measurement errors with the same dispersion, independent of pH. The dispersion value is used to model the boundaries of the dissolution profile using the Monte Carlo method. A procedure has been developed for assessing the upper and lower boundaries of release profiles in the body by the Monte Carlo method by generating release values for 100 trials based on the developed release kinetics model. The model was used in the development and industrial implementation of the formulation of matrix tablets of a prolonged form of 2-ethyl-3-methyl-6-hydroxypyridine succinate (trade name “Armadin”) in LLC “Mikrokhim”.

Model averaging fails to improve the extrapolation capability of the island species–area relationship

AbstractAimOne of the main applications of the island species–area relationship (SAR) is to predict species richness in areas of habitat too large to be sampled, but there are few clear guidelines for choosing an appropriate model for this purpose. We therefore aimed to test whether a multi‐model averaging approach could improve the accuracy of predictions made by extrapolating the ISAR. Specifically, we compared the performance of multi‐model averaging with that of the default ISAR model of choice, the power model, in predicting species richness in large habitat islands.LocationGlobalTaxaVertebrates, invertebrates and plantsMethodsWe removed the largest islands from 120 habitat island datasets, and fitted both the power model and a multi‐model average curve (averaging the predictions of up to 20 ISAR models) to this filtered dataset. We then assessed the accuracy of both approaches in predicting the species richness of the largest island in the original dataset using the log error of extrapolation (LEE) metric. A generalized additive regression modelling framework was used to determine whether any dataset characteristics could explain variation in the LEE values for the power model (LEE‐POW).ResultsThe power model gave the more accurate richness predictions for 58% of the analysed datasets and the multi‐model averaged curve gave the more accurate predictions for the remaining 42%. Both the power models (61% of LEE‐POW values were positive) and the multi‐model averaged curve (60% were positive) had a slightly greater tendency to over predict the observed richness. The confidence intervals were also on average narrower for the power model predictions (median 95% confidence interval width = 18 species) than for the multi‐model averaged curve predictions (median 95% confidence interval width = 78). The range in island areas and richness values explained a small amount of the variation in LEE‐POW.Main conclusionsContrary to expectation, multi‐model averaging was less accurate than the power model in the majority of cases, and thus does not appear to be a panacea for uncertainty in model choice when extrapolating the ISAR. However, further research is urgently needed to evaluate the performance of a multi‐model averaging approach at larger spatial scales.

Relations between the Spectral Indices and Flux Densities of Eight Blazars

Relations between the flux densities (F) and spectral indices (α) can help us analyze the emission process. In this paper, we choose 8 blazars (0235+164, 0430+052, 1156+295, 3C345, 1308+326, 1413+135, 3C454.3, and 1749+096) from the University of Michigan Radio Observatory (UMRAO) database to study the relations between the spectral indices (α) and flux densities at 14.5GHz (F14.5). The main results are the following. (1) There are strong anticorrelations between α and F14.5, with the correlation coefficient r in the range from -0.33 to -0.87. (2) The α-F14.5 distributions show elliptic appearance, which have been fitted by elliptic curves. (3) For most of the sources, the time intervals of α-F14.5 elliptic circle (Tc) are consistent with the quasi-periodicities calculated by the averaged light curves and spectral variances (PαF¯).

Maser flare simulations from oblate and prolate clouds

We investigated, through numerical models, the flaring variability that may arise from the rotation of maser clouds of approximately spheroidal geometry, ranging from strongly oblate to strongly prolate examples. Inversion solutions were obtained for each of these examples over a range of saturation levels from unsaturated to highly saturated. Formal solutions were computed for rotating clouds with many randomly chosen rotation axes, and corresponding averaged maser light curves plotted with statistical information. The dependence of results on the level of saturation and on the degree of deformation from the spherical case were investigated in terms of a variability index and duty cycle. It may be possible to distinguish observationally between flares from oblate and prolate objects. Maser flares from rotation are limited to long timescales (at least a few years) and modest values of the variability index ($\lesssim 100$), and can be aperiodic or quasi-periodic. Rotation is therefore not a good model for H$_2$O variability on timescales of weeks to months, or of truly periodic flares.

Sars: an R package for fitting, evaluating and comparing species–area relationship models

The species–area relationship (SAR) constitutes one of the most general ecological patterns globally. A number of different SAR models have been proposed. Recent work has shown that no single model universally provides the best fit to empirical SAR datasets: multiple models may be of practical and theoretical interest. However, there are no software packages available that a) allow users to fit the full range of published SAR models, or b) provide functions to undertake a range of additional SAR‐related analyses. To address these needs, we have developed the R package ‘sars’ that provides a wide variety of SAR‐related functionality. The package provides functions to: a) fit 20 SAR models using non‐linear and linear regression, b) calculate multi‐model averaged curves using various information criteria, and c) generate confidence intervals using bootstrapping. Plotting functions allow users to depict and scrutinize the fits of individual models and multi‐model averaged curves. The package also provides additional SAR functionality, including functions to fit, plot and evaluate the random placement model using a species–sites abundance matrix, and to fit the general dynamic model of oceanic island biogeography. The ‘sars’ R package will aid future SAR research by providing a comprehensive set of simple to use tools that enable in‐depth exploration of SARs and SAR‐related patterns. The package has been designed to allow other researchers to add new functions and models in the future and thus the package represents a resource for future SAR work that can be built on and expanded by workers in the field.