Proton Spin-Lattice Relaxation of Water Molecules in Ferrous-Ferric/Agarose Gel System

Proton spin-lattice relaxation time (T1) of water in aqueous solutions of ferrous and ferric ions and in the corresponding agarose gel systems have been studied in the light of NMR relaxation theory. The theoretical analysis of 1/T1\u27s has revealed that, at the microscopic level, changes in the solvation states of paramagnetic ions in aqueous or gel environment are greater than difference in the paramagnetism between ferric and ferrous ions. The former change is the primary factor for the exhibition of radiation effect. At the phenomenological level, we have confirmed and demonstrated that: (1) Radiation effect is almost exclusively exhibited through changes in 1/T1 caused by the interactions between water proton and ferrous or ferric ions; and (2) fraction of conversion of ferrous to ferric ions induced by radiation is the “true” representation of the spatial distribution of radiation dose

Field Estimates of Parentage Reveal Sexually Antagonistic Selection on Body Size in a Population of Anolis Lizards

Sexual dimorphism evolves when selection favors different phenotypic optima between the sexes. Such sexually antagonistic selection creates intralocus sexual conflict when traits are genetically correlated between the sexes and have sex‐specific optima. Brown anoles are highly sexually dimorphic: Males are on average 30% longer than females and 150% heavier in our study population. Viability selection on body size is known to be sexually antagonistic, and directional selection favors large male size whereas stabilizing selection constrains females to remain small. We build on previous studies of viability selection by measuring sexually antagonistic selection using reproductive components of fitness over three generations in a natural population of brown anoles. We estimated the number of offspring produced by an individual that survived to sexual maturity (termed RSV), a measure of individual fitness that includes aspects of both individual reproductive success and offspring survival. We found directional selection on male body size, consistent with previous studies of viability selection. However, selection on female body size varied among years, and included periods of positive directional selection, quadratic stabilizing selection, and no selection. Selection acts differently in the sexes based on both survival and reproduction and sexual conflict appears to be a persistent force in this species

A search for the Perseus flasher and the limits on optical burst rates

We conducted a study of the error box of the possible optical burster, reported by Katz et al. (1986). This “Perseus Flasher” was subsequently identified with satellite glints by Maley (1987), a conclusion with which we fully concur. Our study, completed before Maley’s report, involved a search for highly-variable objects on archival and newly-taken plates, with a total integration time of about 260 hours, a proper-motion survey of the area, deep optical imaging with a CCD, and a single-dish radio monitoring. We found no optical or radio bursts or any other unusual objects in this area. Our upper limit to the optical flash rate from the error box of the flash photographed by Katz et al. is at least 20 times lower than the flash rate reported by those authors. Similar negative results were achieved independently by other groups; like them, we conclude that the photographed flash was most likely caused by an Earth-orbiting artifact and that most of the remaining, visually-detected flashes were spurious. From our data, we derive limits on the optical flash rates from astrophysically-interesting sources

Procjena učinka nitriranja plazmom titanovih legura za primjenu u medicini

The surface layers obtained on selected titanium alloys, used in medicine, by the nitriding under glow discharge condition were investigated. The results concern of: α- titanium alloy Grade 2 and α + β alloys Grade 5 and Grade 5 ELI nitrided in temperature below 873 K. The nitriding experiments were performed in a current glow-discharge furnace JON-600 with assisting of unconventional methods. After nitriding surface layers were characterised by surface microhardness measurements, chemical depth profiles, microhardness depth profiles and wear resistance tests.Istraživan je površinski sloj dobiven nitriranjem pri toplinskim postupcima odabranih titanovih legura, a koje se rabe u medicini. Rezultati se odnose na α-titanovu leguru 2. stupnja i α + β legure 5. stupnja i 5. stupnja ELI nitriranim na temperaturama ispod 873 K. Pokusi nitriranja su provedeni u prolaznoj toplinskoj peći JON-600 primjenom nekonvencijalnih metoda. Poslije nitriranja površinski slojevi su karakterizirani mjerenjem površinske tvrdoće, te po presjecima dubinski kemijski i mikrotvrdoće te otpor na trošenje

A Machine Learning Method to Infer Fundamental Stellar Parameters from Photometric Light Curves

A fundamental challenge for wide-field imaging surveys is obtaining follow-up spectroscopic observations: there are > $10^9$ photometrically cataloged sources, yet modern spectroscopic surveys are limited to ~few x $10^6$ targets. As we approach the Large Synoptic Survey Telescope (LSST) era, new algorithmic solutions are required to cope with the data deluge. Here we report the development of a machine-learning framework capable of inferring fundamental stellar parameters (Teff, log g, and [Fe/H]) using photometric-brightness variations and color alone. A training set is constructed from a systematic spectroscopic survey of variables with Hectospec/MMT. In sum, the training set includes ~9000 spectra, for which stellar parameters are measured using the SEGUE Stellar Parameters Pipeline (SSPP). We employed the random forest algorithm to perform a non-parametric regression that predicts Teff, log g, and [Fe/H] from photometric time-domain observations. Our final, optimized model produces a cross-validated root-mean-square error (RMSE) of 165 K, 0.39 dex, and 0.33 dex for Teff, log g, and [Fe/H], respectively. Examining the subset of sources for which the SSPP measurements are most reliable, the RMSE reduces to 125 K, 0.37 dex, and 0.27 dex, respectively, comparable to what is achievable via low-resolution spectroscopy. For variable stars this represents a ~12-20% improvement in RMSE relative to models trained with single-epoch photometric colors. As an application of our method, we estimate stellar parameters for ~54,000 known variables. We argue that this method may convert photometric time-domain surveys into pseudo-spectrographic engines, enabling the construction of extremely detailed maps of the Milky Way, its structure, and history

Antibodies to Enteroviruses in Cerebrospinal Fluid of Patients with Acute Flaccid Myelitis.

Acute flaccid myelitis (AFM) has caused motor paralysis in >560 children in the United States since 2014. The temporal association of enterovirus (EV) outbreaks with increases in AFM cases and reports of fever, respiratory, or gastrointestinal illness prior to AFM in >90% of cases suggest a role for infectious agents. Cerebrospinal fluid (CSF) from 14 AFM and 5 non-AFM patients with central nervous system (CNS) diseases in 2018 were investigated by viral-capture high-throughput sequencing (VirCapSeq-VERT system). These CSF and serum samples, as well as multiple controls, were tested for antibodies to human EVs using peptide microarrays. EV RNA was confirmed in CSF from only 1 adult AFM case and 1 non-AFM case. In contrast, antibodies to EV peptides were present in CSF of 11 of 14 AFM patients (79%), significantly higher than controls, including non-AFM patients (1/5 [20%]), children with Kawasaki disease (0/10), and adults with non-AFM CNS diseases (2/11 [18%]) (P = 0.023, 0.0001, and 0.0028, respectively). Six of 14 CSF samples (43%) and 8 of 11 sera (73%) from AFM patients were immunoreactive to an EV-D68-specific peptide, whereas the three control groups were not immunoreactive in either CSF (0/5, 0/10, and 0/11; P = 0.008, 0.0003, and 0.035, respectively) or sera (0/2, 0/8, and 0/5; P = 0.139, 0.002, and 0.009, respectively).IMPORTANCE The presence in cerebrospinal fluid of antibodies to EV peptides at higher levels than non-AFM controls supports the plausibility of a link between EV infection and AFM that warrants further investigation and has the potential to lead to strategies for diagnosis and prevention of disease

Etiology of severe childhood pneumonia in the Gambia, West Africa, determined by conventional and molecular microbiological analyses of lung and pleural aspirate samples.

Molecular analyses of lung aspirates from Gambian children with severe pneumonia detected pathogens more frequently than did culture and showed a predominance of bacteria, principally Streptococcus pneumoniae, >75% being of serotypes covered by current pneumococcal conjugate vaccines. Multiple pathogens were detected frequently, notably Haemophilus influenzae (mostly nontypeable) together with S. pneumoniae

DASCH Discovery of A Possible Nova-like Outburst in A Peculiar Symbiotic Binary

We present photometric and spectroscopic observations of a peculiar variable (designated DASCH J075731.1+201735 or J0757) discovered from our DASCH project using the digitized Harvard College Observatory archival photographic plates. It brightened by about 1.5 magnitudes in B within a year starting in 1942, and then slowly faded back to its pre-outburst brightness from 1943 to the 1950s. The mean brightness level was stable before and after the outburst, and ellipsoidal variations with a period of $P=119.18\pm0.07$ days are seen, suggesting that the star is tidally distorted. Radial-velocity measurements indicate that the orbit is nearly circular ($e=0.02\pm0.01$) with a spectroscopic period that is the same as the photometric period. The binary consists of a $1.1\pm0.3 M_\odot$ M0III star, and a $0.6\pm0.2 M_\odot$ companion, very likely a white dwarf (WD). Unlike other symbiotic binaries, there is no sign of emission lines or a stellar wind in the spectra. With an outburst timescale of ~10 years and estimated B band peak luminosity M_B~0.7, J0757 is different from any other known classic or symbiotic novae. The most probable explanation of the outburst is Hydrogen shell-burning on the WD, although an accretion-powered flare cannot be ruled out.Comment: 12 pages, 6 figures, accepted for publication in Ap

Steps Toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XV. Long-Term Optical Monitoring of NGC 5548

We present the results of three years of ground-based observations of the Seyfert 1 galaxy NGC 5548, which combined with previously reported data, yield optical continuum and broad-line H-beta light curves for a total of eight years. The light curves consist of over 800 points, with a typical spacing of a few days between observations. During this eight-year period, the nuclear continuum has varied by more than a factor of seven, and the H-beta emission line has varied by a factor of nearly six. The H-beta emission line responds to continuum variations with a time delay or lag of 10-20 days, the precise value varying somewhat from year to year. We find some indications that the lag varies with continuum flux in the sense that the lag is larger when the source is brighter.Comment: 29 pages, 6 figures. Accepted for publication in ApJ (1999 Jan 10