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Blazar OJ287 exhibits large thermal flares at least twice every 12 years. The times of these flares have been predicted successfully using the model of a quasi-Keplerian eccentric black hole binary where the secondary impacts the accretion disk of the primary, creating the thermal flares. New measurements of the historical light curve have been combined with the observations of the 2015 November/December flare to identify the impact record since year 1886, and to constrain the orbit of the binary. The orbital solution shows that the binary period, now 12.062 years, is decreasing at the rate of 36 days per century. This corresponds to an energy loss to gravitational waves that is 6.5 ± 4 % less than the rate predicted by the standard quadrupolar gravitational wave (GW) emission. We show that the difference is due to higher order gravitational radiation reaction terms that include the dominant order tail contributions.
The blazar QSO B0218+357 is the first gravitationally lensed blazar detected in the very high energy (VHE, E > 100 GeV) gamma-ray spectral range (Ahnen et al. 2016). It is gravitationally lensed by the intervening galaxy B0218+357G (zl = 0.68466 ± 0.00004, Carilli et al. 1993), which splits the blazar emission into two components, spatially indistinguishable by gamma-ray instruments, but separated by a 10-12 days delay. In July 2014 a flare from QSO B0218+357 was observed by the Fermi-LAT (Large Area Telescope, Atwood et al. 2009, Ackermann et al. 2012), and followed-up by the MAGIC (Major Atmospheric Gamma Imaging Cherenkov) telescopes, a stereoscopic system of two 17m Imaging Atmospheric Cherenkov Telescopes located on La Palma, Canary Islands (Aleksić et al. 2016a, 2016b), during the expected time of arrival of the delayed component of the emission. MAGIC could not observe the leading image due to the Full Moon. The MAGIC and Fermi-LAT observations were accompanied by optical data from KVA telescope at La Palma, and X-ray observations by Swift-XRT (Fig. 1 left). Variability in gamma-rays was of the order of one day, while no variability correlated with gamma-rays was observed at lower energies. The flux ratio of the leading to trailing image in HE gamma-rays was larger than in the flare of QSO B0218+357 observed by Fermi-LAT in 2012 (Cheung et al. 2014). Changes in the observed flux ratio can be caused by gravitational microlensing on individual stars in the host galaxy (Neronov et al. 2015), or by other compact objects like for ex. clumps in giant molecular clouds (Sitarek & Bednarek 2016).
Blazar OJ 287 is one of the best observed extragalactic objects. It's historical light curve goes back to 1890′s. Based on the historical behaviour Sillanpää et al. (1988) showed that OJ 287 displays large periodic outbursts, with a period of 11.7 years. We have monitored OJ 287 intensively for two years, during the OJ-94 project. This project was created for monitoring OJ 287 during its predicted new outburst in 1994. In the data archive we have over 7000 observations on OJ 287, in the radio, infrared and optical bands. This data archive contains the best ever obtained light curves for any extragalactic object. The optical light curve shows continuous variability down to time scales of tens of minutes. The variability observed in OJ 287 can be broken down to (at least) four different categories:
Hippocampal volume reductions in major depression have been frequently reported. However, evidence for functional abnormalities in the same region in depression has been less clear. We investigated hippocampal function in depression using functional magnetic resonance imaging (fMRI) and neuropsychological tasks tapping spatial memory function, with complementing measures of hippocampal volume and resting blood flow to aid interpretation.
A total of 20 patients with major depressive disorder (MDD) and a matched group of 20 healthy individuals participated. Participants underwent multimodal magnetic resonance imaging (MRI): fMRI during a spatial memory task, and structural MRI and resting blood flow measurements of the hippocampal region using arterial spin labelling. An offline battery of neuropsychological tests, including several measures of spatial memory, was also completed.
The fMRI analysis showed significant group differences in bilateral anterior regions of the hippocampus. While control participants showed task-dependent differences in blood oxygen level-dependent (BOLD) signal, depressed patients did not. No group differences were detected with regard to hippocampal volume or resting blood flow. Patients showed reduced performance in several offline neuropsychological measures. All group differences were independent of differences in hippocampal volume and hippocampal blood flow.
Functional abnormalities of the hippocampus can be observed in patients with MDD even when the volume and resting perfusion in the same region appear normal. This suggests that changes in hippocampal function can be observed independently of structural abnormalities of the hippocampus in depression.
1. Radio meteor rates for a calculated mass range 10−6 gm to 10−4 gm have been recorded semi-continuously at Havana, Ill., since July 1965. Automatic equipment samples the rate at four different levels of sensitivity each half hour. A flux vs. mass power law has been derived from these data for each of a number of different weeks of observation. Between September 1965 and December 1966 the mean cumulative influx I of meteors/m2/sec/2π ster can best be described by the equation:
where m is the lower mass limit in grams.
2. A micrometeoroid detection system, which hopefully was to have measured particle velocities and directions of arrival for masses greater than 10−12 gm, has been flown on the OGO-II satellite. A comprehensive in-flight calibration system has confirmed the correct operation of the experiment for more than one year in space. 700 hours of data have been analyzed and no micrometeoroid events have been observed. This excludes several hundred spurious events from the microphone sensors. The effective detection area of the instrument is 0·8 cm2 ster. Thus, to a probability of 0·86, the average flux of particles of mass greater than 10−12 gm must be less than 6 × 10−2 particles/m2/sec/2π ster.
Attentional impairment is a core cognitive feature of major depressive disorder (MDD) and bipolar disorder (BD). However, little is known of the characteristics of response time (RT) distributions from attentional tasks. This is crucial to furthering our understanding of the profile and extent of cognitive intra-individual variability (IIV) in mood disorders.
A computerized sustained attention task was administered to 138 healthy controls and 158 patients with a mood disorder: 86 euthymic BD, 33 depressed BD and 39 medication-free MDD patients. Measures of IIV, including individual standard deviation (iSD) and coefficient of variation (CoV), were derived for each participant. Ex-Gaussian (and Vincentile) analyses were used to characterize the RT distributions into three components: mu and sigma (mean and standard deviation of the Gaussian portion of the distribution) and tau (the ‘slow tail’ of the distribution).
Compared with healthy controls, iSD was increased significantly in all patient samples. Due to minimal changes in average RT, CoV was only increased significantly in BD depressed patients. Ex-Gaussian modelling indicated a significant increase in tau in euthymic BD [Cohen's d = 0.39, 95% confidence interval (CI) 0.09–0.69, p = 0.011], and both sigma (d = 0.57, 95% CI 0.07–1.05, p = 0.025) and tau (d = 1.14, 95% CI 0.60–1.64, p < 0.0001) in depressed BD. The mu parameter did not differ from controls.
Increased cognitive variability may be a core feature of mood disorders. This is the first demonstration of differences in attentional RT distribution parameters between MDD and BD, and BD depression and euthymia. These data highlight the utility of applying measures of IIV to characterize neurocognitive variability and the great potential for future application.
Eating out has been linked to the current obesity epidemic, but the evaluation of the extent to which out of home (OH) dietary intakes are different from those at home (AH) is limited. Data collected among 8849 men and 14 277 women aged 35–64 years from the general population of eleven European countries through 24-h dietary recalls or food diaries were analysed to: (1) compare food consumption OH to those AH; (2) describe the characteristics of substantial OH eaters, defined as those who consumed 25 % or more of their total daily energy intake at OH locations. Logistic regression models were fit to identify personal characteristics associated with eating out. In both sexes, beverages, sugar, desserts, sweet and savoury bakery products were consumed more OH than AH. In some countries, men reported higher intakes of fish OH than AH. Overall, substantial OH eating was more common among men, the younger and the more educated participants, but was weakly associated with total energy intake. The substantial OH eaters reported similar dietary intakes OH and AH. Individuals who were not identified as substantial OH eaters reported consuming proportionally higher quantities of sweet and savoury bakery products, soft drinks, juices and other non-alcoholic beverages OH than AH. The OH intakes were different from the AH ones, only among individuals who reported a relatively small contribution of OH eating to their daily intakes and this may partly explain the inconsistent findings relating eating out to the current obesity epidemic.
The Åland Islands were recently ranked as Finland’s healthiest region with lower prevalence of several non-communicable diseases compared with the national mean. We have compared birth characteristics of 1697 individuals born on the Åland Islands between 1937 and 1944 with contemporaneous data from the Helsinki Birth Cohort Study (HBCS; n=11,808). This is a first step towards a potential future analysis of Ålandic health from a life-course perspective. Mean birth weight and length were calculated for both cohorts. Birth weight was entered into a multiple linear regression model with sex, maternal age, marital status and birth year as predictors. Mean birth weight in the Åland cohort was 3499 g, 87 g (95% CI 62; 111) higher compared with the HBCS. Sex and maternal marital status were the strongest predictors of birth weight. More detailed studies are needed to explore the potential effects of this difference in average birth weight between cohorts.
A review of the literature on forest soil change in North America, Central Europe. Sweden, U.K., and Australia reveals that changes are occurring in both polluted and unpolluted sites at a greater rate than previously suspected. Acid deposition has played a major role in recent acidification in some areas of Europe and, to a more limited extent, in Sweden and eastern North America. However, rapid rates of soil acidification are occurring in western North America and Australia due to internal processes such as tree uptake and nitrification associated with excessive nitrogen fixation. The presence of extremely acid soils is not necessarily an indicator of significant acidic deposition, as evidenced by their presence in unpolluted, even pristine forests of the north-western U.S.A. and Alaska. Numerous studies in Sweden, Australia, and North America show the important effects of tree uptake and harvesting upon soil acidification in managed forests. Furthermore, arguments can be presented that harvesting takes a greater toll upon the pools of potentially limiting cations than leaching.
The rate at which soils are changing in some instances calls for a re-evaluation of the budget analyses used to predict soil change. Specifically, inter-horizon changes due to uptake and recycling by vegetation, the interactions of such changes with naturally- and anthropogenically-produced acids, and the effects of aluminium uptake and recycling need further evaluation and study.
The main purpose of Commission 14 is to foster interactions between the astronomical community and those conducting research to provide data vital to reducing and analysing astronomical observations and conducting theoretical investigations. One way that the Commission accomplishes this goal is through triennial compilations on recent relevant research in astronomy, atomic, molecular and solid state physics, and related fields of chemical analysis. The most recent compilations appear in the accompanying set of Commission 14 WG Triennial Reports, which were produced by members of the Working Groups and the Organizing Committee of Commission 14.
Stainless steels are among the most important engineering materials, finding their principal scope in industry, specifically in cutlery, food production, storage, architecture, medical equipment, etc. Austenitic stainless steels form the largest sub-category of stainless steels having as the main building blocks the paramagnetic substitutional disordered Fe-Cr-Ni-based alloys. Because of that, austenitic steels represent the primary choice for non-magnetic engineering materials. The presence of the chemical and magnetic disorder hindered any previous attempt to calculate the fundamental electronic, structural and mechanical properties of austenitic stainless steels from first-principles theories. Our ability to reach an ab initio atomistic level approach in this exciting field has become possible by the Exact Muffin-Tin Orbitals (EMTO) method. This method, in combination with the coherent potential approximation, has proved an accurate tool in the description of the concentrated random alloys. Using the EMTO method, we presented an insight to the electronic and magnetic structure, and micromechanical properties of austenitic stainless steel alloys. In the present contribution, we will discuss the role of magnetism on the stacking fault energies and elastic properties of paramagnetic Fe-based alloys.
Immobilization of oligonucleotide-functionalized magnetic nanobeads by hybridization in DNA-coils formed by rolling circle amplification has been investigated using transmission electron microscopy (TEM) and atomic force microscopy (AFM). The TEM results supported earlier made observations that small beads with low oligonucleotide surface coverage preferably immobilize in the interior of the DNA-coils and do not tend to link several DNA-coils together whereas large beads with high surface coverage to a larger extent connect several DNA-coils together to clusters of several DNA-coils with beads. AFM provided direct visualization of the DNA-coils as thread-like objects. DNA-coils with immobilized beads appeared as a collection of beads with thread-like features in their near vicinity.
The possible role of neutral PAHs as catalysts for H2 formation in the
interstellar medium is investigated by a combined experimental and density function theory
study of the superhydrogenation of coronene (C24H12). The
calculations suggest efficient hydrogenation of both edge and centre sites, along with
competing abstraction reactions to form H2 in a series of catalytic cycles.
Scanning tunneling microscopy and thermal desorption measurements have been used to
provide direct evidence of the formation of superhydrogenated coronene as a result of
exposure to D atoms. Lower limit estimates for the cross-sections of
1.8 × 10-17, 5.5 × 10-18 and 1.1 × 10-18 cm2
for the formation of singly, doubly and triply hydrogenated coronene are derived. The
results suggest that superhydrogenated PAHs may play an important role in H2
formation in the ISM.
Recent progress in the growth of high quality 6H-SiC single crystals has led to an ideal substrate material for GaN epitaxial films. Nearly matching lattice constants of wurzite GaN to 6H-SiC in the hexagonal plane can reduce strain effects at the interface. We employed the sublimation sandwich method to grow single crystal layers at reasonable growth rates with free carrier concentrations of 2×1017 cm-3. Very sharp x-ray diffraction peaks of the GaN (0002) plane are obtained indicating the high quality of this system (Δ(2θ) < 0.1 degrees). These findings are directly reflected in the optical properties. The photoluminescence is dominated by a single sharp exciton line, impurity related donor acceptor transitions are seen with very weak intensities. However, at lower energies the internal luminescence transitions of the 3d transition metal ions Fe and V are observable. The incorporation of Fe is confirmed by electron paramagnetic resonance.
We study deep defects in AIN crystals in the near infrared by photoluminescence and compare the observed emissions with those in GaN. By below bandgap excitation with an Ar ion laser three no-phonon lines at 1.043 eV, 0.943 eV, and 0.797 eV were detected, which are caused by different residual transition metal contaminants. The weak emission at 1.043 eV and the intensive emission at 0.797 eV show A1N related phonon sidebands, whereas the emission at 0.943 eV has practically no phonon sideband. No hot lines could be detected for the emissions at 0.943 and 0.797 eV in temperature dependent measurements. We discuss possible identifications of the luminescence centers and the similarity between GaN and AIN in view of transition metals.
Schottky diodes on Silicon Carbide (SiC) are of interest for many applications because of the relatively simple fabrication process. In this work we have fabricated Schottky diodes by evaporation of Ti on 6H-SiC and measured their electrical and optical properties. Most of the diodes show good rectifying behaviour with low reverse current and an ideality factor below 1.20. The photoresponse of the diodes has been measured in the range 200 – 400 nm. The peak sensitivity was found to be at 270 nm.
In this investigation, surfactant-mediated growth of SiGe/Si single quantum-well structures is studied by photoluminescence and secondary ion mass spectrometry. The samples were grown by molecular-beam epitaxy and Sb was used as a surfactant. The photon energy of the SiGe-related near-band-edge photoluminescence was used to probe the action of Sb as a surfactant to promote two-dimensional growth and to reduce segregation of Ge during growth. First, the "growth-temperature window" at which Sb acts preferentially as a surfactant was determined. Then, at this optimized temperature of 700°C, the influence of different Sb coverages was investigated and it was found that 0.5 monolayer was a sufficient coverage to obtain full surfactant action. Ge concentration depth profiles obtained by secondary ion mass spectrometry confirmed the effect of surfactant-mediated growth and, in addition, the unintentional incorporation of the Sb surfactant during growth was determined quantitatively. In a final experiment the effect of deposition of Sb on either the lower or the upper heterointerface is addressed.
Sample temperature dependence and excitation power dependence of the photoluminescence intensity were investigated with respect to growth temperature for SiGe single quantum wells grown pseudomorphically to (100)-oriented Si by molecular beam epitaxy. The determined excitation power exponents and thermal activation energies show unambiguously that defect incorporation is effectively reduced at higher growth temperatures. However, at higher growth temperatures the SiGe-related spectral distribution is found to be shifted to higher photon energy which is attributed to intermixing of Ge and Si at the heterointerfaces, governed by diffusion as well as Ge surface segregation during growth. The diffusion process is studied separately by photoluminescence measurements upon thermal annealing at different temperatures and a diffusion model is presented where the diffusion process is assumed to be composed of two different mechanisms, interdiffusion, i.e. lattice-site-exchange diffusion, and point-defectinduced diffusion. The determined activation energies for the two diffusion mechanisms are in good agreement with previous results which confirm that the model gives a realistic picture of the diffusion process.
Low-temperature photoluminescence measurements were performed in order to probe the optical quality of SiGe/Si quantum-well wire structures fabricated by electron-beam lithography and subsequent reactive ion etching, having the patterned polymethylmethacrylate resist as an etch mask. In addition, one set of quantum-well wire structures was post-treated by means of annealing in a hydrogen environment. Our results show that even for the smallest wires of about 100nm in width, the wires exhibit phonon-resolved photoluminescence spectra, similar to that from the molecular beam eptitaxially grown SiGe single quantum well which was used as starting material for the patterning process. After the patterning process a new sharp peak appears in the photoluminescence spectra at 0.97eV in photon energy. Our investigation suggests that this feature is introduced by damage during the patterning process and most probably identical to the G-line, which previously was identified as originating from the dicarbon centre (substitutional carbon-interstitial carbon) in Si. This centre is known to be a very common endproduct of irradiating Si near room temperature which is the case at our patterning process.