bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relativistic Alfvén Waves on the jet of BL Lacertae
Authors: Cohen Marshall H. , Meier David L. 
Published: March 2015

AbstractThe jet of BL Lac displays transverse patterns that propagate downstream superluminally. We suggest that they are transverse Alfvén waves propagating on the longitudinal component of a helical magnetic field. The speed of the wave adds relativistically to the speed of the beam, and the apparent speed of the pattern is greater than the beam speed. Models for the jet and the MHD waves give values for the Lorentz factor of the beam of 3–4.4 and pitch angle of the helical magnetic field of 43° - 65°. These are consistent with other estimates, if the beam and pattern speeds are allowed to differ.
Spectra and fast multi-wavelength variability of compact jets powered by internal shocks
Authors: Malzac Julien , Drappeau Samia 
Published: March 2015

AbstractThe emission of steady compact jets observed in the hard spectral state of X-ray binaries is likely to be powered by internal shocks caused by fluctuations of the outflow velocity. The dynamics of the internal shocks and the resulting spectral energy distribution (SED) of the jet is very sensitive to the shape of the Power Spectral Density (PSD) of the fluctuations of the jet Lorentz factor. It turns out that Lorentz factor fluctuations injected at the base of the jet with a flicker noise power spectrum (i.e. P(f) ∝1/f) naturally produce the canonical flat SED observed from radio to IR band in X-ray binary systems in the hard state. This model also predicts a strong, wavelength dependent, variability that resembles the observed one. In particular, strong sub-second variability is predicted in the infrared and optical bands. The assumed fluctuations of the jet Lorentz factor are likely to be triggered by the variability of the accretion flow which is best traced by the X-ray emission. In the case of GX339-4 for which high quality and simultaneous multi-wavelength data are available, we performed simulations assuming that the fluctuation of the jet Lorentz factor have the same PSD as the observed X-ray PSD. The synthetic SED calculated under this assumption provides a remarkable match to the observed radio to IR SED. In this case the model also produces strong mid-infrared spectral variability that is comparable to that reported in this source.
Lepton-hadronic processes and high-energy neutrinos in NGC 1275
Authors: Fraija N. , Marinelli A. , Luviano-Valenzuela U. , Galván-Gaméz A. , Peterson-Bórquez C. 
Published: March 2015

AbstractThe nearby active galaxy NGC 1275, has been widely detected from radio to gamma rays. Its spectral energy distribution (SED) shows a double-peak feature, which is well explained by synchrotron self-Compton (SSC) model. However, recent TeV detections might suggest that very-high-energy γ-rays (E⩾100 GeV) may not have a leptonic origin. We test a lepto-hadronic model to describe the whole SED through SSC emission and neutral pion decay resulting from pγ interactions. Also, we estimate the neutrino events expected in a km3 Cherenkov telescope.
Hadronic flares and associated neutrinos for Markarian 421
Authors: Marinelli Antonio , Patricelli Barbara , Fraija Nissim 
Published: March 2015

AbstractMarkarian 421 (Mrk 421) is one of the brightest, fastest and closest BL Lac objects known. Its very high energy (VHE) spectrum has been successfully modeled with both leptonic and hadronic models and no conclusive results have been achieved yet about the origin of its VHE emission. Here we investigate the possibility that a fraction of the VHE flares of Mrk 421 are due to hadronic processes and calculate the expected associated neutrino flux. We introduce the obtained neutrino flux in a Monte Carlo simulation to see the expectation for a km3 Cherenkov neutrino telescope.
Understanding jets from sources straddling the Fanaroff-Riley divide
Authors: Kharb Preeti , Stanley Ethan , Lister Matthew , Marshall Herman , O'Dea Chris , Baum Stefi 
Published: March 2015

AbstractResults from Chandra-HST-VLA observations of 13 hybrid sources are presented. Data from ten sources in the literature are analysed along with new data from three hybrid blazars belonging to the MOJAVE sample. Studies of such hybrid sources displaying both FRI and FRII jet characteristics could provide the key to resolving the long-standing Fanaroff-Riley dichotomy issue. A majority of the 13 hybrid sources show FRII-like total radio powers, i.e., they are “hybrid” in radio morphology but not in total radio power. VLBI observations of ten of the 13 sources show that the X-ray jet is on the same side as the one-sided VLBI jet. X-rays are therefore emitted from relativistically-boosted approaching jets. This is consistent with the X-ray emission being IC/CMB in origin in the majority of sources. It is not completely clear from our study that asymmetries in the surrounding medium can create hybrid sources. Hybrid radio morphologies could also be indicative of intrinsically asymmetric jets.
Extragalactic jets of broad absorption line (BAL) quasars
Authors: Kunert-Bajraszewska M. , Cegłowski M. , Roskowiński C. , Gawroński M. 
Published: March 2015

AbstractFast outflows of the ionized plasma, probably lunched in proximity of Supermassive Black Hole, are responsible for blue-shifted Broad Absorption Lines (BALs) in quasar spectrum. Outflows together with powerful jets produced in AGN are important feedback processes. Therefore, understanding physics behind BAL outflows might be a key to comprehend Galaxy Evolution as a whole. Discovery of the existence of radio-loud BAL quasars gave us another opportunity to study the BAL phenomenon, this time on the ground on radio emission. The radio emission is an additional tool to understand the BAL quasars, their orientation and age, by the VLBI imaging (detection of radio jets and their direction, size determination), the radio-loudness parameter distribution and variability study.
The 3C Chandra snapshot survey
Authors: Paggi Alessandro , Massaro F. , Harris D. E. 
Published: March 2015

AbstractWe present a uniform analysis of Chandra archival observations of a complete sample of ~ 200 3C sources at z < 0.5. We measured the X-ray intensity of the nuclei and of any radio hot spots and jet features with associated X-ray emission. X-ray fluxes in three energy bands, i.e., soft, medium, and hard, for all the sources analyzed are also reported. For the stronger nuclei, we also applied the standard spectral analysis, which provides the best-fit values of the X-ray spectral index and absorbing column density. In addition, a detailed analysis of bright X-ray nuclei that could be affected by pile-up has been performed. X-ray emission was detected for all the nuclei of the radio sources in our sample.
On the relation between the AGN jet and accretion disk emissions
Authors: Petrosian Vahe' , Singal Jack 
Published: March 2015

AbstractAGN jets are detected via their radio and/or gamma-ray emissions while the accretion disks are detected by their optical and UV radiation. Observations of the radio and optical luminosities show a strong correlation between the two luminosities. However, part of this correlation is due to the redshift or distances of the sources that enter in calculating the luminosities from the observed fluxes and part of it could be due to the differences in the cosmological evolution of luminosities. Thus, the determination of the intrinsic correlations between the luminosities is not straightforward. It is affected by the observational selection effects and other factors that truncate the data, sometimes in a complex manner [Antonucci (2011) and Pavildouet al. (2010)]. In this paper we describe methods that allow us to determine the evolution of the radio and optical luminosities, and determine the true intrinsic correlation between the two luminosities. We find a much weaker correlation than observed and sub-linear relations between the luminosities. This has a significant implication for the jet and accretion disk physics.
Inhomogeneous SSC model for the γ-ray production in jets of microquasars
Authors: Banasinski Piotr , Bednarek Wlodek 
Published: March 2015

AbstractWe present an inhomogeneous synchrotron self-Compton (SSC) model for active parts of jets in low mass microquasars. We compare results of our model computed, for typical parameters of microquasars, with the sensitivity of Fermi-LAT.
The story of one Seyfert: from intriguingly ultrasoft to unremarkably average
Authors: Starling R. L. C. , Done C. , Jin C. 
Published: March 2015

AbstractWe use 4 broadband SEDs spanning 7 years to study the spectral shape and long term variability of RE J2248-511: an unusual AGN discovered in the extreme-UV by the ROSAT Wide Field Camera. This implies a large ultrasoft X-ray flux, which is typical of narrow-line Seyfert 1s, yet its optical lines are clearly broader than the NLS1 definition allows. Here we show that the continuum SED for the brightest epoch dataset is consistent with the mean SED of a standard quasar, and matches well to that from an XMM–SDSS sample of AGN with M/M⊙ ~ 108 and L/LEdd ~ 0.2. All the correlated optical and soft X-ray variability can be due entirely to a major absorption event. The only remarkable aspect of this AGN is that there is no measurable intrinsic X-ray absorption column in the brightest epoch dataset. The observed FUV flux is determined by the combination of this and the fact that the source lies within a local absorption hole. RE J2248-511, which once defied classification, demonstrates that characterisation of such objects requires multi-epoch, multi-wavelength campaigns.
Study of pulse structure and radiative mechanisms associations of long GRBs atz~1
Authors: Quirola Jonathan , Vásquez Nicolás 
Published: March 2015

AbstractIn this work, we have studied five different GRBs detected bySwift: GRB 071010B (z= 0.94), GRB 080411 (z= 1.03), GRB 080413B (z= 1.10), GRB 091208B (z= 1.06) and GRB 110715A (z= 0.82); Those GRBs, with similarzand have well defined pulses. To obtain spectral lag, we fit the light curves with a model having exponential rise and decay parts. In addition, we performed spectral analysis using three spectral models for different GRBs' regions:power law,cutoff power lawandband model. Additionaly, we releated spectral parameters such as photon index and luminosity with spectral lag. The analysis suggests that there are two types of pulses associated to specific radiation mechanisms which would reveal the radiation process of long gamma-ray bursts.
The “Christmas burst” GRB 101225A revisited
Authors: Thöne C. C. , de Ugarte Postigo A. , Fryer C. L. , Kann D. A. 
Published: March 2015

AbstractLong GRBs are related to the death of massive stars and reveal themselves through synchrotron emission from highly relativistic jets. The ‘Christmas Burst’ GRB 101225A was an exceptionally long GRB with a thermal afterglow, very different from the standard GRB. Initially, no spectroscopic redshift could be obtained and SED modeling yielded z=0.33. A plausible model was a He-NS star merger where the He-star had ejected part of its envelope in the common envelope phase during inspiral. The interaction between the jet and the previously ejected shell can explains the thermal emission. We obtained deep spectroscopy of the host galaxy which leads to a correction of the redshift to z=0.847. Despite the higher redshift, our model is still valid and theoretically better justified than the alternative suggestion of a blue supergiant progenitor proposed by Levan et al. (2014) for several “ultra-long” GRBs.
Land Grabbing, Sustainable Development and Human Rights
Authors: Grant Evadné , Das Onita 
Published: March 2015

AbstractIncreasing investment in agricultural land by global corporations and investors from wealthy developed nations in poorer, less developed countries has significant human rights and environmental impacts. Proponents of such land deals argue that they provide opportunities for improvements in agricultural practices and generate employment, which will benefit economic growth in host countries. However, there is growing evidence that the phenomenon known as ‘land grabbing’ displaces poor and vulnerable populations and damages the environment, which in turn exacerbates poverty and food insecurity. This article explores the impact of land grabbing in Ethiopia and examines the human rights and sustainable development frameworks within which land grabbing takes place. The article argues that a human rights approach is fundamental to reconcile the sustainable development imperatives of economic development and environmental protection in the context of land grabbing. It advocates an integrated human rights and sustainable development approach as a holistic framework for assessing the impact of land grabbing and for the development of policy and regulatory responses.
Unravelling the hidden ancestry of American admixed populations
Authors: Montinaro Francesco , Busby George B.J. , Pascali Vincenzo L. , Myers Simon , Hellenthal Garrett , Capelli Cristian 
Published: March 2015

AbstractThe movement of people into the Americas has brought different populations into contact, and contemporary American genomes are the product of a range of complex admixture events. Here we apply a haplotype-based ancestry identification approach to a large set of genome-wide SNP data from a variety of American, European and African populations to determine the contributions of different ancestral populations to the Americas. Our results provide a fine-scale characterization of the source populations, identify a series of novel, previously unreported contributions from Africa and Europe and highlight geohistorical structure in the ancestry of American admixed populations.
Trainable hardware for dynamical computing using error backpropagation through physical media
Authors: Hermans Michiel , Burm Michaël , Van Vaerenbergh Thomas , Dambre Joni , Bienstman Peter 
Published: March 2015

AbstractNeural networks are currently implemented on digital Von Neumann machines, which do not fully leverage their intrinsic parallelism. We demonstrate how to use a novel class of reconfigurable dynamical systems for analogue information processing, mitigating this problem. Our generic hardware platform for dynamic, analogue computing consists of a reciprocal linear dynamical system with nonlinear feedback. Thanks to reciprocity, a ubiquitous property of many physical phenomena like the propagation of light and sound, the error backpropagation—a crucial step for tuning such systems towards a specific task—can happen in hardware. This can potentially speed up the optimization process significantly, offering important benefits for the scalability of neuro-inspired hardware. In this paper, we show, using one experimentally validated and one conceptual example, that such systems may provide a straightforward mechanism for constructing highly scalable, fully dynamical analogue computers.
Portable Microfluidic Integrated Plasmonic Platform for Pathogen Detection
Authors: Tokel Onur , Yildiz Umit Hakan , Inci Fatih , Durmus Naside Gozde , Ekiz Okan Oner , Turker Burak , Cetin Can , Rao Shruthi , Sridhar Kaushik , Natarajan Nalini , Shafiee Hadi , Dana Aykutlu , Demirci Utkan 
Published: March 2015

AbstractTimely detection of infectious agents is critical in early diagnosis and treatment of infectious diseases. Conventional pathogen detection methods, such as enzyme linked immunosorbent assay (ELISA), culturing or polymerase chain reaction (PCR) require long assay times and complex and expensive instruments, which are not adaptable to point-of-care (POC) needs at resource-constrained as well as primary care settings. Therefore, there is an unmet need to develop simple, rapid and accurate methods for detection of pathogens at the POC. Here, we present a portable, multiplex, inexpensive microfluidic-integrated surface plasmon resonance (SPR) platform that detects and quantifies bacteria, i.e., Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) rapidly. The platform presented reliable capture and detection of E. coli at concentrations ranging from ~105 to 3.2 × 107 CFUs/mL in phosphate buffered saline (PBS) and peritoneal dialysis (PD) fluid. The multiplexing and specificity capability of the platform was also tested with S. aureus samples. The presented platform technology could potentially be applicable to capture and detect other pathogens at the POC and primary care settings.
Configuration of ripple domains and their topological defects formed under local mechanical stress on hexagonal monolayer graphene
Authors: Park Yeonggu , Choi Jin Sik , Choi Taekjib , Lee Mi Jung , Jia Quanxi , Park Minwoo , Lee Hoonkyung , Park Bae Ho 
Published: March 2015

AbstractRipples in graphene are extensively investigated because they ensure the mechanical stability of two-dimensional graphene and affect its electronic properties. They arise from spontaneous symmetry breaking and are usually manifested in the form of domains with long-range order. It is expected that topological defects accompany a material exhibiting long-range order, whose functionality depends on characteristics of domains and topological defects. However, there remains a lack of understanding regarding ripple domains and their topological defects formed on monolayer graphene. Here we explore configuration of ripple domains and their topological defects in exfoliated monolayer graphenes on SiO2/Si substrates using transverse shear microscope. We observe three-color domains with three different ripple directions, which meet at a core. Furthermore, the closed domain is surrounded by an even number of cores connected together by domain boundaries, similar to topological vortex and anti-vortex pairs. In addition, we have found that axisymmetric three-color domains can be induced around nanoparticles underneath the graphene. This fascinating configuration of ripple domains may result from the intrinsic hexagonal symmetry of two-dimensional graphene, which is supported by theoretical simulation using molecular dynamics. Our findings are expected to play a key role in understanding of ripple physics in graphene and other two-dimensional materials.
MicroRNA-26a prevents endothelial cell apoptosis by directly targeting TRPC6 in the setting of atherosclerosis
Authors: Zhang Yong , Qin Wei , Zhang Longyin , Wu Xianxian , Du Ning , Hu Yingying , Li Xiaoguang , Shen Nannan , Xiao Dan , Zhang Haiying , Li Zhange , Zhang Yue , Yang Huan , Gao Feng , Du Zhimin , Xu Chaoqian , Yang Baofeng 
Published: March 2015

AbstractAtherosclerosis, a chronic inflammatory disease, is the major cause of life-threatening complications such as myocardial infarction and stroke. Endothelial apoptosis plays a vital role in the initiation and progression of atherosclerotic lesions. Although a subset of microRNAs (miRs) have been identified as critical regulators of atherosclerosis, studies on their participation in endothelial apoptosis in atherosclerosis have been limited. In our study, we found that miR-26a expression was substantially reduced in the aortic intima of ApoE−/− mice fed with a high-fat diet (HFD). Treatment of human aortic endothelial cells (HAECs) with oxidized low-density lipoprotein (ox-LDL) suppressed miR-26a expression. Forced expression of miR-26a inhibited endothelial apoptosis as evidenced by MTT assay and TUNEL staining results. Further analysis identified TRPC6 as a target of miR-26a and TRPC6 overexpression abolished the anti-apoptotic effect of miR-26a. Moreover, the cytosolic calcium and the mitochondrial apoptotic pathway were found to mediate the beneficial effects of miR-26a on endothelial apoptosis. Taken together, our study reveals a novel role of miR-26a in endothelial apoptosis and indicates a therapeutic potential of miR-26a for atherosclerosis associated with apoptotic cell death.
Entrainment of heterogeneous glycolytic oscillations in single cells
Authors: Gustavsson Anna-Karin , Adiels Caroline B. , Mehlig Bernhard , Goksör Mattias 
Published: March 2015

AbstractCell signaling, gene expression and metabolism are affected by cell-cell heterogeneity and random changes in the environment. The effects of such fluctuations on cell signaling and gene expression have recently been studied intensively using single-cell experiments. In metabolism heterogeneity may be particularly important because it may affect synchronisation of metabolic oscillations, an important example of cell-cell communication. This synchronisation is notoriously difficult to describe theoretically as the example of glycolytic oscillations shows: neither is the mechanism of glycolytic synchronisation understood nor the role of cell-cell heterogeneity. To pin down the mechanism and to assess its robustness and universality we have experimentally investigated the entrainment of glycolytic oscillations in individual yeast cells by periodic external perturbations. We find that oscillatory cells synchronise through phase shifts and that the mechanism is insensitive to cell heterogeneity (robustness) and similar for different types of external perturbations (universality).
Multiscale visualization of the structural and characteristic changes of sewage sludge biochar oriented towards potential agronomic and environmental implication
Authors: Zhang Jining , Lü Fan , Zhang Hua , Shao Liming , Chen Dezhen , He Pinjing 
Published: March 2015

AbstractSewage sludge biochars were obtained at different pyrolysis temperatures from 300°C to 900°C and their macro- and microscale properties were analyzed. The biochar's plant-available nutrients and humus-like substances in the water-extractable phase and fixed nutrients in the solid fraction were evaluated for their potential agronomic implications. FT-IR, Raman, XRD, XPS and SEM techniques were used to investigate the chemical structure, functional groups and microcrystal structure on the surface of the biochar. The results revealed minor chemical changes and dramatic mass loss in the biochar obtained at 300–500°C, whereas significant chemical changes in the biochar were obtained at 600–900°C. The concentrations of plant-available nutrients as well as fulvic- and humic-acid-like materials decreased in the biochar samples obtained at higher temperatures. These results implied that the biochar samples pyrolyzed at 300–500°C could be a direct nutrient source and used to neutralize alkaline soil. The surface area and porosity of the biochar samples increased with temperature, which increased their adsorption capacity. Rearrangement occurred at higher temperature 600–900°C, resulting in the biochar becoming increasingly polyaromatic and its graphite-like carbon becoming organized.
Probing the intrinsic failure mechanism of fluorinated amorphous carbon film based on the first-principles calculations
Authors: Zhang Ren-hui , Wang Li-ping , Lu Zhi-bin 
Published: March 2015

AbstractFluorinated amorphous carbon films exhibit superlow friction under vacuum, but are prone to catastrophic failure. Thus far, the intrinsic failure mechanism remains unclear. A prevailing view is that the failure of amorphous carbon film results from the plastic deformation of substrates or strong adhesion between two contacted surfaces. In this paper, using first-principles and molecular dynamics methodology, combining with compressive stress-strain relation, we firstly demonstrate that the plastic deformation induces graphitization resulting in strong adhesion between two contacted surfaces under vacuum, which directly corresponds to the cause of the failure of the films. In addition, sliding contact experiments are conducted to study tribological properties of iron and fluorinated amorphous carbon surfaces under vacuum. The results show that the failure of the film is directly attributed to strong adhesion resulting from high degree of graphitization of the film, which are consistent with the calculated results.