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1
Wilks, Linda. "Communicating an arts foundation’s values: sights, sounds and social media." Arts and the Market 6, no. 2 (October 3, 2016): 206–23. http://dx.doi.org/10.1108/aam-08-2015-0014.
Повний текст джерелаАнотація:
Purpose The purpose of this paper is to test and refine the long-established signal transmission model of the communication process by examining the ways in which a newly formed nonprofit arts foundation communicated its professed values to its stakeholders. Design/methodology/approach The study uses a mixed method case study approach. Interviews with key informants and observations of the foundation’s webpages enabled the identification of the professed values of the arts foundation. Next, a questionnaire survey established whether these values had been successfully decoded by stakeholders and identified the channels via which the values-related signals had been received. Findings The transmission model was found to be relevant as a model. However, to improve its fit within a nonprofit arts context, a modification to the model is suggested which highlights the importance of multi-sensory channels, the importance of context and the increasingly important role of the stakeholder. Research limitations/implications This study is a small-scale case study, although its mixed methods help to ensure validity. Practical implications The findings will help nonprofit arts organisations to decide how to best communicate their values to their stakeholders. Social implications The improved communications model will contribute to the enabling of organisations to uphold and transmit their values and thus improve society’s overall quality of life. Originality/value Literature which provides in-depth examination of the communication of values within a nonprofit arts context via a range of channels, including traditional, online and multi-sensory, is sparse. The opportunity to study a newly formed nonprofit arts organisation is also rare. The results of this study provide valuable evidence that even in today’s social media-rich world, people, sounds, sights and material objects in physical space still have a vital role to play in the communication of values.
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Elsheshtawy, Yasser. "Beyond Artwashing: An Overview of Museums and Cultural Districts in Arabia." Built Environment 46, no. 2 (May 14, 2020): 88–101. http://dx.doi.org/10.2148/benv.46.2.248.
Повний текст джерелаАнотація:
In recent years many cities have a empted to integrate cultural developments within their overall planning strategy. Within the wider Arab region, the Gulf Arab states have been at the forefront of such developments, which they see as a way of diversifying their economies. Through such initiatives the region is also se ing its sights on claiming the mantle as the Arab world's cultural leader. Large-scale institutions and the smaller spaces of art districts are seen as a way to modernize the Gulf states' local populations and integrate them within a wider cultural context. Yet such approaches have risks such as gentrification and potential marginalization of a larger part of the population who may see themselves excluded from cultural spaces. This paper aims to unpack these issues by situating the development of spectacular museums ('big spaces') and art districts ('small spaces') in the Gulf region within a wider global context. It is structured in three parts. First, a theoretical exploration looks at the changing nature of museums in the twenty-first century, and the proliferation of art districts as a way of a racting creatives and spurring economic and urban development. Second, the paper reviews the global spread of creative districts, distinguishing between planned and organic developments. The third and main part shifts the discussion to the Gulf Arab states, where the proliferation of museums and art districts is presented in more detail, se ing their development within a wider context. The conclusion outlines a series of directives that could lead the Gulf to the forefront of an urban renaissance in the region. Yet for that to happen there needs to be a substantial shift in their overall planning paradigm, including accounting for 'artwashing'.
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Dara, H. C., C. E. Alissandrakis, and S. Koutchmy. "Small Scale Motions Over Concentrated Magnetic Field Regions of the Quiet Sun." Symposium - International Astronomical Union 138 (1990): 153–56. http://dx.doi.org/10.1017/s0074180900044090.
Повний текст джерелаАнотація:
Using a time sequence of filtergrams in the magnetically sensitive λ6103A CaI line (with circular polarization measurements), obtained with the SPO Vacuum Tower Telescope and the universal filter we mapped the line of sight velocity and the longitudinal magnetic field in three quiet solar regions. After elimination of the effect of the 5-minute photospheric oscillations we found in two regions of concentrated magnetic field no association with the line of sight velocity, while the third region was associated with small (<300 m/s) downflows.
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Jentoft, Svein. "Life above water: small-scale fisheries as a human experience." Maritime Studies 19, no. 4 (November 9, 2020): 389–97. http://dx.doi.org/10.1007/s40152-020-00203-0.
Повний текст джерелаАнотація:
Abstract“Life under water” is UN Sustainable Development Goal No. 14, under which small-scale fisheries fall. Yet, most of what is happening in small-scale fisheries, and certainly those things that are interesting to social scientists, are taking place above water—on the water and by the water. Small-scale fishers make their living off the fish that swims in the ocean, but they do so with the lives they construct for themselves and with others on land. Therefore, small-scale fishers depend on their communities as much as they depend on the fish, their boats, and gear. It is as members of communities that fishers acquire the knowledge, energy, motivation, and meaning they need to carry out their work. For fisheries social scientists, the community is a unit of analysis. However, fisheries communities are not isolated from what is happening outside them. Consequently, social scientists focus on forces at higher scales. Still, I argue that it is important that they do not lose sight of local communities, because if they do they also lose the sight of small-scale fisheries.
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Martin, Sara F. "Small-Scale Magnetic Features Observed in the Photosphere." Symposium - International Astronomical Union 138 (1990): 129–46. http://dx.doi.org/10.1017/s0074180900044077.
Повний текст джерелаАнотація:
Small-scale solar features identifiable on the quiet sun in magnetograms of the line-of-sight component consist of network, intranetwork, ephemeral region magnetic fields, and the elementary bipoles of ephemeral active regions. Network fields are frequently observed to split into smaller fragments and equally often, small fragments are observed to merge or coalesce into larger clumps; this splitting and merging is generally confined to the borders and vertices of the convection cells known as supergranules. Intranetwork magnetic fields originate near the centers of the supergranule convection cells and appear to increase in magnetic flux as they flow in approximate radial patterns towards the boundaries of the cells.
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Meyer, David M., та J. C. Blades. "Small-Scale Interstellar Medium Structure: The Remarkable Sight Line toward μ Crucis". Astrophysical Journal 464, № 2 (20 червня 1996): L179—L182. http://dx.doi.org/10.1086/310111.
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Smith, K. T., M. A. Cordiner, and P. J. Sarre. "Diffuse Interstellar Bands as Probes of Small-Scale Interstellar Structure." Proceedings of the International Astronomical Union 9, S297 (May 2013): 141–43. http://dx.doi.org/10.1017/s1743921313015779.
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AbstractWe present observations which probe the small-scale structure of the interstellar medium using diffuse interstellar bands (DIBs). Towards HD 168075/6 in the Eagle Nebula, significant differences in DIB absorption are found between the two lines of sight, which are separated by 0.25 pc, and λ 5797 exhibits a velocity shift. Similar data are presented for four stars in the μ Sgr system. We also present a search for variations in DIB absorption towards κ Vel, where the atomic lines are known to vary on scales of ~ 10 AU. Observations separated by ~ 9 yr yielded no evidence for changes in DIB absorption strength over this scale, but do reveal an unusual DIB spectrum.
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Warwick, R., I. Hutchinson, R. Willingale, K. Kuntz, and S. Snowden. "Tracing Small-Scale Fluctuations in the Soft X-ray Background." International Astronomical Union Colloquium 166 (1997): 321–24. http://dx.doi.org/10.1017/s0252921100071189.
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AbstractAn overlapping set of ROSAT PSPC observations made in a region of very low Galactic foreground column density, has been used to investigate variations in the soft X-ray background on angular scales of 15′ – 5°. In the ¼ keV band there is a clear inverse correlation of the count-rate with the line-of-sight hydrogen column density. However, after correcting for this absorption effect, strong residual fluctuations remain in the data, with an amplitude which is significantly larger than that due to the counting statistics or the confusion of unresolved discrete sources. In contrast a similar analysis for the ¾ and 1.5 keV ROSAT bands shows no evidence for an excess signal. The most likely origin of the ¼ keV fluctuations would seem to be in a patchy distribution of ~ 106 K gas in the Galactic halo.
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Kaithakkal, A. J., and S. K. Solanki. "Cancelation of small-scale magnetic features." Astronomy & Astrophysics 622 (February 2019): A200. http://dx.doi.org/10.1051/0004-6361/201833770.
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Aims. We investigate small-scale flux cancelations in a young active region observed with the high-resolution imaging magnetograph IMaX on the SUNRISE balloon-borne solar observatory. Methods. The observed Stokes profiles of the photospheric Fe I 5250.2 Å line were inverted using the SPINOR code to obtain the atmospheric parameters, including magnetic field vector and the line-of-sight velocity. We then identified 11 opposite-polarity canceling pairs using an automatic detection code, studied their evolution in detail, and derived their statistical properties. We classified the cancelations into two groups. Class I events are those for which cancelation happens between a pre-existing large magnetic feature of one polarity and a smaller feature of the other polarity that emerged or appeared nearby. For Class II events cancelations occur between two pre-existing, previously unconnected features that converge. Results. All studied events have an apparent cancelation time of less than ten minutes and display a significant transient linear polarization signal along the polarity inversion line. The cancelation events are characterized by a flux decay rate of about 1015 Mx s−1. For Class I events, the Doppler velocity of the disappearing patch gradually switches from blueshift during the initial phase of cancelation to redshift toward the end of the cancelation. For class II events, the Doppler velocity is consistently redshifted. Horizontal convergence speeds of Class II pairs fall between 0.3 and 1.22 km s−1. The elements often do not converge directly toward each other, so that the proper motion speeds of the individual elements is higher, in the range of 1–2.7 km s−1. Conclusions. We propose that these cancelation events result from either field-line submergence (Class I), or reconnection followed by submergence (Class II and/or Class I). Ohmic dissipation of magnetic energy could also play a role for both classes. The dynamics and evolution of these events are influenced by neighboring granular motions. We also propose that, at least for the Class II events, the granular motions could possibly be driving magnetic reconnection, rather than the supergranular motions proposed for the larger cancelation events studied earlier. Specific flux cancelation rates of the Class II events seem to indicate that they belong to somewhat different category of cancelations when compared with those studied in SOT/Hinode and MDI/SOHO data.
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Reig, J., M. T. Martínez-Inglés, L. Rubio, V. M. Rodrigo-Peñarrocha, and J. M. Molina-García-Pardo. "Fading Evaluation in the 60 GHz Band in Line-of-Sight Conditions." International Journal of Antennas and Propagation 2014 (2014): 1–12. http://dx.doi.org/10.1155/2014/984102.
Повний текст джерелаАнотація:
An exhaustive analysis of the small-scale fading amplitude in the 60 GHz band is addressed for line-of-sight conditions (LOS). From a measurement campaign carried out in a laboratory, we have estimated the distribution of the small-scale fading amplitude over a bandwidth of 9 GHz. From the measured data, we have estimated the parameters of the Rayleigh, Rice, Nakagami-m, Weibull, andα-μdistributions for the small-scale amplitudes. The test of Kolmogorov-Smirnov (K-S) for each frequency bin is used to evaluate the performance of such statistical distributions. Moreover, the distributions of the main estimated parameters for such distributions are calculated and approximated for lognormal statistics in some cases. The matching of the above distributions to the experimental distribution has also been analyzed for the lower tail of the cumulative distribution function (CDF). These parameters offer information about the narrowband channel behavior that is useful for a better knowledge of the propagation characteristics at 60 GHz.
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Pingel, Thomas J., and Victor R. Schinazi. "The Relationship Between Scale and Strategy in Search-Based Wayfinding." Cartographic Perspectives, no. 77 (November 3, 2014): 33–45. http://dx.doi.org/10.14714/cp77.1232.
Повний текст джерелаАнотація:
We present the results of a study that investigated the interaction of strategy and scale on search quality and efficiency for vista-scale spaces. The experiment was designed such that sighted participants were required to locate “invisible” objects whose locations were marked only with audio cues, thus enabling sight to be used for search coordination, but not for object detection. Participants were assigned to one of three conditions: a small indoor space (~20 m2), a medium-sized outdoor space (~250 m2), or a large outdoor space (~1000 m2), and the entire search for each participant was recorded either by a laser tracking system (indoor) or by GPS (outdoor). Results revealed a clear relationship between the size of space and search strategy. Individuals were likely to use ad-hoc methods in smaller spaces, but they were much more likely to search large spaces in a systematic fashion. In the smallest space, 21.5% of individuals used a systematic gridline search, but the rate increased to 56.2% for the medium-sized space, and 66.7% for the large-sized space. Similarly, individuals were much more likely to revisit previously found locations in small spaces, but avoided doing so in large spaces, instead devoting proportionally more time to search. Our results suggest that even within vista-scale spaces, perceived transport costs increase at a decreasing rate with distance, resulting in a distinct shift in exploration strategy type.
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Thiel, V., A. Belloche, K. M. Menten, A. Giannetti, H. Wiesemeyer, B. Winkel, P. Gratier, H. S. P. Müller, D. Colombo, and R. T. Garrod. "Small-scale physical and chemical structure of diffuse and translucent molecular clouds along the line of sight to Sgr B2." Astronomy & Astrophysics 623 (March 2019): A68. http://dx.doi.org/10.1051/0004-6361/201834467.
Повний текст джерелаАнотація:
Context. The diffuse and translucent molecular clouds traced in absorption along the line of sight to strong background sources have so far been investigated mainly in the spectral domain because of limited angular resolution or small sizes of the background sources. Aims. We aim to resolve and investigate the spatial structure of molecular clouds traced by several molecules detected in absorption along the line of sight to Sgr B2(N). Methods. We have used spectral line data from the EMoCA survey performed with the Atacama Large Millimeter/submillimeter Array (ALMA), taking advantage of its high sensitivity and angular resolution. The velocity structure across the field of view is investigated by automatically fitting synthetic spectra to the detected absorption features, which allows us to decompose them into individual clouds located in the Galactic centre (GC) region and in spiral arms along the line of sight. We compute opacity maps for all detected molecules. We investigated the spatial and kinematical structure of the individual clouds with statistical methods and perform a principal component analysis to search for correlations between the detected molecules. To investigate the nature of the molecular clouds along the line of sight to Sgr B2, we also used archival Mopra data. Results. We identify, on the basis of c-C3H2, 15 main velocity components along the line of sight to Sgr B2(N) and several components associated with the envelope of Sgr B2 itself. The c-C3H2 column densities reveal two categories of clouds. Clouds in Category I (3 kpc arm, 4 kpc arm, and some GC clouds) have smaller c-C3H2 column densities, smaller linewidths, and smaller widths of their column density PDFs than clouds in Category II (Scutum arm, Sgr arm, and other GC clouds). We derive opacity maps for the following molecules: c-C3H2, H13CO+, 13CO, HNC and its isotopologue HN13C, HC15N, CS and its isotopologues C34S and 13CS, SiO, SO, and CH3OH. These maps reveal that most molecules trace relatively homogeneous structures that are more extended than the field of view defined by the background continuum emission (about 15′′, that is 0.08–0.6 pc depending on the distance). SO and SiO show more complex structures with smaller clumps of size ~5–8′′. Our analysis suggests that the driving of the turbulence is mainly solenoidal in the investigated clouds. Conclusions. On the basis of HCO+, we conclude that most line-of-sight clouds towards Sgr B2 are translucent, including all clouds where complex organic molecules were recently detected. We also conclude that CCH and CH are good probes of H2 in both diffuse and translucent clouds, while HCO+ and c-C3H2 in translucent clouds depart from the correlations with H2 found in diffuse clouds.
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Fischer, C. E., J. M. Borrero, N. Bello González, and A. J. Kaithakkal. "Observations of solar small-scale magnetic flux-sheet emergence." Astronomy & Astrophysics 622 (February 2019): L12. http://dx.doi.org/10.1051/0004-6361/201834628.
Повний текст джерелаАнотація:
Aims. Two types of flux emergence were recently discovered in numerical simulations: magnetic loops and magnetic sheet emergence. While magnetic loop emergence has been documented well in recent years using high-resolution full Stokes data from ground-based telescopes as well as satellites, magnetic sheet emergence is still an understudied process. We report here on the first clear observational evidence of a magnetic sheet emergence and characterise its development. Methods. Full Stokes spectra from the Hinode spectropolarimeter were inverted with the Stokes Inversion based on Response functions (SIR) code to obtain solar atmospheric parameters such as temperature, line-of-sight velocities, and full magnetic field vector information. Results. We analyse a magnetic flux emergence event observed in the quiet-Sun internetwork. After a large-scale appearance of linear polarisation, a magnetic sheet with horizontal magnetic flux density of up to 194 Mx cm−2 hovers in the low photosphere spanning a region of 2–3 arcsec. The magnetic field azimuth obtained through Stokes inversions clearly shows an organised structure of transversal magnetic flux density emerging. The granule below the magnetic flux sheet tears the structure apart leaving the emerged flux to form several magnetic loops at the edges of the granule. Conclusions. A large amount of flux with strong horizontal magnetic fields surfaces through the interplay of buried magnetic flux and convective motions. The magnetic flux emerges within 10 minutes and we find a longitudinal magnetic flux at the foot points of the order of ∼1018 Mx. This is one to two orders of magnitude larger than what has been reported for small-scale magnetic loops. The convective flows feed the newly emerged flux into the pre-existing magnetic population on a granular scale.
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YAMAMOTO, Toshikazu. "COMPARING LARGE SCALE MAPS WITH SMALL SCALE MAPS FOR ORIENTATION AND MOBILITY IN EARLY BLIND AND SIGHTED SUBJECTS." Japanese Journal of Educational Psychology 34, no. 3 (1986): 197–203. http://dx.doi.org/10.5926/jjep1953.34.3_197.
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Kameswara Rao, N., David L. Lambert, Arumalla B. S. Reddy, Ranjan Gupta, S. Muneer, Baba Varghese, and Harinder P. Singh. "Unveiling Vela – variability of interstellar lines in the direction of the Vela supernova remnant – III. Na D and Ca ii K." Monthly Notices of the Royal Astronomical Society 493, no. 1 (February 3, 2020): 497–517. http://dx.doi.org/10.1093/mnras/staa231.
Повний текст джерелаАнотація:
ABSTRACT High-resolution optical spectra were obtained in 2017–2019 with The Southern African Large Telescope of 15 stars in the direction of the Vela supernova remnant. Interstellar Ca ii H & K and Na i D lines are discussed in this paper. In particular, the line profiles are compared with profiles at a comparable spectral resolution obtained in 1993–1996 by Cha and Sembach. Ten of the lines of sight show changes to one or more of the components in that line of sight. Changes include small changes (1–2 km s−1) in radial velocity and/or increases/decreases in equivalent width over the two decades between the periods of observation. Changes are more obvious in the Ca K line than in the Na D lines. These changes are attributed to gas disturbed by interactions between the supernova ejecta and the surrounding interstellar medium. A representative time-scale may be 20–50 yr. Small-scale variations in line profiles across the face of the remnant suggest, as previously remarked, that a linear scale for interactions is a small fraction of the 40 pc size of the present remnant.
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Walther, Michael, Joseph F. Hennawi, Hector Hiss, Jose Oñorbe, Khee-Gan Lee, Alberto Rorai та John O’Meara. "A New Precision Measurement of the Small-scale Line-of-sight Power Spectrum of the LyαForest". Astrophysical Journal 852, № 1 (28 грудня 2017): 22. http://dx.doi.org/10.3847/1538-4357/aa9c81.
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Chen(陈昱光), Yuguang, Charles C. Steidel, Cameron B. Hummels, Gwen C. Rudie, Bili Dong(董比立), Ryan F. Trainor, Milan Bogosavljević, et al. "The Keck Baryonic Structure Survey: using foreground/background galaxy pairs to trace the structure and kinematics of circumgalactic neutral hydrogen at z ∼ 2." Monthly Notices of the Royal Astronomical Society 499, no. 2 (September 23, 2020): 1721–46. http://dx.doi.org/10.1093/mnras/staa2808.
Повний текст джерелаАнотація:
ABSTRACT We present new measurements of the spatial distribution and kinematics of neutral hydrogen in the circumgalactic and intergalactic medium surrounding star-forming galaxies at z ∼ 2. Using the spectra of ≃3000 galaxies with redshifts 〈z〉 = 2.3 ± 0.4 from the Keck Baryonic Structure Survey, we assemble a sample of more than 200 000 distinct foreground-background pairs with projected angular separations of 3–500 arcsec and spectroscopic redshifts, with 〈zfg〉 = 2.23 and 〈zbg〉 = 2.57 (foreground, background redshifts, respectively.) The ensemble of sightlines and foreground galaxies is used to construct a 2D map of the mean excess $\rm{H\,{\small I}}$$\rm Ly\,\alpha$ optical depth relative to the intergalactic mean as a function of projected galactocentric distance (20 ≲ Dtran/pkpc ≲ 4000) and line-of-sight velocity. We obtain accurate galaxy systemic redshifts, providing significant information on the line-of-sight kinematics of $\rm{H\,{\small I}}$ gas as a function of projected distance Dtran. We compare the map with cosmological zoom-in simulation, finding qualitative agreement between them. A simple two-component (accretion, outflow) analytical model generally reproduces the observed line-of-sight kinematics and projected spatial distribution of $\rm{H\,{\small I}}$. The best-fitting model suggests that galaxy-scale outflows with initial velocity vout ≃ 600 km s$^{-1}\,$ dominate the kinematics of circumgalactic $\rm{H\,{\small I}}$ out to Dtran ≃ 50 kpc, while $\rm{H\,{\small I}}$ at Dtran ≳ 100 kpc is dominated by infall with characteristic vin ≲ circular velocity. Over the impact parameter range 80 ≲ Dtran/pkpc ≲ 200, the $\rm{H\,{\small I}}$ line-of-sight velocity range reaches a minimum, with a corresponding flattening in the rest-frame $\rm Ly\,\alpha$ equivalent width. These observations can be naturally explained as the transition between outflow-dominated and accretion-dominated flows. Beyond Dtran ≃ 300 pkpc (∼1 cMpc), the line-of-sight kinematics are dominated by Hubble expansion.
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Taparugssanagorn, Attaphongse, Matti Hämäläinen, and Jari Iinatti. "Wideband and Ultrawideband Channel Models in Working Machine Environment." Modelling and Simulation in Engineering 2012 (2012): 1–10. http://dx.doi.org/10.1155/2012/702917.
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We present statistical models for wideband and ultrawideband (UWB) radio channels in a working machine cabin environment. Based on a set of measurements, it was found that such a small and confined space causes mostly diffuse multipath scattering rather than specular paths. The amplitude of the channel impulse responses in the wideband case is mostly Rayleigh distributed small-scale fading signal, with only a few paths exhibiting Ricean distributions, whereas the ones in the UWB case tend to be log-normally distributed. For the path amplitude, we suggest an exponential decay profile, which has a constant slope in dB scale, with the corresponding parameters for the UWB case. For the wideband case, a twofold exponential decay profile provides excellent fits to the measured data. It was also noted that the root-mean-square (RMS) delay spread is independent of the line-of-sight/obstructed line-of-sight situations of the channel. The multipath components contributing significant energy play a major role in such a small environment if compared to the direct path. In addition, the radio channel gains are attenuated with the presence of a driver inside the cabin.
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Rauch, Michael, Wallace L. W. Sargent, Thomas A. Barlow, and Robert A. Simcoe. "Small‐Scale Structure at High Redshift. IV. Low‐Ionization Gas Intersecting Three Lines of Sight to Q2237+0305." Astrophysical Journal 576, no. 1 (September 2002): 45–60. http://dx.doi.org/10.1086/341267.
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Reig, Juan, Vicent Miquel Rodrigo Penarrocha, Lorenzo Rubio, Maria Teresa Martinez-Ingles, and Jose Maria Molina-Garcia-Pardo. "The Folded Normal Distribution: A New Model for the Small-Scale Fading in Line-of-Sight (LOS) Condition." IEEE Access 7 (2019): 77328–39. http://dx.doi.org/10.1109/access.2019.2921340.
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Siebenmorgen, R., N. V. Voshchinnikov, S. Bagnulo, N. L. J. Cox, J. Cami, and C. Peest. "Large Interstellar Polarisation Survey." Astronomy & Astrophysics 611 (March 2018): A5. http://dx.doi.org/10.1051/0004-6361/201731814.
Повний текст джерелаАнотація:
It is well known that the dust properties of the diffuse interstellar medium exhibit variations towards different sight-lines on a large scale. We have investigated the variability of the dust characteristics on a small scale, and from cloud-to-cloud. We use low-resolution spectro-polarimetric data obtained in the context of the Large Interstellar Polarisation Survey (LIPS) towards 59 sight-lines in the Southern Hemisphere, and we fit these data using a dust model composed of silicate and carbon particles with sizes from the molecular to the sub-micrometre domain. Large (≥6 nm) silicates of prolate shape account for the observed polarisation. For 32 sight-lines we complement our data set with UVES archive high-resolution spectra, which enable us to establish the presence of single-cloud or multiple-clouds towards individual sight-lines. We find that the majority of these 35 sight-lines intersect two or more clouds, while eight of them are dominated by a single absorbing cloud. We confirm several correlations between extinction and parameters of the Serkowski law with dust parameters, but we also find previously undetected correlations between these parameters that are valid only in single-cloud sight-lines. We find that interstellar polarisation from multiple-clouds is smaller than from single-cloud sight-lines, showing that the presence of a second or more clouds depolarises the incoming radiation. We find large variations of the dust characteristics from cloud-to-cloud. However, when we average a sufficiently large number of clouds in single-cloud or multiple-cloud sight-lines, we always retrieve similar mean dust parameters. The typical dust abundances of the single-cloud cases are [C]/[H] = 92 ppm and [Si]/[H] = 20 ppm.
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MAO, JIRONG. "JITTER POLARIZATION FOR GRB PROMPT EMISSION." International Journal of Modern Physics: Conference Series 28 (January 2014): 1460175. http://dx.doi.org/10.1142/s2010194514601756.
Повний текст джерелаАнотація:
The radiation of relativistic electrons in random and small-scale magnetic field is called jitter radiation. We apply jitter process to study the polarization feature of GRB prompt emission. A two-dimensional compressed slab which contains stochastic magnetic field is applied in our model. If jitter condition is satisfied, the high degree polarization can be achieved when the angle between line-of-sight and slab plane is small. Moreover, micro-emitters with mini-jet structure and jet off-axis effect are considered.
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Thonhofer, Stefan, Luis R. Bellot Rubio, Dominik Utz, Arnold Hanslmeier, and Jan Jurçák. "Parallelization of the SIR code for the investigation of small-scale features in the solar photosphere." Proceedings of the International Astronomical Union 10, S305 (December 2014): 251–56. http://dx.doi.org/10.1017/s1743921315004858.
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AbstractMagnetic fields are one of the most important drivers of the highly dynamic processes that occur in the lower solar atmosphere. They span a broad range of sizes, from large- and intermediate-scale structures such as sunspots, pores and magnetic knots, down to the smallest magnetic elements observable with current telescopes. On small scales, magnetic flux tubes are often visible as Magnetic Bright Points (MBPs). Apart from simple V/I magnetograms, the most common method to deduce their magnetic properties is the inversion of spectropolarimetric data. Here we employ the SIR code for that purpose. SIR is a well-established tool that can derive not only the magnetic field vector and other atmospheric parameters (e.g., temperature, line-of-sight velocity), but also their stratifications with height, effectively producing 3-dimensional models of the lower solar atmosphere. In order to enhance the runtime performance and the usability of SIR we parallelized the existing code and standardized the input and output formats. This and other improvements make it feasible to invert extensive high-resolution data sets within a reasonable amount of computing time. An evaluation of the speedup of the parallel SIR code shows a substantial improvement in runtime.
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Ishikawa, Ryohtaroh T., Motoki Nakata, Yukio Katsukawa, Youhei Masada, and Tino L. Riethmüller. "Multi-scale deep learning for estimating horizontal velocity fields on the solar surface." Astronomy & Astrophysics 658 (February 2022): A142. http://dx.doi.org/10.1051/0004-6361/202141743.
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Context. The dynamics in the photosphere is governed by the multi-scale turbulent convection termed as granulation and supergranulation. It is important to derive three-dimensional velocity vectors to understand the nature of the turbulent convection and to evaluate the vertical Poynting flux toward the upper atmosphere. The line-of-sight component of the velocity can be obtained by observing the Doppler shifts. However, it is difficult to obtain the velocity component perpendicular to the line of sight, which corresponds to the horizontal velocity in disk center observations. Aims. We present a new method based on a deep neural network that can estimate the horizontal velocity from the spatial and temporal variations of the intensity and vertical velocity. We suggest a new measure for examining the performance of the method. Methods. We developed a convolutional neural network model with a multi-scale deep learning architecture. The method consists of multiple convolutional kernels with various sizes of receptive fields, and performs convolution for spatial and temporal axes. The network is trained with data from three different numerical simulations of turbulent convection. Furthermore, we introduced a novel coherence spectrum to assess the horizontal velocity fields that were derived for each spatial scale. Results. The multi-scale deep learning method successfully predicts the horizontal velocities for each convection simulation in terms of the global correlation coefficient, which is often used to evaluate the prediction accuracy of the methods. The coherence spectrum reveals the strong dependence of the correlation coefficients on the spatial scales. Although the coherence spectra are higher than 0.9 for large-scale structures, they drastically decrease to less than 0.3 for small-scale structures, wherein the global correlation coefficient indicates a high value of approximately 0.95. By comparing the results of the three convection simulations, we determined that this decrease in the coherence spectrum occurs around the energy injection scales, which are characterized by the peak of the power spectra of the vertical velocities. Conclusions. The accuracy for the small-scale structures is not guaranteed solely by the global correlation coefficient. To improve the accuracy on small scales, it is important to improve the loss function for enhancing the small-scale structures and to utilize other physical quantities related to the nonlinear cascade of convective eddies as input data.
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Tereshchenko, E. D., B. Z. Khudukon, M. T. Rietveld, B. Isham, T. Hagfors, and A. Brekke. "The relationship between small-scale and large-scale ionospheric electron density irregularities generated by powerful HF electromagnetic waves at high latitudes." Annales Geophysicae 24, no. 11 (November 21, 2006): 2901–9. http://dx.doi.org/10.5194/angeo-24-2901-2006.
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Abstract. Satellite radio beacons were used in June 2001 to probe the ionosphere modified by a radio beam produced by the EISCAT high-power, high-frequency (HF) transmitter located near Tromsø (Norway). Amplitude scintillations and variations of the phase of 150- and 400-MHz signals from Russian navigational satellites passing over the modified region were observed at three receiver sites. In several papers it has been stressed that in the polar ionosphere the thermal self-focusing on striations during ionospheric modification is the main mechanism resulting in the formation of large-scale (hundreds of meters to kilometers) nonlinear structures aligned along the geomagnetic field (magnetic zenith effect). It has also been claimed that the maximum effects caused by small-scale (tens of meters) irregularities detected in satellite signals are also observed in the direction parallel to the magnetic field. Contrary to those studies, the present paper shows that the maximum in amplitude scintillations does not correspond strictly to the magnetic zenith direction because high latitude drifts typically cause a considerable anisotropy of small-scale irregularities in a plane perpendicular to the geomagnetic field resulting in a deviation of the amplitude-scintillation peak relative to the minimum angle between the line-of-sight to the satellite and direction of the geomagnetic field lines. The variance of the logarithmic relative amplitude fluctuations is considered here, which is a useful quantity in such studies. The experimental values of the variance are compared with model calculations and good agreement has been found. It is also shown from the experimental data that in most of the satellite passes a variance maximum occurs at a minimum in the phase fluctuations indicating that the artificial excitation of large-scale irregularities is minimum when the excitation of small-scale irregularities is maximum.
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Joly, Marine, and Elke Zimmermann. "Do solitary foraging nocturnal mammals plan their routes?" Biology Letters 7, no. 4 (April 27, 2011): 638–40. http://dx.doi.org/10.1098/rsbl.2011.0258.
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Large-brained diurnal mammals with complex social systems are known to plan where and how to reach a resource, as shown by a systematic movement pattern analysis. We examined for the first time large-scale movement patterns of a solitary-ranging and small-brained mammal, the mouse lemur ( Microcebus murinus ), by using the change-point test and a heuristic random travel model to get insight into foraging strategies and potential route-planning abilities. Mouse lemurs are small nocturnal primates inhabiting the seasonal dry deciduous forest in Madagascar. During the lean season with limited food availability, these lemurs rely on few stationary food resources. We radio-tracked seven lemurs and analysed their foraging patterns. First change-points coincided with out-of-sight keystone food resources. Travel paths were more efficient in detecting these resources than a heuristic random travel model within limits of estimated detection distance. Findings suggest that even nocturnal, solitary-ranging mammals with small brains plan their route to an out-of-sight target. Thus, similar ecological pressures may lead to comparable spatial cognitive skills irrespective of the degree of sociality or relative brain size.
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Seki, Daikichi, Kenichi Otsuji, Hiroaki Isobe, Takako T. Ishii, Takahito Sakaue, and Kumi Hirose. "Increase in the Amplitude of Line-of-sight Velocities of the Small-scale Motions in a Solar Filament before Eruption." Astrophysical Journal 843, no. 2 (July 7, 2017): L24. http://dx.doi.org/10.3847/2041-8213/aa7559.
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Li, Kai Way, Chang Sun, and Nailiang Li. "Distance and Visual Angle of Line-of-Sight of a Small Drone." Applied Sciences 10, no. 16 (August 9, 2020): 5501. http://dx.doi.org/10.3390/app10165501.
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Determining the distance of the line-of-sight (LOS) of a small drone is essential in both regulating drone operation and drone operator training considering public safety. A field experiment was conducted to determine the LOS distance and visual angle of a small drone. Human participants were requested to observe a drone in one of the predetermined locations in the air. They responded whether they could see and hear the drone using a five-point scale. It was found that auditory signals were insignificant in drone detection because most of the participants could not hear the drone while they could still see the drone in most of the test locations. Logistic regression analyses were conducted to predict the probability of catching the drone visually. Two models were built considering the “definitely yes” and “definitely or probably yes” criteria of visual detection. These models may be used to estimate the LOS distance and visual angle. Assuming a 50% probability of visual catching and the “definitely or probably yes” criterion, the distance and visual angle of the LOS for the Mavic Air drone without a protector were approximately 307 m and 0.065°, respectively.
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David-Uraz, Alexandre, and Anthony F. J. Moffat. "Using the orbiting companion to trace WR wind structures in the 29d WC8d + O8-9IV binary CV Ser." Proceedings of the International Astronomical Union 6, S272 (July 2010): 499–500. http://dx.doi.org/10.1017/s1743921311011161.
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AbstractWe have used continuous, high-precision, broadband visible photometry from the MOST satellite to trace wind structures in the WR component of CV Ser over more than a full orbit. Most of the small-scale light-curve variations are likely due to extinction by clumps along the line of sight to the O companion as it orbits and shines through varying columns of the WR wind. Parallel optical spectroscopy from the Mont Megantic Observatory is used to refine the orbital and wind-collision parameters, as well as to reveal line emission from clumps.
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Karaçaylı, Naim Göksel, and Nikhil Padmanabhan. "Anatomy of cosmic tidal reconstruction." Monthly Notices of the Royal Astronomical Society 486, no. 3 (April 5, 2019): 3864–73. http://dx.doi.org/10.1093/mnras/stz964.
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Abstract 21-cm intensity surveys aim to map neutral hydrogen atoms in the universe through hyper-fine emission. Unfortunately, long-wavelength (low-wavenumber) radial modes are highly contaminated by smooth astrophysical foregrounds that are six orders of magnitude brighter than the cosmological signal. This contamination also leaks into higher radial and angular wavenumber modes and forms a foreground wedge. Cosmic tidal reconstruction aims to extract the large-scale signal from anisotropic features in the local small-scale power spectrum through non-linear tidal interactions; losing small-scale modes to foreground wedge will impair its performance. In this paper, we review tidal interaction theory and estimator construction, and derive the theoretical expressions for the reconstructed spectra. We show the reconstruction is robust against peculiar velocities. Removing low line-of-sight k modes, we demonstrate cross-correlation coefficient r is greater than 0.7 on large scales (k ≲ 0.1 h Mpc−1) even with a cut-off value $k^c_{\Vert }=0.1$h Mpc−1. Discarding wedge modes yields 0.3 ≲ r ≲ 0.5 and completely removes the dependency on $k^c_{\Vert }$. Our theoretical predictions agree with these numerical simulations.
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Väisälä, M. S., F. A. Gent, M. Juvela, and M. J. Käpylä. "The supernova-regulated ISM." Astronomy & Astrophysics 614 (June 2018): A101. http://dx.doi.org/10.1051/0004-6361/201730825.
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Context.Efforts to compare polarization measurements with synthetic observations from magnetohydrodynamics (MHD) models have previously concentrated on the scale of molecular clouds.Aims.We extend the model comparisons to kiloparsec scales, taking into account hot shocked gas generated by supernovae and a non-uniform dynamo-generated magnetic field at both large and small scales down to 4 pc spatial resolution.Methods.We used radiative transfer calculations to model dust emission and polarization on top of MHD simulations. We computed synthetic maps of column densityNH, polarization fractionp, and polarization angle dispersionS, and studied their dependencies on important properties of MHD simulations. These include the large-scale magnetic field and its orientation, the small-scale magnetic field, and supernova-driven shocks.Results.Similar filament-like structures ofSas seen in thePlanckall-sky maps are visible in our synthetic results, although the smallest scale structures are absent from our maps. Supernova-driven shock fronts andSdo not show significant correlation. Instead,Scan clearly be attributed to the distribution of the small-scale magnetic field. We also find that the large-scale magnetic field influences the polarization properties, such that, for a given strength of magnetic fluctuation, a strong plane of the sky mean field weakens the observedS, while strengtheningp. The anticorrelation ofpandS, and decreasingpas a function ofNHare consistent across all synthetic observations. The magnetic fluctuations follow an exponential distribution, rather than Gaussian characteristic of flows with intermittent repetitive shocks.Conclusions.The observed polarization properties and column densities are sensitive to the line-of-sight distance over which the emission is integrated. Studying synthetic maps as the function of maximum integration length will further help with the interpretation of observations. The effects of the large-scale magnetic field orientation on the polarization properties are difficult to be quantified from observations solely, but MHD models might turn out to be useful for separating the effect of the large-scale mean field.
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Vrouwenvelder, J. S., S. M. Bakker, M. Cauchard, R. Le Grand, M. Apacandié, M. Idrissi, S. Lagrave, et al. "The membrane fouling simulator: a suitable tool for prediction and characterisation of membrane fouling." Water Science and Technology 55, no. 8-9 (April 1, 2007): 197–205. http://dx.doi.org/10.2166/wst.2007.259.
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A new tool–the Membrane Fouling Simulator (MFS) – is developed to measure membrane fouling (pressure drop increase) in a small and simple system, representative for spiral wound membranes applied in water treatment. With the MFS, fouling development can be monitored systematically by (i) pressure drop, (ii) in situ and non-destructive (visual) observations using the sight glass and (iii) analysis of coupons sampled from the membrane sheet in the MFS. A comparison study of the MFS with spiral wound membrane elements (test rigs and a full scale installation) showed the same fouling. The MFS provided reproducible data. The small size and low water and chemical use of the MFS facilitate to perform systematic parallel studies. With the MFS, fouling of membranes applied in water treatment can be characterised.
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Spangler, Steven R., and Catherine A. Whiting. "Radio remote sensing of the corona and the solar wind." Proceedings of the International Astronomical Union 4, S257 (September 2008): 529–41. http://dx.doi.org/10.1017/s1743921309029834.
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AbstractModern radio telescopes are extremely sensitive to plasma on the line of sight from a radio source to the antenna. Plasmas in the corona and solar wind produce measurable changes in the radio wave amplitude and phase, and the phase difference between wave fields of opposite circular polarization. Such measurements can be made of radio waves from spacecraft transmitters and extragalactic radio sources, using radio telescopes and spacecraft tracking antennas. Data have been taken at frequencies from about 80 MHz to 8000 MHz. Lower frequencies probe plasma at greater heliocentric distances. Analysis of these data yields information on the plasma density, density fluctuations, and plasma flow speeds in the corona and solar wind, and on the magnetic field in the solar corona. This paper will concentrate on the information that can be obtained from measurements of Faraday rotation through the corona and inner solar wind. The magnitude of Faraday rotation is proportional to the line of sight integral of the plasma density and the line-of-sight component of the magnetic field. Faraday rotation provides an almost unique means of estimating the magnetic field in this part of space. This technique has contributed to measurement of the large scale coronal magnetic field, the properties of electromagnetic turbulence in the corona, possible detection of electrical currents in the corona, and probing of the internal structure of coronal mass ejections (CMEs). This paper concentrates on the search for small-scale coronal turbulence and remote sensing of the structure of CMEs. Future investigations with the Expanded Very Large Array (EVLA) or Murchison Widefield Array (MWA) could provide unique observational input on the astrophysics of CMEs.
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Schranz, Franziska, Jonas Hagen, Gunter Stober, Klemens Hocke, Axel Murk, and Niklaus Kämpfer. "Small-scale variability of stratospheric ozone during the sudden stratospheric warming 2018/2019 observed at Ny-Ålesund, Svalbard." Atmospheric Chemistry and Physics 20, no. 18 (September 15, 2020): 10791–806. http://dx.doi.org/10.5194/acp-20-10791-2020.
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Abstract. Middle atmospheric ozone, water vapour and zonal and meridional wind profiles have been measured with the two ground-based microwave radiometers GROMOS-C and MIAWARA-C. The instruments have been located at the Arctic research base AWIPEV at Ny-Ålesund, Svalbard (79∘ N, 12∘ E), since September 2015. GROMOS-C measures ozone spectra in the four cardinal directions with an elevation angle of 22∘. This means that the probed air masses at an altitude of 3 hPa (37 km) have a horizontal distance of 92 km to Ny-Ålesund. We retrieve four separate ozone profiles along the lines of sight and calculate daily mean horizontal ozone gradients which allow us to investigate the small-scale spatial variability of ozone above Ny-Ålesund. We present the evolution of the ozone gradients at Ny-Ålesund during winter 2018/2019, when a major sudden stratospheric warming (SSW) took place with the central date at 2 January, and link it to the planetary wave activity. We further analyse the SSW and discuss our ozone and water vapour measurements in a global context. At 3 hPa we find a distinct seasonal variation of the ozone gradients. The strong polar vortex during October and March results in a decreasing ozone volume mixing ratio towards the pole. In November the amplitudes of the planetary waves grow until they break in the end of December and an SSW takes place. From November until February ozone increases towards higher latitudes and the magnitude of the ozone gradients is smaller than in October and March. We attribute this to the planetary wave activity of wave numbers 1 and 2 which enabled meridional transport. The MERRA-2 reanalysis and the SD-WACCM model are able to capture the small-scale ozone variability and its seasonal changes.
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Gupta, Girjesh R., and Sushree S. Nayak. "Spectroscopic and imaging observations of transient hot and cool loops by IRIS and SDO." Monthly Notices of the Royal Astronomical Society 512, no. 3 (March 31, 2022): 3149–62. http://dx.doi.org/10.1093/mnras/stac657.
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ABSTRACT Coronal loops are the basic building blocks of the solar atmosphere and are observed on various length scales. However, their formation mechanism is still unclear. In this paper, we present spectroscopic and imaging observations of small-scale transients and the subsequent formation of transient loops. For this purpose, we have utilized the multiwavelength observations recorded by the Atmospheric Imaging Assembly (AIA) and the Interface Region Imaging Spectrograph (IRIS) slit-jaw imager (SJI), along with spectroscopic measurements provided by IRIS. For the photospheric magnetic field data, we obtained line-of-sight magnetogram data provided by the Helioseismic and Magnetic Imager (HMI). Small-scale transients are simultaneously observed with several EUV and UV passbands of AIA and IRIS/SJI. The HMI magnetogram provides evidence of negative flux cancellations beneath these transients. Differential emission measure (DEM) analysis shows that one of the transients attains temperatures up to 8 MK whereas another one only reaches 0.4 MK. These transients further lead to the formation of small-scale loops with similar temperature distributions, thus termed hot and cool loops respectively. During the course of events, the IRIS slit was rastering the region and thus provided spectroscopic measurements at both transients and associated loops. This enabled us to perform in-depth investigations of the hot and cool loops. Using a density-sensitive O iv line pair, we obtained average electron densities along the hot and cool loops to be 1011.2 and 1010.8 cm−3 respectively. Energy estimates suggest that flux cancellation could easily power the hot transient, while it is insufficient for the cool transient. Lifetime estimates and magnetic field extrapolation suggest the presence of small-scale and fine structures within these loops. The results provide crucial ingredients for the physics of loop formation and the thermodynamics involved.
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Starosielski, Nicole. "Resource Operations of the Ecological Digital Humanities." Publications of the Modern Language Association of America 131, no. 2 (March 2016): 401–9. http://dx.doi.org/10.1632/pmla.2016.131.2.401.
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Large-scale industrial processes and networks of extraction, slow violences wrought across toxic landscapes, and rapidly shifting atmospheric, oceanic, and hydrologic cycles are altering the conditions of human and nonhuman existence in ways that challenge the limits of existing media technologies. The last of these transformations—the fluctuating distributions of water—is the focus of this essay. Hydrologists are struggling to model and predict the intensities of drought, the changing supply of watersheds, the dispersions of chemicals through streams and rivers, and the failures of aging infrastructure. Water transports contaminants too small to identify by sight, requiring technologies that can register tiny particles on a massive scale. Water complicates boundary-making projects—it moves easily across local and regional zones, human and nonhuman bodies, and atmospheric, terrestrial, and marine ecologies. Global weather patterns and distribution infrastructures shape its circulation, yet its material effects depend greatly on local conditions.
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Payne, Alison L., and Peter J. Jarman. "Macropod studies at Wallaby Creek. X. Responses of eastern grey kangaroos to cattle." Wildlife Research 26, no. 2 (1999): 215. http://dx.doi.org/10.1071/wr95037.
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The instantaneous behavioural and spatial responses of eastern grey kangaroos to the presence of cattle were studied at Wallaby Creek, north-eastern New South Wales. Kangaroo groups were distributed closer to cattle groups than would be expected by chance, both at a study-site scale (154-ha) and at a 1-ha scale; large males were recorded on average further from cattle than were smaller males. Nearest-neighbouring kangaroo groups were located such that cattle groups rarely interrupted the lines of sight between them. Observed disturbance and displacement by cattle provoked a minimal response in kangaroos, which fled only tens of metres and soon resumed their previous activity. The presence of cattle had few detectable instantaneous effects on the behaviour of the kangaroos, except to increase their alertness and the feeding time of small (but not large) kangaroo groups. These effects indicate that cattle pose little threat to kangaroos.
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Canizares, Claude R. "Gravitational Lenses as Tools in Observational Cosmology." Symposium - International Astronomical Union 124 (1987): 729–46. http://dx.doi.org/10.1017/s0074180900159844.
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The study of gravitational lenses is intimately tied to observational cosmology. When we observe a gravitationally lensed quasar, we are viewing a single object along two or more neighboring paths (null geodesics) of cosmological dimensions (Figure 1). What we see depends on bulk properties of the universe, such as Ho and qo, on the large scale structure and inhomogeneities along the paths, and on the small scale structure in and around the primary deflector. Furthermore, the deflection of light depends on the gravitational field along the line of sight, so it is sensitive to all forms of matter: luminous or dark, baryonic or exotic. Thus the images of gravitationally lensed quasars contain an imprint of the universe that is virtually inaccessible by any other means. The hope of decoding this imprint has stimulated observers and theorists to expend many thousands of hours of telescope time, computer time and cogitation on the elucidation of gravitational lens properties.
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Mary, Benjamin, Luca Peruzzo, Jacopo Boaga, Myriam Schmutz, Yuxin Wu, Susan S. Hubbard, and Giorgio Cassiani. "Small-scale characterization of vine plant root water uptake via 3-D electrical resistivity tomography and mise-à-la-masse method." Hydrology and Earth System Sciences 22, no. 10 (October 23, 2018): 5427–44. http://dx.doi.org/10.5194/hess-22-5427-2018.
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Abstract. The investigation of plant roots is inherently difficult and often neglected. Being out of sight, roots are often out of mind. Nevertheless, roots play a key role in the exchange of mass and energy between soil and the atmosphere, in addition to the many practical applications in agriculture. In this paper, we propose a method for roots imaging based on the joint use of two electrical noninvasive methods: electrical resistivity tomography (ERT) and mise-à-la-masse (MALM). The approach is based on the key assumption that the plant root system acts as an electrically conductive body, so that injecting electrical current into the plant stem will ultimately result in the injection of current into the subsoil through the root system, and particularly through the root terminations via hair roots. Evidence from field data, showing that voltage distribution is very different whether current is injected into the tree stem or in the ground, strongly supports this hypothesis. The proposed procedure involves a stepwise inversion of both ERT and MALM data that ultimately leads to the identification of electrical resistivity (ER) distribution and of the current injection root distribution in the three-dimensional soil space. This, in turn, is a proxy to the active (hair) root density in the ground. We tested the proposed procedure on synthetic data and, more importantly, on field data collected in a vineyard, where the estimated depth of the root zone proved to be in agreement with literature on similar crops. The proposed noninvasive approach is a step forward towards a better quantification of root structure and functioning.
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Duan, Yutong, and Daniel Eisenstein. "Tests of acoustic scale shifts in halo-based mock galaxy catalogues." Monthly Notices of the Royal Astronomical Society 490, no. 2 (September 16, 2019): 2718–31. http://dx.doi.org/10.1093/mnras/stz2578.
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ABSTRACT We utilize mock catalogues from high-accuracy cosmological N-body simulations to quantify shifts in the recovery of the acoustic scale that could potentially result from galaxy clustering bias. The relationship between galaxies and dark matter haloes presents a complicated source of systematic errors in modern redshift surveys, particularly when aiming to make cosmological measurements to sub-per cent precision. Apart from a scalar, linear bias parameter accounting for the density contrast ratio between matter tracers and the true matter distribution, other types of galaxy bias, such as assembly and velocity biases, may also significantly alter clustering signals from small to large scales. We create mocks based on generalized halo occupation populations of 36 periodic boxes from the abacus cosmosrelease, and test various biased models along with an unbiased base case in a total volume of $48 \, h^{-3} \, {\rm Gpc}^{3}$. Two reconstruction methods are applied to galaxy samples and the apparent acoustic scale is derived by fitting the two-point correlation function multipoles. With respect to the baseline, we find a 0.3 per cent shift in the line-of-sight acoustic scale for one variation in the satellite galaxy population, and we find a 0.7 per cent shift for an extreme level of velocity bias of the central galaxies. All other bias models are consistent with zero shift at the 0.2 per cent level after reconstruction. We note that the bias models explored are relatively large variations, producing sizeable and likely distinguishable changes in small-scale clustering, the modelling of which would further calibrate the baryon acoustic oscillations standard ruler.
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Miller, Joel S. A., James S. Bolton та Nina Hatch. "Searching for the shadows of giants: characterizing protoclusters with line of sight Lyman-α absorption". Monthly Notices of the Royal Astronomical Society 489, № 4 (7 вересня 2019): 5381–97. http://dx.doi.org/10.1093/mnras/stz2504.
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ABSTRACT We use state-of-the-art hydrodyamical simulations from the Sherwood, EAGLE, and Illustris projects to examine the signature of Mz = 0 ≃ 1014 M⊙ protoclusters observed in Ly α absorption at z ≃ 2.4. We find that there is a weak correlation between the mass overdensity, δm, and the Ly α effective optical depth relative to the mean, $\delta _{\tau _\textrm{eff}}$, averaged over $15~h^{-1}\, \textrm{cMpc}$ scales, although scatter in the δm–$\delta _{\tau _\textrm{eff}}$ plane means it is not possible to uniquely identify large-scale overdensities with strong Ly α absorption. Although all protoclusters are associated with large-scale mass overdensities, most sightlines through protoclusters in a ∼106$\rm cMpc^{3}$ volume probe the low column density Ly α forest. A small subset of sightlines that pass through protoclusters exhibit coherent, strong Ly α absorption on $15h^{-1}\rm \, cMpc$ scales, although these correspond to a wide range in mass overdensity. Assuming perfect removal of contamination by Ly α absorbers with damping wings, more than half of the remaining sightlines with $\delta _{\tau _{\rm eff}}\gt 3.5$ trace protoclusters. It is furthermore possible to identify a model-dependent $\delta _{\tau _{\rm eff}}$ threshold that selects only protoclusters. However, such regions are rare: excluding absorption caused by damped systems, less than 0.1 per cent of sightlines that pass through a protocluster have $\delta _{\tau _{\rm eff}}\gt 3.5$, meaning that any protocluster sample selected in this manner will also be highly incomplete. On the other hand, coherent regions of Ly α absorption also provide a promising route for identifying and studying filamentary environments at high redshift.
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Rahbek, Carsten, Nicholas J. Gotelli, Robert K. Colwell, Gary L. Entsminger, Thiago Fernando L. V. B. Rangel, and Gary R. Graves. "Predicting continental-scale patterns of bird species richness with spatially explicit models." Proceedings of the Royal Society B: Biological Sciences 274, no. 1607 (October 20, 2006): 165–74. http://dx.doi.org/10.1098/rspb.2006.3700.
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The causes of global variation in species richness have been debated for nearly two centuries with no clear resolution in sight. Competing hypotheses have typically been evaluated with correlative models that do not explicitly incorporate the mechanisms responsible for biotic diversity gradients. Here, we employ a fundamentally different approach that uses spatially explicit Monte Carlo models of the placement of cohesive geographical ranges in an environmentally heterogeneous landscape. These models predict species richness of endemic South American birds (2248 species) measured at a continental scale. We demonstrate that the principal single-factor and composite (species-energy, water-energy and temperature-kinetics) models proposed thus far fail to predict ( r 2 ⩽0.05) the richness of species with small to moderately large geographical ranges (first three range-size quartiles). These species constitute the bulk of the avifauna and are primary targets for conservation. Climate-driven models performed reasonably well only for species with the largest geographical ranges (fourth quartile) when range cohesion was enforced. Our analyses suggest that present models inadequately explain the extraordinary diversity of avian species in the montane tropics, the most species-rich region on Earth. Our findings imply that correlative climatic models substantially underestimate the importance of historical factors and small-scale niche-driven assembly processes in shaping contemporary species-richness patterns.
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Poorman, Christopher C. "Drone Nation." Texas A&M Journal of Property Law 2, no. 3 (April 2015): 511–31. http://dx.doi.org/10.37419/jpl.v2.i3.6.
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This Comment aims to show that current regulation, or more precisely non-regulation of commercial UAS should be modified, and operators should be allowed to conduct commercial operations without subjecting UAS to the high standards of other “aircraft.” Per Congress’s mandate, the FAA should immediately create and enforce practically sound standards for small-scale, commercial UAS that operate inside the NAS while avoiding unnecessary and costly administrative burdens. Congress should modify the currently voluntary standards, instead of mandating that operators adhere to specific commercial use guidelines without requiring an arduous approval process for commercial flight, such as the current Special Airworthiness Certificate and Section 333 exemption. This Comment will not address the issues facing larger, interstate drones that will operate outside of the visual sight or immediate area of the operator.
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Griv, Evgeny, Michael Gedalin, and Ing-Guey Jiang. "The spiral density-wave structure of the Milky Way in the 3-kpc-scale solar neighbourhood: line-of-sight velocities of 252 young open clusters." Monthly Notices of the Royal Astronomical Society 512, no. 1 (February 22, 2022): 1169–76. http://dx.doi.org/10.1093/mnras/stac426.
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ABSTRACT Following Lin and Shu, the spiral structure in the Milky Way disc is considered as an oscillating density-wave pattern. As such, regular enhancements in density are relatedly linked to systematic variations in velocity of young stars and stellar clusters, and interstellar gas. We explain measured line-of-sight velocities of 252 open clusters with ages <100 Myr of Tarricq et al. in the 3-kpc-scale solar neighbourhood in terms of a density wave. New estimates of the parameters of solar peculiar motion and Galactic differential rotation corrected for the effects of small-amplitude density waves, the radial and tangential components of systematic motion of clusters due to the spiral arms as well as the geometrical and dynamical parameters of the waves are suggested.
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Salas, L., and I. Cruz-González. "AN ALTERNATIVE APPROACH TO THE FINGER OF GOD IN LARGE SCALE STRUCTURES." Revista Mexicana de Astronomía y Astrofísica 55, no. 1 (May 31, 2019): 93–104. http://dx.doi.org/10.22201/ia.01851101p.2019.55.01.10.
Повний текст джерелаАнотація:
It is generally accepted that linear theory of growth of structure under gravity produces a squashed structure in the two-point correlation function (2PCF) along the line of sight (LoS). The observed radial spread out structure known as Finger of God (FoG) is attributed to non-linear effects. We argue that the squashed structure associated with the redshift-space (s−) linear theory 2PCF is obtained only when this function is displayed in real-space (r−), or when the mapping from r − to s−space is approximated. We solve for the mapping function s(r) that allows us to display thes −space 2PCF in a grid in s−space, by using plane of the sky projections of the r − and s − 2PCFs. Even in the simplest case of a linear Kaiser spectrum with a conservative power-law r−space 2PCF, a structure quite similar to the FoG is observed in the small scale region, while in the large scale the expected squashed structure is obtained. This structure depends on only three parameters.
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Rusk, Raymond, and Ann C. M. Rusk. "Alignment of milliarcsecond with arcsecond scale structure in core-dominated radio sources." Canadian Journal of Physics 64, no. 4 (April 1, 1986): 440–44. http://dx.doi.org/10.1139/p86-079.
Повний текст джерелаАнотація:
Models of compact radio sources as relativistic jets aligned nearly along the line of sight predict large magnifications of intrinsic jet bends due to projection effects. Several authors have examined the distribution of observed bend angles, for small samples of sources, to provide constraints on the relativistic beaming models. In this study, we examine the alignment of Very Long Baseline Interferometry scale structure with arcsecond scale structure for a much larger sample of core-dominated radio sources and compare the distribution of observed misalignment angles with theoretical distributions calculated from models using a range of intrinsic bend angles, ξ, and Lorentz factors, γ. The theoretical distributions produced by simple relativistic beam models are found to be consistent with the data. However, the values of ξ and γ required to fit the data are highly correlated, with equally good fits produced by γ = 5, ξ = 11° and γ = 10, ξ = 5°, for instance. Either ξ or γ must be known independently for an analysis of the misalignment angle distribution to provide a significant constraint on beam parameters.
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Shamsan, Z. A. "Statistical Analysis of 5G Channel Propagation using MIMO and Massive MIMO Technologies." Engineering, Technology & Applied Science Research 11, no. 4 (August 21, 2021): 7417–23. http://dx.doi.org/10.48084/etasr.4264.
Повний текст джерелаАнотація:
Multiple Input Multiple Output (MIMO) and massive MIMO technologies play a significant role in mitigating five generation (5G) channel propagation impairments. These impairments increase as frequency increases, and they become worse at millimeter-waves (mmWaves). They include difficulties of material penetration, Line-of-Sight (LoS) inflexibility, small cell coverage, weather circumstances, etc. This paper simulates the 5G channel at the E-band frequency using the Monte Carlo approach-based NYUSIM tool. The urban microcell (UMi) is the communication environment of this simulation. Both MIMO and massive MIMO use uniformly spaced rectangular antenna arrays (URA). This study investigates the effects of MIMO and massive MIMO on LOS and Non-LOS (NLOS) environments. The simulations considered directional and omnidirectional antennas, the Power Delay Profile (PDP), Root Mean Square (RMS) delay spread, and small-scale PDP for both LOS and NLOS environments. As expected, the wide variety of the results showed that the massive MIMO antenna outperforms the MIMO antenna, especially in terms of the signal power received at the end-user and for longer path lengths.
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Młyńczak, Jakub, Piotr Folęga, and Ireneusz Celiński. "Specifics of the traffic scene identification problem observed at level crossings, analysed from the train driver’s perspective." Archives of Transport 58, no. 2 (June 30, 2021): 81–97. http://dx.doi.org/10.5604/01.3001.0014.8799.
Повний текст джерелаАнотація:
Level crossing is an element of the transport infrastructure of a particular type. This is where streams of regulated and unregulated traffic interact. Vehicles of regulated, rail traffic affect on unregulated, road traffic vehicles. This process takes place over a relatively small area. But the associated processes are concerned with long distances and medium speeds. Importantly, the impact may be mutual (mainly on level crossing cat. D). Consequently, a number of diverse problems can be observed at level crossings as well as in their direct vicinity. One of them is very particular, since its intensity and scale are significantly higher compared to other points of the transport network. This is a problem of how the sight organs of a rail vehicle driver function. At level crossings, a rail vehicle driver is incapable of registering all events connected with moving objects in a horizontal plane of the field of view (often, dozens or hundreds of vehicles and pedestrians, rail vehicles, signs etc.). Especially in agglomeration areas, near the railway stations, people may violently trespass into the tracks. Before reaching a level crossing, the driver’s sight organs perform specific movements of variable dynamics, having a direct impact on the traffic safety. Given the context in question, the article discusses the methods used to measure the characteristics of the train driver’s sight organs by means of eye tracking devices. The measured characteristics are: saccadic movements, fixation point locations, blinking etc. The relevant studies were supported by using additional equipment and techniques, including visual and vibroacoustic ones. These studies have been illustrated with reference to the measurements performed in different sections of the railway network. The aim of the research was to analyse the behaviour of drivers of traction vehicles. The research results have been discussed in quantitative terms, thus introducing several new descriptive characteristics. The data thus obtained, e.g. concerning the functions of the driver’s sight organs, have been analysed using numerical data set characteristics. With regard to the context this article the authors also conduct research addresses measurements of the characteristics of the road vehicle driver’s sight organs performed by means of eye tracking devices.
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Burgess, Tristan L., M. Tim Tinker, Melissa A. Miller, James L. Bodkin, Michael J. Murray, Justin A. Saarinen, Linda M. Nichol, Shawn Larson, Patricia A. Conrad, and Christine K. Johnson. "Defining the risk landscape in the context of pathogen pollution: Toxoplasma gondii in sea otters along the Pacific Rim." Royal Society Open Science 5, no. 7 (July 2018): 171178. http://dx.doi.org/10.1098/rsos.171178.
Повний текст джерелаАнотація:
Pathogens entering the marine environment as pollutants exhibit a spatial signature driven by their transport mechanisms. The sea otter ( Enhydra lutris ), a marine animal which lives much of its life within sight of land, presents a unique opportunity to understand land–sea pathogen transmission. Using a dataset on Toxoplasma gondii prevalence across sea otter range from Alaska to California, we found that the dominant drivers of infection risk vary depending upon the spatial scale of analysis. At the population level, regions with high T. gondii prevalence had higher human population density and a greater proportion of human-dominated land uses, suggesting a strong role for population density of the felid definitive host of this parasite. This relationship persisted when a subset of data were analysed at the individual level: large-scale patterns in sea otter T. gondii infection prevalence were largely explained by individual exposure to areas of high human housing unit density, and other landscape features associated with anthropogenic land use, such as impervious surfaces and cropping land. These results contrast with the small-scale, within-region analysis, in which age, sex and prey choice accounted for most of the variation in infection risk, and terrestrial environmental features provided little variation to help in explaining observed patterns. These results underscore the importance of spatial scale in study design when quantifying both individual-level risk factors and landscape-scale variation in infection risk.
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Shelchkova, Natalya, Christie Tang, and Martina Poletti. "Task-driven visual exploration at the foveal scale." Proceedings of the National Academy of Sciences 116, no. 12 (March 1, 2019): 5811–18. http://dx.doi.org/10.1073/pnas.1812222116.
Повний текст джерелаАнотація:
Humans use saccades to inspect objects of interest with the foveola, the small region of the retina with highest acuity. This process of visual exploration is normally studied over large scenes. However, in everyday tasks, the stimulus within the foveola is complex, and the need for visual exploration may extend to this smaller scale. We have previously shown that fixational eye movements, in particular microsaccades, play an important role in fine spatial vision. Here, we investigate whether task-driven visual exploration occurs during the fixation pauses in between large saccades. Observers judged the expression of faces covering approximately 1°, as if viewed from a distance of many meters. We use a custom system for accurately localizing the line of sight and continually track gaze position at high resolution. Our findings reveal that active spatial exploration, a process driven by the goals of the task, takes place at the foveal scale. The scanning strategies used at this scale resemble those used when examining larger scenes, with idiosyncrasies maintained across spatial scales. These findings suggest that the visual system possesses not only a coarser priority map of the extrafoveal space to guide saccades, but also a finer-grained priority map that is used to guide microsaccades once the region of interest is foveated.