14,114 research outputs found
New Measurements of the Ionizing Ultraviolet Background over 2 < z < 5 and Implications for Hydrogen Reionization
We present new measurements of the intensity of the ionizing ultraviolet
background and the global emissivity of ionizing photons over 2 < z < 5. Our
results are based on a suite of updated measurements of physical properties of
the high-redshift intergalactic medium (IGM), including gas temperatures and
the opacity of the IGM to Ly-alpha and ionizing photons. Consistent with
previous works, we find a relatively flat hydrogen photoionization rate over 2
< z < 5, although our measurements are roughly a factor of two higher than the
2008 values of Faucher-Giguere et al., due primarily to our lower gas
temperatures. The ionizing emissivity we derive is also generally higher than
other recent estimates due to a combination of lower gas temperatures, higher
ionizing opacity, and an accounting of cosmological radiative transfer effects.
We find evidence that the emissivity increases from z~3 to 5, reaching ~5
ionizing photons per atom per gigayear at z=4.75 for realistic galaxy spectra.
We further find that galaxies must dominate the emissivity near 1 Ryd at z > 4,
and possibly at all redshifts z > 2.4. Our results suggest that the
globally-averaged ionizing "efficiency" of star-forming galaxies increases
substantially with redshift over 3.2 < z < 4.75. This trend is consistent with
the conclusion often drawn from reionization models that the ionizing
efficiency of galaxies must be higher during reionization in order for galaxies
to reionize the IGM by z=6. Our emissivity values at z~5 suggest that ionizing
photons may have been a factor of two more abundant during the final stages of
reionization than previously indicated. The evolution of the ionizing
emissivity over 2 < z < 5 suggests, moreover, that the steep decline in the
photoionization rate from z~5 to 6 may indicate a rapid evolution in the mean
free path at z > 5.Comment: 19 pages, 14 figures, MNRAS, in pres
Occurrences of \u3ci\u3eEumorpha Fasciata, Hyles Gallii, Sphinx Franckii\u3c/i\u3e and \u3ci\u3eS. Vashti\u3c/i\u3e (Lepidoptera: Sphingidae) in Illinois
A recent survey of private and institutional collections in Illinois and surrounding states has provided specific information on the occurrences of four species of sphingids within Illinois: Eumorpha fasciata, Hyles gallii, Sphinx franckii, and S. vashti. Geographical and phenological data for these species are provided
Characteristics of Waterfowl Harvest at Horseshoe Lake, Madison County, Illinois
Division of Wildlife Resources Migratory Bird Section, Periodic Report No. 13Report issued on: April 21, 197
Geometry-Oblivious FMM for Compressing Dense SPD Matrices
We present GOFMM (geometry-oblivious FMM), a novel method that creates a
hierarchical low-rank approximation, "compression," of an arbitrary dense
symmetric positive definite (SPD) matrix. For many applications, GOFMM enables
an approximate matrix-vector multiplication in or even time,
where is the matrix size. Compression requires storage and work.
In general, our scheme belongs to the family of hierarchical matrix
approximation methods. In particular, it generalizes the fast multipole method
(FMM) to a purely algebraic setting by only requiring the ability to sample
matrix entries. Neither geometric information (i.e., point coordinates) nor
knowledge of how the matrix entries have been generated is required, thus the
term "geometry-oblivious." Also, we introduce a shared-memory parallel scheme
for hierarchical matrix computations that reduces synchronization barriers. We
present results on the Intel Knights Landing and Haswell architectures, and on
the NVIDIA Pascal architecture for a variety of matrices.Comment: 13 pages, accepted by SC'1
High frequency ultrasonic characterization of sintered SiC
High frequency (60 to 160 MHz) ultrasonic nondestructive evaluation was used to characterize variations in density and microstructural constituents of sintered SiC bars. Ultrasonic characterization methods included longitudinal velocity, reflection coefficient, and precise attenuation measurements. The SiC bars were tailored to provide bulk densities ranging from 90 to 98 percent of theoretical, average grain sizes ranging from 3.0 to 12.0 microns, and average pore sizes ranging from 1.5 to 4.0 microns. Velocity correlated with specimen bulk density irrespective of specimen average grain size, average pore size, and average pore orientation. Attenuation coefficient was found to be sensitive to both density and average pore size variations, but was not affected by large differences in average grain size
Range Extension of Bull Trout, Salvelinus confluentus, to the Central Northwest Territories, with Notes on Identification and Distribution of Dolly Varden, Salvelinus malma, in the Western Canadian Arctic
The presence of bull trout (Salvelinus confluentus) is reported from four locations in the Sahtu Settlement Area of the Northwest Territories centered about 64°30'N and 125°00'W. These reports extend the geographical range of this species approximately 500 km north of the previous northernmost published localities in the southern Northwest Territories (~61°N, 125°W, Prairie Creek, Liard River drainage). The identity of these char is confirmed using quantitative criteria in a linear discriminant function from the literature shown to be 100% effective in distinguishing bull trout from Dolly Varden (S. malma). Regular captures of these fish at one location over several years indicate that these records likely represent established populations and not extralimital occurrences. We hypothesize that bull trout are more extensively distributed in high-gradient streams and rivers of the south-central Mackenzie River valley and likely also occur north of this area. Only limited scientific work has been done in the area, and data on taxonomy and distributions of species are generally lacking. In much of the previous literature, reports of char (other than lake trout, S. namaycush) have identified the fish as Dolly Varden or arctic char (S. alpinus). These identifications are suspect, and care must be taken when interpreting such literature. The presence and vulnerability of bull trout present significant challenges for their conservation and management in this area.On a rapportĂ© la prĂ©sence de l'omble Ă tĂȘte plate (Salvelinus confluentus) Ă quatre endroits de l'Ă©tablissement du Sahtu (Territoires du Nord-Ouest), dont la position est environ 64° 30' de lat. N. et 125° 00' de long. O. Ces rapports prolongent l'habitat de cette espĂšce d'environ 500 km au nord des lieux les plus septentrionaux mentionnĂ©s prĂ©cĂ©demment dans la documentation, lieux situĂ©s dans la partie sud des Territoires du Nord-Ouest (~ 61° de lat. N., 125° de long. O., bassin de la Liard). L'identitĂ© de ces ombles est confirmĂ©e grĂące Ă l'utilisation de critĂšres quantitatifs dans une fonction discriminante linĂ©aire qui a Ă©tĂ© prouvĂ©e 100 p. cent efficace pour Ă©tablir la distinction entre omble Ă tĂȘte plate et Dolly Varden (S. malma). Les prises rĂ©guliĂšres de ce poisson Ă un endroit au cours de plusieurs annĂ©es rĂ©vĂšlent que ces donnĂ©es reprĂ©sentent probablement des populations Ă©tablies et non des occurrences hors limites. Nous Ă©mettons l'hypothĂšse que la distribution de l'omble Ă tĂȘte plate est plus large dans les ruisseaux et riviĂšres ayant une pente Ă forte dĂ©clivitĂ© situĂ©s dans le centre-sud de la vallĂ©e du Mackenzie, et qu'on le trouve probablement aussi au nord de cette rĂ©gion. Les travaux scientifiques effectuĂ©s dans la rĂ©gion sont d'une envergure limitĂ©e, et les donnĂ©es sur la classification et la distribution des espĂšces sont dans l'ensemble inexistantes. Dans un grand nombre de documents publiĂ©s, les rapports concernant les ombles (autres que le touladi, S. namaycush) ont identifiĂ© le poisson comme Ă©tant le Dolly Varden ou l'omble chevalier (S. alpinus). Ces identifications sont douteuses et il faut interprĂ©ter cette documentation avec prudence. La prĂ©sence et la vulnĂ©rabilitĂ© de l'omble Ă tĂȘte plate prĂ©sentent d'importants dĂ©fis quant Ă la prĂ©servation et Ă la gestion de l'espĂšce Ă l'intĂ©rieur de cette zone
Conflict of Laws (2017)
Statesâ and nationsâ laws collide when foreign factors appear in a lawsuit. Nonresident litigants, incidents outside the forum, and judgments from other jurisdictions can create problems with personal jurisdiction, choice of law, and the recognition of foreign judgments. This article reviews Texas conflict cases from Texas state and federal courts during the Survey period from December 1, 2015, through November 30, 2016. The article excludes cases involving federalâstate conflicts; intrastate issues, such as subject matter jurisdiction and venue; and conflicts in time, such as the applicability of prior or subsequent law within a state. State and federal cases are discussed together because conflict of laws is mostly a state-law topic, except for a few constitutional limits, resulting in the same rules applying to most issues in state and federal courts.
Although no data are readily available to confirm this, Texas is no doubt a primary state in the production of conflict-of-laws precedents. This results not only from its size and population, but also from its placement bordering four states and a civil-law nation, and its significant international trade volume. Texas state and federal courts provide a fascinating study of conflicts issues every year, but the volume of case law now greatly exceeds this Surveyâs ability to report on them, a function both of journal space and authorsâ time. In addition, the current Survey covers one year and will accordingly limit its review to a few highlight cases and an examination of a couple of trends
An Investigation of the Association Between Tourist Pre-Trip Planning Time and Length of Trip, Lodging Choice, Tourist Psychographics and Demographics: An Application of Correspondence Analysis and CramĂ©râs V Effect Size
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