Locality-Adaptive Parallel Hash Joins Using Hardware Transactional Memory

Previous work [1] has claimed that the best performing implementation of in-memory hash joins is based on (radix-)partitioning of the build-side input. Indeed, despite the overhead of partitioning, the benefits from increased cache-locality and synchronization free parallelism in the build-phase outweigh the costs when the input data is randomly ordered. However, many datasets already exhibit significant spatial locality (i.e., non-randomness) due to the way data items enter the database: through periodic ETL or trickle loaded in the form of transactions. In such cases, the first benefit of partitioning — increased locality — is largely irrelevant. In this paper, we demonstrate how hardware transactional memory (HTM) can render the other benefit, freedom from synchronization, irrelevant as well. Specifically, using careful analysis and engineering, we develop an adaptive hash join implementation that outperforms parallel radix-partitioned hash joins as well as sort-merge joins on data with high spatial locality. In addition, we show how, through lightweight (less than 1% overhead) runtime monitoring of the transaction abort rate, our implementation can detect inputs with low spatial locality and dynamically fall back to radix-partitioning of the build-side input. The result is a hash join implementation that is more than 3 times faster than the state-of-the-art on high-locality data and never more than 1% slower

Modeling the physical properties in the ISM of the low-metallicity galaxy NGC4214

We present a model for the interstellar medium of NGC4214 with the objective to probe the physical conditions in the two main star-forming regions and their connection with the star formation activity of the galaxy. We used the spectral synthesis code Cloudy to model an HII region and the associated photodissociation region (PDR) to reproduce the emission of mid- and far-infrared fine-structure cooling lines from the Spitzer and Herschel space telescopes for these two regions. Input parameters of the model, such as elemental abundances and star formation history, are guided by earlier studies of the galaxy, and we investigated the effect of the mode in which star formation takes place (bursty or continuous) on the line emission. Furthermore, we tested the effect of adding pressure support with magnetic fields and turbulence on the line predictions. We find that this model can satisfactorily predict (within a factor of ~2) all observed lines that originate from the ionized medium ([SIV] 10.5um, [NeIII] 15.6um, [SIII] 18.7um, [SIII] 33.5um, and [OIII] 88um), with the exception of [NeII] 12.8um and [NII] 122um, which may arise from a lower ionization medium. In the PDR, the [OI] 63um, [OI] 145um, and [CII] 157um lines are matched within a factor of ~5 and work better when weak pressure support is added to the thermal pressure or when the PDR clouds are placed farther away from the HII regions and have covering factors lower than unity. Our models of the HII region agree with different evolutionary stages found in previous studies, with a more evolved, diffuse central region, and a younger, more compact southern region. However, the local PDR conditions are averaged out on the 175 pc scales that we probe and do not reflect differences observed in the star formation properties of the two regions.Comment: accepted for publication in A&

Dissecting the spiral galaxy M83: mid-infrared emission and comparison with other tracers of star formation

We present a detailed mid-infrared study of the nearby, face-on spiral galaxy M83 based on ISOCAM data. M83 is a unique case study, since a wide variety of MIR broad-band filters as well as spectra, covering the wavelength range of 4 to 18\mu m, were observed and are presented here. Emission maxima trace the nuclear and bulge area, star-formation regions at the end of the bar, as well as the inner spiral arms. The fainter outer spiral arms and interarm regions are also evident in the MIR map. Spectral imaging of the central 3'x3' (4 kpc x 4 kpc) field allows us to investigate five regions of different environments. The various MIR components (very small grains, polycyclic aromatic hydrocarbon (PAH) molecules, ionic lines) are analyzed for different regions throughout the galaxy. In the total 4\mu m to 18\mu m wavelength range, the PAHs dominate the luminosity, contributing between 60% in the nuclear and bulge regions and 90% in the less active, interarm regions. Throughout the galaxy, the underlying continuum emission from the small grains is always a smaller contribution in the total MIR wavelength regime, peaking in the nuclear and bulge components. The implications of using broad-band filters only to characterize the mid-infrared emission of galaxies, a commonly used ISOCAM observation mode, are discussed. We present the first quantitative analysis of new H-alpha and 6cm VLA+Effelsberg radio continuum maps of M83. The distribution of the MIR emission is compared with that of the CO, HI, R band, H-alpha and 6cm radio. A striking correlation is found between the intensities in the two mid-infrared filter bands and the 6cm radio continuum. To explain the tight mid-infrared-radio correlation we propose the anchoring of magnetic field lines in the photoionized shells of gas clouds.Comment: 22 pages, 15 figures. Accepted for publication in A&

Variations of the Mid-IR Aromatic Features Inside and Among Galaxies

We present the results of a systematic study of mid-IR spectra of Galactic regions, Magellanic HII regions, and galaxies of various types (dwarf, spiral, starburst), observed by the satellites ISO and Spitzer. We study the relative variations of the 6.2, 7.7, 8.6 and 11.3 micron features inside spatially resolved objects (such as M82, M51, 30 Doradus, M17 and the Orion Bar), as well as among 90 integrated spectra of 50 objects. Our main results are that the 6.2, 7.7 and 8.6 micron bands are essentially tied together, while the ratios between these bands and the 11.3 micron band varies by one order of magnitude. This implies that the properties of the PAHs are remarkably universal throughout our sample, and that the relative variations of the band ratios are mainly controled by the fraction of ionized PAHs. In particular, we show that we can rule out both the modification of the PAH size distribution, and the mid-infrared extinction, as an explanation of these variations. Using a few well-studied Galactic regions (including the spectral image of the Orion Bar), we give an empirical relation between the I(6.2)/I(11.3) ratio and the ionization/recombination ratio G0/ne.Tgas^0.5, therefore providing a useful quantitative diagnostic tool of the physical conditions in the regions where the PAH emission originates. Finally, we discuss the physical interpretation of the I(6.2)/I(11.3) ratio, on galactic size scales.Comment: Accepted by the ApJ, 67 pages, 70 figure

Putting research into practice: An exploration of Sheffield iSchool approaches to connecting research with practice

The relationship between research and practice in the work of members of the University of Sheffield's Information School (iSchool) was examined through a mixed-methods study carried out in two stages. Two focus groups with doctoral students and faculty members explored motivations for undertaking research, views about the impact of research, and the role of social media in its dissemination. Personal enjoyment and pursuit of knowledge for its own sake emerged as strong motivators but were also linked with expressing professional identity and contributing something useful to practice in the field. Differing stakeholder definitions of research impact were perceived as problematic, and multiple channels of communication were advocated, including judicious use of professional and social networks. A content analysis of journal articles written by iSchool faculty collected qualitative and quantitative data on the subject matter, methodology, references, and other dimensions of published output, including statements relating the research to practice. Published outputs highlighted diversity in the methods used, demonstrated collaboration with practitioners in conducting and communicating research, and identified five distinct ways of connecting research with practice. The study concludes with ten recommendations for strengthening the research-practice relationship in library and information studies. © 2013 The Board of Trustees, University of Illinois

Host cell-intrinsic innate immune recognition of SARS-CoV-2

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) emerged at the end of 2019 and caused the pandemic of coronavirus disease 2019 (COVID-19). Basic and clinical investigations indicate that severe forms of COVID-19 are due in part to dysregulated immune responses to virus infection. The innate immune system is the first line of host defense against most virus infections, with pathogen recognition receptors detecting SARS-CoV-2 RNA and protein components and initiating pro-inflammatory and antiviral responses. Notwithstanding this response, SARS-CoV-2 proteins evade, inhibit, and skew innate immune signaling early in infection. In this review, we highlight the components of cell-based recognition of SARS-CoV-2 infection and the mechanisms employed by the virus to modulate these innate immune host defense pathways

The Decomposition Theorem For Two-Dimensional Shifts Of Finite Type

A one-dimensional shift of finite type can be described as the collection of bi-infinite walks along an edge graph. The Decomposition Theorem states that every conjugacy between two shifts of finite type can be broken down into a finite sequence of splittings and amalgamations of their edge graphs. When dealing with two-dimensional shifts of finite type, the appropriate edge graph description is not as clear; we turn to Nasu\u27s notion of a textile system for such a description and show that all two-dimensional shifts of finite type can be so described. We then define textile splittings and amalgamations and prove that every conjugacy between two-dimensional shifts of finite type can be broken down into a finite sequence of textile splittings, textile amalgamations, and a third operation called an inversion

Putting The Pieces Together: Understanding Robinson’s Nonperiodic Tilings

A discussion of Robinson\u27s nonperiodic tilings and nonperiodic tilings with nonsquare tiles (Penrose and pinwheel)

Projectional Entropy In Higher Dimensional Shifts Of Finite Type

Any higher dimensional shift space (X, ℤᵈ) contains many lower dimensional shift spaces obtained by projection onto r-dimensional sublattices L of ℤᵈ where r \u3c d. We show here that any projectional entropy is bounded below by the ℤᵈ entropy and, in the case of certain shifts of finite type satisfying a mixing condition, equality is achieved if and only if the shift of finite type is the infinite product of a lower dimensional projection

Renewal Systems, Sharp-Eyed Snakes, And Shifts Of Finite Type

Johnson and Madden look at collections of bi-infinite strings of symbols that occur in several different areas of mathematics and ask whether these collections are the same in some sense. A dynamical systems property called entropy can be used to show that the shifts of finite type are not all conjugate to uniquely decipherable renewal systems