In this study, we evaluated the elastic and mechanical properties of a new type of cement-stabilised material made with steel slag, varying the content of cement and steel slag. To study the elastic ...properties of these mixes, we measured their density, compressive strength and ultrasound pulse velocity at curing ages of 7, 28 and 90 days. The aggregate type and curing age greatly affected the elastic properties and varied much depending on the cement content. The Poisson's ratio chosen in analyses had little influence on the dynamic modulus. Various expressions given by building codes were used to predict the elastic properties of the mixtures. These codes generated very different values of the static modulus of elasticity, making most of them unsuitable for predicting the elastic properties of cement-stabilised materials. Using our experimental data, we provide the best combination of existing equations to predict elastic properties, and we conclude that measuring the ultrasound pulse velocity is a suitable way to predict the mechanic and elastic properties of cement-stabilised materials.
Seven different concrete mixtures were prepared to estimate the possibility of using pervious concrete for light traffic urban areas. The total porosity, density, compressive strength, flexural ...strength, abrasion resistance, and traffic noise absorption capacity were tested for all the concrete specimens. The first mixtures corresponded to a standard dense concrete mixture (M1), while the other mixtures were pervious concrete mixtures involving two different types of aggregates (dolomite and steel slag) and different proportions of aggregate fractions. The total porosity, density, compressive strength, flexural strength, abrasion resistance, and traffic noise absorption capacity were tested in the case of all concrete specimens. The total porosity increased, whereas the compressive and flexural strength decreased simultaneously with an increase in the share of coarse aggregate fractions. The abrasion resistance and acoustic characteristics improved if only a fraction of the aggregate was used in pervious concrete preparation.
Maintenance-mode feedback from low-accretion-rate active galactic nuclei (AGNs), manifesting itself observationally through radio-loudness, is invoked in all cosmological galaxy formation models as a ...mechanism that prevents excessive star formation in massive galaxies (M* 3 × 1010 M ). We demonstrate that at a fixed mass the incidence of radio-loud (RL) AGNs (L > 1023 W Hz−1) identified in the Faint Images of the Radio Sky at Twenty centimeter and NRAO Very Large Array Sky Survey radio surveys among a large sample of quiescent (non-star-forming) galaxies selected from the Sloan Digital Sky Survey is much higher in geometrically round galaxies than in geometrically flat, disk-like galaxies. As found previously, the RL AGN fraction increases steeply with stellar velocity dispersion * and stellar mass, but even at a fixed velocity dispersion of 200-250 km s−1 this fraction increases from 0.3% for flat galaxies (projected axis ratio of q < 0.4) to 5% for round galaxies (q > 0.8). We rule out the hypothesis that this strong trend is due to projection effects in the measured velocity dispersion. The large fraction of RL AGNs in massive, round galaxies is consistent with the hypothesis that such AGNs deposit energy into their hot gaseous halos, preventing cooling and star formation. However, the absence of such AGNs in disk-like quiescent galaxies-most of which are not satellites in massive clusters, raises important questions. Is maintenance-mode feedback a generally valid explanation for quiescence? If so, how does that feedback avoid manifesting at least occasionally as an RL galaxy?
Drawing from the LEGA-C data set, we present the spectroscopic view of the stellar population across a large volume- and mass-selected sample of galaxies at large look-back time. We measure the 4000 ...break (Dn4000) and Balmer absorption line strengths (probed by Hδ) from 1019 high-quality spectra of z = 0.6-1.0 galaxies with M* = 2 × 1010M to 3 × 1011M . Our analysis serves as a first illustration of the power of high-resolution, high signal-to-noise ratio continuum spectroscopy at intermediate redshifts as a qualitatively new tool to constrain galaxy formation models. The observed Dn4000-EW(Hδ) distribution of our sample overlaps with the distribution traced by present-day galaxies, but z ∼ 0.8 galaxies populate that locus in a fundamentally different manner. While old galaxies dominate the present-day population at all stellar masses >2 × 1010M , we see a bimodal Dn4000-EW(Hδ) distribution at z ∼ 0.8, implying a bimodal light-weighted age distribution. The light-weighted age depends strongly on stellar mass, with the most massive galaxies >1 × 1011M being almost all older than 2 Gyr. At the same time, we estimate that galaxies in this high-mass range are only ∼3 Gyr younger than their z ∼ 0.1 counterparts, at odds with purely passive evolution given a difference in look-back time of >5 Gyr; younger galaxies must grow to >1011M in the meantime, or small amounts of young stars must keep the light-weighted ages young. Star-forming galaxies at z ∼ 0.8 have stronger Hδ absorption than present-day galaxies with the same Dn4000, implying larger short-term variations in star formation activity.
We present a comparison of the observed, spatially integrated stellar and ionized gas velocity dispersions of ∼1000 massive ( ) galaxies in the Large Early Galaxy Astrophysics Census survey at 0.6 z ...1.0. The high S/N ∼ 20 −1 afforded by 20 hr Very Large Telescope/Visible Multi-Object Spectrograph spectra allows for joint modeling of the stellar continuum and emission lines in all galaxies, spanning the full range of galaxy colors and morphologies. These observed integrated velocity dispersions (denoted as and ) are related to the intrinsic velocity dispersions of ionized gas or stars, but also include rotational motions through beam smearing and spectral extraction. We find good average agreement between observed velocity dispersions, with . This result does not depend strongly on stellar population, structural properties, or alignment with respect to the slit. However, in all regimes we find significant scatter between and , with an overall scatter of 0.13 dex of which 0.05 dex is due to observational uncertainties. For an individual galaxy, the scatter between and translates to an additional uncertainty of ∼0.24 dex on dynamical mass derived from , on top of measurement errors and uncertainties from Virial constant or size estimates. We measure the z ∼ 0.8 stellar mass Faber-Jackson relation and demonstrate that emission line widths can be used to measure scaling relations. However, these relations will exhibit increased scatter and slopes that are artificially steepened by selecting on subsets of galaxies with progressively brighter emission lines.
Višestruko rezistentne bakterije, uzročnici hospitalnih infekcija, kao što su Acinetobacter baumannii i Klebsiella pneumoniae, predstavljaju globalni problem 21. stoljeća. Osobito zabrinjava sve ...učestalija pojava otpornosti ovih mikroorganizama na komercijalno dostupne dezinficijense. Cilj našeg istraživanja bio je utvrditi učinkovitost dezinfekcije proizvoda „Sanosil super25“, u odnosu na vodikov peroksid i to na višestruko rezistentne izolate A. baumannii i K. pneumoniae. Ispitane su vrijednosti MTC (maksimalno tolerirajuća koncentracija); MIC (minimalna inhibirajuća koncentracija) i MBC (minimalna baktericidna koncentracija). MTC Sanosila (<1.25 ppm) bila je dvostruko manja u odnosu na vodikov peroksid. MIC-e Sanosila (1.25 ili <1.25 ppm) su bile 4 puta manje u odnosu na vodikov peroksid. MBC koja rezultira izostankom vijabilnih bakterija za Sanosil je bila <1.25 ppm već nakon 5 min kontakta, što je barem 8 puta niža koncentracija u odnosu na vodikov peroksid. Rezultati su pokazali da je Sanosil super25 bio učinkovitiji u sve tri kategorije, u odnosu na vodikov peroksid.
Bacterium Acinetobacter baumannii is a leading cause of hospital infections. Over the last decade, its occurrence in natural environments outside hospital settings has been reported. The aim was to ...examine the survival of A. baumannii in water media exposed to different ranges of oxygen supply in order to predict its behaviour in the environment. The abundance of five A. baumannii isolates was monitored in nutrient-depleted and nutrient-rich water media in aerated, intermediate and anaerobic conditions (oxygen saturation 96, 56 and 0%, respectively). A. baumannii survived in both media in all tested oxygen concentrations for 50 days. In nutrient-rich water survival of A. baumannii was lowest in anaerobic conditions, while in nutrient-depleted water there was no difference in survival regardless of oxygen availability. A. baumannii formed translucent small colony variants as the fast response (after 1 day) and dormant cells as the prolonged response (after 14 days) to anaerobic conditions. Transmission electron microscopy (TEM) images showed the outer membrane of coccobacillus dormant cells was up to four times thicker than in regular cells. Once in the environment, A. baumannii is able to survive regardless of the availability of dissolved oxygen, which represents a serious public health concern.
The paper investigates whether a supportive control environment is associated with the internal audit effectiveness and what characteristics of a control environment are important in this respect. A ...survey was conducted via a questionnaire on 54 mostly large companies in Croatia. Appropriate methods of statistical analysis were used in order to analyse the survey results. According to the research results, in the case of a supportive control environment there is a greater chance that the internal audit will be effective and that its recommendations will be taken into account to a greater extent. In addition, the survey results showed a statistically significant correlation between perceived internal audit effectiveness and a higher level of supportive control environment.
In order to fulfill requirements of sustainable road construction, new materials for pavement construction are investigated with the main goal to preserve natural resources and achieve energy ...savings. One of such sustainable pavement material is pervious concrete as a new solution for low volume pavements. To accommodate required strength and porosity as the measure of appropriate drainage capability, four mixtures of pervious concrete are investigated and results of laboratory tests of compressive and flexural strength and porosity are presented. For defining the optimal pervious concrete mixture in a view of aggregate and financial savings, optimization model is utilized and optimal mixtures defined according to required strength and porosity characteristics. Results of laboratory research showed that comparing single-sized aggregate pervious concrete mixtures, coarse aggregate mixture result in increased porosity but reduced strengths. The optimal share of the coarse aggregate turn to be 40.21%, the share of fine aggregate is 49.79% for achieving required compressive strength of 25 MPa, flexural strength of 4.31 MPa and porosity of 21.66%.
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