Self-Similarity in Random Collision Processes

Kinetics of collision processes with linear mixing rules are investigated analytically. The velocity distribution becomes self-similar in the long time limit and the similarity functions have algebraic or stretched exponential tails. The characteristic exponents are roots of transcendental equations and vary continuously with the mixing parameters. In the presence of conservation laws, the velocity distributions become universal.Comment: 4 pages, 4 figure

Durability parameters of reinforced recycled aggregate concrete: Case study

Recycled concrete aggregate (RA) from pavement demolition was used to make concrete. Ten concrete mixtures with different replacement percentages of RA (coarse and fine) were made. The corrosion rate of steel and the electrical resistivity of concrete were determined on reinforced concrete specimens subjected to wetting-drying cycles (3.5% solution of NaCl). Corrosion rate was determined using the electrochemical technique of linear polarization resistance, while the electrical resistivity was measured by electrochemical impedance spectroscopy. The results show that the use of RA introduces more interfaces in concrete, which accelerates the steel corrosion process because the porosity increases and the electrical resistivity decreases. However, steel corrosion and the electrical resistivity in concrete are not significantly influenced by replacing a maximum 30% of coarse aggregate or 20% of fine aggregate with RA.Peer ReviewedPreprin

Discovery of an extended G giant chromosphere in the 2019 eclipse of γ Per

The November 2019 eclipse of γ Per was a rare opportunity to seek evidence for a chromosphere of the G8 giant, hitherto suspected but not detected. Twenty-nine years after the only other observed eclipse, we aim to find chromospheric absorption in the strong Caa II H&K lines, and to determine its column densities and scale height. Using the Telescopio Internacional de Guanajuato Rob\uf3tico-Espectrosc\uf3pico (TIGRE) in Guanajuato (central Mexico) before, during and after the 8 days of total eclipse, we obtained good S/N spectra of the G8 giant alone and composite spectra of the partial phases, near eclipse and far from eclipse. In the near UV of the Caa II H&K and H\ucfμ lines, the G giant spectrum that was adequately scaled was subtracted from the composite spectra in partial phases, near and far from eclipse, to obtain the A3 companion spectra with and without traces of chromospheric absorption. In addition, we used PHOENIX full non-local thermodynamic equilibrium model atmospheres on the blue A star spectrum, iSpec spectral analysis of the red G giant spectrum, and evolution tracks to study both components of γ Per. For the first time, we present evidence for this rare type of a not very extended G giant chromosphere, reaching out about half of an A-star radius (~1.5 Gm) with a scale height of only 0.17 Gm. By its location in the Hertzsprung-Russell diagram, the γ Per G8 giant is very close to the onset of more extended chromospheres. Furthermore, we show that this giant has a rather inactive chromosphere, and a recent 5 ksec XMM pointing reveals only a very faint, low-energy corona. While the γ Per primary has a mass of ~3.6 M\u27, and its A3 companion has one of ~2.4 M\u27, the latter is too cool (8400 \ub1 300 K), which is too evolved on the main sequence to be the same age as the primary. The high eccentricity of the 5329.08 days long-period orbit may therefore be reminiscent of a rare capture event. Using the eclipse method, we resolve a pivotal case of a G giant chromosphere, which seems to represent a low-gravity analogue of the inactive Sun. A systematic change of giant chromospheric extent by Hertzsprung-Russell diagram position is confirmed. Compared to the solar chromosphere, the density scale height increases with gravity by \uc9\ua1\u271.5

Strength, elastic properties and fiber–matrix interaction mechanism in geopolymer composites

The current geopolymers have limited mechanical strength against the effect of tension, which makes them susceptible to brittle failure. However, owing to their potential as a sustainable construction material, there is growing interest in improving the poor mechanical properties of geopolymers. This study experimentally investigated crucial properties of polypropylene-fiberreinforced fly ash-based geopolymer composites. The effects of polypropylene fibers (PPF) addition (0.5%, 1.0% and 1.5% by volume) on the mechanical properties of the geopolymer composites were investigated with respect to compressive and flexural strength, deformation behavior of Young’s and shear moduli, and resilience capacity. In addition, scanning electron microscopy was performed to establish the morphology of the geopolymeric matrix and the fiber–matrix interfacial interaction. The addition of PPF significantly increased the flexural strength: compared with the control, at 7 days it was 27% greater for the 0.5% PPF composite and 65% greater for the 1.0% PPF composite. By 14 days it was 31% and 61% greater, respectively. By contrast, the 1.5% PPF composite had lower strength parameters compared with the control because the fiber dispersion increased the porosity. Similar trends were seen for resilience. The SEM observations showed the dispersion of the fibers and helped elucidate the fiber–matrix interaction mechanismPeer ReviewedPostprint (published version

Total quality management practices, competitive strategies and financial performance: the case of the Palestinian industrial SMEs

"This is an Accepted Manuscript of an article published by Taylor & Francis in Total Quality Management and Business Excellence on 19 Aug 2013, available online: http://wwww.tandfonline.com/10.1080/14783363.2013.824714."The purpose of this paper is to examine the relationship between Total Quality Management (TQM) practices, competitive strategies - cost leadership and differentiation- and firm performance in the Palestinian economy. Within this study total quality management has been conceptualized as soft and hard practices, in congruence with the literature. An empirical analysis based upon an extensive validation process was applied to refine TQM, competitive strategies and financial performance scales. Data were collected through surveying 202 in Palestinian industrial small and medium enterprises (SMEs). Structural Equation Modeling was carried out to test the anticipated relationships. Results derived from this study show that TQM practices have indirect, positive and significant relationship with financial performance through competitive strategies. In addition, a direct, positive and significant relationship between competitive strategies and financial performance was observed. Results derived from this study might help managers to implement TQM practices in order to effectively allocate resources and improve financial performance

The Atapuerca sites and the Ibeas hominids

The Atapuerca railway Trench and Ibeas sites near Burgos, Spain, are cave fillings that include a series of deposits ranging from below the Matuyama/Bruhnes reversal up to the end of Middle Pleistocene. The lowest fossil-bearing bed in the Trench contains an assemblage of large and small Mammals including Mimomys savini, Pitymys gregaloides, Pliomys episcopalis, Crocuta crocuta, Dama sp. and Megacerini; the uppermost assemblage includes Canis lupus, Lynx spelaea, Panthera (Leo) fossilis, Felis sylvestris, Equus caballus steinheimensis, E.c. germanicus, Pitymys subtenaneus, Microtus arvalis agrestis, Pliomys lenki, and also Panthera toscana, Dicerorhinus bemitoechus, Bison schoetensacki, which are equally present in the lowest level. The biostratigraphic correlation and dates of the sites are briefly discussed, as are the paleoclimatic interpretation of the Trench sequences. Stone artifacts are found in several layers; the earliest occurrences correspond to the upper beds containing Mimomys savini. A set of preserved human occupation floors has been excavated in the top fossil-bearing beds. The stone-tool assemblages of the upper levels are of upper-medial Acheulean to Charentian tradition. The rich bone breccia SH, in the Cueva Mayor-Cueva del Silo, Ibeas de Juarros, is a derived deposit, due to a mud flow that dispersed and carried the skeletons of many carnivores and humans. The taxa represented are: Vrsus deningeri (largely dominant), Panthera (Leo) fossilis, Vulpes vulpes, Homo sapiens var. Several traits of both mandibular and cranial remains are summarized. Preliminary attempts at dating suggest that the Ibeas fossil man is older than the Last Interglacial, or oxygen-isotope stage 5

Role of age and comorbidities in mortality of patients with infective endocarditis

Purpose: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. Methods: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015. Patients were stratified into three age groups:<65 years, 65 to 80 years, and = 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. Results: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 = 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients =80 years who underwent surgery were significantly lower compared with other age groups (14.3%, 65 years; 20.5%, 65-79 years; 31.3%, =80 years). In-hospital mortality was lower in the <65-year group (20.3%, <65 years;30.1%, 65-79 years;34.7%, =80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%, =80 years; p = 0.003).Independent predictors of mortality were age = 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI = 3 (HR:1.62; 95% CI:1.39–1.88), and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared, the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. Conclusion: There were no differences in the clinical presentation of IE between the groups. Age = 80 years, high comorbidity (measured by CCI), and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group