Integrating Dynamics and Wear Modelling to Predict Railway Wheel Profile Evolution

The aim of the work described was to predict wheel profile evolution by integrating multi-body dynamics simulations of a wheelset with a wear model. The wear modelling approach is based on a wear index commonly used in rail wear predictions. This assumes wear is proportional to Tγ, where T is tractive force and γ is slip at the wheel/rail interface. Twin disc testing of rail and wheel materials was carried out to generate wear coefficients for use in the model. The modelling code is interfaced with ADAMS/Rail, which produces multi-body dynamics simulations of a railway wheelset and contact conditions at the wheel/rail interface. Simplified theory of rolling contact is used to discretise the contact patches produced by ADAMS/Rail and calculate traction and slip within each. The wear model combines the simplified theory of rolling contact, ADAMS/Rail output and the wear coefficients to predict the wear and hence the change of wheel profile for given track layouts

Morphology of a new blister beetle (Coleoptera, Meloidae) larval type challenges the evolutionary trends of phoresy-related characters in the genus Meloe

The discovery of some specimens of a new first instar larval type in blister beetles, collected in Iran on Anthophora bees, confirms the existence of repetitive and parallel trends in morphological specialization to phoresy in distinct lineages of Meloidae and in particular in the subfamily Meloinae. The new Iranian larva, herein described and illustrated, shows several characters and a peculiar phoretic strategy that closely parallel that of the Meloe subgenus Lampromeloe, with similar modifications of the fronto-clypeal setae into strong lanceolate spines used to pierce the intersegmental membranes of the bees. Both parallel and shared derived evolution of these characters seem possible. The coexistence in this larva of characters in both primitive and derived state is of particular interest in order to analyse the different rates and trends of evolution of phoretic adaptations. A morphological comparison (SEM) of this new meloine larva (incertae sedis), tentatively assignable to Meloe, with the M. (Lampromeloe) larvae is carried out in order to discuss the evolutionary implications of its placement in Lampromeloe, and the relative characters that would support it, vs other possible alternative scenarios

Mathematical Model of Easter Island Society Collapse

In this paper we consider a mathematical model for the evolution and collapse of the Easter Island society, starting from the fifth century until the last period of the society collapse (fifteen century). Based on historical reports, the available primary sources consisted almost exclusively on the trees. We describe the inhabitants and the resources as an isolated system and both considered as dynamic variables. A mathematical analysis about why the structure of the Easter Island community collapse is performed. In particular, we analyze the critical values of the fundamental parameters driving the interaction humans-environment and consequently leading to the collapse. The technological parameter, quantifying the exploitation of the resources, is calculated and applied to the case of other extinguished civilization (Cop\'an Maya) confirming, with a sufficiently precise estimation, the consistency of the adopted model.Comment: 9 pages, 1 figure, final version published on EuroPhysics Letter

The low-frequency radio catalog of flat spectrum sources

A well known property of the gamma-ray sources detected by COS-B in the 1970s, by the Compton Gamma-ray Observatory in the 1990s and recently by the Fermi observations is the presence of radio counterparts, in particular for those associated to extragalactic objects. This observational evidence is the basis of the radio-gamma-ray connection established for the class of active galactic nuclei known as blazars. In particular, the main spectral property of the radio counterparts associated with gamma-ray blazars is that they show a flat spectrum in the GHz frequency range. Our recent analysis dedicated to search blazar-like candidates as potential counterparts for the unidentified gamma-ray sources (UGSs) allowed us to extend the radio-gamma-ray connection in the MHz regime. We also showed that below 1 GHz blazars maintain flat radio spectra. Thus on the basis of these new results, we assembled a low-frequency radio catalog of flat spectrum sources built by combining the radio observations of the Westerbork Northern Sky Survey (WENSS) and of the Westerbork in the southern hemisphere (WISH) catalog with those of the NRAO Very Large Array Sky survey (NVSS). This could be used in the future to search for new, unknown blazar-like counterparts of the gamma-ray sources. First we found NVSS counterparts of WSRT radio sources and then we selected flat spectrum radio sources according to a new spectral criterion specifically defined for radio observations performed below 1 GHz. We also described the main properties of the catalog listing 28358 radio sources and their logN-logS distributions. Finally a comparison with with the Green Bank 6-cm radio source catalog has been performed to investigate the spectral shape of the low-frequency flat spectrum radio sources at higher frequencies.Comment: 10 pages, 10 figures, 1 table, ApJS published in 2014 (pre-proof version uploaded

Optical spectroscopic observations of blazars and gamma-ray blazar candidates in the Sloan Digital Sky Survey Data Release Nine

We present an analysis of the optical spectra available in the Sloan Digital Sky survey data release nine (SDSS DR9) for the blazars listed in the ROMA-BZCAT and for the gamma-ray blazar candidates selected according to their IR colors. First, we adopt a statistical approach based on MonteCarlo simulations to find the optical counterparts of the blazarslisted in the ROMA-BZCAT catalog. Then we crossmatched the SDSS spectroscopic catalog with our selected samples of blazars and gamma-ray blazar candidates searching for those with optical spectra available to classify our blazar-like sources and, whenever possible, to confirm their redshifts. Our main objectives are determining the classification of uncertain blazars listed in the ROMA-BZCAT and discovering new gamma-ray blazars. For the ROMA-BZCAT sources we investigated a sample of 84 blazars confirming the classification for 20 of them and obtaining 18 new redshift estimates. For the gamma-ray blazars, indicated as potential counterparts of unassociated Fermi sources or with uncertain nature, we established the blazar-like nature of 8 out the 27 sources analyzed and confirmed 14 classifications.Comment: 7 pages, 2 figures, 4 tables, AJ published in 2014 (pre-proof version

Early carotid atherosclerosis and cardiac diastolic abnormalities in hypertensive subjects

Despite the fact that it is known that hypertension may be associated to early atherosclerosis manifestations, few data are to date available on the relationship between early carotid abnormalities and left ventricular diastolic dysfunction. To address this issue, 142 hypertensive patients (64 females and 78 males) younger than 55 years, at the first diagnosis of mild-to-moderate essential hypertension (WHO/ISH criteria), were selected from a database consisting of 3541 subjects referred to ultrasound cardiovascular laboratory in the last 5 years. Carotid intima-media thickness (IMT) was detected by high-resolution vascular ultrasound and left ventricular structure and function by the use of Doppler echocardiography. According to carotid IMT values, all patients were subgrouped into two groups consisting of 89 (62.6%) pts with IMT > or = 1 mm (A) and 53 (37.4%) pts with IMT < 1 mm (B). Our results show that isovolumic relaxation time (IVRT), deceleration time of E velocity (EDT) and left ventricular relative wall thickness (LV-RWT) were significantly (P < 0.05) higher in group A (IVRT 112 +/- 8.9 ms; EDT 288 +/- 21.8 ms; LV-RWT 0.40 +/- 0.08) than in group B (IVRT 92.3 +/- 4.6 ms; EDT 203.3 +/- 27.01 ms; LV- RWT 0.37 +/- 0.06). Moreover, the prevalence of left ventricular hypertrophy (LVH) was significantly (P < 0.01) higher in group A (30/89; 33.7%) than in group B (8/53; 15%). A positive correlation (P < 0.001) between IMT, EDT and IVRT was found only in hypertensives without LVH. These results are consistent with the indication that IMT evaluation has to be recommended both in hypertensive patients with LVH and in those without LVH, but with left ventricular diastolic dysfunction. This approach might improve the prognostic stratification of hypertensive subjects and it might be suitable to recognize the subset of patients at a higher risk of cardiovascular disease or events early

Investigating post-processing impact on fatigue performance of LPBF Ti6Al4V with heat treatment, high pressure heat treatment, and dry electropolishing strategies

This study investigates the impact of post-processing techniques on the fatigue behaviour of specimens in Ti6Al4V made by laser powder bed fusion (LPBF) for relevant applications, such as motorsport. Despite the LPBF advantages in terms of complex design and weight reduction, challenges such as reduced fatigue performance persist. Therefore, the application of post-processing treatments can play a critical role. In addition to traditional sandblasting (SB), three post-processing conditions were investigated to enhance mechanical properties under quasi-static and fatigue loading conditions: heat treatment (HT) and the innovative High Pressure Heat Treatment (HPHT) along with dry electropolishing (EP) treatment. The results indicate that both the HT and HPHT treatments produced a macrostructure with equiaxial grains composed of fine α + β lamellae. Mechanical analyses demonstrated that the HPHT-SB-EP condition exhibits properties comparable to those of forged Ti6Al4V used in the automotive field, with a good balance between strength and ductility. The EP treatment effectively reduced surface roughness and inherent surface irregularities caused by the LPBF process. The best fatigue results were achieved with the HPHT-SB-EP condition, despite data scattering. An increase in fatigue resistance was observed by using SB at a higher pressure

Exploring the canthariphilous species of the Tolfa Mountains (Latium, Central Italy): taxonomic diversity, phenology, and putative sources of cantharidin

Canthariphilous species are those arthropods attracted to cantharidin (CTD), a defensive compound produced by two beetle families (Meloidae and Oedemeridae). Although several species are known to be attracted to CTD, canthariphily was recently discovered in new species, suggesting that the list of canthariphilous species is still far from being complete. A systematic sampling focused to detect canthariphilous species has never been performed in Italy. The present research provides a list of seven canthariphilous species (Diptera: Ceratopogonidae, Anthomyiidae; Coleoptera: Anthicidae) from the Tolfa Mountains (Latium, Central Italy) resulting from a one-year sampling with CTD-baited and control traps. New species (Atrichopogon atriscapulus and A. tolfensis) were found to be attracted to CTD, and other species, already known as canthariphilous, were recorded for the first time in the Italian fauna (A. atriscapulus and A. meloesugans). A new scenario about the ecological significance of CTD in the sexual selection of canthariphilous species was speculated in A. meloesugans. Finally, a list of CTD-producing species occurring in the sample area was provided to suggest putative natural CTD sources

Rosetta Philae SD2 Drill System and Its Operation on 67p/Churyumov-Gerasimenko

Rosetta Lander Philae approached and landed on the surface of comet 67P/Churyumov-Gerasimenko on the 12th of November 2014. Among the specific Subsystems and instruments carried on board, the Drill, Sample and Distribution System (SD2) which was in charge to drill the surface of the comet, take comet’s soil sample(s) and distribute the collected sample to different instruments. Rosetta has been launched in 2004 and, after very complex orbital trajectories and specific commissioning events, met and carried out a rendezvous with the comet; after ten years cruise and three subsequent touch down, Philae eventually landed on the comet surface. On the 14th of November 2014 SD2 was decided to be operated on the comet. This paper provides an overview of the achievements during the operational phase on the comet and will summarize the basic characteristics and peculiarities of SD2 drill system