investigation of bearings overloads due to misaligned splined shafts

Abstract Bearings may be subjected to overloads due to shaft unwanted loads, caused, as an example, by tiling moments related to spline coupling misalignment. Misalignment is mainly generated by manufacturing of mounting errors (due to machining tolerances) or by the transmission working conditions. These kind of overload is critical because may reduce both bearing life and system efficiency, moreover it is quite complicated to be evaluated. In this work, the overload generated on bearings supporting a misaligned splined shafts have been investigated by means of a commercial simulation software (Romax Designer). The simulations have been performed considering a standard transmission scheme composed of two shafts connected by a spline coupling and supported by four roller bearings (two for each shaft), mounted in isostatic configuration. The effect of spline coupling teeth microgeometry has been taken into account along with the misalignment angle magnitude and the torque level. In particular, the influence of these parameters on teeth contact pressure has been evaluated, as tilting moment is mainly driven by the contact pressure distribution among engaging teeth and by the position of maximum pressure distribution along teeth in axial direction. Results obtained in this work may be useful to designers, suggesting some basic criteria to reduce the bearings overload, allowing designing more reliable and efficient machines

Caratterizzazione fisiografica, geomorfologica e bionomica della <i>Rias</i> di Santa Teresa di Gallura: Sardegna nord-orientale = Physiographic, geomorphological and bionomic characterization of the Santa Teresa di Gallura <i>Rias</i> (N.E. Sardinia)

An underwater survey in the Rias of S. Teresa di Gallura was made to characterize the benthic environment by integrating three methods: Side Scan Sonar, ROV, SCUBA diving. The main bionomic features at different depths were described and mapped. The presence of Savalia savaglia, a rare Mediterranean species contributed to enhance the environmental value of the study area

Nervous facilitation in cardiodynamic response of exercising athletes to superimposed mental tasks: implications in depressive disorder

Introduction : Motor commands to perform exercise tasks may also induce activation of cardiovascular centres to supply the energy needs of the contracting muscles. Mental stressors per se may also influence cardiovascular homeostasis. We investigated the cardiovascular response of trained runners simultaneously engaged in mental and physical tasks to establish if aerobically trained subjects could develop, differently from untrained ones, nervous facilitation in the brain cardiovascular centre. Methods : Cardiovascular responses of 8 male middle-distance runners (MDR), simultaneously engaged in mental (colour-word interference test) and physical (cycle ergometer exercise) tasks, were compared with those of 8 untrained subjects. Heart rate, cardiac (CI) and stroke indexes were assessed by impedance cardiography while arterial blood pressures were assessed with a brachial sphygmomanometer. Results : Only in MDR simultaneous engagement in mental and physical tasks induced a significant CI increase which was higher (p<0.05) than that obtained on summing CI values from each task separately performed. Conclusion : Aerobic training, when performed together with a mental effort, induced a CI oversupply which allowed a redundant oxygen delivery to satisfy a sudden fuel demand from exercising muscles by utilizing aerobic sources of ATP, thus shifting the anaerobic threshold towards a higher work load. From data of this study it may also be indirectly stated that, in patients with major depressive disorder, the promotion of regular low-intensity exercise together with mental engagement could ameliorate the perceived physical quality of life, thus reducing their heart risk associated with physical stress

Colloidal synthesis and characterization of Bi2S3 nanoparticles for photovoltaic applications

Bismuth sulfide is a promising n-type semiconductor for solar energy conversion. We have explored the colloidal synthesis of Bi2S3 nanocrystals, with the aim of employing them in the fabrication of solution-processable solar cells and to replace toxic heavy metals chalcogenides like PbS or CdS, that are currently employed in such devices. We compare different methods to obtain Bi2S3 colloidal quantum dots, including the use of environmentally benign reactants, through organometallic synthesis. Different sizes and shapes were obtained according to the synthesis parameters and the growth process has been rationalized by comparing the predicted morphology with systematic physical-chemistry characterization of nanocrystals by X-ray diffraction, FT-IR spectroscopy, Transmission Electron Microscopy (TEM)

Charged excitons, Auger recombination and optical gain in CdSe/CdS nanocrystals.

CdSe/CdS colloidal nanocrystals are members of a novel class of light-emitting nanoparticles with remarkable optical properties such as suppressed fluorescence blinking and enhanced emission from multiexciton states. These properties have been linked to the suppression of non-radiative Auger recombination. In this work we employ ultrafast spectroscopy techniques to identify optical signatures of neutral and charged excitonic and multiexcitonic states. We show that Auger recombination of biexcitons is not suppressed, while we observe optical gain and amplified spontaneous emission from multiexciton states and from long-lived charged-exciton states

Active elderly and health-can moderate exercise improve health and wellbeing in older adults? Protocol for a randomized controlled trial

Abstract Background: Aging is marked by a progressive rise in chronic diseases with an impact on social and healthcare costs. Physical activity (PA) may soothe the inconveniences related to chronic diseases, has positive effects on the quality of life and biological rhythms, and can prevent the decline in motor functions and the consequent falls, which are associated with early death and disability in older adults. Methods: We randomized 120 over-65 males and females into groups of similar size and timing and will give each either moderate physical activity or cultural and recreational activities. Being younger than 65 years, inability to participate in physical activity for any medical reason, and involvement in a massive program of physical exercise are the exclusion criteria. The primary outcome measures are quality of life, walking speed, and postural sway. Participants are tested at baseline, post-treatment, and 6-month (24 weeks) and 12-month (48 weeks) follow-ups. Discussion: This study aims at improving the quality of life, wellness, and cognitive functioning in the elderly through a low-cost affordable program of moderate physical activity. Given the growing aging of the world population and the social and economic burden of disability in the elderly, our results might have a major impact on future practices

Structured and shared CT radiological report of gastric cancer: a consensus proposal by the Italian Research Group for Gastric Cancer (GIRCG) and the Italian Society of Medical and Interventional Radiology (SIRM)

Objectives Written radiological report remains the most important means of communication between radiologist and referring medical/surgical doctor, even though CT reports are frequently just descriptive, unclear, and unstructured. The Italian Society of Medical and Interventional Radiology (SIRM) and the Italian Research Group for Gastric Cancer (GIRCG) promoted a critical shared discussion between 10 skilled radiologists and 10 surgical oncologists, by means of multi-round consensus-building Delphi survey, to develop a structured reporting template for CT of GC patients. Methods Twenty-four items were organized according to the broad categories of a structured report as suggested by the European Society of Radiology (clinical referral, technique, findings, conclusion, and advice) and grouped into three "CT report sections" depending on the diagnostic phase of the radiological assessment for the oncologic patient (staging, restaging, and follow-up). Results In the final round, 23 out of 24 items obtained agreement ( >= 8) and consensus ( 0.05). Conclusions The structured report obtained, shared by surgical and medical oncologists and radiologists, allows an appropriate, clearer, and focused CT report essential to high-quality patient care in GC, avoiding the exclusion of key radiological information useful for multidisciplinary decision-making

A chemical survey of exoplanets with ARIEL

Thousands of exoplanets have now been discovered with a huge range of masses, sizes and orbits: from rocky Earth-like planets to large gas giants grazing the surface of their host star. However, the essential nature of these exoplanets remains largely mysterious: there is no known, discernible pattern linking the presence, size, or orbital parameters of a planet to the nature of its parent star. We have little idea whether the chemistry of a planet is linked to its formation environment, or whether the type of host star drives the physics and chemistry of the planet’s birth, and evolution. ARIEL was conceived to observe a large number (~1000) of transiting planets for statistical understanding, including gas giants, Neptunes, super-Earths and Earth-size planets around a range of host star types using transit spectroscopy in the 1.25–7.8 μm spectral range and multiple narrow-band photometry in the optical. ARIEL will focus on warm and hot planets to take advantage of their well-mixed atmospheres which should show minimal condensation and sequestration of high-Z materials compared to their colder Solar System siblings. Said warm and hot atmospheres are expected to be more representative of the planetary bulk composition. Observations of these warm/hot exoplanets, and in particular of their elemental composition (especially C, O, N, S, Si), will allow the understanding of the early stages of planetary and atmospheric formation during the nebular phase and the following few million years. ARIEL will thus provide a representative picture of the chemical nature of the exoplanets and relate this directly to the type and chemical environment of the host star. ARIEL is designed as a dedicated survey mission for combined-light spectroscopy, capable of observing a large and well-defined planet sample within its 4-year mission lifetime. Transit, eclipse and phase-curve spectroscopy methods, whereby the signal from the star and planet are differentiated using knowledge of the planetary ephemerides, allow us to measure atmospheric signals from the planet at levels of 10–100 part per million (ppm) relative to the star and, given the bright nature of targets, also allows more sophisticated techniques, such as eclipse mapping, to give a deeper insight into the nature of the atmosphere. These types of observations require a stable payload and satellite platform with broad, instantaneous wavelength coverage to detect many molecular species, probe the thermal structure, identify clouds and monitor the stellar activity. The wavelength range proposed covers all the expected major atmospheric gases from e.g. H2O, CO2, CH4 NH3, HCN, H2S through to the more exotic metallic compounds, such as TiO, VO, and condensed species. Simulations of ARIEL performance in conducting exoplanet surveys have been performed – using conservative estimates of mission performance and a full model of all significant noise sources in the measurement – using a list of potential ARIEL targets that incorporates the latest available exoplanet statistics. The conclusion at the end of the Phase A study, is that ARIEL – in line with the stated mission objectives – will be able to observe about 1000 exoplanets depending on the details of the adopted survey strategy, thus confirming the feasibility of the main science objectives.Peer reviewedFinal Published versio