Minimal two-sphere model of the generation of fluid flow at low Reynolds numbers

Locomotion and generation of flow at low Reynolds number are subject to severe limitations due to the irrelevance of inertia: the "scallop theorem" requires that the system have at least two degrees of freedom, which move in non-reciprocal fashion, i.e. breaking time-reversal symmetry. We show here that a minimal model consisting of just two spheres driven by harmonic potentials is capable of generating flow. In this pump system the two degrees of freedom are the mean and relative positions of the two spheres. We have performed and compared analytical predictions, numerical simulation and experiments, showing that a time-reversible drive is sufficient to induce flow.Comment: 5 pages, 3 figures, revised version, corrected typo

All Sky Camera, LIDAR and Electric Field Meter: auxiliary instruments for the ASTRI SST-2M prototype

ASTRI SST-2M is the end-to-end prototype telescope of the Italian National Institute of Astro- physics, INAF, designed to investigate the 10-100 TeV band in the framework of the Cherenkov Telescope Array, CTA. The ASTRI SST-2M telescope has been installed in Italy in September 2014, at the INAF ob- serving station located at Serra La Nave on Mount Etna. The telescope is foreseen to be completed and fully operative in spring 2015 including auxiliary instrumentation needed to support both operations and data anal- ysis. In this contribution we present the current status of a sub-set of the auxiliary instruments that are being used at the Serra La Nave site, namely an All Sky Camera, an Electric Field Meter and a Raman Lidar devoted, together with further instrumentation, to the monitoring of the atmospheric and environmental conditions. The data analysis techniques under development for these instruments could be applied at the CTA sites, where similar auxiliary instrumentation will be installed.Comment: Proceedings of the 2nd AtmoHEAD Conference, Padova (Italy) May 19-21, 201

From “sliding” to “winding” filaments theory: A narrative review of mechanisms behind skeletal muscle contraction

The physiological mechanisms behind muscle contraction are a main concept in sport medicine and rehabilitation. The sarcomere is the functional unit of skeletal muscle and several proteins definite its complex structure. The most common theory to explain muscle contraction was proposed in the last 50’s and has become widely popular and accepted: the “sliding filaments” theory. Even if this hypothesis was able to justify some form of muscle contraction, other processes are not fully described by it. Eccentric contraction and some phenomena, like the “force enhancement during stretch” concept described in the 2002, are not explicable according to the sliding filament theory. Therefore, several hypotheses have been suggested over the years, such as the “popping sarcomeres” theory and the “winding filament” theory. Some other proteins, like titin, have gained a main role in the physiology of the sarcomere and should be relevant to explain mechanisms of eccentric contraction, where the sarcomere generates highest level of tension while it is lengthening. The aim of this review is to summarize the physiological theories of muscle contraction and to define concepts applicable in sport medicine and in rehabilitation areas

Two-dimensional topological quantum walks in the momentum space of structured light

Quantum walks are powerful tools for quantum applications and for designing topological systems. Although they are simulated in a variety of platforms, genuine two-dimensional realizations are still challenging. Here we present an innovative approach to the photonic simulation of a quantum walk in two dimensions, where walker positions are encoded in the transverse wavevector components of a single light beam. The desired dynamics is obtained by means of a sequence of liquid-crystal devices, which apply polarization-dependent transverse "kicks" to the photons in the beam. We engineer our quantum walk so that it realizes a periodically-driven Chern insulator, and we probe its topological features by detecting the anomalous displacement of the photonic wavepacket under the effect of a constant force. Our compact, versatile platform offers exciting prospects for the photonic simulation of two-dimensional quantum dynamics and topological systems.Comment: Published version of the manuscrip

Energy flows and greenhouses gases of EU (European Union) national breads using an LCA (Life Cycle Assessment) approach

Abstract Bread represents a staple food in many parts of the world including Europe. Depending on the region of origin and the respective cultural heritage bread is made with different ingredients and is consumed in various forms. This work consists of an environmental sustainability assessment of 21 different types of bread, representing a wide spectrum of typologies of such food consumed across the European Union, via a Life Cycle Assessment approach. The embedded energy and equivalent greenhouse gas emissions of each type of bread were estimated, from cradle to bakery gate, by considering a mass, a nutritional value and a price based functional unit. Overall, the results have highlighted the variability of the embedded energy and the equivalent GHG (greenhouse gas) emissions associated to the consumption of the 21 kinds of bread rooted in the cultural environment of 21 EU countries. When considering a functional unit of 1 kg of bread, the Cumulative Energy Demand results range from 9 MJ/kg to 32.9 MJ/kg. The Global Warming Potential indicator has a minimum value of 0.5 kgCO 2eq /kg and a maximum of 6.6 kgCO 2eq /kg. For a functional unit amounting to a 100 kcal provided by the consumption of bread, the Cumulative Energy Demand results vary from 0.33 MJ/100 kcal to 0.93 MJ/100 kcal whilst the Global Warming Potential indicator varies from 0.019 kgCO 2eq /100 kcal to 0.135 kgCO 2eq /100 kcal. For a functional unit amounting to the quantity of bread purchased with 1€ (weighted according to the purchasing price of each nation in the European Union), the Cumulative Energy Demand results vary from 1.197 MJ/€ to 3.708 MJ/€ whilst the Global Warming Potential indicator varies from 0.15 kgCO2 eq /€ to 0.376 kgCO2 eq /€. The study has pinpointed the importance of evaluating food, in terms of environmental sustainability, with more than one type of functional unit in order to account not only for the bread's nutritional purposes but also the need to satisfy social, cultural, hedonistic and other qualitative functions. Specifically, when using a mass based functional unit, the less impactful results involve bread types with simple recipes, based essentially on flour, yeast and water. By assessing the breads with an energy based functional unit, bread types which also contain vegetable oils and small amounts of animal based ingredients result as more carbon and energy friendly. The use of a price based functional unit indicates that the higher priced bread types, manufactured with more expensive ingredients that are produced in an environmentally efficient manner, are the more sustainable ones. Overall, for many types of bread, the energy consumption during the production phase, in particular the baking process, represents a hot spot and is dependent on the size and shape of the bread. Furthermore, the efficiency of ingredient production (in terms of material and energy use and in terms of the respective yields of each nation in the European Union), such as that of milk and flour, also influences the sustainability of the bread types

Factors controlling natural subsidence in the Po Plain

Understanding the causes and mechanisms of land subsidence is crucial, especially in densely populated coastal plains. In this work, we calculated subsidence rates (SR) in the Po coastal plain, averaged over the last 5.6 and 120 kyr, providing information about land movements on intermediate (103–105 years) time scales. The calculation of SR relied upon core-based correlation of two lagoon horizons over tens of km. Subsidence in the last 120 kyr appears to be controlled mainly by the location of buried tectonic structures, which in turn controlled sedimentation rates and location of highly compressible depositional facies. Numerical modelling shows that subsidence in the last 5.6 kyr is mainly due to compaction of the Late Pleistocene and Holocene deposits (uppermost 30 m)

New tools for old questions: studying vocal communication in the Zebra Finch (Taeniopygia guttata).

The Adult Zebra finches (Taeniopygia guttata) have a crystallised song and different types of calls. However, the exact number of the calls and their function is not completely understood. The pattern of calls might be associated with a specific context and with the kind of relationships between two interacting birds. The aim of this project is: to test the correlation between an experimentally controlled context and the pattern of the calls-songs elicited. The acoustic signals produced by the same pairs of Zebra finches exposed to three different conditions were recorded. Each pair of birds was first kept in a small sound box, then two couples were placed together in a larger aviary and finally nest material was added. The birds were equipped with a miniaturised microphones tied on their back, in order to ascertain the identity of the bird emitting the sound. Video recording was used to correlate the birds’ behaviour with vocalizations. The males were implanted with an electrode suitable for Local Field Potential (LFP) recording placed in Nucleus Robustus of Arcopallium (RA). This nucleus is involved in the modulation of the learned features of songs and calls and in perceptual processing. Quantitative analysis of temporal association between individual calls reveals that are used in bidirectional communication: precise patterns of association of calls are established into the pair. The type of relationship existing between two birds, for instance “members of a couple” or “dominance hierarchy between males”, and the environmental context, for example “being in a favourable breeding condition” are likely to be described by patterns of temporal associations of calls combinations. It was possible to describe the change of activity of the RA during songs\calls production through the analysis of the LFP signal. Moreover the LFP showed a repeatable signal after several days, this demonstrate the suitability of this device for studying the development of long processes, for instance song learning