A Compact Atom Interferometer for Future Space Missions

Atom interferometry represents a quantum leap in the technology for the ultra-precise monitoring of accelerations and rotations and, therefore, for the science that relies on these quantities. These sensors evolved from a new kind of optics based on matter-waves rather than light-waves and might result in an advancement of the fundamental detection limits by several orders of magnitude. This paper describes the current status of the Space Atom Interferometer project (SAI), funded by the European Space Agency. In a multi-pronged approach, SAI aims to investigate both experimentally and theoretically the various aspects of placing atom interferometers in space: the equipment needs, the realistically expected performance limits and potential scientific applications in a micro-gravity environment considering all aspects of quantum, relativistic and metrological sciences. A drop-tower compatible atom interferometry acceleration sensor prototype has been designed, and the manufacturing of its subsystems has been started. A compact modular laser system for cooling and trapping rubidium atoms has been assembled. A compact Raman laser module, featuring outstandingly low phase noise, has been realized. Possible schemes to implement coherent atomic sources in the atom interferometer have been experimentally demonstrated.     

In vitro safety toxicology data for evaluation of gold nanoparticles-chronic cytotoxicity, genotoxicity and uptake

Safety and toxic effects of nanoparticles are still largely unexplored due to the multiple aspects that influence their behaviour toward biological systems. Here, we focus the attention on 12 nm spherical gold nanoparticle coated or not with hyaluronic acid compared to its precursor counterpart salt. Results ranging from the effects of a 10-days exposure in an in vitro model with BALB/c 3T3 fibroblast cells show how 12 nm spherical gold nanoparticles are internalized from 3T3 cells by endo-lysosomal pathway by an indirect measurement technique; and how gold nanoparticles, though not being a severe cytotoxicant, induce DNA damage probably through an indirect mechanism due to oxidative stress. While coating them with hyaluronic acid reduces gold nanoparticles cytotoxicity and slows their cell internalization. These results will be of great interest to medicine, since they indicate that gold nanoparticles (with or without coating) are suitable for therapeutic applications due to their tunable cell uptake and low toxicity.     

Thermal conductance at millikelvin temperatures of woven ribbon cable with phosphor-bronze clad superconducting wires

Woven Nomex® ribbon cables made up with superconducting niobium-titanium wire are used at millikelvin temperatures in many large cryogenic instruments. It is important to know how much heat in transmitted down such cables. However, the conductivity of the materials used is not well known. Another problem is that the wires are normally clad with alloys which exhibit some magnetism. This is a potential problem for instruments employing superconducting detectors. A safe non-magnetic alternative to the usual materials is phosphor-bronze clad niobium-titanium wiring. However, there is little experience with such wires. We have therefore measured the conductance of a ribbon cable made up with these wires. The measured values are in good agreement with our predictions, suggesting that the values we have used to model the cable are sufficiently accurate, and could therefore be used to predict the performance of ribbon cables using other cladding materials, so long as the conductivity of the cladding is reasonably well known. As part of our analysis, we consider the likely variation in thermal conductivity values for C51000 phosphor bronze caused by legitimate variations in composition.     

Human Powered Centrifuges on the Moon or Mars

Exposure to microgravity leads to “cardiovascular deconditioning” (CVD), because of the fluids shift toward the thorax. CVD is characterised by: 1) a decrease of plasma and interstitial fluid volumes, 2) a relative increase of the erythrocytes mass, 3) a decrease of arterial diastolic pressure, of the stroke volume, of the end-diastolic volume and of the left ventricular mass. CVD can be expected to occur also in astronauts living permanently on Lunar or Martian bases, since on these celestial bodies the acceleration of gravity is about 0.165 and 0.379 the Earth value. In these conditions, cycling on appropriately constructed tracks may be useful to recreate artificial gravity and to allow the astronauts to perform physical exercise. Indeed, a cyclist riding a bicycle on a circular track, generates an outward acceleration vector which depends on the radius of the track and on the ground speed. The vectorial sum of this last and the acceleration of gravity acts in the head to feet direction, thus increasing the effects of gravity on the cardiovascular system. We propose to construct on a Lunar or Martian base a circular “track tunnel” with a radius of 25 m. We show here that when cycling on this track tunnel at speeds between 10 to 15 m · s^???1, astronauts will generate a g vector acting along the head to feet axis ranging from 0.44 to 0.99 of the Earth value. We suggest that the logistics and feasibility of these track-tunnels should be studied in view of their possible implementation.     

Molecular‐Level Switching of Polymer/Nanocrystal Non‐Covalent Interactions and Application in Hybrid Solar Cells

Hybrid composites obtained upon blending conjugated polymers and colloidal semiconductor nanocrystals are regarded as attractive photo­active materials for optoelectronic applications. Here it is demonstrated that tailoring nanocrystal surface chemistry permits to control non‐covalent and electronic interactions between organic and inorganic components. The pending moieties of organic ligands at the nanocrystal surface are shown to not merely confer colloidal stability while hindering charge separation and transport, but drastically impact morphology of hybrid composites during formation from blend solutions. The relevance of this approach to photovoltaic applications is demonstrated for composites based on poly(3‐hexylthiophene) and lead sulfide nanocrystals, considered as inadequate until this report, which enable the fabrication of hybrid solar cells displaying a power conversion efficiency that reaches 3%. By investigating (quasi)steady‐state and time‐resolved photo‐induced processes in the nanocomposites and their constituents, it is ascertained that electron transfer occurs at the hybrid interface yielding long‐lived separated charge carriers, whereas interfacial hole transfer appears hindered. Here a reliable alternative aiming to gain control over macroscopic optoelectronic properties of polymer/nanocrystal composites by mediating their non‐covalent interactions via ligands' pending moieties is provided, thus opening new possibilities towards efficient solution‐processed hybrid solar cells.     

E-learning and the third age

As a result of the general improvement in living conditions in industrialised Western countries, people aged over 60 years usually reach the ‘third age’ in good mental and physical condition. Contemporary society has thus had to endeavour to offer the ‘new old’ not only social services but also pastimes, leisure, social, cultural and educational activities. Among the range of opportunities being made available is that of acquiring skills in the use of information and communication technology (ICT), an area of ever‐increasing prominence. This can be seen not only as an opportunity for individual cultural growth but also the basic condition for conceiving a range of practical network‐based services and applications of great social significance for the elderly population. This article refers to one of these initiatives, developed in Liguria (one of the Italian regions with the oldest population), whose purpose was to train about 600 over‐60s in the use of ICT. What we will analyse here in particular are the results of e‐learning activities offered to a sample of participants and with reference to a segment of the entire training process envisaged by the regional initiative. The specific objectives of the activity were to verify the real possibility of proposing short, online learning modules on the use of Internet for older users; to survey users' attitudes/reactions to e‐learning; and to analyse the follow‐up of distance training activities.     

Purely neural,rule-based diagnostic systems. I. Production rules

This is the first of two articles presenting an approach to rule-based expert systems for diagnostic tasks exploiting a purely neural architecture. Here, we outline the methodological options motivating this approach, and describe a forward and backward chaining mechanism on a system of production rules. This inference engine is furnished with an informative justification module, which exploits the fact that most individual neurons get a precise semantic assignment in terms of the literals appearing in production rules. the control and synchronization functions needed to schedule these processes are carried out by a neural network, too. © 1995 John Wiley & Sons, Inc.     

An Analysis of Error Behavior in the Implementation of 2-D Orthogonal Transformations

The paper analyzes the effect of finite-length arithmetic in the calculation of 2-D linear transformations employed in some picture coding algorithms. Since the condition of zero-error in general direct and reverse transformations leads to results of little practical importance, an analysis is carried out on the statistical properties of error in 2-D linear transformation with given length of arithmetics. Then the important case of discrete cosine transform (DCT) applied to real images is considered in detail. The results of the paper allow a circuit designer to determine the representation accuracy of the one- and two-dimensional coefficients required to satisfy a preassigned reconstruction error on the image.     

Combustion synthesis and mechanical properties of dense NiTi-TiC intermetallic-ceramic composites

Combustion synthesis (SHS) coupled with a quasi-isostatic densification step was employed to produce dense NiTi-TiC composites. The synthesis and characterization of five composites are presented, including ceramic-intermetallic (≥50 pct ceramic) composites and intermetallic-ceramic (≥50 pct intermetallic) composites. Particle size, X-ray diffraction (XRD), and scanning electron microscopy (SEM) analysis was conducted to characterize the microstructure of the composites. Refractory TiC and NiTi intermetallic phases become more stoichiometric and the TiC particle size decreases with increasing intermetallic content. Micro- and nanoindentation and quasi-static compression tests were performed, to determine mechanical and material properties. The Vickers hardness decreases as the matrix shifts from ceramic to intermetallic. Modulus and compressive strength decreases with increasing amounts of Ni-Ti intermetallic. The SEM photomicrographs of fractured surfaces are included.