Advances in Force and Moments Measurements by an Innovative Six-axis Load Cell

In this paper the design, the accuracy assessment and the calibration procedure of an innovative six axis load cell are presented. The load cell is able to measure the three forces and three moments and has been designed at the Politecnico di Milano (Technical University of Milan) as a result of 10 years of research in this field. The sensing structural element of the six-axis load cell is a three spoke structure constrained to the frame of the load cell by means of special joints conceived to avoid friction. Strain gauges are conveniently located on highly stressed areas. Mathematical models, both analytical and numerical, are implemented and presented in order to describe the behaviour of the load cell, to optimize its parameters and to theoretically assess its accuracy. A special device has been designed and constructed in order to accurately and quickly calibrate the load cell. Particular attention has been devoted to the processing of the strain gauges signals. An electronic DSP board, located inside the load cell, has been realized able to compute the six components of the generalized force from the strain gauge signals and return six voltage signals proportional to the measured forces. Software selectable filters and gains are implemented on the DSP board.     

Photoswitchable Tetraethynylethene‐Dihydroazulene Chromophores

The synthesis, characterization, and photophysical as well as electrochemical properties of the photochromic hybrid systems 11 – 16 and 18 , which contain photoswitchable tetraethynylethene (TEE; 3,4‐diethynylhex‐3‐ene‐1,5‐diyne) and dihydroazulene (DHA) moieties, are presented. The molecular photoswitches were synthesized by a Sonogashira cross‐coupling reaction between an appropriate TEE precursor ( 6 – 10 and 17 ) and an iodinated DHA 1 or its vinylheptafulvene (VHF) isomer ( 4 ) (Schemes 5 – 7). X‐Ray crystal structures of five DHA derivatives ( 1 , trans‐ 11a , cis‐ 11a , 12 , and 13 ) are discussed (Figs. 2 – 5). In all compounds, the cyclohexatriene moiety of the DHA chromophore adopts a clear boat conformation (Table 1). Presumably due to crystal‐packing effects, the arylated TEE moieties in the hybrid systems show substantial distortions from planarity, with the dihedral angles between the planes of the central TEE core and the adjacent aryl substituents amounting to 44°. The switching properties were investigated by electronic absorption spectroscopy. Upon light absorption, DHAs 1 , 12 – 16 , and 18 underwent retro‐electrocyclization in solution to give the corresponding VHFs (Figs. 6, 11, and 12). The reaction is thermally reversible, with half‐lives τ_1/2 between 3.9 and 5.8 h at 25° in CH₂Cl₂ (Figs. 7 and 13 and Table 3). A comparatively slower (E)→(Z) isomerization process about the central C=C bond of the TEE moiety was also observed. The N,N‐dimethylanilino‐(DMA) substituted TEE‐DHA hybrid systems trans‐ 11a and cis‐ 11a did not react to the corresponding VHFs upon irradiation (Scheme 9). Instead, only the reversible (E)→(Z) photoisomerization of the TEE core occurred (Fig. 16 and Table 4). This process was further investigated for photofatigue by electronic‐emission spectroscopy (Fig. 17). After protonation of the DMA group, the usual DHA→VHF photoreaction took place. Compound 11 represents a three‐way chromophoric molecular switch with three addressable sub‐units (TEE core, DHA/VHF moiety, and proton sensitive DMA group) that can undergo individual, reversible switching cycles (Scheme 9). A process modeling the function of an `AND' logic gate (Fig. 19) and three write/erase processes could be performed with this system. Cyclic and linear sweep‐voltammetry studies in CH₂Cl₂ (+Bu₄NPF₆) revealed the occurrence of characteristic first‐reduction steps in the TEE‐DHA hybrid systems between −1.6 and −1.8 V vs. Fc/Fc⁺ (ferrocene/ferricinium couple) (Table 5). Oxidations occur at ca. +1.10 V. After photoisomerization to the VHF derivatives, reduction steps at more positive and oxidation steps at more negative potentials were recorded. No DHA→VHF isomerization took place upon electrochemical oxidation or reduction (Fig. 20).     

Quasi-fission — The mass-drift mode in heavy-ion reactions

The binary and ternary products from reactions of ²³⁸U beams with targets of ¹⁶O, ²⁷Al, ⁴⁸Ca, ⁴⁵Sc, ⁴⁸Ti, ⁵⁸Fe, ⁶⁴Ni and ⁸⁹Y have been recorded at 6.0 MeV/u bombarding energy with four position-sensitive avalanche detectors, operated in coincidence. A few runs at 5.4 MeV/u have also been performed. Accurate triple-differential cross sections, $\text{d}{}^3\text{σ}\text{d}\text{A}\text{d}\text{θ}{}_{\mathrm{<mtext>c.m.</mtext>}}\text{dTKE}$, are obtained for the binary events within the full range of mass A and total kinetic energy TKE, and within almost the full range of center-of-mass angle θ_c.m.. Similar cross sections are obtained with somewhat less accuracy for triple events stemming from the sequential fission of uranium-like products. The distributions are discussed in terms of quasielastic and strongly damped scattering, where the products have partially relaxed energies and negligible average drift in mass, as opposed to capture where the products emerge with fully relaxed energies after a more or less pronounced mass drift towards symmetry. Apart from the reaction with ¹⁶O, all the capture product distributions are dominated by the non-equilibrium quasi-fission (or fast fission) process. The central feature of this reaction mechanism is the evolution of the reaction complex towards mass symmetry. With the ²⁷Al target the evolution towards symmetry is almost complete, whereas the heavier targets show very broad mass distributions with clear evidence of dissociation taking place before symmetry is reached. At the same time, the cross section for quasi-fission diminishes as the target Z-value increases. With the ⁸⁹Y target the strongly damped scattering component dominates completely. The capture cross sections are discussed in terms of the extra-push concept, and the mass and angular distributions in quasi-fission are analyzed in terms of interaction time and mass rearrangement as functions of target Z-value and excess kinetic energy in the entrance channel.     

Mass drift in reactions between a heavy and a light nucleus

The dynamics of heavy-ion collisions is studied experimentally for metastable composite systems with interaction times between the collision time of quasi- and deep-inelastic processes and the capture time of fast-fission and compound-nucleus-fission reactions. Detailed angular, total kinetic energy and mass distributions are measured for reaction products with masses between the target and projectile masses including the symmetric masses. The mass drift is observed as a function of total kinetic energy and scattering angle.     

A searching and reporting system for relational databases using a graph-based metadata representation

Relational databases are the current standard for storing and retrieving data in the pharmaceutical and biotech industries. However, retrieving data from a relational database requires specialized knowledge of the database schema and of the SQL query language. At Anadys, we have developed an easy-to-use system for searching and reporting data in a relational database to support our drug discovery project teams. This system is fast and flexible and allows users to access all data without having to write SQL queries. This paper presents the hierarchical, graph-based metadata representation and SQL-construction methods that, together, are the basis of this system's capabilities.