Controlling natural convection in a closed thermosyphon using neural networks

The aim of this paper is to present a neural network-based approach to identification and control of a rectangular natural circulation loop. The first part of the paper defines a NARMAX model for the prediction of the experimental oscillating behavior characterizing the fluid temperature. The model has been generalized and implemented by means of a Multilayer Perceptron Neural Network that has been trained to simulate the system experimental dynamics. In the second part of the paper, the NARMAX model has been used to simulate the plant during the training of another neural network aiming to suppress the undesired oscillating behavior of the system. In order to define the neural controller, a cascade of several couples of neural networks representing both the system and the controller has been used, the number of couples coinciding with the number of steps in which the control action is exerted.     

Impact of laser on bismuth thin-films

We used the newly developed low-α mode of SOLEIL synchrotron to observe optically induced strain waves in 200 nm bismuth thin-films.     

Quantification of 17 beta-estradiol residues in bovine serum by liquid chromatography-tandem mass spectrometry with atmospheric pressure chemical ionization.

A method for the quantification of the natural hormone 17 beta-estradiol (17 beta-E2) in bovine serum by liquid chromatography atmospheric pressure chemical ionization tandem mass spectrometry (LC-APCI-MS-MS) was developed. Ethinylestradiol (EE2) was used as internal standard. Analytes were extracted from serum using acetate buffer, purified by C18 solid-phase extraction (SPE) and chromatographed on a polymeric reversed-phase (PLRP-S) LC column. They were ionized in a heated nebulizer (HN) interface operating in the negative ion mode, where only the intact deprotonated molecules, [M - H]-, were generated at m/z 271 and 295 for 17 beta-E2 and EE2, respectively. These served as precursor ions for collision-induced dissociation (CID) and diagnostic product ions were identified for the unambiguous hormone confirmation by selected reaction monitoring (SRM) LC-APCI-MS-MS. The method was validated on bovine serum and the limit of quantification (LOQ) was 30 pg ml-1 for 17 beta-E2. The inter-day precision (relative standard deviation, RSD) and accuracy (relative error, RE) derived from the analyses of validation samples at three concentrations ranged from 1.76 to 3.76 and from -4.18 to -2.01%, respectively. This method is currently being successfully applied to measure the bovine serum concentration of 17 beta-E2 in order to discriminate between the physiological concentrations of 17 beta/E2 and the hormone levels resulting from illegal administration.     

Structure and dynamics of water confined in silica hydrogels: X-ray scattering and dielectric spectroscopy studies

Liquid ⁴He immersed in porous media such as aerogel, Vycor, and Geltech silica are excellent examples of bosons in disorder and confinement. Of special interest is the impact of disorder on Bose-Einstein condensation (BEC), on the elementary excitations of the superfluid and on their connection to the superfluid properties. Indeed, the modifications induced by disorder can be used to reveal the interdependence of BEC, the excitations and superfluidity. To date, the superfluid properties in porous media are much more completely documented than BEC or the excitations. In this paper, we review measurements of the excitations by neutron scattering, focusing particularly on their temperature dependence and the existence of phonon-roton excitations at higher temperatures. The weight of single excitation response at higher temperatures suggests the existence of localized BEC above the superfluid-normal transition temperature in porous media. We sketch several recent predictions made for BEC, the excitations, and the superfluid properties in disorder. Connections with other Dirty Bose systems are made.Received: 1 January 2003, Published online: 21 October 2003PACS: 03.75.Kk Dynamic properties of condensates; collective and hydrodynamic excitations, superfluid flow - 61.12.Ex Neutron scattering (including small-angle scattering) - 67.40.Yv Boson degeneracy and superfluidity of ⁴He: Impurities and other defects     

Dynamic control for a natural circulation loop

In the present paper a control strategy is outlined to avoid instabilities in a rectangular natural circulation loop. A mathematical model linearized using the stationary solutions was used together with a standard P.I.D. control to counteract the birth of the instabilities inside the loop. The proposed strategy was tested both with numerical simulation and with experimental tests. In both cases the strategy control was suitable to avoid the flow inversion of the working fluid inside the loop.     

Chelation of Theranostic Copper Radioisotopes with S-Rich Macrocycles: From Radiolabelling of Copper-64 to In Vivo Investigation

Copper radioisotopes are generally employed for cancer imaging and therapy when firmly coordinated via a chelating agent coupled to a tumor-seeking vector. However, the biologically triggered Cu²⁺-Cu⁺ redox switching may constrain the in vivo integrity of the resulting complex, leading to demetallation processes. This unsought pathway is expected to be hindered by chelators bearing N, O, and S donors which appropriately complements the borderline-hard and soft nature of Cu²⁺ and Cu⁺. In this work, the labelling performances of a series of S-rich polyazamacrocyclic chelators with [⁶⁴Cu]Cu²⁺ and the stability of the [⁶⁴Cu]Cu-complexes thereof were evaluated. Among the chelators considered, the best results were obtained with 1,7-bis [2-(methylsulfanyl)ethyl]-4,10,diacetic acid-1,4,7,10-tetraazacyclododecane (DO2A2S). DO2A2S was labelled at high molar activities in mild reaction conditions, and its [⁶⁴Cu]Cu²⁺ complex showed excellent integrity in human serum over 24 h. Biodistribution studies in BALB/c nude mice performed with [⁶⁴Cu][Cu(DO2A2S)] revealed a behavior similar to other [⁶⁴Cu]Cu-labelled cyclen derivatives characterized by high liver and kidney uptake, which could either be ascribed to transchelation phenomena or metabolic processing of the intact complex.