The effect of support morphology on the reaction of oxidative dehydrogenation of ethane to ethylene at short contact times

The oxidative dehydrogenation of ethane is carried out in short contact time reactors over Pt and LaMnO₃ based catalysts supported on a large number of different ceramic substrates (45, 60 and 80 ppi foam monoliths and 200, 400, 600, 900 and 1200 cpsi honeycomb monoliths). Experimental results, obtained under the same conditions at varying the C₂H₆/O₂ ratio, showed that the highest performance in terms of ethylene selectivity and yield is always attained on LaMnO₃ catalysts. Furthermore, the results are significantly influenced by the morphology and cell density of the support, with 45 and 60 ppi foams and 400 and 600 cpsi honeycombs giving the best performance. The experimental results are explained by means of geometrical and fluid dynamic considerations on the support, and by means of a 2D mathematical model, which clearly indicates an optimal intermediate cell density for maximising ethylene selectivity and yield.     

The labeled maximum matching problem

Given a graph G where a label is associated with each edge, we address the problem of looking for a maximum matching of G using the minimum number of different labels, namely the labeled maximum matching problem. It is a relatively new problem whose application is related to the timetabling problem. We prove it is NP-complete and present four different mathematical formulations. Moreover, we propose an exact algorithm based on a branch-and-bound approach to solve it. We evaluate the performance of our algorithm on a wide set of instances and compare our computational times with the ones required by CPLEX to solve the proposed mathematical formulations. Test results show the effectiveness of our procedure, that hugely outperforms the solver.     

Force-clamp spectroscopy with a small dithering of AFM tip, and its application to explore the energy landscape of single avidin-biotin complex

We have recently developed a new method for directly measuring the spring constant of single molecules and molecular complexes on a real-time basis [L.A. Chtcheglova, G.T. Shubeita, S.K. Sekatskii, G. Dietler, Biophys. J. 86 (2004) 1177]. The technique combines standard force spectroscopy with a small dithering of tip. Changes in the amplitude of the oscillations are measured as a function of the pulling-off force to yield the spring constant of the complex. In this report, we present the first results of combination of this approach with the force-clamp spectroscopy. The standard atomic-force microscope has been supplemented with an electronic unit, which is capable of realizing an arbitrary force function, and permits the force-loading regime to be interrupted at any time. Using this method, the time needed to rupture a single bond can be measured as a function of the force that is required to maintain the complex in a stretched condition. The energy landscape of the avidin-biotin complex is explored and discussed.     

Energy-aware lazy scheduling algorithm for energy-harvesting sensor nodes

The main problem in dealing with energy-harvesting (EH) sensor nodes is represented by the scarcity and non-stationarity of powering, due to the nature of the renewable energy sources. In this work, the authors address the problem of task scheduling in processors located in sensor nodes powered by EH sources. Some interesting solutions have appeared in the literature in the recent past, as the lazy scheduling algorithm (LSA), which represents a performing mix of scheduling effectiveness and ease of implementation. With the aim of achieving a more efficient and conservative management of energy resources, a new improved LSA solution is here proposed. Indeed, the automatic ability of foreseeing at run-time the task energy starving (i.e. the impossibility of finalizing a task due to the lack of power) is integrated within the original LSA approach. Moreover, some modifications have been applied in order to reduce the LSA computational complexity and thus maximizing the amount of energy available for task execution. The resulting technique, namely energy-aware LSA, has then been tested in comparison with the original one, and a relevant performance improvement has been registered both in terms of number of executable tasks and in terms of required computational burden.     

Performance of antireflecting coating-AlGaAs window layer couplingfor terrestrial concentrator GaAs solar cells

In this paper, we present the performance of optical coating systems coupled with AlGaAs window layers over GaAs solar cells. Single, double, and triple antireflecting coatings and window layers with constant and graded aluminum content are considered. Comparison between constant and graded window layers is established. To better represent reality, practical factors such as absorption of materials even for antireflecting coatings and the oxidation at window layer surface due to its high aluminum content are also included in the calculations. The design criteria to determine the optimum thickness of each layer is the achievement of maximum photogenerated current density. For this purpose and to account for terrestrial concentrator GaAs solar cells, the inclusion of direct terrestrial solar spectrum together with the internal spectral response of the device are taken into account. Finally, the best antireflecting coating/AlGaAs window layer couplings for different cases are presented     

Capacitance DNA bio-chips improved by new probe immobilization strategies

Label-free DNA detection plays a crucial role in developing point-of-care biochips. Capacitance detection is a promising technology for label-free detection. However, data published in literature often show evident time drift, large standard deviation, scattered data points, and poor reproducibility. To address these problems, mercapto-hexanol or similar alkanethiols are usually considered as blocking agents. The aim of the present paper is to investigate new blocking agents to further improve DNA probe surfaces. Data from AFM, SPR, florescence microscopy, and capacitance measurements are used to investigate new lipoate and ethylene-glycol molecules. The new surfaces offer further improvements in terms of diminished detection errors. Film structures are investigated at the nano-scale to justify the detection improvements in terms of probe surface quality. This study demonstrates the superiority of lipoate and ethylene-glycol molecules as blocking candidates when immobilizing molecular probes onto spot surfaces in label-free DNA biochip.     

Reduced Impact of Induced Gate Noise on Inductively Degenerated LNAs in Deep Submicron CMOS Technologies

Designers of radio-frequency inductively-degenerated CMOS low-noise-amplifiers have usually not followed the guidelines for achieving minimum noise figure. Nonetheless, state-of-the-art implementations display noise figure values very close to the theoretical minimum. In this paper, we point out that this is due to the effect of the parasitic overlap capacitances in the MOS device. In particular, we show that overlap capacitances lead to a significant induced-gate-noise reduction, especially when deep sub-micron CMOS processes are used.Paolo Rossi was born in Milan, Italy, in 1975. He received the Laurea degree (summa cum laude) in electrical engineering from the University of Pavia, Pavia, Italy, in 2000, where he is currently working toward the Ph.D. degree. His research interests are in the field of analog integrated circuits for wireless transceivers in CMOS and BiCMOS technology, with particular focus on the analysis and design of LNA and mixer for multi-standard applications.Francesco Svelto received the Laurea and Ph.D. degrees in electrical engineering from the University of Pavia, Pavia, Italy, in 1991 and 1995, respectively. From 1996 to 1997, he held a grant from STMicroelectronics to design CMOS RF circuits. In 1997, he was appointed Assistant Professor at the University of Bergamo, Italy, and in 2000, he joined the University of Pavia, where he is an Associate Professor. His current research interests are in the field of RF design and high-frequency integrated circuits for telecommunications. Dr. Svelto has been a member of the technical program committee of the IEEE Custom Integrated Circuits Conference since 2000 and the Bipolar/BiCMOS Circuits and Technology Meeting (BCTM) since 2003, and the European Solid State Circuits Conference in 2002. He served as Guest Editor of the March 2003 special issue of the IEEE Journal of Solid-State Circuits, of which he is currently an Associate Editor.Andrea Mazzanti was born in Modena (Italy) in 1976. He received the Laurea degree (summa cum Laude) in Electrical Engineering from the University of Modena and Reggio Emilia, Modena, Italy in 2001. Since 2001 he is pursuing his PhD in Electrical Engineering at University of Modena and Reggio Emilia, Italy. His major research interest are modelling of microwave semiconductor devices and design of CMOS RF integrated circuits, with particular focus on low noise oscillators and analog frequency dividers. During the summer of 2003 he was with Agere Systems, Allentown, PA as an internship student, working on the design of an highly integrated CMOS FM transmitter.Pietro Andreani received the M.S.E.E. from the University of Pisa, Italy, in 1988. He joined the Dept. of Applied Electronics, Lund University, Sweden, in 1990, where he contributed to the development of software tools for digital ASIC design. After working at the Dept. of Applied Electronics, University of Pisa, as a CMOS IC designer during 1994, he rejoined the Dept. of Applied Electronics in Lund as an Associate Professor, where he was responsible for the analog IC course package between 1995 and 2001, and where he received the Ph.D. degree in 1999. He is currently a Professor at the Center for Physical Electronics, ØrstedDTU, Technical University of Denmark, Kgs. Lyngby, Denmark, with analog/RF CMOS IC design as main research field.