A Bidirectional WDM/TDM-PON Using DPSK Downstream Signals and a Narrowband AWG

We present an innovative architecture to realize a single feeder bidirectional amplified wavelength-division-multiplexing/time-division-multiplexing passive optical network based on modified nonreturn-to-zero differential phase-shift keying (DPSK) downstream signals at 20 Gb/s and a narrowband arrayed waveguide grating (AWG). The AWG plays at the same time the role of channel distributor, simultaneous demodulator for all DPSK channels, and eliminates the need for chromatic dispersion compensation. A saturated semiconductor optical amplifier (SOA) provides bidirectional amplification to compensate the splitter losses. The remodulated upstream signals are obtained at 1 Gb/s by means of a reflective SOA. Experimental results show error-free operation on both downstream and upstream signal.     

Activation of Glycerophosphocholine Phosphodiesterase in Friend Leukemia Cells Upon In-Vitro Induced Erythroid Differentiation. 31P and 1H NMR Studies

This paper reports the results of ³¹P and ¹H NMR studies on alterations of glycerophosphocholine phosphodiesterase (EC 3.1.4.2) activity in Friend leukemia cells, upon in vitro induced erythroid differentiation, in which cells undergo a transition from a highly proliferative (proerythroblastic) to a more mature (normoblastic) state. Experiments on cell homogenates incubated in the presence of added glycerophosphocholine (GroPCho) demonstrated that in differentiated cells the activity of GroPCho phosphodiesterase was at least three times higher than in undifferentiated control cells. Activation of the same enzyme was also observed in previous studies on FLC tumors implanted in syngeneic mice and treated in vivo with antitumor cytokines. These results, together with the decrease of GroPCho reported also in other cell systems undergoing cell transitions to more mature forms, suggest the hypothesis that an activation of GroPCho phosphodiesterase might play a role in cell maturation and, perhaps, also in tumor cell proliferation. An interpretation is then proposed of the alterations observed in the levels of phospholipid precursors and/or catabolites in FLC in vitro and in vivo, in light of possible correlations between phospholipid turnover, cell stimulation, and signal transduction.     

A microfluidic sensor in coplanar waveguide configuration for localized micrometric liquid spectroscopy in microwaves regime

Microsystem Technologies - In this work, we present a sensor suitable for performing the spectroscopy on a localized micrometric volume of a generic liquid, in the spectral range comprised between...     

Microscopic Modelling of Quantum Open Systems: A Generalized Wigner-Function Approach

A microscopic approach for the simulation of quantum-transport phenomena in systems with open boundaries is proposed. We show that the application of the conventional Wigner-function formalism to this problem leads to unphysical results, like injection of coherent electronic states from the contacts. To overcome such basic limitation, we propose a generalization of the standard Wigner-function formulation, able to properly describe the incoherent nature of carrier injection at the device spatial boundaries. The latter constitutes a quantum mechanical derivation of the phenomenological injection model commonly employed in the simulation of open quantum devices.     

Analysis of range queries and self-spatial join queries on realregion datasets stored using an R-tree

In this paper, we study the node distribution of an R-tree storing region data, like, for instance, islands, lakes, or human-inhabited areas. We will show that real region datasets are packed in an R-tree into minimum bounding rectangles (MBRs) whose area distribution follows the same power law, named REGAL (REGion Area Law), as that for the regions themselves. Moreover, these MBRs are packed in their turn into MBRs following the same law, and so on iteratively, up to the root of the R-tree. Based on this observation, we are able to accurately estimate the search effort for range queries, using a small number of easy-to-retrieve parameters. Furthermore, since our analysis exploits, through a realistic mathematical model, the proximity relations existing among the regions in the dataset, we show how to use our model to predict the selectivity of a self-spatial join query posed on the dataset. Experiments on a variety of real datasets (islands, lakes, human-inhabited areas) show that our estimations are accurate, enjoying a geometric average relative error ranging from 22 percent to 32 percent for the search effort of a range query, and from 14 percent to 34 percent for the selectivity of a self-spatial join query. This is significantly better than using a naive model based on uniformity assumption, which gives rise to a geometric average relative error up to 270 percent and up to 85 percent for the two problems, respectively     

Totally correct logic program transformations via well-founded annotations

We address the problem of proving the total correctness of transformations of definite logic programs. We consider a general transformation rule, called clause replacement, which consists in transforming a program P into a new program Q by replacing a set Γ ₁ of clauses occurring in P by a new set Γ ₂ of clauses, provided that Γ ₁ and Γ ₂ are equivalent in the least Herbrand model M(P) of the program P. We propose a general method for proving that transformations based on clause replacement are totally correct, that is, M(P)=M(Q). Our method consists in showing that the transformation of P into Q can be performed by: (i) adding extra arguments to predicates, thereby deriving from the given program P an annotated program $\overline{P}$ , (ii) applying a variant of the clause replacement rule and transforming the annotated program $\overline{P}$ into a terminating annotated program $\overline{Q}$ , and (iii) erasing the annotations from $\overline{Q}$ , thereby getting Q. Our method does not require that either P or Q are terminating and it is parametric with respect to the annotations. By providing different annotations we can easily prove the total correctness of program transformations based on various versions of the popular unfolding, folding, and goal replacement rules, which can all be viewed as particular cases of our clause replacement rule.     

Modeling of APCVD-doped silicon dioxide deposition process by amodular neural network

This paper describes a methodology based on the combined utilization of both a multisensor system and an optimized artificial neural network that has been applied to equipment utilized for the production of doped silicon dioxide films. The model exhibits an average relative error around 1% in predicting the concentrations of dopants and the thickness of the oxide layer. One of the major benefits of such a predictor is the ability of providing an on-line estimate of the process yield, thus avoiding off-line testing and gaining a significant reduction of risks of wafer loss. The neural model here described is currently utilized as a control tool at the Texas Instruments Avezzano, Italy, plant     

Reliable response of RF MEMS LTCC packaged switches after mechanical and thermal stress

Space components need a ground characterization based on several solicitations, including mechanical and thermal stress, before their final qualification. In this paper, RF MEMS switches designed for redundancy logic have been extensively measured with promising results in terms of thermal and mechanical cycles. Packaging contributions have also been discussed.     

Design of single and coupled microwave meta-material resonators in microsystem technology

In this paper Coupled Triangular Resonators in coplanar waveguide have been studied for S (2–4 GHz) and C (4–8 GHz) Band microwave applications. The peculiarity of the triangular structure to exhibit multiple resonances is usually proposed for dual and three-band purposes, to obtain efficient unit cells for high performance microwave tunable oscillators. One more characteristic of the triangular shape is the meta-material behavior, which allows a significant size decrease of the device. Coupled resonating configurations are proposed in this contribution, to be manufactured in Microsystem Technology by using polymeric layers as spacers between individual resonators organized in a vertical stack. Electromagnetic simulations have been performed to study narrow-band filters characterized by reduced dimensions, low insertion loss and steep band edges. Lumped element models are presented which can be easily implemented in commercial circuital software packages for the design of networks using these resonators.