Perspectives for present and future CDMA-based communications systems

In this article the main boosters of future CDMA communication systems are presented and described in order to highlight the ways to cope with the more challenging requirements of future systems and services. Particular attention is devoted to the inherent weak points of CDMA systems and detection techniques that can be used to overcome their impairments. Moreover, high-data-rate transmissions in wireless channels require proper link adaptation techniques; these are thoroughly described as well. Finally, the last part of this article focuses on the design of suitable protocol strategies for new heterogeneous multimedia packet services characterized by strict QoS requirements     

Modification of styrene-divinyl benzene copolymers using monoacrylates as ter-monomer

Porous styrene-divinyl benzene (St-DVB) copolymers were synthesized by incorporation of cyclohexanol during copolymerization. It led to copolymers of high porosity, high surface area and high % swelling. However these copolymers exhibit very poor compressive strength. Therefore they have been modified by terpolymerization in order to achieve styrene-DVB copolymers of adequate compressive strength with high surface area and % swelling. These terpolymers were synthesized by suspension copolymerization of styrene, DVB and variable amount of monoacrylates in presence of cyclohexanol as a diluent. Methylacrylate, ethyl acrylate, butyl acrylate, methylmethacrylate and glycidyl methacrylate were taken as ter-monomers for the present study and influence of these ter-monomers on formation of porous structure of the copolymer was investigated by % swelling, surface area, bulk density, compressive strength measurement and surface morphology. Incorporation of ter-monomers resulted into increased compressive strength and bulk density with adequate surface area and % swelling with the increased content of monoacrylates. Further at constant ter-monomer concentration, physical properties and thermal stability of the ter-polymers were found to be in the order: MMA > MA > EA > BA > GMA.     

Efficient network coding techniques for time constrained multicast narrowband power line communications

Nowadays, power line communication (PLC) technology is receiving a renewed attention in many application fields. In particular, PLC is quite attractive for what concerns novel paradigms as smart microgrid systems and smart buildings. This paper deals with a proposal of a PLC scheme that efficiently allows multicast services based on the use of an efficient network coding (NC) scheme. Furthermore, an analytical approach is outlined to pursue the performance optimization of the proposed solution. Finally, the good behavior of the proposed NC approach is highlighted by presenting performance comparisons with the classical NC alternative.     

Performance Evaluation of a Virtual Queuing – Channel Allocation Scheme for Microcellular Networks

This paper deals with the performance evaluation of a novel distributed channel allocation scheme that attains a high resource reuse in cellular networks. A suitable interference model has been envisaged. Resources are nominally assigned to cells with Fixed Channel Allocation (FCA), according to a given reuse distance. Whenever a channel demand from a mobile user does not find a free nominal resource in a cell, a channel is temporarily borrowed violating the reuse distance constraint, provided that the co-channel interference level is acceptable. As soon as a nominal channel becomes available in this cell, the borrowed resource is released (virtual queuing). The performance of the proposed channel allocation scheme has been evaluated considering both uniform and non-uniform traffic patterns. A performance analysis approach has been also developed and validated by simulations. Comparisons with the classical FCA scheme and other dynamic and borrowing channel allocation strategies have permitted to highlight the good performance of the proposed technique.     

Looking for residues involved in the muscle acylphosphatase catalytic mechanism and structural stabilization: role of Asn41, Thr42, and Thr46

Asn41, Thr42, and Thr46 are invariant residues in both muscle and erythrocyte acylphosphatases isolated so far. Horse muscle acylphosphatase solution structure suggests their close spatial relationship to Arg23, the main substrate binding site. The catalytic and structural role of such residues, as well as their influence on muscle acylphosphatase stability, was investigated by preparing several gene mutants (Thr42Ala, Thr46Ala, Asn41Ala, Asn41Ser, and Asn41Gln) by oligonucleotide-directed mutagenesis. The mutated genes were cloned and expressed in Escherichia coli, and the mutant enzymes were purified by affinity chromatography and investigated as compared to the wild-type enzyme. The specific activity and substrate affinity of Thr42 and Thr46 mutants were not significantly affected. On the contrary, Asn41 mutants showed a residual negligible activity (about 0.05-0.15% as compared to wild-type enzyme), though maintaining an unchanged binding capability of both substrate and inorganic phosphate, an enzyme competitive inhibitor. According to the 1H nuclear magnetic resonance spectroscopy and circular dichroism results, all mutants elicited well-constrained native-like secondary and tertiary structures. Thermodynamic parameters, as calculated from circular dichroism data, demonstrated a significantly decreased stability of the Thr42 mutant under increasing temperatures and urea concentrations. The reported results strongly support a direct participation of Asn41 to the enzyme catalytic mechanism, indicating that Asn41 mutants may well represent a useful tool for the investigation of the enzyme physiological function by the negative dominant approach.     

Numerical modeling for LEMP effect evaluation inside atelecommunication exchange

This paper presents a numerical modeling method developed for evaluating electromagnetic (EM) interference on the equipment inside a telecommunication exchange caused by a direct lightning stroke to a telecommunication tower close (i.e., a few meters) to the exchange building. Considering two different bonding configurations, EM interference is evaluated by calculating the electrical parameters: the EM fields, voltages, and currents. A special method of moment (MOM) wire-grid procedure using “dipole” and “loop” type basis and test functions was used as a numerical tool. A simple model was also developed for simulating the equipment mechanical structures which modify the field distribution inside the building. The voltages and currents induced on shielded cables were evaluated by means of a mixed technique, where the MOM procedure is combined with a SPICE analysis. Numerical modeling was used for two different situations: to simulate some experimental tests carried out in the field, where a 1.6 kA lightning current of a pulse generator was injected on the top of the 25 m high telecommunication tower close to a small exchange building; and to calculate the same parameters when a real lightning current strikes the telecommunication tower     

Neutron spectrometry around a high-energy electron-positron collider using a multi-sphere system with passive detectors

At the INFN LNF (Frascati), the 510 MeV electron-positron collider DAPhiNE is operating since 1997. The neutron fields in the areas around the accelerator were characterised using a Bonner sphere system. The sensitivity of the system was extended up to 10(2) MeV by means of a lead loaded 12(') sphere. Recently developed thermoluminescence dosemeters (TLDs), with improved neutron sensitivity and gamma rejection properties, were used as central detectors. The new TLD-based spectrometric system was characterised by irradiation in quasi-monoenergetic or radionuclide neutron fields. In addition, numerical verifications with the Monte Carlo code MCNP were performed. This work addresses this new TLD-based spectrometer and presents the spectral measurements performed in a point of test around DAPhiNE. The results are compared with those obtained, in the same point, with a previously validated Bonner sphere system based on an active (6)LiI(Eu) scintillator.     

Computational Fluid Dynamics (CFD) Modeling for Bread Baking Process—A Review

Computational fluid dynamics (CFD) modeling of entire bread baking process is very complicated due to involvement of simultaneous physiochemical and biological transformations. Bread baking is a fickle process where composition, structure, and physical properties of bread change during the process. CFD finds its application in modeling of such complex processes. This paper provides the basics of CFD modeling, different radiation models used for modeling of heating in electrical heating ovens, modeling of bread baking process along with the predictions of bread temperature, starch gelatinization, and browning index. In addition, some recent approaches in numerical modeling of bread baking process are highlighted. Moreover, current limitations, recent developments, and future applications in CFD modeling of bread baking process are discussed in detail.     

Nuclear medicine approaches for detection of axillary lymph node metastases

Rhopalosiphum padi virus (RhPV) is an aphid virus that has been considered a member of the Picornaviridae based on physicochemical properties. The 10,011-nt polyadenylated RNA genome of RhPV was completely sequenced. Analysis of the sequence revealed the presence of two open reading frames (ORFs). The predicted amino acid sequence of ORF1, representing the first 6600 nt of the RhPV genome, showed significant similarity to the nonstructural proteins of several plant and animal RNA viruses. Direct sequence analysis of the RhPV capsid proteins showed that ORF2, which represents the last 2900 nt, encodes the three structural proteins (28, 29, and 30 kDa). The predicted amino acid sequence of ORF2 is very similar to the corresponding regions of Drosophila C virus, Plautia stali intestine virus, and to a partial sequence from the 3' end of the cricket paralysis virus genome. The site of initiation of protein synthesis for ORF2 could not be determined from the amino acid and nucleotide sequences. ORF1 is preceded by 579 nt of noncoding RNA and the two ORFs are separated by more than 500 nt of noncoding RNA. Like picornaviruses, these regions may function to facilitate the cap-independent initiation of translation of the two ORFs. These data suggest that RhPV, Drosophila C virus, Plautia stali intestine virus, and probably cricket paralysis virus are members of a unique group of small RNA viruses that infect primarily insects.