Understanding the electrocatalytic activity of PtxSny in direct ethanol fuel cells

In the present work, the activity of Pt_xSn_y/C catalysts towards ethanol, acetaldehyde and acetic acid electrooxidation reactions is investigated for each one separately by means of cyclic voltammetry. To this purpose, a series of Pt_xSn_y/C catalysts with different atomic ratio (x:y = 2:1, 3:2, 1:1) and small particle size (∼3 nm) are fast synthesized by using the pulse microwave assisted polyol method. The catalysts are well dispersed over the carbon support based on the physicochemical characterization by means of XRD and TEM. Concerning the ethanol electrooxidation, it is found that the Sn addition strongly enhances Pt's electrocatalytic activity and the contributing effect of Sn depends on: (i) the Sn content and (ii) the operating temperature. More precisely, at lower temperatures, Sn-rich catalysts exhibit better ethanol electrooxidation performance while at higher temperatures Sn-poor catalysts give better performance. In the case of acetaldehyde electrooxidation, Pt₁Sn₁/C catalyst exhibits the highest activity at all the investigated temperatures; due to the role of Sn, which could effectively remove C₂ species and inhibit the poison formation by supplying oxygen-containing species. Finally, it is found that the Pt_xSn_y/C catalysts are almost inactive (little current was measured) towards the acetic acid electrooxidation. The above findings indicate that Sn cannot substantially promote the electrooxidation of acetic acid to C₁ species.     

Modulation of the antioxidant/pro-oxidant balance,cytotoxicity and antiviral actions of grape seed extracts

Grape seed extracts (GSEs) were investigated in yeast cells harbouring defects in their antioxidant system (regarding the cellular growth and growth recovery from H₂O₂ insult). GSEs antioxidant activity was detected in wild-type and mutant strains Δcta1, Δgsh1 and Δoye2glr1, while pro-oxidant activity in Δsod1 cells was seen. Assessment of proliferation of prostate cancer PC3 and HBV-replicating HepG2 2.2.15 cells treated with GSEs has shown higher cytotoxicity of red grape seed extract (RW) than white grape seed extract (WW) subjective to dose and period of administration. No antiviral effect was detected by measuring the secreted virion particles in HepG2 2.2.15 cells treated with GSEs. The GSEs play a dual antioxidant/pro-oxidant role in vivo according with the cellular antioxidant system deficiencies and exhibit cytotoxic properties in PC3 and HepG2 2.2.15 cell lines, but no antiviral action against HBV.     

Modeling and Control of a Titania Aerosol Reactor

We focus on modeling and control of an aerosol flow reactor used to produce titania powder. We initially present a detailed population balance model for the process which accounts for simultaneous nucleation, Brownian and shearinduced coagulation, and convective transport and describe the spatio-temporal evolution of the aerosol volume distribution. Then, under the assumption of lognormal aerosol volume distribution, the method of moments is employed for the derivation of a model that describes the evolution of the three leading moments of the volume distribution. The moment model, together with the fundamental model that describes the temperature in the reactor and concentrations of the gas-phase species, are subsequently used to synthesize a nonlinear output feedback controller which manipulates the temperature of the reactor wall to achieve an aerosol size distribution in the outlet of the reactor with desired geometric average particle diameter. The nonlinear controller is successfully implemented on the process model and is shown to deal effectively with external disturbances.     

Modification of Niven's medium for the enumeration of histamine-forming bacteria and discussion of the parameters associated with its use

The objective of this study was to improve Niven's medium (NM) for the optimized enumeration of histamine-forming bacteria (HFB). The parameters modified related to solidification of the agar at low pH values (pH 5.3 to 5.8), incubation time (24, 48, and 72 h) and temperature (30 and 37 degrees C), number of colonies developed on the plate to allow enumeration of HFB, and color differentiation. Strains of HFB, Morganella morganii, Klebsiella pneumoniae, and Hafnia alvei were examined for their ability to change color on NM. The three microorganisms produced different colors on the medium, which can be used for preliminary identification of HFB. Quantitative analysis of HFB proved to be achievable, with the prerequisite that only 1 to 80 colonies developed on the medium allow effective enumeration. A larger number of colonies results in color development throughout the medium, making the distinction between HFB and other bacteria unachievable. Growth of prolific HFB was noticeably better at pH values from 5.3 to 5.5, compared to 6.3, on NM. Growth at 5.3 and 5.5 on NM also presented a significant advantage in comparison to growth on plate count agar (PCA; pH 7) at the same incubation temperature. The increased agar concentration of 3% was found to give better solidification at pH 5.3 to 6.0, compared to 2%. This agar concentration also allows autoclaving for 12 min at 121 degrees C, overcoming the hydrolysis problems that appear at the lower concentration of 2%. The construction of a color chart for the recognition of the pH change due to histidine decarboxylase activity was also achieved.     

MIMO Channel Characterization for Short Range Fixed Wireless Propagation Environments

This paper reports results from wideband MIMO measurements performed in short range fixed wireless environments at 5.2 GHz. The objective is to provide MIMO channel characterization results for the measured environments and contribute to the limited available similar studies. Two kinds of propagation scenarios are investigated, rooftop to rooftop and street to rooftop, at three different sites always under LOS propagation conditions. The analysis of measurement data is performed in the context of non physical modeling, providing insight into the statistics of the measured channels. In particular, the slow time varying nature of the channel is studied and the narrow Doppler spectrum shape is approximated. Furthermore, frequency correlation results are obtained and the typical delay dispersion measures are extracted. Then, the antenna correlation is studied and the error of the Kronecker product approximation is evaluated. Finally, capacity results are provided and the channel measurements are characterized in terms of spatial multiplexing quality and multipath richness through condition number analysis. Nikolaos D. Skentos received his Diploma in Electrical and Computer Engineering from the National Technical University of Athens (NTUA), Greece in October 2000. Since January 2001 he has been a research associate at the Mobile Radio Communications Laboratory at the NTUA, and he is currently working towards the Ph.D. degree. His research interests include channel measurements, MIMO channel characterization, MIMO algorithms and space time processing. He has been active in the IST STINGRAY project, the COST 273 Action and the ACE Network of Excellence. He is also a member of the National Technical Chamber of Greece since 2001. Athanasios G. Kanatas received the Diploma in Electrical Engineering from the National Technical University of Athens, Greece, in 1991, the M.Sc. degree in Satellite Communication Engineering from the University of Surrey, Surrey, UK in 1992, and the Ph.D. degree in Mobile Satellite Communications from the National Technical University of Athens, Greece in February 1997. From 1993 to 1994 he was with National Documentation Center of National Research Institute. In 1995 he joined SPACETEC Ltd. where he was Technical Project Manager for VISA/EMEA VSAT Project in Greece. In 1996 he joined the Mobile Radio Communications Laboratory as a research associate. From 1999 to 2002 he was with the Institute of Communication & Computer Systems. In 2000 he became a member of the Board of Directors of OTESAT S.A. He is an Assistant Professor in the Department of Technology Education and Digital Systems at University of Piraeus. His current research interests include channel characterization and estimation, simulation and modeling for mobile, mobile satellite, and future wireless communication systems. He has been a Senior Member of IEEE since 2002, and is also a member of the Technical Chamber of Greece. In 1999 he was elected Chairman of the Communications Society of the Greek IEEE Section. Panagiotis I. Dallas was born 1967 in Thessaloniki, Greece. He obtained his diploma and Ph.D. degree from the Electrical and Computer Engineering Department of Aristotle University of Thessaloniki, Greece, in 1990 and 1997, respectively. Since 1998 he joined with INTRACOM where he currently is Section Manager of Advanced Communications Technologies branch of Emerging Technologies & Markets department, leading the next generation of broadband wireless access systems for internal and EU projects. He runs the relevant standardization activities (IEEE 802.16 and ETSI/BRAN HIPERMAN) in INTRACOM and he represents the company in WiMAX forum. Finally, he has over 30 publications in international journals and conferences. Philip Constantinou received the Diploma in Physics from the National University of Athens in 1972, the Master of Applied Science in Electrical Engineering from the University of Ottawa, Ontario, Canada in 1976, and the Ph.D. degree in Electrical Engineering in 1983 from Carleton University, Ottawa, Ontario, Canada. From 1976 to 1979 he was with Telesat Canada as a Communications System Engineer. In 1980 he joined the Ministry of Communications in Ottawa, Canada where he was engaged in the area of Mobile Communication. From 1984 to 1989 he was with the National Research Center Demokritos in Athens, Greece where he was involved in several research projects in the area of Mobile Communications. In 1989 he joined the National Technical University of Athens where he is currently a Professor and Director of the Mobile Radio Communications Laboratory. His current research interests include Personal Communications, Mobile Satellite Communications, and Interference Problems on Digital Communications Systems.     

A synchronization algorithm for distributed multimedia environments

Network synchronization plays a significant role in transmitting multimedia objects over computer networks. Even packets from a single channel must be synchronized due to the problems in a packet switching environment, such as network jitter, frequency, and time offsets. We present an algorithm that determines the set of packets generated periodically by various participants arriving at a node. The basic advantage of the proposed algorithm is that the receiver estimates the reference times (expected arrival times of the packets) and achieves synchronization, without knowledge of the packet delays. The accuracy is improved and the complexity is reduced by predicting the time/frequency offsets between the clocks at the source and the mixer. The error is calculated by the Chernoff bound, demonstrated by simulation, and shown to be acceptable in practical applications.     

Growth and energy generation by Enterococcus faecium FAIR-E 198 during citrate metabolism

Citrate metabolism by Enterococcus faecium FAIR-E 198, isolated from Greek Feta cheese, was studied in various growth media containing citrate either in the presence of glucose, or as the sole carbon source, both under aerobic and anaerobic conditions. In de Man-Rogosa-Sharpe (MRS) broth with increasing citrate concentrations, cometabolism of citrate and glucose took place. Glucose was stoichiometrically converted into lactate, while citrate into acetate. Glucose consumption and biomass yield were enhanced with increasing initial citrate concentrations, even though maximum specific growth rate was not. When citrate was used as the sole carbon source in increasing initial concentrations, the main end product was acetate. Small amounts of lactate, formate, ethanol, and acetoin were also produced. In all cases, no significant differences were observed between aerobic and anaerobic conditions. However, when citrate was used as sole carbon source, formate production was favored in the absence of oxygen. The present work shows that E. faecium is able to utilize citrate in synthetic media, either in the presence of glucose or as the sole carbon source, resulting in energy production and the formation of aroma compounds.     

Coalitional tracking

We propose a novel tracking method that uses a network of independent particle filter trackers whose interactions are modeled using coalitional game theory. Our tracking method is general, it maintains pixel level accuracy, and can negotiate surface deformations and occlusions. We tested our method on a substantial video set featuring non-trivial motion from over 40 objects in both the infrared and visual spectra. The coalitional tracker demonstrated fault tolerant behavior that exceeds by far the performance of single particle filter trackers. Our method represents a shift from the typical tracking paradigms and may find application in demanding imaging problems across the electromagnetic spectrum.