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121.
CORD: contention resolution by delay lines 总被引:10,自引:0,他引:10
Chlamtac I. Fumagalli A. Kazovsky L.G. Melman P. Nelson W.H. Poggiolini P. Cerisola M. Choudhury A.N.M.M. Fong T.K. Hofmeister R.T. Chung-Li Lu Mekkittikul A. Sabido D.J.M. IX Chang-Jin Suh Wong E.W.M. 《Selected Areas in Communications, IEEE Journal on》1996,14(5):1014-1029
The implementation of optical packet-switched networks requires that the problems of resource contention, signalling and local and global synchronization be resolved. A possible optical solution to resource contention is based on the use of switching matrices suitably connected with optical delay lines. Signalling could be dealt with using subcarrier multiplexing of packet headers. Synchronization could take advantage of clock tone multiplexing techniques, digital processing for ultra-fast clock recovery, and new distributed techniques for global packet-slot alignment. To explore the practical feasibility and effectiveness of these key techniques, a consortium was formed among the University of Massachusetts, Stanford University, and GTE Laboratories. The consortium, funded by ARPA, has three main goals: investigating networking issues involved in optical contention resolution (University of Massachusetts), constructing an experimental contention-resolution optical (CRO) device (GTE Laboratories), and building a packet-switched optical network prototype employing a CRO and novel signaling/synchronization techniques (Stanford University). This paper describes the details of the project and provides an overview of the main results obtained so far 相似文献
122.
RC Melcangi MA Riva F Fumagalli V Magnaghi G Racagni L Martini 《Canadian Metallurgical Quarterly》1996,711(1-2):10-15
Astrocytes possess steroid receptors as well as several enzymes typical of steroid target cells, such as 5 alpha-reductase, which converts testosterone (T) and progesterone (P) into their respective 5 alpha-reduced metabolites, and the 3 alpha-hydroxysteroid dehydrogenase (3 alpha-HSD). Because of this, it was deemed of interest to analyze whether the original hormones P and T, and their 5 alpha-reduced metabolites dihydrotestosterone (DHT), 5 alpha-androstan-3 alpha, 17 beta-diol (3 alpha-diol), dihydroprogesterone (DHP) and 5 alpha-pregnan-3 alpha-ol-20-one (THP), might exert some effects on the expression of the most typical astrocytic marker, i.e. the glial fibrillary acidic protein (GFAP). Cultures of rat type 1 astrocytes were exposed to the various steroids for 2, 6, and 24 h, and the variations of GFAP mRNA were measured by Northern blot analysis. A significant elevation of GFAP mRNA levels was observed after exposure to either P or DHP; the effect of DHP appeared more promptly (at 2 h) than that of P (at 6 h). This result suggests that the effect of P might be linked to its conversion into DHP; this hypothesis has been confirmed by showing that the addition of finasteride (a specific blocker of the 5 alpha-reductase) is able to completely abolish the effect of P. After exposure to DHP or THP, a decrease of GFAP gene expression was observed at later intervals (24 h). In the case of androgens, T and 3 alpha-diol did not change GFAP expression at any time of exposure, while DHT produced a significant decrease of GFAP mRNA only after 24 h of exposure. Taken together, the data indicate that the 5 alpha-reduced metabolites of P and T may modulate the expression of GFAP in type 1 rat astrocytes. 相似文献
123.
Anna Maria Polcaro Annalisa Vacca Michele Mascia Simonetta Palmas 《Electrochimica acta》2005,50(9):1841-1847
The electrochemical oxidation of cyanuric acid (CA) is examined by bulk electrolyses at boron doped diamond (BDD) electrode. The influence of operating conditions on the reaction trend is investigated and suitable conditions for oxidative demolition of CA are individuated. In particular a strong effect of current density and pH is evidenced, being neutral pH and high current the most favourable conditions to achieve CA mineralisation. The paper also presents the results from atrazine (2-Cl-4-ethylamino-6-isopropylamino-1,3,5-triazine) and 2-Cl-4,6-diammino-1,3,5-triazine oxidation at BDD anode. Triazine compounds are scarcely degraded even with powerful methods such as photocatalytic TiO2-mediated processes, being CA generally obtained as final product of their oxidation. Individuation of favourable conditions for CA demolition has allowed to find suitable conditions to mineralise also triazine compounds. 相似文献
124.
Michele Mascia Annalisa Vacca Simonetta Palmas Anna Maria Polcaro 《Journal of Applied Electrochemistry》2007,37(1):71-76
This paper presents the results of a numerical study of the kinetics of electrochemical oxidation of different organic substances
at boron doped diamond (BDD).
It is well established that oxidation of organics at BDD anodes takes place in the potential region of oxygen evolution, through
reaction steps in which OH radicals are involved: these radicals can react with organic compounds to give more oxidised substances,
or with water to give oxygen. Because of the high reactivity of OH radicals these reactions are confined to a thin film adjacent
to the electrode surface. A mathematical model was implemented, which accounts for chemical and electrochemical reactions,
as well as for the transport phenomena involved in the process: the parameters of the model were derived from experimental
data. The model allowed calculation of the trend with time of reactant concentration, reaction intermediates and oxidisable
agents: their space profiles in the reactor were also obtained. The numerical predictions of the model were compared with
experimental results obtained from galvanostatic electrolyses of different organic compounds: (a) 2,4,6-trihydroxy-1,3,5 triazine
also known as cyanuric acid (CA), which is well known to be refractory to oxidation with OH; (b) atrazine (ATR) the most oxidisable
precursor of CA, and (c) phenol which is considered as an OH scavenger because of its high reactivity. The agreement between
experimental and model predicted data was good in all the examined conditions. 相似文献
125.
C. Spaggiari S. Bertoni G.F. Cerofolini P. Fumagalli L. Meda 《Ceramics International》1993,19(6):399-405
SiO2 precipitation in oxygen-supersaturated silicon was studied. Oxygen was inserted by ion implantation into single-crystal silicon. Evidence is given for a special phenomenon of oxygen blocking due to hot clouds resulting from collisional cascades. In the region where blocking is active, precipitates are formed in as-implanted conditions. A model is formulated and specialized to predict the dependence on depth of precipitate density and size. The existence of a buried region of precipitates is useful for producing a thin buried oxide. The
ow-
ose SIM
(LODOX) structure obtained provides a solution for many problems that are typical of silicon substrates for CMOS applications. 相似文献
126.
A series of umbelliferone aminoalkyl derivatives, previously studied as inhibitors of squalene-hopene cyclase, were tested
as inhibitors of yeast (Saccharomyces cerevisiae) oxidosqualene cyclase (OSC) and OSC from Trypanosoma cruzi and Pneumocystis carinii expressed in yeast. Enzymes from these pathogens were included in this study to provide a preliminary screening for antiparasitic
activity. Tests were carried out both on cell homogenates incubated with radiolabeled oxidosqualene and on spheroplasts incubated
with radiolabeled acetate. Derivatives bearing a methylallylamino group were the most effective on all of the three enzymes.
The P. carinii enzyme was the most susceptible to the action of the inhibitors, with IC50 values for almost all of them ranging from 0.1 to 1μM. The T. cruzi enzyme was appreciably inhibited (IC50 4–5 μM) only by derivatives bearing a methylallylaminoalkyl flexible chain. Results identify a particularly promising new
family of OSC inhibitors, for the development of novel antiparasitic agents. 相似文献
127.
Dario Perdicchia Michael S. Christodoulou Gaia Fumagalli Francesco Calogero Cristina Marucci Daniele Passarella 《International journal of molecular sciences》2016,17(1)
2-Piperidineethanol (1) and its corresponding N-protected aldehyde (2) were used for the synthesis of several natural and synthetic compounds. The existence of a stereocenter at position 2 of the piperidine skeleton and the presence of an easily-functionalized group, such as the alcohol, set 1 as a valuable starting material for enantioselective synthesis. Herein, are presented both synthetic and enzymatic methods for the resolution of the racemic 1, as well as an overview of synthesized natural products starting from the enantiopure 1. 相似文献
128.
B. Mazza P. Pedeferri D. Sinigaglia A. Cigada G. Fumagalli G. Re 《Corrosion Science》1979,19(11):907-921
This paper describes the results of a study concerning the electrochemical and corrosion behaviour of AISI Types 304L and 316L stainless steels, cold worked under various conditions, in 1M H2SO4 and in 0.1M HCl de-aerated solutions. Anisotropic behaviour of specimen surfaces with different orientations to the direction of deformation has been observed. Stress corrosion cracking of the deformed steels can occur at room temperature in the 0.1M HCl solution both in the active and transition regions of the polarization curves. 相似文献
129.
Simonetta Oliaro-Bosso Emanuela Calcio Gaudino Stefano Mantegna Enrico Giraudo Claudia Meda Franca Viola Giancarlo Cravotto 《Lipids》2009,44(10):907-916
Octacosa-10,19-dien-1-ol is a newly synthesized long-chain alcohol, an unsaturated analogue of 1-octacosanol, the major component
of policosanol, the purified natural mixture of different higher aliphatic alcohols obtained from sugarcane wax. Our efficient
synthetic protocol (five steps with 50% overall yield) is well suited for gram scale preparations and a rapid generation of
analogues with different degrees of unsaturation. Beneficial effects of policosanol in the prevention of atherosclerosis and
thromboembolic disorders have been reported and related to the inhibition of sterol biosynthesis possibly by the regulation
of the activity of HMGCoA reductase mediated by AMP-dependent kinase AMPK. We have compared the effect of octacosadienol and
policosanol on the regulation of HMGCoA reductase in HUVEC and HepG2 human hepatoma cells. Octacosadienol was as effective
as policosanol in inhibiting the upregulation of HMGCoA reductase, in inducing the phosphorylation of AMPK and in downregulating
the HMGCoA reductase mRNA. 相似文献
130.
Vladimir Akimov Eleonora Alfinito Joan Bausells Iryna Benilova Ignacio Casuso Paramo Abdelhamid Errachid Giorgio Ferrari Laura Fumagalli Gabriel Gomila Jeanne Grosclaude Yanxia Hou Nicole Jaffrezic-Renault Claude Martelet Edith Pajot-Augy Cecilia Pennetta Marie-Annick Persuy Mateu Pla-Roca Lino Reggiani Santiago Rodriguez-Segui Oscar Ruiz Roland Salesse Josep Samitier Marco Sampietro Alexey P. Soldatkin Jasmina Vidic Guillermo Villanueva 《Analog Integrated Circuits and Signal Processing》2008,57(3):197-203
The animal olfactory system represents the gold standard of biosensors, due to its ability to identify and discriminate thousands of odorant compounds with very low thresholds. Using olfactory receptors (ORs) as sensing elements instead of chemical sensors, biosensors would benefit the naturally optimized molecular recognition of odorants to develop a new generation of bioelectronic noses. The purpose of SPOT-NOSED European project was the development of nanobiosensors based on single ORs anchored between nanoelectrodes, to mimic the performances of natural olfactory system. Nanobiosensors arrays could then increase odorant sensitivity or widen the odorant detection spectrum. ORs were expressed in yeasts plasmic membrane, and their functionality tested in whole yeasts. Then, nanosomes bearing the ORs were prepared from S. cerevisiae, and Surface Plasmon Resonance was performed on nanosomes for quantitative evaluation of OR response to odorant stimulation. ORs retain full activity and discrimination power in immobilized nanosomes, thus allowing their use in the fabrication of the nanobiosensors. Nanoelectrodes were fabricated using conventional photolithography and focused ion beam milling, with sizes in adequation with the nanosomes. ORs borne by nanosomes were specifically immobilized onto conducting substrates via mixed Self Assembled Monolayers, neutravidin and specific antibody to the ORs. The process was optimized by microcontact printing, and the anchored nanovesicles visualized by Atomic Force Microscopy. A transimpedance preamplifier suited for low-noise wide-bandwidth measurements was designed to be directly connected to the nanoelectrodes. Electrochemical Impedancemetric Spectroscopy detected significant changes upon electrodes functionalization, grafting of ORs carried by nanosomes, and ORs conformational change induced by odorant binding. 相似文献