Multigigabit/s demultiplexing in optical domain using coherence properties of pulse trains from multiple, asynchronous mode-locked lasers

It is shown that the unique coherence properties of mode-locked lasers can be exploited to provide new opportunities for high-speed data transmission. Using passive Mach-Zehnder optical delay stages, very high bit rate optical data streams constructed from asynchronously combined transmitters can be demultiplexed directly in the optical domain, without imposing restrictions on the source wavelength. Potential implementation and performance of the technique are discussed.<>     

Crystallinity and lateral crystallite size of different UHMW PE materials

Nascent high-molecular-weight (UHMW) polyethylene (PE) samples of different origins show a rather high crystallinity of about 70–75% and contain both a major portion of orthorhombic extended chain crystallites and a minor portion of triclinic crystallites. The triclinic content is greater the higher the molecular weight of the sample and the higher the activity of the used catalyser. A melting / recooling treatment results in a reduction of crystallinity by about 15–25% and disappearance of the triclinic phase. Further, an irreversible conversion of nascent orthorhombic extended chain crystallites to orthorhombic folded chain crystallites of increased lateral dimensions and crystalline perfections takes place during the melting / recooling treatment. The results are compared to those obtained for lower-molecular-weight PE samples and for high-strength / modulus PE fibers of different origins.     

Predominant expression of monoamine oxidase B isoform in rabbit renal proximal tubule: regulation by I2 imidazoline ligands in intact cells

Previous studies have shown that a subpopulation of the catecholamine-degrading enzymes monoamine oxidase (MAO) A and B holds a previously unknown regulatory site, the I2-imidazoline binding site (I2BS). In the present work, we characterized the isoforms of monoamine oxidases expressed in the rabbit renal proximal tubule, defined their relationship with I2BS, and investigated the ability of I2BS ligands to inhibit enzyme activity in intact cells. Two findings indicate that MAO-B is the predominant isoform expressed in the renal proximal tubule cells: 1) Western blot performed with an anti-MAO-A/MAO-B polyclonal antiserum revealed a single 55-kDa band corresponding to MAO-B; 2) enzyme assays showed an elevated MAO-B activity ([14C]beta-phenylethylamine oxidation: Vmax = 1.31 +/- 0.41 nmol/min/mg protein), whereas MAO-A activity was only detectable ([14C]5-HT oxidation: Vmax = 80.3 +/- 19 pmol/min/mg protein). Photoaffinity labeling with the I2BS ligand [125I]2-(3-azido-4-iodophenoxy)-methylimidazoline revealed a single 55-kDa band, which indicates that MAO-B of the renal proximal tubule cells holds the I2 imidazoline binding site. [3H]Idazoxan binding studies and enzyme assays showed that, in intact cells, I2BS ligands bind to and inhibit MAO-B. Indeed, the increase in the accessibility of intracellular compartment by cell permeabilization did not enhance [3H]idazoxan binding, which indicates that, in intact cells, intracellular I2BS are fully occupied by imidazoline ligands. In addition, enzyme assays showed that incubation of proximal tubule cells with imidazoline ligands leads to a complete, dose-dependent inhibition of MAO activity. These data show the predominant expression of MAO-B in rabbit renal proximal tubule and its regulation by imidazoline ligands in intact cells.     

A multilevel soliton communication system

A multilevel soliton communication system is proposed and assessed. In this system, at the transmitter end each channel transmits its data via fundamental solitons with a pre-specified amplitude (i.e., soliton width). At the receiver end we take advantage of the sensitive relationship between the amount or fundamental soliton self-wavelength shift and the width of the soliton in the subpicosecond region. We first compress the incoming soliton noises to the subpicosecond level and pass them through a short length of fiber at the end of which the pulses have become separated in the wavelength domain since each soliton, corresponding to a data channel, has experienced a different Raman self-wavelength shift. The channels are then easily separated by optical filters. We have derived the design constraint relations for such a system. We have then heuristically designed a 40 Gbs (four channels) system for a 1000 km propagation distance (total data-rate distance product of 40 Tb/km). Numerical simulations and noise analyses have verified the feasibility and practicality of the proposed system with very good design margins. The wavelength jitter is found to be much smaller than the desired filter spacing, and thus its contribution to the bit error rate is negligible. We also argue that the system is more tolerant to Gordon-Haus timing jitter than conventional TDM soliton systems. The system is all fiber and is, therefore very cost effective as it does not require sophisticated electro-optic and microwave circuits for demultiplexing. The system can potentially operate at much higher speeds than those achievable in conventional soliton systems and it can be used in parallel with WDM soliton system     

A menu-driven environment for automated urban and regional analysis: a GIS application for educational purposes

Geographical information systems (GIS) constitute an important development offering wide application potential in geography, urban and regional planning and associated disciplines. Current debates entail two kinds of criticism; the first involves GIS themselves and the fact that they are often cumbersome and difficult to use; the second involves the ‘poverty‘ of some GIS applications. The result is a worldwide endeavour to produce answers to both questions. The main objective of the system proposed here, known as URAP (urban and regional analysis for planning), is to make a contribution to these goals, by upgrading conventional GIS capabilities, while simplifying the means by which results from advanced statistical analysis are obtained and subsequently plotted. It entails a menu-driven environment and involves the dynamic formation of customised databases to meet the geographical, methodological and other choices made by the user. While the arguments in the paper involve an emphasis on education, the system is also suitable for supporting public policy making.     

Lysis of human monocytic leukemia cells by extracellular adenosine triphosphate: mechanism and characterization of the adenosine triphosphate receptor

The present study shows that extracellular adenosine triphosphate (ATP) has the capacity to mediate dose-dependent lysis of the monocytic leukemia cell line THP-1. The lysis, assessed by 51Cr release, was found to be selective for ATP, because adenosine diphosphate (ADP) or other nucleotides were less effective in their ability to lyse the cells. The amount of 51Cr released was particularly enhanced by the stimulation of the cells with 1,000 U/mL of interferon gamma (IFN-gamma) for 3 days, and the sensitivity was time and dose dependent. Analysis of the mechanism of lysis indicated that the fully ionized form, ATP4-, mediated the lysis, because the addition of cation chelators or the absence of the divalent cations, Ca2+ and Mg2+, in the culture medium of a 6-hour 51Cr release assay increased the percent specific lysis. Therefore, the ATP receptors on THP-1 cells were classified as P2Z purinoceptors. Moreover, it is shown here that the Ca2+/calmodulin complex plays a role in the regulation of the lysis by extracellular ATP of THP-1 cells, because antagonists of this complex, such as trifluoperazine or KN-62, were found to inhibit the ATP-mediated cell lysis.     

Synthesis and release of ATP by soluble mitochondrial F1 in complex with its inhibitor protein during dimethylsulfoxide-water transitions

Soluble mitochondrial F1 and F1 in complex with the natural ATPase inhibitor protein (F1-IP) catalyze the spontaneous synthesis of [gamma-32P]ATP from medium [32P]phosphate and enzyme-bound ADP when incubated in media with dimethylsulfoxide (Me2SO); under these conditions, the synthesized [gamma-32P]ATP is not released into the media, it remains tightly bound to the enzymes [Gómez-Puyou, A., Tuena de Gómez-Puyou, M. & de Meis, L. (1986) Eur. J. Biochem. 159, 133-140]. Some of the characteristics of the synthesized [gamma-32P]ATP were studied in F1 and F1-IP (ATPase activities of 70 and 1-3 micromol x min(-1) x mg(-1), respectively). In Me2SO media, gamma-phosphate of synthesized ATP in F1 or F1-IP exchanges with medium phosphate. From the rates of the exchange reaction, the half-times for hydrolysis of the synthesized ATP in F1 and F1-IP were calculated: 45 min and 58 min for F1 and F1-IP, respectively. The course that synthesized [gamma-32P]ATP follows after dilution of the Me2SO synthetic mixture with aqueous buffer was determined. After dilution, the half-life of synthesized ATP in F1 was less than 1 min. In F1-IP, ATP was also hydrolyzed, but at significantly lower rates. In F1-IP, dilution also produced release of the synthesized [gamma-32P]ATP. This was assayed by the accessibility of [gamma-32P]ATP to hexokinase. About 25% of [gamma-32P]ATP synthesized in F1-IP, but not in F1, was released into the media after dilution with aqueous buffer that contained 20 mM phosphate. Release of tightly bound ATP required the binding energy of phosphate and solvation of F1-IP, however, the particular kinetics of F1-IP were also central for medium ATP synthesis in the absence of electrochemical H+ gradients.