Directly modulated and fully tunable hybrid silicon lasers for future generation of coherent colorless ONU.

We propose and demonstrate asymmetric 10 Gbit/s upstream--100 Gbit/s downstream per wavelength colorless WDM/TDM PON using a novel hybrid-silicon chip integrating two tunable lasers. The first laser is directly modulated in burst mode for upstream transmission over up to 25 km of standard single mode fiber and error free transmission over 4 channels across the C-band is demonstrated. The second tunable laser is successfully used as local oscillator in a coherent receiver across the C-band simultaneously operating with the presence of 80 downstream co-channels.

Modeling nonlinearity in coherent transmissions with dominant intrachannel-four-wave-mixing.

By extending a well-established time-domain perturbation approach to dual-polarization propagation, we provide an analytical framework to predict the nonlinear interference (NLI) variance, i.e., the variance induced by nonlinearity on the sampled field, and the nonlinear threshold (NLT) in coherent transmissions with dominant intrachannel-four-wave-mixing (IFWM). Such a framework applies to non dispersion managed (NDM) very long-haul coherent optical systems at nowadays typical baudrates of tens of Gigabaud, as well as to dispersion-managed (DM) systems at even higher baudrates, whenever IFWM is not removed by nonlinear equalization and is thus the dominant nonlinearity. The NLI variance formula has two fitting parameters which can be calibrated from simulations. From the NLI variance formula, analytical expressions of the NLT for both DM and NDM systems are derived and checked against recent NLT Monte-Carlo simulations.

Epidermal growth factor receptor irreversible inhibitors: chemical exploration of the cysteine-trap portion.

Covalent EGFR irreversible inhibitors showed promising potential for the treatment of gefitinib-resistant tumors and for imaging purposes. They contain a cysteine-reactive portion forming a covalent bond with the protein. Irreversible kinase inhibitors have been advanced to clinical studies, mostly characterized by an acrylamide or butynamide warhead. However, the clinical usefulness of these compounds has been hampered by resistances, toxicity and pharmacokinetic problems. Investigation on the structure-activity and structure-reactivity relationships may provide useful information for compounds with improved selectivity and pharmacokinetic properties. This review focuses on the exploration of the cysteine-trap portions able to irreversibly inhibit EGFR and other erbB receptors.

SOA gain recovery wavelength dependence: simulation and measurement using a single-color pump-probe technique.

Measurements to date of the wavelength dependency of gain recovery time in semiconductor optical amplifiers (SOAs) have mostly used pump-probe techniques with a pump and probe operated on distinct wavelengths. Choice of pump wavelength, and its relative proximity to the probe wavelength, could influence measurements and impede unambiguous observation of wavelength dependence on recovery dynamics. We use a single-color pump-probe measurement technique to directly access the wavelength dependence of the gain recovery time in bulk InGaAsP SOAs. We used ultrashort pulses from a single mode locked laser to measure unambiguously the spectral dependency and temporal behavior of SOAs. Simulation results using a model that takes into account intra-band and inter-band contributions to SOA saturation, as well as experimental results for the SOA tested, show recovery rate dependency similar to gain spectrum.

Structure-property relationships on histamine H3-antagonists: binding of phenyl-substituted alkylthioimidazole derivatives to rat plasma proteins.

The binding of a series of H3-antagonists to rat plasma proteins was investigated by dialysis experiments, with RP-HPLC measurement of the free ligand. The series was composed of 4(5)-phenyl-2-[[2-[4(5)-imidazolyl]ethyl]thio]imidazoles having, on the phenyl ring, meta- and para-substituents, with different physico-chemical characteristics. As high protein binding had been proposed as being one of the features limiting brain access for the reference H3-antagonist thioperamide, the title series was employed to test the possibility of achieving lower protein binding by modulation of lipophilicity, while maintaining good receptor affinity. The compounds tested showed quotas of bound drug ranging from 60 to 97.5%, while for thioperamide a 78% bound drug quota was observed at high total concentrations, with a steep increase in bound percentage at lower concentrations. Two of the tested compounds, having a carboxamide substituent, showed lower protein binding compared to thioperamide over a wide range of total concentration, without a significant loss in affinity with respect to the parent compound. A strict dependence of protein binding on lipophilicity was observed, and a QSPR model was derived which could also account for the protein binding observed for thioperamide, while receptor affinity had been reported to be quite insensitive to phenyl ring substitution. It is therefore possible to modulate protein binding of these H3-antagonists, through lipophilicity adjustment, without losing receptor affinity; this finding could help in the design of new compounds with improved brain access.

Synthesis and biological assays of new H3-antagonists with imidazole and imidazoline polar groups.

New histamine H3-receptor antagonists were synthesised and tested on rat brain membranes and on electrically stimulated guinea-pig ileum. The new compounds have a central polar group represented by a 2-alkylimidazole or a 2-thioimidazoline nucleus. The effect of the polar group basicity on the optimal length of the alkyl chain, connecting this group to a 4(5)-imidazolyl ring, was investigated. The best affinity values, obtained by displacement of [3H]-RAMHA from rat brain, were obtained for the 2-alkylimidazole derivatives (2a-f) with tetramethylene chain (pKi 8.03-8.97), having an intermediate basicity between that of the previously reported 2-thioimidazoles (1a-i) and that of 2-alkylthioimidazolines (3a-h). In contrast, a general lowering of affinity (pKi 5.90-7.63) was observed for compounds of the last series (3a-h), with a complex dependence on the terminal lipophilic group and chain length.