Performance of optical chaotic communication systems using multimode vertical cavity surface emitting lasers

Influence of side modes on the performance of optical chaotic communication systems is studied theoretically. Three coding techniques, namely chaotic modulation, chaotic masking and chaotic shift keying, are also considered in the investigation. It can be shown that communication system using chaotic shift keying has better immunity to side mode. On the other hand, frequency division multiplexing using multimode vertical cavity surface emitting laser is proposed to double the transmission capacity of the communication system.     

Engaging Copper(III) Corrole as an Electron Acceptor: Photoinduced Charge Separation in Zinc Porphyrin–Copper Corrole Donor–Acceptor Conjugates

An electron‐deficient copper(III) corrole was utilized for the construction of donor–acceptor conjugates with zinc(II) porphyrin (ZnP) as a singlet excited state electron donor, and the occurrence of photoinduced charge separation was demonstrated by using transient pump–probe spectroscopic techniques. In these conjugates, the number of copper corrole units was varied from 1 to 2 or 4 units while maintaining a single ZnP entity to observe the effect of corrole multiplicity in facilitating the charge‐separation process. The conjugates and control compounds were electrochemically and spectroelectrochemically characterized. Computational studies revealed ground state geometries of the compounds and the electron‐deficient nature of the copper(III) corrole. An energy level diagram was established to predict the photochemical events by using optical, emission, electrochemical, and computational data. The occurrence of charge separation from singlet excited zinc porphyrin and charge recombination to yield directly the ground state species were evident from the diagram. Femtosecond transient absorption spectroscopy studies provided spectral evidence of charge separation in the form of the zinc porphyrin radical cation and copper(II) corrole species as products. Rates of charge separation in the conjugates were found to be of the order of 10¹⁰ s^?1 and increased with increasing multiplicity of copper(III) corrole entities. The present study demonstrates the importance of copper(III) corrole as an electron acceptor in building model photosynthetic systems.     

Cs oxide aggregation in SIMS craters in organic samples for optoelectronic application

This paper presents evidence for Cesium (Cs) oxide aggregation in secondary ion mass spectrometry (SIMS) craters in organic samples used for optoelectronic devices, after exposure to air. The morphology of craters after Cs⁺ bombardment at low impact energy was investigated under vacuum and after exposure to air by different techniques, including surface roughness characterization by Atomic Force Microscopy (AFM), surface chemical mapping and quantification by SIMS, Auger Electron Spectroscopy (AES) and X-ray Photon Spectroscopy (XPS). Altogether, two different organic molecules used in optoelectronic devices, Tris(8‐hydroxyquinolinato) aluminum (Alq₃) and Copper Phthalocyanine (CuPc), different layer thicknesses and deposition methods were studied as a function of depth and as a function of duration to air exposure. The results show that, after exposure to air, Cs containing particles appear at the crater bottom under certain conditions. These results are useful to understand the behavior of implanted Cs in view of avoiding artifacts when Cs-implanted samples need to be transferred by air to other instruments for subsequent analyses (e.g. the analysis technique mentioned above).     

5-HT1A receptor pharmacophores to screen for off-target activity of α1-adrenoceptor antagonists

The α₁-adrenoceptors (α₁-ARs), in particular the α_1A-AR subtype, are current therapeutic targets of choice for the treatment of urogenital conditions, such as benign prostatic hyperplasia (BPH). Due to the similarity between the transmembrane domains of the α₁-AR subtypes, and the serotonin receptor subtype 1A (5-HT_1A-R), currently used α₁-AR subtype-selective drugs to treat BPH display considerable off-target affinity for the 5-HT_1A-R, leading to side effects. We describe the construction and validation of pharmacophores for 5-HT_1A-R agonists and antagonists. Through the structural diversity of the training sets used in their development, these pharmacophores define the properties of a compound needed to bind to 5-HT_1A receptors. Using these and previously published pharmacophores in virtual screening and profiling, we have identified unique chemical compounds (hits) that fit the requirements to bind to our target, the α_1A-AR, selectively over the off-target, the 5-HT_1A-R. Selected hits have been obtained and their affinities for α_1A-AR, α_1B-AR and 5-HT_1A-R determined in radioligand binding assays, using membrane preparations which contain human receptors expressed individually. Three of the tested hits demonstrate statistically significant selectivity for α_1A-AR over 5-HT_1A-R. All seven tested hits bind to α_1A-AR, with two compounds displaying K _i values below 1 μM, and a further two K _i values of around 10 μM. The insights and knowledge gained through the development of the new 5-HT_1A-R pharmacophores will greatly aid in the design and synthesis of derivatives of our lead compound, and allow the generation of more efficacious and selective ligands.     

Local electrochemical impedance spectroscopy: A window into heterogeneous interfaces

The ability to probe surface reactivity on a local scale has led to a new insight into the comprehension of the electrochemical reactivity in relation with the microstructure of the surface. Among the different techniques developed in recent years, local electrochemical impedance spectroscopy has the advantage of using a transient approach to locally characterize a stationary electrochemical system without the need to add any redox mediator in solution, which is a great advantage for the study of different systems.In this review, particular attention is paid to the different ways of measuring the local impedance, and the technique implementing a local current measurement in solution is deeply discussed. This local electrochemical impedance spectroscopy journey also encompasses a discussion about technical and experimental limitations.     

A phase-shifted linearly chirped fiber Bragg grating with tunable bandwidth

We demonstrate a new method to broaden and adjust the transmission bandwidth of a phase-shifted linearly chirped fiber Bragg grating (PS-LCFBG) after its fabrication. A movable thermal head is used to heat the PS-LCFBG at a small contact point. The original ultra-narrow transmission bandwidth of the PS-LCFBG can be broadened due to both the presence of the passband peak caused by the thermally-induced temporary phase shift and the passband caused by the thermally-induced local Bragg wavelength shift. The transmission bandwidth of the new passband peak can be adjusted by changing the position of the thermal head. The transmission bandwidth of the PS-LCFBG can be broadened from <10 pm to 0.16 nm, and can be tuned from 0.16 to 1.05 nm.     

Hamilton cycles in cubic (m,n)-metacirculant graphs withm divisible by 4

It is shown that every connected cubic (m, n)-metacirculant graph withm divisible by 4 has a Hamilton cycle.This work is supported in part by the Vietnamese National Basic Research Program in Natural Sciences