Porphyrin-naphthodiimide interactions as a structural motif in foldamers and supramolecular assemblies

pi-pi Stacking interactions between electron deficient naphthalenediimides (NDI) and electron-rich porphyrins (POR) leading to charge transfer are shown to be prevalent in linked NDI-POR and POR-NDI-POR structures. For flexibly-linked systems, intramolecular interactions lead to S-shaped foldamers in solution, whereas intermolecular association is predominant in more rigid systems. The foldamer structures can be interrupted by competing aromatic solvents, by six-coordination of metallated porphyrin derivatives, by protonation of the free base porphyrin in non-metallated structures, and in facially sterically hindered porphyrins.     

Dual-Wavelength Erbium Fiber Laser in a Simple Ring Cavity

Abstract

By controlling the cavity loss of the modes using a variable optical attenuator, specific intensities of distributed modes can be fed back into the erbium-doped fiber to produce signals without mode competition, thus resulting in stable lasing as a means to overcome mode competition in a homogenous gain medium. Two lasing signals were obtained with peak powers of approximately ?3.475 dBm and ?4.386 dBm for wavelengths of 1,540 nm and 1,548 nm, respectively, with a side mode suppression ratio of more than 43 dB.     

Loading and release of ibuprofen in multi- and monofilament surgical sutures

The preparation of mono- and multifilament sutures incorporating ibuprofen as an anti-inflammatory agent is considered. Poly(p-dioxanone) monofilament samples can be loaded by a molecular diffusion process using a swelling agent such as dichloromethane. The mechanical properties have been measured and have not shown a significant change for the ibuprofen loaded samples in knot tensile assays. The kinetics of both the loading process and the release in a S?rensen's medium at 37 degrees C have been investigated. Diffusion coefficients have also been estimated from film and slab poly(p-dioxanone) samples containing ibuprofen and their release behavior compared to that shown by monofilaments. Release from a coating copolymer based on lactide, epsilon-caprolactone and trimethylene carbonate (PLA/PCA/PTMC 10/60/30) has also been studied. This coating solubilizes ibuprofen molecules well and can be used for braided sutures or when a rapid dose of ibuprofen is preferred.     

120 nm wide band switchable fiber laser

A novel method of producing switchable tunable output that spans the S-, C- and L-bands is presented. The achievable tuning range is about 120 nm. The design consists of a wide band SOA, 1 × 16 AWG and an optical selectable switch in a ring configuration. The measured average output powers for S-, C- and L-bands for different output wavelengths are −7.0 dBm, −6 dBm and −6.5 dBm respectively. The SMSR for these wavelengths is about 72 dB.     

Determining the time-frequency parameters of low-power bright picosecond optical pulses by using the interferometric technique

We present an approach to the characterization of low-power bright picosecond optical pulses with an internal frequency modulation simultaneously in both time and frequency domains in practically much used case of the Gaussian shape. This approach exploits the Wigner time-frequency distribution, which can be found for these bright pulses by using a novel interferometric technique under our proposal. Then, the simplest two-beam scanning Michelson interferometer is selected for shaping the field-strength auto-correlation function of low-power picosecond pulse trains. We are proposing and considering in principle the key features of a new experimental technique for accurate and reliable measurements of the train-average width as well as the value and sign of the frequency chirp of pulses in high-repetition-rate trains. This technique is founded on an ingenious algorithm for the advanced metrology, assumes using a specially designed supplementary semiconductor cell, and suggests carrying out a pair of additional measures with exploiting this semiconductor cell. Such a procedure makes possible constructing the Wigner distribution and describing the above-listed time-frequency parameters of low-power bright picosecond optical pulses. In the appendix, we follow one of possible avenues for deriving the joint Wigner time-frequency distribution via choosing the Weil's correspondence between classical functions and operators.     

Mössbauer study of the evolution of a laterite iron mineral based catalyst: Effect of the activation treatment

The syngas reaction has been studied using a laterite iron mineral, promoted with K and Mn. In situ activation under syngas, as well as pre-treatment with H₂ followed by CO under mild and more severe conditions were tested. These activation procedures led to different iron phase compositions and to different catalytic selectivities. The C₂-C₄/CH₄ ratio was significantly lower for those catalysts which after reaction showed the presence of hexagonal carbide and magnetite compared to the solid, which showed the highest proportion of Hägg carbide.     

Flat output and switchable fiber laser using AWG and broadband FBG

The switchable multiwavelength fiber laser (SMWLSs) using AWG and broadband FBG with tuning range 11.7 nm and 0.75 nm spacing are demonstrated. The switchable lasers for every channel shows flatness output power with variation 3.7 dBm and peak power around −6.1 dBm. The side mode suppression ratio (SMSR) of the laser is significantly improved for every channel when using broadband FBG. The improvement is about 27.7 dBm. The laser for every channel also shows the good stability within the 2 h operation.     

Polymer electrolyte liquid crystal mixtures as phase-dependent thermoelectric materials

Organic thermoelectric materials have gained a trajectory in recent years given its advantages of processability, low cost and flexibility. In this paper, polymer electrolyte liquid crystal (PELC) mixtures composed of polyvinyl alcohol, potassium iodide, and 4-Cyano-4'-pentylbiphenyl (5CB) liquid crystal are fabricated, the 5CB acts as a ‘temperature switch’, i.e., a strong correlation between the thermoelectric properties and the transition from Ne-Iso transition of the 5CB, is observed. The electrical conductivity and Seebeck coefficient of the PELC mixtures both decrease above the Ne-Iso transition temperature. This thermoelectric behavior is discussed in terms of the carrier concentration, carrier mobility, and order-disorder transition.