Quantitative Determination of HD Internal State Distributions via (2+1) REMPI

The relationship between quantum state populations and ion signals in (2+1) resonance-enhanced multiphoton ionization (REMPI) detection of HD is investigated both experimentally, by measurements of hot-nozzle population distributions, and theoretically, by calculations of the two-photon E,F ¹Σ_g⁺—X¹Σ_g⁺ transition moments. The experimental and theoretical relative rotational cross-sections are in good agreement for v″ = 0 and v″ = 1, but differ for v″ = 2 and for the relative vibrational cross-sections. Arguments are presented that saturation of the E,F-X transition is the main cause of these discrepancies. In spite of the presence of saturation, this calibration gives confidence in determining the relative internal state populations of HD from its (2+1) REMPI spectrum.     

Synthesis,characterization and thermal behaviors of polymers containing organosilicon groups

Various bis(silyl)ethenyl groups were attached to the aromatic ring of poly(α-methylstyrene) via Peterson olefination reaction of (RMe₂Si)₃CLi (R = H, Me and Ph) with formylated poly(α-methylstyrene) (Pα-MS-CHO) to give poly(α-methylstyrene)-co-[2,2-bis(silyl)ethenyl(α-methylstyrene)] as functionalized poly(α-methylstyrene) (Pα-MS-SiMe₂H, Pα-MS-SiMe₃ and Pα-MS-SiMe₂Ph). The trimethylsilyl groups of Pα-MS-SiMe₃ have been converted to 2,2-dibromoethenyl and epoxybis(silanes) groups via NBS-based bromodesilylation and MCPBA-based epoxidation respectively. The thermal degradation behaviors of the polymers were studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC).     

pHEMA: An Overview for Biomedical Applications

Poly(2-hydroxyethyl methacrylate) (pHEMA) as a biomaterial with excellent biocompatibility and cytocompatibility elicits a minimal immunological response from host tissue making it desirable for different biomedical applications. This article seeks to provide an in-depth overview of the properties and biomedical applications of pHEMA for bone tissue regeneration, wound healing, cancer therapy (stimuli and non-stimuli responsive systems), and ophthalmic applications (contact lenses and ocular drug delivery). As this polymer has been widely applied in ophthalmic applications, a specific consideration has been devoted to this field. Pure pHEMA does not possess antimicrobial properties and the site where the biomedical device is employed may be susceptible to microbial infections. Therefore, antimicrobial strategies such as the use of silver nanoparticles, antibiotics, and antimicrobial agents can be utilized to protect against infections. Therefore, the antimicrobial strategies besides the drug delivery applications of pHEMA were covered. With continuous research and advancement in science and technology, the outlook of pHEMA is promising as it will most certainly be utilized in more biomedical applications in the near future. The aim of this review was to bring together state-of-the-art research on pHEMA and their applications.     

Design of nanoscale molecular wire based on diphenylacetylene: Role of linkage

Theoretical investigation has been performed on electron transport properties of diphenylacetylene-based molecules sandwiched between two gold surfaces. Different linkers such as sulfur, nitrogen, oxygen, CS, CO, CN, NS, NO and NN have been considered to study the role of linkage in the conduction properties of the molecular wire. The charge transfer across the metal–molecule and bonding nature at the interfacial contact are illustrated by natural bond orbital analysis. It is found that Au can covalently bond to diphenylacetylene through nitrogen or sulfur linkages while its weak interaction through oxygen linkage has non-covalent character in nature. The dependence of the molecular electronic structure of the gold–molecule complexes on the external electric field has been also studied. The electronic conduction has been analyzed from the change in the shape of molecular orbitals and the evolution of the HOMO–LUMO gap of the molecule-gold complexes under the influence of the electric filed.     

Direct monitoring of absorption in solution by cavity ring-down spectroscopy

Cavity ring-down spectroscopy is applied to the liquid phase by placing the target solution directly into the optical cavity. We demonstrate that solutions in the cavity can be stirred and more importantly monitored in a flow. We report a minimum detectable absorption of 10(-6) cm(-1) for a range of organic solvents. This detection limit corresponds to picomolar concentrations for strong absorbers.     

Cavity ring-down spectroscopy as a detector for liquid chromatography

We have demonstrated the use of cavity ring-down spectroscopy (CRDS) as a detector for high performance liquid chromatography (HPLC). For this use, we have designed and implemented a Brewster's angle flow cell such that cavity ring-down spectroscopy can be performed on microliter volumes of liquids. The system exhibits a linear dynamic range of 3 orders of magnitude (30 nM to 30 microM quinalizarin at 470 nm) for static measurements and 2 orders of magnitude (0.5 microM to 50 microM) for HPLC measurements. For the static measurements, the baseline noise is 2.8 x 10(-6) AU rms and 1.0 x 10(-5) AU peak-to-peak, and for the HPLC separations, it is 3.2 x 10(-6) AU rms and 1.3 x 10(-5) AU peak-to-peak. The baseline noise is determined after the data are smoothed by an 11-point boxcar average. The peak areas detected from HPLC separations are reproducible to within 2-3%. The HPLC mass detection limit for a molecule with epsilon = 9 x 10(3) M(-1) cm(-1) in a 300-microm path length cell (illuminated volume, 0.5 microL) is reported as 2.5 x 10(-8) g/mL. These results were obtained using a simple pulsed CRDS system and are comparable to, if not better than, a high-quality commercial UV-vis absorption detector for the same path length.     

Strategy for on-line preconcentration in chromatographic separations

In chromatographic separations, the heights of peaks are proportional to the concentrations of sample components present in an injected mixture. In general, an increase in the peak height cannot be achieved by simply increasing the injection time or the sample plug length. An exception occurs if some form of on-line preconcentration is possible. We present a new strategy for achieving on-line preconcentration by the use of a porous chromatographic material that acts as a solid-phase extractor as well as a stationary-phase separator. We are able to realize significant on-line preconcentration using capillary columns filled with a photopolymerized sol-gel (PSG). More than 2-cm plugs of sample solution can be loaded into the capillary and concentrated using a running buffer that is the same as the injection buffer (to avoid solvent gradient effects). As a demonstration, mixtures of three different polycyclic aromatic hydrocarbons, eight different alkyl phenyl ketones, and five different peptides in solutions of aqueous acetonitrile have been injected onto the PSG column and separated by capillary electrochromatography. The preconcentration is marked in terms of peak heights, with up to 100-fold increase for the PAH mixture, 30-fold for the alkyl phenyl ketone mixture, and 20-fold for the peptide mixture. Preconcentration takes place because of the high mass-transfer rates possible in the highly porous structure, and the extent of preconcentration follows the retention factor k for a given analyte.     

On-line preconcentration in capillary electrochromatography using a porous monolith together with solvent gradient and sample stacking

Preconcentration effects of solvent gradient and sample stacking are investigated on a photopolymerized sol-gel (PSG) in capillary electrochromatography. The porous PSG monolith has a high mass-transfer rate. This characteristic promotes preconcentration of dilute samples. Plugs of samples more than 2 cm in length prepared in the separation solution (nongradient condition) are injected onto the PSG column. The extent of preconcentration is quite significant, showing up to a 100-fold increase in peak heights of the separated analytes. Even larger preconcentrations are achieved under gradient conditions by dissolving the sample in a matrix with a higher concentration of noneluting solvent (water). For eight alkyl phenyl ketones and four polycyclic aromatic hydrocarbons that serve as neutral test analytes, improvements in peak heights obtained under gradient conditions can be more than a 1000-fold. Indeed, injection of a 91.2-cm plug, which is more than 3 times the total length of the capillary, was possible with only a minor loss in resolution. Five peptides serve as charged test analytes. Nongradient conditions in which the sample is hydrodynamically injected onto the PSG column show sizable preconcentration because of sample stacking. The use of a solvent gradient with the same ionic strength, however, does not appear to have practical value because of destacking caused by the changing organic composition that affects the conductivity. As an alternative preconcentration method, we demonstrate that electric field-enhanced sample injection on the PSG yielded up to a 1000-fold improvement in detection sensitivity for the test peptides.     

A NEW HYBRID EVOLUTIONARY OPTIMIZATION ALGORITHM FOR DISTRIBUTION FEEDER RECONFIGURATION

This article extends a hybrid evolutionary algorithm to cope with the feeder reconfiguration problem in distribution networks. The proposed method combines the Self-Adaptive Modified Particle Swarm Optimization (SAMPSO) with Modified Shuffled Frog Leaping Algorithm (MSFLA) to proceed toward the global solution. As with other population-based algorithms, PSO has parameters which should be tuned to have a suitable performance. Thus, a self-adaptive framework is proposed to adjust the parameters dynamically. In SAMPSO, the PSO learning factors are considered to be the new control variables and are changed in the evolutionary process. To enhance the quality of the solutions, the SAMPSO is combined with MSFLA and a new hybrid algorithm is proposed to minimize the electrical energy losses of the distribution system by feeder reconfiguration. The effectiveness of the proposed method is demonstrated through two test systems.     

Performance Evaluation of ANN and ANFIS Models for Estimating Garlic Crop Evapotranspiration

Estimation of evapotranspiration (ET) is necessary in water resources management, farm irrigation scheduling, and environmental assessment. Hence, in practical hydrology, it is often necessary to reliably and consistently estimate evapotranspiration. In this study, two artificial intelligence (AI) techniques, including artificial neural network (ANN) and adaptive neuro-fuzzy inference system (ANFIS), were used to compute garlic crop water requirements. Various architectures and input combinations of the models were compared for modeling garlic crop evapotranspiration. A case study in a semiarid region located in Hamedan Province in Iran was conducted with lysimeter measurements and weather daily data, including maximum temperature, minimum temperature, maximum relative humidity, minimum relative humidity, wind speed, and solar radiation during 2008–2009. Both ANN and ANFIS models produced reasonable results. The ANN, with 6-6-1 architecture, presented a superior ability to estimate garlic crop evapotranspiration. The estimates of the ANN and ANFIS models were compared with the garlic crop evapotranspiration (ETc) values measured by lysimeter and those of the crop coefficient approach. Based on these comparisons, it can be concluded that the ANN and ANFIS techniques are suitable for simulation of ETc.