Impact of chromatic dispersion on DPSK and DQPSK direct-detection optical systems

Chromatic dispersion (CD) limitations for binary and quaternary phase-modulated systems using direct detection receivers are analyzed by numerical simulation, comparing the results with intensity-modulated systems, considering both IMDD (Intensity-Modulation Direct-Detection) and Duobinary formats. Three different receiver structures are assumed and many transmitter and receiver filter bandwidths are spanned, to find out how much CD penalty varies depending on such alternative solutions. Penalty was assessed by means of a very accurate performance estimation semi-analytical technique based on Karhunen-Loève series, which theoretically converges to the exact bit-error rate for direct detection optical systems in the presence of both ase noise and inter-symbol interference. The results show that DQPSK is the most resilient format to CD, as expected, but it is also the less sensitive format to filter bandwidth variations.     

Systemic effects of Heterobasidion annosum on ferulic acid glucoside and lignin of presymptomatic ponderosa pine phloem,and potential effects on bark-beetle-associated fungi

Concentrations of soluble phenolics and lignin in the phloem of ponderosa pines inoculated with the pathogen Heterobasidion annosum were assessed over a period of 2 years in a 35-year-old plantation in northern California, USA. The major effect of the pathogen on phloem-soluble phenolics consisted of a significant accumulation of ferulicacid glucoside: 503 ± 27 g/g fresh weight (FW), compared with 366 ± 26 g/g FW for mock-treated and 386 ± 27 g/g FW for control trees. Lignin content was negatively correlated with ferulic acid glucoside concentration, and there was an indication of lignin reduction in the cell walls of inoculated trees. Lignin had a negative effect on the in vitro growth of two common bark beetle fungal associates, Ceratocystiopsis brevicomi and Ophiostoma minus. For this reason it, is hypothesized that lower lignification may facilitate the growth of beetle-associated fungi, resulting in greater susceptibility of the presymptomatic host to bark beetle colonization.     

Turbidimetric detection method in flow-assisted separation of dispersed samples

Characterization of dispersed samples is an outstanding trend in analytical science. Among flow-assisted separation techniques for dispersed samples, size exclusion chromatography, hydrodynamic chromatography, and field-flow fractionation are the most widely applied. With dispersed analytes separated by these techniques, the UV/vis spectrophotometric detectors work as turbidimeters. To directly convert the analytical signal for quantitative analysis, the extinction properties of the dispersed analyte must be known. A new method is proposed to experimentally obtain-by single-run, flow-assisted separation with UV/vis diode-array detectors-the mass-size (or number-size) distribution function of the analytes when a retention-to-size relationship is either theoretically or empirically available for the chosen separation technique. This approach needs neither standards nor reliance on a method to predict the optical properties of the analytes. Theory and original algorithms are presented. Algorithms are then tested to optimize the numerical routines. Accuracy and robustness of the method are evaluated by simulation, and limitations for the application to experimental data are described. Finally, first application to field-flow fractionation shows validity of the method when applied to a few real cases.     

DC performance, AC loss and transient field stability of five medium size NbTi cable-in-conduit conductors with parametric variations

Five medium size NbTi cable-in-conduit conductors with parametric variations in the cable layout were fabricated of three different strands to investigate their DC performance, AC loss behaviour and transient stability by means of the SULTAN facility. A comparison of measured strand data and the cable performances at the same background field indicates that the current carrying capacity of the conductors is limited by the total magnetic field on the high field side. Due to the self-field contribution the total magnetic field on the high field side is considerably larger than the background field at high currents. The take-off electric fields were found to decrease with increasing quench currents, resulting in sudden take-offs for large overall current densities. Effective self-field factors are used to describe the DC performance in the current range, where the critical current and the current sharing temperature are accessible. The quench behaviour of the conductors is discussed in the framework of a model based on peak-field-induced quenches. Differences in the DC performance of the conductors are related to the variation in the transverse resistance determining the ability of the conductors to redistribute the current in the case of a current imbalance originated at the joints. This aspect was studied in more detail by modifying one of the joints allowing a defined number of subcables to be disconnected. The voltage-current characteristics of strands and cable-in-conduit conductors are compared. The reasons for cable n values deviating from the strand n values are discussed. Moreover, the effect of different transverse resistances on the AC loss behaviour and the transient field stability was investigated. Ni coating of the strands was found to be sufficient to eliminate the interstrand coupling current loss. Thus, additional subcable wraps provided no significant further loss reduction.     

Effects of Fertilization and Fungal and Insect Attack on Systemic Protein Defenses of Austrian Pine

Despite their economic and ecological importance, defense responses of conifers to pests are little understood. In a 3-year experiment, we monitored systemic fungal (Diplodia pinea)- and insect (Neodiprion sertifer)-induced defense protein activities and total soluble proteins in needles and phloem of Austrian pine (Pinus nigra) across a soil fertility gradient. In both years, total soluble protein content of foliage and phloem declined with increasing fertility across induction treatments, while defensive protein activities generally increased with increasing fertility. In 2005, total soluble protein content in branch phloem was increased by fungal inoculation of the stem. Peroxidase activity was suppressed in needles by insect defoliation in 2006, while polyphenol oxidase activity was systemically induced in branch phloem by insect attack in 2005. Trypsin inhibitor activities in phloem did not respond to any induction or fertility treatment. Nutritive quality of Austrian pine tissue declined with increasing fertility, while several protein-based defenses simultaneously increased.     

Assessment of the greenhouse gas emissions from cogeneration and trigeneration systems. Part I: Models and indicators

The diffusion of cogeneration and trigeneration plants as local generation sources could bring significant energy saving and emission reduction of various types of pollutants with respect to the separate production of electricity, heat and cooling power. The advantages in terms of primary energy saving are well established. However, the potential of combined heat and power (CHP) and combined cooling heat and power (CCHP) systems for reducing the emission of hazardous greenhouse gases (GHG) needs to be further investigated. This paper presents and discusses a novel approach, based upon an original indicator called trigeneration CO₂emission reduction (TCO₂ER), to assess the emission reduction of CO₂ and other GHGs from CHP and CCHP systems with respect to the separate production. The indicator is defined in function of the performance characteristics of the CHP and CCHP systems, represented with black-box models, and of the GHG emission characteristics from conventional sources. The effectiveness of the proposed approach is shown in the companion paper (Part II: Analysis techniques and application cases) with application to various cogeneration and trigeneration solutions.     

Fast and Chemoselective Transfer Hydrogenation of Aldehydes Catalyzed by a Terdentate CNN Ruthenium Complex [RuCl(CNN)(dppb)]

Aromatic, aliphatic and α,β‐unsaturated aldehydes are quickly, quantitatively and chemoselectively reduced to primary alcohols with 2‐propanol using 0.05–0.01 mol % of the terdentate CNN ruthenium complex RuCl(CNN)(dppb) ( 1 ) [HCNN=6‐(4′‐methylphenyl)‐2‐pyridylmethylamine; dppb=Ph₂P(CH₂)₄PPh₂] in the presence of potassium carbonate (K₂CO₃; 1–10 mol %) as a weak base, affording TOF values up to 5.0×10⁵ h⁻¹.     

Effect of organic enrichment and thermal regime on denitrification and dissimilatory nitrate reduction to ammonium (DNRA) in hypolimnetic sediments of two lowland lakes

We analyzed benthic fluxes of inorganic nitrogen, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates in hypolimnetic sediments of lowland lakes. Two neighbouring mesotrophic (Ca' Stanga; CS) and hypertrophic (Lago Verde; LV) lakes, which originated from sand and gravel mining, were considered. Lakes are affected by high nitrate loads (0.2-0.7 mM) and different organic loads. Oxygen consumption, dissolved inorganic carbon, methane and nitrogen fluxes, denitrification and DNRA were measured under summer thermal stratification and late winter overturn.Hypolimnetic sediments of CS were a net sink of dissolved inorganic nitrogen (−3.5 to −4.7 mmol m⁻² d⁻¹) in both seasons due to high nitrate consumption. On the contrary, LV sediments turned from being a net sink during winter overturn (−3.5 mmol m⁻² d⁻¹) to a net source of dissolved inorganic nitrogen under summer conditions (8.1 mmol m⁻² d⁻¹), when significant ammonium regeneration was measured at the water-sediment interface. Benthic denitrification (0.7-4.1 mmol m⁻² d⁻¹) accounted for up to 84-97% of total NO₃⁻ reduction and from 2 to 30% of carbon mineralization. It was mainly fuelled by water column nitrate. In CS, denitrification rates were similar in winter and in summer, while in LV summer rates were 4 times lower. DNRA rates were generally low in both lakes (0.07-0.12 mmol m⁻² d⁻¹). An appreciable contribution of DNRA was only detected in the more reducing sediments of LV in summer (15% of total NO₃⁻ reduction), while during the same period only 3% of reduced NO₃⁻ was recycled into ammonium in CS.Under summer stratification benthic denitrification was mainly nitrate-limited due to nitrate depletion in hypolimnetic waters and parallel oxygen depletion, hampering nitrification. Organic enrichment and reducing conditions in the hypolimnetic sediment shifted nitrate reduction towards more pronounced DNRA, which resulted in the inorganic nitrogen recycling and retention within the bottom waters. The prevalence of DNRA could favour the accumulation of mineral nitrogen with detrimental effects on ecosystem processes and water quality.     

Reactive compatibilizer precursors for LDPE/PA6 blends. III: ethylene-glycidylmethacrylate copolymer

The effectiveness of a commercial ethylene-glycidylmethacrylate copolymer (Lotader GMA AX 8840) as a compatibilizer precursor (CP) for blends of low density polyethylene (LDPE) with polyamide-6 (PA) has been evaluated by an investigation of the thermal properties and the morphology of binary (LDPE/CP and PA/CP) and ternary (LDPE/PA/CP) blends, as well as by solvent fractionation experiments. It has been demonstrated that the epoxy groups of the CP react quite easily, during melt blending, with both the amine and the carboxyl end groups of PA to give CP-g-PA copolymers, which, depending on the relative amounts of PA and CP, may be partially cross-linked. The composition of the graft copolymers has been approximately determined by gravimetric and calorimetric measurements. The compatibilizing efficiency of the CP employed in this work has been found to be comparable to that of the ethylene-acrylic acid copolymers, and lower than that of a maleic anhydride-functionalized polyethylene, which had been used in previous works.     

Polymer-dispersed liquid-crystal polymers (PDLCPs). Morphology of the LCP droplets

“Synthetic blends” of a flexible polymer forming the matrix and a liquid-crystalline polymer (LCP) forming the dispersed phase have been prepared by transesterification of PET with a mixture of sebacic acid (S), 4,4′-diacetoxybiphenyl (B) and 4-acetoxybenzoic acid (H) in the mole ratio 1:1:2. A change of the synthesis conditions causes marked variations of the chemical composition and the morphology of the phases. The SEM investigation of the inner morphology of the LCP droplets of blends consisting of two phases with fairly different aromatic content has shown that the LCP macromolecules are aligned tangentially at the matrix surface boundary, and that the nematic director configuration is toroidal. When the two phases have closer chemical composition, and are therefore supposed to possess improved mutual compatibility, a perpendicular anchoring of the LCP fibrils to the matrix cavity surface, and an axial configuration of the nematic director, are observed. The expected effect of the nematic configuration of the LCP droplets on their ability to deform into fibrils under appropriate flow conditions is preliminarily discussed.