α-OXIDASE ACTIVITY IN PLANTS AS PROMOTOR OF ELECTRONIC ENERGY

Abstract The a-oxidase activity of higher plants acting on long chain fatty acids generates the lower aldehyde in the ground state; however if chlorophyll or chioroplasts are present the chlorophylls are excited most likely by a chemically initiated electron exchange (CIEEL) luminescence process with the putative a-peroxylactone intermediate. When the aldehyde is substituted for the acid, the lower aldehyde appears in the triplet state. The chiral discrimination observed in the quenching by D- and L-tryptophan of the chlorophyll sensitized emission indicates that the triplet aldehyde is generated within the enzymatic preparation and transfers energy while still bound to the enzyme.
Chlorophylls in chioroplasts are excited by addition of a long chain fatty acid or aldehyde. The mechanism, however, is unknown.     

CHEMIEXCITATION IN THE ARACHIDONIC ACID CASCADE

As investigated in neutrophils, the very weak luminescence accompanying the arachidonic acid cascade is associated with the lipoxygenase pathway. The emission is dramatically enhanced by energy transfer to chlorophyll a. The number of chlorophyll molecules excited to the fluorescent state per oxygen consumed, (the S1/O2 ratio), equal to the product of the quantum yields of chemiexcitation and of energy transfer, is 5.4 x 10(-6). The quantum yield of chemiexcitation is inferred to be higher than 1 x 10(-3). The two most likely chemiexcitation routes point to triplet conjugated carbonyls as the most likely candidates for the excited species that transfer to chlorophyll. As such the emission intensity may reflect the level of hydroperoxyeicosatetraenoic acid. This is the first case where addition of a biotic substrate to a cellular system results in substantial generation of electronic excited states without any drastic loss of cell viability. Whether the formation of excited states in the arachidonic acid cascade in neutrophils is accidental or has a biological role is an open question.     

A theoretical study of the 21Ag ← 11Ag two-photon transition and its vibronic band in trans-stilbene

The two-photon spectrum of the 2¹A_g ← 1¹A_g transition in trans-stilbene has been calculated at the complete active space self-consistent field (CASSCF) level of theory. Energies were obtained at the complete active space second-order perturbation (CASPT2) level of theory, while the geometries of both the initial and final states were optimized at the CASSCF level. The energy and the geometry optimizations were performed using an active space of 14 electrons in 14 active π orbitals. The vibrational frequencies of both states and the two-photon transition (TPT) cross-section were calculated with a smaller active space where the two lowest π orbitals were kept inactive. A newly implemented algorithm, in the quantum chemical package Molcas was used to determine the two-photon transition intensity. This method requires only the linear response of the CASSCF wavefunction. Furthermore, the vibronic structure of this TPT was studied. The Franck-Condon factors were obtained by calculating the overlap between the vibrational states involved, which were determined from the force fields of both the initial and final states, at the CASSCF level of theory. The results are in agreement with experiment.     

A study of the behaviour of ampicillin in aqueous solution and thermodynamic characterization of its aggregation

The aggregation of ampicillin in water has been examined by conductivity measurements over the temperature range 288.15–313.15 K and light scattering. These measurements indicate the formation of two critical concentrations over the range 0–0.35 mol kg^?1. Aggregation number and effective aggregate charge were calculated from the static light scattering data according to the Anacker and Westwell treatment. Thermodynamic parameters of aggregate formation were obtained from a form of the mass action model applicable to systems of low aggregation number. This method was applied at both critical concentrations. A valence of one was used for the monomers present in the first equilibrium. The second equilibrium was between aggregates of two different sizes, in this case, the valence of the aggregates being the effective charge calculated from the Anacker and Westwell treatment. Experimental results show that free energies of micellization for ampicillin are higher for the first critical concentration and in the same range, but lower than for other penicillins. The enthalpies of micellization become negative when the temperature is increased, but the variation is three times greater for the first critical concentration than for the second.     

Metropolitan Optical Networks: When to Change to DWDM

In this article we propose a new methodology to estimate the change in the bandwidth demand in time, mainly in residential areas. The bandwidth demand forecast is a basic aspect to decide the evolution of metropolitan optical networks. The word evolution refers to the necessity of making changes in networks, either by upgrading or replacing different elements that are part of the network. This analysis, along with a technological alternatives analysis, provides the operator the needed information to achieve the appropriate network planning and to make investment decisions.     

POSSIBILITIES AND LIMITATIONS OF USING HISTORIC PROVENANCE TESTS TO INFER FOREST SPECIES GROWTH RESPONSES TO CLIMATE CHANGE

Abstract. Under projected changes in global climate, the growth and survival of existing forests will depend on their ability to adjust physiologically in response to environmental change. Quantifying their capacity to adjust and whether the response is species‐ or population‐specific is important to guide forest management strategies. New analyses of historic provenance tests data are yielding relevant insights about these responses. Yet, differences between the objectives used to design the experiments and current objectives impose limitations to what can be learned from them. Our objectives are (i) to discuss the possibilities and limitations of using such data to quantify growth responses to changes in climate and (ii) to present a modeling approach that creates a species‐ and population‐specific model. We illustrate the modeling approach for Larix occidentalis Nutt. We conclude that the reanalysis of historic provenance tests data can lead to the identification of species that have population‐specific growth responses to changes in climate, provide estimates of optimum transfer distance for populations and species, and provide estimates of growth changes under different climate change scenarios. Using mixed‐effects modeling techniques is a sound statistical approach to overcome some of the limitations of the data.