Theoretical Investigation Of Model Polymers For Eumelanins. I. Finite And Infinite Polymers

We investigate the electronic structure of ideal ordered polymers of 5,6-indolequinone, in one or other redox form. These molecules are the most abundant constituents of eumelanin, the pigment appearing in human skin. Our study is carried out through Hückel π-electron theory, which allows us to follow the trends in electronic structure from a single monomer - the isolated molecules - to finite polymers of up to 10 units, and to infinite polymers. We have chosen different polymerization directions which produce semiconducting chains. The comparison between finite and infinite polymers is very useful and leads us to propose a model that accounts for some of the known properties of eumelanins. © 1990 American Institute of Physics.9242630263

Theoretical Investigation Of Model Polymers For Eumelanins. Ii. Isolated Defects

We investigate here defects in initially ordered polymers of 5,6-indolequinone, in one or other redox form. The defects studied include aggregation of the carboxyl radical into one skeleton monomer, the aggregation of a host monomer in a lateral misplaced position, and faults in the polymerization sequencing. Our study is carried out, as in the first paper I, through Hückel π-electron theory, and results are compared to the perfect structures in I. Our results indicate that the end-type defect suggested as an electron capture center in I is not deactivated by these other structural defects, and that new capture centers might be introduced that could also be responsible for the acceptor behavior of melanins. © 1990 American Institute of Physics.9342848285

Polymerization Of 5,6-indolequinone: A View Into The Band Structure Of Melanins

We present for the first time a study of finite and infinite polymers of 5,6-indolequinone. We show that the band structure of the infinite polymer presents semiconductor characteristics, and that the intrinsic paramagnetism of eumelanin can be modeled through electron trapping at deep "end- effect" defects. © 1988 American Institute of Physics.8864088409

Justice and efficiency: Managing the value conflict

DINÂMIA, Dezembro de 2007.Presently, in Portugal, there is an incomplete network of “Julgados de Paz” (small claims courts). The government is committed to extending the network throughout the country. The goal of extending the network is constrained by budgetary considerations. Out of those constraints a conflict between the right to justice and efficiency emerges. In this paper an approach is advanced to help manage this value conflict between justice and efficiency in setting up criteria for the extension of the network of “Julgados de Paz”.À présent, au Portugal, le réseau des “Julgados de Paz” (Juges de Proximité) reste incomplet. Le gouvernement veut étendre le réseau à l’ensemble du territoire national. Cet objectif est limité par des contraintes budgétaires. De là découle une tension entre le droit à la justice et la poursuite de l’efficience. Dans cet exposé nous proposons une approche qui pourrait aider à répondre au besoin de gérer le conflit entre justice et efficience dans l’élaboration de critères pour l’extension du réseau de “Julgados de Paz” au territoire du Portugal.FC

Role Of Disorder In The Conduction Mechanism In Polyanilines

We present the first theoretical calculations of the electronic structure of long (200 rings) linear chains of polyaniline, ranging in composition from leucoemeraldine to emeraldine, allowing for compositional disorder in that the sequence of quinoid-benzenoid groups is random. We show that random protonation of the disordered polymers may induce p-type conductivity: This process pulls the Fermi energy down into the valence band, past localized band tails, to extended states. The effect is only seen if disorder is taken into account. © 1989 The American Physical Society.63778678

Conductivity Of Polymer Chains: A Tunneling Approach

We investigate the effect of disorder in the conductivity of polyaniline chains. We adopt a tunneling approach coupled to a simplified Hamiltonian, in which we model the ring-structured polymer as a linear chain of pseudoatoms. To adjust the Hamiltonian parameters, we rely on previously published data on the electronic structure for such chains. Our results agree with available data on the behavior of conductivity with protonation dose, and thus give support to the disordered-chain model of polyanilines. © 1991 The American Physical Society.44126073607

Variation in Broccoli Cultivar Phytochemical Content under Organic and Conventional Management Systems: Implications in Breeding for Nutrition

Organic agriculture requires cultivars that can adapt to organic crop management systems without the use of synthetic pesticides as well as genotypes with improved nutritional value. The aim of this study encompassing 16 experiments was to compare 23 broccoli cultivars for the content of phytochemicals associated with health promotion grown under organic and conventional management in spring and fall plantings in two broccoli growing regions in the US (Oregon and Maine). The phytochemicals quantified included: glucosinolates (glucoraphanin, glucobrassicin, neoglucobrassin), tocopherols (d-, ¿-, a-tocopherol) and carotenoids (lutein, zeaxanthin, ß-carotene). For glucoraphanin (17.5%) and lutein (13%), genotype was the major source of total variation; for glucobrassicin, region (36%) and the interaction of location and season (27.5%); and for neoglucobrassicin, both genotype (36.8%) and its interactions (34.4%) with season were important. For d- and ¿- tocopherols, season played the largest role in the total variation followed by location and genotype; for total carotenoids, genotype (8.41–13.03%) was the largest source of variation and its interactions with location and season. Overall, phytochemicals were not significantly influenced by management system. We observed that the cultivars with the highest concentrations of glucoraphanin had the lowest for glucobrassicin and neoglucobrassicin. The genotypes with high concentrations of glucobrassicin and neoglucobrassicin were the same cultivars and were early maturing F1 hybrids. Cultivars highest in tocopherols and carotenoids were open pollinated or early maturing F1 hybrids. We identified distinct locations and seasons where phytochemical performance was higher for each compound. Correlations among horticulture traits and phytochemicals demonstrated that glucoraphanin was negatively correlated with the carotenoids and the carotenoids were correlated with one another. Little or no association between phytochemical concentration and date of cultivar release was observed, suggesting that modern breeding has not negatively influenced the level of tested compounds. We found no significant differences among cultivars from different seed companies

The Opportunity Cost of the Conservation Reserve Program: A Kansas Land Example

The effects of the Conservation Reserve Program (CRP) on farmland values is investigated using a set of parcel-level data for land sales in Kansas over the period 1998 to 2014. The sales data are used to estimate a hedonic model of land values that allows for the opportunity cost of CRP enrollment to vary across space and time. Factors impacting the opportunity costs include the relative productivity of land, returns to farming, and the time remaining under the CRP contracts. We find that the discount associated with having land under CRP contract averages 7%

Behandeling en stigmamanagement bij opzettelijke zelfverwonding: het smalle pad tussen te veel en te weinig interveniëren

Opzettelijke zelfverwonding wordt gedefinieerd als de intentionele directe beschadiging van het eigen lichaam, zonder bewuste suïcidale intentie. De behandeling varieert van gedwongen opname in een psychiatrische instelling (in het Britse Gemenebest), tot een permissieve aanpak zonder behandeling en uiteenlopende behandelingsmogelijkheden er tussenin. Eerst wordt de gepastheid van de mate van interveniëren besproken in functie van verschillende diagnosen. Het tweede gedeelte van het artikel bespreekt het advies dat door hulpverleners verstrekt wordt aangaande de omgang met wonden en littekens en aangaande de mogelijkheden voor een (gewezen) zelfverwonder om het stigma van een deviante identiteit te vermijden. Een rondvraag bij Belgische hulpverleners bracht aan het licht dat velen onder hen adviseren om littekens te verbergen, terwijl er anderzijds aanwijzingen zijn dat niet-verbergen een teken van herstel is. Aangezien verbergen en smoesjes verzinnen ook kunnen leiden tot de instandhouding van een deviante identiteit, wordt gewezen op meer gepaste vormen van stigmamanagement