Many-Body Perturbation Theory (MBPT) and Time-Dependent Density-Functional Theory (TD-DFT): MBPT Insights About What is Missing in, and Corrections to, the TD-DFT Adiabatic Approximation

In their famous paper Kohn and Sham formulated a formally exact density-functional theory (DFT) for the ground-state energy and density of a system of $N$ interacting electrons, albeit limited at the time by certain troubling representability questions. As no practical exact form of the exchange-correlation (xc) energy functional was known, the xc-functional had to be approximated, ideally by a local or semilocal functional. Nowadays however the realization that Nature is not always so nearsighted has driven us up Perdew's Jacob's ladder to find increasingly nonlocal density/wavefunction hybrid functionals. Time-dependent (TD-) DFT is a younger development which allows DFT concepts to be used to describe the temporal evolution of the density in the presence of a perturbing field. Linear response (LR) theory then allows spectra and other information about excited states to be extracted from TD-DFT. Once again the exact TD-DFT xc-functional must be approximated in practical calculations and this has historically been done using the TD-DFT adiabatic approximation (AA) which is to TD-DFT very much like what the local density approximation (LDA) is to conventional ground-state DFT. While some of the recent advances in TD-DFT focus on what can be done within the AA, others explore ways around the AA. After giving an overview of DFT, TD-DFT, and LR-TD-DFT, this article will focus on many-body corrections to LR-TD-DFT as one way to building hybrid density-functional/wavefunction methodology for incorporating aspects of nonlocality in time not present in the AA.Comment: 56 pages, 17 figure

Determinants biològics i fisiològics del Pagre (Pagrus pagrus). Punts claus per al seu cultiu intensiu

The sparid teleost red porgy (PagntS pagn¡s) is an species with increasing potential and interest in the commercial aquaculture of the Mediterranean area. Although many of the aspects concerning its reproduction and nutrition are not well known, spontaneous spawning has been obtained in fish farms and growth rates obtained with commercial food are similar to those of sea bass and sea bream. Concerning culture conditions and stress influences, the results seem to suggest that red porgy shows a lower degree of adaptation compared to other Mediterranean sparids

Estrès, drogues i activitat cerebral

Si bé la relació entre l'estrès i algunes addiccions pot semblar evident, no totes les persones actuen de la mateixa manera enfront de les drogues o a situacions de gran tensió emocional. Aquesta tesi doctoral analitza l'activació del Sistema Nerviós Central (SNC) de rates, per intentar comprendre la influència de les diferències individuals a la resposta enfront d'aquest tipus de estímuls

Desarrollo postlarvario y dimorfismo sexual de Maja brachydactyla (Brachyura: Majidae)

The post-larval development of the majid crab Maja brachydactyla Balss, 1922 was studied using laboratory-reared larvae obtained from adult individuals collected in the NE Atlantic. The morphology of the first juvenile stage is described in detail, while the most relevant morphological changes and sexual differentiation are highlighted for subsequent juvenile stages, until juvenile 8. The characteristic carapace spines of the adult phase are present in the first juvenile stage, though with great differences in the degree of development and relative size. The carapace shows a high length/weight ratio, which becomes similar to that of adults at stage 7-8. Males and females can be distinguished from juvenile stage 4, based on sexual dimorphism in the pleopods and the presence of gonopores. In addition, the allometric growth of the pleon is sex-dependent from juvenile stage 4, with females showing a positive allometry (b=1.23) and males an isometric allometry (b=1.02).El desarrollo postlarvario del májido Maja brachydactyla ha sido estudiado en el laboratorio después del cultivo larvario realizado a partir de individuos adultos capturados en el NE del Atlántico. La morfología del primer estadio juvenil se ha descrito en detalle y el desarrollo juvenil, hasta el estadio 8, ha sido estudiado en lo referente a los cambios morfológicos y la diferenciación sexual. En el primer juvenil, las espinas del cefalotórax características de los adultos están presentes, pero existen grandes diferencias en el grado de desarrollo y el tamaño relativo. El cociente longitud/anchura muestra valores elevados que tienden a parecerse a los de los adultos a partir del juvenil 7-8. Machos y hembras se pueden diferenciar a partir del cuarto estadio juvenil, según el dimorfismo sexual en los pleópodos y la presencia de gonoporos. Además, existen diferencias sexuales en el crecimiento alométrico del pleon a partir del cuarto estadio juvenil: las hembras muestran una alometría positiva (b= 1.23) y los machos muestran un crecimiento isométrico (b= 1.02)

Peixos transgènics

La generació d'organismes modificats genèticament (OMG) ha representat un avanç tecnològic molt important en totes les àrees de recerca biològica. Així, la producció d'animals transgènics ha estat una eina molt valuosa per a l'establiment d'organismes model en recerca biomèdica, la producció massiva de macromolècules biològicament actives i el desenvolupament de cultius d'aliments, entre d'altres. Malgrat que tradicionalment els mamífers han estat els vertebrats més emprats per a la generació d'animals transgènics, els peixos constitueixen una alternativa excel·lent. Comparats amb els mamífers, els peixos presenten tot un conjunt de característiques, tant evolutives com fisiològiques, i també una sèrie d'interessos comercials i tecnològics, que estan fent d'aquests organismes els animals amb més potencial en els diferents camps d'aplicació de la tecnologia de manipulació genètica. En aquesta revisió, a més de presentar els darrers avenços tecnològics disponibles per a la generació de peixos transgènics, es repassen les diferents aplicacions de la transferència gènica en peixos, i també els beneficis i els possibles riscos derivats d'aquest ús. Paraules clau: peix, transgènesi, vector, tècniques de transferència gènica, aqüicultura,The generation of genetically modified organisms (GMOs) has provided an important technological advance to many areas of biological research. The production of these GMOs has been a valuable tool for the establishment of model organisms for biomedical research and the commercial production of biologically active macromolecules and food, amongst others. Traditionally, mammals have been used as the model organisms however in recent years the production of transgenic fish has provided an excellent alternative. Compared with mammals, fish presents some ideal physiological characteristics and evolutionary features, which together with recent technological advances and commercial interests, make fish an ideal candidate for genetic manipulation. This paper provides a brief summary of the most recent relevant data in this field

Water calcium concentration modifies whole-body calcium uptake in sea bream larvae during short-term adaptation to altered salinities

Whole-body calcium uptake was studied in gilthead sea bream larvae (9–83·mg) in response to changing environmental salinity and [Ca2+]. Calcium uptake increased with increased fish size and salinity. Fish exposed to calcium-enriched, diluted seawater showed increased calcium uptake compared with fish in diluted seawater alone. Calcium uptake was unchanged in Na+- enriched, diluted seawater. Overall, [Ca2+], and not salinity/osmolarity per se, appears to be the main factor contributing to calcium uptake. By contrast, drinking was reduced by a decrease in salinity/osmolarity but was little affected by external [Ca2+]. Calculations of the maximum contribution from drinking-associated calcium uptake showed that it became almost insignificant (less than 10%) through a strong decrease in drinking rate at low salinities (0–8‰). Diluted seawater enriched in calcium to the concentration present in full-strength seawater (i.e. constant calcium, decreasing salinity) restored intestinal calcium uptake to normal. Extra-intestinal calcium uptake also benefited from calcium addition but to a lesser extent

Progress in Time-Dependent Density-Functional Theory

The classic density-functional theory (DFT) formalism introduced by Hohenberg, Kohn, and Sham in the mid-1960s, is based upon the idea that the complicated N-electron wavefunction can be replaced with the mathematically simpler 1-electron charge density in electronic struc- ture calculations of the ground stationary state. As such, ordinary DFT is neither able to treat time-dependent (TD) problems nor describe excited electronic states. In 1984, Runge and Gross proved a theorem making TD-DFT formally exact. Information about electronic excited states may be obtained from this theory through the linear response (LR) theory formalism. Begin- ning in the mid-1990s, LR-TD-DFT became increasingly popular for calculating absorption and other spectra of medium- and large-sized molecules. Its ease of use and relatively good accuracy has now brought LR-TD-DFT to the forefront for this type of application. As the number and the diversity of applications of TD-DFT has grown, so too has grown our understanding of the strengths and weaknesses of the approximate functionals commonly used for TD-DFT. The objective of this article is to continue where a previous review of TD-DFT in this series [Annu. Rev. Phys. Chem. 55: 427 (2004)] left off and highlight some of the problems and solutions from the point of view of applied physical chemistry. Since doubly-excited states have a particularly important role to play in bond dissociation and formation in both thermal and photochemistry, particular emphasis will be placed upon the problem of going beyond or around the TD-DFT adiabatic approximation which limits TD-DFT calculations to nominally singly-excited states. Posted with permission from the Annual Review of Physical Chemistry, Volume 63 \c{opyright} 2012 by Annual Reviews, http://www.annualreviews.org

Theoretical insights into the formation and stability of radical oxygen species in cryptochrome

International audienceCryptochrome is a blue-light absorbing flavoprotein containing a flavin adenine dinucleotide (FAD) cofactor. FAD can accept up to two electrons and two protons, which can be subsequently transferred to substrates present in the binding pocket. It is well known that reactive oxygen species are generated when triplet molecular oxygen is present in the cavity. Here, we investigate the formation and stability of radical oxygen species in Drosophila melanogaster cryptochrome using molecular dynamics simulations and electronic structure calculations. We find that superoxide and hydroxyl radicals in doublet spin states are stabilized in the pocket due to attractive electrostatic interactions and hydrogen bonding with partially reduced FAD. These finding validate from a molecular dynamics perspective that [FAD •−-HO • 2 ] or [FADH •-O •− 2 ] can be alternative radical pairs at the origin of magnetoreception