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

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

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

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

Assessment of dressed time-dependent density-functional theory for the low-lying valence states of 28 organic chromophores

Almost all time-dependent density-functional theory (TDDFT) calculations of excited states make use of the adiabatic approximation, which implies a frequency-independent exchange-correlation kernel that limits applications to one-hole/one-particle states. To remedy this problem, Maitra et al. [N.T. Maitra, F. Zhang, R.J. Cave, K. Burke, Double excitations within time-dependent density functional theory linear response theory, J. Chem. Phys. 120 (2004) 5932 ] proposed dressed TDDFT (D-TDDFT), which includes explicit two-hole/two-particle states by adding a frequency-dependent term to adiabatic TDDFT. This paper offers the first extensive test of D-TDDFT, and its ability to represent excitation energies in a general fashion. We present D-TDDFT excited states for 28 chromophores and compare them with the benchmark results of Schreiber et al. [M. Schreiber, M.R. Silva-Junior, S.P.A. Sauer, W. Thiel, Benchmarks for electronically excited states: CASPT2, CC2, CCSD, and CC3, J. Chem. Phys. 128 (2008) 134110]. We find the choice of functional used for the A-TDDFT step to be critical for positioning the 1h1p states with respect to the 2h2p states. We observe that D-TDDFT without HF exchange increases the error in excitations already underestimated by A-TDDFT. This problem is largely remedied by implementation of D-TDDFT including Hartree-Fock exchange. © 2011 Elsevier B.V. All rights reserved.This work has been carried out in the context of the French Rhône-Alpes Réseau thématique de recherche avancée (RTRA): Nanosciences aux limites de la nanoélectronique and the Rhône-Alpes Associated Node of the European Theoretical Spectroscopy Facility (ETSF). A. R. acknowledges funding by the Spanish MEC (FIS2007-65702-C02-01), ACI-promciona project (ACI2009-1036), “Grupos Consolidados UPV/EHU del Gobierno Vasco” (IT-319-07), the European Research Council through the advance grant DYNamo (267374), the MICINN project (FIS2010-21282-C02-01), and the European Community through projects e-I3 ETSF (Contract No. 211956) and THEMA (228539).Peer Reviewe

L'Espermatogènesi en els crancs (Crustacea, Brachyura) : un model atípic de condensació del nucli espermàtic

Els espermatozoides dels crustacis decàpodes es caracteritzen per tenir un nucli amb cromatina poc condensada, un acrosoma complex i un citoplasma reduït sense flagel. Es disposa d'una àmplia informació sobre la ultraestructura i variabilitat morfològica dels espermatozoides dels crustacis decàpodes, i particularment dels braquiürs, ja que la seva especificitat ha permès utilitzar-los com a caràcter filogenètic, però el procés d'espermatogènesi i la naturalesa de les proteïnes associades a la cromatina dels espermatozoides són qüestions encara no resoltes. En aquest treball hem tractat aquestes dues qüestions utilitzant com a model dues espècies de braquiürs: la cabra de mar, Maja brachydactyla, i el bou de mar, Cancer pagurus. D'aquesta manera, hem realitzat una breu descripció de la morfologia de l'aparell reproductor masculí de M. brachydactyla, hem localitzat el lloc on es desenvolupa l'espermatogènesi i hem descrit la formació dels espermatòfors que són transferits a la femella. A continuació, hem comparat el procés d'espermatogènesi de M. brachydactyla, amb els estudis fets en altres espècies, considerant de manera preferent la formació de l'acrosoma. Finalment, hem descrit diferents aspectes del nucli dels espermatozoides dels braquiürs, fent un estudi específic de les proteïnes associades al nucli de l'espermatozoide de C. pagurus.Decapods crustacean spermatozoa are characterized by a nucleus containing a low condensed chromatin, a complex acrosome and reduced cytoplasm lacking of flagellum. Large information on ultrastructure and morphological variability of the spermatozoa is available in crustacean particularly, in Brachyuran, since their specificity has been used as a phylogenetic character. However, the spermatogenesis and the nature of the proteins associated to chromatin in the nucleus of the spermatozoa are still unclear. In the present study, we have dealt both topics using two brachyuran species as model: the spider crab, Maja brachydactyla and the edible crab, Cancer pagurus. Thus, we have briefly described the morphology of the male reproductive system of M. brachydactyla in order to locate the spermatogenesis process and to describe the formation of the spermatophore transferred to the female. Finally, we have also described and compared with previous studies, the spermatogenesis process of M. brachydactyla with special attention to the acrosomal vesicle. We have finished our study describing the different characters presented in the nucleus of the spermatozoa, with special reference to the proteins associated to chromatin in C. pagurus