On Semiclassical Limits of String States

We explore the relation between classical and quantum states in both open and closed (super)strings discussing the relevance of coherent states as a semiclassical approximation. For the closed string sector a gauge-fixing of the residual world-sheet rigid translation symmetry of the light-cone gauge is needed for the construction to be possible. The circular target-space loop example is worked out explicitly.Comment: 12 page

A multi-wavelength study of the evolution of Early-Type Galaxies in Groups: the ultraviolet view

ABRIDGED- The UV-optical color magnitude diagram (CMD) of rich galaxy groups is characterised by a well developed Red Sequence (RS), a Blue Cloud (BC) and the so-called Green Valley (GV). Loose, less evolved groups of galaxies likely not virialized yet may lack a well defined RS. This is actually explained in the framework of galaxy evolution. We are focussing on understanding galaxy migration towards the RS, checking for signatures of such a transition in their photometric and morphological properties. We report on the UV properties of a sample of ETGs galaxies inhabiting the RS. The analysis of their structures, as derived by fitting a Sersic law to their UV luminosity profiles, suggests the presence of an underlying disk. This is the hallmark of dissipation processes that still must have a role in the evolution of this class of galaxies. SPH simulations with chemo-photometric implementations able to match the global properties of our targets are used to derive their evolutionary paths through UV-optical CDM, providing some fundamental information such as the crossing time through the GV, which depends on their luminosity. The transition from the BC to the RS takes several Gyrs, being about 3-5 Gyr for the the brightest galaxies and more long for fainter ones, if it occurs. The photometric study of nearby galaxy structures in UV is seriously hampered by either the limited FoV of the cameras (e.g in HST) or by the low spatial resolution of the images (e.g in the GALEX). Current missions equipped with telescopes and cameras sensitive to UV wavelengths, such as Swift-UVOT and Astrosat-UVIT, provide a relatively large FoV and better resolution than the GALEX. More powerful UV instruments (size, resolution and FoV) are obviously bound to yield fundamental advances in the accuracy and depth of the surface photometry and in the characterisation of the galaxy environment.Comment: 12 pages, 6 figures: accepted for publication in Astrophysics & Space Science as contributions to the workshop: "UV astronomy, the needs and the means

An engineering approach to synthesis of gold and silver nanoparticles by controlling hydrodynamics and mixing based on a coaxial flow reactor

In this work we present a detailed study of flow technology approaches that could open up new possibilities for nanoparticle synthesis. The synthesis of gold and silver nanoparticles (NPs) in a flow device based on a coaxial flow reactor (CFR) was investigated. The CFR comprised of an outer glass tube of 2 mm inner diameter (I.D.) and an inner glass tube whose I.D. varied between 0.142 and 0.798 mm. A split and recombine (SAR) mixer and coiled flow inverter (CFI) were further employed to alter the mixing conditions after the CFR. The ‘Turkevich’ method was used to synthesize gold NPs, with a CFR followed by a CFI. This assembly allows control over nucleation and growth through variation of residence time. Increasing the total flow rate from 0.25 ml/min to 3 ml/min resulted initially in a constant Au NP size, and beyond 1 ml/min to a size increase of Au NPs from 17.9 ± 2.1 nm to 23.9 ± 4.7 nm. The temperature was varied between 60 – 100 °C and a minimum Au NP size of 17.9 ± 2.1 nm was observed at 80 °C. Silver NPs were synthesized in a CFR followed by a SAR mixer, using sodium borohydride to reduce silver nitrate in the presence of trisodium citrate. The SAR mixer provided an enhancement of the well‐controlled laminar mixing in the CFR. Increasing silver nitrate concentration resulted in a decrease in Ag NP size from 5.5 ± 2.4 nm to 3.4 ± 1.4 nm. Different hydrodynamic conditions were studied in the CFR operated in isolation for silver NP synthesis. Increasing the Reynolds number from 132 to 530 in the inner tube created a vortex flow resulting in Ag NPs in the size range between 5.9 ± 1.5 nm to 7.7 ± 3.4 nm.. Decreasing the inner tube I.D. from 0.798 mm to 0.142 mm resulted in a decrease in Ag NP size from 10.5 ± 4.0 nm to 4.7 ± 1.4 nm. Thus, changing the thickness of the inner stream enabled control over size of the Ag NPs

Galaxy evolution in nearby groups. II. Galaxy evolution in nearby loose groups. II. Photometric and kinematic characterization of USGC U268 and USGC U376 group members in the Leo cloud

We present the photometric and kinematic characterization of two groups, USGC U268 and USGC U376 located in different regions of the Leo cloud. U268, composed of 10 catalogued members and 11 new added members, has a small fraction (~24%) of early-type galaxies (ETGs). U376 has 16 plus 8 new added members, with ~38% of ETGs. We find the presence of significant substructures in both groups suggesting that they are likely accreting galaxies. U268 is located in a more loose environment than U376. For each member galaxy, broad band integrated and surface photometry have been obtained in far-UV and near-UV with GALEX, and in u,g, r, i, z (SDSS) bands. H_alpha imaging and 2D high resolution kinematical data have been obtained using PUMA Scanning Fabry-Perot interferometer at the 2.12 m telescope in San Pedro M\'artir, (Baja California, M\'exico). We improved the galaxy classification and we detected morphological and kinematical distortions that may be connected to either on-going and/or past interaction/accretion events or environmental induced secular evolution. U268 appears more active than U376, with a large fraction of galaxies showing interaction signatures (60% vs. 13%). The presence of bars among late-type galaxies is ~10% in U268 and ~$29% in U376. The cumulative distribution of (FUV - NUV) colours of galaxies in U268 is significantly different than that in U376 with galaxies in U268 bluer than those in U376. In the (FUV-r vs. M_r) and (NUV-r vs. M_r) planes no members of U268 are found in the `red sequence', even early-type galaxies lie in the `blue sequence' or in the `green valley'. Most (80%) of the early-type members in U376 inhabits the `red sequence, a large fraction of galaxies, of different morphological types, are located in the `green valley', while the `blue sequence' is under-populated with respect to U268.Comment: 27 pages, 11 figures, 8 tables, accepted for publication in MNRAS (abridged abstract

Thermodynamic modelling and evaluation of a two-stage thermal process for waste gasification

Tar generation and ash disposal represent the strongest barrier for use of fluid bed gasification for waste treatment, whereas sufficing for both is only possible with expensive cleaning systems and further processing. The use of plasma within an advanced two-stage thermal process is able to achieve efficient cracking of the complex organics to the primary syngas constituents whilst limiting the electric power demand. This study focused on the thermodynamic assets of using a two-stage thermal process over the conventional single-stage approach. These include, for example, the fact that the primary thermal waste decomposition is performed in conditions of optimal stoichiometric ratio for the gasification reactants. Furthermore, staging the oxidant injection in two separate intakes significantly improves the efficiency of the system, reducing the plasma power consumption. A flexible model capable of providing reliable quantitative predictions of product yield and composition after the two-stage process has been developed. The method has a systematic structure that embraces atom conservation principles and equilibrium calculation routines, considering all the conversion stages that lead from the initial waste feed to final products. The model was also validated with experimental data from a demonstration plant. The study effectively demonstrated that the two-stage gasification system significantly improves the gas yield of the system and the carbon conversion efficiency, which are crucial in other single stage systems, whilst maintaining high energy performances

JORNAL O DIÁRIO: A CENSURA E O PAPEL DA PUBLICIDADE NOS ANOS DE CHUMBO (1968-1974)

Revisitar a história do jornal O Diário é resgatar um pouco da história da imprensa no Espírito Santo. A referida publicação circulou em terras capixabas entre 1955 e 1980, e deixou como legado a formação de uma brilhante geração de profissionais, que, mais tarde, ocuparam as mais destacadas posições da imprensa local. Trata mais detidamente acerca da relação entre o jornal O Diário e a censura, sobretudo nos Anos de Chumbo (1968-1974). Em boa parte do período em que O Diário circulou, o Brasil estava imerso em uma ditadura militar (1964-1985), que impôs o cerceamento da liberdade de expressão aos veículos de comunicação. O controle sobre o que era noticiado era intenso. As sanções sobre quem ousasse enfrentar o regime eram imensas. Jornalistas foram pressionados, ameaçados, torturados e até presos. A censura se fez presente na atividade diária do profissional da imprensa. A maioria dos veículos de comunicação, em grande parte, dependente do Estado, seja na liberação de empréstimos ou no recebimento de anúncios publicitários, acabaram por acatar as determinações oficiais sob o risco de sofrer com retaliações. Estabelecia-se, assim, uma relação assimétrica de poder sobre aquilo que era publicado e divulgado pelos veículos de comunicação. Estratégias de resistência foram montadas por parte das publicações, a fim de fugir da censura, bem como buscar meios de noticiar as reportagens produzidas. Nesse ínterim, um novo elemento entra em destaque: publicidade. Por meio dela, o governo externou o seu humor e simpatia aos veículos. Àqueles que caminhassem de acordo com os ditames propostos pelos militares, o governo acenava com a possibilidade de recebimento de bons volumes de anúncios de propaganda. Já aos que intentassem enfrentar o regime vigente, havia não só a retirada dos anúncios oficiais, como também dos oriundos de empresas particulares, em função das pressões do Estado. O jornal O Diário vivenciou amplamente a censura em sua prática diária. Diretores foram chamados constantemente para prestar esclarecimentos, jornalistas foram detidos várias vezes, sendo que um deles até perdeu o emprego por causa de uma matéria em que divulgou o patrimônio de políticos capixabas. Apesar da constante atmosfera de medo, o jornal O Diário era considerado um jornal alinhado e simpático à proposta ideológica sugerida pelos militares no poder. Por conta própria, a publicação incluía em suas páginas matérias e anúncios em consonância aos ideais do regime autoritário. Em contrapartida, em várias ocasiões, O Diário foi beneficiado no recebimento de anúncios publicitários vindos de fontes oficiais, bem como por empresas particulares dependentes financeiramente do Estado. Os diretores do Diário enxergaram aí um filão a ser explorado e não mediram esforços a fim de potencializar a relação com os militares e obter, com isso, favorecimentos financeiros, além de trabalhar para que se evitasse que o jornal entrasse em choque direto com a pesada mão dos militares