(Português) Programa de Pós-Graduação em Física da UFSC, Florianópolis

EL PROGRAMA DE POSGRADO EN FÍSICA invita a todos para lo seminario:

University of Caen-Basse Normandie (France)

 Sub-saturation equation of state for Core-Collapse Supernovae and Neutron Stars 

Francesca Gulminelli – LPC/Ensicaen and University of Caen (France)

Resumen:

The construction of a realistic equation of state for dense matter as it can be found in core-collapse supernovae and neutron stars is a formidable task which is not yet completely achieved. The structure of very high density matter in the neutron star core is by far the most uncertain part of the EoS modeling. However, even in the least exotic regime of sub-saturation matter, where the degrees of freedom are purely nucleonic and relatively well-known, the presence of clustering due to the Coulomb quenching of the nuclear liquid-gas phase transition requires beyond mean-field methods properly treating all the complexity of nuclear structure, in a regime of neutron-rich matter where no experimental data exist to validate the available effective interactions.

Self-consistent mean-field approaches with realistic effective interactions are still routinously applied at zero temperature. This is justified thanks to the Wigner-Seitz structure of stellar matter, which reduces the thermodynamic limit to a single nucleus problem. However, a consistent treatment at finite temperature in principle implies beyond mean-field configuration mixing. This is presently a problem since existing models are either done in the single nucleus approximation, or do not recover the single-nucleus Wigner-Seitz limit of zero temperature.

In this talk we will present a density-functional formalism which, by introducing explicit cluster degrees of freedom, consistently describes the neutron-rich nuclei immersed in the gas of their continuum states in the inner crust, and the nuclear statistical equilibrium of different in-medium modified nuclear species in supernova matter. The influence of the effective interaction, and specifically the density dependence of the symmetry energy, will also be discussed.

                                                        Fecha: 22 de mayo de 2015 – (viernes) – Lugar: Sala 212 Auditorio del Departamento de Física – Horário: 10h15min

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El Programa de Posgrado en Física invita a todos para:

Examen de Cualificación al Doctorado

 Daniel Salvador

 TRANSIÇÕES DE FASE NO MODELO DE POTTS COM MODULAÇÃO APERIÓDICA

Jurados

 Prof. Dr. Nilton da Silva Branco – (presidente) – FSC/UFSC

Prof. Dr. Jürgen Fritz Stilck – (miembro externo) – UFF/IF

Prof. Dr. Wagner Figueiredo – (miembro titular) – UFSC/FSC

Prof. Dr. Daniel Girardi – (miembro titular) – UFSC/Blumenau

Prof. Dr. Marcelo Henrique Romano Tragtenberg – (miembro suplente) – UFSC/FSC

Fecha: 31 de marzo de 2015-terça-feira- Horario: 4:20 pm – Lugar: Auditório do LAED – (planta baja del Departamento de Matemática)

El programa de Posgrado en Física invita a todos para la:

 Sustentación de Disertación

 Luiza Gomes Ferreira

 UM MODELO SIMPLIFICADO PARA A DINÂMICA DE MOTORES MOLECULARES

Jurados

 Prof. Dr. Wagner Figueiredo – (presidente) – UFSC/FSC

Profª. Drª. Carla Goldman – (miembro externo) – USP/IF

Prof. Dr. Nilton da Silva Branco – (miembro titular) – UFSC/FSC

Prof. Dr. Lucas Nicolao – (miembro titular) – UFSC/FSC

Prof. Dr. Eduardo Cerutti Mattei – (miembro suplente) – UFSC/FSC

Fecha: 31 de marzo de 2015 – martes– Horario: 10:00 am – Lugar: Sala 212 – Auditorio del Departamento de Física

El programa de Posgrado en Física invita a todos para la:

 Sustentación de Disertación

 Rodrigo Sergio Tiedt

 EFEITO DA RADIAÇÃO ULTRAVIOLETA NA FORMAÇÃO DE NÚCLEOS DE CONDENSAÇÃO DE NUVENS EM MISTURAS DE ÁGUA E DIMETILSULFETO

Jurados

 Prof. Dr. Manoel Gustavo Petrucelli Homem – (presidente) – UFSCar/QMC

Prof. Dr. Reinaldo Luiz Cavasso Filho – (miembro externo) – UFABC/CCNH

Prof. Dr. Renato Ramos da Silva – (miembro titular) – UFSC/Meteorologia

Prof. Dr. Danilo de Paiva Almeida – (miembro titular) – UFSC/FSC

Prof. Dr. Wendell Rondinelli Gomes Farias – (miembro suplente) – UFSC/FSC

Fecha: 31 de marzo de 2015 – martes– Horario: 2:00 pm – Lugar: Sala 212 – Auditorio del Departamento de Física

 EL PROGRAMA DE POSGRADO EN FÍSICA invita a todos para lo seminario:

  Hydrogen from Sunlight – Photoelectrochemical Water Splitting with Li-doped TiO2 Nanotubes  

Prof. Dr. Giovanni Zangari

Department of Materials Science and Engineering, University of Virginia – Charlottesville, VA, USA

Resumen:

 While solar energy is one of the few energy sources capable of meeting the world’s energy demands,¹ the transient nature of sunlight necessitates the development of technologies to store that energy for on-demand use to supplement photovoltaics.² Photoelectrochemical solar cells use sunlight to electrolyze water to produce hydrogen as a storable fuel, which can then be converted to electricity by a fuel cell. TiO₂ nanotubes formed by the anodization of titanium foils in electrolytes containing fluoride ions produce aligned arrays of tube-like structures 70-100 nm in width and tunable length on the order of microns as shown in Figure 1(a, b). These structures are a promising architecture for photoelectrochemical applications³ because of their high stability in solution and under irradiation, high surface area, and 1-dimensional charge transport for efficient movement of photogenerated charges. While hundreds of microns long nanotubes in principle may be grown, one major limitation on the performance of TiO₂ nanotubes is the presence of defects in the crystal structure which facilitate the recombination of photogenerated electron-hole pairs;⁴ the best photoelectrochemical performance of TiO₂ nanotubes for water splitting has been observed in Nb-doped TiO₂ with a length of 7 mm and an associated photocurrent of 1.0 mA/cm².⁵ Electrochemical Li doping was demonstrated to passivate the trap states in TiO₂ nanotubes, suppressing recombination. This process resulted in up to a 2 fold increase in the photoelectrochemical performance of 1 mm long TiO₂ nanotubes compared to the undoped samples.⁶ For long TiO₂ nanotubes, a new optimum length of 15 mm was achieved, resulting in 1.5 mA/cm² of photocurrent at 1.0 V_SCE under simulated sunlight as seen in Figure 1(c). These results demonstrate the ability to produce high performance TiO₂ nanotubes for photoelectrochemical solar energy devices using simple electrochemical techniques.

Figure 1. (a) Cross section and (b) surface view of TiO₂ nanotubes grown by anodization. (c) Lithium intercalation enhances the photocurrent by trap state passivation, resulting in up to 1.5 mA/cm² of photocurrent at 15 m.

References

(1)            Lewis, N. S.; Nocera, D. G. Proc. Natl. Acad. Sci. U. S. Amer. 2006, 103, 15729.
(2)            Cook, T. R.; Dogutan, D. K.; Reece, S. Y.; Surendranath, Y.; Teets, T. S.; Nocera, D. G. Chem. Rev. 2010, 110, 6474.
(3)            Tsui, L. -k.; Zangari, G. J. Electrochem. Soc. 2014, 161, D3066
(4)            Tsui, L.; Zangari, G. Electrochim. Acta 2014, 121, 203.
(5)            Das, C.; Roy, P.; Yang, M.; Jha, H.; Schmuki, P. Nanoscale 2011, 3, 3094.
(6)            Tsui, L.; Saito, M.; Homma, T.; Zangari, G. J. Mater. Chem. A 2015, 3, 360.

Fecha: 27 de marzo de 2015 – (viernes) – Lugar: Sala 212 Auditorio del Departamento de Física – Horário: 10h15min

El Programa de Posgrado en Física invita a todos para:

 Examen de Cualificación al Doctorado

Paulo Roberto Innocente

 Estudo da Geração de H2 com Fotocatodo de Cu2O

Jurados

 Prof. Dr. André Avelino Pasa – (presidente) – FSC/UFSC

Prof. Dr. Andre Santarosa Ferlauto – (miembro externo) – UFMG/FSC

Prof. Dr. Rafael Gallina Delatorre – (miembro titular) – UFSC – Joinville

Prof. Dr. Kleber Ersching – (miembro titular) – IFC/Camboriú

Drª Silvia Pelegrini – (miembro suplente) – UFSC/FSC

Fecha: 20 de marzo de 2015–sexta-feira– Horario: 10:00 am – Lugar: Sala 114 – Sala de Reuniones del Departamento de Física