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Sci Rep ; 5: 7893, 2015 Jan 20.
Artigo em Inglês | MEDLINE | ID: mdl-25599915


Graphene's isolation launched explorations of fundamental relativistic physics originating from the planar honeycomb lattice arrangement of the carbon atoms, and of potential technological applications in nanoscale electronics. Bottom-up fabricated atomically-precise segmented graphene nanoribbons, SGNRs, open avenues for studies of electrical transport, coherence, and interference effects in metallic, semiconducting, and mixed GNRs, with different edge terminations. Conceptual and practical understanding of electric transport through SGNRs is gained through nonequilibrium Green's function (NEGF) conductance calculations and a Dirac continuum model that absorbs the valence-to-conductance energy gaps as position-dependent masses, including topological-in-origin mass-barriers at the contacts between segments. The continuum model reproduces the NEGF results, including optical Dirac Fabry-Prot (FP) equidistant oscillations for massless relativistic carriers in metallic armchair SGNRs, and an unequally-spaced FP pattern for mixed armchair-zigzag SGNRs where carriers transit from a relativistic (armchair) to a nonrelativistic (zigzag) regime. This provides a unifying framework for analysis of coherent transport phenomena and interpretation of forthcoming experiments in SGNRs.

Phys Rev Lett ; 97(9): 090401, 2006 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-17026345


We present a variational many-body wave function for repelling bosons in rotating traps, focusing on rotational frequencies that do not lead to restriction to the lowest Landau level. This wave function incorporates correlations beyond the Gross-Pitaevskii (GP) mean-field approximation, and it describes rotating boson molecules (RBMs) made of localized bosons that form polygonal-ring-like crystalline patterns in their intrinsic frame of reference. The RBMs exhibit characteristic periodic dependencies of the ground-state angular momenta on the number of bosons in the polygonal rings. For small numbers of neutral bosons, the RBM ground-state energies are found to be always lower than those of the corresponding GP solutions, in particular, in the regime of GP vortex formation.

Phys Rev Lett ; 93(23): 230405, 2004 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-15601132


Strongly-interacting bosons in two-dimensional harmonic traps are described through breaking of rotational symmetry at the Hartree-Fock level and subsequent symmetry restoration via projection techniques, thus incorporating correlations beyond the Gross-Pitaevskii (GP) solution. The bosons localize and form polygonal-ringlike crystalline patterns, both for a repulsive contact potential and a Coulomb interaction, as revealed via conditional-probability-distribution analysis. For neutral bosons, the total energy of the crystalline phase saturates in contrast to the GP solution, and its spatial extent becomes smaller than that of the GP condensate. For charged bosons, the total energy and dimensions approach the values of classical pointlike charges in their equilibrium configuration.

Nephrol Dial Transplant ; 19(3): 608-13, 2004 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-14767016


BACKGROUND: The aim of this study was to describe the urological complications associated with nephrogenic diabetes insipidus (NDI) due to a mutation in aquaporin-2 (AQP2), a collecting-duct protein activated by ADH signalling. METHODS: We provide a case series description of a group of seven patients with autosomal recessive NDI due to AQP2 gene mutation, receiving routine medical management since diagnosis in the first months of life. RESULTS: Mean urine osmolarity at diagnosis and last follow-up was 89+/-25 and 83+/-18 mosm/l, respectively. Hydroureteronephrosis was observed in all children, beginning at age 3 years. Two children have daytime enuresis at ages 7 and 10 years and all children older than 6 years continue to have nocturnal enuresis. Markedly enlarged bladders were observed as early as age 4 years in all patients. Trabeculated bladder walls were found in three children. Urodynamic studies performed in two daytime incontinent children revealed a hypotonic-large-capacity type of neurogenic bladder. No impairment in kidney function is currently observed. CONCLUSIONS: The severe renal concentrating defect in this type of NDI is associated with the development of hydroureteronephrosis followed by bladder enlargement and dysfunction. Careful follow-up is needed in order to assure that no bladder outlet obstruction and/or renal insufficiency develop.

Aquaporinas/genética , Diabetes Insípido Nefrogênico/genética , Diabetes Insípido Nefrogênico/fisiopatologia , Mutação , Bexiga Urinária/fisiopatologia , Adolescente , Adulto , Aquaporina 2 , Árabes/genética , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , Linhagem , Radiografia , Estudos Retrospectivos , Ultrassonografia , Bexiga Urinária/diagnóstico por imagem