JUAN EUGENIO ALZATE DUQUE - Academia.edu (original) (raw)
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UFMG - The Federal University of Minas Gerais
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Papers by JUAN EUGENIO ALZATE DUQUE
Physical Review B, 2014
We present resonant Raman scattering experiments on nanotube samples enriched in metallic armchai... more We present resonant Raman scattering experiments on nanotube samples enriched in metallic armchair single-wall carbon nanotubes (SWCNTs). We establish the transverse optical (AT O) phonon frequency for the (5,5) through (10,10) armchair species, ranging in diameter from 0.68 to 1.36 nm. The frequencies show a strong diameter dependence similar to that previously observed in semiconducting nanotubes. We show that the AT O frequencies in armchair SWCNTs are dramatically upshifted from those of semiconducting SWCNTs. Furthermore, using electrochemical doping, we demonstrated that the AT O frequencies in armchair SWCNTs are independent of the position of the Fermi level. These results suggest that the upshift is a result of a Kohn anomaly involving a forward-scattering mechanism of electrons close to the Fermi level. This is in contrast to the wellknown Kohn anomaly that dominates the downshift of the ALO and E2g phonons in non-armchair metallic SWCNTs and graphene, respectively.
Surgery, 2015
Background-The role of immune cells in arteriovenous fistulae (AVF) maturation is poorly understo... more Background-The role of immune cells in arteriovenous fistulae (AVF) maturation is poorly understood and has received, until quite recently, little attention. This study examines the role of T lymphocytes in AVF vascular remodeling. Methods-Experimental fistulae were created in athymic rnu nude rats lacking mature T lymphocytes and euthymic control animals by anastomosing the left superior epigastric vein to the nearby femoral artery. Blood flow rates, wall morphology and histological changes were assessed in AVF 21 days after creation. The effect of CD4 + lymphocytes on AVF maturation in athymic animals was analyzed by adoptive transfer of cells after fistula creation. Results-The absence of T lymphocytes compromised blood flow in experimental fistulae. Histopathological inspection of AVF from athymic rats revealed that T cell immunodeficiency negatively affected venous vascular remodeling, as evidenced by a reduced lumen, a thick muscular layer and a low number of inflammatory cells compared to control animals. Adoptive transfer of CD4 + lymphocytes from euthymic rats into athymic animals before and after fistula creation improved blood flow and reduced intima-media thickness. Conclusion-These results point at the protective role of CD4 + lymphocytes in the remodeling of the AVF vascular wall.
Physical Review B, 2014
We present resonant Raman scattering experiments on nanotube samples enriched in metallic armchai... more We present resonant Raman scattering experiments on nanotube samples enriched in metallic armchair single-wall carbon nanotubes (SWCNTs). We establish the transverse optical (AT O) phonon frequency for the (5,5) through (10,10) armchair species, ranging in diameter from 0.68 to 1.36 nm. The frequencies show a strong diameter dependence similar to that previously observed in semiconducting nanotubes. We show that the AT O frequencies in armchair SWCNTs are dramatically upshifted from those of semiconducting SWCNTs. Furthermore, using electrochemical doping, we demonstrated that the AT O frequencies in armchair SWCNTs are independent of the position of the Fermi level. These results suggest that the upshift is a result of a Kohn anomaly involving a forward-scattering mechanism of electrons close to the Fermi level. This is in contrast to the wellknown Kohn anomaly that dominates the downshift of the ALO and E2g phonons in non-armchair metallic SWCNTs and graphene, respectively.
Surgery, 2015
Background-The role of immune cells in arteriovenous fistulae (AVF) maturation is poorly understo... more Background-The role of immune cells in arteriovenous fistulae (AVF) maturation is poorly understood and has received, until quite recently, little attention. This study examines the role of T lymphocytes in AVF vascular remodeling. Methods-Experimental fistulae were created in athymic rnu nude rats lacking mature T lymphocytes and euthymic control animals by anastomosing the left superior epigastric vein to the nearby femoral artery. Blood flow rates, wall morphology and histological changes were assessed in AVF 21 days after creation. The effect of CD4 + lymphocytes on AVF maturation in athymic animals was analyzed by adoptive transfer of cells after fistula creation. Results-The absence of T lymphocytes compromised blood flow in experimental fistulae. Histopathological inspection of AVF from athymic rats revealed that T cell immunodeficiency negatively affected venous vascular remodeling, as evidenced by a reduced lumen, a thick muscular layer and a low number of inflammatory cells compared to control animals. Adoptive transfer of CD4 + lymphocytes from euthymic rats into athymic animals before and after fistula creation improved blood flow and reduced intima-media thickness. Conclusion-These results point at the protective role of CD4 + lymphocytes in the remodeling of the AVF vascular wall.