Flexible control of the Peierls transition in metallic C60_{60} polymers

The metal-semiconductor transition of peanut-shaped fullerene (C$_{60}$) polymers is clarified by considering the electron-phonon coupling in the uneven structure of the polymers. We established a theory that accounts for the transition temperature $T_c$ reported in a recent experiment and also suggests that $T_c$ is considerably lowered by electron doping or prolonged irradiation during synthesis. The decrease in $T_c$ is an appealing phenomenon with regard to realizing high-conductivity C$_{60}$-based nanowires even at low temperatures.Comment: 3 pages, 3 figure

Ar-39Ar geochronology of hydrothermal veins in sedimentary rocks of the Paja Formation (lower cretaceous) southern of the Santander department (Cordillera Oriental, Colombia)

Los agregados de micas potásicas de relleno de venas que cortan lodolitas calcáreas orgánicas de la Formación Paja (Cretácico Inferior), aflorante al sur del Dpto. de Santander, registran el evento hidrotermal principal asociado a su formación con edad de aproximadamente 54 Ma, correspondiente al Eoceno temprano, tal como se deriva del análisis geocronológico 40Ar-39Ar. Este evento hidrotermal, al parecer se relaciona temporal y espacialmente con la falla cabalgante El Guamito, la cual debió servir de canal de escape de fluidos migratorios profundos. En este contexto, el episodio hidrotermal-deformacional mencionado es un evento más dentro de la compleja historia geológica que tiene lugar con anterioridad al clímax de la orogenia pre-Andina en el Eoceno medio.The K mica aggregates of vein filling, cutting through the organic calcareous mudstone of the Paja Formation (Lower Cretáceous) that crops out to the south of the Dpto. de Santander, register the main hydrothermal event associated to their formation. Their 40Ar-39Ar age is about 54 Ma, corresponding to the early Eocene. Such hydrothermal event is related in time and space with The Guamito thrust fault, which may have served as channel for the escape of deepmigratory fluids. In this context, the mentioned hydrothermal-deformation episode is an important additional event within the complex geological history that takes place prior to the clímax of the pre-Andean orogeny in the middle Eocene

Phonon dispersion and electron-phonon interaction in peanut-shaped fullerene polymers

We reveal that the periodic radius modulation peculiar to one-dimensional (1D) peanut-shaped fullerene (C$_{60}$) polymers exerts a strong influence on their low-frequency phonon states and their interactions with mobile electrons. The continuum approximation is employed to show the zone-folding of phonon dispersion curves, which leads to fast relaxation of a radial breathing mode in the 1D C$_{60}$ polymers. We also formulate the electron-phonon interaction along the deformation potential theory, demonstrating that only a few set of electron and phonon modes yields a significant magnitude of the interaction relevant to the low-temperature physics of the system. The latter finding gives an important implication for the possible Peierls instability of the C$_{60}$ polymers suggested in the earlier experiment.Comment: 9 pages, 8 figure

Vibrational spectra of C60C8H8 and C70C8H8 in the rotor-stator and polymer phases

C60-C8H8 and C70-C8H8 are prototypes of rotor-stator cocrystals. We present infrared and Raman spectra of these materials and show how the rotor-stator nature is reflected in their vibrational properties. We measured the vibrational spectra of the polymer phases poly(C60C8H8) and poly(C70C8H8) resulting from a solid state reaction occurring on heating. Based on the spectra we propose a connection pattern for the fullerene in poly(C60C8H8), where the symmetry of the C60 is D2h. On illuminating the C60-C8H8 cocrystal with green or blue light a photochemical reaction was observed leading to a similar product to that of the thermal polymerization.Comment: 26 pages, 8 figures, to appear in Journal of Physical Chemistry B 2nd version: minor changes in wording, accepted version by journa

Glycan multivalency effects toward albumin enable N-glycan-dependent tumor targeting

© 2016 Elsevier Ltd. All rights reserved.Multivalent interactions play an essential role in molecular recognition in living systems. These effects were employed to target tumor cells using albumin clusters bearing ∼10 molecules of asparagine-linked glycans (N-glycans). Noninvasive near-infrared fluorescence imaging clearly revealed A431 tumors implanted in BALB/cA-nu/nu mice after 1 h in an N-glycan structure-dependent manner, thereby demonstrating the efficient use of glycan multivalency effects for tumor targeting in vivo

Petrología y geocronología K-Ar del complejo Marañón (Región Huánuco-Tingo María), Cordillera Oriental de los Andes Peruanos: consideraciones tectónicas preliminares

El Complejo Marañón incluye un conjunto de rocas metamórficas de grado bajo y de edad PreOrdoviciana, las que se encuentran expuestas de manera semi-continua a lo largo de la Cordillera Oriental Peruana, entre los ríos Marañón y Huallaga. Las relaciones de campo sugieren que se trata de una secuencia metamórfica, de bajo grado constituida por un intervalo de esquistos cuarzo-micáceos, intercalados con algunas meta-tufos y rocas carbonatadas, y otra de muy bajo grado constituida por pizarras y meta-arentias. Estructuralmente se observan 3 a 4 fábricas formadas en condiciones dúctiles en las rocas de más alto grado, y 2 en las de bajo grado. En la primera, la foliación principal está definida por las micas, y por Sn anterior siendo preservada en microlitones. Las otras fábricas son crenulaciones menores y plegamientos regionales sin recristalización metamórfica. Las rocas de más bajo grado presentan una estructura planar aparentemente subparalela con la estratificación, sobre la que se sobrepone un plegamiento asociado a un clivaje espaciado. Las características microestructurales de las rocas de bajo grado en la zona de Tingo-María, muestran el predominio de texturas elásticas relictas, y minerales detríticos (plagioclasas, feldespato-K, turmalina, muscovita). La deformación observada en meta-arenitas y rocas calcáreas, incluye calcitas con macias del tipo II y III, extinción ondulatoria, formación de subgranos, migración del borde de granos en el cuarzo y formación de sericita. En las pizarras son comunes residuos insolubles en zonas de crenulación y venas de cuarzo típicas de procesos de disolución por presión. Estos elementos indican temperaturas entre 200°-350° C (Ferrill, 1991, Burkhard, 1993, Passchier y Trouw, 1996, Ferril et al, in press)

Far-infrared study of the Jahn-Teller distorted C60 monoanion in C60 tetraphenylphosphoniumiodide

We report high-resolution far-infrared transmission measurements on C(60)-tetraphenylphosphoniumiodide as a function of temperature. In the spectral region investigated (20-650 cm(-1)), we assign intramolecular modes of the C(60) monoanion and identify low-frequency combination modes. The well-known F(1u)(1) and F(1u)(2) modes are split into doublers at room temperature, indicating a D(5d) or D(3d) distorted ball. This result is consistent with a dynamic Jahn-Teller effect in the strong-coupling limit or with a static distortion stabilized by low-symmetry perturbations. The appearance of silent odd modes is in keeping with symmetry reduction of the hall, while activation of even modes is attributed to interband electron-phonon coupling and orientational disorder in the fulleride salt. Temperature dependences reveal a weak transition in the region 125-150 K in both C(60)(-) and counterion modes, indicating a bulk, rather than solely molecular, effect. Anomalous softening (with decreasing temperature) in several modes may correlate with the radial character of those vibrations. [S0163-1829(98)03245-7]

Far-infrared vibrational properties of high-pressure-high-temperature C60 polymers and the C60 dimer

We report high-resolution far-infrared transmission measurements of the 2 + 2 cycloaddition C-60 dimer and two-dimensional rhombohedral and one-dimensional orthorhombic high-pressure high-temperature C60 polymers. In the spectral region investigated(20-650 cm(-1)), we see no low-energy interball modes, but symmetry breaking of the linked C-60 balls is evident in the complex spectrum of intramolecular modes. Experimental features suggest large splittings or frequency shifts of some IhC60-derived modes that are activated by symmetry reduction, implying that the balls are strongly distorted in these structures. We have calculated the vibrations of all three systems by first-principles quantum molecular dynamics and use them to assign the predominant IhC60 symmetries of observed modes. Pur calculations show unprecedentedly large downshifts of T-1u(2)-derived modes and extremely large splittings of other modes, both of which are consistent with the experimental spectra. For the rhombohedral and orthorhombic polymers, the T-1u(2)-derived mode that is polarized along the bonding direction is calculated to downshift below any T-1u(1)-derived modes. We also identify a previously unassigned feature near 610 cm(-1) in all three systems as a widely split or shifted mode derived from various silent IhC60 vibrations, confirming a strong perturbation model for these linked fullerene structures