small crystal approach for the electronic properties of double wall carbon nanotubes

A small crystal approach (SCA) is a real-space approach that allows one to introduce local symmetry breaking which is difficult to consider in a reciprocal space approach. We apply the SCA to the case of double-wall nanotubes, for which the effects of the orientation-dependent intertube interactions have to be taken into account. The results suggest a solution for the usual difficulties in assigning the resonance Raman spectra of double-wall nanotubes since important variations of the electronic spectra of these carbon nanotubes are found with respect to those of the constituent single-wall nanotubes

Excitonic properties of armchair graphene nanoribbons from exact diagonalization of the Hubbard model

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exact diagonalization of hubbard models for the optical properties of single wall carbon nanotubes

Excitonic states of single-walled carbon nanotubes (SWNTs) have usually been calculated using many-body perturbation theories or mean field approaches because a large number of sites cannot be considered within an exact diagonalization (ED) calculation based on the Hubbard model. We use a small crystal approach and show that, for the π structure of nanotubes, an ED calculation is possible. We apply this approach to small-diameter SWNTs and the results show that a crossing of the first bright state with the second excited states occurs when U, the correlation parameter of the Hubbard model, equals 4t, where t is the hopping integral. Two or three strong two-photon absorption (TPA) states are found at energies above the first bright state for U/t≤3. Beyond this value, these states become relevant for TPA below the first bright state. A number of dark states are always calculated below the first bright state at energies that, in the intermediate coupling regime, are of the order of tens to hundreds of meV. This result seems to be consistent with recent experiments

Single File Flow of Biomimetic Beads for Continuous SERS Recording in a Microfluidic Device

A major challenge in cancer treatment is the quantification of biomarkers associated with a specific cancer type. Important biomarkers are the circulating tumor cells (CTCs) detached from the main cancer and circulating in the blood. CTCs are very rare and their identification is still an issue. Although CTCs quantification can be estimated by using fluorescent markers, all the fluorescence techniques are strongly limited by the number of emissions (therefore markers) that can be discriminated with one exciting line, by their bleaching characteristics, and by the intrinsic autofluorescence of biological samples. An emerging technique that can overcome these limitations is Surface Enhanced Raman Scattering (SERS). Signals of vibrational origin with intensity similar to those of fluorescence, but narrower bandwidths, can be easily discriminated even by exciting with a single laser line. We recently showed the benefit of this method with cells fixed on a surface. However, this approach is too demanding to be applied in clinical routine. To effectively increase the throughput of the SERS analysis, microfluidics represents a promising tool. We report two different hydrodynamic strategies, based on device geometry and liquids viscosity, to successfully combine a microfluidic design with SERS

Manipulating chemistry through nanoparticle morphology

We demonstrate that the protonation chemistry of molecules adsorbed at nanometer distances from the surface of anisotropic gold nanoparticles can be manipulated through the effect of surface morphology on the local proton density of an organic coating. Direct evidence of this remarkable effect was obtained by monitoring surface-enhanced Raman scattering (SERS) from mercaptobenzoic acid and 4-aminobenzenethiol molecules adsorbed on gold nanostars. By smoothing the initially sharp nanostar tips through a mild thermal treatment, changes were induced on protonation of the molecules, which can be observed through changes in the measured SERS spectra. These results shed light on the local chemical environment near anisotropic colloidal nanoparticles and open an alternative avenue to actively control chemistry through surface morphology.LL and LML-M acknowledge funding from European Commission Grant (EUSMI 731019). Funding is also acknowledged from the Spanish MINECO (MAT2017-86659-R and MDM-2017-0720 to LML-M; MAT2017-88492-R and SEV2015-0522 to JGA) and the European Research Council (Advanced Grant 787510 4DBIOSERS to LML-M; Advanced Grant 789104-eNANO to JGA)

Manipulating chemistry through nanoparticle morphology

We demonstrate that the protonation chemistry of molecules adsorbed at nanometer distances from the surface of anisotropic gold nanoparticles can be manipulated through the effect of surface morphology on the local proton density of an organic coating. Direct evidence of this remarkable effect was obtained by monitoring surface-enhanced Raman scattering (SERS) from mercaptobenzoic acid and 4-aminobenzenethiol molecules adsorbed on gold nanostars. By smoothing the initially sharp nanostar tips through a mild thermal treatment, changes were induced on protonation of the molecules, which can be observed through changes in the measured SERS spectra. These results shed light on the local chemical environment near anisotropic colloidal nanoparticles and open an alternative avenue to actively control chemistry through surface morphology.LL and LML-M acknowledge funding from European Commission Grant (EUSMI 731019). Funding is also acknowledged from the Spanish MINECO (MAT2017-86659-R and MDM-2017-0720 to LML-M; MAT2017-88492-R and SEV2015-0522 to JGA) and the European Research Council (Advanced Grant 787510 4DBIOSERS to LML-M; Advanced Grant 789104-eNANO to JGA)

Análise de redes sociais como instrumento de compreensão da dinâmica organizativa de uma comunidade rural no Amazonas.

O texto apresenta uma análise das relações sociais que se estabelecem na comunidade do Lago do Santana, localizada no Município de Manacapuru, AM, como estratégia de superação de problemas individuais e coletivos da comunidade. É um estudo que utiliza como base de análise as redes sociais dessa comunidade. Buscou-se entender como ela está organizada, como se relaciona e quais dinâmicas estão presentes e são capazes de impulsionar a resolução de problemas, garantindo avanços individuais e coletivos. Foram analisados aspectos como: faixa etária, nível de escolaridade e infraestrutura da comunidade. No âmbito da estrutura econômica, analisaram-se as questões pertinentes às relações do trabalho e o estabelecimento da relação de ajuda mútua. O objetivo da pesquisa foi entender e mensurar a forma como a comunidade estabelece relações e define estratégias para o viver bem, desenvolvendo a agricultura e utilizando seus recursos naturais, a terra, a floresta e a água

SERRS Multiplexing with Multivalent Nanostructures for the Identification and Enumeration of Epithelial and Mesenchymal Cells

Liquid biopsy represents a new frontier of cancer diagnosis and prognosis, which allows the isolation of tumor cells released in the blood stream. The extremely low abundance of these cells needs appropriate methodologies for their identification and enumeration. Herein we present a new protocol based on surface enhanced resonance Raman scattering (SERRS) gold multivalent nanostructures to identify and enumerate tumor cells with epithelial and mesenchimal markers. The validation of the protocol is obtained with spiked samples of peripheral blood mononuclear cells (PBMC). Gold nanostructures are functionalized with SERRS labels and with antibodies to link the tumor cells. Three types of such nanosystems were simultaneously used and the protocol allows obtaining the identification of all individual tumor cells with the help of a Random Forest ensemble learning method

Caracterização da produção da agricultura familiar no projeto de assentamento Panelão no município de Careiro Castanho-AM.

O contexto vivenciado com a criação de assentamentos traz novas reflexões sobre a realidade econômica, social e política da agricultura familiar no Brasil, que pode representar bases para impulsionar a construção de uma nova realidade rural no país. O referido trabalho, através da caracterização da produção da agricultura familiar no Assentamento Panelão, no município de Careiro Castanho, no Estado do Amazonas, procura contribuir na construção de parâmetros que sirvam de base para a introdução de tecnologias adequadas em comunidades rurais amazônicas de acordo com seus perfis. O levantamento exploratório realizado com agricultores familiares no assentamento permitiu algumas reflexões: a necessidade de reformular o olhar sobre as comunidades, assim como a geração de tecnologias adequadas para o ambiente em estudo, fortalecendo a importância da produção de alimentos voltados à comercialização, ao autoconsumo, contribuindo assim, para a manutenção das famílias no campo