Polarization-Sensitive Photoluminescence from Aligned Carbon Chains Terminated by Gold Clusters.

We synthesize a thin film composed of long carbyne chains terminated by gold clusters and study its optical properties. The presence of gold particles stabilizes longer chains and leads to their alignment. We show that the gold clusters also act as a source of electron doping, thus, changing the intensity of photoluminescence from quadratic dependence on the pumping intensity without gold to linear with gold. We also observe that the excitation of the film at the gold plasmon frequency causes the blue shift of photoluminescence and estimate, on the basis of this effect, the minimum length of the carbyne chains. The high degree of alignment of the gold-terminated carbyne chains results in strongly anisotropic light absorption characterized by a distinctive cosine dependence on the angle between the carbyne molecule and polarization plane of the excitation. This paves the way for a new class of ultimately thin polarization sensitive emitters to be used in future integrated quantum photonics devices.

Quasi-exact solutions for guided modes in two-dimensional materials with tilted Dirac cones.

We show that if the solutions to the (2+1)-dimensional massless Dirac equation for a given one-dimensional (1D) potential are known, then they can be used to obtain the eigenvalues and eigenfunctions for the same potential, orientated at an arbitrary angle, in a 2D Dirac material possessing tilted, anisotropic Dirac cones. This simple set of transformations enables all the exact and quasi-exact solutions associated with 1D quantum wells in graphene to be applied to the confinement problem in tilted Dirac materials such as 8-Pmmn borophene. We also show that smooth electron waveguides in tilted Dirac materials can be used to manipulate the degree of valley polarization of quasiparticles travelling along a particular direction of the channel. We examine the particular case of the hyperbolic secant potential to model realistic top-gated structures for valleytronic applications.

Publisher Correction: Two-dimensional Dirac particles in a Pöschl-Teller waveguide.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Two-dimensional Dirac particles in a Pöschl-Teller waveguide.

We obtain exact solutions to the two-dimensional (2D) Dirac equation for the one-dimensional Pöschl-Teller potential which contains an asymmetry term. The eigenfunctions are expressed in terms of Heun confluent functions, while the eigenvalues are determined via the solutions of a simple transcendental equation. For the symmetric case, the eigenfunctions of the supercritical states are expressed as spheroidal wave functions, and approximate analytical expressions are obtained for the corresponding eigenvalues. A universal condition for any square integrable symmetric potential is obtained for the minimum strength of the potential required to hold a bound state of zero energy. Applications for smooth electron waveguides in 2D Dirac-Weyl systems are discussed.

Terahertz science and technology of carbon nanomaterials.

The diverse applications of terahertz (THz) radiation and its importance to fundamental science makes finding ways to generate, manipulate and detect THz radiation one of the key areas of modern applied physics. One approach is to utilize carbon nanomaterials, in particular, single-wall carbon nanotubes and graphene. Their novel optical and electronic properties offer much promise to the field of THz science and technology. This article describes the past, current, and future of THz science and technology of carbon nanotubes and graphene. We will review fundamental studies such as THz dynamic conductivity, THz nonlinearities and ultrafast carrier dynamics as well as THz applications such as THz sources, detectors, modulators, antennas and polarizers.

Cell differentiation and cell-cycle alterations by tyrosine kinase inhibitors in human melanoma cells.

Differentiation therapy is an attractive option for malignant melanoma, as traditional forms of chemotherapy seem to have little effect on this type of tumour. Among the several pathways for the experimental induction of differentiation of melanoma, we have focused on signal transduction mediated by protein kinases. We have examined the effects of calphostin C (a protein kinase C inhibitor), genistein and methyl 2,5-dihydroxycinnamate (tyrosine kinase inhibitors), and exogenous phosphotyrosine (an activator of protein tyrosine phosphatases) on the growth, morphology and differentiation of malignant melanomas in vitro. All four compounds tested were able to inhibit cell proliferation, but only genistein and methyl 2,5-dihydroxycinnamate were able to induce morphological changes, yielding a more dendritic or a rounder phenotype, respectively. The latter two drugs were also able to induce specific cell-cycle alterations, in contrast to calphostin C and phosphotyrosine. Melanin content was increased greatly in phophotyrosine treated cells and, to a smaller extent, in cells treated with genistein. RNA expression of specific genes encoding cytolytic T-cell antigens was not altered by the two tyrosine kinase inhibitors, in spite of the phenotypic changes observed. Together, these results suggest that tyrosine kinases are involved in cell cycle, growth, and differentiation pathways in malignant melanomas; however, these pathways may not be co-dependent. The results also suggest that these pathways may be sensitive to specific tyrosine kinase inhibitors or activators of protein tyrosine phosphatases.

Acne fulminans: tratamento de 11 pacientes com o acido 13-cis-retinoico. / Acne fulminans: treatment of 11 patients with 13-cis-retinoic acid

Acne fulminans e uma forma particularmente severa de acne que acomete pacientes jovens e que, por seu quadro clinico-laboratorial, pode ser separada dos outros tipos Sao apresentados onze pacientes com esta doenca. Alem dos aspectos diagnosticos e clinicos, e discutido, com especial atencao, o tratamento com o acido 13-cis-retinoico (isotretinoina, RO 4-3780, Accutane: EUA, Roaccutan: Europa) que apresentou em todos os pacientes uma melhora substancial