Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 4 de 4
Mais filtros

Base de dados
Intervalo de ano de publicação
Soft Robot ; 7(1): 59-67, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31460833


Multimaterial mechanisms are seen throughout natural organisms across all length scales. The different materials in their bodies, from rigid, structural materials to soft, elastic materials, enable mobility in complex environments. As robots leave the lab and begin to move in real environments, including a range of materials in 3D robotics mechanisms can help robots handle uncertainty and lessen control requirements. For the smallest robots, soft materials combined with rigid materials can facilitate large motions in compact spaces due to the increased compliance. However, integrating various material components in 3D at the microscale is a challenge. We present an approach for 3D microscale multimaterial fabrication using two-photon polymerization. Two materials with three orders of magnitude difference in Young's moduli are printed in consecutive cycles. Integrating a soft elastic material that is capable of more than 200% strain along with a rigid material has enabled the formation of hybrid elements, strongly adhered together, with layer accuracy below 3-µm resolution. We demonstrate a multilink multimaterial mechanism showing large deformation, and a 3D-printed 2-mm wingspan flapping wing mechanism, showing rapid prototyping of complex designs. This fabrication strategy can be extended to other materials, thus enhancing the functionality and complexity of small-scale robots.

J Am Chem Soc ; 142(1): 257-263, 2020 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-31825211


Molecular helices based on self-organized aromatic oligoamide foldamers have been designed and prepared in their two enantiomeric forms in order to probe their second-order nonlinear chiroptical properties in solution. The quinoline oligoamides were rationally functionalized by electron-donating and electron-withdrawing groups to afford a gradual increase of the electronic polarization of the helical architectures. Their hyper-Rayleigh scattering (HRS) responses in solution were accordingly assessed, using either linearly polarized or circularly polarized incident light. Both methods allowed us to observe nonlinear optical activity that was quantified, for the first time for molecular systems, through circular differential scattering intensity ratios. The hyper-Rayleigh optical activity study reveals important charge-transfer differences within the aromatic oligomers, depending on the helix handedness and on the extent of electronic polarization induced by the appended substituents. The origin of the enantiomeric difference is discussed considering both achiral and chiral contributions. Overall, using aromatic oligoamide foldamers as a chiral model, we demonstrate the capabilities of HRS as a complementary chiroptical method, ideally suited for the analysis of various chiral molecular and supramolecular systems in solution. The reliability and chiral discrimination sensitivity of the method can be further improved through dynamic measurements using standard polarization modulation and heterodyning techniques.

Chem Commun (Camb) ; 55(66): 9825-9828, 2019 Aug 13.
Artigo em Inglês | MEDLINE | ID: mdl-31360956


Quinoline oligoamide foldamers appended with non-chiral fluorophores and derivatized with a camphanyl chiral inducer display strong chiroptical properties at tunable wavelengths as proved by CD and CPL spectroscopies. Induced CPL activity with high luminescence dissymmetry factors was observed in the visible range at wavelengths specific to the fluorophores.

Antonie Van Leeuwenhoek ; 111(4): 563-572, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29124466


Plant rhizobacteria have been successfully used as biocontrol agents against fungal phytopathogens. However, their potential to control two important avocado diseases, namely Fusarium dieback (FD) and Phytophthora root rot (PRR), has been poorly studied. FD is an emerging disease triggered by fungi associated with two ambrosia beetle species (Euwallacea fornicatus species complex), while PRR is caused by Phytophthora cinnamomi, a soil-borne oomycete. In the present work, the antifungal activity of bacteria isolated from avocado rhizosphere was tested in dual culture assays against Fusarium euwallaceae, Graphium euwallaceae and Graphium sp., causal agents of FD, and against P. cinnamomi. In 2015, rhizosphere soil samples of FD infested and non-infested avocado trees were collected from a commercial avocado orchard in Escondido, California. In an initial screening, 72 of the 168 assessed bacterial isolates reduced mycelial growth of F. euwallaceae by up to 46%. Eight bacterial isolates showing inhibition percentages larger than 40% were then selected for further antagonism assays against the other fungal pathogens. Five bacterial isolates, determined by 16S rDNA sequencing to belong to the Bacillus subtilis/Bacillus amyloliquefaciens species complex, successfully inhibited the mycelial growth of both Graphium species by up to 30%. The same isolates and an additional isolate identified as Bacillus mycoides, inhibited the growth of P. cinnamomi by up to 25%. This is the first report of avocado rhizobacteria with antifungal activity against pathogens responsible for FD and PRR in avocado.

Ascomicetos/fisiologia , Bacillus/isolamento & purificação , Fusarium/fisiologia , Interações Microbianas/fisiologia , Persea/microbiologia , Phytophthora/fisiologia , Rizosfera , Animais , Antifúngicos/metabolismo , Bacillus/classificação , Bacillus/metabolismo , California , Insetos Vetores/microbiologia , Doenças das Plantas/microbiologia , Raízes de Plantas/microbiologia , RNA Ribossômico 16S/genética , Gorgulhos/microbiologia