Teaching Story without Struggle: Using Graded Readers and Their Audio Packs in the EFL Classroom

In recent years the support for extensive reading (ER) in English as a second or foreign language (ESL/EFL) programs has been compelling. When practicing extensive reading, the learner reads a wide variety of texts for pleasure and achieves a general understanding of the content while deciphering unknown words through context. This approach contrasts with intensive reading, a more traditional approach based on a slow, careful reading of a text, with goals of complete comprehension and the identification of specific details and information

Optical-limiting properties of 1-(P-N,N-dimethylamino)-4-(P-cyanophenyl)-1,3-butadiene

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Optical-limiting properties of a push-pull diphenyl-butadiene

The optical-limiting behavior of 1-(p-N,N-dimethylamino)-4-(p-cyanophenyl)-1,3-butadiene (DCB) solution in dichloromethane was experimentally and theoretically studied at 532 nm with nanosecond and picosecond pulses. Energy-dependent transmissivity measurements were fitted using a three-level molecular model including two-photon absorption. The best fits were obtained with very high two-photon absorption cross-sections, indicating that two-photon absorption is the predominant mechanism of the strong optical limiting behavior observed in a DCB solution

Charge-Transfer Chemical Reactions in Nanofluidic Fabry-Pérot Cavities

We investigate the chemical reactivity of molecular populations confined inside a nanofluidic Fabry-Pérot cavity. Due to strong light-matter interactions developing between a resonant electromagnetic cavity-mode and the electric dipole moment of the confined molecules, a polariton is formed. The former gets dressed by environmental vibrational and rotational degrees of freedom of the solvent. We call the resulting polariton dressed by its cloud of environmental excitation a "reacton", since it further undergoes chemical reactions. We characterize how the reacton formation modifies the kinetics of a photoisomerization chemical reaction involving an elementary charge-transfer process. We show that the reaction driving-force and reorganization energy are both modulated optically by the reactant concentration, the vacuum Rabi splitting and the de-tuning between the Fabry-Pérot cavity frequency and targeted electronic transition. Finally, we compute the ultrafast picosecond dynamics of the whole photochemical reaction. We predict that despite optical cavity losses and solvent-mediated non-radiative relaxation, measurable signatures of the reacton formation can be found in state-of-the-art pump-probe experiments.Réactions Chimiques, Transfert de Charges et d'Energie en Cavité ElectromagnétiqueUniversity of Bordeaux Graduate Scholl in Light Sciences & Technologie

Direct Mechanical Detection and Measurement of Wave-Matter Orbital Angular Momentum Transfer by Nondissipative Vortex Mode Conversion

International audienceWe quantitatively report on the rotational mechanical effect of wave orbital angular momentum on matter by nondissipative vortex mode conversion. Our experiments consist of ultrasonic waves reflected off freely spinning helical acoustic mirrors that are capillary trapped at a curved air-water interface. Considering helical mirrors with integer topological charges these results represent the demonstration of the experiment proposed by Allen et al. originally introduced in the optical domain [Phys. Rev. A 45, 8185 (1992)], whose quantitative implementation remains elusive to date whatever the nature of the wave. The study is further generalized to helical mirrors with fractional charges

Control of Photochemical Properties of Monolayers and Langmuir-Blodgett Films of Amphiphilic Chromoionophores

Control of the structure of ultrathin films that determine the steric conditions of the passing of intermolecular interactions is one of the most promising methods of implementing the advantages of planar supramolecular systems as basic elements of nanosize information devices. This work studies the behavior of Langmuir monolayers of a new amphiphilic crown-substituted chromoionophore I on a water subphase. It is found that dithiaazacrown ether in molecule I selectively binds Hg2+ cations both in organic solvents and from aqueous subphase. The electronic absorption spectra of the monolayer showed that H-aggregation occurs actively in the course of two-dimensional compression on deionized water, which hinders the complexation process, while the presence of Na+ and Ba2+ cations in the subphase results in the effective inhibition of this aggregation. This conclusion is confirmed by spectral fluorimetric studies of monolayers of a dye with a similar structure that contains a chromophoric group with a much higher fluorescence quantum yield. Monolayer aggregation on deionized water at the surface pressure values of just 4-6 mN/m leads to the three to fourfold fluorescence quenching, while in the case of subphases containing inert (noncomplementary to the dye ionophoric fragment) cations, the compression of the monolayer to pressures of 25-30 mN/m reduces the fluorescence intensity by no more than 25-35%. It was thus found that variations in the subphase composition allows one to monitor the degree of aggregation of the monolayer and the efficiency of cation recognition

Supramolecular assemblies of crown-containing 4-styrylpyridine in the presence of metal cations

International audienceOptical and x-ray experiments showed the possibility of studying 4-styrylpyridine with a 15-crown-5 ether fragment to bind metal cations through the participation of two centres: the crown ether moiety and the heterocyclic part. The metal cations studied can be divided into three groups. Alkaline earth metal cations form complexes with the crown ether centre, H+, Co2+ and Cd2+ prefer coordination with the N-atom of heterocyclic part and Hg2+ cations form complexes through coordination with both binding centres

Development of Functionalized Cyclotriveratrylene Analogues: Introduction of Withdrawing and π-Conjugated Groups

International audienceCyclotriveratrylene analogues (CTVs) are supramolecular bowl-shaped molecules known for their ability to complex organic and organometallic guests, to form liquid crystals, polymers, or nanostructures. In this Article, we report the synthesis of new cyclotriveratrylene analogues with fluorescence properties in which various electron-withdrawing or π-extended conjugated groups are appended to the wide rim ortho to the methoxy-donating groups. Synthetically, these functionalized CTVs cannot be obtained as CTVs with electron-rich functions by the typical method (i.e., the trimerization of the corresponding benzyl alcohol) but are prepared from a common key intermediate, the C3-triiodocyclotriveratrylene (CTV-I3), in good yields. Despite the synthetic difficulties encountered due to the presence of three reactive centers, we have demonstrated the possibility of performing Sonogashira coupling and Huisgen cycloaddition reactions directly to the CTV core for the first time. CTVs with π-extended conjugated groups reveal interesting fluorescence profiles. More broadly, this study utilizes CTV-I3 to introduce novel functionalities into CTVs to keep exploring their potential applications. Cyclotriveratrylene analogues (CTVs) are supramolecular bowl-shaped molecules known for their ability to complex organic and organometallic guests, to form liquid crystals, polymers, or nanostructures. In this Article, we report the synthesis of new cyclotriveratrylene analogues with fluorescence properties in which various electron-withdrawing or π-extended conjugated groups are appended to the wide rim ortho to the methoxy-donating groups. Synthetically, these functionalized CTVs cannot be obtained as CTVs with electron-rich functions by the typical method (i.e., the trimerization of the corresponding benzyl alcohol) but are prepared from a common key intermediate, the C3-triiodocyclotriveratrylene (CTV-I3), in good yields. Despite the synthetic difficulties encountered due to the presence of three reactive centers, we have demonstrated the possibility of performing Sonogashira coupling and Huisgen cycloaddition reactions directly to the CTV core for the first time. CTVs with π-extended conjugated groups reveal interesting fluorescence profiles. More broadly, this study utilizes CTV-I3 to introduce novel functionalities into CTVs to keep exploring their potential applications