El Premi Nobel de Química 2014: la microscòpia de fluorescència amb superresolució

El Premi Nobel de Química 2014 va ser concedit als investigadors Eric Betzig, Stefan W. Hell i William E. Moerner per les seves contribucions al desenvolupament de la microscòpia de fluorescència amb superresolució, un nou grup de tècniques que permeten la caracterització òptica de la matèria a escala nanomètrica. En aquest article es descriuen els principals fonaments d'aquest tipus de microscòpia, així com les descobertes realitzades pels tres guardonats en aquest camp.The Nobel Prize in Chemistry 2014 has been awarded to physicists Eric Betzig, Stefan W. Hell and William E. Moerner for their contributions to the development of super-resolved fluorescence microscopy, a new group of techniques that allow the optical characterization of matter to be brought down to the nanometre scale. This article reviews the fundamentals of this type of microscopy, as well as the main discoveries made by the Nobel laureates in this area

Jitter and Shimmer measurements for speaker diarization

Jitter and shimmer voice quality features have been successfully used to characterize speaker voice traits and detect voice pathologies. Jitter and shimmer measure variations in the fundamental frequency and amplitude of speaker's voice, respectively. Due to their nature, they can be used to assess differences between speakers. In this paper, we investigate the usefulness of these voice quality features in the task of speaker diarization. The combination of voice quality features with the conventional spectral features, Mel-Frequency Cepstral Coefficients (MFCC), is addressed in the framework of Augmented Multiparty Interaction (AMI) corpus, a multi-party and spontaneous speech set of recordings. Both sets of features are independently modeled using mixture of Gaussians and fused together at the score likelihood level. The experiments carried out on the AMI corpus show that incorporating jitter and shimmer measurements to the baseline spectral features decreases the diarization error rate in most of the recordings.Peer ReviewedPostprint (published version

A local view on single and coupled molecules

The paper focuses on a novel approach to reveal ultrafast dynamics in single molecules. The main strength of the approach is towards ultrafast processes in extended multi-chromophoric molecular assemblies. Excitonically coupled systems consisting of 2 and 3 rigidly linked perylene-diimide units in a head to tail configuration are studied. Superradiance and inhibited intramolecular decay are observed and discrete jumps in femtosecond response upon break-up of the strong coupling are revealed

Advances in nanophotonics: ultrafast & ultrasensitive

In this tutorial on NanoPhotonics recent advances are highlighted with focus on near field optical methods, ultra-fast probing of single molecules and ultra-sensitive detection of individual non-fluorescent nanoparticles

The use of long-term features for GMM- and i-vector-based speaker diarization systems

Several factors contribute to the performance of speaker diarization systems. For instance, the appropriate selection of speech features is one of the key aspects that affect speaker diarization systems. The other factors include the techniques employed to perform both segmentation and clustering. While the static mel frequency cepstral coefficients are the most widely used features in speech-related tasks including speaker diarization, several studies have shown the benefits of augmenting regular speech features with the static ones. In this work, we have proposed and assessed the use of voice-quality features (i.e., jitter, shimmer, and Glottal-to-Noise Excitation ratio) within the framework of speaker diarization. These acoustic attributes are employed together with the state-of-the-art short-term cepstral and long-term prosodic features. Additionally, the use of delta dynamic features is also explored separately both for segmentation and bottom-up clustering sub-tasks. The combination of the different feature sets is carried out at several levels. At the feature level, the long-term speech features are stacked in the same feature vector. At the score level, the short- and long-term speech features are independently modeled and fused at the score likelihood level. Various feature combinations have been applied both for Gaussian mixture modeling and i-vector-based speaker diarization systems. The experiments have been carried out on Augmented Multi-party Interaction meeting corpus. The best result, in terms of diarization error rate, is reported by using i-vector-based cosine-distance clustering together with a signal parameterization consisting of a combination of static cepstral coefficients, delta, voice-quality, and prosodic features. The best result shows about 24% relative diarization error rate improvement compared to the baseline system which is based on Gaussian mixture modeling and short-term static cepstral coefficients.Peer ReviewedPostprint (published version

Wavelength-Tunable Light-Induced Polymerization of Cyanoacrylates Using Photogenerated Amines

Cyanoacrylate photopolymerization has already been described, but it generally requires the use of organometallic photoinitiators and highly reactive monomers, which often leads to photoinitiator-monomer mixtures with limited stability. In this work we report a method to tackle these limitations, which relies on the use of amines bearing photoremovable protecting groups as light-responsive nucleophilic cyanoacrylate initiators. By exploiting the versatility of amine photorelease strategies, we have developed a series of all-organic initiators that (a) enable fast, on demand photocuring of commercial formulations of various cyanoacrylates, including less reactive, biologically relevant long alkyl chain monomers; (b) show wavelength tunability along the UV-vis spectrum and good thermal stability in the dark; and (c) lead to polymeric materials with excellent adhesive behavior. Because of this combination of properties, photogenerated amines appear as ideal candidates to bring cyanoacrylate photopolymerization into real application, especially in the biomedical field

Ab initio ground potential energy surface and quasiclassical trajectory study of the O(1D)+CH4(X1A1)→OH(X 2Π)+CH3(X 2A ″2) reaction dynamics

An ab initio study of the ground potential energy surface (PES) of the O(1D)+CH4→OH+CH3 reaction has been performed using the second and fourth order Møller-Plesset methods with a large basis set. From the ab initio data a triatomic analytical ground PES with the methyl group treated as an atom of 15.0 amu has been derived. This PES has been employed to study the dynamics of the reaction by means of the quasiclassical trajectory (QCT) method. A good agreement between the experimental and QCT OH rovibrational distributions at a collision energy of 0.212 eV with the methane molecule at 298 K has been obtained. The analysis of the microscopic reaction mechanism shows that the reaction takes place almost exclusively through the insertion of the O(1D) atom into a C-H bond, due to the presence of the deep (CH3)OH minimum, and the resulting trajectories may be direct or nondirect (short-lived collision complexes mainly) with about the same probability. The OH vibrational distribution arising from the direct mechanism is inverted, while the nondirect mechanism leads to a noninverted one. There is some tendency to give broader OH rotational distributions peaking at higher N′ values, particularly for the vibrational levels v′ = 0-1, in the case of the nondirect trajectories. The PES derived here may be used in dynamics studies under conditions where the methyl group motions are not strongly coupled to the motions leading to reaction

Ab initio ground potential energy surface, VTST and QCT study of the O(3P) + CH4(X1A1) → OH(X2Π) + CH3(X2A2'') reaction

An ab initio study of the ground potential energy surface (PES) of the O(3P)+CH4→OH+CH3 reaction has been performed using the second- and fourth-order Mo/ller-Plesset methods with a large basis set. A triatomic analytical ground PES with the methyl group treated as an atom of 15.0 a.m.u. has been derived. This PES has been employed to study the kinetics [variational transition state theory (VTST) and quasiclassical trajectory (QCT) rate constants] and dynamics (QCT method) of the reaction. The ab initio points have also been used directly to calculate the VTST rate constant considering all atoms of the system. The best VTST methods used lead to a good agreement with the experimental rate constant for 1000-2500 K, but QCT rate constant values are about one-third the experimental ones for 1500-2500 K. The cold QCT OH(v=0) rotational distribution arising from the simulation of the reaction with O(3P) atoms produced in the photodissociation of NO2 at 248 nm is in good agreement with experiment, while the very small QCT OH(v=1) population obtained is consistent with measurements. The triatomic PES model derived in this work may be used in studies of the kinetics and dynamics under conditions where the methyl group motions are not strongly coupled to the motions leading to reaction

The L2F - UPC Speaker Recognition System for NIST SRE 2010

This document describes the joint submission of the INESC-ID’s Spoken Language Systems Laboratory (L 2 F) and the TALP Research Center from the Technical University of Catalonia (UPC) to the 2010 NIST Speaker Recognition evaluation. The L2F-UPC primary system is composed by the fusion of five individual sub-systems. Speaker recognition results have been submitted only for the core-core conditionPostprint (published version

Ab initio study of the O(1D) + CH4(X1A1) → OH(X2Π) + CH3(X2A2'') reaction: ground and excited potential energy surfaces

The two potential energy surfaces (1 1A and 2 1A PESs) adiabatically correlating the reactants and products asymptotes of the title reaction were studied by means of the CASSCF and CASPT2 ab initio methods. The minimum energy path determined for the ground PES evolved through the barrierless insertion of the O(1D) atom into a C-H bond. The OH + CH3 products result from the dissociation of the CH3OH methanol intermediate formed. Reactivity on the excited 2 1A PES was found to proceed via an abstraction pathway. The energy barrier involved is low enough to expect the 2 1A PES to play a non-negligible role in the title reaction, even at the usual conditions attained in the experiments. The crossing between the 11A and 31A PESs was also investigated, the latter surface correlating with the excited OH(A 2Σ+) product