2,123 research outputs found
Electrically injected cavity polaritons
We have realised a semiconductor quantum structure that produces
electroluminescence while operating in the light-matter strong coupling regime.
The mid-infrared light emitting device is composed of a quantum cascade
structure embedded in a planar microcavity, based on the GaAs/AlGaAs material
system. At zero bias, the structure is characterised using reflectivity
measurements which show, up to room temperature, a wide polariton anticrossing
between an intersubband transition and the resonant cavity photon mode. Under
electrical injection the spectral features of the emitted light change
drastically, as electrons are resonantly injected in a reduced part of the
polariton branches. Our experiment demonstrates that electrons can be
selectively injected into polariton states up to room temperature.Comment: 10 pages, 4 figure
Optical amplification enhancement in photonic crystals
Improving and controlling the efficiency of a gain medium is one of the most
challenging problems of laser research. By measuring the gain length in an opal
based photonic crystal doped with laser dye, we demonstrate that optical
amplification is more than twenty-fold enhanced along the Gamma-K symmetry
directions of the face centered cubic photonic crystal. These results are
theoretically explained by directional variations of the density of states,
providing a quantitative connection between density of the states and light
amplification
Chemical shift imprint of intersubunit communication in a symmetric homodimer
Regulatory signals between protein subunits depend on communication between sequential binding events. How such long-range communication, or allostery, operates at the subdomain level has been elusive, especially for homooligomeric proteins. To address this problem, homodimers of thymidylate synthase were generated for optimized study of individual protomers of the singly bound dimer. Mixed 15N-labeled dimers were created with a single functional active site, allowing site-specific, protomer-specific chemical shifts to report on step-wise binding effects. Long-range intersubunit communication was observed although this communication was apparent only in the second ligand-binding step, in which changes were in the first ligand-bound region. Visualization of up to four peaks for each residue amide provides a unique way to assess the allosteric mechanism
Anomaly detection in temporal graph data: An iterative tensor decomposition and masking approach
Sensors and Internet-of-Things scenarios promise a wealth of interaction data that can be naturally represented by means of timevarying graphs. This brings forth new challenges for the identification and removal of temporal graph anomalies that entail complex correlations of topological features and activity patterns. Here we present an anomaly detection approach for temporal graph data based on an iterative tensor decomposition and masking procedure. We test this approach using highresolution social network data from wearable sensors and show that it successfully detects anomalies due to sensor wearing time protocols.published_or_final_versio
The Effect of Protein Mass Modulation on Human Dihydrofolate Reductase
Dihydrofolate reductase (DHFR) from Escherichia coli has long served as a model enzyme with which to elucidate possible links between protein dynamics and the catalyzed reaction. Such physical properties of its human counterpart have not been rigorously studied so far, but recent computer-based simulations suggest that these two DHFRs differ significantly in how closely coupled the protein dynamics and the catalyzed C-H→C hydride transfer step are. To test this prediction, two contemporary probes for studying the effect of protein dynamics on catalysis were combined here: temperature dependence of intrinsic kinetic isotope effects (KIEs) that are sensitive to the physical nature of the chemical step, and protein mass-modulation that slows down fast dynamics (femto- to picosecond timescale) throughout the protein. The intrinsic H/T KIEs of human DHFR, like those of E. coli DHFR, are shown to be temperature-independent in the range from 5–45 °C, indicating fast sampling of donor and acceptor distances (DADs) at the reaction’s transition state (or tunneling ready state – TRS). Mass modulation of these enzymes through isotopic labeling with 13C, 15N, and 2H at nonexchangeable hydrogens yield an 11% heavier enzyme. The additional mass has no effect on the intrinsic KIEs of the human enzyme. This finding indicates that the mass-modulation of the human DHFR affects neither DAD distribution nor the DAD’s conformational sampling dynamics. Furthermore, reduction in the enzymatic turnover number and the dissociation rate constant for the product indicate that the isotopic substitution affects kinetic steps that are not the catalyzed C-H→C hydride transfer. The findings are discussed in terms of fast dynamics and their role in catalysis, the comparison of calculations and experiments, and the interpretation of isotopically-modulated heavy enzymes in general
Introduction
Psychiatry is the branch of medicine appointed to the diagnosis, treatment, and prevention of mental disorders. Throughout ages, the concept of mental illness had changed many times, and today, the biopsychosocial model tries to explain mental disorders as the result of the complex interaction between biological correlates, psychological factors, and the socio-cultural background. The psychiatric interview is the fundamental element for the evaluation of the subject with mental illness. It allows to have access to the patient’s psychic state, enabling to collect the information that will guide the professional in formulating a diagnosis and through the choice of therapy
The unitary ability of IQ in the WISC-IV and its computation
Flanagan and Kaufman (2009) use a difference of 23 IQ points between the highest score (Max) and the lowest score (Min) reported by subjects in the 4 Indexes of Verbal Comprehension, Perceptual Reasoning, Working Memory and Processing Speed to define unitarity of IQ in the WISC-IV. Such a difference in scores is considered very rare and the authors therefore conclude that the total IQ scores in these cases cannot be interpreted. Hereby, we want to argue against the choice of this cut-off threshold value by showing that it was based on the wrong standard deviation value when first computed
Multi-Satellite Rain Sensing: Design Criteria and Implementation Issues
In this paper, we propose a novel opportunistic multi-satellite sensor system which overcomes the limitations of the conventional single-satellite solutions of the literature. The considerable robustness to the possible unavailability of some satellites, besides being well suited for powerful 2D reconstruction techniques of the rain field, makes it an appealing solution for experimental tests within national and EU-funded research projects
Cavity Quantum Electrodynamics with Anderson-localized Modes
A major challenge in quantum optics and quantum information technology is to
enhance the interaction between single photons and single quantum emitters.
Highly engineered optical cavities are generally implemented requiring
nanoscale fabrication precision. We demonstrate a fundamentally different
approach in which disorder is used as a resource rather than a nuisance. We
generate strongly confined Anderson-localized cavity modes by deliberately
adding disorder to photonic crystal waveguides. The emission rate of a
semiconductor quantum dot embedded in the waveguide is enhanced by a factor of
15 on resonance with the Anderson-localized mode and 94 % of the emitted
single-photons couple to the mode. Disordered photonic media thus provide an
efficient platform for quantum electrodynamics offering an approach to
inherently disorder-robust quantum information devices
Statistical theory of a quantum emitter strongly coupled to Anderson-localized modes
A statistical theory of the coupling between a quantum emitter and
Anderson-localized cavity modes is presented based on a dyadic Green's function
formalism. The probability of achieving the strong light-matter coupling regime
is extracted for an experimentally realistic system composed of InAs quantum
dots embedded in a disordered photonic crystal waveguide. We demonstrate that
by engineering the relevant parameters that define the quality of light
confinement, i.e. the light localization length and the loss length, strong
coupling between a single quantum dot and an Anderson-localized cavity is
within experimental reach. As a consequence of disorder-induced light
confinement provides a novel platform for quantum electrodynamics experiments.Comment: 5 pages, 4 figure
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