Routine transthoracic echocardiography in ischaemic stroke or transient ischaemic attack of undetermined cause: a prospective multicentre study.

BACKGROUND: Guidelines recommend routine transthoracic echocardiography (TTE) after ischaemic stroke or transient ischaemic attack of undetermined cause; yet, only limited scientific evidence exists. Therefore, we aimed to determine in these patients the prevalence of TTE-detected major cardiac sources of embolism (CSE), which are abnormalities leading to therapeutic changes. METHODS: Six Dutch hospitals conducted a prospective observational study that enrolled patients with ischaemic stroke or transient ischaemic attack of undetermined cause. Patients underwent TTE after comprehensive diagnostic evaluation on stroke units, including blood chemistry, 12-lead electrocardiogram (ECG), ≥ 24 h continuous ECG monitoring, brain imaging and cervical artery imaging. Primary outcome measure was the proportion of patients with TTE-detected major CSE. RESULTS: From March 2018 to October 2020, 1084 patients, aged 66.6 ± 12.5 years, were enrolled; 456 (42.1%) patients were female and 869 (80.2%) had ischaemic stroke. TTE detected major CSE in only 11 (1.0%) patients. Ten (90.9%) of these patients also had major ECG abnormalities (previous infarction, major repolarisation abnormalities, or previously unknown left bundle branch block) that would have warranted TTE assessment regardless of stroke evaluation. Such ECG abnormalities were present in 11.1% of the total study population. A single patient (0.1%) showed a major CSE despite having no ECG abnormality. CONCLUSIONS: This multicentre cross-sectional study in patients who-after workup on contemporary stroke units-were diagnosed with ischaemic stroke or transient ischaemic attack of undetermined cause found TTE-detected major CSE in only 1% of all patients. Most of these patients also had major ECG abnormalities. These findings question the value of routine TTE assessment in this clinical setting.

Quasinormal mode solvers for resonators with dispersive materials.

Optical resonators are widely used in modern photonics. Their spectral response and temporal dynamics are fundamentally driven by their natural resonances, the so-called quasinormal modes (QNMs), with complex frequencies. For optical resonators made of dispersive materials, the QNM computation requires solving a nonlinear eigenvalue problem. This raises a difficulty that is only scarcely documented in the literature. We review our recent efforts for implementing efficient and accurate QNM solvers for computing and normalizing the QNMs of micro- and nanoresonators made of highly dispersive materials. We benchmark several methods for three geometries, a two-dimensional plasmonic crystal, a two-dimensional metal grating, and a three-dimensional nanopatch antenna on a metal substrate, with the perspective to elaborate standards for the computation of resonance modes.

Nanoscale probing of charge transport in an organic field-effect transistor at cryogenic temperatures.

We studied charge transport in a field-effect transistor based on an anthracene crystal by single-molecule spectroscopy at cryogenic temperatures. When applying a control voltage to the gate, source and drain electrodes, we observe spectral drifts of the probe molecules' lines, which follow strongly non-exponential (stretched) kinetics, from seconds to tens of minutes. Applying a gate voltage alone, we find a dependence of the spectral shift as the logarithm of time. When an additional source-drain voltage is applied, the spectral shift follows a power law of time, similar to the elementary step of conduction in amorphous solids, postulated in the continuous-time random walk theory of Scher and Montroll.

Magneto-Raman scattering of graphene on graphite: electronic and phonon excitations.

Magneto-Raman-scattering experiments from the surface of graphite reveal novel features associated to purely electronic excitations which are observed in addition to phonon-mediated resonances. Graphene-like and graphite domains are identified through experiments with ∼1 µm spatial resolution performed in magnetic fields up to 32 T. Polarization resolved measurements emphasize the characteristic selection rules for electronic transitions in graphene. Graphene on graphite displays the unexpected hybridization between optical phonon and symmetric across the Dirac point inter Landau level transitions. The results open new experimental possibilities--to use light scattering methods in studies of graphene under quantum Hall effect conditions.

The excited spin-triplet state of a charged exciton in quantum dots.

We report on spectroscopic studies of resonances related to ladder of states of a charged exciton in single GaAlAs/AlAs quantum dot structures. Polarization-resolved photoluminescence, photoluminescence excitation and photon-correlation measurements were performed at low (T = 4.2 K) temperature also in magnetic field applied in Faraday configuration. The investigated resonances are assigned to three different configurations of a positively charged exciton. Together with a singlet ground state and a conventional triplet state (involving an electron from the ground state electronic s-shell), an excited triplet state, which involved an electron from the excited electronic p-shell was identified in single dots. The appearance of an emission line related to the latter complex is due to a partially suppressed electron relaxation in the investigated dots. An analysis of this emission line allows us to scrupulously determine properties of the excited triplet state and compare them with those of the conventional triplet state. Both triplets exhibit similar patterns of anisotropic fine structure and Zeeman splitting, however their amplitudes significantly differ for those two states. Presented results emphasize the role of the symmetry of the electronic state on the properties of the triplet states of two holes + electron excitonic complex.

Intermolecular intersystem crossing in single-molecule spectroscopy: Terrylene in anthracene crystal.

We present a spectroscopic study of terrylene in anthracene crystals at the ensemble and single-molecule levels. In this matrix, single-molecule fluorescence is reduced by three orders of magnitude. Correlation measurements allow us to identify a new relaxation channel, matrix-enhanced intersystem crossing. This process starts with a singlet-to-triplet energy transfer from guest to host, after which the triplet exciton is transferred back to the guest. The intermolecular intersystem crossing is expected whenever the lowest triplet state of the host is located between the lowest singlet S(1) and lowest triplet T(1) excited states of the guest. It must be considered when searching for new host-guest systems for single-molecule spectroscopy.

[The value of epidural analgesia in acute pancreatitis]. / Intérêt de l'analgésie par voie épidurale lors de pancréatite aiguë.

We report on a patient with acute pancreatitis whose pain was resistant to simultaneous administration of morphine, procaine and Buscopan. This episode was complicated by development of hypertension, tachycardia, angina pectoris, ventricular arrhythmias and electrocardiographic modifications. Analgesia was provided by epidural administration of fentanyl and bupivacaine and brought about rapid resolution of all symptoms. The usefulness of epidural analgesia in acute pancreatitis is discussed.

[EEG and clinical study of 107 patients with acute severe traumatic comas (author's transl)]. / Surveillance électroclinique de 107 comas traumatiques graves aigus.

The authors describe the EEG recordings of 107 patients with acute severe cranial trauma and signs of axial lesions. The initial EEG included: sleep patterns, alternating tracings, alpha band tracings which were either nonreactive pseudo-alpha or modulated alpha often reactive, and diffuse slow wave tracings. They found no particular tracing corresponding to a precise level of rostrocaudal destructuration, but some associations were seen more frequently. EEG sleep patterns and alternating tracings were never observed in brain stem lesions, the activity recorded being of low voltage, rigid, and non-reactive. The presence of spontaneous fluctuations (with sleep rhythms in some cases) and reactivity in other levels (mesodiencephalic junction, diencephalic and cortical-subcortical) are good prognostic signs. Focalised EEG signs are seen especially in the more rostral levels.