Early lung ultrasound assessment for the prognosis of patients hospitalized for COVID-19 pneumonia. A pilot study.

OBJECTIVE: SARS CoV-2 is an epidemic viral infection that can cause mild to severe lung involvement. Newly apprehended knowledge on thoracic imaging abnormalities and the growing clinical experience on the evolution of this disease make the radiographic follow-up of hospitalized patients relevant. The value of consecutive bedside lung ultrasonography in the follow-up of hospitalized patients with SARS CoV-2 pneumonia and its correlation with other clinical and laboratory markers needs to be evaluated. METHODS: We assessed 39 patients [age: 64 y(60.1-68.7)] with confirmed SARS CoV-2 pneumonia. A total of 24 patients were hospitalized until the follow-up test, 9 were discharged early and 6 required a transfer to critical care unit. Two ultrasound scans of the lung were performed on day 1 and 4 of patients' hospitalization. Primary endpoint was the magnitude of association between a global lung ultrasound score (LUS) and clinical and laboratory markers. Secondary endpoint was the association between the evolution of LUS with the corresponded changes in clinical and laboratory outcomes during hospitalization period. RESULTS: LUS score on admission was higher among the deteriorating patients and significantly (P=0.038-0.0001) correlated (Spearman's rho) with the levels of C-reactive protein (0.58), lymphocytes (-0.33), SpO2 (-0.48) and oxygen supplementation (0.48) upon admission. The increase in LUS score between the two scans was significantly correlated (0.544, P=0.006) with longer hospital stay. CONCLUSION: Lung ultrasound assessment can be a useful as an imaging modality for SARS CoV-2 patients. Larger studies are needed to further investigate the predictive role of LUS in the duration and the outcome of the hospitalization of these patients.

Magnetoinductive breathers in metamaterials.

The existence and stability of discrete breathers (DBs) in one- and two-dimensional magnetic metamaterials (MMs), which consist of periodic arrangements (arrays) of split-ring resonators (SRRs), are investigated numerically. We consider different configurations of the SRR arrays, which are related to the relative orientation of the SRRs in the MM, in both one and two spatial dimensions. In the latter case we also consider anisotropic MMs. Using standard numerical methods we construct several types of linearly stable breather excitation in both Hamiltonian and dissipative MMs (dissipative breathers). The study of stability in both cases is performed using standard Floquet analysis. In both cases we find that the increase of dimensionality from one to two spatial dimensions does not destroy the DBs, which may also exist in the case of moderate anisotropy (in two dimensions). In dissipative MMs, the dynamics is governed by a power balance between the mainly Ohmic dissipation and driving by an alternating magnetic field. In that case it is demonstrated that DB excitation locally alters the magnetic response of MMs from paramagnetic to diamagnetic. Moreover, when the frequency of the applied field approaches the SRR resonance frequency, the magnetic response of the MM in the region of the DB excitation may even become negative (extremely diamagnetic).

Single-mutation-induced stability loss in protein lysozyme.

Recent NMR experiments have revealed that a single residue mutation W62G on protein hen's-egg white lysozyme can cause a dramatic loss of long-range interactions and protein stability; however, the molecular mechanism for this surprising phenomenon is not completely clear. In this mini-review, we have summarized some of our recent work on the molecular mechanism with large-scale molecular modelling, and also utilized a new wavelet method to analyse the local structural clusters present in both the wild-type and mutant folding trajectories. These extensive MD (Molecular Dynamics) simulations (10+ micros) were performed in 8 M urea, mimicking the experimental condition. Detailed analyses revealed that the Trp(62) residue is the key to a co-operative long-range interaction within the wild-type protein: it acts as a bridge between neighbouring basic residues, mainly arginine residues, through pi-type hydrogen bonds or pi-cation interactions to form an Arg-Trp-Arg 'sandwich-like' local structure. The local cluster near Trp(62) further extends its interaction to other clusters, such as the one near Trp(111), through Arg(112), which is involved in such an Arg-Trp-Arg bridging structure, thus achieving the long-range interactions for the wild-type. On the other hand, the mutant does not have this bridging effect and forms much less local clusters or contacts, and therefore results in a much less stable structure. Overall, these findings not only support the general conclusions of the experiment, but also provide a detailed but somewhat different molecular picture of the disruption of the long-range interactions.

Discrete breathers in nonlinear magnetic metamaterials.

Magnetic metamaterials composed of split-ring resonators or U-type elements may exhibit discreteness effects in THz and optical frequencies due to weak coupling. We consider a model one-dimensional metamaterial formed by a discrete array of nonlinear split-ring resonators where each ring interacts with its nearest neighbors. On-site nonlinearity and weak coupling among the individual array elements result in the appearance of discrete breather excitations or intrinsic localized modes, both in the energy-conserved and the dissipative system. We analyze discrete single and multibreather excitations, as well as a special breather configuration forming a magnetization domain wall and investigate their mobility and the magnetic properties their presence induces in the system.

Shape profile of compactlike discrete breathers in nonlinear dispersive lattice systems.

We study the spatial decay profile of compactlike discrete breathers in nonlinear dispersive lattices. We show that the core region of such nonlinear localized excitations can be described by a cosinelike spatial shape while the tail region decays with a faster than exponential law, such as a superexponential one. We discuss the relation of the tail decay to properties of space-time separability.

Compactlike breathers: bridging the continuous with the anticontinuous limit

We consider discrete nonlinear lattices characterized by on-site nonlinear potentials and nonlinear dispersive interactions that, in the continuous limit, support exact compacton solutions. We show that the compact support feature of the solutions in the continuous limit persists all the way to the anticontinuous limit. While in the large coupling regime the compact discrete breather solution retains the essential simple cosinelike compacton shape, in the close vicinity of the anticontinuous limit it acquires a spatial shape characterized by a fast stretched exponential decay, preserving thus its essentially compact nature. The discrete compact breathers in the anticontinuous limit are generated through a numerically exact procedure and are shown to be generally stable.