Wavelet estimation by Bayesian thresholding and model selection

Many wavelet-based algorithms have been proposed in recent years to solve the problem of function estimation from noisy samples. In particular it has been shown that threshold approaches lead to asymptotically optimal estimation and are extremely effective when dealing with real data. Working under a Bayesian perspective, in this paper we first study optimality of the hard and soft thresholding rules when the function is modelled as a stochastic process with known covariance function. Next, we consider the case where the covariance function is unknown, and propose a novel approach that models the covariance as a certain wavelet combination estimated from data by Bayesian model selection. Simulated data are used to show that the new method outperforms traditional threshold approaches as well as other wavelet-based Bayesian techniques proposed in the literature.     

Variable echo time imaging for detecting the short T2* components of the sciatic nerve: a validation study

Objective

The aim of this study was to develop and validate an MRI protocol based on a variable echo time (vTE) sensitive to the short T2* components of the sciatic nerve.

Materials and methods

15 healthy subjects (M/F: 9/6; age: 21–62) were scanned at 3T targeting the sciatic nerve at the thigh bilaterally, using a dual echo variable echo time (vTE) sequence (based on a spoiled gradient echo acquisition) with echo times of 0.98/5.37 ms. Apparent T2* (aT2*) values of the sciatic nerves were calculated with a mono-exponential fit and used for data comparison.

Results

There were no significant differences in aT2* related to side, sex, age, and BMI, even though small differences for side were reported. Good-to-excellent repeatability and reproducibility were found for geometry of ROIs (Dice indices: intra-rater 0.68–0.7; inter-rater 0.70–0.72) and the related aT2* measures (intra-inter reader ICC 0.95–0.97; 0.66–0.85) from two different operators. Side-related signal-to-noise-ratio non-significant differences were reported, while contrast-to-noise-ratio measures were excellent both for side and echo.

Discussion

Our study introduces a novel MR sequence sensitive to the short T2* components of the sciatic nerve and may be used for the study of peripheral nerve disorders.

     

Therapeutic Role of Tocilizumab in SARS-CoV-2-Induced Cytokine Storm: Rationale and Current Evidence

Among patients suffering from coronavirus disease 2019 (COVID-19) syndrome, one of the worst possible scenarios is represented by the critical lung damage caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2)-induced cytokine storm, responsible for a potentially very dangerous hyperinflammatory condition. Within such a context, interleukin-6 (IL-6) plays a key pathogenic role, thus being a suitable therapeutic target. Indeed, the IL-6-receptor antagonist tocilizumab, already approved for treatment of refractory rheumatoid arthritis, is often used to treat patients with severe COVID-19 symptoms and lung involvement. Therefore, the aim of this review article is to focus on the rationale of tocilizumab utilization in the SARS-CoV-2-triggered cytokine storm, as well as to discuss current evidence and future perspectives, especially with regard to ongoing trials referring to the evaluation of tocilizumab’s therapeutic effects in patients with life-threatening SARS-CoV-2 infection.     

Stress, strain and energy splittings for anisotropic elastic solids under volumetric constraints

We define stress and strain splittings appropriate to linearly elastic anisotropic materials with volumetric constraints. The treatment includes rigidtropic materials, which develop no strains under a stress pattern that is a null eigenvector of the compliance matrix. This model includes as special case incompressible materials, for which the eigenvector is hydrostatic stress. The main finding is that pressure and volumetric strain must be redefined as effective quantities. Using this idea, an energy decomposition that exactly separates deviatoric and volumetric energy follows.     

Time-critical underwater sensor diffusion with no proactive exchanges and negligible reactive floods

In this paper we study multi-hop ad hoc routing in a scalable underwater sensor network (UWSN), which is a novel network paradigm for ad hoc investigation of the world below the water surface. Unlike existing underwater acoustic networks (UAN), the new UWSN paradigm dispatches large number (in the thousands) of unmanned low-cost sensor nodes to locally monitor and report otherwise not easily accessible underwater events in a time-critical manner. Due to the large propagation latency and very low bandwidth of the acoustic channel, a new protocol stack and corresponding models are required as conventional approaches fail. In particular, we show that neither proactive routing message exchange nor reactive/on-demand flooding is adequate in the challenging new underwater environment. Unlike the terrestrial scenarios, on-demand flooding cannot be both reliable and efficient due to widespread collisions caused by the large propagation delay. On the other hand, as in terrestrial scenarios, proactive routing is more expensive and less efficient than on-demand routing in typical underwater environments. We propose a “conservative” communications architecture that minimizes the number of all packet transmissions to avoid possible acoustic collisions. This is implemented in the non-intrusive underwater diffusion (UWD), which is a multi-hop ad hoc routing and in-network processing protocol with no proactive routing message exchange and negligible amount of on-demand floods. To achieve its design goal, UWD does not rely on GPS or power hungry motors to control currents. Instead, UWD is designed in a minimalist’s framework, which assumes homogeneous GPS-free nodes and random node mobility. Our simulation study verifies the effectiveness and efficiency of our design.     

Plasma Lipid Profiling Contributes to Untangle the Complexity of Moyamoya Arteriopathy

Moyamoya arteriopathy (MA) is a rare cerebrovascular disorder characterized by ischemic/hemorrhagic strokes. The pathophysiology is unknown. A deregulation of vasculogenic/angiogenic/inflammatory pathways has been hypothesized as a possible pathophysiological mechanism. Since lipids are implicated in modulating neo-vascularization/angiogenesis and inflammation, their deregulation is potentially involved in MA. Our aim is to evaluate angiogenic/vasculogenic/inflammatory proteins and lipid profile in plasma of MA patients and control subjects (healthy donors HD or subjects with atherosclerotic cerebrovascular disease ACVD). Angiogenic and inflammatory protein levels were measured by ELISA and a complete lipidomic analysis was performed on plasma by mass spectrometry. ELISA showed a significant decrease for MMP-9 released in plasma of MA. The untargeted lipidomic analysis showed a cumulative depletion of lipid asset in plasma of MA as compared to HD. Specifically, a decrease in membrane complex glycosphingolipids peripherally circulating in MA plasma with respect to HD was observed, likely suggestive of cerebral cellular recruitment. The quantitative targeted approach demonstrated an increase in free sphingoid bases, likely associated with a deregulated angiogenesis. Our findings indicate that lipid signature could play a central role in MA and that a detailed biomarker profile may contribute to untangle the complex, and still obscure, pathogenesis of MA.     

Finite element solution of free‐surface ship‐wave problems

An unstructured finite element solver to evaluate the ship‐wave problem is presented. The scheme uses a non‐structured finite element algorithm for the Euler or Navier–Stokes flow as for the free‐surface boundary problem. The incompressible flow equations are solved via a fractional step method whereas the non‐linear free‐surface equation is solved via a reference surface which allows fixed and moving meshes. A new non‐structured stabilized approximation is used to eliminate spurious numerical oscillations of the free surface. Copyright © 1999 John Wiley & Sons, Ltd.     

A Tryptophan 6‐Halogenase and an Amidotransferase Are Involved in Thienodolin Biosynthesis

The biosynthetic gene cluster for the plant growth‐regulating compound thienodolin was identified in and cloned from the producer organism Streptomyces albogriseolus MJ286‐76F7. Sequence analysis of a 27 kb DNA region revealed the presence of 21 ORFs, 14 of which are involved in thienodolin biosynthesis. Three insertional inactivation mutants were generated in the sequenced region to analyze their involvement in thienodolin biosynthesis and to functionally characterize specific genes. The gene inactivation experiments together with enzyme assays with enzymes obtained by heterologous expression and feeding studies showed that the first step in thienodolin biosynthesis is catalyzed by a tryptophan 6‐halogenase and that the last step is the formation of a carboxylic amide group catalyzed by an amidotransferase. The results led to a hypothetical model for thienodolin biosynthesis.     

Study of the NOχ reaction with reducing gases on Fe/ZrO2 catalyst

The Fe/ZrO₂ catalyst (1% Fe by weight) shows a strong adsorption capacity toward the nitric oxide (at room temperature the ratio NOFe is ca. 0.5) as a consequence of the formation of a highly dispersed iron phase after reduction at 500–773 K. Nitric oxide is adsorbed mainly as nitrosyl species on the reduced surface where the Fe²⁺ sites are prevailing, but it is easily oxidised by oxygen forming nitrito and nitrato species adsorbed on the support. However, in the presence of a reducing gas such as hydrogen, carbon monoxide, propane and ammonia at 473–573 K the Fe-nitrosyl species react producing nitrogen, nitrous oxide, carbon dioxide and water, as detected by FTIR and mass spectrometers. The results show that nitric oxide reduction is more facile with hydrogen containing molecules than with CO, probably due the co-operation of spillover effects. Experiments carried out with the same gases in the presence of oxygen show, however, a reduced dissociative activity of the surface iron sites toward the species NO_χ formed by NO oxidation and therefore the reactivity is shifted to higher temperatures.