Mono- and bi-plane sonographic approach for difficult accesses in the emergency department - A randomized trial.

BACKGROUND: The insertion of peripheral intravenous (PIV) catheters is one of the most performed invasive procedures in acute healthcare settings. However, peripheral difficult vascular access (PDVA) is not uncommon and can lead to delays in administering essential medications. Ultrasound (US) has emerged as a valuable tool for facilitating PIV cannulation. Advancements in technology have introduced a technique known as bi-plane imaging, allowing the simultaneous display of both longitudinal and transverse views of vessels. We aimed to investigate whether the utilization of bi-plane imaging, as opposed to the single-plane approach, would yield superior results for PDVA in the emergency department (ED). METHODS: This study was a single-center randomized controlled trial. We included adult patients admitted to the ED who required PIV cannulation. Patients were randomly assigned to undergo cannulation using either the mono-plane or bi-plane approach, both performed by skilled providers. The primary outcome of the study was to compare the first attempt success rates between the two techniques. RESULTS: A total of 442 patients were enrolled, with 221 undergoing cannulation attempts using the mono-plane approach. Successful placement of a functioning PIV catheter was achieved in a single attempt for 313 out of 442 patients (70.8%). There was no significant difference in the success rates between the two study groups: 68.3% in the mono-plane group and 73.3% in the bi-plane group (p = 0.395). The median time required for a successful attempt differed between the groups, with 45 s (range 18-600) in the mono-plane group and 35 s (range 20-600) in the bi-plane group (p = 0.03). CONCLUSIONS: Our study confirms that US is a highly effective tool for facilitating PIV cannulation in patients with PDVA presenting to the ED. However, our investigation into the use of bi-plane imaging did not reveal a significant improvement when compared to mono-plane imaging.

Kinetic Heating by Alfvén Waves in Magnetic Shears.

With first-principles kinetic simulations, we show that a large-scale Alfvén wave (AW) propagating in an inhomogeneous background decays into kinetic Alfvén waves (KAWs), triggering ion and electron energization. We demonstrate that the two species can access unequal amounts of the initial AW energy, experiencing differential heating. During the decay process, the electric field carried by KAWs produces non-Maxwellian features in the particle velocity distribution functions, in accordance with space observations. The process we present solely requires the interaction of a large-scale AW with a magnetic shear and may be relevant for several astrophysical and laboratory plasmas.

Turbulence-Driven Ion Beams in the Magnetospheric Kelvin-Helmholtz Instability.

The description of the local turbulent energy transfer and the high-resolution ion distributions measured by the Magnetospheric Multiscale mission together provide a formidable tool to explore the cross-scale connection between the fluid-scale energy cascade and plasma processes at subion scales. When the small-scale energy transfer is dominated by Alfvénic, correlated velocity, and magnetic field fluctuations, beams of accelerated particles are more likely observed. Here, for the first time, we report observations suggesting the nonlinear wave-particle interaction as one possible mechanism for the energy dissipation in space plasmas.

Gap-plasmon enhanced water splitting with ultrathin hematite films: the role of plasmonic-based light trapping and hot electrons.

Hydrogen is a promising alternative renewable fuel for meeting the growing energy demands of the world. Over the past few decades, photoelectrochemical water splitting has been widely studied as a viable technology for the production of hydrogen utilizing solar energy. A solar-to-hydrogen (STH) efficiency of 10% is considered to be sufficient for practical applications. Amongst the wide class of semiconductors that have been studied for their application in solar water splitting, iron oxide (α-Fe2O3), or hematite, is one of the more promising candidate materials, with a theoretical STH efficiency of 15%. In this work, we show experimentally that by utilizing gold nanostructures that support gap-plasmon resonances together with a hematite layer, we can increase the water oxidation photocurrent by two times over that demonstrated by a bare hematite film at wavelengths above the hematite bandgap. Moreover, we achieve a six-fold increase in the oxidation photocurrent at near-infrared wavelengths, which is attributed to hot electron generation and decay in the gap-plasmon nanostructures. Theoretical simulations confirmed that the metamaterial geometry with gap plasmons that was used allows us to confine electromagnetic fields inside the hematite semiconductor and to enhance the surface photochemistry.

Observation of charge transfer cascades in α-Fe2O3/IrOx photoanodes by operando X-ray absorption spectroscopy.

Electrochemical devices for energy conversion and storage are central for a sustainable economy. The performance of electrodes is driven by charge transfer across different layer materials and an understanding of the mechanistics is pivotal to gain improved efficiency. Here, we directly observe the transfer of photogenerated charge carriers in a photoanode made of hematite (α-Fe2O3) and a hydrous iridium oxide (IrOx) overlayer, which plays a key role in photoelectrochemical water oxidation. Through the use of operando X-ray absorption spectroscopy (XAS), we probe the change in occupancy of the Ir 5d levels during optical band gap excitation of α-Fe2O3. At potentials where no photocurrent is observed, electrons flow from the α-Fe2O3 photoanode to the IrOx overlayer. In contrast, when the composite electrode produces a sustained photocurrent (i.e., 1.4 V vs. RHE), a significant transfer of holes from the illuminated α-Fe2O3 to the IrOx layer is clearly demonstrated. The analysis of the operando XAS spectra further suggests that oxygen evolution actually occurs both at the α-Fe2O3/electrolyte and α-Fe2O3/IrOx interfaces. These findings represent an important outcome for a better understanding of composite photoelectrodes and their use in photoelectrochemical systems, such as hydrogen generation or CO2 reduction from sunlight.

Charged-particle chaotic dynamics in rotational discontinuities.

The interplanetary plasma is characterized by a high level of complexity over a broad range of spatial scales. Spacecraft have detected a large variety of embedded structures that have been identified as discontinuities in the magnetic field vector. They can be either generated within the solar corona and advected by the plasma flow or locally generated as a result of the turbulent cascade of the solar wind turbulence. Since magnetic field fluctuations and structures influence the energetic particle propagation, here we set up a numerical model to study the interaction between charged particles and an ideal magnetohydrodynamics rotational discontinuity. This interaction is strongly influenced by the model parameters, such as the rotation angle of the discontinuity, the orientation of the mean-field direction with respect to the normal to the discontinuity direction, the initial particle pitch angle, and the initial particle gyrophase. Numerical results clearly show that the motion of particles crossing the discontinuity is extremely complex and highly sensitive to the initial conditions of the system, with transitions to a chaotic behavior. We find that particles can be temporarily trapped in rotational discontinuity and that the trapping times have a nearly power-law distribution. Also, the separatrix in the initial conditions phase space between crossing and noncrossing trajectories has a fractal structure. Implications for energetic particle propagation in space plasmas are discussed.

Fast algorithm for a three-dimensional synthetic model of intermittent turbulence.

Synthetic turbulence models are useful tools that provide realistic representations of turbulence, necessary to test theoretical results, to serve as background fields in some numerical simulations, and to test analysis tools. Models of one-dimensional (1D) and 3D synthetic turbulence previously developed still required large computational resources. A "wavelet-based" model of synthetic turbulence, able to produce a field with tunable spectral law, intermittency, and anisotropy, is presented here. The rapid algorithm introduced, based on the classic p-model of intermittent turbulence, allows us to reach a broad spectral range using a modest computational effort. The model has been tested against the standard diagnostics for intermittent turbulence, i.e., the spectral analysis, the scale-dependent statistics of the field increments, and the multifractal analysis, all showing an excellent response.

Smart windows for building integration: a new architecture for photovoltachromic devices.

A new architecture for multifunctional photoelectrochemical devices, namely photovoltachromic devices, is disclosed here, capable of producing electric energy by solar conversion also modulating the devices' optical transmittance in a smart and aesthetically sounding fashion. These devices generally consist of a titanium dioxide photoelectrode and of a bifunctional patterned counter electrode made of platinum and amorphous tungsten oxide. The innovative configuration described hereafter proposes to split the single patterned counter electrode into two distinct electrodes, physically overlapped: the central one is suitably drilled in order to allow the electrolyte to fill both communicating chambers. These three electrode devices allow three independent operating modes: photovoltaic, photoelectrochromic, and photovoltachromic. In this paper, we report the optical, electrical, and electrochemical characterization of this innovative device, varying both available catalytic surface area and the type of sensitizing dye. We eventually obtained the following conversion efficiencies, 2.75%, 2.35%, and 1.91%, in samples having different catalytic areas (397, 360, and 320 mm(2), respectively). We inferred that the higher the platinum area on the interposed platinum-poly(ethylene naphthalate)-indium tin oxide counter electrode, the higher the photovoltaic conversion efficiency. On the other hand, a decrease of the intercommunication openings generates a slowdown of bleaching processes.

Flexible carbon nanotube-based composite plates as efficient monolithic counter electrodes for dye solar cells.

We demonstrate a general approach to fabricate a novel low-cost, lightweight and flexible nanocomposite foil that can be effectively implemented as a monolithic counter-electrode in dye solar cells. The pivotal aim of this work was to replace not only the platinum catalyzer film, but even the underlying transparent conductive oxide-coated substrate, by means of a monolithic counter electrode based on carbonaceous materials. According to our approach, a proper dispersion of multiwalled carbon nanotubes (MWCNTs) has been added to a dilute polypropylene solution in toluene. The composite solution has been then adequately mixed and subsequently dried by means of a controlled solvent evaporation process; the resulting powder has been modeled by compression molding into thin plates. Four different series of plates have been realized by tuning the carbon nanotubes concentration from 5 wt % to 20 wt %. Finally, a specifically setup reactive ion etching treatment with oxygen plasma has been carried out onto the plate surface to remove the residual polymeric capping layer and allow the embedded CNTs to protrude on top of the surface. A fine-tuning of the morphological features has been made possible by adjusting the plasma etching conditions. For all the treated surfaces, the most meaningful electrochemical parameters have been quantitatively analyzed by means of both electrochemical impedance spectroscopy and cyclic voltammetry measurements. An as high as 13.8 mA/cm(2) photocurrent density, along with a solar conversion efficiency of 6.67%, has been measured for a dye solar cell mounting a counter-electrode based on a 20 wt % CNT nanocomposite.

Nanoflares and MHD turbulence in coronal loops: a hybrid shell model.

A model to describe injection, due to footpoint motions, storage, and dissipation of MHD turbulence in coronal loops, is presented. The model is based on the use of the shell technique in the wave vector space applied to the set of reduced MHD equations. Numerical simulation showed that the energy injected is efficiently stored in the loop where a significant level of magnetic and velocity fluctuations is obtained. Nonlinear interactions among these fluctuations give rise to an energy cascade towards smaller scales where energy is dissipated in an intermittent fashion. The statistical analysis performed on the intermittent dissipative events compares well with all observed properties of nanoflare emission statistics.