Intracellular delivery of molecular cargo is the basis for a plethora of therapeutic applications, including gene therapy and cancer treatment. A very efficient method to perform intracellular delivery is the photo-activation of nanomaterials that have been previously directed to the cell vicinity and bear releasable molecular cargo. However, potential in vivo applications of this method are limited by our ability to deliver nanomaterials and light in tissue. Here, we demonstrate intracelullar delivery using a needle-like optofluidic probe capable of penetrating soft tissue. Firstly, we used the optofluidic probe to confine an intracellular delivery mixture, composed of 100 nm gold nanoparticles (AuNP) and membrane-impermeable calcein, in the vicinity of cancer cells. Secondly, we delivered nanosecond (ns) laser pulses (wavelength: 532 nm; duration: 5 ns) using the same probe and without introducing a AuNP cells incubation step. The AuNP photo-activation caused localized and reversible disruption of the cell membrane, enabling calcein delivery into the cytoplasm. We measured 67% intracellular delivery efficacy and showed that the optofluidic probe can be used to treat cells with single-cell precision. Finally, we demonstrated targeted delivery in tissue (mouse retinal explant) ex vivo. We expect that this method can enable nanomaterial-assisted intracellular delivery applications in soft tissue (e.g. brain, retina) of small animals.
Solid oxide fuel cells (SOFCs) working under direct reforming or catalytic partial oxidation may experience severe thermal gradients due to cooling or overheating at the fuel cell inlet. In this work, we show that the ohmic resistance measurement of thick electrolyte cells composed of smaller cathodes displaced along the opposite side of a full-size anode provides excellent results to evaluate the temperature gradients along cells submitted to such processes. Taking the catalytic partial oxidation of methane in single-chamber SOFC, as an example, we evaluate an overheating of more than within the first centimeter length of the cell.
La 0.5 Sr 0.5 MnO 3 thin films were deposited onto sapphire substrates by means of the pulsed-laser deposition technique. These films were characterized by several techniques including x-ray diffraction, Rutherford backscattering spectrometry, energy-dispersive x-ray, atomic-force microscopy, scanning electron microscopy, and x-ray photoelectron spectroscopy (XPS). The cation ratios are the same in the deposited films as in the target. However, strontium segregation occurs at the film surface with an enrichment in this element compared to Mn and La, as shown by XPS. In addition, a clear correlation between the three different contributions which compose the O(1s) XPS signal and the Sr, La, and Mn surface concentrations has been established. Annealing the films at a sufficiently high-temperature produces the same crystal structure as in the target.
The continuous development of nonlinear loads raises harmonic pollution to a considerable extent on power systems and requires new tools to analyze these disturbances. For simplified studies, a statistical approach of harmonic propagation conditions in meshed systems is an efficient alternative to the tedious implementation of a simulation process. Under these circumstances, a new method has been designed to give a probabilistic estimate of harmonic disturbance levels. It consists of defining statistical models for the impedances of the system. This method has been validated by a specific set of measurements on the French 400 kV system.
Sn-containing Si and Ge alloys belong to an emerging family of semiconductors with the potential to impact group IV semiconductor devices. Indeed, the ability to independently engineer both lattice parameter and band gap holds the premise to develop enhanced or novel photonic, optoelectronic, and electronic devices. With this perspective, we present detailed investigations of the influence of Ge1-y-xSixSny layers on the optical properties of Si- and Ge-based heterostructures and nanowires. We found that adding a thin Ge1-x-ySixSny capping layer on Si or Ge greatly enhances light absorption especially in the near IR range leading to an increase in short-circuit current density. For the Ge1-y-xSixSny structure at thicknesses below 30 nm, a 14-fold increase in the short-circuit current is predicted with respect to bare Si. This enhancement decreases by reducing the capping layer thickness. Conversely, decreasing the shell thickness was found to improve the short-circuit current in Si/Ge1-y-xSixSny and Ge/Ge1-y-xSixSny core/shell nanowires. The optical absorption becomes very important when increasing the Sn content. Moreover, by exploiting optical antenna effect, these nanowires show an extreme light absorption reaching an enhancement factor, with respect to Si or Ge nanowires, on the order of ~104 in Si/Ge0.84Si0.04Sn0.12 and ~12 in Ge/Ge0.84Si0.04Sn0.12 core/shell nanowires. Furthermore, we analyzed the optical response of the addition of a dielectric capping layer consisting of Si3N4 to the Si/Ge1-y-xSixSny core-shell nanowire and found about 50% increase in short-circuit current density for a dielectric layer thickness of 45 nm and a core radius and shell thickness superior to 40 nm. The core/shell optical antenna benefits from a multiplication of enhancements contributed by leaky mode resonances in the semiconductor part and antireflection effects in the dielectric part.
Photoluminescence (PL) properties of nanostructured Si-based films produced by pulsed laser ablation in a residual gas are studied. Two types of PL signals have been identified. Signals of the first type are sensitive to the ablation conditions with the PL peak position depending on the gas pressure during the deposition. Signals of the second type with PL peaks around 1.6–1.7 and 2.2– 2.3 eV are almost independent of the ablation conditions and are mainly determined by the presence of oxygen-related complexes in the film composition. These complexes can be formed through a prolonged natural oxidation or thermal annealing of the films, or through the direct laser ablation in the presence of oxygen. Possible mechanisms of PL signals are discussed.
We consider processes in which a focused laser beam is used to induce the melting of silicium. The first goal of this paper is to propose a simple three-dimensional (3D) model of this melting process. Our model is partly based on an energy balance equation. This model leads to a nontrivial ODE describing the evolution in time of the dimension of the melt region. The second goal of this paper is to obtain approximate analytical solutions of this ODE. After using basic solution methods, we propose an original geometrical method to derive asymptotic solutions for $\textrm{time} \rightarrow \infty$. These solutions turn out to be the most useful for the description of this process.
Abstract Investigating snow avalanches using a purely statistical approach raises several issues. First, even in the heavily populated areas of the Alps, there are few data on avalanche motion or extension. Second, most of the field data are related to the point of furthest reach in the avalanche path (run-out distance or altitude). As data of this kind are tightly dependent on the avalanche path profile, it is a priori not permissible to extrapolate the cumulative distribution function fitted to these data without severe restrictions or further assumptions. Using deterministic models is also problematic, as these are not really physically based models. For instance, they do not include all the phenomena occurring in the avalanche movement, and the rheological behaviour of the snow is not known. Consequently, it is not easy to predetermine extreme-event extensions. Here, in order to overcome this problem, we propose to use a conceptual approach. First, using an avalanche-dynamics numerical model, we fitted the model parameters (friction coefficients and the volume of snow involved in the avalanches) to the field data. Then, using these parameters as random variables, we adjusted appropriate statistical distributions. The last steps involved simulating a large number of (fictitious) avalanches using the Monte Carlo approach. Thus, the cumulative distribution function of the run-out distance can be computed over a much broader range than was initially possible with the historical data. In this paper, we develop the proposed method through a complete case study, comparing two different models.
