Facile Synthesis of Ordered Mesoporous Orthorhombic Niobium Oxide (T-Nb2_2O5_5) for High-Rate Li-Ion Storage with Long Cycling Stability

Herein, we describe the synthesis and evaluation of hierarchical mesoporous orthorhombic niobium oxide (T-Nb$_2$O$_5$) as an anode material for rechargeable lithium-ion batteries (LIB). The as-synthesized material addresses key challenges such as beneficial porous structure, poor rate capability, and cycling performance of the anode for Li-ion devices. The physicochemical characterization results reveal hierarchical porous nanostructure morphology with agglomerated particles and a 20 to 25 nm dimension range. Moreover, the sample has a high specific surface area (~65 m$^2$ g$^{−1}$) and pore volume (0.135 cm3 g$^{−1}$). As for the application in Li-ion devices, the T-Nb$_2$O$_5$ delivered an initial discharging capacity as high as 225 mAh g$^{−1}$ at 0.1 A g$^{−1}$ and higher rate capability as well as remarkable cycling features (~70% capacity retention after 300 cycles at 250 mA g$^{−1}$) with 98% average Coulombic efficiency (CE). Furthermore, the scan rate-dependent charge storage mechanism of the T-Nb$_2$O$_5$ electrode material was described, and the findings demonstrate that the electrode shows an evident and highly effective pseudocapacitive Li intercalation behaviour, which is crucial for understanding the electrode process kinetics. The origin of the improved performance of T-Nb$_2$O$_5$ results from the high surface area and mesoporous structure of the nanoparticles

EFFICIENCY AND RADIATIVE RECOMBINATION RATE ENHANCEMENT IN GAN/ALGAN MULTI-QUANTUM WELL-BASED ELECTRON BLOCKING LAYER FREE UV-LED FOR IMPROVED LUMINESCENCE

In this paper, an electron blocking layer (EBL) free GaN/AlGaN light emitting diode (LED) is designed using Atlas TCAD with graded composition in the quantum barriers of the active region. The device has a GaN buffer layer incorporated in a c-plane for better carrier transportation and low efficiency droop. The proposed LED has quantum barriers with aluminium composition graded from 20% to ~2% per triangular, whereas the conventional has square barriers. The resulted structures exhibit significantly reduced electron leakage and improved hole injection into the active region, thus generating higher radiative recombination. The simulation outcomes exhibit the highest internal quantum efficiency (IQE) (48.4%) indicating a significant rise compared to the conventional LED. The designed EBL free LED with graded quantum barrier structure acquires substantially minimized efficiency droop of ~7.72% at 60 mA. Our study shows that the proposed structure has improved radiative recombination by ~136.7%, reduced electron leakage, and enhanced optical power by ~8.084% at 60 mA injected current as compared to conventional GaN/AlGaN EBL LED structure

Ultrafast laser micro-nano structuring of transparent materials with high aspect ratio

Ultrafast lasers are ideal tools to process transparent materials because they spatially confine the deposition of laser energy within the material's bulk via nonlinear photoionization processes. Nonlinear propagation and filamentation were initially regarded as deleterious effects. But in the last decade, they turned out to be benefits to control energy deposition over long distances. These effects create very high aspect ratio structures which have found a number of important applications, particularly for glass separation with non-ablative techniques. This chapter reviews the developments of in-volume ultrafast laser processing of transparent materials. We discuss the basic physics of the processes, characterization means, filamentation of Gaussian and Bessel beams and provide an overview of present applications

Targeting RGS4 Ablates Glioblastoma Proliferation

Glioblastoma (GBM) is the most common type of adult primary brain tumor with a median survival rate of less than 15 months, regardless of the current standard of care. Cellular heterogeneity, self-renewal ability and tumorigenic glioma cancer stem cell (GSC) populations contribute to the difficulty in treating GBM. G-protein-coupled receptors (GPCRs) are the largest group of membrane proteins and mediate many cellular responses. Regulators of G-protein signaling 4 (RGS4) are negative regulators of G-protein signaling, and elevated levels of RGS4 are reportedly linked with several human diseases, including cancer. This study investigates the effect of silencing RGS4, resulting in inhibition of GSC growth, invasion and migration. Data obtained from The Cancer Genome Atlas (TCGA) demonstrated poor patient survival with high expression of RGS4. Immunohistochemistry and immunoblot analysis conducted on GBM patient biopsy specimens demonstrated increased RGS4 expression correlative with the TCGA data. RNA sequencing confirmed a significant decrease in the expression of markers involved in GSC invasion and migration, particularly matrix metalloproteinase-2 (MMP2) in knockout of RGS4 using CRISPR plasmid (ko-RGS4)-treated samples compared to parental controls. Gelatin zymography confirmed the reduced activity of MMP2 in ko-RGS4-treated samples. Silencing RGS4 further reduced the invasive and migratory abilities and induction of apoptosis of GSCs as evidenced by Matrigel plug assay, wound healing assay and human apoptosis array. Collectively, our results showed that the silencing of RGS4 plays an important role in regulating multiple cellular functions, and is an important therapeutic target in GBM

Spatial and temporal laser pulse design for material processing on ultrafast scales

International audienceThe spatio-temporal design of ultrafast laser excitation can have a determinant influence on the physical and engineering aspects of laser-matter interactions,with the potential of upgrading laser processing effects. Energy relaxation channels can be synergetically stimulated as the energy delivery rate is synchronized with the material response on ps timescales. Experimental and theoretical loops based on the temporal design of laser irradiation and rapid monitoring of irradiation effects are, therefore, able to predict and determine ideal optimal laser pulse forms for specific ablation objectives.We illustrate this with examples on manipulating the thermodynamic relaxation pathways impacting the ablation products and nanostructuring of bulk and surfaces using longer pulse envelopes. Some of the potential control factors will be pointed out. At the same time the spatial character can dramatically influence the development of laser interaction. We discuss spatial beam engineering examples such as parallel and non-diffractive approaches designed for highthroughput, high-accuracy processing events

Post-compression of 8.6 mJ ps-pulses from an Yb:YAG Innoslab amplifier using a compact multi-pass cell

We demonstrate post-compression of a high energy Yb:YAG laser in a 2m long Argon-filled multi-pass cell (MPC). 1.2 ps pulses with 8.6 mJ are compressed to 44 fs with an MPC transmission of 93%

Ultrafast laser processing of refractive index changes in bulk Ge15As15S70 chalcogenide glass for photonics applications in the mid-infrared

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Factor Hundred Compression of Multi-mJ 1.2 ps Pulses at 1030 nm to Few Cycles using Multi-Pass Cells

Multi-pass cells (MPCs) enable the accumulation of a large amount of B-integral while preserving the spatial mode of a laser beam and ensuring a uniform spectral distribution [1], [2]. In addition, MPCs used for post-compression allow achieving very large compression factors, without considerable degradation in temporal quality [3]. These qualities of MPCs, in combination with the high average power and pulse energy that Ytterbium-based lasers can deliver, open up the generation of ultrashort laser pulses with unprecedented properties [4]

Approaching the TW-regime with mJ-class picosecond pulses post-compressed to 13 fs

We demonstrate efficient post compression of 9.45 mJ, 1.2 ps pulses to 13 fs at 1 kHz repetition rate using a two stage gas filled multi pass cell system reaching near terawatt peak power