Broadband luminescence in defect-engineered electrochemically produced porous Si/ZnO nanostructures

The fabrication, by an all electrochemical process, of porous Si/ZnO nanostructures with engineered structural defects, leading to strong and broadband deep level emission from ZnO, is presented. Such nanostructures are fabricated by a combination of metal-assisted chemical etching of Si and direct current electrodeposition of ZnO. It makes the whole fabrication process low-cost, compatible with Complementary Metal-Oxide Semiconductor technology, scalable and easily industrialised. The photoluminescence spectra of the porous Si/ZnO nanostructures reveal a correlation between the lineshape, as well as the strength of the emission, with the morphology of the underlying porous Si, that control the induced defects in the ZnO. Appropriate fabrication conditions of the porous Si lead to exceptionally bright Gaussian-type emission that covers almost the entire visible spectrum, indicating that porous Si/ZnO nanostructures could be a cornerstone material towards white-light-emitting devices

CD28null CD4 T-cell expansions in autoimmune disease suggest a link with cytomegalovirus infection

Immunosenescence is thought to contribute to the increase of autoimmune diseases in older people. Immunosenescence is often associated with the presence of an expanded population of CD4 T cells lacking expression of CD28 (CD28null). These highly cytotoxic CD4 T cells were isolated from disease-affected tissues in patients with rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis, or other chronic inflammatory diseases and their numbers appeared to be linked to disease severity. However, we recently demonstrated that the common herpes virus, cytomegalovirus (CMV), not ageing, is the major driver of this subset of cytotoxic T cells. In this review, we discuss how CMV might potentiate and exacerbate autoimmune disease through the expansion of CD28null CD4 T cells

Microglia-astrocyte crosstalk in the amyloid plaque niche of an Alzheimer's disease mouse model, as revealed by spatial transcriptomics

The amyloid plaque niche is a pivotal hallmark of Alzheimer's disease (AD). Here, we employ two high-resolution spatial transcriptomics (ST) platforms, CosMx and Spatial Enhanced Resolution Omics-sequencing (Stereo-seq), to characterize the transcriptomic alterations, cellular compositions, and signaling perturbations in the amyloid plaque niche in an AD mouse model. We discover heterogeneity in the cellular composition of plaque niches, marked by an increase in microglial accumulation. We profile the transcriptomic alterations of glial cells in the vicinity of plaques and conclude that the microglial response to plaques is consistent across different brain regions, while the astrocytic response is more heterogeneous. Meanwhile, as the microglial density of plaque niches increases, astrocytes acquire a more neurotoxic phenotype and play a key role in inducing GABAergic signaling and decreasing glutamatergic signaling in hippocampal neurons. We thus show that the accumulation of microglia around hippocampal plaques disrupts astrocytic signaling, in turn inducing an imbalance in neuronal synaptic signaling

A Nonvolatile MOSFET Memory Device Based on Mobile Protons in SiO(2) Thin Films

It is shown how mobile H{sup +} ions can be generated thermally inside the oxide layer of Si/SiO{sub 2}/Si structures. The technique involves only standard silicon processing steps: the nonvolatile field effect transistor (NVFET) is based on a standard MOSFET with thermally grown SiO{sub 2} capped with a poly-silicon layer. The capped thermal oxide receives an anneal at {approximately}1100 C that enables the incorporation of the mobile protons into the gate oxide. The introduction of the protons is achieved by a subsequent 500-800 C anneal in a hydrogen-containing ambient, such as forming gas (N{sub 2}:H{sub 2} 95:5). The mobile protons are stable and entrapped inside the oxide layer, and unlike alkali ions, their space-charge distribution can be controlled and rapidly rearranged at room temperature by an applied electric field. Using this principle, a standard MOS transistor can be converted into a nonvolatile memory transistor that can be switched between normally on and normally off. Switching speed, retention, endurance, and radiation tolerance data are presented showing that this non-volatile memory technology can be competitive with existing Si-based non-volatile memory technologies such as the floating gate technologies (e.g. Flash memory)

Cytomegalovirus infection exacerbates autoimmune mediated neuroinflammation

Tumorimmunolog

Nonvolatile Field Effect Transistors Based on Protons and Si/SiO{Sub 2}Si Structures

Recently, the authors have demonstrated that annealing Si/SiO{sub 2}/Si structures in a hydrogen containing ambient introduces mobile H{sup +} ions into the buried SiO{sub 2} layer. Changes in the H{sup +} spatial distribution within the SiO{sub 2} layer were electrically monitored by current-voltage (I-V) measurements. The ability to directly probe reversible protonic motion in Si/SiO{sub 2}/Si structures makes this an exemplar system to explore the physics and chemistry of hydrogen in the technologically relevant Si/SiO{sub 2} structure. In this work, they illustrate that this effect can be used as the basis for a programmable nonvolatile field effect transistor (NVFET) memory that may compete with other Si-based memory devices. The power of this novel device is its simplicity; it is based upon standard Si/SiO{sub 2}/Si technology and forming gas annealing, a common treatment used in integrated circuit processing. They also briefly discuss the effects of radiation on its retention properties

Automatic extraction of recurrent patterns of high dominant frequency mapping during human persistent atrial fibrillation

Purpose: Identifying targets for catheter ablation remains challenging in persistent atrial fibrillation (persAF). The dominant frequency (DF) of atrial electrograms during atrial fibrillation (AF) is believed to primarily reflect local activation. Highest DF (HDF) might be responsible for the initiation and perpetuation of persAF. However, the spatiotemporal behaviour of DF remains not fully understood. Some DFs during persAF were shown to lack spatiotemporal stability, while others exhibit recurrent behaviour. We sought to develop a tool to automatically detect recurrent DF patterns in persAF patients. Methods: Non-contact mapping of the left atrium (LA) was performed in 10 patients undergoing persAF HDF ablation. 2048 virtual electrograms (vEGMs, EnSite Array, Abbott Laboratories, USA) were collected for up to 5 min before and after ablation. Frequency spectrum was estimated using fast Fourier transform and DF was identified as the peak between 4-10 Hz and organization index (OI) was calculated. The HDF maps were identified per 4-second window and an automated pattern recognition algorithm was used to find recurring HDF spatial patterns. Dominant patterns (DPs) were defined as the HDF pattern with the highest recurrence. Results: DPs were found in all patients. Patients in atrial flutter after ablation had a single DP over the recorded time period. The time interval (median [IQR]) of DP recurrence for the patients in AF after ablation (7 patients) decreased from 21.1 s [11.8 49.7s] to 15.7 s [6.5 18.2 s]. The DF inside the DPs presented lower temporal standard deviation (0.18±0.06 Hz vs. 0.29±0.12 Hz, p<0.05) and higher OI (0.35±0.03 vs. 0.31±0.04, p<0.05). The atrial regions with the highest proportion of HDF region were the septum and the left upper pulmonary vein. Conclusion: Multiple recurrent spatiotemporal HDF patterns exist during persAF. The proposed method can identify and quantify the spatiotemporal repetition of the HDFs, where the high recurrences of DP may suggest a more organised rhythm. DPs presented a more consistent DF and higher organisation compared with non-DPs, suggesting that DF with higher OI might be more likely to recur. Recurring patterns offer a more comprehensive dynamic insight of persAF behaviour, and ablation targeting such regions may be beneficial

Facile Synthesis of ZnO Nanorods by Microwave Irradiation of Zinc–Hydrazine Hydrate Complex

ZnO nanorods have been successfully synthesized by a simple microwave-assisted solution phase approach. Hydrazine hydrate has been used as a mineralizer instead of sodium hydroxide. XRD and FESEM have been used to characterize the product. The FESEM images show that the diameter of the nanorods fall in the range of about 25–75 nm and length in the range of 500–1,500 nm with an aspect ratio of about 20–50. UV–VIS and photoluminescence spectra of the nanorods in solution have been taken to study their optical properties. A mechanism for microwave synthesis of the ZnO nanorods using hydrazine hydrate precursor has also been proposed

Origin of defect-related green emission from ZnO nanoparticles: effect of surface modification

We investigated the optical properties of colloidal-synthesized ZnO spherical nanoparticles prepared from 1-octadecene (OD), a mixture of trioctylamine (TOA) and OD (1:10), and a mixture of trioctylphosphine oxide (TOPO) and OD (1:12). It is found that the green photoluminescence (PL) of samples from the mixture of TOA/OD and TOPO/OD is largely suppressed compared with that from pure OD. Moreover, it is found that all spherical nanoparticles have positive zeta potential, and spherical nanoparticles from TOA/OD and TOPO/OD have a smaller zeta potential than those from OD. A plausible explanation is that oxygen vacancies, presumably located near the surface, contribute to the green PL, and the introduction of TOA and TOPO will reduce the density of oxygen vacancies near the surfaces. Assuming that the green emission arises due to radiative recombination between deep levels formed by oxygen vacancies and free holes, we estimate the size of optically active spherical nanoparticles from the spectral energy of the green luminescence. The results are in good agreement with results from TEM. Since this method is independent of the degree of confinement, it has a great advantage in providing a simple and practical way to estimate the size of spherical nanoparticles of any size. We would like to point out that this method is only applicable for samples with a small size distribution

ZnO Nanorods via Spray Deposition of Solutions Containing Zinc Chloride and Thiocarbamide

In this work we present the results on formation of ZnO nanorods prepared by spray of aqueous solutions containing ZnCl2and thiocarbamide (tu) at different molar ratios. It has been observed that addition of thiocarbamide into the spray solution has great impact on the size, shape and phase composition of the ZnO crystals. Obtained layers were characterized by scanning electron microscopy (SEM) equipped with energy selected backscattered electron detection system (ESB), X-ray diffraction (XRD) and photoluminescence spectroscopy (PL). Small addition of thiocarbamide into ZnCl2solution (ZnCl2:tu = 1:0.25) supports development of significantly thinner ZnO nanorods with higher aspect ratio compared to those obtained from ZnCl2solution. Diameter of ZnO rods decreases from 270 to 100 nm and aspect ratio increases from ∼2.5 to 12 spraying ZnCl2and ZnCl2:tu solutions, respectively. According to XRD, well crystallized (002) orientated pure wurtzite ZnO crystals have been formed. However, tiny ‘spot’—like formations of ZnS were detected on the side planes of hexagonal rods prepared from the thiocarbamide containing solutions. Being adsorbed on the side facets of the crystals ZnS inhibits width growth and promotes longitudinalc-axis growth