Self-assembled Au and Pt nanoparticles in Poly(methyl methacrylate).

Nanocomposites formed by metal nanoparticles self-assembled in an insulator matrix are of great technological importance. Applications include surface enhanced Raman spectroscopy based biosensors, optical devices, photovoltaic cells, and more. Self-assembling of nanocomposites using low energy ion implantation offers a fast and low cost process. We report here on our work on nanocomposites formed by very low energy ion implantation of gold and platinum nanoparticles into Poly(methyl methacrylate) (PMMA), with description of the nanoparticle evolution as a function of implantation dose. The Au-PMMA and Pt-PMMA nanocomposites were characterized by transmission electron microscopy, thus determining the nanoparticle density, their size distribution, and the distance between particles as a function of implantation dose. A comparison between Au-PMMA and Pt-PMMA reveals substantial differences in the formation processes of the nanoparticles. The results provide insight into basic nanoparticle formation processes, as well as crucial information important for design applications. In addition, the tunneling decay length ξ and the electron affinity ε of the implantation-modified PMMA were obtained using a new and simple approach.

Autoimmune Hemolytic Anemia in a 24-Year-Old Patient With COVID-19 Complicated by Secondary Cryptococcemia and Acute Necrotizing Encephalitis: A Case Report and Review of Literature.

Since the initial reported outbreak of coronavirus disease 2019 (COVID-19), many unique case reports have been published in the medical literature. Here we report a complicated clinical course of a young patient with COVID-19 who presented initially with recurrent autoimmune hemolytic anemia (AIHA). He subsequently developed bilateral pulmonary emboli, and ultimately succumbed to encephalitis and cryptococcemia in the context of being treated with high dose immunosuppression for the AIHA. Combining immunosuppression with active COVID-19 infection presents some truly challenging diagnostic and management scenarios which this case summarizes and highlights very well. Based on this case, we propose some strategies on how to approach these difficult decisions while also recognizing the significant gaps that exist in such an evolving topic. Lastly, this case also represents a potentially novel presentation of secondary fungal infection of the central nervous system (CNS) related to COVID-19.

Low-Energy Ion-Species-Dependent Induction of DNA Double-Strand Breaks: Ion Energy and Fluence Thresholds.

The goal of this study was to determine the critical ion-radiation conditions under which heavy ion beams can induce DNA double-strand breaks. Helium, nitrogen and argon-ion beams in the energy range of 20 eV to 2 keV were used to irradiate naked DNA plasmid pGFP to fluences of 1, 2 and 4 × 1015 ions/cm2. The topological forms of DNA were subsequently analyzed using gel electrophoresis. The DNA forms were changed from the original supercoiled to damaged relaxed and linear forms, depending on the ion mass, energy, fluence and inertia. We found ion energy and fluence thresholds above which direct double-strand breaks can occur. The threshold is discussed in terms of the areal ion-energy density and the cross-section.

Controlling nitrogen migration through micro-nano networks.

Nitrogen fertilizer unabsorbed by crops eventually discharges into the environment through runoff, leaching and volatilization, resulting in three-dimensional (3D) pollution spanning from underground into space. Here we describe an approach for controlling nitrogen loss, developed using loss control fertilizer (LCF) prepared by adding modified natural nanoclay (attapulgite) to traditional fertilizer. In the aqueous phase, LCF self-assembles to form 3D micro/nano networks via hydrogen bonds and other weak interactions, obtaining a higher nitrogen spatial scale so that it is retained by a soil filtering layer. Thus nitrogen loss is reduced and sufficient nutrition for crops is supplied, while the pollution risk of the fertilizer is substantially lowered. As such, self-fabrication of nano-material was used to manipulate the nitrogen spatial scale, which provides a novel and promising approach for the research and control of the migration of other micro-scaled pollutants in environmental medium.