Unravelling a simple method for the low temperature synthesis of silicon nanocrystals and monolithic nanocrystalline thin films

In this work, we present new results on the plasma processing and structure of hydrogenated polymorphous silicon (pm-Si:H) thin films. pm-Si:H thin films consist of a low volume fraction of silicon nanocrystals embedded in a silicon matrix with medium range order, and they possess this morphology as a significant contribution to their growth comes from the impact on the substrate of silicon clusters and nanocrystals synthesized in the plasma. Quadrupole mass spectrometry, ion flux measurements, and material characterization by transmission electron microscopy (TEM) and atomic force microscopy all provide insight on the contribution to the growth by silicon nanocrystals during PECVD deposition. In particular, cross-section TEM measurements show for the first time that the silicon nanocrystals are uniformly distributed across the thickness of the pm-Si:H film. Moreover, parametric studies indicate that the best pm-Si:H material is obtained at the conditions after the transition between a pristine plasma and one containing nanocrystals, namely a total gas pressure around 2 Torr and a silane to hydrogen ratio between 0.05 to 0.1. From a practical point of view these conditions also correspond to the highest deposition rate achievable for a given RF power and silane flow rate.ope

International Consensus Statement on Rhinology and Allergy: Rhinosinusitis

Background: The 5 years since the publication of the first International Consensus Statement on Allergy and Rhinology: Rhinosinusitis (ICAR‐RS) has witnessed foundational progress in our understanding and treatment of rhinologic disease. These advances are reflected within the more than 40 new topics covered within the ICAR‐RS‐2021 as well as updates to the original 140 topics. This executive summary consolidates the evidence‐based findings of the document. Methods: ICAR‐RS presents over 180 topics in the forms of evidence‐based reviews with recommendations (EBRRs), evidence‐based reviews, and literature reviews. The highest grade structured recommendations of the EBRR sections are summarized in this executive summary. Results: ICAR‐RS‐2021 covers 22 topics regarding the medical management of RS, which are grade A/B and are presented in the executive summary. Additionally, 4 topics regarding the surgical management of RS are grade A/B and are presented in the executive summary. Finally, a comprehensive evidence‐based management algorithm is provided. Conclusion: This ICAR‐RS‐2021 executive summary provides a compilation of the evidence‐based recommendations for medical and surgical treatment of the most common forms of RS

Controlling magnetic properties of iron oxide nanoparticles using post-synthesis thermal treatment

Changes in morphological and magnetic properties of Fe3O4 nanoparticles before and after annealing are investigated in the present work. The nanoparticles are synthesized in a standard capacitively coupled plasma enhanced chemical vapour deposition system with two electrodes using ferrocene as the source compound. Post annealing, due to the sintering process, the particles fuse along with recrystallization. This results in increased size of the nanoparticles and the interparticle interaction, which play a major role in deciding the magnetic properties. X-ray diffraction patterns of the samples before and after annealing indicate a phase change from Fe3O4 to Fe2O3. Annealing at 200 C-a similar to causes the apparent saturation magnetization to increase from 6 emu g(-1) to 15 emu g(-1). When annealed at 500 C-a similar to, the magnetic properties of the nanoparticles resemble those of the bulk material. The evidence for the transition from a superparamagnetic state to a collective state is also observed when annealed at 500 C-a similar to. Variation of the magnetic relaxation data with annealing also reflects the change in the magnetic state brought about by the annealing. The correlation between annealing temperature and the magnetic properties can be used to obtain nanocrystallites of iron oxide with different sizes and magnetic properties

Analytical study of higher order modes of elliptical cavities using oblate spheroidal eigenvalue solution

The oblate spheroidal shape is close to the commonly used elliptical rf cavity shape employed in accelerators. Here we solve the oblate spheroidal radial and angular wave functions to obtain the frequencies of the axisymmetric TM and TE modes. We develop a semianalytic formalism to calculate the characteristic parameters, such as shunt impedance, of higher order modes (HOMs). Our formulation is applied to calculate the HOM frequencies of the INDUS-2 and ILC cavities, and the agreement with three-dimensional finite element calculations is excellent. Using this formalism we investigate the effect of changing the oblate shape, and predict an optimized range of ξ_{0} (one of the key parameters to define the geometry), to reduce the number of significant HOMs

Ignition delay study of aluminium oxide liquid nano-fuel in a shock tube

The ignition delay of aluminium oxide (Al2O3) liquid nano-fuel was compared with that of base-fuel to study the feasibility of its use for high-speed aerospace applications. The base-fuel was aviation turbine fuel that was mixed with Al2O3 nanoparticles to produce a nano-fuel which could be used for regenerative cooling of the combustor walls before injection. The experiments were carried out in a shock tube. The fuel was introduced into the shock tube in the form of a wall droplet. The ignition delay time of the nano-fuel was observed to increase slightly, by about 11% (maximum) in comparison with the baseline, at an equivalence ratio of unity