Effects of temperature and carrier gas flow amount on the formation of GaN nanorods by the HVPE method

We fabricated one-dimensional GaN nanorods on AlN/Si (1 1 1) substrates at various temperatures, and carrier gas flow amount, using the hydride vapor phase epitaxy (HVPE) method. An AlN buffer layer of 50 nm thickness was deposited by RF sputtering for 25 min. Stalagmite-like GaN nanorods formed at a growth temperature of 650 °C. The diameters and lengths of GaN nanorods increase with growth time, whereas the density of nanorods decreases. And we performed the experiments by changing the carrier gas flow amount at a growth temperature of 650 °C and HCl:NH₃ flow ratio of 1:40. GaN nanorods, with an average diameter of 50 nm, were obtained at a carrier gas flow amount of 1340 sccm. The shape, structures, and optical characteristics of the nanorods were investigated by field-emission scanning electron microscopy, X-ray diffraction, and photoluminescence.     

A methodology for knowledge discovery to support product family design

This paper introduces a methodology for knowledge discovery related to product family design that integrates an ontology with data mining techniques. In the proposed methodology, the ontology represents attributes for the components of products in functional hierarchies. Fuzzy clustering is employed for data mining to first partition product functions into subsets for identifying modules in a given product family and then identify the similarity level of components in a module. Module categorization is introduced to support association rule mining for knowledge discovery related to platform design. We apply the proposed methodology to first develop and then utilize design knowledge for a family of power tools. Based on the developed design knowledge, a new platform is suggested to improve commonality in the power tool family.     

A bootstrap mechanism for non-colloidal suspension viscosity

The role of friction in non-colloidal suspensions is examined with a model which splits the viscosity into a frictionless component (τ*) plus a frictional component which depends on the ratio of the particle pressure (P) to the shear stress (τ). The model needs the input by computation of τ* and P and a suitable choice of particle friction coefficient (μ). It can be extended to elongational flows and cases where sphere roughness is important; volume fractions up to 0.5 are considered. It is shown that friction acts in a feedback or “bootstrap” manner to increase the suspension viscosity. The analysis is also useful for deducing the friction coefficient in suspensions from experimental data. It was applied to several sets of experimental data and reasonable correlations of the viscosities were demonstrated. An example of the correlation for spheres in a silicone oil is shown for volume fractions 0.1–0.5.

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Graphical abstract

     

1H(17F,α)14O反应截面测量

14O （α,p）17F是天体X射线暴中重要的突破反应。本工作通过厚靶方法测量其逆反应1H （17F,α）14O的反应截面来研究这一关键反应。本实验工作是在日本东京大学原子核科学研究中心（CNS）的低能次级束流线（CRIB）上完成的,后续的扣除本底实验是在兰州放射性束流线（RIBLL1）上完成的。CRIB实验是通过2H （16O,n）17F转移反应产生17F次级束,经过CRIB分离提纯之后,利用该次级束轰击氢气靶。在氢气靶后布置了三套望远镜探测器系统,用以探测不同实验角度的反冲α粒子,在数据处理的过程中经过动力学重构后得到了1H （17F,α）14O反应在质心系能区E_c.m.=2.7~3.4 MeV的反应截面。实验结果在3 MeV以上的高能区与前人的薄靶实验数据是一致的,在低能区本工作获得了新的实验数据,倾向于支持干涉相消的理论预言结果。The 14O(α, p)17F reaction is one of the important breakout reactions in type I X-ray burst. This work reported a new cross section measurement of its reverse reaction of 1H(17F,α)14O. The experiment was performed using the CNS radioactive ion beam separator (CRIB), located at the Center for Nuclear Study (CNS), the University of Tokyo. The sequent background measurement was carried out at Radioactive Beam Line in Lanzhou (RIBLL1). 17F beam was produced via the transfer reaction of 2H(16O, n)17F, subsequently separated and purified by CRIB and bombarded a thick hydrogen H₂ gas target. The recoiling α particles were measured by three △E-E silicon telescopes at three different angles. The total cross sections of 1H(17F,α)14O have been derived at E_c.m.=2.7~3.4 MeV based on an isotropic angular distribution assumption. Our results are consistent with the previous ones in the energy region of E_c.m.>3 MeV, and we also obtained some new data in the low energy region, which partly support the destructive interference between the direct and resonant reaction mechanism predicted by the theory.     

Pore-controlled polymer membrane with Mn (II) ion trapping effect for high-rate performance LiMn2O4 cathode

Journal of Solid State Electrochemistry - Since Li+ ions can transport through porous channels in the separator containing liquid electrolyte, the electrochemical and structural properties of the...     

Extracellular Surface Potential Mapping by Scanning Ion Conductance Microscopy Revealed Transient Transmembrane Pore Formation Induced by Conjugated Polymer Nanoparticles

In‐depth understanding of the biophysicochemical interactions at the nano–bio interface is important for basic cell biology and applications in nanomedicine and nanobiosensors. Here, the extracellular surface potential and topography changes of live cell membranes interacting with polymeric nanomaterials using a scanning ion conductance microscopy‐based potential imaging technique are investigated. Two structurally similar amphiphilic conjugated polymer nanoparticles (CPNs) containing different functional groups (i.e., primary amine versus guanidine) are used to study incubation time and functional group‐dependent extracellular surface potential and topographic changes. Transmembrane pores, which induce significant changes in potential, only appear transiently in the live cell membranes during the initial interactions. The cells are able to self‐repair the damaged membrane and become resilient to prolonged CPN exposure. This study provides an important observation on how the cells interact with and respond to extracellular polymeric nanomaterials at the early stage. This study also demonstrates that extracellular surface potential imaging can provide a new insight to help understand the complicated interactions at the nano–bio interface and the following cellular responses.     

Colloidal Template Synthesis of Nanomaterials by Using Microporous Organic Nanoparticles: The Case of C@MoS2 Nanoadsorbents

The so‐called colloidal template synthesis has been applied to the preparation of surface‐engineered nanoadsorbents. Colloidal microporous organic network nanotemplates (C‐MONs), which showed a high surface area (611 m² g^?1) and enhanced microporosity, were prepared through the networking of organic building blocks in the presence of poly(vinylpyrrolidone) (PVP). Owing to entrapment of the PVP in networks, the C‐MONs showed good colloidal dispersion in EtOH. MoS₂ precursors were incorporated into the C‐MONs and heat treatment afforded core–shell‐type C@MoS₂ nanoparticles with a diameter of 80 nm, a negative zeta potential (?39.5 mV), a high surface area (508 m² g^?1), and excellent adsorption performance towards cationic dyes (q_max=343.6 and 421.9 mg g^?1 for methylene blue and rhodamine B, respectively).     

High-resolution spectroscopy near the continuum limit: the microwave spectrum of trans-3-bromo-1,1,1,2,2-pentafluoropropane

ABSTRACT

The microwave spectrum of 3-bromo-1,1,1,2,2-pentafluoropropane has been observed using CP-FTMW spectroscopy. Potential energy scans have been performed and confirm the existence of two conformers – trans and gauche – for which further structural optimisations and electric field gradient calculations have been performed in order to get highly accurate nuclear quadrupole coupling constants for assignment purposes. The combination of multiple conformers and large nuclear quadrupole coupling constants produce a very dense spectrum at an estimated 1?transition/MHz, near the continuum limit. This spectral density makes it necessary to have very sophisticated computational approaches in order to get geometric and electronic structures that are very close to experimental observation. Analysis of the spectrum allowed for the assignment of the trans conformer, but the gauche proved to be prohibitive, although it is believed to be present in the current spectrum. Full analysis of the rotational spectroscopic parameters of two isotopologues – the⁷⁹Br and⁸¹Br – have been observed and are reported. Geometric analysis of the experimentally observed conformer is also reported using Kraitchman coordinate and second moments arguments. Further analysis of the spectrum reveals the occurrence of dipole-forbidden, nuclear quadrupole allowed transitions with one forbidden transition possessing the first known x-type forbidden transition linkage pathway.     

Switchable Solvatochromic Probes for Live‐Cell Super‐resolution Imaging of Plasma Membrane Organization

Visualization of the nanoscale organization of cell membranes remains challenging because of the lack of appropriate fluorescent probes. Herein, we introduce a new design concept for super‐resolution microscopy probes that combines specific membrane targeting, on/off switching, and environment sensing functions. A functionalization strategy for solvatochromic dye Nile Red that improves its photostability is presented. The dye is grafted to a newly developed membrane‐targeting moiety composed of a sulfonate group and an alkyl chain of varied lengths. While the long‐chain probe with strong membrane binding, NR12A, is suitable for conventional microscopy, the short‐chain probe NR4A, owing to the reversible binding, enables first nanoscale cartography of the lipid order exclusively at the surface of live cells. The latter probe reveals the presence of nanoscopic protrusions and invaginations of lower lipid order in plasma membranes, suggesting a subtle connection between membrane morphology and lipid organization.