Mechanical characteristics and morphological effect of complex crossed structure in biomaterials: fracture mechanics and microstructure of chalky layer in oyster shell

The complex crossed structures with a polymorph of calcite, termed a chalky layer, which make up much of the shell of an oyster, are composed of flames and leaflets. Two layers, folia and the chalky layer in the giant Pacific oyster (Crassostrea gigas) were examined using SEM (scanning electron microscope), micro-area-XRD (X-ray diffraction) and FT-IR (Fourier transform infrared spectrometer) to determine their morphologies and component characteristics. The chalky layer was also tested using microindentation to assess its mechanical properties, and a microcrack was generated to study the fracture mechanism of the chalky layer. From an analysis of the secondary protein structure, it was shown that the ordered structures of the two layers, α-helix and β-structure, are similar but that the unordered structures are different. Moreover, the foliated rods at the interface of the chalky layer play a key role in the crystal growth of the chalky layers. Comparing the morphology and the preferred orientation of foliated laths, the advantages of the relatively high density and low hardness of the chalky layer have interesting implications regarding the development of sophisticated complex composites.     

Symmetrically glass-clad photonic crystal nanocavities with ultrahigh quality factors

We design and fabricate ultra-high-quality (Q) photonic nanocavities in a symmetrically glass-clad silicon (Si) two-dimensional (2D) photonic crystal (PhC) structure. We theoretically investigate the dependence of the refractive index of the glass on the Q factors for asymmetric and symmetric structures. We show that the index-symmetric distribution of the glass is a critical factor to realize ultrahigh Q factors for glass-clad 2D PhC structures. We fabricate symmetrically glass-clad Si PhC nanocavities and achieve a record Q factor of 1×10(6), comparable with the highest Q factors of nanocavities in air-bridge structures.     

Plasma Characteristics of Internal Inductively Coupled Plasma Source with Ferrite Module

Electrical and plasma properties of a U-shaped internal inductively coupled plasma (ICP) source with/without a Ni-Zn ferrite module installed above the ICP antenna were investigated. By installing the ferrite module on the antenna, the increase of plasma density and the decrease of plasma potential could be observed. The increase of plasma density was related to the efficient inductive coupling to the plasma by concentrating the induced magnetic field between the antenna and the substrate. At 800 W of ICP power and 20mTorr Ar, a high density plasma on the order of 4.5′10¹¹/cm³ could be obtained.     

Cleaved Iron Oxide Nanoparticles as T2 Contrast Agents for Magnetic Resonance Imaging

Iron oxide nanoparticles as contrast agents are reported to effectively improve magnetic resonance imaging of tissues and cells. In this work, cleaved iron oxide nanoparticles (CIONPs) were generated from hydrophobic FeO nanoparticles (HIONPs) by coating their surfaces with PEG‐phospholipids, oxidizing them under water, and slowly removing the residual FeO phase in phthalate buffer. The synthesized CIONPs showed good r₂ values of up to 258 s^?1 mM ^?1. Thus, the CIONPs can be employed as vectors for drug delivery due to their unique structure with an empty inner space, which enables their use in a wide range of applications.     

Monolayer assembly and striped architecture of Co nanoparticles on organic functionalized Si surfaces

We present a new strategy to fabricate a monolayer assembly of Br-terminated Co nanoparticles on functionalized Si surfaces by using chemical covalent bonding and microcontact printing method. Self-assembled monolayers (SAMs) of the Co nanoparticles formed on the hydroxyl-terminated Si surface exhibit two-dimensional island networks with locally ordered arrays via covalent linkage between nanoparticles and surface. On the other hand, SAMs of the nanoparticles on the aminopropyl-terminated Si surface show an individual and random distribution over an entire surface. Furthermore, we have fabricated striped architectures of Co nanoparticles using a combination of microcontact printing and covalent linkage. Microcontact printing of octadecyltrichlorosilane and selective covalent linkage between nanoparticles and functionalized Si surfaces lead to a hybrid nanostructure with selectively assembled nanoparticles stripes on the patterned functionalized Si surfaces. PACS 81.07.Ta; 61.46.+w; 81.16.Dn; 81.16.Be; 68.37.Hk; 82.80.Pv     

The emission wavelength tuning of InAs/InP quantum dots with thin GaAs, InGaAs, InP capping layers by MOCVD

InAs quantum dots (QDs) were grown on InP substrates by metalorganic chemical vapor deposition. The width and height of the dots were 50 and 5.8 nm, respectively on the average and an areal density of 3.0×10¹⁰ cm⁻² was observed by atomic force microscopy before the capping process. The influences of GaAs, In_0.53Ga_0.47As, and InP capping layers (5–10 ML thickness) on the InAs/InP QDs were studied. Insertion of a thin GaAs capping layer on the QDs led to a blue shift of up to 146 meV of the photoluminescence (PL) peak and an InGaAs capping layer on the QDs led to a red shift of 64 meV relative to the case when a conventional InP capping layer was used. We were able to tune the emission wavelength of the InAs QDs from 1.43 to 1.89 μm by using the GaAs and InGaAs capping layers. In addition, the full-width at half-maximum of the PL peak decreased from 79 to 26 meV by inserting a 7.5 ML GaAs layer. It is believed that this technique is useful in tailoring the optical properties of the InAs QDs at mid-infrared regime.     

A simple statistical modeling of random phase reference in holographic memory

We present a simple modeling of random phase reference in holographic memory. The proposed model is analyzed by a statistical approach. Improvement on selectivity using random phase reference is shown in comparison with uniform phase plane wave reference and Gaussian beam reference. This simple and efficient model provides a physical insight and is verified by some experiments.