Enhanced and stable green emission of ZnO nanoparticles by surface segregation of Mg

The effects of Mg addition on the emission of green photons from ZnO nanoparticles were studied. Energy dispersive x-ray spectroscopy (EDS) and Auger electron spectroscopy (AES) data demonstrated that ZnO nanoparticles with surface segregation of MgO (ZnO:MgO) were precipitated from colloidal reactions between Zn(2+),Mg(2+) and OH(-) ions suspended in ethanol. The photoluminescence emission spectra showed stronger green emission from suspended ZnO:MgO versus ZnO nanoparticles. ZnO:MgO also exhibited a stable green emission colour, which was slightly red-shifted from 495 to 520?nm with 168 days of ageing. It was postulated that the presence of MgO on the surface of ZnO prevented both the aggregation of ZnO nanoparticles via electrostatic stabilization of the suspension, and the formation of non-radiative recombination states on the surface, resulting in more intense, stable photoemission from ZnO. The red shift of the green emission from suspended ZnO nanoparticles with extended ageing was attributed to filling of radiative surface trap states in the bandgap.     

Recurrent RBFN-based fuzzy neural network control for X-Y-theta motion control stage using linear ultrasonic motors

A recurrent radial basis function network (RBFN) based fuzzy neural network (FNN) control system is proposed to control the position of an X-Y-theta motion control stage using linear ultrasonic motors (LUSMs) to track various contours in this study. The proposed recurrent RBFN-based FNN combines the merits of self-constructing fuzzy neural network (SCFNN), recurrent neural network (RNN), and RBFN. Moreover, the structure and the parameter learning phases of the recurrent RBFN-based FNN are performed concurrently and on line. The structure learning is based on the partition of input space, and the parameter learning is based on the supervised gradient decent method using a delta adaptation law. The experimental results due to various contours show that the dynamic behaviors of the proposed recurrent RBFN-based FNN control system are robust with regard to uncertainties.     

In vivo release of rhBMP-2 loaded porous calcium phosphate cement pretreated with albumin

In this study, the release of rhBMP-2 loaded porous Ca-P cement was studied in vitro and in vivo. We hypothesized that adsorption sites of Ca-P ceramic with high affinity for rhBMP-2 can be blocked by pretreatment of the ceramic with albumin prior to rhBMP-2 loading, which would result in weaker rhBMP-2 binding and enhanced release of rhBMP-2. Preset porous Ca-P cement discs with a diameter of 6.35 mm (volume: 75 mm³) were pretreated by incubation in a solution of 10% rat serum albumin for 24 h or in ddH₂O (control group) prior to administration of 5 μg radiolabeled ¹³¹I-rhBMP-2. Release was assessed in vitro in phosphate buffered saline (PBS) and fetal calf serum and in vivo by longitudinal scintigraphic imaging of radiolabeled ¹³¹I-rhBMP-2 and gamma counting of dissected implants. In vitro release from pretreated discs was higher during the first day. For both formulations, release in PBS was limited compared to release in serum. In vivo release considerably exceeded in vitro release. In vivo release kinetics showed no significant difference of half-lives between pretreated and control discs. Both formulations showed sustained release during at least 4 weeks. Ex vivo gamma counting of retrieved samples confirmed scintigraphic results and showed that the capsule and surrounding tissues only contained a minor fraction rhBMP-2. We conclude that 1. scintigraphy of ¹³¹I-labeled rhBMP-2 provides a reliable method for longitudinal measurement of rhBMP-2 release kinetics in vivo. 2. albumin pretreatment of porous Ca-P cement does not results in relevant increase of initial release of rhBMP-2 in vivo, and 3. preset rhBMP-2 loaded porous Ca-P cement discs exhibit one phase exponential release kinetics in the rat ectopic model, characterized by a retention of 20–30% after 4 weeks.     

Matrix approach to quantitative refractive index analysis by Fourier domain optical coherence tomography

The rapid development in the field of optical coherence tomography has demanded increasingly sophisticated numerical models to enable the interpretation of image data and extract quantitative results. We use a matrix formulation of Fresnel's equations for multilayered media to extract layer-dependent thickness and refractive index directly from Fourier domain optical coherence tomography spectrograms. An eigenanalysis spectral decomposition approach is used to constrain the least squares fitting algorithm, avoiding the need for initial estimates of the parameter values. We demonstrate this novel quantitative analysis approach by using a multilayered phantom and show good agreement with the known layer parameter values. This approach introduces a powerful tool for the analysis of layer-dependent optical properties that could have an important role in the differentiation of healthy and diseased tissue.     

Mode conversion in rectangular-core optical fibers

Mode conversion from the fundamental to a higher-order mode in a rectangular-core optical fiber is accomplished by applying pressure with the edge of a flat plate. Modal analysis of the near and far field images of the fiber's transmitted beam determines the purity of the converted mode. Mode conversion reaching 75% of the targeted higher-order mode is achieved using this technique. Conversion from a higher-order mode back to the fundamental mode is also demonstrated with comparable efficiency. Propagation of a higher-order mode in a rectangular-core fiber allows for better thermal management and bend-loss immunity than conventional circular-core fibers, extending the power-handling capabilities of optical fibers.     

The shear mode of multilayer graphene

The quest for materials capable of realizing the next generation of electronic and photonic devices continues to fuel research on the electronic, optical and vibrational properties of graphene. Few-layer graphene (FLG) flakes with less than ten layers each show a distinctive band structure. Thus, there is an increasing interest in the physics and applications of FLGs. Raman spectroscopy is one of the most useful and versatile tools to probe graphene samples. Here, we uncover the interlayer shear mode of FLGs, ranging from bilayer graphene (BLG) to bulk graphite, and suggest that the corresponding Raman peak measures the interlayer coupling. This peak scales from ~43 cm(-1) in bulk graphite to ~31 cm(-1) in BLG. Its low energy makes it sensitive to near-Dirac point quasiparticles. Similar shear modes are expected in all layered materials, providing a direct probe of interlayer interactions.     

Discrimination of Escherichia coli strains using glycan cantilever array sensors

Carbohydrate-based sensors, that specifically detect sugar binding molecules or cells, are increasingly important in medical diagnostic and drug screening. Here we demonstrate that cantilever arrays functionalized with different mannosides allow the real-time detection of several Escherichia coli strains in solution. Cantilever deflection is thereby dependent on the bacterial strain studied and the glycan used as the sensing molecule. The cantilevers exhibit specific and reproducible deflection with a sensitivity range over four orders of magnitude.     

Photocatalytic performance of nanocrystalline Bi5Ti3FeO15 layered perovskite under visible light

Nanocrystalline Bi5Ti3FeO15 layered perovskite exhibiting Aurivillius phase was synthesized by polymerized complex (PC) method and investigated for its physico-chemical as well as optical properties. The crystallization of Bi5Ti3FeO15 synthesized by PC method was found to occur in the temperature range of 800-1050 degress C, whereas the single crystalline Bi5Ti3FeO15 formed at 1030 degrees C by solid state reaction (SSR) method. The observation of highly pure phase and such lower crystallization temperature in Bi5Ti3FeO15 prepared by PC method, is in total contrast to that observed in Bi5Ti3FeO15 prepared by the conventional solid-state reaction (SSR) method. The band gap of nanocrystalline Bi5Ti3FeO15 determined from UV-Vis diffusion reflectance spectrometer was 2.38 eV (525 nm). The photocatalytic activity of Pt/Bi5Ti3FeO15 prepared by PC method was investigated with the photodecomposition of isopropyl alcohol (IPA) and hydrogen production from water-methanol mixed solution under visible light (lambda > or = 420 nm). The respective activities for PC sample were higher than that of Pt/Bi5Ti3FeO15 prepared by SSR as well as Pt/TiO(2-x)N(x).     

RAFT-derived polymer-drug conjugates: poly(hydroxypropyl methacrylamide) (HPMA)-7-ethyl-10-hydroxycamptothecin (SN-38) conjugates

A series of well‐defined polymer–drug conjugates were prepared in order to modify the physical properties of a known cytotoxic drug, 7‐ethyl‐10‐hydroxycamptothecin (SN‐38), the active metabolite of irinotecan (CPT‐11). Reversible addition–fragmentation chain transfer (RAFT) polymerisation was used to covalently and site‐specifically append a defined N‐(2‐hydroxypropyl)methacrylamide (HPMA) polymer to SN‐38 using a graft‐from process. These poly‐HPMA–SN‐38 conjugates displayed excellent aqueous solubility and stability, whilst retaining the cytotoxic activity of the parent SN‐38. In vitro co‐culture assays containing both cancer and noncancer cell lines demonstrated the specificity of RAFT‐derived poly‐HPMA–SN‐38 conjugates for cancerous cells. The concept of post‐optimisation modification of small‐molecule drugs through a graft‐from polymer conjugation method is introduced.     

Pool boiling of nanoparticle-modified surface with interlaced wettability

ABSTRACT: This study investigated the pool boiling heat transfer under heating surfaces with various interlaced wettability. Nano-silica particles were used as the coating element to vary the interlaced wettability of the surface. The experimental results revealed that when the wettability of a surface is uniform, the critical heat flux increases with the more wettable surface; however, when the wettability of a surface is modified interlacedly, regardless of whether the modified region becomes more hydrophilic or hydrophobic, the critical heat flux is consistently higher than that of the isotropic surface. In addition, this study observed that critical heat flux was higher when the contact angle difference between the plain surface and the modified region was smaller.