Enhanced Osteoblast Adhesion to Epoxide‐Functionalized Surfaces

As an alternative to expensive extracellular matrix (ECM) proteins generally applied as coatings in Petri dishes used for cell binding, an innovative system based on epoxide‐functionalized monolayers capable of protein binding is proposed. Since cells bind to material surfaces through proteins, protein‐binding surfaces should also promote cell binding. Here we investigate how the cell‐binding properties of an epoxide‐functionalized surface compares with ECM protein gel coated surfaces and tissue culture polystyrene control surfaces. Glass surfaces are functionalized with glycidoxypropyltriethoxysilane (GOPS), which results in an epoxide‐functionalized surface capable of binding proteins through an epoxide–amine reaction. Advancing contact angle measurements and atomic force microscopy measurements confirm the formation of a homogeneous GOPS monolayer. This monolayer is micropatterned with fluorescein‐labeled ECM protein gel by microcontact printing (µCP). Confocal laser scanning microscopy (CLSM) shows accurately transferred ECM protein gel micropatterns. Osteoblasts that are seeded on these micropatterned substrates show a clear preference for adhering to the epoxide‐functionalized areas. The morphology of these cultured osteoblasts is needle‐like with high aspect ratios. As controls, osteoblasts are cultured on GOPS‐functionalized surfaces, unstructured ECM protein gel surfaces, and tissue culture polystyrene (TCPS). The GOPS surfaces demonstrate a drastic increase in cell adhesion after 2 h, whilst the other tests show no adverse effects of this surface on the osteoblasts as compared to ECM and TCPS. CLSM shows healthy cell morphologies on each surface. It is demonstrated for the first time that epoxide groups outperform ECM protein gel in cell adhesion, thereby providing new routes for cost‐effective coatings that improve biocompatibility as well as exciting, new methodologies to control and direct cell adhesion.     

Ultranarrow Bandwidth Organic Photodiodes by Exchange Narrowing in Merocyanine H‐ and J‐Aggregate Excitonic Systems

Ultranarrowband organic photodiodes (OPDs) are demonstrated for thin film solid state materials composed of tightly packed dipolar merocyanine dyes. For these dyes the packing arrangement can be controlled by the bulkiness of the donor substituent, leading to either strong H‐ or strong J‐type exciton coupling in the interesting blue (H‐aggregate) and NIR (J‐aggregate) spectral ranges. Both bands are shown to arise from one single exciton band according to fluorescence measurements and are not just a mere consequence of different polymorphs within the same thin film. By fabrication of organic thin‐film transistors, these dyes are demonstrated to exhibit hole transport behavior in spin‐coated thin films. Moreover, when used as organic photodiodes in planar heterojunctions with C₆₀ fullerene, they show wavelength‐selective photocurrents in the solid state with maximum external quantum efficiencies of up to 11% and ultranarrow bandwidths down to 30 nm. Thereby, narrowing the linewidths of optoelectronic functional materials by exciton coupling provides a powerful approach to produce ultranarrowband organic photodiodes.     

On the Design of Cauer Filters

Simple formulas are given which relate the parameters of Cauer Filters.     

Imaging performance of A-PET: a small animal PET camera

The evolution of positron emission tomography (PET) imaging for small animals has led to the development of dedicated PET scanner designs with high resolution and sensitivity. The animal PET scanner achieves these goals for imaging small animals such as mice and rats. The scanner uses a pixelated Anger-logic detector for discriminating 2 x 2 x 10 mm3 crystals with 19-mm-diameter photomultiplier tubes. With a 19.7-cm ring diameter, the scanner has an axial length of 11.9 cm and operates exclusively in three-dimensional imaging mode, leading to very high sensitivity. Measurements show that the scanner design achieves a spatial resolution of 1.9 mm at the center of the field-of-view. Initially designed with gadolinium orthosilicate but changed to lutetium- yttrium orthosilicate, the scanner now achieves a sensitivity of 3.6% for a point source at the center of the field-of-view with an energy window of 250-665 keV. Iterative image reconstruction, together with accurate data corrections for scatter, random, and attenuation, are incorporated to achieve high-quality images and quantitative data. These results are demonstrated through our contrast recovery measurements as well as sample animal studies.     

Rationally Engineered Electrodes for a High‐Performance Solid‐State Cable‐Type Supercapacitor

Wire‐shaped electrodes for solid‐state cable‐type supercapacitors (SSCTS) with high device capacitance and ultrahigh rate capability are prepared by depositing poly(3,4‐ethylenedioxythiophene) onto self‐doped TiO₂ nanotubes (D‐TiO₂) aligned on Ti wire via a well‐controlled electrochemical process. The large surface area, short ion diffusion path, and high electrical conductivity of these rationally engineered electrodes all contribute to the energy storage performance of SSCTS. The cyclic voltammetric studies show the good energy storage ability of the SSCTS even at an ultrahigh scan rate of 1000 V s^?1, which reveals the excellent instantaneous power characteristics of the device. The capacitance of 1.1 V SSCTS obtained from the charge–discharge measurements is 208.36 µF cm^?1 at a discharge current of 100 µA cm^?1 and 152.36 µF cm^?1 at a discharge current of 2000 µA cm^?1, respectively, indicating the ultrahigh rate capability. Furthermore, the SSCTS shows superior cyclic stability during long‐term (20 000 cycles) cycling, and also maintains excellent performance when it is subjected to bending and succeeding straightening process.     

Multifunctional Optical Terminals for Microsatellite Clusters – Design Tradeoffs

We study optical terminals with both communication and ranging capabilities for their potential use in short range free-space applications, typically encountered within a cluster of microsatellites. For our considerations we assume satellites with a unit mass between 10 kg and 100 kg, with mutual distances on the order of a few km, and per link data rates range from a few kbits/s to some 100 Mbit/s. We discuss possible network topologies and multiple access methods, andcompare the performance characteristics of different intensity modulation formats, taking into account not only the task of communication but also that of accurate intra-cluster distance measurement. Our considerations revealbasic tradeoffs to be observed when designing such multifunctional optical terminals.     

Fast MPEG-4 Motion Estimation: Processor Based and Flexible VLSI Implementations

MPEG-4 is a new multimedia standard combining interactivity, object-based natural and synthetic digital video, audio and computer-graphics. For the implementation of the video part of the MPEG-4 standard a high degree of flexibility is required, where the motion estimation requires the highest part of the computational power. Therefore, in this paper fast algorithms for MPEG-4 motion estimation are evaluated in terms of visual quality and computational power requirements for processor based implementations. Due to the object-based nature of MPEG-4 also new VLSI architectures for MPEG-4 motion estimation are required. Therefore known motion estimation architectures are evaluated on their capability of being modified for MPEG-4 support. Based on this evaluation a new dedicated, but flexible MPEG-4 motion estimation architecture targeted for low-power handheld applications is presented, which resulted to be advantageous to processor based implementations by magnitudes of order.     

Printed microinductors on flexible substrates for power applications

A low-profile microinductor was fabricated on a copper-clad polyimide substrate where the current carrying coils were patterned from the existing metallization layer and the magnetic core was printed using a magnetic ceramic-polymer composite material. Highly loaded ferrite-polymer composite materials were formulated, yielding adherent films with 4/spl pi/M/sub s//spl ap/3900 G at +5000 Oe applied DC field. These composite magnetic films combine many of the superior properties of high temperature ceramic magnetic materials with the inherent processibility of polymer thick films. Processing temperatures for the printed films were between 100/spl deg/C and 130/spl deg/C, facilitating integration with a wide range of substrates and components. The quality factor of the microinductor was found to peak at Q=18.5 near 10 MHz, within the optimal frequency range for power applications. A flat, nearly frequency independent inductance of 1.33 /spl mu/H was measured throughout this frequency range for a 5 mm/spl times/5 mm component, with a DC resistance of 2.6 /spl Omega/ and a resonant frequency of 124 MHz. The combination of printed ceramic composites with organic/polymer substrates enables new methods for embedding passive components and ultimately the integration of high Q inductors with standard integrated circuits for low profile power electronics.     

Recent advances in amplify-and-forward two-hop relaying [Accepted from Open Call]

In this article we review an important class of wireless cooperation protocols known as amplify-and-forward relaying. One or more low-complexity relay nodes assist the communication between sources and destinations without having to decode the signal. This makes AF relaying transparent to modulation and coding of the source/destination communication protocol. It is therefore a highly flexible technology that also qualifies for application in heterogeneous networks comprising many nodes of different complexity or even standards. Recently, two-way relaying was introduced, which is readily combined with AF relaying. It is a spectrally efficient protocol that allows for bidirectional communication between sources and destinations. In order to investigate the potential of wireless AF relaying, we introduce three distributed network scenarios that differ in the amount of cooperation between nodes. New challenges arise in those networks, and we discuss approaches to overcome them. For the most general case of a completely distributed system, we present coherent relaying solutions that offer a distributed spatial multiplexing gain even for single-antenna nodes. Based on real-world experiments, we validate the feasibility of all schemes in our laboratory.     

Polyphenylene Dendrimer‐Templated In Situ Construction of Inorganic–Organic Hybrid Rice‐Shaped Architectures

A novel dendrimer‐templating method for the synthesis of CuO nanoparticles and the in situ construction of ordered inorganic–organic CuO–G2Td(COOH)₁₆rice‐shaped architectures (RSAs) with analogous monocrystalline structures are reported. The primary CuO nanoparticles are linked by the G2Td(COOH)₁₆ dendrimer. This method provides a way to preserve the original properties of primary CuO nanoparticles in the ordered hybrid nanomaterials by using the 3D rigid polyphenylene dendrimer (G2Td(COOH)₁₆) as a space isolation. The primary CuO nanoparticles with diameter of (6.3 ± 0.4) nm are synthesized via four successive reaction steps starting from the rapid reduction of Cu(NO₃)₂ by using NaBH₄ as reducer and G2Td(COOH)₁₆ as surfactant. The obtained hybrid CuO–G2Td(COOH)₁₆ RSA, formed in the last reaction step, possesses a crystal structure analogous to a monocrystal as observed by transmission electron microscopy(TEM). In particular, the formation process of the RSA is monitored by UV–vis, TEM, and X‐ray diffraction. Small angle X‐ray scattering and Fourier transform infrared spectroscopy are used to investigate the role of the dendrimer in the RSA formation process. The obtained results illuminate that Cu²⁺? COO^? coordination bonds play an indispensable role in bridging and dispersing the primary CuO nanoparticles to induce and maintain the hybrid RSA. More importantly, the RSA is retained through the Cu²⁺? COO^?coordination bonds even with HCl treatment, suggesting that the dendrimers and Cu²⁺ ions may form rice‐shaped polymeric complexes which could template the assembly of CuO nanoparticles towards RSAs. This study highlights the feasibility and flexibility of employing the peculiar dendrimers to in‐situ build up hybrid architectures which could further serve as templates, containers or nanoreactors for the synthesis of other nanomaterials.