Nano‐Explosions of Nanoparticles for Sudden Release of Substances by Embedded Azo‐Components as Obtained via the Miniemulsion Process

The solid and thermally instable azoinitiators V‐65 and VR‐110 were embedded within a polymer particle by using the miniemulsion process and afterwards quickly decomposed by thermal treatment below the glass temperature of the polymer. The resulting nitrogen gas overpressure inside the particles leads to a disruption of the polymer particle and a possible sudden release of encapsulated substances. It is shown, by electron microscopic measurements, that the number of burst particles correlates with the applied temperatures as well as the heating time. The surface deformation could be verified by scanning electron microscope analyses.

     

Improved compressed sensing reconstruction for $$^{19}$$ F magnetic resonance imaging

Magnetic Resonance Materials in Physics, Biology and Medicine - In magnetic resonance imaging (MRI), compressed sensing (CS) enables the reconstruction of undersampled sparse data sets. Thus,...     

Frequency distribution and signal formation around a vessel

We describe the NMR signal formation properties of a single vessel. Instead of assuming the frequency distribution to be a simple Lorentzian or Gaussian one, we take into account that the frequency distribution around the vessel is a complex function. Considering the static dephasing regime we find a relationship between signal formation and frequency distribution. Analytical expressions for the frequency distribution in a voxel and the magnetization decay are obtained. In the case of small volume fractions of blood and week magnetic fields the results can be used for describing signal formation processes in a vascular network. A relationship between the frequency distribution and the properties of the vascular network is derived. The magnetization decay in different time regimes is discussed. The result is relevant for describing signal formation processes around a vessel for arbitrary pulse sequences.     

Encapsulation of magnetic nickel nanoparticles via inverse miniemulsion polymerization

In this work, the encapsulation of magnetic nickel nanoparticles in polyacrylamide particles was performed via inverse miniemulsion polymerization. The dispersion of nickel nanoparticles was characterized in polar solvents including water, ethanol, and dimethyl sulfoxide using different stabilizers. The best results were obtained when the nonionic stabilizer poly(ethylene glycol) octadecyl ether (Brij 76) was used to stabilize the nickel nanoparticles in dimethyl sulfoxide. In addition, the block copolymer poly(ethylene‐co‐butylene)‐b‐poly(ethylene oxide) was used as a surfactant to create inverse miniemulsions while minimizing the coalescence of the miniemulsion droplets. Different types of salts such as zinc, nickel, and sodium nitrates were tested as lipophobes to retard Ostwald ripening. Transmission electron microscopy images of polyacrylamide/nickel particles synthesized with zinc and nickel salts as lipophobes indicate that nickel nanoparticles are embedded in the polyacrylamide matrix. Magnetization curves show that the saturation magnetization of polyacrylamide/nickel particles is only slightly below that of the pure nickel nanoparticles. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Symbolic system-level design methodology for multi-mode reconfigurable systems

Modern embedded systems provide a variety of functionality as operational modes, each corresponding to a mutually exclusive phase of operation. This paper provides a system level design methodology tailored for such multi-mode systems. By incorporating knowledge about the temporal behavior, it is possible to share hardware by means of partial reconfiguration on sophisticated Field Programmable Gate Arrays (FPGAs), and thus, reduce costs and improve performance. The presented methodology is based on an exploration model, which specifies the temporal behavior of the system functionality as well as the architectural characteristics of nowadays reconfigurable technology. We develop a symbolic encoding of this system specification, which enables unified system synthesis by applying sophisticated optimization techniques to perform allocation, binding, placement of partially reconfigurable modules, and routing the on-chip communication. The presented system-level design methodology complies with the state-of-the-art synthesis tools and communication technologies for partially reconfigurable systems. We demonstrate this by experiments on test cases from the image processing domain applying state-of-the-art technology. The results give evidence of the efficiency of the methodology and show the superiority in terms of runtime and quality of the found solutions compared to existing system-level synthesis approaches.     

Biomimetic Hydroxyapatite Crystallization in Gelatin Nanoparticles Synthesized Using a Miniemulsion Process

Here, we report a novel biomimetic strategy to synthesize hydroxyapatite (HAP) inside of crosslinked gelatin nanoparticles, which serve as a nanoenvironment for crystal growth in the aqueous phase. The synthesis of gelatin nanoparticles with the inverse miniemulsion technique is very intriguing because of the flexibility offered by the technique in tailoring the properties of the gelatin nanoparticles. It can be shown that the nanoenvironment promotes a different growth environment for the crystal because of the confinement inside the particle. The formation of HAP inside the particles follows Ostwald's rule of stages. At first an amorphous phase is formed, which itself has a great potential to be used as a resorbable bone substitute. This further transforms into single crystalline HAP via an octacalcium phosphate intermediate. The solution‐mediated transformation into the HAP phase without any calcination step is studied in detail using transmission electron microscopy (TEM) and X‐ray diffraction (XRD) measurements.     

Nanostructured ordering of fluorescent markers and single proteins on substrates

Highly ordered hexagonal nanopatterns of gold clusters on glass substrates were used as anchoring points for the specific attachment of fluorescence dyes and proteins labeled with fluorescence dyes. Thiol- or disulfide-containing linker molecules were used for the binding to the gold dots. In order to ensure specific binding on the gold dots only, the surface area in between the dots was protected against unspecific adsorption. For the attachment of polar low-molecular-weight fluorescence dyes, an octadecyltrichlorosilane self-assembled monolayer was prepared on the surface in between the gold dots, whereas a layer prepared from star-shaped poly(ethylene oxide-stat-propylene oxide) prepolymers was used to prevent unspecific adsorption of proteins between the gold dots. Fluorescence microscopy proved the specific binding of the dyes as well as of the proteins. Scanning force microscopy studies show that each gold dot is only capable of binding one protein at a time.