Single-source-precursor synthesis and high-temperature evolution of a boron-containing SiC/HfC ceramic nano/micro composite

A boron-containing SiHfC(N,O) amorphous ceramic was synthesized upon pyrolysis of a single-source-precursor at 1000 °C in Ar atmosphere. The high-temperature microstructural evolution of the ceramic at high temperatures was studied using X-ray powder diffraction, Raman spectroscopy, solid-state nuclear magnetic resonance spectroscopy and transmission electron microscopy. The results show that the ceramic consists of an SiHfC(N,O)-based amorphous matrix and finely dispersed sp²-hybridized boron-containing carbon (i.e. B_yC). High temperature annealing of B_yC/SiHfC(N,O) leads to the precipitation of HfC_xN_1-x nanoparticles as well as to β-SiC crystallization. After annealing at temperatures beyond 1900 °C, HfB₂ formation was observed. The incorporation of boron into SiHfC(N,O) leads to an increase of its sintering activity, consequently providing dense materials possessing improved mechanical properties as compared to those of boron-free SiC/HfC. Thus, hardness and elastic modulus values up to 25.7 ± 5.3 and 344.7 ± 43.0 GPa, respectively, were measured for the dense monolithic SiC/HfC_xN_1-x/HfB₂/C ceramic nano/micro composite.     

Elucidating the interactions between carbon nanotubes and carbon black with styrene butadiene rubber

The reinforcement mechanism of carbon nanotubes (CNT) on styrene butadiene rubber is studied through dynamic and swelling tests. Compounds containing carbon black (CB) and an unfilled one were prepared for comparison purposes. The dynamic properties are interpreted through the Maier-Göritz model to distinguish the contributions of stable and unstable crosslinks to the storage modulus, finding that the unstable ones become more relevant in samples containing a CNT concentration higher than 5 phr. In addition, the crosslinks density estimated by swelling and the stable contribution obtained with dynamical properties present the same tendency with the CNT amount. The former presents lower values, which can be explained considering that only stable crosslinks remain in the equilibrium-swollen state, while in the second one both stable and unstable are considered. In addition, differences in the filler-polymer interaction mechanisms are observed according to the morphology and aspect ratio of CNT in contrast to CB.     

Low-weight fractions of graphene and hydroxyapatite enhance mechanics in photocured methacrylate adhesives

In many applications, it is desirable for photocured adhesives to have high-mechanical strength in the cured state, but relatively low viscosity when liquid. This was achieved by adding less than 0.5 wt% hydroxyapatite and graphene to methyl methacrylate with diurethane dimethacrylate (UDMA-MMA). Nanoindentation shows hardness increasing by 30–40% and indentation modulus by >30% compared to UDMA-MMA on its own. Rheometry shows only a small increase in uncured viscosity for the liquid state. The additives affect the optical properties, mobility of free radicals, photocuring, and degree of conversion, the effects of which are seen in Fourier transform infrared and micro-Raman spectra. Thermographic images taken during curing show that the additives impact the photocuring process. In addition, changes in intermolecular bonding are seen in the vibrational spectra when the additives are present. The enhanced mechanical properties are attributed to the observed changes in photocuring and bonding.     

Tumor Resection Induces Alterations on Serum Phospholipidome of Liver Cancer Patients

Hepatocellular carcinoma and cholangiocarcinoma are the most common primary malignant liver tumors. Since the liver plays a key role in lipid metabolism, the study of serum phospholipid (PL) profiles may provide a better understanding of alterations in hepatic lipid metabolism. In this study, we used a high-resolution HILIC-LC–MS lipidomic approach to establish the serum phospholipidome profile of patients with liver cancer before (T0) and after tumor resection (T1) and a control group (CT) of healthy individuals. After the analysis of PL profiles, we observed that the phospholipidome of patients with liver cancer was significantly modified after the tumor resection procedure. We observed an upregulation of some phosphatidylcholine (PtdCho) species, namely, PtdCho(36:6), PtdCho(42:6), PtdCho(38:5), PtdCho(36:5), PtdCho(38:6) and choline plasmalogens (PlsCho), and/or 1-O-alkyl-2-acyl-glycerophosphocholine (PakCho) in patients with liver cancer at T0 compared to the CT group, and a downregulation after tumor resection (T1) when compared to T0. These results show that LC–MS can detect different serum PL profiles in patients with liver cancer, before and after tumor resection, by defining a specific PL fingerprint that was used to determine the effect of tumor and tumor resection on lipid metabolism.     

Realization of an optical communication tunable filter using a diffraction-based optical system

Optical bandpass tunable filters are key elements for dense WDM optical communication systems. Recently, a realization of optical linear transformation using a spatial diffraction optical system was presented and theoretically analyzed [J. Opt. Soc. Am. A21, 732 (2004)]. We present an optical bandpass tunable filter based on this optical system and a spatial light modulator. The mathematical analysis and additional computer simulations for testing the filter's basic parameters using the Fresnel diffraction theory are presented. Some newly obtained laboratory experimental results of the device in the optical visible spectrum will be shown.     

Low-frequency acoustic phonon temperature distribution in electrically biased graphene

On the basis of scanning thermal microscopy (SThM) measurements in contact and lift modes, the low-frequency acoustic phonon temperature in electrically biased, 6.7-9.7 μm long graphene channels is found to be in equilibrium with the anharmonic scattering temperature determined from the Raman 2D peak position. With ～100 nm scale spatial resolution, the SThM reveals the shifting of local hot spots corresponding to low-carrier concentration regions with the bias and gate voltages in these much shorter samples than those exhibiting similar behaviors in the infrared emission maps.     

Dynamic solid phase DNA extraction and PCR amplification in polyester-toner based microchip

A variety of substrates have been used for fabrication of microchips for DNA extraction, PCR amplification, and DNA fragment separation, including the more conventional glass and silicon as well as alternative polymer-based materials. Polyester represents one such polymer, and the laser-printing of toner onto polyester films has been shown to be effective for generating polyester-toner (PeT) microfluidic devices with channel depths on the order of tens of micrometers. Here, we describe a novel and simple process that allows for the production of multilayer, high aspect-ratio PeT microdevices with substantially larger channel depths. This innovative process utilizes a CO(2) laser to create the microchannel in polyester sheets containing a uniform layer of printed toner, and multilayer devices can easily be constructed by sandwiching the channel layer between uncoated cover sheets of polyester containing precut access holes. The process allows the fabrication of deep channels, with ~270 μm, and we demonstrate the effectiveness of multilayer PeT microchips for dynamic solid phase extraction (dSPE) and PCR amplification. With the former, we found that (i) more than 65% of DNA from 0.6 μL of blood was recovered, (ii) the resultant DNA was concentrated to greater than 3 ng/μL (which was better than other chip-based extraction methods), and (iii) the DNA recovered was compatible with downstream microchip-based PCR amplification. Illustrative of the compatibility of PeT microchips with the PCR process, the successful amplification of a 520 bp fragment of λ-phage DNA in a conventional thermocycler is shown. The ability to handle the diverse chemistries associated with DNA purification and extraction is a testimony to the potential utility of PeT microchips beyond separations and presents a promising new disposable platform for genetic analysis that is low cost and easy to fabricate.     

Biological activity of fluidized bed ethanol extracts from several edible mushrooms

In vitro antioxidant and anti-inflammatory activities of fluidized bed ethanol extracts of Pleurotus ostreatus PQMZ91109, PBS281009, M2191 (obtained from a laboratory greenhouse), Agaricus bisporus, Marasmius oreades, Craterellus cornucopioides, and Tuber melanosporum were investigated using free radical scavenging activities, metal chelating effects, inhibition of lipid peroxidation (inhibition of peroxyl radicals), xanthine oxidase, and lipoxygenase, and identification of antioxidant compounds. Levels of different compounds with antioxidant properties demonstrated the presence of more tocopherols than polyphenol carboxylic acids and flavones. HPLC showed that T. melanosporum extracts had high correlation values between levels of different active compounds and antioxidant assay results. Tocopherol levels were highly correlated (R ²=0.867) with anti-inflammatory activities and inhibition of lipid peroxidation. Fluidized bed ethanol extracts from dried mushroom fruit bodies can be a source of products rich in tocopherols, and can constitute an important ingredient in food supplements.     

Transition metal loaded silicon carbide-derived carbons with enhanced catalytic properties

Carbide-derived carbons (CDC) with incorporated transition metal nanoparticles (～2.5 nm) were prepared using a microemulsion approach. Time-consuming post synthesis functionalization of the carbon support material can thus be avoided and nanoparticle sizes can be controlled by changing the microemulsion composition. This synthesis strategy is a technique for the preparation of highly porous carbon materials with a catalytically active component. In particular we investigated the integration of ruthenium, palladium, and platinum in a concentration ranging from 4.45 to 12 wt.%. It was found that the transition metal has a considerable influence on sorption properties of resulting nanoparticle-CDC composite materials. Depending on the used metal salt additive the surface area and the pore volume ranges from 1480 m²/g and 1.25 cm³/g for Pt to 2480 m²/g and 2.0 cm³/g for Ru doped carbons. Moreover, members of this material class show impressive properties as heterogeneous catalysts. The liquid phase oxidation of tetralin and the partial oxidation of methane were studied, and electrochemical applications were also investigated. Primarily Pt doped CDCs are highly active in the oxygen reduction reaction, which is of great importance in present day fuel cell research.