Controlling DNA/Surface Interactions for Potential Pulse‐Assisted Preparation of Multi‐Probe DNA Microarrays

The possibility of selectively modifying microarray electrodes with different DNA sequences in a controlled way without the need for local positioning of solutions or local modification of array surfaces is demonstrated. Potential pulse sequences are employed to perform sequential surface modification of a 32‐gold‐electrode array with two different thiolated DNA capture sequences, surface passivation and regeneration of selected microarray electrodes, all by adjusting the potential intensities of the same potential pulse‐assisted method. We achieve reproducible and controlled DNA immobilization together with minimization of false signals originating from unspecific adsorption or undesired co‐immobilization. This methodology is not limited to DNA chips and it is potentially suitable for a wide range of applications employing Au?S chemistry. It can be employed in laboratory conditions for localizing different reactive chemistries onto predefined electrodes of an array without the need for complex and expensive apparatus and special conditions.     

Assessment of the origin and geothermal potential of the thermal waters by hydro-isotope geochemistry: Eskisehir province,Turkey

The thermal fluids vented over Eskisehir province have been investigated for their origin and to estimate the geothermal potential of the area. Thermal waters as well as bubbling and dissolved gases were collected and analysed for their chemical and isotopic features. Their isotopic composition varies in the range from ?11.5 to ?7.7?‰ for δ¹⁸O, ?84 and ?57?‰ for δ²H, and 0–7.2 TU for tritium. The gases (bubbling and dissolved) are mostly N₂-dominated with a significant amount of CO₂. The helium isotopic ratios are in the range of 0.2–0.66?R/Rac, indicate remarkable mantle-He contribution ranging between 2 and 10?% in the whole study area. Considering the estimated geothermal gradient about three times higher than the normal gradient, and the reservoir temperatures estimated to be between 50 and 100?°C using quartz and chalcedony geothermometers, a circulation model was built where possible mixing with shallow waters cool down the uprising geothermal fluids.     

An alternative method for the determination of element concentrations in schizophrenic, lung cancer and leukaemia patient bloods

Concentration of the elements present in schizophrenic, lung cancer and leukaemia patients’ bloods were determined using energy-dispersive X-ray fluorescence (EDXRF) method. EDXRF spectrometer with an annular and sources was applied for the analysis of blood samples. A sample preparation procedure suitable for the EDXRF, the experimental approach, analytical method used in this study and the results were presented. EDXRF technique has been successfully used for the determination of elements present in blood.     

Psychophysical tuning curves at very high frequencies

For most normal-hearing listeners, absolute thresholds increase rapidly above about 16 kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966-985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206-13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12-17.5 kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17 kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17 kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.     

Quantization of surface rust by using laser imaging techniques

Laser speckle interferometry^1,2 and image processing^3,4 have been used to detect and quantize the rust build-up on metal surfaces under water. Speckle information from the sample metal surface was captured by a CCD camera and a frame grabber card. Software techniques were used to convert the image data files into ASCII files in an appropriate format. Three-dimensional surface plots were generated to define the numerical values for the amout of rust build-up.     

A Comparative Study of Receptor-Targeted Magnetosome and HSA-Coated Iron Oxide Nanoparticles as MRI Contrast-Enhancing Agent in Animal Cancer Model

Magnetosomes are specialized organelles arranged in intracellular chains in magnetotactic bacteria. The superparamagnetic property of these magnetite crystals provides potential applications as contrast-enhancing agents for magnetic resonance imaging. In this study, we compared two different nanoparticles that are bacterial magnetosome and HSA-coated iron oxide nanoparticles for targeting breast cancer. Both magnetosomes and HSA-coated iron oxide nanoparticles were chemically conjugated to fluorescent-labeled anti-EGFR antibodies. Antibody-conjugated nanoparticles were able to bind the MDA-MB-231 cell line, as assessed by flow cytometry. To compare the cytotoxic effect of nanoparticles, MTT assay was used, and according to the results, HSA-coated iron oxide nanoparticles were less cytotoxic to breast cancer cells than magnetosomes. Magnetosomes were bound with higher rate to breast cancer cells than HSA-coated iron oxide nanoparticles. While 250 μg/ml of magnetosomes was bound 92 ± 0.2%, 250 μg/ml of HSA-coated iron oxide nanoparticles was bound with a rate of 65 ± 5%. In vivo efficiencies of these nanoparticles on breast cancer generated in nude mice were assessed by MRI imaging. Anti-EGFR-modified nanoparticles provide higher resolution images than unmodified nanoparticles. Also, magnetosome with anti-EGFR produced darker image of the tumor tissue in T2-weighted MRI than HSA-coated iron oxide nanoparticles with anti-EGFR. In vivo MR imaging in a mouse breast cancer model shows effective intratumoral distribution of both nanoparticles in the tumor tissue. However, magnetosome demonstrated higher distribution than HSA-coated iron oxide nanoparticles according to fluorescence microscopy evaluation. According to the results of in vitro and in vivo study results, magnetosomes are promising for targeting and therapy applications of the breast cancer cells.     

Shape Memory Hydrogel based on a Hydrophobically‐Modified Polyacrylamide (HMPAM)/α‐CD Mixture via a Host‐Guest Approach

A novel thermally sensitive shape memory (SM) hydrogel is prepared by block copoly­merization of a cationic surfactant monomer, dimethylhexadecyl[2‐(dimethylamino)ethylmethacrylate]ammoniumbromide (C₁₆DMAEMA), and acrylamide (AM) in the presence of α‐cyclodextrin (α‐CD) using N,N’‐methylenebisacrylamide (MBA) as a crosslinker. XRD, solid state ¹³C NMR, and DSC measurements show that the crystalline domains, induced by the hydrogen bonds between α‐CDs threaded on the hydrophobic units of the polymer chains through the host‐guest approach, can reversibly melt and crystallize at different temperatures. Rheological measurements show that both the elastic modulus G’ and viscous modulus G’’ drastically change due to the formation and dissolution of the crystalline domains. These thermo‐sensitive crystalline domains serve as reversible physical crosslinks, endowing the hydrogel with excellent SM properties. Cyclic experiments show that the hydrogel can recover to almost 100% of the deformation in each cycle and can be reused several times.

     

Nanosurface Mechanical Properties of Polymers Based on Continuous Stiffness Indentation

A systematic experimental study of the large strain surface mechanical properties of a number of polymers {polymethylmethacrylate (PMMA), polyetheretherketone (PEEK), polystyrene (PS), polycarbonate (PC), polypropylene (PP), and ultra-high molecular weight polyethylene (UHMWPE)} at the nanometer scale is described. The polymeric surfaces were indented and the data were analyzed using a contact compliance method in conjunction with a nano-indenter system. The indentation experiments were performed using a Berkovich Tip indenter with a continuous contact compliance indentation mode. The indentations were performed using a constant loading rate (300 μN/sec) to a maximum penetration depth of 5 μm. The experimental results showed a considerable strain-rate hardening effect for the polymers and a peculiarly harder response of these surfaces at the near-to-surface (submicron) layers. PMMA was the hardest polymer of the selection, whereas UHMWPE and PP were observed to be the softest polymers. The paper includes practical consideration of a creeping effect and appropriateness of tip calibration using harder surfaces for nanoindentation experimentation of polymers.     

Porous superhydrophobic membranes: hydrodynamic anomaly in oscillating flows

We have fabricated and characterized a novel superhydrophobic system, a meshlike porous superhydrophobic membrane with solid area fraction Φ(s), which can maintain intimate contact with outside air and water reservoirs simultaneously. Oscillatory hydrodynamic measurements on porous superhydrophobic membranes as a function of Φ(s) reveal surprising effects. The hydrodynamic mass oscillating in phase with the membranes stays constant for 0.9?Φ(s)≤1, but drops precipitously for Φ(s)<0.9. The viscous friction shows a similar drop after a slow initial decrease proportional to Φ(s). We attribute these effects to the percolation of a stable Knudsen layer of air at the interface.     

Aerobic ligand-free domino Suzuki coupling—Michael addition reaction catalyzed by in situ generated palladium nanoparticles in water: a general method for the synthesis of benzo[c]chromene derivatives

A general method has been developed for the synthesis of benzo[c]chromene derivatives via aerobic ligand-free domino Suzuki coupling and Michael addition reaction catalyzed by in situ generated palladium nanoparticles in water leading to C–C and C–O bond formations simultaneously.