Ultrasensitive label-free DNA analysis using an electronic chip based on carbon nanotube nanoelectrode arrays

We report the detection of DNA PCR amplicons using an ultrasensitive label-free electronic technique based on multiwalled carbon nanotube (MWNT) nanoelectrode arrays embedded in an SiO(2) matrix. Specific PCR amplicons are reliably detected using electrochemical (EC) methods through allele-specific oligonucleotide hybridization. The inherent guanine bases in the DNA amplicon target of [Formula: see text] bases serve as signal moieties with the aid of Ru(bpy)(3)(2+) mediators, providing an amplified anodic current associated with the oxidation of guanine groups at the nanoelectrode surface. The reduced size and density of the nanoelectrode array provided by MWNTs dramatically improves the sensitivity of EC detection. In addition, the abundant guanine bases in target DNA produce a large signal. Less than [Formula: see text] target amplicons can be detected on a microspot, approaching the sensitivity limit of conventional laser-based fluorescence techniques. This method also eliminates the labelling requirement and makes the measurements much simpler. This platform can be employed for developing highly automated electronic chips with multiplex nanoelectrode arrays for quick DNA analysis.     

Preliminary study of a polycaprolactone membrane utilized as epidermal substrate

Solvent-cast sheets of polycaprolactone were biaxially stretched to produce 10–15 m thick films. PCL films were found to have a tensile strength of 55 MPa which is about two and a half times stronger than native skin. One of our previous studies using non-coated PCL membranes showed that only 36% of the membrane surface was covered with keratinocytes after 9 days of culture. The present study examined the effects of coating the surface of PCL membranes with fibrin on the proliferation of keratinocytes. Qualitative analysis revealed that the cells attached and proliferated better on coated PCL films. Keratinocytes exhibited healthy cobblestone morphology and proliferated as continuous monolayers over a period of 16 days. The results indicated that fibrin coated PCL films would support the attachment and proliferation of human keratinocytes and have the potential to be applied as a matrix material for tissue engineering an epidermal equivalent.     

Experimental investigation of silica gel–water adsorption chillers with and without a passive heat recovery scheme

We experimentally show that for the same heat exchanger inventory allocation, a four-bed adsorption chiller delivers a 12% higher ultimate cooling capacity than its two-bed counterpart. In addition it delivers a significantly improved quality of instantaneous cooling than a two-bed chiller at the same cooling capacity. The COP-enhancing feature of a passive heat recovery scheme that does not involve additional pumping action or valves is experimentally proven. It improves the COPs of a two-bed chiller and a four-bed chiller by as much as 38 and 25%, respectively, without any effect on their cooling capacities. The highest COPs achieved with a two-bed and four-bed chillers are 0.46±0.02 and 0.45±0.02, respectively. These are measured at a hot-water inlet temperature of 85 °C, cooling-water inlet temperature of 29.4 °C and chilled-water inlet temperature of 12.2 °C.     

Fourier-transform method of data compression and temporal fringe pattern analysis

Temporal fringe pattern analysis is invaluable in studies of transient phenomena but necessitates large data storage for two essential sets of data, i.e., fringe pattern intensity and deformation phase. We describe a compression scheme based on the Fourier-transform method for temporal fringe data storage that permits retrieval of both the intensity and the deformation phase. When the scheme was used with simulated temporal wavefront interferometry intensity fringe patterns, a high compression ratio of 10.77 was achieved, with a significant useful data ratio of 0.859. The average root-mean-square error in phase value restored was a low 0.0015 rad. With simulated temporal speckle interferometry intensity fringe patterns, the important paremeters varied with the modulation cutoff value applied. For a zero modulation cutoff value, the ratio of data points and the compression ratio values obtained were roughly the same as in wavelength interferometry, albeit the average root-mean-square error in the phase value restored was far higher. By increasing the modulation cutoff value we attained significant reduction and increase in the ratio of data points and the compression ratio, respectively, whereas the average root-mean-square error in the restored phase values was reduced only slightly.     

Performance enhancement of DS-CDMA system using overlapping sectors with interference avoidance

A cellular system with overlapping sectors is proposed to enhance system performance through interference avoidance. Due to the overlapping effect, each user is allowed to select one sector out of many for operation. It is shown that the mutual interference among users in different regions within a cell can be minimized by choosing a good sector combination. The potential benefits of the proposed technique are investigated in two scenarios: orthogonal and nonorthogonal code division multiple access systems. In the former case, it is shown that when compared with the traditional nonoverlapping sectors system, one is able to reduce the number of spreading codes required to support all users by using appropriate code allocation in the proposed system. A theoretical framework based on combinatorial enumeration is developed to assess the performance of the proposed system. For the latter case, the enhancement takes the form of multiple access interference reduction. Simulation results show that its improvement is significant and can be further enhanced by increasing the number of overlapping sectors.     

The role of mechanical twinning on microcrack nucleation and crack propagation in a near-γ TiAl alloy

The role of mechanical twinning on microcrack nucleation and crack propagation in a near-γ TiAl alloy was investigated in 4-point bend specimens using selected area channeling patterns and electron channeling contrast imaging to obtain the true crystal orientation image crystal defects. Two types of bend specimens were used, a conventional specimen that was deformed to a surface strain of about 1.4%, but not fractured, and a bi-layer notched specimen with an aluminum backing that prevented catastrophic fracture so that crack arrest features could be examined. Most grains showed activity of 1–4 twinning systems, and their activity correlated closely with the Schmid factor. Grain boundary microcracks were most frequently found where twins interacted with the grain boundary, and crystallographic analysis indicated that the twinning shear caused these cracks to open. In the crack growth specimen, extensive twinning and dislocation activity occurred in the grain with the arrested crack tip, but with continued straining, these same twins caused grain boundary microcracks to form and link-up to form full intergranular cracks, resulting in renucleation of the primary failure crack.     

The biodegradation of N-methyl-2-pyrrolidone in water by sewage bacteria

The biodegradability of N-methyl-2-pyrrolidone was studied using a static die-away system and a semi-continuous activated sludge system. The biodegradation was followed by gas-liquid chromatographic analysis as well as by monitoring the change in chemical oxygen demand of the culture mixture. Results show that N-methyl-2-pyrrolidone is readily degradable under these conditions. However, the metabolite has an appreciable oxygen demand and is shown by infra-red spectroscopy to be a carbonyl compound.     

Fabrication of Single-Crystal α-Al2O3 Nanorods by Displacement Reactions

Nanometer-sized Al₂O₃ rods are fabricated by sintering a powder mixture of Al and SiO₂. The sintered product is leached in HF–HNO₃ solution, followed by rinsing and washing before the nanorods are collected. The yield of the product is about 50 wt%. Transmission electron microscopy reveals that these rods are 1 to 2 μm long and have a diameter of 20 to 100 nm, while electron diffraction confirms that these rods are single crystals of α-Al₂O₃. It is observed that these rods have either round or slightly sharp tips, which is different from those having droplet-like tips that are usually found in products fabricated by catalytic reactions.     

Synthesis of dysprosium oxide by homogeneous precipitation

Nanocrystals of uniform dysprosium oxide (Dy₂O₃) particles have been prepared by homogeneous precipitation technique. The particles were produced by aging DyCl₃solution in presence of urea at elevated temperature. The particles were characterized with respect to their size, shape, and thermal decomposition behavior. It was found that the precipitated particles were spherical, uniform in size, and amorphous in nature. Upon heating in air, these particles decomposed into oxide and no change in morphology was observed. The dysprosium ion concentration was found to have significant effect on the particle size and its distribution.     

Pituitary-adrenal suppression in preterm, very low birth weight infants after inhaled fluticasone propionate treatment

Systemic corticosteroids prescribed for treatment of pulmonary diseases in preterm, very low birth weight infants caused severe suppression of the hypothalamic-pituitary-adrenal axis and produced serious physiological and metabolic disturbances. However, the effect of inhaled corticosteroids on their pituitary-adrenal functions is not known. We prospectively evaluate the pituitary-adrenal function using the human CRH stimulation test in a cohort of very low birth weight infants at risk for hypothalamic-pituitary-adrenal axis suppression in a double blind, randomized pilot study designed for assessing the efficacy and adverse effects of inhaled fluticasone propionate in newborn preterm infants who required mechanical ventilation for treatment of respiratory distress syndrome. Twenty-five preterm (< 32 gestational weeks), very low birth weight (< 1500 g) infants were randomized to receive inhaled fluticasone propionate (n = 13) or a placebo inhaler (n = 12). The medication was given every 12 h (fluticasone propionate, 1,000 micrograms/day) for 14 days. All surviving infants had their pituitary-adrenal functions assessed by human CRH test on the following morning immediately after completion of the 2-week course. All basal (0 min) and post-stimulation (15, 30, and 60 min) plasma ACTH and serum cortisol concentrations were significantly suppressed in the inhaled fluticasone group compared to their corresponding levels in the placebo group [basal plasma ACTH concentrations (F = 6.0; P = 0.02), poststimulation plasma ACTH concentrations (F > 8.6; P < 0.01), basal serum cortisol concentrations (F = 5.6; P = 0.03), and poststimulation serum cortisol concentrations (F > 15.6; P < 0.001)]. This is the first study in very low birth weight infants that demonstrates unequivocally that cumulative high dose inhaled corticosteroids can induce moderately severe suppression of both the pituitary and adrenal glands. The systemic bioactivity is probably associated with pulmonary vascular absorption, which effectively circumvents the hepatic first pass metabolism. Until the question of safety can be adequately addressed, inhaled fluticasone propionate should be used with cautionin preterm infants.