Advances in Porous Organic Polymers for Efficient Water Capture

Desiccant driven dehumidification for maintaining the proper humidity levels and atmospheric water capture with minimum energy penalty are important aspects in heat pumps, refrigeration, gas and liquid purifications, gas sensing, and clean water production for improved human health and comfort. Water adsorption by using nanoporous materials has emerged as a viable alternative to energy-intensive industrial processes, thus understanding the significance of their porosity, high surface areas, vast pore volumes, chemical and structural features relative to the water adsorption is quite important. In this review article, important features of nanoporous materials are presented, including zeolites, porous carbons, as well as crystalline and amorphous porous organic polymers (POPs) to define the interactions between the water molecules and the polar/non-polar functional groups on the surface of these nanoporous materials. In particular, focus is placed on the recent developments in POPs in the context of water capture as a result of their remarkable stability towards water and wide range of available synthetic routes and building blocks for their synthesis. We also highlighted recent approaches to increase the water sorption capacity of POPs by modifying their structure, morphology, porosity, and chemical functionality while emphasizing their promising future in this emerging area.     

Effect of gamma irradiation on Burkholderia thailandensis (Burkholderia pseudomallei surrogate) survival under combinations of pH and NaCl

This study evaluated the effect of gamma irradiation on Burkholderia thailandensis (Burkholderia pseudomallei surrogate; potential bioterrorism agent) survival under different levels of NaCl and pH. B. thailandensis in Luria Bertani broth supplemented with NaCl (0–3%), and pH-adjusted to 4–7 was treated with gamma irradiation (0–0.5 kGy). Surviving cell counts of bacteria were then enumerated on tryptic soy agar. Data for the cell counts were also used to calculate D₁₀ values (the dose required to reduce 1 log CFU/mL of B. thailandensis). Cell counts of B. thailandensis were decreased (P<0.05) as irradiation dose increased, and no differences (P≥0.05) in cell counts of the bacteria were observed among different levels of NaCl and pH. D₁₀ values ranged from 0.04 to 0.07 kGy, regardless of NaCl and pH level. These results indicate that low doses of gamma irradiation should be a useful treatment in decreasing the potential bioterrorism bacteria, which may possibly infect humans through foods.     

Magnetite-coated metal foams as one-body catalysts for Fenton-like reactions

The possibility of preparing one-body catalyst was investigated for heterogeneous Fenton-like reactions by coating magnetite powder on metal foams. Up to 10 wt% magnetite could be coated onto metal foams with strong enough adhesion. The catalytic efficiency of the catalyst was investigated using a model reaction of methylene blue degradation at a circumneutral pH using H₂O₂ as the source of OH radicals and oxalic acid as the chelating agent. Comparison with conventional magnetite powder indicated that the catalytic efficiency of magnetite-coated metal foam was better than that of the powder only due to a larger exposed surface area. After treatment, separation of the one-body catalyst was easier and cleaner than that of conventional magnetite powder catalyst.     

Synthesis and characterization of chemically modified polystyrene as processable carbon fiber precursors

In this study, the chemically modified polystyrene was studied for improvement of polystyrene which had low carbon yield, as a carbon fiber precursor. The polystyrene was synthesized with divinylbenzene which was used as a cross-linking agent by the solution polymerization method. Then the synthesized polystyrene was nitrated with sulfuric and nitric acids solution (H₂SO₄/HNO₃) followed by reduction to form nitrogen-functional groups. The surface properties of the modified polystyrene were investigated by Fourier transfer infrared spectroscopy to confirm the introduction of functional groups on the modified polystyrene surfaces. The thermal properties of the modified polystyrene were measured by thermogravimetric analysis and differential scanning calorimetry. The morphologies of the electrospun polystyrene fibers by a chemical modification were observed by scanning electron microscopy. From the results, the nitrogen-functional groups were introduced on the modified polystyrene surfaces which affected the quantity of functional groups. Also, the chemical treatment affected the carbon yield of the polystyrene owing to the introduction of nitrogen-functional groups on polystyrene surfaces. Consequently, it was concluded that the chemical treatment of polystyrene fibers enables it to be used as a possible carbon fiber precursor.     

Polymer-based electrospray device with multiple nozzles to minimize end effect phenomenon

In this paper, “end effect”, which represents the deflection of meniscus of boundary nozzles in an array due to asymmetric electric field and repulsive forces between adjacent nozzles, is experimentally investigated and a polymer-based electrospray device is fabricated and tested to minimize the end effect. For the electrically conductive nozzles of electrospray, the end effect could be reduced by dummy nozzles, through which no liquid is supplied, mounted at the boundary of the array. However, the polymer-based electrospray device can eliminate the end effect without using the dummy dry nozzles due to dielectric characteristic. A novel multiple nozzles of Polymethyl Methacrylate (PMMA)-based electrospray device was successfully fabricated and evaluated for reducing the end effect, showing no deflection of menisci through the boundary nozzles. And ten nozzles device was fabricated and observed to eject liquid jet simultaneously. The electrical current of the spray issued from the nozzles of the polymer-based electrospray device is measured with respect to flow rate and shows a good agreement with the scaling law.     

Cysteine-179 of IkappaB kinase beta plays a critical role in enzyme activation by promoting phosphorylation of activation loop serines

IkappaB kinase beta (IKKbeta) subunit of IKK complex is essential for the activation of NF-kappaB in response to various proinflammatory signals. Cys-179 in the activation loop of IKKbeta is known to be the target site for IKK inhibitors such as cyclopentenone prostaglandins, arsenite, and antirheumatic gold compounds. Here we show that a mutant IKKbeta in which Cys-179 is substituted with alanine had decreased activity when it was expressed in HEK-293 cells, and TNF stimulation did not restore the activity. Phosphorylation of activation loop serines (Ser-177 and Ser-181) which is required for IKKbeta activation was reduced in the IKKbeta (C179A) mutant. The activity of IKKbeta (C179A) was partially recovered when its phosphorylation was enforced by coexpression with mitogen-activated protein kinase kinase kinases (MAPKKK) such as NF-kappaB inducing kinase (NIK) and MAPK/extracellular signal-regulated kinase kinase kinase 1(MEKK1) or when the serine residues were replaced with phospho-mimetic glutamate. The IKKbeta (C179A) mutant was normal in dimer formation, while its activity abnormally responded to the change in the concentration of substrate ATP in reaction mixture. Our results suggest that Cys-179 of IKKbeta plays a critical role in enzyme activation by promoting phosphorylation of activation-loop serines and interaction with ATP.     

A simple taste analyzing system design for visual and quantitative analysis of different tastes using multi-array chemical sensors and pattern recognition techniques

In this paper, we describe design of a simple taste analyzing system using sensory system based on a multi-array chemical sensor (MACS) and personal digital assistant (PDA) for visual and quantitative analysis of different tastes using pattern recognition techniques. The sensory system is communicated with PDA, which has several interesting benefits for data analysis and display, via wireless using the Bluetooth. A various pattern recognition techniques are adapted including spider map, principal component analysis (PCA) and fuzzy C-means (FCM) algorithm to classify visually data patterns detected by the sensory system. The proposed techniques can be determined the cluster centers and membership grade of patterns through the unsupervised way. The membership grade of an unknown pattern, which does not shown previously, can be visually and analytically determined. Throughout the experimental trails, the taste analyzing system is demonstrated robust performance through data acquisition via wireless communication and visual and quantitative analysis of different tastes for the liquids. The system, which is implemented as a simple hand-held taste analyzing instrument, can be applicable to on-site taste monitoring.     

Elliptic equations with measurable coefficients in Reifenberg domains

We prove W1,p estimates for elliptic equations in divergence form under the assumption that for each point and for each sufficiently small scale there is a coordinate system so that the coefficients have small oscillation in (n−1) directions. We assume the boundary to be δ-Reifenberg flat and the coefficients having small oscillation in the flat direction of the boundary.     

Isotope ratio monitoring gas chromatography/Mass spectrometry of D/H by high temperature conversion isotope ratio mass spectrometry

Of all the elements, hydrogen has the largest naturally occurring variations in the ratio of its stable isotopes (D/H). It is for this reason that there has been a strong desire to add hydrogen to the list of elements amenable to isotope ratio monitoring gas chromatography/mass spectrometry (irm-GC/MS). In irm-GC/MS the sample is entrained in helium as the carrier gas, which is also ionized and separated in the isotope ratio mass spectrometer (IRMS). Because of the low abundance of deuterium in nature, precise and accurate on-line monitoring of D/H ratios with an IRMS requires that low energy helium ions be kept out of the m/z 3 collector, which requires the use of an energy filter. A clean mass 3 (HD(+.)) signal which is independent of a large helium load in the electron impact ion source is essential in order to reach the sensitivity required for D/H analysis of capillary GC peaks. A new IRMS system, the DELTA(plus)XL(trade mark), has been designed for high precision, high accuracy measurements of transient signals of hydrogen gas. It incorporates a retardation lens integrated into the m/z 3 Faraday cup collector. Following GC separation, the hydrogen bound in organic compounds must be quantitatively converted into H(2) gas prior to analysis in the IRMS. Quantitative conversion is achieved by high temperature conversion (TC) at temperatures >1400 degrees C. Measurements of D/H ratios of individual organic compounds in complicated natural mixtures can now be made to a precision of 2 per thousand (delta notation) or, better, with typical sample amounts of approximately 200 ng per compound. Initial applications have focused on compounds of interest to petroleum research (biomarkers and natural gas components), food and flavor control (vanillin and ethanol), and metabolic studies (fatty acids and steroids). Copyright 1999 John Wiley & Sons, Ltd.