Effects of UV 254 irradiation on residual chlorine and DBPs in chlorination of model organic-N precursors in swimming pools

Ultraviolet (UV) irradiation is commonly applied as a secondary disinfection process in chlorinated pools. UV-based systems have been reported to yield improvements in swimming pool water and air chemistry, but to date these observations have been largely anecdotal. The objectives of this investigation were to evaluate the effects of UV irradiation on chlorination of important organic-N precursors in swimming pools.Creatinine, L-arginine, L-histidine, glycine, and urea, which comprise the majority of the organic-N in human sweat and urine, were selected as precursors for use in conducting batch experiments to examine the time-course behavior of several DBPs and residual chlorine, with and without UV₂₅₄ irradiation. In addition, water samples from two natatoria were subjected to monochromatic UV irradiation at wavelengths of 222 nm and 254 nm to evaluate changes of liquid-phase chemistry. UV₂₅₄ irradiation promoted formation and/or decay of several chlorinated N-DBPs and also increased the rate of free chlorine consumption. UV exposure resulted in loss of inorganic chloramines (e.g., NCl₃) from solution. Dichloromethylamine (CH₃NCl₂) formation from creatinine was promoted by UV exposure, when free chlorine was present in solution; however, when free chlorine was depleted, CH₃NCl₂ photodecay was observed. Dichoroacetonitrile (CNCHCl₂) formation (from L-histidine and L-arginine) was promoted by UV₂₅₄ irradiation, as long as free chlorine was present in solution. Likewise, UV exposure was observed to amplify cyanogen chloride (CNCl) formation from chlorination of L-histidine, L-arginine, and glycine, up to the point of free chlorine depletion. The results from experiments involving UV irradiation of chlorinated swimming pool water were qualitatively consistent with the results of model experiments involving UV/chlorination of precursors in terms of the behavior of residual chlorine and DBPs measured in this study.The results indicate that UV₂₅₄ irradiation promotes several reactions that are involved in the formation and/or destruction of chlorinated N-DBPs in pool settings. Enhancement of DBP formation was consistent with a mechanism whereby a rate-limiting step in DBP formation was promoted by UV exposure. Promotion of these reactions also resulted in increases of free chlorine consumption rates.     

Untersuchungen zur Längssteifigkeit von Stahlstützen mit kastenförmigem Querschnitt

Experimental tests and theoretical analyses of longitudinal stiffness of closed cross‐sections steel columns. In structures made of thin‐walled elements it is of great importance to establish how the compressed elements change their stiffness while loading increases. Nonuniform change of longitudinal stiffness induces change of force and stress redistribution. More ductile elements take less loading and more stiff, tensed, ones are being overloaded. Columns with closed cross‐sections, box cross‐sections and hollow circular cross‐sections need to be distinguished from steel elements with longitudinal stiffness decreasing while loading increases. Shortening of column working in elastic‐plastic phase comes from material compression, cross‐section walls buckling and increased displacement of column as a whole. Imperfections that depend on fabrication process of cross‐section have a great influence on stiffness variation of an element. It can be designated, among other factors, from the equilibrium paths of tested elements. Those equilibrium paths, up to the limit point, were obtained by applying incremental method of numerical integration of equilibrium equations assuming initial displacements and residual stresses of column's walls and initial displacements of column's axes. Some numerical analyses were calculated using FEA software LUSAS. All theoretical analyses were verified by experimental tests carried out by the authors with full scale elements: box cross‐section columns – length 5280 mm, cold‐formed welded cross‐section columns – length 2000 mm. The research results and analyses by others were also used.     

An Integrative Theory of Urban Design

The ideas that inform urban design usually coalesce around contending approaches, each associated with one or two leading writers. This article finds that these approaches share an intellectual foundation: They implicitly acknowledge the “noncommodifiability” of the human experience across property boundaries. They share the view that good design seeks to reintegrate the human experience of urban form in the face of real estate markets that would treat land and buildings as discrete commodities. The great writers on urban design have more or less explicitly defended this intellectual position by appeal to the nebulous concept of the “organic.” Rather than just asserting that everything is part of an organic whole, this article identifies the integrative principles through which urban environments can transcend commodification. These principles include good form, legibility, vitality, and meaning.     

Netherlands Planning: The Higher Truth

Progressive planners—those who are involved in radical reform—confront dilemmas in their work that do not apply to traditional social reformers. Because they seek to transform society into something other than what it is, progressive planners must evolve new responses to everyday problems. At the same time, they must change commonly held perceptions of how society defines those problems. Finally, they cannot avoid working with traditional political and economic organizations. The ability of progressive planners to perceive and confront those dilemmas can affect the success of their initiatives.     

A Bold Vision and a Brand Identity for the Planning Profession

R. W. Firestone's Cityscape Pink is a bold image capturing the essence of a city. In this Longer View essay, Bruce McClendon argues that the profession of planning needs a similarly bold vision and compelling brand identity in order to claim its proper place among many competitors offering similar services. He aims to distinguish the planning profession in the eyes of the public and the minds of planners themselves. Three commenters respond with different perspectives on the status of the profession and how best to improve it.

Firestone is a psychotherapist with a PhD in clinical psychology from the University of Denver and the author of nine books. He grew up in the New York City area and opened his private practice in Los Angeles, treating patients suffering from schizophrenia. With a group of friends he has sailed to many parts of the world, and both his practice and his travels figure into the subjects of his artwork.

Planning has become a generic product in a confusing, overcrowded, and highly competitive marketplace. The public does not know what planning is or how to differentiate among planning specialists. Relying on a bold back-to-the-future approach, I argue that it is the production, administration, and implementation of comprehensive plans that once was and still is the profession's unique and distinctive technical competency and core mission. By using branding techniques to define, link, and reconnect planners with comprehensive planning, it will be possible to tell the planning story in a way that communicates the emotional benefits and value of the profession and strengthens the public's respect and appreciation for planners.     

Determination of mass density, dielectric, elastic, and piezoelectric constants of bulk GaN crystal

Mass density, dielectric, elastic, and piezoelectric constants of bulk GaN crystal were determined. Mass density was obtained from the measured ratio of mass to volume of a cuboid. The dielectric constants were determined from the measured capacitances of an interdigital transducer (IDT) deposited on a Z-cut plate and from a parallel plate capacitor fabricated from this plate. The elastic and piezoelectric constants were determined by comparing the measured and calculated SAW velocities and electromechanical coupling coefficients on the Z- and X-cut plates. The following new constants were obtained: mass density p = 5986 kg/m(3); relative dielectric constants (at constant strain S) ε(S)(11)/ε(0) = 8.6 and ε(S)(11)/ε(0) = 10.5, where ε(0) is a dielectric constant of free space; elastic constants (at constant electric field E) C(E)(11) = 349.7, C(E)(12) = 128.1, C(E)(13) = 129.4, C(E)(33) = 430.3, and C(E)(44) = 96.5 GPa; and piezoelectric constants e(33) = 0.84, e(31) = -0.47, and e(15) = -0.41 C/m(2).     

Semiautomated high-throughput extraction and cleanup method for the measurement of polybrominated diphenyl ethers and polybrominated and polychlorinated biphenyls in breast milk

A semiautomated extraction and cleanup method has been developed to measure eight polybrominated diphenyl ethers (PBDEs), 2,2',4,4',5,5'-hexabromobiphenyl (BB-153), and 2,2',4,4',5,5'-hexachlorobiphenyl (CB-153). The method employs solid-phase dispersion on diatomaceous earth in a solid-phase extraction cartridge followed by automated addition of internal standards ((13)C-labeled). Extraction is then performed using an automated modular solid-phase extraction system. The extraction procedure includes drying the sample on diatomaceous earth by pressurized nitrogen and eluting target analytes and lipids with dichloromethane. Lipid content is determined gravimetrically. Lipid determinations performed using this method are compared with other standard methods and with a certified reference material. A relative standard deviation of 7.9% was obtained for 130 determinations of the lipid content in a breast milk quality control sample. Final analytical determination of target analytes was performed by gas chromatography-isotope dilution high-resolution mass spectrometry. Relative standard deviations for the measurements of target analytes for which a labeled internal standard was available were below 10% for analytes at concentrations above 1 ng/g of lipid. Mean recoveries of the (13)C-labeled internal standards ranged from 60 to 89% for the eight PBDE congeners; 74 and 113% were recovered for BB-153 and CB-153, respectively.     

Steam purification for the removal of graphitic shells coating catalytic particles and the shortening of single-walled carbon nanotubes

Purification and shortening of single-walled carbon nanotubes (SWNTs) is carried out by treatment with steam. During the steam purification the graphitic shells coating the catalytic metal particles are removed. Consequently, the exposed catalytic particles can be easily dissolved by treatment with hydrochloric acid. No damage to the carbon nanotube tubular structure is observed, even after prolonged treatment with steam. Samples are characterized by HRTEM, TGA, magnetic measurements, Raman spectroscopy, AFM, and XPS.     

Plasmon resonant amplification of a hot electron-driven photodiode

Nano Research - We report plasmon resonant excitation of hot electrons in a photodetector based on a metal/oxide/metal (Au/Al2O3/graphene) heterostructure. In this device, hot electrons, excited...