Surface and interfacial fourier transform infrared spectroscopic studies of latexes. XIV. Surface phase separation in polystyrene/poly-n-butyl acrylate latex films

This study focuses on the behavior of sodium dioctylsulfosuccinate (SDOSS) in 50/50 w/w % polystyrene/poly(butyl acrylate) (p-Sty/p-BA) latex films. Specifically, mobility and orientation are examined in the context of the film formation by the use of dynamic mechanical thermal analysis and attenuated total reflectance (ATR) Fourier transform infrared (FT-IR) spectroscopy. While for the homopolymer blends of p-Sty and p-BA, two T_g values resulting from a phase separation of p-Sty and p-BA phases are observed, only a single T_g is detected for a copolymer of the same mixture, indicating a single phase within the film. ATR FTIR spectroscopic data indicate that the phase separation of p-Sty and p-BA blends does not occur uniformly across the film. After coalescence, p-Sty particles produce a significant degree of stratification at approximately 1.6 μm from the film surface. At this depth, the polystyrene rings assume preferentially parallel orientation to the film surface. At the same time, the hydrophilic groups of SDOSS surfactant (SO⁻₃Na⁺) are oriented preferentiallyparallel to the surface. Under high relative humidity conditions, water is able to diffuse into the film and swells the surface layers, thus causing them to expand. As a result, the top, predominately poly-n-BA surface becomes “thicker», and p-Sty phase appears to be near 2.3 μm from the surface. The polystyrene rings maintain their preferential parallel orientation to the surface, but the hydrophilic groups of SDOSS are able to diffuse into the film with the water uptake and are thus not present at the filmair interface. © 1996 John Wiley & Sons, Inc.     

Ecosystemic effects of salmon farming increase mercury contamination in wild fish

Net-pen salmon aquaculture has well-known effects on coastal ecosystems: farm waste increases sediment organic content and the incidence of sediment anoxia, supports increased production of deposit-feeding invertebrates, and attracts higher densities of demersal fish and other mobile carnivores. These impacts are widely considered to be localized and transitory, and are commonly managed by imposing a period of fallowing between cycles of production. The implications of these ecosystemic effects for contaminant cycling, however, have not previously been considered. We found elevated levels of mercury in demersal rockfishes near salmon farms in coastal British Columbia, Canada, attributable to a combination of higher rockfish trophic position and higher mercury levels in prey near farms. Mercury concentrations in long-lived species such as rockfishes change over a longer time scale than cycles of production and fallowing, and thus at least some important effects of fish farms may not be considered transitory.     

An Industrial Method for Determining the Amount of Organics in Representative Samples of Aluminum Scrap

In recycling plants, especially those specializing in the recycling of low-grade aluminum scrap for wrought aluminum alloys, timely and accurate information about the amount of organics and other impurities in the incoming scrap is an important parameter in achieving both economic benefits and standard metallurgical quality of the recycled metal. To use aluminum scrap combined with organics as a source of aluminum for producing wrought aluminum alloys of standard quality, its metallurgical composition and the content of organic and other impurities should be quickly and cost-effectively analyzed on representative samples. In this work, an industrial thermogravimetric/differential thermal analysis of representative scrap samples was developed as an efficient analytical methodology for analyzing the humidity and organic impurities in incoming scrap. When performed in continuous mode, under a flowing atmosphere of argon with 1?wt.% of oxygen, this methodology enables a routine measurement of the humidity, the quantity of organics, and the carbon content in representative samples of incoming scrap in less than 15?min within an accuracy of ±0.5%.     

On-target labeling of intracellular metabolites combined with chemical mapping of individual hyphae revealing cytoplasmic relocation of isotopologues

A microscale analytical platform integrating microbial cell culture, isotopic labeling, along with visual and mass spectrometric imaging with single-cell resolution has been developed and applied in the monitoring of cellular metabolism in fungal mycelium. The method implements open chips with a two-dimensional surface pattern composed of hydrophobic and hydrophilic zones. Two hydrophilic islands are used as medium reservoirs, while the hydrophobic area constitutes the support for the growing aerial hyphae, which do not have direct contact with the medium. The first island, containing (12)C(6)-glucose medium, was initially inoculated with the mycelium (Neurospora crassa), and following the initial incubation period, the hyphae progressed toward the second medium island, containing an isotopically labeled substrate ((13)C(6)-glucose). The (13)C atoms were gradually incorporated into cellular metabolites, which was revealed by MALDI-MS. The fate of the chitin-biosynthesis precursor, uridine diphosphate N-acetylglucosamine (UDP-GlcNAc), was monitored by recording mass spectra with characteristic isotopic patterns, which indicated the presence of various (12)C/(13)C isotopologues. The method enabled mapping the (13)C-labeled UDP-GlcNAc in fungal mycelium and recording its redistribution in hyphae, directly on the chip.     

Velocity measurement by vibro-acoustic Doppler

We describe the theoretical principles of a new Doppler method, which uses the acoustic response of a moving object to a highly localized dynamic radiation force of the ultrasound field to calculate the velocity of the moving object according to Doppler frequency shift. This method, named vibro-acoustic Doppler (VAD), employs two ultrasound beams separated by a slight frequency difference, Δf, transmitting in an X-focal configuration. Both ultrasound beams experience a frequency shift because of the moving objects and their interaction at the joint focal zone produces an acoustic frequency shift occurring around the low-frequency (Δf) acoustic emission signal. The acoustic emission field resulting from the vibration of the moving object is detected and used to calculate its velocity. We report the formula that describes the relation between Doppler frequency shift of the emitted acoustic field and the velocity of the moving object. To verify the theory, we used a string phantom. We also tested our method by measuring fluid velocity in a tube. The results show that the error calculated for both string and fluid velocities is less than 9.1%. Our theory shows that in the worst case, the error is 0.54% for a 25° angle variation for the VAD method compared with an error of -82.6% for a 25° angle variation for a conventional continuous wave Doppler method. An advantage of this method is that, unlike conventional Doppler, it is not sensitive to angles between the ultrasound beams and direction of motion.     

Critical parameters for the scale-up synthesis of quantum dots

The optical properties of quantum dots strongly depend on the synthesis conditions including the reagent grade of the chemicals. We developed a synthesis set-up allowing the reproducible preparation of quantum dots with a high control over chemical and physical parameters. Here, we report on the effects of the injection speed, the stirring velocity and the reagent grade of the chemicals on the photoluminescence behaviour of CdSe quantum dots. Additionally we compared the commonly used hot-injection method with a novel one-pot approach leading to a slightly larger particle size distribution of the resulting high quality quantum dots in the latter case.     

北京昌平东沙河两岸城市设计

昌平东沙河两岸规划设计项目旨在彰显昌平区的内在气质。我们通过使用中国传统建筑尺度．着重同时塑造开放空间和私密空间,采用传统建筑材料等手段．力图将建筑植根于昌平．植根于中国。与此同时,我们采用了更加现代的材料表现方法重塑传统．更加动感的几何体突破传统,这使我们的设计不仅反映了昌平的昨天,更反映了昌平区明天的发展气象。五组地块的建筑穿插于绿带之间．形成朝向中心绿化区的动态效果。