Atmospheric pressure photoionization fourier transform ion cyclotron resonance mass spectrometry for complex mixture analysis

We have coupled atmospheric pressure photoionization (APPI) to a home-built 9.4-T Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometer. Analysis of naphtho[2,3-a]pyrene and crude oil mass spectra reveals that protonated molecules, deprotonated molecules, and radical molecular ions are formed simultaneously in the ion source, thereby complicating the spectra (>12 000 peaks per mass spectrum and up to 63 peaks of the same nominal mass), and eliminating the "nitrogen rule" for nominal mass determination of number of nitrogens. Nevertheless, the ultrahigh mass resolving power and mass accuracy of FT-ICR MS enable definitive elemental composition assignments, even for doublets as closely spaced as 1.1 mDa (SH3(13)C vs (12)C4). APPI efficiently ionizes nonpolar compounds that are unobservable by electrospray and allows nonpolar sulfur speciation of petrochemical mixtures.     

A human gastric simulator (HGS) to study food digestion in human stomach

The objective of this study was to develop an in vitro stomach model, the Human Gastric Simulator (HGS), for studying gastric digestion of foods. The HGS is designed in such a way as to simulate the continuous peristaltic movement of stomach walls, with similar amplitude and frequency of contraction forces as reported in vivo. The HGS mainly consists of a latex vessel, simulating the stomach chamber, and a series of rollers secured on belts that are driven by motor and pulleys to create a continuous contraction of the latex wall. It also incorporates gastric secretion, emptying systems, and temperature control that enable accurate simulation of dynamic digestion process for detailed investigation of the changes in the physical chemical properties of ingested foods. The simulated gastric contraction force demonstrates a similar pattern as in vivo stomach forces. The precise control of gastric secretion and emptying and the adjustable mechanical forces in the HGS provide a useful tool to study transformation of food constituents under simulated physiological conditions.     

Assessing anthropogenic pressures on estuarine fish nurseries along the Portuguese coast: a multi-metric index and conceptual approach

Estuaries are among the most productive ecosystems and simultaneously among the most threatened by conflicting human activities which damage their ecological functions, namely their nursery role for many fish species. A thorough assessment of the anthropogenic pressures in Portuguese estuarine systems (Douro, Ria de Aveiro, Mondego, Tejo, Sado, Mira, Ria Formosa and Guadiana) was made applying an aggregating multi-metric index, which quantitatively evaluates influences from key components: dams, population and industry, port activities and resource exploitation. Estuaries were ranked from most (Tejo) to least pressured (Mira), and the most influential types of pressure identified. In most estuaries overall pressure was generated by a dominant group of pressure components, with several systems being afflicted by similar problematic sources. An evaluation of the influence of anthropogenic pressures on the most important sparidae, soleidae, pleuronectidae, moronidae and clupeidae species that use these estuaries as nurseries was also performed. To consolidate information and promote management an ecological conceptual model was built to identify potential problems for the nursery function played by these estuaries, identifying pressure agents, ecological impacts and endpoints for the anthropogenic sources quantified in the assessment. This will be important baseline information to safeguard these vital areas, articulating information and forecasting the potential efficacy of future management options.     

Bilinear sparse coding for invariant vision

Recent algorithms for sparse coding and independent component analysis (ICA) have demonstrated how localized features can be learned from natural images. However, these approaches do not take image transformations into account. We describe an unsupervised algorithm for learning both localized features and their transformations directly from images using a sparse bilinear generative model. We show that from an arbitrary set of natural images, the algorithm produces oriented basis filters that can simultaneously represent features in an image and their transformations. The learned generative model can be used to translate features to different locations, thereby reducing the need to learn the same feature at multiple locations, a limitation of previous approaches to sparse coding and ICA. Our results suggest that by explicitly modeling the interaction between local image features and their transformations, the sparse bilinear approach can provide a basis for achieving transformation-invariant vision.     

Health and safety practices in the nanomaterials workplace: results from an international survey

This article reports the findings of an international survey of nanomaterials firms and laboratories regarding their environmental health and safety (EHS) programs, engineering controls, personal protective equipment (PPE), exposure monitoring, waste disposal, product stewardship, and risk beliefs. While many participants reported not believing that nanomaterials pose special risks, nanospecific EHS programs were still widely reported. Most nanospecific EHS programs appeared to build from general EHS programs but included nanospecific workplace engineering controls and recommendations for clothing, gloves, eye protection, and respirators. Organizations with nanospecific EHS programs also reported providing product (safe use) guidance to consumers. However, workplace monitoring and nanospecific waste disposal were uneven and were only associated with the subset of organizations believing in special risks. A majority of organizations expressed a need for more toxicological information and EHS guidance. Overall, this study suggests that nanomaterials firms and laboratories are already attentive to nanospecific EHS and product stewardship issues. However, improved risk communication is needed to further the implementation of related programs. Organizations that are wholly inattentive to EHS would likely engage in nanospecific EHS upon implementing a staffed, general EHS program.     

DDE in sediments of the Palos Verdes Shelf, California: in situ transformation rates and geochemical fate

From 1947 to 1971 the world's largest manufacturer of DDT discharged process wastes into the sewers of Los Angeles County. Roughly 870-1450 t of DDT were released to the ocean off Palos Verdes, CA, a portion of which (approximately 100 t) resides in sediments on the continental shelf and slope. The most abundant DDT compound in the sediments, p,p'-DDE, is degrading by reductive dechlorination, but the rate of transformation and factors controlling it are not well understood. In order to estimate in situ transformation rates and predict the long-term fate of p,p'-DDE, box cores were collected in 1992 and 2003 from a single location on the Palos Verdes Shelf and analyzed for 8 DDT compounds and 84 polychlorinated biphenyl (PCB) congeners. The PCBs show no evidence of dechlorination, and inventories did not change between 1992 and 2003. By contrast, the inventory of p,p'-DDE decreased by 43%, whereas that of p,p'-DDMU, the putative reductive dechlorination product, increased by 34%. The first-order transformation rate for p,p'-DDE at the study site is 0.051 +/- 0.006 yr(-1). A multistep reaction model suggests that inventories of p,p'-DDE and p,p'-DDMU will continue to decline, whereas that of p,p'-DDNU will reach a maximum around 2014.     

天津临港工业区地基土抗剪强度指标分析研究

介绍了天津临港工业区的工程地质条件,对该区深基坑支护设计中最常采用的快剪和固结快剪强度指标参数进行了统计分析,并查明该工业区不同土层直剪试验指标区域分布规律和特点,以指导该区基坑支护设计工作,为其提供科学的抗剪强度指标依据,从而保证基坑工程的经济安全。