Activated sludge exopolymers: separation and identification using size exclusion chromatography and infrared micro-spectroscopy

Extracellular polymeric substances were extracted from activated sludge using a resin exchange method and analyzed. The separation and identification of EPS were carried out by size exclusion chromatography and Fourier transform infrared micro-spectroscopy. Chromatograms of extracted EPS exhibited seven peaks. Proteins varying in molecular weights from 670 to 45 kDa were present in all the peaks. Polysaccharides corresponding to molecular weights of approximately 1 and approximately 0.5 kDa were present in only three peaks. Strong association of polysaccharides and proteins was observed. Infrared results revealed the presence of one type of polysaccharide and two types of proteins (A and B). Proteins differed mainly in the length of their associated alkyl chains and in the ratio of ester/acidic functionalities.     

Short-term memory and time estimation: Beyond the 2-second "critical" value.

The authors showed previously that when time intervals around two sec are reproduced concurrently with a memory task, intervals are positively related to duration of memory processing. However, some data in research on timing as well as in memory research suggest that 2 sec might be a critical duration beyond which different mechanisms or structures would support performance. This implies that the interference observed between memory processing and 2-sec productions could be specific to these durations, and would not be obtained with longer durations. In this experiment, intervals ranging from 1.85 to 6.45 sec were reproduced by participants (16 females and 12 males, aged 18-33 yrs), who were searching simultaneously for a memory probe. At all durations, reproductions were positively related to memory set size. These findings have implications with regards to previous research indicating a discontinuity around 2-3 sec in time perception. They suggest in particular that the role of memory is similar in reproduction of durations around 2 sec and of longer durations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Walking in a cube: novel metaphors for safely navigating large virtual environments in restricted real workspaces

Immersive spaces such as 4-sided displays with stereo viewing and high-quality tracking provide a very engaging and realistic virtual experience. However, walking is inherently limited by the restricted physical space, both due to the screens (limited translation) and the missing back screen (limited rotation). In this paper, we propose three novel locomotion techniques that have three concurrent goals: keep the user safe from reaching the translational and rotational boundaries; increase the amount of real walking and finally, provide a more enjoyable and ecological interaction paradigm compared to traditional controller-based approaches. We notably introduce the "Virtual Companion", which uses a small bird to guide the user through VEs larger than the physical space. We evaluate the three new techniques through a user study with travel-to-target and path following tasks. The study provides insight into the relative strengths of each new technique for the three aforementioned goals. Specifically, if speed and accuracy are paramount, traditional controller interfaces augmented with our novel warning techniques may be more appropriate; if physical walking is more important, two of our paradigms (extended Magic Barrier Tape and Constrained Wand) should be preferred; last, fun and ecological criteria would favor the Virtual Companion.     

A Survey of Ocean Simulation and Rendering Techniques in Computer Graphics

This paper presents a survey of ocean simulation and rendering methods in computer graphics. To model and animate the ocean’s surface, these methods mainly rely on two main approaches: on the one hand, those which approximate ocean dynamics with parametric, spectral or hybrid models and use empirical laws from oceanographic research. We will see that this type of methods essentially allows the simulation of ocean scenes in the deep water domain, without breaking waves. On the other hand, physically‐based methods use Navier–Stokes equations to represent breaking waves and more generally ocean surface near the shore. We also describe ocean rendering methods in computer graphics, with a special interest in the simulation of phenomena such as foam and spray, and light’s interaction with the ocean surface.     

The impact of driver age on lost life years for other road users in France: A population based study of crash-involved road users

BACKGROUND: One of the concerns in road safety is the threat older drivers may pose to other road users. Using the rate of lost life years, the present study provides a public health approach to quantify this potential threat. METHODS: A total of 1570686 motorised vehicle drivers or motorcycle riders and 652246 non-drivers, i.e. vehicle passengers, pedestrians and cyclists involved in injury crashes in France between 1996 and 2004, were included in a population based cross-sectional study. Fatality rates and rate of lost life years for each crash-involved driver age class were calculated for the drivers themselves and for other road users. RESULTS: The study has shown a significant reduction in the rate of lost life years for crash-involved other road users (whether passengers, pedestrians, cyclists or opposing drivers) as driver age increases. Other road users lost half as many years of life when involved in crashes with drivers aged over 85 than with drivers under 65 (1.26 and 2.32 per 100 expected remaining life years, respectively). CONCLUSION: Our findings suggest that among road users involved in injury crashes, older drivers are less dangerous for the other road users. By attributing other road users' lost life years to each driver age, this study represents a new contribution to the debate about ageing and road safety.     

Impact of a highly contaminated river on a more important hydrologic system: changes in organic markers

The Fensch River is a tributary of the Moselle River. It is a highly contaminated river that drains an industrial area. The objective of this preliminary study is to determine its impact on the Moselle River by analysing the extractable organic matter (EOM) coming from the sediments at the molecular scale. EOM is described in term of aromatic hydrocarbons, aliphatic hydrocarbons and polar compounds. EOM coming from Fensch River sediments is mainly composed of anthropogenic molecules. Aromatic hydrocarbons are dominated by parent Polycyclic Aromatic Hydrocarbons (PAHs) underlining the pyrogenic origin of this fraction. Aliphatic hydrocarbons consist of diagenetic hopanes and a broad UCM that are characteristics of thermal mature organic matter. Upstream the confluence the EOM of the Moselle River is mainly from vegetal origin. It is composed of high molecular weight n-alkanes with an odd over even predominance, degredation products of phytol and stigmasterol. The occurrence of PAHs and diagenetic hopanes underlines that the Moselle River is already contaminated before the confluence. The Fensch River input drastically changes the EOM of the Moselle River. Amount of PAHs is doubled and the fingerprints of both aliphatic hydrocarbons and polar compounds highlight the combination of both natural and anthropogenic sources.     

氢化脱氢钛粉末颗粒的整形及其机理研究

HDH(氢化脱氢)钛粉末颗粒形状不规则、流动性较差,不利于注射成形和提高其制品性能.本研究利用PCS系统对HDH钛粉末颗粒进行整形,考察了处理工艺,用扫描电镜和粒度分析表征处理结果,推测PCS的整形机理不是传统的粉碎过程,而是钛粉末颗粒的棱角被打磨掉再与大颗粒吸附嵌入,较好地解释了粒度分布等测试结果.整形后的HDH钛粉末颗粒尖锐的棱角被钝化,变为近球形,粉末的流动性显著提高.     

Formation of satellite droplets in flow-focusing junctions: volume and neck rupture

This work focuses on the rupture of the neck of a main droplet, leading to the formation of satellite droplets in a flow-focusing junction. The size of these satellites is determined by image analysis. Emphasis is given to the influence of viscosity and rheological behaviour of the fluids, using both Newtonian and non-Newtonian fluids as continuous phases. The scaling of the size of the satellite droplet with the capillary number of the continuous phase shows two different areas separated by a critical capillary number of 10^?2. Below this critical capillary number, the size of satellites hardly changes. Above this critical value, the size of the droplet increases almost linearly with the capillary number. This critical value appears also as a difference in shape of the rupture of the neck of the droplet for Newtonian continuous fluids: symmetrical for low capillary numbers and asymmetrical rupture of the neck of the droplet for higher capillary numbers. The higher the viscosity ratio (viscosity of dispersed phase/viscosity of continuous phase), the bigger is the main satellite droplet. For more viscous dispersed phases, numerous satellite droplets can be formed. When the continuous phase is non-Newtonian (polyacrylamide solutions) the number of satellites droplets is even higher and their sizes are found interdependent according to a cascade scenario.     

Single-stranded DNA binding protein-assisted fluorescence polarization aptamer assay for detection of small molecules

Here, we describe a new fluorescence polarization aptamer assay (FPAA) strategy which is based on the use of the single-stranded DNA binding (SSB) protein from Escherichia coli as a strong FP signal enhancer tool. This approach relied on the unique ability of the SSB protein to bind the nucleic acid aptamer in its free state but not in its target-bound folded one. Such a feature was exploited by using the antiadenosine (Ade)-DNA aptamer (Apt-A) as a model functional nucleic acid. Two fluorophores (fluorescein and Texas Red) were introduced into different sites of Apt-A to design a dozen fluorescent tracers. In the absence of the Ade target, the binding of the labeled aptamers to SSB governed a very high fluorescence anisotropy increase (in the 0.130-0.200 range) as the consequence of (i) the large global diffusion difference between the free and SSB-bound tracers and (ii) the restricted movement of the dye in the SSB-bound state. When the analyte was introduced into the reaction system, the formation of the folded tertiary structure of the Ade-Apt-A complex triggered the release of the labeled nucleic acids from the protein, leading to a strong decrease in the fluorescence anisotropy. The key factors involved in the fluorescence anisotropy change were considered through the development of a competitive displacement model, and the optimal tracer candidate was selected for the Ade assay under buffer and realistic (diluted human serum) conditions. The SSB-assisted principle was found to operate also with another aptamer system, i.e., the antiargininamide DNA aptamer, and a different biosensing configuration, i.e., the sandwich-like design, suggesting the broad usefulness of the present approach. This sensing platform allowed generation of a fluorescence anisotropy signal for aptamer probes which did not operate under the direct format and greatly improved the assay response relative to that of the most previously reported small target FPAA.