Coagulation of humic substances and dissolved organic matter with a ferric salt: an electron energy loss spectroscopy investigation

Transmission electron microscopy (TEM) coupled with electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDXS) was used to investigate the coagulation of natural organic matter with a ferric salt. Jar-test experiments were first conducted with a reconstituted water containing either synthetic or natural extracts of humic substances, and then with a raw water from Moselle River (France). The characterization of the freeze-dried coagulated sediment by EELS in the 250-450 eV range, showed that Fe-coagulant species predominantly associate with the carboxylic groups of organic matter, and that this interaction is accompanied by a release of previously complexed calcium ions. The variation of Fe/C elemental ratio with iron concentration provides insightful information into the coagulation mechanism of humic substances. At acid pH, Fe/C remains close to 3 over the whole range of iron concentrations investigated, while a much lower atomic ratio is expected from the value of optimal coagulant dosage. This suggests that a charge neutralization/complexation mechanism is responsible for the removal of humic colloids, the aggregates being formed with both iron-coagulated and proton-neutralized organic compounds. At pH 8, the decrease in Fe/C around optimal coagulant concentration is interpreted as a bridging of stretched humic macromolecules by Fe-hydrolyzed species. Aggregation would then result from a competition between reconformation of humic chains around coagulant species and collision of destabilized humic material. EELS also enabled a fingerpriting of natural organic substances contained in the iron-coagulated surface water, N/C elemental analyses revealing that humic colloids are removed prior to proteinic compounds.     

The effects of disc degeneration and muscle dysfunction on cervical spine stability from a biomechanical study

Disc degeneration and muscle dysfunction are common spinal degenerations in the elderly. This in vitro study was carried out to investigate the effects of these two degenerative changes on spinal stability. The stability of nine porcine cervical spines (C2-T1) with mechanically simulated cervical muscles (sternocleidomastoid (SCM), splenius capitis (SPL), semispinalis capitis (SSC)) was tested before and after experiment-induced disc degeneration. The patterns of muscle recruitments included: no muscle recruitment, normal recruitment of SCM/SPL/SSC, and SCM/SPL/SSC muscle dysfunctions. The neutral zone (NZ) and the range of motion (ROM) in the sagittal plane were measured to determine spinal stability. The results showed that the NZ and the ROM of a degenerative spine were larger than those of an intact spine under no muscle recruitment, but not under muscle recruitments. For both intact and degenerative spines, the NZ and the ROM were greatest under no muscle recruitment, followed by SSC dysfunction, SCM dysfunction, and SPL dysfunction, and smallest under normal muscle recruitment. In conclusion, muscle recruitments stabilize both intact and degenerative cervical spines, while dysfunctional muscles do not maintain stability efficiently as normal muscles do. Thus, spinal stability is more significantly affected by muscle dysfunction than by disc degeneration. Muscle training is suggested for the elderly with spinal degeneration to improve stability.     

High efficiency multichannel collimator for structural studies of liquids and low-Z materials at high pressures and temperatures

A high efficiency multichannel collimator (MCC) device has been developed at the high pressure beamline ID27 of the European Synchrotron Radiation Facility to drastically reduce the x-ray background from the sample environment in the Paris-Edinburgh press. The main technical difficulty, which resides in the minimum slits size achievable using the classical mono-bloc design, has been resolved using an original concept based on a set of independent slits. Then, a very small slit size of 50 μm was manufactured resulting in a great improvement of the signal to background ratio. In addition, the transfer function of the MCC has been measured using the x-ray diffusion signal of a metal doped glass and efficiently applied to correct the raw data. The potential of this new device is illustrated in two challenging examples: iron-sulfur liquid structures and C(60) polymerization process at high pressure and high temperature.     

小浪底大坝防渗墙和灌浆工程特殊处理技术

本文介绍了在小浪底水利枢纽工程建造中地下混凝土防渗墙体系的不同施工技术。大坝的地下截渗和上游围堰防渗灌浆采用了不同的施工，包括岩石灌浆、帷幕灌浆、冲积地层中建造地下混凝土防渗墙和高压旋喷灌浆等技术。特别要说明的是在建造地下混凝土防治在墙体系中采用了许多新技术，进行了多项的技术革新，缩短了施工工期，解决了河床底底部地形轮廓条件下清的施工技术难题。     

Benefits, limitations and uncertainty of in situ spectrometry.

In situ spectrometers are comparable robust instruments and can be operated long term with relatively low maintenance demand. The decisive factor for their applicability is the development of a medium and installation location specific correlation model, which estimates the concentration of the requested target parameter from the measured absorption values. In some cases it might turn out, that the development of a single site specific correlation model is not sufficient, due to frequent and substantial variations of the (waste) water composition.In order to assess the total uncertainty of in situ spectrometry, a comprehensive lab test was carried out. It includes a detailed investigation of the uncertainty of CODreference methods (DIN and small tube tests), a precision analysis of the absorption spectra and the impact of those two factors on the total uncertainty of the COD(EQ) correlation model.     

An experimental design to optimize the flow extraction parameters for the selective removal of Fe(III) and Al(III) in aqueous samples using salicylic acid grafted on Amberlite XAD-4 and final determination by GF-AAS

In this paper, a multivariable approach has been applied for the selective removing of Fe(III) and Al(III), in the range 0-200 microg l(-1), in water samples onto a modified organic support (salicylic acid grafted on XAD-4). An empirical mathematical model was designed which establishes the relationship between the variation of the responses (extraction yields), and the variation of three factors (sample volume, sample percolation flow rate and amount of metallic ions present in the sample). To estimate the coefficients of the developed model, an uniform shell Doehlert design has been applied; these experiments consisted in GF-AAS determination of aluminium and iron amounts in eluates after percolation of samples through modified support. Results show a similar behaviour of the resin towards aluminium and iron with a preponderant effect of the percolation flow rate value; however this one is crucial for aluminium extraction and should be maintained below to 0.55 ml min(-1) to reach a 95% Al3+ extraction yield (versus 2.25 ml min(-1) for Fe3+). The optima determined by this experimental design approach have been further applied to the selective extraction of aluminium and iron from multielement synthetic samples and from real samples at the outlet of potable water treatment units.     

Limits of the quasi-induced exposure method when compared with the standard case-control design. Application to the estimation of risks associated with driving under the influence of cannabis or alcohol

The disparities between the quasi-induced exposure (QIE) method and a standard case–control approach with crash responsibility as disease of interest are studied. The 10,748 drivers who had been given compulsory cannabis and alcohol tests subsequent to involvement in a fatal crash in France between 2001 and 2003 were used to compare the two approaches. Odds ratios were assessed using conditional and unconditional logistic regressions. While both approaches found that drivers under the influence of alcohol or cannabis increased the risk of causing a fatal crash, the two approaches are not equivalent. They differ mainly with regards to the driver sample selected. The QIE method results in splitting the overall road safety issue into two sub-studies: a matched case–control study dealing with two-vehicle crashes and a case–control study dealing with single-vehicle crashes but with a specific control group. Using a specific generic term such as “QIE method” should not hide the real underlying epidemiological design. On the contrary, the standard case–control approach studies drivers involved in all type of crashes whatever the distribution of the responsibility in each crash. This method also known as “responsibility analysis” is the most relevant for assessing the overall road safety implications of a driver characteristic.     

Quantifying neutral base recombination and the effects ofcollector-base junction traps in UHV/CVD SiGe HBTs

This work quantifies neutral base recombination in UHV/CVD SiGe heterojunction bipolar transistors (HBTs) using calibrated two-dimensional (2-D) simulation. The simulated collector-base conductance through neutral base recombination (NBR) modulation is far below the experimentally observed values, and hence does not explain the measured output resistance degradation under forced-I_B operation. In spite of the output resistance degradation, these UHV/CVD SiGe HBTs have approximately the same base current as the silicon control, and hence higher current gain. Based on the observation of the majority carrier concentration limited recombination in the CB junction depletion layer, as opposed to the minority carrier concentration limited recombination in the neutral base, local presence of traps in the CB junction depletion layer is suggested. This explains the measured CB conductance modulation and the related output resistance degradation without compromising the current gain. Numerical simulations using traps locally introduced into the CB junctions successfully reproduced the measured collector-base conductance from simulation without appreciable degradation in current gain     

The effects of geometrical scaling on the frequency response andnoise performance of SiGe HBTs

We examine the geometrical scaling issues in SiGe HBT technology. Width Scaling, length scaling, and stripe-number scaling are quantified from a radio frequency (RF) design perspective at 2 GHz. We conclude that a SiGe HBT with emitter area A_E=0.5×20×6 μm² is optimum for low noise applications at J_c=0.1 mA/μm² and f=2 GHz using the design methodology, which guarantees optimal noise and input impedance matching with the simplest matching network. Finally, the optimal device sizes at f=4 and 6 GHz for low noise applications are also obtained using the same method