Détermination du bore inorganique dans l'Estuaire du Saint-Laurent

A precise and accurate method for the determination of inorganic boron in estuarine and coastal waters has been developed. The method takes into account the effects of ionic interactions in seawater on the electrode's junction potential, and on the ionization constant of the mannitol–borate complex. The analytical error is less than ±0.3% over the range of 0.35–4.45 mg B/kg seawater. This method, applied to 42 samples from the St. Lawrence Estuary, has allowed us to show that the B–Cl ratio varies in the region studied, and to localize regions that are deficient in dissolved inorganic boron.

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Urban Wastewater Discharge and Bacteriological Quality of Receiving Coastal Waters: Processes and Modelling

Water Science & Technology ◽

10.2166/wst.1993.0306 ◽

1993 ◽

Vol 27 (12) ◽

pp. 223-226

Author(s):

J.-F. Guillaud ◽

M. Pommepuy ◽

E. Dupray ◽

J.-C. Salomon ◽

B. Thouvenin

Keyword(s):

Coastal Zone ◽

Coastal Waters ◽

Wastewater Treatment Plants ◽

Enteric Bacteria ◽

Wastewater Discharge ◽

Urban Wastewater ◽

Bacteria Transport

The aim of this paper is to present some results of bacterial studies which were developed by IFREMER in coastal discharge areas of urban wastewaters; they are focused on the determination of bacterial inputs by wastewater treatment plants, the role of environmental factors on the enteric bacteria survival in the coastal zone, and the modelling of bacteria transport and disappearance in order to provide useful management information for minimizing faecal pollution in the coastal zone.

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Development of an HPLC-UV Method for Quantification of Stattic

Current Pharmaceutical Analysis ◽

10.2174/1573412914666180523092957 ◽

2019 ◽

Vol 15 (6) ◽

pp. 568-573

Author(s):

Soheil Sedaghat ◽

Ommoleila Molavi ◽

Akram Faridi ◽

Ali Shayanfar ◽

Mohammad Reza Rashidi

Keyword(s):

High Performance ◽

Accurate Method ◽

Plasma Samples ◽

Promising Target ◽

Relative Standard ◽

Dimerization Inhibitor ◽

Oncogenic Protein ◽

First Time ◽

Transcription 3

Background: Signal transducer and activator of transcription 3 (STAT3), an oncogenic protein found constitutively active in many types of human malignancies, is considered to be a promising target for cancer therapy. Objective: In this study for the first time, a simple and accurate method has been developed for the determination of a STAT3 dimerization inhibitor called stattic in aqueous and plasma samples. Methods: A reverse-phase high-performance liquid chromatography (RP-HPLC) composed of C18 column as stationary phase, and the mixture of acetonitrile (60%) and water (40%) as mobile phase with a UV detection at 215 nm were applied for quantification of stattic. The developed method was validated by Food and Drug Administration (FDA) guideline. Results: The method provided a linear range between 1-40 and 2.5-40 µg mL-1 for aqueous and plasma samples, respectively, with a correlation coefficient of 0.999. The accuracy (as recovery) of the developed method was found to be between 95-105% for aqueous medium and 85-115% for plasma samples. The precision (as relative standard deviation) for aqueous and plasma samples was less than 6% and 15%, respectively. The sensitivity of the developed method based on FDA guideline was 1 µg mL-1 for aqueous and 2.5 µg mL-1 for plasma samples. Conclusion: These results show that the established method is a fast and accurate quantification for stattic in aqueous and plasma samples.

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Is it necessary to calculate Young’s modulus in AFM nanoindentation experiments regarding biological samples?

Micro and Nanosystems ◽

10.2174/1876402912666200214123734 ◽

2020 ◽

Vol 12 ◽

Author(s):

S.V. Kontomaris ◽

A. Malamou ◽

A. Stylianou

Keyword(s):

Young’S Modulus ◽

Biological Samples ◽

Young's Modulus ◽

Reference Sample ◽

Nonlinear Behavior ◽

Accurate Method ◽

Accurate Solution ◽

Hertz Model ◽

Work Done

Background: The determination of the mechanical properties of biological samples using Atomic Force Microscopy (AFM) at the nanoscale is usually performed using basic models arising from the contact mechanics theory. In particular, the Hertz model is the most frequently used theoretical tool for data processing. However, the Hertz model requires several assumptions such as homogeneous and isotropic samples and indenters with perfectly spherical or conical shapes. As it is widely known, none of these requirements are 100 % fulfilled for the case of indentation experiments at the nanoscale. As a result, significant errors arise in the Young’s modulus calculation. At the same time, an analytical model that could account complexities of soft biomaterials, such as nonlinear behavior, anisotropy, and heterogeneity, may be far-reaching. In addition, this hypothetical model would be ‘too difficult’ to be applied in real clinical activities since it would require very heavy workload and highly specialized personnel. Objective: In this paper a simple solution is provided to the aforementioned dead-end. A new approach is introduced in order to provide a simple and accurate method for the mechanical characterization at the nanoscale. Method: The ratio of the work done by the indenter on the sample of interest to the work done by the indenter on a reference sample is introduced as a new physical quantity that does not require homogeneous, isotropic samples or perfect indenters. Results: The proposed approach, not only provides an accurate solution from a physical perspective but also a simpler solution which does not require activities such as the determination of the cantilever’s spring constant and the dimensions of the AFM tip. Conclusion: The proposed, by this opinion paper, solution aims to provide a significant opportunity to overcome the existing limitations provided by Hertzian mechanics and apply AFM techniques in real clinical activities.

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An Accurate Method for the Determination of Complex Coefficients of Single Crystal Piezoelectric Resonators II: Design of Measurement and Experiments

IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control ◽

10.1109/tuffc.2004.1295399 ◽

2004 ◽

Vol 51 (2) ◽

pp. 238-248

Author(s):

Xiao-Hong Du ◽

Qing-Ming Wang ◽

a.K. Uchino

Keyword(s):

Single Crystal ◽

Accurate Method ◽

Piezoelectric Resonators ◽

Complex Coefficients

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Benthic fluxes of dissolved organic nitrogen in the lower St. Lawrence estuary and implications for selective organic matter degradation

Biogeosciences ◽

10.5194/bg-10-7609-2013 ◽

2013 ◽

Vol 10 (11) ◽

pp. 7609-7622 ◽

Cited By ~ 13

Author(s):

M. Alkhatib ◽

P. A. del Giorgio ◽

Y. Gelinas ◽

M. F. Lehmann

Keyword(s):

Organic Matter ◽

Dissolved Organic Nitrogen ◽

Organic Nitrogen ◽

Bottom Water ◽

Estuarine Sediments ◽

Internal Source ◽

Lawrence Estuary ◽

Element Partitioning ◽

Sediment Porewaters ◽

St Lawrence Estuary

Abstract. The distribution of dissolved organic nitrogen (DON) and carbon (DOC) in sediment porewaters was determined at nine locations along the St. Lawrence estuary and in the gulf of St. Lawrence. In a previous manuscript (Alkhatib et al., 2012a), we have shown that this study area is characterized by gradients in the sedimentary particulate organic matter (POM) reactivity, bottom water oxygen concentrations, and benthic respiration rates. Based on the porewater profiles, we estimated the benthic diffusive fluxes of DON and DOC in the same area. Our results show that DON fluxed out of the sediments at significant rates (110 to 430 μmol m−2 d−1). DON fluxes were positively correlated with sedimentary POM reactivity and varied inversely with sediment oxygen exposure time (OET), suggesting direct links between POM quality, aerobic remineralization and the release of DON to the water column. DON fluxes were on the order of 30 to 64% of the total benthic inorganic fixed N loss due to denitrification, and often exceeded the diffusive nitrate fluxes into the sediments. Hence they represented a large fraction of the total benthic N exchange, a result that is particularly important in light of the fact that DON fluxes are usually not accounted for in estuarine and coastal zone nutrient budgets. In contrast to DON, DOC fluxes out of the sediments did not show any significant spatial variation along the Laurentian Channel (LC) between the estuary and the gulf (2100 ± 100 μmol m−2 d−1). The molar C / N ratio of dissolved organic matter (DOM) in porewater and the overlying bottom water varied significantly along the transect, with lowest C / N in the lower estuary (5–6) and highest C / N (> 10) in the gulf. Large differences between the C / N ratios of porewater DOM and POM are mainly attributed to a combination of selective POM hydrolysis and elemental fractionation during subsequent DOM mineralization, but selective adsorption of DOM to mineral phases could not be excluded as a potential C / N fractionating process. The extent of this C- versus N- element partitioning seems to be linked to POM reactivity and redox conditions in the sediment porewaters. Our results thus highlight the variable effects selective organic matter (OM) preservation can have on bulk sedimentary C / N ratios, decoupling the primary source C / N signatures from those in sedimentary paleoenvironmental archives. Our study further underscores that the role of estuarine sediments as efficient sinks of bioavailable nitrogen is strongly influenced by the release of DON during early diagenetic reactions, and that DON fluxes from continental margin sediments represent an important internal source of N to the ocean.

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