Analysis of transport phenomena in cellulose diacetate membranes. II — Pressure effects on permeability characteristics in reverse osmosis

Volume flux and solute rejection were determined at 25°C and pressures up to 60 atm for various cellulose diacetate membranes. For most of the membranes studied (Loeb-type or Manjikian-type membranes), an increase in test pressure induces a decrease in hydraulic permeability and an increase in selectivity, whatever the nature of the solute (electrolyte or glucide). Such effects are explained at a molecular level by a reversible loss of free water in the membrane without any modification of the polymer—water interactions. Furthermore, some membranes that exhibit a macroporous structure with thin polymeric walls, present a peculiar behavior under pressure, due to competition between these phenomena and irreversible effects of pore collapse.     

A high spin configuration for six-coordinated iron (IV) in an oxygen lattice

A simple model for the variation of crystal field and of covalency with the distortion of FeO₆ octahedra shows that Fe (IV) with ground term 5A_1g (d¹_xyd¹_yzd¹_zxd¹_z2d⁰_x2?_y2) can be stabilized in an elongated FeO₆ octahedron. Such an electronic configuration has been found actually in a Sr_0.5La_1.5Li_0.5Fe_0.5O₄ phase with K₂NiF₄ structure. Structural ($\text{c}\text{a}\text{? 3.46}$), magnetic (Curie constant $\text{C}\text{? 3.06}$) and Mössbauer resonance (isomer shift at room temperature relative to metallic Fe $\text{δ ? ? 0.19}\text{mms}{}^{\mathrm{?1}}$) studies illustrate this electronic configuration.     

Multiple-scattering-based lidar retrieval: method and results of cloud probings

Recent developments in the search for a practical method of exploiting the multiple-scattering contributions to lidar returns are consolidated in a robust retrieval algorithm. The theoretical basis is the small-angle diffusion approximation. This implies that the algorithm is limited to media of sufficient optical thickness to generate measurable multiple scattering and to geometries for which the receiver's footprint diameter is less than the scattering mean free path. The primary retrieval products are the range-resolved extinction coefficient and the effective particle diameter from which secondary products such as the particle volume mixing ratio and the extinction at other wavelengths can be calculated. We recall briefly earlier validation tests and present new data and analysis that demonstrate and quantify the solutions' accuracy. The results show that systematic lidar probings with the proposed multiple-scattering technique can provide valuable physical information on cloud formation and evolution.     

Fourier transform infra-red study of uniaxially oriented poly(2,6-dimethyl 1,4-phenylene oxide)-atactic polystyrene blends

Infra-red measurements of the dichroic ratio of absorption bands of atactic polystyrene-poly(2,6-dimethyl 1,4-phenylene oxide) blends provide a valuable method to investigate the orientation of the chains of both polymers. The results show that PPO and PS chains orient in a different way when subjected to an uniaxial strain, in spite of the compatible nature of the blend. The PPO orientational behaviour does not depend on PPO concentration in the studied concentration range (0–35%) while PS orientation regularly increases up to 25% PPO then remains constant.     

Convoys of social support: An intergenerational analysis.

Within the Convoy Model, social networks are viewed as dynamic hierarchic structures surrounding the individual throughout life. As a step toward empirical definition of convoy structure and function across the life span, a bicultural sample (N?=?159) of young adult women, their mothers, and their grandmothers were queried. Comparable results were obtained across generations and cultures with regard to network size, the amount of support provided by the network, and the nomination of close family members as primary sources of support. However, there was a marked shift across generations in the balance of familial vs friendship relations. Younger persons included fewer family members and more friends in their networks, and they received more support from friends. These cross-sectional results are consistent with the Convoy Model and suggest that longitudinal research is warranted. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Volatile sulphur compounds composition of monovarietal white wines

The sulphur compounds composition of wines produced experimentally from six white cultivars (Alvarinho, Loureiro, Trajadura, Pedernã, Azal Branco and Avesso) was evaluated during two consecutive vintages. Results show that wines could be differentiated according to their sulphur compounds content. In general, Loureiro, Trajadura and Pedernã cultivars led to wines with low concentrations of sulphur compounds; however, Loureiro wines were characterised by significant amounts of dimethyl sulphone, whereas Trajadura wines possessed a high content of 3-(methylthio)propyl acetate and 4-(methylthio)-1-butanol. Alvarinho and Avesso wines showed high levels of S-methyl thioacetate, 3-mercapto-1-propanol, 3-(ethylthio)-1-propanol and 3-methylthiopropionic acid. Significant amounts of 2-methyltetrahydrothiophen-3-one, cis- and trans-2-methyltetrahydrothiophen-3-ol were also found in Avesso wines. Azal Branco wines were low in 3-(methylthio)propyl acetate and 2-(methylthio)ethanol, and high contents in S-methyl thioacetate, 3-mercapto-1-propanol and 2-mercaptoethanol. A linear discriminant analysis of sulphur compounds levels showed a differentiation of wines according to their varietal origin.     

Electromagnetic Modeling of Quasi‐Square Open Metallic Ring Frequency Selective Surface Using Wave Concept Iterative Procedure

The wave concept iterative procedure (WCIP) is used to analyze a quasi‐square open metallic ring frequency selective surface (FSS). The quasi‐square open metallic ring FSS is dual‐polarized. When the incident plane wave is polarized in a direction parallel to the FSS’ coupled parallel strips, it shows two rejecting bands. Moreover, another rejecting band can be obtained if the source plane wave is perpendicularly polarized with respect to the FSS’ coupled parallel strips. The three resonant frequencies are inversely proportional to the length of the FSS’ coupled strips to provide an easy fine tuning of the FSS structure. The simulated results obtained using WCIP are compared to the measured results, and a good agreement is reported.     

Biobased packaging for improving preservation of fresh common mushrooms (Agaricus bisporus L.)

Freshness of common mushrooms was related to the internal atmosphere composition during modified atmosphere packaging (MAP) experiments at 20 °C and 80% RH with stretchable polyvinylchloride (PVC) film, paper, and the same paper coated with a wheat gluten solution. MAP with the stretchable film led to a detrimental deterioration of mushrooms after only one day of storage: dark brown blotches appeared and almost 30% of mushrooms exhibited open veil. This was due to the formation of condensed water at the inner surface of the material and onto mushrooms combined to a high O₂ partial pressure (16 kPa) in the headspace. Wheat gluten (WG) coated paper was the most effective to improve the shelf-life of mushrooms since it allowed the preservation of a fair colour, unbroken veils, and an acceptable texture during 3 days. This beneficial effect was attributed to the combination of a medium CO₂ (9.5 kPa) and low O₂ (2.5 kPa) partial pressure, without condensation. The main drawback of using WG-coated paper was its high water vapour permeability that led to an important weight loss (3.8 wt.% on day 3). However it did not affect the overall quality of mushrooms within the storage duration.

Industrial relevance

Even with the development of micro-perforated materials that provide the largest range of O₂ and CO₂ permeability values, several limitations are still encountered for synthetic MAP applications such as

– an insufficient perm-selectivity ratio that remains lower than 6 (value of 1 for micro-perforated material): generated atmosphere cannot reach both low O₂ and low CO₂ partial pressures and then are not adapted to CO₂-sensitive fresh produces.

– unattractive water condensation at the inner surface of the packaging that might occur due to a low water vapour permeability, favouring the development of microorganisms.

– their non biodegradability.

Previous studies reported a high selectivity ratio and a high water vapour permeability for biodegradable materials made from crops proteins (wheat gluten, for instance) that appeared well adapted for fresh fruits and vegetables preservation. However, despite low cost and such interesting functional properties, these materials exhibited poor mechanical properties and cannot be used as packaging material. Combination with other materials, such as cellulosic fibres, appeared to one way to get round this major drawback without losing its biodegradability. Indeed paper exhibits an environmental-friendliness potential (recyclability, sustainability, biodegradability, and compostability) and a high versatility in food packaging.By choosing common mushrooms, known to be sensitive to high CO₂ content, and a stretchable PVC film, commonly used to over-wrap mushrooms in tray (on European market), we demonstrate that this material was greatly less effective than a new biobased material (wheat gluten film coated onto paper) developed in collaboration with Smurfit Worldwide Research Center. This work confirms the interest in developing functionalised paper based packaging material with agro-based polymers adapted to the storage of fresh fruits and vegetable storage in ambient temperature.     

A new dual luminescent pillared cerium(IV)sulfate–diphosphonate

A new pillared cerium(IV) sulfate–diphosphonate with formula Ce₂(2H₂O)[(O₃PCH₂)–NC₁₀H₁₈N–(CH₂PO₃)(SO₄)₂] · 6H₂O has been hydrothermally synthesized and its structure has been solved ab initio from laboratory X-ray powder diffraction data.The luminescent and thermal properties of this compound have been preliminarily studied and the encouraging results place it in the field of functional hybrid materials.