Rheology of polyflavonoid tannin–formaldehyde reactions before and after gelling. II. Hardener influence and comparison of different tannins

Good correspondence of the gel‐time values obtained by two different methods, G′ = G″ and 1/η₀→0, was observed for different types of natural and modified tannin extracts. The pH presents the predominant effect on both the activation energies and the gel times observed, while the proportion of a paraformaldehyde hardener has a much lesser effect on these parameters. The rate constants of the different phases of the reaction of polycondensation with formaldehyde, both before and after the gel point, were obtained for the six commercial tannin extracts tested. The viscoelastic properties of the different tannins/formaldehyde gels were measured. The gel stiffness S, relaxation coefficient n, and relaxation time λ were determined and their dependence on the proportion of the formaldehyde hardener, on the temperature, and on the type of tannin was determined. The gel stiffness S appears to be influenced considerably by the proportion of the formaldehyde hardener. Its value decreased as the percentage of the hardener increased: This was due to early network immobilization and the resulting lower level of crosslinking resulting from it. The influence on S of the temperature is not very pronounced. The relaxation coefficient n appears to depend mainly on the reactivity of the tannin used: The faster the reactivity, the higher was the value of n. This appears to be valid exclusively in tannin extracts where the colloidal state is still present, while it is not valid in extracts where the colloidal state was eliminated by, for example, solvent extraction. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 864–871, 2002     

High saturation solar light beam induced current scanning of solar cells

The response of the electrical parameters of photovoltaic cells under concentrated solar irradiance has been the subject of many studies performed in recent times. The high saturation conditions typically found in solar cells that are subjected to highly concentrated solar radiation may cause electrically active cell features to behave differently than under monochromatic laser illumination, normally used in light beam induced current (LBIC) investigations. A high concentration solar LBIC (S-LBIC) measurement system has been developed to perform localized cell characterization. The responses of silicon solar cells that were measured qualitatively include externally biased induced cell current at specific cell voltages, I(V), open circuit voltage, V(oc), and the average rate of change of the cell bias with the induced current, DeltaV/DeltaI(V), close to the zero bias region. These images show the relative scale of the parameters of a cell up to the penetration depth of the solar beam and can be obtained with relative ease, qualifying important electrical response features of the solar cell. The S-LBIC maps were also compared with maps that were similarly obtained using a high intensity He-Ne laser beam probe. This article reports on the techniques employed and initial results obtained.     

Inventory on the dietary assessment tools available and needed in africa: a prerequisite for setting up a common methodological research infrastructure for nutritional surveillance,research, and prevention of diet-related non-communicable diseases

Objective: To carry out an inventory on the availability, challenges, and needs of dietary assessment (DA) methods in Africa as a pre-requisite to provide evidence, and set directions (strategies) for implementing common dietary methods and support web-research infrastructure across countries. Methods: The inventory was performed within the framework of the “Africa's Study on Physical Activity and Dietary Assessment Methods” (AS-PADAM) project. It involves international institutional and African networks. An inventory questionnaire was developed and disseminated through the networks. Eighteen countries responded to the dietary inventory questionnaire. Results: Various DA tools were reported in Africa; 24-Hour Dietary Recall and Food Frequency Questionnaire were the most commonly used tools. Few tools were validated and tested for reliability. Face-to-face interview was the common method of administration. No computerized software or other new (web) technologies were reported. No tools were standardized across countries. Conclusions: The lack of comparable DA methods across represented countries is a major obstacle to implement comprehensive and joint nutrition-related programmes for surveillance, programme evaluation, research, and prevention. There is a need to develop new or adapt existing DA methods across countries by employing related research infrastructure that has been validated and standardized in other settings, with the view to standardizing methods for wider use.     

Structure and properties of amine‐hardened epoxy/benzoxazine hybrids: Effect of epoxy resin functionality

Bifunctional, trifunctional, and tetrafunctional epoxy resins (EP) were hardened with stoichiometric amount of 4,4′‐diaminodiphenyl methane in presence and absence of benzoxazine (BOX). The EP/BOX ratio of the hybrid systems was 100/0, 75/25, 50/50, and 25/75 wt %, respectively. Information on the structure of the hybrid systems was received from differential scanning calorimetry, dynamic‐mechanical thermal analysis, atomic force microscopy, and fractographic studies. The flexural and fracture mechanical properties of the EP/BOX hybrids were determined and compared to those of the reference EPs. The thermal degradation and fire resistance of the hybrids were also studied. It was found that the polymerized BOX was built in the network in from of nanoscale inclusions and acted as antiplasticizer. Incorporation of BOX enhanced the flexural modulus and strength and reduced the glass transition temperature of the parent EP. The fracture toughness and energy were practically not improved by hybridization with BOX. The charring and flame resistance were improved with increasing amount of BOX in the EP/BOX hybrids. The relative improvement in the latter was most prominent for the bifunctional EP/BOX systems. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Structure,thermal, and mechanical properties of DDM‐hardened epoxy/benzoxazine hybrids: Effects of epoxy resin functionality and ETBN toughening

Bifunctional, trifunctional, and tetrafunctional epoxy (EP) resins were hardened with stoichiometric amount of 4,4′‐diaminodiphenyl methane in presence and absence of benzoxazine (BOX). The EP/BOX ratio of the hybrid systems was constant, viz. 50/50 wt %. For the bifunctional EP, the EP/BOX range covered the ratios 75/25 and 25/75 wt %, as well. Epoxy‐terminated liquid nitrile rubber (ETBN) was incorporated in 10 wt % in the systems with trifunctional and tetrafunctional EP, and in 10, 15, and 20 wt % in the EP/BOX with bifunctional EP to improve their toughness. Information on the structure and morphology of the hybrid systems was received from differential scanning calorimetric, dynamic‐mechanical thermal analysis, atomic force microscopic, and scanning electron microscopic studies. The flexural, fracture mechanical properties, thermal degradation, and fire resistance of the EP/BOX and EP/BOX/ETBN hybrids were determined. It was found that some homopolymerized BOX was built in the EP/BOX conetwork in form of nanoscale inclusions, whereas ETBN formed micron scaled droplets of sea‐island structure. Incorporation of BOX improved the charring and fire resistance, enhanced the flexural modulus and strength, reduced the glass transition (T_g), the fracture toughness, and energy. Additional modification with ETBN decreased the charring, fire resistance, flexural modulus and strength, as well as T_g, however, improved the fracture toughness and especially the fracture energy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Current‐voltage characteristics of high‐concentration,photovoltaic arrays

The current–voltage ( I–V ) characteristics of photovoltaic (PV) systems have always been a good indicator of the overall performance of a system. The aim of this paper is to give an overview and elucidate the use of the I–V characteristics of concentrator PV (CPV) modules and arrays as an important diagnostic tool to identify factors that lower a system's performance and the types of mismatch that exist between series‐connected single‐junction cells within a module. Possible causes for mismatch between cells include factors such as; misalignment of optical elements and cells, nonuniform cell material parameters, uneven cell illumination due to dew, dust or degradation of the secondary and main optical elements. The different types of mismatch typically found in CPV are categorized and their effects on the resultant module I–V curves are discussed and shown. The effect of bypass diodes on the module's I–V curves is also illustrated. This paper also reports on, and interprets I–V measurements that were recorded for a commercially available point‐focus concentrator module under various real outdoor conditions. Copyright © 2004 John Wiley & Sons, Ltd.     

Immune Checkpoints,Inhibitors and Radionuclides in Prostate Cancer: Promising Combinatorial Therapy Approach

Emerging research demonstrates that co-inhibitory immune checkpoints (ICs) remain the most promising immunotherapy targets in various malignancies. Nonetheless, ICIs have offered insignificant clinical benefits in the treatment of advanced prostate cancer (PCa) especially when they are used as monotherapies. Current existing PCa treatment initially offers an improved clinical outcome and overall survival (OS), however, after a while the treatment becomes resistant leading to aggressive and uncontrolled disease associated with increased mortality and morbidity. Concurrent combination of the ICIs with radionuclides therapy that has rapidly emerged as safe and effective targeted approach for treating PCa patients may shift the paradigm of PCa treatment. Here, we provide an overview of the contextual contribution of old and new emerging inhibitory ICs in PCa, preclinical and clinical studies supporting the use of these ICs in treating PCa patients. Furthermore, we will also describe the potential of using a combinatory approach of ICIs and radionuclides therapy in treating PCa patients to enhance efficacy, durable cancer control and OS. The inhibitory ICs considered in this review are cytotoxic T-lymphocyte antigen 4 (CTLA4), programmed cell death 1 (PD1), V-domain immunoglobulin suppressor of T cell activation (VISTA), indoleamine 2,3-dioxygenase (IDO), T cell Immunoglobulin Domain and Mucin Domain 3 (TIM-3), lymphocyte-activation gene 3 (LAG-3), T cell immunoreceptor with Ig and ITIM domains (TIGIT), B7 homolog 3 (B7-H3) and B7-H4.     

The role of science in resolution of environmental crises at Kesterson Reservoir and Mono Lake, California

Two events in California's recent history have had a profound impact in shaping present and future water resources policy: the selenium contamination at Kesterson Reservoir and the battle to save Mono Lake. The irrigation-induced selenium toxicity discovered at Kesterson changed public perception of agriculture as a benign consumer of water, eroded the political power of the agricultural lobby, and has contributed to a revision in the allocation of water between the cities, agriculture and the environment. The Mono Lake Decisions of 1983 and 1994 set an equally important precedent in affirming the State's public trust obligation to preserve public resources and to reconsider previous water right allocations in the light of evolving knowledge and changing priorities. Both of these issues were important precursors for the current multibillion dollar State and Federal (CALFED) initiative to 'fix' the myriad of biologic, hydrologic and water quality problems of the San Francisco Bay estuary. In this paper, we compare the Kesterson and Mono Lake controversies and discuss the role of science and research in attempting to resolve these issues. We conclude by drawing linkages to the current CALFED initiative and suggesting implications for future water quality management in California's lakes and reservoirs.