Novel blue emitters based on pi-conjugated block copolymers

A series of new phenyl-based conjugated copolymers has been synthesized and investigated by vibrational and photoluminescence spectroscopy (PL). The materials are: poly( 1,4-phenylene-alt-3,6-pyridazine) (COP-PIR), poly(9,9-dioctylfluorene)-co-quaterphenylene (COP-PPP) and poly[(1,4-phenylene-alt-3,6-pyridazine)-co-(1,4-phenylene-alt-9,9-dioctylfluorene)] (COP-PIR-FLUOR), with 3.5% of fluorene. COP-PPP and COP-PIR-FLUOR have high fluorescence quantum yields in solution. Infrared and Raman spectra were used to check the chemical structure of the compounds. The copolymers exhibit blue emission ranging front 2.8 to 3.6 eV when excited at E(exc)=4.13 eV. Stokes-shift Values were estimated on pristine samples in their condensed state from steady-state PL-emission and PL-excitation spectra. They suggest a difference in the torsional angle between the molecular configuration of the polymer blocks at the absorption and PL transitions and also in the photoexcitation diffusion. Additionally, the time-resolved PL of these materials has been investigated by using 100 fs laser pulses at E(exc)=4.64 eV and a streak camera. Results show very fast biexponential kinetics for the two fluorene-based polymers with decay times below 300 ps indicating both intramolecular, fast radiative recombination and migration of photogenerated electron-hole pairs. By contrast, the PL of COP-PIR is less intense and longer lived, indicating that excitons are confined to the chains in this polymer. (C) 2008 Elsevier B.V. All rights reserved.

Linear viscoelasticity of styrenic block copolymers-clay nanocomposites

In this work, the rheological behavior of block copolymers with different morphologies (lamellar, cylindrical, spherical, and disordered) and their clay-containing nanocomposites was studied using small amplitude oscillatory shear. The copolymers studied were one asymmetric starblock styrene-butadiene-styrene copolymer and four styrene-ethylene/butylenes-styrene copolymers with different molecular architectures, one of them being modified with maleic anhydride. The nanocomposites of those copolymers were prepared by adding organophilic clay using three different preparation techniques: melt mixing, solution casting, and a hybrid melt mixing-solution technique. The nanocomposites were characterized by X-ray diffraction and transmission electron microscopy, and their viscoelastic properties were evaluated and compared to the ones of the pure copolymers. The influence of copolymer morphology and presence of clay on the storage modulus (G`) curves was studied by the evaluation of the changes in the low frequency slope of log G` x log omega (omega: frequency) curves upon variation of temperature and clay addition. This slope may be related to the degree of liquid- or solid-like behavior of a material. It was observed that at temperatures corresponding to the ordered state, the rheological behavior of the nanocomposites depended mainly on the viscoelasticity of each type of ordered phase and the variation of the slope due to the addition of clay was small. For temperatures corresponding to the disordered state, however, the rheological behavior of the copolymer nanocomposites was dictated mostly by the degree of clay dispersion: When the clay was well dispersed, a strong solid-like behavior corresponding to large G` slope variations was observed.

WATER ACTIVITY OF AQUEOUS SOLUTIONS OF ETHYLENE OXIDE-PROPYLENE OXIDE BLOCK COPOLYMERS AND MALTODEXTRINS

The water activity of aqueous solutions of EO-PO block copolymers of six different molar masses and EO/PO ratios and of maltodextrins of three different molar masses was determined at 298.15 K. The results showed that these aqueous solutions present a negative deviation from Raoult`s law. The Flory-Huggins and UNIFAC excess Gibbs energy models were employed to model the experimental data. While a good agreement was obtained with the Flory-Huggins equation, discrepancies were observed when predicting the experimental behavior with the UNIFAC model. The water activities of ternary systems formed by a synthetic polymer, maltodextrin and water were also measured and used to test the predictive capability of both models.

Removal of selected metals from drinking water using modified powdered block carbon

This paper presents the possible alternative removal options for the development of safe drinking water supply in the trace elements affected areas. Arsenic and chromium are two of the most toxic pollutants, introduced into natural waters from a variety of sources and causes various adverse effects on living bodies. Performance of three filter bed method was evaluated in the laboratory. Experiments have been conducted to investigate the sorption of arsenic and chromium on carbon steel and removal of trace elements from drinking water with a household filtration process. The affinity of the arsenic and chromium species for Fe/Fe(3)C (iron/iron carbide) sites is the key factor controlling the removal of the elements. The method is based on the use of powdered block carbon (PBC), powder carbon steel and ball ceramic in the ion-sorption columns as a cleaning process. The PBC modified is a satisfactory and practical sorbent for trace elements (arsenite and chromate) dissolved in water.

On the basic reproduction number and the topological properties of the contact network: An epidemiological study in mainly locally connected cellular automata

We study the spreading of contagious diseases in a population of constant size using susceptible-infective-recovered (SIR) models described in terms of ordinary differential equations (ODEs) and probabilistic cellular automata (PCA). In the PCA model, each individual (represented by a cell in the lattice) is mainly locally connected to others. We investigate how the topological properties of the random network representing contacts among individuals influence the transient behavior and the permanent regime of the epidemiological system described by ODE and PCA. Our main conclusions are: (1) the basic reproduction number (commonly called R(0)) related to a disease propagation in a population cannot be uniquely determined from some features of transient behavior of the infective group; (2) R(0) cannot be associated to a unique combination of clustering coefficient and average shortest path length characterizing the contact network. We discuss how these results can embarrass the specification of control strategies for combating disease propagations. (C) 2009 Elsevier B.V. All rights reserved.

The sorption of toxic elements onto natural zeolite, synthetic goethite and modified powdered block carbon

Inorganic elements analyses of Carapicuiba lake reveal that As, Cr, Pb and Mn are above the recommended drinking water standards. The mean total concentrations of toxic elements in surface water decrease in the order Mn > Cr > Pb > As. At elevated concentrations, toxic elements like Cr can accumulate in soils and enter the food chain, leading to serious health hazards and threatening the long-term sustainability of the local ecosystem. Absorbing materials has often been used to improve water quality. In this investigation three types of material were studied: the natural zeolite (mordenite); synthetic goethite and the powdered block carbon modified. The adsorption of Pb(2+) and Mn(2+) onto natural zeolite as a function of their concentrations was studied at 24 degrees C by varying the metal concentration from 100 to 400 mg L(-1) while keeping all other parameters constant. The low-cost zeolites removed Pb from water without any pretreatment at pH values <6. The maximum adsorption attained was as follows: Pb(2+) 78.7% and Mn(2+) 19.6%. The modified powdered block carbon effectively removed As(V) and Cr(VI) while goethite removed more chromate than arsenate in the pH range 5-6. Results of this study will be used to evaluate the application these materials for the treatment of the Carapicuiba lake`s water.

MACRONUTRIENTS UPTAKE BY POTATO (Solanum tuberosum L.) IN SEED-TUBER PRODUCTION

In greenhouse potato cultivation, mineral nutrition is one of the main factors contributing to high yields and better product quality. Knowledge about the amount of nutrients accumulated in the plants at each growing phase provides important information that helps the establishment of a more balanced fertilizer application. The objective of this research was to determine the time course of macronutrients uptake and accumulation in potato plants for seed-tuber production, grown in nutrient solution. The experiment was carried out in a greenhouse, using in vitro material from the pre-basic category of the `Atlantic` variety. The plants were collected weekly from 14 days after transplanting (DAT) until 70 DAT The experimental design was a completely randomized block with 9 treatments to sampling times and four replicates. The highest nutrient requirement in the plant shoot occurred at the periods between 28 and 56 DAT while in the tubers it was after 49 DAT The maximum accumulation sequence of macronutrients was K > N > S > Ca > P > Mg.

Nitrogen fertilization in common bean crops under no-tillage and conventional systems.

Nitrogen fertilization in common bean crops under no-tillage and conventional systems. Nitrogen fertilizer is necessary for high yields in common bean crops and N responses under conditions of no-tillage and conventional systems are still basic needs. Thus, the objective of this research was to evaluate the effect of N application and common bean yield in no-tillage and conventional systems. The experimental design was a randomized block in a factorial scheme (2x8+1) with four replications. The treatments were constituted by the combination of two N doses (40 and 80 kg ha(-1)) applied at side dressing at eight distinct stadia during vegetative development of the common bean (V(4-3), V(4-4), V(4-5), V(4-6), V(4-7), V(4-8), V(4-9) and V(4-10)), in addition to a control plot without N in side dressing. The experiment was conducted over two years (2002 and 2003) in no-tillage on millet crop residues and conventional plow system. It was concluded that N fertilizer at the V(4) stadium of common bean promotes similar seed yields in no-tillage and conventional systems. Yield differences between no-tillage and conventional systems are inconsistent in the same agricultural area.

Enhanced fibroblast adhesion and proliferation on electrospun fibers obtained from poly(isosorbide succinate-b-L-lactide) block copolymers

Block copolymers containing isosorbide succinate and L-lactic acid repeating units with different mass compositions were synthesized in two steps: bulk ring-opening copolymerization from L-lactide and poli(isosorbide succinate) (PIS) preoligomer, in the presence of tin(II) 2-ethylhexanoate as catalyst. followed by chain extension in solution by using hexamethylene diisocyanate. Poly(L-lactide) (PLLA) and a chain extension product from PIS were also obtained, for comparison. SEC, (1)H and (13)C NMR, MALDI-TOFMS, WAXD, DSC, TG, and contact angle measurements were used in their characterization. The incorporation of isosorbide succinate into PLLA main backbone had minor effect on the thermal stability and the T(g) of the products. However, it reduced the crystallinity and increased the surface energy in relation to PLLA. Nonwoven mats of the block copolymers and PLLA obtained by electrospinning technique were submitted to fibroblasts 3T3-L1 cell culture. The copolymers presented enhanced cell adhesion and proliferation rate as revealed by MTT assay and SEM images. (C) 2009 Elsevier Ltd. All rights reserved.

Influence of Pluronic (R) F68 on Ceftazidime Biological Activity in Parenteral Solutions

beta-Lactam antimicrobials are known to have a low concentration/therapeutic response. However, extending the period in which beta-lactam are free in the plasma does directly influence therapeutic outcomes. The objective of this study was to evaluate the influence of Pluronic (R) F68 on the antimicrobial activity of ceftazidime when admixed with aminophylline in parenteral solutions by the evaluation of its minimal inhibitory concentration (MIC) within 24 h. Ceftazidime, aminophylline, and Pluronics (R) F68 were evaluated using the MIC method against Escherichia coli and Pseudomonas aeruginosa, with these compounds individually and associated in the same parenteral solutions. When Pluronics (R) F68 was admixtured with ceftazidime alone or with ceftazidime and aminophylline, it was possible to observe lower MIC values not only at 24 h but also at 0 h for both microorganisms. This indicates that Pluronics (R) F68 may be able to enhance ceftazidime antimicrobial activity in the presence or absence of aminophylline. This fact suggests that Pluronics (R) F68 can be applied to allow the administration of ceftazidime under continuous infusion in parenteral solutions, beneficiating hospital pharmacotherapy. It may also be possible to reduce ceftazidime doses in formulations achieving the same therapeutic results. (C) 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 100:715-720, 2011

Quercetin inhibits UV irradiation-induced inflammatory cytokine production in primary human keratinocytes by suppressing NF-kappa B pathway

Background: Topical flavonoids, such as quercetin, have been shown to reduce ultraviolet (UV) irradiation-mediated skin damage. However, the mechanisms and signaling pathways involved in this protective effect are not clear. UV irradiation leads to activation of two major signaling pathways, namely nuclear factor kappa B (NF-kappa B) and activator protein-1 (AP-1) pathways. Activation of NF-kappa B pathway by UV irradiation stimulates inflammatory cytokine expression, whereas activation of AP-1 pathway by UV irradiation promotes matrix metalloproteinase (MMP) production. Both pathways contribute to UV irradiation-induced skin damage, such as photoaging and skin tumor formation. Objective: To elucidate the underlying mechanism, we examined the effect of quercetin on UV irradiation induced activation of NF-kappa B and AP-1 pathways. Methods: Primary human keratinocytes, the major skin cell type subjected to physiological solar UV irradiation, were used to study the effects of quercetin on UV irradiation-induced signal transduction pathways. Results: Quercetin decreased UV irradiation-induced NF-kappa B DNA-binding by 80%. Consequently, quercetin suppressed UV irradiation-induced expression of inflammatory cytokines IL-1 beta (similar to 60%), IL-6 (similar to 80%), IL-8 (similar to 76%) and TNF-alpha (similar to 69%). In contrast, quercetin had no effect on UV irradiation activation of three MAP kinases, ERK, JNK, or p38. Accordingly, induction of AP-1 target genes such as MMP-1 and MMP-3 by UV irradiation was not suppressed by quercetin. Conclusion: Our data indicate that the ability of quercetin to block UV irradiation-induced skin inflammation is mediated, at least in part, by its inhibitory effect on NF-kappa B activation and inflammatory cytokine production. (C) 2011 Japanese Society for Investigative Dermatology. Published by Elsevier Ireland Ltd. All rights reserved.

Evaluation of Some Biological Aspects of the Presence of Abrasive Silica and Thickening Silica in Basic Formulations of Dentifrices

The aim of this study was to evaluate some biological characteristics and toxicity of basic formulations of dentifrices containing such substances, and to compare them with two existing products in market which also contains silic in their formulations. In this way, it was evaluated some biological parameters: weight of the animals, oral toxicity, hematological parameters, urinary analysis, and histological evaluation. The thrombocytes were also statistically at normal levels. The glutamate-pyruvate transaminase (TGP) showed normal aspect in 5 of the tested groups, as in control. Meanwhile, the oxalacetic transaminase (AST) in one group had a small increase in the control group. Regarding urine, in exception the rats of one group, the rats of the 4 other experimental groups showed leukocytosis urinary statistically higher than the control group. The histological evaluation of the animals showed that specimens from liver, stomach, kidney and submandibular gland presented normal aspects for these organs, without significant characteristics related to inflammatory infiltrates in any of the 6 samples tested in their respective groups.

Sub-Chronic Exposure to Methylmercury at Low Levels Decreases Butyrylcholinesterase Activity in Rats

In this study, we examined the effects of low levels and sub-chronic exposure to methylmercury (MeHg) on butyrylcholinesterase (BuChE) activity in rats. Moreover, we examined the relationship between BuChE activity and oxidative stress biomarkers [delta-aminolevulinic acid dehydratase (delta-ALA-D) and malondialdehyde levels (MDA)] in the same animals. Rats were separated into three groups (eight animals per group): (Group I) received water by gavage; (Group II) received MeHg (30 mu g/kg/day) by gavage; (Group III) received MeHg (100 mu g/kg/day). The time of exposure was 90 days. BuChE and ALA-D activities were measured in serum and blood, respectively; whereas MDA levels were measured in plasma. We found BuChE and ALA-D activities decreased in groups II and III compared to the control group. Moreover, we found an interesting negative correlation between plasmatic BuChE activity and MDA (r = -0.85; p < 0.01) and a positive correlation between plasmatic BuChE activity and ALA-D activities (r = 0.78; p < 0.01), thus suggesting a possible relationship between oxidative damage promoted by MeHg exposure and the decrease of BuChE activity. In conclusion, long-term exposure to low doses of MeHg decreases plasmatic BuChE activity. Moreover, the decrease in the enzyme is strongly correlated with the oxidative stress promoted by the metal exposure. This preliminary finding highlights a possible mechanism for MeHg to reduce BuChE activity in plasma. Additionally, this enzyme could be an auxiliary biomarker on the evaluation of MeHg exposure.

Expression of Human Recombinant Antibody Fragments Capable of Partially Inhibiting the Phospholypase Activity of Crotalus durissus terrificus Venom

Crotoxin is the main toxic component of the South American rattlesnake Crotalus durissus terrificus venom. It is composed of two different subunits: CA, crotapotin, and CB (basic subunit of cortoxin isolated from C. d. terrificus), a weakly toxic phospholipase A(2) with high enzymatic activity. The phospholipases A(2) are abundant in snake venoms and are responsible for disruption of cell membrane integrity via hydrolysis of its phospholipids. However, in addition to their normal digestive action, a wide range of pharmacological activities, such as neurotoxic, myotoxic, oedema-inducing, hypotensive, platelet-aggregating, cardiotoxic, and anticoagulant effects have been attributed to venom phospholipases A(2). In this study, we used a non-immune human single-chain fragment variable library, Griffin.1 (Medical Research Council, Cambridge, UK) for selection of recombinant antibodies against antigens present in C. d. terrificus venom and identification of specific antibodies able to inhibit the phospholipase activity. Two clones were identified as capable of inhibiting partially this activity in vitro. These clones were able to reduce in vivo the myotoxic and oedema-inducing activity of CB and the lethality of C. d. terrificus venom and crotoxin, but had no effect on the in vitro anticoagulant activity of CB. These results demonstrate the potential of using recombinant single-chain fragment variable libraries in the production of antivenoms.

Enzymatic and structural characterization of a basic phospholipase A(2) from the sea anemone Condylactis gigantea

This work aimed at the isolation and structural/functional characterization of a phospholipase A(2) (CgPLA(2)) from the extract of the anemone Condylactis gigantea. CgPLA2 was isolated with a high purity level through three chromatographic steps, showing pT8.6 and molecular weights of 14,500 and 29,000 for the monomer and dimer, respectively. CgPLA2 showed a high catalytic activity upon fluorescent phospholipids inducing no direct hemolytic activity. This enzyme, which is Ca2+-dependent, showed a lower stability against temperature and pH variations when compared with snake venom enzymes. The enzymatic activity was significantly reduced or completely abolished after chemical modification of CgPLA2 with BPB. Its cDNA was then obtained, with 357 base pairs which codified for a mature protein of 119 amino acid residues. A comparative analysis of the primary structure of CgPLA2 revealed 84%, 61%, 43% and 42% similarity to the PLA2s from Adamsia carciniopados, Nematostella vectensis, Vipera russelli russelli and Both raps jararacussu, respectively. (C) 2010 Elsevier Masson SAS. All rights reserved.