Anodes for glucose fuel cells based on carbonized nanofibers with embedded carbon nanotubes

Electrodes made of carbonized polyacrylonitryle (cPAN) nanofibers, with and without embedded multiwall carbon nanotubes (MWCNTs) were fabricated by the electrospinning (ES) process and evaluated as anodes in glucose fuel cell (FC) application. The effect of several processing and structural characteristics, such as the presence of MWCNTs, polymer concentration in the ES solution and silver electroless plating on FC performance were measured. The carbon electrodes were successful as anodes showing significant activity even without additional silver catalyst, with noticeable improvement by the incorporation of MWCNTs. The orientation of graphitic layers along the fiber axis and the coherence of layer packing were shown to be important for enhanced electrode activity. The maximal values of open circuit voltage (OCV) and peak of power density (PP_D) of unmetalized electrodes, 0.4 V and 30 μW/cm² respectively, were found to be for composite cPAN/CNT electrode. Electroless silver metallization of the carbon nanofiber electrodes leads to much better FC performance. Maximal values of OCV and PP_D of silvered carbon electrodes were measured to be about 0.9 V and 400 μW/cm², respectively. Thus, carbonized nanofibers with embedded MWCNTs may form a good basis for glucose FC anodes, but better metallization and cell-configuration allowing proper mixing are required.     

Synthetic Antibody Mimics Based on Cancer-Targeting Immunostimulatory Peptides

De novo cancer-targeting immunostimulatory peptides have been designed and developed as synthetic antibody mimics. A series of bifunctional peptides incorporating NKp30-binding and NK-cell-activating domains were synthesized as linear dimers and then extended into branching trimeric peptides by the incorporation of GRP78-targeting and tumor-cell-binding sequences. A selected trimeric peptide from this small set of peptides displayed binding capabilities on GRP78⁺ HepG2 and A549 target cells. Cell binding diminished in the presence of an anti-GRP78 peptide blocker, thus suggesting GRP78-binding dependence. Similarly, the selected trimeric peptide was also found to exhibit NK cell binding in an NKp30-dependent manner, which translated into NK cell activation as indicated by cytokine secretion. In co-culture, fluorescence microscopy revealed that the target GFP-expressing A549 cells were visibly associated with the effector NK cells when pre-activated with lead trimeric peptide. Accordingly, A549 cells were found to be compromised, as evidenced by the loss of GFP signal and notable detection of early-/late-stage apoptosis. Investigation of the immunological markers related to toxicity revealed detectable secretion of pro-inflammatory cytokines and chemokines, including IFN-γ, TNF-α, and IL-8. Furthermore, administration of peptide-activated NK cells into A549-tumor-bearing mice resulted in a consistent decrease in tumor growth when compared to the untreated control group. Taken together, the identification of a lead trimeric peptide capable of targeting and activating NK cells’ immunotoxicity directly towards GRP78⁺/B7H6^- tumors provides a novel proof-of-concept for the development of cancer-targeting immunostimulatory peptide ligands that mimic antibody-targeting and -activating functions related to cancer immunotherapy applications.     

Physicochemical study by multi-angle light scattering of water-soluble methacryloylaminophenylarsonate copolymers

The properties of aqueous solutions of polyelectrolytes of sodium o- and p-methacryloylaminophenylarsonate (o- and p- MAPHA-Na) with acrylamide (AAD) or sodium methacrylate (MA-Na): poly(sodium o-methacryloylaminophenylarsonate) (poly(o-MAPHA-Na)), poly(sodium o-methacryloylaminophenylarsonate-co-acrylamide) (poly(o-MAPHA-Na-co-AAD)) (26:74), poly(sodium o-methacryloylaminophenylarsonate-co-sodium methacrylate) (poly(o- MAPHA-Na-co-AM-Na) (35:65) and (14:86), and poly(sodium p-methacryloylaminophenylarsonate-co-sodium methacrylate) (poly(p- MAPHA-Na-co-AM-Na)) (34:66) were studied by off-line, multi-angle light scattering, and in-line using size exclusion chromatography coupled with multi-angle light scattering (SEC-MALS) and refractometric (RI) detection. The M_w value corresponding to the homopolymer poly(o-MAPHA-Na) was 1,300,000 g/mol and for the copolymers the M_w and gyration radius values were decreased when the AAD or AM-Na comonomer composition increased. The macromolecular parameters obtained using SEC-MALS were in agreement with the values measured in the off-line mode. Also, SEC-MALS experiments allowed examination of the radius of gyration-M_w relationship in order to determine the polyelectrolyte conformation (ρ) in solution; these values fell between 0.7-0.53, indicating that the polyelectrolytes are random coils at θ-conditions. In addition, the effect of the pH on the macromolecular parameters was evaluated. At pH 4.5, the M_w and gyration radius values corresponding to poly(o-MAPHA-Na) and poly(o-MAPHA-Na-co-AAD) (26/74) remained very close to those measured at pH 7. However, <r _g ²?>?values for poly(o-MAPHA-Na-co-AM-Na) copolymers at pH 4.5 were less than pH 7, indicating that the presence of AM-Na reduced the size of the copolymer through intermolecular interactions.     

Dose and Radioadaptive Response Analysis of Micronucleus Induction in Mouse Bone Marrow

Enhanced cellular DNA repair efficiency and suppression of genomic instability have been proposed as mechanisms underlying radio-adaptive responses following low-dose radiation exposures. We previously showed that low-dose γ irradiation does not generate radio-adaptation by lowering radiation-induced cytogenetic damage in mouse spleen. Since radiation may exert tissue-specific effects, we extended these results here by examining the effects of γ radiation on cytogenetic damage and proliferative index in bone marrow erythrocytes of C57BL/6 and BALB/c mice. In C57BL/6 mice, the induction of micronuclei in polychromatic erythrocytes (MN-PCE) was observed at radiation doses of 100 mGy and greater, and suppression of erythroblast maturation occurred at doses of >500 mGy. A linear dose–response relationship for MN-PCE frequencies in C57BL/6 mice was established for radiation doses between 100 mGy and 1 Gy, with departure from linearity at doses of >1 Gy. BALB/c mice exhibited increased MN-PCE frequencies above baseline following a 20 mGy radiation exposure but did not exhibit radio-sensitivity relative to C57BL/6 mice following 2 Gy exposure. Radio-adaptation of bone marrow erythrocytes was not observed in either strain of mice exposed to low-dose priming γ irradiation (single doses of 20 mGy or 100 mGy or multiple 20 mGy doses) administered at various times prior to acute 2 Gy irradiation, confirming the lack of radio-adaptive response for induction of cytogenetic damage or suppression or erythrocyte proliferation/maturation in bone marrow of these mouse strains.     

Validation of digital photographs, as a tool in 24-h recall, for the improvement of dietary assessment among rural populations in developing countries

ABSTRACT: BACKGROUND: Improvement of traditional methods for dietary assessment is necessary, especially in rural areas where it is more difficult to succeed with self-reporting methods. This study presents and validates a method for improving accuracy when measuring food and nutrient intake of individuals in rural areas. It is called the "Food photography 24-h recall method" (FP 24-hR) and is a modified 24-h recall with the addition of a digital food photography record and a photo atlas. METHODS: The study was carried out in a rural area in the tropical region of Bolivia; 45 women participated. Validation of the method was made by comparing it with a reference method, the Weighed Food Record (WFR). During the FP 24-hR, digital photographs were taken by the subjects of all food consumed during a day and a 24-h recall questionnaire was conducted by an interviewer. An estimate of the amount of food consumed was made using a photo atlas and the photographs taken by the subjects. For validation, comparison was made between the calculations, by both methods, of the levels of food, and nutrient, intake. RESULTS: The comparison was made in 10 food categories; most of which were somewhat underestimated from [MINUS SIGN]2.3% (cassava) to [MINUS SIGN]6.8% (rice), except for beverages (+1.6%) and leafy vegetables (+8.7%), which were overestimated. Spearman's correlation coefficients were highly significant (r from 0.75 for eggs to 0.98 for potato and cassava). Nutrient intakes calculated with data from both methods showed small differences from -0.90% (vitamin C) to -5.98% (fat). Although all nutrients were somewhat underestimated, Pearson[ACUTE ACCENT]s coefficients are high (>0.93 for all) and statistically significant. Bland Altman analysis showed that differences between both methods were random and did not exhibit any systematic bias over levels of food and nutrient intake, with acceptable 95% limits of agreement. CONCLUSION: The FP 24-hR exhibits acceptable differences when compared with a WFR, digital photos are useful as a memory aid for the subjects during 24-h recall and as an estimation tool. The method is suitable for assessing dietary intake among rural populations in developing countries.     

Structural and chemical changes of thermally treated bone apatite

The thermal behaviour of the animal by-product meat and bone meal (MBM) has been investigated in order to assess how it is affected structurally and chemically by incineration. Initially composed of intergrown collagen and hydroxyapatite (HAP), combustion of the organic component is complete by 650 °C, with most mass loss (50–55%) occurring by 500 °C. No original proteins were detected in samples heated at 400 °C or above. Combustion of collagen is accompanied by an increase in HAP mean crystallite size at temperatures greater than 400 °C, from 10 nm to a constant value of 120 nm at 800 °C or more. Newly formed crystalline phases appear beyond 400 °C, and include β-tricalcium phosphate, NaCaPO₄, halite (NaCl) and sylvite (KCl). Crystallite thickness as judged by small angle X-ray scattering (SAXS) increases from 2 nm (25–400 °C) to 8–9 nm very rapidly at 550 °C, and then gradually increases to approximately 10 nm. The original texture of HAP within a collagen matrix is progressively lost, producing a porous HAP dominated solid at 700 °C, and a very low porosity sintered HAP product at 900 °C.     

Novel nanomaterials based on 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-21H,23H-porphyrin entrapped in silica matrices

The present study is dealing with the obtaining of transparent hybrid silica materials encapsulating 5,10,15,20-tetrakis(3,4-dimethoxyphenyl)-21H,23H-porphyrin designated for advanced optoelectronic devices. The porphyrin was synthesized by three methods: an Adler-type reaction between pyrrole and 3,4-dimethoxybenzaldehyde in propionic acid medium; by Lindsey condensation of pyrrole with 3,4-dimethoxybenzaldehyde in the presence of BF₃·OEt₂ and by a multicomponent reaction by simultaneously using of pyrrole and two different aldehydes: 3,4-dimethoxybenzaldehyde and 3-hydroxybenzaldehyde. The 3,4-dimethoxyphenyl substituted porphyrin was characterized by HPLC, TLC, UV-vis, FT-IR, ¹H NMR and ¹³C NMR analysis. Excitation and emission spectra were also discussed in terms of pH conditions. The hybrid materials, consisting in the porphyrin encapsulated in silica matrices, have been prepared successfully via the two steps acid-base catalyzed hydrolysis and condensation of tetraethylorthosilicate using different approaches of the sol-gel process: in situ, by impregnation and by sonication. The synthetic conditions and the compositions were monitored and characterized by using spectroscopic methods such as FT-IR, fluorescence and UV-vis. Atomic force microscopy (AFM) has been applied to observe the columnar or pyramidal nanostructures which are formed by the immobilization of porphyrin on the silica matrices.     

Biosorption of phenolic compounds by the brown alga Sargassum muticum

Phenol, 2‐chlorophenol (2‐CP), and 4‐chlorophenol (4‐CP) biosorption on Sargassum muticum, an invasive macroalga in Europe, has been investigated. The efficiency of this biosorbent was studied measuring the equilibrium uptake using the batch technique. A chemical pre‐treatment with CaCl₂ has been employed in this study in order to improve the stability as well as the sorption capacity of the algal biomass. The influence of pH on the equilibrium binding and the effect of the algal dose were evaluated. The experimental data at pH = 1 have been analysed using Langmuir and Freundlich isotherms. It was found that the maximum sorption capacity of chlorophenols, q_max = 251 mg g^?1 for 4‐CP and q_max = 79 mg g^?1 for 2‐CP, as well as that of a binary mixture of both chlorophenols, q_max = 108 mg g^?1, is much higher than that of phenol, q_max = 4.6 mg g^?1. Moreover, sorption kinetics have been performed and it was observed that the equilibrium was reached in less than 10 h. Kinetic data have been fitted to the first order Lagergren model, from which the rate constant and the sorption capacity were determined. Finally, biosorption of the phenolic compounds examined in the present study on Sargassum muticum biomass was observed to be correlated with the octanol‐water partitioning coefficients of the phenols. This result allows us to postulate that hydrophobic interactions are the main responsible for the sorption equilibrium binding. Copyright © 2006 Society of Chemical Industry     

Model of local buckling in steel hollow structural elements subjected to biaxial bending

This paper presents a general formulation for the analysis of steel hollow structural beams subjected to biaxial bending. The model has been developed within the framework of lumped damage mechanics. In this approach, the models are based on methods of continuum damage mechanics and the concept of plastic hinge. The model was implemented in a commercial finite element program. In order to calibrate the model, a set of experimental tests were carried out in the Structural Mechanics Laboratory at the Lisandro Alvarado University. The model was evaluated by the numerical simulation of these tests finding a good agreement between the experimental tests and the numerical simulations.