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The control of mercury (Hg) from coal-fired power plants by adsorption in solid sorbents is an attractive way to reduce Hg emissions. In this study, a commercial activated carbon (Norit RB3) was impregnated with gold nanoparticles for the retention of Hg in the gas phase, with the intention to explore their potential to be regenerated in future investigations. The activated carbon (RB3) was impregnated with different gold contents using polyvinyl alcohol (PVA) and tetrakis(hydroxymethyl)phosphonium chloride (THPC) to compare the performance of these two methods. Gold particles of ∼5 nm were obtained in the carbonaceous support for low gold contents (0.1%). With comparative purposes of the sorbent behavior, the Hg0retention capacity was evaluated in a lab-scale device in an O2+ N2atmosphere. Although the Hg retention capacities of these sorbents were similar by the two methods, a higher efficiency was achieved with THPC, being in some cases 80%. The results showed that the use of THPC is a promising means for dropping gold (0.1%) to make carbonaceous sorbents for use in Hg capture.

The six minute walk test (6MWT) is a standardized test that provides information on exercise capacity in patients with COPD. It is considered a submaximal test in opposition to incremental cardiopulmonary exercise tests (CPET) that provide valuable information on all the systems involved in exercise.

We experimentally study the temporal dynamics of amplitude-modulated laser beams propagating through a water dispersion of graphene oxide sheets in a fiber-to-fiber U-bench. Nonlinear refraction induced in the sample by thermal effects leads to both phase reversing of the transmitted signals and dynamic hysteresis in the input–output power curves. A theoretical model including beam propagation and thermal lensing dynamics reproduces the experimental findings.

We analyze the phase shift induced in an amplitude-modulated laser beam propagating through a water dispersion of graphene oxide sheets in a fiber-to-fiber U-bench. This phase shift arises from the thermally induced nonlinear refraction in the sample. The system exhibits strong optical limiting performance for weak continuous-wave signals. A theoretical model including beam propagation and thermal lens focal length oscillation reproduces the experimental findings.

One of the greatest problems associated with greenhouse horticulture is the amount of solid waste e.g. steel, plastics and non-yield biomass, that it produces. In this study, we used life cycle assessment (LCA) to evaluate the environmental burdens associated with crop processes and to investigate the relative importance of different waste management options applied in protected horticulture. Four waste management scenarios were analysed: (a) non-yield biomass was composted and other materials were disposed of in landfill; (b) all waste was disposed of in landfill; (c) all waste was incinerated; and (d) non-yield biomass was composted and other materials were incinerated. The study revealed that source segregation followed by the composting of biodegradable matter was the best way of managing waste to improve the impact assessment for most impact categories considered. Segregation of non-yield biomass and its composting reduced the environmental burden for most of the impact categories considered, reaching its maximum value in the category of climate change, which it was possible to reduce by between 40% and 70% depending, respectively, on the option considered; landfill or incineration.

Poly(N-vinylimidazole) hydrogels immersed in aqueous acid solutions produce an increment in the pH of the bath because of proton uptake by basic imidazole moieties, leading to hydrogel protonation. Both kinetic and equilibrium measurements of the pH of the bath have been performed under a variety of conditions and with different hydrogel samples. The kinetics of the xerogel protonation process (which includes solvent and titrant diffusion, the true protonation reaction or ion–dipole association, and the polymer relaxation to a new conformation) are mostly driven by the size of the hydrogel sample, whereas other magnitudes, such as the initial pH, the effective polymer concentration, and the network structure, governed by the crosslinker ratio and total comonomer concentration in the feeding, have a minor influence. pKa changes with the degree of protonation (α), delimitating two different regions: (1) a broad α range in which pKa decreases with increasing α but less pronouncedly with increasing ionic strength and (2) an α range close to α = 1 in which pKa decreases abruptly, more markedly with sulfate than with chloride counteranions and with larger ionic strengths. In the first region, pKa is determined by repulsive electrostatic interactions and so is larger for titration with H2SO4 than with HCl and increases as the effective polymer concentration and ionic strength increase. Two steps (i.e., two protonation sites) can be observed in the titration curves, the second one corresponding to abrupt changes in the basicity of the second pKa-versus-α region. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2294–2307, 2004

The swelling capacity (S) of poly(N-vinylimidazole) (PVI) hydrogels in aqueous acid solutions was measured as a function of the pH, the nature of the acid, and the polymer network structure. In acid solutions, imidazole groups become protonated and the swelling capacity increases to reach a maximum corresponding to a degree of protonation equivalent to the Manning limit charge density. The variable controlling the degree of protonation, and therefore the swelling capacity, is the mass of dry polymer immersed in a given volume of solution, which was called the gel effective concentration. Divalent counteranions reduce significantly S with respect to the same ionic strength and degree of protonation, obtained with monovalent anions, while non-complexant divalent cations have no specific influence on the PVI swelling capacity. Results were discussed in terms of the effective charge density caused by counterion condensation on protonated PVI, the non-covalent crosslink density caused by ionic interactions with divalent anions, and the non-Gaussian character of chains between crosslinks. Swelling capacity of two PVI samples in aqueous solutions of HCl with two different gel effective concentrations: 10⁻² M and 2.7 × 10⁻² M.

Caption of Hg(II) from acid aqueous solution by immersed poly(N-vinylimidazole) hydrogel particles was studied as a function of pH, counterion, and cation concentration. Fitting parameters to several sorption isotherms have been determined. Their values depend mostly on pH and less, on temperature and counterion, and suggest a large affinity of imidazole groups in the gel and mercury cations. Practically total removal (94.4%) of Hg(II) is achieved at pH = 2, with 10 g of dry gel per liter of solution, when cation concentration was as large as 15,000 ppm (0.075 M). Polymer protonation decreases about fourfold the cation affinity, supporting competitive protonation-complexation mechanisms. By its side, metal uptake decreases polymer protonation. Thermal stability of loaded gels decreases with respect to metal free hydrogels. Scanning electron micrographs reveal no changes in the gel morphology upon cation binding, but Tg increases significantly with the Hg(II) content of loaded gels and swelling decreases moderately, indicating the role of the cation as ionic crosslinker. Practically total elution of Hg(II) is achieved with 1 M HNO3 in consecutive loading-elution cycles. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1467–1475, 2001

The effects of vanadate on the contractility of the guinea-pig isolated trachea was examined. Vanadate (0·1 Mm) produced a sustained contraction that was abolished in Ca2+-free EGTA (0·1 Mm)-containing physiological salt solution but was resistant to verapamil (1 μm). Vanadate (0·1 Mm) depressed tracheal responses to CaCl2(in Ca2+-free depolarizing solution), KCl, acetylcholine, histamine and 5-hydroxytryptamine. For vanadate (10 μm), the inhibition of spasmogenic responses only reached statistical significance for histamine and 5-hydroxytryptamine. Caffeine (1 Mm)-induced spasm (trachea at 20°C in the presence of indomethacin (2·8 μm)) was not affected by vanadate (10 μm-0·1 Mm). Vanadate (0·1 Mm) slightly depressed the responses to KCl (50 Mm), acetylcholine (1 Mm), histamine (1 Mm) or 5-hydroxytryptamine (0·1 Mm) observed in Ca2+-free EGTA (0·1 Mm)-containing physiological salt solution. Vanadate (0·5 Mm) depressed Ca2+(20 μm)-induced contraction of trachea which had been chemically skinned of its plasmalemmal membranes. The mechanism of the inhibitory effect of vanadate on tracheal responses to a variety of spasmogens remains obscure, but, under in-vitro conditions, vanadate clearly does not induce hyper-reactivity of airway smooth muscle to spasmogens.

Degenerate four-wave mixing is analyzed in the case of a two-photon resonant transition between two levels with permanent dipole moments. A comparison is made with the single-photon transition case, where it is found that permanent dipole moments have no influence. Nevertheless, the difference between the permanent dipole moments of the two levels is relevant in the two-photon transition case; the reflectivity of the phase-conjugate wave increases as this difference increases.

Abstract: Plutonium isotopic ratios have been calculated in soils contaminated by the Palomares accident which occurred in 1966 (Almería, Southeastem Spain). Contrasted techniques have been used to determine the radionuclide activities:238Pu and238+240Pu were analysed by agr-spectrometry prior purification on anion-exchange resins, the ratio239Pu/240Pu was estimated by agr-spectra deconvolution and241Pu was directly measured by liquid scintillation counting and indirectly through quantification of in-grown241Am from aged plutonium discs. The mean activity ratios238Pu/239Pu,239Pu/240Pu,241Pu/239Pu, backdated to 1966, were 0.027±0.002 (1sgr), 4.5±0.2 (1sgr) and 8.2±0.8 (1sgr), respectively, characterizing the accident of Palomares as the source term of the measured plutonium.

Single-beam two-photon optical bistability in a Fabry-Perot cavity filled with molecules which change permanent dipole moment upon electronic excitation is analysed under the mean-field and plane-wave approximations. One-photon resonances are discarded. These molecules are assumed to be in a solid matrix. Phonon effects are then taken into account. The Bloch equations of the system are further coupled by a term that is dependent on the electron-phonon interaction, leading to shifts in the switching thresholds which modify the optical bistability character. Such a term becomes irrelevant when the difference between the dipole moments is much greater than the transition dipole moment.

Optical bistability in a micrometre-sized Fabry-Perot cavity, filled with appropriate polar molecules, is analysed after two incident beams (with frequenciesgw1 andgw2) produce in the system a two-photon resonance at frequencygw1 +gw2. One-photon resonances at the frequenciesgw1 andgw2 are discarded. It was not necessary to assume a particular relationship betweengw1 andgw2, and the single-beam two-photon optical bistability whengw1 andgw2 are of the same order or equal is emphasized.

The propagation on the earth's surface of vibrations induced by blasting is predicted by a law that correlates the particle vibration velocity, as a parameter of the damage evaluation, with the explosive mass and the distance to the point where the blasting takes place. The most common are the quadratic and Swedish laws. This paper develops the relation between these laws, by analyzing the meaning of the simplifications that are applied when using the quadratic and Swedish laws instead of the general law. This is performed by the analysis of their geometric representations in the tridimensional space of velocity-explosive mass-distance.

CARIBRO was founded in response to the United Nations declaration that the 1990s be designated the Decade of the Brain. The Program of Action is:1.Annual meetings;2.Training courses of the Caribbean School of Neurosciences;3.Network scientific programs;4.Fellowship programs; and5.Dissemination of information on neuroscience. In the same program, a CARIBRO Laboratory was created in one of the Medical Faculties of Havana with the aim to teach students from the Caribbean in neuroscience research. As part of this program, we have been working in lateralized motor functions. Preliminary results in rats show that reaching acquisition allows classification of the animals as right-handed (40%), left-handed (40%), and ambidextrous (20%). Electrolytic lesion of caudate nucleus or amygdala impairs lateralized response. Contralateral lesions increase reaching attempts. Ipsilateral lesions to the preferred forepaw do not affect the reaction. The results remain the same 10, 20, and 90 d after the interference. Pharmacological experiments showed that trihexiphenidil (0.1 mg/kg ip) induced handedness reversion in 50% of the animals, whereas haloperidol (1 mg/kg ip) produced immobility, tremor, and autonomic symptoms. This effect remained the same in young as well as in old animals. We are also working on mathematical modelation. In this sense, preliminary reports about a model for synaptic modification in the framework of the Fukushima hypothesis is discussed.

We report a change from sub- to superluminal propagation upon increasing the modulation frequency of an amplitude-modulated 1550 nm signal when propagating through highly doped erbium fibers pumped at 980 nm. We show that the interplay between the pump absorption and the pump-power broadening of the spectral hole induced by coherent population oscillations may drastically affect the fractional advancement or delay of the signal for the considered fibers.

We present a theoretical study of the resonance fluorescence of a four-level double-V-type quantum emitter near a plasmonic nanostructure. The quantum system interacts with two orthogonal circularly polarized laser fields with the same frequency and intensity, but with different phases. For the plasmonic nanostructure we consider a two-dimensional array of metal-coated dielectric nanospheres. We show that the presence of the plasmonic nanostructure leads to strong modification of both the resonance fluorescence spectrum and the transition from antibunching to bunching for the fluorescent photons. In addition, we show that both the resonance fluorescence spectrum and the second-order correlation function are strongly phase-dependent so that the relative phase of laser fields can be used for the efficient control of the resonance fluorescence characteristics. The results are explained by using a dressed-state picture. [ABSTRACT FROM AUTHOR]

We theoretically study the resonance fluorescence spectrum of a three-level quantum emitter coupled to a spherical metallic nanoparticle. We consider the case in which the quantum emitter is driven by a single laser field along one of the optical transitions. We show that the development of the spectrum depends on the relative orientation of the dipole moments of the optical transitions in relation to the metal nanoparticle. In addition, we demonstrate that the location and width of the peaks in the spectrum are strongly modified by the exciton-plasmon coupling and the laser detuning, allowing one to achieve a controlled strongly subnatural spectral line. A strong antibunching of the fluorescent photons along the undriven transition is also obtained. Our results may be used for creating a tunable source of photons which could be used for a probabilistic entanglement scheme in the field of quantum information processing. [ABSTRACT FROM AUTHOR]