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Due to the complexity of the radiative transfer equation, light transport problems are commonly solved using either models under restrictive assumptions, e.g., N-flux models where infinite lateral extension is assumed, or numerical methods. While the latter can be applied to more general cases, it is difficult to relate their parameters to the physical properties of the systems under study. Hence in this contribution we present, first, a review of a four-flux formalism to study the light transport problem in a plane-parallel system together with a derivation of equations to evaluate the different contributions to the total absorptance and, second, as a complementary tool, a Monte Carlo algorithm with a direct correspondence between its inputs and the properties of the system. The combination of the four-flux model and the Monte Carlo approach provides (i) all convergence warranties since the formalism has been established as a limit and (ii) new added capabilities, i.e., both temporal (transient states) and spatial (arbitrarily inhomogeneous media) resolution. The support between the theoretical model and the numerical tool is reciprocal since the model is utilized to set a Monte Carlo discretization criterion, while the Monte Carlo approach is used to validate the aforementioned model. This reinforces the parallel approach used in this work. Furthermore, we provide some examples to show its capabilities and potential, e.g., the study of the temporal distribution of a delta-like pulse of light.

Mujer de 59 años que ingresa en UCI por SCACEST. Se realiza coronariografía que objetiva estenosis total de la descendente anterior proximal y se realiza angioplastia primaria. Durante el procedimiento, inestabilidad hemodinámica que justifica la colocación de un dispositivo Impellay posteriormente un dispositivo ECMO VA. Progresiva mejoría hasta conseguir decanular ambos dispositivos al décimo día de ingreso. Veinticuatro horas tras la decanulación se objetiva focalidad motora en miembro superior izquierdo. Se realiza ecocardiografía transtorácica apreciando imagen densa y con movimiento anárquico ocupando el espesor del septo interauricular. En el estudio transesofágico se confirma la presencia de un trombo en un foramen oval permeable y una zona aneurismática del septo interauricular que en situación de shock cardiogénico y ectasia auricular supone un riesgo aumentado de embolismos paradójicos.

In this work we review and—to some extent—upgrade one of the main theories of light flux through homogeneous isotropic media, namely, the Kubelka–Munk (K–M) theory, and in particular the later expansion made by Kubelka to obtain the reflectance of a specimen when a substrate lies underneath. We have completed this solution by calculating the transverse energy density in the specimen and the transmission of the whole. We show that this last result—compatible with Kubelka’s upgrade for layered media—also allows for the calculation of the specimen/substrate absorption split. In order to validate these expressions, the results were reproduced by means of a Monte Carlo simulation working on a layered medium under the same assumptions as the K–M theory. Interestingly, the numerical procedure introduces new capabilities in the model regarding the history of any absorbed or outgoing elemental light beam, such as the recording of its time-of-flight through a given system.

Local field enhancements produced by metal nanoparticles have been widely investigated in the visible range for common metals like gold and silver, but recent interest in ultraviolet plasmonics has required consideration of alternate metals. Aluminum and gallium are particularly attractive, but the native oxide that forms on them consumes the metal in the smallest nanoparticles and limits the usefulness of larger nanoparticles for applications that require contact with a bare metal surface. The widely used catalyst rhodium is a noble metal that forms no native oxide under normal atmospheric conditions and has recently been shown to exhibit UV plasmonic behavior. Here we analyze the plasmonic properties of the most easily synthesized rhodium nanoparticle shapes and sizes and compare them to other UV plasmonic metals. Of particular interest is the tripod star monomer and dimer, for which we show the dependence of the absorption cross-section and the local electric field intensity on the constituent size and shape of tripod arms, and the gap distance in dimers, in representative dielectric hosts. It is shown that rhodium nanoparticles are particularly compelling for UV plasmonic applications requiring nanoparticles smaller than 20 nm.

The practical efficacy of technologically promising metals for use in ultraviolet plasmonics (3–6 eV) is assessed by an exhaustive numerical analysis. This begins with estimates of the near- and far-field electromagnetic enhancement factors of isolated hemispherical and spherical metallic nanoparticles deposited on typical dielectric substrates like sapphire, from which the potential of each metal for plasmonic applications may be ascertained. The ultraviolet plasmonic behavior of aluminum, chromium, copper, gallium, indium, magnesium, palladium, platinum, rhodium, ruthenium, titanium, and tungsten was compared with the well-known behavior of gold and silver in the visible. After exploring this behavior for each metal as a function of nanoparticle shape and size, the deleterious effect caused by the metal’s native oxide is considered, and the potential for applications such as surface-enhanced Raman spectroscopy, accelerated photodegradation and photocatalysis is addressed.

Since polarimetry has extended its use for the study of scattering from surfaces and tissues, Spectralon, a white reflectance standard, is acquiring the role of a polarimetric standard. Both the behavior of Spectralon as a Lambertian surface and its performance as a perfect depolarizer are analyzed in detail. The accuracy of our dynamic polarimeter, together with the polar decomposition to describe the Mueller matrix (MM) depolarizing action, combine to produce a powerful tool for the proper analysis of this scattering surface. Results allowed us to revisit, for confirmation or revision, the role of some MM elements, as described in the bibliography. The conditions under which it can be considered a good Lambertian surface are specified in terms of incidence and scattering angle and verified over a large wavelength range.

In this research, the polar decomposition (PD) method is applied to experimental Mueller matrices (MMs) measured on two-dimensional microstructured surfaces. Polarization information is expressed through a set of parameters of easier physical interpretation. It is shown that evaluating the first derivative of the retardation parameter, δ, a clear indication of the presence of defects either built on or dug in the scattering flat surface (a silicon wafer in our case) can be obtained. Although the rule of thumb thus obtained is established through PD, it can be easily implemented on conventional surface polarimetry. These results constitute an example of the capabilities of the PD approach to MM analysis, and show a direct application in surface characterization.

Studies on single scattering of electromagnetic waves by magnetic particles were reported in the 1980s by Kerker et al. [J. Opt. Soc. Am.73, 765 (1983)]. They obtained that very small spherical particles with electric permittivity and magnetic permeability values such that ε=(4−μ)/(2μ+1) do not produce forward scattering. We show here that this condition contains an interesting exception at (ε=−2, μ=−2) when electric and magnetic resonances are present and around which the scattered field distribution is computed and described showing a polarization-insensitive behavior at the point (ε=−2, μ=−2).

Lorenz-Mie resonances produced by small spheres are analyzed as a function of their size and optical properties (epsi≷0, μ≷0). New generalized (μ≠1) approximate and compact expressions of the first four Lorenz-Mie coefficients (a_1, b_1, a_2, and b_2) are calculated. With these expressions and for small particles with various values of epsi and μ, the extinction cross section (Q_ext) is calculated and analyzed, in particular for resonant conditions. The dependence on particle size of the extinction resonance, together with the resonance shape (FWHM), is also analyzed. In addition to the former analysis, a study of the scattering diagrams for some interesting values of epsi and μ is also presented.

The intensity fluctuations of light scattered from a simple particle aggregate system consisting of two dipole-like particles separated by a fixed distance and floating freely in space are calculated numerically and analyzed statistically. The behavior of two statistical parameters, the second-order factorial moment of the intensity fluctuations and the probability of obtaining zero cross-polarized intensity, are studied as a function of both the particle polarizability and the interparticle distance. Effects of multiple-scattering processes on these statistical parameters are accounted for in particular.

The most important kinetic models developed for acetic fermentation were evaluated to study their ability to explain the behavior of the industrial process of acetification. Each model was introduced into a simulation environment capable of replicating the conditions of the industrial plant. In this paper, it is proven that these models are not suitable to predict the evolution of the industrial fermentation by the comparison of the simulation results with an average sequence calculated from the industrial data. Therefore, a new kinetic model for the industrial acetic fermentation was developed. The kinetic parameters of the model were optimized by a specifically designed genetic algorithm. Only the representative sequence of industrial concentrations of acetic acid was required. The main novelty of the algorithm is the four-composed desirability function that works properly as the response to maximize. The new model developed is capable of explaining the behavior of the industrial process. The predictive ability of the model has been compared with that of the other models studied.

The modeling and optimization of industrial processes requires an intensive study of the factors involved. In this work, a continuous pilot system for studying the industrial process of acetic fermentation is developed. A Doehlert design is applied to the five variables involved in the pilot process. This experimental design allows reduction of the experimental burden and the maximum amount of information to be obtained, studying the factors at different levels depending on their significance. The experimental system provides a robust measure of the specific growth rate and the rates of substrates consumption and acetic acid production, related to the flow of effluent stream evaluated in the steady state. The results demonstrate the growth-associated kinetics of substrates and product, and the yield factors are calculated with low values of variances for the coefficients, i.e., within the range 1−11%. The specific growth rate suits the quadratic model proposed. The response surfaces generated by the model are applied to explain the behavior of the bacterial growth and, therefore, the effects of the process variables studied over the acetic acid production. Very low levels of ethanol or oxygen make the acetification rate decrease, and a saturation effect with high levels of ethanol or oxygen is also deduced. The effects of the aeration rate, agitation, and overpressure suggest a kind of inhibition of the acetic acid production caused by the oxygen that has not been practically studied before. The temperature strengthens the inhibitory effect of the ethanol and the oxygen. The conclusions of this work consolidate the structure of a hybrid model for the acetic fermentation.

LytA amidase breaks down the N-acetylmuramoyl-l-alanine bonds in the peptidoglycan backbone of Streptococcus pneumoniae. Its polypeptide chain has two modules: the NH(2)-terminal module, responsible for the catalytic activity, and the COOH-terminal module, constructed by six tandem repeats of 20 or 21 amino acids (p1-p6) and a short COOH-terminal tail. The polypeptide chain must contain at least four repeats to efficiently anchor the autolysin to the choline residues of the cell wall. Nevertheless, the catalytic efficiency decreases by 90% upon deletion of the final tail. The structural implications of deleting step by step the two last (p5 and p6) repeats and the final COOH-tail and their effects on choline-amidase interactions have been examined by comparing four truncated mutants with LytA amidase by means of different techniques. Removal of this region has minor effects on secondary structure content but significantly affects the stability of native conformations. The last 11 amino acids and the p5 repeat stabilize the COOH-terminal module; each increases the module transition temperature by about 6 degrees C. Moreover, the p5 motif also seems to participate, in a choline-dependent way, in the stabilization of the NH(2)-terminal module. The effects of choline binding on the thermal stability profile of the mutant lacking the p5 repeat might reflect a cooperative pathway providing molecular communication between the choline-binding module and the NH(2)-terminal region. The three sequence motives favor the choline-amidase interaction, but the tail is an essential factor in the monomer <--> dimer self-association equilibrium of LytA and its regulation by choline. The final tail is required for preferential interaction of choline with LytA dimers and for the existence of different sets of choline-binding sites. The p6 repeat scarcely affects the amidase stability but could provide the proper three-dimensional orientation of the final tail.

A rotating-bomb combustion calorimeter specifically designed for the study of sulfur-containing compounds has been assembled and calibrated. Thianthrene has been used as a secondary standard in order to verify the chemistry of the combustion process and the accuracy of the energy corrections involved in the analysis of the results. With this calorimeter, the energy of combustion of 1,3-dithiane has been determined. The vapour pressure of 1,3-dithiane has been measured over a temperature range of about 15 K by the Knudsen effusion technique. From the experimental results, the following quantities for 1,3-dithiane atT=298.15K have been derived: ΔfHmo(cr) =−(65.6±2.2) kJ·mol−1, ΔsubHmo=(62.9±0.7) kJ· mol−1, and ΔfHmo(g) =− (2.7±2.3) kJ· mol−1. A comparison of these results with data for 1,3-dioxane and other reference molecules was carried out.

The scattered field in the far-field region for two small metallic particles on a conducting substrate is analysed as a function of both their separation and the angle of incidence. Special attention is paid to multiple scattering, which appears when the particles are very close, as well as to its related effects such as its influence on the enhanced backscattering phenomenon and depolarization of the incident beam in the plane of incidence.

Light scattering from circular cylinders (diameter sizes from 0.1λ to 4λ) on a conducting substrate are studied by means of a numerical solution of the electromagnetic problem based on the extended boundary conditions of the extinction theorem. Both the cylinder and the substrate are considered real conductors. The evolution of the scattering patterns and the source functions for several angles of incidence allows it to be compared with that found in previous research on perfect conductors. The study shows that, although some of the features are similar in both cases, important differences exist. We found that, for this geometry, the perfect-conductor assumption for real metals is correct only for light polarized perpendicularly to the plane of incidence (which in turn is assumed to be perpendicular to the cylinder axis). Parallel polarized light is far more sensitive to the optical properties of the surfaces, therefore producing different scattering features.

RESUMENEl caballo Losino, Pony sp Losino segun Mason (1960), recibe su denominacion del area oringinal de cria, el Valle de Losa, en el Norte de la provincia de Burgos (Espa?a). Se encuentra emparentado con otras razas autoctonas derivadas del tronco Cantabro-Pirenaico: el garrano portugues, el faco gallego, el caballo asturcon, el thieldon, la jaca soriana, el caballo navarro, el pottoka vasco, el caballo de Merens y el extinguido caballo catalan. La Raza Losina mantuvo sus efectivos hasta los anos 50 pero posteriormente, y debido principalmente a la mecanizacion del campo, al cruce con razas de aptitud carnica y con ganado asnal para la produccion mulatera, su poblacion descendio hasta llegar en 1986 a los limites mas criticos de toda su historia. Ese ano, en vista de la alarmante situacion, se inicio el proyecto de recuperacion de la raza creandose posteriormente en Pancorbo (Burgos) el primer Centro de Cria y Seleccion del caballo Losino. En este Centro se viene manteniendo el sistema natural de crianza en libertad. Los animales, una vez que han sido desbravados y domados, vienen utilizados para la equitaci?n infantil juvenil, en enganches y para realizar las rutas ecuestres por zonas rurales y de monta?a.

The nonlinear transmission properties of C60 and C70 in toluene solution in the ultraviolet and visible spectral regions have been studied using nanosecond laser pulses. Whereas at 308 and 534 nm both fullerenes behave as reverse saturable absorbers, at 337 nm their behavior changes to that of a saturable absorber. A five-level rate equation model was developed that reproduces adequately the dependence of transmittance with intensity at the different irradiation wavelengths and allows us to estimate the absorption cross sections of the first excited singlet state for each fullerene.

Human platelet plasma membrane glycoproteins IIb (GPIIb) and IIIa (GPIIIa) form a Ca2+-dependent heterodimer, the integrin GPIIb/IIIa, which serves as the receptor for fibrinogen and other adhesive proteins at the surface of activated platelets. Below the critical micellar concentration of Triton X100 (TtX), the three glycoproteins do not bind appreciably to TtX and form association products of large size. The size-exclusion chromatographic patterns of GPIIb, GPIIIa and GPIIb/IIIa have been obtained at 0.2% TtX, and the molecular properties of the association products and monomer fractions have been determined by analysis of the detergent bound to the glycoproteins, laser-light scattering, sedimentation velocity, and electron microscopy (TEM). The monomer of the GPIIb-TtX complex was identified by the molecular mass (M) of the glycoprotein moiety (125 ± 15 kDa), the molecular size (9.5 ± 1.5 nm × 11 ±1.5 nm) and globular shape observed by TEM. It has a molecular mass (M*) of 197 ± 20 kDa, a sedimentation coefficient inf20supo* of 5.8±0.1 S, a Stokes radius Rinfssup*of 6.8±0.4 nm, and a frictional ratio f*/infminsup*of 1.7±0.14. The (GPIIb)n-TtX complexes are disulphide-bonded size-heterogeneous association products of GPIIb, tetramers being the smallest species found. GPIIIa has a greater propensity to self-associate than GPIIb, this tendency being lower below 1 mg GPIIIa/ml, 0.1 mM Ca2+, pH 9.0. The (GPIIIa)n-TtX complexes are noncovalent size-heterogeneous association products of GPIIIa, tetramers being the smallest form observed. The monomer of the GPIIIa-TtX complex was identified by the 103 ±15 kDa M determined for the glycoprotein moiety, and the 9 ± 1.5 nm × 10 ± 1.5 nm size and globular shape observed by TEM. It has a M* of 136 ± 15 kDa, a sinf20supo*of 3.9 ± 0.3 S, a Rinfs/p* of 6.4 ± 0.5 nm, a f */finfminsup*of 1.9 ± 0.3, and, when stored at pH 7.4, has a certain tendency to form filamentous association products (20–70 nm × 2–5 nm), as observed by TEM. The GPIIb/IIIa-TtX complex in 0.2% TtX/0.1 mM Ca2+ elutes as a single monomeric fraction, as deduced from the 210 ± 15 kDa M determined for its glycoprotein moiety and the 12 ± 1.5 nm × 14 ± 1.5 nm size of the globular forms observed by TEM. The GPIIb/IIIa-TtX complex has a M* of 315±20kDa, a sinf20sup*of 8.9±0.2 S, a infssup*of 7.4±0.2 nm, a f*/finfminsup*of 1.5±0.12, and appears in the electron micrographs in multiple forms (filled globular, empty oval, head-two-tails, and bilobular shapes), which on lowering the TtX concentration tend to self-associate, forming a bundant rosettes below the TtX critical micellar concentration.

A Laplace Transform (LT) method is used to improve the results obtained in a quasi-elastic scattering (QELS) experiment. This is designed to determine the characteristic parameters of a bimodal solution of spherical and rod-like macromolecules. The theoretical study and the experimental simulation are carried out for low light levels and the results show that the LT technique provides a real alternative to the second order correlation function, g(2)(τ), in QELS measurements for these particularly difficult experimental conditions.

We present light-scattering experiments for well-characterized random conducting surfaces composed of spherical particles on flat substrates. The experiments were carried out for both sparse (low particle-surface density) and dense targets by using particle sizes of the order of the incident wavelength (λ = 0.633 μm). We analyzed both small incidence angles and grazing incidence and present the results for both p and s polarizations. Also, we present the results of computer-simulated light-scattering experiments based on the extinction theorem for a one-dimensional, perfectly conducting surface model for comparison with the experimental results. This model is composed of an array of parallel cylinders upon a flat substrate whose separations follow an exponential distribution corresponding to a pure Poisson process. The possible relevance of these results to radar scattering from the sea surface is also briefly discussed.

Two neutralizing monoclonal antibody (MAb)-resistant variants selected from an isolate of foot-and-mouth disease virus (FMDV) type A5 were repeatedly passaged in cell culture and monitored for susceptibility to neutralization by the selecting MAb. A variant isolated with a MAb to a conformational epitope (1-OG2) lost resistance in 20 passages, while a variant isolated with a MAb to a linear epitope (1-HA6) persisted for 30 passages. In both cases, the virus population emerging after passage was antigenically and genetically indistinguishable from the original wild-type parental virus (FMDV A5 Spain-86). Coinfection assays with the wild type and each variant, and between the variants, showed rapid conversion to a homogeneous population. Wild-type virus prevailed over the variants and for coinfection between the variants, the linear epitope variant 1-HA6. While both variants arose from a single nucleotide substitution and reversion to wild type occurred for each, it appears that the variant based on the continuous epitope (1-HA6) was more stable. We discuss the implications of these results for the antigenic diversity of FMDV and its relationship to virus evolution.

In this work, an analysis is made of the depolarized component of the light scattered by a solution of rod-like macromolecules by measuring the Laplace Transform (LT) of the time interval probability between successive photoelectrons, P(t). The study was performed in forward scattering conditions, which allows direct evaluation of the Rotational Diffusion Coefficient, Dr. Results were obtained by means of computer simulation and are compared with those obtained through the measurement of the second order correlation function, g(2)(τ), for the same experimental conditions.

In this paper, we have characterized an intensity square wave modulated light beam of period P and visibility factor, V, by measuring the moment generating function of the number of photopulses, Qn(s,T), for only one value of the counting time, T. This has been done for different values of the parameter s. A least square fitting procedure has been used to obtain simultaneously the characterizing parameters, P and V. A set of experimental measurements has been carried out for different values of both, the mean intensity per period, m, and the visibility factor, V.

LytA amidase is the best known bacterial autolysin. It breaks down the N-acetylmuramoyl-L-alanine bonds in the peptidoglycan backbone of Streptococcus pneumoniae and requires the presence of choline residues in the cell-wall teichoic acids for activity. Genetic experiments have supported the hypothesis that its 36-kDa chain has evolved by the fusion of two independent modules: the NH2-terminal module, responsible for the catalytic activity, and the COOH-terminal module, involved in the attachment to the cell wall. The structural organization of LytA amidase and of its isolated COOH-terminal module (C-LytA) and the variations induced by choline binding have been examined by differential scanning calorimetry and analytical ultracentrifugation. Deconvolution of calorimetric curves have revealed a folding of the polypeptide chain in several independent or quasi-independent cooperative domains. Elementary transitions in C-LytA are close but not identical to those assigned to the COOH-terminal module in the complete amidase, particularly in the absence of choline. These results indicate that the NH2-terminal region of the protein is important for attaining the native tertiary fold of the COOH terminus. Analytical ultracentrifugation studies have shown that LytA exhibits a monomer <--> dimer association equilibrium, through the COOH-terminal part of the molecule. Dimerization is regulated by choline interaction and involves the preferential binding of two molecules of choline per dimer. Sedimentation velocity experiments give frictional ratios of 1.1 for C-LytA monomer and 1.4 for C-LytA and LytA dimers; values that deviated from that of globular rigid particles. When considered together, present results give evidence that LytA amidase might be described as an elongated molecule consisting of at least four domains per subunit (two per module) designated here in as N1, N2, C1, and C2. Intersubunit cooperative interactions through the C2 domain in LytA dimer occur under all experimental conditions, while C-LytA requires the saturation of low affinity choline binding sites. The relevance of the structural features deduced here for LytA amidase is examined in connection with its biological function.

Five neutralizing monoclonal antibodies (nMAbs) obtained against type A5 Spain-86 foot-and-mouth disease virus were used to generate a series of neutralization-resistant variants. In vitro and in vivo assays showed that the variants were fully refractory to neutralization by the selecting nMAb. On the basis of cross-neutralization and binding assays, two neutralizing antigenic sites have been located on the virus surface; one, located near the C-terminus of VP1, displayed a linear epitope, and the second, located on VP2, displayed two conformational epitopes. Nucleotide sequencing of RNA of the parental and variant capsid protein-coding region P1 has placed the amino acid changes at position 198 of VP1 for the first site and at positions 72 and 79 of VP2 for the related epitopes in the second site. The relative importance of these two sites in the biological properties of foot-and-mouth disease virus is discussed.

Multiple scattering effects are analysed for a simple scattering model consisting of a flat conducting substrate with two small (<< λ ) spherical metallic particles as a function of both their separation and the angle of incidence. When the interaction between the scatterers is important, the enhanced backscattering effect is also analysed for both co- and cross-polarized cases. Finally, a comparison is made between our theoretical predictions and experimental results obtained for surfaces composed of a flat conducting substrate seeded with spherical metallic protuberances with a size comparable to the incident wavelength.