Ethanol Oxidation Reaction Mechanism on Gold Nanowires from Density Functional Theory.

Thin gold nanowires (NWs) are materials that could be used as support in different chemical reactions. Using density functional theory (DFT) it was shown that NWs that form linear atomic chains (LACs) are suitable for stimulating chemical reactions. To this end, the oxidation reaction of ethanol supported on the LACs of Au-NWs was investigated. Two types of LACs were used for the study, one pure and the other with an oxygen impurity. The results showed that the oxygen atom in the LAC fulfills important functions throughout the reaction pathway. Before the chemical reaction, it was observed that the LAC with impurity gains structural stability, that is, the oxygen acts as an anchor for the gold atoms in the LAC. In addition, the LAC was shown to be sensitive to disturbances in its vicinity, which modifies its nucleophilic character. During the chemical reaction, the oxidation of ethanol occurs through two different reaction paths and in two stages, both producing acetaldehyde (CH3 CHO). The different reaction pathways are a consequence of the presence of oxygen in the LAC (oxygen conditions the formation of reaction intermediates). In addition, the oxygen in the LAC also modifies the kinetic behavior in both reaction stages. It was observed that, by introducing an oxygen impurity in the LAC, the activation energy barriers decrease ∼69 % and ∼97 % in the first and second reaction stages, respectively.

Analytical and numerical study of the non-linear noisy voter model on complex networks.

We study the noisy voter model using a specific non-linear dependence of the rates that takes into account collective interaction between individuals. The resulting model is solved exactly under the all-to-all coupling configuration and approximately in some random network environments. In the all-to-all setup, we find that the non-linear interactions induce bona fide phase transitions that, contrary to the linear version of the model, survive in the thermodynamic limit. The main effect of the complex network is to shift the transition lines and modify the finite-size dependence, a modification that can be captured with the introduction of an effective system size that decreases with the degree heterogeneity of the network. While a non-trivial finite-size dependence of the moments of the probability distribution is derived from our treatment, mean-field exponents are nevertheless obtained in the thermodynamic limit. These theoretical predictions are well confirmed by numerical simulations of the stochastic process.

Bilateral Acute Depigmentation of the Iris (BADI) following Covid-19 Infection.

PURPOSE: To present a case of bilateral acute iris depigmentation after covid 19 infection. CASE REPORT: A 55-year-old female presented with binocular pain and blurred vision a month after being diagnosed with severe acute respiratory syndrome - coronavirus-2 (SARS-CoV-2). She presented pigment dispersion in the anterior chamber and pigment depositions on the corneal endothelium. The patient was treated with dexamethasone and during follow-up visits, the pigment dispersion decreased and the symptoms ceased. CONCLUSIONS: Covid-19 infection may be associated with rare ocular disorders such as BADI.

Electronic structure and optical spectra of catechol on TiO2 nanoparticles from real time TD-DFT simulations.

The electronic structure and the optical response of free catechol, [Ti(cat)(3)](2-) complex, and catechol bound to TiO(2) nanoclusters have been analysed using time dependent density functional theory (TD-DFT) performing calculations both in real time and frequency domains. Both approaches lead to similar results providing the basis sets and functionals are similar. For all cases, the simulated spectra agree well with the experimental ones. For the adsorption systems, the spectra show a band at 4.7 eV associated to intramolecular catechol π→π* transitions, and low energy bands corresponding to transitions from catechol to the cluster with a tail that is red-shifted when the coupling between the dye and the cluster is more effective. Thus, dissociative adsorption modes provide longer tails than the molecular mode. Although the bidentate complex is more stable than the monodentate, the energy difference between both is smaller when the cluster size increases. Small cluster models reproduce the main features of the optical response, however, the (TiO(2))(15) cluster constitutes the minimal size to provide a complete picture. In this case, the conventional TD-DFT (frequency domain) calculations are highly demanding computationally, while real time TD-DFT is more efficient and the calculations become affordable.

Broad lifetime distributions for ordering dynamics in complex networks.

We search for conditions under which a characteristic time scale for ordering dynamics toward either of two absorbing states in a finite complex network of interactions does not exist. With this aim, we study random networks and networks with mesoscale community structure built up from randomly connected cliques. We find that large heterogeneity at the mesoscale level of the network appears to be a sufficient mechanism for the absence of a characteristic time for the dynamics. Such heterogeneity results in dynamical metastable states that survive at any time scale.

Ba adsorption on the stoichiometric and defective TiO(2) (110) surface from first-principles calculations.

A theoretical study on Ba adsorption on the rutile TiO(2) (110) surface has been carried out by means of plane-wave, plane augmented waves potential, density functional theory calculations. A model consisting on a (4 x 1) unit cell, which corresponds to coverage of 0.125 monolayer (ML), has been used and several potential adsorption sites on the stoichiometric surface have been tried. It has been found that the most stable site is with the Ba atom in a position where it is bound to two bridging oxygen atoms and an in-plane oxygen atom forming equivalent bonds (OB site). The adsorption energy is 0.71 eV referred to the formation of Ba bulk and is about 0.3 eV more stable than other adsorption sites. The Ba-surface interaction produces some surface relaxation in all cases. The OB site is stable at moderate temperatures; however, after extensive molecular dynamic calculations it is found that atoms diffuse on the surface by means of a jumping mechanism among several stable positions. The presence of bridging oxygen vacancies does not alter significantly this picture since the adsorption close to defects is not energetically favorable and the atoms tend to move away from vacancies. A strong covalent character has been found in the nature of the bonding, which contrasts with previous suggestions of the existence of Ba(2+) species on the surface. When the coverage is increased to 0.25 ML by adding a Ba atom to the supercell, there is a significant repulsion between Ba atoms that move away from each other to occupy OB sites. Thus, the adsorption energy values per atom diminish. For the stoichiometric surface two equivalent adsorption patterns are found, whereas only one is found for the defective surface.

Local versus global interactions in nonequilibrium transitions: A model of social dynamics.

A nonequilibrium system of locally interacting elements in a lattice with an absorbing order-disorder phase transition is studied under the effect of additional interacting fields. These fields are shown to produce interesting effects in the collective behavior of this system. Both for autonomous and external fields, disorder grows in the system when the probability of the elements to interact with the field is increased. There exists a threshold value of this probability beyond which the system is always disordered. The domain of parameters of the ordered regime is larger for nonuniform local fields than for spatially uniform fields. However, the zero field limit is discontinous. In the limit of vanishingly small probability of interaction with the field, autonomous or external fields are able to order a system that would fall in a disordered phase under local interactions of the elements alone. We consider different types of fields which are interpreted as forms of mass media acting on a social system in the context of Axelrod's model for cultural dissemination.

Dynamics of localized structures in vectorial waves

Dynamical properties of topological defects in a two dimensional complex vector field are considered. These objects naturally arise in the study of polarized transverse light waves. Dynamics is modeled by a vector complex Ginzburg-Landau equation with parameter values appropriate for linearly polarized laser emission. Creation and annihilation processes, and self-organization of defects in lattice structures, are described. We find "glassy" configurations dominated by vectorial defects and a melting process associated with topological-charge unbinding.

Stochastic spatiotemporal intermittency and noise-induced transition to an absorbing phase

We introduce a stochastic partial differential equation capable of reproducing the main features of spatiotemporal intermittency (STI). The model also displays a noise-induced transition from STI to laminarity as the noise intensity increases. Simulations and mean-field analysis are used to characterize this transition and to give a quantitative prescription of its loci in the relevant parameter space.

Role of selective digestive decontamination (SDD) in the prevention of nosocomial pneumonia (NP): is gastric decontamination necessary?

In the course of a prospective selective digestive decontamination (SDD) trial to prevent nosocomial pneumonia (NP) during mechanical ventilation (MV), we carried out serial cultures of gastric aspirate to assess the importance of gastric colonization for potential respiratory pathogens and its relationship to the simultaneous gastric pH, to whether the patients were receiving Sucralfate or Ranitidine and to the nutritional biochemical parameters. If NP developed, a bronchial sample was taken by fibreoptic bronchoscopy to determine the causal organisms and its relationship to the previous gastric isolated. Results show: 1) Increase in aerobic Gram negative bacilli colonization during hospitalization. 2) Direct relationship between colonization level and gastric pH. 3) Greater pH in ranitidine vs sucralfate group. 4) Low incidence of NP (11%), the majority of these (66%) being early. 5) No bacteriological correlation between gastric colonization and aetiological agents of NP. 6) Close relationship between pharyngeal colonization and causative germs of pulmonary infection (40%).

Automatic extraction-spectrophotometric method for the determination of ambroxol in pharmaceutical preparations.

The spectrophotometric determination of trace amounts of ambroxol was carried out by liquid-liquid extraction using Bromothymol Blue with a flow-injection system. The determination of ambroxol in the range 8 x 10(-6)-4 x 10(-4) M was possible with a sampling frequency of 40 samples h(-1). The method was satisfactorily applied to the determination of ambroxol in pharmaceutical preparations.

Phase-locked spatial domains and Bloch domain walls in type-II optical parametric oscillators.

We study the role of transverse spatial degrees of freedom in the dynamics of signal-idler phase locked states in type-II optical parametric oscillators. Phase locking stems from signal-idler polarization coupling which arises if the cavity birefringence and/or dichroism is not matched to the nonlinear crystal birefringence. Spontaneous Bloch domain wall formation is observed numerically and the dynamics and chiral properties of the fronts are investigated. Bloch walls connect homogeneous regions of self-phase-locked solutions by means of a polarization transformation. The parameter range for phase locking is found analytically. The polarization properties and the dynamics of walls in one and two transverse spatial dimensions are explained. The transition from Bloch to Ising walls is characterized, the control parameter being the linear coupling strength. The wall dynamics governs spatiotemporal dynamical states of the system, which include transient curvature driven domain growth, persistent dynamics dominated by spiraling defects for Bloch walls, and labyrinthine pattern formation for Ising walls.

Polarization patterns and vectorial defects in type-II optical parametric oscillators.

Previous studies of lasers and nonlinear resonators have revealed that the polarization degree of freedom allows for the formation of polarization patterns and novel localized structures, such as vectorial defects. Type- II optical parametric oscillators are characterized by the fact that the down-converted beams are emitted in orthogonal polarizations. In this paper we show the results of the study of pattern and defect formation and dynamics in a type-II degenerate optical parametric oscillator, for which the pump field is not resonated in the cavity. We find that traveling waves are the predominant solutions and that the defects are vectorial dislocations that appear at the boundaries of the regions where traveling waves of different phase or wave-vector orientation are formed. A dislocation is defined by two topological charges, one associated with the phase and another with the wave-vector orientation. We also show how to stabilize a single defect in a realistic experimental situation. The effects of phase mismatch of nonlinear interaction are finally considered.

Determination of tiopronin in pharmaceuticals using a chemiluminescent flow-injection method.

A flow-injection method for the determination of tiopronin in the range 1 x 10(-7)-7 x 10(-5) M is described. The procedure is based on the chemiluminescent reaction of tiopronin with cerium(i.v.) in sulphuric acid medium using rhodamine 6G and quinine as fluorophors. The flow-injection method is rapid and precise and allows measurements of up to 80 solutions per hour. The applicability of the method to the determination of tiopronin in pharmaceutical preparations was demonstrated by investigating the effect of potential interferences and by analysing commercial preparations.

Flow extraction spectrophotometric method for the determination of diclofenac sodium in pharmaceutical preparations.

The spectrophotometric determination of trace amounts of diclofenac was carried out by liquid-liquid extraction using acridine yellow with a flow system. The determination of diclofenac sodium in the range of 3-80 micrograms ml-1 was possible with a sampling frequency of 40 samples h-1. The method was satisfactorily applied to the determination of diclofenac in pharmaceutical preparations.

Influence in the quality of life of the respiratory patients by environmental control and the acaricide Frontac®.

The present prospective, open, observational study assessed the effect of the use of standard environmental control measures together with the application of an acaricide-containing aerosol of esbiol/benzyl benzoate/piperonyl butoxide/2-phenylphenol (Frontac) on several clinical and environmental parameters in patients suffering from perennial allergic rhinoconjunctivitis related to house dust mites (HDM). Fifty-five patients were enrolled and studied for one year. Both symptoms and the patients' quality of life (evaluated by the Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ)) were assessed at several clinic visits. The amount of HDM antigen was semi-quantitatively estimated using the guanine test. We found a significant decrease (p < 0.001) in most nasal symptoms scores: sneezing, runny nose, stuffy nose and itching. The overall quality of life (QoL) score also showed a significant improvement during the study period; the mean score decrease found was 0.86 (CI 95 %, 0.54-1.17) (p < 0.001). Five of the seven domains included in the questionnaire decreased significantly: non-hayfever symptoms; practical problems; nasal symptoms; eye symptoms, and emotions. These QoL score decreases were found during the first 3 months and later remained stable at lower levels than at baseline. The content of guanine in dust samples decreased significantly from 2.17 0.75 to 1.43 0.68 (p < 0.001). No toxic adverse events were recorded. In conclusion, these results show an improvement in the quality of life and a clinical benefit of the long-term use of the new chemical acaricide tested, together with environmental measures, in the home of patients suffering from allergic respiratory pathology.

[Influence of consensual protocols on the use of antibiotics and bacterial resistance in a general hospital. A prospective study 1995-2000]. / Influencia de la protocolizacion consensuada en el consumo de antibioticos y resistencias bacterianas en un hospital general. Estudio prospectivo 1995-2000.

Reasoned and consensual protocols, by means of diversification of the use of antibiotics, significantly influence their consumption, preventing and reducing the development of bacterial resistance against the Gram-negative microorganisms most frequently isolated in general hospitals. The increase in the consumption of piperacillin-tazobactam was found to be significantly associated with an increased resistance of E. cloacae, but less so in K. pneumoniae and E. coli. Its activity against P. aeruginosa and against P. mirabilis was not affected throughout the study and it maintained a high sensivity to the end against P. aeruginosa and against P. mirabilis and partial recovery of activity against A. baumannii. No statistically significant differences were found between the stable consumption of cefotaxime, ciprofloxacin, ceftazidime and imipenem and bacterial resistance against E. coli, P. aeruginosa, P. mirabilis, K. pneumoniae, E. cloacae and A. baumannii. Imipenem presented greater activity against E. coli, K. pneumoniae, E. cloacae and A. baumannii. Piperacillin-tazobactam showed greater activity against P. aeruginosa, while ciprofloxacin showed the least activity against E. coli and P. mirabilis. Cefotaxime had the least activity against E. cloacae, P. aeruginosa and A. baumannii. Ceftazidime showed stable activity and was similar to piperacillin-tazobactam against E. coli, P. mirabilis, K. pneumoniae, E. cloacae and A. baumannii.

[Ovarian cystadenofibroma. 5-year experience at the "Dr. Manuel Gea González" General Hospital S.S.A. Report of 10 cases]. / Cistoadenofibroma de ovario. Experiencia de cinco años en el Hospital General "Dr. Manuel Gea González" S.S.A. Informe de 10 casos.

The ovarian cystoadenofibroma are tumors not very frequently of superficial epithelium. It can appears at all ages. It can form fibrotic nodules of strong consistency that initially appear with the papillae and it forms nodule when the time goes by; generally, they are unilateral. We studied 10 cases of cystoadenofibromas in a period of 5 years, the patients' age was from 18 to 68 years old being more frequent in the adult age; seven cases were unilateral, three were bilateral, two of these appeared clinically as acute abdomen due to rupture of the tumor the third one was a hysterectomy is finding. In seven cases there was association with uterine leiomiomatosis mainly in older patients. Macroscopically it was seen that in younger patients these tumors were cystic with small papillae, and in older patients they formed fibrotic nodules. The immunohystochemical study with Vimentin and Desmin showed that the Desmin was focally immunopositive in form of fine fibers at the union with superficial epithelium and greatly positive fibrous portion for Vimentina.

Fragmentation transition in a coevolving network with link-state dynamics.

We study a network model that couples the dynamics of link states with the evolution of the network topology. The state of each link, either A or B, is updated according to the majority rule or zero-temperature Glauber dynamics, in which links adopt the state of the majority of their neighboring links in the network. Additionally, a link that is in a local minority is rewired to a randomly chosen node. While large systems evolving under the majority rule alone always fall into disordered topological traps composed by frustrated links, any amount of rewiring is able to drive the network to complete order, by relinking frustrated links and so releasing the system from traps. However, depending on the relative rate of the majority rule and the rewiring processes, the system evolves towards different ordered absorbing configurations: either a one-component network with all links in the same state or a network fragmented in two components with opposite states. For low rewiring rates and finite-size networks there is a domain of bistability between fragmented and nonfragmented final states. Finite-size scaling indicates that fragmentation is the only possible scenario for large systems and any nonzero rate of rewiring.

Dynamics of link states in complex networks: the case of a majority rule.

Motivated by the idea that some characteristics are specific to the relations between individuals and not to the individuals themselves, we study a prototype model for the dynamics of the states of the links in a fixed network of interacting units. Each link in the network can be in one of two equivalent states. A majority link-dynamics rule is implemented, so that in each dynamical step the state of a randomly chosen link is updated to the state of the majority of neighboring links. Nodes can be characterized by a link heterogeneity index, giving a measure of the likelihood of a node to have a link in one of the two states. We consider this link-dynamics model in fully connected networks, square lattices, and Erdös-Renyi random networks. In each case we find and characterize a number of nontrivial asymptotic configurations, as well as some of the mechanisms leading to them and the time evolution of the link heterogeneity index distribution. For a fully connected network and random networks there is a broad distribution of possible asymptotic configurations. Most asymptotic configurations that result from link dynamics have no counterpart under traditional node dynamics in the same topologies.