Charged particles on surfaces: coexistence of dilute phases and periodic structures at interfaces

We consider a mixture of two immiscible oppositely charged molecules strongly adsorbed to an interface, with a neutral nonselective molecular background. We determine the coexistence between a high density ionic periodic phase and a dilute isotropic ionic phase. We use a strong segregation approach for the periodic phase and determine the one-loop free energy for the dilute phase. Lamellar and hexagonal patterns are calculated for different charge stoichiometries of the mixture. Molecular dynamics simulations exhibit the predicted phase behavior. The periodic length scale of the solid phase is found to scale as epsilon/(lB psi3/2), where psi is the effective charge density, lB is the Bjerrum length, and epsilon is the cohesive energy.     

delta-Lactone from Oedogonium capillare and their effects on rat ileum

Antispasmodic activity-guided fractionation together with chemical analysis led to the isolation of one novel delta-lactone named oedogonolide from Oedogonium capillare. Identification was based on spectroscopic methods. The oedogonolide produces a significant antispasmodic effect on the contractions of the rat ileum induced by acetylcholine, histamine and barium chloride.     

Critical parameters influencing the material distribution produced by pulsed laser deposition

The parameters that control the thickness distribution of thin films produced by pulsed laser deposition are investigated. It is found that highly asymmetric material distribution profiles can be obtained in vacuum when high energy densities are used and the target surface is positioned at the lens focus. The asymmetries are due to asymmetries in the spatial distribution of the beam. Under Ar gas pressure, the profile becomes symmetric and the distribution narrows as a consequence of collisions between the ejected species and the gas. In vacuum, decreasing the energy density, by decreasing the laser energy output or by moving the lens to defocus the beam, leads to symmetric distribution profiles. Nevertheless, in the first case a quite broad distribution and a low deposition rate are obtained, whereas in the second case the distribution is narrow and the deposition rate increases.     

Families of discrete advection-reaction operators investigated via divided differences

An infinite matrix formulation of the families of discrete advection-reaction operators is given in order to investigate their relevance to interpolation theory. A basic characteristic under study is the connection of each iteration of the operators to a series of interpolation problems for the canonical polynomial base for selected initial conditions. In order to generalize our results, we extend the definition of advection-reaction operators to sequences of polynomials.     

A Bibliometric Evaluation of the Top 100 Cited Dimethyl Fumarate Articles

Dimethyl fumarate is a cytoprotective and immunomodulatory drug used in the treatment of multiple sclerosis. We performed a bibliometric study examining the characteristics and trends of the top 100 cited articles that include dimethyl fumarate in the title. On 21 September 2020 we carried out an electronic search in the Web of Science (WOS), seeking articles that include the following terms within the title: dimethyl fumarate, BG-12, or Tecfidera. To focus our investigation on original research, we refined the search to include only articles, early access, others, case report, and clinical trials. We obtained a total of 1115 items, which were cited 7169 times, had a citation density of 6.43 citations/item, and an h-index of 40. Around 2010, there was a jump in the number of published articles per year, rising from 5 articles/year up to 12 articles/year. We sorted all the items by the number of citations and selected the top 100 most cited (T100). The T100 had 4164 citations, with a density of 37 citations/year and contained 16 classic research articles. They were published between 1961 and 2018; the years 2010–2018 amassed nearly 80% of the T100. We noted 17 research areas with articles in the T100. Of these, the number one ranking went to neurosciences/neurology with 39 articles, and chemistry ranked second on the T100 list with 14 items. We noticed that the percentage of articles belonging to different journals changed depending on the time period. Chemistry held the highest number of papers during 1961–2000, while pharmacology andneurosciences/neurology led the 2001–2018 interval. A total of 478 authors from 145 institutions and 25 countries were included in the T100 ranking. The paper by Gold R et al. was the most successful with 14 articles, 1.823 citations and a density of 140.23 citations/year. The biotechnological company Biogen led the T100 list with 20 articles. With 59 published articles, the USA was the leading country in publications. We concluded that this study analyzed the use of and research on dimethyl fumarate from a different perspective, which will allow the readership (expert or not) to understand the relevance of classic and recent literature on this topic.     

Optimization of ultra-fast interactions using laser pulse temporal shaping controlled by a deterministic algorithm

Femtosecond laser pulse temporal shaping techniques have led to important advances in different research fields like photochemistry, laser physics, non-linear optics, biology, or materials processing. This success is partly related to the use of optimal control algorithms. Due to the high dimensionality of the solution and control spaces, evolutionary algorithms are extensively applied and, among them, genetic ones have reached the status of a standard adaptive strategy. Still, their use is normally accompanied by a reduction of the problem complexity by different modalities of parameterization of the spectral phase. Exploiting Rabitz and co-authors’ ideas about the topology of quantum landscapes, in this work we analyze the optimization of two different problems under a deterministic approach, using a multiple one-dimensional search (MODS) algorithm. In the first case we explore the determination of the optimal phase mask required for generating arbitrary temporal pulse shapes and compare the performance of the MODS algorithm to the standard iterative Gerchberg–Saxton algorithm. Based on the good performance achieved, the same method has been applied for optimizing two-photon absorption starting from temporally broadened laser pulses, or from laser pulses temporally and spectrally distorted by non-linear absorption in air, obtaining similarly good results which confirm the validity of the deterministic search approach.     

Mathematical modeling of the immune system response to pathogens

The detection and elimination of pathogens in an organism are the main tasks of its immune system. The most important cells involved in these processes are neutrophils and macrophages. These processes might have two resolutions: The first is the possibility of pathogen elimination, and the other the possibility of the inflammation resolution. In this work, we present several mathematical models involving immune cell densities and inflammation levels. Our general goal is to exhibit the possible pathogen eradication or the inflammation resolution. We use bifurcation techniques in order to analyze how parameter variations may change the system evolution. Our results indicate that the elimination of apoptotic neutrophils by macrophages has a dichotomy effect: It contributes to the decrease of the inflammation level, but it may hinder the pathogen elimination. Also, an increment of the average neutrophil life can improve healthy outcomes. Moreover, we find scenarios when pathogens cannot be eliminated, as well as conditions for their successful eradication.     

A Layered Hybrid Perovskite Solar‐Cell Absorber with Enhanced Moisture Stability

Two‐dimensional hybrid perovskites are used as absorbers in solar cells. Our first‐generation devices containing (PEA)₂(MA)₂[Pb₃I₁₀] ( 1 ; PEA=C₆H₅(CH₂)₂NH₃⁺, MA=CH₃NH₃⁺) show an open‐circuit voltage of 1.18 V and a power conversion efficiency of 4.73 %. The layered structure allows for high‐quality films to be deposited through spin coating and high‐temperature annealing is not required for device fabrication. The 3D perovskite (MA)[PbI₃] ( 2 ) has recently been identified as a promising absorber for solar cells. However, its instability to moisture requires anhydrous processing and operating conditions. Films of 1 are more moisture resistant than films of 2 and devices containing 1 can be fabricated under ambient humidity levels. The larger bandgap of the 2D structure is also suitable as the higher bandgap absorber in a dual‐absorber tandem device. Compared to 2 , the layered perovskite structure may offer greater tunability at the molecular level for material optimization.     

Effect of cyclodextrins on the electrochemical behaviour of ascorbic acid on platinum electrodes in acidic and neutral solutions

The effect of β-CD and α-CD on the electrochemical behaviour of H₂A and HA⁻ on platinum is studied. The adsorption of β-CD on this electrode is demonstrated and proved to be dependent on the base electrolyte composition. The maximum adsorption coverage was reached in phosphate solution at pH 6.95. The homogeneous H₂A---β-CD complex formation produced a decrease in the oxidation current and a positive shift in the oxidation peak potential. These effects are predominant in acid solutions. In neutral solutions the opposite behaviour is observed, i.e. an increase in the oxidation current at lower oxidation potentials. The presence of a parallel oxidation route for the vitamin involving strongly adsorbed CO residues is considered, and evidence for a decrease in CO_ad in the presence of β-CD was given by variations in hydrogen adsorption charges. This fact, more important in neutral solutions, must be responsible for the catalytic effect observed. α-CD was not adsorbed, neither did it modify the electro-oxidation behaviour of H₂A and HA⁻.