An efficient numerical scheme for 1D parabolic singularly perturbed problems with an interior and boundary layers

In this paper we consider a 1D parabolic singularly perturbed reaction-convection-diffusion problem, which has a small parameter in both the diffusion term (multiplied by the parameter e2) and the convection term (multiplied by the parameter µ) in the differential equation (e¿(0, 1], µ¿0, 1], µ=e). Moreover, the convective term degenerates inside the spatial domain, and also the source term has a discontinuity of first kind on the degeneration line. In general, for sufficiently small values of the diffusion and the convection parameters, the exact solution exhibits an interior layer in a neighborhood of the interior degeneration point and also a boundary layer in a neighborhood of both end points of the spatial domain. We study the asymptotic behavior of the exact solution with respect to both parameters and we construct a monotone finite difference scheme, which combines the implicit Euler method, defined on a uniform mesh, to discretize in time, together with the classical upwind finite difference scheme, defined on an appropriate nonuniform mesh of Shishkin type, to discretize in space. The numerical scheme converges in the maximum norm uniformly in e and µ, having first order in time and almost first order in space. Illustrative numerical results corroborating in practice the theoretical results are showed

Age-dependent effects of moderate differences in environmental predictability forecasted by climate change, experimental evidence from a short-lived lizard (Zootoca vivipara)

Whether and how differences in environmental predictability affect life-history traits is controversial and may depend on mean environmental conditions. Solid evidence for effects of environmental predictability are lacking and thus, the consequences of the currently observed and forecasted climate-change induced reduction of precipitation predictability are largely unknown. Here we experimentally tested whether and how changes in the predictability of precipitation affect growth, reproduction, and survival of common lizard Zootoca vivipara. Precipitation predictability affected all three age classes. While adults were able to compensate the treatment effects, yearlings and juvenile females were not able to compensate negative effects of less predictable precipitation on growth and body condition, respectively. Differences among the age-classes’ response reflect differences (among age-classes) in the sensitivity to environmental predictability. Moreover, effects of environmental predictability depended on mean environmental conditions. This indicates that integrating differences in environmental sensitivity, and changes in averages and the predictability of climatic variables will be key to understand whether species are able to cope with the current climatic change

P-Stereogenic monophosphines with the 2-p-terphenylyl and 1-pyrenyl substituents. Application to Pd and Ru asymmetric catalysis

tThe synthesis of five optically pure P-stereogenic monophosphines of the type PPhArR (Ar = 2-p-terphenylyl (a), 1-pyrenyl (b); R = OMe, Me, i-Pr) is described. The ligands were fully characterisedand the absolute configurations of PPh(1-pyrenyl)R (3b and 5b; R = OMe and Me respectively) wereconfirmed by X-ray diffraction. The complexation of the monophosphines to Pd and Ru organometal-lic units yielded the neutral complexes [PdCl( 3-2-Me-allyl)P] (10-12) and [RuCl2( 6-p-cymene)P](16-18). Complete characterisation, including the crystal structure determination of [RuCl2( 6-p-cymene)(PMePh(2-p-terphenyl))] (17a) is provided. Neutral palladium complexes appeared as mixturesof two diastereomers in solution according to NMR. The synthesis and characterisation of four cationic[Pd( 3-2-Me-allyl)(P)2]PF6(13 and 14) is also described. The application of neutral Pd complexes tocatalytic styrene hydrovinylation afforded moderate conversions, high chemoselectivities (>92%) to 3-phenyl-1-butene and up to 43% ee with precursor 12a. Cationic Pd complexes were tested as catalyticprecursors in allylic substitution of rac-3-acetoxy-1,3-diphenyl-1-propene (rac-I), with the anion ofdimethylmalonate and benzylamine as nucleophiles, obtaining full conversions and up to 80% ee in alkyl-ation and 60% ee in amination with precursor 13a. Finally, ruthenium complexes were used as catalyticprecursors in transfer hydrogenation of acetophenone, with complete conversions after several hoursbut low enantioselectivities

El sistema dunar de Valdevaqueros: evolución histórica y alternativas de gestión

ResumenLa duna de Valdevaqueros, situada al sur de España, presenta elevadas tasas de migración asociadas a los fuertes vientos de levante que soplan en el estrecho de Gibraltar. Ubicada en una zona de elevada presión humana, su dinámica ha entrado en conflicto con los usos del suelo, provocando una notable repercusión desde los puntos de vista científico y técnico, pero también desde una perspectiva mediática y social. Este trabajo se centra en el análisis de la evolución histórica del sistema dunar desde principios del sigloxx mediante el estudio del material cartográfico y fotográfico disponible, analizando los diferentes estadios que se han sucedido, los mecanismos y agentes naturales que gobiernan su comportamiento, así como las repercusiones derivadas de las diferentes actuaciones en la zona. La intervención sobre el corredor dunar iniciada a principios de 1940 ha condicionado los procesos y la evolución de toda la unidad fisiográfica. La morfodinámica dunar actual se explica por el balance neto de sedimentos. El sistema recibe arena disponible en la zona sumergida transportada por el oleaje de poniente que se acumula en la playa y ensancha la playa seca. El viento de levante erosiona el sedimento en la playa seca y lo transporta hacia la duna. Se estima que en los últimos 50años la playa seca (fetch) ha crecido, en promedio, más de 150m, y que el sistema almacena arena suficiente para mantener estos mecanismos de transporte durante las próximas décadas. A partir de estos resultados, se plantean y analizan diferentes vías de actuación para la gestión integral de la zona.AbstractValdevaqueros dune, in the south of Spain, exhibits high migration rates associated with strong easterly winds in the Strait of Gibraltar. The system is located in an area of high human pressure and its dynamic has collided with land use causing a significant impact from scientific and technical points of view but also from a media and social perspective. This paper focuses on the historical evolution of the dune system since the beginning of the 20th century by studying the available cartographic and photographic material, analyzing the different phases, the mechanisms and natural agents governing the dune behaviour and the implications arising from the activities in the area. The intervention on the dune corridor started in the early 1940s and has conditioned the evolution of all the processes in the physiographic region. The current dune morphodynamics is explained by the sediment budget. The system receives sand from the submerged zone, which is transported by westerly wind waves. This material accumulates and widens the dry beach. The easterly winds erode the sediment in the dry beach and transports it to the dune. In the last fifty years, the dry beach (fetch) has grown, on average, over 150m and the system stores enough sand to sustain these transport mechanisms for decades. From these results, we discuss different alternatives for the integrated management of the area

Island-assisted interface alloying and magnetic polarization at submonolayer V/Cr(001) interfaces

Island-assisted interface alloying was observed during submonolayer deposition on Cr(001) substrates at 525 K. Scanning tunneling spectroscopy suggests atomic interchange at the center of the islands during the early stages of growth, giving rise to a Cr core in the center of the island and a gradually increasing V concentration toward the island rim. The existence of a VCr alloy with equiatomic composition is concluded by comparing tunneling spectra measured at the island rim with density-functional theory calculations. Coalescence of the initial islands gives rise to inhomogeneous alloying at monolayer coverage. Antiferromagnetic coupling between the islands and the Cr(001) substrate is found for coverages up to 0.50 atomic layers. At higher coverages, no magnetic contrast was observed

Neutral and Cationic Palladium Complexes of P-Stereogenic Phosphanes Bearing a Heterocyclic Substituent

The coordination chemistry of 13 optically pure P ‐stereogenic diarylmonophosphanes P(Het)PhR [Het = 4‐dibenzofuranyl (DBF), 4‐dibenzothiophenyl (DBT), 4‐dibenzothiophenyl S ,S ‐dioxide (DBTO2) and 1‐thianthrenyl (TA); R = OMe, Me, i Pr, Fc (ferrocenyl)] to Pd‐allyl moieties is described. Both neutral [PdCl(η3‐(2‐methylallyl)(κP ‐P )] and cationic [Pd{η3‐(2‐methylallyl)(κP ‐P )2}]PF6 complexes have been prepared. Coordination of the heteroatom of the heterocycle was only possible in the case of TA‐based phosphanes; these furnished complexes of the type [Pd{η3‐(2‐methylallyl)(κ2P,S ‐P )}]PF6 after chloride abstraction with TlPF6. The crystal structure of the complex [Pd(η3‐2‐methylallyl)(κ2P,S ‐PPh(OMe)(1‐TA)]PF6 is reported. The neutral Pd complexes were found to be highly active in the hydrovinylation of styrene after activation with AgBF4, except for the TA‐based phosphanes. The cationic Pd complexes were evaluated in allylic alkylation and amination with the model substrate rac ‐trans ‐1,3‐diphenylprop‐2‐enyl acetate (rac ‐I ), achieving total conversions and up to 70 % ee

Ruthenium complexes of P-stereogenic phosphines with a heterocyclic substituent

The synthesis via phosphine-boranes of 13 new optically pure P-stereogenic diarylphosphines P(Het)PhR (Het = 4-dibenzofuranyl (DBF), 4-dibenzothiophenyl (DBT), 4-dibenzothiophenyl-S,S-dioxide (DBTO2) and 1-thianthrenyl (TA); R = OMe, Me, i-Pr, Fc (ferrocenyl)) following the Jugé-Stephan method is described. The ligands were designed with the aim of having a heteroatom in a position capable of interacting with a metal upon coordination. The ligands and their precursors have been fully characterised, including the determination of two crystal structures of phosphine-boranes. Ru neutral complexes of the type [RuCl2(η6-arene)(κP-P)] (arene = p-cymene and methyl benzoate) have been prepared and characterised, including three crystal structure determinations. Treatment of solutions of the complexes with TlPF6 allowed the preparation of well-defined cationic complexes [RuCl(η6-arene)(κ2P,S-P)]PF6 for DBT- and TA-based phosphines. The complexes possess a stereogenic Ru atom and in most of the cases they are present as a single isomer in solution. All the Ru complexes have been used in the asymmetric transfer hydrogenation of acetophenone in refluxing 2-propanol, with good activities and up to 70% ee

Diphosphorus Ligands Containing a P-Stereogenic Phosphane and a Chiral Phosphite or Phosphorodiamidite - Evaluation in Pd-Catalysed Asymmetric Allylic Substitution Reactions

The synthesis of 14 new optically pure C 1‐symmetric phosphane-phosphinite (1 -4 ), phosphane-phosphite (5 -9 ) and phosphane-phosphorodiamidite (10 -14 ) ligands is reported. The ligands were prepared through the condensation of (2‐hydroxyphenyl)phenylphosphanes PPh(2‐PhOH)R (R = Me, t Bu and Ph) with chlorodiisopropylphosphane (1 and 2 ), chlorodiphenylphosphane (3 and 4 ), the chlorodioxaphosphepine derived from both enantiomers of 1,1′‐bi‐2‐naphthol (5 -9 ) and the chlorodiazaphosphepine derived from both enantiomers of N ,N′ ‐dimethyl‐1,1′‐binaphthyl‐2,2′‐diamine (10 -14 ) in the presence of a base. With these ligands, cationic Pd complexes of the type [Pd(η3‐C4H7)(PP′)]PF6 (Pd1 -Pd14 ) were obtained and characterised; the crystal structures of Pd1 , Pd2 and Pd13 were obtained. In solution, the complexes are present as mixtures of two diastereomers because of the lack of symmetry of the ligand and the presence of the methallyl group. The Pd complexes catalyse the allylic alkylation with dimethyl malonate and the amination with benzylamine of the model substrate rac ‐3‐acetoxy‐1,3‐diphenyl‐1‐propene (I ). For the alkylation, full conversions and good enantioselectivities (up to 96 % ee with Pd14 ) were observed

Climate-Driven Changes in Annual Flow Patterns: A Comprehensive Analysis of the Buktyrma River (Kazakhstan)

[EN] This article examines and calculates the annual flows of rivers in the Buktyrma River basin in connection with changing climatic conditions affecting runoff formation. An analysis of climatic characteristics, based on data from meteorological stations of the hydrometeorological service of Kazakhstan, indicates intense warming and a moderate increase in annual precipitation since the early 1980s. The more intense melting of high-mountain snow and glaciers has led to a reduction in glaciated areas. Alongside the noted trend of increasing precipitation, this melting contributes to an increase in surface runoff. According to Global Land Ice Measurements from Space data, there has been a reduction in the area of glaciers in the river basin and a complete disappearance of glaciers in the Sarymsakty River basin. Studying long-term water-flow data in the basin has helped identify periods with consistent patterns. These periods are characterized by different values of probability- distribution-curve parameters. An assessment of the homogeneity of the identified periods of runoff series over the past decades, using known parametric criteria, confirmed the reliability of the calcu- lated values of annual runoff. The observed increase in the norm, depending on elevation, glacier presence, and the spatial orientation of watershed ridges, ranges from 5% to 52%. The observed trends in changes in climatic characteristics and runoff indicators of the rivers in the basin support water-management planning in this region. This includes using the approximation of empirical river-supply curves, which can aid in assessing the calculated hydrological characteristicsSairov, SB.; Serikbay, NT.; Rodrigo-Ilarri, J.; Abdrakhimov, RG.; Rodrigo-Clavero, M. (2024). Climate-Driven Changes in Annual Flow Patterns: A Comprehensive Analysis of the Buktyrma River (Kazakhstan). Water. 16(8). https://doi.org/10.3390/w1608111416

Squamous intraepithelial lesions of the anal squamocolumnar junction: Histopathological classification and HPV genotyping

Background: Human papillomavirus (HPV)-related anal cancer lesions are often found adjacent to the squamocolumnar junction (SCJ). We have assessed the histopathology and associated HPV genotypes in anal SCJ lesions in surgically excised anal warts in HIV-negative and -positive patients. Methods: Histopathology identified 47 squamous intraepithelial lesions (SILs) adjacent to the SCJ amongst a total of 145 cases of clinically diagnosed anal condylomata. The anal SCJ lesions were further analyzed with p16, CK7 and p63 immunohistochemistry and HPV genotyping. Results: Sixteen (16/47) of the excised anal wart lesions contained HSIL; Three were HSIL and exclusively associated with oncogenic HPVs. A further thirteen (13/47) were mixed lesions. Of these eight were HSILs with LSIL and six were HSILs with papillary immature metaplasia (PIM); Ten of the mixed lesions were associated with one or more oncogenic HPVs, while three cases were exclusively associated with HPV6. Conclusions: Clinically diagnosed anal warts cannot be assumed to be limited to low-grade lesions as anal warts of the SCJ often show heterogeneous lesions, with coexistence of LSIL, PIM, and HSIL. Lesions showing PIM, however, may mimic HSIL, because they are hypercellular, but lack the nuclear atypia and conspicuous mitotic activity of HSIL; and are p16 negative