The interpretation and description of natural phenomena, intrinsic to Science, require conceptual abstraction, using observations and theoretical constructs. Concepts like atoms and molecules, along with mathematical equations, have been developed to describe interactions and the temporal evolution of natural properties. Careful analysis of these models, considering thermodynamic parameters, enables the investigation of complex phenomena. Computational tools, such as Molecular Dynamics, allow for the modeling of atomic-molecular systems, aiding in the understanding of matter transformations. The Lennard-Jones potential, an isotropic model proposed in the 1920s, is effective in the thermodynamic description of simple fluids. In this work, we will review this model to construct the temperature and density phase diagram ( T × ρ) using Molecular Dynamics simulations with LAMMPS, available freely online. We will obtain critical temperature and density, as well as the coexistence region of the liquid and vapor phases. This will provide physics teachers at all educational levels with a simple computational approach to teach about phase transitions. phenomena Science abstraction constructs molecules equations properties models parameters tools atomicmolecular atomic molecular systems transformations LennardJones Lennard Jones potential 1920s s fluids work ρ LAMMPS online phases transitions

A interpretação e descrição dos fenômenos naturais, intrínseca à Ciência, demanda abstração conceitual, utilizando observações e construções teóricas. Conceitos como átomos e moléculas, junto a equações matemáticas, foram desenvolvidos para descrever interações e evolução temporal das propriedades naturais. A análise criteriosa desses modelos, considerando parâmetros termodinâmicos, viabiliza a investigação de fenômenos complexos. Ferramentas computacionais, como a Dinâmica Molecular, permitem modelar sistemas atômico-moleculares, auxiliando na compreensão das transformações da matéria. O potencial de Lennard Jones, um modelo isotrópico proposto nos anos 1920, é eficaz na descrição termodinâmica de fluidos simples. Neste trabalho, revisaremos este modelo para construir o diagrama de fases da temperatura versus densidade ( T × ρ) usando simulações de Dinâmica Molecular com o LAMMPS, disponível gratuitamente online. Obteremos a temperatura e densidade críticas, assim como a região de coexistência das fases líquida e vapor. Isso proporcionará aos professores de física, em todos os níveis educacionais, uma abordagem computacional simples para ensinar sobre transições de fase. naturais Ciência conceitual teóricas moléculas matemáticas modelos termodinâmicos complexos computacionais atômicomoleculares, atômicomoleculares atômico moleculares, moleculares atômico-moleculares matéria Jones 1920 trabalho ρ LAMMPS online críticas vapor física educacionais fase 192 19 1

In this work, babassu FAME samples were synthesized by transesterification reaction under alkaline catalysis with sodium glyceroxide and by two steps process with KOH followed by H2SO4 as catalysts. A sequential multi-element method for determination of Zn, Fe, Mg, Ca, Na and K in synthesized babassu FAME by high resolution continuum source flame atomic absorption spectrometry (HR CS FAAS) was developed. The proposed method is based on a microemulsion formation by mixing the babassu FAME samples with 1-propanol and aqueous phase. The mass proportion of the added components was evaluated through a ternary diagram. External and matrix-matching calibration techniques with inorganic and organic standard were investigated. In the five-level spike-recovery test, satisfactory results were obtained by performing the matrix-matching calibration along with inorganic standard solutions. By using the optimized conditions, limits of detection in the range of 0.002-0.12 mg kg-1 were obtained. Accuracy was attested by the agreement of the results obtained in the analysis of three certified reference materials. By applying the microemulsion system and HR-CS FAAS, the sequential determination of six elements was achieved. Therefore, the proposed method was a suitable alternative for metal determination in babassu FAME samples, with good sensitivities, accuracy, and a wide linear working range. work HSO H SO H2SO catalysts multielement multi element Zn Fe Mg Ca HR FAAS developed 1propanol propanol 1 phase diagram matrixmatching matrix matching investigated fivelevel five level spikerecovery spike recovery test solutions conditions 0.0020.12 0002012 0.002 0.12 0 002 12 0.002-0.1 kg1 kg kg- materials HRCS achieved Therefore sensitivities accuracy 0020 0.0020.1 000201 0002 0.00 012 0.1 00 0.002-0. 0.0020. 00020 000 0.0 01 0. 0.002-0 0.0020 0.002-

O equilíbrio líquido-líquido no sistema água-etanol-acetato de etila foi calculado e os resultados foram apresentados em diagramas retangulares e triangulares. Inicialmente, o contexto termodinâmico e as condições de equilíbrio são apresentados, envolvendo a igualdade das atividades e o balanço de massas. A equação de Rachford-Rice é deduzida das oito condições de equilíbrio termodinâmico. Definindo uma nova variável, razão de atividades, esse problema de oito variáveis independentes é transformado em um problema de uma variável independente. Serão apresentadas aplicações, adotando-se o modelo de atividade Non-Random-Two-Liquid, para um equilíbrio ternário, considerando o sistema água-etanol-acetato de etila. Os resultados são apresentados em diagramas retangulares e triangulares. É feita comparação com experimental, mostrando a qualidade e simplicidade da equação de Rachford-Rice. Um algoritmo é apresentado para se calcular as composições de equilíbrio, tornando o material aqui apresentado mais acessível aos alunos de graduação. líquidolíquido líquido águaetanolacetato água etanol acetato triangulares Inicialmente massas RachfordRice Rachford Rice independente aplicações adotandose adotando NonRandomTwoLiquid, NonRandomTwoLiquid Non Random Two Liquid, Liquid Non-Random-Two-Liquid ternário experimental RachfordRice. Rice. graduação

Ternary phase diagrams in liquid-liquid equilibrium, for the water-ethanol-ethyl acetate system, were calculated and the results presented in rectangular and triangular diagrams. Initially, the thermodynamical background and the conditions of equilibrium are presented, involving the equality of activities and the mass balance condition. From this system of equations, the Rachford-Rice equation is deduced, transforming the problem of eight equations into a problem of one equation with one unknown. The Non-Random-Two-Liquid model was adopted to calculate activity coefficients, but other models can be easily adapted. An algorithm is presented to calculate the equilibrium compositions of this ternary system, together with numerical results. The theoretical-experimental comparison is in fair agreement, showing the robustness and simplicity of the Rachford-Rice equations. The material presented here is accessible to undergraduate students. liquidliquid liquid waterethanolethyl water ethanol ethyl Initially condition RachfordRice Rachford Rice deduced unknown NonRandomTwoLiquid Non Random Two Liquid coefficients adapted theoreticalexperimental theoretical experimental agreement students

In the present work, synthetic slags (FeO-SiO2-CaO-P2O5-Al2O3-TiO2-V2O5 system) mimicking the composition of the slag inclusions of Ipanema were solidified at different cooling rates. FactSage software was used to calculate the slag’s phase equilibria from 500ºC to 1600°C to guide the microstructural characterisation. The samples solidified with slower cooling rates featured wüstite dendrites and a eutectic-like matrix, with intradendritic (Al,V,Ti)-containing iron spinel precipitates in the wüstite. The rapidly solidified slag showed refined wüstite dendrites surrounded by a Fe-O-Si-Ca-containing amorphous single-phase matrix without intradendritic (Al,V,Ti)-containing iron spinel precipitation. The comparison of the calculated phase diagram with the as-cast microstructures showed a few discrepancies. For instance, the FactSage’s database must be updated to consider the simultaneous solubility of Al, V and Ti in the thermodynamic description of the spinel phases, such as FToxid-SP-V, FToxid-SPINA, FToxid-TiSp and (FeO)2(TiO2)(s). Finally, the intradendritic precipitation of (Al,V,Ti)-containing iron spinel phases in the wüstite of the slag inclusions indicated that an Ipanema’s iron artefact was exposed to high service temperatures between 750 and 1050ºC. work FeOSiO2CaOP2O5Al2O3TiO2V2O5 FeOSiOCaOPOAlOTiOVO FeO SiO2 CaO P2O5 Al2O3 TiO2 V2O5 SiO P O Al TiO (FeO-SiO2-CaO-P2O5-Al2O3-TiO2-V2O system s ºC 1600C C 1600 characterisation eutecticlike eutectic like Al,V,Ticontaining AlVTicontaining Al,V,Ti containing FeOSiCacontaining Fe Si Ca singlephase single ascast cast discrepancies instance FactSages FToxidSPV, FToxidSPV FToxid SP V, FToxid-SP-V FToxidSPINA, FToxidSPINA SPINA, SPINA FToxid-SPINA FToxidTiSp TiSp FeO2TiO2s. FeO2TiO2s FeOTiOs 2 . (FeO)2(TiO2)(s) Finally Ipanemas 75 1050ºC FeOSiO CaOP FeOSiO2CaOP2O5Al2O3TiO2V2O PO P2O AlO Al2O VO V2O 160 Ticontaining AlVTi (FeO)2(TiO2)(s 7 16 1

Flat band electronic modes are responsible for superconductivity in twisted bilayer graphene rotated at magic angles. From there other magic angles can be found for any multilayered twisted graphene systems. Eventually this lead to the discovery of the highest ever known electron-electron correlated material. Moreover, the quantum phase diagram of twisted bilayer graphene is akin to those observed among high-T c superconductors and thus there is a huge research effort to understand twisted bilayer graphene in the hope of clarifying the physics behind such strong correlations. A particularity of the twisted bilayer graphene is the coexistence of superconductivity and the fractional Quantum Hall effect, yet this relationship is not understood. In this work, a simple 2 × 2 matrix model for twisted bilayer graphene is obtained by taking the square of the original 4 × 4 chiral twisted bilayer graphene hamiltonian. Such squared Hamiltonian contains the magic angles and due to the intrinsic chiral symmetry in twisted bilayer graphene, a lowest energy level related to the quantum Hall effect. The non-Abelian properties of this squared Hamiltonian play a central role in the electronic localization to produce the flat bands and here it is proved that the squared Hamiltonian of the chiral TBG model is equivalent to a single electron Hamiltonian inside of a non-Abelian pseudo-magnetic field produced by electrons in other layers. Therefore, the basic and fundamental elements in the physics of magic angles are determined. In particular, an study is made on these fundamental energy contributions at the Γ-point due to its relation to the recurrence of magic angles and its relationship with the Quantum Hall effect.

Abstract Lead-based (PZT) ferroelectric ceramic materials were prepared utilizing the solid-state reaction method as a pure and doped with different additives. As a pure form, the composition with the chemical formula Pb1.03(Zr0.56Ti0.44)O3 characterized as rhombohedral structure according to the PZT phase diagram region was investigated systematically. Different strategies of doping were followed to investigate the influence of donor and acceptor ions in addition to complex doping on structural and microstructure properties of the parent composition: for the soft ceramic, 2 mol% lanthanum-doped PZT at A-site (PLZT), whereas 2 mol% of scandium-doped PZT at B-site to produce hard ceramic (PSZT). In terms of complex doping, 2 mol% of both La3+ and Sc3+ substituted A- and B-site, respectively (PLSZT). All samples showed dense and homogeneous microstructures, except PSZT ceramic displayed a small grain size. X-ray diffraction results showed that the addition of Sc3+ induced phase transformation and formation of a coexistence region consisting of tetragonal and rhombohedral phases. This region was recognized in both PSZT and PLSZT compositions. Hard ceramic (Sc3+-doped PZT) exhibited the highest values of relative permittivity and lowest dielectric loss at a frequency of 100 kHz.

Abstract Historically, phenol/croton oil deep chemical peeling has been very effective and has generated excellent results compared to other formulas used in dermatological clinics. However, it can cause serious side effects in patients sensitive to phenol. Therefore, this study aimed to develop a liquid crystalline structure containing croton oil (without phenol) as well as to evaluate the physical characteristics and cytotoxicity of this new system. Rational proportions of the croton oil, purified water, and polyethylene glycol hexadecyl ether were designed through a partial phase diagram to obtain 26 formulations. After macroscopic analysis and polarized light microscopy evaluation, formulations with lamellar liquid crystalline phase (4 samples) were identified and chosen to determine pH, size, polydispersion index (PDI), zeta potential, and rheological behavior. After 48 hours, three samples presented phase separation. Formulation 8 remained stable, but hydroxyethyl cellulose (HEC, 0.5%, w/w) was added to the aqueous phase, to prevent coalescence. Sample 8A exhibited a pH compatible with the skin, nanometric size, narrow PDI, negative zeta potential, and stability throughout the study period. The addition of HEC improved the organization of the system, making the formulation more stable. The oil, fractions of the oil, and the sample exhibited increasing cytotoxicity, respectively. This result could be attributed to the fractionation process of the vegetal matrix, and the surfactant present in the formulation increased the cell membrane permeability. The proposed approach successfully achieved a physically stable liquid crystal system containing croton oil. Historically phenolcroton phenol clinics However Therefore without water 2 evaluation 4 ( size PDI , (PDI) potential behavior hours separation HEC, (HEC 05 0 5 0.5% w/w ww w coalescence A skin period respectively matrix permeability (PDI 0.5 0.

RESUMEN En este trabajo se realiza la simulación del diagrama de fases de la aleación termorresistente ACI HK 40, modificada con la adición de diferentes contenidos de aluminio y boro, utilizando el software Thermo-Calc. La aplicación del mismo permitió obtener el diagrama de fases, y evaluar la evolución de las fracciones de fases sólidas, durante la solidificación en condiciones de equilibrio, en los rangos de temperatura y composición pertenecientes a las zonas de precipitación de las fases obtenidas, en correspondencia con las propiedades mecánicas estimadas. Además, se pronosticó la evolución de la microestructura del acero al someterlo a elevadas temperaturas; se previó la precipitación de fases secundarias indeseadas como las fases sigma (σ), y se predijo la viabilidad de aplicar tratamientos térmicos para inducir la precipitación de dichas fases secundarias, que podrían incrementar la termo-resistencia de la aleación.

ABSTRACT In this work, the simulation of the phase diagram of the heat-resistant alloy ACI HK 40 modified with the addition of different contents of elements such as aluminum and boron is carried out, using the Thermo-Calc Software. Its application allowed obtaining the phase diagram and evaluating the evolution of the fractions of solid phases, during solidification, under equilibrium conditions in the temperature and composition ranges corresponding to the precipitation windows of the phases obtained in correspondence with the estimated mechanical properties. As well as, the evolution of the microstructure of the steel when subjected to high temperatures is predicted, prevent the precipitation of unwanted secondary phases such as the sigma phases (σ) and predict the feasibility of applying thermal treatments to induce the precipitation of said secondary phases that could increase the alloy heat resistance.

Titanium-Platinum (TiPt) has a martensitic transformation of about 1300 K, making it potential material for use as a high-temperature shape memory alloy. A third element is expected to improve the properties of TiPt alloys for future use in the aerospace industry. In this study, the effect of the addition of Zr on the stability of TiPt was investigated using the cluster expansion method employing the UNCLE code. A total of 21 new structures on the Pt site and 22 new structures on the Ti site were generated. Only seven (7) structures constituted the ground-state line for the Pt site, and six (6) structures for the Ti site, which suggested that these structures were the most thermodynamically stable phases. The ZrTi2Pt phase was the most thermodynamic stable with heats of a formation value of - 0.455 eV/atom on the Pt site. Thus, a phase diagram for the TiPtZr system was constructed. The findings of this study could benefit the design of new materials in the aerospace industry.

Titaan-Platinum (TiPt) het 'n martensitiese transformasie van ongeveer 1300 K, wat dit 'n potensiële materiaal maak vir gebruik as 'n hoë-temperatuur vormgeheue-legering. 'n Derde element sal na verwagting die eienskappe van TiPt-legerings verbeter vir toekomstige gebruik in die lugvaartbedryf. In hierdie studie is die effek van die byvoeging van Zr op die stabiliteit van TiPt ondersoek deur gebruik te maak van die groepuitbreidingsmetode wat die UNCLE kode gebruik. Altesaam 21 nuwe strukture op die Pt-terrein en 22 nuwe strukture op die Ti-terrein is gegenereer. Slegs sewe strukture het die grondtoestandlyn vir die Pt-terrein gevorm, en ses strukture vir die Ti-terrein, wat daarop dui dat dit die mees termodinamies stabiele fases was. Die ZrTi2Pt fase is die mees energeties stabiele met hitte van 'n formasie waarde van - 0.455 eV/atoom op die Pt terrein. Dus is 'n fasediagram vir die TiPtZr-stelsel saamgestel. Die bevindinge van hierdie studie sal tot voordeel van die ontwerp van nuwe materiale in die lugvaartindustrie wees.

Abstract In this paper, we study the liquid-vapor phase diagram and structural properties of discrete potential fluids using integral equations theory and Monte Carlo simulations in Gibbs ensemble. For this purpose, we considered three discrete fluids, namely, square well, square well-barrier, and square well-barrier-well. They represent simple models of fluids with competing interactions that exhibit rich microscopic and macroscopic phase behavior, depending on the strength and range of attractions and repulsions in the potential. Here, we emphasized a structural behavior near the liquid-vapor coexistence. For the square well-barrier fluid, we observed a possible scenario of a microscopic phase separation associated with a cluster-like formation near the critical region, which could be interpreted as a frustration mechanism of the liquid-vapor transition when either the strength or the range of repulsion increases. This microscopic-like separation can be inhibited by suppressing the repulsion or by adding an extra well to the interaction potential. However, for the square well fluid with long-range potential, we found evidence of a microscopic aggregation driven solely by attractions.

Resumo Introdução: O Acidente Vascular Cerebral (AVC) é uma emergência médica com impacto negativo na vida das pessoas. As intervenções administradas no Serviço de Urgência além de serem determinantes para minimizar as complicações tardias decorrentes do AVC, favorecem a qualidade dos cuidados prestados à pessoa na fase mais aguda do quadro clínico. Objetivo: Mapear as intervenções de enfermagem implementadas ao adulto vítima de AVC agudo, no contexto de Serviço de Urgência. Métodos: Realizou-se uma Revisão Scoping de acordo com a metodologia Joanna Briggs Institute. Definida estratégia de pesquisa nas bases de dados PubMed, CINAHL, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, JBI Database of Systematic Reviews and implementation Reports, SciELO, LILACS e BDENF-Nursing. Dois investigadores independentes realizaram a seleção dos estudos, extração e síntese de dados, com base nos objetivos e nas questões de investigação definidas. Os resultados são apresentados com recurso a diagrama (PRISMA Flow Diagram), tabelas de evidências e uma síntese narrativa. Resultados: Incluiu-se doze artigos, com os critérios de elegibilidade definidos, publicados entre 2011 e 2021. Resultaram de estudos quantitativos, qualitativos, revisões da literatura e declarações científicas baseadas em diretrizes. Mapearam-se intervenções de enfermagem efetivas implementadas à pessoa vítima de AVC agudo em contexto de Serviço de Urgência. A avaliação inicial, triagem, ativação de protocolos de reposta rápida de AVC, avaliação de risco de AVC, estabilização, monitorização, procedimentos de enfermagem invasivos, administração de tratamento intravenoso, preparação e acompanhamento para realização de exames e de procedimentos médicos invasivos, deteção precoce de complicações, transferência/transição de cuidados, colaboração no serviço de atendimento à distância, e intervenções no domínio da qualidade, como sendo práticas de enfermagem implementadas no Serviço de Urgência à pessoa vítima de AVC agudo. A equipa de enfermagem desempenha um papel preponderante no cuidado à pessoa com AVC agudo em contexto de Serviço de Urgência. O reconhecimento precoce de sinais e sintomas de AVC é crucial para a assistência, o tratamento rápido e adequado e, consequentemente, a sobrevivência da pessoa vítima de AVC agudo. Conclusão: A formação contínua, implementação de protocolos baseados em diretrizes científicas e de estudos de investigação contribuirá para uma melhor prática de enfermagem no cuidado à pessoa vítima de AVC agudo no Serviço de Urgência.

Resumen Introducción: El accidente cerebrovascular (ACV) es una emergencia médica con un impacto negativo en la vida de las personas. Las intervenciones administradas en el Servicio de Urgencias, además de ser decisivas para minimizar las complicaciones tardías derivadas del ictus, favorecen la calidad de la atención prestada a la persona en la fase más aguda del cuadro clínico. Objetivo: Mapear las intervenciones de enfermería implementadas para adultos víctimas de ictus agudo, en el contexto del Servicio de Urgencias. Métodos: Se realizó una Scoping Review según la metodología del Instituto Joanna Briggs. Estrategia de búsqueda definida en PubMed, CINAHL, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, JBI Database of Systematic Reviews and Implementation Reports, SciELO, LILACS y BDENF - Nursing. Dos investigadores independientes realizaron la selección del estudio, extracción y síntesis de datos, en base a los objetivos y preguntas de investigación definidas. Los resultados se presentan mediante un diagrama (diagrama de flujo PRISMA), tablas de evidencia y una síntesis narrativa. Resultados: Se incluyeron doce artículos, con criterios de elegibilidad definidos, publicados entre 2011 y 2021. Fueron el resultado de estudios cuantitativos y cualitativos, revisiones de literatura y declaraciones científicas basadas en guías. Se mapearon intervenciones efectivas de enfermería implementadas para víctimas de ictus agudo en el contexto del Servicio de Urgencias. Evaluación inicial, cribado, activación de protocolos de ictus de respuesta rápida, evaluación del riesgo de ictus, estabilización, monitorización, procedimientos de enfermería invasivos, administración de tratamiento intravenoso, preparación y seguimiento de exámenes y procedimientos médicos invasivos, detección precoz de complicaciones, transferencia / transición de la atención , la colaboración en el servicio de teleasistencia, y las intervenciones en el ámbito de la calidad, como prácticas de enfermería implantadas en el Servicio de Urgencias para la víctima de ictus agudo. El equipo de enfermería juega un papel preponderante en la atención de las personas con ictus agudo en el contexto del Servicio de Urgencias. El reconocimiento temprano de los signos y síntomas del ictus es fundamental para la asistencia, el tratamiento oportuno y adecuado y, en consecuencia, la supervivencia de la persona víctima de un ictus agudo. Conclusione: La educación continua, la implementación de protocolos basados en guías científicas y estudios de investigación contribuirán a una mejor práctica de enfermería en la atención de víctimas de ictus agudo en el Servicio de Urgencias.

Abstract Introduction: The cerebrovascular accident (CVA) is a medical emergency with a negative impact on people's lives. Interventions administered in the Emergency Service, in addition to being decisive to minimize late complications resulting from stroke, favor the quality of care provided to the person in the most acute phase of the clinical condition. Objective: To map the nursing technologies implemented for adult victims of acute stroke, in the context of the Emergency Service. Methods: A Scope Review was carried out according to the Joanna Briggs Institute methodology. Search strategy defined in PubMed, CINAHL, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, JBI Database of Systematic Reviews and Reports, SciELO, LILACS and BDENF - Nursing databases. Two independent researchers performed a selection of studies, extraction and data synthesis, based on the objectives and defined research questions. The results are found using a diagram (PRISMA flow diagram), evidence tables and a narrative. Results: Articles with defined eligibility criteria, published between 2011 and 2021, were included. They resulted from quantitative and qualitative studies, literature reviews and scientific statements based on guidelines. Effective nursing actions implemented for the victim of acute stroke in the context of the Emergency Service were mapped. Initial, screening, activation of rapid response stroke protocols, stroke risk assessment, stabilization, monitoring, invasive nursing procedures, administration of intravenous treatment, preparation and follow-up to carry out assessment of invasive medical tests and procedures, detection early complications, transfer/transfer of care, collaboration in the distance care service, and interventions in the domain of quality, as being nursing practices implemented in the Emergency Service for the victim of acute stroke. The nursing team plays a preponderant role in the care of people with acute stroke in the context of the Emergency Service. The early recognition of stroke signs and symptoms is crucial for assistance, prompt and adequate treatment and, consequently, the survival of the person victim of an acute stroke. Conclusion: Continuing education, implementation of protocols based on scientific guidelines and research studies will contribute to a better nursing practice in the care of acute stroke victims in the Emergency Service.

Abstract A simple, precise, accurate and robust high performance liquid chromatographic method has been developed for simultaneous estimation of Torsemide and Eplerenone in tablet dosage form. Design of experiment was applied for multivariate optimization of the experimental conditions of RP-HPLC method. A Central composite design was used to study the response surface methodology and to analyse in detail the effects of these independent factors on responses. Total eleven experiments along with 3 center points were performed. Two factors were selected to design the matrix, one factor is variation in ratio of Acetonitrile and the second factor is flow rate (mL/min). Optimization in chromatographic conditions was achieved by applying Central composite design. The optimized and predicted data from contour diagram comprised mobile phase (acetonitrile, water and methanol in the ratio of 50: 30: 20 v/v/v respectively), at a flow rate of 1.0 ml/min and at ambient column temperature. Using these optimum conditions baseline separation of both drugs with good resolution and run time of less than 5 minutes were achieved. The optimized assay conditions were validated as per the ICH guidelines (2005). Hence, the results showed that the Quality by design approach could successfully optimize RP-HPLC method for simultaneous estimation of Torsemide and Eplerenone.

Resumen Se presenta la variación de los diagramas de interacción en columnas sólidas circulares considerando la posición del acero de refuerzo longitudinal. Se consideran dos posiciones: a) la primera barra coincide con el eje vertical, b) la primera barra se coloca desfasada a la derecha el semiángulo entre barras. Una diferencia de -4.2% a 6.6% se evaluó en 32 pares de diagramas de columnas armadas con cantidades variables de barras (6-11 barras) y cuantía de refuerzo entre 2.42% y 4.13%. El error entre curvas es 2%, 4% y 7% en columnas reforzadas con 10, 7 y 6 barras respectivamente. Así, se concluye la importancia de considerar la posición del acero de refuerzo en columnas circulares sólidas armadas con pocas barras de refuerzo (6-9 barras).

Abstract The variation of the interaction diagrams for solid circular columns is presented considering the position of the longitudinal rebars. Two of them were considered: a) the first rebar coincides with the vertical longitudinal axis, and b) the first rebar is placed out of phase to the right of the semi-angle between two rebars. A variation of -4.2% to 6.6% was evaluated in 32 pairs of interaction diagrams for columns reinforced with a variable quantity of rebars (from 6 to 11 rebars) and steel ratios ranging from 2.42 to 4.13%; the error is 2%, 4%, and 7% in columns reinforced with 10, 7, and 6 rebars, respectively. Therefore, considering the position of the rebars in columns with a small amount of reinforcement (6 to 9 rebars) is very important for the design process.

Resumen Los diagramas de fases de sustancias puras, a modo de gráficos de presión versus temperatura, suelen introducirse en cursos universitarios de química iniciales. Por lo general, se emplean diagramas esquemáticos, fuera de escala, para poder cubrir un rango completo de presiones y temperaturas. En ellos se acentúan o exageran ciertos detalles, con el fin de resaltar ciertos comportamientos de la sustancia considerada. Esto lleva el riesgo de inducir errores conceptuales que no están presentes en un diagrama en escala. Las representaciones gráficas son una herramienta especial para la adquisición de conceptos y el reconocimiento de fenomenologías físicas y químicas. Por esta razón, es necesario que en la enseñanza se preste atención y se realicen las aclaraciones suficientes a los estudiantes, para evitar concepciones erróneas producto de la distorsión inherente a un diagrama de fases esquemático. En el presente trabajo se toma como ejemplo el diagrama de fases del azufre, debido a que, tanto en libros de texto como en artículos científicos, suele mostrarse con algunos errores cualitativos.

Abstract Pure substance phase diagrams, as pressure versus temperature graphs, are usually introduced in first university courses in chemistry. In general, off-scale schematic diagrams are used to cover a full range of pressures and temperatures. In them, to highlight certain behaviors of the substances, some details are accentuated or exaggerated, and this implies a greater risk of inducing comparative misconceptions than using scale diagrams. Taking in account that graphic representations are important tools in the teaching of concepts and in the recognition of physical and chemical phenomenologies, to avoid conceptual errors, schematic diagrams and their inherent distortions should be carefully discussed with students. In the present work, the sulfur phase diagram is taken as an example, because, both in textbooks and in scientific articles, it is often shown with some qualitative errors.

Abstract Recently, within a generalized Hubbard model which includes correlated nearest (Δt) and next-nearest hopping interactions (Δt3), a comparative study between d- and s*- wave superconducting ground states on a square lattice was performed. It was found that the critical temperature of transition T c (n), as a function of the electron concentration n, reaches a maximum (T c-max ) at a given optimal doping (n op ) for each value of the ratio t´/t, where t and t´ are the tight-binding nearest and next-nearest hopping parameter of a square lattice, respectively. From all values obtained for T c - m a x ( t ' / t , n o p ) a global minimum one was encountered for both symmetries. Likewise, in the same space, a minimal ground state energy Eg was also obtained. For d-wave channel both minima are localized around the same optimal doping. However, for s* symmetry, the two minima are located at different electron concentrations. In this work, we additionally study how the p-wave ground-state energy and the critical temperature depend on the hoppings parameters and the electron concentration. The results show that for p-wave, minimum global values of T c-max and Eg in the ( t ' / t , n o p ) space do exist too, and are found around half filling but, as occurs for s *- wave, the minimum of T c-max does not occur at the same point as Eg. Moreover, we present a ground-state phase diagram in the space ( t ' / t , n o p ) where it is possible to find zones of coexistence and competition between the s*-, p- and d-wave symmetries. Also, an analysis of the shape of the Fermi surface and the single-particle energy, as functions of the wave vector of an electron in the Cooper pair, has been done for different regions of the mentioned space.