Estudio electroquímico de las interacciones formadas por el extracto activo de las hojas de Morinda citrifolia en la inhibición de la corrosión de acero estructural

Estudio de la inhibición de la corrosión de diferentes extractos de Morinda citrifolia, en la corrosión de acero estructural AISI1045En el presente trabajo de investigación se reportan los resultados obtenidos en la actividad inhibidora a la corrosión de un extracto-liquido natural proveniente de las hojas de Morinda citrifolia (MC). Además, se investigó la influencia de la polaridad de las moléculas orgánicas empleando diferentes disolventes (hexano-C6H14, acetona-CH3(CO)CH3, etanol-C2H5OH y agua-H2O) para cada una de las extracciones. Al mejor extracto con carácter inhibidor se estudió por diferentes concentraciones (0.4, 0.8, 1.2, 1.6, 2.0 g/L) y diferentes tiempos de exposición al medio desde 1 a 4 h. El material de prueba fue un acero al carbono con especificación AISI 1045 sometido a un medio corrosivo que contiene HCl 0.5 M.Mediante técnicas electroquímicas como la aproximación de Tafel, resistencia a la polarización RP y espectroscopia de impedancia electroquímica EIS se evalúo el carácter de inhibición de los diferentes extractos de MC. Además, se evaluó la velocidad de corrosión para las diferentes fracciones del extracto (Hexano, Acetona, Etanol y Agua). Se determinó que los componentes extraídos con agua proporcionan los valores de inhibición más altos. La eficiencia de inhibición (EI) varía dependiendo de la técnica de caracterización, pero su valor se encuentra en torno a un 66% aproximadamente. Estos valores justifican que se lleva a cabo un mecanismo de fisisorción de las moléculas orgánicas del extracto de agua, con mayor polaridad, sobre la superficie del metal siguiendo una isoterma de Langmuir. La débil interacción entre estas y el sustrato es del tipo electrostático, que puede provocar la desorción de las mismas sobre todo a tiempos largos de inmersión, como se comprobó experimentalmente. Los valores de la energía libre de Gibbs calculados fueron de -21 KJ/mol indicando que el inhibidor está siendo adsorbido de manera espontánea en la superficie metálica. El análisis morfológico por microscopia electrónica en presencia y ausencia del inhibidor confirmó, que las moléculas orgánicas forman una cubierta protectora que inhibe los procesos corrosivos en la superficie del metal.CONACY

Decay of Small Solutions for the Zakharov-Kuznetsov Equation posed on a half-strip

We formulate in a half-strip an initial boundary value problem for the Zakharov-Kuznetsov equation. Assuming the existence of a regular global solution, we prove an exponential decay for small initial data

Searching for the 'Muslims' in Czech Islamophobia and the Effects of Intergroup Contact in Challenging the 'Fear of the Unknown'

Since at least 2014, cross-national surveys have measured the most negative attitudes towards 'Muslims' in the EU among Czech respondents. These attitudes have often been attributed to few contact opportunities with actual Muslims in the country and, thus, public overreliance on the highly negative representations of 'Muslims' in public discourse. However, empirical qualitative assessments of the stereotypes which guide many Czechs' anti-Muslim prejudice and the effects of intergroup contact have been neglected. In an epistemological shortcoming, the survey category 'Muslim' has often been treated as one of analysis rather than of practice. Contrarily, I argue that Czech participants' contingent understandings and racialisation of the category need to be reclaimed as the ontological basis of prejudice. In this study, I relied on the results of a larger constructionist thematic analysis of 31 semi-structured interviews with non-Muslim Czechs and, regardless of citizenship or ethnicity, Muslims living in Czechia conducted in 2020 and 2021. The results show that, in line with public discourse dynamics, 'Muslims' in Czechia are commonly understood as immigrants racialised through their perceived Arabness, Middle Easternness and non-Whiteness. Furthermore, perceptions of Western European 'Muslims' as highly conflictual are juxtaposed with the fragility of Czechia in the face of immigration. Against this backdrop, I examine the mechanisms through which intergroup contact enriches participants' social cognitions of 'Muslims' - namely, subgrouping, positive stereotyping, reduced perceived intergroup threat and anxiety, and (re-)humanisation

Space-based and object-centered gaze cuing of attention in right hemisphere-damaged patients

Gaze cuing of attention is a well established phenomenon consisting of the tendency to shift attention to the location signaled by the averted gaze of other individuals. Evidence suggests that such phenomenon might follow intrinsic object-centered features of the head containing the gaze cue. In the present exploratory study, we aimed to investigate whether such object-centered component is present in neuropsychological patients with a lesion involving the right hemisphere, which is known to play a critical role both in orienting of attention and in face processing. To this purpose, we used a modified gaze-cuing paradigm in which a centrally placed head with averted gaze was presented either in the standard upright position or rotated 90° clockwise or anti-clockwise. Afterward, a to-be-detected target was presented either in the right or in the left hemifield. The results showed that gaze cuing of attention was present only when the target appeared in the left visual hemifield and was not modulated by head orientation. This suggests that gaze cuing of attention in right hemisphere-damaged patients can operate within different frames of reference

Development and Testing of Hardware Simulator for Satellite Proximity Maneuvers and Formation Flying

Satellite Formation Flying (SFF) and Proximity Operations are applications that have increasingly gained interest over the years. These applications foresee the substitution of a single spacecraft with a system of multiple satellites that perform coordinated position and attitude control maneuvers, which in turn results in higher accuracy of payload measurement, higher flexibility, robustness to failure, and reduction of development costs. These systems present however higher difficulties in their design since they have not only absolute but also relative state requirements, which make them also liable to higher control action expense with respect to (wrt) the single satellite systems. Moreover, applications like Automated Rendez-Vous and Docking (RVD) and in general close proximity maneuvers present a high risk of impact between the satellites, which must be treated with an appropriate design of the on board Guidance Navigation and Control (GNC) system. These aspects justify the development and employment of a ground hardware simulator representative of two or more satellites performing coordinate maneuvers, allowing the investigation of these problems with an easily accessible system. The aim of my Ph.D. Activities has consisted in the development and testing of the cooperating SPAcecRaft Testbed for Autonomous proximity operatioNs experimentS (SPARTANS) hardware simulator, which is under development since 2010 at the Center of Studies and Activities for Space (CISAS) of the University of Padova. This ground simulator presents robotic units that allow the reproduction of the relative position and attitude motions of satellites in proximity or in formation, and can be therefore employed for the extensive study of control algorithms and strategies for these types of applications, allowing dedicated hardware in the loop to be tested in a controlled environment. At the beginning of my Ph.D., the testbed consisted in the first prototype of Attitude Module (AM), a platform with three rotational Degrees of Freedom (DOF) of Yaw, Pitch and Roll, controllable through a GNC system based on incremental encoders and air thrusters. A small contribution was initially given in support of the execution of a series of 3 DOF attitude control maneuvers tests with the AM. Subsequently, the first activity consisted in the design and development of the air suspension system that enables a low friction translational motion of the a whole Unit of the testbed over the test table, with the characterization of air skids available in laboratory. The subsequent activity consisted in the design and development of the Translation Module (TM), the lower section of the whole Unit, as modular structure supporting the air suspension system, the AM, and the on board localization system. After this activity the on board localization system for position and Azimuth estimation, based on Optical Flow Sensors (OFS), was developed and tested. The system was installed on a TM base prototype and it was calibrated and tested with the imposition of known motions through rotational and translational motorized stages wich were used in conjunction, presenting max deviations at the level of 0.1° for a total rotational range of 40°, and max deviations of 1 mm for a total translational range of 100 mm. Combined maneuvers, i.e. translational and rotational motions imposed in sequence, were subsequently performed, showing a drift trend, up to approximately 1 cm for a 90° rotation. Subsequently the OFS system was assembled in the TM and integrated with an external vision system, under development in parallel in the context of the SPARTANS project. Results showed a good general concordance between the two systems, but combined maneuvers with extended rotational range showed again a drift trend in the OFS system solution, not only in position but also in Azimuth. A parallel activity consisted in the design and development of the levellable test table for the Units with a modular structure. Another activity consisted in the development of a Matlab Software Simulator for Units tests planning. A series of preliminary standard and optimal control maneuvers were planned with the software simulator. The last activity of my Ph.D. consisted in the analysis of an inspection scenario for satellite removal purposes, with the goal of reproducing the relative dynamics in scale with the SPARTANS simulator. The chosen scenario foresaw the inspection, through a vision system on board an inspection satellite, of the currently freely tumbling Envisat spacecraft . The analysis performed with a Matlab software simulator was focused on the acquisition and maintainance of a circular relative orbit at close range starting from a flyaround orbit, through the employment of Model Predictive Control (MPC) and Linear Quadratic Regulator (LQR) optimal controllers. Simulations results showed a lower tracking error in position with the MPC controller wrt to the LQR controller, but with a higher control action expense: for a 6 hours inspection on a 41 m radius circular relative orbit, the max total delta-v component resulted of 3.3 m/s for MPC, while it resulted of 0.7 m/s for LQR. In the present configuration the SPARTANS testbed presents a first complete Unit and test table to be assembled in the immediate future for the execution of the first position and attitude control maneuvers. The final configuration of the testbed will present a minimum of two Units allowing to perform coordinate control maneuvers for the investigation and study of problems and strategies related to SFF, Automated Rendez-Vous and Docking, and in general proximity manevuers

O Problema da Fonte da Inteligibilidade em Ser e Tempo

O artigo analisa o problema da fonte da inteligibilidade na fenomenologia hermenêutica de Martin Heidegger. Partindo da analítica existencial na qual entes humanos descritos como ser-aí (Dasein) são ser-no-mundo, Heidegger reconhece que os entes ganham identidade e significação no interior do mundo, este, compreendido como espaço de significatividade. Os entes disponíveis no interior do mundo são significativos em função do mundo, desse modo, já aparecem imersos em contextos estruturados de sentido e imediatamente inteligíveis ao ser-aí. Diversos estudiosos da obra do filósofo alemão questionam a origem da inteligibilidade e do que constitui esse espaço de sentido. O ponto central do problema consiste em identificar qual seria a estrutura existencial que é responsável pela constituição do espaço de sentido. O artigo faz uma reconstrução do debate sobre a fonte da inteligibilidade a partir das contribuições de Charles Guignon – o qual defende que a fonte da inteligibilidade é a linguagem – e de Hubert Dreyfus – que sustenta que são as normas ou práticas públicas do impessoal (Das Man) que originam a inteligibilidade. A partir dessas posições, Pierre Keller e David Weberman sustentam que ambas estão equivocadas, e defendem que a origem da inteligibilidade se encontra na temporalidade

Método de implementação do controle estatístico do Processo (CEP): um estudo de caso em uma indústria Alimentícia do Vale do Taquari/RS sob a ótica da Metodologia DMAIC

A preocupação com a qualidade em produtos e serviços é um fator indispensável ao crescimento e amadurecimento das indústrias, sendo que muitos recursos das organizações são destinados para o desenvolvimento e aperfeiçoamento desta área. Para isto, o Controle Estatístico de Processo foi desenvolvido para manter os processos estáveis e para ter uma produção com itens homogêneos ao longo do processo. Desta forma, o presente trabalho traz um método para implementação do CEP em indústria de alimentos do Vale do Taquari/RS, sob a ótica da metodologia DMAIC. Para tanto, foram utilizados os métodos de pesquisa dialético, dedutivo e indutivo. A abordagem é classificada como quantitativa e qualitativa, tendo como objetivo geral do trabalho a pesquisa exploratória. Quanto aos procedimentos técnicos, foram desenvolvidas a pesquisa bibliográfica, a pesquisa documental e o estudo de caso. O estudo de caso consistiu em analisar as reclamações dos clientes para com os produtos da empresa, com finalidade de analisar quais características de qualidade tinham relação com as não-conformidades percebidas. Desta forma, foi realizado a construção da Casa da Qualidade, por meio do desdobramento do QFD, e identificado quais características da qualidade que afetam as principais reclamações dos clientes. Com esta identificação, foi possível realizar, através do planejamento de experimentos, uma análise das variáveis de controle que impactam o resultado final. Também foi identificado, através do cálculo da capabilidade, que o processo atual é incapaz de atender as especificações do produto estudado. Com isto, por meio de ferramentas de qualidade, foram realizadas as propostas de melhorias no processo, bem como uma matriz de priorização para a resolução destas atividades, finalizando com um plano de ação de melhorias e um fluxograma prático de uma proposta de implementação do CEP na empresa. A conclusão do estudo é que a partir do trabalho apresentado, a empresa realize as melhorias propostas e diminua sua variabilidade, tornando o processo capaz e trazendo resultados positivos para a companhia.The concern with the quality in products and services has been an indispensable factor for the growth and maturation of the industries, and many resources of the organizations are destined for the development and improvement of this area. For this, the Statistical Process Control was developed to keep the processes stable and to have a production with homogeneous items throughout the process. In this way, the present work studied a method for implementation of the SPC in a food industry located at Vale do Taquari / RS, following the DMAIC methodology. For this, dialectical, deductive and inductive research methods were used. Regarding the methods of approach, the quantitative and qualitative approaches were used, with the exploratory research as a general objective. Regarding the technical methodologies used, the bibliographical research, the documentary research and the case study were developed. The case study consisted of analyzing customer complaints about the company's products, in order to analyze which quality characteristics were related to perceived nonconformities. In this way, the construction of the Quality House was carried out and identified which quality characteristics affect the main customer complaints. With this identification, it was possible to perform, through the design of experiments, an analysis of the control variables that impact the final result. It was also identified, through the calculation of the capacity, that the current process is unable to reach the specifications of the product studied. With this, through quality tools, proposals were made for improvements in the process, as well as a prioritization matrix for the resolution of these activities, ending with an improvement action plan and a practical flowchart of a SCP implementation proposal in the company. The conclusion of the study is that by making such improvements, the process tends to present capable and the variabilities presented before in the process will be smaller, bringing positive results for the company

Rede de apoio para o aleitamento materno na prematuridade tardia

A prematuridade tardia, nascimento entre 34 e 36 semanas mais 6 dias, é um problema de saúde pública. Estes recém-nascidos representam cerca de 70% de todos os recémnascidos prematuros nascidos. Devido ao fato de terem peso e tamanho semelhantes aos recém-nascidos a termo, na maioria das vezes suas especificidades de cuidados não são observadas, tanto pelos profissionais de saúde como pelas mães e suas famílias. Uma das principais particularidades desses recém-nascidos é a não coordenação respiração sucção-deglutição, o que está diretamente relacionado às dificuldades para se alimentar. Com isso, o aleitamento materno dos recém-nascidos prematuros tardios possui especificidades e acredita-se que, se a mãe não receber apoio adequado na sua chegada no domicílio, após a alta hospitalar, a amamentação exclusiva ou de forma predominante não se estabelece. Os objetivos do estudo foram: descrever e analisar a rede social das mães de prematuros tardios no aleitamento materno; refletir sobre atenção ao aleitamento materno segundo as ações programáticas públicas vigentes. Método: pesquisa qualitativa, exploratório-descritiva, apoiada no Referencial Teórico Metodológico de Rede de Apoio de Sanicola. Foram entrevistadas 15 mães de recém nascidos prematuros tardios por meio de visitas domiciliares, quando seus filhos completaram 15 dias de vida. A coleta de dados ocorreu no período de novembro de 2016 a fevereiro de 2017. A análise dos dados se deu pela interpretação dos mapas de rede de apoio elaborados pelas mães e pelo tipo de apoio recebido. Percebeu-se que as redes de apoio dessas mães eram pequenas e frágeis e que o apoio prestado estava mais relacionado aos cuidados com os afazeres domésticos e com os cuidados com o recém nascido, do que com o aleitamento materno. Ao se refletir sobre a atenção ao aleitamento materno a partir das ações, programas e políticas públicas, percebem-se uma sobreposição de objetivos e a não inclusão desses recém-nascidos nos programas, ações e políticas voltados para os prematuros, o que reforça a invisibilidade deles nos cuidados de saúde.Late prematurity, birth between 34 and 36 weeks plus 6 days, is a public health problem. These newborns account for about 70% of all preterm newborns born. Because they are similar in weight and size to full-term newborns, most often their care specificities are not observed by both health care providers and mothers and their families. One of the main peculiarities of these newborns is the non-coordination breathing-suction-swallowing which is directly related to the difficulties to feed themselves. Thus, breastfeeding of late preterm infants has specificities and it is believed that if the mother does not receive adequate support when she arrives at home after hospital discharge, exclusive or predominant breastfeeding is not established. The objectives of the study were: to describe and analyze the social network of mothers of late preterm infants in breastfeeding; reflect attention to breastfeeding according to the current public programmatic actions. Method: qualitative research, exploratory descriptive, supported in the Theoretical Framework of Sanicola Support Network. Fifteen mothers of late preterm infants were interviewed through home visits, when their children completed 15 days of life. Data collection took place from November 2016 to February 2017. Data analysis was based on the interpretation of the support network maps prepared by the mothers and the type of support received. It was noticed that the support networks of these mothers are small and fragile and that the support provided is more related to the housework and care of the newborn than to breastfeeding. Reflecting on the attention to breastfeeding from the actions, programs and public policies, there is an overlapping of objectives and the non-inclusion of these newborns in the programs, actions and policies aimed at the premature, which reinforces the invisibility of these health care

Representación política y confianza institucional : Una visión latinoamericana

¿Bajo qué condiciones los ciudadanos desconfían de las instituciones políticas? Las respuestas a esta pregunta son variadas y pueden ubicarse en dos grandes corrientes: la culturalista que destaca la importancia de los valores culturales y b) la racional culturalista, según la cual la desconfianza es resultado de los deficientes desempeños de los gobiernos democráticos. La presente investigación analiza tres diferentes dimensiones de la performance, vinculadas todas ellas al concepto de representación y relacionadas con etapas, actividades y actores específicos: 1. la calidad institucional (relativa a las reglas de juego y su funcionamiento); 2. la calidad de la política (relativa a los a la calidad de los procesos de deliberación, negociación y sanción de leyes, así como a la productividad legislativa); 3. la calidad de los resultados (vinculada al impacto de las políticas públicas sobre el bienestar social). Si bien se presentan algunos datos estadísticos, la evidencia empírica es muy preliminarAnder which conditions citizens distrust on political institutions? Answers to this questions are diverse and may be classified in two main approaches: culturalist and rational culturalist. Based on the latter, this paper analyzes the association between quality of political representation and institutional confidence in Latin America. This research is focused on the concept of representation and its dimensions (rules, elites and government effectiveness), and support the hypothesis that people confidence on political institutions is better explained by the performance of representative actors than cultural values of people. Empirical findings are, nevertheless, very preliminaryJornadas realizadas junto con el I Encuentro Latinoamericano de Metodología de las Ciencias Sociales.Facultad de Humanidades y Ciencias de la Educació

Effect of reconstruction algorithms on the accuracy of (99m)Tc sestamibi SPECT/CT parathyroid imaging

The superiority of SPECT/CT over SPECT for (99m)Tc-sestamibi parathyroid imaging often is assumed to be due to improved lesion localization provided by the anatomic component (computed tomography) of the examination. It also is possible that this superiority may be related to the algorithms used for SPECT data reconstruction. The objective of this investigation was to determine the effect of SPECT reconstruction algorithms on the accuracy of MIBI SPECT/CT parathyroid imaging. We retrospectively analyzed preoperative MIBI SPECT/CT parathyroid imaging studies performed on 106 patients. SPECT data were reconstructed by filtered back projection (FBP) and by iterative reconstruction with corrections for collimator resolution recovery and attenuation (IRC). Two experienced readers independently graded lesion detection certainty on a 5-point scale without knowledge of each other\u27s readings, reconstruction methods, other test results or final diagnoses. All patients had surgical confirmation of the final diagnosis, including disease limited to the neck, and location and weight of excised lesion(s). There were 135 parathyroid lesions among the 106 patients. For FBP SPECT/CT and IRC SPECT/CT sensitivity was 76% and 90% (p = 0.003), specificity was 87% and 87% (p = 0.90), and accuracy was 83% and 88% (p = 0.04), respectively. Inter-rater agreement was significantly higher for IRC than for FBP (kappa = 0.76, good agreement , versus kappa = 0.58, moderate agreement , p \u3c 0.0001). We conclude that the improved accuracy of MIBI SPECT/CT compared to MIBI SPECT for preoperative parathyroid lesion localization is due in part to the use of IRC for SPECT data reconstruction