Asymptotic entanglement in a two-dimensional quantum walk

The evolution operator of a discrete-time quantum walk involves a conditional shift in position space which entangles the coin and position degrees of freedom of the walker. After several steps, the coin-position entanglement (CPE) converges to a well defined value which depends on the initial state. In this work we provide an analytical method which allows for the exact calculation of the asymptotic reduced density operator and the corresponding CPE for a discrete-time quantum walk on a two-dimensional lattice. We use the von Neumann entropy of the reduced density operator as an entanglement measure. The method is applied to the case of a Hadamard walk for which the dependence of the resulting CPE on initial conditions is obtained. Initial states leading to maximum or minimum CPE are identified and the relation between the coin or position entanglement present in the initial state of the walker and the final level of CPE is discussed. The CPE obtained from separable initial states satisfies an additivity property in terms of CPE of the corresponding one-dimensional cases. Non-local initial conditions are also considered and we find that the extreme case of an initial uniform position distribution leads to the largest CPE variation.Comment: Major revision. Improved structure. Theoretical results are now separated from specific examples. Most figures have been replaced by new versions. The paper is now significantly reduced in size: 11 pages, 7 figure

Rendimiento diagnóstico de repetir la biopsia guiada por ultrasonido endoscópico después de una primera biopsia negativa en pacientes con lesiones no pancreáticas

ResumenIntroducciónEl ultrasonido endoscópico has sido un método útil para la evaluación de la enfermedad pancreatobiliar por más de una década, sin embargo no es un escenario raro el encontrar resultados patológicos no concluyentes en el tejido obtenido para el diagnóstico. Entre los factores que alteran el rendimiento diagnóstico se encuentran la experiencia del endosonografista, el volumen de procedimientos realizados, el tipo, el tamaño y la localización, entre otros. El objetivo del presente estudio fue evaluar el rendimiento diagnóstico de la segunda USE-BAAF en las lesiones no pancreáticas.Material y métodosSe realizó un estudio retrospectivo y transversal. Se incluyeron pacientes >18 años a los que se les realizó USE-BAAF durante el periodo de 8 años.ResultadosSe realizaron 150 procedimientos en 132 pacientes con lesiones no pancreáticas. Finalmente, el diagnóstico se logró por USE-BAAF en 114/132 pacientes, para un rendimiento diagnóstico global de 86.63%. En total, la mediana (intervalo mínimo-máximo) de biopsias fue de 1 (1-5). El rendimiento diagnóstico de la primera USE-BAAF fue de 77.3% (102/132). Se realizó una segunda biopsia en 16/132 (12.1%) pacientes. Con la segunda USE-BAAF se observó un aumento del rendimiento global a 113/132 pacientes (11/16=68.7%; global 85.6%). No se observaron complicaciones.ConclusiónEl repetir la USE-BAAF en lesiones no pancreáticas es necesario en pacientes con una primera negativa USE-BAAF, ya que mejora el rendimiento diagnóstico.AbstractIntroductionEndoscopic ultrasound has been a useful method for the evaluation of pancreatobiliary pathology for more than a decade, however it is not unusual to find inconclusive pathological results in tissue obtained for diagnosis. The factors affecting diagnostic performance include; endosonographist experience, the volume of procedures performed, type, size and location, amongst others. The aim of this study was to evaluate the diagnostic performance of the second EUS-FNA in non-pancreatic lesions.Material and methodsA retrospective cross-sectional study that includedpatients>18 years who underwent EUS-FNA over a period of 8 years.Results150 procedures were performed in 132 patients with non-pancreatic lesions. Finally, the diagnosis was obtained by EUS-FNA in 114/132 patients for a diagnostic yield of 86.6%. In total, the biopsy median (minimum/maximum interval) was 1 (1-5). The diagnostic yield of the first EUS-FNA was 77.3% (102/132). With the second EUS-FNA 11/16 patients had a histological diagnosis (11/16=68.7%; global 85.6%). No complications were reported.ConclusionRepeat EUS-FNA in patients with non-pancreatic lesions is necessary in patients with a first negative EUS-FNA because it improves the diagnostic yield

Quantum walks: a comprehensive review

Quantum walks, the quantum mechanical counterpart of classical random walks, is an advanced tool for building quantum algorithms that has been recently shown to constitute a universal model of quantum computation. Quantum walks is now a solid field of research of quantum computation full of exciting open problems for physicists, computer scientists, mathematicians and engineers. In this paper we review theoretical advances on the foundations of both discrete- and continuous-time quantum walks, together with the role that randomness plays in quantum walks, the connections between the mathematical models of coined discrete quantum walks and continuous quantum walks, the quantumness of quantum walks, a summary of papers published on discrete quantum walks and entanglement as well as a succinct review of experimental proposals and realizations of discrete-time quantum walks. Furthermore, we have reviewed several algorithms based on both discrete- and continuous-time quantum walks as well as a most important result: the computational universality of both continuous- and discrete- time quantum walks.Comment: Paper accepted for publication in Quantum Information Processing Journa

Determinants of cognitive function in childhood: A cohort study in a middle income context

BACKGROUND: There is evidence that poverty, health and nutrition affect children's cognitive development. This study aimed to examine the relative contributions of both proximal and distal risk factors on child cognitive development, by breaking down the possible causal pathways through which poverty affects cognition. METHODS: This cohort study collected data on family socioeconomic status, household and neighbourhood environmental conditions, child health and nutritional status, psychosocial stimulation and nursery school attendance. The effect of these on Wechsler Pre-School and Primary Scale of Intelligence scores at five years of age was investigated using a multivariable hierarchical analysis, guided by the proposed conceptual framework. RESULTS: Unfavourable socioeconomic conditions, poorly educated mother, absent father, poor sanitary conditions at home and in the neighbourhood and low birth weight were negatively associated with cognitive performance at five years of age, while strong positive associations were found with high levels of domestic stimulation and nursery school attendance. CONCLUSION: Children's cognitive development in urban contexts in developing countries could be substantially increased by interventions promoting early psychosocial stimulation and preschool experience, together with efforts to prevent low birth weight and promote adequate nutritional status

Factors associated with face-to-face educational disruption by COVID-19: Higher education students’ opinions towards virtual education

Esta investigación se realizó durante la suspensión de clases presenciales, debido al alto contagio del SARS-CoV-2. Objetivos: identificar los factores asociados con los problemas para seguir sus estudios de forma virtual, y medir la predisposición estudiantil ante la nueva forma de aprender. En el estudio, se encuestaron a 51 estudiantes, se realizaron tablas 2x2 para determinar el riesgo (OR), chi cuadrado (X2), la prueba exacta de Fisher, además, la escala tipo Likert para valorar sus opiniones y perspectivas sobre su entorno educativo. En el análisis multivariado los factores asociados con los problemas para seguir estudiando de forma virtual fueron: no tener dispositivos para sus clases, comunicación mala o muy mala con sus profesores, forma de trabajo virtual de regular a muy mala, avance no suficiente en los contenidos, tener tres o más familiares estudiando, y las acciones de la universidad ante la pandemia fueron regulares o muy malas. Con la prueba exacta de Fisher se observó que el sexo femenino tiene más desventajas para comunicarse con el profesorado y para continuar sus estudios. En la escala Likert, la falta de comunicación estudiante-docente fue el aspecto peor evaluado. La comunicación deficiente estudiante-docente, en especial del sexo femenino, no es exclusivo y coincide con otros reportes caracterizados por falta de herramientas tecnológicas, conectividad y de atención institucional. El efecto de los factores asociados con los problemas para seguir estudiando, puede reducirse a mejorar la comunicación y la empatía del profesorado ante el contexto socio-económico del alumnado.This research was carried out during the suspension of face-to-face classes due to SARS-CoV-2. Objectives: to identify the factors associated with the problems faced by learners to continue their studies on-line, and to measure the student’s predisposition to this new way of learning. In the study, 51 students were surveyed, 2x2 tables were made to determine the risk (OR), and chi square (X2) and Fisher’s exact tests were conducted. A Likert scale was used to assess students’ opinions and perspectives on their educational environment. In the multivariate analysis the factors associated with the problems to continue studying online were: not having devices for their classes; bad or very bad communication with their teachers; working online was considered from ordinary to very bad; not enough progress in the contents; having three or more family members studying; and the actions taken by the university in the face of the pandemic were held to be ordinary or very bad. The Fisher’s exact test revealed that female students were faced with more problems to communicate with teachers and to continue with their studies. On the Likert scale, the lack of student-teacher communication was the worst evaluated aspect. Poor student-teacher communication, especially as perceived by female students, is not exclusive of this study and coincides with previous research in which lack of technological tools, connectivity and institutional care are also widely mentioned factors. The effect of the factors associated with the problems to continue studying can be summarized as follows: improving the communication and empathy of the teaching staff in view of the socio-economic context of their students.Cette recherche a été menée pendant la suspension des cours en face à face, en raison du niveau élevé d’infection par le SRAS-CoV-2. Objectifs : identifier les facteurs associés aux difficultés à poursuivre leurs études de manière virtuelle, et mesurer la prédisposition des étudiants à cette nouvelle façon d’apprendre. Dans cette étude, 51 étudiants ont été interrogés, des tableaux 2x2 ont été utilisés pour déterminer le risque (OR), le chi-deux (X2), le test exact de Fisher et une échelle de type Likert pour évaluer leurs opinions et perspectives sur leur environnement éducatif. Dans l’analyse multivariée, les facteurs associés aux problèmes de poursuite des études virtuelles étaient les suivants : ne pas disposer d’appareils pour leurs cours, une communication médiocre ou très médiocre avec leurs professeurs, des méthodes de travail virtuelles allant de passables à très diocres, des progrès insuffisants dans le contenu, le fait que trois membres de la famille ou plus étudient, et les actions de l’université face à la pandémie étaient passables ou très médiocres. Avec le test exact de Fisher, il a été observé que le sexe féminin a plus de désavantages dans la communication avec le personnel enseignant et dans la poursuite de leurs études. Sur l’échelle de Likert, le manque de communication entre élèves et enseignants est l’aspect le plus mal évalué. La mauvaise communication entre étudiants et enseignants, en particulier chez les femmes, n’est pas exclusive et coïncide avec d’autres rapports caractérisés par un manque d’outils technologiques, de connectivité et d’attention institutionnelle. L’effet des facteurs associés aux problèmes de poursuite des études peut être réduit à l’amélioration de la communication et de l’empathie des enseignants avec le contexte socio-économique du corps étudiant

Iron deficiency in childhood and adolescence: Retrospective review

Two hundred and thirty-eight subjects of both sexes, age range 7.5 months-16 years, with iron deficiency (ID), were included in a retrospective review of ID causes, to determine the best treatment. Inadequate iron intake was the cause of ID or iron deficiency anemia (IDA) in 59 subjects from the first months of life to adolescence. Blood loss linked to cow's milk intolerance was the cause of ID or IDA in 37 younger children. Meckel's diverticulum (MD) (6 cases), reflux esophagitis (RE) (10 cases), some drugs such as acetyl salicylic acid (11 cases) induced bleeding with ID or IDA in children and adolescents. In pubertal females with ID or IDA, polymenorrhea was observed in 16 cases. Coelic disease (CD) (37 cases), Helicobacter pylori infection (HPI) (39 cases), association of HPI and CD (8 cases), enteromonas infection (15 cases), determining particularly malabsorption, were causes of ID or IDA in patients of a wide age range, unresponsive to iron therapy. Our findings show that iron replacement therapy was not always required and should not be prescribed until the diagnosis is certain