66 research outputs found
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 Most figures have been replaced by new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
Factores de riesgo para el desarrollo psicomotor en lactantes nacidos en óptimas condiciones biológicas
Caracterização dos fatores ambientais e o controle cervical de lactentes nascidos pré-termo
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
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