The skewness of science in 219 sub-fields and a number of aggregates

This paper studies evidence from Thomson Scientific about the citation process of 3.7 million articles published in the period 1998-2002 in 219 Web of Science categories, or sub-fields. Reference and citation distributions have very different characteristics across sub-fields. However, when analyzed with the Characteristic Scores and Scales technique, which is replication and scale invariant, the shape of these distributions over three broad categories of articles appears strikingly similar. Reference distributions are mildly skewed, but citation distributions with a five-year citation window are highly skewed: the mean is twenty points above the median, while 9-10% of all articles in the upper tail account for about 44% of all citations. The aggregation of sub-fields into disciplines and fields according to several aggregation schemes preserve this feature of citation distributions. It should be noted that when we look into subsets of articles within the lower and upper tails of citation distributions the universality partially breaks down. On the other hand, for 140 of the 219 sub-fields the existence of a power law cannot be rejected. However, contrary to what is generally believed, at the sub-field level the scaling parameter is above 3.5 most of the time, and power laws are relatively small: on average, they represent 2% of all articles and account for 13.5% of all citations. The results of the aggregation into disciplines and fields reveal that power law algebra is a subtle phenomenon.

A comparison of the scientific performance of the U.S. and the European Union at the turn of the 21st century.

In this paper, scientific performance is identified with the impact that journal articles have through the citations they receive. In 15 disciplines, as well as in all sciences as a whole, the EU share of total publications is greater than that of the U.S. However, as soon as the citations received by these publications are taken into account the picture is completely reversed. Firstly, the EU share of total citations is still greater than the U.S. in only seven fields. Secondly, the mean citation rate in the U.S. is greater than in the EU in every one of the 22 fields studied. Thirdly, since standard indicators—such as normalized mean citation ratios—are silent about what takes place in different parts of the citation distribution, this paper compares the publication shares of the U.S. and the EU at every percentile of the world citation distribution in each field. It is found that in seven fields the initial gap between the U.S. and the EU widens as we advance towards the more cited articles, while in the remaining 15 fields—except for Agricultural Sciences—the U.S. always surpasses the EU when it counts, namely, at the upper tail of citation distributions. Finally, for all sciences as a whole the U.S. publication share becomes greater than that of the EU for the top 50% of the most highly cited articles. The data used refers to 3.6 million articles published in 1998–2002, and the more than 47 million citations they received in 1998–2007Research performance; Citation analysis; Scientific ranking; European paradox;

The skewness of science in 219 sub-fields and a number of aggregates

This paper studies evidence from Thomson Scientific about the citation process of 3.7 million articles published in the period 1998-2002 in 219 Web of Science categories, or sub-fields. Reference and citation distributions have very different characteristics across sub-fields. However, when analyzed with the Characteristic Scores and Scales technique, which is size and scale independent, the shape of these distributions appear extraordinarily similar. Reference distributions are mildly skewed, but citation distributions with a five-year citation window are highly skewed: the mean is twenty points above the median, while 9-10% of all articles in the upper tail account for about 44% of all citations. The aggregation of sub-fields into disciplines and fields according to several aggregation schemes preserve this feature of citation distributions. On the other hand, for 140 of the 219 sub-fields the existence of a power law cannot be rejected. However, contrary to what is generally believed, at the sub-field level the scaling parameter is above 3.5 most of the time, and power laws are relatively small: on average, they represent 2% of all articles and account for 13.5% of all citations. The results of the aggregation into disciplines and fields reveal that power law algebra is a subtle phenomenon.

A comparison of the scientific performance of the U. S. and the European Union at the turn of the XXI century.

In this paper, scientific performance is identified with the impact journal articles achieve through the citations they receive. The empirical exercise refers to 3.6 million articles published in 1998-2002 in 22 scientific fields, and the more than 47 million citations they receive in 1998-2007. The first finding is that a failure to exclude co-authorship among member countries within the EU (European Union) may lead to a serious upward bias in the assignment of articles to this geographical area. In the second place, standard indicators, such as normalized mean citation ratios, are silent about what takes place in different parts of the citation distribution. Consequently, this paper compares the publication shares of the U.S. and the EU at every percentile of the world citation distribution in each field. In 15 disciplines, as well as in all sciences as a whole, the EU share of total publications is greater than that of the U.S. one. But as soon as the citations received by these publications are taken into account the picture is completely reversed. The mean citation rate in the U.S. is greater than in the EU in every one of the 22 fields. In seven fields, the initial gap between the U.S. and the EU widens up as we advance towards the more cited articles, while in the remaining 15 fields –except for Agricultural Sciences– the U.S. always surpasses the EU when it counts, namely, at the upper tail of citation distributions. For all sciences as a whole, the U.S publication share becomes greater than that of the EU one for the top 50% of the most highly cited articles.

Manifestaciones cutáneas del dengue. Reporte de caso y revisión de la literatura

El dengue es un arbovirosis trasmitido por el mosquito Aedes aegypti (MAe) infectado, que se presenta de forma epidémica o endémica en áreas tropicales y subtropicales. Sus manifestaciones cutáneas (MC) más frecuentemente reportadas son las lesiones eritemato-papulo-purpúricas, las cuales se presentan a partir del segundo a quinto día de la infección. La Organización Mundial de la Salud (OMS) reconoce que la incidencia del dengue ha incrementado extraordinariamente en todo el mundo. En el año 2010, se reportaron de 50 a 100 millones de casos; de éstos, 1.6 correspondieron al continente Americano. En México la frecuencia de dengue ha incrementado.El dengue es una enfermedad transmitida por un vector denominado mosquito Aedes aegypti (MAe), que generalmente está infectado por el virus del serotipo 2. Predomina en regiones tropicales y subtropicales de todo el mundo. El cuadro clínico inicia de 3 a 7 días después de la picadura y sus manifestaciones cutáneas (MC) representan una frecuencia que va del 20% hasta el 65%, la cual varía de acuerdo a cada país. En México los casos han incrementado. Sus lesiones más comunes son: la mácula (M), exantema cutáneo morbiliforme (ECM), lesiones purpúricas (LP), petequias (P), entre otras. El objetivo de este estudio es señalar el panorama que representan las MC del dengue. Se presenta el caso clínico de una mujer joven, en quien se destacan estas manifestaciones, las cuales formaron parte de la tríada del dengue, sin datos de alarma. Las MC del dengue son escasamente referidas en su descripción, por lo que abordamos este tema con el fin de detallar las lesiones encontradas y dar pie a la observación de más casos. No son patognomónicas y generalmente no reflejan la gravedad de la infección. El ECM y las M forman parte de las MC más comunes. Tienen un carácter generalmente benigno. Los frentes de las tormentas actuales pueden impactar en el incremento de nuevos casos

A comparison of the scientific performance of the U.S. and the European Union at the turn of the 21st century

In this paper, scientific performance is identified with the impact that journal articles have through the citations they receive. In 15 disciplines, as well as in all sciences as a whole, the EU share of total publications is greater than that of the U.S. However, as soon as the citations received by these publications are taken into account the picture is completely reversed. Firstly, the EU share of total citations is still greater than the U.S. in only seven fields. Secondly, the mean citation rate in the U.S. is greater than in the EU in every one of the 22 fields studied. Thirdly, since standard indicators—such as normalized mean citation ratios—are silent about what takes place in different parts of the citation distribution, this paper compares the publication shares of the U.S. and the EU at every percentile of the world citation distribution in each field. It is found that in seven fields the initial gap between the U.S. and the EU widens as we advance towards the more cited articles, while in the remaining 15 fields—except for Agricultural Sciences—the U.S. always surpasses the EU when it counts, namely, at the upper tail of citation distributions. Finally, for all sciences as a whole the U.S. publication share becomes greater than that of the EU for the top 50% of the most highly cited articles. The data used refers to 3.6 million articles published in 1998–2002, and the more than 47 million citations they received in 1998–2007European Community's Seventh Framework ProgramPublicad

A comparison of the scientific performance of the U. S. and the European Union at the turn of the XXI century

In this paper, scientific performance is identified with the impact journal articles achieve through the citations they receive. The empirical exercise refers to 3.6 million articles published in 1998-2002 in 22 scientific fields, and the more than 47 million citations they receive in 1998-2007. The first finding is that a failure to exclude co-authorship among member countries within the EU (European Union) may lead to a serious upward bias in the assignment of articles to this geographical area. In the second place, standard indicators, such as normalized mean citation ratios, are silent about what takes place in different parts of the citation distribution. Consequently, this paper compares the publication shares of the U.S. and the EU at every percentile of the world citation distribution in each field. In 15 disciplines, as well as in all sciences as a whole, the EU share of total publications is greater than that of the U.S. one. But as soon as the citations received by these publications are taken into account the picture is completely reversed. The mean citation rate in the U.S. is greater than in the EU in every one of the 22 fields. In seven fields, the initial gap between the U.S. and the EU widens up as we advance towards the more cited articles, while in the remaining 15 fields –except for Agricultural Sciences– the U.S. always surpasses the EU when it counts, namely, at the upper tail of citation distributions. For all sciences as a whole, the U.S publication share becomes greater than that of the EU one for the top 50% of the most highly cited articles

The skewness of science in 219 sub-fields and a number of aggregates

This paper studies evidence from Thomson Scientific about the citation process of 3.7 million articles published in the period 1998-2002 in 219 Web of Science categories, or sub-fields. Reference and citation distributions have very different characteristics across sub-fields. However, when analyzed with the Characteristic Scores and Scales technique, which is size and scale independent, the shape of these distributions appear extraordinarily similar. Reference distributions are mildly skewed, but citation distributions with a five-year citation window are highly skewed: the mean is twenty points above the median, while 9-10% of all articles in the upper tail account for about 44% of all citations. The aggregation of sub-fields into disciplines and fields according to several aggregation schemes preserve this feature of citation distributions. On the other hand, for 140 of the 219 sub-fields the existence of a power law cannot be rejected. However, contrary to what is generally believed, at the sub-field level the scaling parameter is above 3.5 most of the time, and power laws are relatively small: on average, they represent 2% of all articles and account for 13.5% of all citations. The results of the aggregation into disciplines and fields reveal that power law algebra is a subtle phenomenon.European Community's Seventh Framework ProgramThe authors acknowledge financial support from the Spanish MEC through grants SEJ2007-63098, SEJ2006-05710, SEJ2007-67135, and SEJ2007-67436. This paper is part of the SCIFI-GLOW Collaborative Project supported by the European Commission’s Seventh Research Framework Programme, Contract no. SSH7-CT-2008-217436

Experiencia con un repositorio de ejercicios de programación en un campus virtual: de una colección de libre acceso a otra guiada por la progresión del estudiante

El Campus Virtual es el entorno en el que se ha implementado una Virtualización de Casos Prácticos para facilitar el aprendizaje activo de la materia “Introducción a la programación” en la Universidad Complutense de Madrid. El carácter multidisciplinar de esta colección de casos prácticos los hace útiles en diversas titulaciones de la citada universidad. En este artículo se presenta la evolución que ha experimentado la Virtualización de Casos Prácticos, desde una colección de libre acceso a contenidos hasta la actual con un acceso controlado por la progresión del estudiante.Peer Reviewe