1,720,979 research outputs found
Dr. Carlos R. Lanfranco La Hoz
No full textHa fallecido en Lima el Dr. Carlos R. Lanfranco La Hoz, el maestro más representativo que ha tenido la Facultad de Medicina de San Fernando de la Universidad Nacional Mayor de San Marcos en los últimos cuarenta años. Fue médico y maestro universitario, hombre de ciencia, extraordinario semiólogo, gran clínico, pero sobre todo docente por naturaleza. Gremialista cuando los acontecimientos lo requerían, con gran sensibilidad por el dolor humano y ejemplo de muchas generaciones de médicos
Invisible fluorinated materials for optical sensing
No full textFluorinated materials can be produced in order to combine an amorphous, homogenous structure and a refractive index very close to that of water. When in contact with aqueous solutions, such materials become barely visible. In these conditions, the adhesion of small amounts of molecules on their surface induces an optical signal that can be easily detected. This principle was exploited to realize novel label-free optical biosensors using either a dispersion of nanoparticles or a prism of fluorinated polymers as sensing substrates. The detection of specific molecular compounds in solution was achieved by suitable functionalization of the surface of the fluorinated materials
OPTICAL DETECTION OF MOLECULAR INTERACTIONS ON THE SURFACE OF MATERIALS INDEX-MATCHED TO WATER.
Full text linkThe idea to have highly effective autonomous sensors able to measure and share information
about the quality of our environment, and particularly water, in our lakes and
rivers, our water supply system and the outputs of municipal and industrial wastewater
treatment systems is revolutionary and fascinating. These sensors could be densely deployed
at multiple locations, and the information may be available to citizens through
the Internet. This idyllic vision, nowadays, is far away from being reality, despite the
huge effort made to develop innovative molecular sensors. The main challenges related
to the realization of these autonomous sensors network are the biofouling, power supply
and compactness. In fact, despite thousands of papers in literature about development
of novel nanostractured materials for sensing, for instance, there is still not a single
example of any of these device being used in direct contact with water for long-term
environmental monitoring.
The work presented in this thesis proposes a new kind of optical sensor that combines
a fast and low cost method to detect water pollutant with good performance and robustness.
In particular, this work is focused on the detection of small molecular pollutants,
as oils compounds and surfactants. An innovative aspect of the proposed approach relies
on the use of a novel class of materials as sensing substrate which have peculiar and
fascinating optical properties: these are amorphous perfluorinated polymers with refractive
index similar to that of water. When immersed in aqueous solutions, they provide
extremely low reflection or scattering of light, hence they become barely visible. For this
reason, this class of materials is called phantom. In this limit, when a thin molecular layer
spontaneously adsorbs on the surfaces of these materials, the reflected or scattered light
increases, providing the basis for optical detection of molecules.
In this work, three different phantom materials made of perfluorinated polymers
are exploited in the framework of the detection of water contaminants: a prism, microporous
membranes and micro-beads, that represent the building blocks for the assembly
of an invisible chromatography column. The membrane and the micro-beads were produced
for the first time during this work. The use of fluoropolymer prism substrate for
molecular detection was already proposed in recent works to realize label-free biosensors
based on the functionalization of the surface with antibodies. Here I extend the
exploitation of this system to the detection of molecular pollutant through their adsorption
on the bare surface of the fluoropolymer materials, without the need of any surface
treatment. Despite the lack of surface functionalization, a selectivity in the adsorption of
various classes of molecules is demonstrated
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Phantom microbeads chromatography column in microfluidics
No full textWater pollution is one of the biggest concerns of society at the moment. Among all water pollutants, oils and surfactants are especially harmful for human health and the environment; therefore they should be continually monitored to avoid water contamination.[1] In this work we propose a new microfluidic device composed by packed microbeads invisible in water. This system enables an alternative methodology to detect polluting compounds in water samples
Emerging applications of label-free optical biosensors
Full text linkInnovative technical solutions to realize optical biosensors with improved performance are continuously proposed. Progress in material fabrication enables developing novel substrates with enhanced optical responses. At the same time, the increased spectrum of available biomolecular tools, ranging from highly specific receptors to engineered bioconjugated polymers, facilitates the preparation of sensing surfaces with controlled functionality. What remains often unclear is to which extent this continuous innovation provides effective breakthroughs for specific applications. In this review, we address this challenging question for the class of label-free optical biosensors, which can provide a direct signal upon molecular binding without using secondary probes. Label-free biosensors have become a consolidated approach for the characterization and screening of molecular interactions in research laboratories. However, in the last decade, several examples of other applications with high potential impact have been proposed. We review the recent advances in label-free optical biosensing technology by focusing on the potential competitive advantage provided in selected emerging applications, grouped on the basis of the target type. In particular, direct and real-time detection allows the development of simpler, compact, and rapid analytical methods for different kinds of targets, from proteins to DNA and viruses. The lack of secondary interactions facilitates the binding of small-molecule targets and minimizes the perturbation in single-molecule detection. Moreover, the intrinsic versatility of label-free sensing makes it an ideal platform to be integrated with biomolecular machinery with innovative functionality, as in case of the molecular tools provided by DNA nanotechnology
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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