Las matemáticas de lo secreto

En un mundo en que el que cada vez más los medios de comunicación son electrónicos, la seguridad de las transacciones electrónicas nos afecta a todos. La criptografía, la seguridad de la información en general, actualmente está basada en métodos matemáticos, son un campo de nuestra vida cotidiana en el que el aporte de las matemáticas es esencial. En este artículo se muestran algunos sistemas de cifrado artesanales de la criptografía clásica y se introducen los algoritmos de cifrado, de autentificación de documentos y firma digital hoy en día más utilizados: los RSA, que están basados en un resultado clásico de la teoría de números. El estilo del artículo es narrativo, todos los métodos se explican con ejemplos, con comentarios históricos. Su contenido se puede utilizar para diseñar un “taller de matemáticas” dirigido a estudiantes de nivel preuniversitario

Iconoclasm in the Supermarket

What happens when activists re-label your food? Javier Lezaun explores the "Label it Yourself" movement and its ambivalent power

Metamaterials for radiactive cooling

The increasing pressure of society to decrease energy consumption and to enhance energetic efficiency has lead to search novel technologies to accomplish it. Notwithstanding the increasing electricity production of renewable energies, it is a fact that the energy expenses can be drastically reduced in most areas. Among these areas, cooling systems stand out for being energetically inefficient. Furthermore, both economical and energy cost of such systems are increasing due to the global warming, which is aggravated by the energy production for them, making a loop that is increasingly damaging the environment. A solution to this problem has emerged under the name of radiative cooling, which is a physical phenomenon by which any terrestrial object losses heat in form of radiation that is sent to outer space. This process can be explained by black body radiation theory and the atmospheric window. The former states that any object at some temperature above 0 K radiates energy at all wavelengths, with its radiation peak and spectral location modulated by its temperature. The latter is a frequency band in which the atmosphere is transparent to radiation, making possible for waves at certain frequencies to cross freely. These phenomena allows a direct heat transmission between earth and space, which is cold and almost infinite, making a great storage for excess warmth without wasting energy in the process. In this work, it has been studied one of the main technologies that can implement radiative cooling in practice, metamaterials, with the aim to understand how to improve its associated problems of manufacturing and design for radiative cooling applications. In Chapter 1, the fundamentals of radiative cooling are introduced along with the state of the art. Then, Chapter 2 presents the materials used in the literature and in this work to develop later analytical models for thin film multilayered metamaterials and a possible way to automatically design them. To better understand the analytical developments, two appendices introducing the underlying theory and equations are included. Also, the software used in this work is presented. Finally, the performance and analysis of three different radiative cooling devices is exposed in Chapter 3, one of them using the materials and methods of Chapter 2.Máster Universitario en Ingeniería de Telecomunicación por la Universidad Pública de NavarraNafarroako Unibertsitate Publikoko Unibertsitate Masterra Telekomunikazio Ingeniaritza

El «extraño mal» de Teresa Wilms Montt. Romanticismo y transgresión de la normativa de género en la vanguardia chilena

El presente trabajo trata de explicar la naturaleza y el origen de uno de los sintagmas más recurrentes en la obra de Teresa Wilms Montt, el «extraño mal», que aparece tanto en sus Diarios, publicados en un volumen recopilatorio en 1994 por Ruth González Vergara, como en la obra literaria Inquietudes sentimentales de 1917. La investigación parte de la búsqueda de un aparato crítico que sustente el análisis del «extraño mal» como paradigma de su producción intimista que une vida, diarios y obra. Dicho sentimiento refleja la interacción de los factores históricos, psicológicos y sociales en su obra. Como veremos, el «extraño mal» no solo refleja la indiscutible ligazón entre la vida y la obra de la autora que nos concierne, sino que, plasma, asimismo, la unión entre los dos temas más tratados por ella: el amor y la muerte. Empezaremos con un ineludible, pero breve, apartado biográfico y una contextualización social y cultural que nos permita comprender mejor la situación de opresión en la que Teresa escribe, como mujer en la sociedad chilena de finales del siglo XIX y principios del XX. A pesar de que la paulatina modernización del país dará una lenta cabida a la mujer en el terreno público, esta será con desconfianza y represalias, lo cual se ve reflejado en el caso de Teresa. A continuación explicaremos la interrelación entre vida, diarios y obra, además del romanticismo transmitido en todas ellas, ya que fue precisamente esta personalidad romántica la que causó el choque con la sociedad y unas ansias de libertad e ideales superiores, cuya imposibilidad de realización crearon un núcleo melancólico que generó el «extraño mal», expresado primero en forma de enfermedad del amor por la incapacidad de encontrar relaciones sentimentales plenas; y, después, en forma de spleen, tedio, hastío, a causa de la Nada a la que se vio abocada por la frustración de todos sus intentos de encontrar amor y una realidad ideal más allá del mundo conocido

Grappling with a sea change: tensions in expert imaginaries of marine carbon dioxide removal

While research on marine carbon dioxide removal (mCDR) expands apace, significant unknowns persist regarding the risks and benefits of individual mCDR options. This paper analyses the assumptions and expectations that animate expert understandings of mCDR, with a focus on issues that are central to the responsible governance of this emerging field of climate action. Drawing upon interviews with experts involved in mCDR research projects both academic and entrepreneurial, we highlight four thematic tensions that orient their thinking but are often unstated or left implicit in scientific and technical assessments: (1) the relevance of ‘naturalness’ as a criterion of evaluation for mCDR approaches; (2) the perceived need to accelerate research and development activities via alternative paradigms of evidence-building; (3) a framing of mCDR as a form of waste management that will, in turn, generate new (and currently poorly understood) forms of environmental pollutants; and (4) a commitment to inclusive governance mixed with difficulty in identifying specific stakeholders or constituencies in mCDR interventions. Although expert consensus on these four issues is unlikely, we suggest ways of ensuring that consideration of these themes enriches debate on the responsible development of novel mCDR capabilities

Consulting citizens: technologies of elicitation and the mobility of publics

The new centrality of “the public” to the governance of science and technology has been accompanied by a widespread use of public consultation mechanisms designed to elicit from citizens relevant opinions on technoscientific matters. This paper explores the configuration of legitimate constituencies in two such exercises: the UK “GM Nation?” public debate on food biotechnology, and a Swedish “Transparency Forum” on the risks of mobile telephones. We consider the apparently paradoxical combination in these two examples of a tendency to produce static images of the public with a high valuation of mobility—of citizens and their opinions—as the key outcome of deliberation. We discuss the organizers' careful delineation of a distinction between “stakeholders” and the “general public,” and their aversion to any sort of “eventfulness” in public deliberations. Finally, we introduce the classical notion of the “idiot”—the individual who minds exclusively his or her own private affairs— and argue for the need to develop a new vocabulary to evaluate the politics of “listening to the public.

Perceptions of bioenergy with carbon capture and storage in different policy scenarios

There is growing interest in bioenergy with carbon capture and storage (BECCS) as a possible technology for removing CO2 from the atmosphere. In the first study of its kind, we investigate whether and how different forms of incentivisation impact on public perceptions of this technology. We develop a new experimental method to triangulate perceptions of BECCS in different policy scenarios through quantitative measurement and qualitative elicitation. Here we show that the type of policy instrument used to incentivise BECCS significantly affects perceptions of the technology itself. While we find approval of coercive and persuasion-based policy scenarios for incentivisation, supportive instruments proved polarising. Payments based on the amount of CO2 removed from the atmosphere were approved, but guarantees of higher prices for producers selling energy derived from BECCS were strongly opposed. We conclude that public support for BECCS is inextricably linked to attitudes towards the policies through which it is incentivised