The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics

p53 signaling in cancer progression and therapy

The p53 protein is a transcription factor known as the "guardian of the genome" because of its critical function in preserving genomic integrity. The TP53 gene is mutated in approximately half of all human malignancies, including those of the breast, colon, lung, liver, prostate, bladder, and skin. When DNA damage occurs, the TP53 gene on human chromosome 17 stops the cell cycle. If p53 protein is mutated, the cell cycle is unrestricted and the damaged DNA is replicated, resulting in uncontrolled cell proliferation and cancer tumours. Tumor-associated p53 mutations are usually associated with phenotypes distinct from those caused by the loss of the tumor-suppressing function exerted by wild-type p53protein. Many of these mutant p53 proteins have oncogenic characteristics, and therefore modulate the ability of cancer cells to proliferate, escape apoptosis, invade and metastasize. Because p53 deficiency is so common in human cancer, this protein is an excellent option for cancer treatment. In this review, we will discuss some of the molecular pathways by which mutant p53 proteins might perform their oncogenic activities, as well as prospective treatment methods based on restoring tumor suppressive p53 functionsScopu

Limes. lexicograf\ueda y lexicolog\ueda de las lenguas de especialidad

De los trabajos realizados en el \ue1mbito de la investigaci\uf3n del proyecto nacional \u201cGlossari, dizionari, corpora: lessicologia e lessicografia delle lingue europee\u201d coordinado por G. Iamartino y, en lo referido a la lexicograf\ueda biling\ufce \uedtalo-espa\uf1ola, por F. San Vicente y de algunas intervenciones presentadas para el congreso organizado por J. Lillo (\u201cLessicografia e lessicologia dei linguaggi settoriali\u201d, Palermo 21-23/07/2007) surge el volumen que hoy presentamos: "Limes. Lexicograf\ueda y lexicolog\ueda de las lenguas de especialidad." Su contenido, como ilustra la "Introducci\uf3n", abarca principalmente cuestiones relativas a la historia de la terminograf\ueda y de la lexicograf\ueda as\ued como a las lenguas de especialidad, las marcas en general y la fraseolog\ueda en los diccionarios biling\ufces. Cabe se\uf1alar que la observaci\uf3n de lo lexicogr\ue1fico y de las relaciones interling\ufc\uedsticas e interculturales -tanto desde el punto de vista investigativo como did\ue1ctico- es rasgo com\ufan a todos los trabajos que constituyen esta obra. Seis son las lenguas observadas en los art\uedculos que recogemos (catal\ue1n, espa\uf1ol, franc\ue9s, gallego, ingl\ue9s e italiano), si bien el apartado hisp\ue1nico (catal\ue1n, espa\uf1ol, gallego) es mayoritario, la relaci\uf3n italiano-espa\uf1ol, la m\ue1s estudiada, y el espa\uf1ol, lengua y objeto de estudio preponderante. Con prop`\uf3sito de facilitar la consulta de textos, hemos recogido al inicio del volumen -tras haberlas unificado- las siglas de todas las obras lexicogr\ue1ficas citadas ("Siglas lexicogr\ue1ficas") y las referencias lexicogr\ue1ficas completas ("Referencias lexicogr\ue1ficas")