Hodge-Gaussian maps

Let $X$ be a compact K\"{a}hler manifold, and let $L$ be a line bundle on $X.$ Define $I_k(L)$ to be the kernel of the multiplication map $Sym^k H^0 (L) \to H^0 (L^k).$ For all $h \leq k,$ we define a map $\rho : I_k(L) \to Hom (H^{p,q} (L^{-h}), H^{p+1,q-1} (L^{k-h})).$ When $L = K_X$ is the canonical bundle, the map $\rho$ computes a second fundamental form associated to the deformations of $X.$ If $X=C$ is a curve, then $\rho$ is a lifting of the Wahl map $I_2(L) \to H^0 (L^2 \otimes K_C^2).$ We also show how to generalize the construction of $\rho$ to the cases of harmonic bundles and of couples of vector bundles.Comment: 26 pages, LaTe

New big data platforms are more efficient, but pose a serious threat to privacy

Most new systems offer only basic enforcement, whereas traditional ones have various protection frameworks, write Pietro Colombo and Elena Ferrari. The past few years have seen changes in the organisation of business models and work styles, caused by the rapid evolution of data analysis and data management systems. Business strategies are more and more driven by the integrated analysis of huge ..

Access control technologies for Big Data management systems: literature review and future trends

Abstract Data security and privacy issues are magnified by the volume, the variety, and the velocity of Big Data and by the lack, up to now, of a reference data model and related data manipulation languages. In this paper, we focus on one of the key data security services, that is, access control, by highlighting the differences with traditional data management systems and describing a set of requirements that any access control solution for Big Data platforms may fulfill. We then describe the state of the art and discuss open research issues

Fine-Grained Access Control Within NoSQL Document-Oriented Datastores

The recent years have seen the birth of several NoSQL datastores, which are getting more and more popularity for their ability to handle high volumes of heterogeneous and unstructured data in a very efficient way. In several cases, NoSQL databases proved to outclass in terms of performance, scalability, and ease of use relational database management systems, meeting the requirements of a variety of today ICT applications. However, recent surveys reveal that, despite their undoubted popularity, NoSQL datastores suffer from some weaknesses, among which the lack of effective support for data protection appears among the most serious ones. Proper data protection mechanisms are therefore required to fill this void. In this work, we start to address this issue by focusing on access control and discussing the definition of a fine-grained access control framework for document-oriented NoSQL datastores. More precisely, we first focus on issues and challenges related to the definition of such a framework, considering theoretical, implementation, and integration aspects. Then, we discuss the reasons for which state-of-the-art fine-grained access control solutions proposed for relational database management systems cannot be used within the NoSQL scenario. We then introduce possible strategies to address the identified issues, which are at the basis of the framework development. Finally, we shortly report the outcome of an experience where the proposed framework has been used to enhance the data protection features of a popular NoSQL database

Relevance of electron spin dissipative processes to dynamic nuclear polarization via thermal mixing

The available theoretical approaches aiming at describing Dynamic Nuclear spin Polarization (DNP) in solutions containing molecules of biomedical interest and paramagnetic centers are not able to model the behaviour observed upon varying the concentration of trityl radicals or the polarization enhancement caused by moderate addition of gadolinium complexes. In this manuscript, we first show experimentally that the nuclear steady state polarization reached in solutions of pyruvic acid with 15 mM trityl radicals is substantially independent from the average internuclear distance. This evidences a leading role of electron (over nuclear) spin relaxation processes in determining the ultimate performances of DNP. Accordingly, we have devised a variant of the Thermal Mixing model for inhomogenously broadened electron resonance lines which includes a relaxation term describing the exchange of magnetic anisotropy energy of the electron spin system with the lattice. Thanks to this additional term, the dependence of the nuclear polarization on the electron concentration can be properly accounted for. Moreover, the model predicts a strong increase of the final polarization on shortening the electron spin-lattice relaxation time, providing a possible explanation for the effect of gadolinium doping.Comment: 13 pages, 12 figure

Role of the glassy dynamics and thermal mixing in the dynamic nuclear polarization and relaxation mechanisms of pyruvic acid

The temperature dependence of $^1$H and $^{13}$C nuclear spin-lattice relaxation rate $1/T_1$ has been studied in the 1.6 K - 4.2 K temperature range in pure pyruvic acid and in pyruvic acid containing trityl radicals at a concentration of 15 mM. The temperature dependence of $1/T_1$ is found to follow a quadratic power law for both nuclei in the two samples. Remarkably the same temperature dependence is displayed also by the electron spin-lattice relaxation rate $1/T_{1e}$ in the sample containing radicals. These results are explained by considering the effect of the structural dynamics on the relaxation rates in pyruvic acid. Dynamic nuclear polarization experiments show that below 4 K the $^{13}$C build up rate scales with $1/T_{\text{1e}}$, in analogy to $^{13}$C $1/T_1$ and consistently with a thermal mixing scenario where all the electrons are collectively involved in the dynamic nuclear polarization process and the nuclear spin reservoir is in good thermal contact with the electron spin system.Comment: 14 pages, 13 figure

Dealing with Anonymity in Wireless Sensor Networks

NowadaysWireless Sensor Networks (WSN) are used in many application contexts. Data handled by WSN are required to be protected for privacy reasons since they can be directly or indirectly related to individuals. The problem of pre-venting the identification of individuals starting from their data, known as anonymity, is a fundamental requirement for privacy aware systems. This paper proposes a solution to guarantee anonymity for a wide spread type of WSN by means of privacy policies. The solution is based on a UML model that introduces the conceptual elements and guidelines that are needed to build privacy policies for WSN. 1

Creación de un ensayo clínico: algunas sugerencias metodológicas.

Well-designed clinical trials are the gold standard for evidence-based research and for the assessment of the effectiveness of a clinical intervention. Methodological guidelines are available from various sources, such as textbook, funding applications and institutional guidelines. Nevertheless, a high number of published trials still lack methodological rigor, decreasing their utility, quality and scientific validity. In this article, we aim at providing some methodological recommendations for the development and report of a clinical trial, including the definition and recruitment of the sample, the basic study designs, randomization, blindness, data analysis and data report. Finally, we will discuss some of the most important ethical issues. Los ensayos clínicos bien diseñados son el estándar por excelencia para la investigación basada en la evidencia y para la evaluación de la eficacia de una intervención clínica. Las directrices metodológicas se encuentran disponibles en varias fuentes, tales como libros de texto, solicitudes de financiamiento y directrices institucionales. Sin embargo, un gran número de ensayos publicados todavía carecen de rigor metodológico, disminuyendo su utilidad, calidad y validez científica. En este artículo, nuestro objetivo es proporcionar algunas recomendaciones metodológicas para el desarrollo e informe de un ensayo clínico, incluyendo la definición y selección de la muestra, los diseños básicos de estudio, la aleatorización, el cegamiento, el análisis y el reporte de datos. Finalmente, discutiremos algunas de las consideraciones éticas más importantes