Synthesis and characterization of gold nanoparticles

Gold nanoparticles (AuNPs) find a number of applications in many fields of electronics, catalysis, optics and biomedicine. This work reports a robust, fast and easy synthesis protocol, based on the Turkevich method to obtain AuNPs. Simple characterization techniques based on UV-Vis spectroscopy and transmission electronic microscopy are also reported. The resulting AuNPs presents properties at a nanometric scale, high purity and they may find potential uses in the treatment of cancer, antiviral and antibacterial agents and biosensors among others.

A simple characterization of doubly twisted spacetimes

In this note, we characterize [Formula: see text] doubly twisted spacetimes in terms of “doubly torqued” vector fields. They extend Bang–Yen Chen’s characterization of twisted and generalized Robertson–Walker spacetimes with torqued and concircular vector fields. The result is a simple classification of [Formula: see text] doubly-twisted, doubly-warped, twisted and generalized Robertson–Walker spacetimes.

Finding Unavoidable Colorful Patterns in Multicolored Graphs

We provide multicolored and infinite generalizations for a Ramsey-type problem raised by Bollobás, concerning colorings of $K_n$ where each color is well-represented. Let $\chi$ be a coloring of the edges of a complete graph on $n$ vertices into $r$ colors. We call $\chi$ $\varepsilon$-balanced if all color classes have $\varepsilon$ fraction of the edges. Fix some graph $H$, together with an $r$-coloring of its edges. Consider the smallest natural number $R_\varepsilon^r(H)$ such that for all $n\geq R_\varepsilon^r(H)$, all $\varepsilon$-balanced colorings $\chi$ of $K_n$ contain a subgraph isomorphic to $H$ in its coloring. Bollobás conjectured a simple characterization of $H$ for which $R_\varepsilon^2(H)$ is finite, which was later proved by Cutler and Montágh. Here, we obtain a characterization for arbitrary values of $r$, as well as asymptotically tight bounds. We also discuss generalizations to graphs defined on perfect Polish spaces, where the corresponding notion of balancedness is each color class being non-meagre.

The Intricacies of Trust in Technology

The aim of this paper is to demonstrate the intricacies of trust in an institutional setting with the help of a case entailing a clash between Apple and the FBI in a situation that was both politically and emotionally complex. The review of literature covers an extensive amount of academic papers to encapsulate each and every aspect of trust ranging from simple characterization of the concept to the deep-seated complexities of the matter like the effect of ethnicity on trust or the neurological effects during a breach of trust. Finally, it identifies serious gaps in research that are needed to be worked upon by other researchers to further our understanding of the matter.

Mysticism and esotericism as contested taxonomical categories

Esotericism and mysticism are two notoriously elusive concepts. Both are based on referential corpora of works that are so internally diverse as to defy any simple characterization. A definition of mysticism needs to encompass a range of empirical cases that include medieval Christian visionaries, Sufis, and Hindu gurus such as Ramakrishna. Similarly, the term esotericism denotes the work of individuals as diverse as Paracelsus, Swedenborg, and Carl Gustav Jung. Unsurprisingly, in a recent encyclopedia article (Nelstrop 2016) mysticism has been characterized as a ‘taxonomical black hole’, while esotericism has been described by a leading scholar on that topic, Wouter J. Hanegraaff (2005, 2012), as a waste-basket category for a range of currents that have little else in common than having been rejected by mainstream theologians and by rationalists from the Enlightenment to our own time. This article argues that the terms are not only laden with significant definitional problems, but that applying them to any particular phenomenon has little, if any, theoretical added value. Instead, this article advocates a higher-level taxonomy that sees the elements of both sets as examples of a more general category: religious phenomena which are supported by charismatic authority.

Oriented Flip Graphs and Noncrossing Tree Partitions

International audience Given a tree embedded in a disk, we define two lattices - the oriented flip graph of noncrossing arcs and the lattice of noncrossing tree partitions. When the interior vertices of the tree have degree 3, the oriented flip graph is equivalent to the oriented exchange graph of a type A cluster algebra. Our main result is an isomorphism between the shard intersection order of the oriented flip graph and the lattice of noncrossing tree partitions. As a consequence, we deduce a simple characterization of c-matrices of type A cluster algebras.

Nice Invincible Strategy for the Average-Payoff IPD

The Iterated Prisoner's Dilemma (IPD) is a well-known benchmark for studying the long term behaviours of rational agents. Many well-known strategies have been studied, from the simple tit-for-tat (TFT) to more involved ones like zero determinant and extortionate strategies studied recently by Press and Dyson. In this paper, we consider what we call invincible strategies. These are ones that will never lose against any other strategy in terms of average payoff in the limit. We provide a simple characterization of this class of strategies, and show that invincible strategies can also be nice. We discuss its relationship with some important strategies and generalize our results to some typical repeated 2x2 games. It's known that experimentally, nice strategies like the TFT and extortionate ones can act as catalysts for the evolution of cooperation. Our experiments show that this is also the case for some invincible strategies that are neither nice nor extortionate.