The Church-Turing thesis (CTT) underlies tantalizing open questions concerning the fundamental place of computing in the physical universe. For example, is every physical system computable? Is the universe essentially computational in nature? What are the implications for computer science of recent speculation about physical uncomputability? Does CTT place a fundamental logical limit on what can be computed, a computational "barrier" that cannot be broken, no matter how far and in what multitude of ways computers develop? Or could new types of hardware, based perhaps on quantum or relativistic phenomena, lead to radically new computing paradigms that do breach the Church-Turing barrier, in which the uncomputable becomes computable, in an upgraded sense of "computable"? Before addressing these questions, we first look back to the 1930s to consider how Alonzo Church and Alan Turing formulated, and sought to justify, their versions of CTT. With this necessary history under our belts, we then turn to today's dramatically more powerful versions of CTT.
Semiconductor nanocrystals have been shown to have unique advantages over traditional organic photoinitiators for polymerization in solution However, efficient photoinitiation with such nanoparticles in solvent-free and additive-free formulations so far has not been achieved. Herein, the ability to use semiconductor nanocrystals for efficient bulk polymerization as sole initiators is reported, operating under modern UV-blue-LED light sources found in 3D printers and other photocuring applications. Hybrid semiconductor-metal nanorods exhibit superior photoinitiation capability to their pristine semiconductor counterparts, attributed to the enhanced charge separation and oxygen consumption in such systems. Moreover, photoinitiation by semiconductor nanocrystals overcoated by inorganic ligands is reported, thus increasing the scope of possible applications and shedding light on the photoinitiation mechanism; in light of the results, two possible pathways are discussed - ligand-mediated and cation-coordinated oxidation A demonstration of the unique attributes of the quantum photoinitiators is reported in their use for high-resolution two-photon printing of optically fluorescing microstructures, demonstrating a multi-functionality capability. The bulk polymerization demonstrated here can be advantageous over solvent based methods as it alleviates the need of post-polymerization drying and reduces waste and exposure to toxic solvents, as well as broadens the possible use of quantum photoinitiators for industrial and research uses.
This review describes recent developments in the field of conductive nanomaterials and their application in 2D and 3D printed flexible electronics, with particular emphasis on inks based on metal nanoparticles and nanowires, carbon nanotubes, and graphene sheets. We present the basic properties of these nanomaterials, their stabilization in dispersions, formulation of conductive inks and formation of conductive patterns on flexible substrates (polymers, paper, textile) by using various printing technologies and post-printing processes. Applications of conductive nanomaterials for fabrication of various 2D and 3D electronic devices are also briefly discussed.
Abstract. Catchment scale hydrological studies on drylands are lacking because of the scarcity of consistent data: observations are often available at the plot scale, but their relevance for the catchment scale remains unclear. A database of 24 years of stream gauge discharge and homogeneous high-resolution radar data over the eastern Mediterranean allows to describe the properties of moderate floods over catchments spanning from Desert to Mediterranean climates. Comparing two climatic regions, Desert and Mediterranean, we are able to better identify specific rainfall-runoff properties. Despite the large differences in rainfall forcing between the two regions, the resulting unit peak discharges and runoff coefficients are comparable. In Mediterranean areas rain depth and antecedent conditions are the most important properties to shape flood response. In Deserts, instead, storm core properties display a strong correlation with unit peak discharge and, to a less extent, with runoff coefficient. In this region, an inverse correlation with mean catchment annual precipitation suggests also a strong influence of local surface properties. Preliminary analyses suggest that floods in catchments with wet headwater and dry lower section are more similar to desert catchments, with a strong influence of storm core properties on runoff generation.
Various types of devices require hierarchically nano-patterned substrates, where spacing between patterned domains is controlled. Ultra-confined films exhibit extreme morphological sensitivity to slight variations in film thickness when the substrate is highly selective toward one of the blocks. Here, it is shown that using the substrate’s topography as a thickness differentiating tool enables the creation of domains with different surface patterns in a fully controlled fashion from a single, unblended block copolymer. This approach is applicable to block copolymers of different compositions and to different topographical patterns, and thus opens numerous possibilities for hierarchical construction of multifunctional devices.
This article examines smartphone usage among deaf and hard of hearing people, and shows how it is deeply shaped by the core function of the voice call. Indeed, while the smartphone appears accessible, it actually reproduces communicative norms of the hearing hegemony. In-depth interviews highlight the social norms of voice calls both as a communicative practice and as forcing communicative values on textual smartphone interactions. People who cannot perform voice calls must obey these norms of immediacy and priority while interacting accessibly via WhatsApp and video calls. Moreover, users’ auditory diversity is reflected in their responses and practices vis-à-vis voice calls, highlighting this as a representation of the hegemonic hearing society. Critical examination of these phenomena shows how deaf and hard of hearing smartphone users’ communicative practices result from intersections of their audiological capacities and other stigmatized positions, which has profound implications for our understanding of media accessibility.
The presence of heavy metal ions such as copper in the human body at certain concentrations and specific conditions can lead to the development of different diseases. The currently available analytical detection methods remain expensive, time-consuming, and often require sample pre-treatment. The development of specific and quantitative, easy-in-operation, and cost-effective devices, capable of monitoring the level of Cu2+ ions in environmental and physiological media, is necessary. We use silicon nanoribbon (SiNR) ion-sensitive field effect transistor (ISFET) devices modified with a Gly–Gly–His peptide for the detection of copper ions in a large concentration range. The specific binding of copper ions causes a conformational change of the ligand, and a deprotonation of secondary amine groups. By performing differential measurements, we gain a deeper insight into the details of the ion–ligand interaction. We highlight in particular the importance of considering non-specific interactions to explain the sensors' response.
The presence of heavy metal ions such as copper in the human body at certain concentrations and specific conditions can lead to the development of different diseases. The currently available analytical detection methods remain expensive, time-consuming, and often require sample pre-treatment. The development of specific and quantitative, easy-in-operation, and cost-effective devices, capable of monitoring the level of Cu2+ ions in environmental and physiological media, is necessary. We use silicon nanoribbon (SiNR) ion-sensitive field effect transistor (ISFET) devices modified with a Gly–Gly–His peptide for the detection of copper ions in a large concentration range. The specific binding of copper ions causes a conformational change of the ligand, and a deprotonation of secondary amine groups. By performing differential measurements, we gain a deeper insight into the details of the ion–ligand interaction. We highlight in particular the importance of considering non-specific interactions to explain the sensors’ response.
Migrants and refugees from Middle Eastern countries are scattered around the globe, predominantly in the MENA (Middle East and North Africa) Region, Europe and the USA. Between 2005 and 2015, the number of migrants living in the Middle East more than doubled, from about 25 million to around 54 million.11 ‘Middle East’s Migrant Population More than Doubles Since 2005’, Pew Research Center Report (2016), http://www.pewglobal.org/2016/10/18/middle-easts-migrant-population-more-than-doubles-since-2005/.View all notes Some of this growth was due to individuals and families seeking economic opportunities. But the majority of the migration surge, especially after the war in Syria began in 2011, was a consequence of armed conflict and the forced displacement of millions of people from their homes, many of whom have left their countries of birth.22 Ibid.View all notes Furthermore, the estimated number of immigrants to Europe between mid-2010 and mid-2016 was 7 million, not including 1.7 million asylum seekers. Among these European countries, Germany recorded the highest level of immigration, followed by Britain, France, Spain and Italy.33 ‘Migration to Europe in Charts’, BBC News, September 11, 2018, https://www.bbc.co.uk/news/world-europe-44660699.View all notes These migration flows not only reflect the existence of drivers of migration due to conflict in the Middle East, but also reveal the potential formation of new diasporas throughout time and the growing size of the already existing ones in host countries all around the world.
