Tile Number and Space-Efficient Knot Mosaics

In this paper we introduce the concept of a space-efficient knot mosaic. That is, we seek to determine how to create knot mosaics using the least number of non-blank tiles necessary to depict the knot. This least number is called the tile number of the knot. We determine strict bounds for the tile number of a knot in terms of the mosaic number of the knot. In particular, if $t$ is the tile number of a prime knot with mosaic number $m$, then $5m-8 \leq t \leq m^2-4$ if $m$ is even and $5m-8 \leq t \leq m^2-8$ if $m$ is odd. We also determine the tile number of several knots and provide space-efficient knot mosaics for each of them.Comment: The original version of this article was split into two articles during refereein

AI & Agency

In July of 2019, at the Summer Institute on AI and Society in Edmonton, Canada (co-sponsored by CIFAR and the AI Pulse Project of UCLA Law), scholars from across disciplines came together in an intensive workshop. For the second half of the workshop, the cohort split into smaller working groups to delve into specific topics related to AI and Society.I proposed deeper exploration on the topic of “agency,” which is defined differently across domains and cultures, and relates to many of the topics of discussion in AI ethics, including responsibility and accountability. It is also the subject of an ongoing art and research project I’m producing. As a group, we looked at definitions of agency across fields, found paradoxes and incongruities, shared our own questions, and produced a visual map of the conceptual space. We decided that our disparate perspectives were better articulated through a collection of short written pieces, presented as a set, rather than a singular essay on the topic. The outputs of this work are shared here.This set of essays, many of which are framed as provocations, suggests that there remain many open questions, and inconsistent assumptions on the topic. Many of the writings include more questions than answers, encouraging readers to revisit their own beliefs about agency. As we further develop AI systems, and refer to humans and non-humans as “agents”– we will benefit from a better understanding of what we mean when we call something an “agent” or claim that an action involves “agency.” This work is under development and many of us will continue to explore this in our ongoing AI work.  – Sarah Newman, Project Lead, August 201

Determining The SSA4 3’ UTR Sequence Via Reverse Transcription and Molecular Cloning

Transcript export in eukaryotic cells, such as S. cerevisiae, includes the transport of mRNA from the nucleus to the cytoplasm via the nuclear pore complex. This process can serve as an essential step of regulating gene expression, as transcripts must reach the cytoplasm to be translated into protein. For example, under cell stress such as heat shock, the majority of poly-A RNA is retained in the nucleus, inhibiting normal gene expression. However, select transcripts that function in cellular recovery from stress are permitted to export. One of these transcripts, SSA4, which encodes a molecular chaperone, has been demonstrated to selectively export, but the mechanism by which this occurs is not understood. Based on previous studies. We hypothesized that the 3’ UTR sequence allows for SSA4 mRNA export under these conditions. In order to test our hypothesis, we first sought to define the SSA4 3’ UTR sequence. To do this, cells were exposed to stress to induce SSA4 expression, and RNA was isolated and reverse transcribed into cDNA using a poly-T primer. Following this, the levels of SSA4 expression was assessed by Q-PCR, which demonstrated induction following stress. PCR was then performed using primers to bind before and after the 3’ UTR, and then that sequence was cloned into a plasmid, to be cultured and subsequently sequenced. However, gel electrophoresis following colony PCR, demonstrated that SSA4 sequence was not present in cloned plasmids. Current experiments are aimed at attempting this cloning again. Determining the 3’ UTR sequence of SSA4 will allow us to not only learn about mRNA export but will help us better understand the regulation of gene expression in cells

Microlensing

Microlensing observations have now become a useful tool in searching for non--luminous astrophysical compact objects (brown dwarfs, faint stars, neutron stars, black holes and even planets). Originally conceived for establishing whether the halo of the Galaxy is composed of this type of objects, the ongoing searches are actually also sensitive to the dark constituents of other Galactic components (thin and thick disks, outer spheroid, bulge). We discuss here the present searches for microlensing of stars in the Magellanic Clouds and in the Galactic bulge (EROS, MACHO, OGLE and DUO collaborations). We analyse the information which can be obtained regarding the spatial distribution and motion of the lensing objects as well as about their mass function and their overall contribution to the mass of the Galaxy. We also discuss the additional signals, such as the parallax due to the motion of the Earth, the effects due to the finite source size and the lensing events involving binary objects, which can further constrain the lens properties. We describe the future prospects for these searches and the further proposed observations which could help to elucidate these issues, such as microlensing of stars in the Andromeda galaxy, satellite parallax measurements and infrared observations.Comment: Latex file, 59 p., 13 ps figures, to appear in Physics Reports (postcript file replaced by latex file

Understanding Engagement with the Privacy Domain Through Design Research.

This paper reports findings from participatory design research aimed at uncovering how technological interventions can engage users in the domain of privacy. Our work was undertaken in the context of a new design concept “Privacy Trends” whose aspiration is to foster technology users’ digital literacy regarding ongoing privacy risks and elucidate how such risks fit within existing social, organizational and political systems, leading to a longer term privacy concern. Our study reveals two challenges for privacy intervention design: the need to develop technology users’ intrinsic motivations with the privacy domain and the importance of framing the concept of privacy within users’ interests. Setting our study within a design context enables us to identify four design opportunities for fostering engagement with the privacy domain through technology design

Evolution of chemical abundances in Seyfert galaxies

We computed the chemical evolution of spiral bulges hosting Seyfert nuclei, based on updated chemical and spectro-photometrical evolution models for the bulge of our Galaxy, made predictions about other quantities measured in Seyferts, and modeled the photometry of local bulges. The chemical evolution model contains detailed calculations of the Galactic potential and of the feedback from the central supermassive black hole, and the spectro-photometric model covers a wide range of stellar ages and metallicities. We followed the evolution of bulges in the mass range 10^9 - 10^{11} Msun by scaling the star formation efficiency and the bulge scalelength as in the inverse-wind scenario for elliptical galaxies, and considering an Eddington limited accretion onto the central supermassive black hole. We successfully reproduced the observed black hole-host bulge mass relation. The observed nuclear bolometric luminosity is reproduced only at high redshift or for the most massive bulges; in the other cases, at z = 0 a rejuvenation mechanism is necessary. The black hole feedback is in most cases not significant in triggering the galactic wind. The observed high star formation rates and metal overabundances are easily achieved, as well as the constancy of chemical abundances with redshift and the bulge present-day colours. Those results are not affected if we vary the index of the stellar IMF from x=0.95 to x=1.35; a steeper IMF is instead required in order to reproduce the colour-magnitude relation and the present K-band luminosity of the bulge.Comment: 17 pages, 15 figures, 3 tables, accepted for publication in A&

Observation of Parametric Instability in Advanced LIGO

Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been observed in a kilometer-scale interferometer. In this work we describe the first observation of parametric instability in an Advanced LIGO detector, and the means by which it has been removed as a barrier to progress

The clinical features of the piriformis syndrome: a systematic review

Piriformis syndrome, sciatica caused by compression of the sciatic nerve by the piriformis muscle, has been described for over 70 years; yet, it remains controversial. The literature consists mainly of case series and narrative reviews. The objectives of the study were: first, to make the best use of existing evidence to estimate the frequencies of clinical features in patients reported to have PS; second, to identify future research questions. A systematic review was conducted of any study type that reported extractable data relevant to diagnosis. The search included all studies up to 1 March 2008 in four databases: AMED, CINAHL, Embase and Medline. Screening, data extraction and analysis were all performed independently by two reviewers. A total of 55 studies were included: 51 individual and 3 aggregated data studies, and 1 combined study. The most common features found were: buttock pain, external tenderness over the greater sciatic notch, aggravation of the pain through sitting and augmentation of the pain with manoeuvres that increase piriformis muscle tension. Future research could start with comparing the frequencies of these features in sciatica patients with and without disc herniation or spinal stenosis