Recommendations and User Agency: The Reachability of Collaboratively-Filtered Information

Recommender systems often rely on models which are trained to maximize accuracy in predicting user preferences. When the systems are deployed, these models determine the availability of content and information to different users. The gap between these objectives gives rise to a potential for unintended consequences, contributing to phenomena such as filter bubbles and polarization. In this work, we consider directly the information availability problem through the lens of user recourse. Using ideas of reachability, we propose a computationally efficient audit for top-$N$ linear recommender models. Furthermore, we describe the relationship between model complexity and the effort necessary for users to exert control over their recommendations. We use this insight to provide a novel perspective on the user cold-start problem. Finally, we demonstrate these concepts with an empirical investigation of a state-of-the-art model trained on a widely used movie ratings dataset.Comment: appeared at FAccT '2

Fate of anterior capsule tears during cataract surgery

PURPOSE: To determine the incidence of anterior capsule tears, at what stage of surgery they occurred, and their intraoperative behavior. SETTING: Ambulatory surgery center, Cincinnati Eye Institute, Cincinnati, Ohio, USA. METHODS: This 5-year retrospective study was of patients having phacoemulsification with posterior chamber intraocular lens (IOL) implantation complicated by unplanned peripheral extension of the capsulorhexis tear or a radial anterior capsule tear. The operative notes and a videotape of the surgery were reviewed. The stage at which the tear was initially observed and when it extended were identified, as was whether the tear extended to the posterior capsule. Anterior vitrectomy and the design and location of the IOL implanted were also analyzed. RESULTS: A discontinuous anterior capsulorhexis or a break in the anterior capsule rim was observed in 21 eyes of 2646 cases, for an overall incidence of 0.79%. Anterior capsule tears were identified during ophthalmic viscosurgical device injection in 1 eye, capsulorhexis in 13 eyes, hydrodissection in 2 eyes, phacoemulsification in 3 eyes, irrigation/aspiration (I/A) in 1 eye, and implantation of a prosthetic iris device in 1 eye. Seven of the 13 tears identified during the capsulorhexis were managed by redirecting the second edge of the ''safety'' capsulorhexis to incorporate the tear. In 14 eyes, the tear in the anterior capsule extended into the zonules; 4 of these tears were limited. Ten tears extended around the equator and through the posterior capsule, occurring during the hydrodissection in 1 eye, phacoemulsification in 2 eyes, I/A in 1 eye, and IOL implantation in 6 eyes. An anterior vitrectomy was required in 4 eyes that had posterior capsule involvement. Endocapsular fixation of a 1-piece acrylic IOL was achieved in 18 eyes. Three eyes required implantation of a 3-piece acrylic IOL in the ciliary sulcus. CONCLUSIONS: Extension of an anterior capsule tear can complicate cataract surgery at any stage. Extension of the tear through the posterior capsule occurred in almost half the eyes with an anterior capsule tear, often requiring an anterior vitrectomy. Managing an anterior capsule tear can be challenging yet compatible with implantation of a posterior chamber IOL. J Cataract Refract Surg 2006; 32:1638-1642 Q 2006 ASCRS and ESCRS The importance of an intact capsulorhexis for safe phacoemulsification with intraocular lens implantation (IOL) is well recognized. 1 A discontinuous anterior capsule edge that occurs during the capsulorhexis or at any stage of the procedure may result in complications including extension through the posterior capsule, vitreous loss, posterior dislocation of lens fragments, and alteration of the intended type and location of the IOL. 2 This study was done to determine the incidence, origination, and behavior of torn anterior capsules complicating cataract surgery. PATIENTS AND METHODS A retrospective study was designed in which surgical videotapes and intraoperative reports specifying anterior capsule tears were reviewed. The review comprised cataract procedures performed by the same surgeon (R.H.O.) between January 2000 and December 2004. The stage at which the anterior capsule tear was identified, whether it could be salvaged, whether it extended into the zonules, and whether it continued around the equator into the posterior capsule were recorded. In the group of eyes further complicated by a posterior capsule tear, the stage of recognition, and the need for anterior vitrectomy were analyzed, as was the design and placement of the IOL

Precision Tests of the Standard Model

30 páginas, 11 figuras, 11 tablas.-- Comunicación presentada al 25º Winter Meeting on Fundamental Physics celebrado del 3 al 8 de MArzo de 1997 en Formigal (España).Precision measurements of electroweak observables provide stringent tests of the Standard Model structure and an accurate determination of its parameters. An overview of the present experimental status is presented.This work has been supported in part by CICYT (Spain) under grant No. AEN-96-1718.Peer reviewe

Templates for Convex Cone Problems with Applications to Sparse Signal Recovery

This paper develops a general framework for solving a variety of convex cone problems that frequently arise in signal processing, machine learning, statistics, and other fields. The approach works as follows: first, determine a conic formulation of the problem; second, determine its dual; third, apply smoothing; and fourth, solve using an optimal first-order method. A merit of this approach is its flexibility: for example, all compressed sensing problems can be solved via this approach. These include models with objective functionals such as the total-variation norm, ||Wx||_1 where W is arbitrary, or a combination thereof. In addition, the paper also introduces a number of technical contributions such as a novel continuation scheme, a novel approach for controlling the step size, and some new results showing that the smooth and unsmoothed problems are sometimes formally equivalent. Combined with our framework, these lead to novel, stable and computationally efficient algorithms. For instance, our general implementation is competitive with state-of-the-art methods for solving intensively studied problems such as the LASSO. Further, numerical experiments show that one can solve the Dantzig selector problem, for which no efficient large-scale solvers exist, in a few hundred iterations. Finally, the paper is accompanied with a software release. This software is not a single, monolithic solver; rather, it is a suite of programs and routines designed to serve as building blocks for constructing complete algorithms.Comment: The TFOCS software is available at http://tfocs.stanford.edu This version has updated reference

A three-phases model for the simulation of landslide-generated waves using the improved conservative level set method

This work is supported by the National Natural Science Foundation of China (No. 51279050), the Fundamental Research Funds for the Central Universities(No. 2016B05014), Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China(No. 151073), Ministry of Water Resources non-profit specific industry appropriation(No. 201501036, No. 201501034 and No. 201501033), China Scholarship Council, and Qing Lan Project

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely