Distinguishing between “change” and “amount” infinitesimals in first-semester calculus-based physics

From the perspective of an introductory calculus course, an integral is simply a Riemann sum: a particular limit of a sum of small quantities. However, students connect those mathematical quantities to physical representations in different ways. For example, integrals that add up mass and integrals that add up displacement use infinitesimals differently. Students who are not cognizant of these differences may not understand what they are doing when they integrate. Further, they may not understand how to set up an integral. We propose a framework for scaffolding students' knowledge of integrals using a distinction between “change” and “amount” infinitesimals. In support of the framework, we present results from two qualitative studies about student understanding of integration

New SETI Sky Surveys for Radio Pulses

Berkeley conducts 7 SETI programs at IR, visible and radio wavelengths. Here we review two of the newest efforts, Astropulse and Fly's Eye. A variety of possible sources of microsecond to millisecond radio pulses have been suggested in the last several decades, among them such exotic events as evaporating primordial black holes, hyper-flares from neutron stars, emissions from cosmic strings or perhaps extraterrestrial civilizations, but to-date few searches have been conducted capable of detecting them. We are carrying out two searches in hopes of finding and characterizing these mu-s to ms time scale dispersed radio pulses. These two observing programs are orthogonal in search space; the Allen Telescope Array's (ATA) "Fly's Eye" experiment observes a 100 square degree field by pointing each 6m ATA antenna in a different direction; by contrast, the Astropulse sky survey at Arecibo is extremely sensitive but has 1/3,000 of the instantaneous sky coverage. Astropulse's multibeam data is transferred via the internet to the computers of millions of volunteers. These computers perform a coherent de-dispersion analysis faster than the fastest available supercomputers and allow us to resolve pulses as short as 400 ns. Overall, the Astropulse survey will be 30 times more sensitive than the best previous searches. Analysis of results from Astropulse is at a very early stage. The Fly's Eye was successfully installed at the ATA in December of 2007, and to-date approximately 450 hours of observation has been performed. We have detected three pulsars and six giant pulses from the Crab pulsar in our diagnostic pointing data. We have not yet detected any other convincing bursts of astronomical origin in our survey data. (Abridged)Comment: 9 pages, 6 figures, Accepted to Acta Astronautica "Special Issue: Life Signatures

Status of the UC-Berkeley SETI Efforts

We summarize radio and optical SETI programs based at the University of California, Berkeley. The SEVENDIP optical pulse search looks for ns time scale pulses at visible wavelengths using an automated 30 inch telescope. The ongoing SERENDIP V.v sky survey searches for radio signals at the 300 meter Arecibo Observatory. The currently installed configuration supports 128 million channels over a 200 MHz bandwidth with ~1.6 Hz spectral resolution. SETI@home uses the desktop computers of volunteers to analyze over 160 TB of data at taken at Arecibo looking for two types of continuous wave signals and two types of pulsed signals. A version to be released this summer adds autocorrelation analysis to look for complex wave forms that have been repeated (and overlayed) after a short delay. SETI@home will soon be processing data of Kepler exoplanet systems collected at the GBT. The Astropulse project is the first SETI search for $\mu$s time scale dispersed pulses in the radio spectrum. We recently reobserved 114 sky locations where microsecond pulses were detected. This data is in process of being transferred to Berkeley for analysis.Comment: 8 pages, including 1 figure. Presented at SPIE Conf. 8152, San Diego, CA, Aug 25, 201

Secondary analysis of teaching methods in introductory physics: A 50 k-student study

Citation: Von Korff, J., Archibeque, B., Gomez, K. A., Heckendorf, T., McKagan, S. B., Sayre, E. C., . . . Sorell, L. (2016). Secondary analysis of teaching methods in introductory physics: A 50 k-student study. American Journal of Physics, 84(12), 969-974. doi:10.1119/1.4964354Physics education researchers have developed many evidence-based instructional strategies to enhance conceptual learning of students in introductory physics courses. These strategies have historically been tested using assessments such as the Force Concept Inventory (FCI) and the Force and Motion Conceptual Evaluation (FMCE). We have performed a review and analysis of FCI and FMCE data published between 1995 and 2014. We confirm previous findings that interactive engagement teaching techniques are significantly more likely to produce high student learning gains than traditional lecture-based instruction. We also establish that interactive engagement instruction works in many settings, including those with students having a high and low level of prior knowledge, at liberal arts and research universities, and enrolled in both small and large classes. (C) 2016 Author(s)

Understanding the nature and mechanism of foot pain

Approximately one-quarter of the population are affected by foot pain at any given time. It is often disabling and can impair mood, behaviour, self-care ability and overall quality of life. Currently, the nature and mechanism underlying many types of foot pain is not clearly understood. Here we comprehensively review the literature on foot pain, with specific reference to its definition, prevalence, aetiology and predictors, classification, measurement and impact. We also discuss the complexities of foot pain as a sensory, emotional and psychosocial experience in the context of clinical practice, therapeutic trials and the placebo effect. A deeper understanding of foot pain is needed to identify causal pathways, classify diagnoses, quantify severity, evaluate long term implications and better target clinical intervention

Astropulse. A Search for Microsecond Transient Radio Signals Using Distributed Computing

I performed a transient, microsecond timescale radio sky survey, called “Astropulse,” using the Arecibo telescope in Puerto Rico. Astropulse searches for brief (0.4 μs to 204.8 &mus;s), wideband (relative to its 2.5 MHz bandwidth) radio pulses centered at 1,420 MHz, a range that includes the hyperfine hydrogen line.Astropulse is a commensal survey, obtaining its data by sharing telescope time with other surveys, such as PALFA. I scanned the sky visible to Arecibo, between declinations of -1.33 and 38.03 degrees, with varying dwell times depending on the requirements of our partner surveys. I analyzed 1,540 hours of data in each of 7 beams of the ALFA receiver, with 2 polarizations per beam, for a total of 21,600 hours of data. The data were 1-bit complex sampled at the Nyquist limit of 0.4 μs per sample. Examination of timescales less than 12.8 μs would have been impossible if not for my use of coherent dedispersion, a technique that has frequently been used for targeted observations, but has never before been associated with a radio sky survey. I performed nonlinear coherent dedispersion, reversing the broadening effects on signals caused by their passage through the interstellar medium (ISM). Coherent dedispersion requires intensive computations, and needs far more processing power than the more usual incoherent dedispersion. This processing power was provided by BOINC, the Berkeley Open Infrastructure for Network Computing. BOINC is a distributed computing system, which allowed me to utilize hundreds of thousands of volunteers’ computers to perform the necessary calculations for coherent dedispersion. Each volunteer’s computer requires about a week to process a single 8 MB “workunit,” corresponding to 13 s of data from a single beam and polarization. In all, Astropulse analyzed over 48 TB of data. I did not aim to detect any particular astrophysical source, intending rather to perform a survey of the transient radio sky. Astrophysical events that might produce brief radio pulses include giant pulses from pulsars, RRATs, or exploding primordial black holes. In discussing the results of the Astropulse project, I have taken our sensitivity to primordial black holes with a certain size and spatial distribution to indicate our overall sensitivity relative to other surveys.Radio frequency interference (RFI) and noise contaminated the data; these were mitigated by a number of techniques including multi-polarization correlation, DM repetition detection, and frequency profiling. I also made use of a number of programs that specifically blank RFI from the FAA and aerostat radars near Arecibo.Ultimately, Astropulse's sensitivity turned out to be similar to that of other very recent surveys, demonstrating that with enough computing power, a radio sky survey can make use of coherent dedispersion. We were unable to prove decisively that any of the signals came from astrophysical sources, but we did notice a surplus of pulses coming from inside the Galactic disk, as opposed to the halo.In addition to Astropulse, I programmed a “distributed thinking” project called Stardust@home. The two projects are not related by their science content, but they are closely connected by their use of distributed processing methods. The Stardust spacecraft returned pristine interstellar dust samples, and Stardust@home recruited volunteers to locate these dust particles in microscopic-scale images of aerogel. “Distributed thinking” means that volunteers examine our data with their own eyes, judging whether they see the dust particles. In contrast, Astropulse volunteers utilize their computers’ processing power. Both methods create opportunities for public outreach, encouraging non-scientists to participate in scientific research. By signing up for Astropulse or Stardust@home, anyone can learn about astronomy and make a contribution to the field

Teaching integration with layers and representations: A case study

We designed a sequence of seven lessons to facilitate learning of integration in a physics context. We implemented this sequence with a single college sophomore, “Amber,” who was concurrently enrolled in a first-semester calculus-based introductory physics course which covered topics in mechanics. We outline the philosophy underpinning these lessons, which characterizes integration in terms of layers and representations. We describe how Amber learned to give oral presentations in which she told a story about how integration comes from products, sums, and limits in a variety of physics contexts. We conclude that by the end of our lessons, Amber was able to conceptualize and explain integrals using multiple representations. In one case, she was able to solve a novel problem about integration in an unfamiliar context (center of mass.) Based on our previous research about integration, we suggest that these achievements would have been unattainable with the use of a single one or two hour lesson

Quality of Preventive Care for Diabetes: Effects of Visit Frequency and Competing Demands

PURPOSE We sought to determine the association between timely receipt of diabetes-related preventive services and the longitudinal pattern of outpatient service use as characterized by a novel taxonomy that prioritized visits based on the Oregon State Prioritized Health Services List. METHODS We performed a cross-sectional analysis of mail survey and automated health care data for a population-based sample of patients with diabetes enrolled in a health maintenance organization in Washington State (N = 4,463). Outcomes included American Diabetes Association–recommended preventive services, including regular hemoglobin A(1C) (HbA(1C)) monitoring, retinal examination, and microalbuminuria screening. Patients with fewer than 8 visits during the 2-year study period were considered infrequent users, while patients with 8 or more visits were classified as lower-priority users if most visits were for conditions of relatively low rank on the Oregon list and as higher-priority users otherwise. RESULTS After adjustment for social, demographic, and clinical factors, and depression, infrequent users had significantly reduced odds of receiving at least 1 HbA(1C) test (odds ratio [OR] = 0.35, 95% confidence interval [CI], 0.24–0.51), retinal examination (OR = 0.74, 95% CI, 0.63–0.86), and microalbuminuria screening (OR = 0.75, 95% CI, 0.58–0.96) relative to higher-priority users during the previous year. Lower-priority users also had relatively reduced odds of receiving at least 1 HbA(1C) test (OR = 0.59, 95% CI, 0.35–1.01), retinal examination (OR = 0.68, 95% CI, 0.56–0.84), and microalbuminuria screening (OR = 0.79, 95% CI, 0.57–1.09) despite attending a similar mean number of total visits as higher-priority users. CONCLUSIONS Patients who attend relatively few outpatient visits or who attend more frequent visits for predominantly lower-priority conditions are more likely to receive substandard preventive care for diabetes