February 1, 2012
Physics News Highlights of the American Institute of Physics (AIP) contains summaries of interesting research from the AIP journals, notices of upcoming meetings, and other information from the AIP Member Societies. Copies of papers are available to journalists upon request.
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TOPICS IN THIS ISSUE:
- Powering pacemakers with heartbeat vibrations: Sick hearts may help to keep themselves beating longer with a device that could harvest energy from heartbeat-induced chest cavity vibrations.
- Precision Time: A matter of atoms, clocks, and statistics: Time is of the essence, especially in communications, navigation, and electric power distribution, which all demand nanosecond precision or better. Keeping these beating hearts of technology in near-perfect global synchronization requires the blending of statistics, atomic science, and technological innovations.
- Building a better light bulb: Scientists study the movement of charge carriers to design an organic LED that is energy efficient and still casts a warm, natural glow.
- Other content: Upcoming Conferences of Interest; Physics Today: February Articles; AIP Science Communication Awards: Call for Entries.
1. Powering pacemakers with heartbeat vibrations
Though pacemakers require only small amounts of energy (about 1 millionth of a Watt), their batteries have to be replaced periodically, which means multiple surgeries for patients. Researchers have searched for ways to prolong battery life – trying to generate energy to power a pacemaker using blood sugar, or the motion of the hands and legs – but these methods either interfere with metabolism or require a more drastic surgery, such as passing a wire from the limbs to the chest area. Aerospace engineers from the University of Michigan in Ann Arbor have developed a prototype device that could power a pacemaker using a source that is surprisingly close to the heart of the matter: vibrations in the chest cavity that are due mainly to heartbeats.
The authors describe the technique and their progress developing it in a paper recently published in the AIP’s Applied Physics Letters. In their method, vibrations in the chest cavity deform a layer of piezoelectric material, which is able to convert mechanical stress into electrical current. Tests indicate that the device could perform at heart rates from 7 to 700 beats per minute (well below and above the normal range), and that it could deliver eight times the energy required for a pacemaker. Furthermore, the authors write, the amount of energy generated is always larger than the amount required to run a pacemaker, regardless of heart rate. Though the team has yet to develop a prototype that is biocompatible, they say that the potential to package this energy harvester with pacemakers gives it an advantage over competing methods.
Article: “Powering Pacemakers from Heartbeat Vibrations Using Linear and Nonlinear Energy Harvesters” is published in Applied Physics Letters.
Authors: M. Amin Karami (1) and Daniel J. Inman (1).
(1) Department of Aerospace Engineering, University of Michigan
2. Precision Time: A matter of atoms, clocks, and statistics
The ability to accurately measure a second in time is at the heart of many essential technologies; the most recognizable may be the Global Positioning System (GPS). In a paper accepted for publication in the AIP’s journal Review of Scientific Instruments, a researcher at the National Institutes of Standards and Technology (NIST) and the University of Colorado at Boulder discusses how achieving a stable and coordinated global measure of time requires more than just the world’s most accurate timepieces; it also requires approximately 400 atomic clocks working as an ensemble. According to the researcher, however, calculating the average time of an ensemble of clocks is difficult, and complicated statistics are needed to achieve greater accuracy and precision. These statistical calculations are essential to help counter one of the most important challenges in keeping and agreeing on time: distributing data without degrading the performance of the source clocks.
All atomic clocks operate in basically the same way, by comparing an electrical oscillator (a device engineered to keep time) with the transition frequency of an atom (one of nature’s intrinsic time keepers). This atomic transition is a “flip” in the spin in the outermost electron of an atom – an event that is predictable with an accuracy of a few parts per ten quadrillion. Comparing the natural and engineered signals produces the incredibly stable “tick” of an atomic clock. Several algorithms are then used to estimate the time of the reference clock with respect to the ensemble of clocks. These calculations weed out as much error as possible and establish a reliable reference time. The researcher notes that there are strengths and weaknesses in each of these statistical steps, but these weaknesses can be mitigated to some extent by also including retrospective data. So in essence, determining the current time relies on understanding how accurately researchers were able to calculate time in the past. Even the next generation of atomic clocks and frequency standards are unlikely to eliminate the need for these timescale algorithms. However, keeping time and frequency signals and standards the same in all countries is essential and greatly simplifies international cooperation in areas such as navigation, telecommunication, and electric power distribution.
Article: “The Statistical Modeling of Atomic Clocks and the Design of Time Scales” is accepted for publication in the journal Review of Scientific Instruments.
Author: Judah Levine (1).
(1) Time and Frequency Division, National Institutes of Standards and Technology and the University of Colorado at Boulder
3. Building a better light bulb
Incandescent light bulbs are energy hogs, but many people prefer them for the cozy quality of light they emit. Scientists from Dresden University of Technology in Germany have set out to build energy efficient organic LED (OLED) lights that could rival incandescent bulbs in white-light color quality. OLEDs consist of many layers of organic materials with different electrical properties. Excited electrons move through the materials and when the electrons are reunited with positive “holes,” they emit electromagnetic radiation in the form of visible light. To build their white light OLED, the researchers used four separate emitter layers: blue, green, yellow, and red. The different colors are combined to cover all parts of the visible spectrum. Through a detailed study of the movement of electrons through the OLED, the scientists were able to tune the color and quality of the light by adjusting the height of the layers. The final OLED, described in the AIP’s Journal of Applied Physics, casts a color of light very near to warm white point A, a standard measure of the white light spectrum reached by some incandescent bulbs. The OLED also has high color stability, meaning the light can be dimmed without noticeably altering its quality.
Article: “Organic LEDs for Lighting: High Color Quality by Controlling Energy Transfer Processes in Host-Guest-Sytems” is accepted for publication in the Journal of Applied Physics.
Authors: Caroline Weichsel (1), Sebastian Reineke (1), Mauro Furno (1), Björn Lüssem (1), and Karl Leo (1).
(1) Institut für Angewandte Photophysik, Technische Universität Dresden, Germany
Upcoming Conferences of Interest
Physics Today: February Articles
1. A century of cosmic rays: Twenty years after puzzling atmospheric ionization led to the discovery of cosmic rays, their investigation opened up particle physics. Now they’re providing a window on extragalactic astrophysics.
2. Mikhail Lomonosov and the dawn of Russian science: Curiously unsung in the West, Lomonosov broke ground in physics, chemistry, and astronomy; won acclaim as a poet and historian; and was a key figure of the Russian Enlightenment.
3. Women in physics: A tale of limits: A newly completed survey of 15,000 physicists worldwide reveals that women physicists still do not have equal access to the career-advancing resources and opportunities enjoyed by their male colleagues.
AIP Science Communication Awards: Call for Entries
Entries are requested for the American Institute of Physics’ 2012 Science Communication Awards, which recognize effective science communication, both in print and new media, that improves the general public's appreciation of physics, astronomy, and allied science fields.
Categories: Science Writing (books), Children’s Writing, New Media
Prize: $3,000, an engraved presentation piece, and a certificate
Deadline: February 17, 2012
More information and an entry form are available at http://www.aip.org/aip/writing.
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