This happen because of Eddy current
The Falling Slinky
W. G. Unruh
CIAR Cosmology and Gravity Program
Dept. of Physics
University of B. C.
Vancouver, Canada V6T 1Z1
email: unruh@physics.ubc.ca
The slinky, released from rest hanging under its own weight, falls in a peculiar manner. The
bottom stays at rest until a wave hits it from above. Two cases– one unphysical one where the
slinky is able to pass through itself, and the other where the coils of the slinky collide creating a
shock wave travelling down the slinky are analysed. In the former case, the bottom begins to move
much later than in the latter.
CIAR Cosmology and Gravity Program
Dept. of Physics
University of B. C.
Vancouver, Canada V6T 1Z1
email: unruh@physics.ubc.ca
The slinky, released from rest hanging under its own weight, falls in a peculiar manner. The
bottom stays at rest until a wave hits it from above. Two cases– one unphysical one where the
slinky is able to pass through itself, and the other where the coils of the slinky collide creating a
shock wave travelling down the slinky are analysed. In the former case, the bottom begins to move
much later than in the latter.
Vesicles and Micelles from Amphiphilic Zinc(II)–Cyclen Complexes as Highly Potent Promoters of Hydrolytic DNA Cleavage
Benjamin Gruber, Evgeny Kataev, Jana Aschenbrenner, Stefan Stadlbauer, and Burkhard König
Publication Date (Web): November 28, 2011 (Communication)
DOI: 10.1021/ja209247w
A Spectroscopic Analysis of the Role of Side Chains in Controlling Thermochromic Transitions in Polydiacetylenes
Lei Yu and Shaw Ling Hsu*
Polymer Science and Engineering, University of Massachusetts (Amherst), and NSF Materials Research Science & Engineering Center, Amherst, Massachusetts 01003, United States
Macromolecules, Article ASAP
DOI: 10.1021/ma201519v
Publication Date (Web): December 7, 2011
Copyright © 2011 American Chemical Society
A systematic study has been carried out to investigate the role of the side chains in lowering the reversible thermochromic transition temperature of polydiacetylenes. The type of interacting groups also proved to be crucial. Polymers with hydrogen-bonded side chains have consistently behaved differently as compared to polymers with less specific interactions associated with metallic ions. The most striking factor is the orderliness of the polymethylene portion of the side chains. The length of the side chains is critical in determining the transition temperature. In some cases, the packing order of the side chains is of sufficient order to crystallize. When high order exists, a reversible thermochromic transition is difficult to achieve. Conversely, if the side chains are disordered at any temperature, the transition temperatures are low and the transition is always reversible. This is the case for side chains stabilized by the presence of metallic ions. It is apparent that the presence of long-range nonspecific electrostatic interactions is important in determining reversible thermochromic transitions. These structural features are most easily observed using infrared spectroscopy and Raman scattering. Supporting evidence have been obtained using thermal analysis and X-ray diffraction.
Polymer Science and Engineering, University of Massachusetts (Amherst), and NSF Materials Research Science & Engineering Center, Amherst, Massachusetts 01003, United States
Macromolecules, Article ASAP
DOI: 10.1021/ma201519v
Publication Date (Web): December 7, 2011
Copyright © 2011 American Chemical Society
A systematic study has been carried out to investigate the role of the side chains in lowering the reversible thermochromic transition temperature of polydiacetylenes. The type of interacting groups also proved to be crucial. Polymers with hydrogen-bonded side chains have consistently behaved differently as compared to polymers with less specific interactions associated with metallic ions. The most striking factor is the orderliness of the polymethylene portion of the side chains. The length of the side chains is critical in determining the transition temperature. In some cases, the packing order of the side chains is of sufficient order to crystallize. When high order exists, a reversible thermochromic transition is difficult to achieve. Conversely, if the side chains are disordered at any temperature, the transition temperatures are low and the transition is always reversible. This is the case for side chains stabilized by the presence of metallic ions. It is apparent that the presence of long-range nonspecific electrostatic interactions is important in determining reversible thermochromic transitions. These structural features are most easily observed using infrared spectroscopy and Raman scattering. Supporting evidence have been obtained using thermal analysis and X-ray diffraction.
Synthesis of three advanced biofuels from ionic liquid-pretreated switchgrass using engineered Escherichia coli
Gregory Bokinskya,b, Pamela P. Peralta-Yahyaa,b, Anthe Georgea,c, Bradley M. Holmesa,c, Eric J. Steena,d, Jeffrey Dietricha,d,
Taek Soon Leea,e, Danielle Tullman-Erceka,f, Christopher A. Voigtg, Blake A. Simmonsa,c, and Jay D. Keaslinga,b,d,e,f,1�
One approach to reducing the costs of advanced biofuel production from cellulosic biomass is to engineer a single microorganism to both digest plant biomass and produce hydrocarbons that have the properties of petrochemical fuels. Such an organism would require pathways for hydrocarbon production and the capacity to secrete sufficient enzymes to efficiently hydrolyze cellulose and hemicellulose. To demonstrate how one might engineer and coordinate all of the necessary components for a biomass-degrading, hydrocarbon-producing microorganism, we engineered a microorganism na�ve to both processes, Escherichia coli, to grow using both the cellulose and hemicellulose fractions of several types of plant biomass pretreated with ionic liquids. Our engineered strains express cellulase, xylanase, beta-glucosidase, and xylobiosidase enzymes under control of native E. coli promoters selected to optimize growth on model cellulosic and hemicellulosic substrates. Furthermore, our strains grow using either the cellulose or hemicellulose components of ionic liquid-pretreated biomass or on both components when combined as a coculture. Both cellulolytic and
hemicellulolytic strains were further engineered with three biofuel synthesis pathways to demonstrate the production of fuel substitutes or precursors suitable for gasoline, diesel, and jet engines directly from ionic liquid-treated switchgrass without externally supplied hydrolase enzymes. This demonstration represents a
major advance toward realizing a consolidated bioprocess. With improvements in both biofuel synthesis pathways and biomass digestion capabilities, our approach could provide an economical route to production of advanced biofuels.
Taek Soon Leea,e, Danielle Tullman-Erceka,f, Christopher A. Voigtg, Blake A. Simmonsa,c, and Jay D. Keaslinga,b,d,e,f,1�
One approach to reducing the costs of advanced biofuel production from cellulosic biomass is to engineer a single microorganism to both digest plant biomass and produce hydrocarbons that have the properties of petrochemical fuels. Such an organism would require pathways for hydrocarbon production and the capacity to secrete sufficient enzymes to efficiently hydrolyze cellulose and hemicellulose. To demonstrate how one might engineer and coordinate all of the necessary components for a biomass-degrading, hydrocarbon-producing microorganism, we engineered a microorganism na�ve to both processes, Escherichia coli, to grow using both the cellulose and hemicellulose fractions of several types of plant biomass pretreated with ionic liquids. Our engineered strains express cellulase, xylanase, beta-glucosidase, and xylobiosidase enzymes under control of native E. coli promoters selected to optimize growth on model cellulosic and hemicellulosic substrates. Furthermore, our strains grow using either the cellulose or hemicellulose components of ionic liquid-pretreated biomass or on both components when combined as a coculture. Both cellulolytic and
hemicellulolytic strains were further engineered with three biofuel synthesis pathways to demonstrate the production of fuel substitutes or precursors suitable for gasoline, diesel, and jet engines directly from ionic liquid-treated switchgrass without externally supplied hydrolase enzymes. This demonstration represents a
major advance toward realizing a consolidated bioprocess. With improvements in both biofuel synthesis pathways and biomass digestion capabilities, our approach could provide an economical route to production of advanced biofuels.
Inkjet Printing of Conjugated Polymer Precursors on Paper Substrates for Colorimetric Sensing and Flexible Electrothermochromic Display
Bora Yoon , Dae-Young Ham , Oktay Yarimaga , Hyosung An , Chan Woo Lee ,
a n d Jong-Man Kim *
Inkjet-printable aqueous suspensions of conjugated polymer precursorsare developed for fabrication of patterned color images on paper substrates. Printing of a diacetylene (DA)-surfactant composite ink on unmodified paper and photopaper, as well as on a banknote, enables generation of latent images that are transformed to blue-colored polydiacetylene (PDA) structures by UV irradiation. Both irreversible and reversible thermochromism with the PDA printed images are demonstrated and applied to flexible and disposable sensors and to displays.
a n d Jong-Man Kim *
Advanced Materials
Inkjet-printable aqueous suspensions of conjugated polymer precursorsare developed for fabrication of patterned color images on paper substrates. Printing of a diacetylene (DA)-surfactant composite ink on unmodified paper and photopaper, as well as on a banknote, enables generation of latent images that are transformed to blue-colored polydiacetylene (PDA) structures by UV irradiation. Both irreversible and reversible thermochromism with the PDA printed images are demonstrated and applied to flexible and disposable sensors and to displays.
REM Sleep Depotentiates Amygdala Activity to Previous Emotional Experiences
Els van der Helm1, Justin Yao1, Shubir Dutt1, Vikram Rao1, Jared M. Saletin1, Matthew P. Walker1, 2,
Summary
Clinical evidence suggests a potentially causal interaction between sleep and affective brain function; nearly all mood disorders display co-occurring sleep abnormalities, commonly involving rapid-eye movement (REM) sleep [ [1] , [2] , [3] and [4] ]. Building on this clinical evidence, recent neurobiological frameworks have hypothesized a benefit of REM sleep in palliatively decreasing next-day brain reactivity to recent waking emotional experiences [ [5] and [6] ]. Specifically, the marked suppression of central adrenergic neurotransmitters during REM (commonly implicated in arousal and stress), coupled with activation in amygdala-hippocampal networks that encode salient events, is proposed to (re)process and depotentiate previous affective experiences, decreasing their emotional intensity [3]. In contrast, the failure of such adrenergic reduction during REM sleep has been described in anxiety disorders, indexed by persistent high-frequency electroencephalographic (EEG) activity (>30 Hz) [ [7] , [8] , [9] and [10] ]; a candidate factor contributing to hyperarousal and exaggerated amygdala reactivity [ [3] , [11] , [12] and [13] ]. Despite these neurobiological frameworks, and their predictions, the proposed benefit of REM sleep physiology in depotentiating neural and behavioral responsivity to prior emotional events remains unknown. Here, we demonstrate that REM sleep physiology is associated with an overnight dissipation of amygdala activity in response to previous emotional experiences, altering functional connectivity and reducing next-day subjective emotionality.
The Race to X-ray Microbeam and Nanobeam Science
- Science 2 December 2011:
Vol. 334 no. 6060 pp. 1234-1239
DOI: 10.1126/science.1202366
- *To whom correspondence should be addressed. E-mail: icege@ornl.gov
X-ray microbeams are an emerging characterization tool with broad implications for science, ranging from materials structure and dynamics, to geophysics and environmental science, to biophysics and protein crystallography. We describe how submicrometer hard x-ray beams with the ability to penetrate tens to hundreds of micrometers into most materials and with the ability to determine local composition, chemistry, and (crystal) structure can characterize buried sample volumes and small samples in their natural or extreme environments. Beams less than 10 nanometers have already been demonstrated, and the practical limit for hard x-ray beam size, the limit to trace-element sensitivity, and the ultimate limitations associated with near-atomic structure determinations are the subject of ongoing research.
Drug Delivery and Imaging with Polydiacetylene Micelles
and Eric Doris* [a]
Abstract : This concept article summarizes our recent findings regarding photopolymerized micelles obtained
from the self-assembly of diacetylene-containing amphiphiles. Their synthesis and characterization are presented as well as some biomedical applications, such as tumor imaging and drug delivery. Finally, ongoing studies and future challenges are briefly discussed.
Building Designed Granular Towers One Drop at a Time
Phys. Rev. Lett. 107, 208304 (2011) [5 pages]
Received 27 August 2011; published 9 November 2011
A dense granular suspension dripping on an imbibing surface is observed to give rise to slender mechanically stable structures that we call granular towers. Successive drops of grain-liquid mixtures are shown to solidify rapidly upon contact with a liquid absorbing substrate. A balance of excess liquid flux and drainage rate is found to capture the typical growth and height of the towers. The tower width is captured by the Weber number, which gives the relative importance of inertia and capillary forces. Various symmetric, smooth, corrugated, zigzag, and chiral structures are observed by varying the impact velocity and the flux rate from droplet to jetting regime.
Ultralight Metallic Microlattices
- T. A. Schaedler1,*,
- A. J. Jacobsen1,
- A. Torrents2,
- A. E. Sorensen1,
- J. Lian3,
- J. R. Greer3,
- L. Valdevit2,
- W. B. Carter1
- Science 18 November 2011:
Vol. 334 no. 6058 pp. 962-965
DOI: 10.1126/science.1211649
ABSTRACT
Ultralight (<10 milligrams per cubic centimeter) cellular materials are desirable for thermal insulation; battery electrodes; catalyst supports; and acoustic, vibration, or shock energy damping. We present ultralight materials based on periodic hollow-tube microlattices. These materials are fabricated by starting with a template formed by self-propagating photopolymer waveguide prototyping, coating the template by electroless nickel plating, and subsequently etching away the template. The resulting metallic microlattices exhibit densities ρ ≥ 0.9 milligram per cubic centimeter, complete recovery after compression exceeding 50% strain, and energy absorption similar to elastomers. Young’s modulus Escales with density as E ~ ρ2, in contrast to the E ~ ρ3 scaling observed for ultralight aerogels and carbon nanotube foams with stochastic architecture. We attribute these properties to structural hierarchy at the nanometer, micrometer, and millimeter scales.
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