263 research outputs found
Ion Channels in Critical Membranes: Clustering, Cooperativity, and Memory Effects
No full textMuch progress has been made in elucidating the inner workings of voltage-gated ion channels, but less
understood is the influence of lipid rafts on gating kinetics. Here we propose that state-dependent channel
affinity for different lipid species provides a unified explanation for the experimentally observed behaviors of
clustering, cooperativity, and hysteresis. We develop models of diffusing lipids and channels engaged in Isinglike
interactions to investigate the collective behaviors driven by raft formation in critical membranes close to the
demixing transition. The model channels demonstrate lipid-mediated long-range interactions, activation curve
steepening, and long-term memory in ionic currents. These behaviors likely play a role in channel-mediated
cellular signaling and suggest a universal mechanism for self-organization of biomolecular assemblies
Photocurrent and transmission spectroscopy of direct-gap interband transitions in Ge/SiGe quantum wells
No full textThe authors studied the direct-gap interband transitions in strain-compensated Ge/SiGe quantum wells grown by low energy plasma enhanced chemical vapor deposition. A series of excitonic interband absorptions from the quantized hole states to the quantized electronic states at the Gamma edge in the Ge wells is observed up to room temperature by photocurrent and transmission spectroscopy. The results are compared with theory. At low temperature, the quantum confined Stark effect is demonstrated in a Schottky diode geometry
Optical dilution and feedback cooling of a gram-scale oscillator to 6.9 mK
No full textWe report on the use of a radiation pressure induced restoring force, the optical spring effect, to optically dilute the mechanical damping of a 1 g suspended mirror, which is then cooled by active feedback (cold damping). Optical dilution relaxes the limit on cooling imposed by mechanical losses, allowing the oscillator mode to reach a minimum temperature of 6.9 mK, a factor of ~40 000 below the environmental temperature. A further advantage of the optical spring effect is that it can increase the number of oscillations before decoherence by several orders of magnitude. In the present experiment we infer an increase in the dynamical lifetime of the state by a factor of ~200.Thomas Corbitt, Christopher Wipf, Timothy Bodiya, David Ottaway, Daniel Sigg, Nicolas Smith, Stanley Whitcomb, and Nergis Mavalval
Journal of African Christian Biography: v. 6, no. 1
No full textA publication of the Dictionary of African Christian Biography with U.S. offices located at the Center for Global Christianity and Mission at Boston University. This issue focuses on: George Arthur Gatungu Gathuna (Kenya); Philip Kwabi and Daniel Saba (Gold Coast); Casely Essamuah (interview). TABLE OF CONTENTS:
1. Introduction by Editor Michele Miller Sigg
2. Call for Ecclesial Recognition of Bishop George Arthur Gatungu Gathuna, The Founding Father of the African Orthodox Church of Kenya By Fr. Evangelos Thiani
3. Unknown Pioneers and Unsung Heroes: Forgotten Christian Ancestors of the Gold Coast (Ghana) By Maureen O. Iheanacho
4. Accidental Missionary: Called to a Life of Building Bridges for Christ and His Kingdom An Interview with Casely Baiden Essamuah, Secretary, Global Christian Forum
5. Book notes, compiled by BU Head librarian Frances Beth Restrick (African Studies library
Effects of a Single Educational Experience About Complementary Health Approaches and Integrative Health on Student Attitudes
No full textAbstract
Date Presented 3/31/2017
A single educational experience with select community-based complementary health and integrative health (CHAIH) providers positively affected occupational therapy students’ attitudes toward and confidence in discussing CHAIH, but not likelihood of collaborating with or referring to CHAIH providers.
Primary Author and Speaker: Michelle Bradshaw
Additional Authors and Speakers: Vito Boffoli, Franscesca Cotrupe, Jasmine Delsie, Alyssa Olivieri, Marc Recio, Jordan Sigg, Kara Walsh, Anna Waverczak
Contributing Authors: Katie Parini, Felipe Vasquez</jats:p
Single-shot electron bunch length measurements using a spatial electro-optical autocorrelation interferometer
No full textA spatial, electro-optical autocorrelation (EOA) interferometer using the vertically polarized lobes of coherent transition radiation (CTR) has been developed as a single-shot electron bunch length monitor at an optical beam port downstream the 100 MeV preinjector LINAC of the Swiss Light Source. This EOA monitor combines the advantages of step-scan interferometers (high temporal resolution) [D. Mihalcea et al., Phys. Rev. ST Accel. Beams 9, 082801 (2006) and T. Takahashi and K. Takami, Infrared Phys. Technol. 51, 363 (2008)] and terahertz-gating technologies [U. Schmidhammer et al., Appl. Phys. B: Lasers Opt. 94, 95 (2009) and B. Steffen et al., Phys. Rev. ST Accel. Beams 12, 032802 (2009)] (fast response), providing the possibility to tune the accelerator with an online bunch length diagnostics. While a proof of principle of the spatial interferometer was achieved by step-scan measurements with far-infrared detectors, the single-shot capability of the monitor has been demonstrated by electro-optical correlation of the spatial CTR interference pattern with fairly long (500 ps) neodymium-doped yttrium aluminum garnet (Nd:YAG) laser pulses in a ZnTe crystal. In single-shot operation, variations of the bunch length between 1.5 and 4 ps due to different phase settings of the LINAC bunching cavities have been measured with subpicosecond time resolution
An all-optical trap for a gram-scale mirror
No full textWe report on a stable optical trap suitable for a macroscopic mirror, wherein the dynamics of the mirror are fully dominated by radiation pressure. The technique employs two frequency-offset laser fields to simultaneously create a stiff optical restoring force and a viscous optical damping force. We show how these forces may be used to optically trap a free mass without introducing thermal noise, and we demonstrate the technique experimentally with a 1 g mirror. The observed optical spring has an inferred Young's modulus of 1.2 TPa, 20% stiffer than diamond. The trap is intrinsically cold and reaches an effective temperature of 0.8 K, limited by technical noise in our apparatus.Thomas Corbitt, Yanbei Chen, Edith Innerhofer, Helge Müller-Ebhardt, David Ottaway, Henning Rehbein, Daniel Sigg, Stanley Whitcomb, Christopher Wipf, and Nergis Mavalval
Comparison of ultrafast carrier thermalization in Gaxln1-xAs and Ge quantum wells
No full textThe thermalization of photoexcited carriers is investigated using femtosecond pump-probe spectroscopy in both (GaIn)As and Ge quantum wells. In both materials a nonthermal electron distribution is observed. The continuous relaxation from the point of injection toward the ground state and the thermalization of the carrier distribution are monitored on a time scale of up to 500 fs at room temperature. Carriers in (GaIn)As thermalize within 300 fs when injected with an excess energy of 250 meV. Separate carrier distributions for the heavy-hole and light-hole systems are found since the angular momentum transfer required for a transition is slow.
Thermalization in Ge is found to be slightly slower in comparison due to the lack of Fröhlich interaction
Quantum-confined direct-gap transitions in tensile-strained Ge/siGe multiple quantum wells
No full textQuantum-confined direct-gap transitions in tensile-strained Ge/siGe multiple quantum well
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