921 research outputs found
Detuned Mechanical Parametric Amplification as a Quantum Non-Demolition Measurement
Recently it has been demonstrated that the combination of weak-continuous
position detection with detuned parametric driving can lead to significant
steady-state mechanical squeezing, far beyond the 3 dB limit normally
associated with parametric driving. In this work, we show the close connection
between this detuned scheme and quantum non-demolition (QND) measurement of a
single mechanical quadrature. In particular, we show that applying an
experimentally realistic detuned parametric drive to a cavity optomechanical
system allows one to effectively realize a QND measurement despite being in the
bad-cavity limit. In the limit of strong squeezing, we show that this scheme
offers significant advantages over standard backaction evasion, not only by
allowing operation in the weak measurement and low efficiency regimes, but also
in terms of the purity of the mechanical state.Comment: 17 pages, 2 figure
Mechanical Entanglement via Detuned Parametric Amplification
We propose two schemes to generate entanglement between a pair of mechanical
oscillators using parametric amplification. In contrast to existing parametric
drive-based protocols, both schemes operate in the steady-state. Using a
detuned parametric drive to maintain equilibrium and to couple orthogonal
quadratures, our approach can be viewed as a two-mode extension of previous
proposals for parametric squeezing. We find that robust steady-state
entanglement is possible for matched oscillators with well-controlled coupling.
In addition, one of the proposed schemes is robust to differences in the
damping rates of the two oscillators.Comment: 13 pages, 2 figure
Keeping violent offender rehabilitation on track:How the diffusion and redirecting of attentional focus/mood work in the GRIP program
There is an urgent need to understand how programming inside prisons can facilitate rehabilitation and reentry processes, especially among men convicted of violent offenses. GRIP (Guiding Rage into Power) is a year-long âOffender Accountabilityâ program presently spreading through the California prison system. GRIP is a group-therapy and trauma-healing program that follows a somatic-awareness-centered model. We use audiovisual data to investigate the sequenced, second-to-second inner workings of what actually constitutes operational excellence in this evidence-based in-prison rehabilitation program. Making use of interaction ritual theory and conversation analysis, we demonstrate how two processesâthe diffusion and the redirecting of attentional focus/moodâtranspire in GRIP classrooms. The conclusion argues that these two processes may be the âhiddenâ building blocks, or what is lacking, in countless rehabilitation programs and other social work interventionsâboth inside and outside of correctional facilities
An âequal effortâ approach to assessing the NorthâSouth climate finance gap
This study employs a number of Integrated Assessment Models to determine what the optimal financial transfers between high-income and developing economies would be if climate mitigation effort, measured as mitigation costs as a share of gross domestic product, were to be divided equally across regions through a global carbon market. We find these to be larger than both current and planned international climate finance flows. Four out of six models imply that a NorthâSouth annual financial transfer of around US2 trillion. However, the outlook for multi-country carbon markets is not encouraging at the moment. We thus review some potential sources of funds that might be used to fill the climate finance gap, including public aid, private investment, development banks, and special climate-related facilities. We find the shortcomings of public climate finance appear particularly hard to overcome, and argue that expanding private finance, either in the form of Foreign Direct Investment or through the issuance of âgreen bondsâ, appears to be a more promising direction. Policy relevance Climate change is a profoundly asymmetric development issue, as countries at lower stages of development are likely to suffer disproportionate climate damages and mitigation costs. High-income countries have agreed to mobilise $100 billion a year by 2020 âto address the needs of developing countriesâ. However, scaling up climate finance has been slow and, more importantly, targets have not been chosen on the basis of a âscientificâ assessment. This article presents a novel, model-based analysis of the âequal effortâ inter-regional climate finance that could provide useful insights to policy makers in future negotiations. The gap identified by comparing modelsâ projections to current and planned financial flows is large but not prohibitive. In particular, private investment appears to be the most likely channel to fill the gap, although various public policies need to be implemented to improve the risk/return profile of low-carbon investment opportunities
An âequal effortâ approach to assessing the NorthâSouth climate finance gap
This study employs a number of Integrated Assessment Models to determine what the optimal financial transfers between high-income and developing economies would be if climate mitigation effort, measured as mitigation costs as a share of gross domestic product, were to be divided equally across regions through a global carbon market. We find these to be larger than both current and planned international climate finance flows. Four out of six models imply that a NorthâSouth annual financial transfer of around US2 trillion. However, the outlook for multi-country carbon markets is not encouraging at the moment. We thus review some potential sources of funds that might be used to fill the climate finance gap, including public aid, private investment, development banks, and special climate-related facilities. We find the shortcomings of public climate finance appear particularly hard to overcome, and argue that expanding private finance, either in the form of Foreign Direct Investment or through the issuance of âgreen bondsâ, appears to be a more promising direction. Policy relevance Climate change is a profoundly asymmetric development issue, as countries at lower stages of development are likely to suffer disproportionate climate damages and mitigation costs. High-income countries have agreed to mobilise $100 billion a year by 2020 âto address the needs of developing countriesâ. However, scaling up climate finance has been slow and, more importantly, targets have not been chosen on the basis of a âscientificâ assessment. This article presents a novel, model-based analysis of the âequal effortâ inter-regional climate finance that could provide useful insights to policy makers in future negotiations. The gap identified by comparing modelsâ projections to current and planned financial flows is large but not prohibitive. In particular, private investment appears to be the most likely channel to fill the gap, although various public policies need to be implemented to improve the risk/return profile of low-carbon investment opportunities
Cavity optoelectromechanical regenerative amplification
Cavity optoelectromechanical regenerative amplification is demonstrated. An
optical cavity enhances mechanical transduction, allowing sensitive measurement
even for heavy oscillators. A 27.3 MHz mechanical mode of a microtoroid was
linewidth narrowed to 6.6\pm1.4 mHz, 30 times smaller than previously achieved
with radiation pressure driving in such a system. These results may have
applications in areas such as ultrasensitive optomechanical mass spectroscopy
Silsesquioxane polymer as a potential scaffold for laryngeal reconstruction
Cancer, disease and trauma to the larynx and their treatment can lead to permanent loss of structures critical to voice, breathing and swallowing. Engineered partial or total laryngeal replacements would need to match the ambitious specifications of replicating functionality, outer biocompatibility, and permissiveness for an inner mucosal lining. Here we present porous polyhedral oligomeric silsesquioxane-poly(carbonate urea) urethane (POSS-PCUU) as a potential scaffold for engineering laryngeal tissue. Specifically, we employ a precipitation and porogen leaching technique for manufacturing the polymer. The polymer is chemically consistent across all sample types and produces a foam-like scaffold with two distinct topographies and an internal structure composed of nano- and micro-pores. Whilst the highly porous internal structure of the scaffold contributes to the complex tensile behaviour of the polymer, the surface of the scaffold remains largely non-porous. The low number of pores minimise access for cells, although primary fibroblasts and epithelial cells do attach and proliferate on the polymer surface. Our data show that with a change in manufacturing protocol to produce porous polymer surfaces, POSS-PCUU may be a potential candidate for overcoming some of the limitations associated with laryngeal reconstruction and regeneration
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