4,090 research outputs found
Fast gates for ion traps by splitting laser pulses
We present a fast phase gate scheme that is experimentally achievable and has an operation time more than two orders of magnitude faster than current experimental schemes for low numbers of pulses. The gate time improves with the number of pulses following an inverse power law. Unlike
implemented schemes which excite precise motional sidebands, thus limiting
the gate timescale, our scheme excites multiple motional states using discrete
ultra-fast pulses.We use beam-splitters to divide pulses into smaller components
to overcome limitations due to the finite laser pulse repetition rate. This provides
gate times faster than proposed theoretical schemes when we optimize a practical
setup
Alpha/beta and gamma interferons are induced by infection with noncytopathic bovine viral diarrhea virus in vivo
In contrast to the results of previous in vitro studies, experimental infection of calves with noncytopathic bovine viral diarrhea virus (ncpBVDV) was found to induce strong alpha/beta and gamma interferon responses in gnotobiotic animals. These responses were associated with depressed levels of transforming growth factor β (TGF-β) in serum. The results of this study indicate that the immunosuppression caused by ncpBVDV is not associated with low interferon responses or elevated levels of TGF-β
Outcoupling from a Bose-Einstein condensate with squeezed light to produce entangled atom laser beams
We examine the properties of an atom laser produced by outcoupling from a
Bose-Einstein condensate with squeezed light. We model the multimode dynamics
of the output field and show that a significant amount of squeezing can be
transfered from an optical mode to a propagating atom laser beam. We use this
to demonstrate that two-mode squeezing can be used to produce twin atom laser
beams with continuous variable entanglement in amplitude and phase.Comment: 11 pages, 14 figure
The Fate of Oil in the Water Column Following Experimental Oil Spills in the Arctic Marine Nearshore
Petroleum hydrocarbon concentrations in the water column were monitored after a release of crude oil onto the water surface and a subsurface release of chemically dispersed oil. During the surface release, petroleum hydrocarbons did not disperse into the water column deeper than 1 m. The highest concentrations observed under the slick were less than 2 mg/l. The chemically dispersed oil released resulted in concentrations over 50 mg/l in the Bay 9 study area for 12 hours. Estimated exposures of the benthic communities to oil in the three experimental bays were 3 mg/l/h, 30 mg/l/h, and 300 mg/l/h respectively. The highest exposures were to oil retaining many of its more toxic components.Key words: dispersant, oil, fluorometry, gas chromatography, oil spillMots clés: agent de dispersion, fluorométrie, chromatographie en phase gazeuse, déversement de pétrol
Making Space for the Dissertation : a Rural Retreat for Undergraduate Students
This paper examines a residential writing retreat for final year human geography and planning students held in a youth hostel in North Yorkshire, considering how it is experienced by students. This is a curriculum innovation for the dissertation module that combines aspects of geography fieldtrip and writing workshop to support the dissertation writing process and build community. Drawing on the concept of ‘the slow university’ (Berg & Seeber, 2016; O’Neill, 2014) where the ‘slowing down’ and ‘stripping away’ of the usual structures and patterns of teaching and learning create a critical and creative space for thinking and writing, we explore whether and how the Malham retreat makes space for writing. The study is also informed by our spatial approach to the processes and content of research and teaching as geographers (Massey, 2005). Qualitative focus group evidence was gathered on the student and staff experience and used to evaluate the field trip (Breen, 2006; Krueger & Casey, 2009; Stewart & Shamdasani, 2015). This paper presents the results of this evaluation and it is argued that the retreat made space for writing in three ways:
1. The space of countryside, nature and youth hostel.
2. The formal and informal learning spaces staff and students constructed during the retreat
3. ‘Head space’- the social, psychological and emotional room the retreat made for staff and students.
This model of residential writing retreat could be transferable to dissertation and other modules involving a substantive writing project on all kinds of undergraduate courses
Nanocrystallization and Amorphization Induced by Reactive Nitrogen Sputtering in Iron and Permalloy
Thin films of iron and permalloy Ni80Fe20 were prepared using an Ar+N2
mixture with magnetron sputtering technique at ambient temperature. The
nitrogen partial pressure, during sputtering process was varied in the range of
0 to 100%, keeping the total gas flow at constant. At lower nitrogen pressures
RN2<33% both Fe and NiFe, first form a nanocrystalline structure and an
increase in nitrogen partail pressure results in formation of an amorphous
structure. At intermediate nitrogen partial pressures, nitrides of Fe and NiFe
were obtained while at even higher nitrogen partial pressures, nitrides
themselves became nanocrystalline or amorphous. The surface, structural and
magnetic properties of the deposited films were studied using x-ray reflection
and diffraction, transmission electron microscopy, polarized neutron
reflectivity and using a DC extraction magnetometer. The growth behavior for
amorphous film was found different as compared with poly or nanocrystalline
films. The soft-magnetic properties of FeN were improved on nanocrystallization
while those of NiFeN were degraded. A mechanism inducing nanocrystallization
and amorphization in Fe and NiFe due to reactive nitrogen sputtering is
discussed in the present article.Comment: 13 Pages, 15 Figure
Exact solution, scaling behaviour and quantum dynamics of a model of an atom-molecule Bose-Einstein condensate
We study the exact solution for a two-mode model describing coherent coupling
between atomic and molecular Bose-Einstein condensates (BEC), in the context of
the Bethe ansatz. By combining an asymptotic and numerical analysis, we
identify the scaling behaviour of the model and determine the zero temperature
expectation value for the coherence and average atomic occupation. The
threshold coupling for production of the molecular BEC is identified as the
point at which the energy gap is minimum. Our numerical results indicate a
parity effect for the energy gap between ground and first excited state
depending on whether the total atomic number is odd or even. The numerical
calculations for the quantum dynamics reveals a smooth transition from the
atomic to the molecular BEC.Comment: 5 pages, 4 figure
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