8,641 research outputs found
Generation and storage of optical entanglement in a solid state spin-wave quantum memory
This thesis investigates an entangled light source with an
in-built quantum memory based on the protocol of rephased
amplified spontaneous emission (RASE). RASE has promising
applications as a building-block of a quantum repeater: a device
essential for extending the range of current quantum
communication links. To be useful RASE must be able to produce
high fidelity non-classical light with high efficiency, and be
able to store multimode entanglement for long times. This thesis
characterises the RASE source and determines to what degree these
requirements can be met.
The experimental RASE demonstration was conducted in a rare-earth
ion doped crystal. Rare-earth ions provide a particularly
promising platform for developing quantum technologies as they
possess long coherence times on both the optical and hyperfine
transitions.
In the RASE protocol an inverted ensemble of two-level atoms
amplifies the vacuum fluctuations resulting in amplified
spontaneous emission (ASE). This results in entanglement between
the output optical field and the collective modes of the
amplifying ensemble. The collective atomic state dephases due to
the inhomogeneous broadening of the ensemble but this can be
rephased using photon echo techniques. When the ensemble
rephases, a second optical field, the rephased amplified
spontaneous emission (RASE), is emitted and is entangled with the
ASE. In this thesis, a modified four-level rephasing scheme is
used that allows the single photon signals to be spectrally
resolved from any coherent background emission associated with
the bright driving fields. In addition, four-level RASE
incorporates storage on the long-lived hyperfine ground states.
Two experiments are described in this thesis. First, a free-space
four-level RASE demonstration using continuous-variable
detection. In this experiment the different sources of noise were
characterised and low noise operation was shown to be possible.
Entanglement of the ASE and RASE was confirmed by violating the
inseparability criterion with 98.6% confidence. In addition,
entanglement was demonstrated after storage of the collective
atomic state on the spin states and RASE was shown to be
temporally multimode, with almost perfect distinguishability
between two temporal modes demonstrated. The degree of
entanglement between the ASE and RASE was limited by the
rephasing efficiency, which saturated at 3%. It was determined
that distortion of the rephasing pulses as they propagate through
the optically thick ensemble was the probable cause of the low
efficiency.
The second experiment was a preliminary cavity-enhanced RASE
demonstration. Theoretically perfect rephasing efficiency can be
obtained by placing the crystal in an impedance-matched optical
cavity. The initial cavity design showed encouraging evidence of
an enhancement in the rephasing efficiency, with a 4-fold
improvement over the free-space experiment. Improvements to the
cavity design were proposed to allow a further increase in the
rephasing efficiency of RASE.
In summary, this thesis provides an extensive characterisation of
an entangled light source with an in-built quantum memory based
on rephasing spontaneous emission from an ensemble of ions.
Importantly, the RASE scheme allows generation and storage of
entanglement in a single protocol, which holds great promise for
the development of integrated quantum networks
A preliminary investigation of the effect of ethical labeling and moral self-image on the expected and perceived flavor and aroma of beer
Ethical labelling has been shown to influence taste/flavour perception. Across two experiments, the present study examined how ethical labelling and moral self-image influenced both the expected (Experiment One) and perceived (Experiment Two) taste/flavour characteristics of beer. In Experiment One, 170 participants read either a ‘moral’ or ‘control’ label describing a brewery, after which they were presented with an image of a beer. Participants then completed a Beer Taste Perception Questionnaire and the Moral Self-Image Scale. In Experiment Two, 59 participants were exposed to either the moral or control label before tasting a beer and completing the same questionnaires from Experiment One. The results of Experiment One indicated that label type moderated the relationship between moral self-image and the intensity ratings of the beer. Specifically, in the presence of a control label, the expected intensity of the beer’s flavour increased as moral self-image increased. Experiment Two found no evidence that the moral label influenced the perceived taste of the beer. However, the results showed that as moral self-image became more positive the perceived refreshingness of the beer increased. This study provides novel evidence of the potential relationship between an individual’s moral self-image and the expected and perceived taste/flavour characteristics of beer. © 2021 by the authors. Licensee MDPI, Basel, Switzerland
Genetic fat – bullet proofing the Merino ewe
Merino ewes are the backbone of the Australian sheep industry and this is likely to be the case for some time. Stocking rate will remain a key profit driver in Merino enterprises and to maintain or improve profitability producers will need to continually adapt their production systems to deal with even larger changes in feed supply between seasons and years. The reproductive performance of the Merino ewe also needs to improve, largely through improving the survival of twin born lambs, to rebuild flock numbers and meet market demand for lamb and sheep meat. Increasing both stocking rates and reproductive performance need to be achieved in the context of producers wanting to run more sheep per person with less intervention and increased consumer demand for welfare friendly products. Improving genetics and matching sheep genotype to the production and management system will inevitably become more important. We believe this will include defining traits to more easily identify Merino sheep that are more robust, that lose less liveweight when faced with sub-optimum nutrition and that produce more progeny with higher survival rates both pre- and post-weaning.
Increasing genetic fat is the prime candidate for increasing the robustness of Merino ewes and their progeny as the storage and mobilisation of fat is an important mechanism for all animals to cope with fluctuating environments. Fat is stored during favourable times and then mobilised to provide energy for fundamental functions when requirements exceed supply, such as during periods of limited nutrition or during late pregnancy and lactation. The amount of fat stored in fat depots in sheep can be increased by selection for higher subcutaneous fat depth, using Australian Sheep Breeding Values (ASBVs) from MERINOSELECT. However, from a genetic perspective, reducing the fatness of lamb to improve its appeal to the consumer has resulted in a general focus on selection for less fat in Australian sheep breeds. Merino sheep have also become leaner as a result of selection for higher fleece weights and the genetic association between higher fleece weight and reduced fatness (Huisman and Brown 2009). Defining the true value of fat requires an understanding of the effect it has on the value of lamb carcasses as well as its effects on the productivity of the sheep production system in different environments. In this paper we have reviewed published papers and our own unpublished work to test the hypothesis that Merino sheep that are genetically fatter will have improved performance especially under more restricted nutritional conditions
Reduction versus abrupt cessation in smokers who want to quit.
Background\ud
The standard way to stop smoking is to quit abruptly on a designated quit day. A number of smokers have tried unsuccessfully to quit this way. Reducing smoking before quitting could be an alternative approach to cessation. Before this method is adopted it is important to determine whether it is at least as successful as abrupt quitting.\ud
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Objectives\ud
1. To compare the success of reducing smoking to quit and abrupt quitting interventions. 2. To compare adverse events between arms in studies that used pharmacotherapy to aid reduction.\ud
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Search methods\ud
We searched the Cochrane Tobacco Addiction Review Group specialised register, MEDLINE, EMBASE and PsycInfo for topic specific terms combined with terms used to identify trials of tobacco addiction interventions. We also searched reference lists of relevant papers and contacted authors of ongoing trials. Date of most recent search: November 2009.\ud
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Selection criteria\ud
We included randomized controlled trials (RCTs) that recruited adults who wanted to quit smoking. Studies included at least one condition which instructed participants to reduce their smoking and then quit and one condition which instructed participants to quit abruptly.\ud
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Data collection and analysis\ud
The outcome measure was abstinence from smoking after at least six months follow-up. We pooled the included trials using a Mantel-Haenszel fixed-effect model. Trials were split for two sub-group analyses: pharmacotherapy vs no pharmacotherapy, self help therapy vs behavioural support. Adverse events were summarised as a narrative. It was not possible to compare them quantitatively as there was variation in the nature and depth of reporting across studies.\ud
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Main results\ud
Ten studies were relevant for inclusion, with a total of 3760 participants included in the meta-analysis. Three of these studies used pharmacotherapy as part of the interventions. Five studies included behavioural support in the intervention, four included self-help therapy, and the remaining study had arms which included behavioural support and arms which included self-help therapy. Neither reduction or abrupt quitting had superior abstinence rates when all the studies were combined in the main analysis (RR= 0.94, 95% CI= 0.79 to 1.13), whether pharmacotherapy was used (RR= 0.87, 95% CI= 0.65 to 1.22), or not (RR= 0.97, 95% CI= 0.78 to 1.21), whether studies included behavioural support (RR= 0.87, 95% CI= 0.64 to 1.17) or self-help therapy (RR= 0.98, 95% CI= 0.78 to1.23). We were unable to draw conclusions about the difference in adverse events between interventions, however recent studies suggest that pre-quit NRT does not increase adverse events.\ud
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Authors' conclusions\ud
Reducing cigarettes smoked before quit day and quitting abruptly, with no prior reduction, produced comparable quit rates, therefore patients can be given the choice to quit in either of these ways. Reduction interventions can be carried out using self-help materials or aided by behavioural support, and can be carried out with the aid of pre-quit NRT. Further research needs to investigate which method of reduction before quitting is the most effective, and which categories of smokers benefit the most from each method, to inform future policy and intervention development.\ud
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Mock Galaxy Surveys for HST and JWST from the IllustrisTNG Simulations
We present and analyze a series of synthetic galaxy survey fields based on
the IllustrisTNG Simulation suite. With the Illustris public data release and
JupyterLab service, we generated a set of twelve lightcone catalogs covering
areas from 5 to 365 square arcminutes, similar to several JWST Cycle 1
programs, including JADES, CEERS, PRIMER, and NGDEEP. From these catalogs, we
queried the public API to generate simple mock images in a series of broadband
filters used by JWST-NIRCam and the Hubble Space Telescope cameras. This
procedure generates wide-area simulated mosaic images that can support
investigating the predicted evolution of galaxies alongside real data. Using
these mocks, we demonstrate a few simple science cases, including morphological
evolution and close pair selection. We publicly release the catalogs and mock
images through MAST, along with the code used to generate these projects, so
that the astrophysics community can make use of these products in their
scientific analyses of JWST deep field observations.Comment: Accepted to MNRA
Optimising the Efficiency of a Quantum Memory based on Rephased Amplified Spontaneous Emission
We studied the recall efficiency as a function of optical depth of rephased
amplified spontaneous emission (RASE), a protocol for generating entangled
light. The experiments were performed on the
transition in the rare-earth doped crystal
Pr:YSiO, using a four-level echo sequence between four
hyperfine levels to rephase the emission. Rephased emission was observed for
optical depths in the range of = 0.8 to 2.0 with a maximum rephasing
efficiency of 14 % observed while incorporating spin storage. This efficiency
is a significant improvement over the previously reported non-classical result
but is well short of the predicted efficiency. We discuss the possible
mechanisms limiting the protocol's performance, and suggest ways to overcome
these limits.Comment: 5 pages, 5 figure
Graduate students navigating social-ecological research: insights from the Long-Term Ecological Research Network
Interdisciplinary, collaborative research capable of capturing the feedbacks between biophysical and social systems can improve the capacity for sustainable environmental decision making. Networks of researchers provide unique opportunities to foster social-ecological inquiry. Although insights into interdisciplinary research have been discussed elsewhere, they rarely address the role of networks and often come from the perspectives of more senior scientists. We have provided graduate student perspectives on interdisciplinary degree paths from within the Long-Term Ecological Research (LTER) Network. Focusing on data from a survey of graduate students in the LTER Network and four self-identified successful graduate student research experiences, we examined the importance of funding, pedagogy, research design and development, communication, networking, and culture and attitude to students pursuing social-ecological research. Through sharing insights from successful graduate student approaches to social-ecological research within the LTER Network, we hope to facilitate dialogue between students, faculty, and networks to improve training for interdisciplinary scientists
Graduate students navigating social-ecological research: insights from the Long-Term Ecological Research Network
Interdisciplinary, collaborative research capable of capturing the feedbacks between biophysical and social systems can improve the capacity for sustainable environmental decision making. Networks of researchers provide unique opportunities to foster social-ecological inquiry. Although insights into interdisciplinary research have been discussed elsewhere, they rarely address the role of networks and often come from the perspectives of more senior scientists. We have provided graduate student perspectives on interdisciplinary degree paths from within the Long-Term Ecological Research (LTER) Network. Focusing on data from a survey of graduate students in the LTER Network and four self-identified successful graduate student research experiences, we examined the importance of funding, pedagogy, research design and development, communication, networking, and culture and attitude to students pursuing social-ecological research. Through sharing insights from successful graduate student approaches to social-ecological research within the LTER Network, we hope to facilitate dialogue between students, faculty, and networks to improve training for interdisciplinary scientists
How much noise is too much? Methods for identifying thresholds for soundscape quality and ecosystem services
The United States National Park Service mandate is to conserve park resources and provide superlative visitor experience. In the context of acoustic resources, Denali National Park and Preserve provides an advantageous opportunity to understand the effect of aircraft noise on visitor experience because it possesses high levels of air tour traffic in a park renowned for its remote, wilderness character. Park visitors in four different settings were asked to rate the acceptability of recordings of aircraft noise, presented in randomized order relative to noise level. A cumulative link mixed model fitted visitor assessments to acoustic and nonacoustic factors. In addition to noise level, interest in an air tour was an important predictor of sound clip acceptability. For visitors uninterested in an air tour, the probability of rating aircraft noise as unacceptable at 54 dB LAeq,30 s or higher was 26%. For reference, this aligns with federal guidance that identified 55 dB as a threshold for interference with outdoor activities at rural residences and schools. Predictions of visitor response were joined to a spatial model of aircraft noise propagation to map visitor acceptability of aircraft noise in Denali’s entrance area (frontcountry). This map can be used to assess the condition of park management zones, to inform hiking recommendations for visitors, and to predict the range of soundscape conditions experienced by park visitors Soundscapes Threshold Indicators Aircraft noise Spatial analysis Ecosystem servicespublishedVersio
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