Low-Noise Amplification of a Continuous Variable Quantum State

We present an experimental realization of a low-noise, phase-insensitive optical amplifier using a four-wave mixing interaction in hot Rb vapor. Performance near the quantum limit for a range of amplifier gains, including near unity, can be achieved. Such low-noise amplifiers are essential for so-called quantum cloning machines and are useful in quantum information protocols. We demonstrate that amplification and ``cloning'' of one half of a two-mode squeezed state is possible while preserving entanglement.Comment: To appear in Physical Review Letters July 3rd. 4 pages, 4 figure

Finite-Difference Time-Domain Simulation for Three-dimensional Polarized Light Imaging

Three-dimensional Polarized Light Imaging (3D-PLI) is a promising technique to reconstruct the nerve fiber architecture of human post-mortem brains from birefringence measurements of histological brain sections with micrometer resolution. To better understand how the reconstructed fiber orientations are related to the underlying fiber structure, numerical simulations are employed. Here, we present two complementary simulation approaches that reproduce the entire 3D-PLI analysis: First, we give a short review on a simulation approach that uses the Jones matrix calculus to model the birefringent myelin sheaths. Afterwards, we introduce a more sophisticated simulation tool: a 3D Maxwell solver based on a Finite-Difference Time-Domain algorithm that simulates the propagation of the electromagnetic light wave through the brain tissue. We demonstrate that the Maxwell solver is a valuable tool to better understand the interaction of polarized light with brain tissue and to enhance the accuracy of the fiber orientations extracted by 3D-PLI.Comment: 13 pages, 5 figure

Psychological, psychophysical, and ergogenic effects of music in swimming

OBJECTIVES: Existing work using dry land exercise-related activities has shown that the careful application of music can lead to a range of benefits that include enhanced affect, lower perceived exertion, greater energy efficiency, and faster time trial performances. The purpose of this study was to assess the psychological, psychophysical, and ergogenic effects of asynchronous music in swimming using a mixed-methods approach. DESIGN: A mixed-model design was employed wherein there was a within-subjects factor (two experimental conditions and a control) and a between-subjects factor (gender). The experimental component of the study was supplemented by qualitative data that were analysed using inductive content analysis. METHODS: Twenty six participants (Mage = 20.0 years, age range: 18–23 years) underwent a period of habituation with Speedo Aquabeat MP3 players prior to the experimental phase. They were then administered two experimental trials (motivational and oudeterous music at 130 bpm) and a no-music control, during which they engaged in a 200-m freestyle swimming time trial. RESULTS: Participants swam significantly faster when exposed to either music condition relative to control (p = .022, ηp2=.18). Moreover, the music conditions were associated with higher state motivation (p = .016, ηp2=.15) and more dissociative thoughts (p = .014, ηp2=.16). CONCLUSIONS: Findings supported the hypothesis that the use of asynchronous music during a high-intensity task can have an ergogenic effect; this was in the order of 2% when averaged out across the two experimental conditions. The use of music, regardless of its motivational qualities, resulted in higher self-reported motivation as well as more dissociative thoughts

Altered expression of glutamate signaling, growth factor, and glia genes in the locus coeruleus of patients with major depression.

Several studies have proposed that brain glutamate signaling abnormalities and glial pathology have a role in the etiology of major depressive disorder (MDD). These conclusions were primarily drawn from post-mortem studies in which forebrain brain regions were examined. The locus coeruleus (LC) is the primary source of extensive noradrenergic innervation of the forebrain and as such exerts a powerful regulatory role over cognitive and affective functions, which are dysregulated in MDD. Furthermore, altered noradrenergic neurotransmission is associated with depressive symptoms and is thought to have a role in the pathophysiology of MDD. In the present study we used laser-capture microdissection (LCM) to selectively harvest LC tissue from post-mortem brains of MDD patients, patients with bipolar disorder (BPD) and from psychiatrically normal subjects. Using microarray technology we examined global patterns of gene expression. Differential mRNA expression of select candidate genes was then interrogated using quantitative real-time PCR (qPCR) and in situ hybridization (ISH). Our findings reveal multiple signaling pathway alterations in the LC of MDD but not BPD subjects. These include glutamate signaling genes, SLC1A2, SLC1A3 and GLUL, growth factor genes FGFR3 and TrkB, and several genes exclusively expressed in astroglia. Our data extend previous findings of altered glutamate, astroglial and growth factor functions in MDD for the first time to the brainstem. These findings indicate that such alterations: (1) are unique to MDD and distinguishable from BPD, and (2) affect multiple brain regions, suggesting a whole-brain dysregulation of such functions

The ascent of kimberlite: Insights from olivine

Olivine xenocrysts are ubiquitous in kimberlite deposits worldwide and derive from the disaggregation of mantle-derived peridotitic xenoliths. Here, we provide descriptions of textural features in xenocrystic olivine from kimberlite deposits at the Diavik Diamond Mine, Canada and at Igwisi Hills volcano, Tanzania. We establish a relative sequence of textural events recorded by olivine during magma ascent through the cratonic mantle lithosphere, including: xenolith disaggregation, decompression fracturing expressed as mineral- and fluid-inclusion-rich sealed and healed cracks, grain size and shape modification by chemical dissolution and abrasion, late-stage crystallization of overgrowths on olivine xenocrysts, and lastly, mechanical milling and rounding of the olivine cargo prior to emplacement. Ascent through the lithosphere operates as a “kimberlite factory” wherein progressive upward dyke propagation of the initial carbonatitic melt fractures the overlying mantle to entrain and disaggregate mantle xenoliths. Preferential assimilation of orthopyroxene (Opx) xenocrysts by the silica-undersaturated carbonatitic melt leads to deep-seated exsolution of CO2-rich fluid generating buoyancy and supporting rapid ascent. Concomitant dissolution of olivine produces irregular-shaped relict grains preserved as cores to most kimberlitic olivine. Multiple generations of decompression cracks in olivine provide evidence for a progression in ambient fluid compositions (e.g., from carbonatitic to silicic) during ascent. Numerical modelling predicts tensile failure of xenoliths (disaggregation) and olivine (cracks) over ascent distances of 2–7 km and 15–25 km, respectively, at velocities of 0.1 to >4 m s−1. Efficient assimilation of Opx during ascent results in a silica-enriched, olivine-saturated kimberlitic melt (i.e. SiO2 >20 wt.%) that crystallizes overgrowths on partially digested and abraded olivine xenocrysts. Olivine saturation is constrained to occur at pressures <1 GPa; an absence of decompression cracks within olivine overgrowths suggests depths <25 km. Late stage (<25 km) resurfacing and reshaping of olivine by particle–particle milling is indicative of turbulent flow conditions within a fully fluidized, gas-charged, crystal-rich magma

Fish biodiversity patterns of a mesophotic-to-subphotic artificial reef complex and comparisons with natural substrates

Artificial reefs act as high-rugosity habitats and are often deployed to enhance fishing; however, the effects of man-made features on fish communities can be unpredictable and are poorly understood in deeper waters. In this study, we used a submersible to describe a deep-water artificial reef complex (93-245 m) off of Ewa Beach, Oahu, Hawaii, USA, and evaluated possible conservation and/or fisheries-related contributions. Sixty-eight species were recorded, with larger features supporting greater diversity of species. Species composition changed strongly with depth and a faunal break was detected from 113-137 m. While the features supported diverse fish communities, they were not similar to those on natural substrates, and were numerically dominated by only two species, Lutjanis kasmira and Chromis verater. Depth-generalist and endemic species were present at levels comparable to natural substrates, but were less abundant and species-rich than at biogenic Leptoseris reefs at similar depths. While the non-native L. kasmira was highly abundant, its presence and abundance were not associated with discernable changes in the fish community, and was not present deeper than 120 m. Finally, five species of commercially- and recreationally-important \u27Deep 7\u27 fisheries species were also observed, but the artificial reef complex was mostly too shallow to provide meaningful benefits

Explaining unexplained pain to fibromyalgia patients: finding a narrative that is acceptable to patients and provides a rationale for evidence based interventions

As the cause of fibromyalgia is controversial, communicating with patients can be challenging, particularly if the patient adopts the narrative ‘I am damaged and so I need a more powerful pain killer’. Research shows that providing patients with alternative narratives can be helpful, but it remains unclear what particular narratives are most acceptable to patients and at the same time provide a rationale for evidence based psychological and exercise interventions. This article described the development of a new narrative and the written comments made about the narrative by fibromyalgia patients. The narrative derives from a complexity theory model and provides an alternative to biogenic and psychogenic models. The model was presented to 15 patients whose comments about comprehensibility led to the final format of the narrative. In the final form, the body is presented as ‘a very, very clever computer’ where fibromyalgia is caused by a software rather than a hardware problem. The software problem is caused by the body adapting when people have to ‘keep going’ despite ‘stop signals’, such as pain and fatigue. The narrative provides a rationale for engaging in psychological and exercise interventions as a way of correcting the body’s software. This way of explaining fibromyalgia was evaluated by a further 25 patients attending a 7-week ‘body reprogramming’ intervention, where the therapy was presented as correcting the body’s software, and included both exercise and psychological components. Attendance at the course was 85%. Thematic analysis of written patient feedback collected after each session showed that patients found the model believable and informative, it provided hope and was empowering. Patients also indicated that they had started to implement lifestyle change with perceived benefit. Fibromyalgia patients appear to respond positively to a technology-derived narrative based on the analogy of the body as a computer