2,714 research outputs found

    The Effect of Air on Granular Size Separation in a Vibrated Granular Bed

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    Using high-speed video and magnetic resonance imaging (MRI) we study the motion of a large sphere in a vertically vibrated bed of smaller grains. As previously reported we find a non-monotonic density dependence of the rise and sink time of the large sphere. We find that this density dependence is solely due to air drag. We investigate in detail how the motion of the intruder sphere is influenced by size of the background particles, initial vertical position in the bed, ambient pressure and convection. We explain our results in the framework of a simple model and find quantitative agreement in key aspects with numerical simulations to the model equations.Comment: 14 pages, 16 figures, submitted to PRE, corrected typos, slight change

    Coherent control using adaptive learning algorithms

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    We have constructed an automated learning apparatus to control quantum systems. By directing intense shaped ultrafast laser pulses into a variety of samples and using a measurement of the system as a feedback signal, we are able to reshape the laser pulses to direct the system into a desired state. The feedback signal is the input to an adaptive learning algorithm. This algorithm programs a computer-controlled, acousto-optic modulator pulse shaper. The learning algorithm generates new shaped laser pulses based on the success of previous pulses in achieving a predetermined goal.Comment: 19 pages (including 14 figures), REVTeX 3.1, updated conten

    6^6Li-loaded liquid scintillators produced by direct dissolution of compounds in diisopropylnaphthalene (DIPN)

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    The paper describes preparation of 6^6Li-loaded liquid scintillators by methods involving direct dissolution of 6^6Li salts in the commercial diisopropylnaphthalene (DIPN) solvent, without the formation of water-in-oil emulsions. Methods include incorporation of 6^6Li that, unlike previously reported formulations, does not require additions of water or a strong acid such as hydrochloric acid (HCl). Results of the conducted experiments show that dissolution of aromatic and aliphatic 6^6Li salts in DIPN can be easily achieved at 0.1- 0.3% by weight of atomic 6^6Li, using small additions of waterless surfactants, or mild carboxylic acids. An alternative way suggests incorporation of 6^6Li as a part of a surfactant molecule that can be dissolved in DIPN without any solubilizing additions. Proposed methods enable preparation of efficient 6^6Li-loaded liquid scintillators that, at a large scale of 50 cm, exhibit good pulse shape discrimination (PSD) properties combined with up to 107% of light output and up to 115% of the attenuation length measured relative to standard undoped EJ-309 liquid scintillator.Comment: Submitted to Nuclear Instruments and Methods in Physics Research

    Assessing Security in Energy-Efficient Sensor Networks

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    Development of a Molecular Signature to Monitor Pharmacodynamic Responses Mediated by In Vivo Administration of Glucocorticoids

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    © 2018 American College of Rheumatology. Objective: To develop an objective, readily measurable pharmacodynamic biomarker of glucocorticoid (GC) activity. Methods: Genes modulated by prednisolone were identified from in vitro studies using peripheral blood mononuclear cells from normal healthy volunteers. Using the criteria of a \u3e2-fold change relative to vehicle controls and an adjusted P value cutoff of less than 0.05, 64 up-regulated and 18 down-regulated genes were identified. A composite score of the up-regulated genes was generated using a single-sample gene set enrichment analysis algorithm. Results: GC gene signature expression was significantly elevated in peripheral blood leukocytes from normal healthy volunteers following oral administration of prednisolone. Expression of the signature increased in a dose-dependent manner, peaked at 4 hours postadministration, and returned to baseline levels by 48 hours after dosing. Lower expression was detected in normal healthy volunteers who received a partial GC receptor agonist, which is consistent with the reduced transactivation potential of this compound. In cohorts of patients with systemic lupus erythematosus and patients with rheumatoid arthritis, expression of the GC signature was negatively correlated with the percentages of peripheral blood lymphocytes and positively correlated with peripheral blood neutrophil counts, which is consistent with the known biology of the GC receptor. Expression of the signature largely agreed with reported GC use in these populations, although there was significant interpatient variability within the dose cohorts. Conclusion: The GC gene signature identified in this study represents a pharmacodynamic marker of GC exposure

    Evidence for the N(1720)3/2+N'(1720)3/2^+ Nucleon Resonance from Combined Studies of CLAS π+πp\pi^+\pi^-p Photo- and Electroproduction Data

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    The analysis of the nine 1-fold differential cross sections for the γr,vpπ+πp\gamma_{r,v} p \to \pi^+\pi^-p photo- and electroproduction reactions obtained with the CLAS detector at Jefferson Laboratory was carried out with the goal to establish the contributing resonances in the mass range from 1.6~GeV to 1.8~GeV. In order to describe the photo- and electroproduction data with Q2Q^2-independent resonance masses and hadronic decay widths in the Q2Q^2 range below 1.5~GeV2^2, it was found that an N(1720)3/2+N'(1720)3/2^+ state is required in addition to the already well-established nucleon resonances. This work demonstrates that the combined studies of π+πp\pi^+\pi^-p photo- and electroproduction data are vital for the observation of this resonance. The contributions from the N(1720)3/2+N'(1720)3/2^+ state and the already established N(1720)3/2+N(1720)3/2^+ state with a mass of 1.745~GeV are well separated by their different hadronic decays to the πΔ\pi \Delta and ρp\rho p final states and the different Q2Q^2-evolution of their photo-/electroexcitation amplitudes. The N(1720)3/2+N'(1720)3/2^+ state is the first recently established baryon resonance for which the results on the Q2Q^2-evolution of the photo-/electrocouplings have become available. These results are important for the exploration of the nature of the ``missing'' baryon resonances.Comment: accepted for publication in Phys. Lett.
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