Cavity-enhanced optical detection of carbon nanotube Brownian motion

Optical cavities with small mode volume are well-suited to detect the vibration of sub-wavelength sized objects. Here we employ a fiber-based, high-finesse optical microcavity to detect the Brownian motion of a freely suspended carbon nanotube at room temperature under vacuum. The optical detection resolves deflections of the oscillating tube down to 50pm/Hz^1/2. A full vibrational spectrum of the carbon nanotube is obtained and confirmed by characterization of the same device in a scanning electron microscope. Our work successfully extends the principles of high-sensitivity optomechanical detection to molecular scale nanomechanical systems.Comment: 14 pages, 11 figure

Microscopic nanomechanical dissipation in gallium arsenide resonators

We report on a systematic study of nanomechanical dissipation in high-frequency (approximatively 300 MHz) gallium arsenide optomechanical disk resonators, in conditions where clamping and fluidic losses are negligible. Phonon-phonon interactions are shown to contribute with a loss background fading away at cryogenic temperatures (3 K). Atomic layer deposition of alumina at the surface modifies the quality factor of resonators, pointing towards the importance of surface dissipation. The temperature evolution is accurately fitted by two-level systems models, showing that nanomechanical dissipation in gallium arsenide resonators directly connects to their microscopic properties. Two-level systems, notably at surfaces, appear to rule the damping and fluctuations of such high-quality crystalline nanomechanical devices, at all temperatures from 3 to 300K

Searching for biosignatures by their rotational spectrum: global fit and methyl group internal rotation features of dimethylsulphoxide up to 116 GHz

The identification and quantification of molecules in interstellar space and atmospheres of planets in the solar systems and in exoplanets rely on spectroscopicmethods and laboratory work is essential to provide the community with the spectral features needed to analyse cosmological observations. Rotational spectroscopy in particular, with its intrinsic high resolution, allows the unambiguous identification of biomolecular building blocks and biosignature gases which can be correlated with the origin of life or the identification of habitable planets.We report the extension of the measured rotational transition frequencies of dimethylsulphoxide and its 34S and 13C isotopologues in the millimetrewave range (59.6–78.4 GHz) by use of an absorption spectrometer based on the supersonic expansion technique. Hyperfine patterns related to the methyl group internal rotation were analysed in the microwave range region (6–18 GHz) with a Pulsed Jet Fourier Transform spectrometer at extremely high resolution (2 kHz) and reliable predictions up to 116 GHz are provided. The focus on sulphur-bearing molecules is motivated by the fact that sulphur is largely involved in the intra- and inter-molecular hydrogen bonds in proteins and although it is the 10th most abundant element in the known Universe, understanding its chemistry is still amatter of debate.Moreover, sulphur-bearingmolecules, in particular dimethylsulphoxide, have been indicated as possible biosignature gases to be monitored in the search of habitable exoplanets

Damping of optomechanical disks resonators vibrating in air

We report on miniature GaAs disk optomechanical resonators vibrating in air in the radiofrequency range. The flexural modes of the disks are studied by scanning electron microscopy and optical interferometry, and correctly modeled with the elasticity theory for annular plates. The mechanical damping is systematically measured, and confronted with original analytical models for air damping. Formulas are derived that correctly reproduce both the mechanical modes and the damping behavior, and can serve as design tools for optomechanical applications in fluidic environment

Biological characteristics of Trichospilus diatraeae (Hymenoptera: Eulophidae) are influenced by the number of females exposed per pupa of Tenebrio molitor (Coleoptera: Tenebrionidae).

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Optomechanical sideband cooling of a thin membrane within a cavity

We present an experimental study of dynamical back-action cooling of the fundamental vibrational mode of a thin semitransparent membrane placed within a high-finesse optical cavity. We study how the radiation pressure interaction modifies the mechanical response of the vibrational mode, and the experimental results are in agreement with a Langevin equation description of the coupled dynamics. The experiments are carried out in the resolved sideband regime, and we have observed cooling by a factor 350 We have also observed the mechanical frequency shift associated with the quadratic term in the expansion of the cavity mode frequency versus the effective membrane position, which is typically negligible in other cavity optomechanical devices.Comment: 15 pages, 7 figure

Notulae to the Italian flora of algae, bryophytes, fungi and lichens: 5

In this contribution, new data concerning bryophytes, fungi, and lichens of the Italian flora are presented. It includes new records and confirmations for the bryophyte genera Diplophyllum and Ptychostomum, the fungal genera Arrhenia, Gymnosporangium, and Sporidesmium and the lichen genera Arthonia, Coenogonium, Flavoplaca, Gyalolechia, Parmotrema, Peltigera, Pterygiopsis, Squamarina, Tornabea, and Waynea

European Financial Market Integration: A Closer Look at Government Bonds in Eurozone Countries

The European Union made a number of steps not least of them the introduction of a common currency to foster the integration of the European financial markets. A number of papers have tried to gauge the degree of integration for various financial markets looking at the convergence of interest rates. A common finding is that government bond markets are quite well integrated. In this paper stochastic Kernel density estimates are used to take a closer look at the dynamics that drive the process of interest rate convergence. The main finding is that countries with large initial deviations from the mean interest rate do indeed converge. Interestingly the candidates least suspected namely the countries initially with interest rates at the mean level show a pattern of slight divergence