Minimally-destructive detection of magnetically-trapped atoms using frequency-synthesised light

We present a technique for atomic density measurements by the off-resonant phase-shift induced on a two-frequency, coherently-synthesised light beam. We have used this scheme to measure the column density of a magnetically trapped atom cloud and to monitor oscillations of the cloud in real time by making over a hundred non-destructive local density measurments. For measurements using pulses of 10,000-100,000 photons lasting ~10 microsecond, the precision is limited by statistics of the photons and the photodiode avalanche. We explore the relationship between measurement precision and the unwanted loss of atoms from the trap and introduce a figure of merit that characterises it. This method can be used to probe the density of a BEC with minimal disturbance of its phase.Comment: Submitted to New Journal of Physic

Cardiovascular changes after administration of aerosolized salbutamol in horses: five cases

Prevention and treatment of intraoperative hypoxemia in horses is difficult and both efficacy and safety of therapeutic maneuvers have to be taken into account. Inhaled salbutamol has been suggested as treatment of hypoxia in horses during general anesthesia, due to safety and ease of the technique. The present report describes the occurrence of clinically relevant unwanted cardiovascular effects (i.e. tachycardia and blood pressure modifications) in 5 horses undergoing general anesthesia in dorsal recumbency after salbutamol inhalation. Balanced anesthesia based on inhalation of isoflurane in oxygen or oxygen and air and continuous rate infusion (CRI) of lidocaine, romifidine, or combination of lidocaine and guaifenesine and ketamine was provided. Supportive measures were necessary to restore normal cardiovascular function in all horses but no long-term adverse effects were noticed in any of the cases

Nucleon-nucleon bremsstrahlung: An example of the impossibility of measuring off-shell amplitudes

For nearly fifty years theoretical and experimental efforts in nucleon-nucleon bremsstrahlung (NN$\gamma$) have been devoted to measuring off-shell amplitudes and distinguishing among various NN potentials on the basis of their off-shell behavior. New experiments are underway, designed specifically to attain kinematics further off shell than in the past, and thus to be more sensitive to the off-shell behavior. This letter shows that, contrary to these expectations, and due to the invariance of the S-matrix under transformations of the fields, the off-shell NN amplitude is as a matter of principle an unmeasurable quantity in NN$\gamma$.Comment: 9 pages, Latex, using RevTeX; Minor wording changes, title changed, version to be published in Phys. Rev. Letter

Anomalous radio emission from dust in the Helix

A byproduct of experiments designed to map the CMB is the recent detection of a new component of foreground Galactic emission. The anomalous foreground at ~ 10--30 GHz, unexplained by traditional emission mechanisms, correlates with 100um dust emission. We report that in the Helix the emission at 31 GHz and 100um are well correlated, and exhibit similar features on sky images, which are absent in H\beta. Upper limits on the 250 GHz continuum emission in the Helix rule out cold grains as candidates for the 31 GHz emission, and provide spectroscopic evidence for an excess at 31 GHz over bremsstrahlung. We estimate that the 100um-correlated radio emission, presumably due to dust, accounts for at least 20% of the 31 GHz emission in the Helix. This result strengthens previous tentative interpretations of diffuse ISM spectra involving a new dust emission mechanism at radio frequencies. Very small grains have not been detected in the Helix, which hampers interpreting the new component in terms of spinning dust. The observed iron depletion in the Helix favors considering the identity of this new component to be magnetic dipole emission from hot ferromagnetic grains. The reduced level of free-free continuum we report also implies an electronic temperature of Te=4600\pm1200K for the free-free emitting material, which is significantly lower than the temperature of 9500\pm500K inferred from collisionally-excited lines (abridged).Comment: Accepted for publication in Ap

Observation of double radiative capture on pionic hydrogen

We report the first observation of double radiative capture on pionic hydrogen. The experiment was conducted at the TRIUMF cyclotron using the RMC spectrometer, and detected $\gamma$--ray coincidences following $\pi^-$ stops in liquid hydrogen. We found the branching ratio for double radiative capture to be $(3.05 \pm 0.27(stat.) \pm 0.31(syst.)) \times 10^{-5}$. The measured branching ratio and angle-energy distributions support the theoretical prediction of a dominant contribution from the $\pi \pi \to \gamma \gamma$ annihilation mechanism.Comment: 4 Pages, 4 Figures. accepted for publication in Phys. Rev. Let

H2O Maser Observations of Candidate Post-AGB Stars and Discovery of Three High-velocity Water Sources

We present the results of 22 GHz H_2O maser observations of a sample of 85 post-Asymptotic Giant Branch (post-AGB) candidate stars, selected on the basis of their OH 1612 MHz maser and far-infrared properties. All sources were observed with the Tidbinbilla 70-m radio telescope and 21 detections were made. 86 GHz SiO Mopra observations of a subset of the sample are also presented. Of the 21 H_2O detections, 15 are from sources that are likely to be massive AGB stars and most of these show typical, regular H_2O maser profiles. In contrast, nearly all the detections of more evolved stars exhibited high-velocity H_2O maser emission. Of the five sources seen, v223 (W43A, IRAS 18450-0148) is a well known `water-fountain' source which belongs to a small group of post-AGB stars with highly collimated, high-velocity H_2O maser emission. A second source in our sample, v270 (IRAS 18596+0315), is also known to have high-velocity emission. We report the discovery of similar emission from a further three sources, d46 (IRAS 15445-5449), d62 (IRAS 15544-5332) and b292 (IRAS 18043-2116). The source d46 is an evolved post-AGB star with highly unusual maser properties. The H_2O maser emission from d62 is probably associated with a massive star. The source b292 is a young post-AGB star that is highly likely to be a water-fountain source, with masers detected over a velocity range of 210 km s^{-1}.Comment: 47 pages, 9 figures, 4 tables, accepted by Ap

Experiments on a videotape atom chip: fragmentation and transport studies

This paper reports on experiments with ultra-cold rubidium atoms confined in microscopic magnetic traps created using a piece of periodically-magnetized videotape mounted on an atom chip. The roughness of the confining potential is studied with atomic clouds at temperatures of a few microKelvin and at distances between 30 and 80 microns from the videotape-chip surface. The inhomogeneities in the magnetic field created by the magnetized videotape close to the central region of the chip are characterized in this way. In addition, we demonstrate a novel transport mechanism whereby we convey cold atoms confined in arrays of videotape magnetic micro-traps over distances as large as ~ 1 cm parallel to the chip surface. This conveying mechanism enables us to survey the surface of the chip and observe potential-roughness effects across different regions.Comment: 29 pages, 22 figures

SCUBA Mapping of Spitzer c2d Small Clouds and Cores

We present submillimeter observations of dark clouds that are part of the Spitzer Legacy Program, From Molecular Cores to Planet-Forming Disks (c2d). We used the Submillimetre Common User's Bolometer Array to map the regions observed by Spitzer by the c2d program to create a census of dense molecular cores including data from the infrared to the submillimeter. In this paper, we present the basic data from these observations: maps, fluxes, and source attributes. We also show data for an object just outside the Perseus cloud that was serendipitously observed in our program. We propose that this object is a newly discovered, evolved protostar.Comment: 37 pages, accepted to The Astronomical Journa

Correlation between Infrared Colors and Intensity Ratios of SiO Maser Lines

We present the results of SiO millimeter-line observations of a sample of known SiO maser sources covering a wide dust-temperature range. A cold part of the sample was selected from the SiO maser sources found in our recent SiO maser survey of cold dusty objects. The aim of the present research is to investigate the causes of the correlation between infrared colors and SiO maser intensity ratios among different transition lines. In particular, the correlation between infrared colors and SiO maser intensity ratio among the J=1-0 v=1, 2, and 3 lines are mainly concerned in this paper. We observed in total 75 SiO maser sources with the Nobeyama 45m telescope quasi-simultaneously in the SiO J=1-0 v=0, 1, 2, 3, 4 and J=2-1 v=1, 2 lines. We also observed the sample in the 29SiO J=1-0 v=0 and J=2-1 v=0, and 30SiO J=1-0 v=0 lines, and the H2O 6(1,6)-5(2,3) line. As reported in previous papers, we confirmed that the intensity ratios of the SiO J=1-0 v=2 to v=1 lines clearly correlate with infrared colors. In addition, we found possible correlation between infrared colors and the intensity ratios of the SiO J=1-0 v=3 to v=1&2 lines. Two overlap lines of H2O (i.e., 11(6,6) nu_2=1 -> 12(7,5) nu_2=0 and 5(0,5) nu_2=2 -> 6(3,4) nu_2=1) might explain these correlation if these overlap lines become stronger with increase of infrared colors, although the phenomena also might be explained by more fundamental ways if we take into account the variation of opacity from object to object.Comment: 49 pages, 7 figures, 3 tables, accepted for publication in ApJ. Full resolution version available at http://www.asiaa.sinica.edu.tw/~junichi/paper

Renormalization Group Flow Equation at Finite Density

For the linear sigma model with quarks we derive renormalization group flow equations for finite temperature and finite baryon density using the heat kernel cutoff. At zero temperature we evolve the effective potential to the Fermi momentum and compare the solutions of the full evolution equation with those in the mean field approximation. We find a first order phase transition either from a massive constituent quark phase to a mixed phase, where both massive and massless quarks are present, or from a metastable constituent quark phase at low density to a stable massless quark phase at high density. In the latter solution, the formation of droplets of massless quarks is realized even at low density.Comment: 30 pages, 9 figures; typos corrected, section 3 revised, one reference added, two references updated, submitted to Phys. Rev.