289 research outputs found
Radio frequency association of heteronuclear Feshbach molecules
We present a detailed analysis of the production efficiency of weakly bound
heteronuclear KRb-Feshbach molecules using radio frequency association in a
harmonic trap. The efficiency was measured in a wide range of temperatures,
binding energies and radio frequencies. A comprehensive analytical model is
presented, explaining the observed asymmetric spectra and achieving good
quantitative agreement with the measured production rates. This model provides
a deep understanding of the molecule association process and paves the way for
future experiments which rely on Feshbach molecules e.g. for the production of
deeply bound molecules.Comment: 5 pages, 4 figure
Moving the pulsed heating technique beyond monolithic specimens: Experiments with coated wires
Pulsed heating experiments that measure high-temperature thermophysical properties using pyrometric measurement of the temperature-time history of metal specimens rapidly heated by passage of electric current have a 30-year history at the National Institute of Standards and Technology. In recent years, efforts have been made to move beyond the limitations of the standard technique of using costly, black-body geometry specimens. Specifically, simultaneous polarimetry measurement of the spectral emissivity has permitted study of sheet and wire specimens. This paper presents the results of two efforts to expand beyond the macroscopically monolithic, single-phase materials of all previous studies. In the first study the melting temperatures of coatings, including Ti and Ti(Al) alloys, deposited on higher melting Mo substrates are measured. In the second study the melting temperatures of substrates, Ti and Cr, covered by higher melting W and Mo coatings are measure
Interpreting the near-infrared spectra of the 'golden standard' Type Ia supernova 2005cf
We present nine near-infrared (NIR) spectra of supernova (SN) 2005cf at
epochs from -10 d to +42 d with respect to B-band maximum, complementing the
existing excellent data sets available for this prototypical Type Ia SN at
other wavelengths. The spectra show a time evolution and spectral features
characteristic of normal Type Ia SNe, as illustrated by a comparison with SNe
1999ee, 2002bo and 2003du. The broad-band spectral energy distribution (SED) of
SN 2005cf is studied in combined ultraviolet (UV), optical and NIR spectra at
five epochs between ~ 8 d before and ~ 10 d after maximum light. We also
present synthetic spectra of the hydrodynamic explosion model W7, which
reproduce the key properties of SN 2005cf not only at UV-optical as previously
reported, but also at NIR wavelengths. From the radiative-transfer calculations
we infer that fluorescence is the driving mechanism that shapes the SED of SNe
Ia. In particular, the NIR part of the spectrum is almost devoid of absorption
features, and instead dominated by fluorescent emission of both iron-group
material and intermediate-mass elements at pre-maximum epochs, and pure
iron-group material after maximum light. A single P-Cygni feature of Mg II at
early epochs and a series of relatively unblended Co II lines at late phases
allow us to constrain the regions of the ejecta in which the respective
elements are abundant.Comment: 11 pages, 6 figures, accepted for publication in MNRA
Synthetic retinal analogues modify the spectral and kinetic characteristics of microbial rhodopsin optogenetic tools
Optogenetic tools have become indispensable in neuroscience to stimulate or inhibit excitable cells by light. Channelrhodopsin-2 (ChR2) variants have been established by mutating the opsin backbone or by mining related algal genomes. As an alternative strategy, we surveyed synthetic retinal analogues combined with microbial rhodopsins for functional and spectral properties, capitalizing on assays in C. elegans, HEK cells and larval Drosophila. Compared with all-trans retinal (ATR), Dimethylamino-retinal (DMAR) shifts the action spectra maxima of ChR2 variants H134R and H134R/T159C from 480 to 520 nm. Moreover, DMAR decelerates the photocycle of ChR2(H134R) and (H134R/T159C), thereby reducing the light intensity required for persistent channel activation. In hyperpolarizing archaerhodopsin-3 and Mac, naphthyl-retinal and thiophene-retinal support activity alike ATR, yet at altered peak wavelengths. Our experiments enable applications of retinal analogues in colour tuning and altering photocycle characteristics of optogenetic tools, thereby increasing the operational light sensitivity of existing cell lines or transgenic animals
Synthetic retinal analogues modify the spectral and kinetic characteristics of microbial rhodopsin optogenetic tools
Optogenetic tools have become indispensable in neuroscience to stimulate or inhibit excitable cells by light. Channelrhodopsin-2 (ChR2) variants have been established by mutating the opsin backbone or by mining related algal genomes. As an alternative strategy, we surveyed synthetic retinal analogues combined with microbial rhodopsins for functional and spectral properties, capitalizing on assays in C. elegans, HEK cells and larval Drosophila. Compared with all-trans retinal (ATR), Dimethylamino-retinal (DMAR) shifts the action spectra maxima of ChR2 variants H134R and H134R/T159C from 480 to 520 nm. Moreover, DMAR decelerates the photocycle of ChR2(H134R) and (H134R/T159C), thereby reducing the light intensity required for persistent channel activation. In hyperpolarizing archaerhodopsin-3 and Mac, naphthyl-retinal and thiophene-retinal support activity alike ATR, yet at altered peak wavelengths. Our experiments enable applications of retinal analogues in colour tuning and altering photocycle characteristics of optogenetic tools, thereby increasing the operational light sensitivity of existing cell lines or transgenic animals
Time-Resolved Photometry of the Optical Counterpart of Swift J2319.4+2619
Time-resolved CCD photometry is presented of the V~17 optical counterpart of
the newly-discovered, hard-X-ray-emitting polar Swift J2619.4+2619. A total of
~20 hr of data obtained over five nights in various bandpasses (B, V, R, and I)
reveals a strong quasi-sinusoidal modulation in the light curve at a
best-fitting period of 0.1254 d (3.01 hr), which we associate with the orbital
period of the system (one-day aliases of this period at 0.1114 d and 0.1435 d
are considered, but appear to be ruled out by our analysis). The amplitude of
the modulation increases with wavelength from ~0.8 mag in B to ~1.1 mag in R
and I. The increase in amplitude with wavelength is typical of polar systems
where the modulated radiation comes from cyclotron emission. The combination of
the relatively long orbital period and the emission of hard X-rays suggest that
Swift J2619.4+2619 may be a good candidate for an asynchronous polar system.Comment: 15 pages, 5 figures, Accepted for publication in the April 2008 PAS
The Distance to NGC 1316 (Fornax A) From Observations of Four Type Ia Supernovae
The giant elliptical galaxy NGC 1316 (Fornax A) is a well-studied member of
the Fornax Cluster and a prolific producer of Type Ia supernovae, having hosted
four observed events since 1980. Here we present detailed optical and
near-infrared light curves of the spectroscopically normal SN 2006dd. These
data are used, along with previously published photometry of the normal SN
1980N and SN 1981D, and the fast-declining, low-luminosity SN 2006mr, to
compute independent estimates of the host reddening for each supernova, and the
distance to NGC 1316. From the three normal supernovae, we find a distance of
17.8 +/- 0.3 (random) +/- 0.3 (systematic) Mpc for Ho = 72. Distance moduli
derived from the "EBV" and Tripp methods give values that are mutually
consistent to 4 -- 8%. Moreover, the weighted means of the distance moduli for
these three SNe for three methods agree to within 3%. This consistency is
encouraging and supports the premise that Type Ia supernovae are reliable
distance indicators at the 5% precision level or better. On the other hand, the
two methods used to estimate the distance of the fast-declining SN 2006mr both
yield a distance to NGC 1316 which is 25-30% larger. This disparity casts doubt
on the suitability of fast-declining events for estimating extragalactic
distances. Modest-to-negligible host galaxy reddening values are derived for
all four supernovae. Nevertheless, two of them (SN 2006dd and SN 2006mr) show
strong NaID interstellar lines in the host galaxy system. The strength of this
absorption is completely inconsistent with the small reddening values derived
from the supernova light curves if the gas in NGC 1316 is typical of that found
in the interstellar medium of the Milky Way. In addition, the equivalent width
of the NaID lines in SN 2006dd appear to have weakened significantly some
100-150 days after explosion.Comment: 50 pages, 13 figures, 10 tables; constructive comments welcome.
Accepted for publication in A
Some Like It Fat: Comparative Ultrastructure of the Embryo in Two Demosponges of the Genus Mycale (Order Poecilosclerida) from Antarctica and the Caribbean
0000-0002-7993-1523© 2015 Riesgo et al. This is an open access article distributed under the terms of the Creative Commons Attribution License [4.0], which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. The attached file is the published version of the article
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