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Tafassasset: The Saga Continues
In this study, we compare data for two separate Tafassasset stones and supply new oxygen isotope data for our sample. We include a discussion of the debate surrounding the classification of Tafassasset and offer a hypothesis for its origin based upon new information
On-Chip Microwave Quantum Hall Circulator
Circulators are non-reciprocal circuit elements integral to technologies
including radar systems, microwave communication transceivers, and the readout
of quantum information devices. Their non-reciprocity arises from the
interference of microwaves over the centimetre-scale of the signal wavelength
in the presence of bulky magnetic media that break time-reversal symmetry. Here
we realize a completely passive on-chip microwave circulator with size
one-thousandth the wavelength by exploiting the chiral, slow-light response of
a 2-dimensional electron gas (2DEG) in the quantum Hall regime. For an
integrated GaAs device with 330 um diameter and 1 GHz centre frequency, a
non-reciprocity of 25 dB is observed over a 50 MHz bandwidth. Furthermore, the
direction of circulation can be selected dynamically by varying the magnetic
field, an aspect that may enable reconfigurable passive routing of microwave
signals on-chip
Linear Superposition in Nonlinear Equations
Even though the KdV and modified KdV equations are nonlinear, we show that
suitable linear combinations of known periodic solutions involving Jacobi
elliptic functions yield a large class of additional solutions. This procedure
works by virtue of some remarkable new identities satisfied by the elliptic
functions.Comment: 7 pages, 1 figur
Magnetic Ordering in the Spin-Ice Candidate HoRuO
Neutron scattering measurements on the spin-ice candidate material
HoRuO have revealed two magnetic transitions at T 95 K and T
1.4 K to long-range ordered states involving the Ru and Ho sublattices,
respectively. Between these transitions, the Ho moments form
short-ranged ordered spin clusters. The internal field provided by the ordered
S=1 Ru moments disrupts the fragile spin-ice state and drives the
Ho moments to order. We have directly measured a slight shift in the
Ho crystal field levels at 95 K from the Ru ordering.Comment: 4 pages, 5 figures, submitted to Phys. Rev. Letter
Absence of anomalous negative lattice-expansion for polycrystalline sample of Tb2Ti2O7
High resolution X-ray powder-diffraction experiments on a well-characterized
polycrystalline sample of the spin liquid Tb2Ti2O7 reveal that it shows normal
positive thermal-expansion above 4 K, which does not agree with the intriguing
anomalous negative thermal-expansion due to a magneto-elastic coupling reported
for a single crystal sample below 20 K. We also performed a Rietveld profile
refinement of a powder-diffraction pattern taken at a room temperature, and
confirmed that it is consistent with the fully ordered cubic pyrochlore
structure.Comment: 2 pages, 3 figure
Far-ultraviolet imaging of the Hubble Deep Field-North: Star formation in normal galaxies at z < 1
We present far-ultraviolet (FUV) imaging of the Hubble Deep Field-North (HDF-N) taken with the Solar Blind Channel of the Advanced Camera for Surveys (ACS SBC) and the FUV MAMA detector of the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope. The full WFPC2 deep field has been observed at 1600 Å. We detect 134 galaxies and one star down to a limit of FUV_(AB) ~ 29. All sources have counterparts in the WFPC2 image. Redshifts (spectroscopic or photometric) for the detected sources are in the range 0 < z < 1. We find that the FUV galaxy number counts are higher than those reported by GALEX, which we attribute at least in part to cosmic variance in the small HDF-N field of view. Six of the 13 Chandra sources at z < 0.85 in the HDF-N are detected in the FUV, and those are consistent with starbursts rather than active galactic nuclei. Cross-correlating with Spitzer sources in the field, we find that the FUV detections show general agreement with the expected L_(IR)/L_(UV) versus β relationship. We infer star formation rates (SFRs), corrected for extinction using the UV slope, and find a median value of 0.3 M_☉ yr^(-1) for FUV-detected galaxies, with 75% of detected sources having SFR < 1 M_☉ yr^(-1). Examining the morphological distribution of sources, we find that about half of all FUV-detected sources are identified as spiral galaxies. Half of morphologically selected spheroid galaxies at z < 0.85 are detected in the FUV, suggesting that such sources have had significant ongoing star formation in the epoch since z ~ 1
Statistical Mechanics of Learning: A Variational Approach for Real Data
Using a variational technique, we generalize the statistical physics approach
of learning from random examples to make it applicable to real data. We
demonstrate the validity and relevance of our method by computing approximate
estimators for generalization errors that are based on training data alone.Comment: 4 pages, 2 figure
Corrigendum to 'Longitudinal prevalence, faecal shedding and molecular characterization of Campylobacter spp. and Salmonella enterica in sheep' [The Veterinary Journal 202 (2014) 250-254]
A Search for Molecular Gas in GHz Peaked Spectrum Radio Sources
We present searches for molecular gas (CO, OH, CS, and Ammonia) in six GHz
Peaked Spectrum (GPS) radio sources. We do not detect gas in any source and
place upper limits on the mass of molecular gas which are generally in the
range 1E9 to a few times 1E10 solar masses. These limits are consistent with
the following interpretations: (1) GPS sources do not require very dense gas in
their hosts, and (2) The GPS sources are unlikely to be confined by dense gas
and will evolve to become larger radio sources
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