311 research outputs found
Revealing Cosmic Rotation
Cosmological Birefringence (CB), a rotation of the polarization plane of
radiation coming to us from distant astrophysical sources, may reveal parity
violation in either the electromagnetic or gravitational sectors of the
fundamental interactions in nature. Until only recently this phenomenon could
be probed with only radio observations or observations at UV wavelengths.
Recently, there is a substantial effort to constrain such non-standard models
using observations of the rotation of the polarization plane of cosmic
microwave background (CMB) radiation. This can be done via measurements of the
-modes of the CMB or by measuring its TB and EB correlations which vanish in
the standard model. In this paper we show that correlations-based
estimator is the best for upcoming polarization experiments. The based
estimator surpasses other estimators because it has the smallest noise and of
all the estimators is least affected by systematics. Current polarimeters are
optimized for the detection of -mode polarization from either primordial
gravitational waves or by large scale structure via gravitational lensing. In
the paper we also study optimization of CMB experiments for the detection of
cosmological birefringence, in the presence of instrumental systematics, which
by themselves are capable of producing correlations; potentially mimicking
CB.Comment: 10 pages, 3 figures, 2 table
Functional limitations in TBI and their relationship to job maintenance following work re-entry,”
Abstract. Using data from the Job Accommodation Network Information System (JANIS), the utility of self-reported functional limitations was examined in relationship to job maintenance for individuals with traumatic brain injury (TBI) who had returned to work. It was found that memory loss and attention/concentration concerns were the most common functional limitations reported. To further establish which limitations were associated with job maintenance, a binary logistic regression was applied. Results suggested that the presence of medical symptoms and emotional dysregulation were reliably and inversely associated with job maintenance. Implications are provided for further research as well as the practice of rehabilitation counseling
Price Discovery and the Accuracy of Consolidated Data Feeds in the U.S. Equity Markets
Both the scientific community and the popular press have paid much attention
to the speed of the Securities Information Processor, the data feed
consolidating all trades and quotes across the US stock market. Rather than the
speed of the Securities Information Processor, or SIP, we focus here on its
accuracy. Relying on Trade and Quote data, we provide various measures of SIP
latency relative to high-speed data feeds between exchanges, known as direct
feeds. We use first differences to highlight not only the divergence between
the direct feeds and the SIP, but also the fundamental inaccuracy of the SIP.
We find that as many as 60 percent or more of trades are reported out of
sequence for stocks with high trade volume, therefore skewing simple measures
such as returns. While not yet definitive, this analysis supports our
preliminary conclusion that the underlying infrastructure of the SIP is
currently unable to keep pace with the trading activity in today's stock
market.Comment: 18 pages, 20 figures, 2 table
EuroTracker (R) dyes: design, synthesis, structure and photophysical properties of very bright europium complexes and their use in bioassays and cellular optical imaging
The development of the brightest luminescent europium(III) complexes is traced, including analysis of
the C3-symmetric core complex based on a functionalized triazacyclononane and identification of the
most suitable strongly absorbing chromophore. Strategies for the synthesis of the complexes, including
enantiopure analogues, are outlined and opportunities for applications in time-resolved microscopy and
spectral imaging emphasised. Practicable examples are introduced, including selective organelle staining
for cellular optical imaging at 65 nm resolution and the development of new bioassays using time resolved
FRET methods
DNA Testing Reveals the Putative Identity of JB55, a 19th Century Vampire Buried in Griswold, Connecticut
In 1990 in Griswold, Connecticut, archaeologists excavated a burial found in a "skull and crossbones" orientation. The lid of the 19th century coffin had brass tacks that spelled "JB55", the initials of the person lying there and age at death. JB55 had evidence of chronic pulmonary infection, perhaps tuberculosis. It is possible that JB55 was deemed a vampire due to his disease, and therefore had to be "killed" by mutilating his corpse. In an attempt to reveal the identity of JB55, DNA testing was performed. Ancestry informative single nucleotide polymorphism (SNP) analysis using the Precision ID Ancestry Panel indicated European ancestry. A full Y-chromosomal short tandem repeat (Y-STR) profile was obtained, belonging to haplogroup R1b. When the Y-STR profile was searched in the publicly accessible FamilyTreeDNA R1b Project website, the two closest matches had the surname "Barber". A search of historical records led to a death notice mentioning John Barber, whose son Nathan Barber was buried in Griswold in 1826. The description of Nathan Barber closely fits the burial of "NB13," found near JB55. By applying modern forensic DNA tools to a historical mystery, the identity of JB55 as John Barber, the 19th century Connecticut vampire, has been revealed
Photochemistry of Furyl- and Thienyldiazomethanes: Spectroscopic Characterization of Triplet 3-Thienylcarbene
Photolysis (λ \u3e 543 nm) of 3-thienyldiazomethane (1), matrix isolated in Ar or N2 at 10 K, yields triplet 3-thienylcarbene (13) and α-thial-methylenecyclopropene (9). Carbene 13 was characterized by IR, UV/vis, and EPR spectroscopy. The conformational isomers of 3-thienylcarbene (s-E and s-Z) exhibit an unusually large difference in zero-field splitting parameters in the triplet EPR spectrum (|D/hc| = 0.508 cm–1, |E/hc| = 0.0554 cm–1; |D/hc| = 0.579 cm–1, |E/hc| = 0.0315 cm–1). Natural Bond Orbital (NBO) calculations reveal substantially differing spin densities in the 3-thienyl ring at the positions adjacent to the carbene center, which is one factor contributing to the large difference in D values. NBO calculations also reveal a stabilizing interaction between the sp orbital of the carbene carbon in the s-Z rotamer of 13 and the antibonding σ orbital between sulfur and the neighboring carbon—an interaction that is not observed in the s-E rotamer of 13. In contrast to the EPR spectra, the electronic absorption spectra of the rotamers of triplet 3-thienylcarbene (13) are indistinguishable under our experimental conditions. The carbene exhibits a weak electronic absorption in the visible spectrum (λmax = 467 nm) that is characteristic of triplet arylcarbenes. Although studies of 2-thienyldiazomethane (2), 3-furyldiazomethane (3), or 2-furyldiazomethane (4) provided further insight into the photochemical interconversions among C5H4S or C5H4O isomers, these studies did not lead to the spectroscopic detection of the corresponding triplet carbenes (2-thienylcarbene (11), 3-furylcarbene (23), or 2-furylcarbene (22), respectively)
Mechanical design and development of TES bolometer detector arrays for the Advanced ACTPol experiment
The next generation Advanced ACTPol (AdvACT) experiment is currently underway
and will consist of four Transition Edge Sensor (TES) bolometer arrays, with
three operating together, totaling ~5800 detectors on the sky. Building on
experience gained with the ACTPol detector arrays, AdvACT will utilize various
new technologies, including 150mm detector wafers equipped with multichroic
pixels, allowing for a more densely packed focal plane. Each set of detectors
includes a feedhorn array of stacked silicon wafers which form a spline profile
leading to each pixel. This is then followed by a waveguide interface plate,
detector wafer, back short cavity plate, and backshort cap. Each array is
housed in a custom designed structure manufactured from high purity copper and
then gold plated. In addition to the detector array assembly, the array package
also encloses cryogenic readout electronics. We present the full mechanical
design of the AdvACT high frequency (HF) detector array package along with a
detailed look at the detector array stack assemblies. This experiment will also
make use of extensive hardware and software previously developed for ACT, which
will be modified to incorporate the new AdvACT instruments. Therefore, we
discuss the integration of all AdvACT arrays with pre-existing ACTPol
infrastructure.Comment: 9 pages, 5 figures, SPIE Astronomical Telescopes and Instrumentation
conference proceeding
Total Synthesis of (±)-Phomoidride D
Described herein is a synthetic strategy for the total synthesis of (±)‐phomoidride D. This highly efficient and stereoselective approach provides rapid assembly of the carbocyclic core by way of a tandem phenolic oxidation/intramolecular Diels–Alder cycloaddition. A subsequent SmI2‐mediated cyclization cascade delivers an isotwistane intermediate poised for a Wharton fragmentation that unveils the requisite bicyclo[4.3.1]decene skeleton and sets the stage for synthesis completion
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