2,348 research outputs found
Mono Lake or Laschamp geomagnetic event recorded from lava flows in Amsterdam Island (southeastern Indian Ocean)
We report a survey carried out on basalt flows from Amsterdam Island in order
to check the presence of intermediate directions interpreted to belong to a
geomagnetic field excursion within the Brunhes epoch, completing this
paleomagnetic record with paleointensity determinations and radiometric dating.
The directional results corroborate the findings by Watkins and Nougier (1973)
: normal polarity is found for two units and an intermediate direction, with
associated VGPs close to the equator, for the other two units. A notable result
is that these volcanic rocks are well suited for absolute paleointensity
determinations. Fifty percent of the samples yields reliable intensity values
with high quality factors. An original element of this study is that we made
use of the PTRM-tail test of Shcherbakova et al. (2000) to help in the
interpretation of the paleointensity measurements. Doing thus, only the high
temperature intervals, beyond 400 degres C, were retained to obtain the most
reliable estimate of the strength of the ancient magnetic field. The normal
units yield Virtual Dipole Moments (VDM) of 6.2 and 7.7 10e22 Am2 and the
excursional units yield values of 3.7 and 3.4 10e22 Am2. These results are
quite consistent with the other Thellier determinations from Brunhes excursion
records, all characterized by a decrease of the VDM as VGP latitude decreases.
40Ar/39Ar isotopic age determinations provide an estimate of 26+-15 Kyr and
18+-9 Kyr for the transitional lava flows, which could correspond to the Mono
Lake excursion. However, the large error bars associated with these ages do not
exclude the hypothesis that this event is the Laschamp
Optimized Compilation of Aggregated Instructions for Realistic Quantum Computers
Recent developments in engineering and algorithms have made real-world
applications in quantum computing possible in the near future. Existing quantum
programming languages and compilers use a quantum assembly language composed of
1- and 2-qubit (quantum bit) gates. Quantum compiler frameworks translate this
quantum assembly to electric signals (called control pulses) that implement the
specified computation on specific physical devices. However, there is a
mismatch between the operations defined by the 1- and 2-qubit logical ISA and
their underlying physical implementation, so the current practice of directly
translating logical instructions into control pulses results in inefficient,
high-latency programs. To address this inefficiency, we propose a universal
quantum compilation methodology that aggregates multiple logical operations
into larger units that manipulate up to 10 qubits at a time. Our methodology
then optimizes these aggregates by (1) finding commutative intermediate
operations that result in more efficient schedules and (2) creating custom
control pulses optimized for the aggregate (instead of individual 1- and
2-qubit operations). Compared to the standard gate-based compilation, the
proposed approach realizes a deeper vertical integration of high-level quantum
software and low-level, physical quantum hardware. We evaluate our approach on
important near-term quantum applications on simulations of superconducting
quantum architectures. Our proposed approach provides a mean speedup of
, with a maximum of . Because latency directly affects the
feasibility of quantum computation, our results not only improve performance
but also have the potential to enable quantum computation sooner than otherwise
possible.Comment: 13 pages, to apper in ASPLO
Metamagnetism and soliton excitations in the modulated ferromagnetic Ising chain CoV2O6
We report a combination of physical property and neutron scattering
measurements for polycrystalline samples of the one-dimensional spin chain
compound CoV2O6. Heat capacity measurements show that an effective S = 1/2
state is found at low temperatures and that magnetic fluctuations persist up to
6.Tn. Above Tn = 6.3 K, measurements of the magnetic susceptibility as a
function of T and H show that the nearest neighbour exchange is ferromagnetic.
In the ordered state, we have discovered a crossover from a metamagnet with
strong fluctuations between 5 K and Tn to a state with a 1/3 magnetisation
plateau at 2 < T < 5 K. We use neutron powder diffraction measurements to show
that the AFM state has incommensurate long range order and inelastic time of
flight neutron scattering to examine the magnetic fluctuations as a function of
temperature. Above Tn, we find two broad bands between 3.5 and 5 meV and
thermally activated low energy features which correspond to transitions within
these bands. These features show that the excitations are deconfined solitons
rather than the static spin reversals predicted for a uniform FM Ising spin
chain. Below Tn, we find a ladder of states due to the confining effect of the
internal field. A region of weak confinement below Tn, but above 5 K, is
identified which may correspond to a crossover between 2D and 3D magnetic
ordering.Comment: Expanded version, includes results from arXiv:0804.2966 and neutron
powder diffraction. To appear in PR
RANKL-independent osteoclastogenesis in the SH3BP2 cherubism mice
Even though the receptor activator of the nuclear factor-κB ligand (RANKL) and its receptor RANK have an exclusive role in osteoclastogenesis, the possibility of RANKL/RANK-independent osteoclastogenesis has been the subject of a long-standing debate in bone biology. In contrast, it has been reported that calvarial injection of TNF-ɑ elicits significant osteoclastogenesis in the absence of RANKL/RANK in NF-κB2- and RBP-J-deficient mice, suggesting that inflammatory challenges and secondary gene manipulation are the prerequisites for RANKL/RANK-deficient mice to develop osteoclasts in vivo. Here we report that, even in the absence of RANKL (Rankl−/−), cherubism mice (Sh3bp2KI/KI) harboring the homozygous gain-of-function mutation in SH3-domain binding protein 2 (SH3BP2) develop tartrate-resistant acid phosphatase (TRAP)-positive multinucleated osteoclasts spontaneously. The Sh3bp2KI/KIRankl−/− mice exhibit an increase in tooth exposure and a decrease in bone volume/total volume compared to Sh3bp2+/+Rankl−/− mice. The multinucleated cells were stained positively for cathepsin K. Osteoclastic marker gene expression in bone and serum TRAP5b levels were elevated in Sh3bp2KI/KIRankl−/− mice. Elevation of the serum TNF-ɑ levels suggested that TNF-ɑ is a driver for the RANKL-independent osteoclast formation in Sh3bp2KI/KI mice. Our results provide a novel mutant model that develops osteoclasts independent of RANKL and establish that the gain-of-function of SH3BP2 promotes osteoclastogenesis not only in the presence of RANKL but also in the absence of RANKL
trans-4-(2-Amino-5-bromo-6-methylpyrimidin-4-ylamino)-1-methylcyclohexanol
The title compound, C12H19BrN4O, represents the minor component of the two products obtained in a series of transformations involving the Grignard reaction of tert-butoxycarbonyl-protected 4-aminocyclohexanone with MeMgBr, and subsequent interaction of the obtained amino-substituted cyclohexanol with 4-chloro-6-methylpyrimidin-2-amine followed by bromination with N-bromosuccinimide. The X-ray structure showed that this product represents a trans isomer with respect to the amino and hydroxy substituents in the cyclohexyl ring; the dihedral angle between the aminopyrimidine plane and the (noncrystallographic) mirror plane of the substituted cyclohexyl fragment is 33.6 (3)°. Only two of the four potentially ‘active’ H atoms participate in intermolecular N—H⋯O and O—H⋯N hydrogen bonds, linking the molecules into layers parallel to the (10) plane
Association between celiac sprue and cryopyrin associated autoinflammatory disorders: a case report
Cryopyrin-associated diseases may be characterized by rashes, fever, and sensorineural deafness, while celiac disease may present with symptoms of malabsorption and fatigue. Arthritis is seen in both conditions. We report a young child with histologically diagnosed celiac disease and a cryopyrinopathy
Human papillomavirus, p16 and p53 expression associated with survival of head and neck cancer
BACKGROUND: P16 and p53 protein expression, and high-risk human papillomavirus (HPV-HR) types have been associated with survival in head and neck cancer (HNC). Evidence suggests that multiple molecular pathways need to be targeted to improve the poor prognosis of HNC. This study examined the individual and joint effects of tumor markers for differences in predicting HNC survival. P16 and p53 expression were detected from formalin-fixed, paraffin-embedded tissues by immunohistochemical staining. HPV DNA was detected by PCR and DNA sequencing in 237 histologically confirmed HNC patients. RESULTS: Overexpression of p16 (p16+) and p53 (p53+) occurred in 38% and 48% of HNC tumors, respectively. HPV-HR was detected in 28% of tumors. Worse prognosis was found in tumors that were p53+ (disease-specific mortality: adjusted hazard ratios, HR = 1.9, 95% CI: 1.04-3.4) or HPV- (overall survival: adj. HR = 2.1, 1.1-4.3) but no association in survival was found by p16 status. Compared to the molecular marker group with the best prognosis (p16+/p53-/HPV-HR: referent), the p16-/p53+/HPV- group had the lowest overall survival (84% vs. 60%, p < 0.01; HR = 4.1, 1.7-9.9) and disease-specific survival (86% vs. 66%, p < 0.01; HR = 4.0, 1.5-10.7). Compared to the referent, the HRs of the other six joint biomarker groups ranged from 1.6-3.4 for overall mortality and 0.9-3.9 for disease-specific mortality. CONCLUSION: The p16/p53/HPV joint groups showed greater distinction in clinical outcomes compared to results based on the individual biomarkers alone. This finding suggests that assessing multiple molecular markers in HNC patients will better predict the diverse outcomes and potentially the type of treatment targeted to those markers
Platform Development for the Implementation and Testing of New Swarming Strategies
Gemstone Team SWARM-AISwarm robotics--the use of multiple autonomous robots in coordination to accomplish a
task--is useful for mapping, light package transport, and search and rescue operations,
among other applications. Researchers and industry professionals have developed robotic
swarm mechanisms to accomplish these tasks. Some of those mechanisms or “strategies”
have been tested on hardware; however, the technical requirements involved in fielding a
drone swarm can be prohibitive to physical testing. Team SWARM-AI has developed a
platform that provides a starting point for testing new swarming strategies. This platform
allows the user to select vehicles of their choosing- either air, land, or water based, or
some combination thereof- as well as define their own swarming method. Using a novel
decentralized approach to ground control software, this platform provides a user interface
and a system of computational “units” to coordinate drone swarms with a centralized,
decentralized, or combination architecture. Additionally, the platform propagates user
input from the master unit to the rest of the swarm and allows each unit to request sensor
data from other units. The user is free to edit the processes by which each drone interacts
with the environment and the rest of the swarm, giving them freedom to test their
swarming strategy. The software system is then tested with a swarm of quadcopters using
Software in the Loop (SITL) testing
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