6,457 research outputs found
Evidence for 1122 Hz X-Ray Burst Oscillations from the Neutron-Star X-Ray Transient XTE J1739-285
We report on millisecond variability from the X-ray transient XTE J1739-285.
We detected six X-ray type I bursts and found evidence for oscillations at 1122
+/- 0.3 Hz in the brightest X-ray burst. Taking into consideration the power in
the oscillations and the number of trials in the search, the detection is
significant at the 99.96% confidence level. If the oscillations are confirmed,
the oscillation frequency would suggest that XTE J1739-285 contains the fastest
rotating neutron star yet found. We also found millisecond quasiperiodic
oscillations in the persistent emission with frequencies ranging from 757 Hz to
862 Hz. Using the brightest burst, we derive an upper limit on the source
distance of about 10.6 kpc.Comment: To appear in ApJL, 4 page
Cascaded two-photon nonlinearity in a one-dimensional waveguide with multiple two-level emitters
We propose and theoretically investigate a model to realize cascaded optical
nonlinearity with few atoms and photons in one-dimension (1D). The optical
nonlinearity in our system is mediated by resonant interactions of photons with
two-level emitters, such as atoms or quantum dots in a 1D photonic waveguide.
Multi-photon transmission in the waveguide is nonreciprocal when the emitters
have different transition energies. Our theory provides a clear physical
understanding of the origin of nonreciprocity in the presence of cascaded
nonlinearity. We show how various two-photon nonlinear effects including
spatial attraction and repulsion between photons, background fluorescence can
be tuned by changing the number of emitters and the coupling between emitters
(controlled by the separation).Comment: 6 pages, 4 figure
Implications of differences between recent anthropogenic aerosol emission inventories for diagnosed AOD and radiative forcing from 1990 to 2019
This study focuses on implications of differences between recent global emissions inventories for simulated trends in anthropogenic aerosol abundances and radiative forcing (RF) over the 1990–2019 period. We use the ECLIPSE version 6 (ECLv6) and CEDS year 2021 release (CEDS21) as input to the chemical transport model OsloCTM3 and compare the resulting aerosol evolution to corresponding results derived with the first CEDS release, as well as to observed trends in regional and global aerosol optical depth (AOD). Using CEDS21 and ECLv6 results in a 3 % and 6 % lower global mean AOD compared to CEDS in 2014, primarily driven by differences over China and India, where the area average AOD is up to 30 % lower. These differences are considerably larger than the satellite-derived interannual variability in AOD. A negative linear trend over 2005–2017 in global AOD following changes in anthropogenic emissions is found with all three inventories but is markedly stronger with CEDS21 and ECLv6. Furthermore, we confirm that the model better captures the sign and strength of the observed AOD trend over China with CEDS21 and ECLv6 compared to using CEDS, while the opposite is the case for South Asia. We estimate a net global mean aerosol-induced RF in 2014 relative to 1990 of 0.08 W m−2 for CEDS21 and 0.12 W m−2 for ECLv6, compared to 0.03 W m−2 with CEDS. Using CEDS21, we also estimate the RF in 2019 relative to 1990 to be 0.10 W m−2, reflecting the continuing decreasing trend in aerosol loads post-2014. Our results facilitate more rigorous comparison between existing and upcoming studies of climate and health effects of aerosols using different emission inventories.</p
Low-Bandwidth and Non-Compute Intensive Remote Identification of Microbes from Raw Sequencing Reads
Cheap high-throughput DNA sequencing may soon become routine not only for
human genomes but also for practically anything requiring the identification of
living organisms from their DNA: tracking of infectious agents, control of food
products, bioreactors, or environmental samples.
We propose a novel general approach to the analysis of sequencing data in
which the reference genome does not have to be specified. Using a distributed
architecture we are able to query a remote server for hints about what the
reference might be, transferring a relatively small amount of data, and the
hints can be used for more computationally-demanding work.
Our system consists of a server with known reference DNA indexed, and a
client with raw sequencing reads. The client sends a sample of unidentified
reads, and in return receives a list of matching references known to the
server. Sequences for the references can be retrieved and used for exhaustive
computation on the reads, such as alignment.
To demonstrate this approach we have implemented a web server, indexing tens
of thousands of publicly available genomes and genomic regions from various
organisms and returning lists of matching hits from query sequencing reads. We
have also implemented two clients, one of them running in a web browser, in
order to demonstrate that gigabytes of raw sequencing reads of unknown origin
could be identified without the need to transfer a very large volume of data,
and on modestly powered computing devices.
A web access is available at http://tapir.cbs.dtu.dk. The source code for a
python command-line client, a server, and supplementary data is available at
http://bit.ly/1aURxkc
Demand-Orientated Power Production from Biogas: Modeling and Simulations under Swedish Conditions
The total share of intermittent renewable electricity is increasing, intensifying the need for power balancing in future electricity systems. Demand-orientated combined heat and power (CHP) production from biogas has potential for this purpose. An agricultural biogas plant, using cattle manure and sugar beet for biogas and CHP production, was analyzed here. The model Dynamic Biogas plant Model (DyBiM) was developed and connected to the Anaerobic Digestion Model No. 1 (ADM1). Flexible scenarios were simulated and compared against a reference scenario with continuous production, to evaluate the technical requirements and economic implications of demand-orientated production. The study was set in Swedish conditions regarding electricity and heat price, and the flexibility approaches assessed were increased CHP and gas storage capacity and feeding management. The results showed that larger gas storage capacity was needed for demand-orientated CHP production but that feeding management reduced the storage requirement because of fast biogas production response to feeding. Income from electricity increased by 10%, applying simple electricity production strategies to a doubled CHP capacity. However, as a result of the currently low Swedish diurnal electricity price variation and lack of subsidies for demand-orientated electricity production, the increase in income was too low to cover the investment costs. Nevertheless, DyBiM proved to be a useful modeling tool for assessing the economic outcome of different flexibility scenarios for demand-orientated CHP production
Characterisation of a GroEL Single-Ring Mutant that Supports Growth of Escherichia coli and Has GroES-Dependent ATPase Activity.
Optimal joint measurements of complementary observables by a single trapped ion
The uncertainty relations, pioneered by Werner Heisenberg nearly 90 years ago, set a fundamental limitation on the joint measurability of complementary observables. This limitation has long been a subject of debate, which has been reignited recently due to new proposed forms of measurement uncertainty relations. The present work is associated with a new error trade-off relation for compatible observables approximating two incompatible observables, in keeping with the spirit of Heisenberg's original ideas of 1927. We report the first direct test and confirmation of the tight bounds prescribed by such an error trade-off relation, based on an experimental realisation of optimal joint measurements of complementary observables using a single ultracold 40Ca+ ion trapped in a harmonic potential. Our work provides a prototypical determination of ultimate joint measurement error bounds with potential applications in quantum information science for high-precision measurement and information security
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