1,963 research outputs found
Matrix Product State applications for the ALPS project
The density-matrix renormalization group method has become a standard
computational approach to the low-energy physics as well as dynamics of
low-dimensional quantum systems. In this paper, we present a new set of
applications, available as part of the ALPS package, that provide an efficient
and flexible implementation of these methods based on a matrix-product state
(MPS) representation. Our applications implement, within the same framework,
algorithms to variationally find the ground state and low-lying excited states
as well as simulate the time evolution of arbitrary one-dimensional and
two-dimensional models. Implementing the conservation of quantum numbers for
generic Abelian symmetries, we achieve performance competitive with the best
codes in the community. Example results are provided for (i) a model of
itinerant fermions in one dimension and (ii) a model of quantum magnetism.Comment: 11+5 pages, 8 figures, 2 example
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Bayesian retrieval of complete posterior PDFs of oceanic rain rate from microwave observations
A new Bayesian algorithm for retrieving surface rain rate from Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) over the ocean is presented, along with validations against estimates from the TRMM Precipitation Radar (PR). The Bayesian approach offers a rigorous basis for optimally combining multichannel observations with prior knowledge. While other rain-rate algorithms have been published that are based at least partly on Bayesian reasoning, this is believed to be the first self-contained algorithm that fully exploits Bayes’s theorem to yield not just a single rain rate, but rather a continuous posterior probability distribution of rain rate. To advance the understanding of theoretical benefits of the Bayesian approach, sensitivity analyses have been conducted based on two synthetic datasets for which the “true” conditional and prior distribution are known. Results demonstrate that even when the prior and conditional likelihoods are specified perfectly, biased retrievals may occur at high rain rates. This bias is not the result of a defect of the Bayesian formalism, but rather represents the expected outcome when the physical constraint imposed by the radiometric observations is weak owing to saturation effects. It is also suggested that both the choice of the estimators and the prior information are crucial to the retrieval. In addition, the performance of the Bayesian algorithm herein is found to be comparable to that of other benchmark algorithms in real-world applications, while having the additional advantage of providing a complete continuous posterior probability distribution of surface rain rate
Freeze protection in gasholders
In cold weather, the water seals of gasholders need protection from freezing to avoid compromising the seal. These holders have a large reservoir of "tank water" at the base which is below ground. At present freeze-protection is achieved by external heating of the seal water which is in a slotted channel called a cup. Electrical heating or circulation of heated tank water to the cup are examples of systems presently used.
The tank water has a large thermal capacity and National Grid wishes to investigate whether circulation of the tank water without external heating could provide sufficient energy input to avoid freezing. Only tanks in which the tank water is below ground are investigated in the report. The soil temperature under the reservoir at depth of 10m and lower is almost constant
Feedback Control Goes Wireless: Guaranteed Stability over Low-power Multi-hop Networks
Closing feedback loops fast and over long distances is key to emerging
applications; for example, robot motion control and swarm coordination require
update intervals of tens of milliseconds. Low-power wireless technology is
preferred for its low cost, small form factor, and flexibility, especially if
the devices support multi-hop communication. So far, however, feedback control
over wireless multi-hop networks has only been shown for update intervals on
the order of seconds. This paper presents a wireless embedded system that tames
imperfections impairing control performance (e.g., jitter and message loss),
and a control design that exploits the essential properties of this system to
provably guarantee closed-loop stability for physical processes with linear
time-invariant dynamics. Using experiments on a cyber-physical testbed with 20
wireless nodes and multiple cart-pole systems, we are the first to demonstrate
and evaluate feedback control and coordination over wireless multi-hop networks
for update intervals of 20 to 50 milliseconds.Comment: Accepted final version to appear in: 10th ACM/IEEE International
Conference on Cyber-Physical Systems (with CPS-IoT Week 2019) (ICCPS '19),
April 16--18, 2019, Montreal, QC, Canad
Before the Flood: Impact of Coordination of Care and Direct Admissions on Emergency Department Volumes
Background: Transfers of pediatric patients occur to access specialty and subspecialty care, but incur risk, and consume resources. Direct admissions to medical and surgical wards may improve patient experience and mitigate resource utilization.
Objective: We sought to identify common elements for direct admissions, as well as the pattern of disposition for patients referred to our emergency department (ED).
Design: A retrospective qualitative analysis of patients transferred to our pediatric hospital for 12 months was performed. Different physician groups were evaluated for use of direct admissions or evaluation in the ED. Patients referred to the ED were additionally tracked to evaluate their eventual disposition.
Results: A total of 3982 transfers occurred during the 12-month analysis period. Of those, 3463 resulted in admission, accounting for 32.55% of all admissions. Transfers accepted by nonsurgical services accounted for 82% of the transfers, whereas 18% were facilitated by one of the surgical services. Direct admissions accounted for 1707 (44.8%) of all referrals and were used more often by nonsurgical services. Of patients referred to the ED (2101 or 55.2% of all referrals), most patients were admitted and 343 (16% of those referred to the ED) were discharged home.
Conclusions: The direct admission process helped avoid ED assessments for some patients; however, some patients referred to the ED were able to be evaluated, treated, and discharged. Consistent triage of the patients being transferred as direct admissions may improve ED throughput and potentially improve the patient's experience, reduce redundant services, and expedite care
Lack of self-averaging in neutral evolution of proteins
We simulate neutral evolution of proteins imposing conservation of the
thermodynamic stability of the native state in the framework of an effective
model of folding thermodynamics. This procedure generates evolutionary
trajectories in sequence space which share two universal features for all of
the examined proteins. First, the number of neutral mutations fluctuates
broadly from one sequence to another, leading to a non-Poissonian substitution
process. Second, the number of neutral mutations displays strong correlations
along the trajectory, thus causing the breakdown of self-averaging of the
resulting evolutionary substitution process.Comment: 4 pages, 2 figure
Gentamicin induces LAMB3 nonsense mutation readthrough and restores functional laminin 332 in junctional epidermolysis bullosa
Herlitz junctional epidermolysis bullosa (H-JEB) is an incurable, devastating, and mostly fatal inherited skin disease for which there is only supportive care. H-JEB is caused by loss-of-function mutations in LAMA3, LAMB3, or LAMC2, leading to complete loss of laminin 332, the major component of anchoring filaments, which mediate epidermal-dermal adherence. LAMB3 (laminin \u3b23) mutations account for 80% of patients with H-JEB, and 3c95% of H-JEB\u2013associated LAMB3 mutations are nonsense mutations leading to premature termination codons (PTCs). In this study, we evaluated the ability of gentamicin to induce PTC readthrough in H-JEB laminin \u3b23-null keratinocytes transfected with expression vectors encoding eight different LAMB3 nonsense mutations. We found that gentamicin induced PTC readthrough in all eight nonsense mutations tested. We next used lentiviral vectors to generate stably transduced H-JEB cells with the R635X and C290X nonsense mutations. Incubation of these cell lines with various concentrations of gentamicin resulted in the synthesis and secretion of full-length laminin \u3b23 in a dose-dependent and sustained manner. Importantly, the gentamicin-induced laminin \u3b23 led to the restoration of laminin 332 assembly, secretion, and deposition within the dermal/epidermal junction, as well as proper polarization of \u3b16\u3b24 integrin in basal keratinocytes, as assessed by immunoblot analysis, immunofluorescent microscopy, and an in vitro 3D skin equivalent model. Finally, newly restored laminin 332 corrected the abnormal cellular phenotype of H-JEB cells by reversing abnormal cell morphology, poor growth potential, poor cell-substratum adhesion, and hypermotility. Therefore, gentamicin may offer a therapy for H-JEB and other inherited skin diseases caused by PTC mutations
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