6,347 research outputs found
Nucleation at the DNA supercoiling transition
Twisting DNA under a constant applied force reveals a thermally activated
transition into a state with a supercoiled structure known as a plectoneme.
Using transition state theory, we predict the rate of this plectoneme
nucleation to be of order 10^4 Hz. We reconcile this with experiments that have
measured hopping rates of order 10 Hz by noting that the viscosity of the bead
used to manipulate the DNA limits the measured rate. We find that the intrinsic
bending caused by disorder in the base-pair sequence is important for
understanding the free energy barrier that governs the transition. Both
analytic and numerical methods are used in the calculations. We provide
extensive details on the numerical methods for simulating the elastic rod model
with and without disorder.Comment: 18 pages, 15 figure
Power-law carrier dynamics in semiconductor nanocrystals at nanosecond time scales
We report the observation of power law dynamics on nanosecond to microsecond
time scales in the fluorescence decay from semiconductor nanocrystals, and draw
a comparison between this behavior and power-law fluorescence blinking from
single nanocrystals. The link is supported by comparison of blinking and
lifetime data measured simultaneously from the same nanocrystal. Our results
reveal that the power law coefficient changes little over the nine decades in
time from 10 ns to 10 s, in contrast with the predictions of some diffusion
based models of power law behavior.Comment: 3 pages, 2 figures, compressed for submission to Applied Physics
Letter
The Contribution of Participatory Research: On-Farm Research
Participatory research in agriculture may range from research and technology development (R&D), carried out on a research station with some involvement of farmers, through to genuine participatory research involving researchers and farmers working together. The latter involves the end-user in actually carrying out aspects of the research and/or in the development and evaluation of technology that is appropriate to commercial enterprises. Researchers often question the validity of the ‘findings of on-farm participatory research’ as they are more comfortable with the ‘controlled’ environment of the research station. However if research is to be applied appropriately on farms, it must go through a period of evaluation on-farm.
This paper summarises perspectives relating to participatory on-farm research, highlighting some opportunities that new technology is providing by considering five key areas as follows:
• Participatory research within the agricultural research enterprise (current situation);
• On-farm research compared with in-station research (options);
• A New Zealand example of on-farm research;
• New opportunities in on-farm research;
• Future models for participatory on-farm research
Priority setting for new technologies in medicine: A transdisciplinary study
BACKGROUND: Decision makers in health care organizations struggle with how to set priorities for new technologies in medicine. Traditional approaches to priority setting for new technologies in medicine are insufficient and there is no widely accepted model that can guide decision makers. DISCUSSION: Daniels and Sabin have developed an ethically based account about how priority setting decisions should be made. We have developed an empirically based account of how priority setting decisions are made. In this paper, we integrate these two accounts into a transdisciplinary model of priority setting for new technologies in medicine that is both ethically and empirically based. SUMMARY: We have developed a transdisciplinary model of priority setting that provides guidance to decision makers that they can operationalize to help address priority setting problems in their institution
Hysterectomy, endometrial destruction, and levonorgestrel releasing intrauterine system (Mirena) for heavy menstrual bleeding : systematic review and meta-analysis of data from individual patients
Peer reviewedPublisher PD
The bio-inspired artificial pancreas for type 1 diabetes control in the home: System architecture and preliminary results
BACKGROUND: Artificial pancreas (AP) technology has been proven to improve glucose and patient-centered outcomes for people with type 1 diabetes (T1D). Several approaches to implement the AP have been described, clinically evaluated, and in one case, commercialized. However, none of these approaches has shown a clear superiority with respect to others. In addition, several challenges still need to be solved before achieving a fully automated AP that fulfills the users' expectations. We have introduced the Bio-inspired Artificial Pancreas (BiAP), a hybrid adaptive closed-loop control system based on beta-cell physiology and implemented directly in hardware to provide an embedded low-power solution in a dedicated handheld device. In coordination with the closed-loop controller, the BiAP system incorporates a novel adaptive bolus calculator which aims at improving postprandial glycemic control. This paper focuses on the latest developments of the BiAP system for its utilization in the home environment. METHODS: The hardware and software architectures of the BiAP system designed to be used in the home environment are described. Then, the clinical trial design proposed to evaluate the BiAP system in an ambulatory setting is introduced. Finally, preliminary results corresponding to two participants enrolled in the trial are presented. RESULTS: Apart from minor technical issues, mainly due to wireless communications between devices, the BiAP system performed well (~88% of the time in closed-loop) during the clinical trials conducted so far. Preliminary results show that the BiAP system might achieve comparable glycemic outcomes to the existing AP systems (~73% time in target range 70-180 mg/dL). CONCLUSION: The BiAP system is a viable platform to conduct ambulatory clinical trials and a potential solution for people with T1D to control their glucose control in a home environment
Phase transition in the modified fiber bundle model
We extend the standard fiber bundle model (FBM) with the local load sharing
in such a way that the conservation of the total load is relaxed when an
isolated fiber is broken. In this modified FBM in one dimension (1D), it is
revealed that the model exhibits a well-defined phase transition at a finite
nonzero value of the load, which is in contrast to the standard 1D FBM. The
modified FBM defined in the Watts-Strogatz network is also investigated, and
found is the existences of two distinct transitions: one discontinuous and the
other continuous. The effects of the long-range shortcuts are also discussed.Comment: 7 pages, to appear in Europhys. Let
New Discoveries from the Arecibo 327 MHz Drift Pulsar Survey Radio Transient Search
We present Clusterrank, a new algorithm for identifying dispersed
astrophysical pulses. Such pulses are commonly detected from Galactic pulsars
and rotating radio transients (RRATs), which are neutron stars with sporadic
radio emission. More recently, isolated, highly dispersed pulses dubbed fast
radio bursts (FRBs) have been identified as the potential signature of an
extragalactic cataclysmic radio source distinct from pulsars and RRATs.
Clusterrank helped us discover 14 pulsars and 8 RRATs in data from the Arecibo
327 MHz Drift Pulsar Survey (AO327). The new RRATs have DMs in the range pc cm and periods in the range s. The new
pulsars have DMs in the range pc cm and periods in the
range s, and include two nullers and a mode-switching object.
We estimate an upper limit on the all-sky FRB rate of day for
bursts with a width of 10 ms and flux density mJy. The DMs of all
new discoveries are consistent with a Galactic origin. In comparing statistics
of the new RRATs with sources from the RRATalog, we find that both sets are
drawn from the same period distribution. In contrast, we find that the period
distribution of the new pulsars is different from the period distributions of
canonical pulsars in the ATNF catalog or pulsars found in AO327 data by a
periodicity search. This indicates that Clusterrank is a powerful complement to
periodicity searches and uncovers a subset of the pulsar population that has so
far been underrepresented in survey results and therefore in Galactic pulsar
population models.Comment: 41 pages, 16 figures, 4 tables, accepted by ApJ; added minor
corrections to final ApJ proo
A quantitative model of trading and price formation in financial markets
We use standard physics techniques to model trading and price formation in a
market under the assumption that order arrival and cancellations are Poisson
random processes. This model makes testable predictions for the most basic
properties of a market, such as the diffusion rate of prices, which is the
standard measure of financial risk, and the spread and price impact functions,
which are the main determinants of transaction cost. Guided by dimensional
analysis, simulation, and mean field theory, we find scaling relations in terms
of order flow rates. We show that even under completely random order flow the
need to store supply and demand to facilitate trading induces anomalous
diffusion and temporal structure in prices.Comment: 5 pages, 4 figure
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