14,270 research outputs found
Universal Scaling of Optimal Current Distribution in Transportation Networks
Transportation networks are inevitably selected with reference to their
global cost which depends on the strengths and the distribution of the embedded
currents. We prove that optimal current distributions for a uniformly injected
d-dimensional network exhibit robust scale-invariance properties, independently
of the particular cost function considered, as long as it is convex. We find
that, in the limit of large currents, the distribution decays as a power law
with an exponent equal to (2d-1)/(d-1). The current distribution can be exactly
calculated in d=2 for all values of the current. Numerical simulations further
suggest that the scaling properties remain unchanged for both random injections
and by randomizing the convex cost functions.Comment: 5 pages, 5 figure
THE SYMMETRY ANGLE IDENTIFIES LESS CLINICALLY RELEVANT INTER-LIMB ASYMMETRIES THAN THE SYMMETRY INDEX IN HEALTHY ADULTS
There are several methods for calculating inter-limb symmetry, an inter-limb difference ā„15% has been suggested as an indicator of sporting injury risk. The purpose of this study was to compare three common methods for determining symmetry: the Symmetry Index (percentage difference; SI) when referenced to the left limb (SILeft) or the average of both limbs (SIAverage), and the Symmetry Angle (vector difference; SA). 15 recreationally active participants completed a sprint protocol on a non-motorised treadmill. Accelerometers were positioned on both tibias to measure peak resultant acceleration (PRA). The SA identified less clinically relevant PRA inter-limb asymmetries than the SI in healthy adults. Once an appropriate level of asymmetry as measured by the SA is determined, this may help to more correctly identify asymmetry in athletes and patients than the SI
Deep brain stimulation can suppress pathological synchronisation in parkinsonian patients
Background Although deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a highly effective therapeutic intervention in severe Parkinson's disease, its mechanism of action remains unclear. One possibility is that DBS suppresses local pathologically synchronised oscillatory activity.Methods To explore this, the authors recorded from DBS electrodes implanted in the STN of 16 patients with Parkinson's disease during simultaneous stimulation (pulse width 60 mu s; frequency 130 Hz) of the same target using a specially designed amplifier. The authors analysed data from 25 sides.Results The authors found that DBS progressively suppressed peaks in local field potential activity at frequencies between 11 and 30 Hz as voltage was increased beyond a stimulation threshold of 1.5 V. Median peak power had fallen to 54% of baseline values by a stimulation intensity of 3.0 V.Conclusion The findings suggest that DBS can suppress pathological 11-30 Hz activity in the vicinity of stimulation in patients with Parkinson's disease. This suppression occurs at stimulation voltages that are clinically effective
Periodic Bursts of Coherent Radio Emission from an Ultracool Dwarf
We report the detection of periodic (p = 1.96 hours) bursts of extremely
bright, 100% circularly polarized, coherent radio emission from the M9 dwarf
TVLM 513-46546. Simultaneous photometric monitoring observations have
established this periodicity to be the rotation period of the dwarf. These
bursts, which were not present in previous observations of this target, confirm
that ultracool dwarfs can generate persistent levels of broadband, coherent
radio emission, associated with the presence of kG magnetic fields in a
large-scale, stable configuration. Compact sources located at the magnetic
polar regions produce highly beamed emission generated by the electron
cyclotron maser instability, the same mechanism known to generate planetary
coherent radio emission in our solar system. The narrow beams of radiation pass
our line of sight as the dwarf rotates, producing the associated periodic
bursts. The resulting radio light curves are analogous to the periodic light
curves associated with pulsar radio emission highlighting TVLM 513-46546 as the
prototype of a new class of transient radio source.Comment: 12 pages, 3 figures, accepted for publication in ApJ Letter
CP Violation beyond the Standard Model
In this talk a number of broad issues are raised about the origins of CP
violation and how to test the ideas.Comment: 17 pages, LaTeX, 6 postscript figures. Uses iopart10.clo,
iopart12.clo and iopart.cls. Plenary talk given at the BSM Phenomenology
Workshop, Durham, UK, 6-11 May 2001. To appear in the proceeding
Jellyfish Impacts on Marine Aquaculture and Fisheries
Over the last 50 years there has been an increased frequency and severity of negative impacts affecting marine fishery and aquaculture sectors, which claimed significant economic losses due to the interference of stinging gelatinous organisms with daily operational activities. Nevertheless, original scientific information on jellyfish-related incidents, their consequences, and potential preventative and mitigation countermeasures is limited and scattered across gray literature, governmental technical reports, and communication media. A literature scan searching for records of any interactions between jellyfish and the marine fishery/aquaculture sectors was carried out. Out of 553 papers, 90 contained original information, referring to more than 130 cases worldwide of negative impacts of jellyfish on marine fishery/aquaculture over the last century. Calling attention on too often neglected socio-economic and ecological impacts of jellyfish blooms, the purpose of this paper is to review and analyze the most up-to-date research on this subject and to provide a global perspective on the importance of jellyfish impacts and their cascading effects on marine fishery and aquaculture sectors
Dosimetric Comparison of VMAT, IMRT and Proton Therapy for Post- Prostatectomy Radiation Therapy for Prostate Cancer
Purpose/Objectives: Radiation therapy (RT) for the treatment of prostate cancer after radical prostatectomy (RP) is widely accepted. With technological advances, radiation treatment technique and dosimetry may vary. The purpose of this study is to quantify dosimetric difference of proton therapy versus VMAT and IMRT focusing on bladder and rectal dose sparing and target coverage.
American Society for Therapeutic Radiation Oncology (ASTRO) 52nd Annual Meeting October 31 - November 4, San Diego, C
Stretching of polymers in a random three-dimensional flow
Behavior of a dilute polymer solution in a random three-dimensional flow with
an average shear is studied experimentally. Polymer contribution to the shear
stress is found to be more than two orders of magnitude higher than in a
laminar shear flow. The results indicate that the polymer molecules get
strongly stretched by the random motion of the fluid.Comment: 4 pages, 3 figure
- ā¦