1,365 research outputs found
Motion of a Vortex Filament in the Local Induction Approximation: Reformulation of the Da Rios-Betchov Equations in the Extrinsic Filament Coordinate Space
In recognition of the highly non-trivial task of computation of the inverse
Hasimoto transformation mapping the intrinsic geometric parameter space onto
the extrinsic vortex filament coordinate space a reformulation of the Da
Rios-Betchov equations in the latter space is given. The nonlinear localized
vortex filament structure solution given by the present formulation is in
detailed agreement with the Betchov-Hasimoto solution in the small-amplitude
limit and is also in qualitative agreement with laboratory experiment
observations of helical-twist solitary waves propagating on concentrated
vortices in rotating fluids. The present formulation also provides for a
discernible effect of the slipping motion of a vortex filament on the vortex
evolution
On Exceptional Times for generalized Fleming-Viot Processes with Mutations
If is a standard Fleming-Viot process with constant mutation rate
(in the infinitely many sites model) then it is well known that for each
the measure is purely atomic with infinitely many atoms. However,
Schmuland proved that there is a critical value for the mutation rate under
which almost surely there are exceptional times at which is a
finite sum of weighted Dirac masses. In the present work we discuss the
existence of such exceptional times for the generalized Fleming-Viot processes.
In the case of Beta-Fleming-Viot processes with index we
show that - irrespectively of the mutation rate and - the number of
atoms is almost surely always infinite. The proof combines a Pitman-Yor type
representation with a disintegration formula, Lamperti's transformation for
self-similar processes and covering results for Poisson point processes
Experimental and Theoretical Investigation of Recombination Pumped X-ray Lasers Driven by High-Intensity, Short Pulse Lasers
We have experimentally investigated a recombination-pumped soft-x-ray laser on a Lyman-α transition (135 Å) of hydrogenlike lithium. Furthermore, we have modeled the dynamics of this system, including the effects of the multipeaked electron distribution function that is obtained from the sequential, optical-field ionization of an atom. We compare the predictions of our model and our experimental results
Social group size affects Mycobacterium bovis infection in European badgers (Meles meles)
1. In most social animals, the prevalence of directly transmitted pathogens increases in larger groups and at higher population densities. Such patterns are predicted by models of Mycobacterium bovis infection in European badgers (Meles meles). 2. We investigated the relationship between badger abundance and M. bovis prevalence, using data on 2696 adult badgers in 10 populations sampled at the start of the Randomized Badger Culling Trial. 3. M. bovis prevalence was consistently higher at low badger densities and in small social groups. M. bovis prevalence was also higher among badgers whose genetic profiles suggested that they had immigrated into their assigned social groups. 4. The association between high M. bovis prevalence and small badger group size appeared not to have been caused by previous small-scale culling in study areas, which had been suspended, on average, 5 years before the start of the current study. 5. The observed pattern of prevalence might occur through badgers in smaller groups interacting more frequently with members of neighbouring groups; detailed behavioural data are needed to test this hypothesis. Likewise, longitudinal data are needed to determine whether the size of infected groups might be suppressed by disease-related mortality. 6. Although M. bovis prevalence was lower at high population densities, the absolute number of infected badgers was higher. However, this does not necessarily mean that the risk of M. bovis transmission to cattle is highest at high badger densities, since transmission risk depends on badger behaviour as well as on badger density
Options for early breast cancer follow-up in primary and secondary care : a systematic review
Background
Both incidence of breast cancer and survival have increased in recent years and there is a need to review follow up strategies. This study aims to assess the evidence for benefits of follow-up in different settings for women who have had treatment for early breast cancer.
Method
A systematic review to identify key criteria for follow up and then address research questions. Key criteria were: 1) Risk of second breast cancer over time - incidence compared to general population. 2) Incidence and method of detection of local recurrence and second ipsi and contra-lateral breast cancer. 3) Level 1–4 evidence of the benefits of hospital or alternative setting follow-up for survival and well-being. Data sources to identify criteria were MEDLINE, EMBASE, AMED, CINAHL, PSYCHINFO, ZETOC, Health Management Information Consortium, Science Direct. For the systematic review to address research questions searches were performed using MEDLINE (2011). Studies included were population studies using cancer registry data for incidence of new cancers, cohort studies with long term follow up for recurrence and detection of new primaries and RCTs not restricted to special populations for trials of alternative follow up and lifestyle interventions.
Results
Women who have had breast cancer have an increased risk of a second primary breast cancer for at least 20 years compared to the general population. Mammographically detected local recurrences or those detected by women themselves gave better survival than those detected by clinical examination. Follow up in alternative settings to the specialist clinic is acceptable to women but trials are underpowered for survival.
Conclusions
Long term support, surveillance mammography and fast access to medical treatment at point of need may be better than hospital based surveillance limited to five years but further large, randomised controlled trials are needed
Contrasting reservoirs for Schistosoma japonicum between marshland and hilly regions in Anhui, China--a two-year longitudinal parasitological survey.
Schistosoma japonicum remains highly endemic in many counties in China and has recently re-emerged, to a large extent, in previously controlled areas. To test the hypothesis that small rodents and less agriculturally important domestic animals such as dogs and cats may play an important role in the transmission and potential re-emergence of this disease, an annual investigation of S. japonicum among humans, domestic animals and rodents, combined with detailed surveys of the snail intermediate host, was performed across 3 marshland villages and 3 hilly villages in Anhui province of China over 2 consecutive years. The highest infection prevalence and intensity observed across all mammals was in rodents in the hilly region; while in the marshland, bovines were suspected as the main reservoirs. However, relatively high infection prevalence levels were also found in dogs and cats in both regions. Such results may have implications for the current human- and bovine-oriented control policy for this medically and veterinarily important disease, particularly within the hilly regions of mainland China
Perceived Effectiveness, Cost, and Availability of Patient Education Methods and Materials
To determine the efficacy of and need for patient education methods and media, a needs assessment was sent to 816 members of the American Association of Diabetes Educators. Respondents (n=325, 40%) included 62% RNs, 36% RDs, 1% other; 62% CDEs. Their mean number of years experience in diabetes education was 8.5, and 99% routinely provided patient education. Respondents indicated that videotapes and slide tapes were the most educationally effective media and books and audiotapes were the least effective. Booklets and videotapes were the most cost-effective and computer-assisted instruction the least effective. While respondents perceived one-to-one counseling, skills training, and diabetes content sessions to be the three most educationally effective methods, support groups and large and small discussion groups were seen as the three most cost-effective educational methods. Among nine potential barriers to quality patient education listed, educators rated lack of third-party reimbursement as a major barrier most frequently and national availability of quality education materials as a barrier least frequently.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68739/2/10.1177_014572179201800207.pd
The sensitivity of the vortex filament method to different reconnection models
We present a detailed analysis on the effect of using different algorithms to
model the reconnection of vortices in quantum turbulence, using the
thin-filament approach. We examine differences between four main algorithms for
the case of turbulence driven by a counterflow. In calculating the velocity
field we use both the local induction approximation (LIA) and the full
Biot-Savart integral. We show that results of Biot-Savart simulations are not
sensitive to the particular reconnection method used, but LIA results are.Comment: 9 pages, 9 figure
Tree method for quantum vortex dynamics
We present a numerical method to compute the evolution of vortex filaments in
superfluid helium. The method is based on a tree algorithm which considerably
speeds up the calculation of Biot-Savart integrals. We show that the
computational cost scales as Nlog{(N) rather than N squared, where is the
number of discretization points. We test the method and its properties for a
variety of vortex configurations, ranging from simple vortex rings to a
counterflow vortex tangle, and compare results against the Local Induction
Approximation and the exact Biot-Savart law.Comment: 12 pages, 10 figure
Mating system of the Eurasian badger, Meles meles, in a high density population
Badgers are facultatively social, forming large groups at high density. Group-living appears
to have high reproductive costs for females, and may lead to increased levels of inbreeding.
The extent of female competition for reproduction has been estimated from field data, but
knowledge of male reproductive success and the extent of extra-group paternity remains
limited. Combining field data with genetic data (16 microsatellite loci), we studied the mating
system of 10 badger social groups across 14 years in a high-density population. From 923
badgers, including 425 cubs, we were able to assign maternity to 307 cubs, with both parents
assigned to 199 cubs (47%) with 80% confidence, and 14% with 95% confidence. Age had a
significant effect on the probability of reproduction, seemingly as a result of a deficit of
individuals aged two years and greater than eight years attaining parentage. We estimate
that approximately 30% of the female population successfully reproduced in any given
year, with a similar proportion of the male population gaining paternity across the same
area. While it was known there was a cost to female reproduction in high density populations,
it appears that males suffer similar, but not greater, costs. Roughly half of assigned paternity
was attributed to extra-group males, the majority of which were from neighbouring social
groups. Few successful matings occurred between individuals born in the same social group
(22%). The high rate of extra-group mating, previously unquantified, may help reduce inbreeding,
potentially making philopatry a less costly strategy
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