17,366 research outputs found
Diffusion-controlled phase growth on dislocations
We treat the problem of diffusion of solute atoms around screw dislocations.
In particular, we express and solve the diffusion equation, in radial symmetry,
in an elastic field of a screw dislocation subject to the flux conservation
boundary condition at the interface of a new phase. We consider an incoherent
second-phase precipitate growing under the action of the stress field of a
screw dislocation. The second-phase growth rate as a function of the
supersaturation and a strain energy parameter is evaluated in spatial
dimensions d=2 and d=3. Our calculations show that an increase in the amplitude
of dislocation force, e.g. the magnitude of the Burgers vector, enhances the
second-phase growth in an alloy. Moreover, a relationship linking the
supersaturation to the precipitate size in the presence of the elastic field of
dislocation is calculated.Comment: 10 pages, 4 figures, a revised version of the paper presented in
MS&T'08, October 5-9, 2008, Pittsburg
Mesoscopic structure conditions the emergence of cooperation on social networks
We study the evolutionary Prisoner's Dilemma on two social networks obtained
from actual relational data. We find very different cooperation levels on each
of them that can not be easily understood in terms of global statistical
properties of both networks. We claim that the result can be understood at the
mesoscopic scale, by studying the community structure of the networks. We
explain the dependence of the cooperation level on the temptation parameter in
terms of the internal structure of the communities and their interconnections.
We then test our results on community-structured, specifically designed
artificial networks, finding perfect agreement with the observations in the
real networks. Our results support the conclusion that studies of evolutionary
games on model networks and their interpretation in terms of global properties
may not be sufficient to study specific, real social systems. In addition, the
community perspective may be helpful to interpret the origin and behavior of
existing networks as well as to design structures that show resilient
cooperative behavior.Comment: Largely improved version, includes an artificial network model that
fully confirms the explanation of the results in terms of inter- and
intra-community structur
Mystical orientation and the perceiving process : a study among Anglican clergymen
This study examines the hypothesised link between mystical orientation and the perceiving process within the Jungian model of psychological type. Data were provided by 232 Anglican clergymen serving in the Church in Wales who completed both the Francis-Louden Mystical Orientation Scale and the Francis Psychological Type Scales. The data demonstrated that intuitive types recorded significantly higher scores than sensing types on the index of mystical orientation, supporting the hypothesis based on Ross' thesis
Dynamic selective switching in antiferromagnetically-coupled bilayers close to the spin reorientation transition
We have designed a bilayer synthetic antiferromagnet where the order of layer reversal can be selected by varying the sweep rate of the applied magnetic field. The system is formed by two ultra-thin ferromagnetic layers with different proximities to the spin reorientation transition, coupled antiferromagnetically using Ruderman-Kittel-Kasuya-Yosida interactions. The different dynamic magnetic reversal behavior of both layers produces a crossover in their switching fields for field rates in the kOe/s range. This effect is due to the different effective anisotropy of both layers, added to an appropriate asymmetric antiferromagnetic coupling between them. Field-rate controlled selective switching of perpendicular magnetic anisotropy layers as shown here can be exploited in sensing and memory applications.Copyright (2014) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters (volume 105: 092408) and may be found at http://scitation.aip.org/content/aip/journal/apl/105/9/10.1063/1.4895032
Interdependent network reciprocity in evolutionary games
Besides the structure of interactions within networks, also the interactions between networks are of the outmost
importance. We therefore study the outcome of the public goods game on two interdependent networks that are
connected by means of a utility function, which determines how payoffs on both networks jointly influence the
success of players in each individual network. We show that an unbiased coupling allows the spontaneous
emergence of interdependent network reciprocity, which is capable to maintain healthy levels of public
cooperation even in extremely adverse conditions. The mechanism, however, requires simultaneous formation of
correlated cooperator clusters on both networks. If this does not emerge or if the coordination process is
disturbed, network reciprocity fails, resulting in the total collapse of cooperation. Network interdependence can
thus be exploited effectively to promote cooperation past the limits imposed by isolated networks, but only if the
coordination between the interdependent networks is not disturbe
Characterisation of pulmonary function trajectories: results from a Brazilian cohort.
Background: Pulmonary function (PF) trajectories are determined by different exposures throughout the life course. The aim of this study was to investigate characteristics related to PF trajectories from 15 to 22 years in a Brazilian cohort. Methods: A birth cohort study (1993 Pelotas Birth Cohort) was conducted with spirometry at 15, 18 and 22 years. PF trajectories were built based on z-score of forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC) and their ratio using a group-based trajectory model. Associations with exposures reported from perinatal to 22 years were described. Results: Three trajectories, low (LT), average (AT) and high (HT) were identified in 2917 individuals. Wealthiest individuals belonged to the HT of FEV1 (p=0.023). Lower maternal pregestational body mass index (BMI) (22.4±0.2; p<0.001 and 22.1±0.14; p<0.001) and lower birth weight (3164.8±25.4; p=0.029 and 3132.3±19.4; p=0.005) were related to the LT of FEV1 and FVC. Mother's smoking exposure during pregnancy (37.7%; p=0.002), active smoking at ages 18 and 22 years (20.1% and 25.8%; p<0.001) and family history of asthma (44.8%; p<0.001) were related to the LT of FEV1/FVC. Wheezing, asthma and hospitalisations due to respiratory diseases in childhood were related to the LT of both FEV1 and FEV1/FVC. Higher BMIs were related to the HT of FEV1 and FVC at all ages. Conclusions: PF trajectories were mainly related to income, pregestational BMI, birth weight, hospitalisation due to respiratory diseases in childhood, participant's BMI, report of wheezing, medical diagnosis and family history of asthma, gestational exposure to tobacco and current smoking status in adolescence and young adult age
Optimal interdependence between networks for the evolution of cooperation
Recent research has identified interactions between networks as crucial for the outcome of evolutionary
games taking place on them. While the consensus is that interdependence does promote cooperation by
means of organizational complexity and enhanced reciprocity that is out of reach on isolated networks, we
here address the question just how much interdependence there should be. Intuitively, one might assume
the more the better. However, we show that in fact only an intermediate density of sufficiently strong
interactions between networks warrants an optimal resolution of social dilemmas. This is due to an intricate
interplay between the heterogeneity that causes an asymmetric strategy flow because of the additional links
between the networks, and the independent formation of cooperative patterns on each individual network.
Presented results are robust to variations of the strategy updating rule, the topology of interdependent
networks, and the governing social dilemma, thus suggesting a high degree of universality
Accretion Processes for General Spherically Symmetric Compact Objects
We investigate the accretion process for different spherically symmetric
space-time geometries for a static fluid. We analyse this procedure using the
most general black hole metric ansatz. After that, we examine the accretion
process for specific spherically symmetric metrics obtaining the velocity of
the sound during the process and the critical speed of the flow of the fluid
around the black hole. In addition, we study the behaviour of the rate of
change of the mass for each chosen metric for a barotropic fluid.Comment: 10 pages, 15 figures, v2 accepted for publication in 'European
Physical Journal C
Sister Mary Joseph's Nodule at a University Teaching Hospital in Northwestern Tanzania: A Retrospective Review of 34 cases.
Sister Mary Joseph's nodule is a metastatic tumor deposit in the umbilicus and often represents advanced intra-abdominal malignancy with dismal prognosis. There is a paucity of published data on this subject in our setting. This study was conducted to describe the clinicopathological presentation and treatment outcome of this condition in our environment and highlight challenges associated with the care of these patients, and to proffer solutions for improved outcome. This was a retrospective study of histologically confirmed cases of Sister Mary Joseph's nodule seen at Bugando Medical Centre between March 2003 and February 2013. Data collected were analyzed using descriptive statistics. A total of 34 patients were enrolled in the study. Males outnumbered females by a ratio of 1.4:1. The vast majority of patients (70.6%) presented with large umbilical nodule > 2 cm in size. The stomach (41.1%) was the most common location of the primary tumor. Adenocarcinoma (88.2%) was the most frequent histopathological type. Most of the primary tumors (52.9%) were poorly differentiated. As the disease was advanced and metastatic in all patients, only palliative therapy was offered. Out of 34 patients, 11 patients died in the hospital giving a mortality rate of 32.4%. Patients were followed up for 24 months. At the end of the follow-up period, 14(60.9%) patients were lost to follow-up and the remaining 9 (39.1%) patients died. Patients survived for a median period of 28 weeks (range, 2 to 64 weeks). The nodule recurred in 6 (26.1%) patients after complete excision. Sister Mary Joseph's nodule of the umbilicus is not rare in our environment and often represents manifestation of a variety of advanced intra-abdominal malignancies. The majority of the patients present at a late stage and many with distant metastases. The patient's survival is very short leading to a poor outcome. Early detection of primary cancer at an early stage may improve the prognosis
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