1,306 research outputs found
Stability domains for time-delay feedback control with latency
We generalize a known analytical method for determining the stability of
periodic orbits controlled by time-delay feedback methods when latencies
associated with the generation and injection of the feedback signal cannot be
ignored. We discuss the case of extended time-delay autosynchronization (ETDAS)
and show that nontrivial qualitative features of the domain of control observed
in experiments can be explained by taking into account the effects of both the
unstable eigenmode and a single stable eigenmode in the Floquet theory.Comment: 9 pages, 6 figures; Submitted to Physical Review
Iron deficiency in infancy: is an immigrant more at risk?
QUESTIONS UNDER STUDY: Iron deficiency with or without anaemia is the most common deficiency in the world. Its prevalence is higher in developing countries and in low socioeconomic populations. We aimed at determining and comparing the prevalence of iron deficiency in an immigrant and non-immigrant population.
METHODS: Every child scheduled for a routine check-up at 12 months of age was allowed to participate in the study. Haemoglobin, ferritin, anthropometric data, familial and nutritional status were measured.
RESULTS: 586 infants were eligible and 463 were included in the study as they had assessment data at 12 months. Children were divided into two groups: immigrants' children and non-immigrants' children. The global prevalence of iron deficiency was 5.7% at 12 months. A significant difference for iron deficiency was noticed between the groups at 12 months (p = 0.01). Among risk factors, immigration (odds ratio 2.91; 95% CI 1.05-8.04) and unemployment (odds ratio 6.08; 95% CI 1.18-31.30) had the higher odds in the multivariable analysis.
CONCLUSION: The prevalence of iron deficiency in the immigrant population is higher than in non-immigrants. Immigration and the category of employment are risk factors for iron deficiency, as starting baby cereals before 9 months is a protective factor. Good socioeconomic conditions in Switzerland, the quality of food for pregnant women and young infants may be the explanation. A study up to five years of age is necessary before drawing general conclusions on infancy
Comment on "Critique of q-entropy for thermal statistics" by M. Nauenberg
It was recently published by M. Nauenberg [1] a quite long list of objections
about the physical validity for thermal statistics of the theory sometimes
referred to in the literature as {\it nonextensive statistical mechanics}. This
generalization of Boltzmann-Gibbs (BG) statistical mechanics is based on the
following expression for the entropy:
S_q= k\frac{1- \sum_{i=1}^Wp_i^q}{q-1} (q \in {\cal R}; S_1=S_{BG} \equiv
-k\sum_{i=1}^W p_i \ln p_i) .
The author of [1] already presented orally the essence of his arguments in
1993 during a scientific meeting in Buenos Aires. I am replying now
simultaneously to the just cited paper, as well as to the 1993 objections
(essentially, the violation of "fundamental thermodynamic concepts", as stated
in the Abstract of [1]).Comment: 7 pages including 2 figures. This is a reply to M. Nauenberg, Phys.
Rev. E 67, 036114 (2003
Asymptotics of the Farey Fraction Spin Chain Free Energy at the Critical Point
We consider the Farey fraction spin chain in an external field . Using
ideas from dynamical systems and functional analysis, we show that the free
energy in the vicinity of the second-order phase transition is given,
exactly, by
Here is a reduced
temperature, so that the deviation from the critical point is scaled by the
Lyapunov exponent of the Gauss map, . It follows that
determines the amplitude of both the specific heat and susceptibility
singularities. To our knowledge, there is only one other microscopically
defined interacting model for which the free energy near a phase transition is
known as a function of two variables.
Our results confirm what was found previously with a cluster approximation,
and show that a clustering mechanism is in fact responsible for the transition.
However, the results disagree in part with a renormalisation group treatment
Metastability, negative specific heat and weak mixing in classical long-range many-rotator system
We perform a molecular dynamical study of the isolated classical
Hamiltonian , known to
exhibit a second order phase transition, being disordered for and ordered otherwise ( total energy
and ). We focus
on the nonextensive case and observe that, for , a
basin of attraction exists for the initial conditions for which the system
quickly relaxes onto a longstanding metastable state (whose duration presumably
diverges with like ) which eventually crosses over to the
microcanonical Boltzmann-Gibbs stable state. The temperature associated with
the (scaled) average kinetic energy per particle is lower in the metastable
state than in the stable one. It is exhibited for the first time that the
appropriately scaled maximal Lyapunov exponent
, where, for all values of ,
numerically coincides with {\it one third} of its value for , hence
decreases from 1/9 to zero when increases from zero to unity,
remaining zero thereafter. This new and simple {\it connection between
anomalies above and below the critical point} reinforces the nonextensive
universality scenario.Comment: 9 pages and 4 PS figure
Refactoring Process Models in Large Process Repositories.
With the increasing adoption of process-aware information systems (PAIS), large process model repositories have emerged. Over time respective models have to be re-aligned to the real-world business processes through customization or adaptation. This bears the risk that model redundancies are introduced and complexity is increased. If no continuous investment is made in keeping models simple, changes are becoming increasingly costly and error-prone. Though refactoring techniques are widely used in software engineering to address related problems, this does not yet constitute state-of-the art in business process management. Process designers either have to refactor process models by hand or cannot apply respective techniques at all. This paper proposes a set of behaviour-preserving techniques for refactoring large process repositories. This enables process designers to eectively deal with model complexity by making process models better understandable and easier to maintain
Research review: young people leaving care
This paper reviews the international research on young people leaving care. Set in the context of a social exclusion framework, it explores young people's accelerated and compressed transitions to adulthood, and discusses the development and classification of leaving care services in responding to their needs. It then considers the evidence from outcome studies and argues that adopting a resilience framework suggests that young people leaving care may fall into three groups: young people 'moving on', 'survivors' and 'victims'. In concluding, it argues that these three pathways are associated with the quality of care young people receive, their transitions from care and the support they receive after care
Relativistic description of electron scattering on the deuteron
Within a quasipotential framework a relativistic analysis is presented of the
deuteron current. Assuming that the singularities from the nucleon propagators
are important, a so-called equal time approximation of the current is
constructed. This is applied to both elastic and inelastic electron scattering.
As dynamical model the relativistic one boson exchange model is used.
Reasonable agreement is found with a previous relativistic calculation of the
elastic electromagnetic form factors of the deuteron. For the unpolarized
inelastic electron scattering effects of final state interactions and
relativistic corrections to the structure functions are considered in the
impulse approximation. Two specific kinematic situations are studied as
examples.Comment: (19 pages in revtex + 15 figures not included, available upon
request.) report THU-93-10
Time--delay autosynchronization of the spatio-temporal dynamics in resonant tunneling diodes
The double barrier resonant tunneling diode exhibits complex spatio-temporal
patterns including low-dimensional chaos when operated in an active external
circuit. We demonstrate how autosynchronization by time--delayed feedback
control can be used to select and stabilize specific current density patterns
in a noninvasive way. We compare the efficiency of different control schemes
involving feedback in either local spatial or global degrees of freedom. The
numerically obtained Floquet exponents are explained by analytical results from
linear stability analysis.Comment: 10 pages, 16 figure
No evidence of response bias in a populationbased childhood cancer survivor questionnaire survey-Results from the Swiss Childhood Cancer Survivor Study
Purpose
This is the first study to quantify potential nonresponse bias in a childhood cancer survivor questionnaire survey. We describe early and late responders and nonresponders, and estimate nonresponse bias in a nationwide questionnaire survey of survivors.
Methods
In the Swiss Childhood Cancer Survivor Study, we compared characteristics of early responders (who answered an initial questionnaire), late responders (who answered after ≥1 reminder) and nonresponders. Sociodemographic and cancer-related information was available for the whole population from the Swiss Childhood Cancer Registry. We compared observed prevalence of typical outcomes in responders to the expected prevalence in a complete (100% response) representative population we constructed in order to estimate the effect of nonresponse bias. We constructed the complete population using inverse probability of participation weights.
Results
Of 2328 survivors, 930 returned the initial questionnaire (40%); 671 returned the questionnaire after ≥1reminder (29%). Compared to early and late responders, we found that the 727 nonresponders (31%) were more likely male, aged <20 years, French or Italian speaking, of foreign nationality, diagnosed with lymphoma or a CNS or germ cell tumor, and treated only with surgery. But observed prevalence of typical estimates (somatic health, medical care, mental health, health behaviors) was similar among the sample of early responders (40%), all responders (69%), and the complete representative population (100%). In this survey, nonresponse bias did not seem to influence observed prevalence estimates.
Conclusion
Nonresponse bias may play only a minor role in childhood cancer survivor studies, suggesting that results can be generalized to the whole population of such cancer survivors and applied in clinical practice
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