Sensitivity of chaotic behavior to low optical frequencies of a double-beam torsional actuator.

We investigate here how the optical properties at low frequencies affect the actuation dynamics and emerging chaotic behavior in a double-beam torsion actuator at nanoscale separations (<200nm), where the Casimir forces and torques play a major role. In fact, we take into account differences of the Casimir force due to alternative modeling of optical properties at low frequencies, where measurements are not feasible, via the Drude and plasma models, and repercussions by different material preparation conditions. For conservative autonomous actuation, bifurcation and phase portrait analysis indicate that both factors affect the stability of an actuating device in such a way that stronger Casimir forces and torques will favor increased unstable behavior.

Dependence of chaotic behavior on optical properties and electrostatic effects in double-beam torsional Casimir actuation.

We investigate the influence of Casimir and electrostatic torques on double-beam torsional microelectromechanical systems with materials covering a broad range of conductivities of more than three orders of magnitude. For the frictionless autonomous systems, bifurcation and phase space analysis shows a significant difference between stable and unstable operating regimes for equal and unequal applied voltages on both sides of the double torsional system giving rise to heteroclinic and homoclinic orbits, respectively. For equal applied voltages, only the position of a symmetric unstable saddle equilibrium point is dependent on the material optical properties and electrostatic effects, while in any other case stable and unstable equilibrium points are dependent on both factors.

Defect in the Joint Spectrum of Hydrogen due to Monodromy.

In addition to the well-known case of spherical coordinates, the Schrödinger equation of the hydrogen atom separates in three further coordinate systems. Separating in a particular coordinate system defines a system of three commuting operators. We show that the joint spectrum of the Hamilton operator, the z component of the angular momentum, and an operator involving the z component of the quantum Laplace-Runge-Lenz vector obtained from separation in prolate spheroidal coordinates has quantum monodromy for energies sufficiently close to the ionization threshold.

The phase space geometry underlying roaming reaction dynamics.

Recent studies have found an unusual way of dissociation in formaldehyde. It can be characterized by a hydrogen atom that separates from the molecule, but instead of dissociating immediately it roams around the molecule for a considerable amount of time and extracts another hydrogen atom from the molecule prior to dissociation. This phenomenon has been coined roaming and has since been reported in the dissociation of a number of other molecules.

Reaction dynamics through kinetic transition states.

The transformation of a system from one state to another is often mediated by a bottleneck in the system's phase space. In chemistry, these bottlenecks are known as transition states through which the system has to pass in order to evolve from reactants to products. The chemical reactions are usually associated with configurational changes where the reactants and products states correspond, e.

The flux-flux correlation function for anharmonic barriers.

The flux-flux correlation function formalism is a standard and widely used approach for the computation of reaction rates. In this paper we introduce a method to compute the classical and quantum flux-flux correlation functions for anharmonic barriers essentially analytically through the use of the classical and quantum normal forms. In the quantum case we show that for a general f degree-of-freedom system having an index one saddle the quantum normal form reduces the computation of the flux-flux correlation function to that of an effective one-dimensional anharmonic barrier.

Slow hematological recovery in children with IBD-associated anemia in cases of "expectant management".

Background And Objective: Allowing children with inflammatory bowel disease (IBD) to live with subnormal hemoglobin (Hb) levels affects their quality of life. The therapeutic approach to normalize Hb varies according to the cause of IBD-associated anemia. In exclusive iron-deficiency anemia (IDA) repletion of iron stores is obligatory, whereas controlling inflammation is the treatment of choice for anemia of chronic disease (ACD).

The quantum normal form approach to reactive scattering: The cumulative reaction probability for collinear exchange reactions.

The quantum normal form approach to quantum transition state theory is used to compute the cumulative reaction probability for collinear exchange reactions. It is shown that for heavy-atom systems such as the nitrogen-exchange reaction, the quantum normal form approach gives excellent results and has major computational benefits over full reactive scattering approaches. For light atom systems such as the hydrogen-exchange reaction however, the quantum normal approach is shown to give only poor results.

Pediatric Crohn's disease activity at diagnosis, its influence on pediatrician's prescribing behavior, and clinical outcome 5 years later.

Background: No studies have been performed in which therapeutic regimens have been compared between mild and moderate-to-severe pediatric Crohn's disease (CD) at diagnosis. The aim was to analyze pediatric CD activity at diagnosis, its influence on pediatrician's prescribing behavior, and clinical outcome 5 years later.

Methods: In a retrospective multicenter study we divided pediatric CD patients at diagnosis into mild or moderate-severe disease.

Microcanonical rates, gap times, and phase space dividing surfaces.

The general approach to classical unimolecular reaction rates due to Thiele is revisited in light of recent advances in the phase space formulation of transition state theory for multidimensional systems. Key concepts, such as the phase space dividing surface separating reactants from products, the average gap time, and the volume of phase space associated with reactive trajectories, are both rigorously defined and readily computed within the phase space approach. We analyze in detail the gap time distribution and associated reactant lifetime distribution for the isomerization reaction HCN <==> CNH, previously studied using the methods of phase space transition state theory.

Nonuniqueness of the phase shift in central scattering due to monodromy.

Scattering at a central potential is completely characterized by the phase shifts which are the differences in phase between outgoing scattered and unscattered partial waves. In this Letter, it is shown that, for 2D scattering at a repulsive central potential, the phase shift cannot be uniquely defined due to a topological obstruction which is similar to monodromy in bound systems.

[Septic polyarthritis due to an infected nail bed around an ingrown toenail in a previously healthy boy].

A 17-year-old, previously healthy boy was admitted with complaints of fever, malaise and pain in the pubic region and groin. His left elbow was also warm and swollen and could not be extended fully. Cultures of fluid drained from both hips and the elbow, blood and inflamed tissue from the nail bed of the right big toe yielded Staphylococcus aureus.

[Anaemia in adopted children, not always iron deficiency].

Anaemia was diagnosed in four adopted children during a standard screening examination 1-4 weeks after arrival. Further investigation revealed a number of causes which could then be specifically treated. The children were a girl aged 14 months from China with iron-deficiency anaemia, a boy aged 16 months from Nigeria with sickle cell anaemia, a girl aged 5 from Haiti who had alpha-thalassaemia, and a boy aged 7 from Brazil with spherocytosis.

Efficient computation of transition state resonances and reaction rates from a quantum normal form.

A quantum version of a recent formulation of transition state theory in phase space is presented. The theory developed provides an algorithm to compute quantum reaction rates and the associated Gamov-Siegert resonances with very high accuracy. The algorithm is especially efficient for multi-degree-of-freedom systems where other approaches are no longer feasible.

Cyclosporine A withdrawal during follow-up after pediatric liver transplantation.

It is unclear whether cyclosporine A (CsA) can be withdrawn safely during follow-up after pediatric liver transplantation. In our transplant program we have been using a strict protocol to withdraw CsA. The aim of this study was to retrospectively assess the effects of CsA withdrawal after pediatric liver transplantation on the incidence of rejection and renal function.

Efficient procedure to compute the microcanonical volume of initial conditions that lead to escape trajectories from a multidimensional potential well.

A procedure is presented for computing the phase space volume of initial conditions for trajectories that escape or "react" from a multidimensional potential well. The procedure combines a phase space transition state theory, which allows one to construct dividing surfaces that are free of local recrossing and that minimize the directional flux, and a classical spectral theorem. The procedure gives the volume of reactive initial conditions in terms of a sum over each entrance channel of the well of the product of the phase space flux across the dividing surface associated with the channel and the mean residence time in the well of trajectories which enter through the channel.

Phase space conduits for reaction in multidimensional systems: HCN isomerization in three dimensions.

The three-dimensional hydrogen cyanide/isocyanide isomerization problem is taken as an example to present a general theory for computing the phase space structures which govern classical reaction dynamics in systems with an arbitrary (finite) number of degrees of freedom. The theory, which is algorithmic in nature, comprises the construction of a dividing surface of minimal flux which is locally a "surface of no return." The theory also allows for the computation of the global phase space transition pathways that trajectories must follow in order to react.

[Treatment of snoring and sleep apnea. Maxillo-mandibular advancement osteotomy].

In this article, a patient is presented who was treated by a maxillo-mandibular advancement osteotomy, in order to increase the volume of the oropharynx as a final treatment of the obstructive sleep apnea syndrome. This syndrome is a common affliction, characterized by excessive daytime sleepiness and unintentionally falling asleep. It can be diagnosed by patient history and polysomnography.

Peak flow variation in childhood asthma: correlation with symptoms, airways obstruction, and hyperresponsiveness during long-term treatment with inhaled corticosteroids. Dutch CNSLD Study Group.

Background: Guidelines for asthma management focus on treatment with inhaled corticosteroids and on home recording of peak expiratory flow (PEF). The effect of maintenance treatment with inhaled corticosteroids on PEF variation and its relation to other parameters of disease activity were examined in 102 asthmatic children aged 7-14 years.

Methods: During 20 months of treatment with inhaled salbutamol, with or without inhaled budesonide (600 micrograms daily), forced expiratory volume in one second (FEV1), the dose of histamine required to provoke a fall in FEV1 of more than 20% (PD20), the percentage of symptom free days, and PEF variation were assessed bimonthly.

Inaccuracy of portable peak flow meters: correction is not needed. Dutch CNSLD Study Group.

This study examined whether correction of peak expiratory flow (PEF) values for the inaccuracy of the meter would affect asthma management in 102 children (7-14 y old). PEF was recorded with a mini Wright meter twice daily for 2 weeks. As expected, measured PEF overestimated PEF level and asthma control in these children on many diary days.

Peak flow variation in childhood asthma: relationship to symptoms, atopy, airways obstruction and hyperresponsiveness. Dutch CNSLD Study Group.

Although home recording of peak expiratory flow (PEF) is considered useful in managing asthma, little is known about the relationship of PEF variation to other indicators of disease activity. We examined the relationship of PEF variation, expressed in various ways, to symptoms, atopy, level of lung function, and airways hyperresponsiveness in schoolchildren with asthma. One hundred and two asthmatic children (aged 7-14 yrs) recorded symptoms and PEF (twice daily) in a diary for 2 weeks after withdrawal of all anti-inflammatory maintenance medication.

Remission of childhood asthma after long-term treatment with an inhaled corticosteroid (budesonide): can it be achieved? Dutch CNSLD Study Group.

This study was undertaken in order to determine whether long-term treatment with inhaled corticosteroid can induce a remission in childhood asthma, and to decide when stabilization of airway responsiveness occurred. We therefore carried out, an extended follow-up of 28-36 months in one of two groups of children who participated in a long-term intervention study. This former study had shown that long-term (median follow-up 22 months) treatment with inhaled corticosteroid plus beta 2-agonist improves symptoms, airway calibre and airway responsiveness in children with asthma, compared with beta 2-agonist alone.

Cessation of long-term treatment with inhaled corticosteroid (budesonide) in children with asthma results in deterioration. The Dutch CNSLD Study Group.

Inhaled corticosteroid has been shown to be effective in the management of asthma. However, there is a lack of studies that assess the effect of cessation after long-term treatment with inhaled corticosteroid. This question was addressed in 28 children with stable asthma, aged 11 to 18 yr of age, who had completed 28 to 36 months of treatment with inhaled corticosteroid (budesonide 200 micrograms 3 times/day) and inhaled beta-2-agonist (salbutamol 200 micrograms 3 times/day).