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. The latter will be enhanced by unbalanced application of electrostatic voltages in double-beam actuating systems. For the case of a time-periodic driving force, we use a Melnikov function and a phase plane analysis to study the emerging chaotic behavior with respect to the Drude and plasma modeling and material preparation conditions. We find indications that any factor that leads to stronger Casimir interactions will aid chaotic behavior and prevent long term prediction of the actuating dynamics. Moreover, in a double-beam actuator chaoticity will be amplified by the application of unbalanced electrostatic voltages. Therefore, the details of modeling of optical properties and the material preparations conditions must be carefully considered in the design of actuating devices at nanoscale because here Casimir forces are omnipresent and broadband type interactions.

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. For the periodically driven system, a Melnikov function approach is used to show the presence of chaotic motion rendering predictions of whether stiction or stable actuation will take place over long times impossible. Chaotic behavior introduces significant risk for stiction, and it is more likely to occur for the more conductive systems that experience stronger Casimir forces and torques. Indeed, when unequal voltages are applied, the sensitive dependence of chaotic motion on electrostatics is more pronounced for the highest conductivity systems.

[Anaemia in adopted children, not always iron deficiency]. / Anemie bij adoptiekinderen, niet altijd ijzergebrek.

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. Iron deficiency is the most common cause of anaemia in childhood. However, in adopted children from sub-tropical areas other causes of anaemia like haemoglobinopathies or erythrocyte membrane defects should be borne in mind, particularly as a history of disease and family history are often lacking. Additional investigations may be necessary. An incorrect diagnosis of iron deficiency may result in ongoing and unjustified iron supplementation leading to harmful iron accumulation in thalassaemia and a delay in the correct treatment in sickle cell anemia or spherocytosis which could carry considerable risk.

[Septic polyarthritis due to an infected nail bed around an ingrown toenail in a previously healthy boy]. / Septische polyartritis ten gevolge van een geinfecteerd nagelbed rond een ingegroeide teennagel bij een tevoren gezonde jongen.

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. The patient was treated with intravenous antibiotics for septic arthritis of both hips, the left elbow and possibly the pubic symphysis. The infected nail bed, which was the most likely port of entry, was also treated. One year later, the original painful symptoms had disappeared but the right hip was almost immobile. In a patient with indications of septic arthritis, timely diagnosis and adequate therapy reduce the risk of permanent damage to the joint.

[Smoking behavior of medical students, house officers and specialists in Groningen, 1989]. / Rookgedrag van medische studenten, arts-assistenten en specialisten in Groningen, 1989.

Smoking habits and attitudes towards smoking of medical students (n = 725), house officers (n = 126) and consultants (n = 236) of the University Hospital of Groningen were studied in 1989 using a WHO questionnaire. Overall response was 84%. Twenty-seven percent of the medical students, 28% of the house officers and 34% of the consultants are current smokers. The prevalence of smoking in medical students and house officers is lower than that in the Dutch population. Smoking habits of consultants are similar to the general population. The prevalence of smoking Dutch physicians which was 56% in 1983 is decreasing rapidly. Doctors report they want more information about smoking cessation programs.

[Stridor in children]. / Stridor bij kinderen.

Stridor is the presenting symptom of abnormalities of larynx and trachea in children. The anatomical differences in size and consistency of the larynx play a crucial role in stridor in children as compared with adults. From 1983 to 1988, 81 children (65 males, 16 females) with severe or prolonged stridor were admitted to our hospital. Thorough examination, including endoscopy of larynx and trachea and radiology revealed various congenital abnormalities and acquired conditions as the cause of stridor. Congenital laryngeal anomalies accounted for stridor in 26 children, there were 12 children with congenital tracheal or vascular anomalies, 28 with infectious diseases and 15 with other diseases. Intubation and (or) tracheotomy were performed in one-third of the patients: 5 of them died of severe complications. For proper treatment of children with stridor it is essential to investigate its aetiology carefully.

[Nocturnal asthma in children, symptoms and treatment]. / Nachtelijk astma bij kinderen, herkenbaarheid en behandeling.

Nocturnal airflow obstruction is a common symptom in children with asthma. The increase in airflow obstruction overnight is underassessed by children as well as their parents. Worsening of the early morning peak flow values may be an indication for an increase in airflow obstruction overnight. An increase in vagal activity does not, in contrast with the observations in adult patients, contribute to the development of nocturnal airflow obstruction in asthmatic children. However, a nocturnal increase in inflammatory mediators seems to play a role of importance. Treatment of nocturnal airflow obstruction should therefore be focussed on inflammatory processes in the lungs.

[Treatment of snoring and sleep apnea. Maxillo-mandibular advancement osteotomy]. / Behandeling van snurken en slaapapneu. Protrusieosteotomie van de boven- en onderkaak.

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. Nasal-continuous positive airway pressure is the golden standard of treatment. However, in mild to moderate cases of the syndrome, treatment with a mandibular reposition appliance is also an option. The extraoral device of the first treatment option as well as the intraoral appliance of the second treatment option are demanding patients' compliance. Therefore, research into other treatments is necessary. The initial results of the advancement osteotomy among six patients were very good and in accordance with other literature reports. These results justify further research to clarify the importance of this treatment option of the obstructive sleep apnea syndrome.

Smoking habits in medical students and physicians in Groningen, The Netherlands.

Smoking habits and attitudes towards smoking of medical students (n = 725), house officers (n = 126) and consultants (n = 236) of the University Hospital of Groningen were studied, in 1989 by means of a World Health Organization (WHO) questionnaire. Overall response rate was 84%. Twenty seven percent of the medical students are current smokers, 28% of the house officers and 34% of the consultants. There is a remarkable difference among medical specialists i.e: smoking prevalence is highest among psychiatrists and lowest among paediatricians. The prevalence of smoking in medical students and house officers is lower than in the Dutch population. Smoking habits of the consultants are similar to those of the general population. About 75% of the doctors reported having no experience with smoking cessation programmes. Doctors report a need for more skills and knowledge on smoking cessation programmes.

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. The actual numerical differences between measured and corrected PEF on these days were very small (>5% in only five patients, maximum 10%). It is unlikely that such small changes in PEF justify changes in asthma management, even if these changes cause PEF levels to cross arbitrary borders between various levels of asthma control used in self-management plans. The clinical importance of the inaccuracy of portable PEF meters is negligible.

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. On treatment with inhaled corticosteroid plus beta 2-agonist, airway calibre did not further improve after 4 months, whereas the provocative dose of histamine which causes a 20% fall in forced expiratory volume in one second (PD20) histamine showed gradual improvement without reaching an apparent plateau. Remission was defined as being symptom free during any 8 month period. Of the 58 children originally randomized to receive 0.2 mg salbutamol, plus 0.2 mg budesonide, t.i.d., five children withdrew: three due to lack of motivation, one for psychological reasons, and one due to a deterioration of asthma. One patient was hospitalized because of an asthma exacerbation. Airway calibre showed no improvement after 4 months up to 36 months. Mean PD20 histamine stabilized after 20 months at 2.1 doubling doses above baseline, but at a subnormal level of 80 micrograms. Symptoms improved during the first 18 months, and may have been improving further, but slowly, during the period between 18 and 36 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Budesonide and terbutaline or terbutaline alone in children with mild asthma: effects on bronchial hyperresponsiveness and diurnal variation in peak flow.

The effects of treatment with budesonide (200 micrograms twice daily) and terbutaline (500 micrograms four times daily) has been compared with the effects of placebo and terbutaline in 27 children with mild asthma, aged 7-14 years, in a double blind, randomised placebo controlled study over eight weeks. Bronchial responsiveness (PC20 histamine), lung function, the amplitude of diurnal variation in peak expiratory flow (PEF), and symptom scores were measured. Baseline FEV1 was over 70% predicted and PC20 histamine less than 8 mg/ml. Twelve children were treated with budesonide and terbutaline and 15 with placebo and terbutaline. After four and eight weeks of treatment the change in PC20 was significantly greater after budesonide and terbutaline than after terbutaline alone by 2.1 (95% CI 0.5-3.8) and 1.3 (95% CI 0.1-2.5) doubling doses respectively. Mean FEV1 did not change in either group. The change in afternoon and nocturnal PEF was significantly greater after budesonide and terbutaline than after terbutaline alone. The amplitude of diurnal variation in PEF did not change significantly in either group. Peak flow reversibility decreased in the budesonide group. There were no differences between treatments for cough and dyspnoea, but wheeze improved in the budesonide group. The children with mild asthma treated with budesonide and terbutaline showed improvement in bronchial responsiveness, afternoon and nocturnal PEF, and symptoms of wheeze and a fall in peak flow reversibility by comparison with those who received terbutaline alone.

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. PEF variation was computed as the lowest PEF as a percentage of the highest PEF occurring over 14 days, the usual way of expressing PEF variation in asthma self-management plans. For each patient using inhaled corticosteroids within subject correlation coefficients (rho) were computed of PEF variation to the percentage of symptom free days, FEV1, and PD20. RESULTS: PEF variation decreased significantly during the first two months of treatment with inhaled corticosteroids and then remained stable. The same pattern was observed for symptoms and FEV1. In contrast, PD20 histamine continued to improve throughout the whole follow up period. In individual patients predominantly positive associations of PEF variation with symptoms, FEV1, and PD20 were found, but the ranges of these associations were wide. CONCLUSIONS: During treatment with inhaled corticosteroids the changes in PEF variation over time show poor concordance with changes in other parameters of asthma severity. When only PEF is monitored, clinically relevant deteriorations in symptoms, FEV1, or PD20 may be missed. This suggests that home recording of PEF alone may not be sufficient to monitor asthma severity reliably in children.

The effect of an inhaled corticosteroid (budesonide) on exercise-induced asthma in children. Dutch CNSLD Study Group.

The effect of long-term treatment with inhaled corticosteroid on exercise-induced asthma (EIA) was studied in 55 children, aged 7-18 yrs (mean 12 yrs). We also compared the time course of stabilization of EIA to that of other indicators of airway responsiveness, such as peak expiratory flow (PEF) variation and the provocation dose of histamine causing a 20% fall in forced expiratory volume in one second (FEV1). All children participated in an ongoing multicentre study to compare the effects of long-term treatment either with the beta 2-agonist salbutamol (600 micrograms.day-1) plus the inhaled corticosteroid budesonide (600 micrograms.day-1) (BA+CS), or salbutamol plus placebo (BA+PL), on airway calibre, airway responsiveness and symptoms. After a median follow-up of 22 months, the study design had to be changed, because of the high number of drop-outs on BA+PL. At that time, the treatment regimen of all children who had not withdrawn was changed into BA+CS. At the moment of change, and after 2 and 8 months of treatment, a treadmill exercise test was performed in two centres. Eighteen of the 22 children (82%) who were treated with BA+PL from the beginning had EIA, compared to 18 of the 33 children (55%) who were treated with BA-CS (p < 0.05). After 2 and 8 months of treatment with BA+CS in the patients previously on BA+PL this percentage decreased to 59 and 55%, respectively, and was not significantly different between both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

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). The children were randomized in a 1:2 ratio in a double-blind study either to continue budesonide (n = 8) during a period of 6 months or to decrease the dose of budesonide (n = 20) within 2 months, followed by placebo for 4 months. Treatment with salbutamol 600 micrograms daily was continued in both groups. Eight children from the tapering-off group withdrew, mainly due to symptoms of asthma, compared with none in the continuous treatment group. Five patients in the tapering-off group experienced exacerbations for which prednisolone was given, compared with none in the continuous treatment group. After tapering-off, symptoms of asthma and additional bronchodilator use increased, and both FEV1% predicted and PD20 histamine (provocation dose of histamine causing a 20% fall in FEV1) decreased, whereas these all remained unchanged in the group that continued treatment with inhaled corticosteroid. We conclude that in this study long-term treatment with 600 micrograms budesonide daily suppressed underlying mechanisms of asthma, but did not cure the disease.

Effects of 22 months of treatment with inhaled corticosteroids and/or beta-2-agonists on lung function, airway responsiveness, and symptoms in children with asthma. The Dutch Chronic Non-specific Lung Disease Study Group.

In a randomized double-blind multicenter clinical study, 116 children with asthma were randomly assigned to treatment with an inhaled beta-2-agonist (salbutamol 0.2 mg) plus an inhaled corticosteroid (budesonide 0.2 mg) three times a day (BA+CS) or to an inhaled beta-2-agonist (salbutamol 0.2 mg) plus a placebo three times a day (BA+PL). After a median follow-up time of 22 months, 26 patients receiving BA+PL (45%) had withdrawn from randomized treatment, mainly because of asthma symptoms, compared with three withdrawals in the patients receiving BA+CS (p less than 0.0001). The FEV1, expressed as a percentage of the predicted value for age, sex, and height, showed an absolute increase of 7.0% after 2 months of BA+CS compared with a decrease of 4.0% after 2 months of BA+PL. This 11% difference in percent predicted FEV1 (95% confidence interval, 7 to 15%; p less than 0.0001) was then maintained after a median follow-up period of 22 months. Postbronchodilator FEV1 showed an absolute increase of 3.7% predicted within 2 months in patients receiving BA+CS and an absolute decrease of 1.1% predicted in children receiving BA+PL (p = 0.0005). Thereafter, this difference between the two treatment groups was maintained. Average peak expiratory flow rate (PEFR) increased from baseline by 36.6 L/min in the BA+CS group compared with 3.7 L/min in the BA+PL group (p = 0.003). This difference then remained for the median follow-up time of 22 months.(ABSTRACT TRUNCATED AT 250 WORDS)

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. PEF variation was expressed as amplitude % mean, as standard deviation and coefficient of variation of all recordings, and as low % best (lowest PEF as percentage of the highest of all values). Atopy and level of forced expiratory volume in one second (FEV1) % predicted were not significantly related to PEF variation. The provocative dose of histamine causing a 20% fall in FEV1 (PD20) and symptom scores were significantly, but weakly, related to PEF variation. The index, low % best, proved easy to calculate and effective in identifying a short-term episode of reduced PEF. We conclude that peak expiratory flow variation in children with stable, moderately severe asthma is significantly, but weakly, related to symptoms and airways hyperresponsiveness. These three phenomena, therefore, all provide different information on the actual disease state. Expressing peak expiratory flow variation as low % best is easy to perform and appears to be clinically relevant.

Assessment of bronchodilator response in children with asthma. Dutch CNSLD Study Group.

The bronchodilator response (BDR) in forced expiratory volume in one second (FEV1) is routinely assessed to estimate the reversibility of airways obstruction. However, there is no consensus on how the BDR should be expressed, and recommendations applying to children are lacking. Similarly, the relationship between BDR and nonspecific bronchial hyperresponsiveness to histamine (BHR) has not been elucidated. These questions were addressed in 116 children, 7-16 yrs of age, with stable asthma after withdrawal of all pulmonary maintenance medication. Inclusion criteria were an initial FEV1 between 55-90% predicted, and/or FEV1/forced vital capacity (FVC) between 50-75%, as well as a fall in FEV1 of 20% or more when challenged with up to 150 micrograms histamine. The change in FEV1 (delta FEV1) 20 min after inhalation of 800 micrograms salbutamol was expressed in four ways: as an absolute difference (delta FEV1(l)), as a percentage of predicted FEV1 (delta FEV1%pred) or initial FEV1 (delta FEV1%init), and as a percentage of the deficit in FEV1 (delta FEV1%(pred-init)). delta FEV1%init and delta FEV1%pred were not related to age and stature of the children; delta FEV1%(pred-init) was related to stature, whilst delta FEV1(l) was related to both age and stature. All indices correlated with initial FEV1. However, this is an artefact introduced by relating change to initial value, rather than to the mean of initial and final value. In fact, BDR, expressed as delta FEV1%pred, was only slightly greater in children with the lowest initial airway calibre (p = 0.08), unlike delta FEV1%init. BDR was weakly related to BHR.(ABSTRACT TRUNCATED AT 250 WORDS)