The Dutch experience of open access echocardiography.

Cardiac disease is not easy to recognise in general practice. An echocardiogram is an excellent way to provide information about left ventricular mass and diastolic (dys)function and the presence of valvular heart disease. To improve diagnostic care of cardiac patients, an open access echocardiography service was established in the referral area of our hospital, where general practitioners were able to ask for an echocardiogram without referring the patient to the cardiologist. Between December 2002 and October 2006 echocardiograms were requested for 471 patients. Thirteen percent of the patients referred for dyspnoea and 3% of patients with a cardiac murmur had a left ventricular ejection fraction <40%. In 28% of patients no cardiac abnormality could be found. If we looked at the prevalence of hypertension in the referred patients, this was very high with a prevalence of up to 60% in the older age groups. If we included hypertension in the analysis, only 16% of patients had no structural cardiac or vascular abnormality. The study shows that the advantage of open access echocardiography in the Netherlands is that the general practitioner is able to make a better diagnosis and unnecessary referrals of patients with suspected cardiac disease can be avoided. (Neth Heart J 2007;15:342-7.).

Risk factors for sporadic community-acquired Legionnaires' disease. A 3-year national case-control study.

OBJECTIVE: Risk factors for sporadic community-acquired Legionnaires' disease (LD) have been studied in the past, well before the widespread introduction of the urinary antigen test. Our objective was to evaluate the impact of the concomitant decrease in underdiagnosis on established and unknown risk factors for LD. STUDY DESIGN: Prospective case-control study. METHODS: From 1 July 1998 to 30 June 2001, 228 LD cases and 293 controls were included for a national case-control study. Patients were included upon notification provided that they fulfilled international criteria for confirmed LD. RESULTS: A history of diabetes mellitus, current tobacco smoking, travelling abroad, spending one or more nights away from home not leaving the country and being a driver by profession were independent risk factors. LD patients who had travelled abroad during their incubation period differed from LD patients who had not. They appeared healthier than non- or domestic travellers with respect to a history of coronary disease, pulmonary disease, current use of corticosteroids or immunosuppressives and any medication. Also the environmental risk factors differed significantly for the two groups. CONCLUSIONS: The finding of two distinct populations of LD patients calls for a differentiated preventive strategy.

Autosoliton transmission in dispersion-managed systems guided by in-line nonlinear optical loop mirrors.

We examine the feasibility of optical pulse transmission in dispersion-managed fiber systems with in-line nonlinear optical loop mirrors. Applying numerical analysis, we find regimes of stable propagation over long distances in such lines, with a significant increase in the signal-to-noise ratio.

Symmetries, chirp-free points, and bistability in dispersion-managed fiber lines.

We show from an elementary symmetry analysis that, in dispersion-compensated systems for which a lossless model is valid, nonlinearity requires a chirp-free point at the center of symmetry (if such exists) of the map for any kind of unique periodic solution. We also present an example of a more-complex map when the periodic solution is not unique.

Power dependence of dispersion-managed solitons for anomalous, zero, and normal path-average dispersion.

We determine the power dependence of dispersion-managed solitons on map strength and average dispersion, using a combination of numerical simulations and the variational approach. In particular, we investigate the behavior near zero dispersion and identify the region of existence of dispersion-managed solitons in the average normal-dispersion regime.

Soliton collisions with wavelength-division multiplexed systems with strong dispersion management.

We investigate collisions between solitons in a lossless two-channel wavelength-division multiplexed system with strong dispersion management. Numerical results show that the net frequency shift that is due to interchannel collisions is at least 1 order of magnitude smaller than predicted by adiabatic theories. A modified theoretical analysis is presented and shown to be in good agreement with the numerical results.

Dispersion-managed solitons in the normal dispersion regime: a physical interpretation.

We present an analytic description of dispersion-managed soliton propagation based on split-step and variational models. Using these models, we derive the threshold map strength for the existence of dispersion-managed solitons in the normal dispersion regime and obtain a bound on the maximum normal average dispersion.

Immunoadsorption assay for bone alkaline phosphatase compared with wheat germ agglutinin precipitation assay in serum from (pre)pubertal girls.

The performance characteristics of two bone alkaline phosphatase (ALP; EC 3.1.3.1) assays, a wheat germ agglutinin (WGA) precipitation assay and a new immunoadsorption assay (IAA), were compared. The within- and between-run imprecision of the IAA (3.6-4.2% and 3.6-7.7%) was comparable with that of the WGA assay. The mean cross-reactivity with liver ALP appeared to be 4% in the WGA assay and 11% in the IAA. The reference ranges in a group of 155 healthy Caucasian (pre)pubertal schoolgirls were: 149-401 U/L (total ALP, 30 degrees C), 105-349 U/L (bone ALP, 30 degrees C, WGA assay), and 58-205 U/L (bone ALP, 25 degrees C, IAA). Comparison of the WGA assay (x) with the IAA (y) demonstrated a correlation coefficient of 0.95 [Deming regression equation: y = (0.56 +/- 0.01)x + (2.0 +/- 1.5); Sy[symbol: see text]x = 5.3 U/L]. Correlation studies of the WGA assay and the IAA results with total ALP demonstrated r = 0.98 and 0.96, respectively.

Optimization of a high-performance liquid chromatographic method for the determination of nucleosides and their catabolites. Application to cat and rabbit heart perfusates.

A high-performance liquid chromatographic method is described for the separation of nucleosides and related compounds in a single isocratic run. The separation of a standard mixture of at least thirteen compounds is achieved within 15 min on a new type of reversed-phase column 25 cm long, filled with 5-micron particles of Select B. Pre-treatment of the silica particles before silanization has given this type of reversed-phase material unique characteristics for basic and acidic compounds. Chromatograms are shown to compare the effectiveness of the Select B column for the separation of nucleosides with that of other C18 and C8 phases. The separation is achieved with 0.3 M ammonium dihydrogen phosphate (pH 4.00) and a mixture of methanol, acetonitrile and tetrahydrofuran. Detection is carried out with a variable-wavelength UV detector at 254 nm. Sample preparation and the influence of the organic solvents, pH and buffer concentration are described. To illustrate the applicability of the method, representative chromatograms are shown of perfusates of Langendorff preparations and the working hearts of cats and rabbits. Remarkable differences were obtained before and after ischaemia and before and after treatment with a nucleoside transport inhibitor. Baseline separation of cytosine, orotic acid, cytidine, uracil, uric acid, hypoxanthine, xanthine, inosine, guanosine, xanthosine, allopurinol, thymine and adenosine was achieved. The detection limit for these compounds was less than 1 ng per injection.