A simple, calibrated, ultra-low frequency ballistocardiograph

The physical basis of ballistocardiography has now been thoroughly investigated and there is general agreement that the ultra-low frequency system is the most satisfactory. The physiological basis of ballistocardiography and its clinical application require further study. For this purpose a reliable instrument which can be easily operated and calibrated is needed. The design of such an instrument and its calibrating system, with an analysis of its performance and an indication of the results obtained by its use is presented.

---

Zusammenfassung Die physikalische Basis der Ballistokardiographie ist jetzt vollst?ndig erforscht und die allgemeine übereinstimmung geht dahin, da? das Ultrakurzfrequenz-System das geeignetste ist. Die physiologische Basis der Ballistokardiographie und ihre klinische Anwendung erfordert weitere Untersuchungen. Für diesen Zweck ist ein zuverl?ssiges Ger?t n?tig, das leicht bedient und geeicht werden kann. Der Entwurf eines solchen Instrumentes und dessen Eichungssystems, eine Analyse seiner Leistung und die bei seiner Anwendung erzeilten Ergebnisse wird mitgeteilt.

---

Sommaire Les bases physique de la ballistocardiographie ont été maintenant étudiées à fond et de l'avis général le système T.B.F. est le plus satisfaisant. Par contre les bases physiologiques de la ballistocardiographie et son application clinique nécessitent des études supplémentaires. Dans ce but il est indispensable de posséder un appareillage s?r qui puisse être utilisé et étalonné avec facilité. On présente la réalisation d'un tel instrument ainsi que son système d'étalonnage en même temps qu'une analyse de ses performances et une indication des résultats obtenus.

     

A fast method for calibrating video-based motion analysers using only a rigid bar

Video-camera systems are widely used in biomechanics and clinical fields to measure the 3D kinematic measurements of human motion. To be used, they need to be calibrated, that is the parameters which geometrically define the cameras have to be determined. It is shown here how this can be achieved by surveying a rigid bar in motion inside the working volume, and in a very short time: less than 15 s on a Pentium III. The exterior parameters are estimated through the coplanarity constraint, the camera focal lengths through the properties of epipolar geometry and the principal points with a fast evolutionary optimisation which guarantees convergence when the initial principal points cannot be adequately estimated. The method has been widely tested on simulated and real data. Results show that its accuracy is comparable with that obtained using methods based on points of known 3D coordinates (DLT): 0.37 mm RMS error over a volume with a diagonal ≈1.5m. A preferential absolute reference system is obtained from the same bar motion data and is used to guide an intelligent decimation of the data. Finally, the role that the principal points play in achieving a high accuracy, which is questioned in the computer vision domain, is assessed through simulations.     

Psychotropic medications,including short acting benzodiazepines,strongly increase the frequency of falls in elderly

ObjectivesFalls in the elderly are common and often serious. The aim of this study was to examine the association between the use of different classes of psychotropic medications, especially short acting benzodiazepines, and the frequency of falling in elderly.Study design This retrospective cohort study was performed with patients who visited the day clinic of the department of geriatric medicine of the University Medical Center Utrecht in the Netherlands between 1 January 2011 and 1 April 2012.Measurements Frequencies of falling in the past year and medication use were recorded. Logistic regression analysis was performed to assess the relationship between the frequency of falling in the past year and the use of psychotropic medications.ResultsDuring this period 404 patients were included and 238 (58.9%) of them had experienced one or more falls in the past year. After multivariate adjustment, frequent falls remained significantly associated with exposure to psychotropic medications (odds ratio [OR] 1.96; 95% confidence interval [CI] 1.17–3.28), antipsychotics (OR 3.62; 95% CI 1.27–10.33), hypnotics and anxiolytics (OR 1.81; 95% CI 1.05–3.11), short-acting benzodiazepines or Z-drugs (OR 1.94; 95% CI 1.10–3.42) and antidepressants (OR 2.35; 95% CI 1.33–4.16).ConclusionsThis study confirms that taking psychotropic medication, including short-acting benzodiazepines, strongly increases the frequency of falls in elderly. This relation should be explicitly recognized by doctors prescribing for older people, and by older people themselves. If possible such medication should be avoided for elderly patients especially with other risk factors for falling.     

Killer system: a simple method for differentiating Candida albicans strains.

The killer effect of 37 species of Candida, Cryptococcus, Hansenula, Pichia, Rhodotorula, Saccharomyces, and Trichosporon on 100 Candida albicans isolates of human and animal origin was studied. All of the C. albicans cultures were sensitive to one or more killer yeasts. The factors affecting the killer phenomenon on C. albicans were investigated for realizing a simple system for the differentiation of the 100 C. albicans isolates. By using this system, it was possible to differentiate up to 512 isolates of C. albicans according to their susceptibility to the killer effect of nine selected killer yeasts. The use of this method as an epidemiological marker in the case of presumptive nosocomial infections due to C. albicans is also reported.     

A simple method for differentiating vascular smooth muscle cells and fibroblasts in tissue culture

Summary The morphologic differentiation of vascular smooth muscle cells and fibroblasts in tissue culture is difficult if not impossible. By direct immunofluorescence, it is possible to distinguish between vascular smooth muscle cells and fibroblasts after 6 to 10 days in tissue culture. Microfilaments appear from the 6th to the 10th day. After an incubation period of 30 minutes with antibody against smooth muscle actomyosin at room temperature, microfilaments are demonstrable in smooth muscle cells. In contrast, fibroblasts, if incubated for the same period, show strong nuclear fluorescence and a primary fluorescence of the cytoplasm, but filaments are not visible. If fibroblasts are incubated with antiactomyosin for one hour at 37 °C, however, microfilaments are easily detectable.With this method it is possible to differentiate in a simple manner vascular smooth muscle cells from fibroblasts in a heterologous tissue culture.These studies were supported by the Deutsche Forschungsgemeinschaft, SFB 90,Cardiovasculäres System.     

A method for the measurement of ultra-low amounts of prostaglandins in inflammatory exudates using gas chromatography and mass spectrometry

A GC-MS assay for PGE₂ and PGF₂ has been described. The method is highly specific and sensitive down to the sub-picogram level. The assay has been used to measure the time dependence of PG concentration in carrageenan-induced inflammatory exudates and the results compared with a bioassay. Estimates of the extraction and purification yield of PGs from exudates have also been obtained.     

Maximum forces acting on the abdominal wall: experimental validation of a theoretical modeling in a human cadaver study

Incisional hernias following median laparotomy have a high incidence and recurrence rate after repair, so that a better understanding of the linea alba biomechanics is desirable. The mechanical stress exerted on the linea alba in living humans is primarily generated by the musculature. In this human cadaver study, intraabdominal pressure was simulated by insertion of a balloon that was increasingly filled to maximal pressures of 200 mbar. The related forces acting transversely on the linea alba at maximum pressure were found to be between 41.6 and 52.2N/cm (mean=45.9N/cm), which is in agreement with a recent modeling of the related forces.     

Rapid method for differentiating strains of Branhamella catarrhalis.

The ability of Branhamella catarrhalis to cause nosocomial infections is a matter of some controversy. The API ZYM research kit for detecting 89 enzymes was used on 49 isolates of B catarrhalis to select enzymes of potential use in differentiating clinical isolates. Twenty nine enzymes were produced by all isolates (13 strongly positive) and many of these were esterases; 16 enzymes were not detected in any isolate (40 if a more stringent criterion was used). Twenty enzymes were selected to form a prototype biotyping panel which allowed 17 different patterns of reactivity to be recognised. Of the 49, 34 isolates were confined to the three commonest patterns. Only one isolate was untypable using this panel due to lack of reactivity. A kit with these 20 substrates may be sufficiently discriminatory to be useful in the rapid study of outbreaks of infection caused by B catarrhalis.     

Test system for detecting and differentiating the influenza virus by an immunoenzyme method

Detection and differentiation of small amounts of influenza A and B viruses was done by enzyme-immunoassay based on detection of the complex of internal proteins. It was shown that two kinds of sera to the complex of internal proteins could be used: sera against disrupted viruses grown in a different system (mice or cell culture) and containing almost no CAM component for virus detection in the allantoic fluid of chick embryos, and sera to preparations of viruses grown in chick embryos and disrupted with detergents for elimination of virion surface determinants (wastes of subunit vaccine) for virus detection in nasal secretions of vaccinated subjects. The test-systems containing antibodies to the complex of internal proteins were shown to be as sensitive and specific as those containing antibodies to pure M protein and RNP.     

A new method to include the gravitational forces in a finite element model of the scoliotic spine

The distribution of stresses in the scoliotic spine is still not well known despite its biomechanical importance in the pathomechanisms and treatment of scoliosis. Gravitational forces are one of the sources of these stresses. Existing finite element models (FEMs), when considering gravity, applied these forces on a geometry acquired from radiographs while the patient was already subjected to gravity, which resulted in a deformed spine different from the actual one. A new method to include gravitational forces on a scoliotic trunk FEM and compute the stresses in the spine was consequently developed. The 3D geometry of three scoliotic patients was acquired using a multi-view X-ray 3D reconstruction technique and surface topography. The FEM of the patients’ trunk was created using this geometry. A simulation process was developed to apply the gravitational forces at the centers of gravity of each vertebra level. First the “zero-gravity” geometry was determined by applying adequate upwards forces on the initial geometry. The stresses were reset to zero and then the gravity forces were applied to compute the geometry of the spine subjected to gravity. An optimization process was necessary to find the appropriate zero-gravity and gravity geometries. The design variables were the forces applied on the model to find the zero-gravity geometry. After optimization the difference between the vertebral positions acquired from radiographs and the vertebral positions simulated with the model was inferior to 3 mm. The forces and compressive stresses in the scoliotic spine were then computed. There was an asymmetrical load in the coronal plane, particularly, at the apices of the scoliotic curves. Difference of mean compressive stresses between concavity and convexity of the scoliotic curves ranged between 0.1 and 0.2 MPa. In conclusion, a realistic way of integrating gravity in a scoliotic trunk FEM was developed and stresses due to gravity were explicitly computed. This is a valuable improvement for further biomechanical modeling studies of scoliosis.     

A method for increasing the frequency response of voltage clamped myelinated nerve fibres

In voltage clamp experiments on myelinated nerve fibres the time resolution of the current measurement is limited by the low-pass characteristics of the internodes. We increased the corner frequency of the current passing internode by grounding one half of this internode externally. Using a simplified equivalent circuit we calculated an increase in the bandwidth of the internode by a factor of about 6. Consequently, the peak value of the recorded capacity current increased while its duration was considerably shortened.     

A simple manganous chloride and Congo red disc method for differentiating Neisseria gonorrhoeae from Neisseria meningitidis.

Manganous chloride and Congo red incorporated into blotting paper discs have been used to differentiate gonococci from meningococci. The new technique is simple and reliable; the materials for the test are inexpensive. The method will increase the efficiency of distinguishing between the pathogenic Neisseria in any clinical bacteriology laboratory and especially in those in the tropical areas.