The thickness of the calcified layer of articular cartilage

The thickness of both the articular cartilage and its calcified zone were measured at 25 carefully selected points in 8 human femoral heads, and the ratio of one to the other was found to be remarkably constant for each bone. The thickness of the calcified zone therefore shows the same distribution pattern as that of the total cartilage and, since the latter is dependent upon the distribution of the load, the thickness of the calcified region also appears to be related to mechanical stress. The volume of the calcified zone, however, expressed as a percentage of the total cartilage, varied considerably from one bone to another within the range from 3.23 to 8.8%. Too few specimens were examined to allow correlation with age or sex to be either refuted or confirmed

The thickness of the calcified layer in different joints of a single individual

The thickness of the articular cartilage and its calcified zone were both measured at specially chosen places in several limb joints from five subjects. The volume of the calcified zone expressed as a percentage of the total cartilage was not only constant for one joint, but also in all the joints of a single individual. Nevertheless, the variation between subjects ranges from 6.9 to 8.6%. In two cases both sides of the body were investigated. As was the case in an earlier investigation on the femoral head, the bilateral distribution of the thickness was the same. Since the thickness of the total cartilage varies with the local distribution of loading in the joint, it follows that the thickness of the calcified layer also depends upon mechanical factors. Five subjects is too few to allow correlation with age or sex to be either refuted or confirmed. There is some evidence in the existing literature that the thickness of the calcified zone may be altered by diseas

Analyzing non-linear dynamics of organic growth: Evidence from small German new ventures

This paper links theories of growth models with the literature on serial autocorrelation of growth. We study the serial autocorrelation of tendencies of growth trajectories of employment and sales for German new ventures over a nine-year period using mosaic plots as a conceptual framework. The autocorrelation of growth tendencies provides important information on firms growth processes. We find that growing new ventures are subject to negative autocorrelation of tendencies of growth trajectories making sustained growth a very rare occurrence. This indicates that the growth of new ventures is non-linear, prone to interruptions, amplifying forces, and setbacks. Therefore, we interpret the commonly used term ‘stages of growth model’ in a different manner. A stage cannot be defined as a time span but rather as a sort of conditions of circumstances that are all present at a point in time and that are conditionally linked to a preceding sort of circumstances

Computed tomography-osteoaboorptiometry

A method of making a visual display of subchondral mineralization in the major synovial joints is described. Unlike existing procedures, it can be used on the living subject. A modified application of computed tomography-densitometry, computed tomography-osteoabsorptiometry makes it possible to explore the mechanical adaptability to the prevailing mechanical force. This claim is based upon the comparison of information obtained from 20 anatomical specimens with CT-osteoabsorptiometry and x-ray densitometry of sections; both methods yielding virtually identical results. The distribution of the subchondral density was then expressed as a map of the articular surface with the aid of an image analyser. This method can make a useful contribution to basic clinical research, as well as providing a diagnostic technique which can also be used for observing progress after a corrective osteotomy or any other procedure causing a change in mechanical function. Examples of its use on living patients are given

Physiological incongruity of the humero-ulnar joint

Investigations into the distribution of subchondral bone density in the human elbow have suggested that the geometry of the trochlear notch deviates from a perfect fit with the trochlea, and that the load is transmitted ventrally and dorsally rather than through the centre of the humero-ulnar joint. We therefore decided to make a quantitative assessment of the degree of incongruity between the two components in 15 human specimens (age distribution 60 to 93 years) with different types of joint surface. Polyether casts of the joint cavity were prepared under loads of 10,40,160 and 640 N. The thickness of the casts was then measured at 50 predetermined points, and an area distribution of the width of the joint space represented in a two-dimensional template of the trochlear notch. The reproducibility of this procedure was tested by image analysis. At a load of 10 N, only a narrow space was present ventrally and dorsally in the joint, but in the depths of the trochlear notch a width of 0.5 to 1 mm was recorded in the centre, and up to 3 mm at its medial and lateral edges. Specimens with continuous articular cartilage showed a lower degree of incongruity than those with a divided articular surface. As the load was increased to 640 N, however, the original incongruity between the articular surfaces disappeared almost completely. The joint surfaces became more congruous, probably because of the viscoelastic properties of the articular cartilage and the subchondral bone, and the contact areas merged in the centre of the joint. It is suggested that this physiological incongruity brings about an optimal distribution of stress over the articular surface during the transmission of the load, and it may lead to better nourishment of the articular cartilage by providing intermittent mechanical stimulation and circulation of the synovial fluid

Entrepreneurship-Ausbildung an Hochschulen und „Kultur der Selbstständigkeit“

Der Beitrag diskutiert die vermehrt thematisierte so genannte „Kultur der Selbstständigkeit“ im Kontext der akademischen Ausbildung, speziell in Verbindung mit der sich zunehmend etablierenden „Entrepreneurship-Ausbildung“. Sie bezeichnet die Qualifizierung für eine Tätigkeit als unternehmerischer Entscheidungsträger. Aus der Perspektive der wirtschaftswissenschaftlichen Hochschulausbildung liefert der Beitrag eine kritische Auseinandersetzung mit dem Begriff der „Kultur der Selbstständigkeit“ sowie eine Konkretisierung der Erwartungen an diese. Dazu werden auch die darauf bezogenen Operationalisierungsversuche skizziert und reflektiert sowie empirische Evidenzen vorgestellt. Da die Entrepreneurship-Ausbildung an Hochschulen als ein Indikator dieser Kultur verstanden werden kann, geht der Beitrag auch der grundsätzlichen Frage der Lehrbarkeit unternehmerischer Qualifikationen sowie des dazu erforderlichen didaktischen Gerüstes nach und leitet daraus einige elementare Überlegungen zu methodischer Ausgestaltung, Zielgruppen und Praxisorientierung der Entrepreneurship-Ausbildung ab. Der Beitrag zeigt abschließend ihre Kongruenzen mit bildungstheoretischen Leitbildern

A Real-time Image Reconstruction System for Particle Treatment Planning Using Proton Computed Tomography (pCT)

Proton computed tomography (pCT) is a novel medical imaging modality for mapping the distribution of proton relative stopping power (RSP) in medical objects of interest. Compared to conventional X-ray computed tomography, where range uncertainty margins are around 3.5%, pCT has the potential to provide more accurate measurements to within 1%. This improved efficiency will be beneficial to proton-therapy planning and pre-treatment verification. A prototype pCT imaging device has recently been developed capable of rapidly acquiring low-dose proton radiographs of head-sized objects. We have also developed an advanced, fast image reconstruction software based on distributed computing that utilizes parallel processors and graphical processing units. The combination of fast data acquisition and fast image reconstruction will enable the availability of RSP images within minutes for use in clinical settings. The performance of our image reconstruction software has been evaluated using data collected by the prototype pCT scanner from several phantoms.Comment: Paper presented at Conference on the Application of Accelerators in Research and Industry, CAARI 2016, 30 October to 4 November 2016, Ft. Worth, TX, US

Анализ экспериментальных данных по фотообразованию ?+-мезонов для энергии фотонов 230 МэВ

На основе измеренных ранее на электронном синхротроне "Сириус" значений асимметрии фотообразования ?+-мезонов на протоне, а также данных других лабораторий, был проведен феноменологический анализ для =230 МэВ. В результате были получены 5 независимых величин А1, А2, А3, ?, ?, необходимых для вычисления мультипольных амплитуд