Search

Maximizing power generation of renewable energy sources has to do with less primary energy to obtain more power out of the natural potentials. This maximization follows a common characteristic shape to almost all of them regardless of the source, that is, in all cases, the power has a maximum generation point with respect to a set of variables. Such variables refer to the physicochemical quantities governing the power system such as: voltage, current, temperature, humidity, pressure, fluid velocity, chemical reactions. To keep the power conversion always operating at the maximum point, one has to use some tracking algorithm. This paper aims to show similarities in behavior, readings and variable calculations when applying any P&O algorithm of maximum power point tracking for different energy systems, such as fuel cells, photovoltaic panels, planar concentrators and heat exchangers. The results show that the energy density curves, or power, can express all systems studied so far. In particular, power maximization of electrical power sources needs to read current and voltage, and heat exchangers to observe fluid flow and temperature variation.

In this study different state-of-the-art visualization methods such as micro-computed tomography (micro-CT), mid-infrared (MIR) microscopic imaging and energy dispersive X-ray (EDS) mapping were evaluated to study human skeletal remains for the determination of the post-mortem interval (PMI). PMI specific features were identified and visualized by overlaying molecular imaging data and morphological tissue structures generated by radiological techniques and microscopic images gained from confocal microscopy (Infinite Focus (IFM)). In this way, a more distinct picture concerning processes during the PMI as well as a more realistic approximation of the PMI were achieved. It could be demonstrated that the gained result in combination with multivariate data analysis can be used to predict the Ca/C ratio and bone volume (BV) over total volume (TV) for PMI estimation. Statistical limitation of this study is the small sample size, and future work will be based on more specimens to develop a screening tool for PMI based on the outcome of this multidimensional approach.

Operative fixation is the treatment of choice for a rupture of the distal tendon of biceps. A variety of techniques have been described including transosseous sutures and suture anchors. The poor quality of the bone of the radial tuberosity might affect the load to failure of the tendon repair in early rehabilitation.The aim of this study was to determine the loads to failure of different techniques of fixation and to investigate their association with the bone mineral density of the radial tuberosity.Peripheral quantitative computed tomography was carried out to measure the trabecular and cortical bone mineral density of the radial tuberosity in 40 cadaver specimens. The loads to failure in four different techniques of fixation were determined.The Endobutton-based method showed the highest failure load at 270 N (sd22) (p < 0.05). The mean failure load of the transosseous suture technique was 210 N (sd66) and that of the TwinFix-QuickT 5.0 mm was 57 N (sd22), significantly lower than those of all other repairs (p < 0.05). No significant correlation was seen between bone mineral density and loads to failure.The transosseous technique is an easy and cost-saving procedure for fixation of the distal biceps tendon. TwinFix-QuickT 5.0 mm had significantly lower failure loads, which might affect early rehabilitation, particularly in older patients.

AbstractDer Segmenttransport nach der Kallusdistraktionsmethode ermglicht den Wiederaufbau langstreckiger Knochendefekte nach Trauma oder nach Resektion von Knochentumoren. Das in Mnchen entwickelte zentrale Zugseilsystem ist hierzu besonders geeignet. Die Stabilisierung der beiden Hauptfragmente erfolgt durch einen externen Fixateur, der Segmenttransport durch ein einziges, zentral am Knochensegment befestigtes Zugseil und einen externen, programmierbaren Motorantrieb. Zur Messung der dabei auftretenden Zugkrfte wurde ein Messelement, bestckt mit Dehnungsmestreifen, in das Zugseil integriert. Bei 15 Patienten erfolgte die kontinuierliche Messung der Zugkrfte whrend des gesamten Segmenttransports. Die Kraftverlufe lassen Charakteristika des normalen Segmenttranports (Kraftniveau 150 250 N) und eine Abgrenzung zu kritischen Verlufen (Kraftniveau > 250 N) mit der Gefahr einer vorzeitigen berbrckung (Zugkraftanstieg > 10 N/Tag) erkennen. Aus den Messungen ergeben sich Hinweise, da unmittelbar bevor es im Regenerat zur berbrckung kommt eine sehr effektive Form des Segmenttransportes mit guter Knochenneubildung mglich ist, sofern dieser Grenzzustand angesteuert und aufrecht erhalten werden kann. Die zentralen Zugseilsysteme erffnen diese Mglichkeit, da neben einem kontinuierlichen Krftemonitoring auch die Option besteht, die Zugkraft als Steuergre in einem automatischen Regelkreis einzusetzen.Bone transport applying the principle of distraction osteogenesis makes it possible to reconstruct long bone defects caused by trauma or resection of bone tumors. The method employing a central cable, developed in Munich, is especially suitable for such applications. The main bone fragments are stabilized by an external fixateur, and bone transport is effected with a single central cable fixed to the tip of the segment, and driven by an external, programmable motor. In 15 patients the tractive forces during the entire bone transport were measured with a strain gauge incorporated within the cable. On the basis of the force profiles characteristics normal bone transport (forces between 150 250 N) can be distinguished from a critical transport (forces > 250 N) with the risk of premature consolidation. There is some evidence that at a very high level of force, just before premature consolidation a very effective form of bone transport with good bone neoformation can be achieved. Transport systems employing a central cable allow this special form of distraction osteogenesis, since there is continuous force monitoring, and there is the option of employing the traction force as a control factor in a loop.