Osteoporoza u osób w wieku podeszłym — patogeneza, ocena ryzyka złamań i skuteczność przeciwzłamaniowa leków

Osteoporoza jest ważnym problemem zdrowotnym wieku podeszłego. Złamania osteoporotyczne, w większości przypadków będące pierwszą manifestacją choroby, są przyczyną obniżenia jakości życia, zwiększonej umieralności, a także mają poważne konsekwencje ekonomiczne. Gęstość mineralna kości, mierzona przy użyciu badania densytometrycznego, nie jest już jedynym determinantem progu interwencji farmakologicznej. Obecnie decyzję terapeutyczną należy podjąć w zależności od bezwzględnego ryzyka złamania. W ostatnich latach opracowano powszechnie akceptowaną metodę oceny ryzyka złamań osteoporotycznych (FRAX), która jest wykorzystywana w codziennej praktyce klinicznej. Służy ona wczesnemu rozpoczynaniu skutecznego postępowania, a tym samym zmniejszeniu częstości złamań i zwiększeniu efektywności kosztowej leczenia osteoporozy. W artykule autorzy prezentują specyfikę osteoporozy inwolucyjnej, metodę FRAX — narzędzie do oceny ryzyka złamań osteoporotycznych — oraz wyniki badań klinicznych, które wyłoniły leki o udowodnionej skuteczności przeciwzłamaniowej u pacjentów w podeszłym wieku. Medycyna Wieku Podeszłego 2011, 1 (1), 23–2

Combining areal DXA bone mineral density and vertebrae postero-anterior width improves the prediction of vertebral strength

Objective - Areal bone mineral density (aBMD) measured by dual-energy X-ray absorptiometry (DXA) is an important determinant of bone strength (BS), despite the fact that the correlation between aBMD and BS is relatively weak. Parameters that describe BS more accurately are desired. The aim of this study was to determine whether the geometrical corrections applied to aBMD would improve its ability for BS prediction. We considered new parameters, estimated from a single DXA measurement, as well as BMAD (bone mineral apparent density) reported in the literature. Materials and methods - In vitro studies were performed with the L3 vertebrae from 20 cadavers, which were studied with DXA and quantitative computed tomography (QCT). A mechanical strength assessment was carried out. Two new parameters were introduced: vBMD_{min}=\frac{aBMD}{W_{PA}^{min}} and vBMD_{av}=\frac{aBMD}{W_{PA}^{av}} \left ( W^{min}_{PA}-minimal vertebral body width in postero-anterior \left ( PA \right ) view, {W_{PA}}^{av} — average PA vertebral body width\right ). Volumetric BMD measured by QCT (vBMD), aBMD, BMAD, vBMD _{min}, and vBMD_{av} were correlated to ultimate load and ultimate stress \left ( P_{max} \right ) to find the best predictor of vertebrae BS. Results - The coefficients of correlation between P_{max} and vBDM_{min} as well as BMAD, were r = 0.626 (p = 0.005), r = 0.610 (p = 0.006) and r = 0.567 (p = 0.012), respectively. Coefficients for vBMD and aBMD are r = 0.648 (p = 0.003) and r = 0.511 (p = 0.03), respectively. Conclusions. Our results showed that aBMD normalized by vertebrae dimensions describes vertebrae BS better than aBMD alone. The considered indices vBMD_{av}, vBMD_{min} and BMAD can be measured in routine PA DXA and considerably improve BS variability prediction. vBMD_{min} is superior compared to vBMD_{av} and BMAD

Analysis of integral parameters in a single-phase slotless axial-flux machine used in small wind turbines

The design of a ferrite magnet generator with trapezoidal shaped permanent magnets and coils for a wind turbine is studied. Based on the 3-D finite element analysis (FEA), the electromagnetic performances of the two generator prototypes and a simple design modification for one of the axial-flux generator prototypes are analyzed. The best generator is chosen from a range of designs, where the goal is to increase the voltage generated by the 8/8 pole and a single-phase slotless machine. Experimental results from a small size prototype machine validate the 3-D FEA models presented, and hence give confidence in their use for design

A single-phase slotless axial-flux low-power generator with ferrite magnets

The design and development of an axial-flux ferrite magnet slotless generator for use in a small-scale wind turbine is described. The 4/4-pole single-phase machine is designed for simplicity and ease of manufacture and it consists of one slotless stator disc. The generator produces approx. 12 W at 1000 rpm with electrical efficiency of up to 46%. Because the efficiency of the machine is important, the power curve characteristics and voltage produced by the generator are investigated. The presented generator should generate sufficient output DC voltage to charge 4 to 5 batteries of 12 volt each. Finally, the finite element (FE) results are compared with measurements on a prototype. The calculated values coincide to a strong degree with the experimental results

The assessment of energy efficiency of electric machines for domestic appliances drive

In the paper, the division of domestic appliances into categories connected with input power was presented. The authors discussed issues connected with energy efficiency of these devices. An example of such a device power consumption of which affects considerably on overall power consumption from the mains is a vacuum cleaner. Vacuum cleaners are used in almost all households and they were covered by the EU regulations which introduced limitations in power consumption from the mains. In the paper, the assessment of energy efficiency of classic electric motors for vacuum cleaners drive was presented. Results of practical tests of chosen vacuum cleaners were presented. The digital power meter was used to measure electric parameters of tested vacuum cleaners and the PC was used to collect measuring data. The assessment of input power influence on energy consumption and energy efficiency was conducted based on tests results. It was shown in conclusions that the one of development directions of domestic appliances, which can cause improvement of energy efficiency, are alternative technologies of electric machines with much higher efficiency i.e. energy-saving electric machines with electronic commutation

Studies of the permanent magnet dc machine

A hybrid drive of an unmanned aerial vehicle uses two mechanically coupled drives. In one of the drives, an electrical machine is used. Its role is not only limited to a motoring operation, e.g. during achieving the flight ceiling. The electric machine changes its operation into generating after reaching the flight ceiling, this allows not only meeting current electrical energy demands but also battery recharging. This paper presents the results of laboratory tests of a BLDC machine in motoring and generating operation. Mechanical characteristics of the motor for different supply voltages and external characteristics for generator were determined. The possible energy conversion efficiencies for both motoring and generating operations were determined

Analysis of the operation of a switched reluctance motor in the extended constant power range

In this paper, an analysis of the properties of a switched reluctance motor (SRM) 8/6 in an extended constant power range is presented. The typical constant power range to constant torque range ratio is between 2 and 3. In the case of machines designed as an electric vehicle drive, it is important to maximize this ratio. In the case of an SRM, it is possible to achieve this by applying an appropriate control strategy. An analysis of the SRM operation utilizing a modified control algorithm allows control of the maximum value of the motor phase current. As a consequence, using the so-called nonzero initial conditions for the current and flux allows the output power to be maintained in a wide speed range. For the improvement of drive system efficiency, the work of the phase current regulator should be limited to a minimum. The most advantageous work conditions we obtain with single-time current regulator work. Laboratory verification has been performed for selected states of motor work