Nonparametric analysis of clustered data in diagnostic trials: Estimation problems in small sample sizes

In diagnostic trials, clustered data are obtained when several subunits (e.g., organs or vessels) of the same patient are observed where no, several, or all subunits may be diseased or non-diseased as classified by a gold standard. In such a design, repeated measures appear in a natural way since the same patient is observed under different conditions by several readers and the repeated measures may have a quite involved correlation structure. A nonparametric method for clustered data in multiple reader studies to estimate the area under the ROC curve has been previously considered. The disadvantage of this procedure is that the test statistic (a quadratic form) can become negative in case of small samples. Therefore, a slightly different approach by weighting the estimators of the areas under the curves (AUC) is proposed. It is shown that the proposed new estimator of the covariance matrix of the weighted AUC estimators is always positive semidefinite. Simulation studies show that the new statistic maintains the pre-assigned type-I error level quite well even in case of small sample sizes. The method is motivated by a real data example where the previously suggested statistic becomes negative. This example demonstrates the advantage of the new method.     

Passwörter — fünf Mythen und fünf Versäumnisse

Bis heute wird der Zugriff auf Daten und Anwendungen überwiegend durch einen Passwortschutz kontrolliert. Oft ist dieser Passwortschutz jedoch unzureichend, weil sich für die Gestaltung von und den Umgang mit Passworten hartn?ckig unrichtige überzeugungen halten und die falschen Priorit?ten gesetzt werden.     

Investigation of closed-form solutions to estimate fatigue damage on a building

If a stress process is wide-band, it is not obvious what constitutes a cycle and how cycles should be counted so that the Miner's rule can be employed. If a stress process is non-Gaussian, the stress process may cause accelerated fatigue damage. In this study, high-cycle fatigue damage for fasteners of curtain walls on a side face of a square building is estimated by not only closed-form solutions that consider the effects of wide-band and non-Gaussian characteristics, but also rainflow analysis that uses rainflow cycle counting method to determine the number of cycles and the magnitude of stress amplitude or range that are needed to employ Miner's rule. The fatigue damage estimations are compared to investigate the applicability of the closed-form solutions for initial design calculations.     

Fuzzy combination of fuzzy and switching state-feedback controllers for nonlinear systems subject to parameter uncertainties.

This paper presents a fuzzy controller, which involves a fuzzy combination of local fuzzy and global switching state-feedback controllers, for nonlinear systems subject to parameter uncertainties with known bounds. The nonlinear system is represented by a fuzzy combined Takagi-Sugeno-Kang model, which is a fuzzy combination of the global and local fuzzy plant models. By combining the local fuzzy and global switching state-feedback controllers using fuzzy logic techniques, the advantages of both controllers can be retained and the undesirable chattering effect introduced by the global switching state-feedback controller can be eliminated. The steady-state error introduced by the global switching state-feedback controller when a saturation function is used can also be removed. Stability conditions, which are related to the system matrices of the local and global closed-loop systems, are derived to guarantee the closed-loop system stability. An application example will be given to demonstrate the merits of the proposed approach.     

Effect of cleaving environment on the growth of ZnSe on the GaAs (1 1 0) surface by molecular beam epitaxy

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Heat conduction in Ba1?xKxBiO3

We have investigated heat conduction of single crystal Ba_1–xK_xBiO₃ in the temperature range of 2–300 K and in a magnetic field of up to 6 Tesla. Temperature dependence of thermal conductivity(T) reveals the participation of both electrons and phonons with their relative contributions that depend critically on the potassium doping concentration. Crystals underdoped with potassium (samples with higherT _c) exhibit a strong suppression of and a glass-like temperature dependence. In contrast, those with a higher potassium content (lowerT _c) show an increase as temperature decreases with a peak near 23 K. Field dependence of(H) is also very sensitive to the level of potassium doping. Crystals exhibiting a large phonon contribution show an initial drop in(H) at low fields followed by a minimum and then a slow rise to saturation as the field increases. The initial drop is due to the additional phonon scattering by magnetic vortices as the sample enters a mixed state. The high field behavior of(H), arising from a continuous break-up of Cooper pairs, exhibits scaling which suggests the presence of an unconventional superconducting gap structure in this material.     

Specific heat of amorphous3He films and confined liquid3He

We have measured the heat capacities of³He films and liquid³He in porous Vycor glass at 10 to 600 mK. With increasing the film thickness from 1 to 3 atomic layers, the specific heat evolves gradually from that typical to solid to that of liquid³He. At about 2 atomic layers, however, its low-temperature part is nearly temperature-independent; we interpret this as a result of gradual freezing of spins in an amorphous solid³He film with decreasing the temperature. The contribution of liquid³He in the center of the Vycor pores can be described as the specific heat of bulk liquid³He at corresponding pressures in the range 0 to 28 bar. The thickness of amorphous solid on the pore walls increases with external pressure roughly linearly. Preplating the walls with⁴He allows to determine the positions of³He atoms contributing to the surface specific heat at 10 to 50 mK. In addition, the contribution from the specific heat of³ He -⁴He mixing at 100 to 600 mK is discussed as a function of pressure and amount of⁴He.0n leave from ISSP Acad. Sci. of Russia, Chernogolovka, Russia     

Thermal dissociation of multimeric protein complexes by using nanoelectrospray mass spectrometry

The behavior of macromolecular systems at different temperatures is often crucial to their biological activity and function. While heat-induced changes of individual proteins are readily monitored by a number of spectroscopic methods, changes in noncovalent complexes of biomolecules are more challenging to interpret. Nanoelectrospray mass spectrometry is becoming increasingly powerful in the study of large noncovalent complexes, and here we describe the design, characterization, and application of a novel probe that allows the thermocontrol of the solution in the electrospray capillary. The transition temperature for the unfolding of the protein lysozyme is readily obtained and correlates closely with that measured by fluorescence spectroscopy, thereby demonstrating the validity of this approach. We apply this technique to the study of the 200-kDa complex of the small heat shock protein TaHSP16.9, revealing both its dissociation into suboligomeric species and an increase in its size and polydispersity at elevated temperatures. In contrast, gas-phase activation of this complex is also carried out and yields a dissociation pathway fundamentally different from that observed for thermal activation in solution. As such, this probe allows the study of the reversible heat-induced changes of noncovalent complexes in a biologically relevant manner.     

Wear and dynamic properties of piezoelectric ultrasonic motor with frictional materials coated stator

Piezoelectric ultrasonic motors have been studied, developed and utilized by researchers and companies all over the world. Ultrasonic motors (USM) produce rotational motion based on traveling waves made by the resonant vibrations of piezoceramic. These motors have been recently developed and utilized in practical applications. The dynamic properties and life of piezoelectric ultrasonic motors are strongly related to the frictional material Fused on the sliding surface. In this study, effects of frictional material properties on the performances of piezoelectric ultrasonic motors are investigated. It was possible to improve the torque of a traveling wave type ultrasonic motor by stator's coating.