Electron Holography at Atomic Dimensions—Present State

An electron microscope is a wave optical instrument where the object information is carried by an electron wave. However, an important information, the phase of the electron wave, is lost, because only intensities can be recorded in a conventional electron micrograph. Off-axis electron holography solves this “phase problem” by encoding amplitude and phase information in an interference pattern, the so-called hologram. After reconstruction, a rather unrestricted wave optical analysis can be performed on a computer. The possibilities as well as the current limitations of off-axis electron holography at atomic dimensions are discussed, and they are illustrated at two applications of structure characterization of ε-NbN and YBCO-1237. Finally, an electron microscope equipped with a Cs-corrector, a monochromator, and a Möllenstedt biprism is outlined for subangstrom holography.     

Distribution Free Decomposition of Multivariate Data

We present a practical approach to nonparametric cluster analysis of large data sets. The number of clusters and the cluster centres are automatically derived by mode seeking with the mean shift procedure on a reduced set of points randomly selected from the data. The cluster boundaries are delineated using a k-nearest neighbour technique. The proposed algorithm is stable and efficient, a 10,000 point data set being decomposed in only a few seconds. Complex clustering examples and applications are discussed, and convergence of the gradient ascent mean shift procedure is demonstrated for arbitrary distribution and cardinality of the data. Received: 7 October 1998?Accepted: 9 October 1998     

Reallocation of testing resources in validating optimal designs using local domains

We have recently proposed a new method for integrating design optimization with model validation by means of a sequential approach that uses variable-size local domains of the design space and statistical bootstrap techniques. Our work was motivated by the fact that global model validation may be neither affordable nor necessary. The method proceeds iteratively by obtaining test data at a design point, constructing around it a local domain in which the model is considered valid, and optimizing the design within this local domain. Due to test variability, it is important to know how many tests are needed to size each local domain of the sequential optimization process. Conducting an unnecessarily large number of tests may be inefficient, while a small number of tests may be insufficient to achieve the desired validity level. In this paper, we introduce a technique to determine the number of tests required to account for their variability by sizing the local domains accordingly. The goal is to achieve a desired level of model validity in each domain using the correlation between model data at the center and any other point in the local domain. To make the method more cost-effective we avoid generating some testsby statistically predicting a set of local domains along the optimization process. The proposed technique is illustrated with a piston design example.     

Schedulability and sensitivity analysis of multiple criticality tasks with fixed-priorities

Safety-critical real-time standards define several criticality levels for the tasks. In this paper we consider the real-time systems designed under the DO-178B safety assessment process (i.e., Software Considerations in Airborne Systems and Equipment Certification). Vestal introduced a new multiple criticality task model to efficiently take into account criticality levels in the schedulability analysis of such systems. Such a task model represents a potentially very significant advance in the modeling of safety-critical real-time softwares. Baruah and Vestal continue this investigation, with a new scheduling algorithm combining fixed and dynamic priority policies. Another major design issue is to allow a system developer to determine how sensitive is the schedulability analysis to changes in execution time of various software components.     

Ultrasonographic signs of chromosome aberrations]

Factors predictive of psychiatric outcome in the second 6 months following traumatic brain injury (TBI) in 43 children and adolescents were assessed prospectively. The outcome measure was the presence of a psychiatric disorder not present before the injury ("novel"). Out of six models tested, four were predictive of novel psychiatric disorder: preinjury family function, family psychiatric history, socioeconomic class/intellectual function, and behavior/adaptive function. Post hoc analyses suggested that preinjury family functioning measured by a structured interview was a significant predictive variable. Severity of injury, when reclassified as severe versus mild/moderate TBI, significantly predicted novel psychiatric disorders. These data suggest that some children, identifiable through clinical assessment, are at increased risk for psychiatric disorders following TBI.     

Vagus nerve stimulation for the treatment of depression.

Given the debilitating effects of chronic depression and its economic impact on medical care, there is a need for a well-tolerated and effective long-term treatment for patients who do not respond fully to first-line antidepressant therapies such as antidepressant drugs (ADD), psychotherapy and electroconvulsive therapy. This paper discusses a new treatment that can address this need - the vagus nerve stimulation (VNS) therapy system - an implantable device that can electrically pace the vagus nerve. The VNS technology consists of a pulse generator and a lead system. In the VNS system, just like in a cardiac pacemaker, the stimulator resides subcutaneously and sends an electrical pulse to an organ through an implanted electrode. The VNS pulse generator is a programmable bipolar stimulator. The VNS lead system comprises a bipolar electrode pair and a fixation anchor that are wrapped around the left vagus nerve in the neck, near the carotid artery. The clinical safety and effectiveness of the VNS system was assessed. At present, the VNS therapy system can now be used as treatment for chronic or recurrent depression for patients 18 years of age or older who are experiencing a major depressive episode. The system can only be used as adjunctive therapy, which means that patients still need to continue with their ADD medication.