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The topic of this paper is the intraindividual stability of the EEG at rest for repeated recordings with respect to two sets of spectral parameters. Variability arises due to changes in experimental conditions (such as vigilance) and also due to the inherent random elements of the EEG. The two sets of parameters considered are broad-band parameters and(More)
Development in quantitative EEG parameters is studied for a sample of 158 normal children and adolescents aged 6-17 years. This is of interest both for increasing basic knowledge of human neurophysiology and for obtaining age standardized norms, useful in clinical research and applications. After selecting an appropriate epoch and correcting for EOG(More)
Up to now, there is little empirically backed quantitative and qualitative knowledge about self-replicating malware publicly available. This hampers research in these topics because many counter-strategies against malware, e.g., network-and host-based intrusion detection systems , need hard empirical data to take full effect. We present the nepenthes(More)
In this report transformations are evaluated for obtaining normally distributed broad band spectral parameters (both for absolute and relative power) in a sample of healthy individuals. This problem leads automatically to the question of defining a normative sample, both in terms of sampling and recording conditions; as to the latter, the electro-oculogram(More)
A CAPTCHA is a program that generates challenges that are easy to solve for humans but difficult to solve for computers. The most common CAPTCHAs today are text-based ones where a short word is embedded in a cluttered image. In this paper, we survey the state-of-the-art of currently deployed CAPTCHAs, especially of some popular German sites. Surprisingly,(More)
Explorations of the relationship between EEG activity and scores of tests of intelligence have a long history. Results have been rather discrepant and several explanations can be offered for this. Almost all previous studies relied on parameters derived from a visual rather than a computerized analysis of the EEG. Here broad band spectral parameters were(More)
Our investigation was concerned with 25 children, 10-13 years old, with an IQ 50-70 ("mild mental retardation," following the ICD). Among these, 14 attended a school for the mentally retarded and 11 one for the learning disabled. A control group was recruited, matched in age, sex and social class. The unipolar 8-channel record of EEG at rest was subjected(More)
Changes in the ongoing EEG when repeatedly closing and opening the eyes are quantified and compared for a group of mildly retarded children and a matched control group. The most prominent changes occur for the alpha-rhythm at posterior derivations. Blocking of the alpha is faster than its restriction, but there is no group difference in this respect. Many(More)
CAPTCHAs are small puzzles which should be easily solv-able by human beings but hard to solve for computers. They build a security cornerstone of the modern Internet service landscape, deployed in essentially any kind of login service, allowing to distinguish authorized human beings from automated attacks. One of the most popular and successful systems(More)