Maschinelles Lernen Bayes'scher Netze in benutzeradaptiven Systemen

Das Thema der vorliegenden Arbeit ist die Anwendung existierender sowie die Entwicklung neuer, spezifisch auf den Fall benutzeradaptiver Systeme zugeschnittener, maschineller Lernverfahren für Bayes'sche Netze. Bislang werden die in benutzeradaptiven Systemen eingesetzten Bayes'schen Netze meist manuell—anhand von theoretischen Überlegungen (von Experten)—konstruiert. Es bietet sich an, die im System anfallenden Interaktionsdaten im Rahmen des Konstruktions- bzw. Wartungsprozesses durch die Anwendung entsprechender maschineller Lernverfahren zur Verbesserung der Systemperformanz auszunutzen. Dieser Arbeit liegt eine integrative Konzeption des maschinellen Lernens Bayes';scher Netze für benutzeradaptive Systeme zugrunde, die gemäß den Anforderungen der zu modellierenden Domäne mit alternativen Verfahren instanziiert werden kann. In diesem Rahmen werden in dieser Arbeit neu entwickelte maschinelle Lern- bzw. Adaptionsverfahren für Bayes';sche Netze vorgestellt, die das gemeinsame Ziel verfolgen, die besonderen Eigenschaften und Anforderungen des Benutzermodellierungskontexts während des Lern- bzw. Adaptionsvorgangs zu berücksichtigen. Diese neuen Verfahren werden in vergleichenden Studien mit alternativ einsetzbaren existierenden Methoden des maschinellen Lernens Bayes'scher Netze evaluiertThis thesis focuses on the application of existing and the development of new Bayesian network learning methods that are able to deal with or that can exploit the characteristics of domains of user-adaptive systems. So far, Bayesian networks used by user-adaptive systems have typically been specified manually—on the basis of theoretical considerations (of experts). It seems to be a promising approach to exploit the interaction data that can be collected during the systems'; use through the application of machine learning methods in the design and maintenance phases. We present an integrative generic framework that can be instantiated with alternative methods according to the demands of the domain to be modeled. To this end, new Bayesian network learning and adaptation methods are presented that jointly aim to address adequately the characteristics and demands of the user modeling context during the learning and adaptation processes. These methods are evaluated in comparative empirical studies relative to alternative existing standard Bayesian network learning procedures

Spannungsschwankungen und Licht-Flicker nach dem Ausstieg aus der Glühlampentechnologie

In vielen Ländern legen die Normen IEC 61000-3-3 [1] und IEC 61000-3-11 [2] verbindlich fest, welche Spannungsschwankungen von Geräten am öffentlichen Stromversorgungsnetz erzeugt werden dürfen. Die Festlegungen dienen unter anderem der Begrenzung von Licht-Flicker und beruhen auf der alten Annahme, dass in einem Haushalt vorwiegend Glühlampen zur Beleuchtung verwendet werden. Da die Glühlampentechnologie jetzt vom Markt verschwindet, ergibt sich eine neue Situation. Dieser Beitrag beschreibt, wie unter den neuen Bedingungen die EMV bezüglich Licht-Flicker aufrechterhalten werden soll

Familial Childhood Sleep Apnea

We report four siblings who had polysomnographically documented sleep apnea. Two presented with the typical clinical picture of sleep apnea syndrome including daytime somnolence and snoring, had repetitive obstructive apneic episodes during sleep, and were effectively treated with upper airway surgery. The other two were asymptomatic and showed infrequent apneic episodes during sleep. This family illustrates the distinction between the sleep apnea syndrome and infrequent apneic episodes during sleep. The sleep apnea syndrome is associated with daytime symptomatology and requires treatment. The presence of apneic episodes during sleep in all four siblings has implications regarding the predisposing factors (eg, upper airway anatomy and central nervous system dysfunction) versus precipitating factors (eg, obesity, upper airway infection, and central nervous system depressants) in sleep apnea

Sleep-Wake Complaints and Their Relation to Sleep Disturbance

This report is a comparison of patients presenting with 1) an insomnia complaint diagnosed as no objective findings. 2) insomnia diagnosed as being associated with a psychiatric disorder, and 3) daytime sleepiness diagnosed as no objective findings. The sleep of patients with insomnia diagnosed as no objective findings is comparable to that of patients with daytime sleepiness diagnosed as no objective findings and is significantly better than that of patients with insomnia associated with a psychiatric disorder. Significant differences were found in sleep induction, sleep maintenance, and overall sleep efficiency. No major differences were found among any of the groups in terms of sleep staging. All groups showed signs of psychological distress, but as expected this was significantly higher in the patients with insomnia associated with a psychiatric disorder. The fact that patients may present with sleep complaints (either insomnia or daytime somnolence) despite essentially normal sleep has clinical implications. Adequate evaluation of sleep complaints and symptomatic treatment plans are discussed

A Double-Blind Trial of Protriptyline in the Treatment of Sleep Apnea Syndrome

Eight male subjects with sleep apnea syndrome were given placebo and protriptyline in a double-blind crossover design to evaluate the effects of protriptyline on respiration during sleep. Treatment with protriptyline produced significantly better oxygenation and significantly fewer arousals during sleep, but sleep staging was unchanged. The decreased number of respiratory events approached significance and was much greater in six of eight subjects. A rapid eye movement sleep-suppression explanation of the improvement in oxygenation is not supported. Alternative explanations of these findings are discussed

Impact of geometry on chemical analysis exemplified for photoelectron spectroscopy of black silicon

For a smooth surface, the chemical composition can be readily evaluated by a variety of spectroscopy techniques; a prominent example is X-ray photoelectron spectroscopy (XPS), where the relative proportions of the elements are mainly determined by the intensity ratio of the element-specific photoelectrons. This deduction, however, is more intricate for a nanorough surface, such as black silicon, since the steep slopes of the geometry mimic local variations of the local emission angle. Here, we explicitly quantify this effect via an integral geometric analysis, by using so-called Minkowski tensors. Thus, we match the chemical information from XPS with topographical information from atomic force microscopy (AFM). Our method provides reliable estimates of layer thicknesses for nanorough surfaces. For our black silicon samples, we found that the oxide layer thickness is on average comparable to that of a native oxide layer. Our study highlights the impact of complex geometries at the nanoscale on the analysis of chemical properties with implications for a broad class of spectroscopy techniques

Dual PI3K/mTOR inhibitor NVP-BEZ235 enhances radiosensitivity of head and neck squamous cell carcinoma (HNSCC) cell lines due to suppressed Double-Strand Break (DSB) repair by non-homologous end joining

The PI3K/Akt/mTOR pathway is frequently altered in human papillomavirus (HPV)-positive and negative squamous cell carcinoma of the head and neck (HNSCC) and overstimulation is associated with poor prognosis. PI3K drives Akt activation and constitutive signaling acts pro-proliferative, supports cell survival, DNA repair, and contributes to radioresistance. Since the small molecule NVP-BEZ235 (BEZ235) is a potent dual inhibitor of this pathway, we were interested whether BEZ235 could be an efficient radiosensitizer. The 50 nM BEZ235 was found to abrogate endogenous and irradiation-induced phosphorylation of Akt (Ser473). The anti-proliferative capacity of the drug resulted in an increase in G1-phase cells. Repair of radiation-induced DNA double-strand breaks (DSBs) was strongly suppressed. Reduction in DSB repair was only apparent in G1- but not in G2-phase cells, suggesting that BEZ235 primarily affects non-homologous end joining. This finding was confirmed using a DSB repair reporter gene assay and could be attributed to an impaired phosphorylation of DNA-PKcs (S2056). Cellular radiosensitivity increased strongly after BEZ235 addition in all HNSCC cell lines used, especially when irradiated in the G0 or G1 phase. Our data indicate that targeting the PI3K/Akt/mTOR pathway by BEZ235 with concurrent radiotherapy may be considered an effective strategy for the treatment of HNSCC, regardless of the HPV and Akt status

Formation of cristae and crista junctions in mitochondria depends on antagonism between Fcj1 and Su e/g

Crista junctions (CJs) are important for mitochondrial organization and function, but the molecular basis of their formation and architecture is obscure. We have identified and characterized a mitochondrial membrane protein in yeast, Fcj1 (formation of CJ protein 1), which is specifically enriched in CJs. Cells lacking Fcj1 lack CJs, exhibit concentric stacks of inner membrane in the mitochondrial matrix, and show increased levels of F1FO–ATP synthase (F1FO) supercomplexes. Overexpression of Fcj1 leads to increased CJ formation, branching of cristae, enlargement of CJ diameter, and reduced levels of F1FO supercomplexes. Impairment of F1FO oligomer formation by deletion of its subunits e/g (Su e/g) causes CJ diameter enlargement and reduction of cristae tip numbers and promotes cristae branching. Fcj1 and Su e/g genetically interact. We propose a model in which the antagonism between Fcj1 and Su e/g locally modulates the F1FO oligomeric state, thereby controlling membrane curvature of cristae to generate CJs and cristae tips