Large Scale Clustering with Variational EM for Gaussian Mixture Models

How can we efficiently find large numbers of clusters in large data sets with high-dimensional data points? Our aim is to explore the current efficiency and large-scale limits in fitting a parametric model for clustering to data distributions. To do so, we combine recent lines of research which have previously focused on separate specific methods for complexity reduction. We first show theoretically how the clustering objective of variational EM (which reduces complexity for many clusters) can be combined with coreset objectives (which reduce complexity for many data points). Secondly, we realize a concrete highly efficient iterative procedure which combines and translates the theoretical complexity gains of truncated variational EM and coresets into a practical algorithm. For very large scales, the high efficiency of parameter updates then requires (A) highly efficient coreset construction and (B) highly efficient initialization procedures (seeding) in order to avoid computational bottlenecks. Fortunately very efficient coreset construction has become available in the form of light-weight coresets, and very efficient initialization has become available in the form of AFK-MC$^2$ seeding. The resulting algorithm features balanced computational costs across all constituting components. In applications to standard large-scale benchmarks for clustering, we investigate the algorithm's efficiency/quality trade-off. Compared to the best recent approaches, we observe speedups of up to one order of magnitude, and up to two orders of magnitude compared to the $k$-means++ baseline. To demonstrate that the observed efficiency enables previously considered unfeasible applications, we cluster the entire and unscaled 80 Mio. Tiny Images dataset into up to 32,000 clusters. To the knowledge of the authors, this represents the largest scale fit of a parametric data model for clustering reported so far

The Great Escape: The Role of Self-esteem and Self-related Cognition in Terror Management

Integrating terror management theory and objective self-awareness theory, we propose the existential escape hypothesis, which states that people with low self-esteem should be especially prone to escaping self-awareness as a distal response to thoughts of death. This is because they lack the means to bolster the self as a defense, and the propensity to bolster the self reduces the motivation to escape from self-awareness. Five studies supported this hypothesis. Individuals low, but not high, in self-esteem scored lower on a measure of private self-awareness (Study 1), showed less implicit self-activation (Studies 2 & 3), were more likely to choose to write about others than themselves (Study 4), and consumed more alcohol in a field study at a nightclub (Study 5) in response to mortality reminders. Implications for terror management theory (highlighting an additional route to defend against mortality awareness), self-regulation, physical health and well-being are discussed

Gender Differences in the Willingness to Engage in Risky Behavior: A Terror Management Perspective

Two studies examined the effects of mortality salience inductions on men and women\u27s willingness to engage in risk-taking behaviors. In Study 1, a sample of American college students (N = 101) were exposed to either a mortality salient or a control condition and then rated their willingness to engage in a variety of risk-taking activities. In Study 2, a sample of Israeli high-school students (N = 106) completed a self-esteem measure, were exposed to either a mortality salient or control condition, and then rated their willingness to use various psychoactive substances that were offered in three different hypothetical scenarios. In both studies, findings indicated that mortality salience led to higher willingness to engage in risky behaviors in men but not in women. Study 2 also revealed that self-esteem moderated the effect of mortality salience on the willingness to use psychoactive substances but only when they were offered by a friend. The discussion offers a terror management perspective of risk-taking behaviors

Desire in the Face of Death: Terror Management, Attachment, and Sexual Motivation

Four studies examined the impact of mortality salience (MS) on sexual motivation. In Studies 1–3, participants were primed with death‐related thoughts and then rated their desire to engage in sex in different contexts. Study 4 included an assessment of reasons for engaging in sex. Results showed that MS increased the desire for romantic sex, regardless of gender, and the desire for casual sex among more avoidant men. Sexual desire was fueled by distinct patterns of motives among highly anxious and avoidant people. These findings suggest that the variety of meanings sexual behavior has for different people may explain why, in some cases, sexual behavior may function as a defense against mortality concerns, whereas in other cases, it may exacerbate threat

Prenatal Diagnosis of Fryns Syndrome through Identification of Two Novel Splice Variants in the <i>PIGN</i> Gene—A Case Series

Fryns syndrome (FS) is a multiple congenital anomaly syndrome with different multisystemic malformations. These include congenital diaphragmatic hernia, pulmonary hypoplasia, and craniofacial dysmorphic features in combination with malformations of the central nervous system such as agenesis of the corpus callosum, cerebellar hypoplasia, and enlarged ventricles. We present a non-consanguineous northern European family with two recurrent cases of FS: a boy with multiple congenital malformations who died at the age of 2.5 months and a female fetus with a complex developmental disorder with similar features in a following pregnancy. Quad whole exome analysis revealed two likely splicing-affecting disease-causing mutations in the PIGN gene: a synonymous mutation c.2619G>A, p.(Leu873=) in the last nucleotide of exon 29 and a 30 bp-deletion c.996_1023+2del (NM_176787.5) protruding into intron 12, with both mutations in trans configuration in the affected patients. Exon skipping resulting from these two variants was confirmed via RNA sequencing. Our molecular and clinical findings identified compound heterozygosity for two novel splice-affecting variants as the underlying pathomechanism for the development of FS in two patients