Weakly Submodular Functions

Submodular functions are well-studied in combinatorial optimization, game theory and economics. The natural diminishing returns property makes them suitable for many applications. We study an extension of monotone submodular functions, which we call {\em weakly submodular functions}. Our extension includes some (mildly) supermodular functions. We show that several natural functions belong to this class and relate our class to some other recent submodular function extensions. We consider the optimization problem of maximizing a weakly submodular function subject to uniform and general matroid constraints. For a uniform matroid constraint, the "standard greedy algorithm" achieves a constant approximation ratio where the constant (experimentally) converges to 5.95 as the cardinality constraint increases. For a general matroid constraint, a simple local search algorithm achieves a constant approximation ratio where the constant (analytically) converges to 10.22 as the rank of the matroid increases

Synaptic Activity and Bioenergy Homeostasis: Implications in Brain Trauma and Neurodegenerative Diseases

Powered by glucose metabolism, the brain is the most energy-demanding organ in our body. Adequate ATP production and regulation of the metabolic processes are essential for the maintenance of synaptic transmission and neuronal function. Glutamatergic synaptic activity utilizes the largest portion of bioenergy for synaptic events including neurotransmitter synthesis, vesicle recycling, and most importantly, the postsynaptic activities leading to channel activation and rebalancing of ionic gradients. Bioenergy homeostasis is coupled with synaptic function via activities of the sodium pumps, glutamate transporters, glucose transport, and mitochondria translocation. Energy insufficiency is sensed by the AMP-activated protein kinase (AMPK), a master metabolic regulator that stimulates the catalytic process to enhance energy production. A decline in energy supply and a disruption in bioenergy homeostasis play a critical role in multiple neuropathological conditions including ischemia, stroke, and neurodegenerative diseases including Alzheimer’s disease and traumatic brain injuries

The Impact of Child Abuse, Posttraumatic Cognitions, Machiavellianism and Emotional Suppression on Interpersonal Sensitivity and Psychiatric Comorbidity: A Latent Profile Analysis

Much of the detrimental effects child abuse can have on victims’ cognitions, personality traits and emotional regulation strategies have been documented; however, it is unclear whether these effects might coexist with posttraumatic cognitions, Machiavellianism, and emotional suppression to impact interpersonal sensitivity and psychiatric comorbidity. The present study aimed to address this knowledge gap. A sample of 553 Chinese university students from three universities completed the Childhood Trauma Questionnaire-short form, Posttraumatic Cognitions Inventory, Machiavellianism Personality scale, Courtauld Emotional Control Scale, Interpersonal Sensitivity Measure, and General Health Questionnaire-28. Using Latent Profile Analysis, a three-profile solution was achieved. Profile one (high maltreatment group) students reported high levels of abusive experiences, posttraumatic cognitions and Machiavellianism, but a moderate level of emotional suppression; Profile two (moderate maltreatment group) students had moderate levels of abusive experiences, posttraumatic cognitions, Machiavellianism and emotional suppression. Profile three (low maltreatment group) students had low levels of all of the preceding psychological constructs. Profile one reported significantly higher interpersonal sensitivity and psychiatric comorbidity. Students with child abuse experiences, who viewed themselves and others negatively, displayed some dark personality traits, exercised some control over their emotions, tended to be excessively sensitive to others’ behaviors and feelings and prone to psychological distress

Asteroid (3200) Phaethon: colors, phase curve, limits on cometary activity and fragmentation

We report on a multi-observatory campaign to examine asteroid 3200 Phaethon during its December 2017 close approach to Earth, in order to improve our measurements of its fundamental parameters, and to search for surface variations, cometary activity and fragmentation. The mean colors of Phaethon are B-V = 0.702 +/- 0.004, V-R = 0.309 +/- 0.003, R-I = 0.266 +/- 0.004, neutral to slightly blue, consistent with previous classifications of Phaethon as a F-type or B-type asteroid. Variations in Phaethon's B-V colors (but not V-R or R-I) with observer sub-latitude are seen and may be associated with craters observed by the Arecibo radar. High cadence photometry over phases from 20 to 100 degrees allows a fit to the values of the HG photometric parameters; H = 14.57 +/- 0.02, 13.63 +/- 0.02, 13.28 +/- 0.02, 13.07 +/- 0.02; G = 0.00 +/- 0.01, -0.09 +/- 0.01, -0.10 +/- 0.01, -0.08 +/- 0.01 in the BVRI filters respectively; the negative G values are consistent with other observations of F type asteroids. Light curve variations were seen that are also consistent with concavities reported by Arecibo, indicative of large craters on Phaethon's surface whose ejecta may be the source of the Geminid meteoroid stream. A search for gas/dust production set an upper limit of 0.06 +/- 0.02 kg/s when Phaethon was 1.449 AU from the Sun, and 0.2 +/- 0.1 kg/s at 1.067 AU. A search for meter-class fragments accompanying Phaethon did not find any whose on-sky motion was not also consistent with background main belt asteroids.Comment: Accepted by the Astronomical Journal, 15 pages, 8 figures, 1 animated figur

BotTriNet: A Unified and Efficient Embedding for Social Bots Detection via Metric Learning

A persistently popular topic in online social networks is the rapid and accurate discovery of bot accounts to prevent their invasion and harassment of genuine users. We propose a unified embedding framework called BotTriNet, which utilizes textual content posted by accounts for bot detection based on the assumption that contexts naturally reveal account personalities and habits. Content is abundant and valuable if the system efficiently extracts bot-related information using embedding techniques. Beyond the general embedding framework that generates word, sentence, and account embeddings, we design a triplet network to tune the raw embeddings (produced by traditional natural language processing techniques) for better classification performance. We evaluate detection accuracy and f1score on a real-world dataset CRESCI2017, comprising three bot account categories and five bot sample sets. Our system achieves the highest average accuracy of 98.34% and f1score of 97.99% on two content-intensive bot sets, outperforming previous work and becoming state-of-the-art. It also makes a breakthrough on four content-less bot sets, with an average accuracy improvement of 11.52% and an average f1score increase of 16.70%

The concept of self among Chinese university victims of child abuse: an interpretative phenomenological analysis

The impact of child abuse experiences on the concept of self has been documented, however, using the qualitative method to further understand the subjective experiences of victims’ self-concept has not been done. Ten participants aged 19 to 22 reporting a history of child abuse experiences provided subjective feelings of the effects following these experiences in the form of a semi-structured interview. Using interpretative phenomenological analysis (IPA), there were 5 superordinate themes, including self-perceptions, negative perceptions of others/ the world, difficulties in interpersonal relationships, emotional regulation skills and personal characteristics in the present study. The results showed that (1) victims had some negative perceptions of themselves and of others but also had some positive self-perceptions. (2) Victims had some maladaptive characteristics, such as amorality or manipulation, for self-protection and maintaining social harmony; (3) and they easily suppressed their non-anger emotions. (4) They encountered social and intimate relationship difficulties. The subjective feelings of child abuse victims explored many negative perceptions of the self and others and showed the sensitivity of rejection in interpersonal relationships. Some negative personal characteristics and emotional suppression were also found among victims