Query Free Adversarial Transfer via Undertrained Surrogates

Adversarial examples consist of minor perturbations added to a model\u27s input which cause the model to output an incorrect prediction. Deep neural networks have been shown to be highly vulnerable to these attacks, and this vulnerability represents both a security risk for the use of deep learning models in security-conscious fields and an opportunity to improve our understanding of how neural networks generalize to unexpected inputs. Transfer attacks are an important subcategory of adversarial attacks. In a transfer attack, the adversary builds an adversarial attack using a surrogate model, then uses that attack to fool an unseen target model. Recent research in this subfield has focused on attack generation methods which can improve transferability between models and ensemble-based attacks. We show that optimizing a single surrogate model is a more effective method of improving adversarial transfer, using the simple example of an undertrained surrogate. This method of attack generation transfers well across varied architectures and outperforms state-of-the-art methods. To interpret the effectiveness of undertrained surrogate models, we represent adversarial transferability as a function of surrogate model loss function curvature and surrogate gradient similarity to target gradient and show that our approach reduces the presence of local loss maxima which hinder transferability. Our results suggest that finding good single surrogate models is a highly effective and simple method for generating transferable adversarial attacks, and that this method represents a valuable route for future study in this field

Neuropsychological Correlates of Borderline Personality Disorder

In the current study, participants with borderline personality disorder (BPD) displayed deficits in neuropsychological functioning when compared with healthy controls. Participants with BPD performed worse on all measures of cognitive functioning: attention, verbal memory, processing speed and a measure of general neuropsychological functioning. The study found that depression was significantly more prevalent in the BPD sample compared with the control sample and that there was a significant inverse correlation between level of depression and scores on a general index of neuropsychological functioning. Results from ANCOVA analyses revealed significant differences existed in neuropsychological performance on all four measures of cognitive functioning between the two groups after controlling for depression. The role of effort in testing with persons with BPD was explored, with results indicating that participants with BPD provided good effort. Lastly, the study\u27s findings showed that those participants with a BPD diagnosis and a neurological disease performed worse on the measure of general neuropsychological functioning compared with individuals with BPD who had no history of a diagnosed neurological disease. Results from ANCOVA analyses revealed that significant differences in neuropsychological performance on all measures of cognitive functioning existed between the two groups after controlling for presence of a diagnosed neurological disorder. Implications of the study findings have been presented and discussed. Also, possible confounds to the study\u27s findings were identified and discussed in the hope that future replications of the current study will control for such variables and result in robust research findings. Suggestions for future research in this area have been provided to assist in the construction of a more complete neuropsychological profile of BPD

The bias of the submillimetre galaxy population: SMGs are poor tracers of the most massive structures in the z ~ 2 Universe

It is often claimed that overdensities of (or even individual bright) submillimetre-selected galaxies (SMGs) trace the assembly of the most-massive dark matter structures in the Universe. We test this claim by performing a counts-in-cells analysis of mock SMG catalogues derived from the Bolshoi cosmological simulation to investigate how well SMG associations trace the underlying dark matter structure. We find that SMGs exhibit a relatively complex bias: some regions of high SMG overdensity are underdense in terms of dark matter mass, and some regions of high dark matter overdensity contain no SMGs. Because of their rarity, Poisson noise causes scatter in the SMG overdensity at fixed dark matter overdensity. Consequently, rich associations of less-luminous, more-abundant galaxies (i.e. Lyman-break galaxy analogues) trace the highest dark matter overdensities much better than SMGs. Even on average, SMG associations are relatively poor tracers of the most significant dark matter overdensities because of 'downsizing': at z < ~2.5, the most-massive galaxies that reside in the highest dark matter overdensities have already had their star formation quenched and are thus no longer SMGs. At a given redshift, of the 10 per cent most-massive overdensities, only ~25 per cent contain at least one SMG, and less than a few per cent contain more than one SMG.Comment: 6 pages, 3 figures, 1 table; accepted for publication in MNRAS; minor revisions from previous version, conclusions unchange

Probing the distance and morphology of the Large Magellanic Cloud with RR Lyrae stars

We present a Bayesian analysis of the distances to 15,040 Large Magellanic Cloud (LMC) RR Lyrae stars using $V$- and $I$-band light curves from the Optical Gravitational Lensing Experiment, in combination with new $z$-band observations from the Dark Energy Camera. Our median individual RR Lyrae distance statistical error is 1.89 kpc (fractional distance error of 3.76 per cent). We present three-dimensional contour plots of the number density of LMC RR Lyrae stars and measure a distance to the core LMC RR Lyrae centre of ${50.2482\pm0.0546 {\rm(statistical)} \pm0.4628 {\rm(systematic)} {\rm kpc}}$, equivalently ${\mu_{\rm LMC}=18.5056\pm0.0024 {\rm(statistical)} \pm0.02 {\rm(systematic)}}$. This finding is statistically consistent with and four times more precise than the canonical value determined by a recent meta-analysis of 233 separate LMC distance determinations. We also measure a maximum tilt angle of $11.84^{\circ}\pm0.80^{\circ}$ at a position angle of $62^\circ$, and report highly precise constraints on the $V$, $I$, and $z$ RR Lyrae period--magnitude relations. The full dataset of observed mean-flux magnitudes, derived colour excess ${E(V-I)}$ values, and fitted distances for the 15,040 RR Lyrae stars produced through this work is made available through the publication's associated online data.Comment: 7 pages, 8 figure