Learning-based Perception Contracts and Applications

Perception modules are integral in many modern autonomous systems, but their accuracy can be subject to the vagaries of the environment. In this paper, we propose a learning-based approach that can automatically characterize the error of a perception module from data and use this for safe control. The proposed approach constructs a {\em perception contract (PC)\/} which generates a set that contains the ground-truth value that is being estimated by the perception module, with high probability. We apply the proposed approach to study a vision pipeline deployed on a quadcopter. With the proposed approach, we successfully constructed a PC for the vision pipeline. We then designed a control algorithm that utilizes the learned PC, with the goal of landing the quadcopter safely on a landing pad. Experiments show that with the learned PC, the control algorithm safely landed the quadcopter despite the error from the perception module, while the baseline algorithm without using the learned PC failed to do so

Altered chemomechanical coupling causes impaired motility of the kinesin-4 motors KIF27 and KIF7.

Kinesin-4 motors play important roles in cell division, microtubule organization, and signaling. Understanding how motors perform their functions requires an understanding of their mechanochemical and motility properties. We demonstrate that KIF27 can influence microtubule dynamics, suggesting a conserved function in microtubule organization across the kinesin-4 family. However, kinesin-4 motors display dramatically different motility characteristics: KIF4 and KIF21 motors are fast and processive, KIF7 and its Drosophila melanogaster homologue Costal2 (Cos2) are immotile, and KIF27 is slow and processive. Neither KIF7 nor KIF27 can cooperate for fast processive transport when working in teams. The mechanistic basis of immotile KIF7 behavior arises from an inability to release adenosine diphosphate in response to microtubule binding, whereas slow processive KIF27 behavior arises from a slow adenosine triphosphatase rate and a high affinity for both adenosine triphosphate and microtubules. We suggest that evolutionarily selected sequence differences enable immotile KIF7 and Cos2 motors to function not as transporters but as microtubule-based tethers of signaling complexes

Refining Perception Contracts: Case Studies in Vision-based Safe Auto-landing

Perception contracts provide a method for evaluating safety of control systems that use machine learning for perception. A perception contract is a specification for testing the ML components, and it gives a method for proving end-to-end system-level safety requirements. The feasibility of contract-based testing and assurance was established earlier in the context of straight lane keeping: a 3-dimensional system with relatively simple dynamics. This paper presents the analysis of two 6 and 12-dimensional flight control systems that use multi-stage, heterogeneous, ML-enabled perception. The paper advances methodology by introducing an algorithm for constructing data and requirement guided refinement of perception contracts (DaRePC). The resulting analysis provides testable contracts which establish the state and environment conditions under which an aircraft can safety touchdown on the runway and a drone can safely pass through a sequence of gates. It can also discover conditions (e.g., low-horizon sun) that can possibly violate the safety of the vision-based control system

Pre-operative Emotional Health Affects Post-operative Patient Function but not Patient Satisfaction Following Primary Total Hip Arthroplasty

Introduction: Total hip (THA) and knee (TKA) arthroplasty are highly successful treatments for end-stage arthritis. However, a subset of patients experience suboptimal post-operative gain in function. 1, 2 Previous studies have shown that pre-operative emotional health influences outcomes after TKA,3 but there is limited evidence on THA patients. We hypothesized that pre-operative emotional health does not affect patient satisfaction in THA patients. Methods: A secondary analysis of an existing registry at UMass of primary THA patients between 2008 and 2011 was conducted. Baseline demographic, clinical, emotional health (SF-36 MCS), and physical health (SF-36 PCS) data were collected electronically at the pre-operative visit. Post-operative SF-36 MCS, SF-36 PCS, and satisfaction scores were collected electronically between 6 months through 2 years follow-up. Bivariate analyses and multivariate logistic regression models were used. Results: The analysis included 316 primary THA patients with mean age 62±11 years, 55% female, mean BMI 30±5, mean PCS 31±8, and mean MCS 51±11. Patients with lower baseline emotional health scores reported significantly reduced mean post-operative physical function and emotional health (p45 (indicating excellent function, national norm = 50); whereas patients with baseline MCS≥50 had a mean 17±11 point increase in post-operative PCS with 71% of these patients reporting PCS\u3e45 (p\u3c0.001). Conclusion: In THA patients, post-operative emotional health and physical health are positively correlated with baseline emotional health, however post-operative patient satisfaction remains independent of baseline emotional health

A reverberation-based black hole mass for MCG-06-30-15

We present the results of a reverberation campaign targeting MGC-06-30-15. Spectrophotometric monitoring and broad-band photometric monitoring over the course of 4 months in the spring of 2012 allowed a determination of a time delay in the broad Hβ emission line of τ =5.3 ± 1.8 days in the rest frame of the AGN. Combined with the width of the variable portion of the emission line, we determine a black hole mass of MBH = (1.6 ± 0.4) x 106 M_sun. Both the Hβ time delay and the black hole mass are in good agreement with expectations from the RBLR - L and MBH - σ* relationships for other reverberation-mapped AGNs. The Hβ time delay is also in good agreement with the relationship between H and broad-band near-IR delays, in which the effective BLR size is ∼4-5 times smaller than the inner edge of the dust torus. Additionally, the reverberation-based mass is in good agreement with estimates from the X-ray power spectral density break scaling relationship, and with constraints based on stellar kinematics derived from integral field spectroscopy of the inner ∼ 0.5 kpc of the galaxy.Publisher PDFPeer reviewe

Antitumor activity of a pyrrole-imidazole polyamide

Many cancer therapeutics target DNA and exert cytotoxicity through the induction of DNA damage and inhibition of transcription. We report that a DNA minor groove binding hairpin pyrrole-imidazole (Py-Im) polyamide interferes with RNA polymerase II (RNAP2) activity in cell culture. Polyamide treatment activates p53 signaling in LNCaP prostate cancer cells without detectable DNA damage. Genome-wide mapping of RNAP2 binding shows reduction of occupancy, preferentially at transcription start sites, but occupancy at enhancer sites is unchanged. Polyamide treatment results in a time- and dose-dependent depletion of the RNAP2 large subunit RPB1 that is preventable with proteasome inhibition. This polyamide demonstrates antitumor activity in a prostate tumor xenograft model with limited host toxicity

Constraints on the relationship between stellar mass and halo mass at low and high redshift

We use a statistical approach to determine the relationship between the stellar masses of galaxies and the masses of the dark matter halos in which they reside. We obtain a parameterized stellar-to-halo mass (SHM) relation by populating halos and subhalos in an N-body simulation with galaxies and requiring that the observed stellar mass function be reproduced. We find good agreement with constraints from galaxy-galaxy lensing and predictions of semi-analytic models. Using this mapping, and the positions of the halos and subhalos obtained from the simulation, we find that our model predictions for the galaxy two-point correlation function (CF) as a function of stellar mass are in excellent agreement with the observed clustering properties in the SDSS at z=0. We show that the clustering data do not provide additional strong constraints on the SHM function and conclude that our model can therefore predict clustering as a function of stellar mass. We compute the conditional mass function, which yields the average number of galaxies with stellar masses in the range [m, m+dm] that reside in a halo of mass M. We study the redshift dependence of the SHM relation and show that, for low mass halos, the SHM ratio is lower at higher redshift. The derived SHM relation is used to predict the stellar mass dependent galaxy CF and bias at high redshift. Our model predicts that not only are massive galaxies more biased than low mass ones at all redshifts, but the bias increases more rapidly with increasing redshift for massive galaxies than for low mass ones. We present convenient fitting functions for the SHM relation as a function of redshift, the conditional mass function, and the bias as a function of stellar mass and redshift.Comment: 21 pages, 17 figures, discussion enlarged, one more figure, updated references, accepted for publication in Ap

An injured pachypleurosaur (Diapsida:Sauropterygia) from the Middle Triassic Luoping Biota indicating predation pressure in the Mesozoic

Abstract The Middle Triassic Luoping Biota in south-west China represents the inception of modern marine ecosystems, with abundant and diverse arthropods, fishes and marine reptiles, indicating recovery from the Permian–Triassic mass extinction. Here we report a new specimen of the predatory marine reptile Diandongosaurus, based on a nearly complete skeleton. The specimen is larger than most other known pachypleurosaurs, and the body shape, caniniform teeth, clavicle with anterior process, and flat distal end of the anterior caudal ribs show its affinities with Diandongosaurus acutidentatus, while the new specimen is approximately three times larger than the holotype. The morphological characters indicate that the new specimen is an adult of D. acutidentatus, allowing for ontogenetic variation. The fang-like teeth and large body size confirm it was a predator, but the amputated hind limb on the right side indicate itself had been predated by an unknown hunter. Predation on such a large predator reveals that predation pressure in the early Mesozoic was intensive, a possible early hint of the Mesozoic Marine Revolution