B1422+231 and PG1115+080 are gravitational lens systems producing quadruple QSO images where there is real promise that time delays can constrain the Hubble constant. In addition, the lensing galaxies are both part of groups which can play an important role in modelling the lens potential. This article reports redshifts for the lensing galaxies and three neighboring galaxies in each of the two ...

B1422+231 and PG1115+080 are gravitational lens systems producing quadruple QSO images where there is real promise that time delays can constrain the Hubble constant. In addition, the lensing galaxies are both part of groups which can play an important role in modelling the lens potential. This article reports redshifts for the lensing galaxies and three neighboring galaxies in each of the two ...

BACKGROUND Providing augmented visual feedback is one way to enhance robot-assisted surgery (RAS) training. However, it is unclear whether task specificity should be considered when applying augmented visual feedback. METHODS Twenty-two novice users of the da Vinci Surgical System underwent testing and training in 3 tasks: simple task, bimanual carrying (BC); intermediate task, needle passing...

Cryptography based on noncommutative algebra still suffers from lack of schemes and lack of interest. In this work, we show new constructions of cryptosystems based on group invariants and suggest methods to make such cryptosystems secure in practice. Cryptographers still cannot prove security in its cryptographic sense or even reduce it to some statement about regular complexity classes. In th...

We show that for any constant a, ZPP/b(n) strictly contains ZPTIME(n)/b(n) for some b(n) = O(log n log log n). Our techniques are very general and give the same hierarchy for all the common promise time classes including RTIME, NTIME ∩ coNTIME, UTIME, MATIME, AMTIME and BQTIME. We show a stronger hierarchy for RTIME: For every constant c, RP/1 is not contained in RTIME(n)/(log n). To prove this...

We explore the halo structure of four gravitational lenses with well-observed, thin Einstein rings. We find that the gravitational potentials are well described by ellipsoidal density distributions in the sense that the best-fit nonellipsoidal models have parameters consistent with their ellipsoidal counterparts. We find upper limits on the standard parameters for the deviation from an ellipse ...

We develop a theory of Einstein rings and demonstrate it using the infrared Einstein ring images of the quasar host galaxies observed in PG 1115+080, B 1608+656 and B 1938+666. The shape of an Einstein ring accurately and independently determines the shape of the lens potential and the shape of the lensed host galaxy. We find that the host galaxies of PG 1115+080, B 1608+656 and B 1938+666 have...

This paper analyzes the problem of learning the structure of a Bayes net (BN) in the theoretical framework of Gold’s learning paradigm. Bayes nets are one of the most prominent formalisms for knowledge representation and probabilistic and causal reasoning. We follow constraint-based approaches to learning Bayes net structure, where learning is based on observed conditional dependencies between ...

Let (k, s)-SAT refer the family of satisfiability problems restricted to CNF formulas with exactly k distinct literals per clause and at most s occurrences of each variable. Kratochv́ıl, Savický and Tuza [6] show that there exists a function f(k) such that for all s ≤ f(k), all (k, s)-SAT instances are satisfiable whereas for k ≥ 3 and s > f(k), (k, s)-SAT is NP-complete. We define a new functio...