Concurrent Kleene Algebra: Free Model and Completeness

Concurrent Kleene Algebra (CKA) was introduced by Hoare, Moeller, Struth and Wehrman in 2009 as a framework to reason about concurrent programs. We prove that the axioms for CKA with bounded parallelism are complete for the semantics proposed in the original paper; consequently, these semantics are the free model for this fragment. This result settles a conjecture of Hoare and collaborators. Moreover, the techniques developed along the way are reusable; in particular, they allow us to establish pomset automata as an operational model for CKA.Comment: Version 2 includes an overview section that outlines the completeness proof, as well as some extra discussion of the interpolation lemma. It also includes better typography and a number of minor fixes. Version 3 incorporates the changes by comments from the anonymous referees at ESOP. Among other things, these include a worked example of computing the syntactic closure by han

Suicide among persons with childhood leukaemia in Slovenia

Pri osebah, ki so v otroštvu zbolele za rakom, so pogosto prisotne telesne in psihosocialne posledice bolezni ter njenega zdravljenja. Mnoge raziskave so pokazale, da je pri osebah z izkušnjo raka v otroštvu depresivnost in samomorilno vedenje močneje izraženo. V naši raziskavi smo proučili pojavljanje samomorov pri osebah, ki so v otroštvu zbolele za levkemijo, v primerjavi s splošno populacijo v Sloveniji, v obdobju 1978–2010. Pričakovano število samomorov smo izračunali na osnovi kontrolne skupine posameznikov iz splošne populacije, ki je bila s skupino preiskovancev, tj. oseb, ki so v otroštvu zbolele za levkemijo, izenačena po spolu, starosti ob začetku opazovanja, letu začetka opazovanja in dolžini opazovanja. Raziskava je pokazala, da med tistimi, ki so v otroštvu zboleli za levkemijo, v letih 1978–2010 nobena oseba ni storila samomora, kar se statistično značilno ne razlikuje od pričakovanega števila samomorov (0,448) v primerljivi splošni populaciji v Sloveniji. Ugotovitve raziskave nakazujejo, da kljub znano bolj izraženem samomorilnem vedenju med preživelimi raka v otroštvu v Sloveniji v primerjavi s splošno populacijo pojavljanje samomorov pri osebah, zbolelih za levkemijo v otroštvu, ni pogostejše kot v splošni populaciji.Persons with childhood leukaemia often suffer from physical and psychosocial consequences of the disease and its treatment. Several studies have shown that depression and suicidal behaviour are expressed strongly in persons with a childhood cancer experience. In our study, we researched the occurrence of suicides among persons with childhood leukaemia compared to the general population in Slovenia in the period 1978–2010. The expected number of suicides was calculated based on the control group of individuals from the general population with the same gender, age at the beginning of observation, starting year and duration of observation as the research group, thus group of persons with childhood cancer. The study showed that none of the persons with childhood cancer committed suicide in the period 1978-2010, which is not statistically different from the expected number of suicides (0.448) in comparison with the general population in Slovenia. The findings of this study indicate that, despite the significantly increased expression of suicidal behaviour among survivors of childhood leukaemia in Slovenia compared to the general population, suicides do not occur more often among people with childhood leukaemia than among the general population

Reducing Crowding by Weakening Inhibitory Lateral Interactions in the Periphery with Perceptual Learning

We investigated whether lateral masking in the near-periphery, due to inhibitory lateral interactions at an early level of central visual processing, could be weakened by perceptual learning and whether learning transferred to an untrained, higher-level lateral masking known as crowding. The trained task was contrast detection of a Gabor target presented in the near periphery (4°) in the presence of co-oriented and co-aligned high contrast Gabor flankers, which featured different target-to-flankers separations along the vertical axis that varied from 2λ to 8λ. We found both suppressive and facilitatory lateral interactions at target-to-flankers distances (2λ - 4λ and 8λ, respectively) that were larger than those found in the fovea. Training reduces suppression but does not increase facilitation. Most importantly, we found that learning reduces crowding and improves contrast sensitivity, but has no effect on visual acuity (VA). These results suggest a different pattern of connectivity in the periphery with respect to the fovea as well as a different modulation of this connectivity via perceptual learning that not only reduces low-level lateral masking but also reduces crowding. These results have important implications for the rehabilitation of low-vision patients who must use peripheral vision to perform tasks, such as reading and refined figure-ground segmentation, which normal sighted subjects perform in the fovea

Measuring the gravitational field in General Relativity: From deviation equations and the gravitational compass to relativistic clock gradiometry

How does one measure the gravitational field? We give explicit answers to this fundamental question and show how all components of the curvature tensor, which represents the gravitational field in Einstein's theory of General Relativity, can be obtained by means of two different methods. The first method relies on the measuring the accelerations of a suitably prepared set of test bodies relative to the observer. The second methods utilizes a set of suitably prepared clocks. The methods discussed here form the basis of relativistic (clock) gradiometry and are of direct operational relevance for applications in geodesy.Comment: To appear in "Relativistic Geodesy: Foundations and Application", D. Puetzfeld et. al. (eds.), Fundamental Theories of Physics, Springer 2018, 52 pages, in print. arXiv admin note: text overlap with arXiv:1804.11106, arXiv:1511.08465, arXiv:1805.1067

Fidelity Variants of RNA Dependent RNA Polymerases Uncover an Indirect, Mutagenic Activity of Amiloride Compounds

In a screen for RNA mutagen resistance, we isolated a high fidelity RNA dependent RNA polymerase (RdRp) variant of Coxsackie virus B3 (CVB3). Curiously, this variant A372V is also resistant to amiloride. We hypothesize that amiloride has a previously undescribed mutagenic activity. Indeed, amiloride compounds increase the mutation frequencies of CVB3 and poliovirus and high fidelity variants of both viruses are more resistant to this effect. We hypothesize that this mutagenic activity is mediated through alterations in intracellular ions such as Mg2+ and Mn2+, which in turn increase virus mutation frequency by affecting RdRp fidelity. Furthermore, we show that another amiloride-resistant RdRp variant, S299T, is completely resistant to this mutagenic activity and unaffected by changes in ion concentrations. We show that RdRp variants resist the mutagenic activity of amiloride via two different mechanisms: 1) increased fidelity that generates virus populations presenting lower basal mutation frequencies or 2) resisting changes in divalent cation concentrations that affect polymerase fidelity. Our results uncover a new antiviral approach based on mutagenesis

Misperceptions in the Trajectories of Objects undergoing Curvilinear Motion

Trajectory perception is crucial in scene understanding and action. A variety of trajectory misperceptions have been reported in the literature. In this study, we quantify earlier observations that reported distortions in the perceived shape of bilinear trajectories and in the perceived positions of their deviation. Our results show that bilinear trajectories with deviation angles smaller than 90 deg are perceived smoothed while those with deviation angles larger than 90 degrees are perceived sharpened. The sharpening effect is weaker in magnitude than the smoothing effect. We also found a correlation between the distortion of perceived trajectories and the perceived shift of their deviation point. Finally, using a dual-task paradigm, we found that reducing attentional resources allocated to the moving target causes an increase in the perceived shift of the deviation point of the trajectory. We interpret these results in the context of interactions between motion and position systems

Transcriptomic Analyses of Sexual Dimorphism of the Zebrafish Liver and the Effect of Sex Hormones

10.1371/journal.pone.0053562PLoS ONE81