Ultrarelativistic electrons and solar flare gamma-radiation

Ten solar flares with gamma radiation in excess of 10 MeV were observed. Almost all took place within a heliolatitude greater than 60 deg, close to the solar limb, an indication of the essential anisotropy of high-energy gamma radiation. This high-energy solar flare gamma radiation can be explained by the specific features of the bremsstrahlung of ultrarelativistic electrons trapped within the magnetic arc of the solar atmosphere, even if the acceleration of the electrons is anisotropic

Vector Reachability Problem in SL(2,Z)

This paper solves three open problems about the decidability of the vector and scalar reachability problems and the point to point reachability by fractional linear transformations over finitely generated semigroups of matrices from . Our approach to solving these problems is based on the characterization of reachability paths between vectors or points, which is then used to translate the numerical problems on matrices into computational problems on words and regular languages. We will also give geometric interpretations of these results

Decidability of cutpoint isolation for letter-monotonic probabilistic finite automata

We show the surprising result that the cutpoint isolation problem is decidable for probabilistic finite automata where input words are taken from a letter-bounded context-free language. A context-free language $L$ is letter-bounded when $L \subseteq a_1^*a_2^* \cdots a_k^*$ for some finite $k > 0$ where each letter is distinct. A cutpoint is isolated when it cannot be approached arbitrarily closely. The decidability of this problem is in marked contrast to the situation for the (strict) emptiness problem for PFA which is undecidable under the even more severe restrictions of PFA with polynomial ambiguity, commutative matrices and input over a letter-bounded language as well as to the injectivity problem which is undecidable for PFA over letter-bounded languages. We provide a constructive nondeterministic algorithm to solve the cutpoint isolation problem, which holds even when the PFA is exponentially ambiguous. We also show that the problem is at least NP-hard and use our decision procedure to solve several related problems

Decision Questions for Probabilistic Automata on Small Alphabets

We study the emptiness and λ-reachability problems for unary and binary Probabilistic Finite Automata (PFA) and characterise the complexity of these problems in terms of the degree of ambiguity of the automaton and the size of its alphabet. Our main result is that emptiness and λ-reachability are solvable in EXPTIME for polynomially ambiguous unary PFA and if, in addition, the transition matrix is over {0, 1}, we show they are in NP. In contrast to the Skolem-hardness of the λ-reachability and emptiness problems for exponentially ambiguous unary PFA, we show that these problems are NP-hard even for finitely ambiguous unary PFA. For binary polynomially ambiguous PFA with commuting transition matrices, we prove NP-hardness of the λ-reachability (dimension 9), nonstrict emptiness (dimension 37) and strict emptiness (dimension 40) problems

Linear-Time Model Checking Branching Processes

(Multi-type) branching processes are a natural and well-studied model for generating random infinite trees. Branching processes feature both nondeterministic and probabilistic branching, generalizing both transition systems and Markov chains (but not generally Markov decision processes). We study the complexity of model checking branching processes against linear-time omega-regular specifications: is it the case almost surely that every branch of a tree randomly generated by the branching process satisfies the omega-regular specification? The main result is that for LTL specifications this problem is in PSPACE, subsuming classical results for transition systems and Markov chains, respectively. The underlying general model-checking algorithm is based on the automata-theoretic approach, using unambiguous Büchi automata

On Reachability Problems for Low-Dimensional Matrix Semigroup

We consider the Membership and the Half-Space Reachability problems for matrices in dimensions two and three. Our first main result is that the Membership Problem is decidable for finitely generated sub-semigroups of the Heisenberg group over rational numbers. Furthermore, we prove two decidability results for the Half-Space Reachability Problem. Namely, we show that this problem is decidable for sub-semigroups of GL(2,Z) and of the Heisenberg group over rational numbers

ГЕНДЕРНЫЕ ОСОБЕННОСТИ И ТАКТИКА ЛЕЧЕНИЯ ОСТРОГО КОРОНАРНОГО СИНДРОМА БЕЗ ПОДЪЕМА СЕГМЕНТА ST У ЖЕНЩИНЫ МОЛОДОГО ВОЗРАСТА

Acute coronary syndrome in young women is of particular interest for today’s research. There are some data on the different effects of major risk factors among the sex groups, driven by the presence of specific risk factors in the female population. The clinical case reports different clinical course of atherosclerosis in men and women, presented with non-stenotic coronary atherosclerosis with hormonal imbalance and classical risk factors of complicated CAD.Острый коронарный синдром у женщин молодого возраста становится актуальной проблемой. Известны данные о разнонаправленных влияниях основных факторов риска в зависимости от пола и с учетом реализации специфических факторов риска женской популяции. Приводится случай из практики, демонстрирующий иное клиническое течение атеросклероза коронарных артерий у мужчин и женщин: выявление нестенозирующей формы коронарного атеросклероза на фоне нарушения гормонального статуса и «классических» факторов риска осложненного течения ИБС

Vector and scalar reachability problems in SL(2, Z)

This paper solves three open problems about the decidability of the vector and scalar reachability problems and the point to point reachability by fractional linear transformations over finitely generated semigroups of matrices from SL(2, Z). Our approach to solving these problems is based on the characterization of reachability paths between vectors or points, which is then used to translate the numerical problems on matrices into computational problems on words and regular languages. We will also give geometric interpretations of these results

Automatic models of first order theories

10.1016/j.apal.2013.03.001Annals of Pure and Applied Logic1649837-854APAL

Decidability of cutpoint isolation for probabilistic finite automata on letter-bounded inputs

We show the surprising result that the cutpoint isolation problem is decidable for probabilistic finite automata where input words are taken from a letter-bounded context-free language. A context-free language L is letter-bounded when L ⊆ a∗1a∗2 · · · a∗` for some finite ` > 0 where each letter is distinct. A cutpoint is isolated when it cannot be approached arbitrarily closely. The decidability of this problem is in marked contrast to the situation for the (strict) emptiness problem for PFA which is undecidable under the even more severe restrictions of PFA with polynomial ambiguity, commutative matrices and input over a letter-bounded language as well as to the injectivity problem which is undecidable for PFA over letter-bounded languages. We provide a constructive nondeterministic algorithm to solve the cutpoint isolation problem, which holds even when the PFA is exponentially ambiguous. We also show that the problem is at least NP-hard and use our decision procedure to solve several related problems