On SAT representations of XOR constraints

We study the representation of systems S of linear equations over the two-element field (aka xor- or parity-constraints) via conjunctive normal forms F (boolean clause-sets). First we consider the problem of finding an "arc-consistent" representation ("AC"), meaning that unit-clause propagation will fix all forced assignments for all possible instantiations of the xor-variables. Our main negative result is that there is no polysize AC-representation in general. On the positive side we show that finding such an AC-representation is fixed-parameter tractable (fpt) in the number of equations. Then we turn to a stronger criterion of representation, namely propagation completeness ("PC") --- while AC only covers the variables of S, now all the variables in F (the variables in S plus auxiliary variables) are considered for PC. We show that the standard translation actually yields a PC representation for one equation, but fails so for two equations (in fact arbitrarily badly). We show that with a more intelligent translation we can also easily compute a translation to PC for two equations. We conjecture that computing a representation in PC is fpt in the number of equations.Comment: 39 pages; 2nd v. improved handling of acyclic systems, free-standing proof of the transformation from AC-representations to monotone circuits, improved wording and literature review; 3rd v. updated literature, strengthened treatment of monotonisation, improved discussions; 4th v. update of literature, discussions and formulations, more details and examples; conference v. to appear LATA 201

The relationship between serum 25-hydroxyvitamin D and parathyroid hormone concentration in assessing vitamin D deficiency in pet rabbits

Background Vitamin D deficiency and related metabolic bone diseases in pet rabbits have been intermittently debated. In human research, the parathyroid hormone concentration in relation to the 25-hydroxyvitamin D concentration is used to determine vitamin D deficiency. Thus, this study aimed to identify the breakpoint in the 25-hydroxyvitamin D concentration indicating a significant change in the parathyroid hormone concentration in 139 pet rabbits. An enzyme immunoassay kit was used for 25-hydroxyvitamin D analysis and the intact parathyroid hormone (PTH 1-84) immunoradiometric assay kit for parathyroid hormone analysis. The mid-tibial cortical bone density was measured using peripheral quantitative computed tomography. A segmented linear regression analysis was performed, with the 25-hydroxyvitamin D concentration as the independent variable, and parathyroid hormone, ionised calcium, total calcium, inorganic phosphorus concentrations and the mid-tibial cortical density as the dependent variables. Results The breakpoint for the parathyroid hormone concentration occurred at a 25(OH)D concentration of 17 ng/mL, whereas the cortical bone density breakpoint occurred at a 25-hydroxyvitamin D concentration of 19 ng/mL. No breakpoints were found for ionised calcium, total calcium or phosphorus. Conclusions These results suggest that a serum 25-hydroxyvitamin D concentration of 17 ng/mL serves as the threshold for vitamin D deficiency in rabbits. Nearly one-third of the rabbits had a serum 25-hydroxyvitamin D concentration below this threshold. Concerns persist regarding the high prevalence of vitamin D deficiency in pet rabbits and the possible health consequences caused by a chronic vitamin D deficiency, including the risk for metabolic bone diseases.Peer reviewe

Unettomuus yksilön ongelmana:unen ja unettomuuden kehykset Helsingin Sanomissa vuonna 2021

Tiivistelmä. Tämän tutkielman tavoitteena oli kuvata ja analysoida Helsingin Sanomien vuonna 2021 julkaistuissa uni- ja unettomuusaiheisissa jutuissa esiintyviä kehyksiä, sekä kuvata millainen yksilön rooli niissä on. Toteutin tutkielman laadullisella tutkimusotteella. Tutkimusaineisto koostui kuudestatoista artikkelista, kymmenestä henkilöjutusta, kahdeksasta tutkimusuutisesta, viidestä kolumnista ja kahdesta mielipidekirjoituksesta, eli yhteensä neljästäkymmenestäyhdestä lehtijutusta. Aineistolle toteutettiin kehysanalyysi. Tutkielman tulosten mukaan unta ja unettomuutta kehystetään viiden eri kehyksen kautta, jotka ovat teknologiakehys, henkilökohtaisen kokemuksen kehys, asiantuntijakehys, suorittamiskehys sekä yhteiskuntakriittinen kehys. Uniongelmat kehystetään usein ratkaistavissa oleviksi ongelmiksi, ja hyvän unen merkitys terveyden kannalta korostuu tuloksissa. Unesta käytävää keskustelua käydään pitkälti asiantuntijoiden, usein lääkäreiden tai tutkijoiden, sekä tavallisten kokemusasiantuntijoiden toimesta. Uneen liittyvää tietoa jaetaan paljon, niin asiantuntijoiden kuin tavallisten ihmistenkin toimesta. Tulokset osoittavat, että yksilön vastuulla on muokata oma unensa riittävän laadukkaaksi, ja ratkaista mahdolliset uniongelmat. Yhteiskunnalliset muutostarpeet jäivät unettomuudesta käydyn yksilökeskeisen keskustelun taustalle. Tutkielma toi uutta tietoa merkittävästä terveysjournalismin aihealueesta eli siitä, miten unesta ja unettomuudesta puhutaan mediassa. Aihe linkittyy laajempaan terveysjournalismin sekä terveysviestinnän keskusteluun. Tutkielmassa saadut tulokset voivat hyödyttää terveysjournalismin parissa työskenteleviä tekemään parempaa ja lukijoille arvokkaampaa terveysjournalismia

The impact of corotation on gradual solar energetic particle event intensity profiles

Corotation of particle-filled magnetic flux tubes is generally thought to have a minor influence on the time-intensity profiles of gradual Solar Energetic Particle (SEP) events. For this reason many models solve the focussed transport equation within the corotating frame, thus neglecting corotation effects. We study the effects of corotation on gradual SEP intensity profiles at a range of observer longitudinal positions relative to the solar source. We study how corotation affects the duration and decay time constant of SEP events and the variation of peak intensity with observer position. We use a 3D full-orbit test particle code with time-extended SEP injection via a shock-like source. Unlike with focussed transport models, the test particle approach enables us to switch corotation on and off easily. While shock acceleration is not modelled directly, our methodology allows us to study how corotation and the time-varying observer-shock magnetic connection influence intensity profiles detected at six observers. We find that corotation strongly affects SEP profiles, for a monoenergetic population of 5 MeV protons, being a dominant influence during the decay phase. Simulations including corotation display dramatically shortened durations for western events, compared to those which do not include it. When corotation is taken into account, for both eastern and western events the decay time constant is reduced and its dependence on the scattering mean free path becomes negligible. Corotation reduces the peak intensity for western events and enhances it for eastern ones, thus making the east-west asymmetry in peak intensity stronger, compared to the no-corotation case. Modelling SEP intensity profiles without carefully accounting for corotation leads to artificially extended decay phases during western events and profiles with a similar shape regardless of observer longitudinal position.Comment: Submitted to A&A Let

Modelling shock-like injections of solar energetic particles with 3D test particle simulations

Solar Energetic Particle (SEP) acceleration and injection into interplanetary space during gradual SEP events is thought to take place at Coronal Mass Ejection (CME)-driven shocks. Features of measured intensity profiles at 1 au have been attributed to properties of the radial and longitudinal/latitudinal injections at the shock. Focussed transport models are typically used to model acceleration at a CME-shock and subsequent propagation. Test particle simulations are an alternative approach but so far they have been carried out only with instantaneous injection near the Sun. We develop the first temporally extended shock-like injection for our 3D test particle code and investigate how the spatial features of injection affect SEP intensity and anisotropy profiles for observers at 0.3 and 1.0 au. We conduct simulations of a monoenergetic population of 5 MeV protons considering three different radial injection functions and two longitudinal/latitudinal injection functions. We consider a range of scattering conditions with scattering mean free path values ranging from 0.1-1.0 au, and determine intensity and anisotropy profiles at six observers at different longitudinal locations. We find that the radial, longitudinal and latitudinal injection functions play a relatively minor role in shaping the SEP intensity profiles. The dependence of profiles on the value of the scattering mean free path is also weak, unlike what is found from 1D focussed transport models. Spatial factors, such as the time of observer-shock-connection/disconnection and time of shock passage have a much stronger influence on SEP intensities and anisotropies. Persistent anisotropies until shock passage are seen in our simulations. Comparing instantaneous and shock-like injections, we find that the link between duration of injection and of the SEP event is very weak, unlike what is commonly assumed.Comment: Submitted to A&

Forecasting >300 MeV SEP events: Extending SPARX to high energies

The forecasting of solar energetic particles (SEPs) is a prominent area of space weather research. Numerous forecasting models exist that predict SEP event properties at proton energies <100MeV. One of these models is the SPARX system, a physics-based forecasting tool that calculates >10MeV and >60MeV flux profiles within minutes of a flare being detected. This work describes SPARX-H, the extension of SPARX to forecast SEP events above 300MeV . SPARX-H predicts fluxes in three high energy channels up to several hundred MeV. Correlations between SEP peak flux and peak intensity of the associated solar flare are seen to be weak at high energies, but improved when events are grouped based on the field polarity during the event. Initial results from this new high energy forecasting tool are presented here and the applications of high energy forecasts are discussed. Additionally, the new high energy version of SPARX is tested on a set of historic SEP events. We see that SPARX-H performs best when predicting peak fluxes from events with source locations in well-connected regions, where many large SEP events tend to originate.Comment: Accepted for publication in Space Weather 13 pages, 5 figure

Optimization of wireless networks performance: An approach based on a partial penalty method

© 2017, North Atlantic University Union. All rights reserved.We study an optimization problem for a wireless telecommunication network stated as a generalized transportation problem (TP), where m (the number of “sellers”) is the number of network providers, and n (the number of “buyers”) is the number of connections established at a given time moment. Since in practice initial data of such problems are, generally speaking, inexact and/or vary rather quickly, it is more important to obtain an approximate solution of the problem (with a prescribed accuracy) within a reasonable time interval rather than to solve it precisely (but in a longer time). We propose to solve this problem by a technique that explores the idea of penalty functions, namely, the so-called Partial Penalty Method (PPM, for short). As distinct from exact solution methods for TP (e.g., the method of potentials), our approach allows us to further extend the class of considered problems by including to it TP with nonlinear objective functions. As an example, we consider a TP, where the objective function (expenses connected with resource allocation) is such that the price of the unit amount of the resource is not constant but depends on the total purchase size. In addition, we study the limit behavior of solutions to TP whose data are subject to fading disturbances. Since in our approach the initial point is not necessarily admissible, we use an approximate solution of each problem as the initial point for the next one. As expected, under certain requirements to disturbances the sequence of solutions to “disturbed” problems tends to a solution of the limit problem. We prove experimentally that PPM is more efficient than the usual variant of the Penalty Function Method (the Full Penalty Method, or FPM). The preference of PPM over FPM is more evident for n much greater than m

Dual decomposition scheme for resource allocation problem in networks with moving nodes

We consider a two-level, two criteria, optimization problem of resource allocation in communication networks, which consists of maximizing the total network utility, i.e., the fee paid by the consumers, and minimizing the costs of implementing these resources. In this paper we present a new dual iterative method for solving this problem, which enables us to utilize its decomposable structure via sequential solution of families of one-dimensional problems. We compare our new dual method to known methods for solving this problem. In general, we give a new promising approach in the paper to solve resource allocation problems in communication networks. Moreover, we suggest a new way to adjust the basic model to networks with moving nodes. We present numerical results about the computational efficiency of the methods considered. © 2012 IEEE

Optimization problems for distribution of resources in spatial systems

We consider a problem of optimal allocation of a homogeneous resource in spatially distributed systems such as communication networks, where both utilities of consumers and network expenses must be taken into account. This approach leads to a two-objective optimization problem, which involves non-differentiable functions whose values are computed algorithmically. We propose several approaches to define a solution and to construct corresponding solution methods for such problems. In particular, new subgradient methods for non-differentiable Pareto optimization problems are suggested. Their work is illustrated by computational results on test problems

Genetic diversity in table grapes based on RAPD and microsatellite markers

O objetivo deste trabalho foi analisar a diversidade genética de 47 acessos de uvas de mesa, procedentes do Banco de Germoplasma de Videira da Embrapa Semiárido, por meio de 20 marcadores moleculares RAPD e sete marcadores microsatélites. Distâncias genéticas entre pares de acessos foram obtidas com base no índice de similaridade de Jaccard para marcadores RAPD e no complemento aritmético do índice ponderado para dados de microsatélites. Os grupos foram formados de acordo com a análise de agrupamento de Tocher e com o método de agrupamento não ponderado (UPGMA). Os marcadores microsatélites foram mais eficientes do que os RAPD na identificação das relações de parentesco. As informações de distância genética, baseadas em características moleculares e aliadas ao desempenho agronômico das cultivares, permitiram a recomendação de parentais para cruzamentos, para a obtenção de híbridos superiores nas populações segregantes do programa de melhoramento de videira da Embrapa Semiárido.The objective of this work was to analyze the genetic diversity of 47 table grape accessions, from the grapevine germplasm bank of Embrapa Semiárido, using 20 RAPD and seven microsatellite markers. Genetic distances between pairs of accessions were obtained based on Jaccard's similarity index for RAPD data and on the arithmetic complement of the weighted index for microsatellite data. The groups were formed according to the Tocher's cluster analysis and to the unweighted pair-group method with arithmetic mean (UPGMA). The microsatellite markers were more efficient than the RAPD ones in the identification of genetic relationships. Information on the genetic distance, based on molecular characteristics and coupled with the cultivar agronomic performance, allowed for the recommendation of parents for crossings, in order to obtain superior hybrids in segregating populations for the table grape breeding program of Embrapa Semiárido.