A linear-time algorithm for finding a complete graph minor in a dense graph

Let g(t) be the minimum number such that every graph G with average degree d(G) \geq g(t) contains a K_{t}-minor. Such a function is known to exist, as originally shown by Mader. Kostochka and Thomason independently proved that g(t) \in \Theta(t*sqrt{log t}). This article shows that for all fixed \epsilon > 0 and fixed sufficiently large t \geq t(\epsilon), if d(G) \geq (2+\epsilon)g(t) then we can find this K_{t}-minor in linear time. This improves a previous result by Reed and Wood who gave a linear-time algorithm when d(G) \geq 2^{t-2}.Comment: 6 pages, 0 figures; Clarification added in several places, no change to arguments or result

The contact binary VW Cephei revisited: surface activity and period variation

Context. Despite the fact that VW Cephei is one of the well-studied contact binaries in the literature, there is no fully consistent model available that can explain every observed property of this system. Aims. Our motivation is to obtain new spectra along with photometric measurements, to analyze what kind of changes may have happened in the system in the past two decades, and to propose new ideas for explaining them. Methods. For the period analysis we determined 10 new times of minima from our light curves, and constructed a new O$-$C diagram of the system. Radial velocities of the components were determined using the cross-correlation technique. The light curves and radial velocities were modelled simultaneously with the PHOEBE code. All observed spectra were compared to synthetic spectra and equivalent widths of the H$\alpha$ line were measured on their differences. Results. We have re-determined the physical parameters of the system according to our new light curve and spectral models. We confirm that the primary component is more active than the secondary, and there is a correlation between spottedness and the chromospheric activity. We propose that flip-flop phenomenon occurring on the primary component could be a possible explanation of the observed nature of the activity. To explain the period variation of VW Cep, we test two previously suggested scenarios: presence of a fourth body in the system, and the Applegate-mechanism caused by periodic magnetic activity. We conclude that although none of these mechanisms can be ruled out entirely, the available data suggest that mass transfer with a slowly decreasing rate gives the most likely explanation for the period variation of VW Cep.Comment: 13 pages, 18 figures, 9 tables, accepted for publication in Astronomy and Astrophysic

Overtone and multi-mode RR Lyrae stars in the globular cluster M3

The overtone and multi-mode RR Lyrae stars in the globular cluster M3 are studied using a 200-d long, $B,V$ and $I_{\mathrm C}$ time-series photometry obtained in 2012. 70\% of the 52 overtone variables observed show some kind of multi-periodicity (additional frequency at ${f_{0.61}}={f_{\mathrm {1O}}}/0.61$ frequency ratio, Blazhko effect, double/multi-mode pulsation, period doubling). A signal at 0.587 frequency ratio to the fundamental-mode frequency is detected in the double-mode star, V13, which may be identified as the second radial overtone mode. If this mode-identification is correct, than V13 is the first RR Lyrae star showing triple-mode pulsation of the first three radial modes. Either the Blazhko effect or the ${f_{0.61}}$ frequency (or both of these phenomena) appear in 7 double-mode stars. The $P_{\mathrm{1O}}/P_{\mathrm{F}}$ period ratio of RRd stars showing the Blazhko effect are anomalous. A displacement of the main frequency component at the fundamental-mode with the value of modulation frequency (or its half) is detected in three Blazhko RRd stars parallel with the appearance of the overtone-mode pulsation. The ${f_{0.61}}$ frequency appears in RRc stars that lie at the blue side of the double-mode region and in RRd stars, raising the suspicion that its occurrence may be connected to double-mode pulsation. The changes of the Blazhko and double-mode properties of the stars are also reviewed using the recent and archive photometric data.Comment: accepted for publication in ApJ Suppl. 26 pages, 25 figure

Ocorrência e intensidade de antracnose em viveiros de mudas e cultivos comerciais de pupunheira do Paraná e Santa Catarina.

bitstream/item/68273/1/CT-306.pd

Caracterização morfo-fisiológica e patogenicidade de Colletotrichum gloeosporioides da pupunheira.

Isolados de Colletotorichum sp. de folhas de pupunheira (Bactris gasipaes) com sintomas de antracnose foram comparados fenotipicamente, visando a sua caracterização e identificação. Foram analisados 17 isolados, oriundos dos Estados do Acre, Rondônia, Espírito Santo, São Paulo e Paraná. Caracterizaram- se os sintomas da doença e os isolados foram comparados em relação à forma e tamanho de conídios e apressórios, e quanto a coloração das colônias, crescimento micelial e esporulação em meio de cultura. A patogenicidade dos isolados foi confirmada em folhas de pupunheira destacadas. Todos os isolados foram identificados como Colletotrichum gloeosporioides e a fase meiospórica in vitro (Glomerella cingulata) ocorreu apenas em um isolado procedente de Linhares, Espírito Santo

Avaliação de fungicidas para o controle de antracnose em folhas de pupunheira (Bactris gasipaes).

A antracnose, causada pelo fungo Colletotrichum gloeosporioides, é uma doença foliar importante da pupunheira (Bactris gasipaes) nas fases de muda e planta jovem. O objetivo do trabalho foi avaliar a eficiência de fungicidas químicos no controle de antracnose em folhas de pupunheiras jovens, no Noroeste do Paraná. O ensaio foi conduzido com o delineamento experimental em blocos ao acaso, com cinco tratamentos com fungicidas e uma testemunha sem fungicida, com quatro repetições. Foram utilizados os fungicidas chlorotalonil (2 g L-1), chlorotalonil+tiofanato metílico (1 + 0,4 g L-1), tebuconazole (0,2 g L-1), azoxistrobina (80 mg L-1) e calda Viçosa (3 g L-1 de ácido bórico; 5 g L-1 de sulfato de cobre; 6 g L-1 de sulfato de zinco; 3,5 g L-1 de cal hidratada). Cada fungicida foi pulverizado cinco vezes, com intervalo de 15 a 20 dias entre as aplicações. Verificou-se que todos os tratamentos com fungicidas proporcionaram redução estatisticamente significativa na intensidade da doença em relação à testemunha sem fungicida (P=0,05). Os fungicidas mais eficientes no controle da doença foram chlorotalonil e a mistura de tiofanato metílico+chlorotalonil.Nota técnica

Cost-effectiveness analysis of a gender-neutral human papillomavirus vaccination program in the Netherlands

Background: Vaccinating girls against human papillomavirus (HPV) infection is a highly effective and cost-effective intervention to provide protection against HPV-induced cancers. Since vaccination coverage rates among girls is modest in the Netherlands, additional strategies should be implemented to improve the protection against HPV-related cancer. Here we assessed the benefits and cost-effectiveness of gender-neutral vaccination. Methods: We designed a static Markov model with a lifelong time horizon to simulate a cohort of 100,000 12-year-old Dutch boys. The model compares health and economic effects of HPV vaccination taking the current female vaccination coverage into consideration. HPV prevalence in boys was corrected for the predicted herd effects of the female programme in 2017. We extracted transition probabilities from peer-reviewed literature and previously constructed models. The robustness of the model was tested with multiple sensitivity analyses. Results: Vaccinating 30% of 100,000 12-year-old boys prevents 18, 13 and 25 cases of anal, penile, and oropharyngeal cancers in men, respectively. A total of 205 quality-adjusted life-years (QALYs) are saved by preventing cancer-related morbidity and mortality. Assuming a vaccine price of (sic)50 per dose, the incremental cost-effectiveness ratio (ICER) is (sic)17,907 per QALY. In addition, due to vaccine-induced herd effects, we estimated that 110 cases of cancer in females would be additionally prevented and 246 QALYs would be gained in the female cohort, bringing the total to 166 cancers prevented and 451 QALYs gained. Taking these additional benefits of boys' vaccination into account, the overall ICER was estimated at (sic)7310 per QALY gained. The model outcomes are most sensitive to variation in vaccine price, herd immunity from females and vaccine efficacy. Conclusions: Vaccination of boys, additional to girls, will prevent a relevant number of cancers in both boys and girls. Based on the current Dutch situation vaccination of HPV in boys is likely cost-effective. GSK Study identifier: HO-18-19169. (C) 2020 GlaxoSmithKline Biologicals S.A. Published by Elsevier Ltd