On the NP-Hardness of Approximating Ordering Constraint Satisfaction Problems

We show improved NP-hardness of approximating Ordering Constraint Satisfaction Problems (OCSPs). For the two most well-studied OCSPs, Maximum Acyclic Subgraph and Maximum Betweenness, we prove inapproximability of $14/15+\epsilon$ and $1/2+\epsilon$. An OCSP is said to be approximation resistant if it is hard to approximate better than taking a uniformly random ordering. We prove that the Maximum Non-Betweenness Problem is approximation resistant and that there are width-$m$ approximation-resistant OCSPs accepting only a fraction $1 / (m/2)!$ of assignments. These results provide the first examples of approximation-resistant OCSPs subject only to P $\neq$ \NP

A crise social desenhada pelas crianças: imaginação e conhecimento social

A crise social e económica que tem atingido o mundo desde 2008, com efeitos especialmente sentidos nos países do Sul da Europa, causou impactos fortes e visíveis na infância, como o aumento das taxas efetivas e de risco de pobreza e a vulnerabilidade e a exposição a fatores de risco social e de perda consistente de direitos. A análise dessas incidências tem vindo a ser trabalhada num conjunto de relatórios nacionais e internacionais, de ONG’s e estudos académicos. No entanto, poucos estudos têm dedicado atenção ao modo como a interpretação das representações das crianças sobre a crise é feita e sobre as expressões específicas que estas assumem na sua vida quotidiana. As crianças são capazes de observar os modos como a crise impacta o seu próprio grupo geracional, bem como os adultos que mais lhe são próximos. Da mesma forma, promovem interpretações económicas sobre os fenómenos, sejam elas mais “ingénuas” ou mais complexas. Este artigo incide sobre as representações das crianças sobre a crise social e económica em Portugal. São especialmente analisadas narrativas gráficas produzidas por crianças oriundas de classes trabalhadoras, com idades compreendidas entre os 6 e os 10 anos de idade. Por meio dessas narrativas, as crianças constroem formas visuais a partir da sua imaginação sobre a sua condição. Assim, a imaginação das crianças é um modo de acesso ao conhecimento na sociedade onde se inserem e aos seus modos próprios de compreensão de realidades complexas.The social and economic crisis that has hit the world since 2008, with effects strongly felt in the countries of Southern Europe, has had fierce and visible impacts in childhood with the increase of the effective rates, the risk of poverty and vulnerability, and the exposure to factors of social risk and consistent loss of rights. The analysis of these incidents has been worked on in a series of national and international reports from NGOs and academic studies. However, few studies have devoted attention to the way in which the interpretation of the representations of children about the crisis is made and the specific expressions that they assume in their daily lives. Children are able to observe the ways in which the crisis affects their own generational group as well as the adults closest to them. In the same way, they promote economic interpretations of phenomena, whether “naïve” or more complex. This article focuses on the representations of children about the social and economic crisis in Portugal. Graphical narratives produced by children from working classes, aged between 6 and 10 years old, are given focus. From these narratives, children construct visual forms from their imagination about their social condition. Thus, the child’s imagination is a way of accessing knowledge in the society they belong to and their own way of understanding complex realities.CIEC - Centro de Investigação em Estudos da Criança, IE, UMinho (UI 317 da FCT), Portugalinfo:eu-repo/semantics/publishedVersio

Fatores de produção na cultura do milho sob efeito de doses e queima de resíduos orgânicos.

Os resíduos orgânicos quando corretamente manejados e utilizados revertem-se em fornecedores de nutrientes e condicionadores das propriedades físicas e biológicas do solo, garantindo ambiente adequado para o desenvolvimento do sistema radicular das plantas por uma lado e aumentando a produção de alimentos, fibras e energia, por outro. O aproveitamento agrícola dos resíduos de podas das árvores das cidades, na forma de composto orgânico ou in natura tem sido apontado como uma solução adequada, uma vez que, proporciona a liberação de nutrientes para as plantas semcausar grande impacto..

Electron scattering from molecules and molecular aggregates of biological relevance

In this Topical Review we survey the current state of the art in the study of low energy electron collisions with biologically relevant molecules and molecular clusters. We briefly describe the methods and techniques used in the investigation of these processes and summarise the results obtained so far for DNA constituents and their model compounds, amino acids, peptides and other biomolecules. The applications of the data obtained is briefly described as well as future required developments

Unambiguous observation of F-atom core-hole localization in CF4 through body-frame photoelectron angular distributions

Citation: McCurdy, C. W., Rescigno, T. N., Trevisan, C. S., Lucchese, R. R., Gaire, B., Menssen, A., . . . Weber, T. (2017). Unambiguous observation of F-atom core-hole localization in CF4 through body-frame photoelectron angular distributions. Physical Review A, 95(1). doi:10.1103/PhysRevA.95.011401A dramatic symmetry breaking in K-shell photoionization of the CF4 molecule in which a core-hole vacancy is created in one of four equivalent fluorine atoms is displayed in the molecular frame angular distribution of the photoelectrons. Observing the photoejected electron in coincidence with an F+ atomic ion after Auger decay is shown to select the dissociation path where the core hole was localized almost exclusively on that atom. A combination of measurements and ab initio calculations of the photoelectron angular distribution in the frame of the recoiling CF3+ and F+ atoms elucidates the underlying physics that derives from the Ne-like valence structure of the F(1s-1) core-excited atom. © 2017 American Physical Society

Dynamic constriction and fission of endoplasmic reticulum membranes by reticulon

The endoplasmic reticulum (ER) is a continuous cell-wide membrane network. Network formation has been associated with proteins producing membrane curvature and fusion, such as reticulons and atlastin. Regulated network fragmentation, occurring in different physiological contexts, is less understood. Here we find that the ER has an embedded fragmentation mechanism based upon the ability of reticulon to produce fission of elongating network branches. In Drosophila, Rtnl1-facilitated fission is counterbalanced by atlastin-driven fusion, with the prevalence of Rtnl1 leading to ER fragmentation. Ectopic expression of Drosophila reticulon in COS-7 cells reveals individual fission events in dynamic ER tubules. Consistently, in vitro analyses show that reticulon produces velocity-dependent constriction of lipid nanotubes leading to stochastic fission via a hemifission mechanism. Fission occurs at elongation rates and pulling force ranges intrinsic to the ER, thus suggesting a principle whereby the dynamic balance between fusion and fission controlling organelle morphology depends on membrane motility

Erratum to: Is Sensory Loss an Understudied Risk Factor for Frailty? A Systematic Review and Meta-analysis

In the article “Is Sensory Loss an Understudied Risk Factor for Frailty? A Systematic Review and Meta-analysis,” an author was missing. Ana Maseda should be listed as the 11th author. The correct author list is: Benjamin Kye Jyn Tan, Ryan Eyn Kidd Man, Alfred Tau Liang Gan, Eva K Fenwick, Varshini Varadaraj, Bonnielin K Swenor, Preeti Gupta, Tien Yin Wong, Caterina Trevisan, Laura Lorenzo-López, Ana Maseda, José Carlos Millán-Calenti, Carla Helena Augustin Schwanke, Ann Liljas, Soham Al Snih, Yasuharu Tokuda, Ecosse Luc Lamoureux. This error has been corrected

Urinary incontinence related to perineal muscle strength in the first trimester of pregnancy: cross-sectional study

Objective To analyze pelvic floor muscle strength (PFMS), urinary continence and quality of life related to urinary incontinence (UI) of women in the first trimester of pregnancy. Method Cross-sectional study with a sample of 500 women who started prenatal care in a complementary healthcare facility in Guarulhos, state of São Paulo, from 2012 and 2013. Pelvic floor muscle strength was evaluated through perineometry. The pregnant women who presented UI answered the International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF). Results It was found that maternal age (OR=1.06; CI95% 1.02-1.11) and prior UI (OR=15.12; 95%CI 8.19-27.92) are the variables that, in tandem, best explain the occurrence of UI at the beginning of pregnancy. The mean score on the ICIQ-SF was 8.2 (SD=3.9), considered a moderate impact on quality of life. Conclusion Older pregnant women with prior UI are more likely to have UI in the first trimester of pregnancy.
</jats:p