Evidence for the appearance of novel gene products during amphibian blastulation

Genetic information begins to be transcribed during early cleavage in amphibian embryos,(1,2) and the tempo of informational RNA synthesis increases gradually through cleavage and into the early blastula stage. Previous studies from this laboratory (3,4) have shown that at this point a remarkable, near embryo-wide acceleration of informational RNA synthesis occurs, resulting during the mid-tolate blastular period in at least a 20-fold increase in the rate of synthesis of heterogeneously sedimenting, DNA-like RNA

Genomic function during the lampbrush chromosome stage of amphibian oogenesis

Throughout its lengthy developmental history the disposition of the genetic material in the amphibian oocyte nucleus differs from that in other cell types. The chromosomes in the oocyte nucleus, arrested for the whole of oogenesis at the prophase of the first meiotic division, are known to contain at least the tetraploid amount of DNA.(1,2) Oogenesis in amphibia requires months or even years to complete, depending on the species

Risk of childhood leukemia and exposure to outdoor air pollution. Updated review and dose-response meta-analysis

Leukemia is the most frequent malignant disease of childhood. Most epidemiologic studies have suggested that exposure to traffic pollutants may increase the risk of childhood leukemia. We updated our previous review and metaanalysis as some recent studies have now available, and we also performed a dose-response metaanalysis using traffic estimators

Existence and stability of weak solutions of the Vlasov--Poisson system in localized Yudovich spaces

We consider the Vlasov--Poisson system both in the repulsive (electrostatic potential) and in the attractive (gravitational potential) cases. In our first main theorem, we prove the uniqueness and the quantitative stability of Lagrangian solutions $f=f(t,x,v)$ whose associated spatial density $\rho_f=\rho_f(t,x)$ is potentially unbounded but belongs to suitable uniformly-localized Yudovich spaces. This requirement imposes a condition of slow growth on the function $p \mapsto \|\rho_f(t,\cdot)\|_{L^p}$ uniformly in time. Previous works by Loeper, Miot and Holding--Miot have addressed the cases of bounded spatial density, i.e., $\|\rho_f(t,\cdot)\|_{L^p} \lesssim 1$, and spatial density such that $\|\rho_f(t,\cdot)\|_{L^p} \sim p^{1/\alpha}$ for $\alpha\in[1,+\infty)$. Our approach is Lagrangian and relies on an explicit estimate of the modulus of continuity of the electric field and on a second-order Osgood lemma. It also allows for iterated-logarithmic perturbations of the linear growth condition. In our second main theorem, we complement the aforementioned result by constructing solutions whose spatial density sharply satisfies such iterated-logarithmic growth. Our approach relies on real-variable techniques and extends the strategy developed for the Euler equations by the first and fourth-named authors. It also allows for the treatment of more general equations that share the same structure as the Vlasov--Poisson system. Notably, the uniqueness result and the stability estimates hold for both the classical and the relativistic Vlasov--Poisson systems

Existence and stability of weak solutions of the Vlasov-Poisson system in localized Yudovich spaces

We consider the Vlasov-Poisson system both in the repulsive (electrostatic potential) and in the attractive (gravitational potential) cases. In our first main theorem, we prove the uniqueness and the quantitative stability of Lagrangian solutions $f=f(t,x,v)$ whose associated spatial density $\rho_f=\rho_f(t,x)$ is potentially unbounded but belongs to suitable uniformly-localized Yudovich spaces. This requirement imposes a condition of slow growth on the function $p \mapsto \|\rho_f(t,\cdot)\|_{L^p}$ uniformly in time. Previous works by Loeper, Miot and Holding--Miot have addressed the cases of bounded spatial density, i.e., $\|\rho_f(t,\cdot)\|_{L^p} \lesssim 1$, and spatial density such that $\|\rho_f(t,\cdot)\|_{L^p} \sim p^{1/\alpha}$ for $\alpha\in[1,+\infty)$. Our approach is Lagrangian and relies on an explicit estimate of the modulus of continuity of the electric field and on a second-order Osgood lemma. It also allows for iterated-logarithmic perturbations of the linear growth condition. In our second main theorem, we complement the aforementioned result by constructing solutions whose spatial density sharply satisfies such iterated-logarithmic growth. Our approach relies on real-variable techniques and extends the strategy developed for the Euler equations by the first and fourth-named authors. It also allows for the treatment of more general equations that share the same structure as the Vlasov-Poisson system. Notably, the uniqueness result and the stability estimates hold for both the classical and the relativistic Vlasov-Poisson systems

Molecular communications in complex systems of dynamic supramolecular polymers

Supramolecular polymers are composed of monomers that self-assemble non-covalently, generating distributions of monodimensional fibres in continuous communication with each other and with the surrounding solution. Fibres, exchanging molecular species, and external environment constitute a sole complex system, which intrinsic dynamics is hard to elucidate. Here we report coarse-grained molecular simulations that allow studying supramolecular polymers at the thermodynamic equilibrium, explicitly showing the complex nature of these systems, which are composed of exquisitely dynamic molecular entities. Detailed studies of molecular exchange provide insights into key factors controlling how assemblies communicate with each other, defining the equilibrium dynamics of the system. Using minimalistic and finer chemically relevant molecular models, we observe that a rich concerted complexity is intrinsic in such self-assembling systems. This offers a new dynamic and probabilistic (rather than structural) picture of supramolecular polymer systems, where the travelling molecular species continuously shape the assemblies that statistically emerge at the equilibrium

Reconfigurações da nostalgia e do autêntico: memórias, patrimônios e tecnologias

O texto reflete acerca das mudanças ocorridas no conceito de memória e nas práticas das instituições relacionadas a ele. Mostra como a sociedade contemporânea possui traços de nostalgia e preocupação com a construção de patrimônios de naturezas distintas e diversas. Destaca o papel que as tecnologias desempenham nesses processos. Propõe uma investigação exploratória a partir de algumas experiências institucionais e de experiências coletivas voluntárias, em alguns museus e na internet

TRANSFORMAÇÕES DA ESFERA PÚBLICA NA SOCIEDADE DA INFORMAÇÃO: PENSANDO MÍDIA, GUERRA E CULTURA

Reflexão sobre as relações entre formas de experiência, conhecimento e política. Considerações históricas sobre a construção material e cognitiva de uma ordem de inscrição da experiência e do conhecimento. O impacto das novas tecnologias de informação e comunicação na transformação dessa ordem e algumas de suas implicações no mundo contemporâneo

DE BACON À INTERNET: CONSIDERAÇÕES SOBRE A ORGANIZAÇÃO DO CONHECIMENTO E A CONSTITUIÇÃO DA CIÊNCIA DA INFORMAÇÃO

This article discusses topics related to knowledge organization, as well as the building of its scientific field. It proposes a discussion on the philosophical bases upon which science developed, setting the classification theory as one of the main constitutive element in this process, starting in baroque tradition, in which paradigms of modern science are established. This way, considering the Information Science field, the article observes the characteristics of transformation of a field of knowledge in its way of development of a scientific status. Contribution from Bacon, Benjamin and Warburg are discussed in the article, as well as the challenges that the knowledge organization creates through the use of new technologies, especially Internet.O trabalho discute questões relacionadas à organização do conhecimento e à constituição do campo científico. Propõe discutir os alicerces filosóficos em que a ciência se desenvolveu, recolocando a teoria classificatória como um dos elementos constitutivos desse processo, a partir da tradição barroca em que se constroem os paradigmas da ciência moderna. Desse modo, no que diz respeito à Ciência da Informação, o artigo observa as características da transformação de um campo do conhecimento em sua busca de um estatuto científico. São abordadas as contribuições de Bacon, Benjamin e Warburg, bem como os desafios colocados à organização do conhecimento pelas novas tecnologias, em especial a Internet

Meta-Analysis of Potassium Intake and the Risk of Stroke

Background-—The possibility that lifestyle factors such as diet, specifically potassium intake, may modify the risk of stroke has been suggested by several observational cohort studies, including some recent reports. We performed a systematic review and meta-analysis of existing studies and assessed the dose–response relation between potassium intake and stroke risk. Methods and Results-—We reviewed the observational cohort studies addressing the relation between potassium intake, and incidence or mortality of total stroke or stroke subtypes published through August 6, 2016. We carried out a meta-analysis of 16 cohort studies based on the relative risk (RR) of stroke comparing the highest versus lowest intake categories. We also plotted a pooled dose–response curve of RR of stroke according to potassium intake. Analyses were performed with and without adjustment for blood pressure. Relative to the lowest category of potassium intake, the highest category of potassium intake was associated with a 13% reduced risk of stroke (RR=0.87, 95% CI 0.80–0.94) in the blood pressure–adjusted analysis. Summary RRs tended to decrease when original estimates were unadjusted for blood pressure. Analysis for stroke subtypes yielded comparable results. In the spline analysis, the pooled RR was lowest at 90 mmol of potassium daily intake (RRs=0.78, 95% CI 0.70–0.86) in blood pressure–adjusted analysis, and 0.67 (95% CI 0.57–0.78) in unadjusted analysis. Conclusions-—Overall, this dose–response meta-analysis confirms the inverse association between potassium intake and stroke risk, with potassium intake of 90 mmol (!3500 mg)/day associated with the lowest risk of stroke