Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>Risk management has reduced vulnerability to floods and droughts globally<jats:sup>1,2</jats:sup>, yet their impacts are still increasing<jats:sup>3</jats:sup>. An improved understanding of the causes of changing impacts is therefore needed, but has been hampered by a lack of empirical data<jats:sup>4,5</jats:sup>. On the basis of a global dataset of 45 pairs of events that occurred within the same area, we show that risk management generally reduces the impacts of floods and droughts but faces difficulties in reducing the impacts of unprecedented events of a magnitude not previously experienced. If the second event was much more hazardous than the first, its impact was almost always higher. This is because management was not designed to deal with such extreme events: for example, they exceeded the design levels of levees and reservoirs. In two success stories, the impact of the second, more hazardous, event was lower, as a result of improved risk management governance and high investment in integrated management. The observed difficulty of managing unprecedented events is alarming, given that more extreme hydrological events are projected owing to climate change<jats:sup>3</jats:sup>.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Insects, unlike vertebrates, are widely believed to lack male-biased sex steroid hormones<jats:sup>1</jats:sup>. In the malaria mosquito <jats:italic>Anopheles gambiae</jats:italic>, the ecdysteroid 20-hydroxyecdysone (20E) appears to have evolved to both control egg development when synthesized by females<jats:sup>2</jats:sup> and to induce mating refractoriness when sexually transferred by males<jats:sup>3</jats:sup>. Because egg development and mating are essential reproductive traits, understanding how <jats:italic>Anopheles</jats:italic> females integrate these hormonal signals can spur the design of new malaria control programs. Here we reveal that these reproductive functions are regulated by distinct sex steroids through a sophisticated network of ecdysteroid-activating/inactivating enzymes. We identify a male-specific oxidized ecdysteroid, 3-dehydro-20E (3D20E), which safeguards paternity by turning off female sexual receptivity following its sexual transfer and activation by dephosphorylation. Notably, 3D20E transfer also induces expression of a reproductive gene that preserves egg development during <jats:italic>Plasmodium</jats:italic> infection, ensuring fitness of infected females. Female-derived 20E does not trigger sexual refractoriness but instead licenses oviposition in mated individuals once a 20E-inhibiting kinase is repressed. Identifying this male-specific insect steroid hormone and its roles in regulating female sexual receptivity, fertility and interactions with <jats:italic>Plasmodium</jats:italic> parasites suggests the possibility for reducing the reproductive success of malaria-transmitting mosquitoes.</jats:p>

<jats:title>Abstract</jats:title><jats:p>DNA is naturally well suited to serve as a digital medium for in vivo molecular recording. However, contemporary DNA-based memory devices are constrained in terms of the number of distinct ‘symbols’ that can be concurrently recorded and/or by a failure to capture the order in which events occur<jats:sup>1</jats:sup>. Here we describe DNA Typewriter, a general system for in vivo molecular recording that overcomes these and other limitations. For DNA Typewriter, the blank recording medium (‘DNA Tape’) consists of a tandem array of partial CRISPR–Cas9 target sites, with all but the first site truncated at their 5′ ends and therefore inactive. Short insertional edits serve as symbols that record the identity of the prime editing guide RNA<jats:sup>2</jats:sup> mediating the edit while also shifting the position of the ‘type guide’ by one unit along the DNA Tape, that is, sequential genome editing. In this proof of concept of DNA Typewriter, we demonstrate recording and decoding of thousands of symbols, complex event histories and short text messages; evaluate the performance of dozens of orthogonal tapes; and construct ‘long tape’ potentially capable of recording as many as 20 serial events. Finally, we leverage DNA Typewriter in conjunction with single-cell RNA-seq to reconstruct a monophyletic lineage of 3,257 cells and find that the Poisson-like accumulation of sequential edits to multicopy DNA tape can be maintained across at least 20 generations and 25 days of in vitro clonal expansion.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Social capital—the strength of an individual’s social network and community—has been identified as a potential determinant of outcomes ranging from education to health<jats:sup>1–8</jats:sup>. However, efforts to understand what types of social capital matter for these outcomes have been hindered by a lack of social network data. Here, in the first of a pair of papers<jats:sup>9</jats:sup>, we use data on 21 billion friendships from Facebook to study social capital. We measure and analyse three types of social capital by ZIP (postal) code in the United States: (1) connectedness between different types of people, such as those with low versus high socioeconomic status (SES); (2) social cohesion, such as the extent of cliques in friendship networks; and (3) civic engagement, such as rates of volunteering. These measures vary substantially across areas, but are not highly correlated with each other. We demonstrate the importance of distinguishing these forms of social capital by analysing their associations with economic mobility across areas. The share of high-SES friends among individuals with low SES—which we term economic connectedness—is among the strongest predictors of upward income mobility identified to date<jats:sup>10,11</jats:sup>. Other social capital measures are not strongly associated with economic mobility. If children with low-SES parents were to grow up in counties with economic connectedness comparable to that of the average child with high-SES parents, their incomes in adulthood would increase by 20% on average. Differences in economic connectedness can explain well-known relationships between upward income mobility and racial segregation, poverty rates, and inequality<jats:sup>12–14</jats:sup>. To support further research and policy interventions, we publicly release privacy-protected statistics on social capital by ZIP code at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.socialcapital.org">https://www.socialcapital.org</jats:ext-link>.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Low levels of social interaction across class lines have generated widespread concern<jats:sup>1–4</jats:sup> and are associated with worse outcomes, such as lower rates of upward income mobility<jats:sup>4–7</jats:sup>. Here we analyse the determinants of cross-class interaction using data from Facebook, building on the analysis in our companion paper<jats:sup>7</jats:sup>. We show that about half of the social disconnection across socioeconomic lines—measured as the difference in the share of high-socioeconomic status (SES) friends between people with low and high SES—is explained by differences in exposure to people with high SES in groups such as schools and religious organizations. The other half is explained by friending bias—the tendency for people with low SES to befriend people with high SES at lower rates even conditional on exposure. Friending bias is shaped by the structure of the groups in which people interact. For example, friending bias is higher in larger and more diverse groups and lower in religious organizations than in schools and workplaces. Distinguishing exposure from friending bias is helpful for identifying interventions to increase cross-SES friendships (economic connectedness). Using fluctuations in the share of students with high SES across high school cohorts, we show that increases in high-SES exposure lead low-SES people to form more friendships with high-SES people in schools that exhibit low levels of friending bias. Thus, socioeconomic integration can increase economic connectedness in communities in which friending bias is low. By contrast, when friending bias is high, increasing cross-SES interactions among existing members may be necessary to increase economic connectedness. To support such efforts, we release privacy-protected statistics on economic connectedness, exposure and friending bias for each ZIP (postal) code, high school and college in the United States at <jats:ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="https://www.socialcapital.org/">https://www.socialcapital.org</jats:ext-link>.</jats:p>