The main idea of this work is to develop a chronological and descriptive historical review in a summarized form about content on astrobiology, which is a research area considered as an emerging science. This is exploratory research that was developed from document review from scientific articles and books, that related to the themes of astrobiology, exobiology and the search for life outside the Earth were used. Based on the research developed, it was possible to collect data related to the vision of other worlds beyond Earth from the ancient Greeks to the present day. Finally, it was possible to conclude that although astrobiology is a recent area of scientific research, the concept and search for life outside the Earth already existed long before the development of modern science.

Coronavirus disease 2019 (COVID-19) asymptomatic cases are hard to identify, impeding transmissibility estimation. The value of COVID-19 transmissibility is worth further elucidation for key assumptions in further modelling studies. Through a population-based surveillance network, we collected data on 1342 confirmed cases with a 90-days follow-up for all asymptomatic cases. An age-stratified compartmental model containing contact information was built to estimate the transmissibility of symptomatic and asymptomatic COVID-19 cases. The difference in transmissibility of a symptomatic and asymptomatic case depended on age and was most distinct for the middle-age groups. The asymptomatic cases had a 66.7% lower transmissibility rate than symptomatic cases, and 74.1% (95% CI 65.9–80.7) of all asymptomatic cases were missed in detection. The average proportion of asymptomatic cases was 28.2% (95% CI 23.0–34.6). Simulation demonstrated that the burden of asymptomatic transmission increased as the epidemic continued and could potentially dominate total transmission. The transmissibility of asymptomatic COVID-19 cases is high and asymptomatic COVID-19 cases play a significant role in outbreaks.

Tuberculosis (TB) remains a global public health threat. Misdiagnosis and delayed therapy of sputum smear-negative TB can affect the treatment outcomes and promote pathogen transmission. The application of Xpert MTB/RIF assay in bronchoalveolar lavage fluid (BALF) has been recommended but needs clinical evidence. We carried out a prospective study in the Nanjing Public Health Medical Center from September 2018 to August 2019. Pulmonary tuberculosis (PTB) patients were enrolled in the study if they had negative results of sputum smear. We compared the performance of Xpert MTB/RIF assay in sputum and BALF using sputum culture as the reference. In addition to this, we applied parallel tests using sputum culture, sputum-based Xpert MTB/RIF assay and BALF-based Xpert MTB/RIF assay to jointly detect smear-negative PTB using clinical diagnosis as the reference. With mycobacterial culture as the reference standard, Xpert MTB/RIF of BALF showed a higher sensitivity (14/16, 87.5%), but a relatively lower specificity (57/92, 62.0%). Xpert MTB/RIF of sputum showed relatively lower sensitivity (6/10, 60.0%) and higher specificity (63/88, 71.6%). Compared with sputum culture, Xpert MTB /RIF assay reduced the median detection time of MTB from 30 to 0 days, which significantly shortened the diagnosis time of the smear-negative TB patients. Among the combined detections, the positive detection proportion was improved with significant differences comparing with sputum culture only, from 11.1% (10/90) to 46.7% (42/90) (P < 0.05). Our study showed Xpert MTB/RIF in BALF had a better performance in detecting MTB of smear-negative patients.

This article traces the ascent of the International Accounting Standards Committee (IASC) from an obscure group with little influence in the early 1970s to a pre-eminent position as global accounting standard-setter in 2001. I argue that the rise of the IASC can be explained by several factors, including the IASC's ability to build legitimacy through technical expertise, to embed itself in a network of international organizations, and to benefit from rivalries among developed and developing countries and among European and American regulators. But the most important reason for the IASC's success is that its core values aligned strongly with the interests of the most powerful regulator-the US Securities and Exchange Commission.

The stalked barnacle Dosima fascicularis is reported from Uruguayan waters for the first time based on stranded specimens. It is suggested that the Subtropical Front is the main area of occurrence of D. fascicularis in the South Atlantic and its occurrence on the Uruguayan coast was found to be sporadic and mainly related to singular atmospheric and oceanographic factors that cast ‘blue plankton’ ashore (e.g. easterly and south-easterly winds, and prevalence of tropical waters).

The sailfish Istiophorus platypterus is one of the most common billfish species in the Mexican Pacific. Information about its feeding habits in the coastal region of Acapulco, Guerrero is extremely limited. In the present study we quantified the diet of sailfish, based on captures made from March 2008 to December 2009 by the sport fishing fleet of Acapulco. We analysed a total of 561 stomachs, of which 254 contained food (45%). The size interval of examined specimens was between 101 and 212 cm postorbital length and between 15 and 47 kg total weight. In general, teleosts were the most important prey, followed by cephalopods. According to index of relative importance, the most important species in the diet were the fish Auxis thazard (63.04%) and Fistularia commersonii (6.62%), followed by the cephalopod Octopus spp. (4.58%). There were no significant differences in the diet by sex (males and females), sexual maturity (immature and mature), or by season (warm and cold seasons). In all cases the most important prey species was A. thazard. We conclude that the sailfish I. platypterus off Acapulco behaves as a specialist predator because, despite the consumption of a high number of prey items, it feeds preferentially on a reduced number of prey species that form schools, and are available and abundant in the ocean.

We propose a simple model for interaction between gene candidates in the two strands of bacterial DNA (deoxyribonucleic acid). Our model assumes that ‘final’ genes appear in one of the two strands, that they do not overlap (in bacteria there is only a small percentage of overlap), and that the final genes maximize the occupancy rate, which is defined to be the proportion of the genome occupied by coding zones. We are more concerned with describing the organization and distribution of genes in bacterial DNA than with the very hard problem of identifying genes. To this end, an algorithm for selecting the final genes according to the previously outlined maximization criterion is proposed. We study the graphical and probabilistic properties of the model resulting from applying the maximization procedure to a Markovian representation of the genic and intergenic zones within the DNA strands, develop theoretical bounds on the occupancy rate (which, in our view, is a rather intractable quantity), and use the model to compute quantities of relevance to the Escherichia coli genome and compare these to annotation data. Although this work focuses on genomic modelling, we point out that the proposed model is not restricted to applications in this setting. It also serves to model other resource allocation problems.