Dirty density: air quality and the density of American cities

We study whether urban density affects the exposure of city dwellers to ambient air pollution using satellite-derived measures of air quality for the contiguous United States. For identification, we rely on an instrumental variable strategy, which induces exogenous variation in density without affecting pollution directly. For this purpose, we use three variables measuring geological characteristics as instruments for density: earthquake risks, soil drainage capacity and the presence of aquifers. We find a positive and statistically significant pollution-density elasticity of 0.13. We also assess the health implications of our findings and find that doubling density in an average city increases annual mortality costs by as much as $630 per capita. Our results suggest that, despite the common claim that denser cities tend to be more environmentally friendly, air pollution exposure is higher in denser cities. This in turn highlights the possible trade-off between reducing global greenhouse gas emissions and preserving environmental quality within cities

Urban density and Covid-19

This paper estimates the link between population density and COVID-19 spread and severity in the contiguous United States. To overcome confounding factors, we use two Instrumental Variable (IV) strategies that exploit geological features and historical populations to induce exogenous variation in population density without affecting COVID-19 cases and deaths directly. We find that density has affected the timing of the outbreak, with denser locations more likely to have an early outbreak. However, we find no evidence that population density is positively associated with time-adjusted COVID-19 cases and deaths. Using data from Google, Facebook, the US Census and The County Health Rankings and Roadmaps program, we also investigate several possible mechanisms for our findings. We show that population density can affect the timing of outbreaks through higher connectedness of denser locations. Furthermore, we find that population density is positively associated with proxies for social distancing measures, access to healthcare and income, highlighting the importance of these mediating factors in containing the outbreak

Covid-19: cities get hit first, but do not necessarily get hit harder

Is there a link between population density and COVID-19 spread and severity in the United States? Felipe Carozzi, Sandro Provenzano and Sefi Roth (Centre for Economic Performance, LSE) found denser locations were more likely to have an early outbreak, but do not necessarily suffer more in the longer run

Evaluation of the impact of hemotransfusion on hospitalization length and complications in patients with non-variceal upper gastrointestinal bleeding

Background: Upper gastrointestinal bleeding (UGB) is a common emergency associated with high morbidity and mortality. It can be caused by various factors, including peptic ulcers and vascular lesions. The decision to perform blood transfusion in stable UGB patients is still controversial, with more restrictive strategies showing better outcomes. Methods: A retrospective cohort study reviewed 1433 medical records of non-variceal UGB patients in a Brazilian tertiary care setting. Patients were divided into groups based on whether they received blood transfusion or not. Patient characteristics, laboratory values, procedures, and outcomes were analyzed. Logistic and linear regression models were used to assess the association of blood transfusion with complications and hospital stay. Results: Blood transfusion was associated with increased hospitalization length (p<0.001), higher rebleeding rates (p<0.001), and greater clinical severity. However, no association with worse renal outcomes was observed (p=0.203). Adjusting for clinical severity (Glasgow-Blatchford score) reduced the significance of the association with hospitalization length. Conclusion: Blood transfusion in stable UGB patients may serve as a marker of severity, associated with longer hospital stay and increased rebleeding rates. It does not appear to have a direct causal relationship with worse renal outcomes. The study suggests that clinical severity may play a pivotal role in outcomes, as indicated by the association with Glasgow-Blatchford score

Development of chia plants in field conditions at different sowing-date

The objective of this study was to characterize the development of chia plants sown at different dates, and to determine the relation between the duration of the development cycle and the final number of leaves and the leaf appearance rate on the main stem. A field experiment was conducted in the agricultural year of 2016/2017 in five sowing dates (09/22/16, 10/28/16, 01/03/17, 02/08/17 and 03/24/17) in the edaphoclimatic conditions of the central region of the RS, Brazil. A randomized block design with four replicates was used. For each sowing date, the duration of the vegetative and reproductive phases in days and in °C day (Tb = 11 °C), the final number of leaves and the phyllochron of the main stem were determined. The duration of the vegetative phase of chia plants in days and in ºC day varies between the sowing dates, with shorter duration in late sowings in response to the photoperiod reduction. The vegetative phase represents the largest part of the total development cycle in early sowing dates, being overcome by the reproductive phase in late sowing dates (02/08/17 and 03/24/17). The phyllochron for chia varies from 36.23 (very late sowing) to 59.88 ºC day (early sowing). Later sowing has a smaller final number of leaves accumulated in the main stem due to the shorter duration of the vegetative phase.The objective of this study was to characterize the development of chia plants sown at different dates, and to determine the relation between the duration of the development cycle and the final number of leaves and the leaf appearance rate on the main stem. A field experiment was conducted in the agricultural year of 2016/2017 in five sowing dates (09/22/16, 10/28/16, 01/03/17, 02/08/17 and 03/24/17) in the edaphoclimatic conditions of the central region of the RS, Brazil. A randomized block design with four replicates was used. For each sowing date, the duration of the vegetative and reproductive phases in days and in °C day (Tb = 11 °C), the final number of leaves and the phyllochron of the main stem were determined. The duration of the vegetative phase of chia plants in days and in ºC day varies between the sowing dates, with shorter duration in late sowings in response to the photoperiod reduction. The vegetative phase represents the largest part of the total development cycle in early sowing dates, being overcome by the reproductive phase in late sowing dates (02/08/17 and 03/24/17). The phyllochron for chia varies from 36.23 (very late sowing) to 59.88 ºC day (early sowing). Later sowing has a smaller final number of leaves accumulated in the main stem due to the shorter duration of the vegetative phase

MAMÍFEROS DE MÉDIO E GRANDE PORTE ATROPELADOS POR TRENS NO EXTREMO SUL DO BRASIL

O Rio Grande do Sul é detentor da mais densa malha ferroviária da região sul e, ampliações das linhas férreas adicionarão mais de 500 km a essa. Nesse cenário de desenvolvimento se prevê uma ampliação dos impactos gerados, o que representa uma ameaça a fauna de mamíferos. Neste estudo identificamos a mastofauna atropelada em ferrovias em trechos ferroviários na região serrana, Planalto Meridional do Estado. Contabilizamos 52 ocorrências de atropelamentos, envolvendo 13 espécies e 11 famílias. Todos os registros ocorreram em áreas de “relevo baixo”. Este trabalho contribui de forma inédita para o conhecimento do impacto causado na fase de operação de ferrovias sobre a mastofauna terrestre e aponta trechos críticos para travessia deste grupo

PROPOSTA DE OTIMIZAÇÃO PARA UM SISTEMA DE GERAÇÃO DE BIOGÁS DE UMA PROPRIEDADE RURAL DO MUNICÍPIO DE ESPUMOSO-RS

Os resíduos de atividades agrícolas e agropecuárias possuem um grande potencial para produção de biogás, o qual é constituído por um terço de gás metano, um terço de dióxido de carbono e um terço de outros gases. O biogás se apresenta como uma alternativa para substituição de energias não renováveis, contribuindo com a preservação do meio e com a melhoria da qualidade de vida da população. Este trabalho teve como objetivo analisar o sistema de manejo e tratamento de dejetos de animais da bovinocultura de leite através de biodigestor do tipo canadense e a consequente geração de biogás e biofertilizante de uma propriedade rural, além de propor melhorias para a eficiência no processo de tratamento dos resíduos gerados, fortalecendo o desenvolvimento sustentável da mesma através de um novo modelo de biodigestor. Este estudo foi realizado nas instalações de confinamento para bovinocultura de leite de uma propriedade rural localizada no município de Espumoso-RS. Observou-se que o atual sistema de tratamento dos dejetos seria suficiente para tornar a propriedade autossustentável em geração de energia elétrica, entretanto, o tempo de retorno do investimento realizado é em longo prazo. Já com a proposta sugerida, isto é, com a prospecção e utilização de uma maior quantidade de biomassa aliada à implantação de um novo sistema de biodigestão automatizada, percebe-se que apesar da necessidade de um maior investimento, o tempo de retorno diminui em, aproximadamente, quatro anos, com um lucro mensal superior ao sistema atual, tornando a propriedade muito mais autossustentável

BVRI Light Curves for 29 Type Ia Supernovae

BVRI light curves are presented for 27 Type Ia supernovae discovered during the course of the Calan/Tololo Survey and for two other SNe Ia observed during the same period. Estimates of the maximum light magnitudes in the B, V, and I bands and the initial decline rate parameter m15(B) are also given.Comment: 17 pages, figures and tables are not included (contact first author if needed), to appear in the Astronomical Journa