Universidad del Norte, Colombia

About: Universidad del Norte, Colombia is a education organization based out in Barranquilla, Colombia. It is known for research contribution in the topics: Population & Context (language use). The organization has 3562 authors who have published 4355 publications receiving 37861 citations. The organization is also known as: University of the North, Colombia & Uninorte.

Analysis of Connected Air Voids In Warm Mix Asphalt

Abstract: Warm mix asphalt (WMA) are asphalt mixtures produced at reduced temperatures as compared to conventional hot mix asphalt (HMA). Temperature reductions in the order of 10 to 50 C are possible through the incorporation of diverse WMA type additives. However, different aspects, including the mixture internal structure of WMA, are still object of research. Consequently, this paper focused on the assessment of the internal structure of WMA (computed in terms of the Connected Air Voids (CAV) characteristics), fabricated using three WMA additives: Asphamin®, Sasobit®, and Evotherm®. The CAV content corresponds to the fraction of Air Voids (AV) forming connected paths in a compacted specimen and is better related to the asphalt mixture response (e.g., permeability) than the total AV content. The CAV analysis was based on X-ray Computed Tomography scanning and subsequent image analysis. Corresponding results suggested the need of additional research to further characterize field compacted mixtures, produced at densification levels comparable to those achieved in the laboratory. In addition, the inclusion of WMA additives and corresponding temperature reductions did not substantially affect the internal structure of gyratory-compacted specimens (115 mm in height) produced for laboratory mixture evaluation.

Coalescence modeling of intrainfection Bacillus anthracis populations allows estimation of infection parameters in wild populations

Abstract: Bacillus anthracis, the etiological agent of anthrax, is a well-established model organism. For B. anthracis and most other infectious diseases, knowledge regarding transmission and infection parameters in natural systems, in large part, comprises data gathered from closely controlled laboratory experiments. Fatal, natural anthrax infections transmit the bacterium through new host−pathogen contacts at carcass sites, which can occur years after death of the previous host. For the period between contact and death, all of our knowledge is based upon experimental data from domestic livestock and laboratory animals. Here we use a noninvasive method to explore the dynamics of anthrax infections, by evaluating the terminal diversity of B. anthracis in anthrax carcasses. We present an application of population genetics theory, specifically, coalescence modeling, to intrainfection populations of B. anthracis to derive estimates for the duration of the acute phase of the infection and effective population size converted to the number of colony-forming units establishing infection in wild plains zebra (Equus quagga). Founding populations are small, a few colony-forming units, and infections are rapid, lasting roughly between 1 d and 3 d in the wild. Our results closely reflect experimental data, showing that small founding populations progress acutely, killing the host within days. We believe this method is amendable to other bacterial diseases from wild, domestic, and human systems.