RESUMO
The major obstacle to Martian colonization is the mission cost which requires significant reduction. From the structural engineering point of view, importing materials and structural elements from Earth or massive excavations on the surface of Mars require an enormous amount of energy; thus, inflatable and under-surface structures as the main options for Martian colonization seem unrealistically expensive. Construction of affordable buildings onsite using only in situ sources may represent an ideal solution for Martian colonization. On the other hand, solar energy, at the early stage of colonization, would be the only available, practical, and low-cost energy source on Mars. Though, for sustainable and broad colonization, the energy required for construction and the construction cost should be minimized. Here, we propose three types of simple (relatively optimized), perforated, and algorithmic shape-optimized Martian structures to minimize the material and energy required for construction as well as the construction cost using only in situ resources. These structural forms can be considered remarkable steps towards sustainable structural construction and colonization on Mars. Also, these innovative structures were designed to minimize the tensile stress (maximize the compressive stress) and enable the use of in situ concrete. Our data indicate that compared to our previous study, the material and energy required for construction as well as the construction cost can be reduced by more than 50%. Acceptance criteria and limitations appropriate to the Martian environment, and desirable structural and material behaviors were defined to evaluate whether or not the behavior of a structure under the applied loads and conditions will be acceptable. To detect potential issues for onsite construction and evaluate the geometry of the models, a 1:200 3D model of the best structural form was printed.
RESUMO
AIM: The aim of this study was to compare the different phases of chronic Hepatitis B virus (HBV) infection with different values for normal ALT. BACKGROUND: For many years, the upper limit of 40 IU was considered normal for ALT for both sexes, but in recent years this value is challenged and some guidelines have lowered their limit. METHODS: In this cross-sectional study, 2000 HBsAg positive patients who were referred to Taleghani Hospital, Tehran, Iran, from 2011 through 2018 were classified in four groups according to American Association of the study of the liver disease (AASLD), European Association of the study of the liver (EASL) /Asian-Pacific Association of the study of the liver (APASL) and American Collage of Gastroenterology (ACG) guidelines. The frequency of each group based on 3 different guidelines was compared. RESULTS: In HBeAg positive patients (n=100), the percentage of immune tolerance phase was 43% according to AASLD cutoff for normal ALT (35 IU for men, 25 IU for women), while it was 68% and 28% with regard to EASL/APASL and ACG (30 IU for men, 19 IU for women) cutoffs respectively. In HBeAg negative patients (n=1900), 66.68% were inactive carriers according to AASLD, but the percentage changed to 82.89% and 52.42% considering EASL/APASL and ACG values, respectively. CONCLUSION: Using ACG and to a lesser extent AASLD cutoff for ALT, many patients shift from immune tolerance and inactive carrier state into the immune active phase. Thus, more patients are candidates for treatment or intensive workup to determine the extent of liver damage.
