Effect of some biotic factors on microbially-induced calcite precipitation in cement mortar

Sporosarcina pasteurii, a common soil bacterium has been tested for microbial treatment of cement mortar. The present study also seeks to investigate the effects of growth medium, bacterial concentration and different buffers concerning the preparation of bacterial suspensions on the compressive strength of cement mortar. Two growth media, six different suspensions and two bacterial concentrations were used in the study. The influence of growth medium on calcification efficiency of S. pasteurii was insignificant. Significant improvement in the compressive as well as the tensile strength of cement mortar was observed. Microbial mineral precipitation visualized by Scanning Electron Microscopy (SEM) shows fibrous material that increased the strength of cement mortar. Formation of thin strands of fillers observed through SEM micrographs improves the pore structure, impermeability and thus the compressive as well as the tensile strengths of the cement mortar. The type of substrate and its molarity have a significant influence on the strength of cement mortar

Burnout among surgeons before and during the SARS-CoV-2 pandemic: an international survey

Background: SARS-CoV-2 pandemic has had many significant impacts within the surgical realm, and surgeons have been obligated to reconsider almost every aspect of daily clinical practice. Methods: This is a cross-sectional study reported in compliance with the CHERRIES guidelines and conducted through an online platform from June 14th to July 15th, 2020. The primary outcome was the burden of burnout during the pandemic indicated by the validated Shirom-Melamed Burnout Measure. Results: Nine hundred fifty-four surgeons completed the survey. The median length of practice was 10 years; 78.2% included were male with a median age of 37 years old, 39.5% were consultants, 68.9% were general surgeons, and 55.7% were affiliated with an academic institution. Overall, there was a significant increase in the mean burnout score during the pandemic; longer years of practice and older age were significantly associated with less burnout. There were significant reductions in the median number of outpatient visits, operated cases, on-call hours, emergency visits, and research work, so, 48.2% of respondents felt that the training resources were insufficient. The majority (81.3%) of respondents reported that their hospitals were included in the management of COVID-19, 66.5% felt their roles had been minimized; 41% were asked to assist in non-surgical medical practices, and 37.6% of respondents were included in COVID-19 management. Conclusions: There was a significant burnout among trainees. Almost all aspects of clinical and research activities were affected with a significant reduction in the volume of research, outpatient clinic visits, surgical procedures, on-call hours, and emergency cases hindering the training. Trial registration: The study was registered on clicaltrials.gov "NCT04433286" on 16/06/2020

Influence of Severe Hot-Dry Climate on the Mechanical Properties of Fibrous Reinforced Concrete Beams

This paper presents the results of the work carried out to study the influence of curing environment and steel fiber volume fraction on the flexural strength, flexural rigidity, flexural toughness, and ductility of fibrous reinforced concrete (RC) beams. A total of twenty simply supported beams were tested. Ten of the twenty beams were cured under controlled laboratory conditions and the other ten were cured under severe hot dry climate (SHDC) characterized by their intense heat, low relative humidity, direct solar radiation, and large diurnal variations of daily temperatures. Tests were carried out 28 and 90 days after casting.Test results show that for non fibrous RC concrete beams the adverse effects of SHDC have more influence in reducing the flexural toughness than the flexural strength. On the other hand, test results indicate that under any of the two curing environment considered in this study, the flexural strength, flexural rigidity, flexural toughness and ductility of the fibrous RC beams are in direct proportion with the fiber content. Moreover, the results reveal that the enhancements in these engineering properties due to the steel fiber addition are not affected by the above described severe field conditions. Furthermore, inclusion of steel fibers in concrete helps, to some extent, in reducing the adverse effects of SHDC on the properties of concrete

Non-Linear Finite Element Analysis for RC Elements Subjected to In-Plane Loads

A non-linear iterative solution of finite element formulation implemented a 486 personal computer for predicting the cracking shapes and their propagation in reinforced concrete elements subjected to in-plane stresses is presented. The model is based on a smeared crack representation and a plane stress state simulation. It considers the influence of concrete tension stiffening after cracking, compressive stress degradation due to cracking, and single and double crack conditions. The reliability of the model is checked against the experimental results for specimens that were tested by the author as well as those tested by other researchers. Comparisons of the results show that the proposed model predicts the measured results with an overall average error of 2% and a coefficient of variation of 1.48. This work forms an effective tool for investigation of inelastic behavior of a concrete and reinforcing bar composite

Non-Linear Finite Element Analysis for RC Elements Subjected to In-Plane Loads

A non-linear iterative solution of finite element formulation implemented a 486 personal computer for predicting the cracking shapes and their propagation in reinforced concrete elements subjected to in-plane stresses is presented. The model is based on a smeared crack representation and a plane stress state simulation. It considers the influence of concrete tension stiffening after cracking, compressive stress degradation due to cracking, and single and double crack conditions. The reliability of the model is checked against the experimental results for specimens that were tested by the author as well as those tested by other researchers. Comparisons of the results show that the proposed model predicts the measured results with an overall average error of 2% and a coefficient of variation of 1.48. This work forms an effective tool for investigation of inelastic behavior of a concrete and reinforcing bar composite

Mathematical Modeling and Classification of Viruses from Herpesvirus Family

The process of modeling and classifications of viruses that belong to a specific family is an important for biologist and for many biological applications. There are many ways for Viruses families ' classification. The degree of similarity or diversity among the structure of the viruses capsid proteins is very useful in studying the Viruses families ' classification and their genetic evolution. It also important propose if we construct a mathematical model of the virus life cycle to be able to fully understand the life cycle of Viruses families ' activities. In this paper we introduce a proposed mathematical model for some Herpesvirus family viruses simple life cycle and comprehensive study for its classification using sequence alignment algorithms in order to demonstrate their genetic evolution according to the structure of their capsid protein. Herpesvirus family is considered one of the most important family in the families of the enveloped DNA viruses as it contain many dangerous viruses for human health. This family contain one of newly discovered viruses called Epstein–Barr virus (EBV), also called human herpesvirus 4 (HHV-4), which is one of the most common viruses in human. Infection with EBV occurs by the oral transfer of saliva [1] and genital secretions

Spectrum of mutations underlying Propionic acidemia and further insight into a genotype-phenotype correlation for the common mutation in Saudi Arabia

Propionic acidemia (PA) is an autosomal recessive metabolic disorder. PA is characterized by deficiency of the mitochondrial enzyme propionyl CoA carboxylase (PCC) that results in the accumulation of propionic acid. Alpha and beta subunits of the PCC enzyme are encoded by the PCCA and PCCB genes, respectively. Pathogenic variants in PCCA or PCCB disrupt the function of the PCC enzyme preventing the proper breakdown of certain amino acids and metabolites. To determine the frequency of pathogenic variants in PA in our population, 84 Saudi Arabian patients affected with PA were sequenced for both the PCCA and PCCB genes. We found that variants in PCCA accounted for 81% of our cohort (68 patients), while variants in PCCB only accounted for 19% (16 patients). In total, sixteen different sequence variants were detected in the study, where 7 were found in PCCA and 9 in PCCB. The pathogenic variant (c.425G > A; p.Gly142Asp) in PCCA is the most common cause of PA in our cohort and was found in 59 families (70.2%), followed by the frameshift variant (c.990dupT; p.E331Xfs*1) in PCCB that was found in 7 families (8.3%). The p.Gly142Asp missense variant is likely to be a founder pathogenic variant in patients of Saudi Arabian tribal origin and is associated with a severe phenotype. All variants were inherited in a homozygous state except for one family who was compound heterozygous. A total of 11 novel pathogenic variants were detected in this study thereby increasing the known spectrum of pathogenic variants in the PCCA and PCCB genes. Keywords: Propionic acidemia, PCCA, PCCB, Founder mutation, Genotype-phenotype correlatio