Numerical modeling of the tension stiffening in reinforced concrete members via discontinuum models

[prova tipográfica]This study presents a numerical investigation on the fracture mechanism of tension stiffening phenomenon in reinforced concrete members. A novel approach using the discrete element method (DEM) is proposed, where three-dimensional randomly generated distinct polyhedral blocks are used, representing concrete and one-dimensional truss elements are utilized, representing steel reinforcements. Thus, an explicit representation of reinforced concrete members is achieved, and the mechanical behavior of the system is solved by integrating the equations of motion for each block using the central difference algorithm. The inter-block interactions are taken into consideration at each contact point with springs and cohesive frictional elements. Once the applied modeling strategy is validated, based on previously published experimental findings, a sensitivity analysis is performed for bond stiffness, cohesion strength, and the number of truss elements. Hence, valuable inferences are made regarding discontinuum analysis of reinforced concrete members, including concrete-steel interaction and their macro behavior. The results demonstrate that the proposed phenomenological modeling strategy successfully captures the concrete-steel interaction and provides an accurate estimation of the macro behavior

Effect of delirium motoric subtypes on administrative documentation of delirium in the surgical intensive care unit

This study compares the proportions of surgical intensive care unit (ICU) patients with delirium detected using the Confusion Assessment Method for the ICU (CAM-ICU) who received administrative documentation for delirium using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes, stratified by delirium motoric subtypes. This retrospective cohort study was conducted at a surgical ICU from 06/2012 to 05/2013. Delirium was assessed twice daily and was defined as having ≥1 positive CAM-ICU rating. Delirious patients were categorized into hyperactive/mixed and hypoactive subtypes using corresponding Richmond Agitation Sedation Scales. Administrative documentation of delirium was defined as having ≥1 of 32 unique ICD-9-CM codes. Proportions were compared using Pearson’s Chi-square test. Of included patients, 40 % (423/1055) were diagnosed with delirium, and 17 % (183/1055) had an ICD-9-CM code for delirium. The sensitivity and specificity of ICD-9-CM codes for delirium were 36 and 95 %. ICD-9-CM codes for delirium were available for 42 % (95 % CI 35–48 %; 105/253) of patients with hyperactive/mixed delirium and 27 % (95 % CI 20–34 %; 46/170) of patients with hypoactive delirium (relative risk = 1.5; 95 % CI 1.2–2.0; p = 0.002). ICD-9-CM codes yielded a low sensitivity for identifying patients with CAM-ICU positive delirium and were more likely to identify hyperactive/mixed delirium compared with hypoactive delirium

Effect of delirium motoric subtypes on administrative documentation of delirium in the surgical intensive care unit

This study compares the proportions of surgical intensive care unit (ICU) patients with delirium detected using the Confusion Assessment Method for the ICU (CAM-ICU) who received administrative documentation for delirium using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes, stratified by delirium motoric subtypes. This retrospective cohort study was conducted at a surgical ICU from 06/2012 to 05/2013. Delirium was assessed twice daily and was defined as having ≥1 positive CAM-ICU rating. Delirious patients were categorized into hyperactive/mixed and hypoactive subtypes using corresponding Richmond Agitation Sedation Scales. Administrative documentation of delirium was defined as having ≥1 of 32 unique ICD-9-CM codes. Proportions were compared using Pearson’s Chi-square test. Of included patients, 40 % (423/1055) were diagnosed with delirium, and 17 % (183/1055) had an ICD-9-CM code for delirium. The sensitivity and specificity of ICD-9-CM codes for delirium were 36 and 95 %. ICD-9-CM codes for delirium were available for 42 % (95 % CI 35–48 %; 105/253) of patients with hyperactive/mixed delirium and 27 % (95 % CI 20–34 %; 46/170) of patients with hypoactive delirium (relative risk = 1.5; 95 % CI 1.2–2.0; p = 0.002). ICD-9-CM codes yielded a low sensitivity for identifying patients with CAM-ICU positive delirium and were more likely to identify hyperactive/mixed delirium compared with hypoactive delirium

Chlorhexidine bathing and Clostridium difficile infection in a surgical intensive care unit

Background Clostridium difficile is the most common causative pathogen for hospital-acquired infections in the intensive care unit. This study evaluated the effect of chlorhexidine bathing every other day in preventing hospital-acquired C. difficile infection (CDI) using data from the CHlorhexidine Gluconate BATHing (CHG-BATH) randomized trial. Methods The primary endpoint was the proportion of patients acquiring CDIs among patients at risk for incident CDIs. Infections detected >48 h after randomization were classified as incident CDIs. Infections detected before or within 48 h of randomization were classified as prevalent CDIs. Results Of 38 patients (11.7%) who met criteria for potential CDI and underwent adjudication, 24 (7.4%) received oral or enema vancomycin, 18 (5.5%) had a positive C. difficile molecular assay, 14 (4.3%) received an International Classification of Diseases, Ninth Revision, Clinical Modification code for CDI, and 2 (0.6%) had possible pseudomembranous colitis on histopathology reports. The prevalence of CDI was 3.7% (6 of 164) in the soap and water arm and 4.3% (7 of 161) in the chlorhexidine arm. Compared with daily soap and water bathing, 2% chlorhexidine bathing every other day was not associated with the prevention of hospital-acquired CDI (1.3% [2 of 152] soap and water versus 2.0% [3 of 148] chlorhexidine, P = 0.68). Conclusions It is inconclusive if there was an association between chlorhexidine bathing and incidence of CDI among surgical intensive care unit patients in this study as statistical power was limited. There are limited published data evaluating the association between chlorhexidine bathing and CDI, and this study provides data for future systematic reviews and meta-analyses

Chlorhexidine bathing and Clostridium difficile infection in a surgical intensive care unit

Background Clostridium difficile is the most common causative pathogen for hospital-acquired infections in the intensive care unit. This study evaluated the effect of chlorhexidine bathing every other day in preventing hospital-acquired C. difficile infection (CDI) using data from the CHlorhexidine Gluconate BATHing (CHG-BATH) randomized trial. Methods The primary endpoint was the proportion of patients acquiring CDIs among patients at risk for incident CDIs. Infections detected >48 h after randomization were classified as incident CDIs. Infections detected before or within 48 h of randomization were classified as prevalent CDIs. Results Of 38 patients (11.7%) who met criteria for potential CDI and underwent adjudication, 24 (7.4%) received oral or enema vancomycin, 18 (5.5%) had a positive C. difficile molecular assay, 14 (4.3%) received an International Classification of Diseases, Ninth Revision, Clinical Modification code for CDI, and 2 (0.6%) had possible pseudomembranous colitis on histopathology reports. The prevalence of CDI was 3.7% (6 of 164) in the soap and water arm and 4.3% (7 of 161) in the chlorhexidine arm. Compared with daily soap and water bathing, 2% chlorhexidine bathing every other day was not associated with the prevention of hospital-acquired CDI (1.3% [2 of 152] soap and water versus 2.0% [3 of 148] chlorhexidine, P = 0.68). Conclusions It is inconclusive if there was an association between chlorhexidine bathing and incidence of CDI among surgical intensive care unit patients in this study as statistical power was limited. There are limited published data evaluating the association between chlorhexidine bathing and CDI, and this study provides data for future systematic reviews and meta-analyses

Aerobic membrane bioreactors for municipal wastewater treatment

© 2020 Elsevier B.V. All rights reserved. This chapter provides an overview on the development and application of aerobic membrane bioreactor (MBR) systems for municipal wastewater treatment in recent years (after 2008). Nutrient removal in aerobic MBR could be improved by combining with anoxic and/or anaerobic processes, or adding biomass carriers. Nevertheless, wide application of aerobic MBR is still limited by micropollutants removal and membrane fouling. Aerobic MBR systems coupled with reverse osmosis or with addition of biomass carriers significantly improve removal of micropollutants. On the other hand, membrane fouling propensity varies with bound extracellular polymer substances, sludge supernatant (polysaccharides), and operating conditions. The presence of micropollutants stimulates the production of soluble microbial products, which aggravates membrane fouling. Application of powdered activated carbon and plastic carriers could enhance sludge properties and effectively mitigate membrane fouling. Future research trends are finally given, such as development of new media and novel flocculants, etc