Efficacy of powered air purifying respirators (PAPRs) for source control of simulated respiratory aerosols.

BACKGROUND: Loose-fitting powered air purifying respirators (PAPRs) are a popular alternative to the use of filtering facepiece respirators for healthcare workers. Although PAPRs protect the wearer from aerosol particles, their ability to block infectious aerosol particles exhaled by the wearer from being released into the environment (called source control) is unclear. METHODS: The source control performance of four PAPRs with loose-fitting facepieces were tested using a manikin that exhales aerosol particles. The PAPRs were tested by themselves and in combination with a face-worn product intended to provide source control (either a surgical mask or an N95® filtering facepiece respirator.) RESULTS: Two PAPR facepieces with filtration panels significantly reduced the release of exhaled aerosols into the environment, while three facepieces without such panels did not. Wearing a surgical mask or respirator under the facepiece significantly improved the source control performance. CONCLUSIONS: Most PAPR facepieces do not block aerosols exhaled by the wearer. Facepieces designed to filter exhaled particles can prevent aerosols from being released into the environment. Wearing a surgical mask or a filtering facepiece respirator under the facepiece can also provide source control, but PAPRs are not typically certified for use with masks and respirators.

Importance of Source Control in the Subgroup of Intra-Abdominal Infections for Septic Shock Patients: Analysis of 390 Cases.

Background: This study aimed to evaluate the epidemiology of septic shock (SS) associated with intraabdominal infections (IAI) as well as associated mortality and efficacy of early source control in a tertiary-care educational hospital. Methods: Patients who had SS with IAI and consulted by Infectious Diseases consultants between December 2013 and October 2022 during night shifts in our centre were analyzed retrospectively. Results: A total number of 390 patients were included. Overall, 30-day mortality was 42.5% on day 3, while day 14 and 30 mortality rates were 63.3% and 71.3%, respectively. Source control by surgical or percutaneous operation was performed in 123 of 390 cases (31.5%), and the mortality rate was significantly lower in cases that were performed source control at any time during SS (65/123-52.8% vs 213/267-79.8%, p<0.001). In 44 of 123 cases (35.7%), source control was performed during the first 12 hours, and mortality was significantly lower in this group versus others (24/44-54.5% vs 254/346-73.4%, p=0.009). On the other hand, female gender (p<0.001, odds ratio(OR)= 2.943, 95%CI=1.714-5.054), diabetes mellitus (p= 0.014, OR=2.284, 95%CI=1.179-4.424), carbapenem-resistant Gram-negative etiology (p=0.011, OR=4.386, 95%CI=1.398-13.759), SOFA≥10 (p<0.001, OR=3.036, 95%CI=1.802-5.114), lactate >3 mg/dl (p<0.001, OR=2.764, 95%CI=1.562-4.891) and lack of source control (p=0.001, OR=2.796, 95%CI=1.523-5.133) were significantly associated with 30-day mortality in logistic regression analysis. Conclusion: Source control has a vital importance in terms of mortality rates for IAI-related septic shock patients. Our study underscores the need for additional research, as the present analysis indicates that early source control does not manifest as a protective factor in logistic regression.

Importance of timely and adequate source control in sepsis and septic shock.

Source control is defined as the physical measures undertaken to eliminate the source of infection and control ongoing contamination, as well as restore anatomy and function at the site of infection. It is a key component of the management of patients with sepsis and septic shock and one of the main determinants of the outcome of infections that require source control. While not all infections may require source control, it should be considered in every patient presenting with sepsis; it is applicable and necessary in numerous infections, not only those occurring in the abdominal cavity. Although the biological rationale is clear, several aspects of source control remain under debate. The timing of source control may impact outcome; early source control is particularly relevant for patients with abdominal infections or necrotizing skin and soft tissue infections, as well as for those with more severe disease. Percutaneous procedures are increasingly used for source control; nevertheless, surgery-tailored to the patient and infection-remains a valid option for source control. For outcome optimization, adequate source control is more important than the strategy used. It should be acknowledged that source control interventions may often fail, posing a challenge in this setting. Thus, an individualized, multidisciplinary approach tailored to the infection and patient is preferable.

Critical Review of Field Studies of Chemical Surface Coatings to Mitigate Leaching from Mining Wastes.

Source control of mine drainage and leachate from mining wastes is ideal, but there is limited use of control methods aside from removal of wastes to repositories or capping wastes in situ. In some locations, neither removal nor capping is possible; thus, there is renewed interest in understanding technologies for coating mining wastes. This paper presents the current state of knowledge from a critical review of the few field case studies where chemical coating technologies have been applied to mined surfaces (e.g. a highwall) or mining wastes. It also includes laboratory studies where the same technology was examined on the same type of waste material as the field studies. The chemicals used in field studies for coating mining wastes were magnesium oxide, potassium permanganate, silicate compounds, phosphate compounds, and a furfuryl alcohol resin sealant. Descriptions of the methods employed, and results obtained are provided. Limitations of the individual studies and of the technologies in general are discussed. Potential reasons why coating technologies have not been commonly used are presented, along with further research needs.

Management of intra-abdominal infections: recommendations by the Italian council for the optimization of antimicrobial use.

Intra-abdominal infections (IAIs) are common surgical emergencies and are an important cause of morbidity and mortality in hospital settings, particularly if poorly managed. The cornerstones of effective IAIs management include early diagnosis, adequate source control, appropriate antimicrobial therapy, and early physiologic stabilization using intravenous fluids and vasopressor agents in critically ill patients. Adequate empiric antimicrobial therapy in patients with IAIs is of paramount importance because inappropriate antimicrobial therapy is associated with poor outcomes. Optimizing antimicrobial prescriptions improves treatment effectiveness, increases patients' safety, and minimizes the risk of opportunistic infections (such as Clostridioides difficile) and antimicrobial resistance selection. The growing emergence of multi-drug resistant organisms has caused an impending crisis with alarming implications, especially regarding Gram-negative bacteria. The Multidisciplinary and Intersociety Italian Council for the Optimization of Antimicrobial Use promoted a consensus conference on the antimicrobial management of IAIs, including emergency medicine specialists, radiologists, surgeons, intensivists, infectious disease specialists, clinical pharmacologists, hospital pharmacists, microbiologists and public health specialists. Relevant clinical questions were constructed by the Organizational Committee in order to investigate the topic. The expert panel produced recommendation statements based on the best scientific evidence from PubMed and EMBASE Library and experts' opinions. The statements were planned and graded according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) hierarchy of evidence. On November 10, 2023, the experts met in Mestre (Italy) to debate the statements. After the approval of the statements, the expert panel met via email and virtual meetings to prepare and revise the definitive document. This document represents the executive summary of the consensus conference and comprises three sections. The first section focuses on the general principles of diagnosis and treatment of IAIs. The second section provides twenty-three evidence-based recommendations for the antimicrobial therapy of IAIs. The third section presents eight clinical diagnostic-therapeutic pathways for the most common IAIs. The document has been endorsed by the Italian Society of Surgery.

Intra-abdominal infections survival guide: a position statement by the Global Alliance For Infections In Surgery.

Intra-abdominal infections (IAIs) are an important cause of morbidity and mortality in hospital settings worldwide. The cornerstones of IAI management include rapid, accurate diagnostics; timely, adequate source control; appropriate, short-duration antimicrobial therapy administered according to the principles of pharmacokinetics/pharmacodynamics and antimicrobial stewardship; and hemodynamic and organ functional support with intravenous fluid and adjunctive vasopressor agents for critical illness (sepsis/organ dysfunction or septic shock after correction of hypovolemia). In patients with IAIs, a personalized approach is crucial to optimize outcomes and should be based on multiple aspects that require careful clinical assessment. The anatomic extent of infection, the presumed pathogens involved and risk factors for antimicrobial resistance, the origin and extent of the infection, the patient's clinical condition, and the host's immune status should be assessed continuously to optimize the management of patients with complicated IAIs.

Predictors of mortality of Pseudomonas aeruginosa bacteraemia and the role of infectious diseases consultation and source control; a retrospective cohort study.

PURPOSE: To determine predictors of mortality among patients with Pseudomonas aeruginosa bacteraemia. METHODS: Retrospective study. SETTING: This study conducted at the Lausanne University Hospital, Switzerland included adult patients with P. aeruginosa bacteraemia from 2015 to 2021. RESULTS: During the study period, 278 episodes of P. aeruginosa bacteraemia were included. Twenty (7%) isolates were multidrug-resistant. The most common type of infection was low respiratory tract infection (58 episodes; 21%). Sepsis was present in the majority of episodes (152; 55%). Infectious diseases consultation within 48 h of bacteraemia onset was performed in 203 (73%) episodes. Appropriate antimicrobial treatment was administered within 48 h in 257 (92%) episodes. For most episodes (145; 52%), source control was considered necessary, with 93 (64%) of them undergoing such interventions within 48 h. The 14-day mortality was 15% (42 episodes). The Cox multivariable regression model showed that 14-day mortality was associated with sepsis (P 0.002; aHR 6.58, CI 1.95-22.16), and lower respiratory tract infection (P < 0.001; aHR 4.63, CI 1.78-12.06). Conversely, interventions performed within 48 h of bacteraemia onset, such as infectious diseases consultation (P 0.036; HR 0.51, CI 0.27-0.96), and source control (P 0.009; aHR 0.17, CI 0.47-0.64) were associated with improved outcome. CONCLUSION: Our findings underscore the pivotal role of early infectious diseases consultation in recommending source control interventions and guiding antimicrobial treatment for patients with P. aeruginosa bacteraemia.

[Early source control of infection in patients seen in the emergency department: a systematic review]. / Control precoz del foco de infección en los pacientes atendidos en el servicio de urgencias: una revisión sistemática.

OBJECTIVE: The term source (or focus) control encompasses all those physical measures that can be used to reduce the inoculum and modify those factors in the infectious medium that promote microbial growth or foreign antimicrobial defenses of the host. The main objective of this systematic review (SR) is to know and compare whether early detection and control of the focus (in less than 6 hours) in adult patients treated in the ED for severe infection or sepsis, compared to not controlling the focus or delayed focus control (more than 12 hours) is more effective and safer (improves clinical evolution, mortality, complications, hospital stay or need for ICU admission). METHODS: A systematic review is carried out following the PRISMA regulations in the databases of PubMed, Web of Science, EMBASE, Lilacs, Cochrane, Epistemonikos, Tripdatabase and ClinicalTrials.gov from January 2000 to December 31, 2023 without language restrictions and using a combination of MESH terms: "Source Control", "Early" "Infection OR Bacterial Infection OR Sepsis", "Emergencies OR Emergency OR Emergency Department" and "Adults". Observational cohort studies were included. No meta-analysis techniques were performed, but results were compared narratively. RESULTS: A total of 1,658 articles were identified, of which 2 that met the inclusion criteria and were classified as high quality were finally analyzed. The included studies represent a total of 2,404 patients with 678 cases in which an intervention was performed to control the focus (28.20%). In the first study, 28-day mortality was lower in patients who underwent an intervention to control the focus (12.3% vs. 22.5%; P <0.001), with an adjusted HR of 0.538 (95% CI: 0.389-0.744; P<0.001). In the second, it was demonstrated that the time elapsed from when the patient was evaluated for the first time and was hemodynamically stabilized, until the start of surgery was associated with his survival at 60 days with an OR of 0.31 (95% CI: 0.19-0.45; P <0.0001). In fact, for each hour of delay an adjusted OR of 0.29 (95% CI: 0.16-0.47; P<0.0001) is established. So if the intervention is performed before 2 hours at 60 days, 98% of the patients are still alive, if it is performed between 2-4 hours it is reduced to 78%, if it is between 4-6 hours it drops to 55%, but if it is done for more than 6 hours there will be no survivors at 60 days. CONCLUSIONS: This review shows that source control carried out after the evaluation of patients attending the ED reduces short-term mortality (30-60 days) and that it would be advisable to implement any required source control intervention as soon as possible, ideally early (within 6 hours).

Prompt antimicrobial therapy and source control on survival and defervescence of adults with bacteraemia in the emergency department: the faster, the better.

BACKGROUND: Bacteraemia is a critical condition that generally leads to substantial morbidity and mortality. It is unclear whether delayed antimicrobial therapy (and/or source control) has a prognostic or defervescence effect on patients with source-control-required (ScR) or unrequired (ScU) bacteraemia. METHODS: The multicenter cohort included treatment-naïve adults with bacteraemia in the emergency department. Clinical information was retrospectively obtained and etiologic pathogens were prospectively restored to accurately determine the time-to-appropriate antibiotic (TtAa). The association between TtAa or time-to-source control (TtSc, for ScR bacteraemia) and 30-day crude mortality or delayed defervescence were respectively studied by adjusting independent determinants of mortality or delayed defervescence, recognised by a logistic regression model. RESULTS: Of the total 5477 patients, each hour of TtAa delay was associated with an average increase of 0.2% (adjusted odds ratio [AOR], 1.002; P < 0.001) and 0.3% (AOR 1.003; P < 0.001) in mortality rates for patients having ScU (3953 patients) and ScR (1524) bacteraemia, respectively. Notably, these AORs were augmented to 0.4% and 0.5% for critically ill individuals. For patients experiencing ScR bacteraemia, each hour of TtSc delay was significantly associated with an average increase of 0.31% and 0.33% in mortality rates for overall and critically ill individuals, respectively. For febrile patients, each additional hour of TtAa was significantly associated with an average 0.2% and 0.3% increase in the proportion of delayed defervescence for ScU (3085 patients) and ScR (1266) bacteraemia, respectively, and 0.5% and 0.9% for critically ill individuals. For 1266 febrile patients with ScR bacteraemia, each hour of TtSc delay respectively was significantly associated with an average increase of 0.3% and 0.4% in mortality rates for the overall population and those with critical illness. CONCLUSIONS: Regardless of the need for source control in cases of bacteraemia, there seems to be a significant association between the prompt administration of appropriate antimicrobials and both a favourable prognosis and rapid defervescence, particularly among critically ill patients. For ScR bacteraemia, delayed source control has been identified as a determinant of unfavourable prognosis and delayed defervescence. Moreover, this association with patient survival and the speed of defervescence appears to be augmented among critically ill patients.

Relative efficacy of masks and respirators as source control for viral aerosol shedding from people infected with SARS-CoV-2: a controlled human exhaled breath aerosol experimental study.

BACKGROUND: Tight-fitting masks and respirators, in manikin studies, improved aerosol source control compared to loose-fitting masks. Whether this translates to humans is not known. METHODS: We compared efficacy of masks (cloth and surgical) and respirators (KN95 and N95) as source control for SARS-CoV-2 viral load in exhaled breath of volunteers with COVID-19 using a controlled human experimental study. Volunteers (N = 44, 43% female) provided paired unmasked and masked breath samples allowing computation of source-control factors. FINDINGS: All masks and respirators significantly reduced exhaled viral load, without fit tests or training. A duckbill N95 reduced exhaled viral load by 98% (95% CI: 97%-99%), and significantly outperformed a KN95 (p < 0.001) as well as cloth and surgical masks. Cloth masks outperformed a surgical mask (p = 0.027) and the tested KN95 (p = 0.014). INTERPRETATION: These results suggest that N95 respirators could be the standard of care in nursing homes and healthcare settings when respiratory viral infections are prevalent in the community and healthcare-associated transmission risk is elevated. FUNDING: Defense Advanced Research Projects Agency, National Institute of Allergy and Infectious Diseases, Centers for Disease Control and Prevention, the Bill & Melinda Gates Foundation, and The Flu Lab.

A Case of Life-Threatening Postpartum Necrotizing Pancreatitis Requiring Gastrocystostomy With Serial Pancreatic Necrosectomies.

We present a life-threatening case of postpartum acute necrotizing pancreatitis. The patient is a 37-year-old female with no past medical history who delivered a healthy baby boy via cesarean section. Twenty days later, she presented to the emergency department with acute onset of nausea, non-bloody vomiting, abdominal bloating, and epigastric pain radiating to the back. Less than 24 hours later, she progressed into septic shock despite aggressive resuscitation, requiring vasopressor support in the ICU. Initial CT imaging showed multiple patchy hypodensities throughout the pancreas consistent with severe necrotizing pancreatitis. Her hospitalization was further complicated by difficulty obtaining source control of her infection, Clostridium difficile, and nutritional deficiencies that resulted in gross anasarca. She was discharged from the hospital on day 59 after undergoing multiple percutaneous drain placements, IV antibiotics, and endoscopic gastrocystostomy with four pancreatic necrosectomies. Since discharge, the patient has required readmission twice for complications from her pancreatitis.

Intravenous fosfomycin for treatment of severe infections caused by carbapenem-resistant Acinetobacter baumannii: A multi-centre clinical experience.

BACKGROUND: Severe infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) have been reported increasingly over the past few years. Many in-vivo and in-vitro studies have suggested a possible role of intravenous fosfomycin for the treatment of CRAB infections. METHODS: This multi-centre, retrospective study included patients treated with intravenous fosfomycin for severe infections caused by CRAB admitted consecutively to four hospitals in Italy from December 2017 to December 2022. The primary goal of the study was to evaluate the risk factors associated with 30-day mortality in the study population. A propensity score matched analysis was added to the model. RESULTS: One hundred and two patients with severe infections caused by CRAB treated with an intravenous fosfomycin-containing regimen were enrolled in this study. Ventilator-associated pneumonia (VAP) was diagnosed in 59% of patients, primary bacteraemia in 22% of patients, and central-venous-catheter-related infection in 16% of patients. All patients were treated with a regimen containing intravenous fosfomycin, mainly in combination with cefiderocol (n=54), colistin (n=48) or ampicillin/sulbactam (n=18). Forty-eight (47%) patients died within 30 days. Fifty-eight (57%) patients experienced clinical therapeutic failure. Cox regression analysis showed that diabetes, primary bacteraemia and a colistin-containing regimen were independently associated with 30-day mortality, whereas adequate source control of infection, early 24-h active in-vitro therapy, and a cefiderocol-containing regimen were associated with survival. A colistin-based regimen, A. baumannii colonization and primary bacteraemia were independently associated with clinical failure. Conversely, adequate source control of infection, a cefiderocol-containing regimen, and early 24-h active in-vitro therapy were associated with clinical success. CONCLUSIONS: Different antibiotic regimens containing fosfomycin in combination can be used for treatment of severe infections caused by CRAB.

Evaluation of predictors of third-generation cephalosporin non-susceptibility and factors affecting recurrence or death in bacteremia caused by Citrobacter freundii complex, Enterobacter cloacae complex, and Klebsiella aerogenes.

Factors involved in the susceptibility of third-generation cephalosporins (3GCs) to bacteremia caused by Citrobacter freundii complex, Enterobacter cloacae complex, and Klebsiella aerogenes were investigated based on a case-case-control design. Antimicrobial therapy administered 30 days prior to bacteremia and hospitalization within 90 days were common risk factors for the 3GC susceptible and 3GC non-susceptible groups, while hospitalization from an institution or another hospital was a specific risk factor for the 3GC non-susceptible group. We also attempted to examine the factors affecting the clinical outcome of bacteremia. Hospitalization more than 14 days before the onset of bacteremia was an independent factor indicating poor clinical outcome. In contrast, the implementation of source control was an independent predictor of successful treatment. Although a longer hospital stay before the onset of bacteremia was associated with worse clinical outcomes, implementation of source control may have contributed to improved treatment outcomes for bacteremia.

Role of source control in critically ill candidemic patients: a multicenter retrospective study.

PURPOSE: Candidemia is associated with high mortality especially in critically ill patients. Our aim was to identify predictors of mortality among critically ill patients with candidemia with a focus on early interventions that can improve prognosis. METHODS: Multicenter retrospective study. SETTING: This retrospective study was conducted in Intensive Care Units from three European university hospitals from 2015 to 2021. Adult patients with at least one positive blood culture for Candida spp. were included. Patients who did not require source control were excluded. Primary outcome was 14-day mortality. RESULTS: A total of 409 episodes of candidemia were included. Most candidemias were catheter related (173; 41%), followed by unknown origin (170; 40%). Septic shock developed in 43% episodes. Overall, 14-day mortality rate was 29%. In Cox proportional hazards regression model, septic shock (P 0.001; HR 2.20, CI 1.38-3.50), SOFA score ≥ 10 points (P 0.008; HR 1.83, CI 1.18-2.86), and prior SARS-CoV-2 infection (P 0.003; HR 1.87, CI 1.23-2.85) were associated with 14-day mortality, while combined early appropriate antifungal treatment and source control (P < 0.001; HR 0.15, CI 0.08-0.28), and early source control without appropriate antifungal treatment (P < 0.001; HR 0.23, CI 0.12-0.47) were associated with better survival compared to those without neither early appropriate antifungal treatment nor source control. CONCLUSION: Early source control was associated with better outcome among candidemic critically ill patients.

Predictors of Mortality of Streptococcal Bacteremia and the Role of Infectious Diseases Consultation: A Retrospective Cohort Study.

BACKGROUND: Streptococcal bacteremia is associated with high mortality. Thia study aims to identify predictors of mortality among patients with streptococcal bacteremia. METHODS: This retrospective study was conducted at the Lausanne University Hospital, Switzerland, and included episodes of streptococcal bacteremia among adult patients from 2015 to 2023. RESULTS: During the study period, 861 episodes of streptococcal bacteremia were included. The majority of episodes were categorized in the Mitis group (348 episodes; 40%), followed by the Pyogenic group (215; 25%). Endocarditis was the most common source of bacteremia (164; 19%). The overall 14-day mortality rate was 8% (65 episodes). The results from the Cox multivariable regression model showed that a Charlson comorbidity index >4 (P .001; hazard ratio [HR], 2.87; confidence interval [CI]: 1.58-5.22), Streptococcus pyogenes (P = .011; HR, 2.54;CI: 1.24-5.21), sepsis (P < .001; HR, 7.48; CI: 3.86-14.47), lower respiratory tract infection (P = .002; HR, 2.62; CI: 1.42-4.81), and absence of source control interventions within 48 hours despite being warranted (P = .002; HR, 2.62; CI: 1.43-4.80) were associated with 14-day mortality. Conversely, interventions performed within 48 hours of bacteremia onset, such as infectious diseases consultation (P < .001; HR, 0.29; CI: .17-.48) and appropriate antimicrobial treatment (P < .001; HR, .28; CI: .14-.57), were associated with improved outcome. CONCLUSIONS: Our findings underscore the pivotal role of infectious diseases consultation in guiding antimicrobial treatment and recommending source control interventions for patients with streptococcal bacteremia.

The effects of increasing emission Fee rates on Chinese firms' emissions: Evidence from a quasi-experiment.

Over the last four decades, the Chinese government has predominantly employed emission fees as a regulatory strategy to mitigate pollution from firms. However, the effectiveness of escalating emission fee rates on the emission levels of Chinese firms has not been examined. This study utilizes data from more than 80,000 Chinese firms spanning 2004-2013, employing difference-in-differences models to assess the effects of rising emission fee rates on firm emissions. The findings indicate the following: (1) Increased emission fee rates substantially reduce sulfur dioxide and chemical oxygen demand emissions among Chinese firms; (2) These heightened fees encourage firms to implement both end-of-pipe treatment and source control for sulfur dioxide and end-of-pipe treatment for chemical oxygen demand; (3) The emission reduction effects vary according to firm ownership and size. This research offers empirical evidence on the efficacy of emission fee systems and provides valuable insights for developing market incentive-based environmental regulations in the future.

Shifting focus from end-of-pipe treatment to source control: ESG ratings' impact on corporate green innovation.

This study actively explores the pivotal role of environment, society, and governance (ESG) ratings in optimizing corporate green innovation activities as a robust response to ongoing ESG investment divestment. It provides empirical support for implementing corporate green transitions, establishing, and refining market-driven green development framework, and attaining "carbon peaking, carbon neutrality" targets. Furthermore, the research represents a groundbreaking effort to assess the influence of ESG ratings on corporate green innovation with a specific focus on pollution disposal. Specifically, examining data from Chinese A-share listed companies spanning 2011 to 2020, this study utilizes various models, including multi-period difference-in-differences (DID), event study, staggered DID, and synthetic DID (SDID). The ensuing analysis reveals that ESG ratings significantly impact the development of corporate green innovation, catalyzing the transformation of green innovation activities from end-of-pipe to source control. Notably, ESG ratings achieve this transformation by mitigating managerial myopia, enhancing the research and development (R&D) staff ratio, and alleviating financial constraints. However, the study also identifies institutional constraints and corporate digitalization as factors leading to heterogeneous effects on green innovation and its direction. These findings not only provide enhanced theoretical support but also offer empirical validation for corporations and governments looking to implement and generalize ESG ratings, facilitating a successful green transition.

Microscopy of Woven and Nonwoven Face Covering Materials: Implications for Particle Filtration.

A suite of natural, synthetic, and mixed synthetic-natural woven fabrics, along with nonwoven filtration layers from a surgical mask and an N95 respirator, was examined using visible light microscopy, scanning electron microscopy, and micro-X-ray computed tomography (µXCT) to determine the fiber diameter distribution, fabric thickness, and the volume of solid space of the fabrics. Nonwoven materials exhibit a positively skewed distribution of fiber diameters with a mean value of ≈3 µm, whereas woven fabrics exhibit a normal distribution of diameters with mean values roughly five times larger (>15 µm). The mean thickness of the N95 filtration material is 1093 µm and is greater than that of the woven fabrics that span from 420 to 650 µm. A new procedure for measuring the thickness of flannel fabrics is proposed that accounts for raised fibers. µXCT allowed for a quantitative nondestructive approach to measure fabric porosity as well as the surface area/volume. Cotton flannel showed the largest mean isotropy of any fabric, though fiber order within the weave is poorly represented in the surface electron images. Surface fabric isotropy and surface area/volume ratios are proposed as useful microstructural quantities to consider for future particle filtration modeling efforts of woven materials.

Coupling the measures of pollution source control and water replenishment to improve water quality in the catchment scale of Qianshan River Basin.

With the development of the economy, the problem of urban black odorous water bodies has become increasingly significant, having a serious impact on the environment. As important means of remediating aquatic environments, pollution source control and water replenishment are of great significance in improving water quality. This study takes the Qianshan River Basin in Zhuhai City as its study area to simulate their effects on the improvement of water quality. A coupled model of water quantity and quality in Qianshan River Basin was constructed using MIKE11to analyze the water quality compliance rate, with sewage interception rates of 85%, 90%, and 95%, and to investigate the effect of pollution source control on the improvement of the aquatic environment. Using different sewage interception rates, the amount of water replenishment was calculated in order to meet water quality standards, the water replenishment scheme was determined via river-specific and time-specific methods, and the model was used to analyze the replenishment effect of the scheme. The results show that increasing the sewage interception rate can significantly improve the COD compliance rate, and improve the NH3-N and TP compliance rate; however, the enhancement effect is not sufficiently significant. When a sewage interception rate of 95% is implemented, there are still five rivers with a low NH3-N compliance rate, and six rivers with low a TP compliance rate. Comparing the water replenishment effect under different sewage interception rates of 85% and 95%, the water replenishment program alongside a sewage interception rate of 95% can effectively improve the aquatic environment and the water quality essentially meets the standard under different rainfall conditions; this demonstrates that the program presented herein can be used as the aquatic environment remediation program of choice for the Qianshan River Basin.

A closed-loop analysis approach for ensuring stormwater source control design solution to achieve the intended goals.

Stormwater source controls have been adopted worldwide to address hydrological and environmental impairments caused by the spread of impervious surfaces in cities. Current design method in China uses 30-year daily rainfall records to generate relationship of rainfall volume capture ratio (αg) and daily design storm, and then uses design storm to propose design solution. However, source control performance differs from rain to rain, and hence the design solution's actual effect may deviate from αg. Borrowing closed-loop feedback concept from business domain, this study proposes closed-loop analysis (CLA) which uses design solution's 30-year simulated result as data feedback to check design solution's effectiveness and then make improvements if necessary. It consists of four methods: 1) hourly design storm statistical method, for addressing the weakness of current daily design storm; 2) design solution model credibility examination method, for guaranteeing credibility of 30-year simulated results for CLA; 3) appropriate design storms determination method for source control without underdrain; 4) additional design parameters optimization method for source control with underdrain. Taking Xiamen city for example, case study results shows that design solution's 30-year simulated results were consistent/comparable with sizing calculation formula that was used to propose design solution, and therefore they were credible for CLA. Appropriate design storms ensured design solutions without underdrain to achieve the intended αg±3 %. Optimal design parameters combinations ensured design solutions with underdrain to achieve αg but also restore natural runoff events with pre- and post-development runoff frequency spectra similarity being 0.670-0.691. Based on stormwater mathematical model, CLA can drive source control design computation to a new methodological stage.