Contamination Of Equipment Research Articles

Optimal control analysis for a Candida auris nosocomial infection model with environmental transmission

In this paper, we propose a mathematical model to investigate the role of environmental reservoirs in the transmission dynamics of the rising Candida auris infections in nosocomial settings. The ability of the pathogen to resist commonly used hospital disinfectants ensures its persistent contamination of hospital surfaces and medical equipment readily leading to patient colonization. Colonized patients shed the pathogen into their surroundings thereby increasing the fungal concentration in the hospital environment. We analyze the model for its basic mathematical properties, perform sensitivity analysis, and formulate an optimal problem to determine the efficiency of control interventions, namely, standard transmission precautions, proper laboratory identification, and isolation of patients identified with colonization in reducing the contamination and transmission of C. auris infections. We characterize the optimal controls using Pontryagin's Minimum Principle and further prove the uniqueness of the optimality system. Numerical simulations are performed to substantiate the theoretical analysis, and the results are illustrated graphically.

Exposure and Health Effects of Bacteria in Healthcare Units: An Overview

Healthcare units consist of numerous people circulating daily, such as workers, patients, and companions, and these people are vehicles for the transmission of microorganisms, such as bacteria. Bacteria species may have different allergenic, pathogenic, infectious, or toxic properties that can affect humans. Hospital settings foment the proliferation of bacteria due to characteristics present in the indoor hospital environment. This review article aims to identify the potential health effects caused by bacterial contamination in the context of healthcare units, both in patients and in workers. A search was carried out for articles published in PubMed, Web of Science and Scopus, between 1 January 2000 and 31 October 2021, using the descriptor hospital exposure assessment bacteria. This bibliographic research found a total of 13 articles. Bacteria transmission occurs mainly due to the contact between healthcare workers and patients or through the handling of/contact with contaminated instruments or surfaces. The most common bacterial contaminants are Escherichia coli, Pseudomonas aeruginosa, Staphylococcus spp., Staphylococcus aureus and Micrococcus luteus, and the principal health effects of these contaminants are hospital-acquired infections and infections in immunocompromised people. A tight control of the disinfection methods is thus required, and its frequency must be increased to remove the microbial contamination of wards, surfaces and equipment. A better understanding of seasonal variations is important to prevent peaks of contamination.

Contamination of personal protective equipment during COVID-19 autopsies

Confronted with an emerging infectious disease at the beginning of the COVID-19 pandemic, the medical community faced concerns regarding the safety of autopsies on those who died of the disease. This attitude has changed, and autopsies are now recognized as indispensable tools for understanding COVID-19, but the true risk of infection to autopsy staff is nevertheless still debated. To clarify the rate of SARS-CoV-2 contamination in personal protective equipment (PPE), swabs were taken at nine points in the PPE of one physician and one assistant after each of 11 full autopsies performed at four centers. Swabs were also obtained from three minimally invasive autopsies (MIAs) conducted at a fifth center. Lung/bronchus swabs of the deceased served as positive controls, and SARS-CoV-2 RNA was detected by real-time RT-PCR. In 9 of 11 full autopsies, PPE samples tested RNA positive through PCR, accounting for 41 of the 198 PPE samples taken (21%). The main contaminated items of the PPE were gloves (64% positive), aprons (50% positive), and the tops of shoes (36% positive) while the fronts of safety goggles, for example, were positive in only 4.5% of the samples, and all the face masks were negative. In MIAs, viral RNA was observed in one sample from a glove but not in other swabs. Infectious virus isolation in cell culture was performed on RNA-positive swabs from the full autopsies. Of all the RNA-positive PPE samples, 21% of the glove samples, taken in 3 of 11 full autopsies, tested positive for infectious virus. In conclusion, PPE was contaminated with viral RNA in 82% of autopsies. In 27% of autopsies, PPE was found to be contaminated even with infectious virus, representing a potential risk of infection to autopsy staff. Adequate PPE and hygiene measures, including appropriate waste deposition, are therefore essential to ensure a safe work environment.

What are the potential sources of on-farm contamination of raw milk butter with Escherichia coli?

Description of the subject. According to Regulation (EC) No 2073/2005, Escherichia coli must be enumerated in raw milk butter before sales. Hygiene of batches is acceptable when a maximum of two samples out of five have levels of E. coli between 10 and 100 cfu·g-1. E. coli is still a threat to the safety of raw milk butter. Objectives. This study aimed to identify sources of E. coli in six farms facing recurrent contaminations in butter. Method. Farms were visited three times between March and May 2021. Surface samples and dairy products samples were collected throughout the process for E. coli enumeration and assessment of potential correlations between equipment contamination and hygienic quality of food products. Results. Two major sources of contamination were identified: the lack of efficacy of cleaning and disinfection practices on milk pipelines, junctions and cream separators, and absence of milk cooling in case of time-lapse of more than 2 h between milking and skimming. The use of lactic acid starters could be a helpful way to control E. coli during cream maturation, in association to adequate good manufacturing practices. Conclusions. Levels of E. coli in the considered raw milk butter batches were really high. A new decision tree is proposed that could help manufacturers and food controllers to improve hygienic quality of raw milk butter.

Bacterial contamination of medical equipment and surfaces in the main operating theater of Enugu State University Teaching Hospital

Background: Bacterial contamination of operating theaters is a major contributory factor to the high prevalence of post-operative nosocomial infections. The detection of changing trends of microbial counts and micro-flora is key to reducing microbial contamination and good antibiotic stewardship. Objective: The objective of this study was to identify bacterial colonization of surfaces and equipment in Enugu State University Teaching Hospital’s operating theater. It also aimed at determining the sensitivity patterns of the colonized surfaces. Materials and Methods: This cross-sectional study was conducted in the Main Theater of Enugu State University Teaching Hospital (ESUTH), Parklane, Enugu, Nigeria. Samples were collected from equipment, operating room surfaces, and cleaning solutions. Results: Out of 92 samples collected from various sites, bacterial growth was observed in 47 (51.1%) specimens. Coagulase-negative Staphylococcus (CoNS) was the most common isolate (36.2%), followed by Staphylococcus aureus (34%). Among S. aureus isolates, 43.8% were methicillin-resistant S. aureus (MRSA), and the remaining were methicillin-susceptible S. aureus (MSSA). There was high Gram-negative resistance to meropenem. All the Gram-negative isolates were susceptible to imipenem. Conclusion: CoNS and S. aureus were the commonest isolates. Increased efforts are needed to reduce the rate of healthcare-associated and surgical site infections in operating theaters.

АНАЛИЗ КОНТАМИНИРОВАННОСТИ ОДЕЖДЫ И ОБОРУДОВАНИЯ МИКРОСКОПИЧЕСКИМИ ГРИБАМИ ПОСЛЕ ПОСЕЩЕНИЯ ПЕЩЕР КИНДЕРЛИНСКАЯ И ШУЛЬГАН-ТАШ

Caves are extreme ecosystems whose microbiomes are very sensitive to invasion by extraneous microbial species. The entry of such organisms from one cave into another can occur due to anthropogenic transfer, which makes it possible to bypass natural barriers. The article presents materials on the analysis of microscopic fungi contamination of clothing and equipment after working in caves. It is shown that after visiting the cave Kinderlinskaya and Shulgan-Tash, a significant number of micromycete species settle on clothes and equipment. Twenty-one species of microscopic fungi were found, as well as yeast, light and dark-colored sterile forms. The isolated species correspond to the typical species composition of fungi in a particular cave. Gloves turned out to be the most contaminated. Washing made it possible to significantly reduce the number and species richness of micromycetes on clothes. Thus, following simple rules can significantly reduce the risk of anthropogenic transfer of microorganisms between caves.

INVESTIGATION OF THE UNCERTAINTY VALUE AT MEASURING THE TEMPERATURE OF THE COOLANT IN THE PIPELINES WITH OUTSIDE SURFACE MOUNTED TEMPERATURE SENSORS

During performing technological and production processes and monitoring the modes of their operation, the problem of determining the temperature of various media transported through pipelines is solved without incut temperature sensors (TS) in them, i.e. with using outside surface mounted TS (SMTS). This method is allowing to measure mechanical values at technological processes without structure broken and without influence to physicochemical properties of measured media.
 Using of SMTS possible to register heat losses on sections of heating mains, pollution degree of pipelines internal walls, to control serviceability of measurement channels of temperature of the coolant in heat meters, etc.
 In the article authors presents results of research the uncertainty values for measuring of the coolant temperature in heating systems pipelines under different modes of its flow. First of all, the uncertainty value of the measurements results was estimated, which was determined by the results of the study for the calculation model and field tests at existing district heating systems.
 Emphasis is paid on estimating the difference between the registration of temperature in the middle of the pipeline, determined by mortise transducers and the temperature measured by outside surface mounted temperature transducers, taking into account the temperature gradient across the pipeline and the quality of its insulation.
 It is determined that: the temperature measured by temperature transducers on the surface of the pipeline at different points of its perimeter, with proper installation and sufficient thermal insulation does not depend on their location; the average temperature on the surface of the pipeline, measured using the developed method of installation of PT, slightly differs (ΔT ≈- 0.3⁰C) from the average temperature of the coolant in the middle of the flow; temperature transducers have high reproducibility of measurements and small difference in readings between channels at parallel measurements (»0,03⁰С).
 It is substantiated that high metrological performances of temperature transducers allow to use them for solving other tasks: measuring the distribution of heat fluxes in heating systems of residential buildings to perform hydraulic balancing of heating systems and increase their efficiency; estimate of contamination of pipelines and heat exchange equipment to determine the need for their washing; determination of thermal resistance of buildings protective structures to assess their energy efficiency; determination of large pumps efficiency by calorimetric method; checking the correct of operation the temperature measuring channels of heat meters and cold meters; in other technology areas where measurements of small temperature differences with high accuracy are required.

Evaluation of microbial contamination on cuff syringe, cuff pressure gauge, and their surroundings in the operating room

BackgroundSome institutions reuse cuff syringes and do not periodically sterilize cuff pressure gauges. Pathogenic bacterial contamination of such equipment may increase the probability of pathogen transmission to patients during anesthetic procedures. Therefore, microbial contamination on cuff syringes, cuff pressure gauges, and their surroundings was assessed in the operating rooms of a university-affiliated tertiary care hospital in Japan.MethodsThis study was conducted between April and May 2019 in 14 operating suites at a hospital. The following sites in each operating suite were sampled: cuff syringe (inner/outer components), outer components of cuff pressure gauge, cuff syringe and cuff pressure gauge storage drawers, and computer mice. The swabs were directly streaked onto agar plates and incubated. Then, the bacterial species were identified using mass spectrometry.ResultsThe highest bacterial isolation was observed in computer mice, followed by the outside of cuff pressure gauges and the drawers of cuff pressure gauges (92.9, 78.6, and 64.3%, respectively). Most of the identified bacteria belonged to the Bacillus species, with colonization rates of 85.7, 57.1, and 57.1% on computer mice, cuff pressure gauges, and cuff pressure gauge storage drawers, respectively. Coagulase-negative Staphylococcus was found in 35.7% of the specimens and was more prevalent on computer mice (71.4%), followed by on cuff pressure gauges (64.3%).ConclusionAnesthesiologists should be aware of the possible pathogen contamination risk from cuff syringes, cuff pressure gauges, or associated equipment and take appropriate infection control measures to minimize the risk of pathogenic transmission.

Are coveralls required as personal protective equipment during the management of COVID-19 patients?

ObjectivesFew studies have investigated the contamination of personal protective equipment (PPE) during the management of patients with severe-to-critical coronavirus disease (COVID-19). This study aimed to determine the necessity of coveralls and foot covers for body protection during the management of COVID-19 patients.MethodsPPE samples were collected from the coveralls of physicians exiting a room after the management of a patient with severe-to-critical COVID-19 within 14 days after the patient’s symptom onset. The surface of coveralls was categorized into coverall-only parts (frontal surface of the head, anterior neck, dorsal surface of the foot cover, and back and hip) and gown-covered parts (the anterior side of the forearm and the abdomen). Sampling of the high-contact surfaces in the patient’s environment was performed. We attempted to identify significant differences in contamination with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) between the coverall-only and gown-covered parts.ResultsA total of 105 swabs from PPEs and 28 swabs from patient rooms were collected. Of the PPE swabs, only three (2.8%) swabs from the gown-covered parts were contaminated with SARS-CoV-2. However, 23 of the 28 sites (82.1%) from patient rooms were contaminated. There was a significant difference in the contamination of PPE between the coverall-only and gown-covered parts (0.0 vs 10.0%, p = 0.022).ConclusionsCoverall contamination rarely occurred while managing severe-to-critical COVID-19 patients housed in negative pressure rooms in the early stages of the illness. Long-sleeved gowns may be used in the management of COVID-19 patients.

Echocardiography in COVID-19 Pandemic: Clinical Findings and the Importance of Emerging Technology.

COVID-19 could have a direct or indirect effect on the cardiovascular system. To detect cardiac involvement, transthoracic echocardiography is highly recommended. Considering the risk of equipment contamination and personnel exposure, mainly focused echocardiographic evaluations instead of complete examination are recommended and the use of portable devices easy to disinfect with offline reporting is highly suggested. COVID-19 could affect different sections of the heart and it is useful to analyze them separately during an echocardiographic examination. Available echocardiographic data on COVID-19 patients are scarce and do not provide definite evidence and more studies are certainly needed to better evaluate this topic.

Per- and Polyfluoroalkyl Substances (PFAS): Significance and Considerations within the Regulatory Framework of the USA.

Per- and polyfluoroalkyl substances (PFAS) are an emerging environmental crisis. Deemed forever chemicals, many congeners bioaccumulate and are incredibly persistent in the environment due to the presence of the strong carbon-fluorine covalent bonds. Notable PFAS compounds include perfluorooctanesulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and GenX. Robust toxicological knowledge exists for these substances, but regulatory decisions based on this knowledge has fallen behind. The United States Environmental Protection Agency (EPA) has addressed this issue with the PFAS Action Plan and EPA Council on PFAS, but the regulatory framework is severely lacking. Currently, no federal regulations or standards exist. Many occupational and non-occupational human cohorts exist that can lend knowledge on the environmental implications of PFAS and associated health effects. Occupationally, firefighters face significant exposure risks due to use of PFAS containing aqueous film-forming foams (AFFFs) and personal protective equipment contamination. Non-occupationally, wastewater discharge in North Carolina led to chronic and widespread residential exposure to GenX via drinking water contamination. This public health review seeks to convey the current and future significance of PFAS as an environmental contaminate, to lend considerations on regulatory frameworks within the USA, and to help guide and promote the need for future epidemiological studies in order to tackle this environmental emergency. While the PFAS Action Plan creates a scientific and regulatory foundation, it is important to take these lessons and apply them to future environmental health issues.

Feasibility of Implementing Thoracic Radiation Therapy for COVID-19 Pneumonia

Purpose/Objective(s)The value of low dose whole thoracic radiation therapy (LD-WTRT) for SARS-CoV-2 (COVID-19) pneumonia is unknown. Should ongoing clinical trials demonstrate LD-WTRT proves effective for COVID-19 pneumonia recovery, widespread rapid implementation will be helpful globally. Our aim was to outline a pragmatic process that could be implemented successfully in a community hospital.Materials/MethodsTo identify appropriate patients admitted to the hospital with COVID-19 pneumonia, we worked with Nursing Informatics to screen all currently admitted COVID+ patients requiring oxygen supplementation. For patients meeting criteria of the PreVent protocol per chart review, radiation oncologists contacted the hospitalist physician for telehealth consultation with the patient to discuss single dose LD-WTRT. After a patient had confirmed interest in treatment, at time of physical exam, we obtained consent and digitally transferred the signed consent form via secure text to avoid contaminated forms. Chest radiographs were used to estimate AP/PA field size and separation at the carina; diagnostic chest CT data was imported into the treatment planning system for field size and MU calculation before patient arrival, without using the department's CT simulator. Inpatient Nursing transported patients for treatment after clinic hours on a route pre-approved by Infection Control. The treating radiation oncologist and one ‘hot’ radiation therapist assisted with patient set-up supine or prone on the linear accelerator couch. After decontamination, the physician and a ‘cold’ therapist confirmed field size and MU calculations to prepare for treatment delivery. Nursing monitored patient O2 saturation and stayed gowned with the ‘hot’ therapist. After patient departure, Radiation Oncology contacted Facilities for decontamination of the vault before treating cancer patients the following day.ResultsFor the first treated patient, telehealth consultation lasted 40 minutes. In-person exam, evaluation and consent took 60 minutes, of which 30 were for the protocol-required consent form. With the diagnostic CT scan, field design and MU calculations took 20 minutes. Patient arrival to departure took 40 minutes. Once the patient was positioned on the couch, localization, MU confirmation and entry and treatment delivery took 16 minutes.ConclusionWe have developed a process to efficiently provide LD-WTRT for patients with COVID pneumonia that minimizes staff exposure, departmental equipment, and room contamination. Should clinical trials indicate that LD-WTRT helps treat COVID pneumonia patients, this process can work in most hospital-based radiation oncology departments to provide LD-WTRT efficiently and safely. Staff and cancer patient vaccination will further lower the risks of implementing LD-WTRT but is not necessary with careful planning and consultation with infection control.

Challenges of Health Information Systems (HISs) During COVID-19 Pandemics: Lessons Learned from Teaching Hospitals in a Developing Country

Background: Health information systems have major impacts on improving the decision-making process during pandemics. Objectives: The qualitative study explored health information systems (HISs) challenges based on HIS’s manager viewpoint during the COVID-19 outbreak. Methods: In the study, data were collected in two phases: First, in response to an official letter, all participants reported their challenges with HISs. Second, semi-structured interviews were conducted with the same participants. Results: The semantic units were extracted, collected, and coded. Eighteen HIS managers from 18 hospitals reported the challenges of HISs. The 46 HIS challenges and 24 solutions were classified into three categories: Technology, organization, and human. The technology category included three sub-categories: Multiple non-interoperable HISs, inconsistencies between reports of HISs, and lack of suitable hardware equipment. The organizational category encompassed three sub-categories: Data quality, environment and equipment contamination by COVID-19 virus, and lack of sufficient preparedness to respond to the pandemic condition in hospitals. The human category had four subsets: multiple resources of stress, instability in business conditions, and shortage of human resources, and increased workload. Conclusions: It seems that reconstruction of health information systems, revision of medical record documentation processes, holding training courses, and planning to deal with pandemics, human resource support programs are very necessary.

УЛЬТРАЗВУКОВОЕ ИССЛЕДОВАНИЕ И РИСК РАЗВИТИЯ ЯТРОГЕННЫХ ИНФЕКЦИЙ

Ultrasound examination is used in all areas of modern medicine and occupies the leading positions in non-invasive instrumental diagnostics. Ultrasound is believed to be safe for patients. At the same time, there is a dangerous effect of ultrasound, manifested by bacterial and viral contamination of ultrasound equipment and the examined patients. Numerous studies have convincingly shown that ultrasound is dangerous in terms of iatrogenic contamination of a patient with bacterial, fungal and viral infections. Each ultrasound examination includes contact between the probe of the device and the patient’s skin, or his/her mucous membranes, or sterile tissues during intraoperative examinations. When the ultrasonic sensor comes into contact with the patient’s body, it may become contaminated with pathogenic and opportunistic microorganisms. It is also possible to contaminate the ultrasound equipment and the hands of a doctor who conducts this study. All this will subsequently contribute to the microorganisms transmission to other subjects being examined. Therefore, every patient should be considered as a potential source of pathogenic microorganisms and viruses. The purpose of the work was to analyze the literature data on bacterial and viral contamination during ultrasound examination.

Bacterial contamination rates and drug susceptibility patterns of bacteria recovered from medical equipment, inanimate surfaces, and indoor air of a neonatal intensive care unit and pediatric ward at Hawassa University Comprehensive Specialized Hospital, Ethiopia

Introduction: Bacterial contamination of medical equipment, inanimate surfaces, and indoor air of the hospital environment is the main source of hospital-acquired infection in developing countries.Objective: The aim of this study was to determine the bacterial contamination rates for medical equipment, inanimate surfaces, and indoor air, and the drug susceptibility profiles of bacteria, in the neonatal intensive care unit and pediatric ward of Hawassa University Comprehensive Specialized Hospital (HUCSH).Methods: A hospital-based cross-sectional study was carried out from October 20 to December 30, 2020. Samples were collected from medical equipment, inanimate surfaces, and indoor air of the neonatal intensive care unit and pediatric ward, and processed using standard microbiological methods. Data entry and analysis were carried out using SPSS software version 25.0.Results: Of the total samples collected, 171 (74.7%; 95% CI 68.4‒83.5) were culture positive. These comprised 33 (58.9%) of samples taken from medical equipment, 26 (42.6%) from inanimate surfaces, and 112 (100%) from indoor air . Micrococcus species (41.3%), Acinetobacter species (13.7%), and Klebsiella pneumoniae (10.2%) were the most commonly isolated bacteria.Conclusions: High bacterial contamination rates of medical equipment, inanimate surfaces, and indoor air of the neonatal intensive care unit and pediatric ward were found. Most of the bacterial species isolated were known causative agents of hospital-acquired infection. Around one-quarter of the bacteria were multidrug resistant.

Aerosol-generating dental procedures: a reappraisal of analysis methods and infection control measures

Dental aerosol-generating procedures (AGPs) have been associated with risk for transmitting infectious agents. However, existing infection control monitoring studies potentially underestimate the extent of contamination, due to methodological inadequacies. These studies employed settle plate methodology which only captures droplets that land on agar plates, but not those suspended in air. Furthermore, bacterial culture was used to determine the extent of contamination, without accounting for non-bacterial sources of contamination. This study sought to bridge these gaps by establishing a monitoring protocol involving active aerosol sampling and analysis of two dental AGPs, root canal treatment (RCT) and scaling. RCT and scaling were performed with standard aerosol mitigation precautions. Aerosols generated throughout each procedure were sampled using the air sampler device, while contamination of operatory fomites and personal protective equipment was sampled using surface swabs, before and post-treatment. The amount of contamination was quantified using bacterial culture and adenosine triphosphate (ATP) assay. RCT generated insignificant aerosol and splatter, supporting the infection control procedures' effectiveness. Conversely, scaling significantly increased the amount of aerosol and splatter. When comparing bacterial culture and ATP assay, the magnitude of contamination obtained with ATP assay was greater, suggesting that ATP assay may have detected additional contamination of human origin and bacteria that was not recovered by the culture conditions employed. This monitoring protocol is feasible in the dental setting and determines the extent of contamination generated during AGPs. This could be adopted in future studies to overcome the limitations of the existing literature.

Microbial Environmental Pollution in ICUs: Results, Trends, and Suggestions from a Long-Lasting Surveillance

Intensive care units (ICUs) are special areas in hospitals for patients with severe and life-threatening diseases. ICUs are of several categories, such as neonatal ICUs, cardiac ICUs, neurological ICUs, surgical ICUs, etc. The ICUs’ patients may show a high susceptibility for hospital-acquired infections (HAIs) depending on underlying disease, duration of stay and treatment. ICUs are considered potential reservoirs for (opportunistic) pathogenic microbial strains and the risk of acquiring infection in these hospital environments is higher than in others. Several studies show the role of inanimate surface and equipment contamination in the transmission of pathogens to ICU patients. The aim of this study is to describe the results of 124 sampling campaigns performed during 12 years of microbiological surveillance of five ICUs of different categories, for an overall number of 714 samples (232 from air and 482 from surface), to analyze their trends and to elaborate suggestions to improve ICUs’ environmental quality and patients’ safety.

Environmental contamination and personal protective equipment contamination with SARS-CoV-2 virus in a real-life clinical setting.

The importance of SARS-CoV-2 transmission via contact routes and its stability on surfaces is becoming increasingly recognised. There is ongoing concern that patients can become infected through person-to-person spread and environment-to-person spread. This study assessed whether SARS-CoV-2 viral RNA can be detected in the environment either on staff members' personal protective equipment (PPE), on high-touch surfaces or around the bedspace of COVID-19-positive patients in a range of different ward settings to evaluate if there was any contamination of these. Results showed all PPE and high-touch surface swabs were negative. All swabs taken in the negative-pressure room where aerosol-generating procedures (AGPs) were being undertaken detected viral RNA (5/5 positive), whereas there was minimal contamination in the intensive therapy unit (1/5 positive) and none detected in the cohort bay. These findings would be consistent with the understanding that areas where AGPs are regularly performed are at higher risk of environmental contamination.

Design of Microchannel Suitable for Packing with Anion Exchange Resins: Uranium Separation from Seawater Containing a Large Amount of Cesium.

We present a resin-packed microchannel that can reduce the radiation exposure risk and secondary radioactive wastes during uranium (U) separation by downscaling the separation using a microchip. Two types of microchips were designed to densely pack the microchannels with resins. The microchannels had almost the same cross-sectional area, but different outer circumferences. A satisfactory separation performance could be obtained by arranging more than ca. 10 resins along the depth and width of the microchannels. A resin-packed microchannel is an effective separation technique for determining the U concentration via inductively coupled plasma mass spectrometry owing to its ability to avoid the contamination of equipment by cesium, and to reduce the matrix effect. The size of the separation site was scaled down to <1/5000 compared to commonly used counterparts. The radiation exposure risk and secondary radioactive wastes can be reduced by 10- and 800-fold, respectively, using a resin-packed microchannel.

A reactor-scale CFD model of soot formation during high-temperature pyrolysis and gasification of biomass

Soot generation is an important problem in high-temperature biomass gasification, which results in both air pollution and the contamination of gasification equipment. Due to the complex nature of biomass materials and the soot formation process, it is still a challenge to fully understand and describe the mechanisms of tar evolution and soot generation at the reactor scale. This knowledge gap thus motivates the development of a comprehensive computational fluid dynamics (CFD) soot formation algorithm for biomass gasification, where the soot precursor is modeled using a component-based pyrolysis framework to distinguish cellulose, hemicellulose and lignin. The model is first validated with pyrolysis experiments from different research groups, after which the soot generation during biomass steam gasification in a drop-tube furnace is studied under different operating temperatures (900–1200 °C) and steam/biomass ratios. Compared with the predictions based on a detailed tar conversion model, the current algorithm captures the soot generation more reasonably although a simplified tar model is used. Besides, the influence of biomass lignin content and the impact of tar and soot consumptions on the soot yield is quantitatively studied. Moreover, the impact of surface growth on soot formation is also discussed. The current work demonstrates the feasibility of the coupled multiphase flow algorithm in the prediction of soot formation during biomass gasification with strong heat/mass transfer effects. In conclusion, the model is thus a useful tool for the analysis and optimization of industrial-scaled biomass gasification.