Urban-canopy airflow dynamics: A numerical investigation of drag forces and distribution for generic neighborhoods, and their relationships with breathability.

Thorough investigations of urban-canopy drag primarily stemming from pressure drag on building surfaces are necessary given the turbulent flows within complex urban areas. Moreover, a gap persists regarding the relationships between canopy drag and breathability. Therefore, this work delves into the canopy-layer airflow dynamics for generic urban neighborhoods by performing three-dimensional Reynolds-Averaged Navier-Stokes simulations. A total of 32 subcases are examined, encompassing uniform- and varying-height and diverse plan area densities (λp, categorized into groups of sparse: 0.0625/0.067, medium: 0.23/0.25, and dense: 0.53/0.56). Results for the drag distribution highlight the windward-row shelter effect for the medium and the dense, local shelter by taller buildings, and distinct shapes of sectional drag forces (F⁎Z). Local velocity and mean age of air are found strongly positively and negatively correlated to F⁎Z, respectively, with distinct slopes in relation to λp. For the uniform-height, the normalized bulk drag (F⁎bulk, referred to as drag coefficient in literature) peaks for the medium with wake-interference regime; F⁎bulk demonstrates a maximum increase of over two times with height variation; moreover, F⁎bulk for varying-height groups exhibits a marked increase from the sparse to the medium, while remaining comparable values for the dense. The frontal area averaged drag (FAf,ave) exhibits a decreasing trend against λp across all cases. Further, FAf,ave exhibits strong correlations with λp and porosity, and with bulk ventilation indices such as spatially averaged velocity, air change rate, and normalized net escape velocity. Throughout the 'suburban-urban-suburban' canopy, medium neighborhoods exerting larger drag cause greater streamwise outdoor pressure drops and flow reductions compared to the sparse. However, dense neighborhoods with lower drag exhibit even larger pressure losses, which should be carefully scrutinized. The findings can inform urban planners in designing more aerodynamically efficient neighborhoods and guide strategies for improving air quality within urban environments.

Nationwide evaluation of energy and indoor air quality predictive control and impact on infection risk for cooling season.

Since the coronavirus disease 2019, the extended time indoors makes people more concerned about indoor air quality, while the increased ventilation in seeks of reducing infection probability has increased the energy usage from heating, ventilation, and air-conditioning systems. In this study, to represent the dynamics of indoor temperature and air quality, a coupled grey-box model is developed. The model is identified and validated using a data-driven approach and real-time measured data of a campus office. To manage building energy usage and indoor air quality, a model predictive control strategy is proposed and developed. The simulation study demonstrated 18.92% energy saving while maintaining good indoor air quality at the testing site. Two nationwide simulation studies assessed the overall energy saving potential and the impact on the infection probability of the proposed strategy in different climate zones. The results showed 20%-40% energy saving in general while maintaining a predetermined indoor air quality setpoint. Although the infection risk is increased due to the reduced ventilation rate, it is still less than the suggested threshold (2%) in general. Electronic Supplementary Material ESM: The Appendix is available in the online version of this article at 10.1007/s12273-022-0936-6.

Lateral Circumflex Femoral Vascular Chimeric Fascia Flap Reduces Pain and Promotes Wound Healing in Repairing Skin and Tendon Defects of Hand, Foot, and Ankle.

The purpose of this study was to investigate the clinical efficacy of lateral circumflex femoral artery embedded with fascia lata flap in the repair of skin and tendon defects in hand, foot, and ankle. From January 2020 to June 2021, 32 patients with skin and tendon defects of the hand, foot, and ankle admitted to our hospital were selected as the study subjects. According to the random number table method, they were divided into the observation group (16 cases, treated with rotational lateral femoral vascular inlay broad fascial flap repair) and the control group (16 cases, treated with conventional skin flap repair) and followed up for 6 months. The postoperative tendon midactivity measurement scale (TAM), ankle-hindfoot scoring system (AOFAS), and lower limb functional evaluation scale (LEFS) scores were all higher in the observer group than in the control group The number of people with infection, implant necrosis, and subcutaneous hematoma in the observation group (total incidence 6.25%) was less (lower) than that in the control group (50.00%), and the total number of people with significant and fair clinical efficacy in the observation group (total effective rate 100.00%) was more (higher) than that in the control group (68.75%). The application of early plastic surgery to the clinical treatment of patients with deep burns on the hand can reduce the patient's pain and promote the healing of the wound. It is of great significance to reduce the risk of complications such as necrosis of the skin graft and improve the efficacy of the surgery.

A systematic approach to estimating the effectiveness of multi-scale IAQ strategies for reducing the risk of airborne infection of SARS-CoV-2.

The unprecedented coronavirus disease 2019 (COVID-19) pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made more than 125 million people infected and more than 2.7 million people dead globally. Airborne transmission has been recognized as one of the major transmission routes for SARS-CoV-2. This paper presents a systematic approach for evaluating the effectiveness of multi-scale IAQ control strategies in mitigating the infection risk in different scenarios. The IAQ control strategies across multiple scales from a whole building to rooms, and to cubical and personal microenvironments and breathing zone, are introduced, including elevated outdoor airflow rates, high-efficiency filters, advanced air distribution strategies, standalone air cleaning technologies, personal ventilation and face masks. The effectiveness of these strategies for reducing the risk of COVID-19 infection are evaluated for specific indoor spaces, including long-term care facility, school and college, meat plant, retail stores, hospital, office, correctional facility, hotel, restaurant, casino and transportation spaces like airplane, cruise ship, subway, bus and taxi, where airborne transmission are more likely to occur due to high occupancy densities. The baseline cases of these spaces are established according to the existing standards, guidelines or practices. Several integrated mitigation strategies are recommended and classified based on their relative cost and effort of implementation for each indoor space. They can be applied to help meet the current challenge of ongoing COVID-19, and provide better preparation for other possible epidemics and pandemics of airborne infectious diseases in the future.

Combining culturing and 16S rDNA sequencing to reveal seasonal and room variations of household airborne bacteria and correlative environmental factors in nanjing, southeast china.

Exposure to bioaerosols poses important health effects on occupants. To elucidate seasonal and room variations of household airborne bacteria, this study investigated 30 residential homes during summer and winter throughout Nanjing, Southeast China, with a humid subtropical climate. Culturing and 16S rDNA sequencing methods were combined in this study. Results showed that the community structure and composition in the same season but different homes show similarity, however, they in the same home but in different seasons show a huge difference, with Sphingomonas (25.3%), Clostridium (14.8%), and Pseudomonas (7.6%) being the dominant bacteria in summer, and Pseudomonas (57.1%) was dominant bacteria in winter. Culturable concentrations of bacteria were also significantly higher in summer (854 ± 425 CFU/m3 ) than in winter (231 ± 175 CFU/m3 ), but difference by home or room was relatively minor. More than 80% of culturable bacteria (<4.7 µm) could penetrate into lower respiratory tract. The seasonal variations of bacterial community and concentrations were closely associated with seasonal variations of temperature, humidity, and PM2.5 . Higher concentrations and larger sizes were observed in the bathroom and kitchen, typically with higher humidity than other rooms.

Hydrogen Peroxide Emission and Fate Indoors during Non-bleach Cleaning: A Chamber and Modeling Study.

Activities such as household cleaning can greatly alter the composition of air in indoor environments. We continuously monitored hydrogen peroxide (H2O2) from household non-bleach surface cleaning in a chamber designed to simulate a residential room. Mixing ratios of up to 610 ppbv gaseous H2O2 were observed following cleaning, orders of magnitude higher than background levels (sub-ppbv). Gaseous H2O2 levels decreased rapidly and irreversibly, with removal rate constants (kH2O2) 17-73 times larger than air change rate (ACR). Increasing the surface-area-to-volume ratio within the room caused peak H2O2 mixing ratios to decrease and kH2O2 to increase, suggesting that surface uptake dominated H2O2 loss. Volatile organic compound (VOC) levels increased rapidly after cleaning and then decreased with removal rate constants 1.2-7.2 times larger than ACR, indicating loss due to surface partitioning and/or chemical reactions. We predicted photochemical radical production rates and steady-state concentrations in the simulated room using a detailed chemical model for indoor air (the INDCM). Model results suggest that, following cleaning, H2O2 photolysis increased OH concentrations by 10-40% to 9.7 × 105 molec cm-3 and hydroperoxy radical (HO2) concentrations by 50-70% to 2.3 × 107 molec cm-3 depending on the cleaning method and lighting conditions.

Effects of combining transarterial chemoembolization with percutaneous microwave coagulation therapy for hepatocellular carcinoma abutting the diaphragm.

OBJECTIVE: This study aims to explore the clinical effectiveness of a combination therapy of transarterial chemoembolization (TACE) and percutaneous microwave coagulation therapy (PMCT) in treating hepatocellular carcinoma (HCC) abutting the diaphragm. MATERIAL AND METHODS: Six cases with HCC were treated with TACE followed by PMCT one month later with the aid of artificial pneumothorax. RESULTS: CT/MRI revealed complete necrosis in the tumor lesions and the treated tumor margins (≥ 5 mm). Serum alpha-fetoprotein (AFP) levels markedly declined in patients who originally had higher serum AFP levels. Postoperative complications such as fever, mild hepatic dysfunction and pleural effusion were alleviated within a short period of time. All patients were closely monitored through follow-up; all patients survived, except for one patient who received a liver transplantation. CONCLUSIONS: As lesions are either invisible or poorly visible in sonography, determining an effective treatment for HCC abutting the diaphragm remains a particular challenge. TACE and PMCT combined therapy with the aid of artificial pneumothorax proved to be an available treatment option.

Transformation of 2,2',4,4'-tetrabromodiphenyl ether under UV irradiation: potential sources of the secondary pollutants.

A commercial brominated flame retardant 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) was used as the model chemical to investigate the degradation and transformation of polybrominated diphenyl ethers (PBDEs) in gas and liquid phases, respectively, under ultraviolet (UV) irradiation. The results showed that BDE-47 can be transformed to less-brominated BDE analogs. A total of six compounds that are less-brominated BDEs and two brominated phenols were observed as transformation products in the reaction mixtures. Different degradation rates of BDE-47 in n-nonane and in isooctane in the same chamber system were observed. Degradation rate of BDE-47 in n-nonane was faster than in isooctane. Under UV irradiation, the bromine on the ortho positions of the phenyl rings was lost first to form 2,4,4'-tribromodiphenyl ether (BDE-28), which then progressively lead to 4,4'-dibromodiphenyl ether (BDE-15) or 2,4'-dibromodiphenyl ether (BDE-8). An airborne transformation pathway has been proposed according to observed transformation products. The more volatile less-brominated BDEs from transformation of BDE-47 are easily evaporated into air to be a source of secondary pollutants in the environment.

Determination of partition and diffusion coefficients of formaldehyde in selected building materials and impact of relative humidity.

The partition and effective diffusion coefficients of formaldehyde were measured for three materials (conventional gypsum wallboard, "green" gypsum wallboard, and "green" carpet) under three relative humidity (RH) conditions (20%, 50%, and 70% RH). The "green" materials contained recycled materials and were friendly to environment. A dynamic dual-chamber test method was used. Results showed that a higher relative humidity led to a larger effective diffusion coefficient for two kinds of wallboards and carpet. The carpet was also found to be very permeable resulting in an effective diffusion coefficient at the same order of magnitude with the formaldehyde diffusion coefficient in air. The partition coefficient (K(ma)) of formaldehyde in conventional wallboard was 1.52 times larger at 50% RH than at 20% RH, whereas it decreased slightly from 50% to 70% RH, presumably due to the combined effects of water solubility of formaldehyde and micro-pore blocking by condensed moisture at the high RH level. The partition coefficient of formaldehyde increased slightly with the increase of relative humidity in "green" wallboard and "green" carpet. At the same relative humidity level, the "green" wallboard had larger partition coefficient and effective diffusion coefficient than the conventional wallboard, presumably due to the micro-pore structure differences between the two materials. The data generated could be used to assess the sorption effects of formaldehyde on building materials and to evaluate its impact on the formaldehyde concentration in buildings.