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Ginsenoside compound K (GCK) has been previously reported to be a potent antiarthritic and bone-protective agent. Therefore, the present study aimed to explore the potential effects of GCK on osteoarthritis and its regulatory effects on the pyroptosis of chondrocytes. Primary mouse chondrocytes (PMCs) were used for in vitro analysis. ELISA assays revealed that compared with the untreated cells, TNF-a induced a significant increase in IL-6, MMP13, A disintegrin and metalloproteinase with thrombospondin motifs 5 and MMP3 expression but induced a significant decrease in aggrecan and collagen II expression. By contrast, GCK reversed the aforementioned alterations in a dose-dependent manner. Experimental osteoarthritis was subsequently induced in mice through transection of the medial meniscotibial ligament and medial collateral ligament in the right knee [destabilization of the medial meniscus (DMM) mice]. GCK was found to reduce cartilage degradation in vivo in DMM mice, which was assessed using the Osteoarthritis Research Society International (OARSI) score, collagen II and MMP13 expression. Cartilage degradation is associated with higher OARSI score, decreased collagen II and increased MMP13 expression. In PMCs, TNF-a treatment stimulated an increase in the expression of NLR family pyrin domain containing 3 (NLRP3), Gasdermin D-N terminal (GSDMD-NT), cleaved caspase-1 and mature IL-1ß, markers that indicate the occurrence of pyroptosis. However, GCK treatment suppressed the increase of the aforementioned proteins in a dose-dependent manner. Immunohistochemistry staining of the knee joint tissue sections from the DMM mice confirmed that GCK attenuated the NLRP3 and GSDMD-NT expression that was induced by DMM surgery. In conclusion, the present study revealed that GCK can reduce cartilage degradation in an osteoarthritis model by inhibiting the NLRP3-inflammasome activation and subsequent pyroptosis. [ABSTRACT FROM AUTHOR]

Purpose: To improve the accuracy of cerebral blood flow (CBF) measurement in mice by accounting for the anesthesia effects. Methods: The dependence of CBF on anesthesia dose and time was investigated by simultaneously measuring respiration rate (RR) and heart rate (HR) under four different anesthetic regimens. Quantitative CBF was measured by a phasecontrast (PC) MRI technique. RR was evaluated with a mouse monitoring system (MouseOX) while HR was determined using an ultrashort-TE MRI sequence. CBF, RR, and HR were recorded dynamically with a temporal resolution of 1 min in a total of 19 mice. Linear regression models were used to investigate the relationships among CBF, anesthesia dose, RR, and HR. Results: CBF, RR, and HR all showed a significant dependence on anesthesia dose (p < 0.0001). However, the dose in itself was insufficient to account for the variations in physiological parameters, in that they showed a time-dependent change even for a constant dose. RR and HR together can explain 52.6% of the variations in CBF measurements, which is greater than the amount of variance explained by anesthesia dose (32.4%). Based on the multi-parametric regression results, a model was proposed to correct the anesthesia effects in mouse CBF measurements, specifically CBFcorrected = CBF + 0.58RR − 0.41HR − 32.66Dose. We also reported awake-state CBF in mice to be 142.0 ± 8.8 mL/100 g/min, which is consistent with the model-predicted value. Conclusion: The accuracy of CBF measurement in mice can be improved by using a correction model that accounts for respiration rate, heart rate, and anesthesia dose. [ABSTRACT FROM AUTHOR]

Purpose: To improve the accuracy of cerebral blood flow (CBF) measurement in mice by accounting for the anesthesia effects. Methods: The dependence of CBF on anesthesia dose and time was investigated by simultaneously measuring respiration rate (RR) and heart rate (HR) under four different anesthetic regimens. Quantitative CBF was measured by a phase)contrast (PC) MRI technique. RR was evaluated with a mouse monitoring system (MouseOX) while HR was determined using an ultrashort-TE MRI sequence. CBF, RR, and HR were recorded dynamically with a temporal resolution of 1 min in a total of 19 mice. Linear regression models were used to investigate the relationships among CBF, anesthesia dose, RR, and HR. Results: CBF, RR, and HR all showed a significant dependence on anesthesia dose (p < 0.0001). However, the dose in itself was insufficient to account for the variations in physiological parameters, in that they showed a time-dependent change even for a constant dose. RR and HR together can explain 52.6% of the variations in CBF measurements, which is greater than the amount of variance explained by anesthesia dose (32.4%). Based on the multi-parametric regression results, a model was proposed to correct the anesthesia effects in mouse CBF measurements, specifically CBFcorrected ( CBF + 0.58RR − 0.41HR − 32.66Dose. We also reported awake-state CBF in mice to be 142.0 ± 8.8 mL/100 g/min, which is consistent with the model-predicted value. Conclusion: The accuracy of CBF measurement in mice can be improved by using a correction model that accounts for respiration rate, heart rate, and anesthesia dose. [ABSTRACT FROM AUTHOR]

Diabetic encephalopathy is one of the complications of diabetes, closely related to the degeneration and apoptosis of hippocampal neurons. Buyang Huanwu Decoction (BHD) is a classic traditional Chinese medicine prescription, which has the functions of benefit qi, activing blood circulation and dredging collaterals. To investigate the protective effect and mechanism of BHD on hippocampal neurons in diabetes, a high glucose (HG) induced PC12 cell injury model was established, cell proliferation and apoptosis were detected. The protein expression levels were detected by western blot. Rats with type 2 diabetes mellitus were fed high-fat-sugar diet and low dose of streptozotocin for 4 weeks to observe the body weight, fasting blood glucose, etc. The pathological changes of hippocampal CA1 region were observed through hematoxylin-eosin staining, and the expression of related proteins was detected. The results showed that, after BHD intervention, the degree of apoptosis of PC12 cells injured by HG was significantly reduced, and the cell proliferation was significantly increased. In model group, blood glucose increased significantly, weight loss, oral glucose tolerance was abnormal, while BHD group reversed the above changes. Most nerve cells in BHD group had relatively intact structure and less morphological changes. Immunohistochemistry showed that compared with the model group, the expression of Bcl-2 (B-cell lymphoma 2) in BHD group increased, while the expression of Bax (BCL2-associated X) and caspase-3 decreased. The expression of p-PI3K (phosphorylated phosphatidyl inositol 3- kinase), p-AKT (phosphorylated protein kinase B) and Bcl-2 decreased in model and HG group, while the expression of Bax, Caspase-3, and Cleaved Caspase-3 increased. After BHD intervention, p-PI3K, p-AKT, Bcl-2 expression increased, while Bax, Caspase-3 and Cleaved Caspase-3 expression decreased. In conclusion, BHD may play a protective role on diabetic hippocampal neurons by regulating mitochondria related apoptosis protein and up-regulating PI3K-AKT/Bcl-2 signaling pathway. [ABSTRACT FROM AUTHOR]

Unprecedented urbanization in China has led to serious urban heat island (UHI) issues, exerting intense heat stress on urban residents. Based on observed temperature and PM2.5 concentrations in Beijing over 2016-2020, we find diverse influences of aerosol pollution on urban heat island intensity (UHII) under different circulations. When northerly winds are prevalent in urban Beijing, UHII tends to be much higher at both daytime and nighttime and it is less affected by aerosol concentration. However, when southerly and westerly winds are dominant in rural Beijing, UHII is significantly reduced by aerosol pollution. Using coupled aerosol-radiation-weather simulations, we demonstrate the underlying physical mechanism, which is associated with local circulation and resulting spatial distribution of aerosols. Our results also highlight the role of black carbon in aggravating UHI, especially during nighttime. It could thus be targeted for cooperative management of heat islands and aerosol pollution. [ABSTRACT FROM AUTHOR]

Unprecedented urbanization in China has led to serious urban heat island (UHI) issues, exerting intense heat stress on urban residents. Based on observed temperature and PM2.5 concentrations in Beijing over 2016-2020, we find diverse influences of aerosol pollution on urban heat island intensity (UHII) under different circulations. When northerly winds are prevalent in urban Beijing, UHII tends to be much higher at both daytime and nighttime and it is less affected by aerosol concentration. However, when southerly and westerly winds are dominant in rural Beijing, UHII is significantly reduced by aerosol pollution. Using coupled aerosol-radiation-weather simulations, we demonstrate the underlying physical mechanism, which is associated with local circulation and resulting spatial distribution of aerosols. Our results also highlight the role of black carbon in aggravating UHI, especially during nighttime. It could thus be targeted for cooperative management of heat islands and aerosol pollution. [ABSTRACT FROM AUTHOR]

Glycogen plays a central role in glucose homeostasis and is abundant in several types of tissue. We report an MRI method for imaging glycogen noninvasively with enhanced detection sensitivity and high specificity, using the magnetic coupling between glycogen and water protons through the nuclear Overhauser enhancement (NOE). We show in vitro that the glycogen NOE (glycoNOE) signal is correlated linearly with glycogen concentration, while pH and temperature have little effect on its intensity. For validation, we imaged glycoNOE signal changes in mouse liver, both before and after fasting and during glucagon infusion. The glycoNOE signal was reduced by 88 ± 16% (n = 5) after 24 h of fasting and by 76 ± 22% (n = 5) at 1 h after intraperitoneal (i.p.) injection of glucagon, which is known to rapidly deplete hepatic glycogen. The ability to noninvasively image glycogen should allow assessment of diseases in which glucose metabolism or storage is altered, for instance, diabetes, cardiac disease, muscular disorders, cancer, and glycogen storage diseases. [ABSTRACT FROM AUTHOR]

Sepsis-induced acute kidney injury (SAKI) is a major complication of kidney disease associated with increased mortality and faster progression. Therefore, the development of imaging biomarkers to detect septic AKI is of great clinical interest. In this study, we aimed to characterize the endogenous chemical exchange saturation transfer (CEST) MRI contrast in the lipopolysaccharide (LPS)-induced SAKI mouse model and to investigate the use of CEST MRI for detecting such injury. We used a SAKI mouse model that was generated by i.p. injection of 10 mg/kg LPS. The resulting kidney injury was confirmed by the elevation of serum creatinine and histology. MRI assessments were performed 24 h after LPS injection, including CEST MRI at different B1 strengths (1, 1.8 and 3 µT), T1 mapping, T2 mapping and conventional magnetization transfer contrast (MTC) MRI. The CEST MRI results were analyzed using Z-spectra, in which the normalized water signal saturation (Ssat/S0) is measured as a function of saturation frequency. Substantial decreases in CEST contrast were observed at both 3.5 and - 3.5 ppm frequency offset from water at all B1 powers, with the most significant difference obtained at a B1 of 1.8 µT. The average Ssat/S0 differences between injured and normal kidneys were 0.07 (0.55 ± 0.04 versus 0.62 ± 0.04, P = 0.0028) and 0.07 (0.50 ± 0.04 versus 0.57 ± 0.03, P = 0.0008) for 3.5 and - 3.5 ppm, respectively. In contrast, the T1 and T2 relaxation times and MTC contrast in the injured kidneys did not show a significant change compared with the normal control. Our results showed that CEST MRI is more sensitive to the pathological changes in injured kidneys than the changes in T1, T2 and MTC effect, indicating its potential clinical utility for molecular imaging of renal diseases. [ABSTRACT FROM AUTHOR]

Epidemics and pandemics of influenza are characterized by rapid global spread mediated by non-mutually exclusive transmission modes. The relative significance between contact, droplet, and airborne transmission is yet to be defined, a knowledge gap for implementing evidence-based infection control measures. We devised a transmission chamber that separates virus-laden particles by size and determined the particle sizes mediating transmission of influenza among ferrets through the air. Ferret-to-ferret transmission was mediated by airborne particles larger than 1.5 µm, consistent with the quantity and size of virus-laden particles released by the donors. Onward transmission by donors was most efficient before fever onset and may continue for 5 days after inoculation. Multiple virus gene segments enhanced the transmissibility of a swine influenza virus among ferrets by increasing the release of virus-laden particles into the air. We provide direct experimental evidence of influenza transmission via droplets and fine droplet nuclei, albeit at different efficiency. [ABSTRACT FROM AUTHOR]

Background: Cleaning of environmental surfaces in hospitals is important for the control of methicillin-resistant Staphylococcus aureus (MRSA) and other hospital-acquired infections transmitted by the contact route. Guidance regarding the best approaches for cleaning, however, is limited.Methods: In this study, a mathematical model based on ordinary differential equations was constructed to study MRSA concentration dynamics on high-touch and low-touch surfaces, and on the hands and noses of two patients (in two hospitals rooms) and a health care worker in a hypothetical hospital environment. Two cleaning interventions - whole room cleaning and wipe cleaning of touched surfaces - were considered. The performance of the cleaning interventions was indicated by a reduction in MRSA on the nose of a susceptible patient, relative to no intervention.Results: Whole room cleaning just before first patient care activities of the day was more effective than whole room cleaning at other times, but even with 100% efficiency, whole room cleaning only reduced the number of MRSA transmitted to the susceptible patient by 54%. Frequent wipe cleaning of touched surfaces was shown to be more effective that whole room cleaning because surfaces are rapidly re-contaminated with MRSA after cleaning. Wipe cleaning high-touch surfaces was more effective than wipe cleaning low-touch surfaces for the same frequency of cleaning. For low wipe cleaning frequency (≤3 times per hour), high-touch surfaces should be targeted, but for high wipe cleaning frequency (>3 times per hour), cleaning should target high- and low-touch surfaces in proportion to the surface touch frequency. This study reproduces the observations from a field study of room cleaning, which provides support for the validity of our findings.Conclusions: Daily whole room cleaning, even with 100% cleaning efficiency, provides limited reduction in the number of MRSA transmitted to susceptible patients via the contact route; and should be supplemented with frequent targeted cleaning of high-touch surfaces, such as by a wipe or cloth containing disinfectant. [ABSTRACT FROM AUTHOR]

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To explore the novel properties of carbon nanoparticles (CNPs) in nanotoxicity assays, the adsorption of phenol red (a pH indicator for culture medium) by multi-walled carbon nanotubes (MWNTs) and three kinds of carbon blacks (CBs) with nanosize, and its effects on cytotoxicity were studied. Results indicated that the phenol red adsorbed and delivered into cells by CBs was responsible for the toxicity to Hela cells in the medium without serum. The cellular uptake of phenol red was verified using 125I-labeling techniques. The size-dependent cytotoxicity of CBs was found to closely correlate to adsorption of phenol red, cellular uptake of phenol red-CB complexes and the amount of phenol red delivered into the cells by CBs. Although the CBs were either nontoxic or slightly toxic, as vehicles of phenol red, they played an essential role in the cytotoxicity induced by phenol red. However, MWNTs showed an intrinsic cytotoxicity independent of phenol red. The implications associated with these findings are discussed. [ABSTRACT FROM AUTHOR]

The measurement of extracellular pH (pHe) has potential utility for cancer diagnoses and for assessing the therapeutic effects of pH-dependent therapies. A single magnetic resonance imaging (MRI) contrast agent that is detected through paramagnetic chemical exchange saturation transfer (PARACEST) was designed to measure tumor pHe throughout the range of physiologic pH and with magnetic resonance saturation powers that are not harmful to a mousemodel of cancer. The chemical characterization and modeling of the contrast agent Yb3+-1, 4,7,10-tetraazacyclododecane-1,4, 7-triacetic acid,10-o-aminoanilide (Yb-DO3A-oAA) suggested that the aryl amine of the agent forms an intramolecular hydrogen bond with a proximal carboxylate ligand, which was essential for generating a practical chemical exchange saturation transfer (CEST) effect from an amine. A ratio of CEST effects from the aryl amine and amide was linearly correlated with pH throughout the physiologic pH range. The pH calibration was used to produce a parametric pH map of a subcutaneous flank tumor on a mouse model of MCF-7 mammary carcinoma. Although refinements in the in vivo CEST MRI methodology may improve the accuracy of pHe measurements, this study demonstrated that the PARACEST contrast agent can be used to generate parametric pH maps of in vivo tumors with saturation power levels that are not harmful to a mouse model of cancer. [ABSTRACT FROM AUTHOR]

Background. We examined the role of aerosol transmission of influenza in an acute ward setting. Methods. We investigated a seasonal influenza A outbreak that occurred in our general medical ward (with open bay ward layout) in 2008. Clinical and epidemiological information was collected in real time during the outbreak. Spatiotemporal analysis was performed to estimate the infection risk among patients. Airflow measurements were conducted, and concentrations of hypothetical virus-laden aerosols at different ward locations were estimated using computational fluid dynamics modeling. Results. Nine inpatients were infected with an identical strain of influenza A/H3N2 virus. With reference to the index patient's location, the attack rate was 20.0% and 22.2% in the "same" and "adjacent" bays, respectively, but 0% in the "distant" bay (P=.04). Temporally, the risk of being infected was highest on the day when noninvasive ventilation was used in the index patient; multivariate logistic regression revealed an odds ratio of 14.9 (95% confidence interval, 1.7-131.3; P=.015). A simultaneous, directional indoor airflow blown from the "same" bay toward the "adjacent" bay was found; it was inadvertently created by an unopposed air jet from a separate air purifier placed next to the index patient's bed. Computational fluid dynamics modeling revealed that the dispersal pattern of aerosols originated from the index patient coincided with the bed locations of affected patients. Conclusions. Our findings suggest a possible role of aerosol transmission of influenza in an acute ward setting. Source and engineering controls, such as avoiding aerosol generation and improving ventilation design, maywarrant consideration to prevent nosocomial outbreaks. [ABSTRACT FROM AUTHOR]

Simulating turbulent flows in a city of many thousands of buildings using general high-resolution microscopic simulations requires a grid number that is beyond present computer resources. We thus regard a city as porous media and divide the whole hybrid domain into a porous city region and a clear fluid region, which are represented by a macroscopic k– $${\varepsilon}$$ model. Some microscopic information is neglected by the volume-averaging technique in the porous city to reduce the calculation load. A single domain approach is used to account for the interface conditions. We investigated the turbulent airflow through aligned cube arrays (with 7, 14 or 21 rows). The building height H, the street width W, and the building width B are the same (0.15 m), and the fraction of the volume occupied by fluid (i.e. the porosity) is 0.75; the approaching flow is parallel to the main streets. There are both microscopic and macroscopic simulations, with microscopic simulations being well validated by experimental data. We analysed microscopic wind conditions and the ventilation capacity in such cube arrays, and then calculated macroscopic time-averaged properties to provide a comparison for macroscopic simulations. We found that the macroscopic k– $${\varepsilon}$$ turbulence model predicted the macroscopic flow reduction through porous cube clusters relatively well, but under-predicted the macroscopic turbulent kinetic energy (TKE) near the windward edge of the porous region. For a sufficiently long porous cube array, macroscopic flow quantities maintain constant conditions in a fully developed region. [ABSTRACT FROM AUTHOR]

Chinese kangs are widely used today, in nearly 85% of rural homes by 175 million people in Northern China. While Chinese kangs are a potentially energy sustainable solution for home heating, existing systems are characterized by their poor energy efficiency and significant concerns about the impact of indoor air pollution in homes caused by smoke backflow or smoke leakages. Existing kang designs are based on the intuition and historical accumulation of past craftsmanship experiences. As the first attempt, a macroscopic thermal-fluid approach is used to model the airflow and heat transfer process of an elevated kang with a focus on smoke flow. This model considers nonlinear interaction of thermal buoyancy force, wind force and heat transfer from kang plates and chimney walls. Five parameter groups are identified for characterizing the kang systems to guide the kang smoke flow design. Our work has explained the so-called smoke backflow phenomenon that can lead to serious indoor air quality problems in rural homes and based on the results, we have provided some design recommendations for avoiding smoke backflow, and for enhancing energy efficiency by increasing the heat utilization of the kang body. [ABSTRACT FROM AUTHOR]

Following the recent severe acute respiratory syndrome epidemics and worldwide concern about the next pandemic, whether influenza or multiple drug resistant tuberculosis, has underlined the importance of effective interventions into airborne disease transmission in indoor environments in a community. The engineering control measures available include ventilation dilution, use of high-efficiency particulate air filters in a room or in the heating, ventilation, and air-conditioning (HVAC) system, and use of ultraviolet germicidal irradiation devices in ceiling area of a room or in the HVAC system. These methods are known to be effective in controlling or delaying airborne disease transmission in a single enclosure in both healthcare facilities and the community. However, there have been no studies of their relative effectiveness at the community level. This paper presents mathematical modeling of some engineering control strategies with a focus on ventilation and corresponding analysis of their relative effectiveness compared with other public health interventions in disease control in indoor environments at the community level. The results should help us to determine the most effective intervention strategies. We conclude that the engineering intervention methods such as building ventilation can be as effective as public health interventions and the ventilation rates specified in the existing standards such as ASHRAE 62 may be too low for the purpose of preventing or controlling airborne infectious diseases in indoor environments. [ABSTRACT FROM AUTHOR]

Abstract  There is growing evidence in recent years that the pristine fullerene may be endowed with strong pro-oxidant capacity to biological samples. In this investigation we tested the hypothesis that water-soluble fullerene-C60 (nano-C60) may interact with ionizing radiation enhancing its antiproliferative effects. The two tumor cell lines with different radiosensitivity B16 and SMMU-7721 were treated by a combination of pristine fullerene and 60Co ? irradiation. We measured cell survival rates, apoptotic characteristics, reactive oxygen species (ROS) production and alteration of cell diameter with or without ?-irradiation. There was reduced survival with B16 and SMMU-7721 cells exposed to nano-C60, with the inhibitory concentrations reducing the viability by 50% to 65 part per billion (ppb) and 150 ppb respectively. For cells exposed to nano-C60 prior to ?-irradiation, damage to cell membranes and increased numbers of apoptotic cells were detected by morphologic Hoechst-staining analysis and Annexin V/propidium iodide double-staining. In cells exposed to nano-C60, there were increased levels of ROS, as measured by fluorescence detection under laser confocal microscopy. Preincubation with non-toxic pristine C60 before ?-ray caused enlargement of cells with increased diameter. The results show that nano-C60 inhibits the growth of tumor cells at certain concentrations and increases the effects of 60Co ?-irradiation, possibly through the elevated production of cellular ROS and the membrane disruption. Data in this study indicates a possible consideration of using C60 as a candidate of sensitization modifier in tumor radiation biology. [ABSTRACT FROM AUTHOR]

Understanding of bacterial survival in aerosols is crucial for controlling infection transmission via airborne aerosols and/or large droplets routes. The cell viability changes of four bacteria species ( Escherichia coli K12 JM109; Acinetobacter sp. 5A5; Pseudomonas oleovorans X5; and Staphylococcus aureus X8), three Gram-negative and one Gram-positive, in a large evaporating droplet of size 1,800 μm in diameter on teflon-coated slides were measured using the LIVE/DEAD BacLight solution and a microscope. Droplets of three levels of salinity (0, 0.9, and 36% w/ v) were tested. All four species survived well during the droplet evaporation process, but died mostly at the time when droplets were dried out at 40–45 min. The final bacteria survival rate after droplets were completely dried was dependent on bacteria species and the salinity of the suspension solution. Droplet evaporation over the first 35–40 min had no adverse effect on bacterial survival for the droplets tested. The lethal effect of desiccation was found to be the most important death mechanism. [ABSTRACT FROM AUTHOR]

Computational fluid dynamics (CFD) is a widely accepted design and analysis tool for building ventilation. This paper presents a simple method using commercial CFD software to obtain the solution multiplicity characteristics of laminar and turbulent indoor airflows. The method is known as the two-way continuation simulation, which has been developed for identifying multiple solutions in computational fluid dynamics. We consider airflows in a simple two-zone building with four openings, where one of the zones has a constant heat source, modeling the heat or pollutant generation and spread in buildings governed by natural stack forces. Using the new two-way continuation simulation method, we describe the flow variation and physical mechanisms at different heights in the two zones for different Rayleigh numbers. The results show that two steady solutions with the same boundary conditions and building geometry can be obtained step-by-step in the simulation process. Flow multiplicity can also be found as the height ratio of the two zones increases or decreases. As an important physical parameter, the Rayleigh number can also have some significant influences on the flow bifurcation or variation. Compared with conventional CFD simulation, the two-way continuation simulation method can effectively identify the possible existence of multiple solutions of indoor airflows and pollutant spread with different initial conditions. One shortcoming of the two-way method is that it cannot identify unstable solutions. [ABSTRACT FROM AUTHOR]

The nonlinear behavior and solution multiplicity of airflow and natural ventilation in multi-zone buildings are significant for building ventilation and smoke control design. A two-zone building with four openings is considered in this study. Nonlinear dynamic behaviors are analyzed, and we report on the fixed points (steady-state solutions) and their stability and provide a description of the bifurcation of the fixed points and an estimation of the separating curve between two stable fixed points. Different flow modes were identified with the same physical and boundary conditions. A multi-zone airflow and thermal coupled program was also used to evaluate the results. There was good agreement between the numerical and theoretical solutions, except that the unsteady-state solutions could not be predicted by the multi-zone program. These results may have significant implications for multi-zone modeling of natural ventilation and smoke or contaminant spread in buildings, as well as allow us to gain a good understanding of physical flow behavior and solution multiplicity. [ABSTRACT FROM AUTHOR]

Ever since the existence of two stable ventilation solutions in a two-opening building was identified, questions have been asked whether multiple solutions of natural ventilation exist in complex buildings and what are the physical mechanisms that can lead to the existence of multiple solutions in complex buildings. We examined a simple one-zone building with four openings using the simple macroscopic method of thermo-fluid modelling by assuming that the air temperature in the building was uniform. A conventional network modelling computer program was used to simulate the four-opening building ventilated by combined buoyancy and wind forces. The ventilation flow rate in the simple four-opening building was found to be a linear superimposition of that in two corresponding twoopening buildings with opposing and assisting winds respectively. We have shown that when the ventilation flow in the two-opening building with opposing wind is sufficiently strong, two stable solutions and one unstable solution can exist in the corresponding fouropening building. There is a good agreement between the ventilation flow rates predicted by the network modelling method and our simple analytical solutions. The findings suggest the possible existence of multiple solutions in complex building configurations. [ABSTRACT FROM AUTHOR]

One of the intriguing characteristics of the 2003 severe acute respiratory syndrome (SARS) epidemics was the occurrence of super spreading events (SSEs). Here, the authors report the results of identifying the occurrence of SSEs in the Hong Kong and Singapore epidemics using mathematical and statistical analysis. Their predicted occurrence of SSEs agreed well with the reported occurrence of all seven super spreaders in the two cities. Additional unidentified SSEs were also found to exist. It was found that 71.1% and 74.8% of the infections were attributable to SSEs in Hong Kong and Singapore, respectively. There also seemed to be “synchronized” occurrences of infection peaks in both the community and the hospitals in Hong Kong. The results strongly suggested that the infection did not depend on the total number of symptomatic cases, with only a very small proportion of symptomatic individuals being shown to be infectious (i.e., able to infect other individuals). The authors found that the daily infection rate did not correlate with the daily total number of symptomatic cases but with the daily number of symptomatic cases who were not admitted to a hospital within 4 days of the onset of symptoms. [ABSTRACT FROM AUTHOR]

We studied transmission patterns of severe acute respiratory syndrome (SARS) among medical students exposed exclusively to the first SARS patient in the Prince of Wales Hospital in Hong Kong, before his illness was recognized. We conducted a retrospective cohort study of 66 medical students who visited the index patient's ward, including 16 students with SARS and 50 healthy students. The risk of contracting SARS was sevenfold greater among students who definitely visited the index case's cubicle than in those who did not (10/27 [41%] versus 1/20 [5%], relative risk 7.4; 95% confidence interval 1.0 to 53.3). Illness rates increased directly with proximity of exposure to the index case. However, four of eight students who were in the same cubicle, but were not within 1 m of the index case-patient, contracted SARS. Proximity to the index case-patient was associated with transmission, which is consistent with droplet spread. Transmission through fomites or small aerosols cannot be ruled out. [ABSTRACT FROM AUTHOR]

A 3-D finite-element scheme for direct current resistivity modelling is presented. The singularity is removed by formulating the problem in terms of the secondary potential, which improves the accuracy considerably. The resulting system of linear equations is solved using the conjugate gradient method. The incomplete Cholesky preconditioner with a scaled matrix has been proved to be faster than the symmetric successive overrelaxation preconditioner. A compact storage scheme fully utilizes the sparsity and symmetry of the system matrix. The finite-element (FE) and a previously developed finite-difference (FD) scheme are compared in detail. Generally, both schemes show good agreement, the relative error in apparent resistivity for a vertical dike model presented in this paper is less than 0.5 per cent overall. The FD scheme produces larger errors near the conductivity contrast, whereas the FE scheme requires approximately 3.4 times as much storage as the FD scheme and is less robust with respect to coarse grids. As an improvement to the forward modelling scheme, a modified singularity removal technique is presented. A horizontally layered earth or a vertical contact is regarded as the normal structure, the solution of which is the primary potential. The effect of this technique is demonstrated by two examples: a cube in two-layered earth and a cube near a vertical contact. [ABSTRACT FROM AUTHOR]

Presents a finite-element scheme for electromagnetic induction in two-dimensional (2D) anisotropic structures. Comparison between the 2D finite-difference solution and the 2D finite element algorithm; Models used to demonstrate the effect of anisotropy upon the magnetotelluric responses.

The article discusses various reports published within the issue of "Indoor Air."

In this paper water-soluble fullerene derivative C60(OH)xOy was radioiodinated with the iodogen method. The labeling yield was determined by radio-TLC. The effects of pH value, reaction time, temperature and amount of the iodogen on the labeling yield were studied. The labeled product was purified by Sephadex G-25 column chromatography and then the stability of 125I-C60(OH)xOy was examined . The results showed that the radiochemical purity of 125I-C60(OH)xOy solution with benzylalcohol remained 82.7% after 43 hours. [ABSTRACT FROM AUTHOR]