牙科治疗中空气传播的传染性物质及其预防

在许多牙科手术中会产生气溶胶体和飞溅物。许多研究证明这些气溶胶体对疾病的传播是一个潜在的途径。本文就牙科治疗过程中潜在的空气传播污染源及其减少方法作一综述。

Establishment of a Collection and Detection Technology of Mycoplasma hyopneumoniae in Aerosol

ObjectiveThis study was to establish a simple method for collecting and detecting Mycoplasma hyopneumoniae （Mhp） in aerosol. MethodBased on the mechanisms of liquid impinger and filtration sampler, a double concentration aerosol sampler was designed for collecting Mhp aerosol. Firstly, the collection was performed in a closed environment full of artificial aerosol of Mhp. Secondly, collection efficiency was detected by real-time PCR. Thereafter, the clinical feasibility of the designed equipment was tested by collecting aerosol samples in different pig herds. In one assay, the samples were collected at different times from one pig house challenged with Mhp. In another assay, the samples was collected from the delivery room, nursery and fattenning house of a MPS outbreak farm as well as a Mhp infection positive pig farm without obvious clinical symptoms. All the aerosol samples were then detected by real-time PCR or nested PCR. ResultThe collection efficiency of the designed bioaerosol sampler was （37.04±6.43） %, Mhp could be detected 7 d after intratracheal challenge with pneumonic lung homogenate suspension. Aerosol samples of 11 pig houses from the two Mhp positive pig farms with or without clinical symptoms all showed a positive result of PCR, the positivity rate was 100%. ConclusionA high sensitive collecting and detecting technology of aerosol was successfully established, which can be applied to clinical detection of Mhp in aerosol.

汽车行业中的过滤技术(六)

气溶胶体中油滴的平均直径(这对所有气溶胶及其中所含微细及碳黑颗粒都具代表性)仅为约0.9 μm(图29).对这种微粒仅有少数有效的分离方法(图30).按照它们的基本物理性质,可将它们分成弥散型或凝聚型分离器、惯性式或撞击式分离器以及静电分离器等.除此之外汽车行业还要求压差应尽量小(曲轴箱中需要部分真空度)、结构紧凑.为了降低车辆用户的使用成本,分离器最好为无需维护的长寿部件.

Impact of Direct Radiative Forcing of Anthropogenic Aerosols on Diurnal Temperature Range in January in Eastern China

This study investigates the changes in January diurnal temperature range(DTR) in China during 1961-2000.The observed DTR changes during 1981-2000 relative to 1961-80 are first analyzed based on the daily temperature data at 546 weather stations.These observed DTR changes are classified into six cases depending on the changes in daily maximum and minimum temperatures,and then the occurrence frequency and magnitude of DTR change in each case are presented.Three transient simulations are then performed to understand the impact of greenhouse gases(GHGs) and aerosol direct forcing on DTR change:one without anthropogenic radiative forcing,one with anthropogenic GHGs,and another one with the combined forcing of GHGs and five species of anthropogenic aerosols.The predicted daily DTR changes during the years 1981-2000 are also classified into six cases and are compared with the observations.Results show that the previously proposed reason for DTR reduction,a stronger nocturnal warming than a daytime warming,explains only 19.8%of the observed DTR reduction days.DTR reductions are found to generally occur in northeastern China,coinciding with significant regional warming.The simulation with GHG forcing alone reproduces this type of DTR reduction with an occurrence frequency of 32.9%,which is larger than the observed value.Aerosol direct forcing reduces DTR mainly by daytime cooling.Consideration of aerosol cooling improves the simulation of occurrence frequencies of different types of DTR changes as compared to the simulation with GHGs alone,but it cannot improve the prediction of the magnitude of DTR changes.

Response of Mode Water and Subtropical Countercurrent to Greenhouse Gas and Aerosol Forcing in the North Pacific

The response of the North Pacific Subtropical Mode Water and Subtropical Countercurrent (STCC) to changes in greenhouse gas (GHG) and aerosol is investigated based on the 20th-century historical and single-forcing simulations with the Geo-physical Fluid Dynamics Laboratory Climate Model version 3 (GFDL CM3). The aerosol effect causes sea surface temperature (SST) to decrease in the mid-latitude North Pacific, especially in the Kuroshio Extension region, during the past five decades (1950-2005), and this cooling effect exceeds the warming effect by the GHG increase. The STCC response to the GHG and aerosol forcing are opposite. In the GHG (aerosol) forcing run, the STCC decelerates (accelerates) due to the decreased (increased) mode waters in the North Pacific, resulting from a weaker (stronger) front in the mixed layer depth and decreased (increased) subduction in the mode water formation region. The aerosol effect on the SST, mode waters and STCC more than offsets the GHG effect. The response of SST in a zonal band around 40?N and the STCC to the combined forcing in the historical simulation is similar to the response to the aerosol forcing.

Intraseasonal variation and future projection of atmospheric diffusion conditions conducive to extreme haze formation over eastern China

Future projection of diffusion conditions associated with extreme haze events over eastern China is of great importance to government emission regulations and public human health.Here,the diffusion conditions and their changes under future warming scenarios are examined.The relative strength of haze events in the Northern China Plain region increase from 150%during 2006–15 to 190%during 2090–99 under RCP8.5 scenarios,induced by a stronger and longer-lasting anticyclone anomaly in eastern China.The strengthened anticyclone anomaly is mainly induced by increased northern wave train convergence emanating from the Barents–Kara Sea,and the longer duration of the anticyclone anomaly is mainly induced by stronger local feedback that can extract more energy from the basic state to maintain the anticyclone anomaly in eastern China.Aerosol reduction is found to play a dominant role in strengthening the upstream wave train near the Barents–Kara Sea and the downstream anticyclone in eastern China,while the effects from increased greenhouse gases are small.The results of this study indicate that future aerosol emissions reduction can induce deteriorating diffusion conditions,suggesting more stringent regulations on aerosol emissions in China are needed to meet air quality standards.

An algorithm for retrieval of aerosol optical properties over the turbid waters from GOCI

Aimed at high turbid coastal waters, an improved algorithm for retrieval ofaerosol optical properties from Geostationary Ocean Color Imager （GOCI） is proposed.The algorithm adopts support vector machine （SVM） to separate the interfering signalof phytoplankton pigments, suspended matter and chromophoric dissolved organicmatter （CDOM）. Radioactive Transfer Model （RTM） Rstar5b is utilized to simulate thetransmitting process. The algorithm can retrieve aerosol optical depth （AOD） andaerosol types simultaneously. In the study, the aerosol optical depth was retrieved overthe turbid waters in the summer of 2014 and 2015. The results of inversion werecompared with the corresponding AERONET data and GOCI service product toestimate the accuracy of the advanced method. The study shows that this algorithmhas better performance compared with GOCI service algorithm for turbid water in theYellow Sea.

Preparation and Application of the Sol–Gel Combustion Synthesis-Made CaO/CaZrO_3 Sorbent for Cyclic CO_2 Capture Through the Severe Calcination Condition

Calcium looping method has been considered as one of the efficient options to capture C02 in the combustion Ilue gas. CaO-based sorbent is the basis for application of calcium looping and should be subjected to the severe calcination condition so as to obtain the concentrated C02 stream. In this research, CaO/CaZrO3 sorbents were synthesized using the sol-gel combustion synthesis （SGCS） method with urea as fuel. The cyclic reaction performance of the synthesized sorbents was evaluated on a lab-scaled reactor system through calcination at 950 ℃ in a pure C02 atmosphere and carbonation at 650 ℃ in the 15% （by volume） C02. The mass ratio of CaO to CaZr03 as 8：2 （designated as CasZr2） was screened as the best option among all the synthesized CaO sorbents for its high CO2 capture capacity and carbonation conversion at the initial cycle. And then a gradual decay in the C02 capture capacity was observed at the following 10 successive cycles, but hereafter stabilized throughout the later cycles. Furthermore, structural evolution of the carbonated CasZr2 over the looping cycles was investigated. With increasing looping cycles, the pore peak and mean grain size of the carbonated CasZr2 sorbent shifted to the bigger direction but both the surface area （SA） ratio and surface fractal dimension Ds decreased. Finally, morphological transformation of the carbonated CasZr2 was observed. Agglomeration and edge rounding of the newly formed CaC03 grains were found as aggravated at the cyclic carbonation stage. As a result, carbonation of CasZr2 with C02 was observed only confined to the external active CaO by the fast formation of the CaC03 shell outside, which occluded the further carbonation of the unreacted CaO inside. Therefore, enough attention should be paid to the carbonation stage and more effective activation measures should be explored to ensure the unreacted active CaO fully carbonatPd river the extended Ioonin cycles.

Stratospheric Aerosol Extinction Profile Retrieval from SCIAMACHY Limb Measurements

Stratospheric aerosol extinction profiles are retrieved from Scanning Imaging Absorption Spectrometer for Atmospheric Cartography(SCIAMACHY) limb scatter measurements.In the process of retrieval,the SCIATRAN radiative transfer model is used to simulate the limb scattering radiation received by the SCIAMACHY instrument,and an optimal estimation algorithm is used to calculate the aerosol extinction profiles.Sensitivity analyses are performed to investigate the impact of the surface albedo on the accuracy of the retrieved aerosol extinction profiles in the northern midlatitudes.It is found that the errors resulting from the bias of the assumed surface albedo in the retrieval are generally below 6%.The retrieved SCIAMACHY aerosol extinction profiles are compared with corresponding Stratospheric Aerosol and Gas Experiment(SAGE) II measurements,and the results indicate that for the zonal mean profiles,the SCIAMACHY retrievals show good agreement with SAGE II measurements,with the absolute differences being less than 2.3×10-5 km-1 from 14–25 km,and less than 5.9×10-6 km-1 from 25–35 km;and the relative differences being within 20% over the latitude range of 14–35 km.

Global Warming Some Perspectives

Here the authors critically review the IPCC＇s claim that global warming is ＂very likely＂ caused by human activity： such a description underestimates the likelihood of the warming being due to this mechanism. Next examined are known alternative ＂natural＂ mechanisms which could give rise to the warming if, despite many claims, the man-made explanation was false because of compensation effects （greenhouse gases versus aerosol effects）. Also, a number of difficulties, as yet unresolved, in the human-induced warming explanation are considered.

Size Distribution of Particulate Matter of Metals in Urban Aerosols, Comarca Lagunera, Mexico

This paper has demonstrated that there is great variation in the size range and chemical composition of metalliferous PM （particulate matter） present within Comarca Lagunera, M6xico due to the physiography of the terrain together the intense vehicular traffic, unpaved roads, cement and lime plants, marble quarries, brick plants, and the largest smelter of non-ferrous material in Latin America. Cascade impactor PM samples from six size ranges： 〈 0.49 μm, 0.49-0.9 μm, 0.9-1.5μm, 1.5-3.0 p.m, 3.0-7.2 μm and 7.2-10 μm were collected from inside two stacks within G6mez Palacios and Torreon cities. ICP-AES （inductively coupled plasma-atomic emission spectrometry） analysis on collected Whatman fiberglass filters demonstrates that the PM are matrices mostly constituted of carbonates and silicates with abundant fine metalliferous particles. The metals with the most concentrations averaged over all size ranges were Cu, Fe, Mn, Ni, Pb and Ti. The size distributions of metals detected in this work have been plotted as normalized histogram concentration of each size fraction, the total concentration, and the aerodynamic particle diameter, which is a useful method for comparing the contributions of coarse and fine particles to pollutant concentrations.

Numerical simulation study of temperature change over East China in the past millennium

Despite many studies on reconstructing the climate changes over the last millennium in China,the cause of the China's climate change remains unclear.We used the UVic Earth System Climate Model(UVic Model),an Earth system model of intermediate complexity,to investigate the contributions of climate forcings(e.g.solar insolation variability,anomalous volcanic aerosols,greenhouse gas,solar orbital change,land cover changes,and anthropogenic sulfate aerosols) to surface air temperature over East China in the past millennium.The simulation of the UVic Model could reproduce the three main characteristic periods(e.g.the Medieval Warm Period(MWP),the Little Ice Age(LIA),and the 20th Century Warming Period(20CWP)) of the northern hemisphere and East China,which were consistent with the corresponding reconstructed air temperatures at century scales.The simulation result reflected that the air temperature anomalies of East China were larger than those of the global air temperature during the MWP and the first half of 20CWP and were lower than those during the LIA.The surface air temperature of East China over the past millennium has been divided into three periods in the MWP,four in the LIA,and one in the 20CWP.The MWP of East China was caused primarily by solar insolation and secondarily by volcanic aerosols.The variation of the LIA was dominated by the individual sizes of the contribution of solar insolation variability,greenhouse gas,and volcano aerosols.Greenhouse gas and volcano aerosols were the main forcings of the third and fourth periods of the LIA,respectively.We examined the nonlinear responses among the natural and anthropogenic forcings in terms of surface air temperature over East China.The nonlinear responses between the solar orbit change and anomalous volcano aerosols and those between the greenhouse gases and land cover change(or anthropogenic sulfate aerosols) all contributed approximately 0.2℃ by the end of 20th century.However,the output of the energy-moisture balance atmospheric model from UVic showed no obvious nonlinear responses between anthropogenic and natural forcings.The nonlinear responses among all the climate forcings(both anthropogenic and natural forcings) contributed to a temperature increase of approximately 0.27℃ at the end of the 20th century,accounting for approximately half of the warming during this period;the remainder was due to the climate forcings themselves.