This paper offers a brief review on the detection and characterization of biological and other organic-carbon (OC) aerosol particles in atmosphere using laser-induced-fluorescence (LIF) signatures. ...It focuses on single individual particles or aggregates in the micron and super-micron size range when they are successively drawn through the interrogation volume of a point detection system. Related technologies for these systems that have been developed in last two decades are also discussed. These results should provide a complementary view for studying atmospheric aerosol particles, particularly bioaerosol and OC aerosol particles from other analytical technologies.
•Review on the detection and characterization of atmospheric aerosol particles.•Classification of organic-carbon (OC) including biological aerosol particles by fluorescence signatures.•Technology in developing single particle detection and characterization systems based on fluorescence.
Display omitted
•Optically-trapped, chemically-purposed, micron-sized, single-particle reactor (SPR) in air.•Heterogeneous reaction of solid-state Hg(II) halides on the surface SPR.•A new platform ...for the study of surface and heterogeneous chemistry of aerosol particles in air.
We created a micron-sized, single-particle reactor (SPR) freely levitated in air using optical trapping of a single particulate-bound mercury particle formed by mixing HgCl2, HgBr2, or HgBrCl (HgX2, X = Cl, Br) with single-walled carbon nanotubes. Position- and time-resolved, single-particle Raman spectra show clear evidence of reactions of solid-state HgX2 in the presence of excessive O3 under the illumination of 532-nm light. We propose a reaction mechanism: Hg(II)X2 (solid) + O → Hg(I)X + XO, XO + O → O2 + X on the surface of the SPR. This exploratory study demonstrates that the SPR is a new tool for the study the surface and heterogeneous chemistry of mercury at atmospherically relevant surfaces, e.g., aerosols.
•A novel swine enteric alphacoronavirus (tentatively named SeACoV) was isolated from diarrheic piglets in southern China.•SeACoV is likely antigenetically distinct from PEDV, TGEV and PDCoV.•Genomic ...and phylogenetic analysis showed that SeACoV might have originated from the bat coronavirus HKU2.•The extreme amino-terminal domain of SeACoV spike glycoprotein had an extremely high variability compared to that of HKU2.•Experimental infection study showed that SeACoV is infectious and pathogenic in newborn piglets.
Outbreaks of diarrhea in newborn piglets without detection of transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV) and porcine deltacoronavirus (PDCoV), have been recorded in a pig farm in southern China since February 2017. Isolation and propagation of the pathogen in cell culture resulted in discovery of a novel swine enteric alphacoronavirus (tentatively named SeACoV) related to the bat coronavirus HKU2 identified in the same region a decade ago. Specific fluorescence signal was detected in Vero cells infected with SeACoV by using a positive sow serum collected in the same farm, but not by using TGEV-, PEDV- or PDCoV-specific antibody. Electron microscopy observation demonstrated that the virus particle with surface projections was 100–120nm in diameter. Complete genomic sequencing and analyses of SeACoV indicated that the extreme amino-terminal domain of the SeACoV spike (S) glycoprotein structurally similar to the domain 0 of the alphacoronavirus NL63, whereas the rest part of S structurally resembles domains B to D of the betacoronavirus. The SeACoV-S domain 0 associated with enteric tropism had an extremely high variability, harboring 75-amino-acid (aa) substitutions and a 2-aa insertion, compared to that of HKU2, which is likely responsible for the extended host range or cross-species transmission. The isolated virus was infectious in pigs when inoculated orally into 3-day-old newborn piglets, leading to clinical signs of diarrhea and fecal virus shedding. These results confirmed that it is a novel swine enteric coronavirus representing the fifth porcine coronavirus.
Characterization, identification, and detection of aerosol particles in their native atmospheric states remain a challenge. Recently, optical trapping-Raman spectroscopy (OT-RS) has been developed ...and demonstrated for characterization of single, airborne particles. Such particles in different chemical groups have been characterized by OT-RS in recent years and many more are being studied. In this work, we collected single-particle Raman spectra measured using the OT-RS technique and began construction of a library of OT-RS fingerprints that may be used as a reference for potential detection and identification of aerosol particles in the atmosphere. We collected OT-RS fingerprints of aerosol particles from eight different categories including carbons, bioaerosols (pollens, fungi, vitamins, spores), dusts, biological warfare agent surrogates, etc. Among the eight categories, spectral fingerprints of six groups of aerosol particles have been published previously and two other groups are new. We also discussed challenges, limitations, and advantages of using single-particle optical trapping-Raman spectroscopy for aerosol-particle characterization, identification, and detection.
•Optical trapping technique for diverse single particles in air is reviewed.•Technical details of optical trapping for single particles in air are summarized.•Recent applications of single optically ...trapped airborne particles are discussed.
Trapping a single aerosol particle allows detailed investigation of its fundamental properties over extended time periods without external interferences. Optical trapping has developed into a powerful tool to perform such single-particle studies. However, trapping and manipulating a single particle in air, especially an irregularly shaped, absorbing particle, is much more challenging than that of a particle in a liquid solution. Even though the underlying mechanisms are not fully understood, recent experimental developments advanced the technique for trapping single particles in air, making it possible to manipulate and characterize a wide range of single particles. In this paper, we review recently demonstrated optical configurations for trapping and manipulating single airborne particles. Based on different trapping principles, we tentatively categorize them into radiation-pressure traps, photophoretic traps, and universal optical traps (UOTs). Radiation-pressure traps are based on the radiation pressure force resulting from photon momentum transfer; they include the early optical levitation configurations and the well-known optical tweezers. Photophoretic traps are based on the complex photophoretic forces that occur in absorbing particles; they are classified by the optical arrangements and include single-beam, dual-beam, and confocal-beam traps. UOTs can trap a variety of different types of particles, including transparent or absorbing, spherical or irregularly shaped, and liquid or solid particles. In order to evaluate each optical trapping scheme, four key aspects, i.e., simplicity, robustness, flexibility, and efficiency, of an optical trapping configuration are discussed. In addition to the stable optical trapping, optical manipulations from one dimension to three dimensions allow studying various single particles with great flexibility. With the single particle stably trapped and flexibly manipulated in air, other analytical techniques can be used to characterize these particles. Recent updates on optical methods for characterizing and monitoring single particles in air are discussed, such as light scattering, Raman spectroscopy, and cavity ringdown spectroscopy (CRDS).
Optical trapping of airborne particles is emerging as an essential tool in applications ranging from online characterization of living cells and aerosols to particle transport and delivery. However, ...existing optical trapping techniques using a single laser beam can trap only transparent particles (via the radiative pressure force) or absorbing particles (via the photophoretic force), but not particles of either type-limiting the utility of trapping-enabled aerosol characterization techniques. Here, we present the first optical trapping technique capable of trapping both transparent and absorbing particles with arbitrary morphology using a single shaped laser beam. Such a general-purpose optical trapping mechanism could enable new applications such as trapping-enabled aerosol characterization with high specificity.
•The aspect ratio of manifold microchannel was optimized at fixed mass flux.•The manifold microchannel has the optimal aspect ratio at fixed mass flux.•The optimal aspect ratio was analyzed at ...various working fluids and solid materials.•A criterion formula of optimal aspect ratio was given.
In order to provide a basis for the design and optimization of the aspect ratio of the manifold microchannel, the effect of channel aspect ratio on the heat transfer performance of manifold microchannel heat sinks at fixed mass flow rate is numerically investigated in this present work. The results show that the heat transfer performance of the manifold microchannel heat sink reaches the peaks at one specific channel aspect ratio, which is defined as optimal aspect ratio αo. It is found that the optimal aspect ratio is different at various working fluids and solid materials. The optimal aspect rises with the increase of thermal conductivity of the channel wall and dynamic viscosity of working fluid, or the decrease of specific heat capacity of working fluid and thermal conductivity of working fluid. Further numerical simulations are conducted to quantitatively analyze the influence of each thermophysical parameter on αo. Finally, a criterion formula is given to describe the optimal aspect ratio as a function of Re number, Pr number, and the ratio of thermal conductivity between working fluid and channel wall.
•A pin–fin staggered manifold microchannel (PFSMMC) heat sink was designed.•The heat transfer characteristics of PFSMMC in single-phase flow were studied.•The staggered divider length–width ratio of ...PFSMMC was optimized.•The heat transfer characteristics of PFSMMC with different non-uniform heat sources were studied.
Manifold microchannel (MMC) heat sink is an efficient thermal management solution for high heat flux electronic devices. A pin–fin staggered manifold microchannel (PFSMMC) heat sink is proposed to enhance the heat dissipation performance of the MMC heat sink in this paper. The heat transfer performance of the PFSMMC heat sink, the rectangular manifold microchannel (RMMC) and the pin–fin manifold microchannel (PFMMC) are compared by single-phase flow numerical simulation. The results show that the PFSMMC heat sink has better heat transfer capability and more uniform heating surface temperature. The effect of staggered divider length–width ratio on the heat transfer characteristics of PFSMMC heat sink is analyzed. The maximum heating surface temperature of PFSMMC heat sink has a valley with the increase of length–width ratio. The length–width ratio corresponding to the valley value of the maximum heating surface temperature is about 0.32. In addition, the heat characteristics of PFSMMC with different non-uniform heat sources are studied. The results show that the heating surface temperature uniformity deteriorates with the increase of length–width ratio, but the maximum heating surface temperature is lower at the length–width ratio of 0.32.
PDF
