Wavelength selection of bidirectional laser transmission based on Monte Carlo method

The laser detection technology in uncertain and dynamic environments is of utmost importance in many fields. A model of transient radiative transfer of bidirectional path laser based on Monte Carlo method is developed to investigate the optimum wavelength of active detector at complex atmospheric conditions. The radiative parameters of atmosphere are calculated by HITRAN database and Mie theory at several typical atmospheric conditions including the standard atmosphere, urban aerosol, and radiation fog. Transmission characteristics for five spectral bands at the above atmospheric conditions are calculated by this model. The optimal transmission ability occurred in bands 0.2–0.5, 1.4–1.6, and 0.75–1.25 μm on the condition of standard atmosphere, urban aerosol, and radiation fog, respectively. All results provide effective reference and basic support for choosing the optimal spectral band for active detection.     

First-principles prediction and partial characterization of the vibrational states of water up to dissociation

A new, accurate, global, mass-independent, first-principles potential energy surface (PES) is presented for the ground electronic state of the water molecule. The PES is based on 2200 energy points computed at the all-electron aug-cc-pCV6Z IC-MRCI(8,2) level of electronic structure theory and includes the relativistic one-electron mass-velocity and Darwin corrections. For H₂¹⁶O, the PES has a dissociation energy of D₀ = 41 109 cm⁻¹ and supports 1150 vibrational energy levels up to 41 083 cm⁻¹. The deviation between the computed and the experimentally measured energy levels is below 15 cm⁻¹ for all the states with energies less than 39 000 cm⁻¹. Characterization of approximate vibrational quantum numbers is performed using several techniques: energy decomposition, wave function plots, normal mode distribution, expectation values of the squares of internal coordinates, and perturbing the bending part of the PES. Vibrational normal mode labels, though often not physically meaningful, have been assigned to all the states below 26 500 cm⁻¹ and to many more above it, including some highly excited stretching states all the way to dissociation. Issues to do with calculating vibrational band intensities for the higher-lying states are discussed.     

First measurements of the HCFC-142b trend from atmospheric chemistry experiment (ACE) solar occultation spectra

The first measurement of the HCFC-142b (CH₃CClF₂) trend near the tropopause has been derived from volume mixing ratio (VMR) measurements at northern and southern hemisphere mid-latitudes for the 2004–2008 time period from spaceborne solar occultation observations recorded at 0.02 cm⁻¹ resolution with the ACE (atmospheric chemistry experiment) Fourier transform spectrometer. The HCFC-142b molecule is currently the third most abundant HCFC (hydrochlorofluorocarbon) in the atmosphere and ACE measurements over this time span show a continuous rise in its volume mixing ratio. Monthly average measurements at northern and southern hemisphere mid-latitudes have similar increase rates that are consistent with surface trend measurements for a similar time span. A mean northern hemisphere profile for the time span shows a near constant VMR at 8–20 km altitude range, consistent on average for the same time span with in situ results. The nearly constant vertical VMR profile also agrees with model predictions of a long lifetime in the lower atmosphere.     

大气中固体燃烧等离子体与微波相互作用的实验研究

 设计制造了含特定组分的化学药剂，利用热力学方法对其在大气中燃烧所产生的等离子体的电子密度进行了理论计算，对该等离子体对2~15 GHz波段微波的透射衰减和反射进行了测试。测试结果表明，该等离子体对该波段微波具有宽波段强吸收和弱反射性能，波段内的平均吸收大于25 dB，反射信号几乎淹没在背景噪声中。并从理论上分析了带电子与中性粒子的造成这一现象的主要原因是碰撞吸收。     

Evolution of spectroscopic information over the last decade and its effect on line-by-line calculations for validation of radiation codes for climate models

Five HITRAN's editions (since 1992) and three radically new H₂O spectral databases have been tested for their usefulness in line-by-line benchmark calculations for radiation code validations. The longwave calculations for the mid-latitude summer (MLS) atmosphere with the different HITRAN's editions revealed a good convergence (maximal discrepancies since decreased to in our flux calculations with 1992-2002 and 1996-2002 HITRAN's editions, respectively). The shortwave calculations with different HITRAN's editions revealed a good agreement: discrepancies in downward fluxes absorbed by the MLS atmosphere are less than , i.e. 0.5% for the all HITRAN's editions since 1992. It has been determined that it is unreasonable to replace HITRAN by any new H₂O spectral database in benchmark calculations, although they contain essentially more spectral lines than HITRAN (up to ∼10 times). Moreover, it has been found that no new database could be useful for explaining the “anomalous absorption” problem. Two latest water vapor continuum models have been tested as well. It has been found out that these models are the main source of uncertainties in the present and previous calculations: discrepancies for the MLS atmosphere reached ∼3 and in the longwave and shortwave flux calculations, respectively.     

Simultaneous determination of <Emphasis Type="SmallCaps">L</Emphasis>-arginine and its mono- and dimethylated metabolites in human plasma by high-performance liquid chromatography–mass spectrometry

A simple, fast, sensitive, and reproducible isocratic liquid chromatography–mass spectrometry (LC-MS) method coupled with an atmospheric pressure chemical ionization (APCI) interface for simultaneous separation and determination of L-arginine (ARG) and its methylated metabolites, N-monomethyl-L-arginine (MMA), N^G,N^G-dimethylarginine (asymmetric dimethyl arginine, ADMA), and N^G,N^G-dimethylarginine (symmetric dimethyl arginine, SDMA), in human plasma is presented. Sample pretreatment is not required other than deproteinization with 5-sulfosalicylic acid (5-SSA). Satisfactory chromatographic separation was achieved on a 2.0×150-mm Shimadzu VP-ODS column by using a mobile phase consisting of water/acetonitrile (90/10, v/v) containing 0.5% trifluoroacetic acid (TFA). Positive selective ion monitoring (SIM) mode was chosen for quantification of each analyte. The positively protonated molecular ions [M+H]⁺ of ARG, MMA, ADMA, and SDMA were monitored at m/z 175, 189, 203, and 203, respectively. L-Homoarginine was used as the internal standard (IS) for the assay. The limits of quantification (LOQs) were found to be 1.0 mol L^–1 for ARG, and 0.2 mol L^–1 for MMA, ADMA, and SDMA. The inter-assay precision and accuracy were in the range of 1.8–4.9% and –3.0–5.0%, respectively. The intra-assay precision and accuracy were in the order of 1.7–4.6 and –2.6–4.0%, respectively. The recoveries were between 90.0 and 106.6%. The levels of ARG, MMA, ADMA, and SDMA in human plasma were also determined using the developed method.     

Evaluation and applications of a gaseous mercuric chloride source

In this study, a diffusion-type device for generating gaseous mercuric chloride (HgCl₂) was systematically evaluated and applied to validate the annular denuder method for sampling gaseous HgCl₂ species in a synthetic gas stream. The results show that it takes at least 48 h for the system to reach a steady-state condition after the diffusion cell reaches the temperature set-point and the carrier gas is activated. The primary Hg species from the source was proven to be HgCl₂. In the temperature range from –5.00 to 11.80 °C, the Hg emission rates from the source vary from 1.8 to 14.2 pg min^–1. It is shown that, under the experimental conditions examined, KCl-coated annular quartz denuders designed for ambient reactive gaseous mercury (RGM) collection could quantitatively collect HgCl₂. It is also demonstrated that the impactors used to remove coarse airborne particulate matter could lead to a loss of up to one third of the HgCl₂ in the gas stream.     

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用Matlab软件对大气压均匀辉光放电等离子体(OAUGDP)激励器系统的电特性进行了仿真。在仿真模型中,等离子体放电被建模成一个电压控制的电流源:当加在气隙上的电压超过等离子体产生电压时,该受控电流源接通;电流源的输出电流和所加电压之间遵循幂律。建立了一个OAUGDP激励器系统中等离子体放电的电路模型。仿真结果与实际激励器系统的实验数据很吻合。仿真结果表明,在不同的运行条件下,放电电流与电压之间遵循不同的指数幂律,仿真放电电流波形也不同。     

Adaptive modeling, adaptive data assimilation and adaptive sampling

For efficient progress, model properties and measurement needs can adapt to oceanic events and interactions as they occur. The combination of models and data via data assimilation can also be adaptive. These adaptive concepts are discussed and exemplified within the context of comprehensive real-time ocean observing and prediction systems. Novel adaptive modeling approaches based on simplified maximum likelihood principles are developed and applied to physical and physical–biogeochemical dynamics. In the regional examples shown, they allow the joint calibration of parameter values and model structures. Adaptable components of the Error Subspace Statistical Estimation (ESSE) system are reviewed and illustrated. Results indicate that error estimates, ensemble sizes, error subspace ranks, covariance tapering parameters and stochastic error models can be calibrated by such quantitative adaptation. New adaptive sampling approaches and schemes are outlined. Illustrations suggest that these adaptive schemes can be used in real time with the potential for most efficient sampling.     

The elliptical dimension of space-time atmospheric stratification of passive admixtures using lidar data

State-of-the-art airborne lidar data of passive scalars have shown that the spatial stratification of the atmosphere is scaling: the vertical extent (Δz) of structures is typically ≈Δx^H_z where Δx is the horizontal extent and H_z is a stratification exponent. Assuming horizontal isotropy, the volumes of the structures therefore vary as ΔxΔxΔx^H_z=Δx^D_s where the “elliptical dimension” D_s characterizes the rate at which the volumes of typical non-intermittent structures vary with scale. Work on vertical cross-sections has shown that 2+H_z=2.55±0.02 (close to the theoretical prediction 23/9).In this paper we extend these (x, z) analyses to (z, t). In the absence of overall advection, the lifetime Δt of a structure of size Δx varies as Δx^H_t with H_t=2/3 so that the overall space-time dimension is D_st=29/9=3.22…. However, horizontal and vertical advection lead to new exponents: we argue that the temporal stratification exponent H_t≈1 or ≈0.7 depending on the relative importance of horizontal versus vertical advection velocities. We empirically test these space-time predictions using vertical-time (z, t) cross-sections using passive scalar surrogates (aerosol backscatter ratios from lidar) at ∼3 m resolution in the vertical, 0.5-30 s in time and spanning 3-4 orders of magnitude in scale as well as new analyses of vertical (x, z) cross-sections (spanning over 3 orders of magnitude in both x, z directions). In order to test the theory for density fluctuations at arbitrary displacements in (Δz, Δt) and (Δx, Δz) spaces, we developed and applied a new Anisotropic Scaling Analysis Technique (ASAT) based on nonlinear coordinate transformations. Applying this and other analyses to data spanning more than 3 orders of magnitude of space-time scales we determined the anisotropic scaling of space-time finding the empirical value D_st=3.13±0.16. The analyses also show that both cirrus clouds and aerosols had very similar space-time scaling properties. We point out that this model is compatible with (nonlinear) “turbulence” waves, hence potentially explaining the observed atmospheric structures.