23,367 research outputs found
Vertical variation of optical properties of mixed Asian dust/pollution plumes according to pathway of air mass transport over East Asia
© Author(s) 2015. This is an Open Access article made available under the terms of the Creative Commons Attribution License 3.0 https://creativecommons.org/licenses/by/3.0/We use five years (2009-2013) of multiwavelength Raman lidar measurements at Gwangju, South Korea (35.10° N, 126.53° E) for the identification of changes of optical properties of East Asian dust depending on its transport path over China. Profiles of backscatter and extinction coefficients, lidar ratios, and backscatter-related Ångström exponents (wavelength pair 355/532 nm) were measured at Gwangju. Linear particle depolarization ratios were used to identify East Asian dust layers. We used backward trajectory modeling to identify the pathway and the vertical position of dust-laden air masses over China during long-range transport. Most cases of Asian dust events can be described by the emission of dust in desert areas and subsequent transport over highly polluted regions of China. The Asian dust plumes could be categorized into two classes according to the height above ground at which these plumes were transported: (case I) the dust layers passed over China at high altitude levels (> 3 km) until arrival over Gwangju, and (case II) the Asian dust layers were transported near the surface and within the lower troposphere (< 3 km) over industrialized areas before they arrived over Gwangju. We find that the optical characteristics of these mixed Asian dust layers over Gwangju differ depending on their vertical position above ground over China and the change of height above ground during transport. The mean linear particle depolarization ratio was 0.21 ± 0.06 (at 532 nm), the mean lidar ratios were 52 ± 7 sr at 355 nm and 53 ± 8 sr at 532 nm, and the mean Ångström exponent was 0.74 ± 0.31 for case I. In contrast, plumes transported at lower altitudes (case II) showed low depolarization ratios (0.13 ± 0.04 at 532 nm), and higher lidar ratio (63 ± 9 sr at 355 nm and 62 ± 8 sr at 532 nm) and Ångström exponents (0.98 ± 0.51). These numbers show that the optical characteristics of mixed Asian plumes are more similar to optical characteristics of urban pollution. We find a decrease of the linear depolarization ratio of the mixed dust/pollution plume depending on transport time if the pollution layer traveled over China at low heights, i.e., below approximately 3 km above ground. In contrast, we do not find such a trend if the dust plumes traveled at heights above 3 km over China. We need a longer time series of lidar measurements in order to determine in a quantitative way the change of optical properties of dust with transport time.Peer reviewedFinal Published versio
Neuronal glucose transporter isoform 3 deficient mice demonstrate features of autism spectrum disorders.
Neuronal glucose transporter (GLUT) isoform 3 deficiency in null heterozygous mice led to abnormal spatial learning and working memory but normal acquisition and retrieval during contextual conditioning, abnormal cognitive flexibility with intact gross motor ability, electroencephalographic seizures, perturbed social behavior with reduced vocalization and stereotypies at low frequency. This phenotypic expression is unique as it combines the neurobehavioral with the epileptiform characteristics of autism spectrum disorders. This clinical presentation occurred despite metabolic adaptations consisting of an increase in microvascular/glial GLUT1, neuronal GLUT8 and monocarboxylate transporter isoform 2 concentrations, with minimal to no change in brain glucose uptake but an increase in lactate uptake. Neuron-specific glucose deficiency has a negative impact on neurodevelopment interfering with functional competence. This is the first description of GLUT3 deficiency that forms a possible novel genetic mechanism for pervasive developmental disorders, such as the neuropsychiatric autism spectrum disorders, requiring further investigation in humans
Technical note: Absorption aerosol optical depth components from AERONET observations of mixed dust plumes
© Author(s) 2019.Absorption aerosol optical depth (AAOD) as obtained from sun–sky photometer measurements provides a measure of the light-absorbing properties of the columnar aerosol loading. However, it is not an unambiguous aerosol-type-specific parameter, particularly if several types of absorbing aerosols, for instance black carbon (BC) and mineral dust, are present in a mixed aerosol plume. The contribution of mineral dust to total aerosol light absorption is particularly important at UV wavelengths. In this study we refine a lidar-based technique applied to the separation of dust and non-dust aerosol types for the use with Aerosol Robotic Network (AERONET) direct sun and inversion products. We extend the methodology to retrieve AAOD related to non-dust aerosol (AAODnd) and BC (AAODBC). We test the method at selected AERONET sites that are frequently affected by aerosol plumes that contain a mixture of Saharan or Asian mineral dust and biomass-burning smoke or anthropogenic pollution, respectively. We find that aerosol optical depth (AOD) related to mineral dust as obtained with our methodology is frequently smaller than coarse-mode AOD. This suggests that the latter is not an ideal proxy for estimating the contribution of mineral dust to mixed dust plumes. We present the results of the AAODBC retrieval for the selected AERONET sites and compare them to coincident values provided in the Copernicus Atmosphere Monitoring System aerosol reanalysis.We find that modelled and AERONET AAODBC are most consistent for Asian sites or at Saharan sites with strong local anthropogenic sources.Peer reviewe
Estimation of dynamic models with nonparametric simulated maximum likelihood
We propose an easy-to-implement simulated maximum likelihood estimator for dynamic models where no closed-form representation of the likelihood function is available. Our method can handle any simulable model without latent dynamics. Using simulated observations, we nonparametrically estimate the unknown density by kernel methods, and then construct a likelihood function that can be maximized. We prove that this nonparametric simulated maximum likelihood (NPSML) estimator is consistent and asymptotically efficient. The higher-order impact of simulations and kernel smoothing on the resulting estimator is also analyzed; in particular, it is shown that the NPSML does not suffer from the usual curse of dimensionality associated with kernel estimators. A simulation study shows good performance of the method when employed in the estimation of jump diffusion models
Spin relaxation in mesoscopic superconducting Al wires
We studied the diffusion and the relaxation of the polarized quasiparticle
spins in superconductors. To that end, quasiparticles of polarized spins were
injected through an interface of a mesoscopic superconducting Al wire in
proximity contact with an overlaid ferromagnetic Co wire in the single-domain
state. The superconductivity was observed to be suppressed near the
spin-injecting interface, as evidenced by the occurrence of a finite voltage
for a bias current below the onset of the superconducting transition. The spin
diffusion length, estimated from finite voltages over a certain length of Al
wire near the interface, was almost temperature independent in the temperature
range sufficiently below the superconducting transition but grew as the
transition temperature was approached. This temperature dependence suggests
that the relaxation of the spin polarization in the superconducting state is
governed by the condensation of quasiparticles to the paired state. The spin
relaxation in the superconducting state turned out to be more effective than in
the normal state.Comment: 9 pages, 8 figure
Temperature Dependence of the Optical Transition Characteristics of MAPbClBr Single Crystals
Methylammonium-lead-halide compounds have emerged as promising bandgap
engineering materials due to their ability to fine-tune the energy gap through
halogen element mixing. We present a comprehensive investigation of the
temperature-dependent photoluminescence (PL) transition characteristics
exhibited by single crystals of chlorine and bromine-based methylammonium lead
halides. MAPbCl3 and MAPbBr3 crystals exhibit a distinct sharp free exciton
transition with an abrupt transition behavior associated with the structural
phase transition as the temperature varies. However, when the two halogen
elements are mixed within the crystals, no structural phase transition is
observed. This study explores the temperature-dependent variations in
integrated PL intensity, full-width-half-maximum, and peak transition energy of
the crystals. The obtained results discuss the intricate interplay between
temperature, crystal structure, and composition, providing valuable insights
into the optical properties and potential applications of organic-inorganic
hybrid methyl-ammonium lead halide single crystals as tunable energy gap
semiconductor materials.Comment: new research paper 4 figures with 4 supplementary figure
Duplication of horizontally acquired GH5_2 enzymes played a central role in the evolution of longhorned beetles
Atom interferometry with Bose-Einstein condensates in a double-well potential
A trapped-atom interferometer was demonstrated using gaseous Bose-Einstein
condensates coherently split by deforming an optical single-well potential into
a double-well potential. The relative phase between the two condensates was
determined from the spatial phase of the matter wave interference pattern
formed upon releasing the condensates from the separated potential wells.
Coherent phase evolution was observed for condensates held separated by 13
m for up to 5 ms and was controlled by applying ac Stark shift potentials
to either of the two separated condensates.Comment: 4 pages, 4 figure
- …