Does afforestation deteriorate haze pollution in Beijing-Tianjin-Hebei (BTH), China?

Although aggressive emission control strategies have been implemented recently in the Beijing-Tianjin-Hebei area (BTH), China, pervasive and persistent haze still frequently engulfs the region during wintertime. Afforestation in BTH, primarily concentrated in the Taihang and Yan Mountains, has constituted one of the controversial factors exacerbating the haze pollution due to its slowdown of the surface wind speed. We report here an increasing trend of forest cover in BTH during 2001-2013 based on long-term satellite measurements and the impact of the afforestation on the fine-particle (PM2.5) level. Simulations using the Weather Research and Forecast model with chemistry reveal that afforestation in BTH since 2001 has generally been deteriorating the haze pollution in BTH to some degree, enhancing PM2.5 concentrations by up to 6% on average. Complete afforestation or deforestation in the Taihang and Yan Mountains would increase or decrease the PM2.5 level within 15% in BTH. Our model results also suggest that implementing a large ventilation corridor system would not be effective or beneficial to mitigate the haze pollution in Beijing

Effect of isoprene emissions from major forests on ozone formation in the city of Shanghai, China

Ambient surface level concentrations of isoprene (C<sub>5</sub>H<sub>8</sub>) were measured in the major forest regions located south of Shanghai, China. Because there is a large coverage of broad-leaved trees in this region, high concentrations of isoprene were measured, ranging from 1 to 6 ppbv. A regional dynamical/chemical model (WRF-Chem) is applied for studying the effect of such high concentrations of isoprene on the ozone production in the city of Shanghai. The evaluation of the model shows that the calculated isoprene concentrations agree with the measured concentrations when the measured isoprene concentrations are lower than 3 ppb, but underestimate the measurements when the measured values are higher than 3 ppb. Isoprene was underestimated only at sampling sites near large bamboo plantations, a high isoprene source, indicating the need to include geospatially resolved bamboo distributions in the biogenic emission model. The assessment of the impact of isoprene on ozone formation suggests that the concentrations of peroxy radicals (RO<sub>2</sub>) are significantly enhanced due to the oxidation of isoprene, with a maximum of 30 ppt. However, the enhancement of RO<sub>2</sub> is confined to the forested regions. Because the concentrations of NO<sub>x</sub> were low in the forest regions, the ozone production due to the oxidation of isoprene (C<sub>5</sub>H<sub>8</sub> + OH → → RO<sub>2</sub> + NO → → O<sub>3</sub>) is low (less than 2–3 ppb h<sup>−1</sup>). The calculation further suggests that the oxidation of isoprene leads to the enhancement of carbonyls (such as formaldehyde and acetaldehyde) in the regions downwind of the forests, due to continuous oxidation of isoprene in the forest air. As a result, the concentrations of HO<sub>2</sub> radical are enhanced, resulting from the photo-disassociation of formaldehyde and acetaldehyde. Because the enhancement of HO<sub>2</sub> radical occurs in regions downwind of the forests, the enhancement of ozone production (6–8 ppb h<sup>−1</sup>) is higher than in the forest region, causing by higher anthropogenic emissions of NO<sub>x</sub>. This study suggests that the biogenic emissions in the major forests to the south of Shanghai have important impacts on the levels of ozone in the city, mainly due to the carbonyls produced by the continuous oxidation of isoprene in the forest air

Co-registered combined OCT and THz imaging to extract depth and refractive index of a tissue-equivalent test object

Terahertz (THz) imaging and optical coherence tomography (OCT) provide complementary information with similar length scales. In addition to OCT’s extensive use in ophthalmology, both methods have shown some promise for other medical applications and non-destructive testing. In this paper, we present an iterative algorithm that combines the information from OCT and THz imaging at two different measurement locations within an object to determine both the depth of the reflecting layers at the two locations and the unknown refractive index of the medium for both the OCT wavelengths and THz frequencies. We validate this algorithm using a silicone test object with embedded layers and show that the depths and refractive index values obtained from the algorithm agreed with the measured values to within 3.3%. We further demonstrate for the first time that OCT and THz images can be co-registered and aligned using unsupervised image registration. Hence we show that a combined OCT/THz system can provide unique information beyond the capability of the separate modalities alone, with possible applications in the medical, industrial and pharmaceutical sectors

High-capacity quantum secure direct communication based on quantum hyperdense coding with hyperentanglement

We present a quantum hyperdense coding protocol with hyperentanglement in polarization and spatial-mode degrees of freedom of photons first and then give the details for a quantum secure direct communication (QSDC) protocol based on this quantum hyperdense coding protocol. This QSDC protocol has the advantage of having a higher capacity than the quantum communication protocols with a qubit system. Compared with the QSDC protocol based on superdense coding with $d$-dimensional systems, this QSDC protocol is more feasible as the preparation of a high-dimension quantum system is more difficult than that of a two-level quantum system at present.Comment: 5 pages, 2 figur

Global 3-D modeling of atmospheric ozone in the free troposphere and the stratosphere with emphasis on midlatitude regions. Final report

The authors have used several global chemical/transport models (1) to study the contribution of various physical, chemical, and dynamical processes to the budget of mid-latitude ozone in the stratosphere and troposphere; (2) to analyze the potential mechanisms which are responsible for the observed ozone perturbations at mid-latitudes of the lower stratosphere and in the upper troposphere; (3) to calculate potential changes in atmospheric ozone response to anthropogenic changes (e.g., emission of industrially manufactured CFCs, CO, and NO{sub x}) and to natural perturbations (e.g., volcanic eruptions and biomass burning); and (4) to estimate the impact of these changes on the radiative forcing to the climate system and on the level of UV-B radiation at the surface

Summary of research for FY-1995: Progress report

The object of this proposal is to study the reduction in mid-latitude stratospheric ozone and to estimate the budget of tropospheric ozone. The product of this proposal include: (1) the estimation of dilution of air masses processed by polar stratospheric clouds inside the polar vortex during winter; and (2) the destruction of ozone via heterogeneous reactions on the surface of aerosol particles which are present at all latitudes, especially after large volcanic eruptions such as Mt. Pinatubo; (3) to quantify photochemical production and destruction of O{sub 3} in the free troposphere; (4) to quantify export of ozone from polluted to remote regions, and (5) to quantify cross-tropopause exchanges of O{sub 3} and other species. The approach of this proposal is to use and to improve the two-dimensional and three-dimensional global chemical/dynamical models

Spin Precession and Time-Reversal Symmetry Breaking in Quantum Transport of Electrons Through Mesoscopic Rings

We consider the motion of electrons through a mesoscopic ring in the presence of spin-orbit interaction, Zeeman coupling, and magnetic flux. The coupling between the spin and the orbital degrees of freedom results in the geometric and the dynamical phases associated with a cyclic evolution of spin state. Using a non-adiabatic Aharonov-Anandan phase approach, we obtain the exact solution of the system and identify the geometric and the dynamical phases for the energy eigenstates. Spin precession of electrons encircling the ring can lead to various interference phenomena such as oscillating persistent current and conductance. We investigate the transport properties of the ring connected to current leads to explore the roles of the time-reversal symmetry and its breaking therein with the spin degree of freedom being fully taken into account. We derive an exact expression for the transmission probability through the ring. We point out that the time-reversal symmetry breaking due to Zeeman coupling can totally invalidate the picture that spin precession results in effective, spin-dependent Aharonov-Bohm flux for interfering electrons. Actually, such a picture is only valid in the Aharonov-Casher effect induced by spin-orbit interaction only. Unfortunately, this point has not been realized in prior works on the transmission probability in the presence of both SO interaction and Zeeman coupling. We carry out numerical computation to illustrate the joint effects of spin-orbit interaction, Zeeman coupling and magnetic flux. By examining the resonant tunneling of electrons in the weak coupling limit, we establish a connection between the observable time-reversal symmetry breaking effects manifested by the persistent current and by the transmission probability. For a ring formed by two-dimensional electron gas, weComment: 20 pages, 5 figure