The increasing severity of droughts/floods and worsening air quality from increasing aerosols in Asia monsoon regions are the two gravest threats facing over 60% of the world population living in Asian monsoon regions. These dual threats have fueled a large body of research in the last decade on the roles of aerosols in impacting Asian monsoon weather and climate. This paper provides a comprehensive review of studies on Asian aerosols, monsoons, and their interactions. The Asian monsoon region is a primary source of emissions of diverse species of aerosols from both anthropogenic and natural origins. The distributions of aerosol loading are strongly influenced by distinct weather and climatic regimes, which are, in turn, modulated by aerosol effects. On a continental scale, aerosols reduce surface insolation and weaken the land-ocean thermal contrast, thus inhibiting the development of monsoons. Locally, aerosol radiative effects alter the thermodynamic stability and convective potential of the lower atmosphere leading to reduced temperatures, increased atmospheric stability, and weakened wind and atmospheric circulations. The atmospheric thermodynamic state, which determines the formation of clouds, convection, and precipitation, may also be altered by aerosols serving as cloud condensation nuclei or ice nuclei. Absorbing aerosols such as black carbon and desert dust in Asian monsoon regions may also induce dynamical feedback processes, leading to a strengthening of the early monsoon and affecting the subsequent evolution of the monsoon. Many mechanisms have been put forth regarding how aerosols modulate the amplitude, frequency, intensity, and phase of different monsoon climate variables. A wide range of theoretical, observational, and modeling findings on the Asian monsoon, aerosols, and their interactions are synthesized. A new paradigm is proposed on investigating aerosol-monsoon interactions, in which natural aerosols such as desert dust, black carbon from biomass burning, and biogenic aerosols from vegetation are considered integral components of an intrinsic aerosol-monsoon climate system, subject to external forcing of global warming, anthropogenic aerosols, and land use and change. Future research on aerosol-monsoon interactions calls for an integrated approach and international collaborations based on long-term sustained observations, process measurements, and improved models, as well as using observations to constrain model simulations and projections.
The use of UV/ozone surface treatments for achieving low temperature bonds between PMMA and COC microfluidic substrates is evaluated. Low temperature bond strengths, approaching those of native polymer substrates bonded above their glass transition temperatures, are demonstrated for both thermoplastics. To evaluate the effects of the UV/O(3) surface treatment on the operation of bonded microfluidic devices, the relationship between UV/O(3) exposure and polymer hydrophilicity and surface chemistry are measured. Post-treatment surface chemistry is evaluated by XPS (X-ray photoelectron spectroscopy) analysis, and the stability of the treated surfaces following solvent exposure is reported. Electroosmotic flow within fabricated microchannels with modified wall surfaces is also characterized. Overall, UV/O(3) treatment is found to enable strong low temperature bonds between thermoplastic microfluidic substrates using a simple, low cost, and high throughput fabrication technology.
We have measured parity-violating asymmetries in elastic electron-proton scattering over the range of momentum transfers 0.12 < or =Q2 < or =1.0 GeV2. These asymmetries, arising from interference of the electromagnetic and neutral weak interactions, are sensitive to strange-quark contributions to the currents of the proton. The measurements were made at Jefferson Laboratory using a toroidal spectrometer to detect the recoiling protons from a liquid hydrogen target. The results indicate nonzero, Q2 dependent, strange-quark contributions and provide new information beyond that obtained in previous experiments.
We report the first experimental demonstration of the interference-induced spectral line elimination predicted by Zhu and Scully [Phys. Rev. Lett. 76, 388 (1996)] and Ficek and Rudolph [Phys. Rev. A 60, R4245 (1999)]. We drive an exciton transition of a self-assembled quantum dot in order to realize a twolevel system exposed to a bichromatic laser field and observe the nearly complete elimination of the resonance fluorescence spectral line at the driving laser frequency. This is caused by quantum interference between coupled transitions among the doubly dressed excitonic states, without population trapping. We also demonstrate a multiphoton ac Stark effect with shifted subharmonic resonances and dynamical modifications of resonance fluorescence spectra by using double dressing. New physics beyond the Mollow fluorescence triplet arises when a two-level system is exposed to strong bichromatic driving fields, exhibiting a range of nonlinear and multiphoton dynamics of light-matter interaction [22,23]. In particular, it has been pointed out that a dynamical cancellation of the spontaneous emission spectral line, initially predicted for a three-level system [24,25], may be possible in a two-level atom [26,27], which is not due to population trapping, but induced by quantum interferences between different transition channels in a doubly dressed atom. This occurs when a two-level atom is driven by a strong resonant laser with a Rabi frequency 2Ω [28], and a second, weaker laser is detuned by 2Ω from the strong field. The suppression of spontaneous emission spectral lines also appears when the second laser is coupled to the shifted subharmonics of 2Ω, which can be attributed to the multiphoton ac Stark effect [22]. Despite the extensive efforts undertaken to observe this phenomenon [29][30][31][32][33][34], the experimental demonstration of a complete cancellation of spontaneous emission lines has been claimed once in a V-type level atom [29], where there was also an alternative interpretation based on population trapping possible [32]. Here, we use a single QD, doubly dressed by bichromatic fields, to demonstrate unequivocally the complete cancellation of spontaneous emission spectral lines and other features arising from this phenomenon including shifted subharmonic resonances and modifications of sideband spectra.Our experiments are carried out on self-assembled InGaAs QDs embeded in a low-Q planar microcavity (Q ≈ 200) and housed in a cryogen-free bath cryostat operating at 4.2 K, as shown in Fig. 1(a). The measurements are performed on the neutral exciton transition of a single QD with a confocal microscope allowing bichromatic excitations of the QD from the side arm and collection of PRL 114, 097402 (2015) P H Y S I C A L
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