ALBERT

Description: Memristive devices have been widely employed to emulate biological synaptic behavior. In these cases, the memristive switching generally originates from electrical field induced ion migration or Joule heating induced phase change. In this letter, the Ti/ZnO/Pt structure was found to show memristive switching ascribed to a carrier trapping/detrapping of the trap sites (e.g., oxygen vacancies or zinc interstitials) in ZnO. The carrier trapping/detrapping level can be controllably adjusted by regulating the current compliance level or voltage amplitude. Multi-level conductance states can, therefore, be realized in such memristive device. The spike-timing-dependent plasticity, an important Hebbian learning rule, has been implemented in this type of synaptic device. Compared with filamentary-type memristive devices, purely electronic memristors have potential to reduce their energy consumption and work more stably and reliably, since no structural distortion occurs.

Description: Abstract Cenozoic sedimentary rocks in the Tajik Basin record the history of retreat of the Paratethys from central Asia, tectonic activity within the surrounding Pamir and Tian Shan mountains, and Asian aridification. However, there remains a paucity of precise chronological constraints on the sequences from this region. Here, we present an integrated magnetostratigraphic, detrital zircon and monazite U‐Pb geochronologic, and detrital apatite fission track thermochronologic data from the lower Cenozoic sedimentary sequences in the Tajik Basin. Our results indicate that the investigated sedimentary rocks were deposited between ~41 and 23.3 Ma, with a depositional hiatus between ~36 and 31 Ma. The last two marine regressions were dated at ~41 and ~37.4 Ma, respectively. Aeolian sandy loess dominates the sequences from ~31 Ma to ~25 Ma, and gradually transitions to fluvial facies after ~25 Ma, consistent with late Oligocene to early Miocene acceleration of active deformation, uplift, and exhumation of the Pamirs.

Description: Question Plant trait mean values and trait responsiveness to different environmental regimes are both important determinants of plant field distribution, but the degree to which plant trait means vs trait responsiveness predict plant distribution has rarely been compared quantitatively. Because hydrological regime is a key determinant of wetland plant distribution, we hypothesized that both plant trait means and trait responsiveness to experimental submergence could predict plant adaptation to a wet or a dry part of hydrological gradients in wetlands. Location Beijing, China. Methods We measured mean values for 14 plant traits by growing 30 wetland species both on land (control) and partially submerged in a greenhouse, and calculated log response ratios (LnRRs) of these traits to submergence. A distribution pattern index of wetland plants along the moisture gradient (from the zone furthest from the wetland waterline to that nearest to the waterline) was developed based on plant survey data in 3988 field plots in 24 wetlands in Beijing, China. Results LnRRs of performance traits (shoot biomass, root biomass, plant height and total root length; R 2  = 0.249, P  =   0.005) and one out of five morphological traits (i.e. shoot elongation capacity; R 2  = 0.194, P  =   0.015) between partially submerged and control treatments could predict the distribution pattern of the 30 wetland plant species. In contrast, means of plant traits in either control or submergence could not predict species distribution. The trait LnRRs, increasing from very negative to very positive, corresponded positively with the distribution, ranging from the zone furthest from the wetland waterline to that nearest to the waterline. Surprisingly, physiological trait LnRRs that had been expected to underpin performance trait LnRRs did not themselves predict the distribution pattern of these species. Analyses at the level of multivariate trait groups (based on PCA) showed that species LnRRs of the morphological trait group were positively correlated with LnRRs of the performance trait group. Conclusions Our findings demonstrate that screening wetland plant species for performance and morphological trait LnRRs under experimentally flooded conditions is an effective approach to understand and predict their distribution pattern along moisture gradients in the field. Trait responses of wetland plants to hydrological changes may reflect their habitat preference and thus field distribution along the hydrological gradient. We found that response ratios of performance and morphological traits between partially submerged and un-submerged treatments under experimental conditions could well predict field distribution pattern of wetland plant species.

Description: Multiple stimulated emission fluorescence photoacoustic (MSEF-PA) phenomenon is demonstrated in this letter. Under simultaneous illumination of pumping light and stimulated emission light, the fluorescence emission process is speeded up by the stimulated emission effect. This leads to nonlinear enhancement of photoacoustic signal while the quantity of absorbed photons is more than that of fluorescent molecules illuminated by pumping light. The electronic states' specificity of fluorescent molecular can also be labelled by the MSEF-PA signals, which can potentially be used to obtain fluorescence excitation spectrum in deep scattering tissue with nonlinearly enhanced photoacoustic detection. In this preliminary study, the fluorescence excitation spectrum is reconstructed by MSEF-PA signals through sweeping the wavelength of exciting light, which confirms the theoretical derivation well.

Description: The frequency domain analysis of stimulated Raman Photoacoustic (PA) induced by laser pulses with Gaussian and rectangular temporal profiles is presented. Utilizing the pulsed laser with nanosecond and microsecond pulse width with Gaussian temporal profile, the frequency component of the PA signals cannot be differentiated between the stimulated Raman PA and the linear optical absorption PA, which is limited by the response bandwidth of biological tissue. When the laser pulses with rectangular temporal profile are used, we deduced the PA expression and numerically derived its frequency spectrum. The frequency components of PA signal induced by the stimulated Raman phonons is more than that induced by optical absorption in some low frequency ranges, which is inside the bandwidth of tissue system. Therefore, stimulated Raman PA signal can be distinguished from the linear optical absorption PA signal in frequency domain. Numerical simulations were conducted in this paper to demonstrate the proposition and feasibility of stimulated Raman PA in frequency domain, which will be experimentally validated in future work.

Description: The breakage and particle size redistributions in a ultrasound-intensified leaching process were explored experimentally and analyzed statistically. The results showed that particle size distributions (PSD) of this atomic crystal silica may be changed to a certain extent by ultrasound, but the width of PSD cannot be changed in conditions considered. Chemical reactions played important reciprocal causality to the breakage and the particle size redistributions, and the contribution was about a half on mean particle size.Further, the fiercest breakup happened at the maximum volume percentage of PSD rather than at the region of the largest particle size end. The ability of conventional stirring (CS) to break the silica particles may be larger than ones’ intuitive think if the same power was used. The morphology of the silica particles verified that the change before and after leaching is small.

Description: The North China Plain experiences frequent severe haze pollution during all seasons. Here we present the results from a summer campaign that was conducted at Xianghe, a suburban site located between the megacities of Beijing and Tianjin. Aerosol particle composition was measured in situ by an Aerosol Chemical Speciation Monitor along with a suite of collocated measurements during June 1 – 30, 2013. Our results showed that aerosol composition at the suburban site was overall similar to that observed in Beijing, which was mainly composed of organics (39%), nitrate (20%), and sulfate (18%). Positive matrix factorization of organic aerosol (OA) identified four OA factors with different sources and processes. While secondary organic aerosol (SOA) dominated OA, on average accounting for 70%, biomass burning OA (BBOA) was also observed to have a considerable contribution (11%) for the entire study period. The contribution of BBOA was increased to 21% during the BB period in late June, indicating a large impact of agricultural burning on air pollution in summer. Biomass burning also exerted a significant impact on aerosol optical properties. It was estimated that ~60% enhancement of absorption at the ultraviolet spectral region was caused by the organic compounds from biomass burning. The formation mechanisms and sources of severe haze pollution episodes were investigated in a case study. The results highlighted two different mechanisms, i.e., regional transport and local sources, driving the haze life cycles differently in summer in the North China Plain. While secondary aerosol species dominated aerosol composition in the episode from regional transport, organics and black carbon comprised the major fraction in the locally-formed haze episode.

Description: By the conventional mixed oxide method (1− x )Bi(Mg 1/2 Ti 1/2 )O 3 – x BaTiO 3 ((1− x )BMT– x BT, x  = 0.2−1.0) ceramics were prepared. For x  ≤ 0.4, a bismuth-rich phase was observed beside the perovskite phase. For 0.5 ≤  x  ≤ 0.92 ceramics, all the compositions belong to the pseudocubic phase, while the tetragonal phases were formed when x  ≥ 0.94. With the increase of BT content, a change from a relaxor-like behavior to a normal ferroelectric behavior was observed, while the change of T max is in the form of “U” curve. Furthermore, stable dielectric permittivity (1500–3000) and low losses (tan δ 〈 2%) were obtained in the 0.4 ≤  x  ≤ 0.6 ceramics in the temperature range 200°C–400°C, indicating a potential for high-temperature applications.