No abstract

Asian summer monsoon (ASM) variability significantly affects hydro-climate, and thus socio-economics, in the East Asian region, where nearly one-third of the global population resides. Over the last two decades, speleothem δ 18 O records from China have been utilized to reconstruct ASM variability and its underlying forcing mechanisms on orbital to seasonal timescales. Here, we use the Speleothem Isotopes Synthesis and Analysis database (SISAL_v1) to present an overview of hydro-climate variability related to the ASM during three periods: the late Pleistocene, the Holocene, and the last two millennia. We highlight the possible global teleconnections and forcing mechanisms of the ASM on different timescales. The longest composite stalagmite δ 18 O record over the past 640 kyr BP from the region demonstrates that ASM variability on orbital timescales is dominated by the 23 kyr precessional cycles, which are in phase with Northern Hemisphere summer insolation (NHSI). During the last glacial, millennial changes in the intensity of the ASM appear to be controlled by North Atlantic climate and oceanic feedbacks. During the Holocene, changes in ASM intensity were primarily controlled by NHSI. However, the spatio-temporal distribution of monsoon rain belts may vary with changes in ASM intensity on decadal to millennial timescales.

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Biochemical oscillatory reaction induced self-gating process of biological ion channels is essential to life process, characterized as autonomous, continuous and periodic. However, few synthetic nanochannel systems can achieve such excellent self-gating property. Their gating properties work greatly depending on the frequent addition of reactants or the supply of external stimuli. Herein, we report a novel bio-inspired self-gating nanofluidic device that can transport mass in a continuous and periodic manner. This self-gating device is constructed by using a fully-closed-system pH oscillator to control the gating processes of the artificial proton-gated nanochannels. With cyclic oscillation of protons inside the nanochannel induced by the oscillatory chemical reactions of the pH oscillator, surface charge density and polarity of the nanochannels can be self-regulated, resulting in an autonomous and periodic switching of the nanochannel conductance between high and low states as well as the selectivity between cation selective and anion selective states. Moreover, by using Rhodamine B and Ruthenium (II) compound as the cationic cargoes, we also observe periodic release of these charged molecules. Therefore, our work opens up a new avenue to build self-gating nanofluidic devices, which may not only act as ion oscillators, but potentially find applications in controlled-release fields as well.

Bio-inspired polymeric nanochannel (also referred as nanopore)-based biosensors have attracted considerable attention on account of their controllable channel size and shape, multi-functional surface chemistry, unique ionic transport properties, and good robustness for applications. There are already very informative reviews on the latest developments in solid-state artificial nanochannel-based biosensors, however, which concentrated on the resistive-pulse sensing-based sensors for practical applications. The steady-state sensing-based nanochannel biosensors, in principle, have significant advantages over their counterparts in term of high sensitivity, fast response, target analytes with no size limit, and extensive suitable range. Furthermore, among the diverse materials, nanochannels based on polymeric materials perform outstandingly, due to flexible fabrication and wide application. This compressive Review summarizes the recent advances in bio-inspired polymeric nanochannels as sensing platforms for detection of important analytes in living organisms, to meet the high demand for high-performance biosensors for analysis of target analytes, and the potential for development of smart sensing devices. In the future, research efforts can be focused on transport mechanisms in the field of steady-state or resistive-pulse nanochannel-based sensors and on developing precisely size-controlled, robust, miniature and reusable, multi-functional, and high-throughput biosensors for practical applications. Future efforts should aim at a deeper understanding of the principles at the molecular level and incorporating these diverse pore architectures into homogeneous and defect-free multi-channel membrane systems. With the rapid advancement of nanoscience and biotechnology, we believe that many more achievements in nanochannel-based biosensors could be achieved in the near future, serving people in a better way.