ALBERT

Description: A new type of photodegradable poly(vinyl chloride)-bismuth oxyiodide/TiO 2 (PVC-BiOI/TiO 2 ) nanocomposite film was prepared by embedding a nano-TiO 2 photocatalyst modified by BiOI into the commercial PVC plastic. The solid-phase photocatalytic degradation behavior of the as-prepared film was investigated in ambient air at room temperature under UV light irradiation, with the aid of UV-Vis spectroscopy, weight loss monitoring, scanning electron microscopy, and FT-IR spectroscopy. Compared to the PVC-TiO 2 nanocomposite film, the PVC-BiOI nanocomposite film and the pure PVC film, the PVC-BiOI/TiO 2 nanocomposite film exhibited a higher photocatalytic degradation activity. The optimal mass ratio of BiOI to TiO 2 was found to be 0.75 %. The weight loss rate of the PVC-BiOI/TiO 2 nanocomposite film reached 30.8 % after 336 h of irradiation, which is 1.5 times higher than that of the PVC-TiO 2 nanocomposite film under identical conditions. The solid-phase photocatalytic degradation mechanism of the nanocomposite films was briefly discussed. A new type of photodegradable PVC-BiOI/TiO 2 nanocomposite film was prepared. In comparison with the PVC-TiO 2 nanocomposite film, the PVC-BiOI nanocomposite film and the pure PVC film, the PVC-BiOI/TiO 2 nanocomposite film exhibited a higher solid-phase photocatalytic degradation activity.

Description: Replication protein A (RPA) is the main eukaryotic single-stranded DNA (ssDNA) binding protein, having essential roles in all DNA metabolic reactions involving ssDNA. RPA binds ssDNA with high affinity, thereby preventing the formation of secondary structures and protecting ssDNA from the action of nucleases, and directly interacts with other DNA processing proteins. Here, we discuss recent results supporting the idea that one function of RPA is to prevent annealing between short repeats that can lead to chromosome rearrangements by microhomology-mediated end joining or the formation of hairpin structures that are substrates for structure-selective nucleases. We suggest that replication fork catastrophe caused by depletion of RPA could result from cleavage of secondary structures by nucleases, and that failure to cleave hairpin structures formed at DNA ends could lead to gene amplification. These studies highlight the important role RPA plays in maintaining genome integrity. RPA binding to the ssDNA tailed intermediates that are formed during the repair of DNA double-strand breaks prevents annealing between short sequence homologies internal to the ends. When RPA is depleted from cells, or when its DNA binding activity is compromised, annealing between short repeats can lead to mutagenic microhomology-mediated end joining (MMEJ) or hairpin-capped ends.

Description: Abstract Remote detection of geomagnetic fields in the mesosphere would provide a powerful tool for mapping and interpreting Earth's lithospheric magnetic fields, monitoring magnetic disturbances in conjunction with the aurora, and making long‐term measurements of ionospheric currents at polar regions. Based on gated photon counting and direct frequency sweep, a remote magnetometry scheme with precession of mesospheric sodium was demonstrated. The technique of gated photon counting has an advantage in background light suppression and has the potential to achieve altitude‐resolved magnetic field measurements with an optimized laser source. An intensity‐modulated laser beam was utilized to optically pump sodium atoms in the mesopause, and a ground‐based telescope collects fluorescent echoes to infer the magnetic field. The experiment was carried out at Lijiang observatory where we validated this technique and measured the geomagnetic field with a sensitivity of 849 nT/Hz1/2, which can be improved through further optimization.

Description: The stability of the immobilized lipase from Candida sp. 99–125 during biodiesel production was investigated. The lipase was separately incubated in the presence of various reaction components such as soybean oil, oleic acid methyl ester, n -hexane, water, methanol, and glycerol, or the lipase was stored at 60, 80, 100 and 120 °C. Thereafter the residual lipase activity was determined by methanolysis reaction. The results showed that the lipase was rather stable in the reaction media, except for methanol and glycerol. The stability study performed in a reciprocal shaker indicated that enzyme desorption from the immobilized lipase mainly contributed to the lipase inactivation in the water system. So the methanol and glycerol contents should be controlled more precisely to avoid lipase inactivation, and the immobilization method should be improved with regard to lipase desorption. The stability of immobilized Candida sp. 99–125 lipase was investigated. The lipase shows excellent stability in the biodiesel reaction medium. Methanol and glycerol showed the most negative effects on the lipase stability. Desorption was the main reason leading to lipase inactivation in the water system.

Description: [1]  We show evidence that solar wind density enhancements and pressure pulses can lead to intense low-energy particle precipitation and an associated, but unexpected, damping of thermospheric density response. Ground-based indices, used as proxies for thermospheric energy deposition, fail to capture these interactions in forecasting algorithms. Superposed epoch comparison of a group of poorly specified neutral density storms suggests an event-chain of: 1) Multi-hour, pre-storm solar wind density enhancement, followed by solar wind dynamic pressure pulses that trigger excess low-energy particle flux to the upper atmosphere; 2) Enhanced production of thermospheric Nitric Oxide (NO) by precipitating particles and storm heating; 3) NO infrared cooling and damping of the thermosphere; 4) Mis-forecast of neutral density. In the control storms these features are absent or muted. We discuss the roles of solar wind pre-conditioning and solar cycle dependency in the problem storms. These problem neutral-density storms reveal an element of “geo-effectiveness” that highlights competition between hydrodynamic aspects of the solar wind and other interplanetary drivers.

Description: While applying a sigma-point Kalman filter (SPKF) to a high-dimensional system such as the oceanic general circulation model (OGCM), a major challenge is to reduce its heavy burden of storage memory and costly computation. In this study, we propose a new scheme for SPKF to address these issues. First, a reduced rank SPKF was introduced on the high-dimensional model state space using the truncated single value decomposition (TSVD) method (T-SPKF). Second, the relationship of SVDs between the model state space and a low-dimensional ensemble space is used to construct sigma points on the ensemble space (ET-SPKF). As such, this new scheme greatly reduces the demand of memory storage and computational cost and makes the SPKF method applicable to high-dimensional systems. Two numerical models are used to test and validate the ET-SPKF algorithm. The first model is the 40-variable Lorenz model, which has been a test bed of new assimilation algorithms. The second model is a realistic OGCM for the assimilation of actual observations, including Argo and in-situ observations over the Pacific Ocean. The experiments show that ET-SPKF is computationally feasible for high-dimensional systems and capable of precise analyses. In particular, for realistic oceanic assimilations, the ET-SPKF algorithm can significantly improve oceanic analysis and improve ENSO prediction. A comparison between the ET-SPKF algorithm and EnKF (ensemble Kalman filter) is also tribally conducted using the OGCM and actual observations.

Description: Composite granite–quartz veins occur in retrogressed ultrahigh pressure (UHP) eclogite enclosed in gneiss at General's Hill in the central Sulu belt, eastern China. The granite in the veins has a high-pressure (HP) mineral assemblage of dominantly quartz+phengite+ allanite/epidote+garnet that yields pressures of 2.5–2.1 GPa (Si-in-phengite barometry) and temperatures of 850–780 °C (Ti-in-zircon thermometry) at 2.5 GPa (~20 °C lower at 2.1 GPa). Zircon overgrowths on inherited cores and new grains of zircon from both components of the composite veins crystallized at c . 221 Ma. This age overlaps the timing of HP retrograde recrystallization dated at 225–215 Ma from multiple localities in the Sulu belt, consistent with the HP conditions retrieved from the granite. The ε Hf ( t ) values of new zircon from both components of the composite veins and the Sr–Nd isotope compositions of the granite consistently lie between values for gneiss and eclogite, whereas δ 18 O values of new zircon are similar in the veins and the crustal rocks. These data are consistent with zircon growth from a blended fluid generated internally within the gneiss and the eclogite, without any ingress of fluid from an external source. However, at the peak metamorphic pressure, which could have reached 7 GPa, the rocks were likely fluid absent. During initial exhumation under UHP conditions, exsolution of H 2 O from nominally anhydrous minerals generated a grain boundary supercritical fluid in both gneiss and eclogite. As exhumation progressed, the volume of fluid increased allowing it to migrate by diffuse porous flow from grain boundaries into channels and drain from the dominant gneiss through the subordinate eclogite. This produced a blended fluid intermediate in its isotope composition between the two end members, as recorded by the composite veins. During exhumation from UHP (coesite) eclogite to HP (quartz) eclogite facies conditions, the supercritical fluid evolved by dissolution of the silicate mineral matrix, becoming increasingly solute-rich, more ‘granitic’ and more viscous until it became trapped. As crystallization began by diffusive loss of H 2 O to the host eclogite concomitant with ongoing exhumation of the crust, the trapped supercritical fluid intersected the solvus for the granite–H 2 O system, allowing phase separation and formation of the composite granite–quartz veins. Subsequently, during the transition from HP eclogite to amphibolite facies conditions, minor phengite breakdown melting is recorded in both the granite and the gneiss by K-feldspar+plagioclase+biotite aggregates located around phengite and by K-feldspar veinlets along grain boundaries. Phase equilibria modelling of the granite indicates that this late-stage melting records P–T conditions towards the end of the exhumation, with the subsolidus assemblage yielding 0.7–1.1 GPa at 〈670 °C. Thus, the composite granite–quartz veins represent a rare example of a natural system recording how the fluid phase evolved during exhumation of continental crust. The successive availability of different fluid phases attending retrograde metamorphism from UHP (coesite) eclogite to amphibolite facies conditions will affect the transport of trace elements through the continental crust and the role of these fluids as metasomatic agents interacting with the mantle wedge in the subduction channel. This article is protected by copyright. All rights reserved.