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The Philippine Sea is a typical region of aeolian dust reposition and is located within the Western Pacific Warm Pool. Here, we use the paleomagnetic stratigraphy and the grain‐size distributions of Quaternary abyssal deposits in the Central Philippine Sea to investigate the factors controlling regional sedimentary and paleoenvironmental changes. Our principal results are as follows: (a) A reliable geochronologic framework for Quaternary sediments in the Central Philippine Sea is established. (b) An eastward expansion of the regional depocenter in the Middle Pleistocene is observed. (c) The mean grain size of the abyssal sediments is 7–8 µm, and there are only minor differences between the sites. Comparison of the geochronological framework with various paleoenvironmental events during the Mid‐Pleistocene Transition shows that sedimentary processes can be correlated to a major transition in global climate which affected regions from the Asian interior to the tropical Pacific, and that changes in aeolian sedimentation are likely the predominant factor responsible. A derived grain‐size proxy of the sedimentary dynamics and its comparison with various paleoenvironmental proxies show that the relative contributions are roughly estimated as 23%, 9%, and 68% for aeolian inputs, oceanic circulation, and the tropical Pacific zonal SST gradient, respectively, in the studied region. The relative importance of tropical processes in abyssal sedimentary dynamics highlights the possibility of the long‐term influence of (sub)mesoscale eddies in the upper ocean, via regional upwelling and unique submarine topography, on the deepest part (>5,000 m) of the Central Philippine Sea, from meteorological to geological timescales. Plain Language Summary: The Philippine Sea is of paleoclimatic and paleoceanographic significance. Likely because of water depth largely over 5,000 m, the sedimentary processes are relatively poorly understood. In this study, integrating magnetic stratigraphy in the Central Philippine Sea reveals an eastward expansion of regional depocenter since ∼0.8 Ma, and this expansion may be responded to a major transition in climate changes from the Asian interior to the tropical Pacific. By analyzing sediment grain sizes and comparing them with various paleoenvironmental proxies, the influences of aeolian inputs, oceanic circulation, and tropical climate processes are evaluated during the Quaternary. The relative importance of the tropical Pacific zonal SST gradient suggests that the long‐term influence of (sub)mesoscale eddies in the upper ocean may be the major factor dominating abyssal sedimentation on different timescales, via a topography‐induced deep‐reaching effect. Key Points: A geochronologic framework in Central Philippine Sea is established, inferring an eastward expansion of depocenter in Middle PleistoceneA sedimentary transition at ∼1.3–1.2 Ma can be correlated to changes in aeolian sedimentation as the predominant factorSedimentary dynamics are predominantly controlled by ENSO, demonstrating long‐term influence of (sub)mesoscale eddies in upper ocean [ABSTRACT FROM AUTHOR]

Lanthanide‐doped up‐conversion (UC) materials with color tunable property show promising application in many fields, such as biological imaging, optical multiplexing, and information security. Although great efforts have been devoted to regulate UC emission color via modifying chemical composition, crystal structure, or external stimuli condition, it is remain a daunting challenge to develop a general strategy that probably suitable for various lanthanide‐doped nano‐systems. Herein, we verify the cross‐relaxation possibility between sensitizer Yb3+ and activator Er3+ as well as Er3+‐ Er3+ pairs can be well modified by engineering the crystal lattice distortion of matrix, leading to the evident UC emission color variations. Specifically, with incorporating Al3+ or Ca2+ ions into the Yb/Er co‐doped BaF2 nanocrystals (NCs) contained glass ceramics (GCs), the contraction of the crystal lattice lead to the change of UC emission color from green to red. On the contrary, the high laser excitation power results in the lattice expansion of the Al3+‐doped BaF2:Yb/Er GCs at different Yb3+ concentration as well as Al3+ doped CaF2 GCs, which leads to the greatly increased green‐to‐red ratio. These multi‐color UC GCs show potential application in anti‐counterfeiting filed. Our results open up a general avenue for the control of UC emission color via engineering crystal lattice distortion. [ABSTRACT FROM AUTHOR]

Changes in marine export productivity may have played a prominent role in the atmospheric CO2 rise and associated warming of the last deglaciation, via their impact on the air‐sea partitioning of CO2. To study the evolution of marine export production in the western subtropical Pacific Ocean during the last deglaciation and the mechanisms governing these changes, 230Th‐normalization has been applied on a sediment core retrieved from the Okinawa Trough. The reconstructed export productivity record shows two prominent peaks, centered around 14 and 17 ka. Given that phytoplankton growth at our study site is limited by the availability of nutrients today, elevated macro‐nutrient supply must have been responsible for sustaining the two deglacial productivity peaks. Specifically, higher nutrient supply originating from the subpolar gyre via subsurface water advection, with enhanced vertical mixing in the subpolar gyre during early HS1 and enhanced wind‐driven upwelling during the B/A, would have fueled phytoplankton productivity and export. In contrast, reduced nutrient supply to the euphotic zone caused by gyre circulation changes would have lead to decreased export production during the Holocene. These observations lend support to a predominant control of nutrient availability on the evolution of the marine carbon cycle in the subtropical west Pacific Ocean across the last deglaciation. Key Points: 230Th‐normalized export production estimates show two distinct peaks across the last deglaciationNutrient supply by gyre circulation governed the evolution of marine productivityRiverine supply of lithogenic material may have contributed to enhance and sustain marine export production [ABSTRACT FROM AUTHOR]

Lanthanide‐doped fluoride nanoscintillators (NSs) have emerged as promising candidates for X‐ray imaging. However, strong afterglow, long lifetime, and poor irradiation stability pose key challenges for real‐time dynamic X‐ray imaging. In this study, the sub‐10 nm Lu6O5F8:Tb NSs with tunable morphologies are prepared via incorporating Li+/Na+ ions. The X‐ray excited optical luminescence (XEOL) intensity of the Lu6O5F8:15Tb/10Li NSs is stronger than that of NaLuF4:15 Tb NSs with a similar particle size while its afterglow is only ≈2.7% compared to that of NaLuF4:15 Tb NSs. Utilizing the Lu6O5F8:15 Tb/10Li NSs‐integrated film as a scintillator screen, a high resolution of ≈21.6 lp/mm is achieved. Even at a low dose of 0.23 µGy, the fringe detail in the electron device is clearly observed in the X‐ray image. The afterglow intensity of the Lu6O5F8:10Eu/10Li NSs decays to 0.7% at 40 µs, which is better than that of CsI:Tl (3.6%@40 µs). Moreover, the Lu6O5F8:10Eu/10Li NSs with a lifetime of 1.65 µs are verified for use in dynamic 3D X‐ray imaging. These findings represent a significant advancement in the development of new NSs for high‐performance dynamic X‐ray imaging. [ABSTRACT FROM AUTHOR]

Diffracted wavefields with superior illumination encode key geologic information about small‐scale geologic discontinuities or inhomogeneities in the subsurface and thus possess great potential for high‐resolution imaging. However, the weak diffracted wavefield is easily masked by the dominant reflected data. Diffraction separation from specular reflected data still plays an important role and plays a major role in diffraction imaging implementation. To solve this problem, a new diffraction‐separation method is proposed that uses variational mode decomposition to suppress reflected data and separate diffracted wavefields in the common‐offset or poststack domains. The variational mode decomposition algorithm targets reflected wavefield by decomposing seismic data into an ensemble of band‐limited intrinsic mode functions representing linear and strong reflected data. This method is based on the principle of energy sparsity and can utilize the kinematic and dynamic differences between reflected and diffracted wavefields to effectively predict linear reflected data. Synthetic and field data examples using complex body geometries demonstrate the effectiveness and performance of the proposed method in enhancing diffracted wavefield and attenuating reflected data as well as increasing the signal‐to‐noise ratio, which helps to clearly image small‐scale subwavelength geologic structures. [ABSTRACT FROM AUTHOR]

As an ideal carrier of high‐resolution information, seismic diffraction can be used to clarify and locate small‐scale discontinuities or inhomogeneities in the subsurface. However, a diffraction is weak and thus be suppressed by the specular reflection. Furthermore, a diffraction would be destroyed by the conventional imaging method due to the polarity reversal of diffraction. In this paper, we analyse the behaviour of diffraction and reflection. For the image point on a horizontal or oblique reflector, the zone on both sides of the stationary point has the same energy after using a cosine weight function. Based on the behaviour, we propose the adaptive phase filter to adjust the polarity of the energy on both sides, and calculate it through the illumination angle and the reflector dip angle. This method avoids the calculation of the Fresnel zones and can further suppress residual reflection that disturb the diffraction images. Synthetic and field data applications show that the desired imaging results can be obtained by the proposed method. The test results demonstrate that the method is efficient in detecting small‐scale discontinuities or inhomogeneities in the subsurface and can provide high‐resolution information for seismic interpretation. [ABSTRACT FROM AUTHOR]

Tb3+‐doped germanate glass ceramics containing CaF2 nanocrystals were prepared by melt quenching method with subsequent heat treatment. Their microstructures were investigated by XRD and TEM techniques. Their optical properties were studied by the transmittance, the photoluminescence, and the X‐ray excited luminescence (XEL). The luminescence intensity in the glass ceramics under 377 nm light and X‐ray excitations is significantly enhanced. The maximum integrated XEL intensity of the glass ceramics is about 50% of that of the commercial Bi4Ge3O12 (BGO) scintillating crystal. The results indicate that Tb3+‐doped germanate glass ceramic could be a promising scintillating material used in X‐ray detection for slow event. [ABSTRACT FROM AUTHOR]

Evaluating the role of fluvial transfer of terrestrial organic carbon (OC) and subsequent burial in the global carbon cycle requires the sources and fluxes of fluvial OC to be assessed, which remains poorly constrained in the Huanghe (Yellow River). Here, we report the elemental, stable isotopic, and radiocarbon activity of particulate organic carbon (POC) sampled at the outlet of Huanghe in 2012-2013. We show that the Huanghe riverine POC can be explained by binary mixing of fossil (POCfossil) and non-fossil (POCnon-fossil) components, the former may reach ~40% of the total POC. The Huanghe POCnon-fossil is mostly sourced from C3 plants, with a mean residence time of c. 2200 years. The current human-controlled hydrological regime strongly influenced the POC sources, transport modes, and fluxes. In 2012-2013, the Huanghe delivered 0.73 Tg (1 Tg = 1012 g) of POC to the sea, and about 28% of the annual POC flux occurred within a short human induced flood event. Globally, the Huanghe should be one of the largest rivers in the transfer and re-burial of fossil OC. However, the fate of Huanghe fossil OC is still unconstrained and needs to be further investigated. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT Seismic diffracted waves carry valuable information for identifying geological discontinuities. Unfortunately, the diffraction energy is generally too weak, and standard seismic processing is biased to imaging reflection. In this paper, we present a dynamic diffraction imaging method with the aim of enhancing diffraction and increasing the signal-to-noise ratio. The correlation between diffraction amplitudes and their traveltimes generally exists in two forms, with one form based on the Kirchhoff integral formulation, and the other on the uniform asymptotic theory. However, the former will encounter singularities at geometrical shadow boundaries, and the latter requires the computation of a Fresnel integral. Therefore, neither of these methods is appropriate for practical applications. Noting the special form of the Fresnel integral, we propose a least-squares fitting method based on double exponential functions to study the amplitude function of diffracted waves. The simple form of the fitting function has no singularities and can accelerate the calculation of diffraction amplitude weakening coefficients. By considering both the fitting weakening function and the polarity reversal property of the diffracted waves, we modify the conventional Kirchhoff imaging conditions and formulate a diffraction imaging formula. The mechanism of the proposed diffraction imaging procedure is based on the edge diffractor, instead of the idealized point diffractor. The polarity reversal property can eliminate the background of strong reflection and enhance the diffraction by same-phase summation. Moreover,the fitting weakening function of diffraction amplitudes behaves like an inherent window to optimize the diffraction imaging aperture by its decaying trend. Synthetic and field data examples reveal that the proposed diffraction imaging method can meet the requirement of high-resolution imaging, with the edge diffraction fully reinforced and the strong reflection mostly eliminated. [ABSTRACT FROM AUTHOR]

ABSTRACT Simultaneous estimation of velocity gradients and anisotropic parameters from seismic reflection data is one of the main challenges in transversely isotropic media with a vertical symmetry axis migration velocity analysis. In migration velocity analysis, we usually construct the objective function using the l2 norm along with a linear conjugate gradient scheme to solve the inversion problem. Nevertheless, for seismic data this inversion scheme is not stable and may not converge in finite time. In order to ensure the uniform convergence of parameter inversion and improve the efficiency of migration velocity analysis, this paper develops a double parameterized regularization model and gives the corresponding algorithms. The model is based on the combination of the l2 norm and the non-smooth l1 norm. For solving such an inversion problem, the quasi-Newton method is utilized to make the iterative process stable, which can ensure the positive definiteness of the Hessian matrix. Numerical simulation indicates that this method allows fast convergence to the true model and simultaneously generates inversion results with a higher accuracy. Therefore, our proposed method is very promising for practical migration velocity analysis in anisotropic media. [ABSTRACT FROM AUTHOR]