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Background: Efficient and selective utilization of metabolic substrates is one of the key strategies in high-altitude animals to cope with hypoxia and hypothermia. Previous findings have shown that the energy substrate utilization of highland animals varies with evolutionary history and phylogeny. The heart is a proxy for the cardiopulmonary system, and the metabolic substrate utilization in the myocardium is also under the strong selective pressure of chronically hypoxic and hypothermic environments. However, little information is available on the physiological adjustments in relation to metabolic substrate utilization in the myocardium for coping with high-altitude environments. Methods: We compared the metabolic enzyme activities, including hexokinase (HK), phosphofructokinase (PFK), pyruvate kinase (PK), citrate synthase (CS), carnitine palmitoyl transferase 1 (CPT-1), lactic dehydrogenase (LDH), and creatine kinase (CK), and metabolic substrate contents including glucose (Glu), triglyceride (TG), and free fatty acid (FFA) in the myocardium of a typical human commensal species, Eurasian Tree Sparrows (Passermontanus) between the Qinghai-Tibet Plateau (the QTP, 3230 m) and low altitude population (Shijiazhuang, 80 m), and between sexes. Results: Among the seven metabolic enzymes and three substrates investigated, we identified no significant differences in PK, CPT-1, HK, CS, LDH, and CK activities and TG content of the myocardium between high and low altitude populations. However, the QTP sparrows had significantly lower Glu content and PFK activities but higher FFA content relative to their lowland counterparts. In addition, male sparrows had higher myocardial HK and CS activities relative to females, independent of altitude. Conclusions: Our results showed that the QTP sparrows elevated fatty acid utilization rather than glucose preference in the myocardium relative to lowland counterpart, which contributes to uncovering both the physiological adjustments for adapting to the extreme conditions of the QTP, intraspecifically. [ABSTRACT FROM AUTHOR]

The double-porosity, dual-permeability theory is employed to predict the wave attenuation and phase velocity dispersion induced by wave-induced meso copic fluid flow. Instead of using an up-scaled, single-porosity approximation scheme proposed by previous researchers, we develop an analytical method to exactly solve the wave equations for double-porosity materials. We first propose a new form of wave equations formulated in terms of displacements. This new form of wave equations enables us to decouple the field equations into two second-order symmetric dynamic systems, namely, the P -system for compressional waves and the S -system for shear wave. We then implement Newton iteration for solving the cubic dispersion equation for compressional waves. Finally, to understand the loss mechanism caused by mesoscopic flow, we compare the attenuation curves of the first ( P 1-wave), the second ( P 2-wave), and the third compressional waves ( P 3-wave), as well as the shear wave ( S -wave), with the mesoscopic flow present to those with the mesoscopic flow absent. Furthermore, the effects of matrix porosity, pore-fluid viscosity, and values of fluid transport coefficient on wave attenuation are also investigated in numerical examples. [ABSTRACT FROM AUTHOR]

We propose a novel and sensitive water vapour sensing scheme based on enhanced resonances in absorbing ultrathin-film cavity systems. In particular, we experimentally and numerically demonstrate the water vapour sensing ability of such cavity systems, which comprise ultrathin poly(vinyl alcohol) films doped with Rhodamine 6G dye molecules coated on silver substrates. Due to coupling between molecular absorption and Fabry–Perot resonances excited in the ultrathin-film cavity, the studied structure exhibits highly enhanced resonant absorption at certain wavelengths under certain illumination conditions. Upon exposure to water vapour (relative humidity from 10% to 73%) the resonant features show much larger spectral shifts ( ∼ 60 nm) than those (∼20 nm) reported in most previous studies and a three-fold enhancement of the absorption reduction (>40%) as compared to that in an un-doped reference sample. In addition, the proposed ultrathin-film system demonstrates hysteresis-free sensing response to water vapour within a wide RH range (5–75%). Together with its flexibility of tuning sensing performance by adjusting dye-doping concentration, the absorbing ultrathin-film system provides an effective and versatile platform towards further development of practical water vapour sensing. [ABSTRACT FROM AUTHOR]

In this paper, we consider three different notions of recurrence, chain recurrence, strong chain recurrence and generalized recurrence, where the generalized recurrence is introduced by Auslander (1964) and the strong chain recurrence is derived from the idea of a strong chain defined by Easton (1978). We prove that for a quasi-gradient flow in a compact metric space, these three recurrences are equivalent. Finally, we establish an invariance principle, i.e., the ω -limit set of a precompact orbit is contained in the generalized recurrent component of ’zero derivative’ set of a Lyapunov function. [ABSTRACT FROM AUTHOR]

Green's functions for Biot's dynamic equation in the frequency domain can be a highly useful tool for the investigation of dynamic responses of a saturated porous medium. Its applications are found in soil dynamics, seismology, earthquake engineering, rock mechanics, geophysics, and acoustics. However, the mathematical work for deriving it can be daunting. Green's functions have been presented utilizing an analogy between the dynamic thermoelasticity and the dynamic poroelasticity in the frequency domain using the u-p formulation. In this work, a special term 'decoupling coefficient' for the decomposition of the fast and slow dilatational waves is proposed and expressed to present a new methodology for deriving the poroelastodynamic Green's functions. The correctness of the solution is demonstrated by numerically comparing the current solution with Cheng's previous solution. The separation of the two waves in the present methodology allows the more accurate evaluation of Green's functions, particularly the solution of the slow dilatational wave. This can be advantageous for the numerical implementation of the boundary element method (BEM) and other applications. [ABSTRACT FROM AUTHOR]

SUMMARY In this study, the dynamic response of a poroelastic half-space to a point fluid sink is investigated using Biot's dynamic theory of poroelasticity. Based on Biot's theory, the governing field equations are re-formulated in frequency domain with solid displacement and pore pressure. In a cylindrical coordinate system, a method of displacement potentials for axisymmetric displacement field is proposed to decouple the Biot's field equations to three scalar Helmholtz equations, and then the general solution to axisymmetric problems are obtained. The full-space fundamental singular solution for a point sink is also derived using potential methods. The mirror-image method is finally applied to construct the fundamental solution for a point sink buried in a poroelastic half-space. Furthermore, a numerical study is conducted for a rock, that is, Berea sandstone, as a representative example. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Abstract: The complete 3D dynamic Green’s functions in the multilayered poroelastic media are presented in this study. A method of potentials in cylindrical coordinate system is applied first to decouple the Biot’s wave equations into four scalar Helmholtz equations, and then, general solutions to 3D wave propagation problems are obtained. After that, a three vector base and the propagator matrix method are introduced to treat 3D wave propagation problems in the stratified poroelastic half-space disturbed by buried sources. It is known that the original propagator algorithm has the loss-of-precision problem when the waves become evanescent. At present, an orthogonalization procedure is inserted into the matrix propagation loop to avoid the numerical difficulty of the original propagator algorithm. At last, the validity of the present approach for accurate and efficient calculating 3D dynamic Green’s functions of a multilayered poroelastic half-space is confirmed by comparing the numerical results with the known exact analytical solutions of a uniform poroelastic half-space. [Copyright &y& Elsevier]

Spectral and directional reshaping of fluorescence fromdye moleculesembedded in self-assembled hybrid plasmonic–photonic crystalshas been examined. The hybrid crystals comprise two-dimensional hexagonalarrays of dye-doped dielectric nanospheres, capped with silver semishells.Comparing the reshaped fluorescence spectra with measured transmission/reflectionspectra and numerical calculations reveals that the spectral and directionalreshaping of fluorescence is the result of its coupling to photoniccrystal Bloch modes and to void plasmons localized inside the silvercaps. [ABSTRACT FROM AUTHOR]

Based on the solutions of the Green's function for a saturated porous medium obtained by the authors, and using transformation of axisymmetric coordinates, Sommerfeld integrals and superposition of the influence field on a free surface, the authors have obtained displacement solutions of a saturated porous medium subjected to a torsional force in a half-space. The relationship curves of the displacement solutions and various parameters (permeability, frequency, etc.) under action of a unit of torque are also given in this paper. The results are consistent with previous Reissner's solutions, where a two-phase medium decays to a single-phase medium. The solution is useful in solving relevant dynamic problems of a two-phase saturated medium in engineering. [ABSTRACT FROM AUTHOR]

Abstract: The Green’s functions of a two-phase saturated medium subjected to a concentrated force are known to play an important role in seismology, earthquake engineering, soil dynamics, geophysics, and dynamic foundation theory. This paper presents a physical method for obtaining the dynamic Green’s functions of a two-phase saturated medium for materials considered to be isotropic and for low frequencies. First, the pore-fluid pressure in a two-phase saturated medium is divided into two parts: flow pressure and deformation pressure. Next, based on the compatibility condition of Biot’s equation and the property of the δ-function, the problem of coupled_fast and slow dilational waves is solved using the decomposition condition of the potential dilation field. The Green’s function for a concentrated force is then obtained by solving Biot’s complex modular equations, and their physical characteristics are discussed. The behavior of Green’s functions for the solid and fluid phases of a δ-impulsive force is investigated, from which the Green’s functions for a unit Heaviside force are also obtained by time integration. Finally, the present Green’s functions for a unit Heaviside force are compared with those obtained by a purely mathematical method; the two differ in form, but the numerical results are identical. The physical meaning of the expressions of Green’s functions obtained in this paper is evident. Therefore, the results may benefit future research on the dynamic responses of a two-phase saturated medium. [Copyright &y& Elsevier]

In this paper, we introduce the index of an impulsive periodic orbit, which can be used to judge the Zhukovskiǐ quasi-stabilities of periodic orbits. Also, we present an example of predator–prey model to illustrate our results. [ABSTRACT FROM AUTHOR]

[Display omitted] Structural information of grassland changes on the Tibetan Plateau is essential for understanding alterations in critical ecosystem functioning and their underlying drivers that may reflect environmental changes. However, such information at the regional scale is still lacking due to methodological limitations. Beyond remote sensing indicators only recognizing vegetation productivity, we utilized multivariate data fusion and deep learning to characterize formation-based plant community structure in alpine grasslands at the regional scale of the Tibetan Plateau for the first time and compared it with the earlier version of Vegetation Map of China for historical changes. Over the past 40 years, we revealed that (1) the proportion of alpine meadows in alpine grasslands increased from 50% to 69%, well-reflecting the warming and wetting trend; (2) dominances of Kobresia pygmaea and Stipa purpurea formations in alpine meadows and steppes were strengthened to 76% and 92%, respectively; (3) the climate factor mainly drove the distribution of Stipa purpurea formation, but not the recent distribution of Kobresia pygmaea formation that was likely shaped by human activities. Therefore, the underlying mechanisms of grassland changes over the past 40 years were considered to be formation dependent. Overall, the first exploration for structural information of plant community changes in this study not only provides a new perspective to understand drivers of grassland changes and their spatial heterogeneity at the regional scale of the Tibetan Plateau, but also innovates large-scale vegetation study paradigm. [ABSTRACT FROM AUTHOR]

Effective optical absorption is highly desirable for numerous applications in energy harvesting and optoelectronics. Bifacial absorbers can significantly enhance light absorption by capturing albedo light from the environment. Here, we experimentally demonstrate that free-standing silica-silver core–shell nano-resonator arrays allow bifacial and omnidirectional optical absorption across the visible spectrum. Specifically, resonator arrays can highly absorb light (>80%) with all polarizations from a directional range (−40° to 40°) on both front and rear sides of a surface. Numerical simulations reveal that such bifacial and omnidirectional light absorption results from hybridized excitation of surface plasmons and whispering gallery modes in a symmetrical configuration. The absorption band can be flexibly adjusted by changing the silica core size. In addition, the absorbed optical energy quickly decays as the excitation of plasmonic hot electrons as observed using transient absorption spectroscopy. Our work provides a bifacial absorber for many optoelectronic applications in photodetection, photovoltaics, and photocatalysis. [ABSTRACT FROM AUTHOR]

The complete mitochondrial genome of Bryodema luctuosum luctuosum, which was collected from the Qinghai-Xizang Plateau of China, is reported here. It is 15,946 bp in length and contains 74.9% AT. All B. luctuosum luctuosum protein-coding sequences start with a typical ATN codon. The usual termination codon (TAA) and incomplete stop codons (T and TA) were found from 13 protein-coding genes. All tRNA genes could be folded into the typical cloverleaf secondary structure, excluding trnS(AGN) which forms another structure. The sizes of the large and small ribosomal RNA genes are 1316 and 835 bp, respectively. The AT content of the A+T-rich region is 84.8%. [ABSTRACT FROM AUTHOR]

A new strategy named Sampling Error Profile Analysis (SEPA) is proposed in the optimization for some parameters in piecewise direct standardization (PDS), such as the number of principal components and window size, and the evaluation for the calibration transfer. Partial least squares (PLS) with mean-centering is used in PDS for calibration transfer. Random re-sampling is carried out in SEPA to obtain a series of subsets and build same number sub-models that produce corresponding number root mean square errors (RMSE), of which the mean value and standard deviation are calculated. To take both accuracy and stability into account, the sum of the mean value and standard deviation are used for parameter optimization and model evaluation. The performance of the proposed strategy has been tested on two data sets: a ternary mixture dataset and a corn dataset. Compared with PDS, SEPA-PDS obtained lower prediction errors, indicating that the transfer model would be more robust and effective when using the parameters optimized by SEPA. Compared with other two commonly used calibration transfer methods of slope and bias correction (SBC) and spectral space transformation (SST), SEPA-PDS acquired more satisfactory results. [ABSTRACT FROM AUTHOR]

The scattering spectra and intensity of gold nanorods placed at varied distances above gold films have been simulated and measured under various conditions, demonstrating that scattering characteristics of the nanorod-film system are highly dependent on illumination conditions. Studying the surrounding electric fields of nanorods reveals that the illumination-dependent properties of the system are induced by the interference in the nanorod-film system. Both simulations and experiments show that optimising the nanorod-film distance can greatly enhance scattering magnitudes up to ~20 times for certain illumination conditions. We propose an application of the studied system in facilitating photo-thermal conversion. [ABSTRACT FROM AUTHOR]

Nanostructures with various configurations have been extensively used to engineer the emission properties of embedded fluorophores, but lack the flexibility to dynamically control fluorescence. Here we report a thin-film cavity system, comprising a quarter wavelength thick dye-doped dielectric coating on a reflecting surface, in which the fluorescence enhancement and directionality can be significantly modified by altering the illumination angle. The configuration of the cavity yields absorption properties that are highly dependent on illumination angles, due to the coupling between molecular absorption and Fabry-Perot resonances. Therefore the fluorescence intensity relating to the angle-dependent absorbing efficiency varies with illumination angles. In addition, as a result of synergy between intrinsic absorption of the reflecting surface, Fabry-Perot and surface-plasmon-polariton resonances and illumination-angle dependent excitation efficiencies for differently located molecules, the global emission intensity, including emission from dyes at all locations, can be directionally redistributed by altering the illumination angle. [ABSTRACT FROM AUTHOR]

The alpine grassland on the Qinghai-Tibet Plateau covers an area of about 1/3 of China's total grassland area and plays a crucial role in regulating grassland ecological functions. Both environmental changes and irrational use of the grassland can result in severe grassland degradation in some areas of the Qinghai-Tibet Plateau. However, the magnitude and patterns of the physical and anthropogenic factors in driving grassland variation over northern Tibet remain debatable, and the interactive influences among those factors are still unclear. In this study, we employed a geographical detector model to quantify the primary and interactive impacts of both the physical factors (precipitation, temperature, sunshine duration, soil type, elevation, slope, and aspect) and the anthropogenic factors (population density, road density, residential density, grazing density, per capita GDP, and land use type) on vegetation variation from 2000 to 2015 in northern Tibet. Our results show that the vegetation index in northern Tibet significantly decreased from 2000 to 2015. Overall, the stability of vegetation types was sorted as follows: the alpine scrub > the alpine steppe > the alpine meadow. The physical factors, rather than the anthropogenic factors, have been the primary driving factors for vegetation dynamics in northern Tibet. Specifically, meteorological factors best explained the alpine meadow and alpine steppe variation. Precipitation was the key factor that influenced the alpine meadow variation, whereas temperature was the key factor that contributed to the alpine steppe variation. The anthropogenic factors, such as population density, grazing density and per capita GDP, influenced the alpine scrub variation most. The influence of population density is highly similar to that of grazing density, which may provide convenient access to simplify the study of the anthropogenic activities in the Tibet plateau. The interactions between the driving factors had larger effects on vegetation than any single factor. In the alpine meadow, the interaction between precipitation and temperature can explain 44.6% of the vegetation variation. In the alpine scrub, the interaction between temperature and GDP was the highest, accounting for 27.5% of vegetation variation. For the alpine steppe, the interaction between soil type and population density can explain 29.4% of the vegetation variation. The highest value of vegetation degradation occurred in the range of 448–469 mm rainfall in the alpine meadow, 0.61–1.23 people/km2 in the alpine scrub and –0.83–0.15 °C in the alpine steppe, respectively. These findings could contribute to a better understanding of degradation prevention and sustainable development of the alpine grassland ecosystem in northern Tibet. [ABSTRACT FROM AUTHOR]

A novel method called sampling error profile analysis (SEPA) based on Monte Carlo sampling and error profile analysis is proposed for outlier detection, cross validation, pretreatment method and wavelength selection, and model evaluation in multivariate calibration. With the Monte Carlo sampling in SEPA, a number of submodels are prepared and the subsequent error profile analysis yields a median and a standard deviation of the root‐mean‐square error (RMSE) for the submodels. The median coupled with the standard deviation is an estimation of the RMSE that is more predictive and robust because it uses representative submodels produced by Monte Carlo sampling, unlike the normal method, which uses only 1 model. The error profile analysis also calculates skewness and kurtosis for an auxiliary judgment of the estimated RMSE, which is useful for model optimization and model evaluation. The proposed method is evaluated with 3 near‐infrared datasets for wheat, corn, and tobacco. The results show that SEPA can diagnose outliers with more parameters, select more reasonable pretreatment method and wavelength points, and evaluate the model more accurately and precisely. Compared with the results reported in published papers, a better model could be obtained with SEPA concerning RMSECV, RMSEC, and RMSEP estimated with an independent prediction set. A novel method called sampling error profile analysis (SEPA) based on Monte Carlo sampling and error profile analysis is proposed for detecting outliers, cross validation, pretreatment method, and model evaluation in multivariate calibrate. In SEPA, several submodels are prepared, and the subsequent error profile analysis yields a median and a standard deviation of the root‐mean‐square error for the submodels. The analysis also calculates the skewness and kurtosis for auxiliary judgment, which is useful for model optimization and evaluation. [ABSTRACT FROM AUTHOR]