Values Of Γ0 Research Articles

Unified approach for describing rheological behavior of soil and mineral substrates modified with polymers

Studies in the rheology of natural aqueous dispersions (soils and their mineral substrates) as well as the approaches to control rheological parameters of these systems are of the prime importance to progress in the modern agricultural technologies, geoengineering, construction, etc. To advance in these fundamental and applied directions both original processing of the experimental results and search for the promising modifying agents are required. In this paper, rheological behavior of a representative range of virgin and modified aqueous soils, quartz sand and clays was studied. Modification of the above aqueous dispersed systems with polyelectrolytes and their complexes provided variation of the basic viscoelastic parameters corresponding to the linear viscoelastic region (initial storage modulus G0′, initial loss modulus G0", and strain γ0) and to the transition to steady-state flow (storage modulus Gin′ and strain γin) within 1 – 2 orders of magnitude. For samples studied, correlations for these mechanical characteristics were found – with the growth in the values of G0′ and G0′′, the increase in the values of Gin′ and decrease in the values of γ0 and γin were observed. Based on these correlations the master curves for the strain dependences of storage and loss modulus as well as for loss tangent were constructed. The appearance of the master curves reflected the unified regularities of the rheological response of dispersed systems which were attributed to the general features of structural evolution caused by the mechanical loading. Procedure for prediction of the rheological behavior of aqueous soil samples based on the experimental measurement of only two experimental characteristics (initial values of storage and loss modulus G0′ and G0′′ respectively) was proposed. The validity of this approach was tested using independent experimental data. The original approach obtained can be used for express analysis of the rheology of natural aqueous dispersed materials.

Realizing the effect of s-block metals on a charge transfer crystal of indol-2-one for enhanced NLO responses with efficient energetic offsets.

Due to their unique photophysical properties, organic charge transfer crystals are becoming promising materials for next-generation optoelectronic devices. This research paper explores the impact of s-block metals on a charge transfer crystal of indol-2-one for enhanced nonlinear optical (NLO) responses with efficient energetic offsets. The study reveals that alkali metals can enhance NLO performance due to their free electrons. The Perdew-Burke-Ernzerhof functional of DFT with dispersion correction (D3) was used, and the λmax values ranged between 596 and 669nm, with the highest value for dichloromethane (DCM). Leveraging the unique properties of metals allowed for the development of nonlinear optical materials with improved performance and versatility. Softness (σ) values provide insight into electron density changes, with higher values indicating a greater tendency for changes and lower values indicating the opposite. The NLO results for the chromophores MMI1-MMI6 show varying linear polarizability (< α0 >) along with their first (β0) and second (γ0) hyperpolarizabilities. Chromophore MMI4 stands out with the highest NLO performance, having two potassium (K) atoms. Its < α0 > , β0, and γ0 values of 4.19, 7.09, and 17.43 (× 10-24 e.s.u), respectively, indicate a significant enhancement in NLO response compared to the other chromophores. The transitions involving (O20)LP → (C3-N5)π* and (O19)LP → (N12-C13)π* exhibit the highest level of stabilization, followed by (O23)π → (C10-C11)π*, while (C6-N12)π → (C6-C7)π* shows the lowest level of stabilization for chromophore MMI4. The present research work is facile in its nature, and it can be helpful for synthetic scientist to design the new materials for uniting crystal properties with metal doping for efficient NLO devices.

(Second Best Student Paper Award) Blade Test in Atmospheric-Pressure Ar Gas to Characterize Bonded Interface Fabricated Using Atomic Diffusion Bonding

Atomic diffusion bonding (ADB) of wafers using thin films is a promising process to achieve room-temperature wafer bonding [1]. For ADB processing, thin oxide [2] and nitride [3] films are useful for bonding, as are thin metal films [1]. For blade testing, a conventional method to examine the surface free energy at the bonded interface γ, the debonding length L is measured after a thin blade is inserted between the bonded wafers. The value of γ is calculated using L values. For a bonded interface such as Si/SiO2 or SiO2/SiO2, stress corrosion caused by oxygen and water gases in air is well-known to affect the L value as does the bonding strength [4]. For this study, a blade test was applied in Ar gas at atmospheric pressure for wafers bonded using ADB processing. Bonded interfaces of two kinds were examined: interfaces bonded using thin metal films and those bonded using oxide films. Using Maszara’s equation for convenience, we assessed the variation of γ values calculated from L values.Figure 1 presents values of γ for quartz glass wafers bonded using Ti(0.7 nm) film on each side as a function of measurement time t. Two series of data are shown: those measured in Ar and in air. The blade-insertion speed was fixed at 100 μm/s. As t increased, γ measured in air decreased remarkably from the initial value γ0(air) of 3.1 J/m2. The values of γ measured in Ar were higher than those in air. γ in Ar maintained the initial value of γ0(Ar) until t=400 s; it then started decreasing. In fact, γ0(Ar) did not increase concomitantly with increasing blade-insertion speed. Results revealed that the gradual reduction of γ in Ar resulted from oxidation of Ti films with impurities of O2 and H2O in Ar gas. The value obtained without oxidation effects is γ0(Ar).Figure 2 presents values of γ for quartz glass wafers bonded using oxide thin films as a function of t: (A) using Al2O3(2 nm) films and (B) using ZrO2(0.5 nm) films. In both figures, the values of γ measured in Ar are much higher than those measured in air. Actually, γ in Ar for wafers bonded using Al2O3(2 nm) films maintained the initial value γ0(Ar) until t=150 s; then it started decreasing. This suggests that γ0(Ar) corresponds to the value obtained without the effects of water-stress corrosion. However, γ in Ar for wafers bonded using ZrO2(0.5 nm) films did not maintain the initial value γ0(Ar): γ decreased gradually as t increased, which indicates that the water–stress corrosion effects on the values of γ were not suppressed even in Ar. T. Shimatsu and M. Uomoto, ECS Trans., 33 (4), 61 (2010).T. Shimatsu, H. Yoshida, M. Uomoto, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. 51 (2021).M. Uomoto, H. Yoshida, T. Shimatsu, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. 45 (2021).F. Fournel, L. Continni, C. Morales, J. Da Fonseca, H. Moriceau, F. Rieutord, A. Barthelemy, and I. Radu, J. Appl. Phys., 111, 104907 (2012). Figure 1

Experimental investigation on dynamic shear modulus of undisturbed marine soils in the east coast of China

The dynamic shear modulus G is one of the vital parameters for the dynamic properties of marine soils and is crucial for marine geotechnical engineering design. In order to investigate the G characteristics of various marine soils, a series of resonant column tests were performed on undisturbed marine soils with various depths taken from Bohai Bay, Yangtze River estuary, and Jintang Strait, respectively. In addition, the maximum dynamic shear modulus Gmax and strain-compatible G of the tested marine soils were compared with the marine and terrestrial soils from the published literature. A remarkable finding is that, compared with terrestrial soils, the marine soils in different sea area present the stronger nonlinear behavior with lower shear modulus due to the special depositional environment. With the increasing of H, G in each strain range increase, and the dynamic characteristics of the marine soils gradually transition from nonlinear to linear, the Gmax and reference shear strain γ0 value of marine soils in different sea areas increases linearly with the increasing H, but the Gmax and γ0 growth rate varied with the sea environment and soil type. Based on the quantitative prediction equation of the Gmax and G attenuation relationship (G/Gmax ∼ γ) of various marine soils, a new prediction equation can be also established to predict G value in different depth and strain levels of various marine soils. The proposed equation are validated by independent experimental data of marine and terrestrial soils from the literature. In this regard, the proposed procedure provides a significant advantage in the evaluation of dynamic properties of marine soils in practice.

Non-spherical collapse of a cavitation bubble induced by a rigid filament

A combination of high-speed shadowgraph imaging and numerical simulations was used to study the collapse of a bubble near a rigid filament. The dynamic behavior of the collapsing bubble was investigated concerning two non-dimensional parameters: the filament radius (r*) and the initial near-wall distance (γ0). The critical distance (1 < γc < 3) between spherical and non-spherical collapse was positively correlated with r*. The collapsing bubbles were found to exhibit three different morphologies with different γ0 values: flat two-dimensional necking with a strong jet, teardrop-shaped collapse with an weak jet, and spherical collapse with no jet. The first collapse time (T1st) hardly varies with γ0, and the second collapse time (T2nd) shows an increasing and then decreasing trend as γ0 increases, reaching a maximum at γ0 = 1 and stabilizing after γ0 > γc. In addition, when γ0 = 0.76, the pressure difference between the upper and lower surfaces of the bubble is high, the jet is strong, and the maximum pressure and maximum fluid velocity are found in the jet, producing a stronger impact on the rigid wall. When γ0 > 1, as γ0 increases, the jet weakens, the pressure on the wall is far less than the pressure on the bubble surface when it collapses. Our results would deepen the understanding of the kinetics of the bubble collapsing near a slender cylindrical wall and provide an important reference for the improvement of pulp pumps and interpreting the degradation of microfiber-reinforced plastics.

Atomistic modeling of Mg-Al-Zn solid–liquid interfacial free energy

In this study anisotropic solid–liquid interfacial energy, γ, of Mg-Al-Zn system is evaluated based on capillary fluctuation method. To investigate effects of temperature and solute compositions on γ, five simulation cases, Cases I-V, are designed and divided into two group, Group I consist of Cases I-III for evaluation on solute compositions, while Group II consist of Cases I, IV and V for evaluation on temperatures. Interfacial energy stiffness of six differently oriented interfaces is evaluated, average interfacial energy, γ0, and anisotropic parameters of the interfaces are obtained. This study determined melting point of Mg as 964 ± 5 K, which matches the standard value of 923 K. Evaluation on γ0, and γ in high symmetric orientations γBasal, γPrismaticIA and γPrismaticIIA suggests, for Cases I-V, lower γ0 values within 15.74–18.19 mJ/m2 compared with elemental Mg could be related with the insufficiency of selected interatomic potential to describe the solid–liquid interface, and relation of γBasal>γPrismaticIIA>γPrismaticIA was identified. Comparisons within Group I indicate the increase of relative average equilibrium composition, c¯i/c¯j, will improve solute adsorption of element i on interface, which causes γ0 , γBasal, γPrismaticIA and γPrismaticIIA to decrease. As for Group II, temperature increase will result in decline of γ0 , γBasal, γPrismaticIA and γPrismaticIIA, similar trend was found in Al-Sm alloy systems. Primary dendrite growth orientations for Cases I-V were determined as [0001], analysis shown increase in either temperature or c¯i/c¯j stabilize this preference further towards [0001].

Quantum gravitational signatures in next-generation gravitational wave detectors

A recent study established a correspondence between the Generalized Uncertainty Principle (GUP) and Modified theories of gravity, particularly Stelle gravity. We investigate the consequences of this correspondence for inflation and cosmological observables by evaluating the power spectrum of the scalar and tensor perturbations using two distinct methods. First, we employ PLANCK observations to determine the GUP parameter γ0. Then, we use the value of γ0 to investigate the implications of quantum gravity on the power spectrum of primordial gravitational waves and their possible detectability in the next-generation detectors, like Einstein Telescope and Cosmic explorer.

A Parameter Representing Missing Charge Should Be Considered when Calibrating Action Potential Models.

Computational models of the electrical potential across a cell membrane are longstanding and vital tools in electrophysiology research and applications. These models describe how ionic currents, internal fluxes, and buffering interact to determine membrane voltage and form action potentials (APs). Although this relationship is usually expressed as a differential equation, previous studies have shown it can be rewritten in an algebraic form, allowing direct calculation of membrane voltage. Rewriting in this form requires the introduction of a new parameter, called Γ0 in this manuscript, which represents the net concentration of all charges that influence membrane voltage but are not considered in the model. Although several studies have examined the impact of Γ0 on long-term stability and drift in model predictions, there has been little examination of its effects on model predictions, particularly when a model is refit to new data. In this study, we illustrate how Γ0 affects important physiological properties such as action potential duration restitution, and examine the effects of (in)correctly specifying Γ0 during model calibration. We show that, although physiologically plausible, the range of concentrations used in popular models leads to orders of magnitude differences in Γ0, which can lead to very different model predictions. In model calibration, we find that using an incorrect value of Γ0 can lead to biased estimates of the inferred parameters, but that the predictive power of these models can be restored by fitting Γ0 as a separate parameter. These results show the value of making Γ0 explicit in model formulations, as it forces modellers and experimenters to consider the effects of uncertainty and potential discrepancy in initial concentrations upon model predictions.

Fluorescent styryl chromophores with rigid (pyrazole) donor and rigid (benzothiophenedioxide) acceptor – complete density functional theory (DFT), TDDFT and nonlinear optical study

Abstract Density functional theory (DFT) and time-dependent DFT computations were employed to examine linear and nonlinear optical (NLO) characteristics of (E)-4-((1,1-dioxido-3-oxobenzo[b]thiophen-2(3H)-ylidene) ethyl)-1-phenyl-1H-pyrazol-5(4H)-one derived styryl dyes. NLO properties were computed using the two different global hybrid functionals B3LYP, BHandHLYP and three range separated hybrid functionals CAM B3LYP, wB97, wB97X and wB97XD with the basis sets 6–311++G(d,p), cc-pVDZ and cc-pVTZ. The compounds shows higher values of dipole moment around 8–9 Debye than the other compounds. They show higher values of α 0, ß 0 and γ 0 values. The values of γ 0 are around 204–544 × 10−36 e.s.u. with the method, B3LYP/6–311++G(d, p). We have calculated the mean absolute error (MAE) for dipole moment, α 0, ß 0 and γ 0 values. It is observed that MAE is less (0.89) for wB97/6–311++G(d,p) which indicates that wB97 is the most suited functional for all three compounds. Chemical stability and reactivity of these dyes were studied using electrophilicity index and chemical hardness and hyperhardness.

Theoretical exploration of third-order nonlinear optical properties of black phosphorus quantum dots doped with alkali and alkaline-earth metal atoms

The electrical properties and nonlinear optical (NLO) properties of black phosphorus quantum dots (BPQDs) upon doping of alkali and alkaline-earth metal atoms, M@BPQDs (M = Li, Na, K, Be, Mg, and Ca), were systematically investigated based on density functional theory (DFT) method. The results showed that the introduction of metal atoms M could efficiently narrow the wide gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the pristine BPQDs in the range of 2.254–3.098 eV. More importantly, the metal atom M doping can remarkably enhance the second hyperpolarizability (γ0) of BPQDs, due to electron transfer from M to BPQDs. M@BPQDs possess large second hyperpolarizabilities (γ0) in the range of 0.81 × 10−33–3.94 × 10−33 esu, where the alkali-doped complexes are much superior to the alkaline-earth-doped complexes. Furthermore, doping heavier K atom on the large-sized BPQDs can obtain the largest γ0 value of 3.94 × 10−33 esu, which can be understood by its large amplitude distribution of second hyperpolarizability density. Configuration interaction singles (CIS) calculations were performed to get crucial excited states to account for the large γ0 values. The second hyperpolarizability trend estimated from the two-level formula and DFT calculations correlates nicely. These metal-doped complexes have the deep-ultraviolet (deep-UV) transparent region at wavelength ≤ 200 nm, and hence are new deep-UV NLO molecules. These striking results designate such doped BPQDs as excellent candidates for their potential applications in optical devices.

GRB 170817A as a Refreshed Shock Afterglow Viewed Off-axis

Abstract Energy injection into the external shock system that generates the afterglow to a gamma-ray burst (GRB) can result in a rebrightening of the emission. Here we investigate the off-axis view of a rebrightened refreshed shock afterglow. We find that the afterglow light curve, when viewed from outside of the jet opening angle, could be characterized by a slow rise, or long plateau, with a maximum flux determined by the total system energy. Using the broadband afterglow data for GRB 170817A, associated with the gravitational-wave-detected binary neutron star merger GW170817, we show that a refreshed shock model with a simple top-hat jet can reproduce the observed afterglow features. We consider two refreshed shock models: a single episode of energy injection, and an episode of continuous energy injection. The best-fit model parameters give a jet opening angle for our first and second models, respectively, of θ j = 5.° and 6.° , an inclination to the line of sight ι = 16.° and 17.° , an initial on-axis isotropic equivalent kinetic energy and erg, and a total/final, on-axis isotropic equivalent refreshed shock energy and erg. The first model fitting prefers an initial bulk Lorentz factor Γ0,1 &lt; 60, with a comparatively low central value of Γ0,1 = 19.5, indicating that, in this case, the on-axis jet could have been a “failed GRB.” Alternatively, our second model is consistent with a bright GRB for an on-axis observer, with . Due to the low Lorentz factor and/or the jet opening angles at θ j ∼ ι/3, both models are unable to reproduce the γ-ray emission observed in GRB 170817A, which would therefore require an alternative explanation such as cocoon shock breakout.

Characteristics of Long Gamma-Ray Bursts in the Comoving Frame

Abstract We compile a sample of 93 long gamma-ray bursts (GRBs) from the Fermi satellite and 131 from Konus-Wind that have measured redshifts and well-determined spectra, and estimate their pseudo-Lorentz factors (Γ0) using the tight L iso–E p–Γ0 correlation. The statistical properties and pair correlations of the temporal and spectral parameters are studied in the observer frame, rest frame, and comoving frame, respectively. We find that the distributions of the duration, peak energy, isotropic energy, and luminosity in the different frames are basically log-normal, and that their distributions in the comoving frame are narrow, clustering around ∼ 4000 s, ∼ 0.7 keV, ∼ 8 × 1049 erg, and ∼ 2.5 × 1046 erg s−1, where the redshift evolution effect has been taken into account. We also find that the values of Γ0 are broadly distributed between a few tens and several hundreds, with median values of ∼270. We further analyze the pair correlations of all the quantities, confirm the E iso–E p, L iso–E p, L iso–Γ0, and E iso–Γ0 relations, and find that the corresponding relations in the comoving frame do still exist, but with large dispersions. This suggests not only that the well-known spectrum–energy relations are intrinsic correlations, but also that the observed correlations are governed by the Doppler effect. In addition, the peak energies of long GRBs are independent of duration both in the rest frame and in the comoving frame, and there is a weak anticorrelation between the peak energy and Lorentz factor.

Dynamic in-plane compression of Miura-ori patterned metamaterials

The responses of Miura-ori patterned metamaterials to in-plane dynamic compression are studied for several scenarios, namely: compression of uniform density metamaterials at a constant velocity and impulsive loading modelled as an impact with initial velocity, and a mass impact of a metamaterial with graded density. Analytical models of the dynamic strength enhancement, impact velocity attenuation and energy absorption are proposed for materials with uniform initial density and materials with positive density gradient. Attention is paid to the influence of the material topology governed by the initial dihedral angle γ0 on the dynamic response of origami-based stationary blocks with equal densities. The propagation of disturbances—velocity and nominal strains—along the samples is analysed and it is shown that the localisation is more pronounced for small values of γ0. Different from other open cell materials (e.g. foam and honeycomb), the propagation speed of the yield stress, which corresponds to the quasi-static strength, is not related to the elastic properties of the metamaterial in the form of precursor elastic wave as it is governed by the inertial properties of the cells due to the local structural softening. Therefore, the in-plane dynamic compression of Miura-ori patterned metamaterials cannot be directly interpreted by means of the shock wave theory commonly used for cellular materials with different topologies. Nonetheless it is shown that, similarly to other cellular materials, the Miura-ori patterned metamaterials exhibit increased energy absorption capacity when increasing the loading rate. However, the dynamic energy absorption capacity of the analysed metamaterials in not uniquely defined by their relative density and is strongly dependent on their topology. The analytical models are verified by numerical simulations.

Dense Kondo behavior in the low-temperature resistivity and specific heat for amorphous Ce50Al50 alloy

We measured the low-temperature specific heat Cp, resistivity ρ, and magnetoresistance Δρ(H)/ρ(0) for amorphous Ce50Al50 synthesized by a DC high-rate sputter method. The low-temperature Cp (T &amp;lt; 2 K) decreases rapidly toward 0 K and has no indication of phase transition. The value of γ0 which is extrapolated down to 0 K of the Cp/T is 117 mJ/molK2. The temperature dependence of ρ increases with decreasing temperature down to 0.6 K. We found that both a weak localization effect and a coherent Kondo state might be realized in the low-temperature region for the present alloy from the conductivity analysis. Furthermore, in the low-temperature ρ, a T2 term with a very large coefficient A was observed. The ratio of A/γ02 is 0.63 ×10-5 (μΩcm/K2)/(mJ/molK2)2 and is near the value of typical Ce-based heavy-fermion compounds. The magnetoresistances Δρ(H)/ρ(0) at 0.5 K and 2 K are almost constant in the magnetic field region of H &amp;lt; 10 kOe. We considered that the negative magnetoresistance effect is due to the weak localization and the positive magnetoresistance to the heavy-fermion state in the present alloy.

Is the non-isothermal double β-model incompatible with no time evolution of galaxy cluster gas mass fraction?

In this paper, we propose a new method to obtain the depletion factor γ(z), the ratio by which the measured baryon fraction in galaxy clusters is depleted with respect to the universal mean. We use exclusively galaxy cluster data, namely, X-ray gas mass fraction (fgas) and angular diameter distance measurements from Sunyaev–Zel’dovich effect plus X-ray observations. The galaxy clusters are the same in both data set and the non-isothermal spherical double β-model was used to describe their electron density and temperature profiles. In order to compare our results with those from recent cosmological hydrodynamical simulations, we suppose a possible time evolution for γ(z), such as, γ(z)=γ0(1+γ1z). As main conclusions we found that: the γ0 value is in full agreement with the simulations. On the other hand, although the γ1 value found in our analysis is compatible with γ1=0 within 2σ c.l., our results show a non-negligible time evolution for the depletion factor, unlike the results of the simulations. However, we also put constraints on γ(z) by using the fgas measurements and angular diameter distances obtained from the flat ΛCDM model (Planck results) and from a sample of galaxy clusters described by an elliptical profile. For these cases no significant time evolution for γ(z) was found. Then, if a constant depletion factor is an inherent characteristic of these structures, our results show that the spherical double β-model used to describe the galaxy clusters considered does not affect the quality of their fgas measurements.

Aminoalkanoic Acids as Alternatives to Mercaptoalkanoic Acids for the Linker-Assisted Attachment of Quantum Dots to TiO2.

Linear aminoalkanoic acids (AAAs) and mercaptoalkanoic acids (MAAs) were characterized as bifunctional ligands to tether CdSe QDs to nanocrystalline TiO2 thin films and to mediate excited-state electron transfer (ET) from the QDs to TiO2 nanoparticles. The adsorption of 12-aminododecanoic acid (ADA) and 12-mercaptododecanoic acid (ADA) to TiO2 followed the Langmuir adsorption isotherm. Surface adduct formation constants (Kad) were ∼10(4) M(-1); saturation amounts of the ligands per projected surface area of TiO2 (Γ0) were ∼10(-7) mol cm(-2). Both Kad and Γ0 differed by 20% or less for the two linkers. CdSe QDs adhered to ADA- and MDA-functionalized TiO2 films; data were well modeled by the Langmuir adsorption isotherm and Langmuir kinetics. For ADA- and MDA-mediated assembly values of Kad were (1.8 ± 0.4) × 10(6) and (2.4 ± 0.4) × 10(6) M(-1), values of Γ0 were (1.6 ± 0.3) × 10(-9) and (1.2 ± 0.1) × 10(-9) mol cm(-2), and rate constants were (14 ± 5) and (60 ± 20) M(-1) s(-1), respectively. Thus, the thermodynamics and kinetics of linker-assisted assembly were slightly more favorable for MDA than for ADA. Steady-state and time-resolved emission spectroscopy revealed that electrons were transferred from both band-edge and surface states of CdSe QDs to TiO2 with rate constants (ket) of ∼10(7) s(-1). ET was approximately twice as fast through thiol-bearing linker 4-mercaptobutyric acid (MBA) as through amine-bearing linker 4-aminobutyric acid (ABA). Photoexcited QDs transferred holes to adsorbed MBA. In contrast, ABA did not scavenge photogenerated holes from CdSe QDs, which maximized the separation of charges following ET. Additionally, ABA shifted electron-trapping surface states to higher energies, minimizing the loss of potential energy of electrons prior to ET. These trade-offs involving the kinetics and thermodynamics of linker-assisted assembly; the driving force, rate constant, and efficiency of ET; and the extent of photoinduced charge separation can inform the selection bifunctional ligands to tether QDs to surfaces.

Hyper-concentrated flow response to aeolian and fluvial interactions from a desert watershed upstream of the Yellow River

Aeolian and fluvial interactions (AFIs) are critical earth-surface processes in arid zones, especially in desert watersheds. The response of hyper-concentrated flows to seasonal alternate AFIs shows very high rates of sediment transport and has important environmental and ecological consequences from local to global scales. Here, we present the aeolian processes-induced hyper-concentrated (AHC) flows that occurred in the Sudalaer desert watershed upstream of the Yellow River, which primarily transport non-cohesive coarse aeolian sand (>0.08mm) and show a peak suspended sediment concentration (SSC) of 1.1 to 1.4×106mgl−3. Our field study and theoretical analysis indicate that non-cohesive coarse aeolian sand downstream in the channel can be entrained from the bed and can be suspended in the turbulent flow by the significant runoff generated upstream with a SSC γ0 value of 0.5×106mgl−3. Severe aeolian processes can provide an abundant coarse sediment supply in the channel, which, once entrained, can also trigger and promote the development of AHC flows. We define, for the first time, the ratio of the weight percentage of coarse sediment to fine sediment C>0.08mm/C<0.05mm as the optimal grain size indicator (OGI) in suspended sediment, indicating that, as the fraction of coarse sediment increases, the significant runoff gradually changes to hyper-concentrated flows and reaches the peak SSC when OGI=3.25. Due to the high frequency of sandstorms and the infrequency of rainstorms, most of the significant rainfall-induced runoff with a certain SSC γ0 can develop into AHC flows and can substantially contribute to the total sediment yield, even leading to deleterious effects on the downstream river system and ecology. Compared with other desert watersheds in semiarid regions, we propose that a SSC γ0 of 500kgm−3 is the threshold criteria for the occurrence of AHC flows in the arid desert watersheds. Comprehensive governing of soil erosion in the upstream gully-dissected slopes is an essential and effective measure for controlling AHC flows.

STANDWISE CHANGE DETECTION FOR GROWING STOCK USING REPEAT-PASS ALOS PALSAR / PALSAR-2 DATA

Abstract. This study demonstrates the possibility of detecting the changes of growing stocks in mountainous forest stands derived from ALOS PALSAR and PALSAR-2 images. The ALOS PALSAR were obtained over the Kwangneung Experiment Forest (KEF, Korea) during the period of nineteen and a half months from the April 26, 2009 to December 12, 2010, whereas the PALSAR-2 data were acquired on the April 7, 2015. The KEF test site comprises 58 stands, which cover approximately 1,000ha and have steep slope topography. Owing to topographic effects of SAR data in mountainous areas, the DEM-assisted topographic normalized backscattering coefficient γ0 was applied to the evaluation of the relationships between the ALOS PALSAR / PALSAR-2 HV backscatter and the field inventory–based stand stock volume. The results indicate that: 1) the γ0 values for the volume obtained from ALOS PALSAR data on December 12, 2010 show a gradual increase higher than those computed from the data on April 26, 2009, here the γ0 value increases in accordance with an increase in the volume: 2) the γ0 values determined from the PALSAR-2 data increase with the same inventory-based volume, when compared with those computed from both ALOS PALSAR data. They also increase substantially as the values of the volume rise, with the exception of the volume interval from 130 m3 ha−1 to 160 m3 ha−1. This is understandable because the volume of the aforementioned interval has been reduced through clearing. Consequently, the γ0–based relationship between PALSAR-2 HV backscatter and growing stock can lead to detecting the stand growth changes in the KEF of Korea.

Uptake of hydrogen peroxide on the surface of Al2O3 and Fe2O3

The heterogeneous interaction of H2O2 with solid films of Al2O3 and Fe2O3 was investigated under dark conditions and in presence of UV light using a low pressure flow tube reactor coupled with a quadrupole mass spectrometer. The uptake coefficients were measured as a function of the initial concentration of gaseous H2O2 ([H2O2]0 = (0.15–16.6) × 1012 molecule cm−3), irradiance intensity (JNO2=0.002−0.012s−1), relative humidity (RH = 0.003–73%) and temperature (T = 268–320 K). Deactivation of mineral surfaces upon exposure to H2O2 was observed and only initial uptake coefficients of H2O2 were quantified, given by the following expressions: γ0 (Al2O3) = 1.10 × 10−3/(1 + RH0.93) and γ0 (Fe2O3) = 1.05 × 10−3/(1 + RH0.73) (calculated using BET surface area, estimated conservative uncertainty of 30%) at T = 280 K. The initial uptake coefficients were found to be independent of the UV irradiation intensity and concentration of H2O2. Temperature dependence of γ0 measured at RH = 0.3% corresponded to almost temperature independent values of γ0 at lower temperatures of the study (268–280 K) and to rather rapid decrease of γ0 with increase of temperature above 290 K, according to the following expressions: γ0 (Al2O3) = 8.7 × 10−4/(1 + 5.0 × 1013exp(−9700 T−1)) and γ0 (Fe2O3) = 9.3 × 10−4/(1 + 3.6 × 1014exp(−10300 T−1)). The present experimental data support current considerations that uptake of H2O2 on mineral aerosol is potentially an important atmospheric process which should be accounted for in the atmospheric models.

Spectra and mass composition of ultrahigh-energy cosmic rays from point sources

We present spectra and mass composition of cosmic rays incoming to the Earth in the energy range (0.5−2)·1020 eV. As their sources we consider Seyfert galaxies located at distances ≲40 Mpc, following an acceleration model for such moderate-power objects. Mass composition of the particles at sources is assumed to be mixed. Generation spectra are described by a function E−γ0, where γ0 is an arbitrary parameter. It is shown that the assumptions adopted make it possible to describe experimental data provided by HiRes and Pierre Auger Observatory, using different values of γ0.