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The effects of maximum load and loading rate on the creep behavior of the single-phase hexagonal close-packed structured GdHoLaTbY alloy at room temperature were investigated by nanoindentation. The hardness, creep depth, creep rate, and stress exponent strongly dependent on the maximum load and loading rate. The creep behavior of the alloy at different maximum loads shows a significant indentation size effect. The creep behavior is dominated by free diffusion at the sample surface at low load retaining loads and by dislocation sliding at high load retaining loads. The creep behavior of the current alloy is greatly sensitive to the indentation loading rate at different loading rates. High loading rates give rise to stress fields with high dislocation density and high strain gradients, which results in a large stress index during the loading retention stage. [ABSTRACT FROM AUTHOR]

Intermetallic alloys have traditionally been characterized by their inherent brittleness due to their lack of sufficient slip systems and absence of strain hardening. However, here we developed a single-phase B2 high-entropy intermetallic alloy that is both strong and plastic. Unlike conventional intermetallics, this high-entropy alloy features a highly distorted crystalline lattice with complex chemical order, leading to multiple slip systems and high flow stress. In addition, the alloy exhibits a dynamic hardening mechanism triggered by dislocation gliding that preserves its strength across a wide range of temperatures. As a result, this high-entropy intermetallic circumvents precipitous thermal softening, with extensive plastic flows even at high homologous temperatures, outperforming a variety of both body-centered cubic and B2 alloys. These findings reveal a promising direction for the development of intermetallic alloys with broad engineering applications. Intermetallics are traditionally characterised by their inherent brittleness due to a lack of sufficient slip systems and the absence of strain hardening. Here authors show that a single-phase distorted high entropy B2 intermetallic alloy displays notable strength and plasticity at room temperature, along with stable plastic flow at high homologous temperatures. [ABSTRACT FROM AUTHOR]

This work describes the development and optimization of the radiochemical separation of 147Pm and 151Sm. The two main challenges addressed were: the radiochemical separation of the lanthanides by using LN Resin and DGA,N Resin, and the quantification of the chemical recovery of 147Pm with a non-isotopic analogue (i.e. neodymium). The applicability of radiochemical separation procedures was investigated by using spiked samples. The optimized radiochemical separation procedure by using LN Resin was applied to a reactor cooling water primary coolant sample with an automated system. Sector Field Inductively Coupled Plasma Mass Spectrometry (SF-ICP-MS) was used to determine the chemical recoveries. [ABSTRACT FROM AUTHOR]

The excess entropy ΔS with respect to the maternal crystal has been determined for 18 metallic glasses differing in the mixing entropy ΔSmix. Using these data, thermodynamic fragility mΔS has been determined within the Adam–Gibbs model. It has been shown that mΔS increases with ΔSmix but decreases with increasing ΔS, which reflects the degree of structural disorder in a glass. It has been concluded that the so-called "high-entropy glasses" (i.e., having high ΔSmix) are indeed most ordered and their properties are characterized by the slowest relaxation. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the corrosion behavior of the Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11 metallic glass matrix composites (MGMCs) in chlorine-containing (1 M KCl and 1 M H2SO4 solution with different concentrations of KCl) and chlorine-free aqueous (KOH and H2SO4) environments at room temperature. The Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11 MGMCs show an excellent corrosion resistance in 1 M H2SO4 and 1 M KOH solutions, while have poor corrosion resistance in 1 M KCl solutions. With the increase of chloride ion (Cl-) concentration, the corrosion properties of the Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11 MGMCs in 1 M H2SO4 solutions with different concentrations of KCl becomes worse. The corrosion behavior of the Zr-based MGMCs is significantly dependent on the increase of Cu content, the decrease of Nb content, and slightly change of Zr and Ti content in the corrosion product film. The corrosion properties of the MGMCs finally is controlled by a series of chemical reactions and the destruction of passive films due to the penetration of passive films by the Cl- as well. [ABSTRACT FROM AUTHOR]

The effects of the conventional isothermal bainitic transformation (CIT), two-step isothermal bainitic transformation (TIT) on the microstructure, mechanical behavior, and wear resistance of a medium-carbon low-Si steel were investigated. For the bainite reaction, it is well known that the bainite-plate size decreases as the transformation temperature is reduced. In comparison with the CIT, TIT produced finer bainitic ferrite plates with finer carbides, and an optimum combination of strength, ductility, and impact toughness (an ultimate tensile strength of 1500 MPa, total elongation of 8.6%, and V-notch impact value of 42 J), the wear rate is calculated to evaluate its wear performance, and the wear rates of a CIT sample and TIT sample were 0.36 × 10−4 and 1.46 × 10−4 mm3 N−1 m−1, respectively. [ABSTRACT FROM AUTHOR]

In this article, we mainly obtain the measure of Julia limiting directions and transcendental directions of Jackson difference operators of non-trivial transcendental entire solutions for differential-difference equation f n (z) + ∑ k = 0 n a λ k (z) p λ k (z , f) = h (z) , where p λ k (z , f) (λ ∈ ℕ) are distinct differential-difference monomials, a λ k (z) are entire functions of growth smaller than that of the transcendental entire h(z). For non-trivial entire solutions f of differential-difference equation P 2 (z , f) + A 1 (z) P 1 (z , f) + A 0 (z) = 0 , where Pλ(z,f)(λ = 1, 2) are differential-difference polynomials. By considering the entire coefficient associated with Petrenko's deviation, the measure of common transcendental directions of classical difference operators and Jackson difference operators of f was studied. [ABSTRACT FROM AUTHOR]

The fuel tank of the advanced heavy launch vehicle is made of 2219 aluminum alloy with a thickness of 18 mm. Friction stir welding (FSW) technology is used to achieve the welding of the fuel tank. The increase of thickness directly affects welding temperature field, which ultimately affects the welding quality. At present, the temperature distribution law of FSW thick 2219 aluminum alloy is still blank, which is a bottleneck to ensure high welding quality. In this paper, a temperature field measurement and analyses system based on K-type thermocouple and LabVIEW for friction stir welding is developed first. Then experiments are carried out and the temperature data in welding and thickness directions are measured and the temperature law is analyzed. The comparison of temperature distribution of FSW thick and thin 2219 aluminum alloy is made, and the influence of welding thickness on the temperature field is studied. Based on temperature field, weld strength and microstructure, the influence of different process parameters on welding quality is explored. The research results lay a foundation for optimization of the welding process parameters and realization of constant temperature control of FSW. [ABSTRACT FROM AUTHOR]

Unlike the traditional air-cooling method, the AZ31B magnesium alloy surface was treated by laser surface melting in a liquid nitrogen cooling environment (LSM-LN). Microstructure, microhardness, and wear resistance tests were conducted to compare the substrate and laser-melted layer obtained in the liquid nitrogen cooling environment (LSM-LN layer). The grain size of the LSM-LN layer was much finer than that of the substrate, approximately 5.2 μm. The β-Mg17Al12 in the LSM-LN layer was far less than in the substrate. Under the comprehensive competitive factors of thermodynamics and kinetics, the mixed structure of nanocrystalline and amorphous appeared in some regions of the LSM-LN layer. Thermal stress was attributed to the uneven temperature change of the magnesium alloy in the laser heating and cooling process. Coupled with the magnesium alloy's mechanical restraint stress, the LSM-LN layer's dislocation density was greatly increased. Due to more remarkable grain refinement, solid solution strengthening, dislocation strengthening, and the amorphous structure, the microhardness and wear resistance properties of the magnesium alloy treated by LSM-LN were improved. [ABSTRACT FROM AUTHOR]

Indentation tests at various depths confirm that the scale factor, f, which was proposed to modify the Nix-Gao model, is governed only by intrinsic properties of materials, but the connection between f and intrinsic properties is still unknown. From this, a connection is established between f and pertinent parameters, such as activation volume, V, and theoretical strength, G. Moreover, considering the interaction between adjacent indentations, we define a critical scale factor feff to describe the strengthening interface, which is found proportional to indentation depth for the given material. It is also found that larger feff is preferred for high-strength high-entropy alloys and/or medium-entropy alloys than pure metals. Combining f and feff of Ni, CoNi, CoCrNi and FeCoCrNi metals and alloys, a model describing dislocation density distribution in indentation plastic zone is established, in which the plastic zone includes three parts, i.e., the indentation zone of equivalent conical indenter, the detectable dislocation enhancement region, and the low dislocation density region. The inconsonant trends of f and feff can be explained by the existing of dislocation saturation zone in the plastic zone. The gradient plastic zone model proposed here graphically depicts the dislocations motion, as well as its reinforcement effect. Furthermore, this model lends credence to modify the framework which describes the mechanical response of materials under nanoindentation. [ABSTRACT FROM AUTHOR]

Small regulatory RNAs (sRNAs) play important roles as post-transcriptional regulators throughout the life activities of bacteria. To explore the roles of the regulatory sRNA rli41 identified in Listeria monocytogenes (LM), we analyzed the molecular characteristics and expression profiles of sRNA rli41 during cell infection. Then the deletion strain LM-Δrli41 and complementation strain LM-Δrli41-rli41 were constructed and used to investigate the effects of deficiency of rli41 gene on the adhesion, invasion and pathogenicity of LM. Furthermore, sRNA rli41-regulated potential target genes were predicted in silico, followed by the verification of sRNA-mRNA interaction using a dual plasmid reporter system. The results revealed that sRNA rli41 was highly conserved in LM and its expression level was 15.78-fold up-regulated during cell infection as compared to extracellular environment. Compared with the parental strain and complementation strain, cell adhesion and invasion of the deletion strain were significantly reduced. Moreover, LD50 of LM increased and the pathogenicity weakened significantly due to the deficiency of rli41 genes. Additionally, sRNA rli41 could complementarily base pairing with lmo2178 mRNA 5'-UTR, which could facilitate the expression of peptidoglycan-binding protein Lmo2178, which in turn promotes the cell adhesion, invasion and pathogenicity of LM. Taken together, these findings demonstrated for the first time that the regulatory sRNA rli41 is implicated in cell adhesion, invasion and pathogenicity by modulating the expression of virulence factor Lmo2178 in LM. [ABSTRACT FROM AUTHOR]

During the optimization of 36Cl determination in solid wastes from nuclear decommissioning, a residual 36Cl signal was observed in procedural blanks measured after processing active samples. To uncover the possible causes, we investigated the interaction of chlorine with the components of a Pyrolyser-6 Trio™, as well as the chemicals used during the procedure. Different treatments for identifying the source of chlorine carryover were thoroughly investigated, demonstrating that the 36Cl memory effect arises from the interaction with pyrolyser components and that it occurs almost every time when the analysis procedure is performed. Therefore, results obtained using this analysis procedure need to be corrected for this memory effect by measuring procedural blank samples before and after measuring 36Cl-containing samples. [ABSTRACT FROM AUTHOR]

The method based on Granato's interstitialcy theory, which allows us to calculate the temperature dependence of shear modulus G using experimental calorimetry data, has been successfully tested on a number of bulk metallic glasses. The results of prediction in a wide temperature range, including the crystallization of both initial and relaxed metallic glasses, are presented for the first time. The error in calculating the temperature dependence of the shear modulus of metallic glass during crystallization does not exceed 10%. [ABSTRACT FROM AUTHOR]

The development of high-performance ultraelastic metals with superb strength, a large elastic strain limit and temperature-insensitive elastic modulus (Elinvar effect) are important for various industrial applications, from actuators and medical devices to high-precision instruments1,2. The elastic strain limit of bulk crystalline metals is usually less than 1 per cent, owing to dislocation easy gliding. Shape memory alloys3—including gum metals4,5 and strain glass alloys6,7—may attain an elastic strain limit up to several per cent, although this is the result of pseudo-elasticity and is accompanied by large energy dissipation3. Recently, chemically complex alloys, such as ‘high-entropy’ alloys8, have attracted tremendous research interest owing to their promising properties9–15. In this work we report on a chemically complex alloy with a large atomic size misfit usually unaffordable in conventional alloys. The alloy exhibits a high elastic strain limit (approximately 2 per cent) and a very low internal friction (less than 2 × 10−4) at room temperature. More interestingly, this alloy exhibits an extraordinary Elinvar effect, maintaining near-constant elastic modulus between room temperature and 627 degrees Celsius (900 kelvin), which is, to our knowledge, unmatched by the existing alloys hitherto reported.A chemically complex alloy that exhibits a high elastic strain limit and low internal friction is described; it also has an Elinvar effect (invariant elastic modulus) over a large temperature range, up to 627 °C. [ABSTRACT FROM AUTHOR]

The excess internal energies ΔUQ and excess entropies of ten metallic glasses with respect to their parent crystalline states are determined from calorimetric studies. The elastic energy ΔUel of the subsystem of interstitial defects responsible for relaxation phenomena in metallic glasses according to interstitialcy theory is calculated within this theory using the measured high-frequency shear modulus. It is established that the quantities ΔUQ and ΔUel coincide with each other within an accuracy of no less than 10–15%. It is concluded that the excess internal energy and excess entropy of metallic glasses are due primarily to the elastic energy of the subsystem of interstitial defects. The dissipation of this energy into heat under heating reduces ΔUQ and ΔSQ to zero because of the complete crystallization. The entropy per defect is estimated from calorimetric data as Sd ≈ (20–30)kB, which is characteristic of interstitial defects. [ABSTRACT FROM AUTHOR]

The relaxation of the shear elasticity of high-entropy bulk metallic glasses (HEBMGs) in the initial (as-quenched) and relaxed (aged) states is studied by electromagnetic-acoustic transformation. The experimental results are used to determine the temperature dependences of the changes in the molar concentration of defects and the enthalpy of their formation. The isochronous kinetics of changing the molar enthalpy of HEBMGs is shown to be calculated using independent data on the change in the molar concentration of defects. [ABSTRACT FROM AUTHOR]

A method for calculating the fragility of high-entropy bulk metallic glasses using the data on shear elasticity relaxation in the supercooled liquid range is suggested and verified. [ABSTRACT FROM AUTHOR]

In this paper, we consider the existence of extreme points of analytic α -normal functions. First, in terms of α -normal unit-valued set, we obtain a necessary condition for a little α -normal function to be an extreme point of N 0 , 1 α , where N 0 , 1 α is the unit ball of the class of little α -normal functions in the unit disk; second, we prove that the α -normal unit-valued set of a little α -normal function in N 0 , 1 α consists of several simple closed pairwise disjoint analytic curves and several isolated points. [ABSTRACT FROM AUTHOR]

A method is proposed to calculate the temperature dependence of the unrelaxed shear modulus of high-entropy bulk metallic glasses from differential scanning calorimetry data. The results obtained by this method are shown to be in good agreement with the results of specially performed precision measurements of the unrelaxed shear modulus. [ABSTRACT FROM AUTHOR]

To verify the feasibility of preparing fine equiaxed microstructure of Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy through hot deformation of martensite, the isothermal compression tests with three temperatures 600 , 700 , 800 °C and three strain levels 0.7, 1.1, 1.8 were conducted and its concomitant dynamic recrystallization behavior is studied. As deformed at 700 and 800 °C, the constitutive curves reach the peak stress rapidly and then exhibit continuous softening behavior caused by dynamic recovery and recrystallization until a steady state is reached. The Arrhenius-type hot deformation kinetics model and an Avrami-type dynamic recrystallization kinetics model of martensitic microstructure are built, which generally exhibit satisfactory prediction performance. For the specimen deformed to the strain of 1.8 at 800 °C, full recrystallized microstructure was realized, and the weighted average diameter of α grains is only 1.1 μm. Its compressive yield strength and plasticity reach 1188 MPa and 39.7%, respectively, which shows marvelous high product of strength and plasticity as 47.2 GPa%. To sum up, it is an effective way to prepare fine equiaxed microstructure through hot deformation of martensite. However, the hot deformation process should be precisely controlled to suppress the coarsening of recrystallized grains. [ABSTRACT FROM AUTHOR]

Isotopic ratios of radioactive releases into the environment are useful signatures for contamination source assessment. Uranium is known to behave conservatively in sea water so that a ratio of uranium trace isotopes may serve as a superior oceanographic tracer. Here we present data on the atomic 233 U/ 236 U ratio analyzed in representative environmental samples finding ratios of (0.1–3.7) ⋅ 10 − 2 . The ratios detected in compartments of the environment affected by releases of nuclear power production or by weapons fallout differ by one order of magnitude. Significant amounts of 233 U were only released in nuclear weapons fallout, either produced by fast neutron reactions or directly by 233 U-fueled devices. This makes the 233 U/ 236 U ratio a promising new fingerprint for radioactive emissions. Our findings indicate a higher release of 233 U by nuclear weapons tests before the maximum of global fallout in 1963, setting constraints on the design of the nuclear weapons employed. The dominant emission sources of anthropogenic radionuclides come from either atmospheric nuclear weapons tests or the nuclear industry (i.e., reprocessing plants or reactor accidents). Here, the authors identify a new environmental isotope tracer ( 233 U/ 236 U) which can help distinguish emissions from nuclear weapons tests, and can also provide constraints on past weapon designs and fuel sources, for which many details remain classified or lost. [ABSTRACT FROM AUTHOR]

The preparation of metallic glass matrix composites (MGMCs) requires rapid cooling rate under vacuum conditions, and the amorphous matrix is sensitive to high temperature. For the reasons given above, the process of traditional annealing is rarely chosen for MGMCs. In this work, the influence of high-temperature (i.e. higher than the glass transition temperature) annealing on Ti48Zr18V12Cu5Be17 MGMC was investigated. After high-temperature annealing, breakaway corrosion phenomenon induced by the oxidation matrix have been described. Different deformation mechanisms of the as-cast and annealed specimens upon compressive loading have been probed in the present work. And the microporous microstructure, which stems from oxidation and crystallization of the glass matrix, shows a failure characteristic of MGMCs after high-temperature annealing. [ABSTRACT FROM AUTHOR]

We describe a novel methodology for micron-sized silicon carbide particle production via rapid unloading of high-pressure liquid CO2. The method is based on the physical characteristics of liquid CO2 such as low viscosity, high permeability, and a high dilation coefficient. A series of silicon carbide powdering experiments were performed. The overall process includes water saturation, water and silicon carbide filling, pressure initialization, CO2 filling, high pressure initialization, and CO2 gasification, which is a completely physical process. After high-pressure penetration and CO2 gasification expansion, the silicon carbide will immediately be converted into micron-sized particles. Most importantly, this method is much more effective than the most popular method of SiC synthesis (Acheson method). Laser grain size analysis indicates that the grain size of the silicon carbide particles ranges between 30 and 50 μm, and the percent grain size less than 176.9 μm accounts for 90%. The rapid unloading of high-pressure liquid CO2 method is much more environmentally friendly, efficient, energy saving, and effective. [ABSTRACT FROM AUTHOR]

We describe a novel methodology for micron-sized silicon carbide particle production via rapid unloading of high-pressure liquid CO2. The method is based on the physical characteristics of liquid CO2 such as low viscosity, high permeability, and a high dilation coefficient. A series of silicon carbide powdering experiments were performed. The overall process includes water saturation, water and silicon carbide filling, pressure initialization, CO2 filling, high pressure initialization, and CO2 gasification, which is a completely physical process. After high-pressure penetration and CO2 gasification expansion, the silicon carbide will immediately be converted into micron-sized particles. Most importantly, this method is much more effective than the most popular method of SiC synthesis (Acheson method). Laser grain size analysis indicates that the grain size of the silicon carbide particles ranges between 30 and 50 μm, and the percent grain size less than 176.9 μm accounts for 90%. The rapid unloading of high-pressure liquid CO2 method is much more environmentally friendly, efficient, energy saving, and effective. [ABSTRACT FROM AUTHOR]

The deposition morphology of a landslide dam determines the position of initial breach and sequentially affects the direction of lateral erosion. Twenty-seven discrete element numerical simulations were carried out to investigate the deposition morphology of landslide dams concerning three factors, which include the valley shape, the valley bed inclination and the landslide velocity. The simulation results show that the valley shape and the landslide velocity affect the dam morphology in both transverse and longitudinal directions, while the valley bed inclination mainly affects the longitudinal morphology of dams. Further, a flume experiment was carried out to investigate the specific effects of the dam morphology on the overtopping erosion of landslide dams. The results of experiment show that for the dams in different deposition morphologies and with different initial breaches, the breach widths and the total sediment discharges induced by overtopping erosion are different. [ABSTRACT FROM AUTHOR]

Kengyilia thoroldiana is a nutritionally rich grass species of the Qinghai-Tibet Plateau. Here, to improve its quality and biomass via biological fertilization, we sought out plant-growth promoting rhizobacteria. Our screening found one Bacillus species capable of nitrogen fixation, indole-3-acetic acid production, and tolerating the extreme saline-alkali soil of Qinghai Province. We determined the strain's growth performance and antagonistic effects with pathogens (Fusarium graminearum, F. acuminatum) and evaluated its impact on K. thoroldiana. The test strain KKLW1 was identified as Bacillusamyloliquefaciens by morphology, adversity culture, and 16S rDNA and gyrB partial sequence analyses. KKLW1 strongly tolerates saline conditions (11% salt, pH 11), and showed stable nitrogen fixation activity and IAA production capacity; its Phl gene, which we amplified, was significant antagonistic to pathogenic pasture fungi. Furthermore, compared with the control, the strain showed clear germination and growth-promoting activity after soaking grass seeds and root-irrigating with the Bacillus suspension, increasing each by 8 and 10–12%, respectively. In sum, the strain KKLW1 has excellent biological properties and stable physiological characteristics in this extreme environment of the Qinghai-Tibet Plateau. We propose KKLW1 for use as a functional strain of microbial fertilizer to increase production and restore vegetation coverage of the Plateau's grassland. [ABSTRACT FROM AUTHOR]

Fracture and deformation characteristics of the Ti-based metallic glass matrix composite have been studied by the tensile test and the in situ TEM tension test. Typically, the composite exhibits the high strength and considerable plasticity. Microscopically, it was found that shear deformation zone formed at the crack tip in glass phase, which can bring about quick propagation of shear bands. However, the plastic deformation zone nearby the crack tip in dendrites will postpone or retard the crack extension by dislocations. The attributions of micro-deformations to mechanical properties of composites were discussed. [ABSTRACT FROM AUTHOR]

Based on the constant strain rate compressive experiments to a Zr-based bulk metallic glass, the aspect ratio effects on the statistical properties of serration is systematically investigated. In the plastic deformation state, as the aspect ratio decreases, the stress drop magnitude increases dramatically and the reloading time in one serration event increases significantly. Moreover, distribution of the elastic energy density of each serration event is predicted, which obeys the squared exponential decay law. The size effect law is adopted to describe the serration dynamic-related parametric variation with different aspect ratios. It is noted that the scaling exponent reduces with the increase of the aspect ratio. In general, the effect of aspect ratio on the serration flow could be explained by the shear-band stability index. [ABSTRACT FROM AUTHOR]

Summary: This study evaluated the levels of bone turnover markers (BTMs) and investigated relationships between them and bone mineral density (BMD) in postmenopausal women in China suburban district. The prevalence of osteoporosis was 25.03 % at lumbar spine and 6.23 % at femoral neck, and BTMs were negatively correlated with BMDs. Introduction: The aims of this study were to evaluate the levels of bone turnover markers (BTMs), including serum N-terminal procollagen of type I collagen (P1NP), beta C-terminal cross-linked of type I collagen (β-CTX), 25-hydroxyvitamin D [25(OH)D], and parathyroid hormone (PTH), and to investigate relationships between these markers and bone mineral density (BMD) as well the prevalence of osteoporosis in postmenopausal women of suburban district. Methods: A population of 4822 postmenopausal women aged 55-69 years old (62.22 ± 6.75) from the suburban district was recruited voluntarily. BMD was measured at the lumbar spine, femoral neck, and total hip using dual-energy X-ray absorptiometry; 2251 women in this group had the serum BTMs 25(OH)D and PTH tested. Results: The prevalence of osteoporosis was 25.03 % at lumbar spine and 6.23 % at femoral neck. The median (interquartile range) values of serum P1NP, β-CTX, 25(OH)D, and PTH were 59.3 ng/mL (44.7-75.52), 0.370 ng/mL (0.280-0.490), 23.0 ng/mL (17.1-30.5), and 31.4 pg/mL (24.9-39.7), respectively. Serum P1NP and β-CTX levels presented significantly negative correlations with BMDs at the all the sites (Beta = −0.098 to −0.208, respectively, P < 0.001), whereas PTH levels were negatively correlated with BMDs of the femoral neck and total hip (Beta = −0.062 and −0.054, P < 0.01, respectively). Serum 25(OH)D had positive associations with BMDs at total hip (Beta = 0.051, P < 0.01). Conclusions: The BMD of postmenopausal women in China suburban area is higher than that in downtown area, and over 60 % of the participants had their serum 25(OH)D level over 20 ng/mL. BTMs were negatively correlated with BMDs, suggesting that BTMs are reliable factors for early declines in BMD. [ABSTRACT FROM AUTHOR]

Quasi-static and dynamic deformation behaviors, fracture characteristics, and microstructural evolution of an in situ dendrite-reinforced metallic glass matrix composite: TiZrVCuBe within a wide range of strain rates are investigated. Compared with the quasi-static compression, the yielding stress increases, but the macroscopic plasticity significantly decreases upon dynamic compression. The effects of the strain rate on strain hardening upon quasi-static loading and flow stress upon dynamic loading are evaluated, respectively. The Zerilli-Armstrong (Z-A) model based on dendrite-dominated mechanism is employed to further uncover the dependence of the yielding stress on the strain rate. [ABSTRACT FROM AUTHOR]

Let $${\mathcal S}$$ denote the set of all univalent analytic functions $$f(z)=z+\sum _{n=2}^{\infty }a_n z^n$$ on the unit disk $$\mathbb {D}$$ . In 1946, B. Friedman found that the set $$\mathcal S$$ of those functions which have integer coefficients consists of only nine functions. In 1985, authors determine all functions in $${\mathcal S}$$ whose coefficients are integers in complex quadratic fields. The first aim of this paper is to determine the class of univalent sense-preserving harmonic mappings $$f(z)=z+\sum _{n=2}^{\infty }a_n z^n+\sum _{n=1}^{\infty }\overline{b_n} \overline{z^n}$$ with the coefficients $$a_n$$ , $$b_n$$ , $$n=2, 3, \cdots $$ , in a fixed complex quadratic field $$Q(\sqrt{d}i)$$ , where d is a positive square-free integer. Then, under the condition F is sense-preserving in $$\mathbb {D}$$ and $$h'(z)\ne 0$$ or F is sense-reversing in $$\mathbb {D}$$ and $$g(z)\equiv 0$$ , we determine all univalent biharmonic mappings $$F(z)=|z|^2(h(z)+\overline{g(z)})=|z|^2(z+\sum _{n=2}^{\infty }a_n z^n+\sum _{n=1}^{\infty }\overline{b_n} \overline{z^n})$$ , where $$a_n, b_n\in Q(\sqrt{d}i)$$ , $$n=2, 3, \cdots $$ . [ABSTRACT FROM AUTHOR]

Laboratory experiments are conducted to quantify the mean flow structure and turbulence properties downstream of a spanwise suspended linear array in a uniform ambient water flow using Particle Tracking Velocimetry. Eighteen experimental scenarios, with four depth ratios (array depth to water column depth) of 0.35, 0.52, 0.78, and 0.95 and bulk Reynolds number (length scale is the array depth) from 11,600 to 68,170, are investigated. Three sub-layers form downstream of the array: (1) an internal wake zone, where the time-averaged velocity decreases with increasing distance downstream, (2) a shear layer which increases in vertical extent with increasing distance downstream of the array, and the rate of the increase is independent of the bulk Reynolds number or the depth ratio, and (3) an external wake layer with enhanced velocity under the array. The location of the shear layer is dependent on the depth ratio. The spatially averaged and normalized TKE of the wake has a short production region, followed by a decay region which is comparable to grid turbulence decay and is dependent on the depth ratio. The results suggest that the shear layer increases the transfer of horizontal momentum into the internal wake zone from the fluid outside of the array and that the turbulence in the internal wake zone can be modeled similarly to that of grid turbulence. [ABSTRACT FROM AUTHOR]

Let $${\mathcal S}$$ denote the class of all functions of the form $${f(z)=z+a_2z^2+a_3z^3+\cdots}$$ which are analytic and univalent in the open unit disk $${{\mathbb{D}} }$$ and, for $${\lambda > 0}$$ , let $${\Phi_\lambda (n,f)=\lambda a_n^2-a_{2n-1}}$$ denote the generalized Zalcman coefficient functional. Zalcman conjectured that if $${f\in \mathcal S}$$ , then $${|\Phi_1 (n,f)|\leq (n-1)^2}$$ for $${{n\ge 3}}$$ . The functional of the form $${\Phi_\lambda (n,f)}$$ is indeed related to Fekete-Szegő functional of the $${n}$$ -th root transform of the corresponding function in $${\mathcal S}$$ . This conjecture has been verified for a certain special geometric subclasses of $${\mathcal S}$$ but it remains open for $${f\in {\mathcal S}}$$ and for $${n > 6}$$ . In the present paper, we prove sharp bounds on $${|\Phi_\lambda (n,f)|}$$ for $${f\in \mathcal{F}(\alpha )}$$ and for all $${n\geq 3}$$ , in the case that $${\lambda}$$ is a positive real parameter, where $${ \mathcal{F}(\alpha )}$$ denotes the family of all functions $${f\in {\mathcal S}}$$ satisfying the condition where $${-1/2\leq \alpha < 1}$$ . Thus, the present article proves the generalized Zalcman conjecture for convex functions of order $${\alpha}$$ , $${\alpha \in [-1/2,1)}$$ . [ABSTRACT FROM AUTHOR]

Creep behaviors of an AlCoCrFeNi high-entropy alloy with the body-centered cubic structure were investigated by nanoindentation. The enhanced strain gradient induced by higher strain rate leads to decreased strain rate sensitivity during creep process. The present alloy exhibits excellent creep resistance, mainly due to its large entropy of mixing and highly distorted lattice structure. [ABSTRACT FROM AUTHOR]

The microstructures and properties of high-entropy alloys (HEAs) based on the face-centered cubic and body-centered cubic structures have been studied extensively in the literature, but reports on HEAs in the hexagonal close-packed (HCP) structure are very limited. Using an efficient strategy in combining phase diagram inspection, CALPHAD modeling, and ab initio molecular dynamics simulations, a variety of new compositions are suggested that may hold great potentials in forming single-phase HCP HEAs that comprise rare earth elements and transition metals, respectively. Experimental verification was carried out on CoFeReRu and CoReRuV using X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy. [ABSTRACT FROM AUTHOR]

In this study, nanoindentation tests with continuous stiffness measurement technique were measured to investigate the deformation behavior of a high-entropy alloy AlCoCrFeNi under different indentation strain rates at room temperature. Results suggest that the creep behavior exhibits remarkable strain rate dependence. In-situ scanning images showed a conspicuous pileup around the indents, indicating that an extremely localized plastic deformation occurred during the nanoindentation. Under different strain rates, elastic modulus basically remains unchanged, while the hardness decreases with increasing indentation depth due to the indentation size effect. Furthermore, the modulus and hardness of AlCoCrFeNi HEAs are greater than that of the AlCoCrFeNi ( x = 0.3,0.5) at the strain rate of 0.2 s due to its higher negative enthalpy of mixing related to the atomic binding force, and the solid solution strengthening induced by the lattice distortion, respectively. [ABSTRACT FROM AUTHOR]

A systematic study on the thermal properties, deformation behaviors, and thermal workability of ZrCuNiAl bulk metallic glass (BMG) was conducted in the supercooled liquid region (SLR) with strain rates ranging from 2.5 × 10 to 5 × 10 s. The strain-rate jump experimental results show that the homogeneous deformation behavior transforms from non-Newtonian flow to Newtonian flow with decreasing strain rate as well as elevating temperature. In the framework of the Kissinger and free-volume model, this phenomenon can be explained by the transition state theory. The values of the activation volume and activation energy of the BMG are obtained, which are consistent with other BMGs. The optimum domain for thermal workability of the metallic glass has been located by the power dissipation efficiency map where the power dissipation efficiency is larger than 0.8. [ABSTRACT FROM AUTHOR]

High-entropy alloys with composition of AlCoCrFeNiTi ( x: molar ratio; x = 0, 0.2, 0.4) under quasi-static and dynamic compression exhibit excellent mechanical properties. A positive strain-rate sensitivity of yield strength and the strong work-hardening behavior during plastic flows dominate upon dynamic loading in the present alloy system. The constitutive relationships are extracted to model flow behaviors by employing the Johnson-Cook constitutive model. Upon dynamic loading, the ultimate strength and fracture strain of AlCoCrFeNiTi alloys are superior to most of bulk metallic glasses and in situ metallic glass matrix composites. [ABSTRACT FROM AUTHOR]

The electrochemical corrosion behaviors of TiZrVCuBe in situ dendrite-reinforced metallic glass matrix composites (MGMCs) were investigated by potentiodynamic polarization experiments and electrochemical impedance spectroscopy in acidic, salty, and alkaline solutions. TiZrVCuBe in situ dendrite-reinforced MGMCs have an impressive corrosion resistance in strong acidic environment, while their performance was not so great in strong alkaline environment. Further immersion test in same solutions revealed similar chemical corrosion behaviors. XRD and SEM examinations were conducted to check the structure and surface modification of the material during the corrosion process. EDS test indicated that the amorphous matrices, which show excellent corrosion resistance, have a considerable composition variation from its crystalline dendrites counterpart. [ABSTRACT FROM AUTHOR]

In situ high-energy synchrotron X-ray diffraction experiments and micromechanics-based finite element simulations have been conducted to examine the lattice-strain evolution in metallic-glass-matrix composites (MGMCs) with dendritic crystalline phases dispersed in the metallic-glass matrix. Significant plastic deformation can be observed prior to failure from the macroscopic stress-strain curves in these MGMCs. The entire lattice-strain evolution curves can be divided into elastic-elastic (denoting deformation behavior of matrix and inclusion, respectively), elastic-plastic, and plastic-plastic stages. Characteristics of these three stages are governed by the constitutive laws of the two phases (modeled by free-volume theory and crystal plasticity) and geometric information (crystalline phase morphology and distribution). The load-partitioning mechanisms have been revealed among various crystalline orientations and between the two phases, as determined by slip strain fields in crystalline phase and by strain localizations in matrix. Implications on ductility enhancement of MGMCs are also discussed. [ABSTRACT FROM AUTHOR]

Intermittent or serrated plastic flows have been widely observed in irreversible deformation through shear banding in bulk metallic glasses (BMGs). The strain-rate-dependent plasticity under uniaxial compression at 2 × 10, 2 × 10, and 2 × 10 s in a Zr-based BMG is investigated. Serration events have a typical time scale at a relatively higher strain rate (2 × 10 s), while at lower strain rates, there is a lack of typical time scale. During serrations, the stress is falling rapidly, and the amplitude of the stress drop between the neighboring serrations is approximately equal. The stress drop vs time satisfies the exponential decay rule during jerk flows. Due to the serrated flow corresponding to the internal shear process, the free-volume model and stick-slip model are introduced to explain how the shear bands form and propagate and the cooperation of multiple shear bands. The mechanism is explained by relating the atomic-scale deformation with the macroscopic shear-band behavior, offering key ingredients to fundamentally cognize serrations in jerk flows. [ABSTRACT FROM AUTHOR]

Many materials are known to deform under shear in an intermittent way with slip avalanches detected as acoustic emission and serrations in the stress-strain curves. Similar serrations have recently been observed in a new class of materials, called high-entropy alloys (HEAs). Here, we discuss the serration behaviors of several HEAs from cryogenic to elevated temperatures. The experimental results of slow compression and tension tests are compared with the predictions of a slip-avalanche model for the deformation of a broad range of solids. The results shed light on the deformation processes in HEAs. Temperature effects on the distributions of stress drops and the decrease of the cutoff (i.e., of the largest observed slip size) for increasing temperature qualitatively agree with the model predictions. The model is used to quantify the serration characteristics of HEAs, and pertinent implications are discussed. [ABSTRACT FROM AUTHOR]

In this study, new Ti-based metallic glass matrix composites (MGMCs) are fabricated, which contains ~41 vol pct of large dendrites with a size of ~0.8 to 1.2 μm, The newly developed Ti-based MGMCs exhibit excellent tensile strength of ~1650 MPa and a tensile strain of ~2.5 pct at room temperature. During tensile deformation, the work hardening is scarcely found in this alloy. Thus, the deformation of the in situ MGMC is simply described with two stages: (1) elastic and (2) softening deformation stages. Two simple models are adapted to simulate each stage. In the supercooled liquid region [at 613 K (340 °C)], superplastic homogeneous deformation, which is the feature of monolithic bulk metallic glasses, is not observed. The mechanical properties at 613 K (340 °C) are sensitive to the strain rates, the yield strength drops from 1390 to 960 MPa, when the strain rate decreases from 1 × 10 to 1 × 10/s, while the displacement is almost increased by twofold. [ABSTRACT FROM AUTHOR]

In situ Ti-based metallic glass matrix composites are fabricated by the Bridgman solidification, and the mechanical properties are investigated. The fine dendrites about 2 to 10 μm are uniformly distributed in the glass matrix. The compressive results show that the composites have high strength and large plasticity. The fracture strength for the composite at the withdrawal velocity of 1.6 mm/s is as high as 3000 MPa and the total fracture strain is up to 31.5 pct. Particularly, the dendrite size of the current composite would decrease with the increasing of the withdrawal velocity, which leads to the higher yield strength. [ABSTRACT FROM AUTHOR]

A promoter was cloned from Ustilaginoidea virens, a rice false smut fungus. A U. virens mutant library was constructed using a promoter-trapping vector harboring the enhanced green fluorescent protein (egfp) as reporter. Six transformants emitting green fluorescence were screened from 6,500 transformants. One transformant, A880-1, which grew slower and generated more conidia, was chosen for further studies. The insertion of T-DNA in A880-1 was validated by PCR, and the copy number was defined by Southern blot analysis. High-efficiency thermal asymmetric interlaced PCR (hi-TAIL PCR) yielded a 2,038 bp long sequence cloned from genome DNA of A880-1, this sequence being upstream of egfp in T-DNA. The 1,045 bp long upstream region of egfp was used for analysis. This sequence consisted of a CAAT-box, a TATA-box, three TATA-box-like structures, and four other potential eukaryotic regulator elements. This promoter, designated as puv880 (GenBank accession No. KC355189), was the first promoter isolated from U. virens. Four different constructs carrying different 5' deletions of this promoter, along with the downstream egfp sequence, were obtained and transformed into Magnaporthe oryzae strain Guy11 through PEG-mediated transformation to identify the smallest functional promoter region of puv880. All constructs exhibited promoter activity, and the smallest deletion was no more than 444 bp in size. Compared with the wild-type strain 70-22, the growth of A880-1 was slower and produced more conidia at the terminal of hyphae on minimal medium. Studying puv880 can facilitate the understanding of the conidiation and mycelium growth of U. virens. [ABSTRACT FROM AUTHOR]