Search

• Filling improved the deformation capacity and water-blocking effect of cracked sandstone and reduced its anisotropic permeability. • The crack-tip stress intensity factor under seepage-creep was derived. • The creep/permeability properties of cracked sandstone were mainly affected by the filling state. Artificially filled cracked sandstone specimens were subjected to creep tests under multi-level loading of the seepage pressure to reveal the creep behavior, permeability characteristics, and crack initiation mechanism of the filled cracked sandstone under creep paths driven primarily by the seepage pressure. The results show that both filled and unfilled cracked sandstone specimens underwent three stages of creep: initial creep, steady-state creep, and accelerated creep, under multi-level loading of the seepage pressure along creep paths. Shear failure was the main type of failure observed in the specimens. Filling improved the deformation capacity of cracked sandstone, enhanced the water-blocking effect, and reduced the anisotropy of its permeability. At the same seepage pressure, the water-blocking effect of filling increased, then decreased with increasing crack inclination angle. The crack-tip stress intensity factor under seepage-creep was derived, and the strength criterion and critical seepage pressure for crack initiation under the coupled effects of creep and permeability were proposed. High seepage pressure was found to be more likely to initiate cracks and propagate wing-cracks under the coupled effects of creep and permeability. With increasing crack inclination angle, the crack initiation strength and critical seepage pressure decreased, then increased, while the length of wing-crack propagation first increased, then decreased. Grey relational analysis was applied to determine the relationship between the filling state and crack inclination angle. The filling state was found to be the main controlling factor that affects the creep and permeability properties of cracked sandstone, followed by the crack inclination angle. [ABSTRACT FROM AUTHOR]

Catalytic decomposition of hydrazine monohydrate (N 2 H 4 ·H 2 O) represents a promising hydrogen storage/production technology. Nowadays, the development of N 2 H 4 decomposition catalysts is sluggish due primarily to a lack of universal screening rules. Herein, with the aid of first-principles calculations, we identify a reliable descriptor, N 2 H 4 adsorption energy, to properly address N 2 H 4 decomposition kinetics on TM catalysts. Particularly, we extract linear scaling relations between the adsorption energetics of key intermediates, H (and N 2 H 3) vs. NH 2 that exert a fundamental limitation on the H 2 selectivity of N 2 H 4 decomposition over elementary transition metal catalysts. We propose that catalysts with optimum H 2 selectivity may be achieved by independently stabilizing and destabilizing adsorption of H (or N 2 H 3 , or both) and NH 2 , respectively. The disclosed dissociation behaviors of N 2 H 4 and their physical origins are expected to advance the rational design of advanced catalysts for selectively promoting H 2 production from N 2 H 4. The linear scaling relations are expected to advance the rational design of catalysts for selectively promoting H 2 production from N 2 H 4. Image 1 • The N–N bond cleavage dominates the N 2 H 4 decomposition on MoC(111) surface. • A descriptor was identified to address N 2 H 4 decomposition kinetics. • The selectivity is limited by the scaling between energetics of H (N 2 H 3) and NH 2. [ABSTRACT FROM AUTHOR]

The matrix effect is one of the main bottlenecks for the laser-induced breakdown spectroscopy (LIBS) technique. In this work, image-assisted, laser-induced breakdown spectroscopy (IA-LIBS) based on the Lomakin-Scherbe formula was put forward as a correction to the matrix effect. The brightness and area information in the plasma image was extracted to correct the spectral line intensities among which the brightness information characterizes the plasma temperature, and the area information characterizes the ablative mass. To verify the feasibility of this method, the experiment was conducted on metal samples and pressed samples. The method was applied for quantitative analysis of copper (Cu), magnesium (Mg) in metal samples and chromium (Cr), manganese (Mn) in pressed samples. For the metal samples, after correcting the matrix effect by IA-LIBS, the determination coefficient R squared (R2) of Cu I 510.55 nm and Mg I 518.36 nm calibration curves were increased from 0.726 to 0.942 to 0.992 and 0.988, respectively. The root-mean-square-error of cross-validation (RMSECV) and the average relative error (ARE) decreased by 75.10% and 77.18%, respectively. For the pressed samples, R2 of Cr I 520.84 nm and Mn I 403.07 nm calibration curves corrected by IA-LIBS increased from 0.364 to 0.098 to 0.975 and 0.980; and RMSECV and ARE decreased by 77.88% and 83.83%, respectively. The experimental results showed that IA-LIBS had an obvious improvement on elimination of the matrix effect for the different samples and the different elements. Therefore, IA-LIBS will become a promising technology and will greatly promote the development of LIBS in various fields. Image 1 • Correcting the matrix effect is always a big challenge in LIBS. • Image-assisted laser-induced breakdown spectroscopy (IA-LIBS) was proposed to correct the matrix effect. • The plasma image is easily acquired and can directly reflect the shape, brightness and other information of the plasma. • IA-LIBS can effectively eliminate the matrix effect, and it is suitable for different samples and different elements. [ABSTRACT FROM AUTHOR]

Abstract Alzheimer's disease (AD) is the most common cause of dementia in the elderly. It shares clinical and pathological features with other types of dementia, such as vascular dementia (VaD), Lewy body dementia (LBD), and frontotemporal dementia (FTD). We have hypothesized that there might be an overlapping molecular mechanism and genetic basis to the different types of dementia. In this study, we analyzed the mutation pattern of dementia-causal genes in 169 Han Chinese patients with familial and early-onset AD by using whole exome sequencing or targeted resequencing. We identified 9 potentially pathogenic mutations in the AD-causal genes APP , PSEN1 , PSEN2 , and 6 mutations in a group of non-AD dementia-causal genes including the FTD-causal gene GRN and the VaD-causal gene NOTCH3. A common splice-site variant rs514492 in the FTD-causal gene VCP showed a positive association with AD risk (P = 0.0003, OR = 1.618), whereas the rare missense variant rs33949390 (p. R 1628P) in the LBD-causal gene LRRK2 showed a protective effect on AD risk (P = 0.0004, OR = 0.170). The presence of putative pathogenic mutations and risk variants in these causal genes for different types of dementia in clinically diagnosed familial and early-onset AD patients suggests a need to screen for mutations of the dementia-causal genes in cases of AD to avoid misdiagnosis. These mutations also support the idea that there are overlapping pathomechanisms between AD and other forms of dementia. [ABSTRACT FROM AUTHOR]

In this paper, instability boundaries of axially accelerating plates with internal resonance are investigated for the first time. The relation between the acceleration and the longitudinally varying tensions are introduced. The governing equation and the corresponding boundary conditions are derived from the generalized Hamilton principle. The effects of internal resonances and the nonhomogeneous boundary conditions on the instability boundaries are highlighted. By the method of multiple scales, the modified solvability conditions in principal parametric and internal resonances are established. The Routh-Hurwitz criterion is introduced to determine the instability boundaries. The effects of the viscoelastic coefficient and the viscous damping coefficient on the instability boundaries are examined. Abnormal instability boundaries are detected when the internal resonance is introduced. The phenomenon of local zigzag and V-shape boundaries are explained from the viewpoint of modal interactions. The numerical calculations of the differential quadrature schemes about the first four complex frequencies, the first four complex modes, and the stability boundaries are used to confirm the results of the analytical method. • Abnormal instability boundaries of axially accelerating plates with internal resonance are analytically and numerically investigated. • The effects of internal resonances and the nonhomogeneous boundary conditions on the instability boundaries are highlighted. • Numerical integrations via the differential quadrature support results via the method of multiple scales. [ABSTRACT FROM AUTHOR]

Highlights • An efficient protocol for the high-frequency regeneration of Neolamarckia cadamba use leaf as explant is established. • Based on this highly efficient regeneration protocol, an Agrobacterium tumefaciens -mediated genetic transformation system was successfully developed for N. cadamba. • We constructed a modified binary vector pCAMBIA1305 containing GUS and YFP report genes, which can help us to detect the transformants as soon as possible. • By adopting this protocol, positive transformed plants could be obtained within three months. Abstract Neolamarckia cadamba is a miracle tree species with considerable economic potential used as a timber wood, woody forage and traditional medicine resource. The present study aimed to establish an efficient protocol of plant regeneration and Agrobacterium -mediated genetic transformation for N. cadamba. Greenish callus were induced from different type explants when cultured on Murashige and Skoog's (MS) medium supplemented with thidiazuron (TDZ) and kinetin (KT). The callus could differentiate into somatic embryos or adventitious shoots, and these two regeneration pathways often occurred in the same callus clumps. It was found that MS medium supplemented with 2 mg/L TDZ, 0.2 mg/L KT provided the most suitable medium for leaf explants to induce adventitious shoot, delivering a maximum regeneration frequency with a mean of 8.2 shoots per explant. The micro-shoots developed roots in MS supplemented with 0.05 mg/L α-naphthaleneacetic acid (NAA), and could be successfully acclimatized to a greenhouse with more than 90% survival. Based on this regeneration protocol, an Agrobacterium tumefaciens -mediated genetic transformation system was successfully developed for N. cadamba. Genetic transformation was obtained through the infection of leaf with A. tumefaciens strain GV3101 harboring a modified binary vector pCAMBIA1305 containing the marker genes β-glucuronidase (GUS) and fluorescent protein YFP. The presence of GUS in transformed plants was confirmed using PCR and histological stain, while the expression of YFP was confirmed through fluorescent microscopy and RT-PCR. Out of 276 putative transformants, 15 plants were found to be positive transgenic. Nevertheless, by adopting this protocol, positive transformed plants could be obtained within three months. [ABSTRACT FROM AUTHOR]

Aims Astragaloside IV (AS-IV) is the central active component extracted from Radix astragali , an herbal remedy widely used in traditional Chinese medicine for the treatment of cardiovascular diseases. Aberrant proliferation of vascular smooth muscle cells (VSMCs) is closely involved in the initiation and progression of cardiovascular complications, such as atherosclerosis. Here we investigated whether AS-IV inhibited agonist-induced vascular smooth muscle cells (VSMCs) proliferation and the underlying mechanism. Main methods Quiescent cultured A10 cells (adult rat VSMCs) were treated with Angiotensin II (AngII) or AngII plus AS-IV for 48 h. The growth rate of A10 cells was analyzed by CCK8 assay. RT-PCR analysis was carried out to examine the expression of α-smooth muscle actin (α-SMA), an important phenotypic modulation marker. In addition, whether the interference of AS-IV on AngII-mediated growth of VSMCs via regulation of cell cycle was evaluated by flow cytometry. In order to explore the role of cell cycle machinery, we measured kinase activity of CDK2 by Kinase assay and the protein level of Cdc25 by western blot, respectively. Key findings These data suggested that AS-IV exerted beneficial effects on AngII -induced abnormal growth in rat VSMCs through disturbing cell cycle, especially block G1/S transition by attenuating CDK2 activity, which may hinder the process of pathological vascular remodeling during atherosclerosis. [ABSTRACT FROM AUTHOR]

• A new nonlinear creep model is constructed based on the memory-dependent derivative. • The memory-dependent creep model can well characterize the accelerated creep of rocks. • The memory-dependent creep model has higher accuracy and wider applicability than other models. The creep behavior of soil and rock exhibits significant time-dependence and non-linearity, which are difficult to capture using traditional composite element models. In the framework of memory-dependent derivative theory, a memory-dependent visco-pot element with non-linear creep behavior, no instantaneous deformation, elastic after-effect, and stress relaxation is proposed. By connecting a memory-dependent visco-pot element with strain triggering to the Nishihara model, a memory-dependent derivative creep model is developed and its constitutive equation is derived. The creep test data pertaining to coal, salt, sandstone, and olivine rock are used to validate the model, which can describe the initial creep, steady-state creep, and non-linear accelerated creep deformation characteristics of various soil and rock materials. Comparison with fractional-order models, improved Nishihara models, and Hehai models shows that our model has better fitting results and is more advantageous in characterizing the non-linear features of soil and rock during the accelerated creep stage. [ABSTRACT FROM AUTHOR]