Stability criteria for a class of MIMO networked control systems with network constraints
2009 IEEE International Conference on Systems, Man and Cybernetics, 2009
ABSTRACT This paper is concerned with the stability analysis for a class of MIMO networked contro... more ABSTRACT This paper is concerned with the stability analysis for a class of MIMO networked control systems (NCSs) with network constraints. In view of MIMO NCSs where network is of limited access channels, a discrete-time switched delay model is formulated. By constructing a novel piecewise Lyapunov-Krasovskii functional, a new stability criterion is developed in terms of linear matrix inequalities. A numerical example is given to show the effectiveness of the proposed method.
Cardiovascular disease (CVD) remains a leading cause of mortality worldwide despite advances in i... more Cardiovascular disease (CVD) remains a leading cause of mortality worldwide despite advances in its prevention and management. A comprehensive understanding of factors which contribute to CVD is required in order to develop more effective treatment options. Dysregulation of epigenetic posttranscriptional modifications of histones in chromatin is thought to be associated with the pathology of many disease models, including CVD. Histone acetyltransferases (HATs) and deacetylases (HDACs) are regulators of histone lysine acetylation. Recent studies have implicated a fundamental role of reversible protein acetylation in the regulation of CVDs such as hypertension, pulmonary hypertension, diabetic cardiomyopathy, coronary artery disease, arrhythmia, and heart failure. This reversible acetylation is governed by enzymes that HATs add or HDACs remove acetyl groups respectively. New evidence has revealed that histone acetylation regulators blunt cardiovascular and related disease states in ce...
Piperlongumine attenuates collagen-induced arthritis via expansion of myeloid-derived suppressor cells and inhibition of the activation of fibroblast-like synoviocytes
Molecular medicine reports, 2015
Piperlonguminine (PL), a key compound from the Piper longum fruit, is known to exhibit anti‑tumor... more Piperlonguminine (PL), a key compound from the Piper longum fruit, is known to exhibit anti‑tumor and anti‑inflammatory activities. However, little is known about its effects on collagen‑induced arthritis (CIA). Fibroblast‑like synoviocytes (FLS) have a pivotal role in the development of rheumatoid arthritis (RA). Myeloid‑derived suppressor cells (MDSCs) are able to suppress T cell responses and have important roles in the regulation of autoimmune arthritis. The current study investigated whether PL alters the progression of RA. It was determined that PL reduces the arthritis score and histopathologic lesions in a mouse model of CIA. PL also reduces the expression levels of serum anti‑collagen II antibodies (anti‑CⅡ), tumor necrosis factor‑α (TNF‑α), interleukin (IL)‑1β, IL‑23 and IL‑17 in CIA mice. In draining lymph nodes (DLNs), MDSCs were significantly expanded, however, the number of Th17 cells was markedly decreased by PL treatment. Additionally, PL reduced secretion of IL‑1β, ...
Understanding the impact of grazing intensity on grassland production and soil fertility is of fu... more Understanding the impact of grazing intensity on grassland production and soil fertility is of fundamental importance for grassland conservation and management. We thus compared three types of alpine steppe management by studying vegetation traits and soil properties in response to three levels of grazing pressure: permanent grazing (M1), seasonal grazing (M2), and grazing exclusion (M3) in the alpine steppe in Xainza County, Tibetan Plateau. The results showed that community biomass allocation did not support the isometric hypothesis under different grassland management types. Plants in M1 had less aboveground biomass but more belowground biomass in the top soil layer than those in M2 and M3, which was largely due to that root/shoot ratios of dominant plants in M1 were far greater than those in M2 and M3. The interramet distance and the tiller size of the dominant clonal plants were greater in M3 than in M1 and M2, while the resprouting from rhizome buds did not differ significantl...
Many studies have focused on the relationship between vegetation biomass and environmental factor... more Many studies have focused on the relationship between vegetation biomass and environmental factors in grassland. However, several questions remain to be answered, especially with regards to the spatial pattern of vegetation biomass. Thus, the distributed mechanism will be explored in the present study. Here, plant biomass was measured at 23 sites along a transect survey during the peak growing season in 2006. The data were analyzed with a classification and regression tree (CART) model. The structural equation modeling (SEM) was conducted to explicitly evaluate the both direct and indirect effects of these critical environmental elements on vegetation biomass. The results demonstrated that mean annual temperature (MAT) affected aboveground biomass (AGB) scored at -0.811 (P<0.05). The direct effect of MAT on belowground biomass (BGB) was -0.490 (P<0.05). The results were determined by SEM. Our results indicate that AGB and BGB in semi-arid ecosystems is strongly affected by pre...
Diode-end-pumped high-efficiency single-and dual-wavelength Nd : GdVO 4 lasers have been demonstr... more Diode-end-pumped high-efficiency single-and dual-wavelength Nd : GdVO 4 lasers have been demonstrated. For the single-wavelength operation, the maximum cw output powers of 15.6 W (M 2 = 1.54) at 1063 nm and 7.5 W (M 2 = 1.40) at 1342 nm were achieved under the highest available pump power of 26.5 W, having the respective opticalto-optical conversion efficiencies of 59.2% and 28.2% as well as the average slope efficiencies of 65.1% and 32.2%. For the dual-wavelength operation, under the available pump power of 12.6 W, we obtained the average power outputs of 1.0 W (M 2 = 4.85) at 1063 nm and 1.4 W (M 2 = 3.22) at 1342 nm with the respective pulse durations of 23 ns and 53 ns for quasicw operation, and the power outputs of 1.8 W (M 2 = 5.35) at 1063 nm and 2.0 W (M 2 = 4.76) at 1342 nm for cw operation. PACS 42.65.Ky; 42.79.Nv; 42.70.Mp
Optical properties of heterodiamond B2CN using first-principles calculations
APPLIED PHYSICS LETTERS, 2004
... electron energy-loss spectrum L( ) can be deduced from 1( ) and 2( ).17,18 As sup-portive evi... more ... electron energy-loss spectrum L( ) can be deduced from 1( ) and 2( ).17,18 As sup-portive evidence, we calculate 2( ) and 1( ) of the known cubic diamond, which are in ... eV below the bottom 4.44 eV of CBs corresponds to the intraband transitions from 2p VBs of B and C to EBs. ...
Ab initio investigations of optical properties of the high-pressure phases of ZnO
PHYSICAL REVIEW B, 2005
We present a detailed investigation on optical properties of high-pressure phase ZnO in B1 (NaCl)... more We present a detailed investigation on optical properties of high-pressure phase ZnO in B1 (NaCl) and B2 (CsCl) structures, including dielectric function, refractive index, absorption, and electron energy-loss spectrum. Theoretical calculations are performed using the ab initio ...
Bond ionicities and hardness of B13C2-like structured ByX crystals (X=C,N,O,P,As)
PHYSICAL REVIEW B, 2006
ABSTRACT Based on the fact that ionicity exists in chemical bonds between identical atoms in alph... more ABSTRACT Based on the fact that ionicity exists in chemical bonds between identical atoms in alpha -boron, investigation has been performed on the influences of X atoms on the ionicities of B-B bonds in B13C2 -like structured ByX ( X=C , N, O, P, and As) compounds. For the four types of B-B bonds in the B12 icosahedra of the ByX compounds, their overlap population P , population ionicity fh , and Phillips ionicity fi have been calculated. Comparing to the overlap population Pc value for the structure of the regular B12 icosahedron, the difference between P and Pc in the distorted B12 icosahedron and its origin have been discussed. Our results have shown that the charge transfer occurs between Bp and Be atoms in the distorted B12 icosahedra of ByX crystals, different from the alpha -boron. Electronegativity of the X atom in ByX crystals plays an important role in the ionicities of B-B bonds in the icosahedra. Among the five investigated ByX crystals, the largest ionicity of 0.449 has been found to exist in the Bp-Be bond in the B6O crystal, which is comparable to that found in AlN . By taking into account the effect of the ionicities of B-B bonds in the B12 icosahedra on hardness, the calculated hardness is in agreement with the experimental values for B6O and B13C2 . In addition, the calculations of hardness indicate that B6N is a potential superhard material, but B6P and B6As are not.
Based on first-principles calculation, we predict a tetragonal phase of BC 2 N ͑t-BC 2 N͒, which ... more Based on first-principles calculation, we predict a tetragonal phase of BC 2 N ͑t-BC 2 N͒, which matches the experiment well because the estimated Vickers hardness and the simulated X-ray diffraction ͑XRD͒ and Raman patterns are in excellent agreement with the experimental results besides the low total energy and formation energy. In particular, we acquire the underlying physics behind the apparent lack of the transverse optical mode in the measured Raman spectrum and find the interesting electronic structure transition among the polymorph of superhard BC 2 N compounds.
Computational searches for structures of solid oxygen under pressures in the multi TPa range have... more Computational searches for structures of solid oxygen under pressures in the multi TPa range have been carried out using density-functional-theory methods. We find that molecular oxygen persists to about 1.9 TPa at which it transforms into a semiconducting square spiral-like polymeric structure (I41/acd) with a band gap of ∼3.0 eV. Solid oxygen forms a metallic zig-zag chain-like structure (Cmcm) at about 3.0 TPa, but the chains in each layer gradually merge as the pressure is increased and a structure of F mmm symmetry forms at about 9.5 TPa in which each atom has four nearest neighbors. The superconducting properties of molecular oxygen do not vary much with compression, although the structure becomes more symmetric. The electronic properties of oxygen have a complex evolution with pressure, swapping between insulating, semiconducting and metallic.
Type 2 diabetes mellitus (T2DM) significantly increases risk for vascular complications. Diabetes... more Type 2 diabetes mellitus (T2DM) significantly increases risk for vascular complications. Diabetes-induced aorta pathological changes are predominantly attributed to oxidative stress. Nuclear factor E2-related factor-2 (Nrf2) is a transcription factor orchestrating antioxidant and cytoprotective responses to oxidative stress. Sulforaphane protects against oxidative damage by increasing Nrf2 expression and its downstream target genes. Here we explored the protective effect of sulforaphane on T2DM-induced aortic pathogenic changes in C57BL/6J mice which were fed with high-fat diet for 3 months, followed by a treatment with streptozotocin at 100 mg/kg body weight. Diabetic and nondiabetic mice were randomly divided into groups with and without 4-month sulforaphane treatment. Aorta of T2DM mice exhibited significant increases in the wall thickness and structural derangement, along with significant increases in fibrosis (connective tissue growth factor and transforming growth factor), inf...
Differential expression of Axin1, Cdc25c and Cdkn2d mRNA in 2-cell stage mouse blastomeres
Zygote, 2012
There is increasing evidence to show that 2-cell stage mouse blastomeres have differing developme... more There is increasing evidence to show that 2-cell stage mouse blastomeres have differing developmental properties. Additionally, it has been suggested that such a difference might be due to their distribution of mRNA and/or protein asymmetry. However, to date, the exact genes that are involved in the orientation and order of blastomere division are not known. In this study, some differentially expressed transcripts were identified. Axin1, cell division cycle 25 homolog C (Cdc25c) and cyclin-dependent inhibitor 2D (Cdkn2d) were selected for validation by real-time polymerase chain reaction (PCR) based on published data. Our real-time PCR results demonstrated that Axin1, Cdc25c and Cdkn2d genes had different levels of expression among blastomeres of the mouse 2-cell embryo i.e. the level of Axin1 mRNA was significantly higher in one blastomere when compared with the other blastomeres of the 2-cell embryo (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). The variation in Cdc25c (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) and Cdkn2d (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01) mRNA expression followed a similar trend to that of Axin1. In addition, the highest levels of expression of these three genes were detected in the same blastomere in the 2-cell embryo. We confirmed that there was an asymmetrical distribution pattern for Axin1, Cdc25c and Cdkn2d transcripts in 2-cell embryos. In conclusion, this study demonstrated clearly that there is embryonic asymmetry at the 2-cell stage and that these differentially expressed genes may result in differentiation in expression in embryo development.
carbons (-20+ 100 mesh; 0.149-0.84 mm) were produced by physical activation and chemical activati... more carbons (-20+ 100 mesh; 0.149-0.84 mm) were produced by physical activation and chemical activation with KOH from an Illinois bituminous coal (IBC-106) for natural gas storage. The products were characterized by BET surface area, micropore volume, bulk density, and methane adsorption capacities. Volumetric methane adsorption capacities (V,/V,) of some of the granular carbons produced by physical activation are about 70 cm3/cm3 which is comparable to that of BPL, a commercial activated carbon. V,,,/V, values above 100 cm3/cm3 are obtainable by grinding the granular products to -325 mesh (co.044 mm). The increase in l/,/V, is due to the increase in bulk density of the carbons. Volumetric methane adsorption capacity increases with increasing pore surface area and micropore volume when normalizing with respect to sample bulk volume. Compared with steam-activated carbons, granular carbons produced by KOH activation have higher micropore volume and higher methane adsorption capacities (g/g). Their volumetric methane adsorption capacities are lower due to their lower bulk densities.
Proceedings of the National Academy of Sciences, 2009
Understanding the structural transformations of solid CO2 from a molecular solid characterized by... more Understanding the structural transformations of solid CO2 from a molecular solid characterized by weak intermolecular bonding to a 3-dimensional network solid at high pressure has challenged researchers for the past decade. We employ the recently developed metadynamics method combined with ab initio calculations to provide fundamental insight into recent experimental reports on carbon dioxide in the 60 -80 GPa pressure region. Pressure-induced polymeric phases and their transformation mechanisms are found. Metadynamics simulations starting from the CO 2-II (P42/mnm) at 60 GPa and 600 K proceed via an intermediate, partially polymerized phase, and finally yield a fully tetrahedral, layered structure (P-4m2). Based on the agreement between calculated and experimental Raman and X-ray patterns, the recently identified phase VI [Iota V, et al. (2007) Sixfold coordinated carbon dioxide VI. Nature Mat 6:34 -38], assumed to be disordered stishovite-like, is instead interpreted as the result of an incomplete transformation of the molecular phase into a final layered structure. In addition, an ␣-cristobalite-like structure (P41212), is predicted to be formed from CO2-III (Cmca) via an intermediate Pbca structure at 80 GPa and low temperatures (<300 K). Defects in the crystals are frequently observed in the calculations at 300 K whereas at 500 to 700 K, CO2-III transforms to an amorphous form, consistent with experiment [Santoro M, et al. (2006) Amorphous silica-like carbon dioxide. Nature 441:857-860], but the simulation yields additional structural details for this disordered solid.
Alpine steppe is considered to be the largest grassland type on the Tibetan Plateau. This grassla... more Alpine steppe is considered to be the largest grassland type on the Tibetan Plateau. This grassland contributes to the global carbon cycle and is sensitive to climate changes. The allocation of biomass in an ecosystem affects plant growth and the overall functioning of the ecosystem. However, the mechanism by which plant biomass is allocated on the alpine steppe remains unclear. In this study, biomass allocation and its relationship to environmental factors on the alpine grassland were studied by a meta-analysis of 32 field sites across the alpine steppe of the northern Tibetan Plateau. We found that there is less above-ground biomass (M A ) and below-ground biomass (M B ) in the alpine steppe than there is in alpine meadows and temperate grasslands. By contrast, the root-to-shoot ratio (R:S) in the alpine steppe is higher than it is in alpine meadows and temperate grasslands. Although temperature maintained the biomass in the alpine steppe, precipitation was found to considerably influence M A , M B , and R:S, as shown by ordination space partitioning. After standardized major axis (SMA) analysis, we found that allocation of biomass on the alpine steppe is supported by the allometric biomass partitioning hypothesis rather than the isometric allocation hypothesis. Based on these results, we believe that M A and M B will decrease as a result of the increased aridity expected to occur in the future, which will reduce the landscape's capacity for carbon storage.
Improved stability criteria for neural networks with time-varying delay
Physics Letters A, 2009
ABSTRACT The problem of the stability analysis of neural networks with time-varying delay is cons... more ABSTRACT The problem of the stability analysis of neural networks with time-varying delay is considered in this Letter. By constructing a new augmented Lyapunov functional which contains a triple-integral term, an improved delay-dependent stability criterion is derived in terms of LMI using the free-weighting matrices method. The rate-range of the delay is also considered in the derivation of the criterion. Numerical examples are presented to illustrate the effectiveness of the proposed method.
Structural Prediction and Phase Transformation Mechanisms in Calcium at High Pressure
Physical Review Letters, 2009
High-pressure phase transformations of Ca are studied using the metadynamics method to explore th... more High-pressure phase transformations of Ca are studied using the metadynamics method to explore the anharmonic free-energy surface, together with a genetic algorithm structural search method to identify lowest enthalpy structures. Disagreement between theory and experiment regarding the structure of Ca in the pressure range 32-119 GPa is partially resolved by the demonstration of different phase transition behavior at 300 K from that at low temperatures. A new lowest enthalpy I4(1)/amd structure is obtained with both methods with an estimated superconducting critical temperature in agreement with experiment.
Stability criteria for a class of MIMO networked control systems with network constraints
2009 IEEE International Conference on Systems, Man and Cybernetics, 2009
ABSTRACT This paper is concerned with the stability analysis for a class of MIMO networked contro... more ABSTRACT This paper is concerned with the stability analysis for a class of MIMO networked control systems (NCSs) with network constraints. In view of MIMO NCSs where network is of limited access channels, a discrete-time switched delay model is formulated. By constructing a novel piecewise Lyapunov-Krasovskii functional, a new stability criterion is developed in terms of linear matrix inequalities. A numerical example is given to show the effectiveness of the proposed method.
Cardiovascular disease (CVD) remains a leading cause of mortality worldwide despite advances in i... more Cardiovascular disease (CVD) remains a leading cause of mortality worldwide despite advances in its prevention and management. A comprehensive understanding of factors which contribute to CVD is required in order to develop more effective treatment options. Dysregulation of epigenetic posttranscriptional modifications of histones in chromatin is thought to be associated with the pathology of many disease models, including CVD. Histone acetyltransferases (HATs) and deacetylases (HDACs) are regulators of histone lysine acetylation. Recent studies have implicated a fundamental role of reversible protein acetylation in the regulation of CVDs such as hypertension, pulmonary hypertension, diabetic cardiomyopathy, coronary artery disease, arrhythmia, and heart failure. This reversible acetylation is governed by enzymes that HATs add or HDACs remove acetyl groups respectively. New evidence has revealed that histone acetylation regulators blunt cardiovascular and related disease states in ce...
Piperlongumine attenuates collagen-induced arthritis via expansion of myeloid-derived suppressor cells and inhibition of the activation of fibroblast-like synoviocytes
Molecular medicine reports, 2015
Piperlonguminine (PL), a key compound from the Piper longum fruit, is known to exhibit anti‑tumor... more Piperlonguminine (PL), a key compound from the Piper longum fruit, is known to exhibit anti‑tumor and anti‑inflammatory activities. However, little is known about its effects on collagen‑induced arthritis (CIA). Fibroblast‑like synoviocytes (FLS) have a pivotal role in the development of rheumatoid arthritis (RA). Myeloid‑derived suppressor cells (MDSCs) are able to suppress T cell responses and have important roles in the regulation of autoimmune arthritis. The current study investigated whether PL alters the progression of RA. It was determined that PL reduces the arthritis score and histopathologic lesions in a mouse model of CIA. PL also reduces the expression levels of serum anti‑collagen II antibodies (anti‑CⅡ), tumor necrosis factor‑α (TNF‑α), interleukin (IL)‑1β, IL‑23 and IL‑17 in CIA mice. In draining lymph nodes (DLNs), MDSCs were significantly expanded, however, the number of Th17 cells was markedly decreased by PL treatment. Additionally, PL reduced secretion of IL‑1β, ...
Understanding the impact of grazing intensity on grassland production and soil fertility is of fu... more Understanding the impact of grazing intensity on grassland production and soil fertility is of fundamental importance for grassland conservation and management. We thus compared three types of alpine steppe management by studying vegetation traits and soil properties in response to three levels of grazing pressure: permanent grazing (M1), seasonal grazing (M2), and grazing exclusion (M3) in the alpine steppe in Xainza County, Tibetan Plateau. The results showed that community biomass allocation did not support the isometric hypothesis under different grassland management types. Plants in M1 had less aboveground biomass but more belowground biomass in the top soil layer than those in M2 and M3, which was largely due to that root/shoot ratios of dominant plants in M1 were far greater than those in M2 and M3. The interramet distance and the tiller size of the dominant clonal plants were greater in M3 than in M1 and M2, while the resprouting from rhizome buds did not differ significantl...
Many studies have focused on the relationship between vegetation biomass and environmental factor... more Many studies have focused on the relationship between vegetation biomass and environmental factors in grassland. However, several questions remain to be answered, especially with regards to the spatial pattern of vegetation biomass. Thus, the distributed mechanism will be explored in the present study. Here, plant biomass was measured at 23 sites along a transect survey during the peak growing season in 2006. The data were analyzed with a classification and regression tree (CART) model. The structural equation modeling (SEM) was conducted to explicitly evaluate the both direct and indirect effects of these critical environmental elements on vegetation biomass. The results demonstrated that mean annual temperature (MAT) affected aboveground biomass (AGB) scored at -0.811 (P<0.05). The direct effect of MAT on belowground biomass (BGB) was -0.490 (P<0.05). The results were determined by SEM. Our results indicate that AGB and BGB in semi-arid ecosystems is strongly affected by pre...
Diode-end-pumped high-efficiency single-and dual-wavelength Nd : GdVO 4 lasers have been demonstr... more Diode-end-pumped high-efficiency single-and dual-wavelength Nd : GdVO 4 lasers have been demonstrated. For the single-wavelength operation, the maximum cw output powers of 15.6 W (M 2 = 1.54) at 1063 nm and 7.5 W (M 2 = 1.40) at 1342 nm were achieved under the highest available pump power of 26.5 W, having the respective opticalto-optical conversion efficiencies of 59.2% and 28.2% as well as the average slope efficiencies of 65.1% and 32.2%. For the dual-wavelength operation, under the available pump power of 12.6 W, we obtained the average power outputs of 1.0 W (M 2 = 4.85) at 1063 nm and 1.4 W (M 2 = 3.22) at 1342 nm with the respective pulse durations of 23 ns and 53 ns for quasicw operation, and the power outputs of 1.8 W (M 2 = 5.35) at 1063 nm and 2.0 W (M 2 = 4.76) at 1342 nm for cw operation. PACS 42.65.Ky; 42.79.Nv; 42.70.Mp
Optical properties of heterodiamond B2CN using first-principles calculations
APPLIED PHYSICS LETTERS, 2004
... electron energy-loss spectrum L( ) can be deduced from 1( ) and 2( ).17,18 As sup-portive evi... more ... electron energy-loss spectrum L( ) can be deduced from 1( ) and 2( ).17,18 As sup-portive evidence, we calculate 2( ) and 1( ) of the known cubic diamond, which are in ... eV below the bottom 4.44 eV of CBs corresponds to the intraband transitions from 2p VBs of B and C to EBs. ...
Ab initio investigations of optical properties of the high-pressure phases of ZnO
PHYSICAL REVIEW B, 2005
We present a detailed investigation on optical properties of high-pressure phase ZnO in B1 (NaCl)... more We present a detailed investigation on optical properties of high-pressure phase ZnO in B1 (NaCl) and B2 (CsCl) structures, including dielectric function, refractive index, absorption, and electron energy-loss spectrum. Theoretical calculations are performed using the ab initio ...
Bond ionicities and hardness of B13C2-like structured ByX crystals (X=C,N,O,P,As)
PHYSICAL REVIEW B, 2006
ABSTRACT Based on the fact that ionicity exists in chemical bonds between identical atoms in alph... more ABSTRACT Based on the fact that ionicity exists in chemical bonds between identical atoms in alpha -boron, investigation has been performed on the influences of X atoms on the ionicities of B-B bonds in B13C2 -like structured ByX ( X=C , N, O, P, and As) compounds. For the four types of B-B bonds in the B12 icosahedra of the ByX compounds, their overlap population P , population ionicity fh , and Phillips ionicity fi have been calculated. Comparing to the overlap population Pc value for the structure of the regular B12 icosahedron, the difference between P and Pc in the distorted B12 icosahedron and its origin have been discussed. Our results have shown that the charge transfer occurs between Bp and Be atoms in the distorted B12 icosahedra of ByX crystals, different from the alpha -boron. Electronegativity of the X atom in ByX crystals plays an important role in the ionicities of B-B bonds in the icosahedra. Among the five investigated ByX crystals, the largest ionicity of 0.449 has been found to exist in the Bp-Be bond in the B6O crystal, which is comparable to that found in AlN . By taking into account the effect of the ionicities of B-B bonds in the B12 icosahedra on hardness, the calculated hardness is in agreement with the experimental values for B6O and B13C2 . In addition, the calculations of hardness indicate that B6N is a potential superhard material, but B6P and B6As are not.
Based on first-principles calculation, we predict a tetragonal phase of BC 2 N ͑t-BC 2 N͒, which ... more Based on first-principles calculation, we predict a tetragonal phase of BC 2 N ͑t-BC 2 N͒, which matches the experiment well because the estimated Vickers hardness and the simulated X-ray diffraction ͑XRD͒ and Raman patterns are in excellent agreement with the experimental results besides the low total energy and formation energy. In particular, we acquire the underlying physics behind the apparent lack of the transverse optical mode in the measured Raman spectrum and find the interesting electronic structure transition among the polymorph of superhard BC 2 N compounds.
Computational searches for structures of solid oxygen under pressures in the multi TPa range have... more Computational searches for structures of solid oxygen under pressures in the multi TPa range have been carried out using density-functional-theory methods. We find that molecular oxygen persists to about 1.9 TPa at which it transforms into a semiconducting square spiral-like polymeric structure (I41/acd) with a band gap of ∼3.0 eV. Solid oxygen forms a metallic zig-zag chain-like structure (Cmcm) at about 3.0 TPa, but the chains in each layer gradually merge as the pressure is increased and a structure of F mmm symmetry forms at about 9.5 TPa in which each atom has four nearest neighbors. The superconducting properties of molecular oxygen do not vary much with compression, although the structure becomes more symmetric. The electronic properties of oxygen have a complex evolution with pressure, swapping between insulating, semiconducting and metallic.
Type 2 diabetes mellitus (T2DM) significantly increases risk for vascular complications. Diabetes... more Type 2 diabetes mellitus (T2DM) significantly increases risk for vascular complications. Diabetes-induced aorta pathological changes are predominantly attributed to oxidative stress. Nuclear factor E2-related factor-2 (Nrf2) is a transcription factor orchestrating antioxidant and cytoprotective responses to oxidative stress. Sulforaphane protects against oxidative damage by increasing Nrf2 expression and its downstream target genes. Here we explored the protective effect of sulforaphane on T2DM-induced aortic pathogenic changes in C57BL/6J mice which were fed with high-fat diet for 3 months, followed by a treatment with streptozotocin at 100 mg/kg body weight. Diabetic and nondiabetic mice were randomly divided into groups with and without 4-month sulforaphane treatment. Aorta of T2DM mice exhibited significant increases in the wall thickness and structural derangement, along with significant increases in fibrosis (connective tissue growth factor and transforming growth factor), inf...
Differential expression of Axin1, Cdc25c and Cdkn2d mRNA in 2-cell stage mouse blastomeres
Zygote, 2012
There is increasing evidence to show that 2-cell stage mouse blastomeres have differing developme... more There is increasing evidence to show that 2-cell stage mouse blastomeres have differing developmental properties. Additionally, it has been suggested that such a difference might be due to their distribution of mRNA and/or protein asymmetry. However, to date, the exact genes that are involved in the orientation and order of blastomere division are not known. In this study, some differentially expressed transcripts were identified. Axin1, cell division cycle 25 homolog C (Cdc25c) and cyclin-dependent inhibitor 2D (Cdkn2d) were selected for validation by real-time polymerase chain reaction (PCR) based on published data. Our real-time PCR results demonstrated that Axin1, Cdc25c and Cdkn2d genes had different levels of expression among blastomeres of the mouse 2-cell embryo i.e. the level of Axin1 mRNA was significantly higher in one blastomere when compared with the other blastomeres of the 2-cell embryo (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05). The variation in Cdc25c (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.05) and Cdkn2d (p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; 0.01) mRNA expression followed a similar trend to that of Axin1. In addition, the highest levels of expression of these three genes were detected in the same blastomere in the 2-cell embryo. We confirmed that there was an asymmetrical distribution pattern for Axin1, Cdc25c and Cdkn2d transcripts in 2-cell embryos. In conclusion, this study demonstrated clearly that there is embryonic asymmetry at the 2-cell stage and that these differentially expressed genes may result in differentiation in expression in embryo development.
carbons (-20+ 100 mesh; 0.149-0.84 mm) were produced by physical activation and chemical activati... more carbons (-20+ 100 mesh; 0.149-0.84 mm) were produced by physical activation and chemical activation with KOH from an Illinois bituminous coal (IBC-106) for natural gas storage. The products were characterized by BET surface area, micropore volume, bulk density, and methane adsorption capacities. Volumetric methane adsorption capacities (V,/V,) of some of the granular carbons produced by physical activation are about 70 cm3/cm3 which is comparable to that of BPL, a commercial activated carbon. V,,,/V, values above 100 cm3/cm3 are obtainable by grinding the granular products to -325 mesh (co.044 mm). The increase in l/,/V, is due to the increase in bulk density of the carbons. Volumetric methane adsorption capacity increases with increasing pore surface area and micropore volume when normalizing with respect to sample bulk volume. Compared with steam-activated carbons, granular carbons produced by KOH activation have higher micropore volume and higher methane adsorption capacities (g/g). Their volumetric methane adsorption capacities are lower due to their lower bulk densities.
Proceedings of the National Academy of Sciences, 2009
Understanding the structural transformations of solid CO2 from a molecular solid characterized by... more Understanding the structural transformations of solid CO2 from a molecular solid characterized by weak intermolecular bonding to a 3-dimensional network solid at high pressure has challenged researchers for the past decade. We employ the recently developed metadynamics method combined with ab initio calculations to provide fundamental insight into recent experimental reports on carbon dioxide in the 60 -80 GPa pressure region. Pressure-induced polymeric phases and their transformation mechanisms are found. Metadynamics simulations starting from the CO 2-II (P42/mnm) at 60 GPa and 600 K proceed via an intermediate, partially polymerized phase, and finally yield a fully tetrahedral, layered structure (P-4m2). Based on the agreement between calculated and experimental Raman and X-ray patterns, the recently identified phase VI [Iota V, et al. (2007) Sixfold coordinated carbon dioxide VI. Nature Mat 6:34 -38], assumed to be disordered stishovite-like, is instead interpreted as the result of an incomplete transformation of the molecular phase into a final layered structure. In addition, an ␣-cristobalite-like structure (P41212), is predicted to be formed from CO2-III (Cmca) via an intermediate Pbca structure at 80 GPa and low temperatures (<300 K). Defects in the crystals are frequently observed in the calculations at 300 K whereas at 500 to 700 K, CO2-III transforms to an amorphous form, consistent with experiment [Santoro M, et al. (2006) Amorphous silica-like carbon dioxide. Nature 441:857-860], but the simulation yields additional structural details for this disordered solid.
Alpine steppe is considered to be the largest grassland type on the Tibetan Plateau. This grassla... more Alpine steppe is considered to be the largest grassland type on the Tibetan Plateau. This grassland contributes to the global carbon cycle and is sensitive to climate changes. The allocation of biomass in an ecosystem affects plant growth and the overall functioning of the ecosystem. However, the mechanism by which plant biomass is allocated on the alpine steppe remains unclear. In this study, biomass allocation and its relationship to environmental factors on the alpine grassland were studied by a meta-analysis of 32 field sites across the alpine steppe of the northern Tibetan Plateau. We found that there is less above-ground biomass (M A ) and below-ground biomass (M B ) in the alpine steppe than there is in alpine meadows and temperate grasslands. By contrast, the root-to-shoot ratio (R:S) in the alpine steppe is higher than it is in alpine meadows and temperate grasslands. Although temperature maintained the biomass in the alpine steppe, precipitation was found to considerably influence M A , M B , and R:S, as shown by ordination space partitioning. After standardized major axis (SMA) analysis, we found that allocation of biomass on the alpine steppe is supported by the allometric biomass partitioning hypothesis rather than the isometric allocation hypothesis. Based on these results, we believe that M A and M B will decrease as a result of the increased aridity expected to occur in the future, which will reduce the landscape's capacity for carbon storage.
Improved stability criteria for neural networks with time-varying delay
Physics Letters A, 2009
ABSTRACT The problem of the stability analysis of neural networks with time-varying delay is cons... more ABSTRACT The problem of the stability analysis of neural networks with time-varying delay is considered in this Letter. By constructing a new augmented Lyapunov functional which contains a triple-integral term, an improved delay-dependent stability criterion is derived in terms of LMI using the free-weighting matrices method. The rate-range of the delay is also considered in the derivation of the criterion. Numerical examples are presented to illustrate the effectiveness of the proposed method.
Structural Prediction and Phase Transformation Mechanisms in Calcium at High Pressure
Physical Review Letters, 2009
High-pressure phase transformations of Ca are studied using the metadynamics method to explore th... more High-pressure phase transformations of Ca are studied using the metadynamics method to explore the anharmonic free-energy surface, together with a genetic algorithm structural search method to identify lowest enthalpy structures. Disagreement between theory and experiment regarding the structure of Ca in the pressure range 32-119 GPa is partially resolved by the demonstration of different phase transition behavior at 300 K from that at low temperatures. A new lowest enthalpy I4(1)/amd structure is obtained with both methods with an estimated superconducting critical temperature in agreement with experiment.
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