Electronic structure of carbon dioxide under pressure and insights into the molecular-to-nonmolecular transition

Knowledge of the high-pressure behavior of carbon dioxide (CO₂), an important planetary material found in Venus, Earth, and Mars, is vital to the study of the evolution and dynamics of the planetary interiors as well as to the fundamental understanding of the C–O bonding and interaction between the molecules. Recent studies have revealed a number of crystalline polymorphs (CO₂-I to -VII) and an amorphous phase under high pressure–temperature conditions. Nevertheless, the reported phase stability field and transition pressures at room temperature are poorly defined, especially for the amorphous phase. Here we shed light on the successive pressure-induced local structural changes and the molecular-to-nonmolecular transition of CO₂ at room temperature by performing an in situ study of the local electronic structure using X-ray Raman scattering, aided by first-principle exciton calculations. We show that the transition from CO₂-I to CO₂-III was initiated at around 7.4 GPa, and completed at about 17 GPa. The present study also shows that at ∼37 GPa, molecular CO₂ starts to polymerize to an extended structure with fourfold coordinated carbon and minor CO₃ and CO-like species. The observed pressure is more than 10 GPa below previously reported. The disappearance of the minority species at 63(±3) GPa suggests that a previously unknown phase transition within the nonmolecular phase of CO₂ has occurred.Molecular compounds such as N₂ and H₂O have been known to acquire a nonmolecular structure under compression and ultimately transform into highly disordered and/or amorphous phases (1–4). Other solids, such as group IV oxides SiO₂ (5) and GeO₂ (6), are prone to amorphize under pressure despite the covalent framework structure. However, it was not until recently that CO₂, both a molecular compound and group IV oxide, was also reported to form several polymorphs and a pressure-induced amorphous phase (7–23). Previous experimental evidence on the formation of nonmolecular phases of N₂ and CO₂ was mainly based on the loss of optical vibrons (1) and/or the emergence of a broad IR or Raman band in the stretching mode region. Unfortunately, these new features are often very weak and accurate measurement was hindered by significant noises (17, 22, 23), making it difficult to extract useful information on the local coordination in the amorphous phase. This difficulty is illustrated by studies of the high-pressure high-temperature amorphous a-CO₂ phase in which the polymeric local structure was claimed to be a mixture of tetrahedral and octahedral coordinated carbon based on Raman spectroscopy (17), but to a mixture of tetrahedral and threefold coordinated polymeric CO₂ from a combined theoretical and infrared spectroscopy study (20). Moreover, knowledge of the phase diagram and kinetics for the various phase transitions in solid CO₂ are obscured by significant disparities in the estimated phase transition pressures from different studies and techniques. An example is the pressures reported for the molecular to nonmolecular phase transformation ranging from 48 to 65 GPa (17, 22, 23).The discrepancies between different experiments and ambiguities in the transition pressures in solid CO₂ motivate a thorough investigation of the pressure dependence of the local structural and electronic environment. Here we report a survey of the evolution of the chemical bonding of CO₂ under pressure, using X-ray Raman scattering (XRS)—a nonresonant, hard X-ray photon-in photon-out technique at both the carbon (C) and oxygen (O) K edges. XRS provides a convenient way to measure absorption spectra of low Z materials in high-pressure diamond anvil cell. From analysis of the spectral features, insights into the effects of pressure on the unoccupied π* and σ* orbitals of C and O aided with first-principles calculations have been obtained. The present results provide a framework to further the understanding of the local mechanism of polymerization of CO₂ under pressure.     

Crystal structures of (Mg1-x,Fe(x))SiO3 postperovskite at high pressures

X-ray diffraction experiments on postperovskite (ppv) with compositions (Mg(0.9)Fe(0.1))SiO(3) and (Mg(0.6)Fe(0.4))SiO(3) at Earth core-mantle boundary pressures reveal different crystal structures. The former adopts the CaIrO(3)-type structure with space group Cmcm, whereas the latter crystallizes in a structure with the Pmcm (Pmma) space group. The latter has a significantly higher density (ρ = 6.119(1) g/cm(3)) than the former (ρ = 5.694(8) g/cm(3)) due to both the larger amount of iron and the smaller ionic radius of Fe(2+) as a result of an electronic spin transition observed by X-ray emission spectroscopy (XES). The smaller ionic radius for low-spin compared to high-spin Fe(2+) also leads to an ordered cation distribution in the M1 and M2 crystallographic sites of the higher density ppv structure. Rietveld structure refinement indicates that approximately 70% of the total Fe(2+) in that phase occupies the M2 site. XES results indicate a loss of 70% of the unpaired electronic spins consistent with a low spin M2 site and high spin M1 site. First-principles calculations of the magnetic ordering confirm that Pmcm with a two-site model is energetically more favorable at high pressure, and predict that the ordered structure is anisotropic in its electrical and elastic properties. These results suggest that interpretations of seismic structure in the deep mantle need to treat a broader range of mineral structures than previously considered.     

High Pressure Brillouin Spectroscopy and X-ray Diffraction of Cerium Dioxide

Simultaneous high-pressure Brillouin spectroscopy and powder X-ray diffraction of cerium dioxide powders are presented at room temperature to a pressure of 45 GPa. Micro- and nanocrystalline powders are studied and the density, acoustic velocities and elastic moduli determined. In contrast to recent reports of anomalous compressibility and strength in nanocrystalline cerium dioxide, the acoustic velocities are found to be insensitive to grain size and enhanced strength is not observed in nanocrystalline CeO2. Discrepancies in the bulk moduli derived from Brillouin and powder X-ray diffraction studies suggest that the properties of CeO2 are sensitive to the hydrostaticity of its environment. Our Brillouin data give the shear modulus, G0 = 63 (3) GPa, and adiabatic bulk modulus, KS0 = 142 (9) GPa, which is considerably lower than the isothermal bulk modulus, KT0∼ 230 GPa, determined by high-pressure X-ray diffraction experiments.     

Experimental and Computational Studies of Compression and Deformation Behavior of Hafnium Diboride to 208 GPa

The compression behavior of the hexagonal AlB₂ phase of Hafnium Diboride (HfB₂) was studied in a diamond anvil cell to a pressure of 208 GPa by axial X-ray diffraction employing platinum as an internal pressure standard. The deformation behavior of HfB₂ was studied by radial X-ray diffraction technique to 50 GPa, which allows for measurement of maximum differential stress or compressive yield strength at high pressures. The hydrostatic compression curve deduced from radial X-ray diffraction measurements yielded an ambient-pressure volume V₀ = 29.73 Å3/atom and a bulk modulus K₀ = 282 GPa. Density functional theory calculations showed ambient-pressure volume V₀ = 29.84 Å3/atom and bulk modulus K₀ = 262 GPa, which are in good agreement with the hydrostatic experimental values. The measured compressive yield strength approaches 3% of the shear modulus at a pressure of 50 GPa. The theoretical strain-stress calculation shows a maximum shear stress τ_max~39 GPa along the (1−10) [110] direction of the hexagonal lattice of HfB₂, which thereby can be an incompressible high strength material for extreme-environment applications.     

Thermal conductivity of Fe-Si alloys and thermal stratification in Earth’s core

Light elements in Earth’s core play a key role in driving convection and influencing geodynamics, both of which are crucial to the geodynamo. However, the thermal transport properties of iron alloys at high-pressure and -temperature conditions remain uncertain. Here we investigate the transport properties of solid hexagonal close-packed and liquid Fe-Si alloys with 4.3 and 9.0 wt % Si at high pressure and temperature using laser-heated diamond anvil cell experiments and first-principles molecular dynamics and dynamical mean field theory calculations. In contrast to the case of Fe, Si impurity scattering gradually dominates the total scattering in Fe-Si alloys with increasing Si concentration, leading to temperature independence of the resistivity and less electron–electron contribution to the conductivity in Fe-9Si. Our results show a thermal conductivity of ∼100 to 110 W⋅m⁻¹⋅K⁻¹ for liquid Fe-9Si near the topmost outer core. If Earth’s core consists of a large amount of silicon (e.g., > 4.3 wt %) with such a high thermal conductivity, a subadiabatic heat flow across the core–mantle boundary is likely, leaving a 400- to 500-km-deep thermally stratified layer below the core–mantle boundary, and challenges proposed thermal convection in Fe-Si liquid outer core.

The geodynamo of Earth’s core is thought to be mainly driven by compositional (chemical) convection associated with the crystallization and light-element release of the inner core as well as thermal convection driven by a superadiabatic heat flow across the core–mantle boundary (CMB). The relative importance of these energy sources to the geodynamo, however, remains uncertain (1). The magnitudes of these energy sources can change throughout the evolution of the planet. The thermal gradient across the CMB can be constrained from both heat flow of the core and mantle, where a subadiabatic heat flow out of the core may hinder thermal convection and cause a thermally stratified layer at the top of the outer core (2). A global nonadiabatic structure at the top of the core has been inferred from seismic observations and geomagnetic fluctuations (3, 4), where the mechanisms for the origin rely on accurate determinations of the CMB heat flow and the core conductivity. Based on seismological observations and high-pressure and -temperature (P-T) mineral physics results, Earth’s outer and inner core are mainly composed of Fe (∼85 wt %) alloyed with Ni (∼5 wt %) and ∼8 to 10 wt % and 4–5 wt % of light elements, respectively, such as Si, O, S, C, and H (5–10). The effects of the candidate light elements on the electrical resistivity (ρ_e) and thermal conductivity (κ) of iron and their partitioning between the inner and outer core at relevant P-T conditions are thus of great importance for understanding the thermal state of the core as well as the generation and evolution of Earth’s magnetic field (2, 9, 11, 12). The thermal conductivity of the constituent core alloy controls the heat flow of the core, while the electrical resistivity of the constituent Fe alloy determines the ohmic dissipation rate of the magnetic field.Extensive studies on iron’s transport properties have been conducted via experiments and calculations (e.g., refs. 13–21), and recent studies report a thermal conductivity of ∼100 W⋅m⁻¹⋅K⁻¹ at conditions near the CMB (22, 23). Such a high thermal conductivity reduces the amount of heat that can be transported by convective flow (11) and raises a question as to what powered the convection prior to inner core growth over Earth’s history [the so-called new core paradox (24)]. Thus far, several hypotheses have been proposed to reconcile this paradox, including a possible large conductivity reduction due to nickel and light elements (25–28), a rapid core cooling rate (29), or exsolution of chemically saturated species from the core to the lowermost mantle, such as MgO, SiO₂, or FeO (e.g., refs. 30–32). The general consensus is that incorporation of light element(s) depresses high P-T thermal conductivity of iron by impurity scattering (12); this effect was assumed in our previous modeling of the high P-T transport properties of Fe-Ni alloyed with 1.8 wt % Si (25). The lowered thermal conductivity implies that thermal convection is easier to maintain. The rapid core cooling model would imply a young inner core and requires a hidden core heat source, such as radioactivity, which is not supported by geochemical evidence (29). The exsolution mechanism would offer an additional energy source to drive an early compositionally driven geodynamo (32), although some experiments find exsolution to be unlikely (33). The viability of each of these scenarios depends sensitively on the transport properties of iron alloyed with a significant amount of light element(s) (∼8 to 10 wt %) at core P-T conditions. Information on these electrical and thermal transport properties of iron alloys remain uncertain due to the sparsity of experimental and theoretical data.Here we focus on the geodynamic consequences of the transport properties of iron alloyed with 4 to 10 wt % silicon, which is considered to be one of the major light element candidates in the Earth’s core due to its geo- and cosmochemical abundance (5), high solubility in solid and liquid iron (34), and isotopic evidence (35). Fe-Si alloys have been the subject of previous studies focused on understanding the structural and physical properties of the core material, including its high P-T phase diagram (36–39), elasticity (40–44), melting behavior (36, 45, 46), and transport properties (25, 47–49). The observed density discontinuity of ∼4 to 5% across the inner-core boundary (ICB) indicates that excess light elements partition into the outer core during inner-core solidification (6, 50). We should note that the concentration of Si in the core remains uncertain. While some experiments have shown that Fe alloyed with ∼9 wt % Si can satisfy the density profile of the outer core and Fe alloyed with ∼4 wt % Si for the inner core, respectively (37, 40, 41, 51, 52), other studies indicate that a dominant Si light alloying component is unable to reproduce both the density and sound velocity distribution in the outer core (53, 54).High P-T diamond anvil cell (DAC) experiments had been previously conducted to constrain the electrical and thermal conductivity of Fe-Si alloys (28, 47, 55, 56), specifically their T-dependent resistivity and thermal conductivity at core pressures. The thermal conductivity of Fe-8 wt % Si (hereafter Fe-8Si) was measured using a high-P ultrafast optical pump probe and high P-T flash-heating methods (28). The results showed that 8 wt % silicon in solid hexagonal close-packed (hcp) Fe can strongly reduce the conductivity of pure iron by a factor of ∼2, i.e., giving ∼20 W⋅m⁻¹⋅K⁻¹ at ∼132 GPa and 3,000 K. However, the electrical resistivity of solid Fe-6.5Si at ∼99 GPa and 2,000 K was recently measured to be ∼73 µΩ⋅cm (56), which is higher than that of pure iron (22) by ∼60% at comparable conditions. The results imply a thermal conductivity of ∼66 W⋅m⁻¹⋅K⁻¹ using the Wiedemann–Franz law (TL = ρ_eκ) assuming an ideal Sommerfeld Lorentz number (L = L₀: 2.44 × 10⁻⁸ W⋅m⁻¹⋅K⁻²). Meanwhile, another recent study reported a moderate thermal conductivity of 50 to 70 W⋅m⁻¹⋅K⁻¹ for an Fe-5Ni-8Si alloy near CMB P-T conditions (∼140 GPa and 4,000 K) modeled from the measured resistivity of Fe-10Ni and Fe-1.8Si alloys using the four-probe van der Pauw method in laser-heated DACs (25). The results on Fe-10Ni and Fe-1.8Si alloys reveal a linear relationship between resistivity and temperature at a given high pressure, which is very similar to that of hcp Fe (22), over the range of measurements. In contrast, density functional theory (DFT)-based molecular dynamics simulations predict a small negative T dependence of the resistivity at high pressure when liquid Fe is alloyed with a significant amount of light elements (e.g., ∼13 wt % Si) (27). These experimental and computational results raise the possibility that the high P-T thermal transport behavior and its temperature dependence in Fe-Si alloys with a few wt % Si (e.g., 2 wt %) and a larger wt % Si (e.g., 8 to 10 wt %) can be quite different, making it difficult to evaluate the light element effects on the energetics of the core.In this study, we directly measured the electrical resistivities of polycrystalline hcp Fe-4.3 wt % Si (Fe-4.3Si, or Fe_0.92Si_0.08) and Fe-9 wt % Si (Fe-9Si, or Fe_0.84Si_0.16) alloys to ∼136 GPa and 3,000 K. We also computed the electrical resistivity and thermal conductivity of these Fe-Si alloys in solid and liquid phases using first-principles molecular dynamics (FPMD) and dynamical mean field theory (DMFT) calculations. The calculations include contributions from scattering off of Si as well as both electron–phonon (e-ph) and electron–electron (e-e) scattering. Our results are used to evaluate the Si impurity effects on the transport properties of Fe-Si alloy at P-T conditions of the topmost outer core. Assuming Si is the sole light element in the core, our results are used to constrain core thermal conductivity, which is in turn used to assess core heat flux, thermal state, and energy sources driving the geodynamo through geodynamical modeling.     

Electronic excitations and metallization of dense solid hydrogen

Theoretical calculations and an assessment of recent experimental results for dense solid hydrogen lead to a unique scenario for the metallization of hydrogen under pressure. The existence of layered structures based on graphene sheets gives rise to an electronic structure related to unique features found in graphene that are well studied in the carbon phase. The honeycombed layered structure for hydrogen at high density, first predicted in molecular calculations, produces a complex optical response. The metallization of hydrogen is very different from that originally proposed via a phase transition to a close-packed monoatomic structure, and different from simple metallization recently used to interpret recent experimental data. These different mechanisms for metallization have very different experimental signatures. We show that the shift of the main visible absorption edge does not constrain the point of band gap closure, in contrast with recent claims. This conclusion is confirmed by measured optical spectra, including spectra obtained to low photon energies in the infrared region for phases III and IV of hydrogen.     

Effects of breathing a normoxic helium mixture on exercise tolerance-of patients with cystic fibrosis

Breathing helium-oxygen (He? O₂,) mixtures of 20.9% O₂/79.1% He has been shown to increase exercise ventilation and peak oxygen uptake in healthy subjects. The improved exercise performance is thought to be due to the reduced density of He? O₂ compared to air and the resulting increases in ventilation. Patients with cystic fibrosis (CF) frequently have abnormal pulmonary function test results, low exercise ventilations and diminished exercise tolerance. This led to the hypothesis that in CF the exercise tolerance of patients might improve when breathing He? O₂. To test this hypothesis, 11 patients with CF or mild to severe airway obstruction performed spirometry and progressive maximal exercise tests while breathing air or He? O₂2. The He? O₂ mixture significantly increased (P <0.05) forced expiratory volume in 1 sec (FEV₁) by 8.2%, peak expired flow by 39%, and maximal voluntary ventilation (MVV) by 17.9% compared to air, while forced vital capacity (FVC) and forced mid-expiratory flow rate (FEF_25–75%,) were unchanged by breathing He? O₂. Ventilation and oxygen uptake at matched submaximal power outputs were not increased while breathing He? O₂. nor were peak exercise ventilation (V?_Epeak) or peak exercise oxygen uptake (V?_O2peak). Estimated hemoglobin saturation and total exercise time were also unchanged during He? O₂, breathing. However, there was a trend for the subjects with the better FEV₁, to increase V?_O2peak. Increases in V?_O2peak when breathing He? O₂, and air were correlated (r = 0.67, P<0.05) with the percent of predicted FEV, values. Still, in the 11 patients as a group, breathing He? O₂, did not significantly improve V?_O2peak V?_Epeak or exercise tolerance. Therefore He? O₂, is unlikely to have additional benefits to patients with CF who use an exercise program to help optimize their health status. Pediatr Pulmonol. 1994;18:206–210 . ©1994 Wiley-Liss, Inc.     

On the mechanical behavior of WS2 nanotubes under axial tension and compression

The mechanical properties of materials and particularly the strength are greatly affected by the presence of defects; therefore, the theoretical strength ( approximately 10% of the Young's modulus) is not generally achievable for macroscopic objects. On the contrary, nanotubes, which are almost defect-free, should achieve the theoretical strength that would be reflected in superior mechanical properties. In this study, both tensile tests and buckling experiments of individual WS(2) nanotubes were carried out in a high-resolution scanning electron microscope. Tensile tests of MoS(2) nanotubes were simulated by means of a density-functional tight-binding-based molecular dynamics scheme as well. The combination of these studies provides a microscopic picture of the nature of the fracture process, giving insight to the strength and flexibility of the WS(2) nanotubes (tensile strength of approximately 16 GPa). Fracture analysis with recently proposed models indicates that the strength of such nanotubes is governed by a small number of defects. A fraction of the nanotubes attained the theoretical strength indicating absence of defects.     

The Effect of Yttrium on the Solution and Diffusion Behaviors of Helium in Tungsten: First-Principles Simulations

We systematically investigated the influence of yttrium (Y) on the evolution behavior of helium (He) in tungsten (W) by first-principles calculations. It is found that the addition of Y reduces the solution energy of He atoms in W. Interestingly, the solution energy of He decreases with decreasing distance between Y and He. The binding energies between Y and He are inversely correlated with the effective charge of He atoms, which can be attributed to the closed shell structure of He. In addition, compared with pure W, the diffusion barrier (0.033 eV) of He with Y is lower, calculated by the climbing-image nudged elastic band (CI-NEB) simulations, reflecting that the existence of Y contributes to the diffusion of He in W. The obtained results provide a theoretical direction for understanding the diffusion of He.     

骨水泥倒U型分布对经皮椎体成形术治疗骨质疏松椎体压缩性骨折效果的影响

目的探讨经皮椎体成形术(percutaneous vertebroplasty,PVP)中骨水泥倒U型注射分布对治疗骨质疏松性椎体压缩性骨折(osteoporosis vertebral compression fracture,OVCF)临床治疗效果的影响.方法回顾性研究2014年7月至2018年6月因住院并行PVP治疗的70例患者,男性10例,女性60例;年龄60~87岁,平均年龄(73.02±7.74)岁;病程3h^2个月,平均病程(15.35±5.45)d.根据CT检查明确骨水泥的分布情况,依次将患者分为骨水泥呈"倒U型"弥散分布组和骨水泥不规则弥散组.记录术前、术后3 d,3、6个月及1年时的疼痛视觉模拟评分(visual analogue scale,VAS)、椎体高度(body height,BH)及局部后凸Cobb角,对比分析两组上述指标的差异,并记录相关并发症.结果两组患者术前基线特征比较差异无统计学意义(P>0.05),术后VAS较术前均明显降低(P<0.05),倒U型分布组由术前的(7.4±0.8)分降低至术后第3天的(2.5±0.6)分,不规则分布组由(7.5±0.9)分降低至(2.7±0.6)分,但组间比较差异无统计学意义(P>0.05).两组患者术前椎体后凸角度(kyphosis angle,KA)、椎体缘高度(anterior body heights,ABH)和椎体中间高度(middle body heights,MBH)比较,差异无统计学意义(P>0.05),术后倒U型分布组均优于不规则分布组(P<0.05).术后并发症方面,倒U型分布组出现8例骨水泥渗漏,不规则分布组出现5例骨水泥渗漏,总体渗漏率为28.9%,所有骨水泥渗漏均无临床症状.继发相邻椎体骨折倒U型分布组4例,不规则分布组6例;非相邻节段骨折倒U型分布组2例,不规则分布组3例.两组间邻近节段骨折发生率比较,差异无统计学意义(P>0.05).术后1年随访倒U型分布组1例出现骨折椎体再次塌陷,再骨折率为3.1%;不规则分布组5例出现骨折椎体再次塌陷,再骨折率为14.3%.结论PVP可有效缓解胸腰段OVCF患者的疼痛,骨水泥在椎体内弥散分布情况对术后近期治疗效果无明显影响,但可能是PVP术后患椎再骨折的重要影响因素.     

分泌型卷曲相关蛋白2对HepG2细胞生物学行为的影响

目的 了解分泌型卷曲相关蛋白2(sFRP2)对HepG2细胞增殖、侵袭和迁移等生物学行为的影响.方法 采用sFRP2重组腺病毒感染HepG2细胞,四甲基偶氮唑盐法检测HepG2细胞增殖,流式细胞术检测细胞周期分布,免疫组织化学法检测肿瘤转移相关因子的表达,Westernblot检测β连环素的表达,Tmnswell小室检测细胞迁移能力.结果 sFRP2明显抑制HepG2细胞增殖,限制细胞周期从Go/G<,1>期进入S期;sFRP2显著增强nepG2细胞CD44和CD82/KAI1等与肿瘤转移抑制相关蛋白的表达,而明显降低有助于肿瘤侵袭转移的细胞外基质金属蛋白酶诱导因子的表达; sFRP2可降低HepG2细胞的迁移能力.sFRP2感染前后,HepG2细胞均有β连环素的表达,且其表达差异无统计学意义.结论 sFRP2的重组腺病毒能成功感染HepG2细胞,并对H印G2细胞的增殖、侵袭和转移具有抑制效应.     

Distinct thermal behavior of GeO2 glass in tetrahedral, intermediate, and octahedral forms

One fascinating high-pressure behavior of tetrahedral glasses and melts is the local coordination change with increasing pressure, which provides a structural basis for understanding numerous anomalies in their high-pressure properties. Because the coordination change is often not retained upon decompression, studies must be conducted in situ. Previous in situ studies have revealed that the short-range order of tetrahedrally structured glasses and melts changes above a threshold pressure and gradually transforms to an octahedral form with further pressure increase. Here, we report a thermal effect associated with the coordination change at given pressures and show distinct thermal behaviors of GeO(2) glass in tetrahedral, octahedral, and their intermediate forms. An unusual thermally induced densification, as large as 16%, was observed on a GeO(2) glass at a pressure of 5.5 gigapascal (GPa), based on in situ density and x-ray diffraction measurements at simultaneously high pressures and high temperatures. The large thermal densification at high pressure was found to be associated with the 4- to 6-fold coordination increase. Experiments at other pressures show that the tetrahedral GeO(2) glass displayed small thermal densification at 3.3 GPa arising from the relaxation of intermediate range structure, whereas the octahedral glass at 12.3 GPa did not display any detectable thermal effects.     

稳心颗粒对慢性心力衰竭大鼠血浆内皮素及心肌细胞结构的影响

目的观察稳心颗粒对慢性心力衰竭（CHF）大鼠血浆内皮素（ET）水平及心肌细胞结构的影响,探讨稳心颗粒治疗CHF的作用机制。方法腹腔注射阿霉素（ADR）法复制CHF大鼠模型,采用放射免疫法测定ET的含量,电镜观察心肌细胞结构。结果与正常对照组大鼠血浆ET的含量（129±26）ng/L比较,CHF模型组大鼠血浆ET的含量显著升高[（280±25）ng/L,P<0.01];各给药组与模型组比较,血浆ET水平均显著降低[稳心颗粒低剂量组（239±35）ng/L,中剂量组（219±32）ng/L,高剂量组（191±15）ng/L,地高辛组（187±17）ng/L,P<0.01]。稳心颗粒高剂量组与阳性对照组（地高辛）比较无显著性差异。稳心颗粒各给药组均不同程度改善CHF大鼠心肌细胞的结构。结论稳心颗粒能显著降低CHF血浆ET水平,明显改善CHF心肌细胞结构,是改善CHF的有效药物。     

白细胞介素－2对肾小球上皮细胞部分生物学功能的影响

白细胞介素－２（ＩＬ－２）是免疫系统中重要的调节因子。原发性肾病综合征时，可见ＩＬ－２的产生和血清水平发生改变。为了探讨ＩＬ－２在肾病综合征发生、发展中的意义，本文运用肾小球细胞体外培养和双同位素标记方法，分别观察了ＩＬ－２对肾小球上皮细胞（ＧＥＣ）掺入３５Ｓ和３Ｈ－亮氨酸、３Ｈ－ＴｄＲ的影响。结果显示，ＩＬ－２抑制ＧＥＣ的增殖，但明显促进ＧＥＣ合成含硫化合物和蛋白质。     

Effect of Diamond Polishing and Thermal Treatment on Carbon Paramagnetic Centers’ Nature and Structure

Diamonds contain carbon paramagnetic centers (stable carbon radicals) in small concentrations (at the level of ~1 × 10¹² spins/mg) that can help in elucidating the structure of the nitrogen atoms’ contaminants in the diamond crystal. All diamonds that undergo polishing are exposed to high temperatures, owing to the friction force during the polishing process, which may affect the carbon-centered radicals’ concentration and structure. The temperature is increased appreciably; consequently, the black body radiation in the visible range turns orange. During polishing, diamonds emit an orange light (at a wavelength of about 600 nm) that is typical of a black body temperature of 900 °C or higher. Other processes in which color-enhanced diamonds are exposed to high temperatures are thermal treatments or the high-pressure, high-temperature (HPHT) process in which the brown color (resulting from plastic deformation) is bleached. The aim of the study was to examine how thermal treatment and polishing influence the paramagnetic centers in the diamond. For this purpose, four rough diamonds were studied: two underwent a polishing process, and the other two were thermally treated at 650 °C and 1000 °C. The diamonds were analyzed pre- and post-treatment by EPR (Electron Paramagnetic resonance), FTIR (Fourier transform infrared, fluorescence, and their visual appearance. The results indicate that the polishing process results in much more than just thermal heating the paramagnetic centers.     

The Effect of Stretching on the Crystal Structure and Crystal Orientation of PA510/SiO2 Films

In order to explore the relationship between the microstructure and macroscopic properties of PA510/SiO₂ films, the effect of the stretching on the crystal structure and crystal orientation of stretched PA510/SiO₂ films was studied. It could be seen from the transmission electron microscopy (TEM) graphs that the layered SiO₂ molecules were mainly oriented toward the machine direction (MD) and the dispersion could be improved by stretching. Through wide-angle X-ray scattering (WAXS) analysis, PA510/SiO₂ stretched films only contained a γ crystal form. During uniaxial stretching, especially for 1 × 3 film, the γ₁(100) crystal form was obviously oriented in the equatorial direction, and the orientation of γ₂(004) and γ₃(006) crystal forms could be observed in the meridian direction. According to the Herman orientation function, the orientation of the b-axis in the MD increased with the increase of the stretching ratio. It was worth noting that the orientation of the crystal region was more obvious. The addition of SiO₂ and the orientation of the crystalline and amorphous regions could improve the barrier properties of the films. The changes in the optical properties of stretched films were affected by the dispersion state of SiO₂ and the surface roughness.     

环氧合酶2对血管内皮细胞增殖和凋亡的影响

环氧合酶(cyclooxygenase,COX)是以花生四烯酸为底物合成前列腺素的首要限速酶,COX-2作为其亚型之一,主要受细胞内外的各种刺激因素诱导表达.大量的研究表明,COX-2与血管的发生密切相关,它能够通过其衍生的各种前列腺素来影响血管内皮细胞的增殖与凋亡,并由此来参与各种慢性炎症性疾病和肿瘤的发生.弄清COX-2对血管内皮细胞增殖与凋亡的影响,及其相关的作用机制,有助于我们更好的认识其在疾病发生中的作用,从而避弊取利,为临床治疗提供更多更好的方案.