Effect of vacancies and foreign metal ions on the valent state of samarium in SmB6

Conclusions The mixed-configuration state of samarium in SmB₆ is stable and unaffected by defectiveness of structure and the presence of vacancies of metallic states in the lattice. The introduction of atoms of stable integral valence into the SmB₆ crystal lattice alters the valent state of the samarium atoms. The introduction of divalent atoms of atomic radius larger than that of samarium increases the lattice constant of the boride and results in the effective valence gradually growing to the integral value 3. The larger the atomic radius of the addition metal, the lower is the concentration of this addition at which a change in the valence of the samarium atoms is observed. The introduction of trivalent atoms shifts the mixed-configuration state of Sm ions toward smaller values of effective valence, but an integral value is not attained. The effect of substitution of magnetic elements (Eu and Gd) for samarium is the same as that of substitution of nonmagnetic elements (Yb and La).Translated from Poroshkovaya Metallurgiya, No. 10(238), pp. 78–82, October, 1982.     

Luminescent Properties of Samarium Ion in Calcium Molybdate

Trivalent samarium ion (Sm^3 ) activated calcium molybdate (CaMoO4) phosphor was prepared by solid-state reaction in air. The XRD pattern of the powder CaMoO4: Sm shows that the CaMoO4: Sm single phase is developed fully through our preparation procedure. The excitation spectrum of CaMoO4: Sm is composed of a broad absorption of host and some sharp lines of the f-f transition absorption of Sm^3 . Illustrated in photoluminescence spectrum, CaMoO4 doped with Sm^3 displays orange red emission that is ascribed to the inner 4f^5 electron transitions ^6H7/2(orange)and ^6H9/2(red)of Sm^3 . Different from the sites of Sm^3 in CdWO4, the Sm^3 ions substitute for the Ca^2 and form only one type emission center in the CaMoO4 crystal lattice.     

Reverse-phase capillary high performance liquid chromatography/high performance electrospray ionization mass spectrometry: an essential tool for the characterization of complex glycoprotein digests

The B-domain of recombinant human Factor VIII comprises 909 amino acids and is extensively N- and O-glycosylated, in that at least 20 different sites are occupied by numerous carbohydrate structures. This domain was incubated with trypsin and subjected to liquid chromatography electrospray ionization mass spectrometry analysis, using an electrospray orthogonal acceleration time-of-flight mass spectrometer as the detector for a capillary reversed phase HPLC separation of the digest. The inherent high mass resolution afforded by this instrument provides both ion charge state determination and high accuracy mass measurement that are of significant advantage in defining such highly complex mixtures.     

Lattice Parameter Change of Nd∶Gd3Ga5O12 Crystal with Growth Direction

The lattice parameter change of Nd∶GGG crystal was studied by X-ray powder diffraction and the least square fitting method. The results indicate that the lattice parameters of Nd∶GGG increase along the crystal growth direction. By analyzing the Nd∶GGG crystal structure and ions occupying site, the reason of lattice parameter change is mainly attributed to the volatilization of gallium ingredient and lead to the Ga vacancy sites(Oxygen octahedral center) were occupied by Gd3 with large ionic radii, and that the substitute increases with the crystal growth direction. In addition, the Gd sites(oxygen dodecahedron center) were occupied by dopant Nd3 with large ionic radii and the Nd3 distribution coefficient in GGG crystal is smaller than 1, therefore, the substitute also increased with the crystal growth direction, which is another reason led to the lattice parameter increase along the crystal growth direction. In order to decrease the lattice parameter change and improve the crystal quality, some methods were adopted to restrain effectively the Ga2O3 volatilization and decrease the Nd3 concentration change along the crystal growth direction.     

Long range order and defect concentrations in NiAl and CoAl

X-ray diffractometry has been used to determine both the concentrations of vacancies and the fractions of lattice sites occupied by anti-site atoms in both CoAl and NiAl as a function of aluminum concentration. It is shown that both compounds can achieve the maximum possible order both at their stoichiometric compositions and when Al-poor. However, Al-rich compositions are less ordered than possible, indicating the presence of constitutional vacancies, a feature consistent with the maxima in the lattice constants at the stoichiometric compositions. Assuming that both constitutional vacancies and Al anti-site atoms exist, it is shown that in Co-52 Al, 2% of the Co-sites were occupied by vacancies and 3% by Al atoms, whilst in Ni55Al, the vacancies and anti-site atoms occupied 7 and 6% of the Ni sites, respectively. Thus, it is shown that CoAl has similar defect characteristics to NiAl.     

The identification of hydrogen trapping states in an Al-Li-Cu-Zr alloy using thermal desorption spectroscopy

Thermal desorption spectroscopy (TDS) was utilized to identify several metallurgical states in an Al -2Li - 2Cu-0.1Zr (wt pct) alloy, which trap absorbed hydrogen. Six distinct metallurgical desorption states for hydrogen were observed for tempers varying from the T3 to peakaged condition. Lower energy thermal desorption states were correlated with interstitial sites, lithium in solid solution, and δ′ (Al₃Li) precipitates. These states have trap-binding energies ≤25.2 kJ/mol. Under the charging conditions utilized, approximately 4 pct of the total (e.g., trapped and lattice) hydrogen content was associated with interstitial sites, consistent with the view that the intrinsic lattice solubility of hydrogen in aluminum is very low. In contrast, dislocations, grain boundaries, and T₁ (Al₂CuLi) particles were found to be higher energy-trap states with trap-binding energies ≥31.7 kJ/mol. Approximately 78 pct of all absorbed hydrogen occupied these states. Moreover, greater than 13 pct of the available trap sites at grain boundaries were occupied. Such a high hydrogen coverage at grain-boundary sites supports the notion that hydrogen contributes to grain-boundary environmental cracking in Al-Li-Cu-Zr alloys. Also, it points out the error in assuming that hydrogen cannot play a major role in cracking of Al-based alloys due to the low lattice solubility.     

Hydrogen trapping in thoria-dispersed nickel

Trapping of hydrogen in thoria-dispersed nickel has been investigated by the hydrogen thermal desorption technique. It has been found that voids are formed at the particle-matrix interface during cold-working. Annealing at high temperature removes these extra trapping sites, allowing an intrinsic trapping effect due to the thoria particle-matrix interface to be measured. The trapbinding energy and trap-activation energy of hydrogen at the ThO₂-nickel matrix interface are estimated as 35 kJ mole^-1 and 48.7 kJ mole^-1, respectively, using the mathematical models derived from the existing trap theory. The energy level of hydrogen around the ThO₂-lattice interface is derived from the above values. The saddle-point energy of hydrogen at the ThO₂-lattice interface, 13.7 kJ mole^-1, is lower than the activation energy for hydrogen diffusion through a normal lattice, 40.2 kJ mole^-1. It is suggested that during thermal desorption from thoria-dispersed nickel, some of the hydrogen atoms in normal lattice interstitial sites are retrapped at ThO₂-matrix lattice interfaces which are not occupied with hydrogen at the charging temperature. Trap sites at ThO₂-matrix interfaces are dilutely occupied under 1-atm hydrogen pressure in the temperature range of 598 to 773 K. The fractional occupancy of traps ranged from 0.14 to 0.05. SUNG-MAN LEE, formerly with the Korea Advanced Institute of Science and Technology     

Microstructure and growth kinetics of the fibrous composite subscale formed by internal oxidation of SmCo5

The oxidation of SmCo₅ is an unusual example of selective internal oxidation in which the subscale formed consists of a composite microstructure containing samarium oxide fibers and β-cobalt. The oxide fiber size increases with oxidation temperature, and the orientation of the fibers is generally perpendicular to the subscale-alloy interface. The unusual structure results because of the high concentration of samarium in the intermetallic compound, coupled with a low solubility of samarium in metallic cobalt resulting in a subscale consisting of 39 vol pct oxide. Growth of the subscale follows the parabolic oxidation law, and the kinetics have been determined between 100 and 1125°C. The kinetics are too fast to be explained by lattice diffusion in either the oxide or the cobalt phases. Oxygen diffusion down the cobalt-oxide fiber interface appears to be the transport mechanism for this diffusion controlled process. The oxidation behavior of PrCo₅ is identical with that of SmCo₅.     

Intracellular behaviour of samarium and europium in lactating mammary gland

The subcellular localization of samarium and europium, two rare-earths, increasingly used in both medical and industrial fields, has been studied in several organs such as liver and kidney but never in the mammary gland despite of its importance in the biology of lactation and nutrition domains. The intracellular behaviour of samarium and europium after their intra-peritoneal administration in the lactating mammary gland cells was investigated. The results showed the presence of very electron dense deposits in the glandular epithelial cell lysosomes. These particular lysosomes were never observed in the mammary cell lysosomes of control rats. These intralysosomal deposits were probably composed of insoluble samarium or europium phosphates by analogy with previous studies, the transmission electron microscopy, the ion mass microscopy and the electron probe microanalysis, and other techniques allowing the identification of the chemical structure of the intralysosomal deposits.     

Effect of Samarium on Mn Activated Zinc Borosilicate Storage Glasses

Electron-trapping materials (ETMs) are such kindof materials that can store the energy of incident lightrangingfromenergetic radiation to visible light that canbe releasedfromthetraps bythethermal or optical stim-ulationinthe formof thermoluminescence (TL) or opti-cally/photo stimulated luminescence (OSL/PSL) .ETMsare widely usedinthe filed of detectingradiation,infor-mation storage ,radiology,space exploring,indicator inthe dark and craft ,etc[1 ~6].In ETMs ,in additiontothe activation …     

On the distribution of carbon in martensite

The statistical-mechanics of a generalized perfect lattice gas is used to describe the distribution of interstitial solute atoms in martensite. In untempered martensite, partitioning of mobile interstitial carbon occurs between normal octahedral interstitial sites and those distorted sites around immobile dislocations. The statistics adopted acknowledge the finite number of each kind of site per unit volume of martensite. The dislocation density, fraction of twinned martensite, and the arrangement of dislocations are all input variables in the calculations. The principal quantities calculated are the fraction of carbon atoms segregated to dislocations and the fraction of distorted sites occupied as functions of the carbon content and substructure. The equilibrium distribution of carbon is also determined for tempering conditions where either ∈-carbide or cementite may precipitate. Here, the change in the solubility limit of ferrite with dislocation density is predicted. In untempered low carbon martensites (at 300°K) 85 pct of the carbon will be segregated to dislocations at equilibrium. This value decreases to 60 pct in an 0.80 wt pct C steel. Less than 5 pct of the distorted sites are filled when the dislocation distribution is uniform. Much higher concentrations occur when the long range stresses of the dislocations are relaxed and the mean carbon/dislocation interaction energy increases. Analogous results are presented for the equilibrium among carbides, normal sites, and distorted sites. The predictions of the lattice gas model are in agreement with numerous independent experimental observations. David Kalish, formerly withLockheed-Georgia Co. E. M. Roberts, formerly with Lockheed-Georgia Co.     

A permanent ion binding site located between two gates of the Shaker K+ channel

K+ channels can be occupied by multiple permeant ions that appear to bind at discrete locations in the conduction pathway. Neither the molecular nature of the binding sites nor their relation to the activation or inactivation gates that control ion flow are well understood. We used the permeant ion Ba2+ as a K+ analog to probe for K+ ion binding sites and their relationship to the activation and inactivation gates. Our data are consistent with the existence of three single-file permeant-ion binding sites: one deep site, which binds Ba2+ with high affinity, and two more external sites whose occupancy influences Ba2+ movement to and from the deep site. All three sites are accessible to the external solution in channels with a closed activation gate, and the deep site lies between the activation gate and the C-type inactivation gate. We identify mutations in the P-region that disrupt two of the binding sites, as well as an energy barrier between the sites that may be part of the selectivity filter.     

Potentiation and inhibition of neuronal nicotinic receptors by atropine: competitive and noncompetitive effects

Atropine, the classic muscarinic receptor antagonist, inhibits ion currents mediated by neuronal nicotinic acetylcholine receptors expressed in Xenopus laevis oocytes. At the holding potential of -80 mV, 1 microM atropine inhibits 1 mM acetylcholine-induced inward currents mediated by rat alpha2beta2, alpha2beta4, alpha3beta2, alpha3beta4, alpha4beta2, alpha4beta4, and alpha7 nicotinic receptors by 12-56%. Inward currents induced with a low agonist concentration are equally inhibited (alpha3beta2, alpha3beta4), less inhibited (alpha2beta4, alpha7), or potentiated (alpha4beta2, alpha4beta4) by 1 microM atropine. Effects on the more sensitive alpha4beta4 nicotinic receptors were investigated in detail by systematic variation of acetylcholine and atropine concentrations and of membrane potential. At high agonist concentration, atropine inhibits alpha4beta4 nicotinic receptor-mediated ion current in a noncompetitive, voltage-dependent way with IC50 values of 655 nM at -80 mV and of 4.5 microM at -40 mV. At low agonist concentration, 1 microM atropine potentiates alpha4beta4 nicotinic receptor-mediated ion current. This potentiating effect is surmounted by high concentrations of acetylcholine, indicating a competitive interaction of atropine with the nicotinic receptor, and potentiation is also reversed at high atropine concentrations. Steady state effects of acetylcholine and atropine are accounted for by a model for combined receptor occupation and channel block, in which atropine acts on two distinct sites. The first site is associated with noncompetitive ion channel block. The second site is associated with competitive potentiation, which appears to occur when the agonist recognition sites of the receptor are occupied by acetylcholine and atropine. The apparent affinity of atropine for the agonist recognition sites of the alpha4beta4 nicotinic acetylcholine receptor is estimated to be 29.9 microM.     

Hydrogen retrapping after thermal charging of hydrogen in iron single crystal

A theory to estimate and describe the behavior of supersaturated hydrogen in interstitial sites of a normal lattice and in trap sites is suggested, and the experimental proof is provided by thermal analysis. In this theory, variation with temperature changes of the equilibrium state between hydrogen in trapping sites and in normal lattice sites, which occurs during rapid cooling after hydrogen charging at high temperature, is considered. Two evolution rate peaks of hy-drogen corresponding to a reversible trap, a dislocation, and to an irreversible trap, a microvoid, are observed, respectively, at 388 and 538 K in a thermal analysis plot. The hydrogen amount released from the reversible trap is increased with decreasing microvoid concentration, even though the reversible trap density is maintained at the same level. According to the theoretical analysis, supersaturated hydrogen dissolved in a normal lattice site by a rapid cooling of hydrogen-charged iron from high temperature is predominantly retrapped into the vacant irreversible trap-ping sites. The remaining hydrogen exists in the normal lattice interstitial sites and will maintain local equilibrium with hydrogen in the reversible trap sites. The apparent hydrogen diffusivities at 293 K with each type of trap are estimated to be 1 × 10^-6 cm²/s for reversible traps and 4 × 10^-8 cm²/s for microvoid traps, based on changes in the hydrogen amount released from each type of trap with the room-temperature anneal time in vacuum. Formerly Graduate Student, Korea Advanced Institute of Science and Technology     

氮化过程中Ti薄膜的电子结构分析

建立不同类型的原子团簇模型,利用电荷自洽离散变分法计算了Ti薄膜中不同晶体结构的原子间化学键键能,分析了薄膜中晶体的局域态密度和全态密度,探讨了其电子结构和Ti-N原子间的交互作用变化.结果表明,N原子占据八面体间隙中心位置后,强Ti-N键的形成和原有Ti-Ti键的弱化,促使hcp-Ti中(00.1)面上的Ti原子沿着<01.0>方向发生迁移,成为hcp-fcc相变中fcc-Ti亚晶格形成的根源.随着进入hcp-Ti晶格中N原子数的增多,Ti-N结合键数目增加,N 2p/Ti 3d-4p杂化价电带的电子密度也随之增大,Ti的外层电子平均能量降低,保证了fcc-TiNy的稳定生长.     

硫化钐中硫和钐的分离与测定

研究了一种可同时测定硫化钐中硫和钐含量的方法。硫化钐样品经氢氧化钠、过氧化钠熔融,将负二价硫全部氧化为正六价,经两次氨水分离,滤液在pH值为2~5的条件下,煮沸加入氯化钡溶液沉淀硫酸根,计算硫含量;氨水分离两次后的氢氧化钐沉淀经盐酸酸化后,用EDTA标准溶液滴定,测定钐含量。通过正交实验确定了熔样条件为550 ℃熔融10 min,氯化钡溶液沉淀硫酸根时沉淀不需陈化;由方差分析得出氨水分离次数和沉淀pH值为影响实验结果的显著因素,进一步试验确定氨水分离次数为2次、沉淀时pH值为2~5;此外,通过实验证明方法采用镍坩埚熔样所引入的镍并不影响测定结果。按实验方法对硫化钐样品进行精密度考察,硫和钐测定结果的相对标准偏差(RSD)分别为0.73%、0.18%;加标回收试验表明,硫和钐的回收率分别在101%~103%、100%~102%之间。采用实验方法对两个硫化钐样品进行测定,并分别与氯化钡滴定法测定硫及草酸盐重量法测定钐的结果进行对照,吻合较好。实验方法相比单元素测定法,避免了重复熔样,减少了样品预处理过程,实现了硫和钐的联合测定,可用于日常生产分析。     

包头市某稀土钐冶炼厂职业性有害因素风险评估

识别稀土钐冶炼厂存在的职业性有害因素,评价其浓度、强度,提出职业性有害因素防护建议,为稀土钐冶炼职业病预防、氧化钐安全性评价提供科学依据。通过现场职业卫生调查,该厂主要职业性有害因素为稀土粉尘、氧化钐、氧化镧、噪声、工频电场等。采集作业场所空气中粉尘、氧化钐、氧化镧样品,实验室检测空气中总尘浓度及氧化钐、氧化镧浓度,检测现场噪声强度、工频电场强度。打磨车间的总粉尘浓度为9.33 mg/m^3,原料车间的总粉尘浓度为14.84 mg/m^3,均超过了我国稀土粉尘职业接触限值,粉尘检测不合格率为66.67%;打磨车间的噪声强度为90 dB(A),超过了我国噪声职业接触限值,噪声检测合格率为66.67%。生产车间、原料车间氧化钐、氧化镧的风险等级均为极高风险;打磨车间氧化钐的风险等级为极高风险,氧化镧的风险等级为高风险。粉尘、噪声、氧化钐是稀土钐冶炼厂的职业性有害因素防治的重点,应加强防护。     

ICP-AES法测定镨钕氧化物及镨钕金属中的镧、铈、钐、钇、铝和硅量

重点研究了镨钕配分对测定镨钕中镧、铈、钐、钇、铝、硅量的影响。通过研究镨钕配分与其空白值之间的关系,采用一定校正方法,成功地用一套标样解决了不同镨钕配分试样中的镧、铈、钐、钇、铝和硅量的测定问题。方法简单易行,结果稳定可靠。与ICP-M S的对照结果令人满意。     

Increase of heat-shock protein and induction of gamma/delta T cells in peritoneal exudate of mice after injection of live Fusobacterium nucleatum

The herpes simplex virus-1 (HSV-1) capsid shell has 162 capsomers arranged on a T = 16 icosahedral lattice. The major capsid protein, VP5 MW = 149,075) is the structural component of the capsomers. VP5 is an unusually large viral capsid protein and has been shown to consist of multiple domains. To study the conformation of VP5 as it is folded into capsid promoters, we identified the sequence recognized by a VP5-specific monoclonal antibody and localized the epitope on the capsid surface by cryoelectron microscopy and image reconstruction. The epitope of mAb 6F10 was mapped to residues 862-880 by immunoblotting experiments performed with (1) proteolytic fragments of VP5, (2) GST-fusion proteins containing VP5 domains, and (3) synthetic VP5 peptides. As visualized in a three-dimensional density map of 6F10-precipitated capsids, the antibody was found to bind at sites on the outer surface of the capsid just inside the openings of the trans-capsomeric channels. We conclude that these sites are occupied by peptide 862-880 in the mature HSV-1 capsid.     

改进的热裂解法制备高纯钛的研究

对传统的以高价钛卤盐(TiI4)热裂解制备高纯钛的实验方法进行了改进,使用了低价钛卤盐(TiI2)的热裂解法制备4N高纯钛,使得卤化源区温度、热裂解区(又称沉积区)温度更为优越。并对卤化源区及沉积区温度、高价卤化物的生成、原料中杂质行为以及沉积区低价碘化物的蒸汽压等影响钛沉积速率的因素进行了分析。结果表明:炉内两区温度更易于控制,且可使钛卤盐保持较高的蒸汽压与转移速度,可以有效抑制部分杂质卤化物的转移分解,从而得到制备高纯钛较为理想的沉积速率。