Thermodynamic properties and high-temperature behavior of lanthanum selenides La3Se4-La2Se3

The enthalpy of the La₃Se₄ and La₂Se₃ boundary compositions of the La_3?xSe₄ phase (0 ≤ x ≤ 1/3) at temperatures from 370 to 2260 K is studied calorimetrically. The values obtained are used and the equilibria of the La-Se system are analyzed to establish, for the first time, the temperature-concentration relationships for the thermodynamic properties of La_3?xSe₄ selenides in the homogeneity region at 298 K ≤ T ≤ 2123 K. The enthalpy function (J/mole) of La^3?xSe₄ is given by H(T) ? (298 K) = (3837 · 10³T^?1 ? 85852 + 266.925 · T ? 8.7503 · 10^?2 T² + 3.437 · 10^?5 T³) · e^?0.2869x. The formation and melting enthalpies of La₃Se₄ are determined: Δ_fH °(298 K) = ?1340 ± ± 28 kJ/mole), Δ_mH = 147.5 ± 9.6 kJ/mole. It is shown that the high-temperature stability of different La_3?xSe₄ compositions is strongly dependent on pressure: as pressure decreases and temperature increases, the selenium content is reduced and the composition tends to La₃Se₄.     

Gas evolution from powders of the copper selenide Cu1.985 Se

Conclusions At low temperatures water predominates in the compositions of desorbed gases. As the temperature is raised, CO₂, CO, O₂, CH₄, and H₂ begin to be liberated, their amount increasing with rising temperature, while the amount of H₂O decreases. Prolonged (30-h) vacuum annealing at 523–573°K enables a specimen of the material to be almost completely degassed. A degassed specimen exhibits increased sorptive power, especially with respect to water.Translated from Poroshkovaya Metallurgiya, No. 7(259), pp. 25–29, July, 1984.     

Chemistry of the Ca–Se(IV)–H2O and Ca–Se(VI)–H2O systems at 25 °C

The Ca–Se(IV)–H₂O and Ca–Se(VI)–H₂O systems were studied by contacting either selenious acid or selenic acid solution with calcium oxide to attain equilibrium at 25 °C for one month. Analysis of the final solid phases and the associated solution, together with X-ray diffraction analysis and a study into the graphed relationships, showed the existence of three calcium selenites in the Ca–Se(IV)–H₂O system — Ca₂SeO₃(OH)₂·2H₂O (Se(IV) = 4.8 × 10^− 5–2.8 × 10^− 4 M); CaSeO₃·H₂O (Se(IV) = 2.8 × 10^− 4–0.86 M) and Ca(HSeO₃)₂·H₂O (Se(IV) > 0.86 M). It also showed four calcium selenates in the Ca–Se(VI)–H₂O system — Ca₂SeO₄(OH)₂ (Se(VI) = 0.21–0.39 M); CaSeO₄·2H₂O (Se(VI) = 0.40–9.1 M); CaSeO₄ (Se(VI) = 10.2 M) and CaSe₂O₇ (Se(VI) > 10.8 M). The X-ray diffraction analyses reported and SEM analyses indicate a high degree of crystallinity of all seven compounds. The stability and solubility regions for these compounds were defined versus pH, and the conventional solubility constants and conditional free energies of formation for the less soluble CaSeO₃·H₂O, Ca₂SeO₃(OH)₂·2H₂O, CaSeO₄·2H₂O and Ca₂SeO₄(OH)₂ were calculated from solubility data obtained.     

Mesure de Stress Psychologique (MSP): Se sentir stressé-e.

Studied the development and validity of an instrument designed to measure stress by evaluating subjective feelings of stress without referring to "stress" or "stressors." Human subjects: 696 male and female Canadian adults, divided into 6 groups. Group I (15 Ss) were asked to provide a list of stress indicators for themselves, their spouses, and others. These indicators were used to establish the content validity of the Mesure de Stress Psychologique (MSP) ("Psychological State of Stress Measure"). Group II (98 university students) Ss were given a 95-item stress questionnaire; the results were analyzed statistically and used to select 74 items for the MSP. Group III (97 university students) Ss were given the 74-item MSP to determine the internal consistency of the instrument. Group IV (188 married couples with a primary school child) Ss were asked to answer the MSP for themselves and for their spouses. These results were analyzed statistically according to sex, family structure, and socioeconomic variables. Group V (66 adults aged 20–60 yrs) and Group VI (44 dental students) Ss were given a 53-item MSP on 2 to 4 occasions to evaluate test–retest and hypothetical-deductive validity. The results were evaluated using a multivariate analysis of variance (MANOVA). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Molecular genetics of alpha-L-fucosyltransferase genes (H, Se, Le, FUT4, FUT5 and FUT6)

The records of 1018 patients with low back pain in a tertiary spine referral practice were reviewed. One hundred thirty-nine out of 1018 (13.6%) underwent technetium-99m planar bone scanning as part of their investigation. Seventy-three out of 139 scans (52%) showed increased uptake in some area, but only 27 out of 139 (19.4%) showed increased uptake specifically in the low back. Scans consistently yielded no findings with reference to the back when the prescan diagnosis was spinal stenosis, lumbar pain syndrome, herniated nucleus pulposus, or postlaminectomy syndrome. Some scans gave positive findings in patients with a diagnosis of degenerative disc disease, pseudarthrosis, spondylolisthesis, fracture, infection, metabolic disorder, or tumor. Positive scans were generally obtained early after presentation (within 3 months) and negative scans obtained later (after 6 months), suggesting that clinical suspicion is still the main indication for early scanning. Planar bone scanning was helpful in both diagnosis and therapeutic decision-making in many conditions.     

A thermodynamic investigation of crystalline and amorphous Se−Te alloys

The heats of formation, referred to the component elements in their stable crystalline forms, of crystalline Se?Te alloys containing 0 to 100 at. pct Te and amorphous alloys containing 0 to 30 at. pct Te were measured by liquid metal solution calorimetry. The heats of formation of the crystalline and amorphous alloys changed nonmonotonically with composition in a parallel manner. The crystalline alloys had negative heats of formation in the range of 0 to approximately 17 at. pct Te; the largest negative value of approximately?0.235 kcal/g-atom occurred at 10 at. pct Te. At 20 at. pct Te the heat of formation was positive and had a value of approximately 0.115 kcal/g-atom and at higher tellurium concentrations it again turned negative but was very small. The heats of formation of all amorphous alloys investigated were positive. A minimum of approximately 0.810 kcal/g-atom at 10 at.pct Te and a maximum of 1.040 kcal/g-atom at 20 at. pct Te corresponded to the largest negative value and the largest positive value of the heat of formation of the crystalline alloys of the respective compositions. The temperatures of maximum rates of crystallization and fusion and the heat effects associated with the crystallization and fusion of the amorphous alloys were measured by differential scanning calorimetry. With increasing tellurium concentration the temperature of crystallization decreased and the heat effect and the temperature associated with fusion increased.     

闪蒸法制备N型Bi2( Te0.95Se0.05)3薄膜的微结构及热电性能研究

采用闪蒸法在温度为473 K的玻璃基体上沉积了厚度为800 nm的N型Bi2(Te0.95Se0.05)3热电薄膜,并在373 ～573 K进行1h的真空退火处理.利用X射线衍射(XRD)、场发射扫描电子显微镜(FESEM)分别对薄膜的物相结构和表面形貌进行分析.采用表面粗糙度测量仪测定薄膜厚度,薄膜的电阻率采用四探针法进行测量,采用温差电动势法在室温下对薄膜的Seebeck系数进行表征.沉积态薄膜表明了(015)衍射峰为最强峰,退火处理后最强衍射峰为(006);沉积态薄膜由许多纳米晶粒组成,晶粒大小分布较均匀,平均晶粒尺寸大约45 nm,退火处理后出现了斜方六面体的片状晶体结构.退火温度从373 K增加到473 K,薄膜的电阻率和Seebeck系数增加,激活能也随退火温度的增加而增大,退火温度从523 K增加到573 K,薄膜的电阻率和Seebeck系数都缓慢下降.从373 ～473 K,热电功率因子随退火温度的升高而单调增加,退火温度为473 K时,电阻率和Seebeck系数分别是2.7 mΩ.cm和-180μV·K-1,热电功率因子最大值为12 μW.cmK-2.退火温度从523 K增加到573 K,热电功率因子的值逐渐下降.     

Selenium (Se) deficiency in women with ovarian cancer undergoing chemotherapy and the influence of supplementation with this micro-element on biochemical parameters

A clinical study was undertaken to evaluate the influence of a preparation containing selenium and vitamins with antioxidant properties (Protecton Zellaktiv from Smith Kline Naturarznei-Germany) on: (a) concentration of Se in serum and hair, (b) activity of glutathione peroxidase (GSH-Px), and (c) concentration of malondialdehyde (MDA) in serum, before and during supplementation. Women undergoing chemotherapy for ovarian cancer received selenium during three months at a daily dose of 200 micrograms. The results were compared with controls not receiving selenium supplementation. Administration of selenium significantly increased the serum and hair concentrations of selenium in the study group. After three months of supplementation the activity of GSH-Px was significantly higher in the study group. After one month of supplementation a difference in the concentration of MDA between the study and control groups was found. On the basis of the present results the administration of selenium in patients with ovarian cancer undergoing multi-drug chemotherapy is recommended.     

Isotope dilution analysis of Se in human blood serum by using high-power nitrogen microwave-induced plasma mass spectrometry coupled with a hydride generation technique

To establish a method for sensitive, accurate, and precise determination of Se in real samples, isotope dilution analysis using high-power nitrogen microwave-induced plasma mass spectrometry (N2 MIP-IDMS) was conducted. In this study, freeze-dried human blood serum (Standard Reference Material, NIES No. 4) provided by NIES (National Institute for Environmental Studies) was used as a real sample. The measured isotopes of Se were 78Se and 80Se which are the major isotopes of Se. The appropriate amount of a Se spike solution was theoretically calculated by using an error multiplication factor (F) and was confirmed experimentally for the isotope dilution analysis. The mass discrimination effect was corrected for by using a standard Se solution for the measurement of Se isotope ratios in the spiked sample. However, the sensitivity for the detection of Se was not so good and the precision of the determination was not improved (2-3%) by N2 MIP-IDMS with use of the conventional nebulizer. Therefore, a hydride generation system was connected to N2 MIP-IDMS as a sample introduction system (HG-N2 MIP-IDMS) in order to establish a more sensitive detection and a more precise determination of Se. A detection limit (3 sigma) of 10 pg mL-1 could be achieved, and the RSD was less than 1% at the concentration level of 5.0-10.0 ng mL-1 by HG-N2 MIP-IDMS. The analytical results were found to be in a good agreement with those obtained by the standard addition method using conventional Ar ICPMS.     

铜阳极泥脱硒的工艺探讨及设计研究

探讨了从铜阳极泥中脱硒的主要工艺,重点阐述回转窑蒸硒工艺,包括工艺流程、主要设备选型,并结合目前国内工业生产实践及工程设计经验,优化设计。     

CVD方法制备ZnSe系统中尾气的处理

CVDZnSe是目前光学性能最好的红外光学材料之一。但在制备CVDZnSe时，尾气中未反应完全的剧毒硒化氢气体，对操作人员及环境的危害很大。采用逆流填料塔来吸收CVD方法制备ZnSe系统中的剧毒尾气硒化氢。为加快传质速率，提高吸收率，选用NaOH溶液作吸收液；利用H2Se气体与此溶液反应，降低气体在水溶液中的浓度，加大传质推动力；选择了具有高效分离因子的填料以减小塔身的高度和直径。并且对循环吸收液进行氧化，双重过滤等处理。最后用型号为TX—FMD的H2Se检测仪测量处理后的尾气中H2Se气体的含量，达到排放要求。     

Distribution equilibria of Sn,Se and Te between FeO-Fe2O3-SiO2-AI2O3-CuO0.5 slag and metallic copper

The distribution of tin, selenium and tellurium between alumina-containing fayalitic slags and metallic copper was measured at 1200 and 1300°C under controlled CO-CO₂ atmosphere with oxygen partial pressure (pO₂) in the rangePO ₂ = 10_-6 to 10_-11 atm (1 atm = 1.013 x 10² kPa). The solubility of Sn in slag was observed to increase linearly with increasing P^1/2O₂. It was deduced that Sn is present in the slag in the form of SnO or Sn² and the activity coefficient of SnO in the slag was calculated to be 1.9 at 1200°C and 0.8 at 1300°C. The solubility of Se in the slag decreases with increasing oxygen partial pressure up topO ₂l = 4 x 10₋₈ atm, but above this oxygen partial pressure it becomes practically constant and the ratio (pet Se in slag/pet Se in copper) = 0.018 (at 1200°C) and 0.036 (at 1300°C). The solubility of Te shows a similar variation with oxygen partial pressure and the ratio (pet Te in slag/pet Te in copper) = 0.026 (at 1200°C) and 0.032 (at 1300°C) abovepol ₂ = 10⁶ atm. A concept of molecular dissolution of chalcogen elements in slag was developed on the basis of thermodynamic properties of slag, and the observed solubility of Se and Te was explained in terms of the chemical stability of the molecular cluster FeSe and FeTe iη the slag. M. Nagamori is with Centre de Recherche Industrielle du Québec, Ste-Foy, Quebec and P. J. Mackey is Smelter Technical Superintendent, Noranda Mines Limited, Noranda, Quebec, Canada. Both authors were Formerly with Noranda Research Centre, Pointe Claire, Quebec.     

A Study of the Higher Electronic Transitions of Selenoformaldehyde, CH2Se

The pi --> pi* and n --> 5s absorption spectra of selenoformaldehyde, CH2Se and CD2Se, are reported. Both spectra are diffuse. The pi --> pi* transition extends from 243 to 210 nm with an extensive Franck-Condon profile and intensity maximum estimated at 230 nm. The Rydberg n --> 5s transition is superimposed on the pi --> pi* system. While still diffuse, the system is less extensive and shows an intensity maximum at 235 nm. The corresponding Rydberg transition of the deuterated species is blue shifted by 140 cm-1. Copyright 1999 Academic Press.     

高铅、高银酸泥中亚硫酸钠浸硒的工艺研究

酸泥中含硒、铅、银、铜、锌等金属,用亚硫酸钠浸出其中的硒。在浸出过程中,主要研究了Na2SO3浓度、温度、时间、液固比等因素的影响。结果表明,在浸出过程中,硒进入溶液,而其他元素Ag,Cu,Zn,Fe等留在浸出渣中,浸出过程具有良好的选择性,硒的浸出率达到85%～90%。并获得了浸出过程的最佳条件:Na2SO3浓度220 g·L-1,温度120～125℃,反应时间120 min,液固比4∶1。同时研究了在亚硫酸钠浸硒体系中氯化钠及碳酸钠对硒浸出率的影响,在有添加剂氯化钠的条件下,硒浸出率能达到94%～96%,氯化钠的最佳用量是20～25 g·L-1;在添加碳酸钠的条件下,硒浸出率能达到96%～98%,碳酸钠的最佳用量是60～80 g·L-1。     

Regional variation in As, Cu, Hg, and Se and interaction between them

A comparative survey of trace elements in hair samples from three different regions of the world was carried out. The concentrations of the same trace elements in tissues from infants and adults from Glasgow are also presented. It was found that the Se levels in hair samples from Iceland are significantly lower than the levels found for the Glasgow area. The level of Hg was in the same range as that for the Glasgow area and the As level is much lower in Iceland. Comparison of the levels of Hg, As, and Se in hair samples from Iran and Glasgow revealed significantly lower levels of these trace elements in samples from Iran, but the Cu levels were similar. Comparison of adult and infant levels of Se and Cu revealed fetal storage of Cu in the livers of infants. Arsenic levels were higher in adult tissues. In the study of the interaction among trace elements in human tissues, a positive correlation between Hg and Cu in liver samples from the Glasgow area and hair samples from Iran was found. A positive correlation between Se and As was also found in spleen and lung tissues.     

Effects of O,Se, and Te on the rate of nitrogen dissolution in molten iron

The effects of oxygen, selenium, and tellurium on the rate of nitrogen dissolution into molten iron have been investigated at 1973 K using an isotope-exchange reaction and the results are summarized as follows. The rate constant of nitrogen dissolution measured at lower oxygen concentration ([mass pct O] < 0.015) is larger than previously reported ones under an atmospheric pressure and agrees well with the value from desorption rate under reduced pressures. Selenium and tellurium retard the nitrogen dissolution into liquid iron more significantly than oxygen, and the degree of the retarding effect is in the order of tellurium, selenium, and oxygen. The adsorption coefficients are calculated to be K_O = 144, K_Se = 1120, and K_Te = 1640 with respect to [1 mass pct solute] from present results. A model that surface active elements and nitrogen are adsorbed on the same site at the interface and the dissociation reaction of nitrogen molecule on the site represented by the equation is the rate-determining step reasonably expresses the retarding effect of the surface active elements on the reaction rate on the assumption that all sites at the metal surface have a uniform adsorption energy for each solute.     

从铜阳极泥高压釜浸出液中回收碲和硒的新工艺

在铜阳极泥加压氧化浸出过程中,超过65％的碲在脱铜过程中同时析出.在浸出条件恶劣的情况下,大约10％ ～15％的硒也会同时溶解.目前对浸出液的处理方式是让浸出液通过一层铜屑进行循环.浸出液经沉积形成碲化铜和硒化铜,溶液再经过滤进行分离.为了提高反应效率,降低工艺成本,尽量减少铜的加入量,缩短停留时间,降低能耗,在实验室中研究了一种化学还原剂,并进行了沉积工艺试验.本文给出了试验结果,并对工艺化学进行了探讨.     

高镍铜阳极泥中硒、碲、铜的顺序脱除

针对高含镍铜阳极泥,采用直接添加氢氧化钠焙烧-碱浸-酸浸流程进行Se、Te、Cu的脱除试验研究,并对过程的反应机理进行了分析。研究发现,加碱氧化焙烧过程中硒化物和碲化物中的Cu变成Cu O和Cu3Te O6;Se、Te分别转变成在碱性溶液中易溶的Na2Se O3和不溶的Ag2Te O3、Cu3Te O6,为Se、Te、Cu的选择性脱除奠定了基础。试验结果表明,最佳焙烧-碱浸的条件为:Na OH剂量为阳极泥的10%,焙烧时间1.5h,焙烧温度500℃。碱浸时间1.0h、Na OH浓度20g/L、碱浸温度80℃、液固比5∶1。在此条件下Se的浸出率为95.50%,碱浸渣中Se的含量从3.93%下降到0.23%。碱浸渣酸浸除铜碲的最佳条件为:H2SO4浓度为90g/L、酸浸温度70℃、酸浸时间1.0h、液固比20∶1;在此条件下,Cu、Te的脱除率分别为96.18%、98.48%。     

Plasma trace element (Se, Zn, Cu) concentrations in maternal and umbilical cord blood in Poland. Relation with birth weight, gestational age, and parity

Selenium (Se), copper (Cu), and zinc (Zn) concentrations were determined in plasma of 64 mothers at delivery, 58 nonpregnant women, 64 neonates, and 12 infants, aged 2-12 mo. Se and Zn concentrations in mothers at delivery were significantly lower, and Cu higher than in nonpregnant women. Mean Se and Cu concentrations in newborns were statistically lower than those in mothers at delivery, and Zn and Cu concentrations in preterm infants (n = 13) were significantly higher than in fullterm infants (n = 51). Maternal parity had no significant influence on the distribution of plasma trace element levels. No significant differences were observed in Se and Zn levels in maternal and cord blood plasma according to birth weight, contrary to maternal Cu concentration. Significant correlations were found between maternal and cord blood Se content, and between maternal plasma Cu concentration and birth weight of neonates.