Thermoactivated spectroscopy of heterovalent impurity traps in CdWO4

Abstract

Recombination luminescence emission spectra, TSL and trap spectra estimated by fractional glow technique (FGT), in nominally pure and Li-, Bi- and Ho-doped CdWO₄, crystals are reported. According to the investigations by FGT heterovalent impurities Li, Bi and Ho causes localized electronic states which act as traps for charge carriers. It is shown that TSL results in emission of known blue-green luminescence band by emptying of the Li⁺-related traps in CdWO₄-Li and yellow luminescence band by emptying of the Bi³⁺-related traps in CdWO₄-Bi. It is proposed that blue-green and yellow luminescence occur by recombination correspondingly of free holes and free electrons at different intrinsic tungstate group related luminescence centers.     

Gas Chromatographic Method Optimization and Statistical Validation for the Determination of Trace Impurities in Street Doses of Heroin

This study aims to utilize the manufacturing impurities found in illicit heroin to predict whether the samples had originated from a common production batch. From highly cut heroin samples, twelve frequently extractable neutral/acidic impurities were selected for investigation. A gas chromatographic method was optimized using three locally seized samples containing the target impurities and a control sample consisting of n-alkanes. The method optimization procedures are reported in detail. The capability of the optimized method was further assessed using five simulated links prepared from unrelated heroin seizures. With the aid of principal component analysis (PCA), it was found that the statistical data pretreatment (normalization followed by standardization, N + S) showed promising results for sample classification using profiles obtained with the optimized method. Similarly, 252 street doses of highly cut samples were analyzed and the profiles were statistically decomposed by PCA after the N + S pretreatment. The statistics suggested that the locally seized samples could have originated from more than one production batch.     

Effects of electron–electron interaction on the collinear indirect exchange coupling in graphene nanoflakes

Using the Hubbard model in the framework of the tight-binding formulation, we studied the effects of the electron–electron (e–e) interaction on the indirect magnetic exchange coupling between the magnetic impurities embedded in triangular graphene nanoflakes. The results show that the magnitude of the coupling enhances in the presence of the e–e interaction and Rashba spin–orbit interaction (RSOI). The RKKY coupling magnitude depends on the impurity positions in nanoflake and the size of the system, as well.     

Gamma-ray,X-ray and ultraviolet light induced low temperature thermoluminescencez of KN3 and NaN3

Abstract

On évalue, pour une chaine atomique linéaire, la variation du coefficient de dilatation thermique Δ α lorsque la chaine est sous contrainte. On en déduit la variation du module de Young avec la température. L'accord raisonnable, sur ce second point, avec les résultats expérimentaux montre que le sens de variation trouvé pour Δ α demeure, au moins qualitativement, pour un cristal à 3 dimensions.

On montre alors que, pour un cristal irradié sous contrainte par des particules de grande énergie, cette variation Δ α peut entrainer une contribution négative au fluage.

THERMAL EXPANSION OF A LINEAR CHAIN UNDER STRESS APPLICATION TO CREEP UNDER IRRADIATION

Variations of thermal expansion coefficient Δ α of a linear atomic row under stress, are evaluated. Variations of Young's modulus with temperature are deduced. A reasonable agreement, on this point, with experimental measurements indicates that at least the sign obtained for Δ α subsists qualitatively for a 3-dimensional crystal.

It is then shown that, for a crystal irradiated under stress with high energy particles, this variation Δ α may lead to a negative contribution to creep.     

Photoluminescence with Peaked Structure: Inherent to Nanoparticles or Resulting From Impurities in Sample Vial Caps?

We show that fluorescence emission in the visible spectral range reported in the case of many nanoparticles, polymers, complexes and liquid crystals with molecular type signatures could originate from the organic impurities leaching from the caps of glass vials.     

A comparative analysis of infra-red luminescence spectra of ZnSe crystals doped with Yb,Gd or Cr impurities

Infra-red (IR) photoluminescence (PL) spectra of ZnSe crystals doped with Yb, Gd rare-earth impurities and Cr impurity are investigated. The influence of stoichiometric deviation on the spectra is studied and the structure of complex IR PL bands is analysed. The good coincidence between the structures of IR PL spectra of the samples doped with Yb, Gd, and Cr is shown. Correlation between the component parts of the bands at 1 and 2 μm is found and possibility to control the composition of IR PL spectra by enrichment of the samples with Zn or Se is discussed. The models that explain the formation of complexes based on rare-earth and background Cr and Cu impurities, responsible for IR PL bands, are proposed. Keywords: IR luminescence, ZnSe, Rare-earth impurities, Cr impurity.     

超高真空下过渡金属Nb与Nb、Ta、Ti、W相互间粘附特性的试验研究

本文在超高真空(10~(-7)Pa)条件下量测了Nb-Nb(110)、Nb-Ta(110)、Nb-W(110)及Nb-Ti4个粘附对的粘附力,并从接触表面形貌的角度求得了真实接触面积,进而得到了各粘附对间的粘附强度,结果与采用简单紧束缚自洽矩方法计算所得理论结果一致。研究表明,超高真空下过渡金属间存在一种相互作用——由两金属间共用电子引起的化学键,而且主要由其外层d电子态密度所决定。过渡金属Nb与Nb、Ta、W、Ti之间粘附强度的实测值介于每对原子0.2～2.0eV之间。当样品受热升温后,由于C、N、B、S等少量非金属杂质的表面偏析致使粘附强度明显降低。     

Impurity Profile Study of Venlafaxine Hydrochloride,an Antipsychotic Drug Substance

Venlafaxine hydrochloride is a phenyl ethylamine derivative, used for the treatment of depression. During the process development of venlafaxine hydrochloride, six process-related potential impurities were detected in high-performance liquid chromatography. All these impurities were identified, synthesized, and subsequently characterized by their respective spectral data (IR, mass, ¹H NMR, and ¹³C NMR) as described in this article.     

Determination of impurities and counterions of pharmaceuticals by capillary electromigration methods

The review presents a survey of recent applications of high‐performance capillary electromigration methods—capillary zone electrophoresis, nonaqueous capillary electrophoresis, capillary isotachophoresis, micellar electrokinetic chromatography, microemulsion electrokinetic chromatography and capillary electrochromatography—for the determination of impurities of pharmaceuticals, including chiral impurities, for the period 2007–2013. In addition, due to the missing evaluation of the determination of counterions of pharmaceuticals by capillary electromigration methods in the last 20 years, the publications dealing with this topic since 1995 are included in this review. General aspects of both these types of applications of capillary electromigration methods in pharmaceutical analysis are discussed, and detailed experimental conditions used for determination of various chemical impurities and counterions of many particular drugs are described.     

Application of the Electrolysis for the Purposes of Receiving Titanium-based Powders from Fluoride Fusions

A short review of industrial technologies used for receiving titanic powders is provided. Shortcomings of existing industrial chloride production technologies of titanium are shown. The need to develop, the essentially new fluoride technology for the purposes of receiving titanic powders from low-temperature fluoride fusions is shown. The preparation technique for fluoride fusions uses the process of hydrofluoration of fluorides from lithium and sodium non-aqueous HF with the allocated decomposition of potassium hydrofluoride is given. The processes occurring during the electrolysis of titanic powders from fluoride fusions with the use of tetrafluoride as a reagent for the titanium are described.