X-ray-fluorescence analysis of high-purity holmium oxide for common rare earth impurities

Summary An X-ray fluorescence analysis method for determination of Gd, Tb, Dy, Er, Tm and Yb in Holmium oxide is described. Samples are converted to oxalate form and mixed with boric acid in the ratio 31. A double layer pellet is obtained by pressing about 800 mg of this mixture on a boric acid pellet. Selection of experimental parameters and analysis lines are discussed. The estimation limit ranges from 0.005% to 0.5%.

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Röntgenfluorescenzspektrometrische Analyse von hochreinem Holmiumoxid auf Verunreinigung von Seltenen Erden

Zusammenfassung Die Proben werden in die Oxalatform übergeführt, mit Borsäure vermischt (31) und in Mengen von 800 mg als zweite Schicht auf eine Borsäuretablette gepreßt. Die Auswahl der experimentellen Parameter und der Analysenlinien wird diskutiert. Die Erfassungsgrenzen für Gd, Tb, Dy, Er, Tm und Yo liegen im Bereich von 0,005–0,5%.

     

On the coefficients of a function analytic in the unit disc having slow rate of growth

Summary For a function f, analytic in z < 1, the notions of generalized orders are introduced that are specially suited for the study of the growth of f, if it is of slow growth. The characterizations of the generalized orders are found in terms of the coefficients in the Taylor series development of f. A decomposition theorem is proved for functions of hirregular growth. The results of the present paper generalize the results in [G. P. Kapoor - K. Gopal, J. Math. Anal. Appl., 74 (1980), pp. 446–455].     

X-ray fluorescence spectrometric and optical emission spectrographic analysis of river sand for thorium,yttrium and zirconium

Analytical and Bioanalytical Chemistry -     

Carbon Nanosheets Synthesis in a Gliding Arc Reactor: On the Reaction Routes and Process Parameters

Non-thermal plasma is a promising technology for high purity nanomaterial synthesis in a fast, flexible and controllable process. Gliding arc discharge, as one of the most efficient non-thermal plasmas, has been widely used in gas treatment but rarely studied for the nanomaterial synthesis. In this study, a comparison study for carbon nanosheets synthesis including toluene dissociation and graphite exfoliation was investigated in a 2D gliding arc reactor at atmospheric pressure. The effects of gas flow rate, precursor concentration and power input on the structures of carbon nanosheets produced through the two synthesis routes were explored and compared. Amorphous carbon nanosheets were produced in both approaches with a few crystalline structures formation in the case of toluene dissociation. The thickness of carbon nanosheets synthesized from graphite exfoliation was less than 3 nm, which was thinner and more uniform than that from toluene dissociation. The flow rate of carrier gas has direct influence on the morphology of carbon nanomaterials in the case of toluene dissociation. Carbon spheres were also produced along with nanosheets when the flow rate decreased from 2 to 0.5 L/min. However, in the case of graphite exfoliation, only carbon nanosheets were observed regardless of the change in flow rate of the carrier gas. The generated chemical species and plasma gas temperatures were measured and estimated for the mechanism study, respectively.

     

Towards a practical Fourier transform infrared chemical imaging protocol for cancer histopathology

Fourier transform infrared (FTIR) chemical imaging is a strongly emerging technology that is being increasingly applied to examine tissues in a high-throughput manner. The resulting data quality and quantity have permitted several groups to provide evidence for applicability to cancer pathology. It is critical to understand, however, that an integrated approach with optimal data acquisition, classification, and validation is necessary to realize practical protocols that can be translated to the clinic. Here, we first review the development of technology relevant to clinical translation of FTIR imaging for cancer pathology. The role of each component in this approach is discussed separately by quantitative analysis of the effects of changing parameters on the classification results. We focus on the histology of prostate tissue to illustrate factors in developing a practical protocol for automated histopathology. Next, we demonstrate how these protocols can be used to analyze the effect of experimental parameters on prediction accuracy by analyzing the effects of varying spatial resolution, spectral resolution, and signal to noise ratio. Classification accuracy is shown to depend on the signal to noise ratio of recorded data, while depending only weakly on spectral resolution.     

Photo-, thermally, and pH-responsive microgels

Microgels with photo-, thermally, and pH-responsive properties in aqueous suspension have been synthesized and characterized using dynamic light scattering and UV-visible spectroscopy. The new route involved first preparing poly(N-isopropylacrylamide) (PNIPAM)-allylamine copolymer microgels and a spiropyran photochrome (SP) bearing a carboxylic acid group. Then the functionalized spiropyran was coupled to the microgel via an amide bond. The dark-equilibrated gel particles feature spiropyran molecules in the polar, merocyanine form. After irradiation of visible light, the particle size becomes smaller because spiropyran changes to the relatively nonpolar, closed spiro form. The PNIPAM-SP microgels undergo a volume phase transition in water from a swollen state to a collapsed state with increasing temperature under all light conditions. However, the transition temperature range of the PNIPAM-SP is much broader than that for the PNIPAM without SP. The PNIPAM-SP microgels are monodisperse and self-assemble into a crystalline lattice while in suspension. The UV-visible spectra of an aqueous suspension of PNIPAM-SP microgel in the dark-adapted, merocyanine form showed both an absorption peak around 512 nm due to the merocyanine (giving a reddish color to the suspension) and two sharp peaks from Bragg diffraction of colloidal crystallites. Upon visible irradiation, the 512-nm band bleached significantly due to spiropyran photoisomerization. The spiropyran photoisomerization and accompanying color changes of the suspension were reversible upon alternating dark, UV, and visible light irradiation. Due to the residues of amine groups, the swelling capability of PNIPAM-SP microgels reduces as the pH value is changed from 7 to 10.     

Parameters of monovalent ions in the AMBER-99 forcefield: assessment of inaccuracies and proposed improvements

The monovalent ion parameters used by the AMBER-99 forcefield are shown to exhibit physically inaccurate behavior in molecular dynamics simulations of strong 1:1 electrolytes. These errors arise from an ad hoc adaptation of Aqvist's cation parameters. The result is the rapid formation of large, unphysical clusters at concentrations that are well below solubility limits. The observed unphysical behavior poses a serious challenge for simulating ions around highly charged polymers such as nucleic acids. In this communication, we explain the source of this unphysical behavior. To facilitate the continued use of the popular AMBER parameters, we prescribe a simple fix whereby Aqvist's cations and anions are used in conjunction with the AMBER forcefield for nucleic acids. A preliminary test of this strategy suggests that the proposed fix is reasonable and is likely to be generalizable for simulating diffuse and specific ion binding to nucleic acids.     

Carboranyl thymidine analogues for neutron capture therapy

Neutron capture therapy (NCT) is a binary radio-chemotherapeutic modality for the treatment of cancer. A major focus of NCT-related research is the development of novel tumor-selective agents that serve as the chemical component in NCT. Thymidine analogues substituted with a boron-containing carborane cluster at the N3 position, designated 3CTAs (3-carboranyl thymidine analogues), constitute one class of these new improved NCT agents. Their chemical, structural and biological properties are discussed in this Feature Article.