Supercritical fluid chromatography tandem-column method development in pharmaceutical sciences for a mixture of four stereoisomers

A tandem-column method using Chiralpak AD-H and Chiralcel OD-H columns was achieved for baseline separation of a mixture of chiral pharmaceutical compounds (i.e., four stereoisomers) via supercritical fluid chromatography (SFC) with a mobile phase consisting of 90% liquid carbon dioxide and 10% ethanol:isopropanol (50:50 v/v). On the contrary, this mixture (mixture A) could not be baseline separated by SFC conditions explored with individual Chiralpak AD-H and Chiralcel OD-H columns. The effects of various mobile phases on elution order, capacity factor, selectivity, and resolution were determined with mixture A on the individual aforementioned columns to develop the tandem-column method.     

Efficient white light emission by upconversion in Yb(3+)-, Er(3+)- and Tm(3+)-doped Y2BaZnO5

We report efficient white upconversion luminescence in Yb(3+)-, Er(3+)- and Tm(3+)-doped monophasic and biphasic Y(2)BaZnO(5) phosphors under 977 nm near-infrared excitation and at low excitation power densities (down to ～25 mW mm(-2)).     

Mechanical Properties of Dense Zeolitic Imidazolate Frameworks (ZIFs): A High‐Pressure X‐ray Diffraction,Nanoindentation and Computational Study of the Zinc Framework Zn(Im)2, and its Lithium?Boron Analogue,LiB(Im)4

The dense, anhydrous zeolitic imidazolate frameworks (ZIFs), Zn(Im)₂ ( 1 ) and LiB(Im)₄ ( 2 ), adopt the same zni topology and differ only in terms of the inorganic species present in their structures. Their mechanical properties (specifically the Young’s and bulk moduli, along with the hardness) have been elucidated by using high pressure, synchrotron X‐ray diffraction, density functional calculations and nanoindentation studies. Under hydrostatic pressure, framework 2 undergoes a phase transition at 1.69 GPa, which is somewhat higher than the transition previously reported in 1 . The Young’s modulus (E) and hardness (H) of 1 (E≈8.5, H≈1 GPa) is substantially higher than that of 2 (E≈3, H≈0.1 GPa), whilst its bulk modulus is relatively lower (≈14 GPa cf. ≈16.6 GPa). The heavier, zinc‐containing material was also found to be significantly harder than its light analogue. The differential behaviour of the two materials is discussed in terms of the smaller pore volume of 2 and the greater flexibility of the LiN₄ tetrathedron compared with the ZnN₄ and BN₄ units.     

Synthesis and Characterization of the Synthetic Minerals Villyaellenite and Sarkinite,Mn5(AsO4)2(HAsO4)2 · 4H2O and Mn2(AsO4)(OH)

Using hydrothermal methods, two manganese arsenates have been synthesized and characterized by single crystal X‐ray diffraction. The products Mn₅(AsO₄)₂(HAsO₄)₂ ?4H₂O ( 1 ) and Mn₂AsO₄(OH) ( 2 ), the Mn end‐members of the minerals villyaellenite and sarkinite, respectively, have been obtained (crystal data 1 : monoclinic, C2/c, a = 18.109(4), b = 9.332(2), c = 9.809(2) Å, β = 96.172(4)?, Z = 4; 2 : monoclinic, P2₁/c, a = 10.219(2), b = 13.613(2), c = 12.780(2) Å, β = 108.834(2)?, Z = 16). In both compounds a three‐dimensional framework of edge‐sharing MnO polyhedra is observed. Based on the availability of the all Mn2containing form of villyaellenite ( 1 ), the ordering scheme of the impurity cations of the natural samples could be confirmed. Magnetic susceptibility measurements of 1 indicate the presence of high‐spin Mn²⁺ ions. The comparison of the data on sarkinite ( 2 ) with the data obtained from the natural sample indicates that the mineral has either a very high Mn content, or an absence of impurity cation ordering.     

Siderophore-Mediated Iron Uptake Promotes Yeast–Bacterial Symbiosis

In the present study, siderophore produced by the marine yeast Aureobasidium pullulans was characterized as hydroxamate by chemical and bioassays. The hydroxamate assignment was supported by the appearance of peaks at 1,647.21?C1,625.99?cm^?1 and at 1,435.04?cm^?1 in the infrared spectrum. The purified siderophore exhibited specific growth-promoting activity under iron-limited conditions for siderophore auxotrophic probiotic bacteria. Cross-utilization of siderophore indicates a symbiotic relationship between the yeast A. pullulans and the selected probiotic bacterial strains. Statistical optimization of medium components for improved siderophore production in A. pullulans was depicted by response surface methodology. The shift in UV?CVis spectroscopy indicates the photoreactive property and subsequent oxidative cleavage of purified siderophore on exposure to sunlight.     

A high-field C-NMR study of the aqueous copolymerisation of acrylonitrile and vinyl acetate. Microstructural observations

A detailed examination has been undertaken of the high field ¹³C-NMR spectrum of various acrylonitrile/vinyl acetate copolymers prepared by radical initiation in a heterogeneous aqueous batch reaction (taken to low conversion). It has been possible to establish the triad, tetrad and pentad sequences for copolymers employing sequence patterns and peak fractions as an aid to peak assignments. These results indicate that the copolymer cotacticity is virtually independent of the comonomer feed ratio.     

Travelling Modes in Wave-Heated Plasma Sources

This paper describes a theoretical and experimental study of surface- and helicon-wave-heated plasma sources in which standing waves are set up in the cavity between the closed end plate to a plasma vessel and a wave launcher while travelling waves propagate from the opposite side of the launcher into a region which is long compared with the attenuation distance of the waves. We model the situation as a lossy transmission line of finite length coupled at the launcher to a lossy transmission line of infinite extent. RF power applied to the launcher divides in the ratio of the input impedances of the two transmission lines. For a conducting end plate, the power delivered to the travelling waves is a maximum when the cavity length is an odd number of 1/4 wavelengths long for which its input impedance is a maximum. Similarly, for an insulated end plate, the power delivered to the travelling waves is a maximum for a cavity with a length equal to an integer number of half wavelengths for which its input impedance is again a maximum.      

Two coordination polymers created via in situ ligand synthesis involving C-N and C-C bond formation

We report the synthesis and crystal structures of two transition metal-based coordination polymers comprising ligand molecules not included in the original reaction mixtures but instead formed in situ during hydrothermal treatment. Zinc meso-iminodisuccinate hydrate (I), Zn(2)(C(8)H(7)NO(8)).0.57H(2)O, formed from zinc acetate and L-aspartic acid, and tetraaquanickel(II) 5,10-dioxo-5,10-dihydro-4,9-dioxa-pyrene-2,7-dicarboxylate (II), Ni(H(2)O)(4)(C(16)H(4)O(8)), formed from nickel acetate and 5-hydroxyisophthalic acid. We show that the formation of I takes place via a fumaric acid intermediate, while the formation of II requires the formation of a new C-C bond. The structure of I consists of weakly interacting sheets, while the structure of II consists of strongly hydrogen-bonded chains. Crystal data: for I, P2(1)/n (14), a = 10.073 A, b = 9.894 A, c = 12.053 A, beta = 105.605 degrees, V = 1156.87(13) A(3), Z = 4; for II, P1 (2), a = 5.011 A, b = 6.526 A, c = 12.305 A, alpha = 76.868 degrees, beta = 84.988 degrees, gamma = 87.619 degrees, V = 390.3(4) A(3), Z = 1.