Nuclear quadropole resonance in arsenic and bismuth metal

Nuclear quadrupole resonance of ⁷⁵As and ²⁰⁹Bi have been observed in metallic arsenic and bismuth respectively. The quadrupole constant for ⁷⁵As extrapolated to 0 K was 47.360 MHz, in good agreement with the value deduced from low-temperature specific heat measurements. The quadrupole coupling constant for ²⁰⁹Bi was 51.2 MHz at 195 K, in agreement with the value deduced from the high-field NMR spectrum.     

Temperature and pressure variation of the electric field gradient in arsenic metal

The variation of the NQR frequency ⁷⁵v_Q for arsenic metal has been measured at 195 and 295 K for pressures up to 2 kbar and at atmospheric pressure between 77 and 525 K. The data are compared with those for other metallic elements.     

19F NMR in the S=12 antiferromagnets CuF2 and AgaF2

¹⁹F NMR has been observed in the antiferromagnetic phases of CuF₂ and AgF₂. These compounds, which are known to have very similar magnetic structures, have been shown to have similar magnetization curves and to have saturation sublattice magnetizations that scale approximately as their Neel temperatures.     

Ending Aging in Super Glassy Polymer Membranes

Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4‐methyl‐2‐pentyne) (PMP), and polymers with intrinsic microporosity (PIM‐1) reduces gas permeabilities and limits their application as gas‐separation membranes. While super glassy polymers are initially very porous, and ultra‐permeable, they quickly pack into a denser phase becoming less porous and permeable. This age‐old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO₂ permeability for one year and improving CO₂/N₂ selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.     

Kadsufolins A – D and Related Cytotoxic Lignans from Kadsura oblongifolia

Kadsufolins A–D ( 1 – 4 , resp.), four new dibenzocyclooctane‐type lignans, were isolated from the roots and stems of Kadsura oblongifolia, together with eleven known lignans. Their structures and configurations were elucidated by spectroscopic methods including 2D‐NMR techniques. The compounds were also evaluated for cytotoxic activity against human tumor cell lines A549 (lung carcinoma), DU145 (prostate carcinoma), KB (epidermoid carcinoma of the nasopharynx), and HCT‐8 (ileocecal carcinoma). Kadsufolin A ( 1 ), kadsufolin D ( 4 ), angeloylbinankadsurin A, and heteroclitin B were found to show cytotoxic activities against A549, DU145, KB and HCT‐8 with GI₅₀ values of 5.1–20.0 μg/ml.     

NQR study of ternary chalcogenides A3BX3, ABX2, and ABX where A = Cu,Ag, or TI, B = As or Sb,and X = S or Se

¹²¹Sb, ¹²³Sb, ⁷⁵As, ⁶³Cu, and ⁶⁵Cu NQR resonances are reported for CuSbSe₂, Tl₃SbSe₃, Tl₃SbS₃, Tl₃AsS₃, Tl₃AsSe₃, Ag₃AsSe₃, TlSbS₂, CuAsS, AgAsS, and Cu₅SbS₃I₂. Tl₃SbSe₃ is an incongruently melting compound not observed in an earlier phase-diagram study of the pseudobinary system Tl₂SeSb₂Se₃. For isostructural arsenic and antimony chalcogenides the ratio of ⁷⁵As to ¹²¹Sb quadrupole coupling constants is 0.42, and for the BX₃ group in binary or ternary corresponding pairs of sulfide and selenides the ratio of quadrupole coupling constants for ⁷⁵As or ¹²¹Sb is 0.83. A reversible phase transition was observed at 130 K for Ag₃AsSe₃. Unit cell parameters are reported for crystals of TlSbS₂ and Cu₅SbS₃I₂.     

NMR: hyperfine interactions in oxides and metals

A NMR characterisation is given of various polymorphs of TiO₂ (anatase, rutile and brookite), Ti₂O₃, perovskites CaTiO₃ and BaTiO₃, FeTiO₃, TiB₂, titanium metal, the titanium aluminides Ti₃Al, TiAl, TiAl₂, TiAl₃, and TiAg. Values of chemical or Knight shift, nuclear quadrupole coupling constant and asymmetry parameter were derived from the (1/2, −1/2) powder lineshapes. For TiB₂, titanium metal, TiAl, and TiAl₃, where ±(1/2, 3/2), and higher satellite transitions were observed, a value for the axial component of the Knight shift was obtained.     

NMR: hyperfine interactions in MoO3, MoS2, MoSe2 Mo3Se4, MoSi2 and Mo2C

Nuclear hyperfine interactions have been obtained by nuclear magnetic resonance (NMR) for in a number of binary Mo compounds, both insulators and metals, which illustrate the interplay between nuclear quadrupole and chemical (Knight) shift terms. The insulating phases are characterised by nuclear spin lattice relaxation times greater than 100 s, demonstrating the ineffectiveness of indirect phonon Raman relaxation for these compounds.