Density-functional studies of tungsten trioxide, tungsten bronzes, and related systems

Tungsten trioxide adopts a variety of structures which can be intercalated with charged species to alter the electronic properties, thus forming `tungsten bronzes'. Similar optical effects are observed upon removing oxygen from WO_3, although the electronic properties are slightly different. Here we present a computational study of cubic and hexagonal alkali bronzes and examine the effects on cell size and band structure as the size of the intercalated ion is increased. With the exception of hydrogen (which is predicted to be unstable as an intercalate), the behaviour of the bronzes are relatively consistent. NaWO_3 is the most stable of the cubic systems, although in the hexagonal system the larger ions are more stable. The band structures are identical, with the intercalated atom donating its single electron to the tungsten 5d valence band. Next, this was extended to a study of fractional doping in the Na_xWO_3 system (0 < x < 1). A linear variation in cell parameter, and a systematic change in the position of the Fermi level up into the valence band was observed with increasing x. In the underdoped WO_3-x system however, the Fermi level undergoes a sudden jump into the conduction band at around x = 0.2. Lastly, three compounds of a layered WO_4&#215;a,wdiaminoalkane hybrid series were studied and found to be insulating, with features in the band structure similar to those of the parent WO_3 compound which relate well to experimental UV-visible spectroscopy results.Comment: 12 pages, 16 figure

catena-Poly[[bis­(N-ethyl­ethylene­di­amine-κ2 N,N′)copper(II)]-μ-cyanido-κ2 N:C-[dicyanido-κ2 C-palladium(II)]-μ-cyanido-κ2 C:N]

The title compound, [CuPd(CN)4(C4H12N2)2]n, consists of one-dimensional chains. The Cu and Pd atoms are both located on centers of symmetry in an alternating array of [Cu(N-Eten)2]2+ (N-Eten = N-ethyl­ethylenediamine) and [Pd(CN)4]2− units. The Pd—C distances of 1.991 (3) and 1.992 (3) Å are inter­mediate values compared with the analogous NiII and PtII complexes [Akitsu & Einaga (2007 ▶). Inorg. Chim. Acta, 360, 497–505]. Due to Jahn–Teller effects, the axial Cu—N bond distance of 2.548 (2) Å is noticeably longer than the equatorial distances [Cu—NH2 = 2.007 (2) and Cu—NHC2H5 = 2.050 (2) Å]. There are interchain hybrogen bonds, with N(—H)⋯N = 3.099(4) Å

Thermodynamic Stabilities of U(VI) Minerals: Estimated and Observed Relationships

Gibbs free energies of formation ({Delta}G{degree}{sub f}) for several structurally related U(VI) minerals are estimated by summing the Gibbs energy contributions from component oxides. The estimated {Delta}G{degree}{sub f} values are used to construct activity-activity (stability) diagrams, and the predicted stability fields are compared with observed mineral occurrences and reaction pathways. With some exceptions, natural occurrences agree well with the mineral stability fields estimated for the systems SiO{sub 2}-CaO-UO{sub 3}-H{sub 2}O and CO{sub 2}-CaO-UO{sub 3}H{sub 2}O, providing confidence in the estimated thermodynamic values. Activity-activity diagrams are sensitive to small differences in {Delta}G{degree}{sub f} values, and mineral compositions must be known accurately, including structurally bound H{sub 2}O. The estimated {Delta}G{degree}{sub f} values are not considered reliable for a few minerals for two major reasons: (1) the structures of the minerals in question are not closely similar to those used to estimate the {Delta}G{sub f}* values of the component oxides, and/or (2) the minerals in question are exceptionally fine grained, leading to large surface energies that increase the effective mineral solubilities. The thermodynamic stabilities of uranium(VI) minerals are of interest for understanding the role of these minerals in controlling uranium concentrations in oxidizing groundwaters associated with uranium ore bodies, uranium mining and mill tailings and geological repositories for nuclear waste

Aqueous hydroxylation mediated synthesis of crystalline calcium uranate particles

Metal uranates(VI) are solubility limiting U(VI) phases under high pH conditions and may act as suitable long-term wasteforms. The precipitation and thermal phase development mechanisms of calcium uranate particles formed via aqueous hydroxylation reactions are studied in order to address the lack of aqueous synthesis methods currently available. Hydrous Ca-deficient uranate particles formed from aqueous solutions saturated in U(VI) oligomers were found to thermally decompose via several weight-loss steps between 100 and 800 °C. Crystalline calcium uranate (Ca2U3O11) is initially formed at 700 °C via dehydration and dehydroxylation-olation reactions under redox-neutral conditions. This initial phase decomposes to biphasic CaUO4-UO2 particles at 800 °C via a reductive pathway

Breast cancer associated CD169+ macrophages possess broad immunosuppressive functions but enhance antibody secretion by activated B cells

CD169+ resident macrophages in lymph nodes of breast cancer patients are for unknown reasons associated with a beneficial prognosis. This contrasts CD169+ macrophages present in primary breast tumors (CD169+ TAMs), that correlate with a worse prognosis. We recently showed that these CD169+ TAMs were associated with tertiary lymphoid structures (TLSs) and Tregs in breast cancer. Here, we show that CD169+ TAMs can be monocyte-derived and express a unique mediator profile characterized by type I IFNs, CXCL10, PGE2 and inhibitory co-receptor expression pattern. The CD169+ monocyte-derived macrophages (CD169+ Mo-M) possessed an immunosuppressive function in vitro inhibiting NK, T and B cell proliferation, but enhanced antibody and IL6 secretion in activated B cells. Our findings indicate that CD169+ Mo-M in the primary breast tumor microenvironment are linked to both immunosuppression and TLS functions, with implications for future targeted Mo-M therapy

Safely probing the chemistry of Chernobyl nuclear fuel using micro-focus X-ray analysis

Detailed chemical analysis of the solidified molten fuel still residing in the stricken Chernobyl reactor unit 4 are inferred using multi-modal micro-focus X-ray analysis of a low-radioactivity proxy. A fascinating mixture of molten UO2, nuclear fuel cladding, concrete, stainless steel and other nuclear reactor components, these materials behaved like lava, solidifying to form a complex, highly radioactive glass-ceramic. Using element-specific chemical probes (micro-X-ray fluorescence and X-ray absorption spectroscopy), coupled with micro-diffraction analysis, the crystalline phase assemblage of simulants of these heterogeneous materials was established, which included “chernobylite” and a range of compositions in the (U1−xZrx)O2 solid solution. Novel insight to nuclear accident fuel chemistry was obtained by establishing the oxidation state and local coordination of uranium not only in these crystalline phases, but uniquely in the amorphous fraction of the material, which varied depending on the history of the nuclear lava as it flowed through the reactor. This study demonstrates that micro-focus X-ray analysis of very small fractions of material can yield rich chemical information, which can be applied to nuclear-melt down materials to aid decommissioning and nuclear fuel management at nuclear accident sites