Risk factors for biliary stent infections in malignant biliary obstruction secondary to unresectable malignancies.

BACKGROUND: Palliative biliary drainage in patients with unresectable malignant biliary obstruction (MBO) frequently leads to biliary stent infection (BI), which could impact medical care. The aim of this study was to assess the risk factors for BI occurrence in patients after stenting procedure and the impact of BI on patient survival. METHODS: All consecutive patients hospitalized from 2014 to 2018 for MBO and biliary stenting were retrospectively included. Demographic, clinical, and microbiological characteristics of each BI episode during a 1-year follow-up were described. Documented BI was defined as the association of BI episode and confirmed blood stream infection (BSI). Univariate and multivariate analyses were performed to evaluate risk factors for the first BI occurrence. RESULTS: Among 180 patients, 56% were men (mean age of 69±12), and 54% have pancreatic cancer, 16% biliary cancer, 2% hepatic cancer, and 28% lymph node or metastatic compression; metallic stent was placed in 92%. A total of 113 BI episodes occurred in 74 patients, 55% of the first episodes occurring within 3 months after stenting. BI was documented in 56% of the episodes. Enterobacteriaceae were the most frequent pathogens found, while no yeasts were documented. Mortality rate in patients with BI was 64%. Multivariate analysis showed a significant difference in BI occurrence for two criteria: WHO score 3-4 (OR=8.79 [1.79-42.89]; p=0.007) and transpapillary stenting location (OR=3.72 [1.33-10.44]; p=0.013). CONCLUSION: Since transpapillary stenting is a risk factor for BI, preserving the papilla as much as possible is a priority so as to avoid BI.

Insight into the structural, elastic and electronic properties of a new orthorhombic 6O-SiC polytype.

Different polytypes of SiC are described and predicted in literature. Here, we report the first occurrence of an orthorhombic 6O-SiC polytype as rock-forming mineral in the nickel laterite mine of Tiebaghi (New Caledonia). This new class of SiC crystallizes in the space group Cmc21 with 12 atoms per unit cell [a = 3.0778(6) Å, b = 5.335(2) Å, c = 15.1219(6) Å, α = 90°, ß = 90°, γ = 120°]. The density of 6O-SiC is about 3.22 g/cm3 and the calculated indirect bandgap at room temperature of 3.56 eV is identical to 6H-SiC. Our results suggest that 6O-SiC is the intermediate state in the wurtzite to rocksalt transformation of 6H-SiC.

Raman Open Database: first interconnected Raman-X-ray diffraction open-access resource for material identification.

Detailed crystallographic information provided by X-ray diffraction (XRD) is complementary to molecular information provided by Raman spectroscopy. Accordingly, the combined use of these techniques allows the identification of an unknown compound without ambiguity. However, a full combination of Raman and XRD results requires an appropriate and reliable reference database with complete information. This is already available for XRD. The main objective of this paper is to introduce and describe the recently developed Raman Open Database (ROD, http://solsa.crystallography.net/rod). It comprises a collection of high-quality uncorrected Raman spectra. The novelty of this database is its interconnectedness with other open databases like the Crystallography Open Database (http://www.crystallography.net/cod and Theoretical Crystallography Open Database (http://www.crystallography.net/tcod/). The syntax adopted to format entries in the ROD is based on the worldwide recognized and used CIF format, which offers a simple way for data exchange, writing and description. ROD also uses JCAMP-DX files as an alternative format for submitted spectra. JCAMP-DX files are compatible to varying degrees with most commercial Raman software and can be read and edited using standard text editors.

A new ß-CdTeO3 polymorph with a structure related to α-CdTeO3.

A new ß-CdTeO3 polymorph was obtained by hydrothermal synthesis and its structure was solved ab initio from powder X-ray diffraction data. It appears that the structure of ß-CdTeO3 (Pnma, Z = 16, a = 7.45850(3) Å, b = 14.52185(6) Å, c = 11.04584(5) Å) is closely related to that of α-CdTeO3 (P21/c, Z = 8, a = 7.790(1) Å, b = 11.253(2) Å, c = 7.418(1) Å, ß = 113.5(1)°) previously reported. The 3D framework of ß-CdTeO3 is built of both [CdO6] distorted octahedra and [CdO7] mono-capped trigonal prisms and three different tellurium polyhedra: trigonal pyramids [TeIVO3E] and trigonal bipyramids [TeIVO4E] and [TeIVO3+1E] (E denotes the lone pair of TeIV). The electronic structure calculations based on density functional theory methods show that at the ground state α-CdTeO3 is slightly more stable than ß-CdTeO3 with an energy difference of 4.64 kJ mol-1. The band structures confirm the results of optical UV-Vis spectroscopy measurements: both polymorphs are wide bandgap semiconductors with Eg = 3.55 eV for ß-CdTeO3 and Eg = 3.91 eV for α-CdTeO3. The DOS calculations for both polymorphs enable one to understand that the presence of the [TeIVO4E] polyhedra in ß-CdTeO3 (absent in α-CdTeO3) lowers its bandgap. Above 540 °C ß-CdTeO3 transforms into α-CdTeO3 in a first order phase transition.

The nature of chemical bonding in actinide and lanthanide ferrocyanides determined by X-ray absorption spectroscopy and density functional theory.

The electronic properties of actinide cations are of fundamental interest to describe intramolecular interactions and chemical bonding in the context of nuclear waste reprocessing or direct storage. The 5f and 6d orbitals are the first partially or totally vacant states in these elements, and the nature of the actinide ligand bonds is related to their ability to overlap with ligand orbitals. Because of its chemical and orbital selectivities, X-ray absorption spectroscopy (XAS) is an effective probe of actinide species frontier orbitals and for understanding actinide cation reactivity toward chelating ligands. The soft X-ray probes of the light elements provide better resolution than actinide L3-edges to obtain electronic information from the ligand. Thus coupling simulations to experimental soft X-ray spectral measurements and complementary quantum chemical calculations yields quantitative information on chemical bonding. In this study, soft X-ray XAS at the K-edges of C and N, and the L2,3-edges of Fe was used to investigate the electronic structures of the well-known ferrocyanide complexes K4Fe(II)(CN)6, thorium hexacyanoferrate Th(IV)Fe(II)(CN)6, and neodymium hexacyanoferrate KNd(III)Fe(II)(CN)6. The soft X-ray spectra were simulated based on quantum chemical calculations. Our results highlight the orbital overlapping effects and atomic effective charges in the Fe(II)(CN)6 building block. In addition to providing a detailed description of the electronic structure of the ferrocyanide complex (K4Fe(II)(CN)6), the results strongly contribute to confirming the actinide 5f and 6d orbital oddity in comparison to lanthanide 4f and 5d.

Hydrothermal Synthesis and Dehydration of CaTeO3(H2O): An Original Route to Generate New CaTeO3 Polymorphs.

CaTeO3(H2O) was obtained from microwave-assisted hydrothermal synthesis as a polycrystalline sample material. The dehydration reaction was followed by thermal analysis (thermogravimetric/differential scanning calorimetry) and temperature-dependent powder X-ray diffraction and leads to a new δ-CaTeO3 polymorph. The crystal structures of CaTeO3(H2O) and δ-CaTeO3 were solved ab initio from PXRD data. CaTeO3(H2O) is non-centrosymmetric: P21cn; Z = 8; a = 14.785 49(4) Å; b = 6.791 94(3) Å; c = 8.062 62(3) Å. This layered structure is related to the ones of MTeO3(H2O) (M = Sr, Ba) with layers built of edge-sharing [CaO6(H2O)] polyhedra and are capped of each side by [Te(IV)O3E] units. Adjacent layers are stacked along the a-axis and are held together by H-bonds via the water molecules. The dehydration reaction starts above 120 °C. The transformation of CaTeO3(H2O) into δ-CaTeO3 (P21ca; Z = 8; a = 13.3647(6) Å; b = 6.5330(3) Å; c = 8.1896(3) Å) results from topotactic process with layer condensation along the a-axis and the 1/2b⃗ translation of intermediate layers. Thus, δ-CaTeO3 stays non-centrosymmetric. The characteristic layers of CaTeO3(H2O) are also maintained in δ-CaTeO3 but held together via van der Waals bonds instead of H-bonds through water molecules. Electron localization function and dipole moment calculations were also performed. For both structures and over each unit cell, the dipole moments are aligned antiparallel with net dipole moments of 3.94 and 0.47 D for CaTeO3(H2O) and δ-CaTeO3, respectively. The temperature-resolved second harmonic generation (TR-SHG) measurements, between 30 and 400 °C, show the decreasing of the SHG intensity response from 0.39 to 0.06 × quartz for CaTeO3(H2O) and δ-CaTeO3, respectively.

Tris(tetra-butyl-ammonium) tris-(nitrato-κO,O')tetra-kis-(thio-cyanato-κN)thorium(IV).

The title compound, (C(16)H(36)N)(3)[Th(NCS)(4)(NO(3))(3)], was obtained from the reaction of Th(NO(3))(4)·5H(2)O with (Bu(4)N)(NCS). The Th(IV) atom is in a ten-coordinate environment of irregular geometry, being bound to the N atoms of the four thio-cyanate ions and to three bidentate nitrate ions. The average Th-N and Th-O bond lengths are 2.481 (10) and 2.57 (3) Å, respectively.

The dehydration of SrTeO3(H2O)--a topotactic reaction for preparation of the new metastable strontium oxotellurate(IV) phase ε-SrTeO3.

Microcrystalline single-phase strontium oxotellurate(IV) monohydrate, SrTeO(3)(H(2)O), was obtained by microwave-assisted hydrothermal synthesis under alkaline conditions at 180 °C for 30 min. A temperature of 220 °C and longer reaction times led to single crystal growth of this material. The crystal structure of SrTeO(3)(H(2)O) was determined from single crystal X-ray diffraction data: P2(1)/c, Z = 4, a = 7.7669(5), b = 7.1739(4), c = 8.3311(5) Å, ß = 107.210(1)°, V = 443.42(5) Å(3), 1403 structure factors, 63 parameters, R[F(2)>2σ(F(2))] = 0.0208, wR(F(2) all) = 0.0516, S = 1.031. SrTeO(3)(H(2)O) is isotypic with the homologous BaTeO(3)(H(2)O) and is characterised by a layered assembly parallel to (100) of edge-sharing [SrO(6)(H(2)O)] polyhedra capped on each side of the layer by trigonal-prismatic [TeO(3)] units. The cohesion of the structure is accomplished by moderate O-H···O hydrogen bonding interactions between donor water molecules and acceptor O atoms of adjacent layers. In a topochemical reaction, SrTeO(3)(H(2)O) condensates above 150 °C to the metastable phase ε-SrTeO(3) and transforms upon further heating to δ-SrTeO(3). The crystal structure of ε-SrTeO(3), the fifth known polymorph of this composition, was determined from combined electron microscopy and laboratory X-ray powder diffraction studies: P2(1)/c, Z = 4, a = 6.7759(1), b = 7.2188(1), c = 8.6773(2) Å, ß = 126.4980(7)°, V = 341.20(18) Å(3), R(Fobs) = 0.0166, R(Bobs) = 0.0318, Rwp = 0.0733, Goof = 1.38. The structure of ε-SrTeO(3) shows the same basic set-up as SrTeO(3)(H(2)O), but the layered arrangement of the hydrous phase transforms into a framework structure after elimination of water. The structural studies of SrTeO(3)(H(2)O) and ε-SrTeO(3) are complemented by thermal analysis and vibrational spectroscopic measurements.

A versatile precursor for non-aqueous neptunyl(V) chemistry.

The polymeric complex [(NpO(2)Py(5))(KI(2)Py(2))](n) is prepared from dry "NpO(2)Cl" by anion exchange with potassium iodide in pyridine affording the first convenient starting material for the development of NpO(2)(+) coordination chemistry in anhydrous organic media.

The reaction chemistry of plutonyl(VI) chloride complexes with triphenyl phosphineoxide and triphenyl phosphinimine.

The reaction between Ph(3)PO dissolved in acetone and "PuO(2)Cl(2)" in dilute HCl resulted in the formation of [PuO(2)Cl(2)(Ph(3)PO)(2)]. Crystallographic characterization of the acetone solvate revealed the expected axial trans plutonyl dioxo, with trans Cl and Ph(3)PO in the equatorial plane. Spectroscopic analyses ((31)P NMR, (1)H NMR, and vis/nIR) indicate the presence of both cis and trans isomers in solution, with the trans isomer being more stable. Confirmation of the higher stability of the trans versus cis isomers for [AnO(2)Cl(2)(Ph(3)PO)(2)] (An = U and Pu) was obtained through quantum chemical computational analysis, which also reveals the Pu-O(TPPO) bond to be more ionic than the U-O(TPPO) bond. Slight variation in reaction conditions led to the crystallization of two further minor products, [PuO(2)(Ph(3)PO)(4)][ClO(4)](2) and cis-[PuCl(2)(Ph(3)PO)(4)], the latter complex revealing the potential for reduction to Pu(IV). In addition, the reaction of Ph(3)PNH with [PuO(2)Cl(2)(thf)(2)](2) in anhydrous conditions gave evidence for the formation of both cis- and trans-[PuO(2)Cl(2)(Ph(3)PNH)(2)] in solution (by (31)P NMR). However, the major reaction pathway involved protonation of the ligand with the crystallographic characterization of [Ph(3)PNH(2)](2)[PuO(2)Cl(4)]. We believe that HCl/SiMe(3)Cl carried through from the small scale preparation of [PuO(2)Cl(2)(thf)(2)](2) was the source of both protons and chlorides. The fact that this chemistry was significantly different from previous uranium studies, where cis-/trans-[UO(2)Cl(2)L(2)] (L = Ph(3)PO or Ph(3)PNH) were the only products observed, provides further evidence of the unique challenges and opportunities associated with the chemistry of plutonium.

Addition of whole, semiskimmed, and skimmed bovine milk reduces the total antioxidant capacity of black tea.

Epidemiological studies have shown that populations consuming fruits, vegetables, tea, cocoa, and red wine have lower incidences of cardiovascular disease, certain cancers, and eye disease. These health effects have largely been attributed to the polyphenol content of the foods and drinks studied. Black tea is rich in a range of polyphenolic compounds that could potentially have health-promoting properties. The scale of consumption of tea in the United Kingdom means that it could be an appropriate vehicle for increasing the antioxidant activity and polyphenol content of human plasma. However, it is common practice in the United Kingdom to add milk to tea, and some studies have suggested that this may decrease the overall antioxidant capacity. The objective of the present study was to analyze and compare the antioxidant capacity of 5 brands of tea and to test the hypothesis that the addition of different volumes of whole milk, semiskimmed, and skimmed milk may affect the antioxidant capacity. Each of the teas analyzed was a significant source of antioxidants. The addition of 10, 15, and 20 mL of whole, semiskimmed, and skimmed bovine milk to a 200-mL tea infusion decreased the total antioxidant capacity of all the brands of tea. Skimmed milk decreased the total antioxidant capacity of the tea infusion significantly (P < .05) more than either whole milk or semiskimmed milk. We conclude that black tea is a valuable source of antioxidants and that the effect of milk on the total antioxidant capacity may be related to the fat content of the milk.

Synthesis and characterizations of cyclic octanuclear mixed-valence vanadium(IV,V) clusters with polyoxometalate counterions.

Hydrothermal reaction of Na2WO4, VOSO4, 2,2'-bpy and H3PO4 has afforded in high yield the compound [V(IV)2V(V)6O14(bpy)8(PO4)2][PW11V(V)O40](bpy).12H2O (1). Compound 1 contains a novel octanuclear mixed valence V(IV,V) cluster, [V(IV)2V(V)6O14(bpy)8(PO4)2]4+, with [PW11V(V)O40]4- as counterion. In the vanadium cluster, four V(V) centers are localized and the remaining two V(IV) and two V(V) ions are disordered over four crystallographically equivalent positions. The isostructural compound [V(IV)2V(V)6O14(bpy)8(PO4)2][PMo11V(V)O40](bpy).3H2O (2) has also been synthesized. Thermodiffractometry experiments indicate that 2 is stable up to 360 degrees C. Redox activities for both the vanadium and molybdenum centers have been observed by solid-state electrochemical measurements performed on mechanically attached microparticles of 2. Magnetic measurements performed on have shown the occurrence of weak ferromagnetic interactions between the V(IV) centres (J = +0.34 cm(-1), H(ex) = -JS1 x S2), and combined with DFT calculations, have allowed to propose a localization of the two V(IV) centers on two of the four equivalent crystallographic sites. Finally high field electron paramagnetic resonance has evidenced the magnetic axial anisotropy of the paramagnetic centers (g(x) = g(y) = 1.975(3); g(z) = 1.939(4)).

Exchange interactions and theoretical analysis of (31)P NMR spectra in VO(HPO(4)).0.5H(2)O.

Based on combined DFT/broken symmetry approach, a theoretical analysis of the exchange interactions in the VO(HPO(4)).0.5H(2)O solid is performed. Depending on the crystallographic structures reported in the literature, two very different spin models are formulated. In addition, a complete fit of the temperature-dependent (31)P NMR chemical shift is performed to determine exchange and hyperfine constants. The magnetic models used in the fit are those obtained by our theoretical calculations. The comparison between the calculated and fitted exchange constants confirms the adequacy of an isolated dimer model and rules out the alternating antiferromagnetic chain model for VO(HPO(4)).0.5H(2)O.

Ab initio simulation of paramagnetic NMR spectra: the 31P NMR in oxovanadium phosphates.

A theoretical analysis of the temperature-dependent (31)P NMR signals for the ambient pressure vanadyl pyrophosphate AP-(VO)(2)P(2)O(7) and the oxovanadium hemihydrate hydrogenophosphate VO(HPO(4)).0.5H(2)O phases is reported. The ab initio calculation of the magnetic exchange parameters and the hyperfine constants gives access to an original ab initio simulation of NMR spectra. Such a strategy allows one to clarify the crystallographic nature of the different experimentally studied phases. For the vanadyl pyrophosphate ambient pressure structure, our simulations strongly support the presence of a monoclinic phase. Based on this assumption, hyperfine constants are extracted from the fit of the experimental data. These values are directly compared to the ab initio ones.

Exchange interactions in the three phases of vanadyl pyrophosphate (VO)(2)P(2)O(7).

The magnetic exchange constants of vanadyl pyrophosphate (VO)(2)P(2)O(7) have been calculated on the basis of a combined DFT/broken symmetry approach. The three reported phases, ambient-pressure orthorhombic, ambient-pressure monoclinic, and high-pressure orthorhombic, have been explicitly considered. Calculations have been performed on four types of model clusters extracted from the crystal lattices. The singularity of each phase is clearly reflected through the number and values of exchange parameters. Our results show that the exchange interactions can be described in first approximation within the alternating antiferromagnetic chain model. The largest exchange coupling along the chain occurs through O-P-O bridges. The interchain interactions are much weaker and are of ferromagnetic nature.