A new mechanism of strain transfer in polycrystals.

At the grain boundaries of plastically deforming polycrystals, strain transfer mechanisms can accommodate the shear strain carried by slip bands and mechanical twins to prevent stress build-ups and damage. So far, only the accommodation obtained through slip (and twinning) alone has been considered in the mechanism known as slip (and twin) transfer. Here, a strain transfer mechanism that also requires the rotation of the crystal lattice is demonstrated. A region of accumulated slip develops perpendicular to the active slip plane in the impinged grain. The slip gradients enable a localized lattice rotation that accommodates the shear strain in the incoming band, preventing the build-up of interfacial stresses. The mechanism operates preferentially at the boundaries between highly misoriented grains. Facilitating strain transfer at these interfaces opens up new possibilities to improve the mechanical properties of polycrystals, as discussed.

Prolonged and large outbreak of invasive group A Streptococcus disease within a nursing home: repeated intrafacility transmission of a single strain.

OBJECTIVES: Multiple invasive group A Streptococcus (GAS) infections were reported to public health by a skilled nursing facility (facility A) in Illinois between May 2014 and August 2016. Cases continued despite interventions including antibiotic prophylaxis for all residents and staff. Two other geographically close facilities reported contemporaneous outbreaks of GAS. We investigated potential reasons for ongoing transmission. METHODS: We obtained epidemiologic data from chart review of cases and review of facility and public health records from previous investigations into the outbreak. Infection control practices at facility A were observed and evaluated. Whole genome sequencing followed by phylogenetic analysis was performed on available isolates from the three facilities. RESULTS: From 2014 to 2016, 19 invasive and 60 noninvasive GAS infections were identified at facility A occurring in three clusters. Infection control evaluations during clusters 2 and 3 identified hand hygiene compliance rates of 14% to 25%, appropriate personal protective equipment use in only 33% of observed instances, and deficient wound-care practices. GAS isolates from residents and staff of all three facilities were subtype emm89.0; on phylogenetic analysis, facility A isolates were monophyletic and distinct. CONCLUSIONS: Inadequate infection control and improper wound-care practices likely led to this 28-month-long outbreak of severe infections in a skilled nursing facility. Whole genome sequencing and phylogenetic analysis suggested that intrafacility transmission of a single highly transmissible GAS strain was responsible for the outbreak in facility A. Integration of genomic epidemiology tools with traditional epidemiology and infection control assessments was helpful in investigation of a facility-wide outbreak.

Reduced partitioning of plastic strain for strong and yet ductile precipitate-strengthened alloys.

When a material that contains precipitates is deformed, the precipitates and the matrix may strain plastically by different amounts causing stresses to build up at the precipitate-matrix interfaces. If premature failure is to be avoided, it is therefore essential to reduce the difference in the plastic strain between the two phases. Here, we conduct nanoscale digital image correlation to measure a new variable that quantifies this plastic strain difference and show how its value can be used to estimate the associated interfacial stresses, which are found to be approximately three times greater in an Fe-Ni2AlTi steel than in the more ductile Ni-based superalloy CMSX-4®. It is then demonstrated that decreasing these stresses significantly improves the ability of the Fe-Ni2AlTi microstructure to deform under tensile loads without loss in strength.

Softening non-metallic crystals by inhomogeneous elasticity.

High temperature structural materials must be resistant to cracking and oxidation. However, most oxidation resistant materials are brittle and a significant reduction in their yield stress is required if they are to be resistant to cracking. It is shown, using density functional theory, that if a crystal's unit cell elastically deforms in an inhomogeneous manner, the yield stress is greatly reduced, consistent with observations in layered compounds, such as Ti3SiC2, Nb2Co7, W2B5, Ta2C and Ta4C3. The mechanism by which elastic inhomogeneity reduces the yield stress is explained and the effect demonstrated in a complex metallic alloy, even though the electronegativity differences within the unit cell are less than in the layered compounds. Substantial changes appear possible, suggesting this is a first step in developing a simple way of controlling plastic flow in non-metallic crystals, enabling materials with a greater oxidation resistance and hence a higher temperature capability to be used.

Stable Speckle Patterns for Nano-scale Strain Mapping up to 700 °C.

The digital image correlation (DIC) of speckle patterns obtained by vapour-assisted gold remodelling at 200 - 350 °C has already been used to map plastic strains with submicron resolution. However, it has not so far proved possible to use such patterns for testing at high temperatures. Here we demonstrate how a gold speckle pattern can be made that is stable at 700 °C, to study deformation in a commercial TiAl alloy (Ti-45Al-2Nb-2Mn(at%)-0.8 vol% TiB2). The pattern is made up of a uniformly sized random array of Au islands as small as 15 nm in diameter, depending on reconstruction parameters, with a sufficiently small spacing to be suitable for nano-scale, nDIC, strain mapping at a subset size of 60 × 60 nm2. It can be used at temperatures up to 700 °C for many hours, for high cycle fatigue testing for instance. There is good particle attachment to the substrate. It can withstand ultra-sound cleaning, is thermally stable and has a high atomic number contrast for topography-free backscatter electron imaging.

Pentacoordinate silicon complexes with dynamic motion resembling a pendulum on the S(N)2 reaction pathway.

A series of glutarimide derivatives which has two carbonyl coordination sites for intramolecular pentacoordination at silicon with a X(1+n)SiC(3-n)O moiety have been synthesised and characterized. The substituent (leaving group) effects on the Si-O bond exchange between the two coordination sites (resembling a pendulum) have been studied by comparison of the differently substituted (X = F, Cl, OTf, Br and I) structures. The activation parameters for the Si-O bond exchange process were measured by NMR and separately computed and are consistent with the strength of Si-O bond coordination and the nature of the leaving group, X. The temperature-dependent (29)Si NMR spectroscopy is supported by X-ray crystallography and shows that the tetrahedral reactant is converted into pentacoordinate intermediates by intramolecular O-Si association followed by reversion to a tetrahedral geometry by Si-X dissociation. The two association/dissociation patterns offer a model for nucleophilic substitution at a silicon atom. A continuum of structures on the S(N)2 reaction profile from the glutarimide derivatives correlates reasonably well with the structural data obtained from derivatives of lactams, diketopiperazines and quinolones.

Structural characterization of TiN/NbN multilayers: X-ray diffraction, energy-filtered TEM and Fresnel contrast techniques compared.

Two TiN/NbN multilayers with wavelength 13.6 and 6.15 nm have been characterized by X-ray diffraction (XRD), Fresnel contrast analysis (FCA) and energy-filtered transmission electron microscopy (EFTEM). Good agreement between the composition profile obtained by FCA and EFTEM is obtained if the lower resolution of the EFTEM images is taken into account. The relative advantages and disadvantages of the techniques are discussed. Used together the two TEM techniques provide a quantitative characterization that is consistent with, and for some parameters provides more precise values than, that from XRD. The analysis shows that the multilayers have narrow interfaces (< 1 nm) and a composition amplitude close to 95% for the longer wavelength.

Preparation, structure, and properties of the corner-shared double cubes [Mo(6)HgQ(8)(H(2)O)(18)](8+) (Q = S, Se) and tungsten analogues.

The purple corner-shared double cube [Mo(6)HgS(8)(H(2)O)(18)](8+) derivative of green [Mo(3)S(4)(H(2)O)(9)](4+), obtained under air-free conditions by the reaction with Hg(0) (metal), is also formed with Hg(I)(2). The Hg(I)(2) reaction is accounted for by the disproportionation Hg(I)(2) <==> Hg(0) + Hg(II), which is a source of Hg(0). X-ray crystallographic information on the blue partially Cl(-) substituted cucurbituril supramolecular assemblies [Mo(6)HgQ(8)Cl(4)(H(2)O)(14)](C(36)H(36)N(24)O(12))Cl(4).14H(2)O (1) and of the Se analogue [Mo(6)HgSe(8)Cl(4) (H(2)O)(14)](C(36)H(36)N(24)O(12))Cl(4).14H(2)O (2) have been determined. The product [W(6)HgSe(8)Cl(4)(H(2)O)(14)](C(36)H(36)N(24) O(12)) Cl(4).14H(2)O (3) has also been obtained, but there is no evidence for [W(6)HgS(8)(H(2)O)(18)](8+) and related forms. The formation of [Mo(6)HgS(8)(H(2)O)(18)](8+) by the reaction of [Mo(3)S(4) (H(2)O)(9)](4+) with Hg(0) under anaerobic conditions maximizes after approximately 40 h in 2.0 M HCl, but requires longer reaction time ( approximately 120 h) in 2.0 M Hpts (p-toluenesulfonic acid) and in 2 M HClO(4) ( approximately 6 days). In 2.0 M HCl there is little absorbance increase until [Mo(3)S(4)(H(2)O)(9)](4+) exceeds 1.2 x 10(-)(3) M, which is explained by a dependence of the formation K (265 M(-1)) on [Mo(3)S(4)(H(2)O)(9)(4+)](2). Furthermore, on dilution of column-purified [Mo(6)HgS(8)(H(2)O)(18)](8+), Beer's law is not obeyed and equilibria involving 2[Mo(3)S(4)(H(2)O)(9)](4+) are apparent. The kinetics of formation of [Mo(6)HgS(8)(H(2)O)(18)](8+) is first-order in [Mo(3)S(4)(H(2)O)(9)](4+), consistent with rate-determining formation of the single cube [Mo(3)HgS(4)(H(2)O)(x)](4+). The oxidations of [Mo(6)HgS(8)(H(2)O)(18)](8+) with [Fe(H(2)O)(6)](3+) and [Co(dipic)(2)](-) are complicated by the release of [Hg(H(2)O)(6)](2+), which also functions as an oxidant. Similar results are obtained for [Mo(6)HgSe(8)(H(2)O)(18)](8+) and the less extensively studied [W(6)HgSe(8)(H(2)O)(18)](8+).

Preparation, structure, and reactivity of Ge-containing heterometallic cube derivatives of [M(3)E(4)(H2O)(9)](4+) (M = Mo, W; E = S, Se).

Studies leading to the incorporation of Group 14 germanium into the incomplete cuboidal clusters [M(3)E(4)(H2O)(9)](4+) (M = Mo, W; E = S, Se) have been carried out. From the clusters [Mo(3)E(4)(H2O)(9)](4+), corner-shared double cubes [Mo(6)GeE(8)(H2O)(18)] are obtained with GeO, by heating with Ge powder at 90 degrees C, or by heating with GeO(2) in the presence of H(3)PO(2) as reductant at 90 degrees C, illustrating the dominance of the double cubes. The yellow-green single cube [Mo(3)GeS(4) (H2O)(12)](6+) is only obtained by controlled air oxidation of [Mo(6)GeS(8)(H2O)(18)](8+) over a period of approximately 4 days followed by Dowex purification. In the case of the trinuclear clusters [W(3)E(4)(H2O)(9)](4+), the single cubes [W(3)GeE(4)(H2O)(12)](6+) are dominant and prepared by the reactions with GeO, or GeO(2)/H(3)PO(2). Conversion of [W(3)GeE(4)(H2O)(12)](6+) to the corresponding double cubes is achieved by reductive addition with BH(4)(-) in the presence of a further equivalent of [W(3)E(4)(H2O)(9)](4+). The crystal structures (pts(-) = p-toluene-sulfonate) of [Mo(6)GeS(8)(H2O)(18)](pts)(8).28H2O, (1); [W(6)GeS(8)(H2O)(18)](pts)(8).23H2O, (2); and [Mo(6)GeSe(8)(H2O)(18)](pts)(8).8H2O, (3); have been determined, of which (2) is the first structure of a W(6) double cube. The M-M bond lengths of approximately 2.7 A are consistent with metal-metal bonding, and the M-Ge of approximately 3.5 A corresponds to nonbonding separations. Of the Group 13-15 corner-shared double cubes from [Mo(3)S(4)(H2O)(9)](4+), [Mo(6)GeS(8)(H2O)(18)](8+) is the least reactive with [Co(dipic)(2)](-) as oxidant (0.077 M(-1) s(-1)), and [Mo(6)SnS(8)(H2O)(18)](8+) is next (14.9 M(-1) s(-1)). Both Ge and Sn (Group 14) have an even number of electrons, resulting in greater stability. In contrast, [W(6)GeS(8)(H2O)(18)](8+) is much more reactive (7.3 x 10(3) M(-1) s(-1)), and also reacts more rapidly with O(2).

Synthesis, crystal structure determination, and biological properties of the DNA-dependent protein kinase (DNA-PK) inhibitor 3-cyano-6-hydrazonomethyl-5-(4-pyridyl)pyrid-[1H]-2-one (OK-1035).

The first reported synthesis of the DNA-PK inhibitor 3-cyano-6-hydrazonomethyl-5-(4-pyridyl)pyrid-[1H]-2-one (OK-1035) is described. The structure of OK-1035 was validated by X-ray crystallography. An IC(50) value of 100 microM was determined for inhibition of DNA-PK, and this is approximately 12-fold higher than that reported previously.

Isomeric icosaboranes B20H26: the synchrotron structure of 1,1'-bis(nido-decaboranyl).

An isomer of B20H26, isolated from the autolysis of nido-B10H14 in a silent electrical discharge, is shown to be the title compound 1,1'-bis(nido-decaboranyl). The molecule has crystallographic inversion symmetry and a long intercage B-B bond of 1.704 (3) A.

Macrochelation, cyclometallation and G-quartet formation: N3- and C8-bound PdII complexes of adenine and guanine.

The reactions of Pd(II) ions with a series of chelate-tethered derivatives of adenine and guanine have been studied and reveal a difference in the reactivity of the purine bases. Reactions of [PdCl2(MeCN)2] and A-alkyl-enH x Cl (alkyl = propyl or ethyl, A adenine, en = ethylenediamine) yield the monocationic species [PdCl(A-N3-Et-en)]+ (1) and [PdCl(A-N3-Pr-en)]+ (2). Both involve co-ordination at the minor groove site N3 of the nucleobase as confirmed by single-crystal X-ray analysis. Reactions with the analogous G-alkyl-enH x Cl derivatives (G=guanine, alkyl = ethyl or propyl) were more complex with a mixture of species being observed. For G-Et-en HCI a product was isolated which was identified as [PdCl(G-C8-Et-en)]+ (3). This compound contains a biomolecular metal-carbon bond involving C8 of the purine base. Crystallography of a product obtained from reaction of G-Pr-enH x Cl and [Pd(MeCN)4][NO3]2 reveals an octacationic tetrameric complex (4), in which each ligand acts to bridge two metal ions through a combination of a tridentate binding mode involving the diamine and N3 and monodentate coordination at N7.

The synthesis of cyclic tetrapeptoid analogues of the antiprotozoal natural product apicidin.

A novel synthetic strategy is described which may be used to prepare analogues of the antimalarial, fungal metabolite apicidin. Compared to the natural product, one analogue shows potent and selective activity in vitro against the parasite Trypanosoma brucei and low mammalian cell toxicity.

Triple linking of the decaboranyl cluster. Structure of [(SMe2)2B10H10(B10H13)2] as determined by synchrotron X-ray diffraction analysis.

In an attempt to find generic routes to multiple inter-cluster sigma-linking, mild thermolysis of [6,9-(SMe2)2-arachno-B10H12] 1 in inert hydrocarbon solution gives the tridecaboranyl species [6,9-(SMe2)2-arachno-B10H(10)-1,5-(6'-nido-B10H13)2] 3 (23%).

Synthesis and structure of the novel mixed anion-dianion lithium cage compound [(6-LiCH2Py-2-OLi)4(6-CH3Py-2-OLi)2(THF)9].

The title compound crystallises as a novel homometallic mixed anion-dianion cage incorporating two four-coordinate diorgano lithiate centres, in addition to eight lithium centres coordinated only by oxygen and nitrogen atoms.

Two isostructural triboluminescent lanthanide complexes.

(4-Dimethylaminopyridine)tris(2,2,6,6-tetramethylheptane-3, 5-dionato)terbium(III), [Tb(C(11)H(19)O(2))(3)(C(7)H(10)N(2))], and its samarium analogue, [Sm(C(11)H(19)O(2))(3)(C(7)H(10)N(2))], are isostructural. Their polar space group is consistent with observed second harmonic generation and with the involvement of piezoelectric charging in their intense triboluminescence properties, which are of interest for the development of damage sensors in composite materials. The metals display irregular seven-coordination by one substituted pyridine and three chelating diketonate ligands, bond lengths to Tb being shorter than those to Sm.

Tetracycline hydrochloride: a synchrotron microcrystal study.

The title compound, [(4S,4aS,5aS,6S,12aS)-2-aminohydroxymethylene-1, 2,3,4,4a,5,5a,6,11,12a-decahydro-6,10,12,12a-tetrahydroxy-6-methyl -1, 3,11-trioxonaphthacen-4-yl]dimethylammonium chloride, C(22)H(25)N(2)O(8)(+).Cl(-), a well known antibiotic, has been structurally characterized from an individual coarse powder grain by use of high-intensity synchrotron radiation, in conjunction with an exercise in ab initio powder diffraction structure solution. Free refinement of all H atoms establishes the major tautomeric form of the protonated tetracycline molecule without prejudice. The molecule has extensive intramolecular hydrogen bonding involving most of the potential donors and acceptors, and all intermolecular hydrogen bonding uses the chloride anion as acceptor.