8 research outputs found
Application of biocompatible magnetite nanoparticles for the removal of arsenic and copper from water
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Synthesis, Bonding, and Reactivity of Group 15 Amides
No full textThis thesis discusses the effects of ligand design on the chemistry of heavy Group 15 elements. The correlation of molecular geometry with frontier molecular orbital energies is a well-known principal. This principle was exploited to systematically tune the frontier molecular orbitals in heavy Group 15 amides. The geometry of antimony and bismuth complexes tethered with a N,N,N-triamido ligand deviate from idealized pyramidal geometries and showed planar metal centers. These compounds were examined in the solid, solution, and gas-phase. Gas-phase calculations were used to assess the change in properties of the bismuth compound upon planarization, such as the lower LUMO energies, and increased Lewis acidity, for which both steric and electronic effects were examined.
A new class of antimony hydrides that participate in the first example of additive-free hydrostibanation of \ch{C+C}, C=C, C=O, and N=N bonds was developed. These hydrometallation reactions were unlocked through changing the geometry of the ligand, and consequently tuning the energy of the \acrfull{fmos}. The careful choice of a bis(silylamino)naphthalene ligand accomplished the desired outcome and provides a second example of frontier molecular orbital engineering in this work. Mechanistic studies suggest that hydrostibanation proceeds via a radical mechanism. Recycling of the stinbinyl hydride during the hydrostibanation of terminal alkynes to yield the Z-olefin product was also achieved.
A one-step, high yield synthesis of thermally-robust bismuthanylstibanes provided the first examples of neutral Bi–Sb -bonds in the solid-state. The reaction chemistry of the Bi–Sb bond was debuted by showing the insertion of a sulfur atom, providing the first documented example of a Bi–S–Sb bonding moiety. DFT calculations indicated that the bis(silylamino)naphthalene scaffold is particularly efficient in increasing interaction energies through a combination of inductive effects and dispersion donor effects, foreshadowing the use of this ligand in the isolation of other labile bonding environments, such as bismuth carbamates.
These studies reveal design rules for the rational pursuit of catalytically relevant systems, and seamlessly connect the realms of fundamental and applied chemistry
Synthesis of Group 4 Complexes That Contain the Tridentate Diamido/Donor Ligands [(ArylNCH<sub>2</sub>CH<sub>2</sub>)<sub>2</sub>O]<sup>2-</sup> and Zirconium Complexes That Contain [(ArylNCH<sub>2</sub>CH<sub>2</sub>)<sub>2</sub>S]<sup>2-</sup> and an Evaluation of Their Activity for the Polymerization of 1-Hexene
No full textCompounds of the type (ArylNHCH2CH2)2O (Aryl = 2,6-Me2C6H3 (H2[1a]), 2,6-Et2C6H3
(H2[1b]), 2,6-i-Pr2C6H3 (H2[1c])) can be prepared by treating (TsOCH2CH2)2O (TsO = tosylate)
with the lithium anilides in THF. [1a,b]TiCl2, [1a,b]TiMe2, [1a]Ti(CH2Ph)2, [1a−c]M(NMe2)2
(M = Zr or Hf), [1a−c]MCl2, and [1a−c]MR2 (R = Me, Et, i-Bu) were prepared. An X-ray
study of [1a]Ti(CH2Ph)2 revealed the structure to be a distorted trigonal bipyramid (type B)
in which the two amido nitrogens and one benzyl ligand occupy equatorial positions. An
X-ray study of [1a]ZrMe2 showed it to be a distorted trigonal bipyramid that contains “axial”
amido groups (type A), while an X-ray study of [1c]HfEt2 revealed it to have a structure
halfway between type A and type B, i.e., a distorted square pyramid with one alkyl in the
apical position. Analogous compounds were also prepared that contain a sulfur donor instead
of oxygen, i.e., [(2,6-Me2C6H3NHCH2CH2)2S] (H2[2a]), [(2,6-i-Pr2C6H3NHCH2CH2)2S] (H2[2c]),
[2a,c]Zr(NMe2)2, [2a,c]ZrCl2, [2a,c]ZrMe2, and [2c]Zr(CH2CHMe2)2. An X-ray study of [2a]ZrMe2 revealed it to be closest to a type B structure. Addition of 1 equiv of [PhNMe2H][B(C6F5)4] in C6D5X (X = Br, Cl) to [1a,c]MMe2 (M = Zr, Hf) gave cationic complexes that
contain coordinated dimethylaniline, with which free aniline does not exchange readily on
the NMR time scale at 60 °C. Addition of excess ether to {[1a]MMe(NMe2Ph)}[B(C6F5)4]
(M = Zr, Hf) led to {[1a]MMe(ether)}[B(C6F5)4] (M = Zr, Hf) complexes in high yield.
Analogous cations can be prepared in the sulfur ligand system, but they do not appear to be
as stable as in the oxygen ligand system. Zr and Hf dimethyl complexes that contain an
oxygen donor or a sulfur donor ligand can be activated with [Ph3C][B(C6F5)4] to yield efficient
catalysts for polymerization of 1-hexene, although the molecular weight of the poly(1-hexene)
chains is limited to ∼20 000−∼25 000 under the conditions employed. Neither {[1c]ZrMe(ether)}[B(C6F5)4] nor {[1c]HfMe(ether)}[B(C6F5)4] will polymerize 1-hexene in C6D5Br at
room temperature, and neither will polymerize ethylene readily at 1 atm and 25 °C. It is
proposed that a solvated five-coordinate cation must lose the solvent in order to react with
an olefin and that β-hydride elimination in the four-coordinate cation limits chain length
Influence of Dopant Nature on Biological Properties of ZnO Thin-Film Coatings on Ti Alloy Substrate
No full textIn this paper, ZnO and Co2+/Mg2+-doped ZnO thin films on TiAlV alloy substrates were obtained. The films were deposited by spin coating of sol-gel precursor solutions and thermally treated at 600 °C for 2 h, in air and slow cooled. The doping ions concentration was 1.0 mol%. The study’s aim was to obtain implantable metallic materials with improved biocompatibility and antibacterial qualities. The characteristics of the thin films were assessed from the point of view of microstructure, morphology, wetting properties, antibacterial activity and biological response in the presence of amniotic fluid stem cells (AFSC). The results proved that all deposited samples were nanostructured, suggesting a very good antibacterial effect and proving to be suitable supports for cellular adhesion and proliferation. All properties also depended on the doping ion nature
Global surveillance of trends in cancer survival 2000-14 (CONCORD-3): analysis of individual records for 37 513 025 patients diagnosed with one of 18 cancers from 322 population-based registries in 71 countries.
No full textBACKGROUND: In 2015, the second cycle of the CONCORD programme established global surveillance of cancer survival as a metric of the effectiveness of health systems and to inform global policy on cancer control. CONCORD-3 updates the worldwide surveillance of cancer survival to 2014. METHODS: CONCORD-3 includes individual records for 37·5 million patients diagnosed with cancer during the 15-year period 2000-14. Data were provided by 322 population-based cancer registries in 71 countries and territories, 47 of which provided data with 100% population coverage. The study includes 18 cancers or groups of cancers: oesophagus, stomach, colon, rectum, liver, pancreas, lung, breast (women), cervix, ovary, prostate, and melanoma of the skin in adults, and brain tumours, leukaemias, and lymphomas in both adults and children. Standardised quality control procedures were applied; errors were rectified by the registry concerned. We estimated 5-year net survival. Estimates were age-standardised with the International Cancer Survival Standard weights. FINDINGS: For most cancers, 5-year net survival remains among the highest in the world in the USA and Canada, in Australia and New Zealand, and in Finland, Iceland, Norway, and Sweden. For many cancers, Denmark is closing the survival gap with the other Nordic countries. Survival trends are generally increasing, even for some of the more lethal cancers: in some countries, survival has increased by up to 5% for cancers of the liver, pancreas, and lung. For women diagnosed during 2010-14, 5-year survival for breast cancer is now 89·5% in Australia and 90·2% in the USA, but international differences remain very wide, with levels as low as 66·1% in India. For gastrointestinal cancers, the highest levels of 5-year survival are seen in southeast Asia: in South Korea for cancers of the stomach (68·9%), colon (71·8%), and rectum (71·1%); in Japan for oesophageal cancer (36·0%); and in Taiwan for liver cancer (27·9%). By contrast, in the same world region, survival is generally lower than elsewhere for melanoma of the skin (59·9% in South Korea, 52·1% in Taiwan, and 49·6% in China), and for both lymphoid malignancies (52·5%, 50·5%, and 38·3%) and myeloid malignancies (45·9%, 33·4%, and 24·8%). For children diagnosed during 2010-14, 5-year survival for acute lymphoblastic leukaemia ranged from 49·8% in Ecuador to 95·2% in Finland. 5-year survival from brain tumours in children is higher than for adults but the global range is very wide (from 28·9% in Brazil to nearly 80% in Sweden and Denmark). INTERPRETATION: The CONCORD programme enables timely comparisons of the overall effectiveness of health systems in providing care for 18 cancers that collectively represent 75% of all cancers diagnosed worldwide every year. It contributes to the evidence base for global policy on cancer control. Since 2017, the Organisation for Economic Co-operation and Development has used findings from the CONCORD programme as the official benchmark of cancer survival, among their indicators of the quality of health care in 48 countries worldwide. Governments must recognise population-based cancer registries as key policy tools that can be used to evaluate both the impact of cancer prevention strategies and the effectiveness of health systems for all patients diagnosed with cancer. FUNDING: American Cancer Society; Centers for Disease Control and Prevention; Swiss Re; Swiss Cancer Research foundation; Swiss Cancer League; Institut National du Cancer; La Ligue Contre le Cancer; Rossy Family Foundation; US National Cancer Institute; and the Susan G Komen Foundation
Enamel Based Composite Layers Deposited on Titanium Substrate with Antifungal Activity
No full textThe goal of this paper was to investigate the antifungal activity of Enamel layers deposited on titanium substrate (Ti-Enamel) and Enamel layers deposited on titanium substrate previously coated with a vinyl polydimethylsiloxane layer (Ti-PDMS-Enamel). The physicochemical properties were also investigated. The Candida albicans biofilm development on the obtained layers was examined after 24 h, 48 h, and 72 h by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM) after ethidium bromide staining. A significant inhibition of the fungal adherence and biofilm development was observed on Ti-Enamel layers. The antifungal results demonstrated that the use of new Ti-Enamel composite layers could represent a promising perspective for the prevention of fungal biofilms associated implant infections
Prosodic accommodation and salience: The nuclear contours of Andalusian Spanish speakers in Asturias
No full textThis study investigates the convergent accommodating behaviour of Andalusian speakers (Southern Spain) relocated in Asturias (Northern Spain), a context of dialect contact, in terms of intonation. We aim to address three research questions: (1) is there evidence for accommodation? (2) Do social factors determine accommodation? And (3) does salience predict which prosodic features are more likely to be adopted by relocated speakers? We elaborated a corpus of spontaneous speech including an experimental group of Andalusian speakers in Asturias and two control groups of Asturian and Andalusian people. The relocated Andalusians were interviewed by a speaker of Andalusian Spanish and a speaker of Amestáu (hybrid variety between Asturian and Spanish), and their intonation patterns were compared to the ones found in the control populations. During the interviews, we also gathered data about how integrated these relocated speakers were in Asturias. We found that all participants show a tendency towards convergent accommodation to the Amestáu interlocutor, producing late falling pitch contours in nuclear position in declaratives and final falling contours in absolute interrogatives. The most integrated speakers in the Asturian community are the ones showing more features of the varieties spoken in the area. Finally, the most salient features to an Andalusian ear—the presence of final falls in Asturian, Asturian Spanish and Amestáu absolute interrogatives as opposed to final rises in Andalusian and Standard Peninsular Spanish—were the ones showing the highest percentages of adoption in relocated speakers. We could conclude, then, that the most salient prosodic features are acquired more easily by the most integrated relocated speakers
