On the Use of Triarylsilanols as Catalysts for Direct Amidation of Carboxylic Acids.

Triarylsilanols have been reported as the first silicon-centered molecular catalysts for direct amidation of carboxylic acids with amines as identified after a screen of silanols, silanediols, disiloxanediols, and incompletely condensed silsesquioxanes as potential homogeneous catalysts. Subsequent synthesis and testing of various electronically differentiated triarylsilanols have identified tris(p-haloaryl)silanols as more active than the parent triarylsilanol, where the bromide congener is found to be the most active. Catalyst decomposition can be observed by NMR methods, but RPKA methods reveal that product inhibition is operative, where tertiary amides are more inhibitory than secondary amides. Studies using an authentically synthesized triaryl silylester as a putative intermediate in the catalytic system enable a plausible mechanism to be proposed as supported by computationals.

Trace Minerals Nutrition in Goats.

This article is an overview of trace mineral nutrition, disease association with dietary inadequacy of trace minerals, and the associated diseases in goats. The trace minerals most commonly associated with deficiency-related diseases encountered in clinical veterinary medicine, Copper, Zinc, and Selenium, are discussed in greater detail than those less commonly associated with diseases. However, Cobalt, Iron, and Iodine are also discussed. The signs of deficiency-associated diseases, along with diagnostic evaluation to confirm such diseases, are also discussed.

COVID-19 prevalence and infection control measures at homeless shelters and hostels in high-income countries: a scoping review.

BACKGROUND: The COVID-19 pandemic has disproportionately impacted homeless populations and service workers, especially within homeless shelter/hostel settings. To date, there have been few evidence syntheses examining outbreaks of COVID-19 among both homeless shelter residents and service workers and no critical review of infection control and prevention (IPAC) measures. This scoping review offers a much-needed synthesis of COVID-19 prevalence within homeless shelters and a review of pertinent IPAC measures.  METHODS: We conducted a scoping review that aimed to synthesize academic and gray literature published from March 2020 to July 2021 pertaining to (1) the prevalence of COVID-19 among both residents and staff in homeless shelters and hostels in high-income countries and (2) COVID-19 IPAC strategies applied in these settings. Two reviewers independently screened the literature from several databases that included MEDLINE, PsycInfo, and the WHO's COVID-19 Global Health Portal. The extracted data was mapped, categorized, and thematically discussed. RESULTS: Thematic analysis of 77 academic and gray literature documents revealed four key themes: (1) the demographics of COVID-19 in homeless shelters, (2) asymptomatic spread, (3) pre-existing vulnerability of people experiencing homelessness and shelters, and (4) the inconsistency and ineffectiveness of IPAC implementation. CONCLUSION: This review offers a useful glimpse into the landscape of COVID-19 outbreaks in homeless shelters/hostels and the major contributing factors to these events. This review revealed that there is no clear indication of generally accepted IPAC standards for shelter residents and workers. This review also illustrated a great need for future research to establish IPAC best practices specifically for homeless shelter/hostel contexts. Finally, the findings from this review reaffirm that homelessness prevention is key to limiting disease outbreaks and the associated negative health outcomes in shelter populations. Limitations of this review included the temporal and database constraints of the search strategy, the exclusion of quality assessments of the literature, and the absence of investigation on the influence of emerging variants on public health policy. SYSTEMATIC REVIEW REGISTRATION: This scoping review has not been registered on any database; the protocol is available on York University's Institutional Repository https://dx.doi.org/10.25071/10315/38513 .

Flexibility is the key to tuning the transport properties of fluorinated imide-based ionic liquids.

Ionic liquids are becoming increasingly popular for practical applications such as biomass processing and lithium-ion batteries. However, identifying ionic liquids with optimal properties for specific applications by trial and error is extremely inefficient since there are a vast number of potential candidate ions. Here we combine experimental and computational techniques to determine how the interplay of fluorination, flexibility and mass affects the transport properties of ionic liquids with the popular imide anion. We observe that fluorination and flexibility have a large impact on properties such as viscosity, whereas the influence of mass is negligible. Using targeted modifications, we show that conformational flexibility provides a significant contribution to the success of fluorination as a design element. Contrary to conventional wisdom, fluorination by itself is thus not a guarantor for beneficial properties such as low viscosity.

Diaryl dithiocarbamates: synthesis, oxidation to thiuram disulfides, Co(III) complexes [Co(S2CNAr2)3] and their use as single source precursors to CoS2.

Air and moisture stable diaryl dithiocarbamate salts, Ar2NCS2Li, result from addition of CS2 to Ar2NLi, the latter being formed upon deprotonation of diarylamines by nBuLi. Oxidation with K3[Fe(CN)6] affords the analogous thiuram disulfides, (Ar2NCS2)2, two examples of which (Ar = p-C6H4X; X = Me, OMe) have been crystallographically characterised. The interconversion of dithiocarbamate and thiuram disulfides has also been probed electrochemically and compared with that established for the widely-utilised diethyl system. While oxidation reactions are generally clean and high yielding, for Ph(2-naphthyl)NCS2Li an ortho-cyclisation product, 3-phenylnaphtho[2,1-d]thiazole-2(3H)-thione, is also formed, resulting from a competitive intramolecular free-radical cyclisation. To demonstrate the coordinating ability of diaryl dithiocarbamates, a small series of Co(III) complexes have been prepared, with two examples, [Co{S2CN(p-tolyl)2}3] and [Co{S2CNPh(m-tolyl)}3] being crystallographically characterised. Solvothermal decomposition of [Co{S2CN(p-tolyl)2}3] in oleylamine generates phase pure CoS2 nanospheres in an unexpected phase-selective manner.

Biomimics of [FeFe]-hydrogenases incorporating redox-active ligands: synthesis, redox properties and spectroelectrochemistry of diiron-dithiolate complexes with ferrocenyl-diphosphines as Fe4S4 surrogates.

[FeFe]-Ase biomimics containing a redox-active ferrocenyl diphosphine have been prepared and their ability to reduce protons and oxidise H2 studied, including 1,1'-bis(diphenylphosphino)ferrocene (dppf) complexes Fe2(CO)4(µ-dppf)(µ-S(CH2)nS) (n = 2, edt; n = 3, pdt) and Fe2(CO)4(µ-dppf)(µ-SAr)2 (Ar = Ph, p-tolyl, p-C6H4NH2), together with the more electron-rich 1,1'-bis(dicyclohexylphosphino)ferrocene (dcpf) complex Fe2(CO)4(µ-dcpf)(µ-pdt). Crystallographic characterisation of four of these show similar overall structures, the diphosphine spanning an elongated Fe-Fe bond (ca. 2.6 Å), lying trans to one sulfur and cis to the second. In solution the diphosphine is flexible, as shown by VT NMR studies, suggesting that Fe2⋯Fe distances of ca. 4.5-4.7 Å in the solid state vary in solution. Cyclic voltammetry, IR spectroelectrochemistry and DFT calculations have been used to develop a detailed picture of electronic and structural changes occurring upon oxidation. In MeCN, Fe2(CO)4(µ-dppf)(µ-pdt) shows two chemically reversible one-electron oxidations occurring sequentially at Fe2 and Fc sites respectively. For other dppf complexes, reversibility of the first oxidation is poor, consistent with an irreversible structural change upon removal of an electron from the Fe2 centre. In CH2Cl2, Fe2(CO)4(µ-dcpf)(µ-pdt) shows a quasi-reversible first oxidation together with subsequent oxidations suggesting that the generated cation has some stability but slowly rearranges. Both pdt complexes readily protonate upon addition of HBF4·Et2O to afford bridging-hydride cations, [Fe2(CO)4(µ-H)(µ-dcpf)(µ-pdt)]+, species which catalytically reduce protons to generate H2. In the presence of pyridine, [Fe2(CO)4(µ-dppf)(µ-pdt)]2+ catalytically oxidises H2 but none of the other complexes do this, probably resulting from the irreversible nature of their first oxidation. Mechanistic details of both proton reduction and H2 oxidation have been studied by DFT allowing speculative reaction schemes to be developed.

Effect of the cation structure on the properties of homobaric imidazolium ionic liquids.

In this work we investigate the structure-property relationships in a series of alkylimidazolium ionic liquids with almost identical molecular weight. Using a combination of theoretical calculations and experimental measurements, we have shown that re-arranging the alkyl side chain or adding functional groups results in quite distinct features in the resultant ILs. The synthesised ILs, although structurally very similar, cover a wide spectrum of properties ranging from highly fluid, glass forming liquids to high melting point crystalline salts. Theoretical ab initio calculations provide insight on minimum energy orientations for the cations, which then are compared to experimental X-ray crystallography measurements to extract information on hydrogen bonding and to verify our understanding of the studied structures. Molecular dynamics simulations of the simplest (core) ionic liquids are used in order to help us interpret our experimental results and understand better why methylation of C2 position of the imidazolium ring results in ILs with such different properties compared to their non-methylated analogues.

A Case Report of Hypotension and Methemoglobinemia Associated With Gunshot Residue Poisoning: Nitrite-Induced Methemoglobinemia.

A patient with gunshots within inches of the skin developed intraoperative vasodilatory hypotension and methemoglobinemia, both recognized consequences of nitrite poisoning. A 1- mg/kg dose of methylene blue transiently and partially reversed methemoglobinemia, but the color of the methylene blue faded rapidly, consistent with bleaching of methylene blue by nitrite in vivo. Methylene blue did not raise blood pressure, consistent with inhibition of nitric oxide (NO) synthase. Because NO production from nitrite uses an NO synthase (NOS)-independent pathway, methylene blue is expected to have little effect on reversing hypotension from nitrite poisoning. Consider nitrite toxicity in gunshot patients with refractory vasodilatory hypotension and elevated methemoglobin.

First example of solid-state luminescent borasiloxane-based chiral helices assembled through N-B bonds.

The reaction between differently substituted borasiloxanes and 2,5-bis(3-pyridylethynyl)thiophene provided the first example of luminescent borasiloxane-based chiral helices held together by N-B bonds. The starting building blocks and the helices were fully characterized, and the nature of the N-B bond rationalized by means of theoretical calculations.

The effect of structural heterogeneity upon the microviscosity of ionic liquids.

The behaviour of two molecular rotors, one charged - 3,3'-diethylthiacarbocyanine iodide (Cy3) and one neutral - 8-[4-decyloxyphenyl]-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY-C10), have been studied in various ionic liquids. The fluorescent decay lifetime has been used to elucidate the structure of the immediate region around the rotor. The neutral BODIPY-C10 was found to prefer the non-polar alkyl chain environment, leading to two trends in the lifetime of the dye: one when it was fully partitioned into the non-polar domain, and one when it also sampled polar moieties. The positively charged Cy3 dye showed a complex relationship between the bulk viscosity of the ionic liquid and lifetime of the molecular rotor. This was attributed to a combination of polarity related spectral changes, changes in anion cages around the dye, and temperature dependent fluorescent lifetimes alongside the dependence of the rotor upon the viscosity.

Stable metal-organic frameworks with low water affinity built from methyl-siloxane linkers.

A tetracarboxylic acid with a methyl-substituted siloxane core (L-H4) has been prepared and applied in the construction of water stable MOFs with low water affinity. L-H4 itself crystallizes as an interpenetrated 3D hydrogen-bonded network. Reaction of L-H4 with ZrIV/HfIV gave IMP-32-Zr/Hf - both 3D MOFs of scu topology.

MAS NMR Investigation of Molecular Order in an Ionic Liquid Crystal.

The structure and molecular order in the thermotropic ionic liquid crystal (ILC), [choline][geranate(H)octanoate], an analogue of Choline And GEranate (CAGE), which has potential for use as a broad-spectrum antimicrobial and transdermal and oral delivery agent, were investigated by magic-angle spinning (MAS) nuclear magnetic resonance (NMR), polarizing optical microscopy, small-angle X-ray scattering (SAXS), and mass spectrometry. Mass spectrometry and the 1H NMR chemical shift reveal that CAGE-oct is a dynamic system, with metathesis (the exchange of interacting ions) and hydrogen exchange occurring between hydrogen-bonded/ionic complexes such as [(choline)(geranate)(H)(octanoate)], [(choline)(octanoate)2(H)], and [(choline)(geranate)2(H)]. These clusters, which are shown by mass spectrometry to be significantly more stable than expected for typical electrostatic ion clusters, involve hydrogen bonding between the carboxylic acid, carboxylate, and hydroxyl groups, with rapid hydrogen bond breaking and re-formation observed to average the 1H chemical shifts. The formation of a partial bilayer liquid crystal (LC) phase was identified by SAXS and polarizing optical microscopy at temperatures below ∼293 K. The occurrence of this transition close to room temperature could be utilized as a potential temperature-induced "switch" of the anisotropic properties for particular applications. The presence of an isotropic component of approximately 23% was observed to coexist with the LC phase, as detected by polarizing optical microscopy and quantified by both 1H-13C dipolar-chemical shift correlation (DIPSHIFT) and 1H double-quantum (DQ) MAS NMR experiments. At temperatures above the LC-to-isotropic transition, intermediate-range order (clustering of polar and nonpolar domains), a feature of many ILs, persists. Site-specific order parameters for the LC phase of CAGE-oct were obtained from the MAS NMR measurement of the partially averaged 13C-1H dipolar couplings (DCH) by cross-polarization (CP) build-up curves and DIPSHIFT experiments, and 1H-1H dipolar couplings (DHH) by double-quantum (DQ) build-up curves. The corresponding order parameters, SCH and SHH, are in the range 0-0.2 and are lower compared to those for smectic (i.e., layered) phases of conventional nonionic liquid crystals, resembling those of lamellar phases formed by lyotropic surfactant-solvent systems.

Conformational design concepts for anions in ionic liquids.

The identification of specific design concepts for the in silico design of ionic liquids (ILs) has been accomplished using theoretical methods. Molecular building blocks, such as interchangeable functional groups, are used to design a priori new ILs which have subsequently been experimentally investigated. The conformational design concepts are developed by separately and systematically changing the central (imide), bridging (sulfonyl) and end (trifluoromethyl) group of the bis(trifluoromethanesulfonyl)imide [N(Tf)2]- anion and examining the resultant potential energy surfaces. It is shown that these design concepts can be used to tune separately the minimum energy geometry, transition state barrier height and relative stability of different conformers. The insights obtained have been used to design two novel anions for ILs, trifluoroacetyl(methylsulfonyl)imide [N(Ms)(TFA)]- and acetyl(trifluoromethanesulfonyl)imide [N(Tf)(Ac)]-. The computationally predicted structures show excellent agreement with experimental structures obtained from X-ray crystallography. [C4C1im][N(Tf)(Ac)] and [C4C1im][N(Ms)(TFA)] ILs have been synthesised and ion diffusion coefficients examined using pulsed field gradient stimulated echo NMR spectroscopy. Significantly increased diffusion was observed for the more flexible [N(Tf)(Ac)]- compared with the more rigid [N(Ms)(TFA)]- analogue. Furthermore, a pronounced impact on the fluidity was observed. The viscosity of the IL with the rigid anion was found to be twice as high as the viscosity of the IL with the flexible anion. The design concepts presented in this work will enable researchers in academia and industry to tailor anions to provide ILs with specific desired properties.

Correction: Modelling and prediction of the thermophysical properties of aqueous mixtures of choline geranate and geranic acid (CAGE) using SAFT-γ Mie.

[This corrects the article DOI: 10.1039/C9RA07057E.].

Structural and Dynamic Properties of Gallium Alkoxides.

A comparison of chlorido-gallium functionalized alkoxides as precursors for aerosol-assisted chemical vapor deposition (AACVD) was carried out. Variable-temperature (VT)-NMR studies were used to probe the fluxional behavior of these alkoxides in solution, and hence their utility as precursors. The synthesis involved the initial isolation of the dimer [GaCl(NMe2)2]2 via a salt metathesis route from GaCl3 and 2 equiv of LiNMe2. This dimer was then reacted with 4 equiv of HOCH2CH2CH2NEt2, resulting in the formation of Ga[µ-(OCH2CH2CH2NEt2)2GaCl2]3 (1). Mass spectrometry and VT-NMR confirmed the oligomeric structure of 1. Tuning of the ligand properties, namely, the chain length and substituents on N, resulted in formation of the monomers [GaCl(OR)2] (R = CH2CH2NEt2, (2); CH2CH2CH2NMe2, (3)). VT-NMR studies, supported by density functional theory calculations, confirmed that the ligands in both 2 and 3 possess a hemilabile coordination to the gallium center, owing to either a shorter carbon backbone (2) or less steric hindrance (3). Both 2 and 3 were selected for use as precursors for AACVD: deposition at 450 °C gave thin films of amorphous Ga2O3, which were subsequently annealed at 1000 °C to afford crystalline Ga2O3 material. The films were fully characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, UV-visible spectroscopy, and energy dispersive X-ray analysis.

Evaluating Colposcopy with Dynamic Spectral Imaging During Routine Practice at Five Colposcopy Clinics in Wales: Clinical Performance.

BACKGROUND: The diagnostic accuracy of colposcopy is poor for detecting precancerous cervical lesions. OBJECTIVES: We assessed the performance of colposcopy for identifying cervical intraepithelial neoplasia grade 2 or worse (CIN2+), before and after including a dynamic spectral imaging (DSI) map that quantifies and maps acetowhitening to assist subsequent biopsy of suspicious lesions. METHODS: Four hundred and twenty-five women were examined at a multi-center setting in Wales, of which 393 women were included in the final analysis. RESULTS: For all referrals, the sensitivity of conventional colposcopy for histologically confirmed CIN2+ was 51.5%, the specificity was 92.0%, the positive predictive value was 56.7%, and the negative predictive value (NPV) was 90.4%. With the incorporation of the DSI map in predicting CIN2+, these became 84.8, 61.5, 30.8, and 95.3% respectively. The increase of sensitivity was statistically significant (p < 0.001). For the 236 women having colposcopy after low-grade (LG) cytology, with the incorporation of DSI, the sensitivity for CIN2+ increased from 27.3 to 86.4% (p < 0.001) and the NPV from 92.6 to 97.8%. CONCLUSIONS: Colposcopy with DSI results in improved sensitivity to detect CIN2+ and maintains a high NPV for all referrals and especially for those with LG referral cytology.

Tetramethyl Orthosilicate (TMOS) as a Reagent for Direct Amidation of Carboxylic Acids.

Tetramethyl orthosilicate (TMOS) is shown to be an effective reagent for direct amidation of aliphatic and aromatic carboxylic acids with amines and anilines. The amide products are obtained in good to quantitative yields in pure form directly after workup without the need for any further purification. A silyl ester as the putative activated intermediate is observed by NMR methods. Amidations on a 1 mol scale are demonstrated with a favorable process mass intensity.

A single-source precursor approach to solution processed indium arsenide thin films.

This paper reports the synthesis of the novel single-source precursor, [{(MeInAs t Bu)3}2(Me2InAs( t Bu)H)2] and the subsequent first report of aerosol-assisted chemical vapour deposition of InAs thin films. Owing to the use of the single-source precursor, highly crystalline and stoichiometric films were grown at a relatively low deposition temperature of 450 °C. Core level XPS depth profiling studies showed some partial oxidation of the film surface, however this was self-limiting and disappeared on etch profiles. Valence band XPS analysis matched well with the simulated density of state spectrum. Hall effect measurements performed on the films showed that the films were n-type with promising resistivity (3.6 × 10-3 Ω cm) and carrier mobility (410 cm2 V-1 s-1) values despite growth on amorphous glass substrates.

Phase behaviour and conductivity of supporting electrolytes in supercritical difluoromethane and 1,1-difluoroethane.

We present investigations into a variety of supporting electrolytes and supercritical fluids probing the phase and conductivity behaviour of these systems and show that they not only provide sufficient electrical conductivity for an electrodeposition bath, but match the requirements imposed by the different precursors and process parameters, e.g. increased temperature, for potential deposition experiments. The two supercritical fluids that have been explored in this study are difluoromethane (CH2F2) and 1,1-difluoroethane (CHF2CH3). For CH2F2, the phase behaviour and electrical conductivity of eight ionic compounds have been studied. Each compound consists of a cation and an anion from the selected candidates i.e. tetramethylammonium ([N(CH3)4](+)), tetrabutylammonium ([N((n)C4H9)4](+)), 1-ethyl-3-methylimidazolium ([EMIM](+)) and 1-butyl-3-methylimidazolium ([BMIM](+)) for cations, and tetrakis(perfluoro-tert-butoxy)aluminate ([Al(OC(CF3)3)4](-)), chloride (Cl(-)), trifluoromethyl sulfonimide ([NTf2](-)) and tris(pentafluoroethyl)trifluorophosphate ([FAP](-)) for anions. For CHF2CH3, [N((n)C4H9)4][BF4] and [N((n)C4H9)4][B{3,5-C6H3(CF3)2}4] have been investigated for comparison with the previously measured solubility and conductivity in CH2F2. We have found that [N((n)C4H9)4][Al(OC(CF3)3)4], [N((n)C4H9)4][FAP] and [N(CH3)4][FAP] have much higher molar conductivity in scCH2F2 at similar conditions than [N((n)C4H9)4][BF4], a widely used commercial electrolyte. Additionally, scCHF2CH3 shows potential for use as the solvent for supercritical fluid electrodeposition, especially at high temperatures since high density of this fluid can be achieved at lower operating pressures than similar fluids that can be used to produce electrochemical baths with comparable conductivity.