Performance of Canadian clinical laboratories processing throat culture proficiency testing surveys

Proficiency testing results obtained from simulated throat swab cultures sent between 1999 and 2013 were analyzed to evaluate the ability of participants to process, analyze, and properly report results for these cultures. Eight percent of all pathogen-positive samples were reported as false negatives, and 11 % of the pathogen-negative ones were reported as false positives. More than 90 % of the participants achieved acceptable grades in each of the proficiency testing samples containing Streptococcus pyogenes. Laboratories were less successful in reporting other significant pathogens including group C and G streptococcus and Arcanobacterium haemolyticum, although an overall increase in performance was observed for each subsequent survey. Most laboratories recognized other respiratory pathogens as not being agents of pharyngitis; a common issue with these specimens was the suggestion of the organism’s clinical significance when their presence was reported. The presence of small colony-forming β-hemolytic streptococcus (Streptococcus anginosus group) proved to be challenging for many laboratories as 66 % of all unacceptable grades for pathogen-negative throat swabs occurred in these PT samples. Moreover, performance in this group did not improve with subsequent surveys. Results obtained in this study support the added value of clinical relevancy challenges for proficiency testing as laboratories that may not have problems with the analytical aspect of the testing process struggle with the appropriate interpretation of results.     

The e-exchange basis graph and matroid connectedness

Let $M$ be a matroid and $e\in E\left(M\right)$. The $e$-exchange basis graph of $M$ has vertices labeled by bases of $M$, and two vertices are adjacent when the bases labeling them have symmetric difference $\{e,x\}$ for some $x\in E\left(M\right)$. In this paper we show that a connected matroid is exactly a matroid with the property that for every element $e\in E\left(M\right)$, the $e$-exchange basis graph is connected.     

The Potential of π-Bonded Organometallic Polymers in Catalyst Design

Reductive substitution, the process whereby a hydrocarbon ligand, usually a cyclopentadienyl group, in a transition metal complex is replaced by another unsaturated hydrocarbon with concomitant metal reduction has been utilized to prepare novel complexes of Cr°, Cr^I, Mn^I, Co^I and Ni°. Similarly, ligand substitution, defined more generally as replacement of ligand(s) of a metal complex by an unsaturated hydrocarbon but with no change in the oxidation state of the metal, has resulted in the synthesis of a series of tetraphenylborate and substituted tetraphenylborate complexes of Fe^II, Mo^I, Cr^I, W^I, and Co^I. These procedures and the complexes derived therefrom are considered models for polymers incorporating a variety of novel features.     

Spectroscopic and catalytic characterization of a functional Fe(III)Fe(II) biomimetic for the active site of uteroferrin and protein cleavage

A mixed-valence complex, [Fe(III)Fe(II)L1(μ-OAc)(2)]BF(4)·H(2)O, where the ligand H(2)L1 = 2-{[[3-[((bis(pyridin-2-ylmethyl)amino)methyl)-2-hydroxy-5-methylbenzyl](pyridin-2-ylmethyl)amino]methyl]phenol}, has been studied with a range of techniques, and, where possible, its properties have been compared to those of the corresponding enzyme system purple acid phosphatase. The Fe(III)Fe(II) and Fe(III)(2) oxidized species were studied spectroelectrochemically. The temperature-dependent population of the S = 3/2 spin states of the heterovalent system, observed using magnetic circular dichroism, confirmed that the dinuclear center is weakly antiferromagnetically coupled (H = -2JS(1)·S(2), where J = -5.6 cm(-1)) in a frozen solution. The ligand-to-metal charge-transfer transitions are correlated with density functional theory calculations. The Fe(III)Fe(II) complex is electron paramagnetic resonance (EPR)-silent, except at very low temperatures (<2 K), because of the broadening caused by the exchange coupling and zero-field-splitting parameters being of comparable magnitude and rapid spin-lattice relaxation. However, a phosphate-bound Fe(III)(2) complex showed an EPR spectrum due to population of the S(tot) = 3 state (J= -3.5 cm(-1)). The phosphatase activity of the Fe(III)Fe(II) complex in hydrolysis of bis(2,4-dinitrophenyl)phosphate (k(cat.) = 1.88 × 10(-3) s(-1); K(m) = 4.63 × 10(-3) mol L(-1)) is similar to that of other bimetallic heterovalent complexes with the same ligand. Analysis of the kinetic data supports a mechanism where the initiating nucleophile in the phosphatase reaction is a hydroxide, terminally bound to Fe(III). It is interesting to note that aqueous solutions of [Fe(III)Fe(II)L1(μ-OAc)(2)](+) are also capable of protein cleavage, at mild temperature and pH conditions, thus further expanding the scope of this complex's catalytic promiscuity.     

Searching for cyclin-dependent kinase inhibitors using a new variant of the cope elimination

beta-Piperidinoethylsulfides are oxidized by m-chloroperbenzoic acid to intermediates containing both N-oxide and sulfone functions. These undergo a Cope-type elimination to a vinylsulfone that can be captured by amines to afford beta-aminoethylsulfones. When a beta-aminoethylsulfone group is linked to the 4-position of a phenyl group attached at N-2 of O6-cyclohexylmethylguanine, the resulting derivatives are inhibitors of the cyclin-dependent kinase CDK2. One of the most potent inhibitors (IC50 = 45 nM) contained a N-3-hydroxypropyl group on the aminoethylsulfonyl substituent. The crystal structure of this inhibitor bound to CDK2/cyclin A was determined and shows an unusual network of hydrogen bonds. The synthetic methodology developed can be utilized in multiple-parallel format and has numerous potential applications in medicinal chemistry.     

Manifold preprocessing for laser‐induced breakdown spectroscopy under Mars conditions

Laser‐induced breakdown spectroscopy (LIBS) is currently being used onboard the Mars Science Laboratory rover Curiosity to predict elemental abundances in dust, rocks, and soils using a partial least squares regression model developed by the ChemCam team. Accuracy of that model is constrained by the number of samples needed in the calibration, which grows exponentially with the dimensionality of the data, a phenomenon known as the curse of dimensionality. LIBS data are very high dimensional, and the number of ground‐truth samples (i.e., standards) recorded with the ChemCam before departing for Mars was small compared with the dimensionality, so strategies to optimize prediction accuracy are needed. In this study, we first use an existing machine learning algorithm, locally linear embedding (LLE), to combat the curse of dimensionality by embedding the data into a low‐dimensional manifold subspace before regressing. LLE constructs its embedding by maintaining local neighborhood distances and discarding large global geodesic distances between samples, in an attempt to preserve the underlying geometric structure of the data. We also introduce a novel supervised version, LLE for regression (LLER), which takes into account the known chemical composition of the training data when embedding. LLER is shown to outperform traditional LLE when predicting most major elements. We show the effectiveness of both algorithms using three different LIBS datasets recorded under Mars‐like conditions. Copyright © 2015 John Wiley & Sons, Ltd.     

1,3-Difunctionalizations of [1.1.1]Propellane via 1,2-Metallate Rearrangements of Boronate Complexes

1,3-Disubstituted bicyclo[1.1.1]pentanes (BCPs) are valuable bioisosteres of para-substituted aromatic rings. The most direct route to these structures is via multicomponent ring-opening reactions of [1.1.1]propellane. However, challenges associated with these transformations mean that difunctionalized BCPs are more commonly prepared by multistep reaction sequences with BCP-halide intermediates. Herein, we report three- and four-component 1,3-difunctionalizations of [1.1.1]propellane with organometallic reagents, organoboronic esters, and a variety of electrophiles. This process is achieved by trapping intermediate BCP-metal species with boronic esters to form boronate complexes, which are versatile intermediates whose electrophile-induced 1,2-metallate rearrangement chemistry enables a broad range of C−C bond-forming reactions.     

Efficient recovery of rare earth elements from coal based resources: a bioleaching approach

Rare earth element (REE) resources in coal-related materials are vast. Assuming a coal production rate of 600 million short tons per year with an average REE content of 200 ppm, the potential REE resource is 120,000 tons per year, which is similar to the annual global production of REEs. Most of those resources that are associated with coal-related materials are found in association with the gangue or ash-based content from the coal ore. Under normal coal plant operation, the REEs often end up in refuse piles or tailings impoundments. In many cases, these REEs can be recovered at low cost using appropriate coal preparation, heap leaching, solvent extraction and/or selective precipitation, followed by subsequent separation and purification of individual REEs. In the present research, the processing approach uses a natural pyrite stream, which was removed during coal cleaning and used to enhance leaching. Bio-oxidation has been used commercially to accelerate leaching, and this approach has been applied to coal-based materials. The ferric ions generated from bio-oxidation oxidize sulfide minerals such as pyrite, which generates acid. Both acid and ferric ions are helpful for leaching REEs, as well as for removing residual sulfides, thereby preventing future acid mine drainage and related liabilities. It can be seen that, recovery of REEs from coal waste materials can enable coal producers to use untapped REEs resources to produce revenue and extend resource life while simultaneously reducing future environmental issues and costs.