The double centralizer theorem for division algebras

AssumeV is a finite-dimensional vector space over a division ringD having centerF. It is shown that ifT∈ End _D (V) is algebraic overF then the double centralizerC(C(T)) ofT is the setF[T] of all polynomials inT with coefficients fromF. Consequently, eachn×n matrix ring overD is an algebraicF-algebra if and only ifC(C(T))=F[T] for allT and all finite-dimensionalV.     

Catalytic Stereoselective Borylative Transannular Reactions

Medium‐sized carbocycles containing an α,β‐unsaturated ketone moiety as Michael acceptor site and a ketone moiety as internal electrophilic site are ideal substrates to conduct Cu(I)‐catalyzed conjugated borylation followed by electrophilic intramolecular trapping that results into a pioneer transannular borylative ring closing reaction. The relative configuration of three adjacent stereocenters is controlled, giving access to a single diastereoisomer for a wide range of substrates tested. Moreover, when a chiral ligand is incorporated, the reaction provides enantioenriched polycyclic products with up to 99 % ee.     

Favoring Trienamine Activation through Unconjugated Dienals: Organocatalytic Enantioselective Remote Functionalization of Alkenes

Unconjugated 2,5‐dienals are more reactive substrates than the corresponding fully conjugated α,β,γ,δ‐unsaturated aldehydes towards organocatalytic activation through trienamine intermediates. This difference in reactivity has been demonstrated in the Diels–Alder reaction with nitroalkenes, a reaction that proceeds with clean β,ε‐selectivity to afford the final products in high yields and stereoselectivities, the related polyconjugated 2,4‐dienals being completely unreactive.     

Acyclic amino acid-catalyzed direct asymmetric aldol reactions: alanine, the simplest stereoselective organocatalyst

The linear amino acid-catalyzed direct asymmetric intermolecular aldol reaction is presented; simple amino acids such as alanine, valine, isoleucine, aspartate, alanine tetrazole and serine catalyzed the direct catalytic asymmetric intermolecular aldol reactions between unmodified ketones and aldehydes with excellent stereocontrol and furnished the corresponding aldol products in up to 98% yield and with up to > 99% ee.     

Accurate mass screening of pharmaceuticals and fungicides in water by U-HPLC–Exactive Orbitrap MS

The use of pharmaceuticals in livestock production is a potential source of surface water, groundwater and soil contamination. Possible impacts of antibiotics on the environment include toxicity and the emergence of antibiotic resistance. Monitoring programs are required to record the presence of these substances in the environment. A rapid, versatile and selective multi-method was developed and validated for screening 43 pharmaceutical and fungicides compounds, in surface and groundwater, in one single full-scan MS method, using benchtop U-HPLC-Exactive Orbitrap MS at 50,000 (FWHM) resolution. Detection was based on calculated exact masses and on retention time. Sample volume, pH conditions and solid-phase extraction (SPE) sample clean-up conditions were optimized. In the final method, 74 % of the compounds had recoveries higher than 80 %, 15 % of the compounds had recoveries between 60 % and 80 %, and 7 % of the compounds had recoveries between 40 % and 50 %. One of the compounds (itraconazole) had a recovery lower than 10 % and nystatin was not detected. The level of detection was 10 ng L(-1) for 61 % of the compounds, 50 ng L(-1) for 32 % and 100 ng L(-1) for 5%. In-house validation, based on EU guidelines, proves that the detection capability CCβ is lower than 10 ng L(-1) (for β error 5 %) for 37 % of the compounds, lower than 50 ng L(-1) for 35 % of the compounds and lower than 100 ng L(-1) for 14 % of compounds. This study demonstrates that the ultra-high resolution and reliable mass accuracy of Exactive Orbitrap MS permits the detection of pharmaceutical residues in a concentration range of 10-100 ng L(-1), applying a post target screening approach, in the multi-method conditions.     

Electronic Filtering of Interferometric Homodyne Crosstalk in WDM Systems with Absolute Frequency Reference

Electronic high pass filtering of interferometric crosstalk noise is investigated theoretically and experimentally in systems with absolute frequency reference employing external modulation and DC balanced coding. 4 dB improvement in the tolerance to crosstalk is demonstrated.