Identification of the oxidation products of cysteamine and cystamine by CE-MS interfaced by a noncommercial electrospray ionization source

Sodium cysteamine phosphate is a prodrug derivative of cysteamine that can be used in cystinosis treatment. Although titrimetric assays are very well established and precise, iodimetric determination of sodium cysteamine phosphate requires considerably more carefulness and time from the analyst than usual. The possibility to assess sodium cysteamine phosphate by CE was evaluated by means of the quantification of its oxidation product, cystamine, which is a more suitable substance to be used as primary standard than sodium cysteamine phosphate. Apparently, this approach should be straightforward, but systematic differences between the results obtained with CE and titrimetric assays were noticed. MS and CE-MS were employed to aid in the investigation of the possible causes of imprecision of the sodium cysteamine phosphate titration and CE determination. For this purpose, a simple and inexpensive ESI source was constructed. It was observed that cystamine is not the final product of the cysteamine and/or sodium cysteamine phosphate iodine-oxidation and other species besides cystamine may be formed depending on the reaction conditions, which explains the difficulties observed in the sodium cysteamine phosphate quantification.     

Unified origin for baryonic visible matter and antibaryonic dark matter

We present a novel mechanism for generating both the baryon and dark matter densities of the Universe. A new Dirac fermion X carrying a conserved baryon number charge couples to the standard model quarks as well as a GeV-scale hidden sector. CP-violating decays of X, produced nonthermally in low-temperature reheating, sequester antibaryon number in the hidden sector, thereby leaving a baryon excess in the visible sector. The antibaryonic hidden states are stable dark matter. A spectacular signature of this mechanism is the baryon-destroying inelastic scattering of dark matter that can annihilate baryons at appreciable rates relevant for nucleon decay searches.     

Quantum Monte Carlo simulation of the high-pressure molecular-atomic crossover in fluid hydrogen

A first-order liquid-liquid phase transition in high-pressure hydrogen between molecular and atomic fluid phases has been predicted in computer simulations using ab initio molecular dynamics approaches. However, experiments indicate that molecular dissociation may occur through a continuous crossover rather than a first-order transition. Here we study the nature of molecular dissociation in fluid hydrogen using an alternative simulation technique in which electronic correlation is computed within quantum Monte Carlo methods, the so-called coupled electron-ion Monte Carlo method. We find no evidence for a first-order liquid-liquid phase transition.     

Titanium dioxide-coated nanofibers for advanced filters

This article reports on titanium dioxide (TiO₂)-coated nanofibers deposited on a filter surface by the electrospinning process. After depositing a micrometer-thick film of polyamide 11 nanofibers on polypropylene fabric, TiO₂ nanoparticles can be directly electrosprayed onto the nanofibers. X-ray diffraction and Raman spectroscopy showed minimal change in the phase composition (anatase and rutile) and no change in the particle size of nanocrystalline TiO₂ after coating. Scanning electron microscopy demonstrated that nanofibers were uniformly coated by titanium dioxide nanoparticles without agglomeration. TiO₂-coated filters showed excellent photocatalytic-bactericidal activity and photo-induced hydrophilicity.     

Plasmonic nanoparticle chains via a morphological, sphere-to-string transition

Au nanoparticles encapsulated within polystyrene-block-poly(acrylic acid) (PS-b-PAA) micelles assemble into regular, one-dimensional arrays when they are exposed to solvent conditions that relax interfacial curvature in the micellar shell. Nanoparticle chaining was induced by adding salt, acid, or cationic carbodiimide to the suspension of purified encapsulated Au nanoparticles (Au@PS-b-PAA). The resulting assemblies were characterized by scanning and transmission electron microscopies, by dark-field optical microscopy, and by visible absorption spectroscopy. The length of the chains was modulated by varying the concentration of additive. More importantly, the spacing between Au nanoparticles was dictated entirely by the shell thickness of the Au@PS-b-PAA starting material. Far-field polarization microspectroscopy demonstrated directional surface plasmon coupling in a straightened nanoparticle chain, which is a basic requirement for the use of these assemblies as plasmon waveguides.     

A 51-dimensional embedding of the Ree–Tits generalized octagon

We construct an embedding of the Ree–Tits generalized octagon defined over a field K in a 51-dimensional projective space over K arising from a 52-dimensional Lie algebra J of type . This construction derives from a quadratic map (related to a ‘standard’ duality of ) from the 26-dimensional module (see K. Coolsaet, Adv Geometry, to appear) into J. (This embedding is full if and only if K is a perfect field.) We provide explicit formulas for the coordinates of the points of the octagon in this embedding, in terms of their Van Maldeghem coordinates. We apply these results to compute the dimensions of subspaces generated by various special subsets of points of the octagon: the sets of points at a fixed distance from a given point or a given line and the Suzuki suboctagons. The results depend on whether K is the field of 2 elements, or not.      

Perspectives on updates,clarifications and controversies in chromatographic assay guidance for bioanalytical method validation from major regulatory agencies and organizations

Bioanalysis, a key supporting function for generating data for pre‐clinical and clinical studies in drug development, is under the regulation of local agencies as well as global organizations to ensure the data integrity and quality in submission. As major regulatory agencies and organizations, the US Food and Drug Administration, the European Medicines Agency and the International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use have been updating their industry guidance for bioanalytical method validation, to keep up with the development new modalities, technologies and regulations. This article summarizes the recent updates and any clarifications and controversies triggered by those updates. Perspectives and recommendations are given based on our own experience as well as commonly accepted practice in the bioanalytical community.     

Reorganizing freshman business mathematics II: authentic assessment in mathematics through professional memos

The first part of this two-part paper (13) described the developmentof a new freshman business mathematics (FBM) course at our college.In this paper, we discuss our assessment tool, the businessmemo, as a venue for students to apply mathematical skills,via mathematical modelling, to realistic business problems.These memos have proven a crucial step in turning our FBM coursearound from a dreaded course with little connection to students’intended careers into a course where students experience thepower of mathematics for solving problems and informing decisions.Comments from students in the course throughout its 6-year historyclearly point to the course's value and importance.