Microcrystalline testing used in combination with Raman micro‐spectroscopy for absolute identification of novel psychoactive substances

Two new psychoactive substances, namely 4‐methylmethcathinone (mephedrone) and 5,6‐methylenedioxy‐2‐aminoindane (MDAI) were analysed with a novel combination of microcrystalline tests followed by Raman micro‐spectroscopy to facilitate their absolute identification. The discrimination power of the proposed combination was successfully demonstrated through the analysis of the positional isomers 2‐ and 3‐methylmethcathinone. The addition of mercury dichloride as a microcrystalline test reagent produced specific microcrystals of each tested analyte. The robustness of the method was evaluated in the presence of common cutting agents (caffeine and benzocaine) as well as on street samples. The crystal lattice structures of mephedrone, 2‐methylmethcathinone and MDAI mercury dichloride microcrystals were determined by single crystal X‐ray diffraction. This confirmed the presence of both drug and reagent together in the lattice and accounts for the distinct habit of the observed microcrystals. Raman spectra of the formed microcrystals differed from those obtained from their standard salt form by loss and/or gain of some vibrational modes. Particularly important was the appearance of the mercury chloride link to each tested drug molecule which showed as strong bands at low wavenumbers. Its presence was corroborated by its detection in the crystal lattice. It was therefore concluded that microcrystalline testing followed by Raman micro‐spectroscopy satisfies the technique combination requirement for psychoactive substances recommended by the Scientific Working Group for the Analysis of Seized Drugs (SWGDRUG) and provides a rapid and cheap analysis route. The proposed technique combination also aids the development of new microcrystalline tests as it allows for confirmation of the uniqueness of the developed microcrystals almost in‐situ rather than growing single crystals for often long periods of time needed for single crystal X‐ray diffraction analysis. Copyright © 2016 John Wiley & Sons, Ltd.     

Logic gates and elementary computing by enzymes

Different selected enzymes, glucose oxidase (GOx), catalase (Cat), glucose dehydrogenase (GDH), horseradish peroxidase (HRP), and formaldehyde dehydrogenase (FDH), are used alone or coupled to construct eight different logic gates. The added substrates for the respective enzymes, glucose and H(2)O(2), act as the gate inputs, while the biocatalytically generated gluconic acid or NADH are the output signals that follow the operation of the gates. Different enzyme-based gates are XOR, INHIBIT A, INHIBIT B, AND, OR, NOR, Identity and Inverter gates. By combining the AND and XOR or the XOR and INHIBIT A gates, the half-adder and half-subtractor are constructed, respectively, opening the way to elementary computing by the use of enzymes.     

An electrochemical/photochemical information processing system using a monolayer-functionalized electrode

An electroactive and photoisomerizable monolayer associated with a Au electrode acts as a Write-Read-Erase information processing system and as a flip-flop Set/Reset memory element.     

Configurational entropies of lipids in pure and mixed bilayers from atomic-level and coarse-grained molecular dynamics simulations

Single-chain and single-fragment configurational entropies of lipid tails in hydrated lipid bilayers are evaluated from molecular dynamics simulations using the quasi-harmonic approximation. The entropy distribution along individual acyl tails is obtained and compared to that of corresponding hydrocarbon chains in the liquid phase. We consider pure dipalmitoylphosphatidylcholine and mixed dioleoylphosphatidylcholine/dioleoylphosphatidylethanolamine bilayers. The systems are modeled at different levels of spatial resolution: In an atomic-level (AL) model all (heavy) atoms are explicitly simulated; in a coarse-grained (CG) model particles (beads) representing groups of covalently bound atoms are used, which map approximately four non-hydrogen atoms to one interaction site. Single-chain and single-fragment entropies and correlations between the motions of (single) acyl chains are compared. A good correspondence is found between the flexibility of the AL and CG models. The loss in configurational entropy due to the reduction in the number of degrees of freedom upon coarse-graining of the model is estimated. The CG model shows about 4 times faster convergence of the chain entropies than the more detailed AL model. Corrections to the quasi-harmonic entropy estimates were found to be small for the CG model. For the AL model, the correction due to mode anharmonicities is small, but the correction due to pairwise (supralinear) mode correlations is sizable.     

Continuous review inventory models for perishable items ordered in batches

This paper is an in-depth treatment of an inventory control problem with perishable items. We focus on two prototypes of perishability for items that have a common shelflife and that arrive in batches with zero lead time: (i) sudden deaths due to disasters (e.g., spoilage because of extreme weather conditions or a malfunction of the storage place) and (ii) outdating due to expirations (e.g., medicine or food items that have an expiry date). By using known mathematical tools we generalize the stochastic analysis of continuous review (s, S) policies to our problems. This is achieved by integrating with each inventory cycle stopping times that are independent of the inventory level. We introduce special cases of compound Poisson demand processes with negative jumps and consider demands (jumps) that are exponentially distributed or of a unit (i.e., Poisson) demand. For these special cases we derive a closed form expression of the total cost, including that of perishable items, given any order up to level. Since the stochastic analysis leads to tractable expressions only under specific assumptions, as an added benefit we use a fluid approximation of the inventory level to develop efficient heuristics that can be used in general settings. Numerical results comparing the solution of the heuristics with exact or simulated optimal solutions show that the approximation is accurate.     

The state-dependent <Emphasis Type="Italic">M</Emphasis> / <Emphasis Type="Italic">G</Emphasis> / 1 queue with orbit

We consider a state-dependent single-server queue with orbit. This is a versatile model for the study of service systems, where the server needs a non-negligible time to retrieve waiting customers every time he completes a service. This situation arises typically when the customers are not physically present at a system, but they have a remote access to it, as in a call center station, a communication node, etc. We introduce a probabilistic approach for the performance evaluation of this queueing system, that we refer to as the queueing and Markov chain decomposition approach. Moreover, we discuss the applicability of this approach for the performance evaluation of other non-Markovian service systems with state dependencies.     

Synthesis of key intermediates for a concise and convergent approach to the marine natural product eleutherobin

Synthesis of 1,6-syn-5,6-anti-2-methyl-5-isopropyl-bicyclo[4.3.0]-non-2-en-8-one in three steps from (rac)-phellandrene; and 1,6-syn-1-methyl-6-methoxy-3-aza-9-oxabicyclo[4.2.1]-non-7-en-4-one in five steps from 2-methoxy-5-methylfuran and tetrabromoacetone, provided these key intermediates for the construction of the skeleton of eleutherobin.     

Solvent-free synthesis of unsaturated amino esters in a ball-mill

The ball-milling technique was used under solvent-free conditions to perform a Horner-Wadsworth-Emmons reaction in the presence of a mild carbonate base. Starting from a phosphonate-substituted glycine, this method gave access to Boc-protected unsaturated amino esters in excellent yield and selectivity in many cases. The scope of the reaction was delineated.     

n-Alkane hydroconversion on Zeogrid and colloidal ZSM-5 assembled from aluminosilicate nanoslabs of MFI framework type

n-Alkane hydroisomerisation and hydrocracking experiments reveal that ZSM-5 materials synthesized by self-assembly of nanoslabs show different molecular shape selectivity than ZSM-5 synthesized by hydrothermal methods.