Synergistic pseudo-hydroxide extraction: synergism and anion selectivity in sodium extraction using a crown ether and a series of weak lipophilic acids

The nature of the weak lipophilic acid used in synergistic combination with a model crown ether cation host was shown to have a strong effect on the strength and selectivity of sodium hydroxide separation from alkaline aqueous salt solutions. Sodium ion-pair extraction employing only cis-syn-cis-dicyclohexano-18-crown-6 (1) in nitrobenzene (NB) was correlated with the standard Gibbs energy (deltaG(p)o) of anion partitioning into NB and was notably weak and nonselective for the hydroxide ion, in accord with Hofmeister bias. The Hofmeister order can be selectively overcome for NaOH by utilization of acid-base chemistry coupled with complexation of sodium ion in the NB phase. Upon addition of a lipophilic organic acid into the solution of 1 in NB, sodium extraction was selectively enhanced due to the initiation of an exchange reaction between the aqueous sodium ion and the ionizable proton of the organic acid. A series of weak lipophilic hydroxy acids (HA) including fluorinated alcohols and phenols was tested. The resulting synergistic pseudo-hydroxide extraction correlates with the pKa of the employed HA; the most acidic cation exchangers provide the greatest synergism. The synergistic factor obtained using a fluorinated benzyl alcohol 7 was as high as 256. Ion-pair extraction of neutral sodium salts was not changed or only mildly enhanced by addition of HA into the NB solution of 1. This enhancement was explained by hydrogen bonding of HA with the anion as related to the hardness of the anion and the acidity of HA. In comparison with the synergism observed for NaOH, this enhancement was weak and unable to overcome the Hofmeister effect. Examination of extraction selectivity revealed that the combination of 1 and 7 preferentially extracted NaOH over all other sodium salts, including the normally preferred nitrate and perchlorate salts. Quantitative recovery of NaOH from the NB phase was demonstrated via hydrolysis of the organic acid upon a single contact of the loaded solvent with water.     

Design criteria and optical characteristics of one-dimensional photonic crystals based on periodically grooved silicon

Photonic bandgap (PBG) regions have been calculated for periodically grooved Si structures, acting as a one-dimensional photonic crystal. The wavelength range of the PBG as a function of the ratio (DSi/A) is presented, where DSi is the width of the Si walls and A is the grooved silicon lattice constant. The influence of the parameter DSi, the refractive index of the space between the Si walls and the number of structure periods, m, on the forming of PBG regions is discussed. A good correlation between the calculated and the experimentally observed PBG regions is obtained.     

Stabilization and activation of {alpha}-chymotrypsin in water-organic solvent systems by complex formation with oligoamines

Formation of enzyme–oligoamine complexes was suggestedas an approach to obtain biocatalysts with enhanced resistancetowards inactivation in water–organic media. Complex formationresults in broadening (by 20–40% v/v ethanol) of the rangeof cosolvent concentrations where the enzyme retains its catalyticactivity (stabilization effect). At moderate cosolvent concentrations(20–40% v/v) complex formation activates the enzyme (by3–6 times). The magnitude of activation and stabilizationeffects increases with the number of possible electrostaticcontacts between the protein surface and the molecules of oligoamines(OA). Circular dichroism spectra in the far-UV region show thatcomplex formation stabilizes protein conformation and preventsaggregation in water–organic solvent mixtures. Two populationsof the complexes with different thermodynamic stabilities werefound in -chymotrypsin (CT)–OA systems depending on theCT/OA ratio. The average dissociation constants and stoichiometriesof both low- and high-affinity populations of the complexeswere estimated. It appears that it is the low-affinity siteson the CT surface that are responsible for the activation effect.     

Enrichment of Inorganic Martian Dust Simulant with Carbon Component can Provoke Neurotoxicity

Carbon is the most abundant dust-forming element in the interstellar medium. Tremendous amount of meteorites containing plentiful carbon and carbon-enriched dust particles have reached the Earth daily. National Institute of Health panel accumulates evidences that nano-sized air pollution components may have a significant impact on the central nervous system (CNS) in health and disease. During inhalation, nano-/microsized particles are efficiently deposited in nasal, tracheobronchial, and alveolar regions and can be transported to the CNS. Based on above facts, here we present the study, the aims of which were: 1) to upgrade inorganic Martian dust simulant derived from volcanic ash (JSC-1a/JSC, ORBITEC Orbital Technologies Corporation, Madison, Wisconsin) by the addition of carbon components, that is, nanodiamonds and carbon dots; 2) to analyse acute effects of upgraded simulant on key characteristics of synaptic neurotransmission; and 3) to compare above effects with those of inorganic dust and carbon components per se. Acute administration of carbon-containing Martian dust analogues resulted in a significant decrease in transporter-mediated uptake of L-[¹⁴C]glutamate (the major excitatory neurotransmitter) and [³H]GABA (the main inhibitory neurotransmitter) by isolated rat brain nerve terminals. The extracellular level of both neurotransmitters increased in the presence of carbon-containing Martian dust analogues. These effects were associated with action of carbon components of upgraded Martian dust simulant, but not with its inorganic constituent. This fact indicates that carbon component of native Martian dust can have deleterious effects on extracellular glutamate and GABA homeostasis in the CNS, and so glutamate- and GABA-ergic neurotransmission disballansing exitation and inhibition.     

Combining Multiple Cues for Visual Madlibs Question Answering

International Journal of Computer Vision - This paper presents an approach for answering fill-in-the-blank multiple choice questions from the Visual Madlibs dataset. Instead of generic and commonly...     

Take care of your belongings today – securing accessibility to complex electronic business processes

Most of today’s business processes are based solely on digital data. Input, output, and intermediate results are pure digital objects. Keeping such data accessible and meaningful but even more importantly keeping the business processes functional is challenging. With regards to complex electronic business processes traditional archiving does not provide satisfactory results. Due to the fast technical life-cycle the time gap between archiving and re-enactment or reuse of a process poses risks and increases the uncertainty on achievable results. We propose a novel strategy bridging this specific time gap. For this we present a scalable and cost-effective infrastructure with associated workflows focusing on a process’ execution context. Most importantly the process’ developers are able to assess the preserved results in a timely manner, and thus, reduce the uncertainty on future re-enactment results.