5‐Aminonaphthalene‐1‐sulfonic acid and its manganese,nickel and cobalt salts

5‐Ammonionaphthalene‐1‐sulfonate monohydrate, C₁₀H₉NO₃S·H₂O, contains layers of zwitterionic molecules with the acidic sulfonic acid H atom transferred to the amine N atom. Within each layer, the charged groups (NH₃⁺ and SO₃⁻) are directed to the surface of the layer and are inverted on adjacent molecules. The naphthalene rings in a given layer are all parallel. The layers are held together by N—H...O and O—H...O hydrogen bonds involving the ammonium, sulfonate and water atoms. The Mn and Ni salts crystallize as fully aquated trihydrates, namely hexaaquamanagnese(II) bis(5‐aminonaphthalene‐1‐sulfonate) trihydrate, [Mn(H₂O)₆](C₁₀H₈NO₃S)₂·3H₂O, (II), and hexaaquanickel(II) bis(5‐aminonaphthalene‐1‐sulfonate) trihydrate, [Ni(H₂O)₆](C₁₀H₈NO₃S)₂·3H₂O, (III), in which layers of hexaaquametal(II) complexes alternate with layers of 5‐aminonaphthalene‐1‐sulfonate anions. The cations reside on twofold rotation axes and display regular octahedral coordination. The additional water molecules are found in the inorganic layer between the complex cations, one on a twofold axis and one in a general position. The anions are packed in a herring‐bone arrangement with the rings of neighboring rows of anions approximately 43° out of parallel. The NH₂ and SO₃⁻ groups line the surface of the layer, where they participate in numerous hydrogen bonds with the water molecules. Whereas the Mn and Ni salts are orthorhombic, the Co salt, hexaaquacobalt(II) bis(5‐aminonaphthalene‐1‐sulfonate) dihydrate, [Co(H₂O)₆](C₁₀H₈NO₃S)₂·2H₂O, (IV), crystallizes in a triclinic cell of similar dimensions, with the cations situated on centers of inversion. The overall packing is very similar to that of the Mn and Ni salts, with the main differences being the absence of the solvent water molecule on the special position and subtle modifications in the positioning of the anions within their layers. This series of salts is compared with those of the same metals with the 5‐aminonaphthalene‐2‐sulfonate and 4‐aminonaphthalene‐1‐sulfonate isomers, allowing for similarities and differences in packing to be discussed on the basis of the differing substitution of the naphthalene ring and, in some cases, differing degrees of hydration.     

Soft Ionization of Saturated Hydrocarbons, Alcohols and Nonpolar Compounds by Negative-Ion Direct Analysis in Real-Time Mass Spectrometry

Large polarizable n-alkanes (approximately C18 and larger), alcohols, and other nonpolar compounds can be detected as negative ions when sample solutions are injected directly into the sampling orifice of the atmospheric pressure interface of the time-of-flight mass spectrometer with the direct analysis in real time (DART) ion source operating in negative-ion mode. The mass spectra are dominated by peaks corresponding to [M + O₂]￣^?. No fragmentation is observed, making this a very soft ionization technique for samples that are otherwise difficult to analyze by DART. Detection limits for cholesterol were determined to be in the low nanogram range.

In situ and ex situ characterization of a Fe-Cr-Ni alloy in mouthwashes and Hank’s solution

The aim of the present study was to classify the surface oxide layers formed on a Fe-Cr-Ni alloy according to their corrosion resistance in Hank’s solution and mouthwashes by SEM and electrochemical techniques. The SEM micrographs showed the presence of localized corrosion and the polarization curves showed that the passive layer is less stable in the presence of Hank’s solution than of mouthwashes, as a result of the presence of chloride ions.     

A new protocol for predicting novel GSK-3β ATP competitive inhibitors

Glycogen synthase kinase 3β (GSK-3β) is a potential therapeutic target for cancer, type-2 diabetes, and Alzheimer's disease. This paper proposes a new lead identification protocol that predicts new GSK-3β ATP competitive inhibitors with topologically diverse scaffolds. First, three-dimensional quantitative structure-activity relationship (3D QSAR) models were built and validated. These models are based upon known GSK-3β inhibitors, benzofuran-3-yl-(indol-3-yl) maleimides, by means of comparative molecular field analysis (CoMFA) and comparative molecular similarity indices analysis (CoMSIA). Second, 28?826 maleimide derivatives were selected from the PubChem database. After filtration via Lipinski's rules, 10?429 maleimide derivatives were left. Third, the FlexX-dock program was employed to virtually screen the 10?429 compounds against GSK-3β. This resulted in 617 virtual hits. Fourth, the 3D QSAR models predicted that from the 617 virtual hits, 93 compounds would have GSK-3β inhibition values of less than 15 nM. Finally, from the 93 predicted active hits, 23 compounds were confirmed as GSK-3β inhibitors from literatures; their GSK-3β inhibition ranged from 1.3 to 480 nM. Therefore, the hits rate of our virtual screening protocol is greater than 25%. The protocol combines ligand- and structure-based approaches and therefore validates both approaches and is capable of identifying new hits with topologically diverse scaffolds.     

Few-cycle pulse characterization with an acousto-optic pulse shaper

An acousto-optic pulse shaper has been used to characterize few-cycle pulses generated in a hollow-core fiber. A grism pair precompensates for the dispersion of the acousto-optic crystal, allowing the full pulse-shaping window to be used for replica generation rather than self-compensation. A 9.4 fs pulse was measured, the shortest ever measured with an acousto-optic pulse shaper, to our knowledge.     

An analytical approximated solution and numerical simulations of a non-ideal system with saturation phenomenon

Nonlinear Dynamics - Nowadays, researches about non-ideal problems have been increased considerably in technical-scientific community. Nonlinear problems have been widely studied due to their...     

Instantons in a two-dimensional conformal invariant model with a liouville term

We obtain the instanton solutions to a class of two-dimensional conformal invariant field theories with a Liouville term. The invariance and stability properties of the solutions are discussed.     

The NMR spectra of porphyrins. 27—proton NMR spectra of chlorophyll-a and pheophytin-a

The 500 MHz proton NMR spectra of chlorophyll-a in several non-aggregating solvents, at high dilution, are given and that of pheophytin-a in CDCl₃ at 360 MHz and at high dilution is reported. Under these conditions, the dispersion is such that separate resonances are observed and can be assigned for all protons in the molecules, except P-5 to P-15 in phytyl side-chain. The complex spin systems of the C-7 propionic ester side-chains, and of the P-1/P-2 fragment, are analysed and the couplings obtained are interpreted in terms of possible conformations of the side-chain.     

Resonance Capture in a Three Degree-of-Freedom Mechanical System

We study the phenomena of resonance capture in a three degree-of-freedom dynamical system modeling the dynamics of an unbalanced rotor, subject to a small constant torque, supported by orthogonal, linearly elastic supports, which is constrained to move in the plane. In the physical system the resonance exists between translational motions of the frame and the angular velocity of the unbalanced rotor. These equations, valid in the neighborhood of the resonance, possess a small parameter which is related to the imbalance. In the limit 0, the unperturbed system possesses a homoclinic orbit which separates bounded periodic motion corresponding to resonant solutions from unbounded motion which corresponds to solutions passing through the resonance. Using a generalized Melnikov integral, we characterize the splitting distance between the invariant manifolds which govern capture and escape from resonance for 0. It is shown that as certain slowly varying parameters evolve, the separation distance alternates sign, indicating that both capture into, and escape from resonance occur. We find that although a measurable set of initial conditions enter into a sustained resonance, as the system further evolves the orientation of the manifolds reverses and many of these captured solutions will subsequently escape.