Structural,Spectroscopic and Thermal Analysis of Cocrystals of Carbamazepine and Piracetam with Hydroquinone

Abstract  

Cocrystals of two important active pharmaceutical ingredients, carbamazepine and piracetam, with hydroquinone are reported. Cocrystal formation between the selected APIs and hydroquinone is investigated with the aid of solid-state grinding methods. Both the crystal structures belong to the triclinic, P [`1]P \bar{1} space group, with the cocrystal involving carbamazepine and hydroquinone having the unit cell parameters a = 6.9725 (14) ?, b = 8.8175 (18) ?, c = 15.083 (3) ?, α = 106.96 (3)°, β = 92.16 (3)°, γ = 103.23 (3)°, V = 858.0 (4) ?³ and Z = 2; and the cocrystal involving piracetam and hydroquinone has the unit cell parameters a = 6.4909 (13) ?, b = 6.5410 (13) ?, c = 11.612 (2) ?, α = 103.92 (3)°, β = 104.53 (3)°, γ = 91.06 (3)°, V = 461.59 (18) ?³ and Z = 2. Analysis of the cocrystals revealed that they are sustained by an alcohol–carboxamide heterosynthon. In addition, the cocrystal of carbamazepine and hydroquinone features an amide–alcohol heterosynthon and an alcohol–alcohol homosynthon. The cocrystal of piracetam and hydroquinone features an amide–amide dimer synthon. Cocrystal formation was evidenced from the shifts in the vibrational frequencies corresponding to the functional groups present on the cocrystal components.     

Über die Differentialgleichungen der Himmelsmechanik

Ohne Zusammenfassung     

Lightlike submanifolds of semi-Riemannian manifolds

The purpose of this paper is to initiate a study of the differential geometry of lightlike (degenerate) submanifolds of semi-Riemannian manifolds. We construct the transversal vector bundle for an arbitrary lightlike submanifold and obtain results on the geometric structures induced on it.     

International Symposium on 'Nanoparticles: Technology and Sustainable Development,' Taipei,Taiwan, September 9–10, 2002

Journal of Nanoparticle Research -     

Aerosol Charge Neutralization by a Radioactive Alpha Source

The performance of a Po-210 radioactive ionizer for aerosol charge neutralization and bipolar charging has been evaluated. Monodisperse neutral and singly charged aerosols have been passed through the ionizer and their approach to the steady-state Boltzmann charge measured by measuring the fraction of particles that are electrically charged. The result shows that an Nt of approximately 2.5 × 10⁵ cm^?3 s is needed for the development of a steady-state charge fraction equal to that given by the Boltzmann' s law where N is the ion concentration and t is the residence time of the aerosol in the neutralizer. In addition, the performance of the ionizer for particle charge neutralization in a vibrating-orifice aerosol generator has been evaluated and the result shows that the source is less effective for this application and the residual charge on the particles is considerably higher than that given by the Boltzmann's law.     

Interactions between block copolymers and single-walled carbon nanotubes in aqueous solutions: a small-angle neutron scattering study

The amphiphilic copolymers of the Pluronic family are known to be excellent dispersants for single-walled carbon nanotubes (SWCNT) in water, especially F108 and F127, which have rather long end-blocks of poly(ethylene oxide) (PEO). In this study, the structure of the CNT/polymer hybrid formed in water is evaluated by measurements of small-angle neutron scattering (SANS) with contrast variation, as supported by cryo-transmission electron microscopy (cryo-TEM) imaging. The homogeneous, stable, inklike dispersions exhibited very small isolated bundles of carbon nanotubes in cryo-TEM images. SANS experiments were conducted at different D(2)O/H(2)O content of the dispersing solvent. The data for both systems showed surprisingly minimal intensity values at 70% D(2)O solvent composition, which is much higher than the expected value of 17% D(2)O that is based on the scattering length density (SLD) of PEO. At this near match point, the data exhibited a q(-1) power law relation of intensity to the scattering vector (q), indicating rodlike entities. Two models are evaluated, as extensions to Pederson's block copolymer micelles models. One is loosely adsorbed polymer chains on a rodlike CNT bundle. In the other, the hydrophobic block is considered to form a continuous hydrated shell on the CNT surface, whereas the hydrophilic blocks emanate into the solvent. Both models were found to fit the experimental data reasonably well. The model fit required special considerations of the tight association of water molecules around PEO chains and slight isotopic selectivity.     

A mild and efficient palladium-catalyzed cyanation of aryl chlorides with K4[Fe(CN)6

An efficient palladium-catalyzed cyanation of aryl chlorides is established. In the presence of a highly effective Pd/CM-phos catalyst, cyanation of aryl chlorides proceeds at 70 °C in general, which is the mildest reaction temperature achieved so far for this process. Common functional groups such as keto, aldehyde, ester, nitrile and -NH(2), and heterocyclic coupling partners including N-H indoles are well tolerated. Moreover, a sterically hindered nonactivated ortho,ortho-disubstituted electrophile is shown to be a feasible coupling partner in cyanation.     

Potential theory of infinite dimensional Lévy processes

We study the potential theory of a large class of infinite dimensional Lévy processes, including Brownian motion on abstract Wiener spaces. The key result is the construction of compact Lyapunov functions, i.e., excessive functions with compact level sets. Then many techniques from classical potential theory carry over to this infinite dimensional setting. Thus a number of potential theoretic properties and principles can be proved, answering long standing open problems even for the Brownian motion on abstract Wiener space, as, e.g., formulated by R. Carmona in 1980. In particular, we prove the analog of the known result, that the Cameron-Martin space is polar, in the Lévy case and apply the technique of controlled convergence to solve the Dirichlet problem with general (not necessarily continuous) boundary data.     

Only the first term of some series counts

Let X,X₁,X₂,… be i.i.d. random variables, and set S_n=X₁+?+X_n. We prove that for three important distributions of X, namely normal, exponential and geometric, series of the type ∑_n≥1a_nP(|S_n|≥xb_n) or ∑_n≥1a_nP(S_n≥xb_n) behave like their first term as x→∞.