Sensitive ergotamine determination in pharmaceuticals and biological samples using cloud point preconcentration and spectrofluorimetric detection

A new cloud point extraction (CPE) method for ergotamine analysis using fluorimetric detection is described. Ergotamine from an aqueous solution was preconcentrated into a smaller surfactant-rich phase using nonionic surfactant polyoxyethylene(7.5)nonylphenylether (PONPE 7.5). Differently from the conventional CPE procedure in which the resulting surfactant-rich phase is diluted by a fluidificant before its analysis, in this method the fluorescence measurements were carried out directly onto the undiluted surfactant-rich phase. The high viscosity provided by the undiluted surfactant rich phase greatly improved the fluorescence emission of ergotamine, leading to a total enhancement factor of 1325. This spectral advantage plus the preconcentration factor achieved, contributed to the method sensitivity allowing the ergotamine determination at trace level concentration. Under optimal experimental conditions, a linear calibration curve was obtained from 3.81 × 10⁻⁷ to 1.10 μg mL⁻¹, with detection and quantification limits of 0.11 and 0.38 pg mL⁻¹, respectively. The accuracy and versatility of the present methodology were proved by analyzing ergotamine in real samples of different natures such as pharmaceuticals, urine and saliva.     

Enthalpic characterisation of activated carbon monoliths obtained from lignocellulosic materials

In this study, energetic interactions between activated carbon monoliths and various liquids were evaluated by determining immersion enthalpies in C₆H₆, H₂O and aqueous solutions of NaOH and HCl. Immersion enthalpies depend on both the surface chemistry and the interactions between specific groups, and were compared with results from volumetric titrations. Immersion enthalpies of activated carbon monoliths were between ?95.85 and ?176.5 J g^?1 for C₆H₆ and between ?11.19 and ?68.31 J g^?1 for H₂O; whereas immersion enthalpies in NaOH and HCl solutions were between ?20.36 and ?82.25 J g^?1 and ?18.81 and ?96.16 J g^?1, respectively. In support of these results, a high level of acidic groups was found on the surface of the activated carbon monoliths by Boehm volumetric titrations, with values between 719 and 1,290 g mol^?1, in agreement with the higher immersion enthalpies observed in NaOH. Correlations were established between immersion enthalpies in the liquids and the surface chemistry properties of the activated carbon monoliths determined by volumetric titrations, demonstrating that immersion enthalpy is a useful parameter for characterisation of these materials in specific liquids.     

Inhomogeneous Dirichlet-boundary value problem for one dimensional nonlinear Schrödinger equations via factorization techniques

We consider the inhomogeneous Dirichlet-boundary value problem for the cubic nonlinear Schrödinger equations on the half line. We present sufficient conditions of initial and boundary data which ensure asymptotic behavior of small solutions to equations by using the classical energy method and factorization techniques     

Synthesis of hydrogels based on poly(NIPAM) inserted into collagen sponge

The study presents the preparation of a semi-synthetic hydrogel based on poly(N-isopropyl acrylamide-co-diethylene glycol diacrylate) inserted onto the collagen porous membrane. The synthesis of the hydrogels was performed through radical copolymerization of N-isopropyl acrylamide (NIPAM) with diethylene glycol diacrylate (DEGDA) also as crosslinking agent, using ammonium persulfate as initiator and N,N,N',N'-tetramethylethylene diamine as activator, and it was achieved in the presence of the collagen matrix. The prepared hydrogels were characterized by Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. The swelling behaviour of the semi-interpenetrated polymer network related on the hydrogel composition, it was also evaluated. The pore sizes of the synthesized hydrogels, much larger than the typical mesh size of a conventional hydrogel, allow to consider the hybrid hydrogel based on the inserted poly(NIPAM-co-DEGDA) onto collagen fibrils as a super-porous hydrogel.     

CO<Subscript>2</Subscript> adsorption on binderless activated carbon monoliths

A series of activated carbon monoliths have been prepared by chemical activation of two lignocellulosic precursors, coconut shell (CACM) and African palm stones (PACM). The incorporation of a conforming step between the impregnation with H₃PO₄ and the activation step allows the successful development of disc-shape monoliths without the use of a binder. Textural characterization results using N₂ adsorption at 77 K show that the effect of the activating agent highly depends on the nature of the carbon precursor used. While chemical activation with phosphoric acid has mainly no effect when using coconut shell, a large development of both micro- and mesoporosity is observed for African palm stones. Large concentrations of the activating agent produce the partial shrinkage of the narrow microporous structure independently of the precursor used. Concerning the adsorption of CO₂ at atmospheric pressure and 273 K, both series of activated carbon monoliths exhibit an improved adsorption behaviour with the activation degree up to an optimum value around ∼164 mg CO₂/g, for sample CACM-32, and ∼162 mg CO₂/g, for sample PACM-28, the amount adsorbed decreasing thereafter. Apparently, the total amount of CO₂ adsorbed under these experimental conditions is defined by the volume of narrow micropores (V _n ).     

Novel subjet observables for jet quenching in heavy-ion collisions

Using a novel observable that relies on the momentum difference of the two most energetic subjets within a jet \(\varDelta S_{12}\) we study the internal structure of high-energy jets simulated by several Monte Carlo event generators that implement the partonic energy-loss in a dense partonic medium. Based on inclusive jet and dijet production we demonstrate that \(\varDelta S_{12}\) is an effective tool to discriminate between different models of jet modifications over a broad kinematic range. The new quantity, while preserving the collinear and infrared safety of modern jet algorithms, it is experimentally attractive because of its inherent resilience against backgrounds of heavy-ion collisions.     

Synthesis and properties of 1-aryl-2-alkyl-1,4,5,6-tetrahydropyrimidines

A general method is described for the synthesis of 1-aryl-2-alkyl-1,4,5,6-tetrahydropyrimidines 1 , by cyclization of N-acyl-N′-aryltrimethylenediamines 2 with trimethylsilyl polyphosphate. Precursors 2 were obtained by aminolysis of the corresponding N-(3-bromopropyl)amides 3. The ¹H nmr spectra of tetrahydropyrimidines 1 are analyzed, discussing the influence of substituents in positions 1 and 2 of the heterocyclic ring. Alkaline hydrolysis of compounds 1 , which originates exclusively N-acyl-N′-aryltrimethylenediamines 2 , through an intermediate carbinolamine, was also studied. Cleavage of such an intermediate is discussed in the light of the stereoelectronic control theory. Reduction of compounds 1 with borane, leads regiospecifically to N-alkyl-N′-aryltrimethylenediamines 6.     

Prediction of Thermal Damage upon Ultrafast Laser Ablation of Metals

Ultrafast lasers micromachining results depend on both the processing parameters and the material properties. The obtained thermal effects are negligible if a good combination of processing parameters is chosen. However, optimizing the processing parameters leading to the required surface quality on a given material can be quite complex and time consuming. We developed a semi-empirical model to estimate the heat accumulation on a surface as a function of the laser fluence, scanning speed and repetition rate. The simulation results were correlated with experimental ones on different materials, and compared with the transient temperature distributions calculated using an analytical solution to the heat transfer equation. The predictions of the proposed model allow evaluating the heat distribution on the surface, as well as optimizing the ultrafast laser micromachining strategy, yielding negligible thermal damage.