A barium perchlorate complex with a lateral macrobicycle derived from 1,10‐di­aza‐15‐crown‐5 containing a phenol Schiff base spacer

In the crystal structure of (acetonitrile‐κN)[13‐methyl‐39‐oxido‐1,17,25‐tri­aza‐9‐azonia‐28,31,36‐trioxapentacyclo[23.8.5.1^11,15.0^3,8.0^18,23]nonatriaconta‐3,5,7,9,11,13,15(39),16,18,20,22‐un­decaene‐κ⁷N¹,N¹⁷,N²⁵,O²⁸,O³¹,O³⁶,O³⁹](perchlorato‐κ²O,O′)barium(II) perchlorate acetonitrile hemisolvate, [Ba(ClO₄)(C₂H₃N)(C₃₃H₄₀N₄O₄)]ClO₄·0.5CH₃CN, the barium(II) cation is asymmetrically situated in the macrobicyclic cavity and is bound to seven of the eight heteroatoms of the macrobicyclic ligand, to the N atom of an aceto­nitrile mol­ecule and to two O atoms of one perchlorate group. The azonia N atom is not coordinated to the barium(II) cation and is involved in an intramolecular hydrogen‐bonding interaction with the oxido O atom.     

Quantitation of nifedipine in human plasma by on-line solid-phase extraction and high-performance liquid chromatography

An analytical methodology for nifedipine quantitation in plasma by on-line solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC) is described. The SPE cartridges contain C₂ and the analytes nifedipine and nitrendipine (internal standard) are separated on a C₁₈ column with a mobile phase consisting of acetonitrile–13 mM phosphate buffer pH 7 (65:35, v/v) followed by UV detection at 338 nm. Validation of the method demonstrated good recoveries (>90%), sensitivity (limit of quantification, 2 ng/ml), based on a 500 μl sample volume, accuracy and precision (<5.5% in concentrations greater than the limit of quantitation). This methodology has been used for bioequivalence studies.     

Organic bee pollen: botanical origin, nutritional value, bioactive compounds, antioxidant activity and microbiological quality

Organic bee pollen (BP, n = 22) harvested from the Douro International Natural Park (DINP, Portugal) was studied. Nine botanical families were found in the mixture of the samples. The water activity and pH ranged 0.21-0.37 and 4.3-5.2, respectively. The BP analyses averaged 67.7% carbohydrates, 21.8% crude protein, 5.2% crude fat and 2.9% ash. The energy ranged from 396.4 to 411.1 kcal/100 g. The principal fatty acid found was linolenic, followed by linoleic acid, palmitic acid and oleic acid. The phenolic and flavonoid contents varied from 12.9 to 19.8 mg of gallic acid equivalents/g of extract and from 4.5 to 7.1 mg of catechin equivalents/g of extract, respectively. The scavenger activity and β-carotene bleaching assays values (EC??) were 3.0 ± 0.7 mg/mL and 4.6 mg/mL ± 0.9 mg/mL, respectively. E. coli, sulphite-reducing Clostridia, Salmonella and S. aureus were not found. Since there are studies indicating appreciable differences among BPs from different regions, the full characterization of BP from diverse origins still appears to be a sound research priority in order to obtain reliable data about this beehive product.     

Arsenic determination by ICP-QMS with octopole collision/reaction cell. Overcome of matrix effects under vented and pressurized cell conditions

The determination of arsenic by inductively coupled plasma mass spectrometry (ICP-MS) in natural waters with high sodium and chloride content has been investigated. The instrument used is equipped with an octopole collision/reaction cell to overcome spectroscopic interferences. Thus, the optimization of collision/reaction gas flow rates is required when using a pressurized cell. A mixture of 2.9 mL min⁻¹ of H₂ and 0.5 mL min⁻¹ of He has been found to be suitable for the removal of ⁴⁰Ar³⁵Cl⁺ interference.The effect of the introduction of small amounts of alcohol has also been studied in this work under both vented and pressurized cell conditions. It has been observed that the presence of 4% (v/v) of ethanol or methanol results in an increase in arsenic sensitivity. Moreover, under vented cell conditions the addition of alcohol also decreases the formation of polyatomic interference. However, this decrease is not observed under pressurized cell conditions.Different elements have been studied as possible internal standards for arsenic determination in presence of high amounts of sodium. Good results have been obtained for rhodium and yttrium under both vented and pressurized cell conditions. Although the presence of alcohol in the sample matrix also affects their behaviour, rhodium and yttrium are still the most suitable elements to correct for these matrix effects.Different experimental conditions have been compared for arsenic determination in spiked, certified and natural waters with high sodium and chloride content. The best results have been obtained under pressurized cell conditions, in the presence of ethanol and using rhodium as internal standard.     

Energy barrier distributions in magnetic systems from the Tln(t/τ0) scaling

A method based in the Tln(t/τ₀) scaling is proposed to obtain the energy barrier distribution of a randomly oriented assembly of magnetic entities. It essentially consists on performing the logarithmic time derivative of the master relaxation curve. The method has been applied to two small particle systems and the obtained distributions are in good agreement with the ones used to fit the master curves to the magnetization decay of a system following the Arrhenius law. The effect of the specific shape of the distribution functions on the low temperature behaviour of the relaxation rate and the possibility to erroneously attribute this behaviour to non-thermal processes is also discussed.     

Full predictivistic modeling of stock market data: Application to change point problems

In change point problems in general we should answer three questions: how many changes are there? Where are they? And, what is the distribution of the data within the blocks? In this paper, we develop a new full predictivistic approach for modeling observations within the same block of observation and consider the product partition model (PPM) for treating the change point problem. The PPM brings more flexibility into the change point problem because it considers the number of changes and the instants when the changes occurred as random variables. A full predictivistic characterization of the model can provide a more tractable way to elicit the prior distribution of the parameters of interest, once prior opinions will be required only about observable quantities. We also present an application to the problem of identifying multiple change points in the mean and variance of a stock market return time series.     

Lichen based biomonitoring of air quality in Havana City west side

Summary An epiphytic lichen (Physcia alba sp.) grown over Roystonea regia tree was used as biomonitor of air quality in the Havana City west side. During the survey, 81 sampling sites were selected according to traffic and industry conditions. The concentration for 14 elements (Mg, Al, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sr, Cd and Pb) was determined by flame atomic absorption spectrometry (FAAS) and anodic stripping voltammetry (ASV). Contents of Cu, Zn, Cd and Pb obtained by both techniques were compared. Several biological reference materials (RM's) were analyzed in order to assure the quality of analytical results. Some pollution sources were identified using principal component analysis. A total of 5 factors were achieved, of which 4 could be interpreted in terms of anthropogenic pollution sources. However, the expected correlation between traffic influence and lead concentration in lichen could not be demonstrated. The factor values patterns are presented.     

One teflon-like channelled nanoporous polymer with a chiral and new uninodal 4-connected net: sorption and catalytic properties

Zn(C17H8F6O4) is the first example of a fluoro-lined nanotube organo-inorganic 3D polymeric chiral structure, which possesses two different types of isolated channels, one of them being laid out with a double spiral of CF3-groups from the ligand molecule; the structure is a new uninodal 4-connected net that only exists when bent ligands connect the centres, and the compound exhibits selective sorption and catalytic chiral recognition properties.     

Unprecedented asymmetric induction through configurationally stable lithium N-(alpha-methylbenzyl)phosphinamides. A new entry to enantiomerically pure gamma-aminophosphinic acids and esters

The first examples of configurationally stable N-benzyl-N-phosphinoyl carbanions are described. Their applications to the synthesis of homochiral gamma-aminophosphinic acids and esters via highly enantioselective dearomatising reactions are shown.