Insights on the Pseudo-Enantiomeric Properties of Bifunctional Cinchona Alkaloid Squaramide-Derived Organocatalyst

The use of pseudo enantiomers is a well-known method of achieving products of complementary stereochemistry. Only rarely can different enantiomers of a product be accessed without modulation of the catalyst. Recently, a system was reported wherein two different enantiomers of spirocycles were obtained by a cascade reaction of unsaturated pyrrolin-4-ones with mercaptoacetaldehyde catalyzed by a single optimized cinchona alkaloid squaramide-derived organocatalyst. It was originally proposed that the E/Z geometry of the unsaturated pyrrolin-4-one dictated the stereochemistry of the spirocycle product, but this was not investigated further. In the present work, we have investigated the nature of a pseudo-enantiomeric organocatalyst conformation applying density functional theory calculations for investigating the transition states for the reaction. Furthermore, the influence of the double-bond geometry of the pyrrolin-4-one has been studied beyond what is possible to test experimentally. The results provide a greater understanding for this class of reactions that may be applicable in future methodology development.     

Structural, Spectroscopic and Thermal Characterisation of bis (dibenzoylmethanato)Cd(II) Adducts with Dimethylsulfoxide and Water

Abstract  Adducts of cadmium(II) dibenzoylmethate, Cd(dbm)₂X₂ (X = DMSO, H₂O) were synthesized and analyzed by thermogravimetric analysis (TGA), differential-scanning calorimetry (DSC), hot-stage microscopy (HSM), single crystal X-ray diffraction, FTIR and Raman spectroscopy, and elemental analysis. Products obtained by thermal decomposition of the two Cd(II) complexes in oxygen, were used for quantitative analysis of cadmium in the adduct molecules. Single-crystal X-ray diffraction analysis of the DMSO adduct revealed that it has cis configuration. The DMSO adduct crystallizes in P2₁/a space group, a = 17.2494(6) ?, b = 8.3251(4) ?, c = 22.2746(9) ?, β = 93.836(3)°, V = 3191.53(7) ?³, Z = 4. Graphical abstract   Structural, Spectroscopic and Thermal Characterisation of bis (dibenzoylmethanato)Cd(II) Adducts With Dimethylsulfoxide and Water Ivan Halasz, Michaela Horvat, Tomislav Biljan, Ernest Meštrović Two adducts of bis(dibenzoylmethanato)Cd(II), Cd(dbm)₂X₂ (X = DMSO, H2O) have been synthesized and characterized.      

Products of unit distance graphs

Some graphs admit drawings in the Euclidean plane (k-space) in such a (natural) way, that edges are represented as line segments of unit length. We say that they have the unit distance property.The influence of graph operations on the unit distance property is discussed. It is proved that the Cartesian product preserves the unit distance property in the Euclidean plane, while graph union, join, tensor product, strong product, lexicographic product and corona do not. It is proved that the Cartesian product preserves the unit distance property also in higher dimensions.     

On ergodic and mixing properties of the triangle map

In this paper, we study in detail, both analytically and numerically, the dynamical properties of the triangle map, a piecewise parabolic automorphism of the two-dimensional torus, for different values of the two independent parameters defining the map. The dynamics is studied numerically by means of two different symbolic encoding schemes, both relying on the fact that it maps polygons to polygons: in the first scheme we consider dynamically generated partitions made out of suitable sets of disjoint polygons, in the second we consider the standard binary partition of the torus induced by the discontinuity set. These encoding schemes are studied in detail and shown to be compatible, although not equivalent. The ergodic properties of the triangle map are then investigated in terms of the Markov transition matrices associated to the above schemes and furthermore compared to the spectral properties of the Koopman operator in L²(T²). Finally, a stochastic version of the triangle map is introduced and studied. A simple heuristic analysis of the latter yields the correct statistical and scaling behaviours of the correlation functions of the original map.     

Element content and element correlations in Chinese human liver

The amounts of the 19 elements As, Br, Ca, Cd, Ce, Co, Cr, Cs, Fe, K, La, Mo, Na, Rb, Sb, Sc, Se, Sm, and Zn in 92 lyophilized autopsy human liver samples from normal subjects have been analyzed by instrumental neutron-activation analysis (INAA). For intercomparison and quality control ten samples were independently analyzed in two institutes, the Institute of High Energy Physics in China and the Joef Stefan Institute in Slovenia. Most of the element contents determined by the two institutes were in quite good agreement, even though different experimental conditions were applied, indicating the reliability of the analytical results. Analysis of the chemical species of mercury present in the ten liver samples was also performed in Slovenia. Possible differences between the element content of male and female liver samples were studied by means of Students t-test, but significant differences were found only for Ce, Co, Fe, La, Mo, and Zn. The results obtained were also compared with those reported from other areas of the world; no appreciable differences were observed. Correlation among the various elements in the human liver samples was studied using multivariate statistics. It was found that there was relatively close correlation between some elements, for example As–Fe, Ca–Fe, Cd–Co, Cd–Zn, Mo–Zn, Co–Se, Cs–Rb, Br–Rb, Sc–Sm, La–Sm, La–Ce, etc.; these correlations could be rationally explained by the similarity of the electronic structures of the elements and/or their physiological functions in the human body.     

Simple and Rapid Method for Determination of Selenium in Breast Milk by HG-AFS

A digestion procedure using H₂SO₄/HNO₃/H₂O₂ was found to be effective for destruction of human milk samples. In conjunction with a sensitive hydride generation atomic fluorescence spectrometry detection system, it is suitable for determination of selenium in those samples where the available mass of breast milk and the low selenium concentration are limiting factors. Only 1g of milk sample is needed. The procedure is simple, rapid and of low contamination potential since it is performed in the same Teflon tube from weighing to measurement. The digestion of 20 samples is completed in three hours. The detection limit is 0.25±0.04ngg^–1 of a measured solution of sample or 2.5ngg^–1 of milk. The relative uncertainty is 10% (coverage factor of 2.3, 95% probability). Because of these advantages the method is particularly suitable for epidemiological studies. The mean concentration of selenium in 62 samples of human milk from lactating women residing in the North East of Italy was 12±3ngg^–1, which is in the range of reference data.     

Towards the Expression of Sex Hormone Receptors in the Human Vocal Fold

BACKGROUND: The human larynx is assumed to be a steroid receptor target organ. There are only very limited data on the evidence of steroid receptors in the vocal folds, although voice alterations due to hormonal influence and treatment have been found. GOAL OF THE STUDY: To investigate the expression of estrogen alpha, progesterone, and androgen receptors in human vocal folds (vocalis muscle, glands, lamina propria, epithelium). METHODS: Immunohistochemically, vocal fold cadaver specimens of 15 autopsied patients (6 women, 9 men), which were taken approximately 4 to 8 hours postmortem were investigated. Furthermore, one (male) vocal fold biopsy obtained intraoperatively during a laryngectomy was tested. RESULTS: No specific immunohistochemical staining for the different types of steroid hormones investigated could be observed in either the postmortem taken biopsies nor the intraoperatively one. However, several unspecific staining patterns could be observed. CONCLUSION: The results of this study contradict recently published data and question the expression of sex hormone receptors in the vocal folds. Main causes of false interpretations of unspecific staining are discussed.     

Superabsorbent,High Porosity,PAMPS‐Based Hydrogels through Emulsion Templating

Swell! Superabsorbent, mechanically robust, high‐porosity hydrogels based on poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid) have been successfully synthesized by templating within high internal phase emulsions (HIPEs). These hydrogel polyHIPEs (HG‐PHs) exhibit unusually high uptakes of water and of artificial urine through structure‐ and crosslinking‐dependent hydrogel‐swelling‐driven void expansion. An HG‐PH with 3.1 mmol g⁻¹ of highly accessible sulfonic acid groups exhibits a 7 meq NaOH ion exchange capacity per gram polymer and rapid dye absorption. The highly swollen HG‐PHs do not fail at compressive strains of up to 60%, they retain water and recover their shapes upon the removal of stress. Unusually, the dry hydrogels have relatively high compressive moduli and achieve relatively high stresses at 70% strain.