Thermal and Photophysical Properties of Highly Quadrupolar Liquid-Crystalline Derivatives of the [closo-B12H12]2− Anion

Two series of 1,12-bis-zwitterionic derivatives of the [closo-B₁₂H₁₂]²⁻ anion ( B ), containing either two 4-alkoxypyridinium groups ( 1B[n]-p ) or one 4-alkoxypyridinium and one 4-pentylthianium groups ( 2B[n]-p ), were prepared and their structural (XRD, DFT), thermal, and photophysical properties were compared with those of the analogous derivatives of the [closo-B₁₀H₁₀]²⁻ anion ( 1A[n]-p and 2A[n]-p ). Some 1,7-derivatives of B were isolated and investigated. Both series 1[n] and 2[n] exhibit nematic and crystalline polymorphism; the 12-vertex derivatives ( B ) have higher transition temperatures than those of the 10-vertex analogues ( A ). All compounds fluoresce with quantum yields higher for 1B (Φ_F=0.37 for 1B[7]-p and Φ_F=0.27 for 2B[7]-p ) than those for the 10-vertex analogues (Φ_F=0.04 for 2A[5]-p ). DFT calculations demonstrate an order of magnitude lower first hyperpolarizability, β_(−ω,ω,0), for 2B[7]-p than that for the 10-vertex analogue 2A[7]-p (1.7×10⁻³⁰ vs. 18.9×10⁻³⁰ esu at ω=0).     

Calcification of aortic human valves studied in situ by Raman microimaging: following mineralization from small grains to big deposits

A Raman microimaging‐based approach has been used in the current study to evaluate formation and progression of calcification in situ in human stenotic aortic valves obtained during surgical valve replacement. The capability of the method to visualize distribution of the calcified deposits resulted in structural characterization of deposits in the various phases of development. A high spatial resolution of the method along with the confocal depth profiling enabled to identify extremely small salt inclusions (of ca. 0.5 µm in diameter), formed probably at the very early stage of calcification. Structurally, these inclusions are built from an octacalcium phosphate‐like compound that during grains' growth transforms into tricalcium phosphate, mixed with the salt containing the acidic phosphate groups (HPO₄²⁻) and, finally, into stable B‐type hydroxyapatite that is the only salt present in large‐area calcium salt deposits. Copyright © 2013 John Wiley & Sons, Ltd.     

Effects of high pressure treatment on the quality of chicken patties

The effects of high pressure treatment (500 MPa, 10 min, 20 °C) on the quality of commercial chicken patties (breaded and unbreaded) were evaluated. Physical, chemical and microbiological tests were performed 24 h after high pressure processing (HPP), as well as after 14 and 21 days of storage in refrigerated conditions. It was concluded that the use of high pressures extends the shelf life of vacuum-packaged chicken patties by up to 3 weeks, based on the condition of storage during refrigeration. After this period, the number of mesophilic, psychrotrophic and lactic acid bacteria in the pressure-treated patties was five to six logarithmic cycles lower than that in the control products. HPP did not considerably influence the amount of storage drip loss, texture or colour of the patties; however, it quickened the process of lipid oxidation.     

Effects of high pressure treatment on the quality of cooked pork ham prepared with different levels of curing ingredients

The aim of this study was to define the effects of high-pressure treatment (600 MPa, 10 min, 20 °C) on the quality of cooked pork ham prepared with two different levels of curing ingredients in brine. Physical, chemical, microbiological, and sensory tests were performed 24 h after high pressure processing (HPP), as well as after 6 and 8 weeks of storage in refrigerator conditions. The results indicate that HPP causes significant improvement of shelf life of vacuum packed ham, including the samples with reduced level of curing ingredients in brine to 8 weeks in refrigerator conditions (4–6 °C). HPP did not have significant effect on the texture or color of ham. However, it significantly increased the drip loss during storage in the packed samples. This may indicate that HPP has negative effects on water holding capacity of cooked products.     

Enthalpic interaction coefficients of NaI–alkanediol pairs in methanol and in water

The dissolution enthalpies of NaI in the mixtures of methanol with 1,2-alkanediols (1,2-propanediol, 1,2-butanediol, 1,2-pentanediol) and with ??,??-alkanediols (1,3-propanediol, 1,4-butanediol, 1,5-pentanediol), as well NaI in the mixtures of water with 1,3-propanediol and 1,2-pentanediol, were determined at 298.15?K. The energetic effect of interactions between the investigated alkanediols and NaI in methanol and in water was calculated using the enthalpic pair interaction coefficients (h _xy ) model. These results along with the other data concerning the NaI?Cnon-electrolyte pairs taken from our earlier reports and from the literature were analyzed with respect to the effect of the non-electrolyte properties on the variations of the h _xy values. The group contributions illustrating the interactions of NaI with selected functional groups in non-electrolyte (alkanediol and alkanol) molecules, namely: CH₂ and OH groups were calculated and discussed.     

Symmetrization of Cationic Hydrogen Bridges of Protonated Sponges Induced by Solvent and Counteranion Interactions as Revealed by NMR Spectroscopy

The properties of the intramolecular hydrogen bonds of doubly ¹⁵N‐labeled protonated sponges of the 1,8‐bis(dimethylamino)naphthalene (DMANH⁺) type have been studied as a function of the solvent, counteranion, and temperature using low‐temperature NMR spectroscopy. Information about the hydrogen‐bond symmetries was obtained by the analysis of the chemical shifts δ_H and δ_N and the scalar coupling constants J(N,N), J(N,H), J(H,N) of the ¹⁵NH¹⁵N hydrogen bonds. Whereas the individual couplings J(N,H) and J(H,N) were averaged by a fast intramolecular proton tautomerism between two forms, it is shown that the sum |J(N,H)+J(H,N)| generally represents a measure of the hydrogen‐bond strength in a similar way to δ_H and J(N,N). The NMR spectroscopic parameters of DMANH⁺ and of 4‐nitro‐DMANH⁺ are independent of the anion in the case of CD₃CN, which indicates ion‐pair dissociation in this solvent. By contrast, studies using CD₂Cl₂, [D₈]toluene as well as the freon mixture CDF₃/CDF₂Cl, which is liquid down to 100 K, revealed an influence of temperature and of the counteranions. Whereas a small counteranion such as trifluoroacetate perturbed the hydrogen bond, the large noncoordinating anion tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate B[{C₆H₃(CF₃)₂}₄]^? (BARF^?), which exhibits a delocalized charge, made the hydrogen bond more symmetric. Lowering the temperature led to a similar symmetrization, an effect that is discussed in terms of solvent ordering at low temperature and differential solvent order/disorder at high temperatures. By contrast, toluene molecules that are ordered around the cation led to typical high‐field shifts of the hydrogen‐bonded proton as well as of those bound to carbon, an effect that is absent in the case of neutral NHN chelates.     

A note on blocks of skeleton tolerances

We provide a full characterization of lattices which can be blocks of the skeleton tolerance relation of a finite lattice. Moreover, we formulate a necessary condition for a lattice to be such a block in the case of finite distributive lattices with at most k-dimensional maximal boolean intervals.     

Studies on the construction and operation of miniaturized potentiometric biosensors

This study aims at presenting the studies on construction and operation of solid-state miniaturized biosensor with potentiometric detection. The performance of sensors with layer which consisted of mixture of aliphatic thiols and thiols containing ferrocene terminal groups or the conductive polymer layer obtained by electrochemical polymerization of 3,4-ethylenedioxythiophene was compared. Both of the applied modifications proved to significantly affect the sensors’ performance, influencing the stability of their working parameters in time. Wherein, the greatest improvement in planar sensors’ operating parameters was achieved by applying conductive polymer layer. Subsequently, a system creating universal platform for the construction of a biosensor, dedicated to almost any analyte determination, depending on the composition of the affinity proteins used in the receptor layer, was developed. For the construction of proposed biosensor, alkaline phosphatase was chosen as a model enzyme, assuming either the role of direct component of receptor layer or a label in affinity biosensor. The affinity biosensor structure was characterized by a sandwich assay, using a highly specific interaction occurring between streptavidin and biotin. Aside from optimization of various components of the constructed sensor, the most adequate analysis conditions were designated in the course of presented research. As it turned out, the composition of buffer solution used has a significant influence on the activity of the applied enzyme as well as on the working parameters of the sensor. Tris buffer was, therefore, found as the one ensuring the best performance of sensors utilizing alkaline phosphatase.     

Benzophenone‐(phenylthio)acetic acid phosphonium salts as initiators of free‐radical photopolymerization of vinyl monomers: Mechanistic studies

The mechanism of the benzophenone‐sensitized photooxidation of phosphonium salts of (phenylthio)acetic acid was studied as a means for understanding how these salts function as coinitiators in the free‐radical photopolymerization of vinyl monomers. Both steady‐state and nanosecond flash photolytic methods were used to determine, in a quantitative manner, the mechanism of primary and secondary photoreactions for three quaternary phosphonium salts containing butyl and/or phenyl groups, i.e., P⁺(C₄H₉)₄, P⁺(C₄H₉)(C₆H₅)₃, and P⁺(C₆H₅)₄. It was found that the initial polymerization rates were the same for all three phoshonium salts of (phenylthio)acetic acid and were equal to those found previously for tetralkyl ammonium salts. The polymerization rates were more than twice the rates found for direct initiation by benzophenone and by the benzophenone‐(phenylthio)acetic acid initiating system. These results correlate well with the large quantum yields of ^?CH₂SC₆H₅ radicals (the main initiating radicals) found in the complementary photochemical investigation. It was found that a detailed knowledge of the photochemical reactions in the photoinitiating systems was critical to understand the kinetics of polymerization. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8013–8022, 2008