A structure rheological study of cellulose trinitrate in ethyl acetate

A structure rheological analysis was undertaken with cellulose trinitrates dissolved in ethyl acetate. Empirical scaling laws with molecular mass and concentration were found for the zero shear viscosity η_o and the critical shear rate $ \dot \gamma _C $ at the onset of shear thinning. Values for the apparent chain element A' were calculated from the concentration dependent network strand M_e and extrapolated to zero concentration. They were compared with dilute solution data. From the concentration dependence of the mass of network strand M_e a network with hindered penetration was inferred.     

Temporal dynamics of dissolved and particulate organic carbon in the northern Adriatic Sea in relation to the mucilage events

The accumulation of dissolved and particulate organic matter may play an important role in mucilage formation in the northern Adriatic. Distributions of dissolved and particulate organic carbon were therefore investigated during the period June 1999-July 2002, when massive mucilage events occurred: in the summer of 2000 and, to a greater extent, of 2002. The seasonal variations in dissolved organic carbon (DOC) concentrations were significant, doubling in summer (up to 150 micromol L(-1)) with respect to winter. The particulate organic carbon (POC) variations were also very large, with a less pronounced seasonal pattern compared to DOC, because the POC changes are much more dependent both on river discharges and on phytoplankton blooms. The comparison of the concentrations between the period before (March-May) and after the onset of mucilage events (June-August) showed that DOC, but particularly POC, were higher in the period before the event of 2002, more markedly in the surface waters of low salinity. The POC increased, reaching mean concentrations of up to 36 micromol L(-1) in March 2002 before the outbreak of the massive mucilage formation in June. This suggests that POC may have a more important role in the mucilage formation than DOC. The highest seasonal variations of organic matter concentrations took place in the upper layer of lower salinity, stressing the importance of stratification and pycnoclines for accumulation and aggregation of the organic matter in the northern Adriatic. The POC contribution to the total organic carbon was low in the oligotrophic waters (DOC/POC ratio >15) and increased with the phytoplankton biomass in the productive waters (DOC/POC ratio <10). Particulate organic carbon predominated over the dissolved inside the mucilage aggregate (DOC/POC ratio <1), probably because aggregation processes, in which colloidal organic carbon is involved, are important. The organic carbon within the aggregates reached a concentration of 13.6 mmol L(-1) which was about 100 times more than in the surrounding waters or in the waters when the mucilages were absent. This indicates that distributions of organic carbon in the northern Adriatic can be extremely patchy during mucilage events.     

Determination of heavy metals by ICP-OES and F-AAS after preconcentration with 2,2'-bipyridyl and erythrosine

The applicability of 2,2'-bipyridyl and erythrosine co-precipitation method for the separation and preconcentration of some heavy metals, such as Cd, Co, Cu, Ni, Pb and Zn in actual samples for their determination by ICP-OES and F-AAS was studied. Experimental conditions influencing the recovery of the investigated metals, such as pH, molar ratio of 2,2'-bipyridyl to erythrosine, the effect of time on co-precipitation were optimized. The analytical characteristics of the method (e.g. limit of detection, sensitivity, linear range and preconcentration factor) were obtained. The limits of detection LOD (ng mL(-1)) of the ICP-OES (F-AAS) method were: Cd: 4.0 (7.75), Co: 3.1 (57.2), Cu: 18 (10.3), Ni 21.3 (32.8), Pb: 35.9 (29.2) and Zn: 10.2 (6.90). The recovery of all the elements tested was more than 93%. The influence of inorganic matrix was examined. The proposed method was applied to determination of Cd, Co, Cu, Ni, Pb and Zn in vegetables and certified reference material (NCS ZC85006 Tomato).     

Some Fungi and Water Molds in Waters of Lake Michigan with Emphasis on Those Associated with the Benthic Amphipod Diporeia spp.

To determine types of fungi in the water and associated with the benthic amphipod Diporeia spp., samples were collected at various depths in Lake Michigan in an area where the Diporeia population was in a severe state of decline. No fungi were found associated with living, freshly-dead, or dried Diporeia cultured separately from Lake Michigan water. When dead Diporeia and other organic substrates (snake skin and hemp seeds) were used to grow fungi in Lake Michigan water, a rich and diverse fungal and water mold community was revealed. A total of 31 species were found, with the most common genera being Achlya, Aphanomyces, Myzocytium, and Pythium. In general, species were homogeneously distributed in the water; that is, few differences were found in species richness between nearshore (10–15 m) and offshore (60–80 m) waters, and between near-surface (1 m) and near-bottom waters (1 m off bottom). Sampling occurred during the unstratified period (April and October) to maximize the number of species collected, which may have contributed to the uniform spatial pattern observed. While conclusions must be placed in context with our methods of detection, we found no evidence that a fungal infestation was associated with Diporeia in this region of the lake.     

Comparison of Quercetin Pharmacokinetics Following Oral Supplementation in Humans

Abstract: The objective of the study was to investigate the absorption of quercetin aglycone in 18 healthy human subjects administered via the following oral carrier systems: suspension of quercetin (quercetin QU995 powder in Tang^® and spring water), nutritional bars (First Strike?), and chews (RealFX? Q‐Plus?). Subjects were divided into 3 groups of 6 individuals each receiving 500 mg quercetin in one of the aforementioned formulations. Blood levels were monitored immediately pre‐ and for 32 h postadministration. The concentration of total quercetin in blood samples was determined by solid phase extraction followed by high‐performance liquid chromatography analysis. Pharmacokinetic parameters were determined by noncompartmental modeling using Kinetica software. The C_max of quercetin was highest with RealFX? Q‐Plus? Chews (1051.9 ± 393.1 μg/L) achieved within 3.3 h as compared to that for First Strike? Bars (698.1 ± 189.5 μg/L in 2.3 h) and Tang^® suspension (354.4 ± 87.6 μg/L in 4.7 h). The results showed no statistically significant difference in quercetin absorption among groups due to high variability within groups receiving quercetin from same dosage form. This study represents the first comprehensive evaluation of quercetin absorption from quercetin fortified oral food products at doses commonly used for quercetin supplementation. Practical Application: The current study describes for the first time, comprehensive evaluation of quercetin PK in humans from quercetin fortified oral food products at doses commonly used for quercetin supplementation. Owing to quercetin's potent antioxidant and anti‐inflammatory actions, quercetin is widely being used as a nutritional supplement. In order to maximize the bioavailability of quercetin for its use in efficacy studies, it is important to determine its ideal oral carrier system and route for its delivery. The current research unveils vital information about quercetin supplementation to the international community, especially to soldiers, athletes, and the dietary supplement industry.     

The application of a supercritical antisolvent process for sustained drug delivery

Supercritical processes for drug delivery system design have attracted considerable attention recently. This present work investigates the application of a supercritical antisolvent coating process for controlled drug release design. Hydrocortisone as the host drug particles and poly(lactide-co-glycolide) (PLGA) as the polymer carrier were selected as the model system for this purpose. In this research the drug particles were suspended in a polymer solution of dichloromethane. The suspension was then sprayed into supercritical CO₂ as an antisolvent. A parallel study of co-precipitation of the drug and polymer using the same supercritical antisolvent process at the same operating conditions was performed for comparison with the coating process. SEM images were used to characterize the drug particles before and after and the assay analysis was carried out using HPLC. The coated particles and co-precipitated particles were evaluated in terms of encapsulation efficiency and drug release profiles. The major advantage of this new approach is the ability to physically coat very fine (< 30 μm) particles without having to dissolve them in an organic solvent. It was found that higher polymer to drug ratios produced higher encapsulation efficiencies and the coated drug particles did show sustained release behavior. The co-precipitation of the drug and polymer (at the same operating conditions), however, did not exhibit any sustained release.     

A comparative study of Vitamin E TPGS/HPMC supersaturated system and other solubilizer/polymer combinations to enhance the permeability of a poorly soluble drug through the skin

In transdermal drug delivery systems (TDDS), it is a challenge to achieve stable and prolonged high permeation rates across skin, because the concentration of the drug dissolved in the matrix has to be high in order to maintain zero order release kinetics of the drug. In case of poorly soluble drugs, due to thermodynamic challenges, there is a high tendency for the drug to nucleate immediately after formulating or even during storage. The present study focuses on the efficiency of vitamin E TPGS/HPMC supersaturated solution and other solubilizer/polymer systems to improve the solubility of the drug and inhibit crystal growth in the transdermal formulation. Effect of several solubilizers, for example, Pluronic F-127, vitamin E TPGS and co-solvent, for example, propylene glycol (PG) were studied on the supersaturated systems of ibuprofen as model drug. Various stabilizers such as hydroxylpropyl methylcellulose (HPMC 3 cps) and polyvinylpyrrolidone (PVP K-30) were examined to evaluate their crystal inhibitory effects. Different analytical tools were used in this study to detect the growth of crystals in the systems. Vitamin E TPGS and HPMC 3 cps formulation produced the highest permeation rate of the drug as compared to other systems. In addition, the onset of crystallization time was shown to be longer with this formulation as compared to other solubilizer/polymer combinations.     

Asymmetric ion track nanopores for sensor technology. Reconstruction of pore profile from conductometric measurements

We reconstruct the profile of asymmetric ion track nanopores from an algorithm developed for conductometric measurements of symmetric nanopores. The validity of the reconstruction is supported by FESEM observations. Our analysis reveals that asymmetric pores fabricated by one-sided etching are funnel-like and not conical. The analysis provides the constriction diameter and the pore profile as a function of etching time. The reconstruction of the pore profile defines the starting conditions of asymmetric nanopores at breakthrough. The deviation from the conical shape is most pronounced at the pore tip. This critical zone dominates transport properties relevant to ion conductance, selectivity, current rectification, resistive pulse sensing and biosensors. The classical cone approximation used until now underestimates the tip diameter by a factor of two. As transport processes in nanopores depend in a highly nonlinear way on the constriction diameter the presented reconstruction must be taken into account when studying ionic and molecular transport processes in asymmetric pores.     

Superionic phase transition in Rb3D(SeO4)2 single crystals

Rb₃D(SeO₄)₂ belongs to the well-known group of hydrogen sulfate and selenate crystals which are promising for fuel cell applications. However, the high temperature properties of this salt have been much less extensively studied than those of Rb₃H(SeO₄)₂. Superionic phase transition in Rb₃D(SeO₄)₂ and Rb₃H(SeO₄)₂ single crystals was studied using impedance spectroscopy and DSC methods. Temperature evolution of the ferroelastic domain structure was observed under a polarizing microscope. Additionally, the X-ray diffraction and Raman scattering measurements for both crystals were carried out at room temperature. Rb₃D(SeO₄)₂ undergoes a structural phase transition from the low temperature ferroelastic phase to the superionic, paraelastic one. A correlation was found between the ferroelastic domains evolution, the anomalies of DSC and the temperature dependence of ionic conductivity. The temperature range of superionic phase transition in the first heating run was much wider and the T_S value was lower in Rb₃D(SeO₄)₂ than in the non-deuterated compound. Additionally, a considerable temperature hysteresis of T_S in Rb₃D(SeO₄)₂ was observed, unlike in Rb₃H(SeO₄)₂. The activation energies of H⁺ and D⁺ conductivity along the c-axis were found to be almost the same. The temperature variation of ionic conductivity in Rb₃D(SeO₄)₂ obtained in the first heating run of a virgin sample was found to differ considerably from that measured in subsequent cooling/heating runs. The small H/D isotope effect of proton conductivity in the crystals studied pointed to a classical activated diffusion mechanism.     

Studies on the impact of glycation on the denaturation of whey proteins

It could be shown for technologically relevant whey protein powders that denaturation of β-lactoglobulin (β-Lg) is affected significantly by the extent of covalent modification of lysine residues by lactose. The amount of acid soluble β-Lg as measured via RP-HPLC with UV detection after heating for 10 min at 80 °C increased from 40% (4.6% lysine modification) to 82% (22.4% lysine modification). An increase in glycation leads to a slower denaturation-induced oligomerisation, as shown by SDS-PAGE. Concomitant with an increase in lysine modification, the denaturation temperature increased from 79.5 to 84 °C, as measured by differential scanning calorimetry (DSC). Covalent attachment of lactose to whey proteins during preparation or storage significantly improves the heat stability of whey proteins, which may be of particular importance for the technological use of whey proteins varying in the degree of lysine modification.