Defining a stable water isotope framework for isotope hydrology application in a large trans-boundary watershed (Russian Federation/Ukraine)

Stable isotopes of hydrogen (²H) and oxygen (¹⁸O) of the water molecule were used to assess the relationship between precipitation, surface water and groundwater in a large Russia/Ukraine trans-boundary river basin. Precipitation was sampled from November 2013 to February 2015, and surface water and groundwater were sampled during high and low flow in 2014. A local meteoric water line was defined for the Ukrainian part of the basin. The isotopic seasonality in precipitation was evident with depletion in heavy isotopes in November–March and an enrichment in April–October, indicating continental and temperature effects. Surface water was enriched in stable water isotopes from upstream to downstream sites due to progressive evaporation. Stable water isotopes in groundwater indicated that recharge occurs mainly during winter and spring. A one-year data set is probably not sufficient to report the seasonality of groundwater recharge, but this survey can be used to identify the stable water isotopes framework in a weakly gauged basin for further hydrological and geochemical studies.     

Two-photon excited intramolecular energy transfer and light-harvesting effect in novel dendritic systems

Two-photon absorption excited intramolecular energy transfer and light-harvesting effects are demonstrated in three novel dendritic systems. These systems contain both an antenna structure that can effectively absorb two-photon energy at approximately 800 nm and emit fluorescence at approximately 515 nm and a core moiety that can absorb one-photon energy at approximately 520 nm and emit at approximately 590 nm. Covalently combining the core and antenna functionalities intrinsically changes the optical behavior of the component pieces. The two-photon energy absorbed by the antenna structure is resonantly transferred to the core, where the core's emission intensity is enhanced by 8, 20, and 34 times for the three dendritic systems.     

Quantitative assessment of Gd-DTPA contrast agent from signal enhancement: an in-vitro study

Quantitative determination of in-vivo gadolinium diethylenetriamine-pentaacid (Gd-DTPA) concentration is attractive in various studies involving perfusion, tracer kinetics and permeability constants. Using a 1.5 T clinical system and a 7 T small-bore system, we evaluated a method for absolute determination of Gd-DTPA concentrations in plasma solutions. Different solutions of Gd-DTPA and (99m)Tc-DTPA were mixed in human plasma and concentrations in the range of 0-5.0 mmol/l (1.5 T system) or 0-3.0 mmol/l (7 T system) of Gd-DTPA were divided into thirteen tubes. All MRI measurements were carried out using conventional sequences (SE, FLASH and GRASS). The MR measured intensity was converted to Gd-DTPA concentration by mathematical interpretation of the sequences. All MRI sequences showed, that the measured concentrations of Gd-DTPA revealed a slight non-linear difference compared with the calculated Gd-DTPA concentrations determined by the plasma (99m)Tc-DTPA using gamma counting. This non-linearity was most pronounced at high Gd-DTPA concentrations, suggesting that the discrepancy could be a result of an increased plasma relaxivity at higher concentrations. Adjustment of measured Gd-DTPA concentration was therefore performed using a selected power function, A[Gd-DTPA](a), which yielded the best linear relationship. Regression analysis showed that the scaling constant (A) varied from 0.11 to 97.45 and the power constant (a) varied from 0.83 to 1.6. Based on these constants, the MRI measured concentrations of Gd-DTPA did not differ from the calculated concentrations of Gd-DTPA obtained from reference measurements of (99m)Tc-DTPA. In the 1.5 T system, a linear relationship (r(2) > or = 0.95) was demonstrated in the range of 0-5.0 mmol/l Gd-DTPA, and in the 7 T system, a linear relationship (r(2) > or = 0.92) was demonstrated in the range of 0-3.0 mmol/l Gd-DTPA. Additionally, the effect of signal-to-noise on measured concentrations of Gd-DTPA was simulated using MR data of the mixed solutions of Gd-DTPA in plasma and the analytical expression of the pulse sequences. The simulations showed that the concentrations were most sensitive to noise in the GRASS sequence. In conclusion, this study demonstrates a novel approach to quantify accurately the Gd-DTPA concentration directly from MRI signal data using different routine sequences.     

Highly selective synthesis of novel (E)-styrylsilatranes via ruthenium-catalyzed trans-silylation

Protocols for the synthesis of cage-substituted 1-vinylsilatranes have been developed and updated. The 1-vinylsilatranes with organic substituents attached to silatrane cage were functionalized in ruthenium-catalyzed trans-silylation with olefins, leading to novel styrylsilatranes in high yields.     

Evaluation of sphingomyelin,cholester, and phosphatidylcholine-based immobilized artificial membrane liquid chromatography to predict drug penetration across the blood-brain barrier

Over the past decades, several in vitro methods have been tested for their ability to predict drug penetration across the blood-brain barrier. So far, in high-performance liquid chromatography, most attention has been paid to micellar liquid chromatography and immobilized artificial membrane (IAM) LC. IAMLC has been described as a viable approach, since the stationary phase emulates the lipid environment of a cell membrane. However, research in IAMLC has almost exclusively been limited to phosphatidylcholine (PC)-based stationary phases, even though PC is only one of the lipids present in cell membranes. In this article, sphingomyelin and cholester stationary phases have been tested for the first time towards their ability to predict drug penetration across the blood-brain barrier. Upon comparison with the PC stationary phase, the sphingomyelin- and cholester-based columns depict similar predictive performance. Combining data from the different stationary phases did not lead to improvements of the models. Figure

Schematic representation of how IAM-LC is used to predict drug penetration across the blood-brain barrier.     

Interplay between spinodal decomposition and glass formation in proteins exhibiting short-range attractions

We investigate the competition between spinodal decomposition and dynamical arrest using aqueous solutions of the globular protein lysozyme as a model system for colloids with short-range attractions. We show that quenches below a temperature Ta lead to gel formation as a result of a local arrest of the protein-dense phase during spinodal decomposition. The rheological properties of these gels allow us to use centrifugation experiments to determine the local densities of both phases and to precisely locate the gel boundary and the attractive glass line close to and within the unstable region of the phase diagram.     

Combining Complex and Radial Slave Boson Fields within the Kotliar–Ruckenstein Representation of Correlated Impurities

The gauge symmetry group of any slave boson representation allows to gauge away the phase of bosonic fields. One benefit of this radial field formulation is the elimination of spurious Bose condensations when saddle-point approximation is performed. Within the Kotliar–Ruckenstein representation, three of the four bosonic fields can be radial while the last one has to remain complex. In this work, the procedure to carry out the functional integration involving constrained fermionic fields, complex bosonic fields, and radial bosonic fields is presented. The correctness of the representation is verified by exactly evaluating the partition function and the Green's function of the Hubbard model in the atomic limit.     

Landau-Level Quantization of the Yellow Excitons in Cuprous Oxide

Lately, the yellow series of P-excitons in cuprous oxide could be resolved up to the principal quantum number n = 25. Adding a magnetic field, leads to additional confinement normal to the field. Thereby, the transition associated with the exciton n is transformed into the transition between the electron and hole Landau levels with quantum number n, once the associated magnetic length becomes smaller than the related exciton Bohr radius. The magnetic field of this transition scales roughly as n^–3. As a consequence of the extended exciton series, we are able to observe Landau level transitions with unprecedented high quantum numbers of more than 75.