Quadrupole relaxation enhancement and polarisation transfer in DMSO solution of [Bi(NO3)3(H2O)3]*18-crown-6 in solid state

ABSTRACT

¹H spin-lattice relaxation studies have been performed for pure [Bi(NO₃)₃(H₂O)₃]*18-crown-6 in powder and its solution in dimethyl sulfoxide (DMSO). The experiments have been carried out in the frequency range of 10?kHz–30?MHz and the temperature range of 240–277?K; at 277?K the solution is already frozen. The ¹H relaxation of pure [Bi(NO₃)₃(H₂O)₃]*18-crown-6 has been interpreted in terms of three dynamical processes. Quadrupole Relaxation Enhancement effects have been observed in the frozen DMSO solution of [Bi(NO₃)₃(H₂O)₃]*18-crown-6. The specific mechanisms of the ¹H spin-lattice relaxation enhancement have been discussed distinguishing between effects caused by time independent (residual) and fluctuating ¹H-²⁰⁹Bi dipole-dipole interactions.     

Analysis of n(87Sr)/n(86Sr), δ88Sr/86SrSRM987 and elemental pattern to characterise groundwater and recharge of saline ponds in a clastic aquifer in East Austria

Elemental and isotopic pattern of n(⁸⁷Sr)/n(⁸⁶Sr) and δ⁸⁸Sr/⁸⁶Sr_SRM987 were used to characterise groundwater and recharge of saline ponds in a clastic aquifer in East Austria. Therefore, shallow, artesian and thermal groundwaters of the investigated aquifer along with rainfall and rivers were analysed using (MC) ICP-MS. The n(⁸⁷Sr)/n(⁸⁶Sr) ratio and elemental pattern changed with aquifer depth as a result of progressing bedrock leaching and dissolution with increasing groundwater residence time. The n(⁸⁷Sr)/n(⁸⁶Sr) ratio of shallow groundwater below saline ponds of 0.71019?±?0.00044 was significantly different from thermal groundwater of 0.71205?±?0.00035 (U, k?=?2). In contrast to previous theories, this result suggested no recharge of saline ponds by upwelling paleo-seawater. Isotope pattern deconvolution revealed that rainfall accounted to about 60% of the n(⁸⁷Sr)/n(⁸⁶Sr) ratio of shallow groundwater below saline ponds. The δ⁸⁸Sr/⁸⁶Sr_SRM987 values of groundwater decreased from about 0.25 ‰ in most shallow, to predominantly negative values of about –0.24 ‰ in artesian groundwater. This result indicated leaching and dissolution of weathered minerals. In turn, the δ⁸⁸Sr/⁸⁶Sr_SRM987 of deep thermal groundwater showed positive values of about 0.12 ‰, which suggested removal of ⁸⁶Sr from solution by carbonate precipitation. These results highlight the potential of δ⁸⁸Sr/⁸⁶Sr_SRM987 signature as an additional geochemical tracer.     

Spectroscopic studies of XeCl-laser-induced plasma on Ti targets in nitrogen containing atmospheres

This work deals with the study of a plasma produced by intense XeCl-excimer-laser irradiation of a titanium surface in nitrogen-containing atmospheres. We observed that the optical emission spectra resulting from irradiation of Ti targets in various ambient atmospheres (N₂, NH₃, N₂+H₂ mixtures) contain lines of atomic and ionized species of the irradiated target material only. The spectra are almost independent of the ambient atmosphere. The expansion velocities of atomic and ionic species in the plasma plume were obtained by time-of-flight measurements at different distances from the target. Mass spectrometry measurements are also performed at low background pressure to identify non-emitting species.     

Picosecond laser ablation of SiO2 layers on silicon substrates

In this work, we report on laser ablation of thermally grown SiO₂ layers from silicon wafer substrates, employing an 8–9 ps laser, at 1064 (IR), 532 (VIS) and 355 nm (UV) wavelengths. High-intensity short-pulse laser radiation allows direct absorption in materials with bandgaps higher than the photon energy. However, our experiments show that in the intensity range of our laser pulses (peak intensities of <2×10¹² W/cm²) the removal of the SiO₂ layer from silicon wafers does not occur by direct absorption in the SiO₂ layer. Instead, we find that the layer is removed by a “lift off” mechanism, actuated by the melting and vaporisation of the absorbing silicon substrate. Furthermore, we find that exceeding the Si melting threshold is not sufficient to remove the SiO₂ layer. A second threshold exists for breaking of the layer caused by sufficient vapour pressure. For SiO₂ layer ablation, we determine layer thickness dependent minimum fluences of 0.7–1.2 J/cm² for IR, 0.1–0.35 J/cm² for VIS and 0.2–0.4 J/cm² for UV wavelength. After correcting the fluences by the reflected laser power, we show that, in contrast to the melting threshold, the threshold for breaking the layer depends on the SiO₂ thickness.     

Principles of demineralization: modern strategies for the isolation of organic frameworks. Part I. Common definitions and history

In contrast to biomineralization phenomena, that are among the most widely studied topics in modern material and earth science and biomedicine, much less is systematized on modern view of demineralization. Biomineralized structures and tissues are composites, containing a biologically produced organic matrix and nano- or microscale amorphous or crystalline minerals. Demineralization is the process of removing the inorganic part, or the biominerals, that takes place in nature via either physiological or pathological pathways in organisms. In vitro demineralization processes, used to obtain mechanistic information, consist in the isolation of the mineral phase of the composite biomaterials from the organic matrix. Physiological and pathological demineralization include, for example, bone resorption mediated by osteoclasts. Bioerosion, a more general term for the process of deterioration of the composite biomaterials represents chemical deterioration of the organic and mineral phase followed by biological attack of the composite by microorganisms and enzymes. Bioerosional organisms are represented by endolithic cyanobacteria, fungi, algae, plants, sponges, phoronids and polychaetes, mollusks, fish and echinoids.In the history of demineralization studies, the driving force was based on problems of human health, mostly dental caries. In this paper we summarize and integrate a number of events, discoveries, milestone papers and books on different aspect of demineralization during the last 400 years. Overall, demineralization is a rapidly growing and challenging aspect of various scientific disciplines such as astrobiology, paleoclimatology, geomedicine, archaeology, geobiology, dentistry, histology, biotechnology, and others to mention just a few.     

Correlation between ablation efficiency and nanoparticle generation during the short-pulse laser ablation of metals

The mechanisms of material ablation and nanoparticle generation from metal samples exposed to intense short laser pulses are experimentally investigated. We performed measurements of the ablated volume using optical microscopy and the analysis of the ablation plume by fast imaging. The results confirm the existence of two distinguished ablation regimes as a function of the laser fluence, and give a deeper insight in the involved physical mechanisms. Thus, both regimes are found to be related to the relative amount of atoms and nanoparticles within the plume. Comparing the results obtained for copper and gold, it is possible to determine the influence of electron-lattice coupling on the sample heat regime and the resulting plume properties.     

Upper Bounds On Wavepacket Spreading For Random Jacobi Matrices

A method is presented for proving upper bounds on the moments of the position operator when the dynamics of quantum wavepackets is governed by a random (possibly correlated) Jacobi matrix. As an application, one obtains sharp upper bounds on the diffusion exponents for random polymer models, coinciding with the lower bounds obtained in a prior work. The second application is an elementary argument (not using multiscale analysis or the Aizenman-Molchanov method) showing that under the condition of uniformly positive Lyapunov exponents, the moments of the position operator grow at most logarithmically in time.     

Analytic gradients for the combined sr-DFT/lr-MP2 method: application to weakly bound systems

The formalism for analytical gradients in short-range density functional schemes with long-range ab initio corrections (sr-DFT/lr-ab initio) is presented. On the density-functional side, both sr-LDA and sr-PBE are available, while on the ab initio side lr-HF and lr-MP2 are possible. Details of the implementation in the Molpro package are given. Results from test calculations using different basis sets on weakly bound systems of the HB6/04, DI6/04, CT7/04 and WI9/04 databases are presented.     

The transition from spark to arc discharge and its implications with respect to nanoparticle production

Indium (III) phthalocyanine (InPc) was encapsulated into nanoparticles of PEGylated poly(d,l-lactide-co-glycolide) (PLGA-PEG) to improve the photobiological activity of the photosensitizer. The efficacy of nanoparticles loaded with InPc and their cellular uptake was investigated with MCF-7 breast tumor cells, and compared with the free InPc. The influence of photosensitizer (PS) concentration (1.8–7.5 μmol/L), incubation time (1–2 h), and laser power (10–100 mW) were studied on the photodynamic effect caused by the encapsulated and the free InPc. Nanoparticles with a size distribution ranging from 61 to 243 nm and with InPc entrapment efficiency of 72 ± 6 % were used in the experiments. Only the photodynamic effect of encapsulated InPc was dependent on PS concentration and laser power. The InPc-loaded nanoparticles were more efficient in reducing MCF-7 cell viability than the free PS. For a light dose of 7.5 J/cm² and laser power of 100 mW, the effectiveness of encapsulated InPc to reduce the viability was 34 ± 3 % while for free InPc was 60 ± 7 %. Confocal microscopy showed that InPc-loaded nanoparticles, as well as free InPc, were found throughout the cytosol. However, the nanoparticle aggregates and the aggregates of free PS were found in the cell periphery and outside of the cell. The nanoparticles aggregates were generated due to the particles concentration used in the experiment because of the small loading of the InPc while the low solubility of InPc caused the formation of aggregates of free PS in the culture medium. The participation of singlet oxygen in the photocytotoxic effect of InPc-loaded nanoparticles was corroborated by electron paramagnetic resonance experiments, and the encapsulation of photosensitizers reduced the photobleaching of InPc.     

Integrated Electro-Optic Switches Based on Ferroelectric Liquid Crystal Waveguides

Two integrated electro-optic switches based on smectic C * ferroelectric liquid crystal (FLC) planar waveguides oriented in the bookshelf geometry have been designed and realized. In order to test the first switch, a particular waveguide structure consisting of a three-stage device, having a thin FLC film middle stage and two glass waveguides as other stages, has been designed and realized. The second one is realized by a planar waveguide with a smectic C * ferroelectric liquid crystal overlayer. In this article the design, the realization, and the experimental characterization of electro-optical switches are reported. The electro-optical behavior and the response time of both devices have been studied for different configurations for both TE and TM polarization. Our main aim was to demonstrate the feasibility of an integrated electro-optic device based on a FLC waveguide, and our experimental results provide a number of interesting indications about device optimization and practical applications.