Preparation and characterization of Thioflavin T doped silica nanoparticles

Fluorescent silica nanoparticles with diameters of about 300nm were synthesized based on Stober's method, using Thioflavin T as fluorescent co-reagent. The particles were characterized via transmission electron microscopy and fluorimetry measurements. Fluorescence intensity of the sols was ten times higher than that of the ethanol phase solutions of Thioflavin T. Release of dye molecules in stable alcosols was investigated by measuring UV-Vis absorbance spectrum of the supernatant. To try an alternative route, we investigated accumulation of dye molecules in native silica particles. No release effect was detected, and slow accumulation was observed. Water contact angles of the particles were assessed from analyzing the Langmuir films, and were found to be 18, very similar to native silica particles. Langmuir-Blodgett films of the particles were deposited on a glass substrate and were examined via UV-Vis spectrophotometry, fluorimetry and scanning electron microscopy. Presence of the film was revealed; the particles formed a continuous, well-packed monolaye

Mechanochemical synthesis of crystalline and amorphous digold(i) helicates exhibiting anion- and phase-switchable luminescence properties

For the first time, mechanochemical synthesis has been used for the preparation of crystalline and amorphous dinuclear gold(i) helicates, [Au2L2](X)2 (L = xantphos; X = CF3SO3, SCN, BF4 and PF6), that show anion- and phase-switchable luminescence properties. This solid-state approach provides strategies for developing switchable luminescent materials

GRA.LE.D. (GRApevine LEaf Digitalization) Software for the Detection and Graphic Reconstruction of Ampelometric Differences Between Vitis Leaves

Raster graphic ampelometric software was not exclusively developed for the estimation of leaf area,but also for the characterization of grapevine (Viti vinifera L.) leaves. The software was written in C++programming language, using the C++ Builder 2007 for Windows 95-XP and Linux operation systems. Ithandles desktop-scanned images. On the image analysed with the GRA.LE.D., the user has to determine11 points. These points are then connected and the distances between them calculated. The GRA.LE.D.software supports standard ampelometric measurements such as leaf area, angles between the veins andlengths of the veins. These measurements are recorded by the software and exported into plain ASCII textfiles for single or multiple samples. Twenty-two biometric data points of each leaf are identified by theGRA.LE.D. It presents the opportunity to statistically analyse experimental data, allows comparison ofcultivars and enables graphic reconstruction of leaves using the Microsoft Excel Chart Wizard. The GRA.LE.D. was thoroughly calibrated and compared to other widely used instruments and methods such asphoto-gravimetry, LiCor Li3100, WinDIAS2.0 and ImageTool. By comparison, the GRA.LE.D. presentedthe most accurate measurements of leaf area, but the LiCor Li3100 and the WinDIAS2.0 were faster, whilethe photo-gravimetric method proved to be the most time-consuming. The WinDIAS2.0 instrument wasthe least reliable. The GRA.LE.D. is uncomplicated, user-friendly, accurate, consistent, reliable and haswide practical application

Stability of Ampelometric Characteristics of Vitis vinifera L. cv. ‘Syrah’ and ‘Sauvignon blanc’ Leaves: Impact of Within-vineyard Variability and Pruning Method/Bud Load

Historically, grapevine (Vitis vinifera L.) leaf characterisation has been a driving force in the identificationof cultivars. In this study, ampelometric (foliometric) analysis was done on leaf samples collected fromhand-pruned, mechanically pruned and minimally pruned ‘Sauvignon blanc’ and ‘Syrah’ vines to estimatethe impact of within-vineyard variability and a change in bud load on the stability of leaf properties.The results showed that within-vineyard variability of ampelometric characteristics was high within acultivar, irrespective of bud load. In terms of the O.I.V. coding system, zero to four class differences wereobserved between minimum and maximum values of each characteristic. The value of variability of eachcharacteristic was different between the three levels of bud load and the two cultivars. With respect to budload, the number of shoots per vine had a significant effect on the characteristics of the leaf laminae. Singleleaf area and lengths of veins changed significantly for both cultivars, irrespective of treatment, while anglebetween veins proved to be a stable characteristic. A large number of biometric data can be recorded on asingle leaf; the data measured on several leaves, however, are not necessarily unique for a specific cultivar.The leaf characteristics analysed in this study can be divided into two groups according to the response toa change in bud load, i.e. stable (angles between the veins, depths of sinuses) and variable (length of theveins, length of the petiole, single leaf area). The variable characteristics are not recommended to be usedin cultivar identification, unless the pruning method/bud load is known

Photoluminescence Study of Eu-Species Incorporated In Lithium Tetraborate and Silica

Steady-state – excitation and emission – photoluminescence spectra of europium species incorporated in single crystal and glassy lithium tetraborate (LTB) and silica are reported. Kinetic features, decay curves of the emission and lifetime data were measured. Spectral characteristics were analyzed with the aim of distinguishing the oxidation state, site-symmetry and morphology of europium species in different solid-state host matrices.Досліджено спектри стаціонарної фотолюмінесценції (збудження та випромінювання) європію, інкорпорованого в монокристалічний і полікристалічний літій тетраборат та кремнезем. Приведено дані кінетичної фотолюмінесценції: криві загасання та час життя збудженого стану іонів європію в зразках. Проведено аналіз спектральних характеристик з метою визначення стану інкорпорованих іонів європію – окислювального та агрегатного, а також локальної симетрії в різних матрицях.Исследованы спектры стационарной фотолюминесценции (возбуждения и излучения) европия, инкорпорированного в монокристаллы и поликристаллы литий тетрабората и кремнезема. Приведены данные кинетической фотолюминесценции: кривые затухания и время жизни возбужденного состояния ионов европия в образцах. Проведен анализ полученных спектральных характеристик с целью определения состояния инкорпорированных ионов европия – окислительного и агрегатного, а также локальной симметрии в разных матрицах

Which mechanism underlies the water-like anomalies in core-softened potentials?

Using molecular dynamics simulations we investigate the thermodynamic of particles interacting with a continuous and a discrete versions of a core-softened (CS) intermolecular potential composed by a repulsive shoulder. Dynamic and structural properties are also analyzed by the simulations. We show that in the continuous version of the CS potential the density at constant pressure has a maximum for a certain temperature. Similarly the diffusion constant, $D$, at a constant temperature has a maximum at a density $\rho_{\mathrm{max}}$ and a minimum at a density $\rho_{\mathrm{min}}<\rho_{\mathrm{max}}$, and structural properties are also anomalous. For the discrete CS potential none of these anomalies are observed. The absence of anomalies in the discrete case and its presence in the continuous CS potential are discussed in the framework of the excess entropy.Comment: 8 page

Dynamical ensembles in stationary states

We propose as a generalization of an idea of Ruelle to describe turbulent fluid flow a chaotic hypothesis for reversible dissipative many particle systems in nonequilibrium stationary states in general. This implies an extension of the zeroth law of thermodynamics to non equilibrium states and it leads to the identification of a unique distribution \m describing the asymptotic properties of the time evolution of the system for initial data randomly chosen with respect to a uniform distribution on phase space. For conservative systems in thermal equilibrium the chaotic hypothesis implies the ergodic hypothesis. We outline a procedure to obtain the distribution \m: it leads to a new unifying point of view for the phase space behavior of dissipative and conservative systems. The chaotic hypothesis is confirmed in a non trivial, parameter--free, way by a recent computer experiment on the entropy production fluctuations in a shearing fluid far from equilibrium. Similar applications to other models are proposed, in particular to a model for the Kolmogorov--Obuchov theory for turbulent flow.Comment: 31 pages, 3 figures, compile with dvips (otherwise no pictures

Simple deterministic dynamical systems with fractal diffusion coefficients

We analyze a simple model of deterministic diffusion. The model consists of a one-dimensional periodic array of scatterers in which point particles move from cell to cell as defined by a piecewise linear map. The microscopic chaotic scattering process of the map can be changed by a control parameter. This induces a parameter dependence for the macroscopic diffusion coefficient. We calculate the diffusion coefficent and the largest eigenmodes of the system by using Markov partitions and by solving the eigenvalue problems of respective topological transition matrices. For different boundary conditions we find that the largest eigenmodes of the map match to the ones of the simple phenomenological diffusion equation. Our main result is that the difffusion coefficient exhibits a fractal structure by varying the system parameter. To understand the origin of this fractal structure, we give qualitative and quantitative arguments. These arguments relate the sequence of oscillations in the strength of the parameter-dependent diffusion coefficient to the microscopic coupling of the single scatterers which changes by varying the control parameter.Comment: 28 pages (revtex), 12 figures (postscript), submitted to Phys. Rev.

Chaotic Scattering Theory, Thermodynamic Formalism, and Transport Coefficients

The foundations of the chaotic scattering theory for transport and reaction-rate coefficients for classical many-body systems are considered here in some detail. The thermodynamic formalism of Sinai, Bowen, and Ruelle is employed to obtain an expression for the escape-rate for a phase space trajectory to leave a finite open region of phase space for the first time. This expression relates the escape rate to the difference between the sum of the positive Lyapunov exponents and the K-S entropy for the fractal set of trajectories which are trapped forever in the open region. This result is well known for systems of a few degrees of freedom and is here extended to systems of many degrees of freedom. The formalism is applied to smooth hyperbolic systems, to cellular-automata lattice gases, and to hard sphere sytems. In the latter case, the goemetric constructions of Sinai {\it et al} for billiard systems are used to describe the relevant chaotic scattering phenomena. Some applications of this formalism to non-hyperbolic systems are also discussed.Comment: 35 pages, compressed file, follow directions in header for ps file. Figures are available on request from [email protected]