Optimisation strategies introduced for CR at health care centres in Estonia

In recent years, starting from 2001, conventional film-screen radiography has been rapidly replaced by digital (mostly by computed radiography, CR) techniques in Estonia. New strategies for optimisation and quality assurance for digital radiography have been introduced by the DIMOND III and SENTINEL partners recently. It includes consideration to diagnostic requirements of a given clinical situation, but also objectivation and standardisation of image quality, e.g. using CDRAD test phantom, and constancy testing. The aim of this work is to evaluate the performance of an automatic exposure control (AEC) at different sensitivities when used with the Fujifilm CR system. Image quality, using threshold contrast-detail detectability (TCDD) and signal-to-noise ratio squared related to dose (SNR(2)/D), was also investigated for different sensitivities and tube potential values for this combination. Based on the image evaluation data, optimum speed modes for the organ programme settings have been proposed.     

FTIR Spectroscopic Study on Nickel(II)-Exchanged Sulfated Alumina: Nature of the Active Sites in the Catalytic Oligomerization of Ethene

The nature of the active sites in nickel(II)-exchanged sulfated alumina in the reaction of ethene oligomerization has been studied by means of FTIR spectroscopy of adsorbed CO. It has been established that isolated nickel(I) species are the active sites in this process. These sites are formed by a reduction process, in which protonic centers are involved. The latter are due to the presence of covalently-bonded sulfate ions on the catalyst surface.     

Correlations Between Precursor Molecular Weight and Dynamic Mechanical Properties of Polyborosiloxane (PBS)

It is possible to tailor the dynamic response of polyborosiloxanes (PBS) based on picking the right molecular weight of a precursor. The molecular weight of hydroxy-terminated polydimethylsiloxane (PDMS) defines the shear-stiffening performance of PBS due to straightforward condensation reaction between hydroxy end groups of PDMS and boric acid. Introduced borono groups behave as stickers, hence, are prone to supramolecular interactions. New correlations are discovered for five PBS synthesized from hydroxy-terminated PDMS with different molecular weights. Si─O─B infrared band intensities for all PBS follow the same trend with molecular weight as the number of PDMS hydroxy groups which confirms the full completion of the reaction. After synthesis, the molecular weight of PBSs remained almost the same, which indicates the absence of significant chain scissoring, polymerization, or crosslinking. During the rheological analysis, it is found that crossover point modulus follows the same trend as the number of PDMS hydroxy groups and Si─O─B band intensities. PBS demonstrates a linear increase in peak forces with molecular weight during the drop weight impact test. The low molecular weight of a precursor, hence, a high number of stickers is a primary requirement for effective protection against low-velocity impact.     

Imaging the selective binding of synapsin to anionic membrane domains

Synapsins are membrane-associated proteins that cover the surface of synaptic vesicles and are responsible for maintaining a pool of neurotransmitter-loaded vesicles for use during neuronal activity. We have used atomic force microscopy (AFM) to study the interaction of synapsin I with negatively charged lipid domains in phase-separated supported lipid bilayers prepared from mixtures of phosphatidylcholines (PCs) and phosphatidylserines (PSs). The results indicate a mixture of electrostatic binding to anionic PS-rich domains as well as some nonspecific binding to the PC phase. Interestingly, both protein binding and scanning with synapsin-coated AFM tips can be used to visualize charged lipid domains that cannot be detected by topography alone.     

Effect of imidazolium ionic liquid type on the properties of nitrile rubber composites

We investigated the influence of hydrophilic and hydrophobic imidazolium ionic liquids on the curing kinetic, mechanical, morphological and ionic conductivity properties of nitrile rubber composites. Two room temperature ionic liquids with a common cation—1‐ethyl‐3‐methylimidazolium thiocyanate (EMIM SCN; hydrophilic) and 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI; hydrophobic)—were used. Magnesium–aluminium layered double hydroxide (MgAl‐LDH; also known as hydrotalcite) was added to carboxylated acrylonitrile–butadiene rubber (XNBR) whereas fumed silica Aerosil 380 was used in acrylonitrile–butadiene rubber (NBR) as reinforcing fillers. NBR compounds were vulcanized with a conventional sulfur‐based crosslinking system whereas XNBR compounds were cured with MgAl‐LDH. The optimum cure time reduction and tensile properties improvement were obtained when both ionic liquids were added at 5 parts per hundred rubber (phr). The results revealed that EMIM SCN and EMIM TFSI induced an increase in the AC conductivity of nitrile rubber composites from 10^?10 to 10^?8 and to 10^?7 S cm^?1, respectively (at 15 phr ionic liquid concentration). The presence of ionic liquids in NBR slightly affected the glass transition temperature (T_g) whereas the presence of EMIM TFSI in XNBR contributed to a shift in T_g towards lower temperatures from ?23 to ?31 °C, at 15 phr loading, which can be attributed to the plasticizing behaviour of EMIM TFSI in the XNBR/MgAl‐LDH system. Dynamic mechanical analysis was also carried out and the related parameters, such as the mechanical loss factor and storage modulus, were determined. © 2013 Society of Chemical Industry     

Numerical and experimental investigations on the influence of preheating and dilution on transition of laminar coflow diffusion flames to Mild combustion regime

A numerical and experimental study has been carried out to acquire knowledge about the structure and stabilization mechanism of coflow flames in their transition to the Mild combustion regime. In total, three CH₄/N₂/oxidizer coflow flames have been studied with a systematic dilution and preheating of the fuel and coflow streams. These flames comprise the non-preheated case (Case NP), preheated case (Case P) and Mild case (Case M), diluted and preheated from ambient temperature up to 1530 K. Radial profiles of temperature and species concentrations have been measured using spontaneous Raman scattering. Detailed computations have been performed by steady-state simulations of these cases using detailed chemistry with the GRI 3.0 mechanism, multi-component mixture-averaged transport and an optically thin approximation for radiative heat losses. An overall good agreement has been found between results of the detailed computations and experiments for Case NP, Case P and at lower axial distances for Case M. The importance of using multicomponent transport and radiative heat losses in the computations has been investigated by performing additional computations with more simplified models for Case NP. A comparison of computed temperature distributions indicates that the progressive preheating and dilution of the oxidizer and fuel leads to a reduction of the temperature rise in the reaction zone with respect to a non-reacting case; this rise in Case M is less than 200 K. Comparison of computed heat release and CH₂O distributions reveals that stabilization of Case NP and P occurs by an edge flame, while for Case M, it takes place by autoignition. Further investigations on the structure of Case M has been done by flamelet analyses in mixture fraction space. It is found that igniting flamelets, in contrast to steady flamelets, represent very well the structure of Case M at lower axial distances. This observation further emphasizes the stabilization of the Mild case by the autoignition phenomena.     

A KPU-200 movable capacitor installation

A movable electrophysical capacitor installation with a 250-kJ maximum bank energy, which generates intense neutron pulses, is described. A current pulse generator with a capacitive energy storage forms the basis of the installation. When the initial voltage at the capacitor bank is up to 35 kV, the installation ensures a flow of current pulses with amplitudes of up to 2 MA in a gas-discharge plasma-focus chamber, which is filled with an equal-component deuterium-tritium (DT) mixture. Under these conditions, the chamber is capable of repeatedly generating single fast-neutron pulses with an energy of 14.1 MeV, a duration of ～70 ns, and an integral yield over 1013 neutrons/pulse.     

Stability of detonation in a circular pipe with porous walls

A stability analysis is carried out taking into account slightly porous walls in an idealized detonation confined to a circular pipe. The analysis is carried out using the normal-mode approach and corrections are obtained to the underlying impenetrable wall case results to account for the effect of the slight porosity. The porous walls are modelled by an acoustic boundary condition for the perturbations linking the normal velocity and the pressure components and thus replacing the conventional no-penetration boundary condition at the wall. This new boundary condition necessarily complicates the derivation of the stability problem with respect to the impenetrable wall case. However, exploiting the expressly slight porosity, the modified temporal stability can be determined as a two-point boundary value problem similar to the case of a non-porous wall.     

Ultrastable nanostructured polymer glasses

Owing to the kinetic nature of the glass transition, the ability to significantly alter the properties of amorphous solids by the typical routes to the vitreous state is restricted. For instance, an order of magnitude change in the cooling rate merely modifies the value of the glass transition temperature (T(g)) by a few degrees. Here we show that matrix-assisted pulsed laser evaporation (MAPLE) can be used to form ultrastable and nanostructured glassy polymer films which, relative to the standard poly(methyl methacrylate) glass formed on cooling at standard rates, are 40% less dense, have a 40 K higher T(g), and exhibit a two orders of magnitude enhancement in kinetic stability at high temperatures. The unique set of properties of MAPLE-deposited glasses may make them attractive in technologies where weight and stability are central design issues.