Influence of accelerated ageing on methacrylate‐based denture resins heterogeneity as viewed by ESR‐spin‐probe method

The electron‐spin‐resonance (ESR) spin‐probe method, was used to study the heterogeneity of denture resins based on poly(methyl methacrylate). Results for three resins processed by microwave energy, conventional curing and cold curing (depending on the curing procedure and exposed to ageing in various environmental conditions) were compared. All three cured resins were stored over the same time (1200 h) in distilled water at ambient temperature and in artificial saliva at 348 K. The temperature‐dependent ESR spectra of a spin probe dispersed in the denture resins are analyzed in terms of line‐shapes and line‐widths. The appearance of two spectral components was taken as an indication of resin heterogeneity. The results reveal that the cold‐cured resin has a lower local density in comparison with microwave and conventionally cured resin. The amount of residual monomer also contributes to the local motion of polymer segments. The change of denture resins exposed to ageing is influenced both by the structure of the original resin and the ageing conditions. Restricted motion of a spin probe incorporated into the acrylic resins exposed to accelerated ageing suggests additional crosslinking of polymer chains. The differences are observed for all the investigated resins, but the highest change is observed with the cold‐cured resin. The ESR results are accompanied by T_g and T_m measurements. Copyright © 2005 Society of Chemical Industry     

Multimodal focus attention and stress detection and feedback in an augmented driver simulator

This paper presents a driver simulator, which takes into account the information about the user’s state of mind (level of attention, fatigue state, stress state). The user’s state of mind analysis is based on video data and biological signals. Facial movements such as eyes blinking, yawning, head rotations, etc., are detected on video data: they are used in order to evaluate the fatigue and the attention level of the driver. The user’s electrocardiogram and galvanic skin response are recorded and analyzed in order to evaluate the stress level of the driver. A driver simulator software is modified so that the system is able to appropriately react to these critical situations of fatigue and stress: some audio and visual messages are sent to the driver, wheel vibrations are generated and the driver is supposed to react to the alert messages. A multi-threaded system is proposed to support multi-messages sent by the different modalities. Strategies for data fusion and fission are also provided. Some of these components are integrated within the first prototype of OpenInterface: the multimodal similar platform.     

Mechanical Alloying for Heat-Resistant Copper Alloys

In the development of heat-resistant, high-conductivity copper alloys, beneficial properties may be obtained through the application of mechanical alloying. Mechanical alloying has been applied to copper-base materials with the ultimate goal of obtaining improved elevated-temperature performance through oxide dispersion strengthening in a complex matrix that has been solute- or precipitation-strengthened. Preliminary results indicate that a random distribution of fine oxide particles can be obtained in a copper matrix through high-energy attritor milling.     

Evaluation of the precision of dimensional measurements of the mandible on panoramic radiographs

The task of objective perimetry is to scan the visual field and find an answer about the function of the visual system. Flicker-burst stimulation--a physiological sensible combination of transient and steady-state stimulation--is used to generate deterministic sinusoidal responses or visually evoked potentials (VEP's) at the visual cortex, which are derived from the electroencephalogram by a suitable electrode array. In this paper we develop a new method for the detection of VEP's. Based on the periodogram of a time-series, we test the data for the presence of hidden periodic components, which correspond to steady-state VEP's. The method is applied successfully to real data.     

The response of human premolars to cyclic loading

Thirty-seven dogs with moderately differentiated, cutaneous mast cell tumors had incomplete surgical excisions as determined by histopathology, but no gross evidence of tumor. All dogs were irradiated to a total dose of between 46.2 and 48.0 Gy using either an orthovoltage source (n = 20) or a linear accelerator (megavoltage) (n = 17). Radiation was delivered to an area bordered by margins of 3 cm or greater around the surgical scar. The mast cell tumors had not recurred in 97% of dogs by one year after radiation therapy and had not recurred in 93% of dogs by three years after radiation. Both orthovoltage and megavoltage radiation provide excellent local control of moderately differentiated mast cell tumors in dogs.     

An adaptive network-based fuzzy inference system (ANFIS) for the forecasting: The case of close price indices

The close price prediction model of the Zagreb Stock Exchange Crobex® index is presented in this paper. For the input/output data plan modeling the Crobex® index close price historical data are retrieved from the Zagreb Stock Exchange official internet pages. The prediction model is created in the way that for each of 5 days in advance it predicts the Crobex® close price. The prediction model is generated based on the input/output data plan by means of the adaptive neuro-fuzzy inference system method, representing the fuzzy inference system. It is of the essence to point out that for each day a separate fuzzy inference system is created by means of the adaptive neuro-fuzzy inference system method based on the same set of input/output data, the only difference being that for every separate fuzzy inference system different subsets for training and checking are used so that input variables are differently created. The input/output data set represents the historical data of the Crobex® index close price from 4 November 2010 to 24 January 2012 and the Crobex® index close price is predicted for the subsequent 5 days, the first day of prediction being 25 January 2012. After that the above mentioned input/output data set is shifted 5 days in advance and the Crobex® index close price is predicted in advance for the next 5 days starting with the last day of the input/output data set. In that way the Crobex® index close prices are predicted until 19 October 2012 based on the Crobex® index close price historical data. At the end of the paper qualitative and quantitative estimates are presented for the given approach of predicting the Crobex® index close price showing that the approach is useful for predicting within its limits.     

Thermodynamical characteristics of thin ferroelectric films

Thermodynamic characteristics of the KDP type ferroelectrics are analysed in the paper. Dispersion laws of the ferroelectric excitations in the thin ferroelectric films are considered. The ordering parameter was investigated at the low temperatures and at the temperatures near the phase transition temperature. The analysis shows that the spontaneous polarization in the film decreases more slowly with increase of the temperature than in the bulk structure. This conclusion is important for practical application because the thin films keep the ferroelectric properties at significantly higher temperatures than the bulk structures.     

Comparison of different formulations of 2D beam elements based on Bond Graph technique

Bond Graphs are well suited for modelling multibody systems. In this paper modelling of planar flexible beams undergoing large overall motions are studied based on finite element (FE) technique. Two well-known approaches are used – the co-rotational (CR) and absolute nodal coordinate (ANC) formulation. Two ANC formulations are analyzed – one in which elastic forces is described using classical beam theory in a local coordinate frame, and another based on a global continuum mechanics approach. Starting from these classical formulations velocity formulations are developed and used to develop Bond Graph FE components. The effect of gravity has been considered as well. These components can be put in libraries and used for systematic Bond Graph flexible body model development. It is shown that Bond Graph technique is capable of dealing with different flexible body formulations and can be used as a general approach in parallel to other modelling approaches. Models are developed and simulations are performed using the object oriented environment of BondSim. Owing to the object oriented approach, transformation from one to the other model is relatively simply. The results are illustrated by suitable examples and they confirm accuracy of the developed models. It was shown that the CR approach offers much better performance than the both ANC formulations.     

Hydrogen-bonded nanotubes as a model for DNA transcription

Using the energy asymmetries in the hydrogen-bonded structures, the model is formulated explaining melting of DNA double chain and also explaining further decay of only one of the obtained single chains. The model is similar to the Scott's model of alpha-helix, where the spiral is substituted with interacting discs. The explanation of mentioned DNA transformation is based on the estimate of free energy of discs with an even number of hydrogen bonds, and an estimate of melting point temperature for the subsystem of odd index fibers and transition temperature of the subsystem of even index fibers.