Classification of detectors for ion chromatography using principal components regression and linear discriminant analysis

Principal components regression (PCR) and linear discriminant analysis (LDA) have been applied to the classification of ion chromatographic detectors using information about the sample and other IC method conditions (19 attributes in total), a training set of 12 693 cases and a randomly-chosen test set of 1410 cases. Missing data was entered as a separate ‘unknown' code. When the value of each attribute was coded in a simple cardinal series (e.g., column=1, 2, 3, etc.), PCR correctly predicted the detector in 27% of the training set and 28% of the test set. By creating a variable (taking a value between 0 (absent) and 1 (present)) for each value of each attribute, the PCR prediction for both sets increased to 60%. LDA was more successful, predicting 69% of the detectors of each set, using a prior probability of the frequency of a given detector in the database, but this included zero hits for detectors that were poorly represented in the database. If equal prior probabilities were chosen the overall success rate dropped to 33% but now the classification of less frequently used detectors was improved. The ability of these numerically-oriented methods to classify discrete, non-numerical data, is surprisingly good and compares with induction methods, neural networks and expert systems reported previously.     

Dielectric behavior of alternating ethylene,propylene, and carbon monoxide co‐ and terpolymers via impedance spectroscopy

Dielectric behavior of alternating ethylene–carbon monoxide (ECO) and ethylene–carbon monoxide/propylene–carbon monoxide elastic terpolymer (EPEC‐48) (48% mole ratio of ECO) have been investigated by impedance spectroscopy. At intermediate frequencies, the co‐ and terpolymer samples display a relaxation peak with an activation energy of 1.40 and 1.12 eV, respectively, due to a rotational motion of the carbonyl groups in the relatively more polar ECO block. However, at low frequency, a relaxation peak was observed only in the EPEC‐48 terpolymer impedance and admittance spectra due to the rotational motion of the polar groups of propylene–carbon monoxide (PCO) block which is attached to ECO repeating units. In addition, it has been found that below 100°C the ECO material is highly resistive, and both dielectric constant and loss factor are dependent on frequency and temperature. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Electrical impedance of ethylene-carbon monoxide/propylene-carbon monoxide (<Emphasis Type="Italic">EPEC</Emphasis>-<Emphasis Type="Italic">69</Emphasis>) thermoplastic polyketone

Electrical impedance technique was employed to investigate the electrical properties of ethylene-carbon monoxide/propylene-carbon monoxide terpolymer (EPEC-69). The measurements were performed in the frequency range 0.1–10⁵ Hz and in the temperature range 30–110 °C. The results reveal that the dielectric constant, loss factor, modulus, and ac conductivity are dependent of frequency and temperature. A Debye relaxation peak was detected in the plot of Z″ versus frequency where the activation energy was determined and found to be 1.26 eV. When the surface phenomenon effects were separated using the imaginary part of the complex admittance a second dielectric dispersion was observed in the low frequency region. Two models were proposed from the impedance measurements depending on temperature range.     

New algebraic expressions for thermodiffusion in binary n‐alkane mixtures

Following a detailed analysis of the experimental data on thermodiffusion coefficients of numerous binary hydrocarbon mixtures from over 90 experiments, four new algebraic expressions are proposed. As per these formulations, the thermodiffusion coefficient of binary n‐alkane mixtures can be expressed as a function of the chemical composition of the mixture and the mixture properties such as density and viscosity. Detailed experimental validation is presented using four n‐alkane series containing a wide range of combinations of n‐alkanes. Additionally, comparison with recently proposed neural network model and a model based on the principles of non‐equilibrium thermodynamics is also presented. It has been found that the proposed algebraic models are simple in formulations, are evaluated with least computational effort and yet have a very high accuracy in predicting the thermodiffusion coefficients. © 2012 Canadian Society for Chemical Engineering     

PFG NMR investigation of hydrocarbon diffusion in large NaX zeolite crystals: Effect of internal field gradients on diffusion data

Self-diffusion coefficients for intracrystalline diffusion of hydrocarbon molecules adsorbed in large crystals of NaX zeolite have been measured by the pulsed field gradient (PFG) NMR technique, at ambient temperature and at different diffusion times (from 6 to 12 ms). Two NMR pulse sequences, stimulated and 13-interval bipolar spin echo, were used to examine the influence of internal field gradients on diffusion data. For both sequences the effective self-diffusion coefficient of the guest molecules was found to decrease with increasing observation times. The extrapolated intracrystalline diffusion coefficient is independent of the NMR sequence. In contrast, the estimated extent of molecular diffusion depends strongly on the pulse program. For the small molecules (butane to hexane), the domain size, R, of restricted diffusion obtained with the stimulated spin-echo sequence is smaller than the crystal dimension whereas R is always comparable to it when the 13-interval pulse sequence is used. This shows the effect of internal field gradients on the diffusion data leading to wrong values of R if the stimulated pulse sequence is used. The light hydrocarbons diffuse freely inside the zeolite particles whereas the crystal boundaries act as reflecting surfaces, as previously observed. On the other hand, even with the 13-interval pulse sequence, the smaller values of R obtained for large molecules as n-heptane and octane shows that their displacement is hindered by restrictions in the NaX macro-crystals.     

Estimation of thermodiffusion coefficients in ternary associating mixtures

Following the non‐equilibrium thermodynamics formulation and taking into account the complexities in the structure of aqueous associating mixtures, expressions are proposed to estimate the thermodiffusion coefficients in ternary associating mixtures, such as water and alcohol mixtures. The model expressions are used to estimate the thermodiffusion coefficients in methanol–ethanol–water, dimethyl sulfoxide (DMSO)–ethanol–water and DMSO–t‐butanol–water mixtures at various concentrations. The perturbed‐chain statistical associating fluid theory (PC‐SAFT) equation of state is used to obtain the mixture properties, such as the derivatives of the chemical potentials needed to evaluate the thermodiffusion coefficient expressions. The results show that at certain concentrations of one component, variation of the concentration of the other two components can cause a sign change in the thermodiffusion coefficients. While the model cannot be evaluated due to the lack of any pertinent experimental data, the model predictions may be used to choose suitable mixture compositions in space experiments to be performed onboard the International Space Station (ISS) in near future. © 2011 Canadian Society for Chemical Engineering     

Adhesion of cast metal alloy and lithium disilicate copings luted to different core build-up materials with self-adhesive resin cement

This study evaluated the shear bond strength of two coping materials (non-nickel chrome-based cast alloy and lithium disilicate ceramic (IPS Empress) to four different core foundation materials (resin composite, cast metal alloy, lithium disilicate, and dentin), luted with adhesive resin cement (RelyX Unicem). Specimens (N = 56) were fabricated and divided into eight groups (n = 7 per group). Each coping material was luted with self-adhesive resin cement (RelyX Unicem) to the core materials. Bond strength was measured in a Universal Testing Machine (0.5 mm/min). Data were statistically analyzed using a two-way analysis of variance (ANOVA) and Tukey’s HSD tests (alpha = 0.05). Both core (p = 0.000) and coping material type (p = 0.000) significantly affected the mean bond strength (MPa) values. Interaction terms were also significant (p = 0.001). The highest bond strength results were obtained when lithium disilicate was bonded to lithium disilicate (21.48) with the resin cement tested. Lithium disilicate in general presented the highest bond results when bonded to all core materials tested (16.55–21.38) except dentin (3.56). Both cast alloy (2.9) and lithium disilicate (3.56) presented the lowest bond results on dentin followed by cast-alloy-cast alloy combination (3.82).     

Evaluation of the ratio of the evaporation energy to the activation energy for estimating the thermodiffusion coefficient

Thermodiffusion has an important role in displacements of hydrocarbon reservoir. The ratio of the evaporation energy to the activation energy of viscous flow in pure limits, τ_pure,k, is of a great importance in estimating the thermodiffusion coefficient for non‐associating fluid mixtures. Several methods may be used to estimate τ_pure,k which causes different values for thermodiffusion coefficients. A fixed value for τ_pure,k was considered to predict the thermodiffusion coefficient. In this paper, Abbasi et al.'s [J. Non‐Equilib. Thermodyn. 2010;35:1–14] model and Shukla and Firoozabadi's model have been applied to predict thermodiffusion coefficients for linear chain hydrocarbon binary mixtures. The results show a very good performance of the simple approach in respect to the previous models in estimating thermodiffusion coefficients. © 2011 Canadian Society for Chemical Engineering     

Ozone in Medicine: Clinical Evaluation and Evidence Classification of the Systemic Ozone Applications,Major Autohemotherapy and Rectal Insufflation,According to the Requirements for Evidence-Based Medicine

Now that indications are clearly defined, applications have mostly become standardized and the active mechanisms have been well confirmed, medical ozone application in the form of the low-dose concept, is established and proven as a complementary medical method in the treatment of chronic inflammations or diseases associated with chronic inflammatory conditions. More than 11,000 systemic ozone treatments in the form of Major Ozone Autohemotherapy (MAH) in 577 patients and ≥ 47,000 Rectal Insufflations (RI) in 716 patients in various clinical studies are subjected to critical clinical assessment and classification according to the criteria of evidence-based medicine (EBM). Statistically significant clinical and/or pharmacological improvements without side-effects or adverse reactions are found in all studies; special attention is drawn to maintaining hygiene when working with blood and to the use of ozone-resistent and biocompatible materials. On summarizing the evidence classification under RCT + CT (Randomized Controlled Trials + Controlled Trials), i.e., Levels Ib and IIa, 12 studies with 657 ozone-treated patients are obtained for MAH and 6 studies with 227 patients for RI. As a result of the evidence here assessed, the two systemic ozone applications, MAH and RI are part of evidence-based medicine. Both applications are effective, safe and economic.