Comparative psychometric analysis of vector and isochrone cardiac activation maps

Isochronal cardiac activation maps can be constructed from local activation times associated with spatial locations, and are frequently used to study cardiac arrhythmias. Cardiac velocity vector mapping has been proposed as an alternative method to study cardiac activation in both clinical and research environments. Velocity vectors inherently contain more information than scalar measures of latency, but it is unknown how vector maps and isochronal maps compare when they are used to identify patterns and features associated with arrhythmias. In order to quantitatively compare these two visualization methods, eight cardiologists were asked to complete forced-choice tasks in which they selected ablation sites based on synthetic vector or isochronal maps. Maps varied in arrhythmia complexity, number of vectors or activation times included, and errors in magnitude or angle for maps of velocity vectors. Quantitative comparison was achieved by using psychometric functions to characterize the learning curve and the total number of measurements needed in order to choose a correct ablation site. For simple arrhythmias, performance with vector maps was superior to isochronal maps. Subjects required fewer measurements, and learned more rapidly by studying vector maps. For more complex arrhythmias, there was no significant difference in performance between vector and isochronal maps. However, arrhythmia features were clearer with vector maps, even though this clarity did not necessarily change the ablation site choice. When errors were added to vector maps, performance was satisfactory for angle errors < 55 degrees, and speed errors did not affect performance.     

Molecular modeling of sigma 1 receptor ligands: a model of binding conformational and electrostatic considerations

We have performed molecular modeling studies on several sigma 1 specific ligands, including PD144418, spipethiane, haloperidol, pentazocine, and others to develop a pharmacophore for sigma 1 receptor-ligand binding, under the assumption that all the compounds interact at the same receptor binding site. The modeling studies have investigated the conformational and electrostatic properties of the ligands. Superposition of active molecules gave the coordinates of the hypothetical 5-point sigma 1 pharmacophore, as follows: R1 (0.85, 7.26, 0.30); R2 (5.47, 2.40, -1.51); R3 (-2.57, 4.82, -7.10); N (-0.71, 3.29, -6.40); carbon centroid (3.16, 4.83, -0.60), where R1, R2 were constructed onto the aromatic ring of each compound to represent hydrophobic interactions with the receptor; and R3 represents a hydrogen bond between the nitrogen atom and the receptor. Additional analyses were used to describe secondary binding sites to electronegative groups such as oxygen or sulfur atom. Those coordinates are (2.34, 5.08, -4.18). The model was verified by fitting other sigma 1 receptor ligands. This model may be used to search conformational databases for other possibly active ligands. In conjunction with rational drug design techniques the model may be useful in design and synthesis of novel sigma 1 ligands of high selectivity and potency. Calculations were performed using Sybyl 6.5.     

Environmental and human factors influencing thermal comfort of office occupants in hot - humid and hot - arid climates

The effects of environmental and individual factors on thermal sensation in air-conditioned office environments were analysed for two large, fully compatible thermal comfort field studies in contrasting Australian climates. In the hot - humid location of Townsville, 836 office workers were surveyed; 935 workers participated in hot - arid Kalgoorlie-Boulder. Overall perceived work area temperature and measured indoor operative temperature correlated moderately with thermal sensation for Townsville (T) subjects but only perceived temperature correlated with Kalgoorlie-Boulder (KB) sensation. Multiple regression analyses confirmed that indoor climatic variables (including Predicted Mean Vote) contributed to actual thermal sensation vote (24% T; 15% KB), with operative temperature having more of an effect in T than in KB. Subsequent analyses of individual characteristics showed no linear contributions to thermal sensation. The remaining variances were significantly related to perceived work area temperature (7% additional explained variance in T; 12% in KB). Mann - Whitney analyses (after correction for climatic variables) showed that T subjects with higher job satisfaction had thermal sensations closer to 'neutral'. Males, healthier subjects, non-smokers, respondents with earlier survey times and underweight occupants had lower median thermal sensations in KB. Townsville occupants appeared more adapted to their outdoor climatic conditions than Kalgoorlie-Boulder respondents, perhaps due to limited home air-conditioning. Further research into non-thermal impacts on gender-related thermal acceptability is suggested.     

Solid Solutions within Selected SrO-LnO1.5-TiO2 Systems

A region of selected SrO-LnO_1.5-TiO₂ (Ln = La, Ce, Pr, or Nd) systems was studied experimentally using X-ray diffractometry (XRD). A series of solid solutions with composition Sr_{4 x} Ln_{2 x/ 3}Ti₄O₁₂ having tetragonally distorted per-ovskite structures was found to exist along the tie line connecting SrTiO₃ and Ln₂Ti₃O₉. Reactions of SrLn₂Ti₄O₁₂, representative compounds of the series, with SrO were also studied. Additionally, the solubility of TiO₂ in Ln₂O₃-(3TiO_{2- m} (Ln = La, Pr, or Nd) at 1300°C was investigated using XRD.     

Self-assessment and task selection in learner-controlled instruction: Differences between effective and ineffective learners

Learner-controlled instruction is often found to be less effective for learning than fixed or adaptive system-controlled instruction. One possible reason for that finding is that students – especially novices – might not able to accurately assess their own performance and select tasks that fit their learning needs. Therefore, this explorative study investigated the differences in self-assessment and task-selection processes between effective and ineffective learners (i.e., in terms of learning gains) studying in a learner-controlled instructional environment. Results indicated that although effective learners could more accurately assess their own performance than ineffective learners, they used the same task aspects to select learning tasks. For effective learners, who were also more accurate self-assessors, the self-assessment criteria predicted subsequent task selection. The results are discussed, particularly with regard to their potential to provide guidelines for the design of a self-assessment and task-selection training.     

Some possible applications of chromatic parameters to thin film optical constants determination

Abstract

Computer simulation of colour parameters of single layer coatings, transparent in the visible spectral region, is carried out with purpose of film thickness d and optical dispersion n(λ) determination. An approach for determination of characteristics of a transparent thin film from transmitted light colour coordinates is proposed. The region in which the proposed method is applicable is estimated from comparison between film characteristics obtained from the colour coordinates and envelope methods for RF deposited transparent BaTiO₃ thin films.     

Structure‐Based Mechanism of Oleate Hydratase from Elizabethkingia meningoseptica

Hydratases provide access to secondary and tertiary alcohols by regio‐ and/or stereospecifically adding water to carbon‐carbon double bonds. Thereby, hydroxy groups are introduced without the need for costly cofactor recycling, and that makes this approach highly interesting on an industrial scale. Here we present the first crystal structure of a recombinant oleate hydratase originating from Elizabethkingia meningoseptica in the presence of flavin adenine dinucleotide (FAD). A structure‐based mutagenesis study targeting active site residues identified E122 and Y241 as crucial for the activation of a water molecule and for protonation of the double bond, respectively. Moreover, we also observed that two‐electron reduction of FAD results in a sevenfold increase in the substrate hydration rate. We propose the first reaction mechanism for this enzyme class that explains the requirement for the flavin cofactor and the involvement of conserved amino acid residues in this regio‐ and stereoselective hydration.     

NMR spectroscopic and thermodynamic studies of the etherate and the α, α′, and γ phases of AlH3

Aluminum hydride (alane; AlH₃) has been identified as a leading hydrogen storage material by the US Department of Energy. With a high gravimetric hydrogen capacity of 10.1 wt.%, and a hydrogen density of 1.48 g/cm³, AlH₃ decomposes cleanly to its elements above 60 °C with no side reactions. This study explores in detail the thermodynamic and spectroscopic properties of AlH₃; in particular the α, α′ and γ polymorphs, of which α′-AlH₃ is reported for the first time, free from traces of other polymorphs or side products. Thermal analysis of α-, α′-, and γ-AlH₃ has been conducted, using DSC and TGA methods, and the results obtained compared with each other and with literature data. All three polymorphs were investigated by ¹H MAS-NMR spectroscopy for the first time, and their ²⁷Al MAS-NMR spectra were also measured and compared with literature values. AlH₃·nEt₂O has also been studied by ¹H and ²⁷Al MAS-NMR spectroscopy and DSC and TGA methods, and an accurate decomposition pathway has been established for this adduct.     

Adsorption of Alkanethiols on Gold Surfaces: PM-IRRAS Study of the Influence of Terminal Functionality on Alkyl Chain Orientation

The present paper focuses on a simplified method to study the orientation and the anisotropy of two different alkanethiols self-assembled monolayers on gold surfaces. The alkanethiols of interest vary only by their terminal functionalities (COOH and COOCH₃), thus allowing one to highlight the influence of these ending chemical groups on the final orientation of the adsorbed molecules. 11-Mercaptoundecanoic acid [HS-(CH₂)₁₀-COOH] and the methyl-11-mercaptoundecanoate [HS-(CH₂)₁₀-COOCH₃] were grafted under adequate conditions to obtain a high grafting density on gold substrates. These latter, before and after the alkanethiol adsorption, were analyzed mainly by the polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) technique to access orientation angles, and by atomic force microscopy (AFM) to check the homogeneity of the grafted layer.

By applying an original PM-IRRAS simplified method, the results showed an orientation closer to the normal of the surface plane in the case of the acid thiol compared with the ester one, which is probably because of the lateral hydrogen bonds established between the adjacent COOH functions. This method offers a direct and simple way to quantify the orientation angles in the alkanethiol nanofilms.