Injury severity analysis: comparison of multilevel logistic regression models and effects of collision data aggregation

This paper describes an empirical study aiming at identifying the main differences between different logistic regression models and collision data aggregation methods that are commonly applied in road safety literature for modeling collision severity. In particular, the research compares three popular multilevel logistic models (i.e., sequential binary logit models, ordered logit models, and multinomial logit models) as well as three data aggregation methods (i.e., occupant based, vehicle based, and collision based). Six years of collision data (2001–2006) from 31 highway routes from across the province of Ontario, Canada were used for this analysis. It was found that a multilevel multinomial logit model has the best fit to the data than the other two models while the results obtained from occupant-based data are more reliable than those from vehicle- and collision-based data. More importantly, while generally consistent in terms of factors that were found to be significant between different models and data aggregation methods, the effect size of each factor differ substantially, which could have significant implications for evaluating the effects of different safety-related policies and countermeasures.

     

Susceptibility to the biological effects of polyaromatic hydrocarbons is influenced by genes of the major histocompatibility complex

Polyaromatic hydrocarbons are ubiquitous environmental chemicals that are important mutagens and carcinogens. The purpose of this study was to determine whether genes within the major histocompatibility complex (MHC) influence their biological activities. Cell-mediated immunity to dimethylbenz(a)anthracene (DMBA) was investigated in congenic strains of mice. On three different backgrounds, H-2(k) and H-2(a) haplotype mice developed significantly greater contact-hypersensitivity responses to DMBA than H-2(b), H-2(d), and H-2(s) mice. In B10.A(R1) mice, which are Kk and Id, a vigorous contact-hypersensitivity response was present, indicating that the response was governed by class I, rather than class II, MHC genes. C3H/HeN (H-2(k)) and C3H.SW (H-2(s)) strains were also compared for the development of skin tumors and the persistence of DMBA-DNA adducts. When subjected to a DMBA initiation, phorbol 12-tetradecanoate 13-acetate (TPA)-promotion skin-tumorigenesis protocol, C3H/HeN mice, (which develop cell-mediated immunity to DMBA) were found to have significantly fewer tumors than C3H.SW mice (a strain that failed to develop a cell-mediated immune response to DMBA). DMBA-DNA adducts were removed more rapidly in C3H/HeN than in C3H.SW mice. The results indicate that genes within the MHC play an important role in several of the biological activities of carcinogenic polyaromatic hydrocarbons. The observations are consistent with the hypothesis that cell-mediated immunity to chemical carcinogens serves to protect individuals by removing mutant cells before they can evolve into clinically apparent neoplasms.     

Bioactive Organotin Materials: Synthesis, Characterization and Antimicrobial Investigation

Antimicrobial properties of some newly prepared oil based organotin polymers by the condensation reaction between fatty amide diol (N,N′-bis(2-hydroxyethyl) castoroil fatty amide) obtained from castoroil and organotin dihydroxides (dibutyltin dihydroxide, dimethyltin dihydroxide and diphenyltin dihydroxide) have been studied by employing both Gram-positive (Lactobacillus, Staphylococcus aureus) and Gram-negative (Pseudomonas putida, Pseudomonas fluorescens, E. coli) bacteria. The structural studies of these three polymers were carried out by FTIR, ¹HNMR and ¹³ CNMR spectroscopic techniques. Standard laboratory methods were used to study the physiochemical characteristics like acid value, hydroxyl value, saponification value, iodine value, specific gravity and viscosity. A comparative study of the thermal stability was analysed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). All three polymers have been found fairly active against the tested bacterial species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Effect of comparator offset on the linearity of charge sharing ADCs

The charge-sharing (CS) switching scheme appeared recently as an alternative to the charge-redistribution (CR) ADC for moderate-resolution low-power applications. One advantage of the CS is that it requires less demanding reference and input buffers. On the other hand, the CS ADC is very sensitive to the comparator offset, because the latter is translated into non-linearity on the ADC transfer curve. This paper examines the mechanism that causes this non-linearity and proposes a closed-form expression for the maximum effective resolution that a CS ADC may achieve in the presence of comparator offset. Finally, the model is verified with behavioral simulations.     

The impact of tree structures on the performance of zerotree-based wavelet video codecs

In this paper we analyze the impact of tree structures on the performance of zerotree-based wavelet video codecs. Since zerotree approach is based on aggregation of insignificant coefficients in trees, therefore design of a tree structure is the key issue for a better performance. We have considered six different tree structures with characteristics varying from a simple to relatively complex and composite tree structures to code the luminance–chrominance components of a video sequence. Their performances are compared in terms of average number of bits generated per bitplane, number of coded bitplanes for a given bit budget, rate-distortion performance, memory requirements and computational complexity. We observe that in general more complex and longer trees do not necessarily improve the coding efficiency. However, the tree structures encapsulating more elements per tree are memory efficient. Therefore, the rate-distortion performance, memory requirements and computational complexities need to be traded-off while selecting a particular tree structure. It is also observed that the additional improvement due to optional entropy coding is also tree structure dependent. Further, the simulation results show that by designing an efficient tree structure, depending on the picture content, the performance of a video coder can be improved by up to 2.0 dB, while reducing the computational complexity by 45–60% as well as the memory requirements by almost 29–35%. Compared to the standard JPEG2000 (for intra-frame), tree-based coders are found to be efficient in terms of coding and complexity, particularly at lower bit rates.