Assessing the reliability of ordered categorical scales using kappa-type statistics

Methods for the analysis of reliability of ordered categorical scales are discussed, focussing on the limitation of the single summary-weighted kappa coefficients. A symmetric matrix of kappa-type coefficients is suggested as an alternative. The method is proposed as being suitable for ordinal scale where there is no underlying continuum. Their application is illustrated using two data sets from reliability studies. If, instead, distances between categories can be specified, a weighted mean of the matrix terms can be used as a summary measure. This is equal to a weighted kappa coefficient with squared weights, provided distances between adjacent categories are equal. When a study design corresponds to a one-way random effects model, estimates of precision of kappa-type coefficient, including the coefficients described here, can be obtained using the delta-method, bootstrap resampling by subjects or jack-knifing by subjects. In the case of interobserver reliability studies, where there may be systematic differences between observers, the investigator may wish to generalise to a population of observers and subjects. In this case, jack-knifing by observer and subject is suggested. Empirical comparisons are made between standard error estimates based on the delta-method, on jack-knifing by subjects and a two-way jack-knife by subjects and observers. The results suggest that standard errors based on the delta-method or jack-knifing by subject alone may be overly precise.     

Sequelae of cesarean and vaginal deliveries: Psychosocial outcomes for mothers and infants.

Mother-infant dyads grouped according to whether the infants had been delivered vaginally (n?=?74) or by planned (n?=?37) or unplanned cesarean (n?=?56) were compared on psychosocial outcomes at 4 and 12 months postpartum. Hypotheses were that unplanned cesarean delivery would be related to less optimal outcomes and that this relationship would be mediated by mother's appraisal of the delivery and would attenuate over time. No delivery-related differences in mother–infant interactions were found at 4 or 12 months postpartum with one exception: Women low in neuroticism who delivered by unplanned cesarean showed less positive affect toward their infants at 4 months than did women high in neuroticism who delivered by unplanned cesarean or women in any other group. There was some evidence of the mediating role of maternal appraisal of the delivery on these effects. In general, the results indicate little cause for concern about the quality of mother–infant interactions following cesarean deliveries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Maternal employment and development of the father–infant relationship in the first year.

This study investigated links between maternal employment and fathers' parenting quality when their infants were 4 and 12 months old. Sixty-three fathers were videotaped interacting with their infants and completed questionnaires regarding their involvement in caregiving, parenting stress, and marital quality, and mothers reported on children's temperament. Fathers whose wives either did not work outside the home or worked part time were more sensitive and responsive to their children when they were more involved in caregiving; men whose wives worked full time exhibited more negative affect and behavior when they participated more in child care. Men whose wives were not employed also were more positive in their interactions when they were happier with their marriage, whereas men whose wives worked either part time or full time exhibited a negative relation between parenting behavior and marital quality. Maternal work circumstances were not related to fathers' parenting stress; rather, marital quality and child temperament predicted parenting stress at 4 and 12 months for all fathers. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemotaxis in shear flow: Similarity solutions of the steady-state chemoattractant and bacterial distributions

When chemotactic bacteria are exposed to a concentration gradient of chemoattractant while flowing along a channel, the bacteria accumulate at the interface between the chemoattractant source and bacterial suspension. Assuming that the interface is no-slip, we can apply the shear flow approximation near the no-slip boundary and solve a steady-state convection-diffusion model for both chemoattractant and bacterial concentrations. We suggest similarity solutions for the two-dimensional problem and identify a critical length scale η_c for bacteria chemotaxis in a given concentration gradient. The analysis identifies three dimensionless groups representing, respectively, chemotactic sensitivity, the chemotaxis receptor constant, and the bacteria diffusion coefficient, which typically show coupled effects in experimental systems. We study the effect of the dimensionless groups separately and provide understanding of the system involving shear flow and chemotaxis.     

Do Pine Voles (Microtus pinetorum) Use Numerous Types of Olfactory Cues to Discriminate Gender?

Olfactory cues can contain information for discrimination of gender that can affect subsequent social interactions. Social rodents are hypothesized to use more olfactory cues than nonsocial rodents to distinguish males from females. The generality of this hypothesis was tested using the pine vole (Microtus pinetorum), a social vole. We examined nine possible sources of odors. A slide containing an odor from a male and a female was presented to each test subject for 3 min. We recorded the amount of time each test subject spent investigating each odor. Females spent significantly more time investigating male urine and male anogenital odors; however, they did not use any other odor sources to discriminate gender. In contrast, males did not use any odor sources to discriminate gender. Our results do not support the hypothesis that all social rodents use numerous odor sources to discriminate gender. Instead, our results are consistent with the alternative hypothesis that use of odor sources to convey information about gender may differ in rodents that live in different microhabitats.     

An Empirically-Based Process for Software Architecture Evaluation

Software systems undergo constant change causing the architecture of the system to degenerate over time. Reversing system degeneration takes extra effort and delays the release of the next version. Improved architecture is intangible and does not translate into visible user features that can be marketed. Due to a lack of representative metrics, technical staff has problems arguing that stopping degeneration is indeed necessary and that the effort will result in an improved architecture that will pay off. We believe that architectural metrics would give technical staff better tools to demonstrate that the architecture has improved. This paper defines and uses a set of architectural metrics and outlines a process for analyzing architecture to support such an argument. The paper reports on a case study from a project where we restructured the architecture of an existing client-server system written in Java while adding new functionality. The modules of the existing version of the system were library-oriented and had a disorganized communication structure. The new architecture is based on components and utilizes the mediator design pattern. The goal of the study is to evaluate the new architecture from a maintainability perspective. The paper describes our evaluation process, the metrics used, and provides some preliminary results. The architectural evaluation shows that the components of the system are only loosely coupled to each other and that an architectural improvement has occurred from a maintenance perspective. The process used to evaluate the architecture is general and can be reused in other contexts.     

Monte Carlo simulations derived from direct observations of individual bacteria inform macroscopic migration models at granular porous media interfaces

Motile bacteria accumulated at the interface between an aqueous solution and a polymer gel suspension. The gel suspension was produced using Gelrite and contained 50-500 microm semisolid gel particulates in aqueous buffer. Smooth-swimming (HCB437) and wild-type (HCB1) Escherchia coli displayed normal swimming behaviors in the aqueous buffer but exhibited no translational motion when obstructed by the semisolid particulates of the gel suspension. Translational motion immediately resumed after the bacteria reoriented in a direction away from the particle surfaces. These observations were incorporated into Monte Carlo simulations that linked individual swimming properties to macroscopic bacterial distributions. The simulations suggested that the apparent surface area of the porous media influenced the degree of bacteria/surface interactions and thatthe mechanism of surface association could concentrate bacterial populations based upon the physical constraints of the porous media system. Population distributions from the Monte Carlo simulations matched a 1-D transport model that characterized the bacteria/surface interactions as an adsorption-like process even though direct observations suggested no physical attachment was occurring. Consequently, the 1-D transport model provided a semiquantitative approach to approximate bacterial migrations within porous media systems. Results suggest that the self-propulsive nature of bacteria can produce nondiffusive migration patterns within high-surface area environments.     

Taking the fungal highway: mobilization of pollutant-degrading bacteria by fungi

The capacity of fungi to serve as vectors for the dispersion of pollutant-degrading bacteria was analyzed in laboratory model systems mimicking water-saturated (agar surfaces) and unsaturated soil environments (glass-bead-filled columns). Two common soil fungi (Fusarium oxysporum and Rhexocercosporidium sp.) forming hydrophilic and hydrophobic mycelia, respectively, and three polycyclic aromatic hydrocarbon degrading bacteria (Achromobacter sp. SK1, Mycobacterium frederiksbergense LB501TG, and Sphingomonas sp. L138) were selected based on the absence of mutual antagonistic effects. It was shown that fungal hyphae act as vectors for bacterial transport with mobilization strongly depending on the specific microorganisms chosen: The motile strain Achromobacter sp. SK1 was most efficiently spread along hyphae of hydrophilic F. oxysporum in both model systems with transport velocities of up to 1 cm d(-1), whereas no dispersion of the two nonmotile strains was observed in the presence of F. oxysporum. By contrast, none of the bacteria was mobilized along the hydrophobic mycelia of Rhexocercosporidium sp. growing on agar surfaces. In column experiments however, strain SK1 was mobilized by Rhexocercosporidium sp. It is hypothesized that bacteria may move by their intrinsic motilitythrough continuous (physiological) liquid films forming around fungal hyphae. The results of this study suggest that the specific stimulation of indigenous fungi may be a strategy to mobilize pollutant-degrading bacteria leading to their homogenization in polluted soil thereby improving bioremediation.     

Air quality and climate change co-benefits for the industrial sector in Durban,South Africa

Industries in Durban, South Africa, are a major source of air pollutant emissions and large users of fossil fuel based energy. Durban’s energy strategy prioritises energy efficiency at industries as a key action, whilst industries are also the focus of the city’s air quality management plan (AQMP). In this paper, measures that have been introduced in industries in Durban to effect air quality improvements and reduce energy consumption are examined in terms of their respective impacts on greenhouse gas (GHG) and air pollutant emissions. It was found that co-benefits for GHG mitigation were achieved when petroleum refineries switched from using heavy fuel oil to refinery gas and methane rich gas. Within other industries, co-benefits for air quality stemmed from reducing fossil fuel energy consumption and the improved efficiency of combustion systems. Air quality and energy policies in the city are being executed independently, without consideration of the trade-offs or synergies of the interventions being implemented. Recommendations are made for authorities and industries to consider the co-benefits for GHG mitigation in their AQMPs and where these are not possible to consider offsetting the increased GHG emissions through improved alignment with energy strategies.     

The analysis of warpage in wafer-level compression molding

Advanced 3D MEMS packaging technologies involving the encapsulation of devices at wafer-level are being developed in order to achieve further minimization and cost reduction of consumer electronic devices. Compression molding using epoxy molding compounds is one technique being considered for wafer-level encapsulation. Excessive out-of-plane deformation has been reported in wafer-level compression molding trials using blank wafers which would negatively impact device reliability and the implementation of successive processes to the molded wafer. This paper presents finite element models of the molded wafer, with and without embedded dies which simulate the observed multi-state warpage characteristics. Molded wafer warpage measurements were also carried out in order to verify the applicability of the small and large deformation theories for layered plates and to verify the finite element model of the molded blank wafer. Possible factors (non-planar mold layer thickness and anisotropic wafer elastic properties) leading to asymmetric warpage in molded blank wafers were also investigated. From the molded wafer model with embedded dies the effects of flip-chip die dimensions and wafer thickness on the out-of-plane deformation together with possible reliability issues were analyzed.