A stochastic model for early placental development

In the human, placental structure is closely related to placental function and consequent pregnancy outcome. Studies have noted abnormal placental shape in small-for-gestational-age infants which extends to increased lifetime risk of cardiovascular disease. The origins and determinants of placental shape are incompletely understood and are difficult to study in vivo. In this paper, we model the early development of the human placenta, based on the hypothesis that this is driven by a chemoattractant effect emanating from proximal spiral arteries in the decidua. We derive and explore a two-dimensional stochastic model, and investigate the effects of loss of spiral arteries in regions near to the cord insertion on the shape of the placenta. This model demonstrates that disruption of spiral arteries can exert profound effects on placental shape, particularly if this is close to the cord insertion. Thus, placental shape reflects the underlying maternal vascular bed. Abnormal placental shape may reflect an abnormal uterine environment, predisposing to pregnancy complications. Through statistical analysis of model placentas, we are able to characterize the probability that a given placenta grew in a disrupted environment, and even able to distinguish between different disruptions.     

‘Don't forget to put the cat out’ — or why collaborative authoring software and everyday writing pass one another by!

Abstract

Hypermedia technology is seen as offering potentially innovative support for the process of writing as much as information access and reading. However authoring environments to date have had little impact in the real-world production of text. One possible reason is our poor conceptualisation of current writing practice. In the present paper, 31 adult writers kept diaries of their writing activities over the course of one week. The results indicate that for most people, real world writing is a short communicative act aimed at a limited audience and that technological support for such writing is less likely to resemble a hypermedia workstation than a portable personal communication device. Implications for work in the design of authoring tools are developed.     

Solving reverse logistics vehicle routing problems with time windows

A vehicle routing problem with simultaneous pick-up and delivery in closed-loop logistics network optimization is studied in this paper. Since, in practice, material pick-up and delivery are only allowed to take place on certain time periods, we consider the reverse logistics vehicle routing problem with time windows. A mixed integer programming model is proposed to formulate the considered problem. A heuristic solution approach for solving the model is developed due to the NP-hard nature of solving the model. The heuristic solution is then used as an initial solution of a simulated annealing procedure for improved solutions. The proposed heuristic method and the simulated annealing procedure yield very promising solutions in much less computational time when compared with optimal solutions generated by exact solution procedures. Numerical examples are presented to illustrate the developed model and solution methods.     

Source apportionment of PM(2.5) and selected hazardous air pollutants in Seattle

The potential benefits of combining the speciated PM(2.5) and VOCs data in source apportionment analysis for identification of additional sources remain unclear. We analyzed the speciated PM(2.5) and VOCs data collected at the Beacon Hill in Seattle, WA between 2000 and 2004 with the Multilinear Engine (ME-2) to quantify source contributions to the mixture of hazardous air pollutants (HAPs). We used the 'missing mass', defined as the concentration of the measured total particle mass minus the sum of all analyzed species, as an additional variable and implemented an auxiliary equation to constrain the sum of all species mass fractions to be 100%. Regardless of whether the above constraint was implemented and/or the additional VOCs data were included with the PM(2.5) data, the models identified that wood burning (24%-31%), secondary sulfate (20%-24%) and secondary nitrate (15%-20%) were the main contributors to PM(2.5). Using only PM(2.5) data, the model distinguished two diesel features with the 100% constraint, but identified only one diesel feature without the constraint. When both PM(2.5) and VOCs data were used, one additional feature was identified as the major contributor (26%) to total VOC mass. Adding VOCs data to the speciated PM(2.5) data in source apportionment modeling resulted in more accurate source contribution estimates for combustion related sources as evidenced by the less 'missing mass' percentage in PM(2.5). Using the source contribution estimates, we evaluated the validity of using black carbon (BC) as a surrogate for diesel exhaust. We found that BC measured with an aethalometer at 370 nm and 880 nm had reasonable correlations with the estimated concentrations of diesel particulate matters (r>0.7), as well as with the estimated concentrations of wood burning particles during the heating seasons (r=0.56-0.66). This indicates that the BC is not a unique tracer for either source. The difference in BC between 370 and 880 nm, however, correlated well exclusively with the estimated wood smoke source (r=0.59) and may be used to separate wood smoke from diesel exhaust. Thus, when multiple BC related sources exist in the same monitoring environment, additional data processing or modeling of the BC measurements is needed before these measurements could be used to represent the diesel exhaust.     

Taking a hands-on approach: Apparent grasping ability scales the perception of object size.

We examined whether the apparent size of an object is scaled to the morphology of the relevant body part with which one intends to act on it. To be specific, we tested if the visually perceived size of graspable objects is scaled to the extent of apparent grasping ability for the individual. Previous research has shown that right-handed individuals perceive their right hand as larger and capable of grasping larger objects than their left. In the first 2 experiments, we found that objects looked smaller when placed in or judged relative to their right hand compared to their left. In the third experiment, we directly manipulated apparent hand size by magnifying the participants' hands. Participants perceived objects to be smaller when their hand was magnified than when their hand was unmagnified. We interpret these results as demonstrating that perceivers use the extent of their hands' grasping abilities as “perceptual rulers” to scale the apparent size of graspable objects. Furthermore, hand size manipulations did not affect the perceived size of objects too big to be grasped, which suggests that hand size is only used as a scaling mechanism when the object affords the relevant action, in this case, grasping. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Assessment of Lignin Model Quality in Lignin Chemical Shift Assignments – Substituent and Solvent Effects1

Typical solution-state ¹³C NMR spectra of lignins obtained with relatively modern instrumention contain well over 100 signals. The use of classical lignin model compounds is no longer sufficient for accurate interpretation of these spectra. Ultimately, the only valid models for etherified C₉ units in lignin (which account for about 80% of the lignin polymer) must be at least trimeric or tetrameric, depending on the linkages involved. One approach that can be used involves NMR substituent effects. This approach avoids tedious syntheses while retaining the much-needed accuracy of chemical shift correlations between models and natural lignins. Appropriate substituent effects have been calculated by the use of an extensive NMR database of dimeric, trimeric and tetrameric lignin model compounds. Effects related to acetylation and solvent have also been determined. For example, accurate chemical shift data for an underivatized milled-wood lignin (MWL) in DMSO-d₆ can be determined on the basis of the chemical shifts of the corresponding acetylated MWL in acetone-d₆.     

Can nitrogen fertiliser and nitrification inhibitor management influence N2O losses from high rainfall cropping systems in South Eastern Australia?

Nitrous oxide (N₂O) is a potent greenhouse gas released from high rainfall cropping soils, but the role of management in its abatement remains unclear in these environments. To quantify the relative influence of management, nitrogen (N) fertiliser and soil nitrification inhibitor was applied to separate but paired raised bed and conventionally flat field experiments in south west Victoria, to measure emissions and income from wheat and canola planted 2 and 3 years after conversion from a long-term pasture. Management included four different rates of N fertiliser, top-dressed with and without the nitrification inhibitor Dicyandiamide (DCD), which was applied in solution to the soil in the second year of experimentation. Crop biomass, grain yield, soil mineral N, soil temperature and soil water and N₂O flux were measured. Static chamber methodology was used to identify relative differences in N₂O loss between management. In the second crop (wheat) following conversion, N₂O losses were up to 72 % lower (P < 0.05) in the furrows, receiving the lower rate of N fertiliser compared with the highest rate, with less frequent reductions observed in the third crop (canola); losses of N₂O from the beds was unaffected by N rate, perhaps from nitrate leakage into the adjacent furrow of the raised bed experiment. On the nearby flat experiment, nitrate leaching may have diminished the effects of N rate and DCD on N₂O flux. Furthermore the extra N did not significantly increase grain yield in either the wheat or canola crops on both experiments. The application of DCD in the canola crop temporarily reduced (P < 0.05) N₂O production by up to 84 % from the beds, 83 % in the adjacent furrows and 75 % on the flat experiment. Grain yield was not significantly (P < 0.001) affected however, canola income was reduced by $1407/ha and $1252/ha, compared with no addition of inhibitor on the respective bed and flat experiments. Although N₂O fluxes are driven by environmental episodic events, management will play a role in N₂O abatement. However, DCD currently appears economically unfeasible and matching N fertiliser supply to meet crop demand appears a better option for minimising N₂O losses from high rainfall cropping systems.     

Biocatalytic oxidase: Batch to continuous

The adoption of more efficient development strategies and manufacturing techniques will be essential for future success in the bio manufacturing sectors. Continuous operation of biocatalytic processes has the potential to offer many advantages over established batch process methodologies. There exist opportunities for improved process control; ease of scale up; minimizing of interruptions in production; reducing reactor size; and economic use of biocatalysts.     

Graduate training in clinical neuropsychology.

Surveyed 65 American Psychological Association-approved clinical graduate training programs about offerings in clinical neuropsychology (N). 32 of these schools encouraged students with a primary interest in N, while 28 offered N as additional training rather than as a separate field. There was considerable evidence indicating that N is rapidly expanding across the nation. (3 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)