Accelerating linear causal model discovery using hoeffding bounds

Efficiently inducing precise causal models accurately reflecting given data sets is the ultimate goal of causal discovery. The algorithms proposed by Dai et al. has demonstrated the ability of the Minimum Message Length (MML) principle in discovering Linear Causal Models from training data. In order to further explore ways to improve efficiency, this paper incorporates the Hoeffding Bounds into the learning process. At each step of causal discovery, if a small number of data items is enough to distinguish the better model from the rest, the computation cost will be reduced by ignoring the other data items. Experiments with data set from related benchmark models indicate that the new algorithm achieves speedup over previous work in terms of learning efficiency while preserving the discovery accuracy.

Wastewater irrigation: the state of play

As demand for fresh water intensifies, wastewater is frequently being seen as a valuable resource. Furthermore, wise reuse of wastewater alleviates concerns attendant with its discharge to the environment. Globally, around 20 million ha of land are irrigated with wastewater, and this is likely to increase markedly during the next few decades as water stress intensifies. In 1995, around 2.3 billion people lived in water-stressed river basins and this could increase to 3.5 billion by 2025. We review the current status of wastewater irrigation by providing an overview of the extent of the practice throughout the world and through synthesizing the current understanding of factors influencing sustainable wastewater irrigation. A theme that emerges is that wastewater irrigation is not only more common in water-stressed regions such as the Near East, but the rationale for the practice also tends to differ between the developing and developed worlds. In developing nations, the prime drivers are livelihood dependence and food security, whereas environmental agendas appear to hold greater sway in the developed world. The following were identified as areas requiring greater understanding for the long-term sustainability of wastewater irrigation: (i) accumulation of bioavailable forms of heavy metals in soils, (ii) environmental fate of organics in wastewater-irrigated soils, (iii) influence of reuse schemes on catchment hydrology, including transport of salt loads, (iv) risk models for helminth infections (pertinent to developing nations), (v) microbiological contamination risks for aquifers and surface waters, (vi) transfer efficiencies of chemical contaminants from soil to plants, (vii) health effects of chronic exposure to chemical contaminants, and (viii) strategies for engaging the public.

The three R`s of resilience: redundancy, requisite variety and resources

This paper offers a way of operationalizing resilience according to the sub-systems that comprise a business (technical, social and economic), the kinds of perturbations that might impact a business (local, national and global) and the criteria that determine resilient capacity (redundancy, requisite variety and resources). When a business system has incorporated redundancy, developed requisite variety and adequately monitors its resources, we might then conclude that such a business is a resilient business. The model offered here is theoretical, and is yet to undergo empirical scrutiny. Empirical modeling will enable us to ascertain the strength of a business's internal characteristics against different levels/kinds of external perturbation. Sensitivity analysis of this kind will lead to more in-depth understanding of the dynamics that generate resilient businesses in a complex world.

Morphological evolution of nanofibers during electrospinning

Electrospinning is a very useful technique to produce polymeric nanofibers. It involves fast-drawing a polymer fluid into nanofibers under a strong electric filed, and depositing randomly on an electrode collector to form non-woven nanofiber mat in most cases [1]. The fibre stretching during electrospinning is a fast and incessant process which can be divided into three consecutive stages: jet initiation, whipping instability and fibre deposition. From the initial jet to dry fibres, the fibre stretching takes place in milliseconds, so it has been hardly so far to observe fiber morphology changes by any normal methods, such as high speed photography [2-5]. In this study, we used a facile and practical approach to realize the observation of nanofiber morphology changes during electrospinning. Through a special collection device with coagulation bath, newly electrospun nanofibers can be solidified at different electro spinning distances, and by associating the fiber morphology with the electrospinning distance (d), the morphological evolution of nanofibers can be established. We used polyacrylonitrile (PAN) and polystyrene (PS) as two model polymers to demonstrate this method in present research. From experimental results, we found the massive jet-thinning happens at the initial stage of the process. The formation of uniform PAN nanofibers (7%) and the beads structure changes on beads-on-string PAN nanofibers (5%) have also been successful observed. Using the same method, we also observed PS nanofiber (10%) morphology changes to understand the beads formation 011 nanofibers during electrospinning process, and how the beads was eliminated when ionic surfactant is added into the PS solution for electrospinning.

Natriuretic peptide regulation of the kidney and urinary bladder in the cane toad, Bufo marinus

The natriuretic peptide system of mammals is important in the control of blood volume but its function in non-mammalian animals is unclear. This study identified a functional natriuretic peptide system in an amphibian and showed that the hormones are involved in the control of fluid balance.