Biomolecular mechanisms for signal differentiation

Cells can sense temporal changes of molecular signals, allowing them to predict environmental vari-ations and modulate their behaviour. This paper elucidates the underlying biomolecular mechanisms of time derivative computation, facilitating the design of reliable synthetic differentiator devices for a variety of applications, ultimately expanding our understanding of cell behaviour. In particular, we describe and analyse three alternative biomolecular topologies that work as signal differentiators of high accuracy to arbitrary input signals around their nominal operation. We propose strategies to preserve their performance even in the presence of high-frequency input signal components, which are detrimental to the performance of most differentiators. We found that the core of the proposed topologies appears in natural regulatory networks and we further discuss their biological relevance. The simple structure of our designs makes them promising tools for realizing derivative control action in synthetic biology.

Reviewing productivity studies of skidders working in coniferous forests and plantations

Skidding is an important element of harvesting operations, which contributes to the extraction of wood. A skidder can be used in different types of harvesting operations, such as thinning, clear fell, native forest thinning or salvage work. The main goal of this article was to review the available stud-ies on productivity of skidding operations in coniferous forests/ plantations. Information on skid-der productivity was collected from publications and then was classified in three regions, including North America, Europe and the Southern Hemisphere. The parameters affecting machine productivity included machine type/ size, tree volume/ log volume/ load volume, average skidding distance and slope of the ground for each reported productivity. The average productivity reported in the published reports ranged from 9.3 m3/PMH to 78.0 m3/PMH. Detailed information and conclusions collected from various studies can be of use to forest academic and industry users to gain knowledge about vari-ations of skidder productivity in different regions and site/ operation conditions, which can be helpful for predicting, controlling and improving current levels of productivity. 

Spatial modelling of PM2.5 concentrations in Tehran using Kriging and inverse distance weighting (IDW) methods

Introduction: Estimating air pollution levels in areas with no measurements is a major concern in health-related studies. Therefore, the aim of this study was to investigate the amount of exposure to particulate matter below 2.5 µ (PM2.5) in the metropolis of Tehran. Materials and methods: The hourly concentrations of PM2.5 during 2017-2018 period were acquired from the Department of Environment (DOE) and Air Quality Control Company of Tehran (AQCC). The hourly concentrations were validated and 24-h concentrations were calculated. Inverse distance weighting (IDW), Universal Kriging, and Ordinary Kriging were used to spa- tially model the PM2.5 over Tehran metropolis area. Root Mean Square Error (RMSE) and Mean Error (ME) were used to measure and control for the ac- curacy of the methods. Results: The results of this study showed that RMSE and MENA values in Kriging method was less than the IDW, which indicates that the Kriging was the best method to estimate PM2.5 concentrations. According to the final map, the highest annual concentrations of PM2.5 were observed in the southern and southwestern areas of Tehran (districts 10, 15, 16, 17, and 18). The lowest exposure to PM2.5 was found to be in districts 1, 2, 3, 6, and 8. Conclusion: It can be concluded that Kriging method can predict spatial vari- ations of PM2.5 more accurately than IDW method.

Accumulation or absorption? Changing disparities of household non-employment in Europe during the Great Recession

This comparative study analyses the impact of the Great Recession on household non-employment across Europe since 2008. We use the EU-SILC (2007 to 2014) for a shift-share analysis that de-composes annual variations in household non-employment in 30 European countries. Investigating whether job-loss is absorbed or accumulated by households, we break down non-employment vari-ations to changes in individual non-employment, household compositions, and polarization. We find that jobless households increased since 2008, especially in crisis countries. There is no evi-dence for widespread absorption of individual non-employment in families or multi-person house-holds. Instead, household dynamics and unequal distribution of non-employment leads to further risk accumulation within households during the crisis. Paradoxically, this pattern occurs in those crisis countries known for their traditional household structures and less accommodating welfare systems which have relied thus far on families to absorb employment risks. The impact of the crisis has aggravated household disparities in joblessness.

Let's Do It!: More indoor games to motivate computational skills

How difficult it is to get children to practice computational skills! Most of us are conti nuously seeking techniques to motivate children to invest their time in learning number recognition, basic facts, and operations on whole numbers and fractions. Dominoes, dice, and cards are three inexpensive materials that can be used to generate teaching games that children are willing to play. Each of these materials is explored here for the possibility of teaching and motivating the development of computational skills. Although several vari ations of each game are suggested, it is hoped that individual teachers will be encouraged to devise still other games that are appropriate to the concepts and skills needed by the children in their own classes.