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If you want to understand an ecosystem, look at what the species within it eat. In studying food webs-how animals and plants in a community are connected through their dietary preferences-ecologists can piece together how energy flows through an ecosystem and how stable it is to climate change and other disturbances. Studying ancient food webs can help scientists reconstruct communities of species, many long extinct, and even use those insights to figure out how modern-day communities might change in the future. There's just one problem: only some species left enough of a trace for scientists to find eons later, leaving large gaps in the fossil record-and researchers' ability to piece together the food webs from the past.

The common challenge of covid-19 has produced very different outcomes around the world, leading to many questions about the determinants of national performance and shortcomings in global performance. Problems of reporting and standards do not make precise comparisons easy, but few would disagree that the roughly 1400 deaths reported by South Korea, Thailand, and Vietnam together represent far better results than the roughly 700 000 deaths reported by Brazil, the United Kingdom, and the United States.1 Adjusting these figures for population-the first group has about a third of the citizens of the second group-does not explain why covid-19 mortality differs by a factor of nearly 500. Neither typical proxy measures such as gross national income per capita nor national rankings on the 2019 Global Health Security Index have any meaningful association with performance on covid-19.2

Optimization is a key tool in machine learning, where the goal is to achieve the best possible objective function value in a minimum amount of time. Obtaining any form of global guarantees can usually be done with convex objective functions, or with special cases such as risk minimization with one-hidden over-parameterized layer neural networks (see the June post). In this post, I will consider low-dimensional problems (imagine 10 or 20), with no constraint on running time (thus get ready for some running-times that are exponential in dimension!).

Red ink isn't a problem as long as the country is spending on the right things.

Thinking and interacting, intellectually, are essential in solving mankind's problems, such as the pandemic now engulfing our existence. In doing so, however, we need to remain vigilant to the possibility of making mistakes that could lead us to wrong conclusions. Recall

Hunger is surging in the heart of the breadbasket, showing just how dire the problem has become during the pandemic.

The problem for consumers up to now has been that the negotiated prices were unknown, or impractical to raise in court due to evidentiary rules. The general rule is that witnesses must testify to facts within their personal knowledge. Notably, if a consumer contests a medical debt collection lawsuit, someone from the hospital must testify that the price charged is reasonable and customary-an assertion that, with regard to chargemasters, involves shading the truth and is vulnerable to cross-examination.

The capitalist economic system has always had a big problem with politics in societies with universal suffrage. Anticipating that, most capitalists opposed and long resisted extending suffrage beyond the rich who possessed capital. Only mass pressures from below forced repeated extensions of voting rights until universal suffrage was achieved-at least legally. To this day, capitalists develop and apply all sorts of legal and illegal mechanisms to limit and constrain suffrage. Among those committed to conserving capitalism, fear of universal suffrage runs deep. Trump and his Republicans exemplify and act on that fear as the 2020 election looms.

"Managing plastics has become a grand and complex environmental challenge, and plastic packaging clearly warrants current efforts on reductions and coordinated material recovery and recycling," said Gregory Keoleian, senior author of a paper published Aug. 25 in the journal Environmental Research Letters.

COVID-19 is a wicked problem for policy makers internationally as the complexity of the pandemic transcends health, environment, social and economic boundaries. Many countries are focusing on two key responses, namely virus containment and financial measures, but fail to recognise other aspects. The systems approach, however, enables policy makers to design the most effective strategies and reduce the unintended consequences. To achieve fundamental change, it is imperative to firstly identify the "right" interventions (leverage points) and implement additional measures to reduce negative consequences. To do so, a preliminary causal loop diagram of the COVID-19 pandemic was designed to explore its influence on socio-economic systems. In order to transcend the "wait and see" approach, and create an adaptive and resilient system, governments need to consider "deep" leverage points that can be realistically maintained over the long-term and cause a fundamental change, rather than focusing on "shallow" leverage points that are relatively easy to implement but do not result in significant systemic change