The sap also rises

Tree hydraulics: how sap rises

Trees transport water from roots to crown—a height that can exceed 100 m. The physics of tree hydraulics can be conveyed with simple fluid dynamics based upon the Hagen–Poiseuille equation and Murray’s law. Here the conduit structure is modelled as conical pipes and as branching pipes. The force required to lift sap is generated mostly by transpiration or capillary action; we investigate the ef...

World medical schools: The sum also rises

OBJECTIVE There is a worldwide shortage of doctors, which is true in most countries and on most continents. To enumerate the number of medical schools in the world at two different times, showing the trends and relating this to population is a beginning. The number is actually going up and has done so for some time; this has increased the supply of physicians and broadened healthcare delivery. ...

Aral Sea basin: a sea dies, a sea also rises.

The thesis of this article is quite different from many other theses of papers, books, and articles on the Aral Sea. It is meant to purposely highlight the reality of the situation in Central Asia: the Aral Sea that was once a thriving body of water is no more. That sea is dead. What does exist in its place are the Aral seas: there are in essence three bodies of water, one of which is being pur...

Introduction - the State Also Rises: the Roots of Contemporary State Activism

Estimating Intergenerational Mobility With Grouped Data: A Critique of Clark’s the Son Also Rises

This article distinguishes three measures of intergenerational economic mobility that emerge when the population is divided into groups: overall individual mobility, within-group mobility, and between-group mobility. We clarify their properties and the relationship between them. We then evaluate Clark’s use of surname between-group persistence as a preferred measure of intergenerational mobilit...