Testing Foundations of Biological Scaling Theory Using Automated Measurements of Vascular Networks

Scientists have long sought to understand how vascular networks supply blood and oxygen to cells throughout the body. Recent work focuses on principles that constrain how vessel size changes through branching generations from the aorta to capillaries and uses scaling exponents to quantify these changes. Prominent scaling theories predict that combinations of these exponents explain how metabolic, growth, and other biological rates vary with body size. Nevertheless, direct measurements of individual vessel segments have been limited because existing techniques for measuring vasculature are invasive, time consuming, and technically difficult. We developed software that extracts the length, radius, and connectivity of in vivo vessels from contrast-enhanced 3D Magnetic Resonance Angiography. Using data from 20 human subjects, we calculated scaling exponents by four methods--two derived from local properties of branching junctions and two from whole-network properties. Although these methods are often used interchangeably in the literature, we do not find general agreement between these methods, particularly for vessel lengths. Measurements for length of vessels also diverge from theoretical values, but those for radius show stronger agreement. Our results demonstrate that vascular network models cannot ignore certain complexities of real vascular systems and indicate the need to discover new principles regarding vessel lengths

Extra dimensions, SN1987a, and nucleon-nucleon scattering data

One of the strongest constraints on the existence of large, compact, "gravity-only" dimensions comes from SN1987a. If the rate of energy loss into these putative extra dimensions is too high, then the neutrino pulse from the supernova will differ from that actually seen. The dominant mechanism for the production of Kaluza-Klein gravitons and dilatons in the supernova is via gravistrahlung and dilastrahlung from the nucleon-nucleon system. In this paper we compute the rates for these processes in a model-independent way using low-energy theorems which relate the emissivities to the measured nucleon-nucleon cross section. This is possible because for soft gravitons and dilatons the leading contribution to the energy-loss rate is from graphs in which the gravitational radiation is produced from external nucleon legs. Previous calculations neglected these mechanisms. We re-evaluate the bounds on toroidally-compactified "gravity-only" dimensions (GODs), and find that consistency with the observed SN1987a neutrino signal requires that if there are two such dimensions then their radius must be less than 1 micron.Comment: 24 pages, 5 figures. Minor changes to first two paragraphs of introductio

The T-shaped “axe” from Northeast Honduras: Observations on chronology and function of a pre Columbian stone tool

This paper provides a description and analysis of a distinctive type of pre-Columbian stone tool, usually termed a T-shaped axe, found almost exclusively in Northeast Honduras, Central America. There have been very few detailed or technical studies of lithics from Honduras. Early archaeological research and the current understanding of the regional prehistory are included, with Northeast Honduras viewed as a frontier zone located between the Mesoamerican and Isthmo-Columbian culture areas. Our study examines, in particular, a collection of these tools curated today at the Cambridge University Museum of Archaeology and Anthropology (CUMAA). The 39 (whole and fragmentary) specimens were collected between 1937 and 1939, from the Bay Islands, Northeast Honduras, but have never been published. This paper classifies the collection specimens into five varieties, based on morphology, with sample statistics, form dimensions, and illustrations provided for each. Manufacturing technology is primarily percussion flaking. The tool type is compared with similar specimens excavated and described from the Bay Islands and adjacent Honduran mainland, and with similar appearing implements from elsewhere in Central America. Insights about the possible age and function of these unusual, and distinctive, lithics are included. Based on preliminary macroscopic and microscopic analyses, it is concluded that the tools may have been employed as agricultural implements (hoes or spades), primarily for digging activities, rather than as axes or weapons used for cutting and slicing. It is most likely that these implements first appeared about 800 CE, and continued in use until at least 1400 CE. The tool type is most probably a local (not imported) product. More functional analysis is encouraged

A National Veterans Strategy: The Economic, Social and Security Imperative

This publication details the foundational logic supporting a call to action, related to a broad-based effort to articulate and institutionalize a National Veterans Strategy. We argue that coordinated, "whole-of-government" action toward this end is essential to meet the nation's most important economic, social, and security obligations. Furthermore, we contend that the second Obama administration, working in close collaboration with executive agencies, Congress, and the private sector, is well-positioned to act on what we perceive to be a historic opportunity -- capitalizing on both the foundations of veteran-focused policy and progress enacted over the past decade and the overwhelming public support for returning veterans and military families -- to craft and institutionalize a National Veterans Strategy.Our purpose is to provide a researched and logically-developed case for action that is grounded in this nation's social and cultural traditions and attuned to the practical realities of our contemporary economic and political climate

From Hadrons to Nuclei: Crossing the Border

The study of nuclei predates by many years the theory of quantum chromodynamics. More recently, effective field theories have been used in nuclear physics to ``cross the border'' from QCD to a nuclear theory. We are now entering the second decade of efforts to develop a perturbative theory of nuclear interactions using effective field theory. This work describes the current status of these efforts.Comment: 141 pages, 58 figs, latex. To appear in the Boris Ioffe Festschrift, ed. by M. Shifman, World Scientifi

Social class in the 21st century: an interview with Mike Savage

by Rebecca Mansell and Ronda Daniel ‘Social Class in the 21st Century’ is a new Penguin book written by Professor Mike Savage in collaboration with a team of sociologists, including the LSE’s Lisa Mckenzie, Sam Friedman and Daniel Laurison. We spoke to Mike Savage, who is also head of the LSE’s sociology department, about the new book, how the team collaborated and social class in London. As well as this, as a renowned social researcher, Mike gave us some pearls of wisdom to first year sociology students at the LSE