Contents
23 June 2017
Vol 356, Issue 6344
Vol 356, Issue 6344
Contents
This Week in Science
Editorial
Editors' Choice
Products & Materials
- New Products
A weekly roundup of information on newly offered instrumentation, apparatus, and laboratory materials of potential interest to researchers.
In Brief
In Depth
- Drowned wildebeest provide ecological feast
Mass migration boosts the productivity of an African river ecosystem.
- A division of labor in cells' protein factories
Ribosomes may specialize to produce select proteins.
- Texas signals support for unproven stem cell therapies
State aims to offer desperately ill patients more options.
- East Africa turmoil imperils giraffes
Slow reproduction compounds impacts of poaching and habitat loss.
- New haul of distant worlds casts doubt on Planet Nine
Icy bodies show no sign of giant's gravitational influence.
- Tallying the tropical toll on trees from lightning
It's a slow death, but bolts still slay rainforest trees.
- A top mathematician joins the Macron revolution
New National Assembly member Cédric Villani sees a “unique and extraordinary” chance to reform France.
Feature
- The footprints of giants
Paleontologist Xing Lida is racing China's rapid growth to find the tracks of dinosaurs and map their ancient habitats.
- Trial balloons
Companies selling stratospheric balloon flights offer scientists a cheap avenue to the edge of space.
Working Life
Letters
Books et al.
Policy Forum
- Brains, environments, and policy responses to addiction
Reward and decision-making circuitry are critical
Perspectives
- Fast exoskeleton optimization
An algorithm optimizes exoskeleton walking assistance in 1 hour
- Ambient quantum optomechanics
Quantum kicks are delivered to a mechanical oscillator in air and at room temperature
- Building chromosomes without bricks
Has the textbook model of DNA compaction into chromosomes been upended?
- The most perfect thing, explained
The requirements of flight best explain the evolution of different egg shapes
- Locked and loaded for apoptosis
Switching between respiration and apoptosis in cytochrome c is finely balanced
Review
Research Articles
- An environment-dependent transcriptional network specifies human microglia identity
Single-cell sequencing of brain microglia reveals ex vivo and in vitro differences in transcription.
- A global brain state underlies C. elegans sleep behavior
Brain imaging in nematode mutants reveals how a brain switches between alert wakefulness and sleep.
- Avian egg shape: Form, function, and evolution
Egg shape is driven by adaptations for flight, not life history or nesting habitat.
- Quantum and isotope effects in lithium metal
Lithium’s ground state has a face-centered cubic structure, and quantum effects alter the phase diagram between the 6Li and 7Li isotopes.
Reports
- Breaking Lorentz reciprocity to overcome the time-bandwidth limit in physics and engineering
Asymmetric materials provide the prospect of designing high–quality-factor devices with high bandwidth.
- Quantum correlations from a room-temperature optomechanical cavity
An optomechanical system containing a Si3N4 nanobeam is used to tease out the effects of quantum backaction.
- On the generation of solar spicules and Alfvénic waves
Simulations explore how spicules form in the solar atmosphere.
- A catalytic fluoride-rebound mechanism for C(sp3)-CF3 bond formation
A gold complex forms carbon-trifluoromethyl bonds via borane-catalyzed cleavage and reformation of a C–F bond.
- Metalloprotein entatic control of ligand-metal bonds quantified by ultrafast x-ray spectroscopy
The local structure of cytochrome c enhances the strength of an iron-sulfur bond in the active site by 4 kilocalories per mole.
- Human-in-the-loop optimization of exoskeleton assistance during walking
An exoskeleton control system can optimize itself by measuring and minimizing human energy use during walking.
- Mitotic chromosome assembly despite nucleosome depletion in Xenopus egg extracts
Mitotic-like chromosomes with condensin-containing axes can be assembled in the near-absence of nucleosomes.
- Local protein kinase A action proceeds through intact holoenzymes
Detailed monitoring reveals how a cyclic AMP–dependent protein kinase really works.
- Assembly principles and structure of a 6.5-MDa bacterial microcompartment shell
The crystal structure of a bacterial microcompartment shell reveals how it is put together.
From the AAAS Office of Publishing and Member Services
About The Cover
COVER Birds lay eggs in a diverse array of colors, patterns, sizes, and shapes, as seen in this assortment from the Western Foundation of Vertebrate Zoology collection. An investigation by Stoddard et al. reveals that egg shape is related to flight ability in birds, overturning classic theories. Additionally, the egg’s flexible membrane—not the shell—might be responsible for the great variety of egg shapes. See pages 1234 and 1249.
Photo: © Frans Lanting