- Avalanche Research
Cracking the code underlying snowslides
- Brent Grocholski
Dangerous snow avalanches require failure of a weak layer buried beneath an overlying cohesive slab of snow. Although this process is mostly understood for some avalanche scenarios, observations of low-angle triggered avalanches challenge the traditional models. Gaume et al. devised a model that better accounts for failure by including the complex interplay between the weak layer and the overlying snow slab. The model agrees well with field data and has the potential to substantially improve life-saving avalanche forecasting.
Cryosphere 10.5194/tc-11-217-2017 (2017).
- Political Science
Scientific curiosity versus polarization
- Barbara R. Jasny
Knowledge does not always change biases, and people tend to absorb information that fits their prejudices. However, rather than studying scientific knowledge, Kahan et al. studied scientific curiosity—the tendency to look for and consume scientific information for pleasure. Two sets of subjects, including several thousand people, were given questions about their interests and activities. Reactions to documentaries and to news stories that contained surprising or unsurprising material were also tracked. The more scientifically curious people were (regardless of their politics), the less likely they were to show signs of politically motivated reasoning. People with higher curiosity ratings were more willing to look at surprising information that conflicted with their political tendencies than people with lower ratings.
Adv. Polit. Psychol. 10.1111/pops.12396 (2017).
- Cell Biology
Dissecting the effects of APOE
- Stella M. Hurtley
Three APOE alleles are expressed in humans: APOE4 allele is the single most important genetic risk factor for Alzheimer's disease, APOE3 is neutral, and APOE2 is protective. Huang et al. suggest a mechanism for the predisposing effect of APOE4 and protective effect of APOE2. APOE is normally produced by glial cells that also secrete many other factors acting on neurons. When human neurons were cultured in the absence of glial cells, APOE stimulated a MAP kinase signaling cascade in neurons, which activated amyloid-β precursor protein (APP) transcription and amyloid-β secretion. In line with their effects on Alzheimer's disease, APOE4 appeared to be more potent in stimulating APP transcription and amyloid-β secretion than APOE3, which in turn was more potent than APOE2.
Cell 10.1016/j.cell.2016.12.044 (2017).
Vocalizations channeled by developmental affordances
- Pamela J. Hines
Like humans, marmoset monkey infants vocalize differently from adults. Maturation of vocalizations depends on parental feedback, as well as development of the vocal apparatus and cognitive controls. Teramoto et al. have set those parameters into a Waddington landscape to understand how the developing marmoset acquires the ability to make mature calls. Key to the theoretical approach is the concept of maximum entropy. Although growth in vocal tract length may lower the pitch, other vocalization changes are caused by changes in muscle control. But it is social feedback—the parental response—that determines just when an individual shifts from infant- to adult-style calls. As development progresses, the shape of the Waddington landscape changes, so that sounds that were formerly too difficult to produce become easier to make with maturity.
eLife 10.7554/eLife.20782 (2017).
Electrical detection of diamond defects
- Ian S. Osborne
Diamonds have many different kinds of defects, each type imbuing the crystal with a distinctive color. The quantum properties of the nitrogen vacancy defect are being intensely studied as vital components of future quantum sensing technologies. The defects behave as microscopic magnets with spin states that are highly sensitive to the minutest magnetic field variations. Although the spin state can be read out optically, the process is inefficient and requires a high-end optical setup. Hrubesch et al. present a technique based on pulsed photoionization and coherent electrical spin manipulation that allows the spin state of the defects to be read out electrically. Such a setup could prove simpler to implement in an integrated platform that is useful for technological applications.
Phys. Rev. Lett. 118, 37601 (2017).
Strengthening the remaining synapses
- Peter Stern
Working memory depends in part on the proper activation of neural circuits in a brain area called the dorsolateral prefrontal cortex (DLPFC). In primates, DLPFC performance during working memory tasks improves through adolescence. Synaptic pruning eliminates unwanted or imprecise connections and strengthens the remaining connections. Chung et al. found that the excitatory synapses on a crucial subgroup of interneurons in the monkey DLPFC also undergo pruning during adolescence. Such synapses are partially regulated by an enzyme called ErbB4. This enzyme exists in alternative splice variants. During development, there is a shift in the dominant alternative splice transcripts, which is accompanied by fewer but stronger excitatory synapses. Shifts in ErbB4 splicing thus modulate the pruning of excitatory synapses on these interneurons during maturation.
Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1610077114 (2017).
A less structured way to better hydrogels
- Marc S. Lavine
Hydrogels are composed of cross-linked polymers that are highly swollen with water. They are typically soft, squishy, and elastic, but they are not known for their strength or toughness. Gonzalez et al. show that unstructured proteins, namely, those that do not have folds or coils, can form the basis for strong, tough, and self-adhesive hydrogels. They genetically engineered Escherichia coli to produce elastic-like polypeptides with domains that are able to either covalently cross-link or form metal bonds with Zn2+ ions. The covalent cross-links provide the strength, and the reversible metal cross-links allow for the dissipation of energy and toughness when the hydrogel is stretched.
Adv. Mater. 10.1002/adma.201604743 (2017).