Selecting the most successful strategy

1476 27 JUNE 2014 • VOL 344 ISSUE 6191 sciencemag.org SCIENCE

PH

OT

OS

: (T

OP

TO

BO

TT

OM

) E

YE

OF

SC

IEN

CE

/S

CIE

NC

E S

OU

RC

E;

NO

RB

ER

T W

U/G

ET

TY

IM

AG

ES

SENSORY BIOLOGY

How hawkmoths sniff out a flower Pollinators such as butterflies

and bees are the true targets

of the flower odors we love

so much. Though we might

imagine insects “following their

noses,” the wealth of odors in

the real world can drown out

the smell of a flower, making it

hard to find. Riffel et al. found

that hawkmoths find angel’s

trumpets by creating a neuronal

picture within their antennal

lobe, the part of the moth brain

that receives olfactory signals

from the antennae (see the

Perspective by Szyszka). The

Edited by Stella HurtleyI N SC IENCE J O U R NA L S

RESEARCHYeast evolves along different paths toward the same goal Kryazhimskiy et al. p. 1519

picture represents both the

flower and the background

odors. Finding a flower involves

a complex reading of both

background and target odors,

and changes in the background

odors—including human

pollutants—can hinder the

process. — SNV

Science, this issue p. 1515; see also p. 1454

EARLY ANIMALS

Building coral reefs in ancient times540 million years ago, in the

dawn before the Cambrian

explosion, evolution was setting

the stage for the global rise of

animals. Before they took over

the seas, the earliest animals

developed strategies to defend

themselves against preda-

tors. These strategies, which

remain common today, include

forming skeletons and building

reefs. Penny et al. discovered

a massive fossil reef deposit in

Namibia made up of tiny cone-

shaped early animals known as

Cloudina. The reef, which is 20

million years older than other

ancient reefs, was probably

formed as the Cloudina adapted

to benefit from reefs, which pro-

tect the animals and allow them

to feed more efficiently. — NW

Science, this issue p. 1504

QUANTUM METROLOGY

Measuring tiny forces with atomic cloudsFor projects such as detecting

gravity waves, physicists need

to measure tiny forces precisely.

Schreppler et al. developed an

extremely sensitive method

for force measurement. They

applied a known force on a cloud

of ultracold rubidium atoms

in an optical cavity. The force

caused the atoms to oscillate,

and the researchers used opti-

cal measurements to monitor

the motion. Under optimal

conditions, the authors could

measure forces with a level

of sensitivity only four times

NONHUMAN GENETICS

Only one way to make an electric organ?

Electric fish have independently evolved electric organs

that help them to communicate, navigate, hunt, and

defend themselves. Gallant et al. analyzed the genome

of the electric eel and the genes expressed in two other

distantly related electric fish. The same genes were

recruited within the different species to make evolutionarily

new structures that function similarly. — LMZ


himskiy et al. p 1

n e

ffere same goal g

p. 1519

Published by AAAS

on

June

30,

201

4w

ww

.sci

ence

mag

.org

Dow

nloa

ded

from

o

n Ju

ne 3

0, 2

014

ww

w.s

cien

cem

ag.o

rgD

ownl

oade

d fr

om

on

June

30,

201

4w

ww

.sci

ence

mag

.org

Dow

nloa

ded

from

http://www.sciencemag.org/



27 JUNE 2014 • VOL 344 ISSUE 6191 1477SCIENCE sciencemag.org

PH

OT

OS

: (T

OP

TO

BO

TT

OM

) S

HA

NN

ON

KR

ING

EN

/F

LIC

KR

; U

LR

ICH

J. L

OR

EN

Z A

ND

AH

ME

D H

. ZE

WA

IL/C

ALT

EC

H

worse than the fundamental

limit imposed by the Heisenberg

uncertainty principle. — JS


VIRUS ENTRY

How Lassa virus breaks and entersLassa virus, which spreads from

rodents to humans, infecting

about half a million people every

year, can lead to deadly hemor-

rhagic fever. Like many viruses,

Lassa virus binds to cell surface

receptors. Jae et al. now show

that to enter a cell, the virus

requires a second receptor, this

one inside the infected cell. This

requirement sheds light on the

“enigmatic resistance” of bird

cells to Lassa virus observed

three decades ago. Although

bird cells have the cell surface

receptor, the intracellular

receptor cannot bind the virus,

stopping it in its tracks. — SMH


HUMAN COGNITION

Selecting the most successful strategy The brain’s prefrontal cortex

helps us to make decisions in

an uncertain and constantly

changing environment. Donoso

et al. present a model of human

reasoning as an algorithm imple-

mented in the prefrontal cortex

(see the Perspective by Hare).

Brain-imaging experiments sup-

ported this model. Depending

on the prevailing circumstances,

human reasoning can either

adapt ongoing behavioral

strategies or switch to previously

learned strategies. Only when

neither approach is appropri-

ate will the brain create new

strategies. — PRS

Science, this issue p. 1481, see also p. 1446

CANCER

Old drug learns new anticancer trickCancer researchers have

been trying to develop drugs

that inhibit angiogenesis, the

Edited by Kristen Mueller

and Jesse SmithIN OTHER JOURNALS

CANCER

Long unwinding road to cancer treatment Cancer chemotherapy is infa-

mous for harming healthy cells.

This collateral damage causes

the side effects that range from

unpleasant (such as hair loss) to

life-threatening (such increased

susceptibility to infection). They

can be particularly devastating

for elderly patients. Promising

new data may one day lead to

a safer treatment for a type of

acute myeloid leukemia, which

first strikes patients at age

66, on average. Mazurek et al.

found that when they blocked

mouse genes from express-

ing an enzyme called DDX5,

the leukemia cells died, but

healthy bone-marrow cells were

unharmed. DDX5 made the

cancer cells proliferate; inhibiting

DDX5 made the cells accumulate

toxic molecules called reactive

oxygen species, which contrib-

uted to cancer cell death. — PAK

Cell Rep. 7, 10.1016/j.celrep.2014.05.010 (2014).

AGING

Metformin’s recipe for a long lifeMetformin, a drug commonly

prescribed to treat type 2

diabetes, has side effects, but

some of these are beneficial, such

as fighting certain cancers and

increasing longevity. By studying

the worm Caenorhabditis elegans,

formation of new blood vessels

that nourish a tumor and allow

it to grow. A few drugs that fight

angiogenesis are now used for

some cancers, but they are not

always effective. Xu et al. report

a potential addition to the anti-

angiogenic armamentarium:

nonsteroidal anti-inflammatory

agents such as celecoxib, familiar

remedies for arthritis. In mice,

celecoxib inhibits blood vessel

growth by a different mecha-

nism than existing angiogenesis

inhibitors. A combination of the

two types of drugs was particu-

larly effective in reducing tumor

growth and spread. — YN

Sci. Transl. Med. 6, 242ra84 (2014).

NANOFLUIDICS

Watching lead flow at the nanoscaleMicrofluidic devices have

recently become useful in com-

mercial chemical synthesis. But

what about fluid dynamics at

the nanometer scale? Lorenz

and Zewail used an electron

microscope with nanosecond

time resolution to capture

images of molten lead flowing

through a nanotube. They flash-

melted the metal with a laser

pulse to begin their flow mea-

surements at a precise time

point. The experiments offered

insights into viscous friction as

well as heat-transfer dynamics

in a channel one-thousandth as

wide as a strand of hair. — JSY


MATERIALS SCIENCE

Getting in shape to stay dry longer

Many textured surfaces commonly found in the natural

world, such as a rose petal, repel liquids extremely well.

Taking a clue from Mother Nature, designers have begun

to routinely incorporate surface textures into products

ranging from waterproof outdoor clothing to self-clean-

ing windows. However, under high humidity or pressure, liquid

can infiltrate some textured surfaces and reduce their super-

hydrophobic properties. Checco et al. used x-rays to probe the

interface region between liquid and a variety of textured silicon

surfaces to show that the specific structure of a textured coat-

ing affects how the coating fails. This strategy could facilitate

the rational design of better water-repellent coatings. — ISO

Phys. Rev. Lett. 112, 216101 (2014).

Conceptual view of molten lead

flowing through zinc oxide nanotubes.

A rose petal’s

textured surface

effectively repels water.

Published by AAAS

SCIENCE sciencemag.org 27 JUNE 2014 • VOL 344 ISSUE 6191 1478-B

RESEARCH

BATTERIES

Watching battery materials in actionWhen batteries get rapidly

charged and discharged

repeatedly, they will often stop

working. This is especially true

when the cycling changes the

crystal structure of the battery

components. Liu et al. exam-

ined the structural changes in

components of a type of lithium

battery (see the Perspective

by Owen and Hector). Their

findings explain why LiFePO4

delivers unexpectedly good

electrochemical performances,

particularly during rapid

cycling. — MSL

Science, this issue p. 1480; see also p. 1451

VALLEYTRONICS

Using the valleys in monolayer MoS

2The electronic structure of the

two-dimensional material MoS2

has two distinct “valleys” of

energy that may help to carry

information in future electronic

devices. Mak et al. observed

the so-called valley Hall effect

in a monolayer of MoS2. The

electrons from different valleys

moved in opposite directions

across the sample, with one

valley being overrepresented

with respect to the other. The

scientists achieved this by shin-

ing circularly polarized light on

the material, which created an

imbalance in the population of

the two valleys. The findings may

enable practical applications in

the newly formed field of val-

leytronics. — JS


MACHINE LEARNING

Discerning clusters of data pointsCluster analysis is used in many

disciplines to group objects

according to a defined measure

of distance. Numerous algo-

rithms exist, some based on the

analysis of the local density of

data points, and others on pre-

defined probability distributions.

Rodriguez and Laio devised a

method in which the cluster

centers are recognized as local

density maxima that are far

away from any points of higher

density. The algorithm depends

only on the relative densi-

ties rather than their absolute

values. The authors tested the

method on a series of data sets,

and its performance compared

favorably to that of established

techniques. — JS


GAS FORMATION

Making of methane deep undergroundTechnologies such as hydraulic

fracturing, or “fracking,” can now

extract natural gas from under-

ground reservoirs. Within the gas,

the ratio of certain isotopes holds

clues to its origins. Stolper et al.

analyzed a wide range of natural

gas, including samples from

some of the most active fracking

sites in the United States. Using a

“clumped isotope” technique, the

authors could estimate the high

temperatures at which methane

formed deep underground, as

well as the lower temperatures

at which ancient microbes pro-

duced methane. The approach

can help to distinguish the

degree of mixing of gas from

both sources. — NW


MEMBRANE TRAFFICKING

Supplying power: Right time, right placeCell membranes are very flexible

and easily molded to shape;

however, to physically pinch off a

membrane vesicle from a mem-

brane tube still requires power.

A type of molecular machine

known as dynamin is involved

in this sort of membrane

remodeling. Dynamins use

guanosine triphosphate (GTP)

rather than the more commonly

used cellular energy source

adenosine triphosphate to work.

Boissan et al. now show that

two separate dynamins found in

the cytoplasm or the mitochon-

dria both use the same sort of

enzyme—nucleoside diphos-

phate kinases—to provide GTP

at just the right time and the

right place to power membrane

fission. — SMH


MICROBIAL EVOLUTION

Clouding evolution’s crystal ballBecause of a sort of mutation

buffering process, different start-

ing mutations can tend to end up

with similar overall affects on an

organism’s fitness. Kryazhimskiy

et al. evolved lines of yeast, each

originating from distinct single

genotypes, under the same

selective regimen. A subset

of clones from these adapted

populations was subjected to

fitness assays and sequenced.

Populations with lower initial fit-

ness, adapted more rapidly than

populations with higher initial

fitness, so that in the end the

fitness levels were similar. — LMZ


Edited by Stella HurtleyALSO IN SCIENCE

Published by AAAS

Documents

Selecting the most successful strategy