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<jats:p> A monthly roundup of recent news and projects of <jats:italic>Science</jats:italic> 's publisher, the American Association for the Advancement of Science. </jats:p>

<jats:title>Enduring Tolerance</jats:title> <jats:p> During an infection, the host organism deploys multiple defense strategies. Disease resistance, the process by which the immune system decreases pathogen burden is perhaps the most well-known, and certainly the mechanism that is best studied and understood. Other defense strategies range from pathogen avoidance, through tolerance of pathogen-induced tissue damage, and endurance of the overall pathogen burden. <jats:bold> Medzhitov <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="936" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1214935">936</jats:related-article> ) review the concept of disease tolerance and suggest that particularly in animals, it is an overlooked mechanism of host defense. </jats:p>

<jats:p>Individual components of rat brain nuclear pores can be almost as old as the animal itself.</jats:p>

<jats:title>Winging It</jats:title> <jats:p> Genes that explain phenotypic variation between species have only been identified within a handful of model organisms, which limits the scope and understanding of the genetics of phenotypic diversification. On investigating the phenotypic diversity in wing size among wasps of the genus <jats:italic>Nasonia</jats:italic> , <jats:bold>Loehlin and Werren</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="943" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1215193">943</jats:related-article> ) have identified the genetic basis of a morphological difference between two closely related species and showed how changes in regulatory elements have evolved to change expression of a single gene, <jats:italic>unpaired-like</jats:italic> ( <jats:italic>upd-like</jats:italic> ), a functionally conserved signaling gene. Overall, it appeared that significant morphological change was achieved through a series of relatively rapid, but small-scale changes. </jats:p>

<jats:title>Tunnel Barriers for Graphene Transistors</jats:title> <jats:p> Transistor operation for integrated circuits not only requires that the gate material has high-charge carrier mobility, but that there is also an effective way of creating a barrier to current flow so that the device can be switched off and not waste power. Graphene offers high carrier mobility, but the shape of its conduction and valence bands enables electron tunneling and makes it difficult to achieve low currents in an “off” state. <jats:bold> Britnell <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="947" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1218461">947</jats:related-article> , published online 2 February) have fabricated field-effect transistors in which a thin tunneling barrier created from a layered material—either hexagonal boron nitride or molybdenum disulfide—is sandwiched between graphene sheets. These devices exhibit on-off switching ratios of ≈50 and ≈10,000, respectively, at room temperature. </jats:p>

<jats:title>Paracrystalline</jats:title> <jats:p> Amorphous silicon has traditionally been represented by a continuous random network model in which there is no long-range ordering for the atoms, and some have less than fourfold coordination, which form dangling bonds—a type of defect. <jats:bold>Treacy and Borisenko</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="950" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1214780">950</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6071" page="929" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1218723">Gibson</jats:related-article> </jats:bold> ) used fluctuation electron microscopy to explain that models including regions of crystalline order are needed to fit the observed local variations in structure. Thus, on the 1- to 2-nanometer-length scale, this material should be thought of as having a paracrystalline structure containing localized crystalline regions. </jats:p>

<jats:title>When the Rain Comes</jats:title> <jats:p> When raindrops fall, frictional forces between the droplet and the surrounding air create a drag that limits the speed at which the raindrop can descend. This drag also dissipates some of the kinetic energy of the falling raindrops within the shear zones surrounding them and is a significant component of the atmospheric energy budget, according to <jats:bold>Pauluis and Dias</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="953" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1215869">953</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6071" page="925" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1219015">Frierson</jats:related-article> </jats:bold> ). Using data from satellites, they find that precipitation-induced energy dissipation is of the same magnitude as that caused by atmospheric turbulence and therefore that of a strengthened hydrological cycle, which is widely expected to occur as a result of climate warming and could have an impact on the strength of atmospheric circulation. </jats:p>

<jats:title>How Dry They Were</jats:title> <jats:p> How much rainfall failure contributed to the disintegration of classical Maya civilization? <jats:bold>Medina-Elizalde and Rohling</jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="956" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1216629">956</jats:related-article> ) analyzed records from three lakes and a stalagmite from the Yucatán Peninsula to quantify the change in precipitation that the region experienced between 800 to 1000 years A.D. Precipitation decreased episodically for up to a decade at a time and in total by as much as 40% during the 200 years of the civilization's fall, probably as a result of a reduction in summer tropical storm rainfall. This finding highlights the sensitivity of this region to modest reductions of rainfall that are projected by some climate model. </jats:p>

<jats:title>Warming and Shrinking</jats:title> <jats:p> In most mammals, individual body sizes tend to be smaller in warmer regions and larger in cooler regions. <jats:bold> Secord <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="959" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1213859">959</jats:related-article> ; see the Perspective by <jats:bold> <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" issue="6071" page="924" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1219233">Smith</jats:related-article> </jats:bold> ) examined a high-resolution 175,000-year record of equid fossils deposited over a past climate shift—the Paleocene-Eocene Thermal Maximum—for changes in body size. Using oxygen isotopes collected from the teeth of co-occurring mammal species to track prevailing environmental temperature, a clear decrease in equid body size was seen during 130,000 years of warming, followed by a distinct increase as the climate cooled at the end of the period. These results indicate that temperature directly influenced body size in the past and may continue to have an influence as our current climate changes. </jats:p>

<jats:title>Cashing Up</jats:title> <jats:p> Do small businesses in developing economies benefit from an infusion of cash or of capital, such as inventory or materials, and is the effect a momentary blip or a sustained expansion? <jats:bold> De Mel <jats:italic>et al.</jats:italic> </jats:bold> (p. <jats:related-article xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="doi" page="962" related-article-type="in-this-issue" vol="335" xlink:href="10.1126/science.1212973">962</jats:related-article> ) have extended their study of one-time cash or capital transfers to a group of randomized business owners in Sri Lanka to look at the status of the businesses 5 years later and find an increased likelihood of survival and higher profits for male-owned enterprises, but no significant effects on female-owned businesses. The authors suggest that capital transfers are more likely to be used by male-owned firms to grow the business, but more likely to be “cashed-out” from female-owned firms and diverted to household uses. </jats:p>