Journals


Human influence on the seasonal cycle of tropospheric temperature

Science

The simulated response of the seasonal cycle to historical changes in human and natural factors has prominent mid-latitude increases in the amplitude of TAC. These features arise from larger mid-latitude warming in the summer hemisphere, which appears to be partly attributable to continental drying. Because of land-ocean differences in heat capacity and hemispheric asymmetry in land fraction, mid-latitude increases in TAC are greater in the Northern Hemisphere than in the Southern Hemisphere. Qualitatively similar large-scale patterns of annual cycle change occur in satellite tropospheric temperature data. We applied a standard fingerprint method to determine (i) whether the pattern similarity between the model "human influence" fingerprint and satellite temperature data increases with time, and (ii) whether such an increase is significant relative to random changes in similarity between the fingerprint and patterns of natural internal variability.


Emergence of coexisting ordered states in active matter systems

Science

Active systems can produce a far greater variety of ordered patterns than conventional equilibrium systems. In particular, transitions between disorder and either polar- or nematically ordered phases have been predicted and observed in two-dimensional active systems. However, coexistence between phases of different types of order has not been reported. We demonstrate the emergence of dynamic coexistence of ordered states with fluctuating nematic and polar symmetry in an actomyosin motility assay. Combining experiments with agent-based simulations, we identify sufficiently weak interactions that lack a clear alignment symmetry as a prerequisite for coexistence.


Exploring cytoskeletal diversity in neurons

Science

Often in biology, form follows function. For example, the ability of neurons to receive, process, and transmit information depends on their polarized organization into axons and dendrites. The cytoskeleton and associated motor proteins shape cells and establish spatial organization. Microtubules (MTs) and actin are core components of the cytoskeleton and are assembled through head-to-tail polymerization of α- and β-tubulin heterodimers and actin monomers, respectively, resulting in asymmetric, polarized polymers with two different ends, called plus and minus ends. The spatially regulated polymerization of MTs and actin can drive morphological transitions, such as local protrusion of the plasma membrane, to drive cell migration or the development of specialized extensions, such as axons or dendrites and their branches.


Hackers easily fool artificial intelligences

Science

Last week, at the International Conference on Machine Learning (ICML) in Stockholm, a group of researchers described a turtle they had 3D printed. Most people would say it looks just like a turtle, but an artificial intelligence (AI) algorithm that can normally recognize turtles saw it differently. Most of the time, it thought the turtle was a rifle. Similarly, it saw a 3D-printed baseball as an espresso. These are examples of "adversarial attacks"--subtly altered images, objects, or sounds that fool AIs without setting off human alarm bells.


AI Magazine

AI Magazine

The purpose of AI Magazine is to disseminate timely and informative articles that represent the current state of the art in AI and to keep its readers posted on AAAI-related matters. The articles are selected for appeal to readers engaged in research and


Programming self-organizing multicellular structures with synthetic cell-cell signaling

Science

A common theme in the self-organization of multicellular tissues is the use of cell-cell signaling networks to induce morphological changes. We used the modular synNotch juxtacrine signaling platform to engineer artificial genetic programs in which specific cell-cell contacts induced changes in cadherin cell adhesion. Despite their simplicity, these minimal intercellular programs were sufficient to yield assemblies with hallmarks of natural developmental systems: robust self-organization into multidomain structures, well-choreographed sequential assembly, cell type divergence, symmetry breaking, and the capacity for regeneration upon injury. The ability of these networks to drive complex structure formation illustrates the power of interlinking cell signaling with cell sorting: Signal-induced spatial reorganization alters the local signals received by each cell, resulting in iterative cycles of cell fate branching. These results provide insights into the evolution of multicellularity and demonstrate the potential to engineer customized self-organizing tissues or materials.


Metal-free three-dimensional perovskite ferroelectrics

Science

Inorganic perovskite ferroelectrics are widely used in nonvolatile memory elements, capacitors, and sensors because of their excellent ferroelectric and other properties. Organic ferroelectrics are desirable for their mechanical flexibility, low weight, environmentally friendly processing, and low processing temperatures. Although almost a century has passed since the first ferroelectric, Rochelle salt, was discovered, examples of highly desirable organic perovskite ferroelectrics are lacking. These attributes make it attractive for use in flexible devices, soft robotics, biomedical devices, and other applications.


Learning from different disciplines

Science

If you knocked on Heaven's door, and God greeted you, what question would you ask? What is the nature of human consciousness, and how can it be expanded? Where does the Universe begin and end? What is time, and why isn't it constant? The Most Unknown, a documentary film in the Simons Foundation Science Sandbox series, takes the viewer on a fantastical journey of nine scientists as they intrepidly knock on Heaven's door.


Reinventing Staten Island - Issue 62: Systems

Nautilus

When the Dutch arrived in New York Harbor in 1609, Staten Island--or Staaten Eylandt, as they named it--was a wild wonderland, woodland in the middle and tidal salt marsh on the edges, populated by the local Lenape tribe, plus an embarrassment of natural riches: eels, bluefish, bitterns, herons, muskrats, ducks, clams, crabs, wild turkeys, porpoises, and more. Jutting midway into the island from the west coast, like a hook in the island's side, was the Fresh Kills estuary, a tidal wetland thriving with plants and critters, created by the retreat of the Wisconsin Ice Sheet some 17,000 years ago. After World War II, the bursting city of New York found itself with a trash problem. In 1948, the city started officially dumping its trash into the marshes and waters of Fresh Kills. What became America's first landfill was meant to be temporary, but it stuck. By 1955, it was the biggest landfill in the world--indeed, at 2,700 acres, it was the biggest human-made structure in the world. By 1991, the landfill contained 150 million tons of tightly packed garbage in more volume than could fill the Great Wall of China. Fresh Kills was wetland no more.


User Profile

AI Magazine

The purpose of AI Magazine is to disseminate timely and informative articles that represent the current state of the art in AI and to keep its readers posted on AAAI-related matters. The articles are selected for appeal to readers engaged in research and