Selected Papers from PNAS (April 7)

We launch a selection of papers from representative journals in each issue, aiming to let researchers keep abreast of the latest developments in research in this field and grasp the pulse of world science.

The following is a selection of papers in the latest issue of the well-known comprehensive journal "PNAS" on April 7, 2015.

Women participate in the science, technology, engineering and mathematics (STEM) community with a large number of female peers

One study found that the presence of female counterparts in science, technology, engineering and math (STEM) work teams may improve the motivation, engagement and career aspirations of female science, technology, engineering and math (STEM) students. Fewer women than men enter science, technology, engineering and math (STEM) fields, and more women leave these fields, resulting in only 1 in 4 of the science, technology, engineering and math (STEM) workforce being women. Nilanjana Dasgupta and colleagues examined whether the gender composition of students' work teams in engineering affects the motivation and participation of girls in science, technology, engineering and mathematics (STEM) settings. The authors divided 120 female undergraduate engineering students into groups of 4 people with different gender compositions, namely female majority, male majority, or gender average. When they collaborated as a team on a task solving an engineering problem, women's behavior was measured. Panelists also answered questions about confidence, motivation for their performance, and gender stereotypes in engineering. Freshmen in predominantly female and gender-equal groups reported lower levels of anxiety than first-year females in female minority groups, while upperclassmen did not report any anxiety based on their group composition. However, girls in all grades participate more verbally in predominantly female groups than in groups with a female minority and gender equals. Girls in gender-equivalent and female-majority groups also had higher self-reported self-confidence and career aspirations than women-majority groups, regardless of how they understood gender stereotypes in engineering. The authors say that creating an environment where women science, technology, engineering and math (STEM) students join a high proportion of women may encourage women to stay in science, technology, engineering and math (STEM) fields.

论文 #14-22822: “Female peers in small work groups enhance women’s motivation, verbal participation, and career aspirations in engineering,” 作者Nilanjana Dasgupta, Melissa McManus Scircle和 Matthew Hunsinger.

Brain network analysis reveals centers and "rich clubs"

Through network analysis of axonal connections, the researchers provided a topological map of cognitively related neuronal connections in the rat cerebral cortex. The process of describing the tissue of the rodent cortex is often based on the connections obtained from functional studies and the skull above the reference cortex. To obtain a topological map of the connections that are critical to cognition, Larry Swanson and colleagues conducted a network analysis of more than 16,000 reported axonal connections in the rat cerebral cortex. The authors reported that 73 cortical regions may be clustered into four histologically distinct units in a shell-core configuration, two units including visual, auditory, and taste-sense regions that make up the core, and two other units, including the anterior cingulate gyrus, olfactory zone, and some parts of the hippocampus. In areas with strong connectivity, a continuous cortical patch consisting of exostory, parasorfactory, and lateral intraorfactory cortex regions involving Alzheimer's disease and epilepsy appears as a network center. The authors also identified centers of dense interconnection, which represent the so-called "club of the rich." For example, it was found that the lateral infestory area belonged to such a wealthy club with the most cortical connections. In addition, statistical analysis raises an interesting possibility that certain pathways of information flow in the cortex may be partially genetically prearranted. The authors say the findings could serve as a fulcrum for mapping cognitively-related cortical connections at the mammalian neuronal type and individual neural levels.

Paper #15-04394: "Architecture of the cerebral cortical association connectome underlying cognition," by Mihail Bota et al

U.S. Biodiversity Conservation Priorities

One study found that designated protected land areas within the United States are currently not adequately protecting natural species ranges that are vulnerable to development and habitat erosion. The establishment of protected areas has proven effective in protecting natural ecosystems and species biodiversity, and it has been implemented globally. To identify future U.S. habitat conservation priorities, Clinton N. Jenkins and colleagues compared biodiversity patterns in the United States with protected area distribution. The authors overlaid a map of the diversity of non-extinct native mammals, birds, reptiles and amphibians, freshwater fish, and tree species in the continental United States on top of a map of currently protected areas. This map overlay reveals that most of the protected land is located in the western United States, while most of the vulnerable species are located in the southeastern United States, suggesting that protected areas often do not coincide with areas with endemic species, leaving many species vulnerable to extinction. To improve the protection of ecosystems as well as vulnerable species, the authors recommend several strategies. These strategies include prioritizing the establishment of land reserves in specific areas of the southeastern United States, California, and Texas, encouraging private landowner participation in conservation projects, and improving assessments of the distribution and endemic phenomena of reptiles and freshwater fish.

论文 #14-18034: “US-protected lands mismatch biodiversity priorities,” 作者Clinton N. Jenkins, Kyle S. Van Houtan, Stuart L. Pimm和Joseph O. Sexton.

Agriculture with caries

An analysis of copy number variation in the human salivary lectin gene DMBT1 revealed that DMBT1 is a rapidly mutated gene whose degree of copy number variation is correlated with the transition to an agricultural lifestyle, suggesting that environmental changes that accompany the transition to agriculture may increase the risk of dental caries by influencing the evolution of the DMBT1 gene. The DMBT1 gene encodes a salivary protein that regulates the attachment of bacteria that cause tooth cavities to teeth.

论文 #14-16531: “Evolution of the rapidly mutating human salivary agglutinin gene (DMBT1) and population subsistence strategy,” 作者 Shamik Polley 等人

Community stigma and economic transactions

An experimental study conducted at online marketplaces in 12 major U.S. metropolitan areas found that sellers from lower-status communities posted items that received fewer responses than sellers from higher-status communities posting the same items, suggesting that community stigma can affect economic transactions.

论文 #14-14139: “Effect of neighborhood stigma on economic transactions,” 作者 Max Besbris, Jacob William Faber, Peter M. Rich和Patrick Sharkey.

Imitates rare earth magnetism

One study found that boron-doped lanthanum and neodymium atomic clusters have a similar number of unpaired electrons and a similar magnetic moment to rare earth elements with the same valence of electrons, suggesting that clusters of atoms may have the ability to mimic the magnetic properties of expensive rare earth elements.

论文 #15-04714: “Mimicking the magnetic properties of rare earth elements using superatoms,” 作者Shi-Bo Cheng, Cuneyt Berkdemir和A. W. Castleman, Jr.

Increasing mammal size

One study found that phylogenetic analysis of the 11 largest extant mammals revealed rapid evolution of 10 of these 11 orders toward larger sizes, most likely the result of selection pressure, which is juxtaposed with similar trends observed in the fossil record, and demonstrated that existing taxonomies may provide insights into evolutionary processes.

论文 #14-19823: “Adaptive evolution toward larger size in mammals,” 作者 Joanna Baker, Andrew Meade, Mark Pagel和Chris Venditti.

Evolution of the way taro snails eat

One study found that behavioral, molecular, and phylogenetic analysis of a worm-eating taro snail, the red brick taro snail, revealed the presence of a venom toxin called δ-taro toxin, which acts on nerve cells in vertebrates and is similar to a venom toxin found in fish-eating taro species, suggesting that this venom toxin made possible the evolutionary transition of taro snails from preying on worms to preying on fish.

论文 #14-24435: “Insights into the origins of fish hunting in venomous cone snails from studies of Conus tessulatus,” 作者Joseph W. Aman 等人

Possible therapy for the treatment of Alzheimer's disease with stroke medications

One study found that treating a mouse model of Alzheimer's disease with edaravone, a drug used to treat acute ischemic stroke, reduced β amyloid peptide deposition, reduced oxidative stress, reduced neuroinflammation, neuronal loss, and synaptic dysfunction, and reversed behavioral deficits in mice suggested that edaravone may represent a potential therapy for Alzheimer's disease.

Paper #14-22998: "Edaravone alleviates Alzheimer's disease-type pathologies and cognitive deficits," by Shu-Sheng Jiao et al

Cortical activity and consciousness

One study found that the magnetoencephalogram and EEG of 12 individuals observing visual stimuli revealed a decrease in the rate of variability of neuronal impulses in the cerebral cortex after stimulation, while EEG records from 116 individuals with brain injuries revealed that some degree of neuronal impulse variability during auditory stimulation was consistent with each individual's level of consciousness, suggesting that the stability of cortical activity may indicate the ability of individuals to perceive consciousness.

论文 #14-18730: “Cortical activity is more stable when sensory stimuli are consciously perceived,” 作者Aaron Schurger, Ioannis Sarigiannidis, Lionel Naccache, Jacobo D. Sitt和 Stanislas Dehaene.

Carbon emissions on the road

A study that took a high-resolution inventory of carbon dioxide emissions from transportation on the road found that urban areas likely accounted for 63 percent of U.S. road emissions in 2012, and that as population density increases nonlinearly, suggesting that the effectiveness of limiting emissions through smart growth policies may be strongly dependent on existing population density.

论文 #14-21723: “Cities, traffic, and CO2: A multidecadal assessment of trends, drivers, and scaling relationships,” 作者Conor K. Gately, Lucy R. Hutyra, 和Ian Sue Wing.

Cortical-cardiac activity during asphyxia

A study of rats undergoing experimental asphyxia found an increase in functional cortical connections during asphyxia, the immediate release of a neurotransmitter, and the activation of a brain-heart connection that can interfere with it, delaying end-stage ventricular fibrillation and prolonging detectable brain activity.

Paper #14-23936: "Asphyxia-activated corticocardiac signaling accelerates onset of cardiac arrest," by author Duan Li et al

Mechanical disguise of the lattice void

One study found that, in the case of preserving the connections between lattice points, the direct transformation of points on a 2D elastic lattice can effectively direct the mechanical pressure near the lattice void, so that the elastic properties of the lattice behave under pressure as if the void does not exist.

Paper #15-01240: "Mechanical cloak design by direct lattice transformation," by Tiemo Bückmann, Muamer Kadic, Robert Schittny and Martin Wegener.

The flow of information in social interactions

A study of 76 people scanned by a connected fMRI scanning device while transmitting nonverbal information in pairs found that the flow of information between the sender and receiver involved cross-brain connectivity between the temporal apex brain regions of the pair members suggested a measure of coupling between the subjects' brains, which was related to the size of the social networks that these subjects actually lived.

论文 #14-21831: “Information flow between interacting human brains: Identification, validation, and relationship to social expertise,” 作者Edda Bilek 等人

Fish sound range during the day and at night

A study of the recording of sounds produced by a school of fish found that there was a difference in the vocal activity of fish that were active during the day and at night, and that the frequency of sound signals during the day overlapped greater than the frequencies of sound signals at night, suggesting that unique sound signals were more important for nocturnally active fish that were deprived of visual cues than fish that were active during the day.

论文 #14-24667: “Environmental constraints drive the partitioning of the soundscape in fishes,” 作者Laetitia Ruppé 等人