Proceedings of the Natural Academy of Sciences

Proceedings of the National Academy of Sciences RSS feed -- current issue
  • Space, time, and number in neonates [Psychological and Cognitive Sciences]
    [Apr 2014]

    A rich concept of magnitude—in its numerical, spatial, and temporal forms—is a central foundation of mathematics, science, and technology, but the origins and developmental relations among the abstract concepts of number, space, and time are debated. Are the representations of these dimensions and their links tuned by extensive experience, or...
    Categories: Journal Articles
  • Value and salience in the human brain [Psychological and Cognitive Sciences]
    [Apr 2014]

    A large body of evidence has implicated the posterior parietal and orbitofrontal cortex in the processing of value. However, value correlates perfectly with salience when appetitive stimuli are investigated in isolation. Accordingly, considerable uncertainty has remained about the precise nature of the previously identified signals. In particular, recent evidence suggests...
    Categories: Journal Articles
  • Exploiting polypharmacology [Systems Biology]
    [Apr 2014]

    Polypharmacology (action of drugs against multiple targets) represents a tempting avenue for new drug development; unfortunately, methods capable of exploiting the known polypharmacology of drugs for target deconvolution are lacking. Here, we present an ensemble approach using elastic net regularization combined with mRNA expression profiling and previously characterized data on...
    Categories: Journal Articles
  • In This Issue [This Week in PNAS]
    [Apr 2014]

    Breast cancer gene implicated in brain size control Deletion of BRCA1 within the neural stemcell/progenitor compartment (Nestin-CRE) in an E12.5 mouse embryo displays abnormally high levels of apoptosis as defined by activated Caspase 3 signal (green). The breast cancer susceptibility gene 1 (BRCA1) is a tumor suppressor gene known to...
    Categories: Journal Articles
  • Catch of the day: the HTL translocon [Biochemistry]
    [Apr 2014]

    Protein transport is a fundamental activity for all living cells and an exciting area for scientific exploration (1, 2). In bacteria, the process depends on the concerted action of at least three membrane-embedded components: the ubiquitous SecYEG complex that forms the polypeptide-conducting membrane pore, the essential YidC insertase that works...
    Categories: Journal Articles
  • Plasmid segregation by a moving ATPase gradient [Cell Biology]
    [Apr 2014]

    Unlike the mitotic segregation of eukaryotic sister chromatids, DNA partitioning in bacteria is still not well understood. Bacterial high–copy-number plasmids can be stably maintained by random distribution of their copies during cell division. In contrast, the faithful transmission of low–copy-number plasmids and many chromosomes depends on an active process mediated...
    Categories: Journal Articles
  • Diet, dementia, and diabetes [Medical Sciences]
    [Apr 2014]

    It is becoming abundantly clear that the insight into the pathological process of Alzheimer’s disease (AD) provided through autosomal dominant variants of the condition is only a partial one. The formation and aggregation of Aβ and the phosphorylation and aggregation of tau are clearly part of the core pathogenesis. However,...
    Categories: Journal Articles
  • Diverse cells at the origin of lung adenocarcinoma [Medical Sciences]
    [Apr 2014]

    Oncogenic mutations in Kirsten rat sarcoma viral oncogene homologue (K-RAS) are found in a broad range of aggressive cancers in many tissues and are common in the most prevalent form of lung cancer, adenocarcinoma (1). Despite knowledge of K-RAS mutations for many years, patients with K-RAS mutant tumors remain without...
    Categories: Journal Articles
  • How biological vision succeeds [Neuroscience]
    [Apr 2014]

    Biological visual systems cannot measure the properties that define the physical world. Nonetheless, visually guided behaviors of humans and other animals are routinely successful. The purpose of this article is to consider how this feat is accomplished. Most concepts of vision propose, explicitly or implicitly, that visual behavior depends on...
    Categories: Journal Articles
  • Multidimensional spectroscopy of photoreactivity [Chemistry]
    [Apr 2014]

    Coherent multidimensional electronic spectroscopy is commonly used to investigate photophysical phenomena such as light harvesting in photosynthesis in which the system returns back to its ground state after energy transfer. By contrast, we introduce multidimensional spectroscopy to study ultrafast photochemical processes in which the investigated molecule changes permanently. Exemplarily, the...
    Categories: Journal Articles
  • Unexpected trapping of particles at a T junction [Engineering]
    [Apr 2014]

    A common element in physiological flow networks, as well as most domestic and industrial piping systems, is a T junction that splits the flow into two nearly symmetric streams. It is reasonable to assume that any particles suspended in a fluid that enters the bifurcation will leave it with the...
    Categories: Journal Articles
  • Tuning threshold voltage of SWNT transistors [Engineering]
    [Apr 2014]

    Tuning the threshold voltage of a transistor is crucial for realizing robust digital circuits. For silicon transistors, the threshold voltage can be accurately controlled by doping. However, it remains challenging to tune the threshold voltage of single-wall nanotube (SWNT) thin-film transistors. Here, we report a facile method to controllably n-dope...
    Categories: Journal Articles
  • Metal availability and N isotope fractionation [Environmental Sciences]
    [Apr 2014]

    Biological nitrogen fixation constitutes the main input of fixed nitrogen to Earth’s ecosystems, and its isotope effect is a key parameter in isotope-based interpretations of the N cycle. The nitrogen isotopic composition (δ15N) of newly fixed N is currently believed to be ∼–1‰, based on measurements of organic matter from...
    Categories: Journal Articles
  • River discharge from satellite images and AMHG [Environmental Sciences]
    [Apr 2014]

    Rivers provide critical water supply for many human societies and ecosystems, yet global knowledge of their flow rates is poor. We show that useful estimates of absolute river discharge (in cubic meters per second) may be derived solely from satellite images, with no ground-based or a priori information whatsoever. The...
    Categories: Journal Articles
  • Marked clones in Drosophila mosaics [Genetics]
    [Apr 2014]

    Chimaeras, fanciful beasts that drew their force from being composed of parts of disparate animals, have stimulated our collective imagination for centuries. In modern terms, chimaeras are composite animals consisting of genetically distinct cell populations and are called “mosaics” if the different cell types have emerged from the same zygote....
    Categories: Journal Articles
  • Phase transitions in dense hydrogen and deuterium [Physics]
    [Apr 2014]

    Raman spectroscopy of dense hydrogen and deuterium performed to 325 GPa at 300 K reveals previously unidentified transitions. Detailed analysis of the spectra from multiple experimental runs, together with comparison with previous infrared and Raman measurements, provides information on structural modifications of hydrogen as a function of density through the...
    Categories: Journal Articles
  • Hybridization gap and Fano resonance in SmB6 [Physics]
    [Apr 2014]

    Hybridization between conduction electrons and the strongly interacting f-electrons in rare earth or actinide compounds may result in new states of matter. Depending on the exact location of the concomitant hybridization gap with respect to the Fermi energy, a heavy fermion or an insulating ground state ensues. To study this...
    Categories: Journal Articles
  • Displacive transformations in colloidal crystals [Physics]
    [Apr 2014]

    The degree to which DNA-linked particle crystals, particularly those composed of micrometer-scale colloids, are able to dynamically evolve or whether they are kinetically arrested after formation remains poorly understood. Here, we study a recently observed displacive transformation in colloidal binary superlattice crystals, whereby a body-centered cubic to face-centered cubic transformation...
    Categories: Journal Articles
  • Science icescapes [Science and Culture]
    [Apr 2014]

    Scientists will go to the ends of the earth for data. They will drop themselves on a featureless ice sheet to measure a temperature or float down a mosquito-infested river for a few tablespoons of water. Seattle-based photographer Chris Linder follows them and uses his camera to bring science’s epic...
    Categories: Journal Articles
  • Testing for executive function in gibbons [Inner Workings]
    [Apr 2014]

    It is a commonly held assumption that we humans have a unique thinking ability that distinguishes us from other animals. However, every time scientists have tested that assumption—whether testing for self-recognition in a mirror, the existence of language, problem-solving ability, knowing what another is thinking (or “theory of mind”), deception,...
    Categories: Journal Articles