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Proceedings of the National Academy of Sciences of the United States of America

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https://www.readbyqxmd.com/read/30030285/quantum-optics-approach-to-radiation-from-atoms-falling-into-a-black-hole
#1
Marlan O Scully, Stephen Fulling, David M Lee, Don N Page, Wolfgang P Schleich, Anatoly A Svidzinsky
We show that atoms falling into a black hole (BH) emit acceleration radiation which, under appropriate initial conditions, looks to a distant observer much like (but is different from) Hawking BH radiation. In particular, we find the entropy of the acceleration radiation via a simple laser-like analysis. We call this entropy horizon brightened acceleration radiation (HBAR) entropy to distinguish it from the BH entropy of Bekenstein and Hawking. This analysis also provides insight into the Einstein principle of equivalence between acceleration and gravity...
July 20, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30030284/direction-of-flagellum-beat-propagation-is-controlled-by-proximal-distal-outer-dynein-arm-asymmetry
#2
Beatrice Freya Lucy Edwards, Richard John Wheeler, Amy Rachel Barker, Flávia Fernandes Moreira-Leite, Keith Gull, Jack Daniel Sunter
The 9 + 2 axoneme structure of the motile flagellum/cilium is an iconic, apparently symmetrical cellular structure. Recently, asymmetries along the length of motile flagella have been identified in a number of organisms, typically in the inner and outer dynein arms. Flagellum-beat waveforms are adapted for different functions. They may start either near the flagellar tip or near its base and may be symmetrical or asymmetrical. We hypothesized that proximal/distal asymmetry in the molecular composition of the axoneme may control the site of waveform initiation and the direction of waveform propagation...
July 20, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30026198/-shepherd-s-crook-neurons-drive-and-synchronize-the-enhancing-and-suppressive-mechanisms-of-the-midbrain-stimulus-selection-network
#3
Florencia Garrido-Charad, Tomas Vega-Zuniga, Cristián Gutiérrez-Ibáñez, Pedro Fernandez, Luciana López-Jury, Cristian González-Cabrera, Harvey J Karten, Harald Luksch, Gonzalo J Marín
The optic tectum (TeO), or superior colliculus, is a multisensory midbrain center that organizes spatially orienting responses to relevant stimuli. To define the stimulus with the highest priority at each moment, a network of reciprocal connections between the TeO and the isthmi promotes competition between concurrent tectal inputs. In the avian midbrain, the neurons mediating enhancement and suppression of tectal inputs are located in separate isthmic nuclei, facilitating the analysis of the neural processes that mediate competition...
July 19, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30026197/rates-of-cavity-filling-by-liquids
#4
Dongjin Seo, Alex M Schrader, Szu-Ying Chen, Yair Kaufman, Thomas R Cristiani, Steven H Page, Peter H Koenig, Yonas Gizaw, Dong Woog Lee, Jacob N Israelachvili
Understanding the fundamental wetting behavior of liquids on surfaces with pores or cavities provides insights into the wetting phenomena associated with rough or patterned surfaces, such as skin and fabrics, as well as the development of everyday products such as ointments and paints, and industrial applications such as enhanced oil recovery and pitting during chemical mechanical polishing. We have studied, both experimentally and theoretically, the dynamics of the transitions from the unfilled/partially filled (Cassie-Baxter) wetting state to the fully filled (Wenzel) wetting state on intrinsically hydrophilic surfaces (intrinsic water contact angle <90°, where the Wenzel state is always the thermodynamically favorable state, while a temporary metastable Cassie-Baxter state can also exist) to determine the variables that control the rates of such transitions...
July 19, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30026196/electrostatic-lock-in-the-transport-cycle-of-the-multidrug-resistance-transporter-emre
#5
Josh V Vermaas, Susan B Rempe, Emad Tajkhorshid
EmrE is a small, homodimeric membrane transporter that exploits the established electrochemical proton gradient across the Escherichia coli inner membrane to export toxic polyaromatic cations, prototypical of the wider small-multidrug resistance transporter family. While prior studies have established many fundamental aspects of the specificity and rate of substrate transport in EmrE, low resolution of available structures has hampered identification of the transport coupling mechanism. Here we present a complete, refined atomic structure of EmrE optimized against available cryo-electron microscopy (cryo-EM) data to delineate the critical interactions by which EmrE regulates its conformation during the transport process...
July 19, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30026195/new-pests-for-old-as-gmos-bring-on-substitute-pests
#6
Robert A Cheke
No abstract text is available yet for this article.
July 19, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30026194/understanding-when-people-will-report-crimes-to-the-police
#7
Mario L Small
No abstract text is available yet for this article.
July 19, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30021855/environmental-limits-of-rift-valley-fever-revealed-using-ecoepidemiological-mechanistic-models
#8
Giovanni Lo Iacono, Andrew A Cunningham, Bernard Bett, Delia Grace, David W Redding, James L N Wood
Vector-borne diseases (VBDs) of humans and domestic animals are a significant component of the global burden of disease and a key driver of poverty. The transmission cycles of VBDs are often strongly mediated by the ecological requirements of the vectors, resulting in complex transmission dynamics, including intermittent epidemics and an unclear link between environmental conditions and disease persistence. An important broader concern is the extent to which theoretical models are reliable at forecasting VBDs; infection dynamics can be complex, and the resulting systems are highly unstable...
July 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30021854/enhanced-expression-of-mycn-cip2a-drives-neural-crest-toward-a-neural-stem-cell-like-fate-implications-for-priming-of-neuroblastoma
#9
Laura Kerosuo, Pushpa Neppala, Jenny Hsin, Sofie Mohlin, Felipe Monteleone Vieceli, Zsofia Török, Anni Laine, Jukka Westermarck, Marianne E Bronner
Neuroblastoma is a neural crest-derived childhood tumor of the peripheral nervous system in which MycN amplification is a hallmark of poor prognosis. Here we show that MycN is expressed together with phosphorylation-stabilizing factor CIP2A in regions of the neural plate destined to form the CNS, but MycN is excluded from the neighboring neural crest stem cell domain. Interestingly, ectopic expression of MycN or CIP2A in the neural crest domain biases cells toward CNS-like neural stem cells that express Sox2...
July 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30021853/inner-workings-after-years-of-listening-with-detectors-buried-in-antarctic-ice-icecube-researchers-trace-neutrino-source
#10
Nola Taylor Redd
No abstract text is available yet for this article.
July 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30021852/stress-testing-the-relationship-between-t-cell-receptor-peptide-mhc-affinity-and-cross-reactivity-using-peptide-velcro
#11
Marvin H Gee, Leah V Sibener, Michael E Birnbaum, Kevin M Jude, Xinbo Yang, Ricardo A Fernandes, Juan L Mendoza, Caleb R Glassman, K Christopher Garcia
T cell receptors (TCRs) bind to peptide-major histocompatibility complex (pMHC) with low affinity ( K d ∼ μM), which is generally assumed to facilitate cross-reactive TCR "scanning" of ligands. To understand the relationship between TCR/pMHC affinity and cross-reactivity, we sought to engineer an additional weak interaction, termed "velcro," between the TCR and pMHC to probe the specificities of TCRs at relatively low and high affinities. This additional interaction was generated through an eight-amino acid peptide library covalently linked to the N terminus of the MHC-bound peptide...
July 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30021851/efficient-compression-in-color-naming-and-its-evolution
#12
Noga Zaslavsky, Charles Kemp, Terry Regier, Naftali Tishby
We derive a principled information-theoretic account of cross-language semantic variation. Specifically, we argue that languages efficiently compress ideas into words by optimizing the information bottleneck (IB) trade-off between the complexity and accuracy of the lexicon. We test this proposal in the domain of color naming and show that ( i ) color-naming systems across languages achieve near-optimal compression; ( ii ) small changes in a single trade-off parameter account to a large extent for observed cross-language variation; ( iii ) efficient IB color-naming systems exhibit soft rather than hard category boundaries and often leave large regions of color space inconsistently named, both of which phenomena are found empirically; and ( iv ) these IB systems evolve through a sequence of structural phase transitions, in a single process that captures key ideas associated with different accounts of color category evolution...
July 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30021850/exopolysaccharide-protects-vibrio-cholerae-from-exogenous-attacks-by-the-type-6-secretion-system
#13
Jonida Toska, Brian T Ho, John J Mekalanos
The type 6 secretion system (T6SS) is a nanomachine used by many Gram-negative bacteria, including Vibrio cholerae , to deliver toxic effector proteins into adjacent eukaryotic and bacterial cells. Because the activity of the T6SS is dependent on direct contact between cells, its activity is limited to bacteria growing on solid surfaces or in biofilms. V. cholerae can produce an exopolysaccharide (EPS) matrix that plays a role in adhesion and biofilm formation. In this work, we investigated the effect of EPS production on T6SS activity between cells...
July 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30021849/role-of-carbon-allocation-efficiency-in-the-temperature-dependence-of-autotroph-growth-rates
#14
Bernardo García-Carreras, Sofía Sal, Daniel Padfield, Dimitrios-Georgios Kontopoulos, Elvire Bestion, C-Elisa Schaum, Gabriel Yvon-Durocher, Samrāt Pawar
Relating the temperature dependence of photosynthetic biomass production to underlying metabolic rates in autotrophs is crucial for predicting the effects of climatic temperature fluctuations on the carbon balance of ecosystems. We present a mathematical model that links thermal performance curves (TPCs) of photosynthesis, respiration, and carbon allocation efficiency to the exponential growth rate of a population of photosynthetic autotroph cells. Using experiments with the green alga, Chlorella vulgaris , we apply the model to show that the temperature dependence of carbon allocation efficiency is key to understanding responses of growth rates to warming at both ecological and longer-term evolutionary timescales...
July 18, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30018065/combined-computational-and-experimental-investigation-of-the-la-2-cuo-4-x-s-x-0-%C3%A2-x-%C3%A2-4-quaternary-system
#15
Hua He, Chuck-Hou Yee, Daniel E McNally, Jack W Simonson, Shelby Zellman, Mason Klemm, Plamen Kamenov, Gayle Geschwind, Ashley Zebro, Sanjit Ghose, Jianming Bai, Eric Dooryhee, Gabriel Kotliar, Meigan C Aronson
The lack of a mechanistic framework for chemical reactions forming inorganic extended solids presents a challenge to accelerated materials discovery. We demonstrate here a combined computational and experimental methodology to tackle this problem, in which in situ X-ray diffraction measurements monitor solid-state reactions and deduce reaction pathways, while theoretical computations rationalize reaction energetics. The method has been applied to the La2 CuO4- x S x (0 ≤ x ≤ 4) quaternary system, following an earlier prediction that enhanced superconductivity could be found in these new lanthanum copper(II) oxysulfide compounds...
July 17, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30018064/biogeographic-regions-and-events-of-isolation-and-diversification-of-the-endemic-biota-of-the-tropical-andes
#16
Nicolas A Hazzi, Juan Sebastián Moreno, Carolina Ortiz-Movliav, Rubén Darío Palacio
Understanding the spatial and temporal evolution of biota in the tropical Andes is a major challenge, given the region's topographic complexity and high beta diversity. We used a network approach to find biogeographic regions (bioregions) based on high-resolution species distribution models for 151 endemic bird taxa. Then, we used dated molecular phylogenies of 14 genera to reconstruct the area history through a sequence of allopatric speciation processes. We identified 15 biogeographical regions and found 26 events of isolation and diversification within their boundaries that are independently confirmed with disjunct distributions of sister taxa...
July 17, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30018063/mavacamten-stabilizes-an-autoinhibited-state-of-two-headed-cardiac-myosin
#17
John A Rohde, Osha Roopnarine, David D Thomas, Joseph M Muretta
We used transient biochemical and structural kinetics to elucidate the molecular mechanism of mavacamten, an allosteric cardiac myosin inhibitor and a prospective treatment for hypertrophic cardiomyopathy. We find that mavacamten stabilizes an autoinhibited state of two-headed cardiac myosin not found in the single-headed S1 myosin motor fragment. We determined this by measuring cardiac myosin actin-activated and actin-independent ATPase and single-ATP turnover kinetics. A two-headed myosin fragment exhibits distinct autoinhibited ATP turnover kinetics compared with a single-headed fragment...
July 17, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30018062/stem-cell-derived-clade-f-aavs-mediate-high-efficiency-homologous-recombination-based-genome-editing
#18
Laura J Smith, Jason Wright, Gabriella Clark, Taihra Ul-Hasan, Xiangyang Jin, Abigail Fong, Manasa Chandra, Thia St Martin, Hillard Rubin, David Knowlton, Jeff L Ellsworth, Yuman Fong, Kamehameha K Wong, Saswati Chatterjee
The precise correction of genetic mutations at the nucleotide level is an attractive permanent therapeutic strategy for human disease. However, despite significant progress, challenges to efficient and accurate genome editing persist. Here, we report a genome editing platform based upon a class of hematopoietic stem cell (HSC)-derived clade F adeno-associated virus (AAV), which does not require prior nuclease-mediated DNA breaks and functions exclusively through BRCA2-dependent homologous recombination. Genome editing is guided by complementary homology arms and is highly accurate and seamless, with no evidence of on-target mutations, including insertion/deletions or inclusion of AAV inverted terminal repeats...
July 17, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30018061/kv2-potassium-channels-meet-vap
#19
Elizabeth Wen Sun, Pietro De Camilli
No abstract text is available yet for this article.
July 17, 2018: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/30018060/oxidative-stress-is-tightly-regulated-by-cytochrome-c-phosphorylation-and-respirasome-factors-in-mitochondria
#20
Alejandra Guerra-Castellano, Antonio Díaz-Quintana, Gonzalo Pérez-Mejías, Carlos A Elena-Real, Katiuska González-Arzola, Sofía M García-Mauriño, Miguel A De la Rosa, Irene Díaz-Moreno
Respiratory cytochrome c has been found to be phosphorylated at tyrosine 97 in the postischemic brain upon neuroprotective insulin treatment, but how such posttranslational modification affects mitochondrial metabolism is unclear. Here, we report the structural features and functional behavior of a phosphomimetic cytochrome c mutant, which was generated by site-specific incorporation at position 97 of p -carboxymethyl-l-phenylalanine using the evolved tRNA synthetase method. We found that the point mutation does not alter the overall folding and heme environment of cytochrome c , but significantly affects the entire oxidative phosphorylation process...
July 17, 2018: Proceedings of the National Academy of Sciences of the United States of America
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