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https://www.readbyqxmd.com/read/28219971/predicting-human-olfactory-perception-from-chemical-features-of-odor-molecules
#1
Andreas Keller, Richard C Gerkin, Yuanfang Guan, Amit Dhurandhar, Gabor Turu, Bence Szalai, Joel D Mainland, Yusuke Ihara, Chung Wen Yu, Russ Wolfinger, Celine Vens, Leander Schietgat, Kurt De Grave, Raquel Norel, Gustavo Stolovitzky, Guillermo A Cecchi, Leslie B Vosshall, Pablo Meyer
It is still not possible to predict whether a given molecule will have a perceived odor or what olfactory percept it will produce. We therefore organized the crowd-sourced DREAM Olfaction Prediction Challenge. Using a large olfactory psychophysical data set, teams developed machine-learning algorithms to predict sensory attributes of molecules based on their chemoinformatic features. The resulting models accurately predicted odor intensity and pleasantness and also successfully predicted 8 among 19 rated semantic descriptors ("garlic," "fish," "sweet," "fruit," "burnt," "spices," "flower," and "sour")...
February 20, 2017: Science
https://www.readbyqxmd.com/read/28219970/an-accreting-pulsar-with-extreme-properties-drives-an-ultraluminous-x-ray-source-in-ngc-5907
#2
Gian Luca Israel, Andrea Belfiore, Luigi Stella, Paolo Esposito, Piergiorgio Casella, Andrea De Luca, Martino Marelli, Alessandro Papitto, Matteo Perri, Simonetta Puccetti, Guillermo A Rodríguez Castillo, David Salvetti, Andrea Tiengo, Luca Zampieri, Daniele D'Agostino, Jochen Greiner, Frank Haberl, Giovanni Novara, Ruben Salvaterra, Roberto Turolla, Mike Watson, Joern Wilms, Anna Wolter
Ultraluminous x-ray sources (ULXs) in nearby galaxies shine brighter than any x-ray source in our Galaxy. ULXs are usually modeled as stellar-mass black holes (BHs) accreting at very high rates or intermediate-mass BHs. We present observations showing that NGC 5907 ULX is instead an x-ray accreting neutron star (NS) with a spin period evolving from 1.43 seconds in 2003 to 1.13 seconds in 2014. It has an isotropic peak luminosity of ~1000 times the Eddington limit for a NS at 17.1 megaparsec. Standard accretion models fail to explain its luminosity, even assuming beamed emission, but a strong multipolar magnetic field can describe its properties...
February 20, 2017: Science
https://www.readbyqxmd.com/read/28209641/mechanisms-for-initiating-cellular-dna-replication
#3
REVIEW
Franziska Bleichert, Michael R Botchan, James M Berger
Cellular DNA replication factories depend on ring-shaped hexameric helicases to aid DNA synthesis by processively unzipping the parental DNA helix. Replicative helicases are loaded onto DNA by dedicated initiator, loader, and accessory proteins during the initiation of DNA replication in a tightly regulated, multistep process. We discuss here the molecular choreography of DNA replication initiation across the three domains of life, highlighting similarities and differences in the strategies used to deposit replicative helicases onto DNA and to melt the DNA helix in preparation for replisome assembly...
February 16, 2017: Science
https://www.readbyqxmd.com/read/28209640/quantized-thermal-transport-in-single-atom-junctions
#4
Longji Cui, Wonho Jeong, Sunghoon Hur, Manuel Matt, Jan C Klöckner, Fabian Pauly, Peter Nielaba, Juan Carlos Cuevas, Edgar Meyhofer, Pramod Reddy
Thermal transport in individual atomic junctions and chains is of great fundamental interest due to unique quantum effects expected to arise in them. Here, by employing novel, custom-fabricated, picowatt-resolution calorimetric scanning probes, we measure the thermal conductance of gold and platinum metallic wires down to single-atom junctions. Our work reveals that the thermal conductance of gold single atom junctions is quantized at room temperature and shows that the Wiedemann-Franz law relating thermal and electrical conductance is satisfied even in single-atom contacts...
February 16, 2017: Science
https://www.readbyqxmd.com/read/28209639/a-macrophage-relay-for-long-distance-signaling-during-postembryonic-tissue-remodeling
#5
Dae Seok Eom, David M Parichy
Macrophages have diverse functions in immunity as well as development and homeostasis. Here we identify a function for these cells in long distance communication during postembryonic tissue remodeling. Ablation of macrophages in zebrafish prevented melanophores from coalescing into adult pigment stripes. Melanophore organization depends on signals provided by cells of the yellow xanthophore lineage via airinemes, long filamentous projections with vesicles at their tips. We show that airineme extension from originating cells, and vesicle deposition on target cells, depend on interactions with macrophages...
February 16, 2017: Science
https://www.readbyqxmd.com/read/28183998/scalable-manufactured-randomized-glass-polymer-hybrid-metamaterial-for-daytime-radiative-cooling
#6
Yao Zhai, Yaoguang Ma, Sabrina N David, Dongliang Zhao, Runnan Lou, Gang Tan, Ronggui Yang, Xiaobo Yin
Passive radiative cooling draws heat from surfaces and radiates it into space as infrared radiation to which the atmosphere is transparent. However, the energy density mismatch between solar irradiance and the low infrared radiation flux from a near-ambient-temperature surface require materials that strongly emit thermal energy and barely absorb sunlight. We embedded resonant polar dielectric microspheres randomly in a polymeric matrix, resulting in a metamaterial that is fully transparent to the solar spectrum while having an infrared emissivity greater than 0...
February 9, 2017: Science
https://www.readbyqxmd.com/read/28183997/a-key-malaria-metabolite-modulates-vector-blood-seeking-feeding-and-susceptibility-to-infection
#7
S Noushin Emami, Bo G Lindberg, Susanna Hua, Sharon Hill, Raimondas Mozuraitis, Philipp Lehmann, Göran Birgersson, Anna-Karin Borg-Karlson, Rickard Ignell, Ingrid Faye
Malaria infection renders humans more attractive to Anopheles gambiae sensu lato mosquitoes than uninfected people. The mechanisms remain unknown. Here, we show that an isoprenoid precursor produced by Plasmodium falciparum, (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), affects A. gambiae s.l. blood meal seeking and feeding behaviors, as well as susceptibility to infection. HMBPP acts indirectly by triggering human red blood cells to increase the release of CO2, aldehydes, and monoterpenes, which together enhance vector attraction, and stimulate vector feeding...
February 9, 2017: Science
https://www.readbyqxmd.com/read/28183996/antibiotic-tolerance-facilitates-the-evolution-of-resistance
#8
Irit Levin-Reisman, Irine Ronin, Orit Gefen, Ilan Braniss, Noam Shoresh, Nathalie Q Balaban
Controlled experimental evolution during antibiotic treatment can shed light on the processes leading to antibiotic resistance in bacteria. Recently, intermittent antibiotic exposures have been shown to lead rapidly to the evolution of tolerance, i.e., the ability to survive under treatment without developing resistance. However, whether tolerance delays or promotes the eventual emergence of resistance is unclear. Here, we used in vitro evolution experiments to explore this question. We found that in all cases tolerance preceded resistance...
February 9, 2017: Science
https://www.readbyqxmd.com/read/28183995/structure-of-a-eukaryotic-voltage-gated-sodium-channel-at-near-atomic-resolution
#9
Huaizong Shen, Qiang Zhou, Xiaojing Pan, Zhangqiang Li, Jianping Wu, Nieng Yan
Voltage-gated sodium (Nav) channels are responsible for the initiation and propagation of action potentials. They are associated with a variety of channelopathies and are targeted by multiple pharmaceutical drugs and natural toxins. Here, we report the cryo-EM structure of a putative Nav channel from American cockroach (designated NavPaS) at 3.8-Å resolution. The voltage sensing domains (VSDs) of the four repeats exhibit distinct conformations. The entrance to the asymmetric selectivity filter vestibule is guarded by heavily glycosylated and disulfide bond-stabilized extracellular loops...
February 9, 2017: Science
https://www.readbyqxmd.com/read/28154242/efficient-and-stable-solution-processed-planar-perovskite-solar-cells-via-contact-passivation
#10
Hairen Tan, Ankit Jain, Oleksandr Voznyy, Xinzheng Lan, F Pelayo García de Arquer, James Z Fan, Rafael Quintero-Bermudez, Mingjian Yuan, Bo Zhang, Yicheng Zhao, Fengjia Fan, Peicheng Li, Li Na Quan, Yongbiao Zhao, Zheng-Hong Lu, Zhenyu Yang, Sjoerd Hoogland, Edward H Sargent
Planar perovskite solar cells made entirely via solution-processing at low temperatures (<150°C) offer promise for simple manufacturing, compatibility with flexible substrates, and perovskite-based tandem devices; however, they require an electron-selective layer that performs well with similar processing. We report a contact passivation strategy using chlorine-capped TiO2 colloidal nanocrystal (NC) film that mitigates interfacial recombination and improves interface binding in low-temperature planar solar cells...
February 2, 2017: Science
https://www.readbyqxmd.com/read/28154241/stellate-cells-drive-maturation-of-the-entorhinal-hippocampal-circuit
#11
Flavio Donato, R Irene Jacobsen, May-Britt Moser, Edvard I Moser
The neural representation of space relies on a network of entorhinal-hippocampal cell types with firing patterns tuned to different abstract features of the environment. To determine how this network is set up during early postnatal development, we monitored markers of structural maturation in developing mice, both in naïve animals and after temporally restricted pharmacogenetic silencing of specific cell populations. We found that entorhinal stellate cells provide an activity-dependent instructive signal that drives maturation sequentially and unidirectionally through the intrinsic circuits of the entorhinal-hippocampal network The findings raise the possibility that a small number of autonomously developing neuronal populations operate as intrinsic drivers of maturation across widespread regions of cortex...
February 2, 2017: Science
https://www.readbyqxmd.com/read/28154240/epigenetic-regulation-of-antagonistic-receptors-confers-rice-blast-resistance-with-yield-balance
#12
Yiwen Deng, Keran Zhai, Zhen Xie, Dongyong Yang, Xudong Zhu, Junzhong Liu, Xin Wang, Peng Qin, Yuanzhu Yang, Guomin Zhang, Qun Li, Jianfu Zhang, Shuangqing Wu, Joëlle Milazzo, Bizeng Mao, Ertao Wang, Huaan Xie, Didier Tharreau, Zuhua He
Crop breeding aims to balance disease resistance with yield, however single resistance (R) genes can lead to resistance breakdown and R gene pyramiding may impact growth fitness. Here we report that the rice Pigm locus contains a cluster of genes encoding nucleotide-binding leucine-rich repeat (NLR) receptors that confer durable resistance to the fungus Magnaporthe oryzae without yield penalty. In the cluster, PigmR confers broad-spectrum resistance, whereas PigmS competitively attenuates PigmR homodimerization to suppress resistance...
February 2, 2017: Science
https://www.readbyqxmd.com/read/28126728/observation-of-the-wigner-huntington-transition-to-metallic-hydrogen
#13
Ranga P Dias, Isaac F Silvera
Producing metallic hydrogen has been a great challenge to condensed matter physics. Metallic hydrogen may be a room temperature superconductor and metastable when the pressure is released and could have an important impact on energy and rocketry. We have studied solid molecular hydrogen under pressure at low temperatures. At a pressure of 495 GPa hydrogen becomes metallic with reflectivity as high as 0.91. We fit the reflectance using a Drude free electron model to determine the plasma frequency of 32.5 ± 2...
January 26, 2017: Science
https://www.readbyqxmd.com/read/28104796/clonal-hematopoiesis-associated-with-tet2-deficiency-accelerates-atherosclerosis-development-in-mice
#14
José J Fuster, Susan MacLauchlan, María A Zuriaga, Maya N Polackal, Allison C Ostriker, Raja Chakraborty, Chia-Ling Wu, Soichi Sano, Sujatha Muralidharan, Cristina Rius, Jacqueline Vuong, Sophia Jacob, Varsha Muralidhar, Avril A B Robertson, Matthew A Cooper, Vicente Andrés, Karen K Hirschi, Kathleen A Martin, Kenneth Walsh
Human aging is associated with an increased frequency of somatic mutations in hematopoietic cells. Several of these recurrent mutations, including those in the gene encoding the epigenetic modifier enzyme TET2, promote expansion of the mutant blood cells. This "clonal hematopoiesis" correlates with an increased risk of atherosclerotic cardiovascular disease. Here we studied the effects of the expansion of Tet2-mutant cells in atherosclerosis-prone, low-density lipoprotein receptor-deficient (Ldlr-/-) mice. We found that partial bone marrow reconstitution with Tet2-deficient cells was sufficient for their clonal expansion and led to a marked increase in atherosclerotic plaque size...
January 19, 2017: Science
https://www.readbyqxmd.com/read/28104795/magnetic-resonance-spectroscopy-of-an-atomically-thin-material-using-a-single-spin-qubit
#15
I Lovchinsky, J D Sanchez-Yamagishi, E K Urbach, S Choi, S Fang, T I Andersen, K Watanabe, T Taniguchi, A Bylinskii, E Kaxiras, P Kim, H Park, M D Lukin
Two-dimensional (2D) materials offer a promising platform for exploring condensed matter phenomena and developing technological applications. However, the reduction of material dimensions to the atomic scale poses a challenge for traditional measurement and interfacing techniques that typically couple to macroscopic observables. We demonstrate a method for probing the properties of 2D materials via nanometer-scale nuclear quadrupole resonance (NQR) spectroscopy using individual atom-like impurities in diamond...
January 19, 2017: Science
https://www.readbyqxmd.com/read/28082413/a-paralogous-decoy-protects-phytophthora-sojae-apoplastic-effector-psxeg1-from-a-host-inhibitor
#16
Zhenchuan Ma, Lin Zhu, Tianqiao Song, Yang Wang, Qi Zhang, Yeqiang Xia, Min Qiu, Yachun Lin, Haiyang Li, Liang Kong, Yufeng Fang, Wenwu Ye, Yan Wang, Suomeng Dong, Xiaobo Zheng, Brett M Tyler, Yuanchao Wang
The extracellular space (apoplast) of plant tissue represents a critical battleground between plants and attacking microbes. Here we show that a pathogen-secreted apoplastic Xyloglucan-specific EndoGlucanase PsXEG1 is a focus of this struggle in the Phytophthora sojae-soybean interaction. We show that soybean produces an apoplastic Glucanase Inhibitor Protein, (GmGIP1), that binds to PsXEG1 to block its contribution to virulence. P. sojae however, secretes a paralogous PsXEG1-Like Protein (PsXLP1) that has lost enzyme activity but binds to GmGIP1 more tightly than does PsXEG1, thus freeing PsXEG1 to support P...
January 12, 2017: Science
https://www.readbyqxmd.com/read/28082411/tzap-a-telomere-associated-protein-involved-in-telomere-length-control
#17
Julia Su Zhou Li, Javier Miralles Fuste, Tatevik Simavorian, Cristina Bartocci, Jill Tsai, Jan Karlseder, Eros Lazzerini Denchi
Telomeres are found at the end of chromosomes and are important for chromosome stability. Here, we describe a specific telomere-associated protein: TZAP (Telomeric Zinc finger-Associated Protein). TZAP binds preferentially to long telomeres that have a low concentration of shelterin complex, competing with the telomeric repeat binding factors TRF1 and TRF2. When localized at telomeres, TZAP triggers "telomere trimming," a process that results in the rapid deletion of telomeric repeats. Based on these results, we propose a model for telomere length regulation in mammalian cells: The reduced concentration of the shelterin complex at long telomeres results in TZAP binding and initiation of telomere trimming...
January 12, 2017: Science
https://www.readbyqxmd.com/read/28059713/time-resolved-x-ray-absorption-spectroscopy-with-a-water-window-high-harmonic-source
#18
Yoann Pertot, Cédric Schmidt, Mary Matthews, Adrien Chauvet, Martin Huppert, Vit Svoboda, Aaron von Conta, Andres Tehlar, Denitsa Baykusheva, Jean-Pierre Wolf, Hans Jakob Wörner
Time-resolved X-ray absorption spectroscopy (TR-XAS) has so far practically been limited to large-scale facilities, to sub-picosecond temporal resolution and to the condensed phase. Here, we report the realization of TR-XAS with a temporal resolution in the low femtosecond range by developing a table-top high-harmonic source reaching up to 350 eV, thus partially covering the spectral region of 280 to 530 eV, where water is transmissive. We use this source to follow previously unexamined light-induced chemical reactions in the lowest electronic states of isolated CF4(+) and SF6(+) molecules in the gas phase...
January 5, 2017: Science
https://www.readbyqxmd.com/read/28008086/nanometer-resolution-imaging-and-tracking-of-fluorescent-molecules-with-minimal-photon-fluxes
#19
Francisco Balzarotti, Yvan Eilers, Klaus C Gwosch, Arvid H Gynnå, Volker Westphal, Fernando D Stefani, Johan Elf, Stefan W Hell
We introduce MINFLUX, a concept for localizing photon emitters in space. By probing the emitter with a local intensity minimum of excitation light, MINFLUX minimizes the fluorescence photons needed for high localization precision. A 22-fold reduction of photon detections over that required in popular centroid-localization is demonstrated. In superresolution microscopy, MINFLUX attained ~1-nm precision, resolving molecules only 6 nm apart. Tracking single fluorescent proteins by MINFLUX increased the temporal resolution and the number of localizations per trace by 100-fold, as demonstrated with diffusing 30S ribosomal subunits in living Escherichia coli As conceptual limits have not been reached, we expect this localization modality to break new ground for observing the dynamics, distribution, and structure of macromolecules in living cells and beyond...
December 22, 2016: Science
https://www.readbyqxmd.com/read/28008085/strong-coupling-of-a-single-electron-in-silicon-to-a-microwave-photon
#20
X Mi, J V Cady, D M Zajac, P W Deelman, J R Petta
Silicon is vital to the computing industry due to the high quality of its native oxide and well-established doping technologies. Isotopic purification, and the resulting seconds-long quantum coherence times, have recently put Si at the forefront of efforts to create a solid state quantum processor. Here we demonstrate strong coupling of a single electron in a silicon double quantum dot to the photonic field of a microwave cavity, as shown by the observation of vacuum Rabi splitting. Strong coupling of a quantum dot electron to a cavity photon would allow for long-range qubit coupling, and the long-range entanglement of electrons in semiconductor quantum dots...
December 22, 2016: Science
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