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Dark matter

Luis Angel Martínez-Martínez, Matthew Du, Raphael Florentino Ribeiro, Stéphane Kéna-Cohen, Joel Yuen-Zhou
Singlet fission is an important candidate to increase energy conversion efficiency in organic pho- tovoltaics; it provides a pathway to increase the quantum yield of excitons per photon absorbed in select materials. We investigate the dependence of exciton quantum yield for acenes in the strong light-matter interaction (polariton) regime, where the materials are embedded in optical microcavi- ties. Starting from an open-quantum-systems approach, we build a kinetic model for time-evolution of species of interest in the presence of quenchers and show that polaritons can decrease or increase exciton quantum yields compared to the cavity-free case...
March 18, 2018: Journal of Physical Chemistry Letters
Karissa L Cross, Payal Chirania, Weili Xiong, Clifford J Beall, James G Elkins, Richard J Giannone, Ann L Griffen, Adam M Guss, Robert L Hettich, Snehal S Joshi, Elaine M Mokrzan, Roman K Martin, Igor B Zhulin, Eugene J Leys, Mircea Podar
The human oral microbiota encompasses representatives of many bacterial lineages that have not yet been cultured. Here we describe the isolation and characterization of previously uncultured Desulfobulbus oralis , the first human-associated representative of its genus. As mammalian-associated microbes rarely have free-living close relatives, D. oralis provides opportunities to study how bacteria adapt and evolve within a host. This sulfate-reducing deltaproteobacterium has adapted to the human oral subgingival niche by curtailing its physiological repertoire, losing some biosynthetic abilities and metabolic independence, and by dramatically reducing environmental sensing and signaling capabilities...
March 13, 2018: MBio
Michael A Beasley, Ignacio Trujillo, Ryan Leaman, Mireia Montes
Massive galaxies are thought to form in two phases: an initial collapse of gas and giant burst of central star formation, followed by the later accretion of material that builds up their stellar and dark-matter haloes. The systems of globular clusters within such galaxies are believed to form in a similar manner. The initial central burst forms metal-rich (spectrally red) clusters, whereas more metal-poor (spectrally blue) clusters are brought in by the later accretion of less-massive satellites. This formation process is thought to result in the multimodal optical colour distributions that are seen in the globular cluster systems of massive galaxies...
March 12, 2018: Nature
Zhineng Hao, Yongguang Yin, Juan Wang, Dong Cao, Jingfu Liu
There are increasing concerns about the adverse effects of released engineered nanoparticles and photochemically formed organohalogen compounds (OHCs) on human health and the environment. Herein, we report that titanium dioxide nanoparticles (TiO2 NPs) can photocatalytically halogenate dissolved organic matter (DOM) to form a large number of organobromine compounds (OBCs) and organoiodine compounds (OICs), as characterized by negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry...
March 7, 2018: Science of the Total Environment
Yong-Zhen Zhang, Mang Shi, Edward C Holmes
We know less about viruses than any other lifeform. Fortunately, metagenomics has led to a massive expansion in the known diversity of the virosphere. Here, we discuss how metagenomics has changed our understanding of RNA viruses and present some of the remaining challenges, including characterization of the "dark matter" of divergent viral genomes.
March 8, 2018: Cell
Ahmed S Abouhend, Adam McNair, Wenye Camilla Kuo-Dahab, Christopher Watt, Caitlyn S Butler, Kim Milferstedt, Jerome Hamelin, Jeongmi Seo, Gitau J Gikonyo, Khalid M El-Moselhy, Chul Park
This study presents the oxygenic photogranule (OPG) process, a light-driven process for wastewater treatment, developed based on photogranulation of filamentous cyanobacteria, non-phototrophic bacteria, and microalgae. Unlike other biogranular processes requiring airlift or upflow-based mixing, the OPG process was operated in stirred-tank reactors without aeration. Reactors were seeded with hydrostatically-grown photogranules and operated in a sequencing-batch mode for five months to treat wastewater. New reactor biomass propagated with progression of photogranulation under periodic light/dark cycles...
March 5, 2018: Environmental Science & Technology
Maria P Yavropoulou, John G Yovos
Epigenetics, present a new discipline that attempts to explain significant differences in phenotypes among patients with the same disease. In contrast to the other epigenetic mechanisms that modulate gene transcription, non-coding RNAs act at the post-transcriptional level. They directly modulate the gene expression of mRNA genes leading to mRNA target cleavage and degradation and translation repression. Bioinformatic predictions indicate that non coding RNAs may be involved in the regulation of 60% of the coding genes and each non-coding RNA can have multiple target genes, and each gene may be regulated by more than one non-coding RNAs...
March 1, 2018: Journal of Musculoskeletal & Neuronal Interactions
Z F Zhang, F Liu, X Zhou, X Z Liu, S J Liu, L Cai
Karst caves are distinctly characterised by darkness, low to moderate temperatures, high humidity, and scarcity of organic matter. During the years of 2014-2015, we explored the mycobiota in two unnamed Karst caves in Guizhou province, China, and obtained 563 fungal strains via the dilution plate method. Preliminary ITS analyses of these strains suggested that they belonged to 246 species in 116 genera, while 23.5 % were not identified to species level. Among these species, 85.8 % (211 species) belonged to Ascomycota ; 7...
December 2017: Persoonia
Jan Novak, Julie Bienertová Vašků, Miroslav Souček
The human genome contains about 22 000 protein-coding genes that are transcribed to an even larger amount of messenger RNAs (mRNA). Interestingly, the results of the project ENCODE from 2012 show, that despite up to 90 % of our genome being actively transcribed, protein-coding mRNAs make up only 2-3 % of the total amount of the transcribed RNA. The rest of RNA transcripts is not translated to proteins and that is why they are referred to as "non-coding RNAs". Earlier the non-coding RNA was considered "the dark matter of genome", or "the junk", whose genes has accumulated in our DNA during the course of evolution...
2018: Vnitr̆ní Lékar̆ství
Adrian Cho
No abstract text is available yet for this article.
March 2, 2018: Science
Rennan Barkana
The cosmic radio-frequency spectrum is expected to show a strong absorption signal corresponding to the 21-centimetre-wavelength transition of atomic hydrogen around redshift 20, which arises from Lyman-α radiation from some of the earliest stars. By observing this 21-centimetre signal-either its sky-averaged spectrum or maps of its fluctuations, obtained using radio interferometers-we can obtain information about cosmic dawn, the era when the first astrophysical sources of light were formed. The recent detection of the global 21-centimetre spectrum reveals a stronger absorption than the maximum predicted by existing models, at a confidence level of 3...
February 28, 2018: Nature
Judd D Bowman, Alan E E Rogers, Raul A Monsalve, Thomas J Mozdzen, Nivedita Mahesh
After stars formed in the early Universe, their ultraviolet light is expected, eventually, to have penetrated the primordial hydrogen gas and altered the excitation state of its 21-centimetre hyperfine line. This alteration would cause the gas to absorb photons from the cosmic microwave background, producing a spectral distortion that should be observable today at radio frequencies of less than 200 megahertz. Here we report the detection of a flattened absorption profile in the sky-averaged radio spectrum, which is centred at a frequency of 78 megahertz and has a best-fitting full-width at half-maximum of 19 megahertz and an amplitude of 0...
February 28, 2018: Nature
Maria Bergemann, Branimir Sesar, Judith G Cohen, Aldo M Serenelli, Allyson Sheffield, Ting S Li, Luca Casagrande, Kathryn V Johnston, Chervin F P Laporte, Adrian M Price-Whelan, Ralph Schönrich, Andrew Gould
Our Galaxy is thought to have an active evolutionary history, dominated over the past ten billion years or so by star formation, the accretion of cold gas and, in particular, the merging of clumps of baryonic and dark matter. The stellar halo-the faint, roughly spherical component of the Galaxy-reveals rich 'fossil' evidence of these interactions, in the form of stellar streams, substructures and chemically distinct stellar components. The effects of interactions with dwarf galaxies on the content and morphology of the Galactic disk are still being explored...
February 26, 2018: Nature
Vedran Brdar, Joachim Kopp, Jia Liu, Xiao-Ping Wang
In 2014, several groups reported hints for a yet unidentified line in astrophysical x-ray signals from galaxies and galaxy clusters at an energy of 3.5 keV. While it is not unlikely that this line is simply a reflection of imperfectly modeled atomic transitions, it has renewed the community's interest in models of keV-scale dark matter, whose decay would lead to such a line. The alternative possibility of dark matter annihilation into monochromatic photons is far less explored, a lapse that we strive to amend in this Letter...
February 9, 2018: Physical Review Letters
R Agnese, T Aramaki, I J Arnquist, W Baker, D Balakishiyeva, S Banik, D Barker, R Basu Thakur, D A Bauer, T Binder, M A Bowles, P L Brink, R Bunker, B Cabrera, D O Caldwell, R Calkins, C Cartaro, D G Cerdeño, Y Chang, Y Chen, J Cooley, B Cornell, P Cushman, M Daal, P C F Di Stefano, T Doughty, E Fascione, E Figueroa-Feliciano, M Fritts, G Gerbier, R Germond, M Ghaith, G L Godfrey, S R Golwala, J Hall, H R Harris, Z Hong, E W Hoppe, L Hsu, M E Huber, V Iyer, D Jardin, A Jastram, C Jena, M H Kelsey, A Kennedy, A Kubik, N A Kurinsky, B Loer, E Lopez Asamar, P Lukens, D MacDonell, R Mahapatra, V Mandic, N Mast, E H Miller, N Mirabolfathi, B Mohanty, J D Morales Mendoza, J Nelson, J L Orrell, S M Oser, K Page, W A Page, R Partridge, M Penalver Martinez, M Pepin, A Phipps, S Poudel, M Pyle, H Qiu, W Rau, P Redl, A Reisetter, T Reynolds, A Roberts, A E Robinson, H E Rogers, T Saab, B Sadoulet, J Sander, K Schneck, R W Schnee, S Scorza, K Senapati, B Serfass, D Speller, M Stein, J Street, H A Tanaka, D Toback, R Underwood, A N Villano, B von Krosigk, B Welliver, J S Wilson, M J Wilson, D H Wright, S Yellin, J J Yen, B A Young, X Zhang, X Zhao
We report the result of a blinded search for weakly interacting massive particles (WIMPs) using the majority of the SuperCDMS Soudan data set. With an exposure of 1690 kg d, a single candidate event is observed, consistent with expected backgrounds. This analysis (combined with previous Ge results) sets an upper limit on the spin-independent WIMP-nucleon cross section of 1.4×10^{-44} (1.0×10^{-44})  cm^{2} at 46  GeV/c^{2}. These results set the strongest limits for WIMP-germanium-nucleus interactions for masses >12  GeV/c^{2}...
February 9, 2018: Physical Review Letters
T M Bersano, V Gokhroo, M A Khamehchi, J D'Ambroise, D J Frantzeskakis, P Engels, P G Kevrekidis
Dilute-gas Bose-Einstein condensates are an exceptionally versatile test bed for the investigation of novel solitonic structures. While matter-wave solitons in one- and two-component systems have been the focus of intense research efforts, an extension to three components has never been attempted in experiments. Here, we experimentally demonstrate the existence of robust dark-bright-bright (DBB) and dark-dark-bright solitons in a multicomponent F=1 condensate. We observe lifetimes on the order of hundreds of milliseconds for these structures...
February 9, 2018: Physical Review Letters
Matthew R Buckley, Anthony DiFranzo
The distributions of dark matter and baryons in the Universe are known to be very different: The dark matter resides in extended halos, while a significant fraction of the baryons have radiated away much of their initial energy and fallen deep into the potential wells. This difference in morphology leads to the widely held conclusion that dark matter cannot cool and collapse on any scale. We revisit this assumption and show that a simple model where dark matter is charged under a "dark electromagnetism" can allow dark matter to form gravitationally collapsed objects with characteristic mass scales much smaller than that of a Milky-Way-type galaxy...
February 2, 2018: Physical Review Letters
Huacheng Xu, Laodong Guo
Dissolved organic matter (DOM) is ubiquitous and plays an important role in regulating water quality, ecological function, and the fate and transport of trace elements and pollutants in aquatic environments. Both the colloidal precursors (i.e. <1 kDa) and bulk DOM collected from a freshwater estuary were incubated in the dark for 21 days to examine dynamic changes in molecular size and composition induced by microbial degradation and self-assembly. Results showed that the concentrations of total organic carbon, carbohydrates, and protein-like substances decreased by 11-30% during incubation, while those of humic- and fulvic-like substances remained relatively constant, indicating humic substances are more resistant to microbial utilization compared to carbohydrates and protein-like DOM...
February 7, 2018: Water Research
Fabio Moraes da Costa, Sarah Dario Alves Daflon, Daniele Maia Bila, Fabiana Valeria da Fonseca, Juacyara Carbonelli Campos
Leachate from urban solid waste landfills is a complex mixture of organic and inorganic substances that cause damage to the environment, due to the high concentration of recalcitrant organic matter and toxicity. The objective of this study was to apply advanced oxidation processes (AOP), namely the dark Fenton and solar photo-Fenton processes, to young and old landfill leachates prior to biological treatment. The leachates were obtained from the Seropedica and Gramacho landfill sites, respectively, located in Rio de Janeiro State, Brazil...
February 19, 2018: Waste Management
Reuven Balkin, Gilad Perez, Andreas Weiler
We examine the dark matter phenomenology of a composite electroweak singlet state. This singlet belongs to the Goldstone sector of a well-motivated extension of the Littlest Higgs with T -parity. A viable parameter space, consistent with the observed dark matter relic abundance as well as with the various collider, electroweak precision and dark matter direct detection experimental constraints is found for this scenario. T -parity implies a rich LHC phenomenology, which forms an interesting interplay between conventional natural SUSY type of signals involving third generation quarks and missing energy, from stop-like particle production and decay, and composite Higgs type of signals involving third generation quarks associated with Higgs and electroweak gauge boson, from vector-like top-partners production and decay...
2018: European Physical Journal. C, Particles and Fields
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