3,101 research outputs found
Limited Lifespan of Fragile Regions in Mammalian Evolution
An important question in genome evolution is whether there exist fragile
regions (rearrangement hotspots) where chromosomal rearrangements are happening
over and over again. Although nearly all recent studies supported the existence
of fragile regions in mammalian genomes, the most comprehensive phylogenomic
study of mammals (Ma et al. (2006) Genome Research 16, 1557-1565) raised some
doubts about their existence. We demonstrate that fragile regions are subject
to a "birth and death" process, implying that fragility has limited
evolutionary lifespan. This finding implies that fragile regions migrate to
different locations in different mammals, explaining why there exist only a few
chromosomal breakpoints shared between different lineages. The birth and death
of fragile regions phenomenon reinforces the hypothesis that rearrangements are
promoted by matching segmental duplications and suggests putative locations of
the currently active fragile regions in the human genome
Thermodynamic analysis of high-temperature pumped thermal energy storage systems: Refrigerant selection, performance and limitations
[EN] One of the bottlenecks for a wider implementation of renewable energies is the development of efficient energy storage systems which can compensate for the intermittency of renewable energy sources. Pumped thermal energy storage (PTES) is a very recent technology that can be a promising site-independent alternative to pumped hydro energy storage or compressed air energy storage, without the corresponding geological and environmental restrictions. Accordingly, this paper presents a full thermodynamic analysis of a PTES system consisting of a high-temperature heat pump (HTHP), which drives an organic Rankine cycle (ORC) by means of an intermediate high-temperature thermal energy storage system (HT-TES). The latter combines both latent and sensible heat thermal energy storage sub-systems to maximize the advantage of the refrigerant subcooling. After validating the proposed model, several parametric studies have been carried out to assess the system performance using different refrigerants and configurations, under a wide range of source and sink temperatures. The results show that for a system that employs the same refrigerant in both the HTHP and ORC, and for a latent heat thermal energy storage system at 133 degrees C, R-1233zd(E) and R-1234ze(Z) present the best performance. Among all the cases studied with a latent heat thermal energy storage system at 133 degrees C, the best system performance, also considering the impact on the environment, has been achieved employing R-1233zd(E) in the HTHP and Butene in the ORC. Such a system can theoretically reach a power ratio of 1.34 under HTHP source and ORC sink temperatures of 100 and 25 degrees C, respectively. (C) 2020 Published by Elsevier Ltd.This work has been partially funded by the grant agreement No. 764042 (CHESTER project) of the European Union's Horizon 2020 research and innovation program.Hassan, A.; O'donoghue, L.; Sánchez Canales, V.; Corberán, JM.; Payá-Herrero, J.; Jockenhoefer, H. (2020). Thermodynamic analysis of high-temperature pumped thermal energy storage systems: Refrigerant selection, performance and limitations. Energy Reports. 6(7):147-159. https://doi.org/10.1016/j.egyr.2020.05.010S14715967Abarr, M., Geels, B., Hertzberg, J., & Montoya, L. D. (2017). Pumped thermal energy storage and bottoming system part A: Concept and model. Energy, 120, 320-331. doi:10.1016/j.energy.2016.11.089Abarr, M., Hertzberg, J., & Montoya, L. D. (2017). Pumped Thermal Energy Storage and Bottoming System Part B: Sensitivity analysis and baseline performance. Energy, 119, 601-611. doi:10.1016/j.energy.2016.11.028Aneke, M., & Wang, M. (2016). Energy storage technologies and real life applications – A state of the art review. Applied Energy, 179, 350-377. doi:10.1016/j.apenergy.2016.06.097Arpagaus, C., Bless, F., Uhlmann, M., Schiffmann, J., & Bertsch, S. S. (2018). High temperature heat pumps: Market overview, state of the art, research status, refrigerants, and application potentials. Energy, 152, 985-1010. doi:10.1016/j.energy.2018.03.166BP plc, 2018. BP Statistical Review of World Energy. London.Budt, M., Wolf, D., Span, R., & Yan, J. (2016). A review on compressed air energy storage: Basic principles, past milestones and recent developments. Applied Energy, 170, 250-268. doi:10.1016/j.apenergy.2016.02.108Cheayb, M., Marin Gallego, M., Tazerout, M., & Poncet, S. (2019). Modelling and experimental validation of a small-scale trigenerative compressed air energy storage system. Applied Energy, 239, 1371-1384. doi:10.1016/j.apenergy.2019.01.222Pereira da Cunha, J., & Eames, P. (2016). Thermal energy storage for low and medium temperature applications using phase change materials – A review. Applied Energy, 177, 227-238. doi:10.1016/j.apenergy.2016.05.097European Comission, 2018. A Clean Planet for all. A European strategic long-term vision for a prosperous, modern, competitive and climate neutral economy. Brussels.European Council, 2014. European Council 23/24 2014 - Conclusions. Brussels.Fan, J., Xie, H., Chen, J., Jiang, D., Li, C., Ngaha Tiedeu, W., & Ambre, J. (2020). Preliminary feasibility analysis of a hybrid pumped-hydro energy storage system using abandoned coal mine goafs. Applied Energy, 258, 114007. doi:10.1016/j.apenergy.2019.114007Frate, G. F., Antonelli, M., & Desideri, U. (2017). A novel Pumped Thermal Electricity Storage (PTES) system with thermal integration. Applied Thermal Engineering, 121, 1051-1058. doi:10.1016/j.applthermaleng.2017.04.127Guo, J., Cai, L., Chen, J., & Zhou, Y. (2016). Performance optimization and comparison of pumped thermal and pumped cryogenic electricity storage systems. Energy, 106, 260-269. doi:10.1016/j.energy.2016.03.053Jockenhöfer, H., Steinmann, W.-D., & Bauer, D. (2018). Detailed numerical investigation of a pumped thermal energy storage with low temperature heat integration. Energy, 145, 665-676. doi:10.1016/j.energy.2017.12.087Kusakana, K. (2019). Hydro aeropower for sustainable electricity cost reduction in South African farming applications. Energy Reports, 5, 1645-1650. doi:10.1016/j.egyr.2019.11.023Laughlin, R. B. (2017). Pumped thermal grid storage with heat exchange. Journal of Renewable and Sustainable Energy, 9(4), 044103. doi:10.1063/1.4994054Lecompte, S., Huisseune, H., van den Broek, M., Vanslambrouck, B., & De Paepe, M. (2015). Review of organic Rankine cycle (ORC) architectures for waste heat recovery. Renewable and Sustainable Energy Reviews, 47, 448-461. doi:10.1016/j.rser.2015.03.089Liu, J.-L., & Wang, J.-H. (2016). A comparative research of two adiabatic compressed air energy storage systems. Energy Conversion and Management, 108, 566-578. doi:10.1016/j.enconman.2015.11.049Ma, T., Yang, H., & Lu, L. (2014). Feasibility study and economic analysis of pumped hydro storage and battery storage for a renewable energy powered island. Energy Conversion and Management, 79, 387-397. doi:10.1016/j.enconman.2013.12.047McTigue, J. D., White, A. J., & Markides, C. N. (2015). Parametric studies and optimisation of pumped thermal electricity storage. Applied Energy, 137, 800-811. doi:10.1016/j.apenergy.2014.08.039Navarro-Peris, E., Corberán, J. M., Falco, L., & Martínez-Galván, I. O. (2013). New non-dimensional performance parameters for the characterization of refrigeration compressors. International Journal of Refrigeration, 36(7), 1951-1964. doi:10.1016/j.ijrefrig.2013.07.007Steinmann, W. D. (2014). The CHEST (Compressed Heat Energy STorage) concept for facility scale thermo mechanical energy storage. Energy, 69, 543-552. doi:10.1016/j.energy.2014.03.049Steinmann, W.-D. (2017). Thermo-mechanical concepts for bulk energy storage. Renewable and Sustainable Energy Reviews, 75, 205-219. doi:10.1016/j.rser.2016.10.065Steinmann, W.-D., Bauer, D., Jockenhöfer, H., & Johnson, M. (2019). Pumped thermal energy storage (PTES) as smart sector-coupling technology for heat and electricity. Energy, 183, 185-190. doi:10.1016/j.energy.2019.06.058Thess, A. (2013). Thermodynamic Efficiency of Pumped Heat Electricity Storage. Physical Review Letters, 111(11). doi:10.1103/physrevlett.111.11060
A Stealth Supersymmetry Sampler
The LHC has strongly constrained models of supersymmetry with traditional
missing energy signatures. We present a variety of models that realize the
concept of Stealth Supersymmetry, i.e. models with R-parity in which one or
more nearly-supersymmetric particles (a "stealth sector") lead to collider
signatures with only a small amount of missing energy. The simplest realization
involves low-scale supersymmetry breaking, with an R-odd particle decaying to
its superpartner and a soft gravitino. We clarify the stealth mechanism and its
differences from compressed supersymmetry and explain the requirements for
stealth models with high-scale supersymmetry breaking, in which the soft
invisible particle is not a gravitino. We also discuss new and distinctive
classes of stealth models that couple through a baryon portal or Z' gauge
interactions. Finally, we present updated limits on stealth supersymmetry in
light of current LHC searches.Comment: 45 pages, 16 figure
Widespread platinum anomaly documented at theYounger Dryas onset in North American sedimentary sequences
Previously, a large platinum (Pt) anomaly was reported in the Greenland ice sheet at the Younger Dryas
boundary (YDB) (12,800 Cal B.P.). In order to evaluate its geographic extent, fire-assay and inductively coupled plasma mass spectrometry (FA and ICP-MS) elemental analyses were performed on 11
widely separated archaeological bulk sedimentary sequences. We document discovery of a distinct Pt anomaly spread widely across North America and dating to the Younger Dryas (YD) onset. The apparent synchroneity of this widespread YDB Pt anomaly is consistent with Greenland Ice Sheet Project 2 (GISP2) data that indicated atmospheric input of platinum-rich dust. We expect the Pt anomaly to serve as a widely-distributed time marker horizon (datum) for identification and correlation of the onset of the YD climatic episode at 12,800 Cal B.P. This Pt datum will facilitate the dating and correlating of archaeological, paleontological, and paleoenvironmental data between sequences, especially those with limited age control
The Impact of Human Conflict on the Genetics of Mastomys natalensis and Lassa Virus in West Africa
Environmental changes have been shown to play an important role in the emergence of new human diseases of zoonotic origin. The contribution of social factors to their spread, especially conflicts followed by mass movement of populations, has not been extensively investigated. Here we reveal the effects of civil war on the phylogeography of a zoonotic emerging infectious disease by concomitantly studying the population structure, evolution and demography of Lassa virus and its natural reservoir, the rodent Mastomys natalensis, in Guinea, West Africa. Analysis of nucleoprotein gene sequences enabled us to reconstruct the evolutionary history of Lassa virus, which appeared 750 to 900 years ago in Nigeria and only recently spread across western Africa (170 years ago). Bayesian demographic inferences revealed that both the host and the virus populations have gone recently through severe genetic bottlenecks. The timing of these events matches civil war-related mass movements of refugees and accompanying environmental degradation. Forest and habitat destruction and human predation of the natural reservoir are likely explanations for the sharp decline observed in the rodent populations, the consequent virus population decline, and the coincident increased incidence of Lassa fever in these regions. Interestingly, we were also able to detect a similar pattern in Nigeria coinciding with the Biafra war. Our findings show that anthropogenic factors may profoundly impact the population genetics of a virus and its reservoir within the context of an emerging infectious disease
Measurement of B(t->Wb)/B(t->Wq) at the Collider Detector at Fermilab
We present a measurement of the ratio of top-quark branching fractions R= B(t
-> Wb)/B(t -> Wq), where q can be a b, s or a d quark, using lepton-plus-jets
and dilepton data sets with integrated luminosity of ~162 pb^{-1} collected
with the Collider Detector at Fermilab during Run II of the Tevatron. The
measurement is derived from the relative numbers of t-tbar events with
different multiplicity of identified secondary vertices. We set a lower limit
of R > 0.61 at 95% confidence level.Comment: 7 pages, 2 figures, published in Physical Review Letters; changes
made to be consistent with published versio
Search for ZZ and ZW Production in ppbar Collisions at sqrt(s) = 1.96 TeV
We present a search for ZZ and ZW vector boson pair production in ppbar
collisions at sqrt(s) = 1.96 TeV using the leptonic decay channels ZZ --> ll nu
nu, ZZ --> l l l' l' and ZW --> l l l' nu. In a data sample corresponding to an
integrated luminosity of 194 pb-1 collected with the Collider Detector at
Fermilab, 3 candidate events are found with an expected background of 1.0 +/-
0.2 events. We set a 95% confidence level upper limit of 15.2 pb on the cross
section for ZZ plus ZW production, compared to the standard model prediction of
5.0 +/- 0.4 pb.Comment: 7 pages, 2 figures. This version is accepted for publication by Phys.
Rev. D Rapid Communication
Measurement of Exclusive rho^0 rho^0 Production in Two-Photon Collisions at High Q^2 at LEP
Exclusive rho rho production in two-photon collisions involving a single
highly virtual photon is studied with data collected at LEP at centre-of-mass
energies 89GeV < \sqrt{s} < 209GeV with a total integrated luminosity of
854.7pb^-1 The cross section of the process gamma gamma^* -> rho rho is
determined as a function of the photon virtuality, Q^2 and the two-photon
centre-of-mass energy, Wgg, in the kinematic region: 1.2GeV^2 < Q^2 < 30GeV^2
and 1.1GeV < Wgg < 3GeV
Studying the Underlying Event in Drell-Yan and High Transverse Momentum Jet Production at the Tevatron
We study the underlying event in proton-antiproton collisions by examining
the behavior of charged particles (transverse momentum pT > 0.5 GeV/c,
pseudorapidity |\eta| < 1) produced in association with large transverse
momentum jets (~2.2 fb-1) or with Drell-Yan lepton-pairs (~2.7 fb-1) in the
Z-boson mass region (70 < M(pair) < 110 GeV/c2) as measured by CDF at 1.96 TeV
center-of-mass energy. We use the direction of the lepton-pair (in Drell-Yan
production) or the leading jet (in high-pT jet production) in each event to
define three regions of \eta-\phi space; toward, away, and transverse, where
\phi is the azimuthal scattering angle. For Drell-Yan production (excluding the
leptons) both the toward and transverse regions are very sensitive to the
underlying event. In high-pT jet production the transverse region is very
sensitive to the underlying event and is separated into a MAX and MIN
transverse region, which helps separate the hard component (initial and
final-state radiation) from the beam-beam remnant and multiple parton
interaction components of the scattering. The data are corrected to the
particle level to remove detector effects and are then compared with several
QCD Monte-Carlo models. The goal of this analysis is to provide data that can
be used to test and improve the QCD Monte-Carlo models of the underlying event
that are used to simulate hadron-hadron collisions.Comment: Submitted to Phys.Rev.
Measurement of the Cross Section for Prompt Diphoton Production in p-pbar Collisions at sqrt(s) = 1.96 TeV
We report a measurement of the rate of prompt diphoton production in
collisions at using a data sample of 207
pb collected with the upgraded Collider Detector at Fermilab (CDF II).
The background from non-prompt sources is determined using a statistical method
based on differences in the electromagnetic showers. The cross section is
measured as a function of the diphoton mass, the transverse momentum of the
diphoton system, and the azimuthal angle between the two photons and is found
to be consistent with perturbative QCD predictions.Comment: 7 pages, 3 figures,revtex4. Version accepted by PRL, but with cross
section tables i
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