2,879 research outputs found
Deciphering The Preservation Of Fossil Insects: A Case Study From The Crato Member, Early Cretaceous Of Brazil
Exceptionally well-preserved three-dimensional insects with fine details and even labile tissues are ubiquitous in the Crato Member Konservat LagerstÀtte (northeastern Brazil). Here we investigate the preservational pathways which yielded such specimens. We employed high resolution techniques (EDXRF, SR-SXS, SEM, EDS, micro Raman, and PIXE) to understand their fossilisation on mineralogical and geochemical grounds. Pseudomorphs of framboidal pyrite, the dominant fossil microfabric, display size variation when comparing cuticle with inner areas or soft tissues, which we interpret as the result of the balance between ion diffusion rates and nucleation rates of pyrite through the originally decaying carcasses. Furthermore, the mineral fabrics are associated with structures that can be the remains of extracellular polymeric substances (EPS). Geochemical data also point to a concentration of Fe, Zn, and Cu in the fossils in comparison to the embedding rock. Therefore, we consider that biofilms of sulphate reducing bacteria (SRB) had a central role in insect decay and mineralisation. Therefore, we shed light on exceptional preservation of fossils by pyritisation in a Cretaceous limestone lacustrine palaeoenvironment. © 2016 Osés et al.20161
Cryptanalysis of an image encryption scheme based on the Hill cipher
This paper studies the security of an image encryption scheme based on the
Hill cipher and reports its following problems: 1) there is a simple necessary
and sufficient condition that makes a number of secret keys invalid; 2) it is
insensitive to the change of the secret key; 3) it is insensitive to the change
of the plain-image; 4) it can be broken with only one known/chosen-plaintext;
5) it has some other minor defects.Comment: 10 pages, three figure
Rol de Bacillus subtilis y dosis de fĂłsforo en la concentraciĂłn, distribuciĂłn y absorciĂłn de macronutrientes en frijol comĂșn
El conocimiento sobre la absorciĂłn y distribuciĂłn de macronutrientes es indispensable en los programas de fertilizaciĂłn en el cultivo de frijol (Phaseolus vulgaris L.). Al respecto, el empleo de rizobacterias promotoras de crecimiento vegetal (PGPR) en combinaciĂłn con la fertilizaciĂłn fosfatada, podrĂan ejercer un efecto sinĂ©rgico y potencializar la absorciĂłn y distribuciĂłn de nutrientes en este cultivo. Se estableciĂł un experimento con el propĂłsito de investigar la respuesta del cultivo de frijol a cuatro dosis de fĂłsforo (P), (0, 25, 50, 100 kg ha-1 P2O5) y a la cepa Bacillus subtilis Q11 (Bs) (inoculaciĂłn a la semilla y un testigo sin inocular) en la concentraciĂłn, distribuciĂłn y acumulaciĂłn de macronutrientes. El experimento se estableciĂł bajo un diseño de parcelas divididas en bloques al azar con tres repeticiones. SegĂșn los resultados obtenidos, la acumulaciĂłn de biomasa se afectĂł de forma individual por el P y Bs. La mayor acumulaciĂłn de biomasa se obtuvo con dosis de P mayores a los 50 kg ha-1, mientras que la inoculaciĂłn con Bs produjo mayor biomasa que el testigo. La interacciĂłn P Ă Bs afectĂł la concentraciĂłn de nitrĂłgeno, fĂłsforo, potasio, calcio y magnesio en los Ăłrganos de la planta en todas las etapas fenolĂłgicas, excepto en la vaina durante la etapa de llenado de grano. La acumulaciĂłn de nutrientes presentĂł un patrĂłn caracterĂstico sigmoidal y se modificĂł individualmente por el P y la inoculaciĂłn con Bs. La dosis de 50 kg ha-1 de P incrementĂł la acumulaciĂłn de macronutrientes, sobre todo en la etapa de llenado de grano, mientras que el uso de Bs incrementĂł la absorciĂłn en las etapas de llenado de grano y madurez fisiolĂłgica. En conclusiĂłn, se comprobĂł la utilidad de la combinaciĂłn de Bs con P en la modificaciĂłn de la concentraciĂłn, absorciĂłn y acumulaciĂłn de nutrientes en frijol
Search for CP violation in D+âÏÏ+ and D+sâK0SÏ+ decays
A search for CP violation in D + â ÏÏ + decays is performed using data collected in 2011 by the LHCb experiment corresponding to an integrated luminosity of 1.0 fbâ1 at a centre of mass energy of 7 TeV. The CP -violating asymmetry is measured to be (â0.04 ± 0.14 ± 0.14)% for candidates with K â K + mass within 20 MeV/c 2 of the Ï meson mass. A search for a CP -violating asymmetry that varies across the Ï mass region of the D + â K â K + Ï + Dalitz plot is also performed, and no evidence for CP violation is found. In addition, the CP asymmetry in the D+sâK0SÏ+ decay is measured to be (0.61 ± 0.83 ± 0.14)%
Differential branching fraction and angular analysis of the decay B0âKâ0ÎŒ+ÎŒâ
The angular distribution and differential branching fraction of the decay B 0â K â0 ÎŒ + ÎŒ â are studied using a data sample, collected by the LHCb experiment in pp collisions at sâ=7 TeV, corresponding to an integrated luminosity of 1.0 fbâ1. Several angular observables are measured in bins of the dimuon invariant mass squared, q 2. A first measurement of the zero-crossing point of the forward-backward asymmetry of the dimuon system is also presented. The zero-crossing point is measured to be q20=4.9±0.9GeV2/c4 , where the uncertainty is the sum of statistical and systematic uncertainties. The results are consistent with the Standard Model predictions
Observation of associated production of a boson with a meson in the~forward region
A search for associated production of a boson with an open charm meson is
presented using a data sample, corresponding to an integrated luminosity of
of proton--proton collisions at a centre-of-mass energy
of 7\,TeV, collected by the LHCb experiment. %% Seven candidate events for
associated production of a boson with a meson and four candidate
events for a boson with a meson are observed with a combined
significance of 5.1standard deviations. The production cross-sections in the
forward region are measured to be where the first uncertainty is statistical and the
second systematic.Comment: 18 pages, 2 figure
Observation of two new baryon resonances
Two structures are observed close to the kinematic threshold in the mass spectrum in a sample of proton-proton collision data, corresponding
to an integrated luminosity of 3.0 fb recorded by the LHCb experiment.
In the quark model, two baryonic resonances with quark content are
expected in this mass region: the spin-parity and
states, denoted and .
Interpreting the structures as these resonances, we measure the mass
differences and the width of the heavier state to be
MeV,
MeV,
MeV, where the first and second
uncertainties are statistical and systematic, respectively. The width of the
lighter state is consistent with zero, and we place an upper limit of
MeV at 95% confidence level. Relative
production rates of these states are also reported.Comment: 17 pages, 2 figure
Measurement of the relative rate of prompt Ïc0, Ïc1 and Ïc2 production at âs=7TeV
Prompt production of charmonium Ïc0, Ïc1 and Ïc2 mesons is studied using proton-proton collisions at the LHC at a centre-of-mass energy of âs=7TeV. The Ïc mesons are identified through their decay to J/ÏÎł, with J/ÏâÎŒ+muâ using photons that converted in the detector. A data sample, corresponding to an integrated luminosity of 1.0fbâ1 collected by the LHCb detector, is used to measure the relative prompt production rate of Ïc1 and Ïc2 in the rapidity range 2.0<y<4.5 as a function of the J/Ï transverse momentum from 3 to 20 GeV/c. First evidence for Ïc0 meson production at a hadron collider is also presented
Model-independent search for CP violation in D0âKâK+ÏâÏ+ and D0âÏâÏ+Ï+Ïâ decays
A search for CP violation in the phase-space structures of D0 and View the MathML source decays to the final states KâK+ÏâÏ+ and ÏâÏ+Ï+Ïâ is presented. The search is carried out with a data set corresponding to an integrated luminosity of 1.0 fbâ1 collected in 2011 by the LHCb experiment in pp collisions at a centre-of-mass energy of 7 TeV. For the KâK+ÏâÏ+ final state, the four-body phase space is divided into 32 bins, each bin with approximately 1800 decays. The p-value under the hypothesis of no CP violation is 9.1%, and in no bin is a CP asymmetry greater than 6.5% observed. The phase space of the ÏâÏ+Ï+Ïâ final state is partitioned into 128 bins, each bin with approximately 2500 decays. The p-value under the hypothesis of no CP violation is 41%, and in no bin is a CP asymmetry greater than 5.5% observed. All results are consistent with the hypothesis of no CP violation at the current sensitivity
Measurements of the , , meson and baryon lifetimes
Measurements of -hadron lifetimes are reported using collision data,
corresponding to an integrated luminosity of 1.0fb, collected by the
LHCb detector at a centre-of-mass energy of Tev. Using the exclusive decays
, , ,
and the average decay
times in these modes are measured to be = 0.004 0.003 ps, =
0.006 0.004 ps, = 0.013
0.005 ps, = 0.027
0.006 ps and = 0.011
0.005 ps, where the first uncertainty is statistical and the second is
systematic. These represent the most precise lifetime measurements in these
decay modes. In addition, ratios of these lifetimes, and the ratio of the
decay-width difference, , to the average width, , in
the system, , are
reported. All quantities are found to be consistent with Standard Model
expectations.Comment: 28 pages, 4 figures. Updated reference
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