23,064 research outputs found
Linear Operator Inequality and Null Controllability with Vanishing Energy for Unbounded Control Systems
No full textWe consider a linear boundary or point control system on a Hilbert space which is null controllable at some time . To every initial state we associate the minimal ``energy'' needed to transfer to in a time (``energy'' of a control being the square of its norm). Clearly, it decreases with the control time . We shall prove that, under suitable spectral properties of the linear system operator, the minimal energy converges to for $ T\to+\infty
Null Subjects in Northeast English
No full textThis paper presents data and analysis relating to null subjects in spoken colloquial English.
While English is not a „pro-drop? language (i.e. subjects must usually be overt), a corpus of
speech collected on Tyneside and Wearside in 2007 shows that null subjects are permitted in
finite clauses in certain contexts. This paper analyses these examples and follow-up
questionnaires, and compares the data with the other types of null subject described in the
literature (pro-drop, topic-drop, early null subjects, aphasics? null subjects and „diary-drop?),
ultimately concluding that the colloquial English phenomenon is most closely related to diary-
drop
The appearance, motion, and disappearance of three-dimensional magnetic null points
No full textN.A.M. acknowledges support from NASA grants NNX11AB61G, NNX12AB25G, and NNX15AF43G; NASA contract NNM07AB07C; and NSF SHINE grants AGS-1156076 and AGS-1358342 to SAO. C.E.P. acknowledges support from the St Andrews 2013 STFC Consolidated grant.While theoretical models and simulations of magnetic reconnection often assume symmetry such that the magnetic null point when present is co-located with a flow stagnation point, the introduction of asymmetry typically leads to non-ideal flows across the null point. To understand this behavior, we present exact expressions for the motion of three-dimensional linear null points. The most general expression shows that linear null points move in the direction along which the magnetic field and its time derivative are antiparallel. Null point motion in resistive magnetohydrodynamics results from advection by the bulk plasma flow and resistive diffusion of the magnetic field, which allows non-ideal flows across topological boundaries. Null point motion is described intrinsically by parameters evaluated locally; however, global dynamics help set the local conditions at the null point. During a bifurcation of a degenerate null point into a null-null pair or the reverse, the instantaneous velocity of separation or convergence of the null-null pair will typically be infinite along the null space of the Jacobian matrix of the magnetic field, but with finite components in the directions orthogonal to the null space. Not all bifurcating null-null pairs are connected by a separator. Furthermore, except under special circumstances, there will not exist a straight line separator connecting a bifurcating null-null pair. The motion of separators cannot be described using solely local parameters because the identification of a particular field line as a separator may change as a result of non-ideal behavior elsewhere along the field line.Peer reviewe
Partial Functional Rescue of Helicoverpa armigera Single Nucleocapsid Nucleopolyhedrovirus Infectivity by Replacement of F Protein with GP64 from Autographa californica Multicapsid Nucleopolyhedrovirus
No full textTwo distinct envelope fusion proteins (EFPs) (GP64 and F) have been identified in members of the Baculoviridae family of viruses. F proteins are found in group II nucleopolyhedroviruses (NPVs) of alphabaculoviruses and in beta- and deltabaculoviruses, while GP64 occurs only in group I NPVs of alphabaculoviruses. It was proposed that an ancestral baculovirus acquired the gp64 gene that conferred a selective advantage and allowed it to evolve into group I NPVs. The F protein is a functional analogue of GP64, as evidenced from the rescue of gp64-null Autographa californica multicapsid nucleopolyhedrovirus (MNPV) (AcMNPV) by F proteins from group II NPVs or from betabaculoviruses. However, GP64 failed to rescue an F-null Spodoptera exigua MNPV (SeMNPV) (group II NPV). Here, we report the successful generation of an infectious gp64-rescued group II NPV of Helicoverpa armigera (vHaBac Delta F-gp64). Viral growth curve assays and quantitative real-time PCR (Q-PCR), however, showed substantially decreased infectivity of vHaBac Delta F-gp64 compared to the HaF rescue control virus vHaBac Delta F-HaF. Electron microscopy further showed that most vHaBac Delta F-gp64 budded viruses (BV) in the cell culture supernatant lacked envelope components and contained morphologically aberrant nucleocapsids, suggesting the improper BV envelopment or budding of vHaBac Delta F-gp64. Bioassays using pseudotyped viruses with a reintroduced polyhedrin gene showed that GP64-pseudotyped Helicoverpa armigera single nucleocapsid nucleopolyhedrovirus (HearNPV) significantly delayed the mortality of infected H. armigera larvae
Publication Bias Against Null Results
No full textStudies suggest a bias against the publication of null (p > .05) results. Instead of significance, we advocate reporting effect sizes and confidence intervals, and using replication studies. If statistical tests are used, power tests should accompany them.publication, bias, null results
Inclusive W and Z production in the forward region at √s=7TeV
No full textMeasurements of inclusive W and Z boson production cross-sections in pp collisions at s√=7TeV using final states containing muons are presented. The data sample corresponds to an integrated luminosity of 37 pb−1 collected with the LHCb detector. The W and Z bosons are reconstructed from muons with a transverse momentum above 20 GeV/c and pseudorapidity between 2.0 and 4.5, and, in the case of the Z cross-section, a dimuon invariant mass between 60 and 120 GeV/c2. The cross-sections are measured to be 831 ± 9 ± 27 ± 29pb for W +, 656 ± 8 ± 19 ± 23 for W − and 76.7 ± 1.7 ± 3.3 ± 2.7pb for Z, where the first uncertainty is statistical, the second is systematic and the third is due to the luminosity. Differential cross-sections, W and Z cross-section ratios and the lepton charge asymmetry are also measured in the same kinematic region. The ratios are determined to be σW+→μ+ν/σW−→μ−ν−=1.27±0.02±0.01 and (σW+→μ+ν+σW−→μ−ν−)/σZ→μμ=19.4±0.5±0.9 . The results are in general agreement with theoretical predictions, performed at next-to-next-to-leading order in QCD using recently calculated parton distribution functions
Triple null mutant for all three <i>TM2D</i> fly genes is phenotypically similar to single null mutants.
No full text(A) Crossing scheme used to generate TM2D triple null mutant flies. (B) A normal embryonic nervous system highlighted by neuronal nuclei marker Elav (green). (C-D) amxΔ amrtΔ double mutants (C) and amxΔ amrtΔ biscΔ triple mutants (D) exhibit a neurogenic phenotype. (E-K) TM2D double and triple null mutants exhibit no overt morphological phenotypes. Head structures of mutants (F, G) appear normal compared to y w control (E). Mutant wings (I, J) and thorax (L, M) also appear normal compared to control (H, K). Scale bars = 100 μm in (B-D).</p
Approaches for the Joint Evaluation of Hypothesis Tests: Classical Testing, Bayes Testing, and Joint Confirmation
No full textThe occurrence of decision problems with changing roles of null and alternative hypotheses has increased interest in extending the classical hypothesis testing setup. Particularly, confirmation analysis has been in the focus of some recent contributions in econometrics. We emphasize that confirmation analysis is grounded in classical testing and should be contrasted with the Bayesian approach. Differences across the three approaches – traditional classical testing, Bayes testing, joint confirmation – are highlighted for a popular testing problem. A decision is searched for the existence of a unit root in a time-series process on the basis of two tests. One of them has the existence of a unit root as its null hypothesis and its non-existence as its alternative, while the roles of null and alternative are reversed for the other hypothesis test.Confirmation analysis, Decision contours, Unit roots
Evidence for the decay B0→J/ψω and measurement of the relative branching fractions of meson decays to J/ψη and J/ψη′
No full textFirst evidence of the B 0 → J / ψ ω decay is found and the B s 0 → J / ψ η and B s 0 → J / ψ η ′ decays are studied using a dataset corresponding to an integrated luminosity of 1.0 fb -1 collected by the LHCb experiment in proton-proton collisions at a centre-of-mass energy of sqrt(s) = 7 TeV. The branching fractions of these decays are measured relative to that of the B 0 → J / ψ ρ 0 decay:frac(B (B 0 → J / ψ ω), B (B 0 → J / ψ ρ 0)) = 0.89 ± 0.19 (stat) - 0.13 + 0.07 (syst),frac(B (B s 0 → J / ψ η), B (B 0 → J / ψ ρ 0)) = 14.0 ± 1.2 (stat) - 1.5 + 1.1 (syst) - 1.0 + 1.1 (frac(f d, f s)),frac(B (B s 0 → J / ψ η ′), B (B 0 → J / ψ ρ 0)) = 12.7 ± 1.1 (stat) - 1.3 + 0.5 (syst) - 0.9 + 1.0 (frac(f d, f s)), where the last uncertainty is due to the knowledge of f d / f s, the ratio of b-quark hadronization factors that accounts for the different production rate of B 0 and B s 0 mesons. The ratio of the branching fractions of B s 0 → J / ψ η ′ and B s 0 → J / ψ η decays is measured to befrac(B (B s 0 → J / ψ η ′), B (B s 0 → J / ψ η)) = 0.90 ± 0.09 (stat) - 0.02 + 0.06 (syst)
MHD wave propagation in the neighbourhood of a two-dimensional null point
No full textThe nature of fast magnetoacoustic and Alfvén waves is investigated in a zero β plasma. This gives an indication of wave propagation in the low β solar corona. It is found that for a two-dimensional null point, the fast wave is attracted to that point and the front of the wave slows down as it approaches the null point, causing the current density to accumulate there and rise rapidly. Ohmic dissipation will extract the energy in the wave at this point. This illustrates that null points play an important role in the rapid dissipation of fast magnetoacoustic waves and suggests the location where wave heating will occur in the corona. The Alfvén wave behaves in a different manner in that the wave energy is dissipated along the separatrices. For Alfvén waves that are decoupled from fast waves, the value of the plasma β is unimportant. However, the phenomenon of dissipating the majority of the wave energy at a specific place is a feature of both wave types
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