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Altered visual perception near the hands: a critical review of attentional and neurophysiological models

Goodhew, Stephanie C.; Edwards, Mark; Ferber, Susanne; Pratt, Jay
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
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26.71%
Visual perception changes as a function of hand proximity. While various theoretical accounts have been offered for this alteration (attentional prioritisation, bimodal cell involvement, detailed evaluation, and magnocellular neuron input enhancement), the current literature lacks consensus on these mechanisms. The purpose of this review, therefore, is to critically review the existing body of literature in light of these distinct theoretical accounts. We find that a growing number of results support the magnocellular (M-cell) enhancement account, and are difficult to reconcile with general attention-based explanations. Despite this key theoretical development in the field, there has been some ambiguity with interpretations offered in recent papers, for example, equating the existing attentional and M-cell based explanations, when in fact they make contrasting predictions. We therefore highlight the differential predictions arising from the distinct theoretical accounts. Importantly, however, we also offer novel perspectives that synthesises the role of attention and neurophysiological mechanisms in understanding altered visual perception near the hands. We envisage that this theoretical development will ensure that the field can progress from documenting behavioural differences...

Improving the safety and efficacy of bimodal electric tissue ablation.

Tiong, Leong Ung
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2012
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Introduction: Bimodal electric tissue ablation (BETA) is a new method of ablation, which combines the process of electrolysis with radiofrequency ablation (RFA) to increase the size of tissue ablations. The cathode of the electrolytic circuit is connected to the radiofrequency (RF) electrode to increase the surrounding tissue hydration. This allows the RFA process to continue for a longer period of time and therefore produce larger ablations. Previous research has shown that BETA could produce larger ablations compared to standard RFA and that it did not produce any significant short or long-term complications. The studies described here aim to increase the knowledge on how BETA works to facilitate its translation into clinical practice to treat liver tumours. Materials & Methods The first study tested whether BETA really acts by increasing the hydration of tissues around the RF electrode. This was achieved by reversing the polarity of the electrolytic circuit, which theoretically would produce smaller ablations compared to standard RFA. The second study assessed where would be the best location (skin, parietal peritoneum or liver) for the anode of the electrolytic circuit during a BETA process. The third experiment determined whether the principle of BETA could be incorporated into the Cool-Tip RF system...

Noninvasive protein structural flexibility mapping by bimodal dynamic force microscopy

Martinez-Martin, D.; Herruzo, E. T.; Dietz, C.; Gomez-Herrero, J.; Garcia, R.
Fonte: American Physical Society Publicador: American Physical Society
Tipo: Artigo de Revista Científica
ENG
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Mapping of the protein structural flexibility with sub-2-nm spatial resolution in liquid is achieved by combining bimodal excitation and frequency modulation force microscopy. The excitation of two cantilever eigenmodes in dynamic force microscopy enables the separation between topography and flexibility mapping. We have measured variations of the elastic modulus in a single antibody pentamer from 8 to 18 MPa when the probe is moved from the end of the protein arm to the central protrusion. Bimodal dynamic force microscopy enables us to perform the measurements under very small repulsive loads (30–40 pN)

The distribution of wave heights and periods for seas with unimodal and bimodal power density spectra

Sharpe, Matthew Michael
Fonte: Escola de Pós-Graduação Naval Publicador: Escola de Pós-Graduação Naval
Tipo: Tese de Doutorado
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CIVINS; Approved for public release ; distribution is unlimited; Observed distributions of wave heights and periods taken from one year of surface wave monitoring near Martha's Vineyard are compared to distributions based on narrow-band theory. The joint distributions of wave heights and periods and the marginal height distributions are examined. The observed significant wave heights and periods of the extreme waves are also studied. Seas are classified by the shapes of their power density spectra. Spectra with a single peak are designated as unimodal and spectra with two peaks as bimodal. Seas are further classified by spectral width, a function of the thee lowest spectral moments. The joint distributions of wave heights and periods from seas with narrow spectral widths take the general shape predicted by narrow-band theory and the statistics of extreme waves for these seas are well described. As spectral width increases, agreement between the theoretical and observed distributions diminishes and the significant wave heights and statistics of extreme waves show increasingly variability. Bimodal seas with wide-banded spectra are found to have larger significant and extreme wave heights and shorter extreme wave periods than unimodal seas of the same width. Theses.; U.S. Naval Postgraduate School...

Interactions of multiple signaling pathways in neuropeptide Y-mediated bimodal vascular smooth muscle cell growth

Pons, Jennifer; Kitlinska, Joanna; Jacques, Danielle; Perreault, Claudine; Nader, Moni; Everhart, Lindsay; Zhang, Ying; Zukowska, Zofia
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /07/2008 EN
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Neuropeptide Y (NPY), a sympathetic cotransmitter, acts via G protein-coupled receptors to stimulate constriction and vascular smooth muscle cell (VSMC) proliferation through interactions with its Y1 receptors. However, VSMC proliferation appears bimodal, with high- and low-affinity peaks differentially blocked by antagonists of both Y1 and Y5 receptors. Here, we sought to determine the signaling mechanisms of NPY-mediated bimodal mitogenesis. In rat aortic VSMCs, NPY's mitogenic effect at all concentrations was blocked by pertussis toxin and was associated with decreased forskolin-stimulated cAMP levels. NPY also increased intracellular calcium levels; in contrast to mitogenesis, this effect was dose dependent. The rise in intracellular Ca2+ depended on extracellular Ca2+ and was mediated via activation of Y1 receptors, but not Y5 receptors. Despite differences in calcium, the signaling pathways activated at low and high NPY concentrations were similar. The mitogenic effect of the peptide at all doses was completely blocked by inhibitors of calcium/calmodulin-dependent kinase II (CaMKII), protein kinase C (PKC), and mitogen-activated protein kinase kinase, MEK1/2. Thus, in VSMCs, NPY-mediated mitogenesis signals primarily via Y1 receptors activating 2 Ca2+-dependent...

Validating a bimodal intravascular ultrasound (IVUS) and near-infrared fluorescence (NIRF) catheter for atherosclerotic plaque detection in rabbits

Abran, Maxime; Stähli, Barbara E.; Merlet, Nolwenn; Mihalache-Avram, Teodora; Mecteau, Mélanie; Rhéaume, Eric; Busseuil, David; Tardif, Jean-Claude; Lesage, Frédéric
Fonte: Optical Society of America Publicador: Optical Society of America
Tipo: Artigo de Revista Científica
Publicado em 14/09/2015 EN
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Coronary artery disease is characterized by atherosclerotic plaque formation. Despite impressive advances in intravascular imaging modalities, in vivo molecular plaque characterization remains challenging, and different multimodality imaging systems have been proposed. We validated an engineered bimodal intravascular ultrasound imaging (IVUS) / near-infrared fluorescence (NIRF) imaging catheter in vivo using a balloon injury atherosclerosis rabbit model. Rabbit aortas and right iliac arteries were scanned in vivo after indocyanine green (ICG) injection, and compared to corresponding ex vivo fluorescence and white light images. Areas of ICG accumulation were colocalized with macroscopic atherosclerotic plaque formation. In vivo imaging was performed with the bimodal catheter integrating ICG-induced fluorescence signals into cross-sectional IVUS imaging. In vivo ICG accumulation corresponded to ex vivo fluorescence signal intensity and IVUS identified plaques.

Mode coupling and photon antibunching in a bimodal cavity containing a dipole-quantum-emitter

Liu, Yu-Long; Wang, Guan-Zhong; Liu, Yu-xi; Nori, Franco
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/06/2015
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We study the effect of mode-coupling on a single-photon device in which a dipole-quantum-emitter (DQE) is embedded in a bimodal whispering-gallery-mode cavity (WGMC). A scatterer is used to induce mode coupling between counter-clockwise and clockwise propagating light fields, which interact with the DQE. In contrast to models for the interaction between a DQE and a (one-mode or two-mode) cavity field, we find that strong photon antibunching can occur even for a weak DQE-field coupling and large dephasing of the DQE, when mode coupling is introduced. We also find that mode coupling can make the device robust against either the frequency mismatch between cavity modes and the DQE or the coupling strength mismatch between the DQE and each mode in the two-mode cavity. Moreover, we find that these mismatches can be used to generate better antibunching in the weak DQE-field coupling regime. Our study shows that mode coupling in a bimodal cavity is very important for the realization of a good single-photon device.; Comment: 12pages,11figures

A Mechanism for the Oxygen and Iron Bimodal Radial Distribution Formation in the Disc of our Galaxy

Acharova, I. A.; Lépine, J. R. D.; Mishurov, Yu. N.; Shustov, B. M.; Tutukov, A. V.; Wiebe, D. S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 03/09/2009
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26.71%
Recently it has been proposed that there are two types of SN Ia progenitors -- short-lived and long-lived. On the basis of this idea, we develope a theory of a unified mechanism for the formation of the bimodal radial distribution of iron and oxygen in the Galactic disc. The underlying cause for the formation of the fine structure of the radial abundance pattern is the influence of spiral arms, specifically, the combined effect of the corotation resonance and turbulent diffusion. From our modelling we conclude that to explain the bimodal radial distributions simultaneously for oxygen and iron and to obtain approximately equal total iron output from different types of supernovae, the mean ejected iron mass per supernova event should be the same as quoted in literature if maximum mass of stars, that eject heavy elements, is $50 M_{\odot}$. For the upper mass limit of $70 M_{\odot}$ the production of iron by a supernova II explosion should be increased by about 1.5 times.; Comment: 7 pages, 6 figures, MNRAS submitted

Spectral Formation in Accreting X-Ray Pulsars: Bimodal Variation of the Cyclotron Energy with Luminosity

Becker, P. A.; Klochkov, D.; Schonherr, G.; Nishimura, O.; Ferrigno, C.; Caballero, I.; Kretschmar, P.; Wolff, M. T.; Wilms, J.; Staubert, R.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 23/05/2012
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26.71%
Accretion-powered X-ray pulsars exhibit significant variability of the Cyclotron Resonance Scattering Feature (CRSF) centroid energy on pulse-to-pulse timescales, and also on much longer timescales. Two types of spectral variability are observed. For sources in group 1, the CRSF energy is negatively correlated with the variable source luminosity, and for sources in group 2, the opposite behavior is observed. The physical basis for this bimodal behavior is currently not understood. We explore the hypothesis that the accretion dynamics in the group 1 sources is dominated by radiation pressure near the stellar surface, and that Coulomb interactions decelerate the gas to rest in the group 2 sources. We derive a new expression for the critical luminosity such that radiation pressure decelerates the matter to rest in the supercritical sources. The formula for the critical luminosity is evaluated for 5 sources, using the maximum value of the CRSF centroid energy to estimate the surface magnetic field strength. The results confirm that the group 1 sources are supercritical and the group 2 sources are subcritical, although the situation is less clear for those highly variable sources that cross over the critical line. We also explain the variation of the CRSF energy with luminosity as a consequence of the variation of the characteristic emission height. The sign of the height variation is opposite in the supercritical and subcritical cases...

Investigation on the Bimodal Distribution of the Duration of Gamma-ray Bursts from BATSE Light Curves

Yu, Wenfei; Li, Tipei; Wu, Mei
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 09/03/1999
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26.71%
We have investigated the bimodal distribution of the duration of BATSE gamma-ray bursts (GRBs) by analyzing light curves of 64 ms time resolution. We define the average pulse width of GRBs from the auto-correlation function of GRB profiles. The distribution of the average pulse width of GRBs is bimodal, suggesting that GRBs are composed of long-pulse GRBs and short-pulse GRBs. The average pulse width of long-pulse GRBs appears correlated with the peak flux, consistent with the time dilation effect anticipated from the cosmological origin of GRBs. However, the correlation between the average pulse width and the peak flux for the short-pulse GRBs doesn't show such a tendency, which needs further study with higher time resolution data.; Comment: 4 pages including 3 figures, poster paper of the 19th Texas Symposium in Paris

A geometric construction of Coxeter-Dynkin diagrams of bimodal singularities

Ebeling, Wolfgang; Ploog, David
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We consider the Berglund-H\"ubsch transpose of a bimodal invertible polynomial and construct a triangulated category associated to the compactification of a suitable deformation of the singularity. This is done in such a way that the corresponding Grothendieck group with the (negative) Euler form can be described by a graph which corresponds to the Coxeter-Dynkin diagram with respect to a distinguished basis of vanishing cycles of the bimodal singularity.; Comment: 18 pages, 8 figures. The published version lists four equations in Table 4 which are not quasismooth. We thank Kazushi Ueda for this observation. In the new version, the equations have been corrected; the results hold without changes

Exact Results for the Kuramoto Model with a Bimodal Frequency Distribution

Martens, E. A.; Barreto, E.; Strogatz, S. H.; Ott, E.; So, P.; Antonsen, T. M.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
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We analyze a large system of globally coupled phase oscillators whose natural frequencies are bimodally distributed. The dynamics of this system has been the subject of long-standing interest. In 1984 Kuramoto proposed several conjectures about its behavior; ten years later, Crawford obtained the first analytical results by means of a local center manifold calculation. Nevertheless, many questions have remained open, especially about the possibility of global bifurcations. Here we derive the system's complete stability diagram for the special case where the bimodal distribution consists of two equally weighted Lorentzians. Using an ansatz recently discovered by Ott and Antonsen, we show that in this case the infinite-dimensional problem reduces exactly to a flow in four dimensions. Depending on the parameters and initial conditions, the long-term dynamics evolves to one of three states: incoherence, where all the oscillators are desynchronized; partial synchrony, where a macroscopic group of phase-locked oscillators coexists with a sea of desynchronized ones; and a standing wave state, where two counter-rotating groups of phase-locked oscillators emerge. Analytical results are presented for the bifurcation boundaries between these states. Similar results are also obtained for the case in which the bimodal distribution is given by the sum of two Gaussians.; Comment: 28 pages...

Resolution-dependent mechanisms for bimodal switching-time distributions in simulated Fe nanopillars

Thompson, S. H.; Brown, G.; Kuhnle, A.; Rikvold, P. A.; Novotny, M. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 06/11/2008
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26.71%
We study the magnetization-switching statistics following reversal of the applied field for three separate computational models representing the same physical system, an iron nanopillar. The primary difference between the models is the resolution of the computational lattice and, consequently, the intrinsic parameters that must be rescaled to retain similarity to the physical system. Considering the first-passage time to zero for the magnetization component in the longitudinal (easy-axis) direction, we look for applied fields that result in bimodal distributions of this time for each system and compare the results to the experimental system. We observe that the relevant fluctuations leading to bimodal distributions are different for each lattice resolution and result in magnetization-switching behavior that is unique to each computational model. Correct model resolution is thus essential for obtaining reliable numerical results for the system dynamics.; Comment: 21 pages, 9 figures (color)

An Explanation for the Bimodal Distribution of Gamma-Ray Bursts: Millisecond Pulsars from Accretion-Induced Collapse

Yi, Insu; Blackman, Eric G.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/10/1997
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26.71%
Cosmological gamma-ray bursts (GRBs) could be driven by dissipation of pure electromagnetic energy (Poynting flux) extracted from rapidly rotating compact objects with strong magnetic fields. One such possibility is a young millisecond pulsar (MSP) formed from accretion-induced collapse (AIC) of a white dwarf. The combination of an efficient magnetic dynamo, likely operating during the first seconds of the initially hot and turbulent MSP interior, and the subsequent modest beaming of gamma-ray emitting outflows, would easily account for energy constraints. But the remarkable feature of such models is that they may naturally explain the hitherto unexplained bimodal distribution in GRB time durations. The two burst classes could correspond to MSPs that form spinning above and below a gravitationally unstable limit respectively. In the former case, the spin-down time scale is due to gravitational radiation emission ($<1s$) while the spin-down time scale of the latter is due to electromagnetic dipole emission ($\gg 1s$). These two time scales account for the short and long GRB durations, i.e. the observed bimodal GRB duration distribution. A natural prediction is that the short duration GRBs would be accompanied by strong gravitational radiation emission which is absent from the longer class. Both would show millisecond variabilities.; Comment: 10 pages...

Phase Diagram of the 3D Bimodal Random-Field Ising Model

Fytas, N. G.; Malakis, A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 01/02/2008
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26.71%
The one-parametric Wang-Landau (WL) method is implemented together with an extrapolation scheme to yield approximations of the two-dimensional (exchange-energy, field-energy) density of states (DOS) of the 3D bimodal random-field Ising model (RFIM). The present approach generalizes our earlier WL implementations, by handling the final stage of the WL process as an entropic sampling scheme, appropriate for the recording of the required two-parametric histograms. We test the accuracy of the proposed extrapolation scheme and then apply it to study the size-shift behavior of the phase diagram of the 3D bimodal RFIM. We present a finite-size converging approach and a well-behaved sequence of estimates for the critical disorder strength. Their asymptotic shift-behavior yields the critical disorder strength and the associated correlation length's exponent, in agreement with previous estimates from ground-state studies of the model.; Comment: 18 pages, 7 figures

$\mu$-constant monodromy groups and Torelli results for marked singularities, for the unimodal and some bimodal singularities

Gauss, Falko; Hertling, Claus
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/11/2015
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This paper is a sequel to [He7]. There a notion of marking of isolated hypersurface singularities was defined, and a moduli space $M_\mu^{mar}$ for marked singularities in one $\mu$-homotopy class of isolated hypersurface singularities was established. One can consider it as a global $\mu$-constant stratum or as a Teichm\"uller space for singularities. It comes together with a $\mu$-constant monodromy group $G^{mar}\subset G_Z$. Here $G_Z$ is the group of automorphisms of a Milnor lattice which respect the Seifert form. It was conjectured that $M_\mu^{mar}$ is connected. This is equivalent to $G^{mar}= G_Z$. Also Torelli type conjectures were formulated. All conjectures were proved for the simple singularities and 22 of the exceptional unimodal and bimodal singularities. In this paper the conjectures are proved for the remaining unimodal singularities and the remaining exceptional bimodal singularities.; Comment: 39 pages, 1 figure

The Bimodal Galaxy Stellar Mass Function in the COSMOS Survey to z~1: A Steep Faint End and a New Galaxy Dichotomy

Drory, N.; Bundy, K.; Leauthaud, A.; Scoville, N.; Capak, P.; Ilbert, O.; Kartaltepe, J. S.; Kneib, J. P.; McCracken, H. J.; Salvato, M.; Sanders, D. B.; Thompson, D.; Willott, C. J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/10/2009
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26.71%
We present a new analysis of stellar mass functions (MF) in the COSMOS field to fainter limits than has been previously probed to z~1. Neither the total nor the passive or star-forming MF can be well fit with a single Schechter function once one probes below 3e9 Msun. We observe a dip or plateau at masses ~1e10 Msun, and an upturn towards a steep faint-end slope of -1.7 at lower mass at any z<1. This bimodal nature of the MF is not solely a result of the blue/red dichotomy. The blue MF is by itself bimodal at z~1. This suggests a new dichotomy in galaxy formation that predates the appearance of the red sequence. We propose two interpretations for this bimodality. If the gas fraction increases towards lower mass, galaxies with M_baryon~1e10 Msun would shift to lower stellar masses, creating the observed dip. This would indicate a change in star formation efficiency, perhaps linked to supernovae feedback becoming much more efficient. Therefore, we investigate whether the dip is present in the baryonic (stars+gas) MF. Alternatively, the dip could be created by an enhancement of the galaxy assembly rate at ~1e11 Msun, a phenomenon that naturally arises if the baryon fraction peaks at M_halo ~1e12 Msun. In this scenario, galaxies occupying the bump around M* would be identified with central galaxies and the second fainter component having a steep faint-end slope with satellites. While the dip is apparent in the total MF at any z...

The Centers of Early-Type Galaxies with HST. VI. Bimodal Central Surface Brightness Profiles

Lauer, Tod R.; Gebhardt, Karl; Faber, S. M.; Richstone, Douglas; Tremaine, Scott; Kormendy, John; Aller, M. C.; Bender, Ralf; Dressler, Alan; Filippenko, Alexei V.; Green, Richard; Ho, Luis C.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/09/2006
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26.71%
We combine the results from several HST investigations of the central structure of early-type galaxies to generate a large sample of parameterized surface photometry. The studies included were those that used the "Nuker law" to characterize the inner light distributions of the galaxies. The sample comprises WFPC1 and WFPC2 V band observations published earlier by our group, R band WFPC2 photometry of Rest et al., NICMOS H band photometry by Ravindranath et al. and Quillen et al., and the BCG WFPC2 I band photometry of Laine et al. The distribution of the logarithmic slopes of the central profiles strongly affirms that the central structure of elliptical galaxies with Mv < -19 is bimodal, based on both parametric and non-parametric analysis. At the HST resolution limit, most galaxies are either power-law systems, which have steep cusps in surface brightness, or core systems, which have shallow cusps interior to a steeper envelope brightness distribution. A rapid transition between the two forms occurs over the luminosity range -22 < Mv < -20, with cores dominating at the highest luminosities, and power-laws at the lowest. There are a few "intermediate" systems that have both cusp slopes and total luminosities that fall within the core/power-law transition...

The Bimodal Ising Spin Glass in dimension three : Corrections to scaling

Hukushima, K.; Campbell, I. A.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/03/2009
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Equilibrium numerical data on the three dimensional bimodal interaction Ising spin glass up to size L=48 show that corrections to scaling, which are known to be strong, behave in a non-monotonic manner with size. Extrapolation to the infinite size thermodynamic limit is difficult; however the large L data indicate that the ordering temperature Tc lies significantly higher than the values which have been estimated from previous numerical work limited to smaller sizes. In view of the present results it is at the least premature to conclude that the three dimensional bimodal and Gaussian Ising spin glasses lie in the same universality class.; Comment: 7 pages, 9 figures

Nonlinear Color-Metallicity Relations of Globular Clusters. V. Nonlinear Absorption-line Index versus Metallicity Relations and Bimodal Index Distributions of M31 Globular Clusters

Kim, Sooyoung; Yoon, Suk-Jin; Chung, Chul; Caldwell, Nelson; Schiavon, Ricardo P.; Kang, Yongbeom; Rey, Soo-Chang; Lee, Young-Wook
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/03/2013
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26.71%
Recent spectroscopy on the globular cluster (GC) system of M31 with unprecedented precision witnessed a clear bimodality in absorption-line index distributions of old GCs. Such division of extragalactic GCs, so far asserted mainly by photometric color bimodality, has been viewed as the presence of merely two distinct metallicity subgroups within individual galaxies and forms a critical backbone of various galaxy formation theories. Given that spectroscopy is a more detailed probe into stellar population than photometry, the discovery of index bimodality may point to the very existence of dual GC populations. However, here we show that the observed spectroscopic dichotomy of M31 GCs emerges due to the nonlinear nature of metallicity-to-index conversion and thus one does not necessarily have to invoke two separate GC subsystems. We take this as a close analogy to the recent view that metallicity-color nonlinearity is primarily responsible for observed GC color bimodality. We also demonstrate that the metallicity-sensitive magnesium line displays non-negligible metallicity-index nonlinearity and Balmer lines show rather strong nonlinearity. This gives rise to bimodal index distributions, which are routinely interpreted as bimodal metallicity distributions...