Unusual Spectrum Research Articles

Dielectric relaxation of water: assessing the impact of localized modes, translational diffusion, and collective dynamics.

A multitude of distinct physical processes and molecular mechanisms have been introduced in the past in an effort to understand the unusual dielectric loss spectrum of water with its pronounced peak at roughly 20 GHz. Our computer simulations including ab initio molecular dynamics provide no evidence for a major impact of cage dynamics or local-diffusive motion on the lineshape below 200 GHz. We also show that the collective motion of hundreds of water molecules and/or their significant diffusive displacements are not required. Instead, the dielectric relaxation of water up to about 200 GHz can be quantitatively described in terms of two unimodal and smoothly decaying spectral contributions.

A class of continuous non-associative algebras arising from algebraic groups including

Abstract We give a construction that takes a simple linear algebraic group G over a field and produces a commutative, unital, and simple non-associative algebra A over that field. Two attractions of this construction are that (1) when G has type $E_8$ , the algebra A is obtained by adjoining a unit to the 3875-dimensional representation; and (2) it is effective, in that the product operation on A can be implemented on a computer. A description of the algebra in the $E_8$ case has been requested for some time, and interest has been increased by the recent proof that $E_8$ is the full automorphism group of that algebra. The algebras obtained by our construction have an unusual Peirce spectrum.

An Unusual Transmission Spectrum for the Sub-Saturn KELT-11b Suggestive of a Subsolar Water Abundance

Abstract We present an optical-to-infrared transmission spectrum of the inflated sub-Saturn KELT-11b measured with the Transiting Exoplanet Survey Satellite (TESS), the Hubble Space Telescope (HST) Wide Field Camera 3 G141 spectroscopic grism, and the Spitzer Space Telescope (Spitzer) at 3.6 μm, in addition to a Spitzer 4.5 μm secondary eclipse. The precise HST transmission spectrum notably reveals a low-amplitude water feature with an unusual shape. Based on free-retrieval analyses with varying molecular abundances, we find strong evidence for water absorption. Depending on model assumptions, we also find tentative evidence for other absorbers (HCN, TiO, and AlO). The retrieved water abundance is generally ≲0.1× solar (0.001–0.7× solar over a range of model assumptions), several orders of magnitude lower than expected from planet formation models based on the solar system metallicity trend. We also consider chemical-equilibrium and self-consistent 1D radiative-convective equilibrium model fits and find that they, too, prefer low metallicities ([M/H] ≲ −2, consistent with the free-retrieval results). However, all of the retrievals should be interpreted with some caution because they either require additional absorbers that are far out of chemical equilibrium to explain the shape of the spectrum or are simply poor fits to the data. Finally, we find that the Spitzer secondary eclipse is indicative of full heat redistribution from KELT-11b’s dayside to nightside, assuming a clear dayside. These potentially unusual results for KELT-11b’s composition are suggestive of new challenges on the horizon for atmosphere and formation models in the face of increasingly precise measurements of exoplanet spectra.

Rotational Dynamics of Nitroxide Biradical in Room-Temperature Ionic Liquids Measured by Quantitative Simulation of EPR Spectra.

Temperature dependences of electron paramagnetic resonance (EPR) spectra of an imidazoline nitroxide biradical spin probe in a series of room-temperature ionic liquids in the temperature range 124-390 K have been quantitatively simulated. The unusual asymmetric EPR spectrum shape previously observed in these systems [Kokorin et al., Appl. Magn. Res. 48 (2016) 287] is shown to originate from anisotropic rotational diffusion of the probe molecule. All experimental spectra were quantitatively reproduced in simulation using a unified set of geometrical and magnetic parameters of the spin probe, which were found to be fully consistent with the biradical geometry obtained from density functional theory calculations. Temperature dependences of rotation diffusion coefficient of the probe characterize the molecular mobility of the ionic liquid, whereas the temperature dependences of the spin-exchange integral J and of the isotropic hyperfine interaction constant, aN, are shown to reflect the intramolecular conformation motions of the biradical probe.

Relativistic Cornell-type mechanism of exotic scalar resonances

The physical masses of the lowest scalar mesons strongly disagree with the calculated $q\overline{q}$ pole values. It is the purpose of this paper to explain theoretically the unusual spectrum of scalar mesons for both the ground and excited states, using the known spectra of the corresponding $q\overline{q}$ states and their connection to the meson resonances. The well-known Cornell coupled-channel mechanism is exploited for this connection together with the quark-chiral Lagrangian without fitting parameters. In addition to the scalars previously obtained using this method, ${f}_{0}(500)$, ${f}_{0}(980)$, ${a}_{0}(980)$, we predict all ground and first excited scalar states, ${f}_{0}(500)$, ${f}_{0}(980)$, ${a}_{0}(980)$, ${a}_{0}(1450)$, ${K}_{0}^{*}(700)$, ${K}_{0}^{*}(1430)$, ${f}_{0}(1370)$, ${f}_{0}(1710)$, which are in reasonably good agreement with experimental data.

The frequency spectrum and geometry of the Ħal Saflieni Hypogeum appear tuned

The Ħal Saflieni Hypogeum is a unique subterranean Maltese Neolithic sanctuary with a well-documented history of interest in its acoustics (Till, 2017; Debertolis et al., 2015; Reznikoff, 2014; Devereux, 2009; Skeates, 2008; Mifsud and Mifsud 1999; Devereux, 1996; Evans, 1971; Zammit, 1910; Griffiths, 1920). Previous studies have noted its unusual strongly-defined frequency spectrum (Debertolis et al., 2015), but it is unknown if this was coincidental. In this paper, we present evidence that the Hypogeum’s creators shaped the site’s geometry to create or amplify its frequency spectrum, or another property closely correlated with the spectrum. Specifically, we show that the observed spectrum required jointly fine-tuning the dimensions of multiple non-contiguous cave walls across multiple independent chambers, to a degree that seems unlikely to be coincidental. We also note that the peak frequencies are evenly spaced and resemble a whole-tone scale in music, which is also unlikely to be coincidental and suggests the spectrum itself might have held some cultural significance. Taken together, it suggests acoustic or spectral properties may have played a motivational or cultural role for the site's Neolithic creators. This work identifies one of the earliest known examples of a manmade structure with a significant musical element to its interior architecture.

A sciaenid swim bladder with long skinny fingers produces sound with an unusual frequency spectrum

Swim bladders in sciaenid fishes function in hearing in some and sound production in almost all species. Sciaenid swim bladders vary from simple carrot-shaped to two-chambered to possessing various diverticula. Diverticula that terminate close to the ears improve hearing. Other unusual diverticula heading in a caudal direction have not been studied. The fresh-water Asian species Boesemania microlepis has an unusual swim bladder with a slightly restricted anterior region and 6 long-slender caudally-directed diverticula bilaterally. We hypothesized that these diverticula modify sound spectra. Evening advertisement calls consist of a series of multicycle tonal pulses, but the fundamental frequency and first several harmonics are missing or attenuated, and peak frequencies are high, varying between < 1–2 kHz. The fundamental frequency is reflected in the pulse repetition rate and in ripples on the frequency spectrum but not in the number of cycles within a pulse. We suggest that diverticula function as Helmholz absorbers turning the swim bladder into a high-pass filter responsible for the absence of low frequencies typically present in sciaenid calls. Further, we hypothesize that the multicycle pulses are driven by the stretched aponeuroses (flat tendons that connect the sonic muscles to the swim bladder) in this and other sciaenids.

Quantum distance and anomalous Landau levels of flat bands.

Semiclassical quantization of electronic states under a magnetic field, as proposed by Onsager, describes not only the Landau level spectrum but also the geometric responses of metals under a magnetic field1-5. Even in graphene with relativistic energy dispersion, Onsager's rule correctly describes the π Berry phase, as well as the unusual Landau level spectrum of Dirac particles6,7. However, it is unclear whether this semiclassical idea is valid in dispersionless flat-band systems, in which an infinite number of degenerate semiclassical orbits are allowed. Here we show that the semiclassical quantization rule breaks down for a class of dispersionless flat bands called 'singular flat bands'8. The singular flat band has a band crossing with another dispersive band that is enforced by the band-flatness condition, and shows anomalous magnetic responses. The Landau levels of a singular flat band develop in the empty region in which no electronic states exist in the absence of a magnetic field, and exhibit an unusual 1/n dependence on the Landau level index n, which results in diverging orbital magnetic susceptibility. The total energy spread of the Landau levels of a singular flat band is determined by the quantum geometry of the relevant Bloch states, which is characterized by their Hilbert-Schmidt quantum distance. We show that there is a universal and simple relationship between the total Landau level spread of a flat band and the maximum Hilbert-Schmidt quantum distance, which can be verified in various candidate materials. The results indicate that the anomalous Landau level spectrum of flat bands is promising for the direct measurement of the quantum geometry of wavefunctions in condensed matter.

Improving spatial synchronization between X-ray and near-infrared spectra information to predict wood density profiles

Wood density is one of the most important physical properties of the wood, used in improvement programs for wood quality of major timber species. Traditional core sampling of standing trees has been widely used to assess wood density profiles at high spatial resolution by X-ray microdensitometry methods, but alternative methods to predict wood properties quality are also needed. Near-infrared (NIR) spectroscopy, a non-destructive technique, is being increasingly used for wood property assessment and has already been demonstrated to be able to predict wood density. However, the estimation of wood density profiles by NIR has not yet been extensively studied, and improved models using spectra information (NIR) and X-ray data need to be developed. To this end, partial least square regression (PLS-R) models for predicting wood density were developed at a 1.4 mm spatial resolution on Pinus pinaster wood cores, with an improved spatial synchronization along the tangential and radial directions of the strip, between X-ray data and NIR spectra. The validation of the best model showed a high coefficient of determination (0.95), low error (0.026) and no outlier. Compression wood samples were not detected as outliers and were correctly predicted by the model. However, pith spectra were detected as outliers and its predicted values were overestimated by 33% due to unusual spectra suggesting a diverse chemical composition. The results suggest that NIR-PLS models obtained can be used for screening maritime pine wood density profiles along the radii at 1.4 mm spatial resolution.

Evolution of Mutation Rate in Astronomically Large Phytoplankton Populations.

Genetic diversity is expected to be proportional to population size, yet, there is a well-known, but unexplained lack of genetic diversity in large populations—the “Lewontin’s paradox.” Larger populations are expected to evolve lower mutation rates, which may help to explain this paradox. Here, we test this conjecture by measuring the spontaneous mutation rate in a ubiquitous unicellular marine phytoplankton species Emiliania huxleyi (Haptophyta) that has modest genetic diversity despite an astronomically large population size. Genome sequencing of E. huxleyi mutation accumulation lines revealed 455 mutations, with an unusual GC-biased mutation spectrum. This yielded an estimate of the per site mutation rate µ = 5.55×10−10 (CI 95%: 5.05×10−10 – 6.09×10−10), which corresponds to an effective population size Ne ∼ 2.7×106. Such a modest Ne is surprising for a ubiquitous and abundant species that accounts for up to 10% of global primary productivity in the oceans. Our results indicate that even exceptionally large populations do not evolve mutation rates lower than ∼10−10 per nucleotide per cell division. Consequently, the extreme disparity between modest genetic diversity and astronomically large population size in the plankton species cannot be explained by an unusually low mutation rate.

Spontaneously broken boosts and the Goldstone continuum

The spontaneous breaking of boost invariance is ubiquitous in nature, yet the associated Goldstone bosons are nowhere to be seen. We discuss why some subtleties are to be expected in the Goldstone phenomenon for spontaneously broken boosts, and derive the corresponding quantum mechanical, non-perturbative Goldstone theorem. Despite similarities with more standard Goldstone theorems, we show by examples that ours can be obeyed by quite unusual spectra of low-energy excitations. In particular, for non- relativistic Fermi liquids, we prove that it is obeyed by the particle-hole continuum. To the best of our knowledge, this is the first example of a Goldstone theorem obeyed by a continuum rather than by (approximately stable) single-particle Goldstone boson states in an interacting theory at zero temperature.

Ionic emissions in comet C/2016 R2 (Pan-STARRS)

ABSTRACT We have carried out observations of a peculiar comet, C/2016 R2 (Pan-STARRS), using a low-resolution spectrograph mounted on the 1.2-m telescope at Mount Abu Infrared Observatory, India. The comet was observed on two dates in 2018 January, when it was at a heliocentric distance of 2.8 au. A study based on our observations has revealed that the optical spectrum of this comet is quite unusual compared with general cometary spectra. Most major cometary emissions, such as C2, C3 and CN, were absent in comet C/2016 R2. However, the comet’s spectrum showed very strong emission bands from ionic species such as CO+ and N$_{2}^{+}$. A mean N2/CO ratio of 0.09 ± 0.02 was derived from the spectra and an extremely low depletion factor of 1.6 ± 0.4 has been estimated for this ratio compared with the solar nebula. We have also detected minor emission features beyond 5400 Å, albeit marginally. The column densities of CO+ and N$_{2}^{+}$ were calculated from their emission bands. The optical spectrum suggests that the cometary ice is dominated by CO. The low depletion factor of the N2/CO ratio in this comet, compared with the solar nebula, and the unusual spectrum of the comet are consequences of distinctive processing at the location of its formation in the early solar nebula.

A Metastable Photoinduced Protein-Flavin Adduct in Choline Oxidase, an Enzyme Not Involved in Light-Dependent Processes.

Photoinduced formation of protein-flavin adducts is crucial in photoresponsive proteins containing light-oxygen-voltage (LOV) domains. LOV proteins typically share an N-terminal sensor domain with FMN and a C-terminal effector domain such as a kinase, a phosphodiesterase, or a DNA-binding protein. Light absorption by FMN results in a covalent flavin-cysteine adduct, which allosterically translates to the linked effector domain. Photoinduced protein-flavin adducts have not been reported in enzymes not involved in light-dependent processes. Here, we have used fluorescence, pH effects, and mutagenesis to follow up a serendipitous observation of an unusual fluorescence excitation spectrum in choline oxidase at alkaline pH (M. Ghanem and G. Gadda, unpublished observations). Physiologically, choline oxidase oxidizes choline to betaine through two FAD-associated reactions and is not a photoenzyme. The enzyme-bound flavin showed a progressive shift of the fluorescence excitation maximum (λex) from 468 to 399 nm with increasing pH values between pH 6.0 and 10.0, consistent with a metastable photoinduced protein-flavin adduct. In contrast, the maximal λem was independent of pH, with values of ∼526 nm. For comparison, fluorescence spectra of FAD in bulk solution had maximal values differing by ≤2 nm at different pH values, with λex at 453 nm and λem at 527 nm. The unusual behavior of the enzyme persisted in the mutated S101A enzyme variant but was eliminated in the H466Q variant, suggesting that the photoinduced species is likely a C4a-N-histidyl-FAD. The results provide evidence that metastable photoinduced formation of a flavin-protein adduct can occur in an enzyme that is not a photoreceptor or a photoenzyme.

Detection of Late-time Optical Emission from SN 1941C in NGC 4136

We report the detection of broad, high-velocity oxygen emission lines from the site of SN 1941C nearly eight decades after outburst, making it the oldest optically detected core-collapse supernova/youngest core-collapse supernova remnant with a well determined age. In contrast to the strongly blueshifted emission line profiles observed for all other late-time CCSNe thought to be due to dust extinction of rear hemisphere ejecta, SN 1941C's spectrum exhibits stronger redshifted than blueshifted emissions of [O I] 6300, 6364 A, [O II] 7319, 7330 A, and [O III] 4959, 5007 A. The oxygen emissions exhibit rest frame expansion velocities of -2200 to +4400 km/s. No other significant broad line emissions were detected including Halpha emission. We discuss possible causes for this unusual spectrum and compare SN 1941C's optical and X-ray luminosities to other evolved CCSNe.

Addressing Ligand-Based Redox in Molybdenum-Dependent Methionine Sulfoxide Reductase.

A combination of pulsed EPR, CW EPR, and X-ray absorption spectroscopies has been employed to probe the geometric and electronic structure of the E. coli periplasmic molybdenum-dependent methionine sulfoxide reductase (MsrP). 17O and 1H pulsed EPR spectra show that the as-isolated Mo(V) enzyme form does not possess an exchangeable H2O/OH- ligand bound to Mo as found in the sulfite oxidizing enzymes of the same family. The nature of the unusual CW EPR spectrum has been re-evaluated in light of new data on the MsrP-N45R variant and related small-molecule analogues of the active site. These data point to a novel "thiol-blocked" [(PDT)MoVO(SCys)(thiolate)]- structure, which is supported by new EXAFS data. We discuss these new results in the context of ligand-based and metal-based redox chemistry in the enzymatic oxygen atom transfer reaction.

Carbon nanotube array as a van der Waals two-dimensional hyperbolic material

We use an ab-initio approach to design and study a novel two-dimensional material - a planar array of carbon nanotubes separated by an optimal distance defined by the van der Waals interaction. We show that the energy spectrum for an array of quasi-metallic nanotubes is described by a strongly anisotropic hyperbolic dispersion and formulate a model low-energy Hamiltonian for its semi-analytical treatment. Periodic-potential-induced lifting of the valley degeneracy for an array of zigzag narrow-gap nanotubes leads to the band gap collapse. In contrast, the band gap is opened in an array of gapless armchair tubes. These unusual spectra, marked by pronounced van Hove singularities in the low-energy density of states, open the opportunity for interesting physical effects and prospective optoelectronic applications.

Singular Characteristics of Optical Thue–Morse Multilayers Composed of PT‐Symmetric Elements

AbstractAperiodic 1D Thue–Morse (TM) multilayer optical structures composed of two parity‐time‐symmetric (PT‐symmetric) elements are constructed. The transfer matrix and scattering matrix are utilized for singular propagation characteristic analysis of the structures. The structures display interesting and singular properties, including an unusual eigenvalue spectra, transparency, and unidirectional reflectionless and unidirectional invisibility. Additionally, even‐generation and odd‐generation structures show a significant difference in the aforementioned four properties. The main reason for this is the symmetry difference between the two structures: for even‐generation structures, each individual element as well as the entire system with respect to the PT‐symmetry; while for the odd‐generation structures, each individual element has PT‐symmetry; however, the system as a whole does not have PT‐symmetry. The propagation characteristics of the entire structure, which is not a PT‐symmetric system being composed of PT‐symmetric elements, have not yet been reported. This work can contribute to the understanding of the TM sequence, as well as contribute to understanding the influence of the degree of PT‐symmetry on the singular optical propagation characteristics of aperiodic optical structures. Additionally, this may open new possibilities for important applications, such as the design of a diverse family of all‐optical devices with intriguing behaviors.

Ultra-luminous quasars at redshift z &amp;gt; 4.5 from SkyMapper

ABSTRACT The most luminous quasars at high-redshift harbour the fastest growing and most massive black holes in the early Universe. They are exceedingly rare and hard to find. Here, we present our search for the most luminous quasars in the redshift range from z = 4.5 to 5 using data from SkyMapper, Gaia, and WISE. We use colours to select likely high-redshift quasars and reduce the stellar contamination of the candidate set with parallax and proper motion data. In ∼12 500 deg2 of Southern sky, we find 92 candidates brighter than Rp = 18.2. Spectroscopic follow-up has revealed 21 quasars at z ≥ 4 (16 of which are within z = [4.5, 5]), as well as several red quasars, Broad-Absorption-Line (BAL) quasars and objects with unusual spectra, which we tentatively label OFeLoBALQSOs at redshifts of z ≈ 1 to 2. This work lifts the number of known bright z ≥ 4.5 quasars in the Southern hemisphere from 10 to 26 and brings the total number of quasars known at Rp &amp;lt; 18.2 and z ≥ 4.5 to 42.

Antiphospholipid syndrome: a case report with an unusual wide spectrum of clinical manifestations

BackgroundAntiphospholipid syndrome (APS) is an autoimmune disease characterized by the occurrence of venous and/or arterial thrombosis, and the detection of circulating antiphospholipid antibodies. The classification criteria for definite APS are actually met when at least one clinical criterion (thrombosis or pregnancy morbidity) is present in association of one laboratory criterion (LAC, aCL antibody or aβ2GPI antibody present on two or more occasions, at least 12 weeks a part), and thrombosis should be confirmed by objective validated criteria. The average age of primary APS patients has been reported to be about 35–40 years and the disease is more common in women than in men.Case presentationIn this report, we described a rare case of an adult male who presented over a period of 9 years with a wide spectrum of clinical manifestations involving different organs that were not initially diagnosed as APS. Dizziness and syncope were his first clinical symptoms, and a non-bacterial thrombotic endocarditis (NBTE) involving the mitral valve was at first diagnosed. Subsequently, the patient also presented with generalized seizures and subsequent head injury. When the patient was admitted to our clinic with bilateral epistaxis and fever, thrombocytopenia was revealed. Moreover, laboratory examinations showed acute pancreatitis with an increase of levels of inflammation markers.ConclusionBased on the patient’s medical history and all the examination results, it was possible to make a diagnosis of primary APS and, starting from diagnosis of thrombocytopenia, we were allowed to conclude that all of manifestation were epi-phenomena of a unique clinical entity, rather than unrelated diseases. Though APS is one of the most common thrombocytophilias, unfortunately, it is not recognized often enough. The lack of prevention in undiagnosed patients may cause severe complications which can in turn result in the death of those patients.

Therapeutic Applications of Ethanol: A Review.

To review knowledge on therapeutic uses of ethanol and the latter's effectiveness and safety profiles in a range of indications. MEDLINE and PubMed databases were searched for relevant peer-reviewed papers published in English between 1888 and 2018 using the following search terms: ethanol, therapeutic, alcohol withdrawal syndrome, antiseptic, antidote, methanol, ethylene glycol, neurolysis, embolization, cyst, sclerosing agent, sclerotherapy, arteriovenous malformations, ablating agent. Studies providing information about association between alcohol and therapeutic indications, or mechanic explanation for the association were included for review. According to the World Health Organization, approximately three millions deaths worldwide are attributable to alcohol consumption each year. However, the low-to-moderate consumption of ethanol has a number of beneficial effects (mainly on cardiovascular mortality and diabetes). Hence, ethanol has an unusual spectrum of effects that seems interesting for therapeutic purposes. Ethanol's risk-benefit ratio appears to be positive in some therapeutic indications such as antidote to methanol or ethylene glycol poisoning, neurolysis, alcohol withdrawal syndrome, or antiseptic. With the development of interventional radio technologies, and thus extremely precise access to anatomical structures, alcohol has been given new indications - particularly as an embolization, sclerosing or ablation agent. Moreover, constant progress in our knowledge of ethanol's pharmacodynamics might highlight other therapeutic indications for this compound in the future. Ethanol's low cost and wide availability make it a valuable therapeutic agent, compared with other reference treatments. Furthermore, ethanol has a long track record of safety and effectiveness in the indications mentioned above.