Pronounced Hump Research Articles

Synbranchus of the Middle to Lower Xingu Basin, Brazil, with the description of a new rheophilic species, S. royal (Synbranchiformes: Synbranchidae)

Synbranchus (swamp eel) specimens exhibiting remarkable variation were collected from different habitats during recent fieldwork in the Xingu Basin, Brazil. For this study, those specimens were first sorted into about six morphotypes based on external morphology, especially color pattern. Representatives of each morphotype and additional specimens extralimital to the Xingu Basin were then sequenced for three mitochondrial genes (ATPase 8/6, 16s, and Cytb) and one nuclear (Rag1). Molecular phylogenetic analyses using Maximum Parsimony and Bayesian methods supported the recognition of five distinct lineages of Synbranchus in the middle to lower Xingu Basin and up to 10 species-level lineages across all samples. Two of the Xingu lineages were subsequently identified as the nominal S. marmoratus and S. madeirae, and another two were provisionally treated as Synbranchus spp. 5 and 7. The fifth lineage is formally described here as Synbranchus royal, distinguished by its extremely pronounced nuchal hump with dorsal head profile distinctly concave and rising steeply from above middle of eye vs. nuchal region moderately bulbous with dorsal profile ascending more gradually, straight or with shallow concavity behind eye (S. marmoratus) or nuchal hump lacking, dorsal profile ascending modestly, straight to scarcely concave behind eye (S. lampreia and S. madeirae); and relatively deep body, maximum depth at middle of TL 4.7–5.4% TL (vs. 3.2–4.8% TL in congeners). Synbranchus royal and Synbranchus sp. 7 were found in rocky rapids of main channels of the middle Xingu on the Brazilian Shield uplands, a sharp departure from the lentic habitats commonly associated with synbranchid (swamp) eels.

Superparamagnetism of potassium-doped tris(diphenacyl) iron

Synthesis and exploration of intriguing physical properties of alkali-metal-doped aromatic hydrocarbons have been the important research topics in the fields of physics, chemistry and materials science. In this work, a powder sample of potassium-doped tris(diphenacyl) iron molecular crystal is prepared by the high-vacuum annealing method. The X-ray diffraction results show that the crystal structure of the synthesized sample is different from that of pristine tris(diphenacyl)iron. The direct current (DC) magnetic susceptibilitiy shows a pronounced hump structure near 8.0 K, which is distinct from the paramagnetism of pristine material in the whole temperature range of 1.8–300 K. The alternating current (AC) magnetic susceptibility shows that the hump has a significant frequency dependence, which can safely rule out the possibility of antiferromagnetism. The combination of the Vogel-Fulcher law, the Néel-Brown model and the critical slowing down model reveals that the hump originates from superparamagnetism with a blocking temperature (<i>T</i><sub>B</sub>) of about 8.0 K. According to the results of Raman spectroscopy, it can be confirmed that the 4s electrons of potassium in the doped material are transferred to the benzene ring of tris(diphenacyl)iron, causing the characteristic Raman modes to be red-shifted and the local magnetic moment to form. Our work is of great significance in exploring alkali-metal-doped aromatic hydrocarbons, and provides a new route for searching organic magnetic materials.

Rhyacophila siparantum sp. nov. (Trichoptera: Rhyacophilidae), a new species of the R. philopotamoides species group from the Republic of Kosovo with molecular and ecological notes

In this study we describe Rhyacophila siparantum sp. nov., a new species of the Rhyacophila philopotamoides species group from the Bjeshkët e Nemuna Mountains in Kosovo, based on morphological (male adults) and molecular (sequencing of the barcode region of the cytochrome c oxidase subunit I gene (COI)) characteristics. The new species is morphologically closest to Rhyacophila schmidinarica Urbanič, Krušnik & Malicky, 2000, and also closely resembling Rhyacophila hirticornis McLachlan, 1879. R. siparantum sp. nov. differs from both its most similar congeners primarily by the shape of the segment X, which is in lateral view short apically and with a pronounced lateral hump on the posterior edge. This difference, combined with other characters related to the shape of the second segment of inferior appendages, spine pattern of parameres and size of ventral teeth on segments VI and VII, make R. siparantum sp. nov. easily distinguishable from both most similar congeners. Phylogenetic and taxonomic relationships were reconstructed using two methods of phylogenetic inference, and two species delimitation methods. All this supports Rhyacophila siparantum sp. nov. as a distinct taxon. 
 The adults of Rhyacophila siparantum sp. nov. were found during the period May – August, nearby a small rheocrene spring inside a forested area. The new species is most probably a microendemic of the Bjeshkët e Nemuna, a mountainous massive known for several other endemic species of caddisflies. Rhyacophila siparantum sp. nov. is the seventeenth known species of the genus Rhyacophila Pictet, 1834 from Kosovo.

Mössbauer studies of spin and charge modulations in BaFe2(As1−xPx)2

The BaFe2(As1-xPx)2 compounds with x = 0 (parent), x = 0.10 (under-doped), x = 0.31, 0.33, 0.53 (superconductors with Tc = 27.3 K, 27.6 K, 13.9 K, respectively) and x = 0.70, 0.77 (over-doped) have been investigated versus temperature using 57Fe M\"ossbauer spectroscopy. Special attention was paid to regions of the spin-density-wave (SDW) antiferromagnetic order, spin-nematic phase, and superconducting transition. The BaFe2(As0.90P0.10)2 compound exhibits a reduced amplitude of SDW as compared to the parent compound and preserved universality class of two-dimensional magnetic planes with one-dimensional spins. The spin-nematic phase region for x = 0.10 is characterized by an incoherent magnetic order. BaFe2(As0.69P0.31)2 shows coexistence of a weak magnetic order and superconductivity due to the vicinity of the quantum critical point. The charge density modulations in the BaFe2(As0.67P0.33)2 and BaFe2(As0.47P0.53)2 superconductors are perturbed near Tc. Pronounced hump of the average quadrupole splitting across superconducting transition is observed for the system with x = 0.33. The phosphorus substitution increases the Debye temperature of the BaFe2(As1-xPx)2 compound. Moreover, experimental electron charge densities at Fe nuclei in this material conclusively show that it should be recognized as a hole-doped system. The measured M\"ossbauer spectral shift and spectral area are not affected by transition to the superconducting state. This indicates that neither the average electron density at Fe nuclei nor the dynamical properties of the Fe-sublattice in BaFe2(As1-xPx)2 are sensitive to the superconducting transition. Theoretical calculations of hyperfine parameters determining the patterns of M\"ossbauer spectra of BaFe2(As1-xPx)2 with x = 0, 0.31, 0.5, and 1.0 are performed within the framework of the density functional theory.

Double yielding behavior of in situ microfibrillar polyolefin elastomer/poly(lactic acid) composites: Effect of microfibrillar morphology

AbstractIn situ microfibrillar composites (MFCs), with polyolefin elastomer as matrix and poly(lactic acid) (PLA) as dispersed phase, were successfully prepared using multistage stretching extrusion system. Interestingly, a peculiar phenomenon of double yielding was observed on the stress‐strain curves of MFCs under tensile loading for the first time. The MFCs with 20 wt% PLA microfibrils exhibited two distinct yield points, and a pronounced hump appeared on the stress‐strain curve of PLA‐20. Two‐dimensional small‐angle X‐ray scattering analyses showed that the equatorial streak scattering became stronger with increase in PLA microfibrillar content; the meridional scattering trace became stronger with increase in tensile strain for PLA‐20. The rheological analysis showed that the G′ of PLA‐20 had a plateau in the low frequency region and did not depend on frequency changes.

Spin partners WbJ from the line shapes of the Zb(10610) and Zb(10650)

In a recent paper Phys.Rev. D98, 074023 (2018), the most up-to-date experimental data for all measured production and decay channels of the bottomonium-like states $Z_b(10610)$ and $Z_b(10650)$ were analysed in a field-theoretical coupled-channel approach which respects analyticity and unitarity and incorporates both the pion exchange as well as a short-ranged potential nonperturbatively. All parameters of the interaction were fixed directly from data, and pole positions for both $Z_b$ states were determined. In this work we employ the same approach to predict in a parameter-free way the pole positions and the line shapes in the elastic and inelastic channels of the (still to be discovered) spin partners of the $Z_b$ states. They are conventionally referred to as $W_{bJ}$'s with the quantum numbers $J^{PC}=J^{++}$ ($J=0,1,2$). It is demonstrated that the results of our most advanced pionful fit, which gives the best $\chi^2/{\rm d.o.f.}$ for the data in the $Z_b$ channels, are consistent with all $W_{bJ}$ states being above-threshold resonances which manifest themselves as well pronounced hump structures in the line shapes. On the contrary, in the pionless approach, all $W_{bJ}$'s are virtual states which can be seen as enhanced threshold cusps in the inelastic line shapes. Since the two above scenarios provide different imprints on the observables, the role of the one-pion exchange in the $B^{(*)}\bar{B}^{(*)}$ systems can be inferred from the once available experimental data directly.

Numerical simulation of air ventilation and its suppression on inclined surface-piercing hydrofoils

Hydrofoils with significant camber and thickness can be hydrodynamically advantageous over thin low-camber hydrofoils commonly used on boats with surface-piercing hydrofoil systems, especially at lower speeds when a pronounced drag hump is usually present and cavitation is not yet an issue. The main drawback of such high-lift hydrofoils is a danger of being ventilated with air that can easily propagate from the atmosphere along the foil suction side resulting in a drop of the foil lift-drag ratio. The air ventilation is a complex physical process, modeling of which remains a challenging task. In this study, a computational fluid dynamics solver STAR-CCM+ is applied for simulating air ventilation phenomena on surface-piercing hydrofoils. A good agreement is obtained with available test data for relevant configurations. It is also shown that small fences appropriately placed on the inclined surface-piercing hydrofoil can suppress both downward air ventilation and upward water spray, resulting in greater performance of high-lift hydrofoils at moderate Froude numbers.

Crossover from localized to itinerant states in hydrocarbon Mott insulators.

Crossover from an itinerant state to an isolated electronic state in electron-doped polycyclic aromatic hydrocarbon (PAH) was studied for the two smallest zigzag-type molecules of naphthalene (NN) and anthracene (AN) by focusing on their 1 : 1 stoichiometry, A1(NN) and A1(AN), with alkali metals (A = K and Rb). The competition between on-site Coulombic repulsion energy (U) and bandwidth (W) was argued in terms of their magnetic and electrical properties upon lattice expansion, when A varies from K, with a smaller ionic radius, to Rb, with a larger ionic radius. The temperature-dependence of magnetic susceptibility shows a pronounced hump associated with antiferromagnetic (AFM) interactions for Rb1(NN), being similar to those of K1(NN) and K1(AN) in the earlier report. On the other hand, Rb1(AN) intriguingly exhibits paramagnetic susceptibility, observed in a nearly localized electron system, being apart from an highly correlated Mott insulating state. Crystal structural analyses of the X-ray diffraction profiles show a small difference in lattice parameters of the ab plane among K1(NN), K1(AN), and Rb1(NN), whereas Rb1(AN) exhibits a significantly larger value than those of the others, being indicative of greatly modified interaction energies. The different magnetic properties observed in Rb1(AN) are interpreted from its modified intermolecular distance. The possibility of an emergent metallic state of K1(AN) under high pressure has also been described, referring to electrical transport measured under high pressure.

Systematic Study of the Electronic States in Electron‐Doped Polyacenes

AbstractHigh‐quality polycrystalline polyacenes (PLAs) of anthracene (AN), tetracene (TN), and pentacene (PN) doped with potassium in the 1:1 and 1:2 stoichiometries are prepared and their physical properties are systematically studied by magnetic measurements. The magnetic susceptibilities as a function of temperature for Kx(PLAs) are interpreted in the framework of a band‐filling model. Clear evidence for the occurrence of charge transfer from K to the organic semiconductors is provided. K1(AN) prepared by a solid‐state diffusion process exhibits a pronounced magnetic hump at 140 K, which is associated with antiferromagnetic interactions ascribed to the on‐site Coulomb repulsion in a Mott insulating state, whereas both K1(TN) and K1(PN) show a conventional Curie–Weiss behavior at low temperatures. We successfully demonstrate the tuning of the electronic states of PLA‐type semiconductors in bulk. Comments are given about the possibility of metallic states in potassium‐doped PLAs, which have recently been reported for other polycyclic aromatic hydrocarbons.

Electrical and thermal transport properties of Dy0.95Pr0.05Ba2(Cu1−x Mx)3O7−δ with (M=Fe, Co, Ni and Zn) bulk superconductors

In the present communication, measurements of transition temperature, thermal conductivity, thermoelectric power and specific heat have been carried out on pristine and co-doped samples of Dy0.95Pr0.05Ba2(Cu0.98 M0.02)3O7−δ system [M=Fe, Co, Ni and Zn]. The electrical resistivity results show that all the samples exhibit metallic behavior. The thermal conductivity results illustrate that for pristine sample of DyBa2Cu3O7−δ, the expected pronounced hump in thermal conductivity is seen below the transition temperature. The hump is suppressed with 5% Pr-doping and this is further suppressed with co-doping. The thermoelectric power measurements show that the pristine sample exhibits hole-like behavior and this continues for doped as well co-doped samples. Pristine sample shows the expected jump in specific heat and with Pr-doping a slope change is observed near the transition temperature.

Tuning of the ground state in electron doped anthracene.

High quality bulk samples of anthracene (AN) doped with potassium (K) in 1 : 1 and 2 : 1 stoichiometries were successfully prepared by a method involving a room temperature solid-state mechanical diffusion process prior to intercalation reactions during heat treatment, and their physical properties were studied using both magnetic and optical measurements. The transfer of almost one electron from K to AN in K1(AN) was confirmed by SQUID and ESR measurements. A pronounced magnetic hump centered at 150 K associated with antiferromagnetic interactions was observed, which can most likely be interpreted in terms of on-site Coulomb repulsions of the Mott insulating states. Optical spectra of K1(AN) clearly showed the insulating states, as well as the electron occupation of the LUMO-derived band of AN. Our results demonstrated tuning of the ground state of a typical bulk hydrocarbon by alkali metal intercalation.

Interaction between cationic surfactant of 1-methyl-3-tetradecylimidazolium bromide and anionic polymer of sodium polystyrene sulfonate

The interaction between long-chain imidazolium ionic liquid (C14mimBr) and anionic polyelectrolyte of sodium polystyrene sulfonate (NaPSS) has been studied using surface tension, isothermal titration microcalorimetry (ITC), dynamic light scatting (DLS) and conductance methods. The result shows that the surface tension plots have a pronounced hump in the surface tension at surfactant concentrations below the critical micelle concentration (cmc) of the surfactant. The cooperative adsorption of surfactant and polymer on the surface (PSS) and the formation of polymer/surfactant aggregate in bulk solution (PSM) provide a rational explanation about it. The formation of surfactant/polymer complexes is affected by the concentration of the surfactant or NaPSS, which is also ascertained by ITC and DLS measurements. Further, the thermodynamic parameters are derived from calorimetric titration and conductance curves, and the effects of polymer concentration and temperature on the parameters are evaluated in detail.

Rediscovery and phylogenetic placement of the endemic Malagasy cichlid Ptychochromoides itasy (Teleostei: Cichlidae: Ptychochrominae)

Ptychochromoides itasy Sparks, 2004, known locally in Madagascar as the trondro mainty or marakely à bosse, a robustjet black cichlid with a pronounced nuchal hump in both sexes, had not been collected in the wild for several decades andwas presumed to be extinct. Recently, a relict population of P. itasy was discovered in a tributary of the Tsiribihina Riverin the central highlands, to the west of the capital, Antananarivo. We report on the rediscovery, and present DNA sequenceevidence to both confirm the identity of the species as a member of Ptychochromoides and to resolve the placement of P. itasy within the genus.

Life Cycle Dynamics of Income Uncertainty and Consumption

We propose a method for estimating household income uncertainty that does not impose restrictions on the underlying income shocks or assumptions about household behaviors. We measure income uncertainty as the variance of linear projection errors at various future horizons, up to 25 years ahead, conditional on only the information available to households when the projection is made. Our uncertainty estimates change substantially over the life cycle. We calibrate an income process to match our estimates, allowing the variances of both transitory and persistent shocks to change over the life cycle. Relative to previous studies, we find lower and less persistent income uncertainties that call for a life cycle consumption profile with a less pronounced hump.

Structure, Properties, and Theoretical Electronic Structure of UCuOP and NpCuOP

The compounds UCuOP and NpCuOP have been synthesized and their crystal structures were determined from low-temperature single-crystal X-ray data. These isostructural compounds crystallize with two formula units in space group P4/nmm of the tetragonal system. Each An atom (An = U or Np) is coordinated to four O and four P atoms in a distorted square antiprism; each Cu atom is coordinated to four P atoms in a distorted tetrahedron. Magnetic susceptibility measurements on crushed single crystals indicate that UCuOP orders antiferromagnetically at 224(2) K. Neutron diffraction experiments at 100 and 228 K show the magnetic structure of UCuOP to be type AFI (+ - + -) where ferromagnetically aligned sheets of U atoms in the (001) plane order antiferromagnetically along [001]. The electrical conductivity of UCuOP exhibits metallic character. Its electrical resistivity measured in the ordered region with the current flowing within the tetragonal plane is governed by the scattering of the conduction electrons on antiferromagnetic spin-wave excitations. The electrical resistivity of single-crystalline NpCuOP shows semimetallic character. It is dominated by a pronounced hump at low temperatures, which likely arises owing to long-range magnetic ordering below about 90 K. Density of state analyses using the local spin-density approximation show covalent overlap between AnO and CuP layers of the structure and dominant contributions from 5f-actinide orbitals at the Fermi level. Calculations on a 2 × 2 × 2 supercell of NpCuOP show ferromagnetic ordering within the Np sheets and complex coupling between these planes. Comparisons of the physical properties of these AnCuOP compounds are made with those of the family of related tetragonal uranium phosphide compounds.

Consumption and Time Use Over the Life Cycle

The authors incorporate home production in a dynamic general equilibrium model of consumption and saving with illiquid housing and a collateralized borrowing constraint. They show that the model is capable of explaining life-cycle patterns of households' time use and consumption of different categories. Specifically, households' market hours and home hours are fairly stable early in the life cycle. Market hours start to decline sharply at age 50, while home hours begin to increase at age 55. Households' consumption of the market good, home input, and housing services all exhibit hump shapes over the life cycle, with the market good having the most pronounced hump, followed by the home input, and then housing services. A plausibly parameterized version of the authors' model predicts that the interaction of the labor efficiency profile and the availability of home production technology explain households' time use over the life cycle. The resulting income profiles, the endogenous borrowing constraint and the presence of home production account for the initial hump in all three consumption goods. The consumption profiles in the second half of the life cycle are mostly driven by the complementarity of home hours, home input, and housing in home production.

Electrical and thermal properties of bulk superconductors Eu 0.95Pr 0.05Ba 2(Cu 1−xM x) 3O 7−δ (M = Fe, Ni, Zn and Mn)

Measurements of transition temperature, magneto-resistance, thermal conductivity, thermo-electric power and specific heat have been carried out on co-doped samples of Eu 0.95Pr 0.05Ba 2(Cu 1− x M x ) 3O 7− δ (M = Fe, Ni, Zn and Mn) compounds. It is found that all samples exhibit metallic behavior, except the co-doped sample of Fe that shows semiconducting behavior. It is seen that the upper-critical field H c 2 decreases with Pr-doping. However, an increase in H c 2 for dopants like Fe and Mn is observed. Thermal conductivity for the pristine sample of EuBa 2Cu 3O 7− δ (Eu-123) exhibits a pronounced hump below the superconducting transition temperature T C . However, the peak height of the hump decreases with Pr-doping and such a feature is further suppressed in the co-doped samples. The negative sign of the measured thermo-electric power of Eu-123 indicates that the dominant carrier in this sample is electron-like, whereas it turns to hole-like for all of the doped samples. A jump in specific heat C P is detected in the pure sample of Eu-123 at T C , while only a change in slope in C P is seen around the transition temperature in the Pr-doped sample.

A Semiparametric Characterization of Income Uncertainty Over the Life Cycle

We propose a novel approach to estimate household income uncertainty at various future horizons and characterize how the estimated uncertainty evolves over the life cycle. We measure income uncertainty as the variance of linear forecast errors conditional on information available to households prior to observing the realized income. This approach is semiparametric because we impose essentially no restrictions on the statistical properties of the forecast errors. Relative to previous studies, we find lower and less persistent income uncertainties that call for a life cycle consumption profile with a less pronounced hump.

Observation of hole accumulation at the interface of an undoped InGaN/GaN heterostructure

A pronounced hump structure at about −5 V in the high-frequency capacitance-voltage (C-V) curve of an undoped InGaN/GaN heterostructure is observed and this hump weakens gradually with decreasing measurement frequency, indicating the occurrence of an inversion behavior in the InGaN/GaN heterostructure. The inversion behavior in the C-V curve is attributed to hole accumulation at the heterointerface where a hole well is formed due to the strong piezoelectric polarization effect in the InGaN/GaN heterostructure. The acceptor traps related to Ga vacancies in the InGaN layer are thought to be the source of the minority carriers. The theoretical calculation of band diagram of the InGaN/GaN heterostructure confirms the formation of the hole well at the heterointerface and supports the behavior of hole accumulation under negative bias voltage.

Post common envelope binaries from the SDSS

We report the discovery of the ninth pre-polar, consisting of a late-type ZAMS secondary and a magnetic white dwarf. The white dwarf accretes at extreme low rate, dot{M} ~ 10**-14 Msun/yr, from the wind of the companion donor star. The source was found in our systematic search for WD/MS binaries within SDSS/SEGUE. Based on seven Sloan-spectra we estimate a binary period of ~200, 230, or 270 min. The UV to IR spectral energy distribution was decomposed into a dM3-dM4 ZAMS secondary and a cool white dwarf, ~9000 K, which consistently imply a distance between 360 and 420 pc. The optical spectrum displays one pronounced cyclotron hump, likely originating from a low-temperature plasma, ~1 keV, in a field of 108 MG. We comment on the evolutionary link between polars and pre-polars.