RFLP Analyses of Chloroplast DNA of the Crested Wheatgrasses

The crested wheatgrasses (Agropyron spp.) are widely distributed Eurasian grasses that have been used to re-vegetate millions of hectares of land in the northern plains and intermountain areas of North America. The genus consists of about 10 species that are based on the ‘P’ genome and includes diploids (2n = 14), tetraploids (2n = 28) and octoploids (2n = 42) (Dewey, 1984, Vogel et al., 1999). The two main agronomic species used in North America are A. cristatum (L.) Gaertner and A. desertorum (Fischer ex Link) Schultes. Chloroplast genomes are predominately maternally inherited through the cytoplasm in angiosperms. Chloroplast DNA (cpDNA) variation can provide information on the evolutionary development of plant species. The objective of this study was to determine if chloroplast DNA polymorphisms occur within and among ploidy levels of these two main species of the Agropyron complex

Criticality without frustration for quantum spin-1 chains

Frustration-free (FF) spin chains have a property that their ground state minimizes all individual terms in the chain Hamiltonian. We ask how entangled the ground state of a FF quantum spin-s chain with nearest-neighbor interactions can be for small values of s. While FF spin-1/2 chains are known to have unentangled ground states, the case s=1 remains less explored. We propose the first example of a FF translation-invariant spin-1 chain that has a unique highly entangled ground state and exhibits some signatures of a critical behavior. The ground state can be viewed as the uniform superposition of balanced strings of left and right parentheses separated by empty spaces. Entanglement entropy of one half of the chain scales as log(n)/2 + O(1), where n is the number of spins. We prove that the energy gap above the ground state is polynomial in 1/n. The proof relies on a new result concerning statistics of Dyck paths which might be of independent interest.Comment: 11 pages, 2 figures. Version 2: minor changes in the proof of Lemma

Surface morphology and magnetic anisotropy in (Ga,Mn)As

Atomic Force Microscopy and Grazing incidence X-ray diffraction measurements have revealed the presence of ripples aligned along the $[1\bar{1}0]$ direction on the surface of (Ga,Mn)As layers grown on GaAs(001) substrates and buffer layers, with periodicity of about 50 nm in all samples that have been studied. These samples show the strong symmetry breaking uniaxial magnetic anisotropy normally observed in such materials. We observe a clear correlation between the amplitude of the surface ripples and the strength of the uniaxial magnetic anisotropy component suggesting that these ripples might be the source of such anisotropy.Comment: 3 pages, 4 figures, 1 table. Replaced with published versio

Non-uniform carrier density in Cd3_3As2_2 evidenced by optical spectroscopy

We report the detailed optical properties of Cd$_3$As$_2$ crystals in a wide parameter space: temperature, magnetic field, carrier concentration and crystal orientation. We investigate high-quality crystals synthesized by three different techniques. In all the studied samples, independently of how they were prepared and how they were treated before the optical experiments, our data indicate conspicuous fluctuations in the carrier density (up to 30%). These charge puddles have a characteristic scale of 100 $\mu$m, they become more pronounced at low temperatures, and possibly, they become enhanced by the presence of crystal twinning. The Drude response is characterized by very small scattering rates ($\sim 1$ meV) for as-grown samples. Mechanical treatment, such as cutting or polishing, influences the optical properties of single crystals, by increasing the Drude scattering rate and also modifying the high frequency optical response. Magneto-reflectivity and Kerr rotation are consistent with electron-like charge carriers and a spatially non-uniform carrier density.Comment: Accepted in Physical Review

Degradation behavior of Ti-Nb alloys: Corrosion behavior through 21 days of immersion and tribocorrosion behavior against alumina

Non-toxic and allergic free beta-type Ti alloys are attractive metallic implant materials due to their lower Young's modulus and good biocompatibility, but the corrosion and tribocorrosion behavior are yet to be fully understood. In this study, corrosion behavior of Ti-15Nb and Ti-40Nb alloys was investigated and compared with the commercial Ti-6Al-4V alloy through an immersion period of 21 days. The tribocorrosion behavior was investigated under open-circuit potential by using a ball-on-plate tribometer. Results suggested that the beta-type Ti-40Nb alloy having 51 GPa Young's modulus had lower corrosion and wear resistance as compared to the alpha + beta-type Ti-15Nb and Ti-6Al-4V alloys.This work is supported by FCTwith the reference project UID/EEA/04436/2019 and M-ERA-NET/0001/2015 (FAPESP proc. #2015/50.280-5), CNPq (307.279/2013-8) and FAPESP (2015/09.480-0). The authors would also like to acknowledge Prof. Graca Minas for the provision of the profilometry. I. Caha is grateful for financial support through PhD grant under NORTE-08-5369-FSE-000012 project

Corrosion and tribocorrosion behaviour of titanium nitride thin films grown on titanium under different deposition times

Ti and its alloys exhibit combination of unique properties for biomedical applications, however their poor tribo-electrochemical behaviour is a major concern. Therefore, TiN coatings were deposited on cp-Ti (grade 4) by sputtering technique aiming the improvement of its tribocorrosion behaviour. The properties of the coated samples, using different TiN deposition times, were characterized by using grazing incidence X-ray diffraction, FIB-SEM, and nanoindentation. The corrosion behaviour was studied by electrochemical impedance spectroscopy and potentiodynamic polarization in 9 g/L NaCl solution at body temperature. Tribocorrosion tests were employed under open circuit potential by using a ball-on-plate tribometer with 1 N normal load, 3 mm total stroke length, 1 Hz frequency, and 1800 s sliding duration. The results suggested that the TiN coatings deposited during 80 min presented better corrosion and tribocorrosion behaviour as compared to the bare metal and TiN coatings deposited during 30 min.This work is supported by FCT with the reference project UID/EEA/04436/2013, COMPETE 2020 with the code POCI-01-0145-FEDER-006941, and M-ERA-NET/0001/2015 (FAPESP proc. #2015/50.280-5) project. I. Caha grateful for financial support through PhD grant under NORTE-08-5369-FSE-000012 project. The authors would also like to acknowledge Dr. Paulo Ferreira and Dr. Enrique Carbo-Argibay (International Iberian Nanotechnology Laboratory) for the provision of FIB facilities, and Prof. Grata Minas (Universidade do Minho) for the provision of profilometry

Interband absorption edge in the topological insulators Bi-2(Te1-xSex)(3)

We have investigated the optical properties of thin films of topological insulators Bi2Te3, Bi2Se3, and their alloys Bi-2(Te1-x Se-x)(3) on BaF2 substrates by a combination of infrared ellipsometry and reflectivity in the energy range from 0.06 to 6.5 eV. For the onset of interband absorption in Bi2Se3, after the correction for the Burstein-Moss effect, we find the value of the direct band gap of 215 +/- 10 meV at 10 K. Our data support the picture that Bi2Se3 has a direct band gap located at the Gamma point in the Brillouin zone and that the valence band reaches up to the Dirac point and has the shape of a downward-oriented paraboloid, i.e., without a camel-back structure. In Bi2Te3, the onset of strong direct interband absorption at 10 K is at a similar energy of about 200 meV, with a weaker additional feature at about 170 meV. Our data support the recent GW band-structure calculations suggesting that the direct interband transition does not occur at the Gamma point but near the Z-F line of the Brillouin zone. In the Bi-2(Te1-x Se-x)(3) alloy, the energy of the onset of direct interband transitions exhibits a maximum near x = 0.3 (i.e., the composition of Bi2Te2Se), suggesting that the crossover of the direct interband transitions between the two points in the Brillouin zone occurs close to this composition

The fine structure of the comparative

The paper provides evidence for a more articulated structure of the comparative as compared with the one in Bobaljik (2012). We propose to split up Bobaljik's cmpr head into two distinct heads, C1 and C2. Looking at Czech, Old Church Slavonic and English, we show that this proposal explains a range of facts about suppletion and allomorphy. A crucial ingredient of our analysis is the claim that adjectival roots are not a-categorial, but spell out adjectival functional structure. Specifically, we argue that adjectival roots come in various types, differing in the amount of functional structure they spell out. In order to correctly model the competition between roots, we further introduce a Faithfulness Restriction on Cyclic Override, which allows us to dispense with the Elsewhere Principle

SiOx Patterned Based Substrates Implemented in Cu(In,Ga)Se2 Ultrathin Solar Cells: Optimum Thickness

Interface recombination in sub-µm optoelectronics has a major detrimental impact on devices’ performance, showing the need for tailored passivation strategies to reach a technological boost. In this work, SiOx passivation based substrates were developed and integrated into ultrathin Cu(In,Ga)Se2 (CIGS) solar cells. This study aims to understand the impact of a passivation strategy, which uses several SiOx layer thicknesses (3, 8, and 25 nm) integrated into high performance substrates (HPS). The experimental study is complemented with 3D Lumerical finite-difference time-domain (FDTD) and 2D Silvaco ATLAS optical and electrical simulations, respectively, to perform a decoupling of optical and electronic gains, allowing for a deep discussion on the impact of the SiOx layer thickness in the CIGS solar cell performance. This study shows that as the passivation layer thickness increases, a rise in parasitic losses is observed. Hence, a balance between beneficial passivation and optical effects with harmful architectural constraints defines a threshold thickness to attain the best solar cell performance. Analyzing their electrical parameters, the 8 nm novel SiOx based substrate achieved a light to power conversion efficiency value of 13.2 %, a 1.3 % absolute improvement over the conventional Mo substrate (without SiOx).info:eu-repo/semantics/submittedVersio

Magneto-optical signature of massless Kane electrons in Cd3As2

We report on optical reflectivity experiments performed on Cd3As2 over a broad range of photon energies and magnetic fields. The observed response clearly indicates the presence of 3D massless charge carriers. The specific cyclotron resonance absorption in the quantum limit implies that we are probing massless Kane electrons rather than symmetry-protected 3D Dirac particles. The latter may appear at a smaller energy scale and are not directly observed in our infrared experiments.Comment: 5 pages, 4 figures + supplementary materials (17 pages), to be published in Phys. Rev. Let