Narrow Stripe Research Articles

ИССЛЕДОВАНИЕ ПАРАМЕТРОВ ПОСТОЯННОЙ ТЕХНОЛОГИЧЕСКОЙ КОЛЕИ, ПРЕДНАЗНЧЕННОЙ ДЛЯ УХОДА ЗА ПОСЕВАМИ СЕЛЬСКОХОЗЯЙСТВЕННЫХ КУЛЬТУР В ЦЕНТРАЛЬНОМ ЧЕРНОЗЕМЬЕ

A study of the parameters of the created and formed permanent tramline intended for the passage of agricultural machinery when caring for crops in the Central Black Earth Region has been completed. It has been established that the width of the lanes used for the passage of agricultural machinery propulsion depends on the type of crops cultivated and the sprayers used, as well as on the location of the tramline on the agricultural field. The average width of the lanes on straight sections when forming a constant tramline for crops, which are sown in a narrow strip method, with a self-propelled sprayer on straight sections was 500 mm, and on turning sections - 900 mm; using a trailed sprayer working in tandem with a tractor, the average stripe width on straight sections was 650 mm, and on turning sections – 900 mm. When creating a constant tramline for sugar beet crops, regardless of the type of agricultural machinery used, the average width of the stripes on straight and turning sections was 900 mm. The length of permanent tramline strips for an agricultural field having a rectangular shape was calculated, and it was found that it depends not only on the geometric shape of the field, but also on the operating parameters of the agricultural machinery used and the nature of the location of straight and turning sections. Based on the data obtained, a calculation was made of the percentage of the allocated area of the agricultural field for its creation or formation. When caring for agricultural crops that are sown in a narrow stripe method using a self-propelled sprayer, the percentage of the allocated field area under a constant tramline is 4.7, and when using a trailed sprayer working in tandem with a tractor, the percentage of the allocated area is 5.9. The percentage of the field area allocated for a constant tramline when cultivating sugar beets is 4.7 and does not depend on the type of agricultural machinery used.

(Invited) Spatially–Resolved Luminescence Properties of Etched Quantum Well Microstructures

Fabrication processes for photonic devices, especially micro- or nano-photonic devices, call for some kind of control of the materials’ optical properties at the stage of the final device. Our study focusses on measuring the optical quality of quantum well (QW) containing materials after device processing, using steps such as etching which allows fabrication of optical waveguides for example. We first designed and realized specific material structures based on an InP substrate, with a series of InAsxP1-x quantum wells such as illustrated on the figure. The samples were grown by gas-phase molecular beam epitaxy. The samples were characterized by spatially-resolved photoluminescence (PL) at low temperature (10 K). The top right part shows a typical spectrum measured from the sample we have grown: sharp lines associated with each QW can be clearly identified thanks to a careful grading of the As/P composition in each QW, while keeping its thickness to a constant value (typically 7 to 8 nm). Then we etched the samples (in the form of rectangular ridges as shown) using different etching processes, based either on wet etching or reactive ion etching (RIE), and recorded the PL spectra with high spatial resolution across the obtained structures. In parallel, the samples after etching were also characterized by cross-sectional scanning electron microscopy. Data processing from the series of PL spectra was then performed in order the characterize the effects of etching on the QW materials.We show PL intensity profiles across a series of etched stripes of different widths resulting from a RIE process. These intensity profiles were obtained from the lines associated with the different QWs in the structure. One can observe, first of all, that the PL intensity gradually increases from the edges to the center of the stripes, over a range of up to 10 µm. One can also observe that for “wide” stripes, i.e. 30 or 50 µm, the PL intensity for each line saturates at the same level in the central part. However, for the narrower stripes (10 or 20 µm), the PL signal does not reach the same level. This is the signature of some PL-limitation phenomenon, which extends its effects far from the etched sidewalls. A “standard” phenomenon resulting solely from non-radiative recombination at the etched sidewalls is excluded. Non-radiative recombination can only affect regions which are less than one charge carrier diffusion length from the sidewalls. Diffusion length in our materials is less than 1 µm. Therefore, some kind of “long range” interaction seems to affect our samples. We propose that this long range interaction is due to some stray static electric field resulting from the presence of residual ions left by the etching process at the sidewalls. The electric field affects the PL intensity through dissociation of excitons. Moreover, we observed that different conditions for the etching process (wet etching versus RIE, crystallographic orientation of the stripes) impact the magnitude of this PL intensity quenching.[1] Pearton S 1997 Materials Science and Engineering: B 44 1–7[2] Landesman J P, Isik-Goktas N, LaPierre R R, Levallois C, Ghanad-Tavakoli S, Pargon E, Petit-Etienne C and Jiménez J 2021 Journal of Physics D: Applied Physics 54 445106[3] Fiore A, Rossetti M, Alloing B, Paranthoen C, Chen J X, Geelhaar L and Riechert H 2004 Physical Review B 70 205311[4] Bludau W and Wagner E 1976 Physical Review B 13 5410–5414 Figure 1

A new species of the genus Homalocerus Schoenherr, 1839 (Coleoptera: Belidae) from south-eastern Brazil

A new species, Homalocerus vanini sp. n., of the subtribe Homalocerina (Belini, Belinae) is described and illustrated from the State of Rio de Janeiro, Brazil. The new species is similar to Homalocerus flavicornis Vanin, 1976 but differs in a thinner and more strongly curved rostrum, a pronotum with narrow lateral stripes of hairs and without a central spot, apices of the base of the elytra without spots of hairs, and larger body size.

A thermo-mechanical model of the thermal evolution and incorporation of metamorphic soles in Tethyan ophiolites: a case study from Oman

Abstract Ophiolites are remnants of oceanic crust and mantle, now typically found within continental mountain ranges like the Alps. Particularly in areas once part of the Tethys Ocean, ophiolites are often accompanied by narrow stripes of metamorphic rocks, commonly referred to as metamorphic soles. These metamorphic soles typically exhibit peak metamorphic conditions characteristic of either granulite or amphibolite facies. Geochronological studies of Tethyan ophiolites indicate that the development of these metamorphic soles occurred almost simultaneously with the crystallization of the ophiolite’s crustal sequence. Geological evidence also suggests that the metamorphism of the sole rocks took place concurrently with deformation, likely at the same time as the ophiolite’s obduction. In our research, we explore the metamorphic effects of shearing in an ophiolite sequence overlying a crustal sequence. Our findings reveal that strong lithologies like ophiolites can produce additional heat through the dissipation of mechanical energy, which can potentially explain the high temperatures found in metamorphic-sole rocks. In addition, heating-driven softening of the footwall rocks eventually leads to the migration of the active shear zone from the mantle sequence into the upper crustal domain. This migration may be responsible for the metamorphic sole incorporation at the base of the ophiolite. Finally, we demonstrate that stopping the shearing process rapidly cools these rocks, corresponding with the findings from thermochronological studies from Oman ophiolite.

On the Child–Langmuir law in one, two, and three dimensions

We consider the limiting current from an emitting patch whose size is much smaller than the anode–cathode spacing. The limiting current is formulated in terms of an integral equation. It is solved iteratively, first to numerically recover the classical one-dimensional Child–Langmuir law, including Jaffe's extension to a constant, nonzero electron emission velocity. We extend to two-dimensions in which electron emission is restricted to an infinitely long stripe with infinitesimally narrow stripe width so that the emitted electrons form an electron sheet. We next extend to three-dimensions in which electron emission is restricted to a square tile (or a circular patch) with an infinitesimally small tile size (or patch radius) so that the emitted electrons form a needlelike line charge. Surprisingly, for the electron needle problem, we only find the null solution for the total line charge current, regardless of the assumed initial electron velocity. For the electron sheet problem, we also find only the null solution for the total sheet current if the electron emission velocity is assumed to be zero, and the total maximum sheet current becomes a finite, nonzero value if the electron emission velocity is assumed to be nonzero. These seemingly paradoxical results are shown to be consistent with the earlier works of the Child–Langmuir law of higher dimensions. They are also consistent with, or perhaps even anticipated by, the more recent theories and simulations on thermionic cathodes that used realistic work function distributions to account for patchy, non-uniform electron emission. The mathematical subtleties are discussed.

An unexpected new species of Anomala Samouelle, 1819 from southern Italy (Coleoptera: Scarabaeidae: Rutelinae), including description of its larva and ecological notes.

Anomala phantasma Uliana, Tomasi & Gallerati, new species is described from the Salento peninsula, southern Italy, including its third-instar larva. The new species is close to Anomala devota (P. Rossi, 1790), from which it differs for characters of the external anatomy, of the paramera and the endophallus. The most striking diagnostic difference is found in the setation of pronotum, limited to a narrow stripe on the midline in A. phantasma, new species, whereas it is present on the whole surface in A. devota. The new species is also compared with A. matzenaueri Reitter, 1918, a poorly known species endemic of the opposite side of the Adriatic coast. Anomala phantasma, new species is a day-active species, possibly limited to maquis and shrublands lining sandy beaches.

Microstructure and Mechanical Properties in a Gd-Modified Extruded Mg-4Al-3.5Ca Alloy

In the present study, the microstructure and mechanical properties of a new Mg-4Al-3.5Ca-2Gd (AXE432) alloy are investigated. The microstructure of the as-cast AXE432 alloy consists of α-Mg, C14 (Mg2Ca), and C36((Mg, Al)2Ca) phases. After the heat treatment at 480 °C for 8 h, the C14 with fine lamellar structure changes from narrow stripes to micro-scale particles, and part of the C36 and the C14 dissolve into the α-Mg matrix, with many short needle-shaped C15 (Al2Ca) phase precipitating in the primary a-Mg grains. The AXE432 alloy extruded at a temperature as high as 420 °C exhibits a refined dynamically recrystallized (DRXed) microstructure with grain sizes less than 1.5 ± 0.5 μm and a strong {0001}<101¯0> basal texture with a maximum intensity of 5.62. A complex combination of the effects from grain size, texture, second-phase particles, and strain hardening results in balanced mechanical properties, with the tensile yield strength (TYS), ultimate tensile strength (UTS), elongation (El), compressive yield strength (CYS), and ultimate compressive strength (UCS) of 331.4 ± 2.1 MPa, 336.9 ± 3.8 MPa, 16.1 ± 2.3%, 270.4 ± 1.6 MPa and 574.5 ± 12.4 MPa, respectively.

Three new species of Entomobryidae (Collembola, Entomobryoidea) from China.

Three new species of entomobryid springtails (Collembola) from China are described here. Homidiapseudozhangisp. nov. is characterised by a narrow irregular longitudinal stripe on the body, smooth chaetae e and l1 of the labial base, and the relative position of the specialized microchaeta on Abd. I; H.qianensissp. nov. by its colour pattern on the antennae and nine sutural macrochaetae on the head; and Entomobryashaanxiensissp. nov. by its colour pattern, labral papillae and the lateral process of labial papilla E. Specimens of Akabosiamatsudoensis Kinoshita, 1919 from China are redescribed, including description of some characters for the first time.

Control of magnetic response in curved stripes by tailoring the cross section

Curved magnetic architectures are key enablers of prospective magnetic devices with respect to size, functionality, and speed. By exploring geometry-governed magnetic interactions, curvilinear magnetism offers a number of intriguing effects in curved magnetic wires and curved magnetic films. The applicability of the current micromagnetic theory requires that the sample has a constant width and thickness, which does not correspond in many cases to the specificity of experimental sample preparation. Here, we put forth a self-consistent micromagnetic framework of the curvilinear magnetism of nanowires and narrow stripes with a spatially inhomogeneous cross section. The influence of the varying cross section is exploited and illustrated by an example of the simplest topological texture, which is a transversal head-to-head (tail-to-tail) domain wall. The cross-section gradient becomes a source of domain wall pinning which competes with the curvature gradient. Eigenfrequencies of the domain wall free oscillations at the pinning potential are determined by both curvature and cross-section gradients. Prospects for curvilinear magnonics and spintronics are discussed.

Nonreciprocal spin waves in ferrimagnetic domain-wall channels

We theoretically investigate the propagation of spin waves confined in a N\'eel-type ferrimagnetic domain-wall channel in the presence of the interfacial Dzyaloshinskii-Moriya interaction (DMI). We observe a nonreciprocal spin-wave propagation induced by the antisymmetric chiral DMI, which can be manipulated by changing the net angular momentum or the polarity of domain walls. Considering that the band gap of spin waves excited in domain walls is significantly reduced, the three-magnon processes are applied to nonlinearly detect this bounded mode in the narrow channel, which enables us to quantify the frequency and the wave vector by analyzing the spectrum of the transmitted spin wave outside the domain wall and to determine the DMI strength. These findings are useful for fabricating energy-efficient magnetic devices and measuring the interfacial DMI in ultra narrow ferrimagnetic stripes.

Identification of Metal Threads from Croatian Fabrics

Abstract This article deals with the analysis of metal threads in weaving from historical Croatian textiles, liturgical vestments, and folk costumes from the seventeenth to the twentieth century. The independent narrow stripes, wires, and the srma that was formed by a combination of metal thread wrapped around a non-metal textile yarn were collected and analysed. Using physicochemical method scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), the metal composition and content in the threads were analysed. By cross-sectional analysis of metal threads by the SEM-EDX method, it was determined whether the metal threads were homogeneous, gilded, or silver-plated. The composition and structure of non-metal textile yarns were determined by light microscopy. Metal threads were primarily made of gold, silver, or copper and their alloys, but recently less valuable metals having a similar shine have generally been used. Non-metal textile threads in srma are most often made of silk, cotton, and linen. The aim of this study was to determine which type and composition of metal threads were used in different regions of Croatia, which can serve as a database for the restoration and conservation of valuable historical textiles. Also, according to the composition of metal threads, the technology of production threads can be determined and the temporal and spatial dating of textile objects can be determined approximately.

Dating seafloor spreading of the southwest sub-basin in the South China Sea

Marine magnetic lineations play important role in interpreting the age and spreading processes of the oceanic crust. However, it is difficult to identify magnetic lineations from sea surface observations in a deep and narrow low-latitude slow-spreading inactive ocean basin for many reasons, such as the highly filtered low-amplitude magnetic anomalies, highly oblique magnetization, contamination from narrow stripes, etc., which may hamper accurate lineation discrimination and identification. The spreading history of the Southwestern Sub-basin of the South China Sea (SW-SCS), which is located in such a low-latitude tectonic setting, has been debated for a long time. Near-seafloor deep-tow magnetic measurements provide high-resolution reversal records, making accurate lineation discrimination feasible. Corrections, including diurnal variation correction, regional field correction, and de-skewing, are explored. The results, calibrated with drill sites from the International Ocean Discovery Program (IODP) Expedition 349, show that the spreading ages of the SW-SCS range from ∼ 21 to 15 Ma (from C6A to C5B) and the full spreading rate ranges from 26 to 46 mm/yr, with an average rate of 37 mm/yr. Spreading was initially symmetric but later became asymmetric, with a rate differential reaching 10%. Combined with two seismic profiles, it is found that the roughness of the oceanic basement to the south of the extinct ridge is mainly influenced by faulted blocks, whereas to the north it is mainly influenced by magmatism. The RMS seafloor roughness is estimated to be 211 m in the south and 191 m in the north respectively. This indicates that SW-SCS seafloor spreading tends to be a transition type between axial high and axial low at the intermediate-slow spreading rate. There is a large valley in the spreading center, but the roughness far away from the center is low. the RMS basement roughness is obviously lower than that of the typical slow spreading oceanic basin. we conjecture that the larger than normal syn-spreading magma may be the reason for the low roughness. A long history of being subducted might be the deep-seated reason for all these behaviors where, and the mantle is rich in water and carbon.

Two new land planarian species (Platyhelminthes: Tricladida) from the Cerrado biome in southwestern Brazil

Most Neotropical land flatworm species are known from areas of the Atlantic Forest. Herein, we describe two new land planarian species from areas of semideciduous forest in the Cerrado biome in southwestern Brazil. Paraba aurantia Marques & Leal-Zanchet, sp. nov. can be distinguished from its congeners by the wide black median band on the dorsum, eyes occupying almost the entire dorsal surface, prostatic vesicle twisted and asymmetrical with proximal portions forked, and female atrium with an ample lumen lined by a low epithelium with stratified appearance. Pasipha liviae Marques & Leal-Zanchet, sp. nov. shows a narrow longitudinal dorsal stripe, collar-shaped pharynx, and prostatic vesicle with a pear-shaped proximal portion and a globose distal portion separated by a constriction. In addition, P. liviae can be distinguished from its congeners by molecular analyses from the cytochrome c oxidase subunit I gene (COI). Phylogenetic analyses suggest that P. liviae is closely related to P. hauseri, which occurs in areas of semidseciduous forest in southern Brazil.

Zebras of all stripes repel biting flies at close range

The best-supported hypothesis for why zebras have stripes is that stripes repel biting flies. While this effect is well-established, the mechanism behind it remains elusive. Myriad hypotheses have been suggested, but few experiments have helped narrow the field of possible explanations. In addition, the complex visual features of real zebra pelage and the natural range of stripe widths have been largely left out of experimental designs. In paired-choice field experiments in a Kenyan savannah, we found that hungry Stomoxys flies released in an enclosure strongly preferred to land on uniform tan impala pelts over striped zebra pelts but exhibited no preference between the pelts of the zebra species with the widest stripes and the narrowest stripes. Our findings confirm that zebra stripes repel biting flies under naturalistic conditions and do so at close range (suggesting that several of the mechanisms hypothesized to operate at a distance are unnecessary for the fly-repulsion effect) but indicate that interspecific variation in stripe width is associated with selection pressures other than biting flies.

Topography of bent crystals with microradian resolution in one dimension.

Optimum performance in x-ray imaging and spectroscopy of plasmas with bent crystals is achievable only when the crystal reflects the x rays theoretically perfectly across its entire surface. However, typical thin quartz (101̄1) crystal samples kept flat by direct attachment to a flat substrate reflect 8keV x rays differently across their surface, on a scale comparable to the ideal rocking curve. Additional processing improves the uniformity. Irradiation of flat crystals with collimated, monochromatic x rays in rocking curve topography shows such problems directly, with microradian resolution. Nonuniform x-ray reflection is more difficult to document for strongly bent crystals because, then, monochromatic, collimated x rays satisfy the Bragg condition only along a narrow stripe that may be too narrow to resolve with the available cameras. However, it can be resolved with a knife edge that moves through the reflected x rays with the necessary spatial precision as demonstrated here for a bent silicon crystal. This shows qualitatively similar imperfections in the reflection as flat quartz and as the bent quartz analyzers reported on previously with lower resolution.

Ballistic guided electrons against disorder in graphene nanoribbons

Graphene nanoribbons (GNRs) are natural waveguides for electrons in graphene. Nevertheless, unlike micrometer-sized samples, conductance is nearly suppressed in these narrow graphene stripes, mainly due to scattering with edge disorder generated during synthesis or cut. A possible way to circumvent this effect is to define an internal waveguide that isolates specific modes from the edge disorder and allows ballistic conductance. There are several proposals for defining waveguides in graphene; in this manuscript, we consider strain folds and scalar potentials and numerically evaluate these proposals’ performance against edge and bulk disorder. Using the Green’s function approach, we calculate conductance and the local density of states of zigzag GNRs and characterize the performance of these different physical waveguiding effects in both types of disorders. We found a general improvement in the electronic conductance of GNR due to the presence of the internal waveguiding, with the emergence of plateaus with quasi-ballistic properties and robustness against edge disorder. These findings are ready to be applied in modern nanotechnology and are being experimentally tested.

Absorption and Emission of Chemically and Electrochemically Doped Graphene Nanoribbons

Graphene nanoribbons (GNRs) are narrow stripes of graphene that exhibit unique optical and electronic properties depending on their width and edge type. Recent advances in the bottom-up synthesis of GNRs have enabled precise control over their structure and thus their bandgap. However, the systematic optical and electrical characterization of GNRs obtained from solution-mediated reactions has so far been prevented by the poor stability and processability of GNR dispersions. Here we employ liquid cascade centrifugation (LCC) to obtain size-selected and stable dispersions of bottom-up synthesized 9-aGNRs in toluene and tetrahydrofuran and investigate their intrinsic optical properties. Dispersions and films of these 9-aGNRs show well-defined absorption and photoluminescence bands between 800 and 1000 nm, with relative intensities depending on the LCC-fraction. The best GNR dispersions show photoluminescence quantum yields of up to 70 %. Trions are charged excitons with red-shifted emission that can be created in doped low-dimensional semiconductors, such as carbon nanotubes. Theoretical studies predict large trion binding energies (> 300 meV) in graphene nanoribbons (depending on their width). Hence their optical properties upon doping and possible new features are of interest. Chemical doping of our 9-aGNR dispersions with the strong molecular p-dopant F4-TCNQ and electrochemical doping of GNR thin films in ambipolar electrolyte-gated field-effect transistors results in the expected bleaching of the main absorption bands but also the emergence of new redshifted, charge-induced absorption peaks that may indicate the existence of trions in GNRs.

Anisotropic growth of domain rays in lithium niobate crystal induced by IR laser scanning

Formation of nanodomain structure after linear scanning by IR laser beam in congruent lithium niobate crystal was attributed to switching under the action of pyroelectric field. The complicated domain patterns consisted of strictly oriented narrow stripe domains (width about 200 nm and depth about 20 µm) arising in a wide switched band. Width of the switched band and domain length density at different distances from the center of the irradiated zone depend on the scanning velocity v s. Relevance of the used model was supported by similarity of the experimental and calculated dependences.

Stable Lateral Far Field of Highly Dense Arrays of Uncoupled Narrow Stripe Ridge Waveguide 1060 nm Lasers

In order to stabilize the lateral far-field profile of a broad area laser diode at high pump currents, the design of an asymmetric InGaAs/AlGaAs/GaAs laser heterostructure was developed. Lasers with an aperture formed by ten optically uncoupled ridge waveguides (each 6.5 μm wide) were developed on its basis. To maintain the single-mode operation of each ridge waveguide without coupling between emitters, a High Dense Microstripe Array (HDMSA, the pitch is 13.5 μm) and a Low Dense Microstripe Array (LDMSA, the pitch is 40 μm) were fabricated with a coupling parameter between adjacent lateral waveguides of 2·10^−5 and 3·10^−19, respectively. The maximum optical output power was 5 W (HDMSA) in CW mode and 25 W (HDMSA) and 26 W (LDMSA) in pulsed mode (130ns/1kHz). It is shown that in both CW and pulsed modes, lasers of both designs provide a stable Gaussian-like distribution in the lateral far field (LFF) with a FWHM of 8–11 degrees for HDMSA and 6.5–10 degrees for LDMSA. It was found that the LFF broadens with a pump current in the range of low currents and stabilizes in the range of high currents for both designs. Studies of the near field in both operating modes at any pump currents showed no array modes and the uncoupling mode is maintained for ridge waveguide arrays.

Nest-Site Specialization in the Helmeted Manakin Antilophia galeata in a Gallery Forest from Southeastern Brazil

Studies on nest-site selection can reveal aspects of habitat requirements of the target species, and can be useful to infer about how habitat changes can affect local populations. The Helmeted Manakin, Antilophia galeata, is a piprid that inhabits mainly the humid gallery forests that occur along watercourses of the savanna-like Cerrado biome from central South America, and like most tropical forest understory passerines, it is poorly known under a nest-site selection perspective. Here we provide nest-site selection assessment based on nine variables for a population of the Helmeted Manakin from southeast Brazil. We found that females strongly selected Miconia nervosa (Melastomataceae) as a nesting plant species. Further, we demonstrated that the presence of nests was positively associated with canopy cover and with the occurrence of the endangered jussara palm trees, Euterpe edulis. These results suggest that the Helmeted Manakin is specialized in reproducing in mature and well-preserved gallery forest tracts. Gallery forests are narrow stripes of riparian vegetation from the endangered Cerrado domain, and here we showed that even in these linear habitats, the Helmeted Manakin can seek for specific portions for nesting. This is one of the few studies reporting nest-site specialization in a Neotropical forest-dwelling passerine.