Interband Spacing Research Articles

Applying cosmetic oil with added aromatic compounds improves tactile sensitivity and skin properties

Tactile sensitivity generally decreases with aging and is associated with impairments in skin properties. Products that hydrate the skin can combat touch deficits and aromatic compounds have been shown to improve skin mechanical properties. Thus, we tested a base cosmetic oil against a perfumed oil, applied to the skin of females aged 40–60 years, on tactile sensitivity and skin properties after repeated application. Tactile detection thresholds were assessed using calibrated monofilaments applied at the index finger, palm, forearm, and cheek. Spatial discrimination on the finger was assessed using pairs of plates with different inter-band spaces. These tests were performed before and after 1 month of base or perfumed oil use. We found that tactile detection thresholds and spatial discrimination improved only in perfumed oil group. A complementary immunohistological study using human skin was conducted to estimate the expression of olfactory receptor OR2A4 and elastic fiber length. Further, the expression of OR2A4 intensity and the length of elastic fibers increased significantly with oil application, where larger effects were seen with the perfumed oil. We conclude that the application of a perfumed oil may be of additional benefit and could repair, and even prevent, tactile decline with aging by ameliorating skin condition.

From Nano-Crystals to Periodically Aggregated Assembly in Arylate Polyesters—Continuous Helicoid or Discrete Cross-Hatch Grating?

This work used several model arylate polymers with the number of methylene segment n = 3, 9, 10, and 12, which all crystallized to display similar types of periodically banded spherulites at various Tc and kinetic factors. Universal mechanisms of nano- to microscale crystal-by-crystal self-assembly to final periodic aggregates showing alternate birefringence rings were probed via 3D dissection. The fractured interiors of the birefringent-banded poly(decamethylene terephthalate) (PDT) spherulites at Tc = 90 °C revealed multi-shell spheroid bands composed of perpendicularly intersecting lamellae bundles, where each shell (measuring 4 μm) was composed of the interior tangential and radial lamellae, as revealed in the SEM results, and its shell thickness was equal to the optical inter-band spacing (4 μm). The radial-oriented lamellae were at a roughly 90° angle perpendicularly intersecting with the tangential ones; therefore, the top-surface valley band region appeared to be a submerged "U-shape", where the interior radial lamellae were located directly underneath. Furthermore, the universal self-assembly was proved by collective analyses on the three arylate polymers.

Crystal-by-Crystal Assembly in Two Types of Periodically Banded Aggregates of Poly(p-Dioxanone).

The exterior and interior lamellar assemblies of poly(p-dioxanone) (PPDO) crystallized at 76 °C yield the most regular ones to interpret the 3D assembly mechanisms and potential for structural coloration iridescence, which are investigated using atomic-force microscopy (AFM), and scanning electron microscopy (SEM). PPDO displays two types of ring-banded spherulites within a range of Tc with dual-type birefringent spherulites (positive and negative-type) only within a narrow range of Tcs = 70−78 °C. At Tc > 80 °C, the inter-band spacing decreases from a maximum and the crystal assembly becomes irregularly corrupted and loses the capacity for light interference. Periodic grating assemblies are probed by in-depth 3D dissection into periodically banded crystal aggregates of poly(p-dioxanone) (PPDO) to disclose such layered gratings possessing iridescence features similar to nature’s structural coloration. This work amply demonstrates that grating assembly by orderly stacked crystal layers is feasible not only for accounting for the periodic birefringent ring bands with polarized light but also the distinct iridescence by interfering with white light.

Grating Assembly Dissected in Periodic Bands of Poly (Butylene Adipate) Modulated with Poly (Ethylene Oxide).

Polarized optical microscopy (POM), scanning electron microscopy (SEM), and synchrotron microbeam wide-angle X-ray diffraction (WAXD) were used to investigate the mechanisms of periodic assemblies leading to ring-banded crystal aggregates with light-grating capacity for iridescence in poly (1,4-butylene adipate) (PBA) modulated with poly (ethylene oxide) (PEO). A critical finding is that the PBA crystal assembly on the top surface and in the interior constitutes a grating architecture, with a cross-bar pitch equaling the inter-band spacing. The inner lamellae are arranged perpendicularly to the substrate under the ridge region, where they scroll, bend, and twist 90° to branch out newly spawned lamellae to form the parallel lamellae under the valley region. The cross-hatch grating with a fixed inter-spacing in the PBA aggregated crystals is proved in this work to perfectly act as light-interference entities capable of performing iridescence functions, which can be compared to those widely seen in many of nature's organic bio-species or inorganic minerals such as opals. This is a novel breakthrough finding for PBA or similar polymers, such as photonic crystals, especially when the crystalline morphology could be custom-made and modulated with a second constituent.

Polymeric photonic quasicrystal: octonacci sequence and elasto-optic effect

Here we would like to discuss the light transmission modulation by the one-dimensional polymeric quasi-multilayer which is formed according to substitutional generalized Octonacci with PMMA and PS as the constituent materials. In particular, we will present some theoretical findings using the well-known transfer matrix method. The width of the PBG, the inter-band spacing and the depth of the PBGs can be managed by choosing the appropriate generation number, whereas the number of the major PBGs is the same for all the considered generation numbers. Regarding the position of the PBGs, we found that, with an increase in generation number, the aroused PBGs are shifted symmetrically towards the designed frequency. It also reveals the aroused forbidden frequency band can be manipulated by changing the applied hydrostatic pressure. With an increase in pressure, the frequency spectra are shifted to a higher frequency. In addition to this, we also found that as the thickness of the polymers increases the PBGs are red-shifted. The proposed structure could be another possible system for optical device design specially multi-band tunable optical reflectors.

Permeability modeling of a basin-bounding fault damage zone in the Rio do Peixe Basin, Brazil

In permeability modeling of fault damage zones affecting porous sandstones, deformation bands are commonly considered low-permeability structures that influence fluid flow. Permeability in damage zones of such rocks exhibits and is influenced by complex networks of deformation bands separated by volumes of seemingly undeformed host rock. This study used deformation band frequency data to delimit and model the fault damage zone subdomains and fault facies in the hanging wall of the Malta Fault segment in the Rio do Peixe Basin, Brazil. We then integrate in situ permeability data collected in deformation bands and interband spaces (deformed host rock located between adjacent deformation bands) with damage zones and fault facies models to estimate the equivalent permeability perpendicular and parallel to the main fault. Our results indicated a logarithmic decrease in deformation band frequency towards the protolith with local variations controlled by minor faults in the damage zone. We identified three damage zone subdomains (inner and outer damage zones and transitional zone), totalizing roughly 200 m of width. Permeabilities of the deformation bands and interband spaces increase towards the protolith non-uniformly due to the difference in deformation intensity. The deformation bands and interband spaces in the inner and outer damage zones, which comprise fault facies representing the highest deformation intensities, exhibit permeability reductions of 1–3 orders of magnitude compared to the undeformed rocks, whereas 0–2.5 orders of magnitude reductions were observed in the transitional zone between the damage zone and the protolith. This study provides new perspectives about the permeability in deformation bands and interband spaces by different subdomains of damage zones and fault facies. This information proved is essential for modeling equivalent permeabilities along damage zones and assessing its implications to siliciclastic reservoirs affected by fault zones, where deformation bands are pervasive.

Microstructural Periodic Arrays in Poly(Butylene Adipate) Featured with Photonic Crystal Aggregates.

Poly(butylene adipate) (PBA) self-aggregation into unique periodicity correlating to its interfacial photonic properties is probed in detail. Investigations on the unique periodic morphology and top-surface and interior architectures in specifically crystallized PBA are focused on its novel photonic patterns with periodic gratings. Detailed analysis of the interior lamellae from ringless to periodically ordered aggregates (crystallized at 33-35 °C vs. Tc = 30 °C) serves as ideal comparisons. Each interior arc-shape shell is composed of tangential and radial lamellae mutually intersecting at 90o angle. The interior layer thickness in SEM-revealed arc-shape shish-kebab shell is exactly equal to the optical inter-band spacing (≈6 µm). A 3D assembly mechanism of periodically banded PBA crystals is proposed, where the orderly arrays on top surfaces as well as the interior microstructures of strut-rib alternate-layered assembly resemble nature's photonic crystals and collectively account for the interfacial photonic properties in the ring-banded PBA crystal that is novel and has potential applications in future.

The influence of different aged Black Saxaul plants on distribution, growth and accumulation of aboveground phytomass of Poa Bulboza L.

The purpose of this study was to determine the nature and degree of influence of different-aged plants of Black Saxaul on Bulbous Bluegrass - one of the dominant species of sagebrush-ephemeral pastures. The study was conducted using phytometer method in the conditions of the desert zone of Uzbekistan on the ephemeroid-wormwood-black saxaul phytocenosis, formed as a result of self-seeding on inter-band spaces of pasture-protective Black Saxaul plantations. It is established that the character of the phytogenic influence of Saxaul on Bluegrass can be characterized as ambiguous conjugacy: in the minimal phytogenic field, the character of this influence is negative and therefore is gradually replaced, as a result of which the number of this species-phytometer significantly decreases, there are zones where bluegrass is absent. Growing specimens are stunted and poorly developed, so they accumulate insignificant aboveground phytomass. The character of the influence of Saxaul in the outer part of the phytogenic field on bluegrass was positive. Therefore, it is numerous here, grows better and accumulates 1,5-3 times more aboveground phytomass than outside the phytogenic field (control). Within the phytogenic field of Black Saxaul for Bluegrass Bulbous most “environmentally comfortable place” is the border of the internal and external parts of this field. In this part of the phytogenic field, due to its ecological and biological properties, the number of phytometer species reaches the highest value; they grow rapidly and accumulate the largest aboveground phytomass. The degree of influence depends on the age status of the Black Saxaul.The highest degree of influence on the abundance, growth and formation of over ground phytomass of Bluegrass Bulbous is observed in the phytogenic field of middle-aged species-edificators: the minimum field increases and reaches its maximum in the area where Bluegrass Bulbous is completely displaced, and on the border of internal and external parts and in the outer part opposed to a phytogenic one field due to the positive influence of species-edificators of the number of phytometra increases sharply, the values of the linear growth of shoots and accumulation of aboveground biomass reach the highest values. The smallest phytogenic effect of the edifier species on the phytometer species is observed in the phytogenic field of virginal plants of the black saxaul. The phytogenic effect on bluegrass is distributed in virginal individuals of the active species outside the crown at a distance of 90 cm, in young generative - by 120 cm and in middle-aged generative - by 150 cm and even 180 cm. When further removed, the distribution, growth and formation of aboveground phytomass of the phytometer species does not depend on the edifier species.

Resolving the spin splitting in the conduction band of monolayer MoS2

Time-reversal symmetry and broken spin degeneracy enable the exploration of spin and valley quantum degrees of freedom in monolayer transition-metal dichalcogenides. While the strength of the large spin splitting in the valance band of these materials is now well-known, probing the 10–100 times smaller splitting in the conduction band poses significant challenges. Since it is easier to achieve n-type conduction in most of them, resolving the energy levels in the conduction band is crucial for the prospect of developing new spintronic and valleytronic devices. Here, we study quantum transport in high mobility monolayer MoS2 devices where we observe well-developed quantized conductance in multiples of e2/h in zero magnetic field. We extract a sub-band spacing energy of 0.8 meV. The application of a magnetic field gradually increases the interband spacing due to the valley-Zeeman effect. Here, we extract a g-factor of ~2.16 in the conduction band of monolayer MoS2.

Nanotube Alignment Mechanism in Floating Evaporative Self-Assembly.

The challenge of assembling semiconducting single-wall carbon nanotubes (s-SWCNTs) into densely packed, aligned arrays has limited the scalability and practicality of high-performance nanotube-based electronics technologies. The aligned deposition of s-SWCNTs via floating evaporative self-assembly (FESA) has promise for overcoming this challenge; however, the mechanisms behind FESA need to be elucidated before the technique can be improved and scaled. Here, we gain a deeper understanding of the FESA process by studying a stationary analogue of FESA and optically tracking the dynamics of the organic ink/water/substrate and ink/air/substrate interfaces during the typical FESA process. We observe that the ink/water interface serves to collect and confine the s-SWCNTs before alignment and that the deposition of aligned bands of s-SWCNTs occurs at the ink/water/substrate contact line during the depinning of both the ink/air/substrate and ink/water/substrate contact lines. We also demonstrate improved control over the interband spacing, bandwidth, and packing density of FESA-aligned s-SWCNT arrays. The substrate lift rate (5-15 mm min-1) is used to tailor the interband spacing from 90 to 280 μm while maintaining a constant aligned s-SWCNT bandwidth of 50 μm. Varying the s-SWCNT ink concentration (0.75-10 μg mL-1) allows the control of the bandwidth from 2.5 to 45 μm. A steep increase in packing density is observed from 11 s-SWCNTs μm-1 at 0.75 μg mL-1 to 20 s-SWCNTs μm-1 at 2 μg mL-1, with a saturated packing density of ∼24 s-SWCNTs μm-1. We also demonstrate the scaling of FESA to align s-SWCNTs on a 2.5 × 2.5 cm2 scale while preserving high-quality alignment on the nanometer scale. These findings help realize the scalable fabrication of well-aligned s-SWCNT arrays to serve as large-area platforms for next-generation semiconductor electronics.

Quasiperiodic one-dimensional photonic crystals with adjustable multiple photonic bandgaps.

We propose an elegant approach to produce photonic bandgap (PBG) structures with multiple photonic bandgaps by constructing quasiperiodic photonic crystals (QPPCs) composed of a superposition of photonic lattices with different periods. Generally, QPPC structures exhibit both aperiodicity and multiple PBGs due to their long-range order. They are described by a simple analytical expression, instead of quasiperiodic tiling approaches based on substitution rules. Here we describe the optical properties of QPPCs exhibiting two PBGs that can be tuned independently. PBG interband spacing and its depth can be varied by choosing appropriate reciprocal lattice vectors and their amplitudes. These effects are confirmed by the proof-of-concept measurements made for the porous silicon-based QPPC of the appropriate design.

Multishell Oblate Spheroid Growth in Poly(trimethylene terephthalate) Banded Spherulites

Unique interior dissection coupled with selective etching techniques for exposing the interiors of poly(trimethylene terephthalate) (PTT) banded spherulites. Three banded PTT spherulite types are present, originating from different nuclei geometries and corresponding to different assemblies of interior lamellae, but all possess similar multishell spheroid layered structures, each with their layer thickness exactly equal to the optical interband spacing. Interior lamellae are alternatingly intersected with mutually perpendicular orientations and clear discontinuity, which evidently disagrees with the conventional models of continuous helical twisting for banding. Interior 3D lamellae assemblies also have been fittingly correlated with top-surface banding patterns.

Thermomechanical and Isothermal Fatigue Behavior of 316LN Stainless Steel with Varying Nitrogen Content

Thermomechanical (TMF) and isothermal (IF) fatigue behavior of 316LN stainless steel alloyed with 0.07, 0.14, and 0.22 wt pct nitrogen is presented in this manuscript. In the TMF tests with temperature cycling in the range of 573 K to 873 K (300 °C to 600 °C), life decreased with increasing nitrogen content for both in-phase (IP) and out-of-phase (OP) cycling, with a peak at 0.07 wt pct N. In contrast, 0.14 wt pct N yielded maximum life under IF cycling carried out at 873 K (600 °C). Cyclic lives are seen to follow the sequence, IP-TMF < IF < OP-TMF cycling, and it remained same irrespective of the nitrogen content in 316LN SS. Lives under IP-TMF are lower than those in OP cycling by a factor of 2 to 2.5, in spite of the higher cyclic stress response in OP cycling. At all the nitrogen contents in the present study, nitrogen and dynamic strain aging induced slip localization in the form of planar slip bands both in IP and OP-TMF, in comparison to IF deformation wherein complete planar slip mode of deformation is evidenced only at 0.22 wt pct N. In TMF studies, increasing nitrogen content promoted strong slip localization (i.e., increase in slip band density with a decrease in interband spacing) in combination with high tensile cyclic stresses that marred the beneficial effect of nitrogen content on TMF life.

Optical Simulation of Dual-Ended Readout of Axially-Oriented 100 mm Long LYSO Crystals for Use in a Compact PET System

Monte Carlo simulations of optical photon transport were performed using DETECT2000 for detectors using dual-ended readout of axially-oriented 100 mm long LYSO crystals. In order to modulate the light transport in the crystals and improve the axial-positioning resolution, systematic etched band patterns were simulated on the long surfaces of the crystals. Roughed surface bands with a width of 1 mm and inter-band spacing of 5 mm over the central 8 cm of the crystal were simulated on the long surfaces of initially polished 3 mm×2 mm×100 mm and 2 mm×2 mm×100 mm crystals. This band pattern was simulated for cases of bands on one surface, bands on two opposite surfaces, and bands on all four surfaces. Each crystal was modeled as Teflon-wrapped and read out at both ends using position sensitive photomultiplier tubes (PSPMTs). Optical photons were simulated as originating at nine central-axis locations, separated by 10 mm, along the crystal length. The ratio of two PMT signals was used to determine the axial-positioning resolution while their sum was used to determine the energy resolution. The DETECT2000 simulation parameters required to give good agreement with measured data were determined in order to benchmark the simulation for this detector geometry. These simulation parameters were then used to examine the effects of alternative banding pattern designs. The best axial-positioning resolution obtained in this work was 3.5 mm FWHM for the case of etched bands along the central 8 cm of the crystal with band size of 4 mm and inter-band-spacing of 20 mm on two opposite surfaces.

The evolved microstructure ahead of an arrested fatigue crack in Haynes 230

The dislocation microstructure beneath surface slip traces produced by fatigue loading of Haynes 230 was revealed to be a function of distance from a crack tip. The microstructure beneath these traces evolves from planar slip bands with increasing dislocation density and decreasing interband spacing as the crack tip approaches one of refined subgrains and lamellar bands at and in the vicinity of the crack tip. Similarly, beneath fatigue striations the microstructure evolves from nanosized subgrains to a banded structure with increasing distance from the fracture surface. These structures are significantly different to those predicted to develop under fatigue loading of a planar slip material. The evolved structures are considered in terms of the microstructure generated by severe plastic deformation.

How do vegetation bands form in dry lands? Insights from numerical modeling and field studies in southern Nevada, USA

Vegetation bands are periodic bands of vegetation, separated by interband spaces devoid of vegetation, oriented parallel to the topographic contour in some gently sloping arid to semiarid environments. Models of vegetation band formation attribute their formation to positive feedbacks among vegetation density, soil porosity/permeability, and infiltration rates. Here we present an alternative model based on field measurements at our study sites in southern Nevada. In this model, interband spaces between vegetation bands form because topographic mounds beneath vegetation bands detain water upslope from vegetation bands, leading to hydrologic and sedimentologic conditions that inhibit the survival of plants in interband spaces. We used terrestrial laser scanning (TLS) to create high‐resolution (∼10 cm2/pixel) raster data sets of bare‐earth topography and canopy height for four study sites. Analyses of the TLS data, in addition to measurements of soil shear strength and particle size, document the potential for detention in interband spaces and a near‐inverse proportionality between band spacing and regional slope. We describe a cellular automaton model (herein called model 1) for vegetation band formation that includes just two user‐defined parameters and that generates vegetation bands similar to those at our field sites, including the inverse proportionality between spacing and regional slope. A second model (model 2) accurately predicts the width of vegetation bands in terms of the number and spacing of plants and the geometry of individual plant mounds. We also present a GIS‐based analysis that predicts where bands occur within a region based on topographic and hydroclimatic controls.

Ductility and toughness of cold-rolled metallic glasses

Cold rolling of Al87Ni7La6 amorphous ribbons was performed on ribbons embedded in pure Al foils and ribbons alone, in order to study their deformation under constraint. A change in behaviour was observed for the two series of samples due to a different load distribution, so that ribbons alone was deformed up to ɛ = 0.029 without formation of cracks while, for composite samples, small fragments were always formed. In ribbons rolled alone, along with a macroscopic strain, a plastic deformation was observed at a finer scale, in the cavities present on the ribbon surface. The locally induced strain was quantified by taking into account the size change of cavities in samples rolled to different extents. The formation of shear bands and fracture occurring during cold rolling was studied for composite samples: the shear offset, interband spacing and distribution of fracture angles were determined. A Zr55Al20Ni12Cu8Ti5 amorphous ribbon was rolled with Al foils and the toughness value was estimated from the shear band offsets finding good agreement with literature data. Therefore, the toughness was estimated also for the Al-based samples obtaining the value of Kc = 28 MPa m1/2.

Effect of temperature on the plastic zone size and the shear band density in a bulk metallic glass

► Subsurface deformation zone of a Zr-based BMG was examined at different temperatures. ► Inter-band spacing increases with increase in temperature. ► Shear band mediated plastic zone remains invariant with temperature. ► Contribution of homogeneous deformation to the total deformation increases with temperature. ► The increased contribution of homogeneous deformation is the reason for increase in pressure sensitivity of BMGs. High temperature bonded interface indentation experiments are carried out on a Zr based bulk metallic glass (BMG) to examine the plastic deformation characteristics in subsurface deformation zone under a Vickers indenter. The results show that the shear bands are semi-circular in shape and propagate in radial direction. At all temperatures the inter-band spacing along the indentation axis is found to increase with increasing distance from the indenter tip. The average shear band spacing monotonically increases with temperature whereas the shear band induced plastic deformation zone is invariant with temperature. These observations are able to explain the increase in pressure sensitive plastic flow of BMGs with temperature.

Geometric Model Describing the Banded Morphology of Particle Films Formed by Convective Assembly

Nanoparticle films coated on smooth substrates by convective assembly from dilute suspensions in dip-coating configuration are known to have discrete film morphologies. Specifically, the film morphology is characterized by alternating bands of densely packed particles and bands of bare substrate. Convective assembly is a frontal film-growth process that occurs at the three-phase contact line formed by the substrate, the suspension in which it is submersed, and the surrounding air. The bands are parallel to this contact line and can be either monolayered or multilayered. Monolayered bands result whenever the substrate is withdrawn from the suspension at a rate too high for particles to assemble into a continuous film. We report a new insight to the mechanism behind this banding phenomenon, namely, that inter-band spacing is strongly influenced by the constituent particle size. We therefore propose a geometric model relating the inter-band spacing to the particle size. By making banded films with systematically varied particle sizes (silica/zeolite, 20 to 500 nm), we are able to quantitatively validate our model. Furthermore, the model correctly predicts that multilayered banded films have higher inter-band spacings than monolayered banded films comprising the same particles.

Some correlations between slip band emergence and dislocation pattern

Various forms of the plastic deformation in single crystals are studied on pure nickel and nickel alloys oriented for single slip [135] and multiple slip [001]. Particular attention is paid to the heterogeneity of deformation observed at two distinct scales: the slip bands and the dislocation organizations. The slip bands emerging at the surface can be studied using the atomic force microscopy (AFM). The height of extrusions and inter-band spacing depends on the orientation of tensile axis, the strain level and the nature of the alloy. At another scale, dislocation organizations typical of fc.c. crystal have been observed, which depend on the orientation of tensile axis and on the stacking fault energy. A study by transmission electronic microscopy (TEM) has enabled us to approach the dimensional characteristics of these structures. In the case of mono-crystal oriented for single slip strained in stage III (γ ≈ 0.8) we observed a correlation between the inter-band spacing (d) and the inter-wall spacing (δ) of the type I dislocation pattern. This result suggests that this kind of walls act as a screen to the mobility of dislocations unlike equiaxed cells that would be only an obstacle to the dislocation mobility. This internal length is lower for Ni16%Cr alloy than for nickel. Consequently, stacking fault energy is probably a parameter which affects the internal length in relation with cross-slip capability. On the other hand, results, obtained of the [001] direction in nickel, are more complex due to multiple slip. Indeed, only equiaxed cells are observed for this orientation with cell size magnitude (δ) far lower than those observed for inter-band spacing (d). As in the case of samples oriented for single-slip, the equiaxed cells observed for samples oriented for multiple-slip seem to be only obstacles to the mobility of dislocations. However, there are probably walls associated with this kind of cells which act as barriers to the movement of dislocations.