weak surface
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2022 ◽  
Vol 0 (0) ◽  
Author(s):  
Peter Luger ◽  
Birger Dittrich

Abstract The electron density distribution (EDD) of a tetrasaccharide composed of four benzoylated fructopyranosyl units was obtained by refinement with scattering factors from the invariom library. X-ray diffraction data was downloaded from the Cambridge Structural Database (CSD). Bond topological and atomic properties were obtained by application of Bader’s QTAIM formalism. From a large number of 105 C–C bonds in the molecule average bond orders for 33 single and 72 aromatic bonds were calculated yielding values of 1.33 and 1.61. Molecular Hirshfeld and electrostatic potential (ESP) surfaces show that only weak non-covalent interactions exist. The phenyl rings of the benzoyl fragments in the outer regions of the molecule generate a positive ESP shell with repulsive properties between adjacent molecules. Weak surface interactions result in a rather unusual low density around 1.3 g cm−3, which is understandable when compared to other carbohydrates where strong O–H⋯O hydrogen bonds allow a 20% more dense packing with densities >1.5 g cm−3 as determined by single crystal X-ray diffraction.


2021 ◽  
Vol 930 ◽  
Author(s):  
Richard Mcnair ◽  
Oliver E. Jensen ◽  
Julien R. Landel

We model the advective Marangoni spreading of insoluble surfactant at the free surface of a viscous fluid that is confined within a two-dimensional rectangular cavity. Interfacial deflections are assumed small, with contact lines pinned to the walls of the cavity, and inertia is neglected. Linearising the surfactant transport equation about the equilibrium state allows a modal decomposition of the dynamics, with eigenvalues corresponding to decay rates of perturbations. Computation of the family of mutually orthogonal two-dimensional eigenfunctions reveals singular flow structures near each contact line, resulting in spatially oscillatory patterns of shear stress and a pressure field that diverges logarithmically. These singularities at a stationary contact line are associated with dynamic compression of the surfactant monolayer. We show how they can be regularised by weak surface diffusion. Their existence highlights the need for careful treatment in computations of unsteady advection-dominated surfactant transport in confined domains.


2021 ◽  
Author(s):  
Jacob R. MacWilliams ◽  
Quentin Chesnais ◽  
Paul Nabity ◽  
Kerry Mauck ◽  
Isgouhi Kaloshian

Abstract Cowpea (Vigna unguiculata) is one of the most important crops in semiarid areas of the world, where it thrives in hot, dry conditions. While cowpea is able to withstand abiotic stresses, it suffers serious losses from biotic antagonists, including infestation by the cowpea aphid (Aphis craccivora). Cowpea aphid infestations are highly destructive, especially on young plants. However, it is unclear whether cowpea aphid damage is the result of aphids having phytotoxic effects on their hosts, or simple density effects. To better understand cowpea aphid damage and the potential for resistance traits to mitigate aphid impacts, we evaluated phenotypic changes in cowpea in response to variable aphid densities and systemic versus local infestations. Low aphid densities induced leaf distortions and pseudogalling, suggesting that cowpea aphids are phytotoxic to cowpea. Resistance to the cowpea aphid has been previously identified in an African cowpea germplasm, and near isogenic lines (NILs) containing resistance quantitative trait loci (QTL) were generated in the California blackeye cultivar background. Using a series of performance assays, we determined that resistance conferred by the two QTL counteracts aphid phytotoxicity and severely limits aphid growth and fecundity. Using choice assays, a preference by cowpea aphids for the susceptible NIL was observed. Electrical penetration graph analysis revealed that the resistance phenotype includes weak surface level deterrence and strong phloem based resistance that manifests during the sap ingestion phase. Our study provides evidence of phytotoxic traits in A. craccivora while identifying a viable means of counteracting aphid damage and reproductive potential through resistance.


2021 ◽  
Vol 317 ◽  
pp. 166-172
Author(s):  
Noor Aisyah Ahmad Shah ◽  
Siti Zulaikha Ngah Demon ◽  
Farah Nabila Diauddin ◽  
Norherdawati Kasim ◽  
Norli Abdullah ◽  
...  

Platinum-multiwall carbon nanotubes (Pt-MWCNTs) was prepared through a chemical reduction and was characterized by using UV–Vis Spectrophotometer, Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray (FESEM/EDX) and Raman Spectroscopy. Through this chemical reduction, Pt ions were reduced by the addition of sodium dodecyl sulfate (SDS) and Pt was in-situ deposited on the exterior walls of MWCNTs. TEM and FESEM/EDX analyses have confirmed the presence of Pt on the surface of MWCNTs. From Raman Spectroscopy, the ID/IG of MWCNT is 0.66 while ID/IG of Pt-MWCNT is 0.71, showing that not much defects were resulted by the functionalization of Pt on the surface of MWCNT, while from UV-Vis spectra, Pt-MWCNT is found to absorb at about 265 nm due to the presence of Pt nanoparticles that caused a weak surface plasmon resonance (SPR) absorption in the UV region which will contribute to the NLR measurement. The resulted Pt-MWCNTs was then investigated its third-order nonlinearity response as suspension in water using continuous wave laser and z-scan measurement at 532 nm. Pt-MWCNT displays good transmittance profile and self-defocusing effect with excitation intensity is in order of 10-9 cm2/W. The presence of Pt on the surface of MWCNT has contributed to intrinsic properties and resulted in nonlinear refractive (NLR) effect. Thus, Pt-MWCNT is considered to possess significant third-order nonlinear responses considering its low Pt content and has potential in the development of photonics devices.


Author(s):  
M.V. Tsvetkov ◽  
A.A. Nikitin

Currently, 70 % of Russian localities with a population of 9 million people are not connected to the transport system of the country by paved roads, especially in the northern regions, where the ambient temperature in winter does not rise above -500C. Road transport accounts for the largest number of transported goods. One of the vehicles of this type is an all-terrain vehicle Trackol, designed to move on roads with a weak surface: on snow, swamp and soil cover of thawed taiga. The analysis of the vehicle Trackol operation has shown insufficient reliability of its transmission. Analysis of of using the vehicle Trackol showed insufficient reliability of its transmission. To improve the situation the mechanical transmission has been replaced with a hydraulic one, taking into account the main disadvantages associated with maintaining the cleanliness of the working fluid. A system for regulating the temperature of the working fluid in the hydraulic drive of an all-terrain vehicle has been developed. The design of the working fluid filter is proposed, allowing capturing not only dirt, but also moisture due to the use of polyvinylformal of the TPVF brand as the filter element material.


2021 ◽  
Author(s):  
Florian Schütte ◽  
Ivy Frenger ◽  
Kristin Burmeister ◽  
Sabrina Speich ◽  
Johannes Karstensen

<p>In ocean research, mesoscale eddies typically are detected through surface signatures based on satellite data. The assumption is that most eddies are surface intensified and have a vertical structure consistent with a surface intensified mode. However, in-situ eddy observations, especially in the tropical oceans, showed that the vertical eddy structure is often more complex than previously assumed (higher baroclinic modes), and a diverse subsurface eddy field is present, which does not show any surface signatures at all. Our objective here is a first step towards a quantification of the occurrence of subsurface relative to surface eddies. To do this, we use an actively eddying model to compare the subsurface eddy field to its surface signatures in order to be able to estimate which vertical eddy structures prevail and how much of the eddy field is hidden in the subsurface. In addition, the model results are compared against an unprecedented assemblage of observations of subsurface eddies in the tropical oceans. In a first step we focus on eddies in the model that are detectable at the surface for more than 120 days. We found that around 60 % of the detected eddies have a vertical structure associated with a surface intensified mode as previously assumed which are characterized by a strong surface signature. Around 40 % of the eddy field have a vertical structure associated to a higher baroclinic mode. They are often called “intrathermocline” eddies and are characterized by a rather weak surface signature. In a second step we track subsurface eddies (lifetime > 120 days) in the model by identifying density layer thickness anomalies and connect them with possible surface signatures. Around 30 % of the total eddy field of the model, are hidden in the subsurface with no detectable surface signature. In conclusion, our results show that subsurface eddies form a substantial contribution to the total eddy field. Consequently it is difficult to estimate the impact of the eddy field on the ocean when only working with surface based satellite data.</p>


2021 ◽  
Vol 9 ◽  
Author(s):  
Heng Luo ◽  
Teng Wang ◽  
Shengji Wei ◽  
Mingsheng Liao ◽  
Jianya Gong

Small-to-moderate earthquakes (e.g. ≤Mw5.5) occur much more frequently than large ones (e.g. >Mw6.0), yet are difficult to study with InSAR due to their weak surface deformation that are severely contaminated by atmospheric delays. Here we propose a stacking method using time-series SAR images that can effectively suppress atmospheric phase screens and extract weak coseismic deformation in centimeter to sub-centimeter level. Using this method, we successfully derive coseismic surface deformations for three small-to-moderate (Mw∼5) earthquakes in Tibet Plateau and Tienshan region from time-series Sentinel-1 SAR images, with peak line-of-sight deformation ranging from 5–6 mm to 13 mm. We also propose a strategy to downsample interferograms with weak deformation signal based on quadtree mesh obtained from preliminary slip model. With the downsampled datasets, we invert for the centroid locations, fault geometries and slips of these events. Our results demonstrate the potential of using time-series InSAR images to enrich earthquake catalog with geodetic observations for further study of earthquake cycle and active tectonics.


Water Waves ◽  
2021 ◽  
Author(s):  
M. D. Groves

AbstractIn the applied mathematics literature solitary gravity–capillary water waves are modelled by approximating the standard governing equations for water waves by a Korteweg-de Vries equation (for strong surface tension) or a nonlinear Schrödinger equation (for weak surface tension). These formal arguments have been justified by sophisticated techniques such as spatial dynamics and centre-manifold reduction methods on the one hand and variational methods on the other. This article presents a complete, self-contained account of an alternative, simpler approach in which one works directly with the Zakharov–Craig–Sulem formulation of the water-wave problem and uses only rudimentary fixed-point arguments and Fourier analysis.


2021 ◽  
Vol 325 ◽  
pp. 01013
Author(s):  
Hasan Arif Efendi ◽  
Gayatri Indah Marliyani ◽  
Subagyo Pramumijoyo

We focused our study to characterize the geometry and activity of Gorontalo fault. We analysed reviewed the ISC seismic catalogue and the BMKG relocated earthquake events available for the time period of 1960 to 2021, located along the expected location of this fault. In addition, we analysed continuous record from local seismic observatory available for the same period. Further, we mapped the lineaments using 8.3-m resolution DEMNAS data. Tens on shallow earthquakes occurred in the vicinity of this fault with a range magnitude of M 2 to 3. Our lineament analysis however does not reveal distinctive pattern that may indicate the fault manifestation at the surface. The NW-SE trending lineaments are coincidence with the mapped trace of Gorontalo Fault. The weak surface manifestation of the fault scarp may be related to the tropical climatic condition of the area which may obliterate the faulting topography. However, we observed alignment of the seismicity distribution with the mapped NW-SE lineament, indicating that the lineament is likely representing active fault and these earthquakes are associated with faulting along this fault. Our study provide indication that the Gorontalo Fault is active and further study is necessary to investigate subsurface geometry and mitigate its seismic hazards.


2021 ◽  
Vol 249 ◽  
pp. 03023
Author(s):  
Luc Oger ◽  
Renaud Delannay ◽  
Yves Le Gonidec

Quasi-periodic collective displacements of grains at the free surface of a tilted grain packing constitute precursors of granular avalanches. Laboratory experiments are commonly performed by slowly tilting the packing from 0° to the maximal stability angle θA. In these conditions, the number of precursors is too small to assess reproducible and robust statistical analyses of the precursor activity. To go beyond this limitation, we have developed a specific experimental protocol consisting of tilting the packing with successive oscillation cycles. We use a high-resolution optical camera and process the images of the packing free surface to identify precursory events during many consecutive cycles of a single packing. We observe the same behavior for all half-cycles, forth and back: appearance of the first precursors after the same variation of inclination, exponential evolution of the weak surface activity for the first precursors and linear growth of stronger surface activity for the following ones. The experimental protocol provides both reproducible precursor measurements based on large sample statistical inferences and a quasi-stationary state after one full-cycle. This approach is very promising for highlighting the effects of external parameters, including humidity and packing geometry.


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