Underlying Surface Structure Research Articles

Evidence of Spontaneous Formation of Two-Dimensional Amorphous Clathrates on Superhydrophilic Surfaces.

Clathrate hydrates reserved in the seabed are often dispersed in the pores of coarse-grained sediments; hence, their formation typically occurs under nanoconfinement. Herein, we show the first molecular dynamics (MD) simulation evidence of the spontaneous formation of two-dimensional (2D) clathrate hydrates on crystal surfaces without conventional nanoconfinement. The kinetic process of 2D clathrate formation is illustrated via simulated single-molecule deposition. 2D amorphous patterns are observed on various superhydrophilic face-centered cubic surfaces. Notably, the formation of 2D amorphous clathrate can occur over a wide range of temperatures, even at room temperature. The strong water-surface interaction, the characteristic properties of guest-gas molecules, and the underlying surface structure dictate the formation of 2D amorphous clathrates. Semiquantitative phase diagrams of 2D clathrates are constructed where representative patterns of 2D clathrates for characteristic gas molecules on prototypical Pd(111) and Pt(111) surfaces are confirmed by independent MD simulations. A tunable pattern of 2D amorphous clathrates is demonstrated by changing the lattice strain of the underlying substrate. Moreover, ab initio MD simulations confirm the stability of 2D amorphous clathrate. The underlining physical mechanism for 2D clathrate formation on superhydrophilic surfaces is elucidated, which offers deeper insight into the crucial role of water-surface interaction.

The Application and Applicability of HEC-HMS Model in Flood Simulation under the Condition of River Basin Urbanization

With the acceleration of urbanization in a river basin, the changes in the underlying surface structure of the basin are more and more intense, which causes frequent floods. This article aims to analyze the applicability of the HEC-HMS model in flood simulation in urbanization basins and the influence of land use changes on catchment runoff. Pu River Basin is a typical urbanization basin and is taken as the research project. Based on land use changes, soil types, and long-term hydrological data in the Pu River Basin, the HEC-HMS hydrological model is constructed using GIS and HEC-geoHMS. Then, the relative error of flood peak and runoff, Nash–Sutcliffe efficiency coefficient, and correlation are used to evaluate the model simulation rating. The results show that the HEC-HMS model is suitable for an urbanization basin, and its performance grade before urbanization is better than that after urbanization. Finally, sensitivity analysis of nine parameters on model performance shows that curve number, initial abstraction, imperviousness, and time lag are the main parameters. The research results will provide a reference for urbanization basins’ flood simulation and stormwater management.

Identifying the influence of surface texture waveforms on colors of polished surfaces using an explainable AI approach

An explainable artificial intelligence approach based on consolidating the Local Interpretable and Model-agnostic Explanation (LIME) model outputs was devised to discern the influence of the surface morphology on the colors exhibited by stainless-steel 304 parts polished with a Magnetic Abrasive Finishing (MAF) process. The MAF polishing process was used to create two regions, each appearing either blue or red to the naked eye. The color distribution was microscopically heterogeneous, i.e., some red microscale patches were dispersed in blue regions, and vice versa. The surface morphology was represented in the frequency domain (using a 2D Fourier transform) to capture the harmonic surface patterns, such as the feed and lay marks from the polishing process. A Convolutional Neural Network (CNN) was employed to identify the color of the region from the frequency characteristics of the surface morphology. The CNN was able to predict the observed colors with test accuracies exceeding 99%, suggesting that the frequency characteristics of the surface morphology of the red regions are distinctly different from those of the blue regions. A LIME model was constructed around each small segment within each region of the surface to identify the frequency features that are influential for differentiating between the colors. To deal with the effect of heterogeneity, an algorithm based on the query by experts was used to reconcile the local influences and gather the global explanations of the frequency characteristics that inform the blue versus red regions. We found that the dominant morphological features in the red regions are those that capture the polishing lay patterns underlying surface structure, whereas those in the blue regions capture the non-uniform and high-frequency waveform patterns, such as those result when oxide films form due to the intense polishing conditions.

Simulation of the Urban Space Thermal Environment Based on Computational Fluid Dynamics: A Comprehensive Review.

Rapid urbanization has made urban space thermal environment (USTE) problems increasingly prominent. USTE research is important for improving urban ecological environment and building energy consumption. Most studies on USTE research progress have focused on meteorological observations and remote sensing methods, and few studies on USTE are based on computational fluid dynamics (CFD). During the past two decades, with the increasing applications of CFD in USTE research, comprehensively summarizing the phased results have become necessary tasks. This paper analyzes the current research status of CFD-based USTE simulation from six perspectives. First, we summarize the current research status of USTE simulation with CFD models that integrate ground observations and remote sensing technology. Second, we define and classify the spatial scope of CFD-based USTE simulations at different scales. Third, we systematically analyze the quantitative relationships among urban land type, the underlying surface structure, water bodies, green space and the corresponding changes in CFD-based USTE simulations. Fourth, we quantitatively analyze the impact of anthropogenic heat in CFD-based USTE simulations. Fifth, we summarize the corresponding USTE mitigation measures and methods based on the CFD simulation results. Finally, the outlooks and the existing problems in current research on CFD simulations of the USTE are analyzed.

Orienting point clouds with dipole propagation

Establishing a consistent normal orientation for point clouds is a notoriously difficult problem in geometry processing, requiring attention to both local and global shape characteristics. The normal direction of a point is a function of the local surface neighborhood; yet, point clouds do not disclose the full underlying surface structure. Even assuming known geodesic proximity, calculating a consistent normal orientation requires the global context. In this work, we introduce a novel approach for establishing a globally consistent normal orientation for point clouds. Our solution separates the local and global components into two different sub-problems. In the local phase, we train a neural network to learn a coherent normal direction per patch ( i.e. , consistently oriented normals within a single patch). In the global phase, we propagate the orientation across all coherent patches using a dipole propagation. Our dipole propagation decides to orient each patch using the electric field defined by all previously orientated patches. This gives rise to a global propagation that is stable, as well as being robust to nearby surfaces, holes, sharp features and noise.

The mechanisms and seasonal differences of the impact of aerosols on daytime surface urban heat island effect

Abstract. The urban heat island intensity (UHII) is the temperature difference between urban areas and their rural surroundings. It is commonly attributed to changes in the underlying surface structure caused by urbanization. Air pollution caused by aerosol particles can affect the UHII through changing (1) the surface energy balance by the aerosol radiative effect (ARE) and (2) planetary-boundary-layer (PBL) stability and airflow intensity by modifying thermodynamic structure, which is referred to as the aerosol dynamic effect (ADE). By analyzing satellite data and ground-based observations collected from 2001 to 2010 at 35 cities in China and using the WRF-Chem model, we find that the impact of aerosols on UHII differs considerably: reducing the UHII in summer but increasing the UHII in winter. This seasonal contrast is proposed to be caused by the different strengths of the ARE and ADE between summer and winter. In summer, the ARE on UHII is dominant over the ADE, cooling down surface temperature more strongly in urban areas than in rural areas because of much higher aerosol loading, and offsets the urban heating, therefore weakening UHII. In winter, however, the ADE is more dominant, because aerosols stabilize the PBL more in the polluted condition, weakening the near-surface heat transport over urban areas in both vertical and horizontal directions. This means that the heat accumulated in urban areas is dispersed less effectively, and thus the UHII is enhanced. These findings shed new light on the impact of the interaction between urbanization-induced surface changes and air pollution on urban climate.

Comparison of surface radiation and turbulent heat fluxes in Olympic Forest Park and on a building roof in Beijing, China

An effective combination of buildings and parks, as the two core elements of cities, plays an important role in regulating urban climate and ecosystem services. We conducted a comprehensive observation campaign at an Olympic Forest Park site and a surrounding building roof site from 2011 to 2012, with half-hour time step details, including observations of meteorological conditions, radiation and surface heat fluxes. We attempted to find out the effects of changes in the surface radiation and energy balance due to the underlying surface structure and used material by statistical analysis. As expected, besides regular heat fluxes exchange, we also observed larger (by 20.35 W/m2) sensible heat fluxes in the park site than in the building roof during winter. We found the horizontal advection disrupts the local energy balance and modifies the near surface air temperature. Specifically, horizontal advection bringing in external energy would reduce the difference of local near surface temperature between the park and the building roof and weaken the cooling effect of the park. The relationship between urban land cover and its structure and urban surface heat fluxes can be analyzed and discussed, which can provide some practical evidence for future urban construction planning and residents' health.

Surface Structuring Combined with Chemical Surface Functionalization: An Effective Tool to Manipulate Cell Adhesion.

In this study, we investigate how a surface structure underneath a surface-attached polymer coating affects the bioactivity of the resulting material. To that end, structured surfaces were fabricated using colloidal lithography (lateral dimensions: 200 nm to 1 µm, height ~15 to 50 nm). The surface structures were further functionalized either with antimicrobial, cell-adhesive polycations or with protein-repellent polyzwitterions. The materials thus obtained were compared to non-functionalized structured surfaces and unstructured polymer monolayers. Their physical properties were studied by contact-angle measurements and atomic force microscopy (AFM). Protein adhesion was studied by surface plasmon resonance spectroscopy, and the antimicrobial activity against Escherichia coli bacteria was tested. The growth of human mucosal gingiva keratinocytes on the materials was analyzed using the Alamar blue assay, optical microscopy, and live-dead staining. The data shows that the underlying surface structure itself reduced protein adhesion and also bacterial adhesion, as evidenced by increased antimicrobial activity. It also enhanced cell adhesion to the surfaces. Particularly in combination with the adhesive polycations, the surfaces increased the cell growth compared to the unstructured reference materials. Thus, functionalizing structured surfaces with adhesive polymer could be a valuable tool for improved tissue integration.

Inverse Linking, Possessive Weak Definites and Haddock Descriptions: A Unified Dependent Type Account

This paper proposes a unified dependent type analysis of three puzzling phenomena: inversely linked interpretations, weak definite readings in possessives and Haddock-type readings. We argue that the three problematic readings have the same underlying surface structure, and that the surface structure postulated can be interpreted properly and compositionally using dependent types. The dependent type account proposed is the first, to the best of our knowledge, to formally connect the three phenomena. A further advantage of our proposal over previous analyses is that it offers a principled solution to the puzzle of why both inversely linked interpretations and weak definite readings (in contrast to Haddock-type readings) are blocked with certain prepositions.

Abrogated Cell Contact Guidance on Amino-Functionalized Microgrooves.

Topographical and chemical features of biomaterial surfaces affect the cell physiology at the interface and are promising tools for the improvement of implants. The dominance of the surface topography on cell behavior is often accentuated. Striated surfaces induce an alignment of cells and their intracellular adhesion-mediated components. Recently, it could be demonstrated that a chemical modification via plasma polymerized allylamine was not only able to boost osteoblast cell adhesion and spreading but also override the cell alignment on stochastically machined titanium. In order to discern what kind of chemical surface modifications let the cell forget the underlying surface structure, we used an approach on geometric microgrooves produced by deep reactive ion etching (DRIE). In this study, we systematically investigated the surface modification by (i) methyl-, carboxyl-, and amino functionalization created via plasma polymerization processes, (ii) coating with the extracellular matrix protein collagen-I or immobilization of the integrin adhesion peptide sequence Arg-Gly-Asp (RGD), and (iii) treatment with an atmospheric pressure plasma jet operating with argon/oxygen gas (Ar/O2). Interestingly, only the amino functionalization, which presented positive charges at the surface, was able to chemically disguise the microgrooves and therefore to interrupt the microtopography induced contact guidance of the osteoblastic cells MG-63. However, the RGD peptide coating revealed enhanced cell spreading as well, with fine, actin-containing protrusions. The Ar/O2-functionalization demonstrated the best topography handling, e.g. cells closely attached even to features such as the sidewalls of the groove steps. In the end, the amino functionalization is unique in abrogating the cell contact guidance.

An integrated flow microcalorimetry, infrared spectroscopy and density functional theory approach to the study of chromate complexation on hematite and ferrihdyrite

An approach to constructing comprehensive predictive models for contaminant interactions with mineral surfaces is to obtain multiples lines of evidence for surface properties and the types of complexes formed under different geochemical conditions. In this study, we used flow adsorption microcalorimetry (FAMC), attenuated total reflection infrared (ATR FTIR) spectroscopy, and density functional theory (DFT) calculations to study chromate complexation on ferrihydrite (FH) and hematite (HT). Under the experimental conditions used, chromate binds via an exothermic inner-sphere complexation on both surfaces, with similar enthalpy values that do not reveal dramatic differences in the sorption mechanism. Due to their underlying surface structure, FH favors more monodentate and HT more bidentate complexation. Chromate complexes were found by ATR and FAMC to be completely reversible, with substantially slower desorption compared to sorption. Both the FAMC and DFT indicated the presence of surface sites with different energetics, whereby lower surface coverages corresponded to higher enthalpies on both FH and HT. Both flow-based ATR and FAMC yielded different surface coverages than batch isotherms under the same conditions, highlighting the need to assess contaminant sorption under realistic conditions. Overall, this integrated approach proved to be an improved paradigm to study ion sorption on mineral surfaces.

Removal of casting defects from CMSX-4®and CMSX-10®alloys by electropolishing in a novel electrolyte; Deep Eutectic Solvent

Here we describe the use of environmentally benign Deep Eutectic Solvents (DESs) to electropolish oxide casting scale from Ni based superalloy turbine blades. These new electrolytes are a viable alternative to hazardous and aggressive aqueous acids and etchants currently used to process these components. In addition we show that the DES electrolytes selectively expose the underlying surface structure of these superalloys. We demonstrate the ability of these electrolytes to preferentially etch either γ or γ′ phases depending on the choice of electrolyte formulation and the applied potential during the electrolytic etch on CMSX-4 ® and CMSX-10 ® alloys.

Electrochemical reduction of carbon dioxide III. The role of oxide layer thickness on the performance of Sn electrode in a full electrochemical cell

A full electrochemical cell was employed to investigate the role of the surface oxide thickness on the activity of Sn-based electrodes for the electrochemical conversion of CO2. The current density showed a negligible dependence on the thickness of the surface SnOx layer of Sn nanoparticles (100 nm), while the selectivity towards the formation of CO and formate exhibited a strong relationship with the initial SnOx thickness. Electrodes with a native SnOx layer of ∼3.5 nm exhibited the highest Faradaic efficiency (64%) towards formate formation at -1.2 V. The Faradaic efficiency towards CO production reached a maximum (35%) for the electrode with an oxide thickness of 7.0 nm, formed by annealing the Sn nanoparticles at 180 °C for 6 hours. The electrodes with a native SnOx layer displayed the highest overall selectivity towards CO2 reduction. The decrease of the selectivity towards CO2 reduction with increasing the thickness of the SnOx layer can be attributed to the enhancement of hydrogen evolution on the Sn clusters with a low-coordination number derived from the reduction of SnOx. The Faradaic efficiency towards hydrogen production was observed to increase with increasing the thickness of the SnOx layer. Our results suggest the importance of the underlying surface structure on the selectivity and activity of the Sn electrode for CO2 reduction and provide an insight into the development of efficient catalysts.

Research on Thermal Environment of Village in Pearl River Delta Region

At present the tradition layout and landscape characteristic of village are disappearing gradually in the Pearl River Delta region. With the rural residential branch out into high-density and multi-storey, the scale space in village is disappearing in the Pearl River Delta region. The wind field, temperature field, moisture and atmospheric particle distribution of village are changed along with the transition, which lead to the village thermal environment deteriorative. In view of this, the thermal environment of village is simulated, based on the 3D microclimate model ENVI-met. The simulation results show that the layout and the underlying surface structure of the village have a direct relationship with the air temperature and wind speed in village in the Pearl River Delta region.

Pearl Microstructure and Expression of Shell Matrix Protein Genes MSI31 and MSI60 in the Pearl Sac Epithelium of Pinctada fucata by In Situ Hybridization

Expression patterns of the shell matrix protein genes MSI31 and MSI60 in the pearl sac epithelium were examined by in situ hybridization 38 days after implantation, and related to pearl quality. A pearl sac that produced a nacreous pearl showed very weak expression of MSI31 and strong expression of MSI60. A pearl sac, which yielded a prismatic pearl, strongly expressed MSI31 and very weakly expressed MSI60. In a complex pearl, whose surface consisted of a mosaic of both nacreous and prismatic layers, the expression pattern of MSI31 and MSI60 similarly corresponded to the underlying surface structures of the pearl. A nacreous pearl whose pearl sac showed strong MSI31 expression had an entirely nacreous surface composed of a laminar structure with unusual tablet growth at the corresponding site. MSI31 and MSI60 are the major components of the shell matrix proteins of the nacreous and prismatic layers. Clearly, high expression of MSI31 does not always result in prismatic secretion. These observations cannot be explained solely on the basis of the expression patterns of MSI31 and MSI60. We propose that, in addition to the MSI genes that form the prismatic and nacreous layers, upstream from these genes there are regulatory master genes that determine whether a nacreous layer (aragonite) or a prismatic layer (calcite) is formed.

SODA: A new method of in-scene atmospheric water vapor estimation and post-flight spectral recalibration for hyperspectral sensors: Application to the HyMap sensor at two locations

A new method of estimating per-pixel atmospheric column water vapor (ACWV) and potential differences in the reported band center wavelengths of the HyMap sensor has been developed. The new method uses variations of a second order derivative algorithm (SODA) to assess the impact of atmospheric residual features on calculated surface reflectance spectra after atmospheric compensation. The SODA method provides an alternative to the current band ratio techniques of ACWV estimation and also allows the same form of algorithm to be used for the estimation of possible band shifts. A comparison of in-situ measured surface reflectance at two field sites in Western Australia demonstrates improvement in the resulting spectra when post-flight updates are made to the reported HyMap band center wavelengths and applied during the atmospheric compensation process. The same SODA methodology was varied to estimate the ACWV on a per-pixel basis and found to significantly reduce the appearance of the underlying surface structure on the resulting ACWV images as well as improve the overall accuracy of the estimation. The ACWV estimated from the HyMap imagery at the two field sites was found to agree with in-situ atmospheric ACWV measurements to within 2% and represented a two fold increase in accuracy over a 3 band ratio Continuum Interpolated Band Ratio (CIBR) technique of ACWV estimation.

A multi-resolution approach for line-edge roughness detection

A wavelet-based line-edge detection framework is presented that proves to be solely image-dependent. In this analysis, surfaces are considered as a combination of an underlying surface structure and a surface detail, corresponding to low-frequency and high-frequency features, respectively. Through the multi-scale analysis offered by wavelet decomposition, the underlying surface structure is extracted and used to define the line-edge searching region, which, in turn, helps characterize the line-edge roughness (LER), providing valuable information for the evaluation of device fabrication and performance. We focus on exploring the optimal wavelet decomposition, to better separate the underlying structure and the surface detail, using a number of metrics including the Shannon’s entropy, k-means clustering and the flatness factor. The impact of different wavelet functions and resolution levels on line-edge roughness characterization is discussed. An SEM image of a plane diffraction grating is studied to demonstrate the application of the proposed framework.

Initial stages of H 2O adsorption and hydroxylation of Fe-terminated α-Fe 2O 3(0 0 0 1) surface

The adsorption modes of H 2O on a Fe-terminated hematite(0 0 0 1) surface have been investigated by first principles Density Functional theory within a periodic slab model and the generalized gradient approximation. Molecular adsorption and dissociative adsorption in monolayer coverage, one H 2O per surface Fe, were both considered. Five plausible orientations were studied to determine the most favorable adsorption position. Molecular adsorption is shown to have a small effect on the underlying surface structure, while hydroxylation has a strong effect on the surface geometry. Electronic densities of state calculations reveal details of these different interactions. The heterolytic dissociation, which produces two types of surface hydroxyls, is the preferable adsorption mode, being slightly favored energetically over the molecular adsorption. Homolytic dissociative adsorption, forming a single hydroxyl on surface Fe, is energetically unfavored, even though strong binding interaction (∼3 eV) is found between the OH radical and surface. Dissociative adsorption on an oxidized ferryl site was also studied to investigate suggested local reactivity enhancement.

Attachment, morphology and adherence of human endothelial cells to vascular prosthesis materials under the action of shear stress

In an effort to improve the long-term patency of vascular prostheses several groups now advocate seeding autologous endothelial cells (ECs) onto the lumen of the vessel prior to implantation, a procedure that involves pre-treating the prosthesis material with fibrin, collagen and/or other matrix molecules to promote cell attachment and retention. In this study, we examined the degree to which human umbilical venous endothelial cells (HUVECs) adhered to three materials commonly used polymeric vascular prosthesis that had been coated with the same commercial extra cellular matrix proteins, and after exposure to fluid shear stresses representative of femoro-distal bypass in a cone-and-plate shearing device. We quantified cell number, area of coverage and degree of cell spreading using image analysis techniques. The response of cells that adhered to the surface of each material, and following exposure to fluid shear stress, depended on surface treatment, topology and cell type. Whereas collagen coating improved primary cellular adhesion and coverage significantly, the degree of spreading depended on the underlying surface structure and on the application of the shear stress. In some cases, fewer than 30% of cells remained on the surface after only 1-h exposure to physiological levels of shear stress. The proportion of the surface that was covered by cells also decreased, despite an increase in the degree to which individual cells spread on exposure to shear stress. Moreover, the behaviour of HUVECs was distinct from that of fibroblasts, in that the human ECs were able to adapt to their environment by spreading to a much greater extent in response to shear. The quality of HUVEC attachment, as measured by extent of cell coverage and resistance to fluid shear stress, was greatest on expanded polytetrafluoroethylene samples that had been impregnated with Type I/III collagen.

Low-cost interactive active range finder

This paper describes a new type of low-cost interactive active range finder and illustrates the effect of introducing interactivity to the range-acquisition process. The new range finder consists of only one camera and a laser pointer to which three LEDs are attached. When a user scans the laser, the camera captures the image of spots (one from the laser and the others from LEDs), and triangulation is carried out using the camera's viewing direction and the optical axis of the laser. The user interaction allows the range finder to acquire range data in which the sampling rate varies across the object depending on the underlying surface structures. Moreover, the processes of separating objects from the background and/or finding parts in the object can be achieved using the operator's knowledge of the objects.