Surface Characteristic Changes Research Articles

Enhanced Biological Nitrate Removal from Groundwater in Humid Tropical Regions Using Corn Cob-Based Permeable Reactive Barriers: A Case Study from Panama

Nitrate contamination in groundwater is a global concern due to its widespread presence and consequential social, environmental, and economic ramifications. This study investigates the efficacy of biological denitrification in a humid tropical setting, utilizing corn cob in batch and column tests to assess nitrate removal under varying conditions. Batch tests demonstrated the nitrate removal efficiencies of 93.14%, 91.58%, 90.77%, and 98.74% for initial concentrations of 22.18 ± 2.82 mg/L, 27.3 mg/L, 69.1 ± 1.2 mg/L and 115.08 ± 1.88 mg/L, respectively. In the column test, the removal efficiency was 99.86%, 87.13%, and 74%, and the denitrification rate was 32.82, 53.43, and 83.53 mg NO3−-N/L d, for a hydraulic retention time (HRT) of 24 h, 16 h, and 7 h, respectively. Predominantly, nitrate removal occurred via biological denitrification, particularly favoring a 24 h HRT. The corn cob effectively removed high nitrate concentrations of up to 115 mg NO3−-N/L. Scanning electron microscopy and Fourier transform infrared spectroscopy revealed surface characteristic changes of the carbon source pre- and post-denitrification. This research sheds light on the potential of biological denitrification using corn cob in humid tropical environments, offering a promising avenue for addressing nitrate contamination challenges in groundwater systems.

Bioinspired N-Oxide-Based Zwitterionic Polymer Brushes for Robust Fouling-Resistant Surfaces

Fouling-resistant surfaces are needed for various environmental applications. Inspired by superhydrophilic N-oxide-based osmolytes in saltwater fish, we demonstrate the use of a trimethylamine N-oxide (TMAO) analogue for constructing fouling-resistant surfaces. The readily synthesized N-oxide monomer of methacrylamide is grafted to filtration membrane surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP). Successful grafting of the amine N-oxide brush layer as confirmed by material characterization endows the surface with increased hydrophilicity, reduced charge, and decreased roughness. Notably, the introduction of the N-oxide layer does not compromise transport properties, i.e., water permeability and water-salt selectivity. Moreover, the modified membrane exhibits improved antifouling properties with a lower flux decline (32.1%) and greater fouling reversibility (18.55%) than the control sample (45.4% flux decline and 3.26% fouling reversibility). We further evaluate foulant-membrane interaction using surface plasmon resonance (SPR) to relate the reduced fouling tendency to the synergic effects of surface characteristic changes after amine N-oxide modification. Our results demonstrate the promise and potential of the N-oxide-based polymer brushes for the design of fouling resistance surfaces for a variety of emerging environmental applications.

Effect of Erosive Agents on Surface Characteristics of Nano-Fluorapatite Ceramic: An In-Vitro Study.

Erosive beverages cause dissolution of natural teeth and intra-oral restorations, resulting in surface characteristic changes, particularly roughness and degradation. The purpose of this study was to evaluate the surface roughness and topography of a dental ceramic following immersion in locally available erosive solutions. A total of 160 disc specimens of a nano-fluorapatite type ceramic (12 mm diameter and 2 mm thickness) were fabricated and equally distributed into two groups (n = 80) and then evenly distributed among the following five testing groups (n = 16): lemon juice, citrate buffer solution, 4% acetic acid, soft cola drink, and distilled water which served as a control. The surface roughness (Ra) and topography were evaluated using a profilometer and scanning electron microscope at baseline, 24 h, 96 h, and 168 h respectively. Data were analyzed using ANOVA and Tukey’s multiple comparisons (p ≤ 0.05). Surface changes were observed upon exposure to all acidic beverages except distilled water. Amongst all immersion media, 4% acetic acid produced the most severe surface roughness across all time periods (i.e., baseline, 24 h, 96 h, and 168 h). A statistically significant difference in the surface roughness values between all immersion media and across all four time intervals was observed. Erosive agents had a negative effect on the surface roughness and topography of the tested ceramic. The surface roughness increased with increased storage time intervals.

Experimental Investigation of Critical Heat Flux on Different Surfaces at Low Pressure and Low Flow

Steady state flow boiling experiments were carried out on several heated tubes with outer diameter 9.14 mm at outlet pressures 120, 200 and 300 kPa, inlet temperatures 64, 78 and 91 °C and approximately 400, 500, 600 and 800 kg/(m2·s) mass flux entering the vertically aligned test annulus until critical heat flux (CHF) was reached. The tubes were made of Inconel 625 with a length of 400 mm. The Inconel tubes were tested in three different modifications as smooth, abraded with 150 grit sandpaper and bead blasted. Multiple experiments were repeated on the same specimen to investigate the effect of surface characteristic changes (i.e., wettability, roughness and oxide layer morphology) on the occurrence of CHF. Despite the changes in initial wettability, the CHF dependency was not clearly observed, however, the changes in roughness led to an increase in CHF. The total number of 115 experimental runs were collected and the results were also compared with other literature experimental data.

Functionalized mesoporous silica nanoparticles by lactose and hydrophilic polymer as a hepatocellular carcinoma drug delivery system

Surface modification has a strong impact on mesoporous silica nanoparticles (MSNs) performance as drug carriers. Here, we described the chemical synthesis; in vitro drug release and cytotoxicity of MSNs decorated with poly ethylene glycol (PEG) or poly propylene glycol PPG as an outer shell wrap for nanoparticles (NPs). The lactose, glucosylgalactose, was used to provide a specific interaction with the asialoglycoprotein receptor which is expressed on the cell surface of hepatoma. Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) confirmed successful chemical surface modification while Dynamic Light Scattering (DLS) confirmed the surface characteristic changes as size; polydispersity index (PI) and zeta potential. Our results showed that the PI was improved from 0.58 to 0.28 while size has been enlarged from 200 to 357 and 580 nm. A higher percentage of drug entrapment (doxorubicin) was observed with functionalized NPs (94%) compared to plain MSNs (63%). In this study, we effectively synthesized lactose-PPG-MSNs targeting HepG2 cells with IC50 of 0.07 mg/mL when loaded with doxorubicin. This study may provide a useful approach for designing and improving the applicability of MSNs as a promising drug delivery system in hepatocellular carcinoma.

Investigation on mechanism of intensifying coal fly ash froth flotation by pretreatment of non-ionic surfactant

The purpose of this research was to investigate the mechanism of intensifying coal fly ash flotation by pretreatment of the non-ionic surfactant Triton X-100 (TX100). Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy dispersive spectroscopy were used to analyze the characteristics of the unburned carbon samples to clarify why unburned carbon floats with difficulty. An attachment time analyzer and surface free energy measurement were used to analyze the surface characteristic changes of the unburned carbon before and after pretreatment with TX100. A Foamscan analyzer was used to study the synergistic effects of TX100 and 2-Octanol on the foam properties. The obtained results demonstrate that the unburned carbon surface is strongly hydrophilic owing to the abundance of oxygen-containing functional groups as well as its rough and porous surface. The pretreatment of TX100 can improve the hydrophobicity of the unburned carbon surface significantly in order to improve the unburned carbon recovery. Moreover, the compound of TX100 with 2-Octanol can improve the foamability and foam stability, as well as decrease the bubble size, which can further promote the coal fly ash flotation performance.

Monte-Carlo simulation of the Siemens Artiste linear accelerator flat 6 MV and flattening-filter-free 7 MV beam line.

The aim of our work is to provide the up-to-now missing information on the Siemens Artiste FFF 7 MV beam line using a Monte-Carlo model fit to the realistic dosimetric measurements at the linear accelerator in clinical use at our department. The main Siemens Artiste 6MV and FFF 7MV beams were simulated using the Geant4 toolkit. The simulations were compared with the measurements with an ionization chamber in a water phantom to verify the validation of simulation and tuning the primary electron parameters. Hereafter, other parameters such as surface dose, spectrum, electron contamination, symmetry, flatness/unflatness, slope, and characteristic off-axis changes were discussed for both Flat and FFF mode. The mean electron energy for the FFF beam was 8.8 MeV and 7.5 MeV for Flat 6 MV, the spread energy and spot size of the selected Gaussian distribution source were 0.4 MeV and 1mm, respectively. The dose rate of the FFF beam was 2.8 (2.96) times higher than for the flattened beam for a field size of 10×10 (20×20) cm2. The electron contamination has significant contribution to the surface dose especially for the flattened beam. The penumbra, surface dose and the mean energy of photons decrease by removing the flattening filter. Finally, the results show that off-axis changes have no strong effect on the mean energy of FFF beams, while this effect was more considerable for the flattened beam.

Comparison of steady and transient flow boiling critical heat flux for FeCrAl accident tolerant fuel cladding alloy, Zircaloy, and Inconel

Steady and transient (with a heating rate of 685 °C/s) internal-flow CHF (Critical Heat Flux) experiments were conducted under atmospheric pressure at a fixed inlet temperature (40 °C or 60 °C) and mass flow (300 kg/m2 s) on Fe-13Cr-6Al alloy, Inconel 600 and Zircaloy-4 tube samples. Multiple experiments were repeated on the same specimen to investigate the effect of surface characteristic changes (i.e., roughness, wettability, and oxide scale morphology) on the occurrence of CHF. Despite notable changes of wettability, roughness, and oxide layer characteristics on samples that had already been subjected to CHF, measured flow CHF remained unchanged throughout repeated experiments for tested materials. This demonstrates that the surface effects on flow CHF are limited in the test conditions. In the steady-state flow boiling condition, Fe-13Cr-6Al alloy demonstrated a 22% and 14% increase in CHF compared to Zircaloy-4 and Inconel 600, respectively. Compared to the 2006 Groeneveld CHF lookup table, Fe-13Cr-6Al alloy gives a 13% increase in the tested flow boiling condition. Material properties are considered primarily responsible for the observed CHF differences among the tested materials. The surface thermal economy parameter (ρcp3/2k) is proposed as an explanation for the observed CHF differences; this parameter is related to material’s ability to avoid an irreversible dry spot formation. The apparent disagreement of Zircaloy-4 CHF with both the look up table predictions and Inconel 600 shows the limitation of departure of nucleate boiling (DNB) evaluations that do not consider cladding materials. The transient Fe-13Cr-6Al CHF is 39% and 23% higher than the lookup table prediction and the steady-state condition experimental result, respectively.

Changes in the Surface Structure of Coal Caused by Igneous Intrusions and Their Effect on the Wettability

In this paper, normal and thermally altered coals were sampled to investigate the surface characteristic changes of coals after igneous intrusions and their effects on the wettability. The chemical compositions, pore structures, surface morphology, and functional groups of coals after igneous intrusions were comparatively analyzed. A contact angle experiment and wetting time test were employed to analyze the wettability of coals. The results showed that the coals after igneous intrusions exhibited much more epigenetic carbonates and higher ash contents as compared to the normal coals, which would improve the wettability of these coals. Pore structure analysis revealed that the macropore volume and surface roughness of the altered coals were further increased due to igneous intrusions. In addition, the altered coals formed much larger pores and more cracks on their surface, which made these coals more easily wetted by water. XPS analysis revealed decreased contents of oxygen-containing groups after igneous...

Experimental study on atmospheric pressure plasma polymerized conducting polymer under coupling and remote conditions

ABSTRACTThis article has analyzed conducting polymer from the viewpoint of material properties, which is polymerized under atmospheric pressure condition for coupling and remote conditions, respectively. The experimental results show that the atmospheric pressure plasma polymerized pyrrole (pPPy) exhibits similar characteristics from the viewpoint of crystallinity, but the shapes and roughness of the particles are significantly distinguished. In the case of coupling condition, a uniform and flat layer like a thin film was obtained. However, in the case of remote condition, the deposited layer had more rough nanoparticles compared to that of coupling condition. The pPPy surface characteristic and morphology changes are discussed by using field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray diffraction (XRD) results. Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis are used to determine the chemical changes introduced by the atmospheric pressure plasma for coupling and remote conditions. The both pPPy materials, which were obtained by coupling and remote conditions, are expected to be applied to various fields, especially for designing the thin conducting electrode layer of polymer light emitting diode (P-LED) or for improving the efficiency by inserting conducting polymer powder on hole injection layer.

Biorecovery mechanism of palladium as nanoparticles by Enterococcus faecalis: From biosorption to bioreduction

In this study, the biorecovery mechanism of palladium ions (Pd(II)) as palladium nanoparticles by Enterococcus faecalis (E. faecalis), a typical Gram-positive bacterium, was explored from acting force, participated substance and reaction process. The XRD and TEM analysis showed that the deposit locations of Pd-NPs depended on the transfer of Pd(II) in biosorption, and the process was invested by effect factors and theory models of isotherm, thermodynamics, and kinetics, which was a spontaneous endothermic process fitted well by Langmuir isotherm and pseudo-second order kinetics. In addition, the surface characteristic changes of E. faecalis during biorecovery of Pd(II) were compared by FTIR and XPS, and it found that carboxyl groups, hydroxyl groups and amine groups were the main participated functional groups in biorecovery. Furthermore, the contrary pH change between biosorption and bioreduction combined with above results proved that electrostatic interaction, complex formation of Pd(II) on the cell and intracellular uptake were the acting forces for biosorption, and the bioreduction of adsorbed Pd(II) was via the hydrolysis and oxidation of sodium formate to deliver electron. Therefore, the biorecovery mechanism of Pd(II) can be divided into the biosorption from solution to cells, and then the bioreduction and crystallization in situ by the electron donor and the link frame of E. faecalis.

The effect of different beverages on surface hardness of nanohybrid resin composite and giomer.

Aims:To investigate the effects of five beverages (apple cider, orange juice, Coca-Cola, coffee, and beer) on microhardness and surface characteristic changes of nanohybrid resin composite and giomer.Materials and Methods:Ninety-three specimens of each resin composite and giomer were prepared. Before immersion, baseline data of Vicker's microhardness was recorded and surface characteristics were examined using scanning electron microscopy (SEM). Five groups of discs (n = 18) were alternately immersed in 25 mL of each beverage for 5 s and in 25 mL of artificial saliva for 5 s for 10 cycles. Specimens were then stored in artificial saliva for 24 h. This process was repeated for 28 days. After immersion, specimens were evaluated and data were analyzed by two-way repeated analysis of variance (ANOVA), Tukey's honestly significant difference (HSD), and a t-test (α = 0.05).Results:Microhardness of all groups significantly decreased after being immersed in the tested beverages (P < 0.05). SEM photomicrographs presented surface degradation of all groups.Conclusions:The effect of these beverages on the surface of both restorative materials also depended upon the exposure time and chemical composition of the restorative materials and beverages.

Low cycle fatigue life improvement of AISI 304 by initial and intermittent wire brush hammering

The effects of hammering by wire brush as a method of improving low cycle fatigue life of highly ductile austenitic stainless steel AISI 304 have been investigated through an experimental study combining imposed strain fatigue tests and assessment of surface characteristic changes under cyclic loading by SEM examinations and XRD analysis. It has been shown that the fatigue life of wire brush hammered surface was increased by 307% at an imposed strain rate of 0.2% and only 17% at an imposed strain rate of 0.5%, comparatively to the turned surface. This increase in fatigue life is explained in terms of fatigue damage that is related to crack networks characteristics and stability which are generated during fatigue on both turned and wire brush hammered surfaces. The improvement of brushed surface is attributed to the role of the surface topography, the near surface stabilized compressive residual stresses and superficial cold work hardening on the fatigue crack network nucleation and growth. It is found that wire brush hammering produces a surface texture that favors, under cyclic loading, nucleation of randomly dispersed short cracks of the order of 40μm in length stabilized by the compressive residual stress field that reached a value of σ0=−749MPa. In contrast, turned surface showed much longer unstable cracks of the order of 200μm in length nucleated in the machining groves with high tendency to propagate under the effect of tensile residual stress field that reached value of σ0=476MPa. This improvement is limited to strain rates lower than 0.5%. At higher strain rates, a cyclic plastic deformation induced martensitic phase alters furthermore the fatigue behavior by producing high cyclic strengthening of the bulk material. This phenomenon lead to a reduction in strain imposed fatigue life. It has also been established that wire brush hammering can be used as an onsite surface treatment to improve the residual fatigue life of components subjected to cyclic loading. The efficiency of this treatment is demonstrated if it is performed at a fraction of service lifetime Ni/Nr lower than 0.5.

Effect of pretreatment on surface topographical features of vegetables during drying

It is well recognized that many adverse changes occur to a food product during drying. Various pretreatment methods have thus been introduced to maintain the quality of the product. Among the various qualities, or properties, of a food product surface characteristics are one of the most important as these affect directly the consumer acceptance of the product. In terms of food safety surface characteristics may also be related to the attachment and hence thermal resistance of pathogenic microorganisms on the product surface. In this study attempt was made to investigate changes of the surface topographical features of vegetables as affected by pretreatment (blanching in hot water or soaking in 0.5–1.5% v/v acetic acid solution) and hot air drying (60 °C); cabbage and spring onion were selected as model vegetables to represent different natural topographical features of vegetables. An image analysis technique was used to monitor the changes of vegetable surfaces after pretreatment and during drying. The surface characteristic changes of vegetables were described quantitatively in terms of the relative roughness factor ( R). It was observed that the surface characteristic changes, as affected by both pretreatment and drying processes, could be well monitored by the evolution of the R value.

Phenotypic and karyotypic properties of hyperdiploid acute lymphoblastic leukaemia of childhood.

The DNA/cell content was measured by flow cytometry in samples obtained from 98 unselected children with acute lymphocytic leukaemia (ALL) at diagnosis. The frequency of anomalies in modal DNA content was compared to that encountered in acute childhood non-lymphocytic leukaemia (ANLL) and disseminated non-Hodgkin's lymphoma (NHL). In ALL the most frequent (35%) aberration in DNA content was an increase by 20% relative to the modal value of normal white blood cells. This subcategory, referred to as hyperdiploid ALL (HD-ALL), was characterized by a close association with the expression of the c-ALL surface marker (20/20 patients) and characteristic numerical chromosome changes, including tri- or tetrasomy of chromosome 21. Moreover, patients with hyperdiploid ALL had a much lower peripheral leucocyte count (P = 0.001) than those with diploid disease and a varying proportion of their leukaemic cells existed in the peripheral blood as morphologically normal lymphocytes expressing the c-ALL antigen. Within the standard risk category, patients with HD-ALL had a longer disease-free survival than those with diploid disease (P = 0.058). It is concluded that routine analysis by flow cytometry can conveniently and consistently detect ALL patients with hyperdiploid chromosome numbers. Hyperdiploid ALL constitutes a fairly large subtype of childhood ALL with specific biological and karyotypic properties, possibly associated with favourable prognosis.