Lamellar Distribution Research Articles

Effects of HIP on Microstructure and Mechanical Properties of LMD Fe36Mn21Cr1815NiAl10 High-Entropy Alloy

To reduce costs, a cobalt-free FeMnCrNi-based HEA has been proposed. Further investigation into the mechanical properties of the Fe36Mn21Cr18Ni15Al10 alloy is essential to expand its application potential. In this study, a cobalt-free Fe36Mn21Cr18Ni15Al10 HEA was fabricated using LMD, and the effects of HIP on its microstructure and mechanical properties were investigated. Results indicated that the as-printed specimen exhibited a dual-phase structure consisting of BCC and FCC phases, with the B2 phase dispersed as fine blocks. After HIP treatment, the content of the FCC phase significantly increased, displaying a lamellar distribution between the BCC phases, with secondary block-like B2 phases forming within the BCC matrix. The HIP process enhanced the density of the high-entropy alloy to 98.2%, while the tensile strength at 25 °C increased to 903.9 MPa. Additionally, the post-fracture elongation improved to 17.4%, thereby increasing the potential for industrial applications of HEAs.

Lamellar Zr-rich phase and its influence on coercivity for Sm(CoFeCuZr)z magnets

The precipitation-hardened Sm-Co permanent magnets relied on the pinning of nanocellular structures to achieve high coercivity, and have an irreplaceable position in high-temperature applications. In this article, by employing micromagnetic simulations and magnetic domain observations, the pinning behavior of lamellar phases (Z-phase) were investigated, which has not been well understood before. The results showed that the Z-phase can serve as a strong pinning position, but due to the parallel lamellar distribution, the magnetic domain walls can move around. Additionally, the effect of Z-phase on coercivity was achieved by changing the morphology of magnetic domain walls during magnetization reversal. For attractive pinning, the coercivity was reduced by the Z-phase, while for repulsive pinning, the Z-phase increased the coercivity when γZ＜0.54γH. Our findings can provide a novel understanding of the coercivity mechanism of precipitation-hardened Sm-Co permanent magnets.

Study on Carbonation of Porcine Blood Hydrogel in the Composite Mortar of Ancient Chinese Architectural Painting.

In the ancient Chinese recipe for composite mortar used in the construction of ground layers for architectural painting, the mixture of porcine blood and lime water is one of the constituent materials. Herein, according to the traditional recipe, the interaction between porcine blood and lime water was systematically and deeply investigated. The experimental investigation demonstrated that porcine blood mixed with lime water at the ratio found in the recipe can form a hydrogel with a hydrophobic surface. During air-drying, the lime water in porcine blood hydrogel can react with CO2 to form calcium carbonate. The crystal morphology of the formed calcium carbonate depends on the surrounding micro-environment of calcium ions in the porcine blood hydrogel. The formed morphology of calcium carbonate includes small calcite crystallites, small graininess calcite crystals with round features, calcite aggregates with layered ladder-like structures, and amorphous calcium carbonate (ACC). Interestingly, the calcium carbonate formed in the inner part of the porcine blood hydrogel exhibits lamellar distribution due to a Liesegang pattern formation. Based on the findings that the porcine blood hydrogel has surface hydrophobicity and brittleness, it can be predicted that in the preparation process of composite mortar for ancient building color painting base course, porcine blood used in the form of a hydrogel is not only easier to be dispersed in hydrophobic tung oil than in liquid porcine blood but also the affinity between porcine blood gel and tung oil is enhanced. As constituent material dispersed in the composite mortar, the layered distribution of calcium carbonate in the porcine blood hydrogel may presumably be beneficial to reduce the internal stress of the composite mortar material.

Study on anti-corrosion performance of composite modified magnesium ammonium phosphate cement-based coatings

Corrosion of metals not only fails the overall stability of a building but causes significant economic losses. Spraying anti-corrosion coatings is the simplest and most effective method of corrosion protection. Magnesium phosphate cement-based coatings are attractive due to their fast-setting speed, high strength and durability. This paper aims to improve the corrosion protection properties of magnesium ammonium phosphate cement-based coatings. Zinc oxide and aluminum tripolyphosphate were used as additives at 3% and 4% by mass of magnesium oxide. Meanwhile, metakaolin and aluminum tripolyphosphate at 15% by mass of magnesium oxide was added as admixtures for compound modification. In addition, the electrode potential and current density, impedance spectra, passivation films and phase composition of the materials were investigated using LPR, EIS, SEM and XRD/TG-DTG measurements. Comparing the anodic slope Ba of the polarization curve shows that the Zinc oxide mixed metakaolin specimens(Zn-CSA) have the highest Ba value, indicating that the coating prevents rusting by inhibiting the anodic electrochemical reaction. The EIS impedance spectroscopy results show that sulfate aluminate cement as a compound modifier of the admixture can effectively improve the corrosion protection of the coating. The addition of ATP is effective in inhibiting the transfer process of the coating in the charge. Furthermore, the addition of Zn is to improve the corrosion resistance of the coating by enhancing the shielding properties of the coating. SEM results show that the Zn-CSA surface is very dense, with a lamellar distribution of crystals consisting of tiny crystals closely packed at the bottom and a lamellar distribution at the top. This effectively prevents the erosion of the substrate by corrosive media. The XRD/TG-DTG results show that the composite modified coating consists mainly of incomplete MgO, the main hydration product MAP, Mg2SiO4 and MgCaSiO4. Moreover, Zn-CSA showed the lowest porosity before and after immersion in the coating porosity test. In the salt spray test, the composite-modified coating showed good corrosion resistance, with no bulging, flaking or rusting of the coating surface after 1440 h of salt spray time. This study has important implications for improving corrosion resistance and reducing corrosion costs.

Cytocompatibility and osteogenic activity of Ta-Ti-O nanotubes anodically grown on Ti6Al4V alloy

Bioactive composition and bionic topography are highly desired in the surface design of biomedical implant materials. Herein, Ta-Ti-O nanotubes (NTs) were anodically grown on a tantalum (Ta) alloyed Ti6Al4V (Ta/TC4) surface. Ta/TC4 shows a scalelike surface and (α'+β) microstructure with a thickness of 11.7 μm, while Ta-Ti-O NTs exhibit a lamellar topography with ∼ 1.0 μm in length and 48.6 nm in diameter. Ta-Ti-O NTs group has the lowest water contact angle of ∼ 16.5° compared with TC4, Ta/TC4, and Ti-O NTs grown under the same electrochemical conditions. In vitro assays show that Ta-Ti-O NTs are non-cytotoxicity to MC3T3-E1 osteoblasts and slightly hamper cellular proliferation, but the adhesion and spreading abilities are significantly enhanced than others. The alkaline phosphatase (ALP), collagen type-1 (COL 1), and extracellular matrix (ECM) mineralization levels of osteoblasts on Ta-Ti-O NTs were also improved and further confirmed by osteogenesis-related gene expressions like ALP, COL 1, OPG, and TGF-β1. The superior osteogenic activities of Ta-Ti-O NTs can be mainly ascribed to the combined effect of Ta2O5 doping and the lamellar distribution of NTs. In summary, Ta-Ti-O NTs film with excellent cytocompatibility and osteogenic activities will find its clinical application in the future.

Ta2O5-doped TiO2 nanotubes on Ti6Al4V alloy with improved cytocompatibility to endothelial cells

Microscopic topography and chemical composition of implant surface play critical roles in cellular response. In this work, Ta2O5-doped TiO2 nanotubes (Ta2O5/TiO2 NTs) were prepared on Ti6Al4V (TC4) to improve its cytocompatibility to endothelial cells. Firstly, a Ta diffusion layer on TC4 (Ta/TC4) was designed by plasma surface Ta-alloying. Then, a Ta2O5/TiO2 NTs film was grown on Ta/TC4 by anodization. The surface morphology, phase composition, and microstructure of the obtained samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). Ta incorporation leads to the lamellar microstructure (α'+β) of Ta/TC4 and the lamellar distribution of Ta2O5/TiO2 NTs. In vitro assays demonstrate that the synergistic effect of Ta2O5 addition and biomimetic nanostructure is responsible for the enhanced proliferation, adhesion, cytoskeletal assembly, and spreading of endothelial cells on Ta2O5/TiO2 NTs. The excellent cytocompatibility of Ta2O5/TiO2 NTs highlights its potential in biomedical applications.

Strengthening and strain hardening mechanisms of a plain medium carbon steel by multiscale lamellar structures

Plain medium carbon steel with the multiscale lamellar structure was produced through quenching and subsequent warm rolling. The microstructure characteristic was conducted based on statistical parameters and physical metallurgy by electron backscattered diffraction (EBSD), the mechanical properties were investigated using uniaxial tensile tests at room temperature. The heterogeneous structure is characterized with multiscale lamellar distribution with three-level grain size spanning the nano-to micro-meter range, which is defined as ultrafine-grained (UFG), fine-grained (FG) and coarse-grained (CG). The results of kernel average misorientation (KAM) and Taylor factor (TF) revealed that the existence of interface effects. The nucleation and accumulation of geometrically necessary dislocation (GND) were activated by multiscale lamellae, to cause the formation of sharp up-turn in strain hardening curves. The results of multiple model fits showed that the Swift model was the most appropriate for the studied steel, and the instantaneous strain hardening values were obtained on its basis. The existence of an extra strengthening mechanism (hetero-deformation induced strengthening) was confirmed by calculating. The results showed WR84 had outstanding mechanical properties and strain hardening ability. The improved toughness of WR84 is mainly attributed to ultrafine grain strengthening, and the reasonable ductility is owing to hierarchical hetero-structured of the lamellae, particle dispersion distribution and the three-level coordinated control of grain size as they can increase the strain hardening ability by the interaction constraint.

Uterine tumor resembling an ovarian sex cord tumor: A case report and review of literature

BACKGROUNDEndometrial stromal tumors originate from the endometrial stroma and account for < 2% of all uterine tumors. Uterine tumor resembling an ovarian sex cord tumor (UTROSCT) is a rare histological class of endometrial stromal and related tumors according to the latest World Health Organization classification of female genital tumors. Here, we report a case of UTROSCT in a 51-year-old woman.CASE SUMMARYA 51-year-old woman had irregular menses for 6 mo. The patient visited a local hospital for vaginal bleeding. Pelvic computed tomography (CT) showed a mass in the pelvic cavity. Five days later, she came to our hospital for further diagnosis. The results of contrast-enhanced CT and pelvic ultrasound at our hospital suggested a malignant pelvic tumor. She then underwent total removal of the uterus with bilateral salpingectomy. Postoperative histological examination showed that the tumor cells had abundant cytoplasm, ovoid and spindle-shaped nuclei, fine chromatin, a high nucleoplasm ratio, and a lamellar distribution. The findings were consistent with UTROSCT, and the results of immunohistochemical analysis supported that diagnosis. The tumor was International Federation of Gynecology and Obstetrics stage IB. No adjuvant therapy was administered after radical surgery. The patient was followed up for 58 mo, and no recurrence was found.CONCLUSIONWe report a case of UTROSCT with abnormal menstruation as a symptom, which is one of the most common symptoms. In patients with vaginal bleeding, ultrasonography can be used as a screening test because of its convenience, speed, and lack of radiation exposure. For patients with long-term tamoxifen use, routine monitoring of the endometrium is recommended. As UTROSCT may have low malignant potential, surgery remains the primary management strategy. Additionally, fertility preservation in patients of childbearing age is a vital consideration.

Enhanced mechanical properties of boron nitride nanosheets/copper composites with a bioinspired laminated structure

ABSTRACT Poor mechanical properties of copper (Cu) hinder its applications as structural materials. Developing bioinspired-laminated structure is among the most promising strategies for obtaining modern structural materials with excellent combination mechanical properties. To explore the possibility of enhancing mechanical properties of Cu, herein, we fabricated boron nitride nanosheets/copper (BNNSs/Cu) composites with a bioinspired laminated structure, achieved by ball milling and spark plasma sintering (SPS). Their mechanical properties were investigated. The results indicate that their tensile strength and toughness are both larger than those of pure Cu: the addition of 0.3 vol% of BNNSs improves the tensile strength from 187 MPa to 216 MPa and the elongation from 41% to 56%, respectively. The enhancement of ductility is due to the unique lamellar distribution of BNNSs in composites, which resulted in retarding cracks propagation; the strengthening effect of BNNSs is determined by the moderate interfacial bonding strength and possible agglomeration of BNNSs.

Eco-Friendly Preparation of Epoxy-Rich Graphene Oxide for Wound Healing.

Despite the ever-growing endangerment caused by the multidrug resistance (MDR) of bacteria, the development of effective antibacterial materials still remains a global challenge. Current antibiotic therapies cannot simultaneously inactivate bacteria and accelerate wound healing. This study aimed to originally separate the intercalation of MnO3+ and the oxidation processes to synthesize epoxy-rich graphene oxide (erGO) nanofilms via an eco-friendly synthetic route, which possessed low density and large lamellar distribution and was rich in epoxide. Importantly, the MnO3+ could be separated from the product and recycled for preparing the next generation of erGO nanofilms, which was quite economical and eco-friendly. The erGO nanofilm was capable of successfully inhibiting Gram-negative bacteria and even had excellent growth-inhibitory effects on Gram-positive bacteria including multidrug resistance (MDR) bacteria, as evidenced by antibacterial phenomena. Additionally, the erGO nanofilm with high •C density formed from epoxide exerted excellent antibacterial effects through tight membrane wrapping and induction of lipid peroxidation. The wound-healing property of the erGO nanofilm was evaluated via treatments of wounds infected by Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), which not only killed bacteria but also accelerated wound healing in mice with a skin infection. The novel erGO nanofilm with dual antimicrobial mechanisms might serve as a promising multifunctional antimicrobial agent for medical wound dressing with high biocompatibility.

Neutrophils in Nail Clipping Histology: A Retrospective Review of 112 Cases

Background: Nail clipping histology is more sensitive than mycology for detecting nail fungi. However, in the absence of fungi, established diagnostic clues for this and other nail dystrophy causes are lacking, namely for nail psoriasis. Neutrophils have been reported in onychomycosis and nail psoriasis samples but have been insufficiently characterized. Objectives: The aim of this paper is to differentiate neutrophil-containing nail clipping samples in nail psoriasis and onychomycosis regarding histology. Methods: We performed a 3-year retrospective review of all nail clipping test results included in our department’s database and re-analyzed samples containing neutrophils. Results: In total,112 neutrophil-containing nail clipping samples were accounted. Onychomycosis was the commonest diagnosis (74.1%), followed by nail psoriasis (18.8%). Onychomycosis samples had more abundant neutrophils, more often arranged in collections (60.2%) (p = 0.002) and with smaller quantities of parakeratosis, in a lamellar distribution. In nail psoriasis, neutrophils were mostly aggregated (57.1%) with parakeratosis in all samples, in increased amounts, and showing no predominant pattern. Conclusions: Neutrophils are present in both nail psoriasis and onychomycosis, warranting careful interpretation. However, less dense aggregates of neutrophils with more abundant parakeratosis are clues of nail psoriasis when all other fungal tests are negative.

A further study on supramolecular structure changes of waxy maize starch subjected to alkaline treatment by extended-q small-angle neutron scattering

Recently, we reported the effect of mild alkaline treatment on the structure and enzymatic hydrolysis of waxy maize starch. Here, we have used extended-q small-angle neutron scattering (SANS) to examine the extent to which this treatment causes structural changes on even greater length scales — to yield a complete picture from the nanometre to micron — including on the lamellar distribution and larger-scale structural features of the same starch. For this A-type polymorph starch containing mostly amylopectin, we found the changes caused by NaOH solution treatment (0.1% or 0.5% (w/v)) were confined mainly to double helices and crystallites, whereas the lamellar and supramolecular structures were conserved. Although the overall lamellar ordering was reduced in the 0.5% (w/v) alkaline treatment for 6 days, further treatment until 12 days could restore the overall lamellar ordering. Despite changes in starch double helical order and crystallites, there were minimal changes at larger length scales (e.g., blocklets and growth rings). This combination of methods reveals the extent of structural changes occurring as a result of mild alkaline treatment of waxy maize starch; it also provides insight into the rational design of granular starch products with varied functionality via hydrolytic control.

Improved microwave absorbing property provided by the filler's alternating lamellar distribution of carbon nanotube/ carbonyl iron/ poly (vinyl chloride) composites

The microwave absorbing properties of composites with filler's uniform and selective distribution were comparatively investigated. The calculated and experimental results demonstrated that, compared with the uniform distribution, filler's selectively alternating lamellar distribution was more effective in decreasing the minimum reflection loss (RL-min) and broadening the effective bandwidth (EB, RL < −10 dB, for 90% microwave absorption). For examples, for the normal blending samples 3#, the multi-layer structure decreased the RL-min from −21.0 to −48.1 dB, broadened the EB from 2.9 to 5.0 GHz. The layer number, filler content and layer arranging sequence also have strong effects on the microwave absorbing properties. The mechanism behind these effects was the competition between two effects (transmission blocking and attenuation enhancement) provided by the multi-layer structure. The matching frequency could be adjusted by changing the layer number rather the sample thickness. This study provided a facile way to construct a filler's selective distribution morphology, and a more effective method to combine different absorbents, which could be applicable in the designing and fabricating of high-efficient structural microwave absorbing materials.

The effect of Gd element and solution treatment on the microstructure of AZ31 magnesium alloy and its kinetic model

The influence of Gd element and solution treatment on the microstructure of AZ31 alloy was investigated in this paper. The microstructure and phase composition were characterized by OM, SEM, EDS and XRD. The results indicate that Mg17Al12 eutectic phase, scattered along the grain boundary, is suppressed effectively with Gd addition and the acicular Al2Gd superlattice with lamellar distribution is formed. Furthermore, the grain size of AZ31 alloy is also refined with Gd addition. In the subsequent process of solution, the migration and growth of Al2Gd phase conforms to Ostwald Ripening Theory. The morphology of Al2Gd phase becomes granular and scatterd in matrix uniformly after solution for 16 h at 813 K.

Sirolimus Encapsulated Liposomes for Cancer Therapy: Physicochemical and Mechanical Characterization of Sirolimus Distribution within Liposome Bilayers

Sirolimus has recently been introduced as a therapeutic agent for breast and prostate cancer. In the current study, conventional and Stealth liposomes were used as carriers for the encapsulation of sirolimus. The physicochemical characteristics of the sirolimus liposome nanoparticles were investigated including the particle size, zeta potential, stability and membrane integrity. In addition atomic force microscopy was used to study the morphology, surface roughness and mechanical properties such as elastic modulus deformation and deformation. Sirolimus encapsulation in Stealth liposomes showed a high degree of deformation and lower packing density especially for dipalmitoyl-phosphatidylcholine (DPPC) Stealth liposomes compared to unloaded. Similar results were obtained by differential scanning calorimetry (DSC) studies; sirolimus loaded liposomes were found to result in a distorted state of the bilayer. X-ray photon electron (XPS) analysis revealed a uniform distribution of sirolimus in multilamellar DPPC Stealth liposomes compared to a nonuniform, greater outer layer lamellar distribution in distearoylphosphatidylcholine (DSPC) Stealth liposomes.

Analysis of spatial lamellar distribution from adaptive-optics second harmonic generation corneal images

The spatial organization of stromal collagen of ex-vivo corneas has been quantified in adaptive-optics second harmonic generation (SHG) images by means of an optimized Fourier transform (FT) based analysis. At a particular depth location, adjacent lamellae often present similar orientations and run parallel to the corneal surface. However this pattern might be combined with interweaved collagen bundles leading to crosshatched structures with different orientations. The procedure here reported provides us with both principal and crosshatched angles. This is also able to automatically distinguish a random distribution from a cross-shaped one, since it uses the ratio of the axes lengths of the best-fitted ellipse of the FT data as an auxiliary parameter. The technique has successfully been applied to SHG images of healthy corneas (both stroma and Bowman’s layer) of different species and to corneas undergoing cross-linking treatment.

Microstructure and Properties of Electron Beam Welded Tantalum-to-Stainless Steel Joints

Abstract The microstructure, defect characteristics, and mechanical properties of electron beam welded (EBW) tantalum-to-stainless steel joints were investigated. Joint formation was influenced by the position of the EBW heat source. with a well-formed joint was obtained when the heat source was deviated by 0.2 mm towards the stainless steel. The weld is composed of fine dendrites with high elemental Fe content and homogenously-dispersed ɛ (Fe 2 Ta) and μ (FeTa or Fe 7 Ta 6 ) phases. However, ɛ and μ phases formed at the tantalum fusion line had lamellar distribution and micro-cracks are easily formed in this region under welding stress. Although the weld zone has high hardness, the poor deformation compatibility of the fusion line at the tantalum side and the existence of crack sources lead to fracturing during the tensile test. The tensile strength of the joints was found to be low, 255 MPa.

Abstract 3032: Role of ruffles and filopodia in adhesion gradient sensing

Abstract Filopodia play a sensory role in directing motility during embryonic development and axon pathfinding. They also show a low prevalence in cancer cells. Here, we determine whether cells from a rat tracheal epithelial line in vitro use filopodia to sense adhesive gradients. Cells exhibit haptotaxis (movement toward a more adhesive surface) when placed on a metal-glass gradient. Tantalum (Ta) and platinum (Pt) gradients were created on glass slides and high (H), middle (M), and low (L) positions defined along the gradient. Cell counts in randomly selected fields confirmed that the cells recognized the gradient. To determine whether the prevalence of protrusions differed at the H, M, and L locations, we measured the values of latent factors 4 (filopodia), 5, and 7. Factor 4 values were high at H and significantly lower at M and L (p&amp;lt;0.05). Cells’ ability to form large protrusions, represented by factors 5 (lamellar distribution) and 7 (nascent neurites), was uniform across the Ta gradient. To detect the cells’ ability to interpret directional cues, we distinguished the cell's top (T) side, i.e. the side oriented toward H location, from the bottom (B) side. Factor 4 values at H-T exceed those at M-B and L-T (Table 1). Trend analysis confirmed a decrease in factor 4 over the gradient with significance of p&amp;lt;0.001 (Ta) and p&amp;lt;0.023 (Pt). On Pt only, factor 5 increased (p=0.000) as the metal content of the substrate declined. Ruffling activity is generally inverse to filopodia but positively related to factor 5 (Heckman et al., doi:10.1016/j.cellsig.2011.08.023). On haptotactic substrates, the former relationship was observed by correlation analysis but was restricted to the L location on the gradient. This suggests that poor adhesion may help to convert mechanisms of filopodia formation to ruffle formation. The above results suggest that sensing depends on net filopodia stabilization at the more adhesive H location. We conclude that filopodia respond to the gradient and that regulation of the sensing and signaling mechanisms can now be evaluated. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 3032. doi:1538-7445.AM2012-3032

Numerical simulation on size effect of copper with nano-scale twins

To understand the tensile deformation of electro-deposited Cu with nano-scale twins, a numerical study was carried out based on a conventional theory of mechanism-based strain gradient plasticity (CMSG). The concept of twin lamella strengthening zone was used in terms of the cohesive interface model to simulate grain-boundary sliding and separation. The model included a number of material parameters, such as grain size, elastic modulus, plastic strain hardening exponent, initial yield stress, as well as twin lamellar distribution, which may contribute to size effects of twin layers in Cu polycrystalline. The results provide information to understand the mechanical behaviors of Cu with nano-scale growth twins.

Mechanism of adsorption of anionic dye from aqueous solutions onto organobentonite

Organobentonite is suggested as potential super-sorbents for the removal of dyes from wastewater. All kinds of organobentonites are synthesized to adsorb dyes; however, the mechanism of the adsorption is still unclear. In this paper, organobentonites were first modified with hexadecyltrimethylammonium bromide at various amounts to reveal the adsorption mechanism. Subsequently, four kinds of organobentonites were utilized to adsorb acid dyes. Results show that the main mechanism of the adsorption of acid dye is an anionic exchange. The counter-ion bromide in the organobentonite was replaced by the dye anion. The study reveals that the adsorption capacity of organobentonite is affected by the surfactant alkyl chain length. When the longer alkyl chain surfactant was modified, bentonite showed higher adsorption capacity. Specific surface areas had no effect on the adsorption. However, the XRD patterns show that interlamellar distance and lamellar distribution have some effects on the adsorption. High adsorption capacity and low residual concentration were obtained by the organobentonite adsorbents. The revelation of the adsorption mechanism makes it possible to obtain more novel and suitable organobentonite adsorbents for anionic dye removal from wastewater.